WorldWideScience

Sample records for acoustic emission characteristics

  1. Acoustic Emission and Damage Characteristics of Alumina

    Institute of Scientific and Technical Information of China (English)

    REN Hui-lan; NING Jian-guo; HE Jian-hua

    2009-01-01

    gy, AE counts, AE amplitude changing with loading time are analyzed for the notched alumina specimen. It is indicated that AE characteristic parameters reflect the damage process and fracture of material.

  2. Acoustic emission

    International Nuclear Information System (INIS)

    This paper is related to our activities on acoustic emission (A.E.). The work is made with different materials: metals and fibre reinforced plastics. At present, acoustic emission transducers are being developed for low and high temperature. A test to detect electrical discharges in electrical transformers was performed. Our experience in industrial tests to detect cracks or failures in tanks or tubes is also described. The use of A.E. for leak detection is considered. Works on pattern recognition of A.E. signals are also being performed. (Author)

  3. Acoustic emission characteristics of instability process of a rock plate under concentrated loading

    OpenAIRE

    S. R. Wang; Li, C. Y.; Z.S. Zou; Liu, X. L.

    2016-01-01

    It can facilitate the understanding of the mechanical properties and failure laws of rocks to research on the rock failure mechanism and evolution characteristics of Acoustic Emission (AE). Under the concentrated loading condition, the fracture and instability test of a rock plate was conducted by using the rock Mechanics Testing System (MTS), meanwhile, these AE events were recorded through the AE recording system. Based on the laboratory test, the numerical simulation was completed by us...

  4. Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

    Directory of Open Access Journals (Sweden)

    Huamin Li

    2015-01-01

    Full Text Available To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

  5. Study Acoustic Emissions from Composites

    Science.gov (United States)

    Walker, James; Workman,Gary

    1998-01-01

    The purpose of this work will be to develop techniques for monitoring the acoustic emissions from carbon epoxy composite structures at cryogenic temperatures. Performance of transducers at temperatures ranging from ambient to cryogenic and the characteristics of acoustic emission from composite structures will be studied and documented. This entire effort is directed towards characterization of structures used in NASA propulsion programs such as the X-33.

  6. Spectral characteristics of Acoustic Emission of rock based on Singular point of HHT Analysis

    Directory of Open Access Journals (Sweden)

    Zhou Xiaoshan

    2016-01-01

    Full Text Available The sandstone test of uniaxial compression acoustic emission (AE test has been studied, the HHT analysis is applied to AE signal processing, and through the analysis of AE signal to reveal the process of rock fracture. The results show that HHT is a method that based on principal component analysis of time-frequency analysis. The method of HHT can very convenient to deal the singular signal; it can be determine the main composition of singular signal. The instantaneous frequency can be used to describe precisely the time-frequency characteristics of singular signal. The method has a very important significance to reveal the frequency characteristics of AE signal. The EMD signal is decomposed into 8 IMF components in the failure process of rock sound. The component of IMF1 ~ IMF4 is the main component, and the IMF5 ~ IMF8 for low frequency noise signal. Through the EMD of AE signal frequency, the rock fracture has been decomposition into three stages: the initial zone, wave zone, quiet zone. This shows that in the analysis of rupture must eliminate noise interference signal characteristics of AE.

  7. Theoretical analysis of characteristics of acoustic emission in rock failure based on statistical damage mechanics

    Institute of Scientific and Technical Information of China (English)

    WEN Guang-cai; YANG Hui-ming; ZOU Yin-hui

    2009-01-01

    Based on statistical damage mechanics, the constitutive model of a rock under three-dimensional stress was established by the law that the statistical strength of rock micro-element obeys Weibull distribution. The acoustic emission (AE) evolution model of rock failure was put forward according to the view that rock damage and AE were consis-tent. Moreover, in the failure process of rock under three-dimensional stress, the change in relationship between stress condition parameter and the characteristic parameters of AE, such as the event number and its change rate, were studied. Also, the rock AE character-istic under uniaxial compression was analyzed in theory and verified with examples. The results indicate that the cumulative event number and change rate of AE in rock failure are determined by stress state parameter F. Along with the gradual increase of F, first the cu-mulative event number increases gradually, then rapidly, and then slowly after the stress peak. The form of change rate of an event by increasing F is consistent with the distribu-tion form of rock micro-element strength. The model explained the phenomenon that a rel-atively quiet period of AE appears before rock rupture that is observed by many research-ers in experiments. Verification examples indicate that the AE evolution model is consis-tent with the test results, so the model is reasonable and correct.

  8. Sources and characteristics of acoustic emissions from mechanically stressed geologic granular media — A review

    Science.gov (United States)

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

    The formation of cracks and emergence of shearing planes and other modes of rapid macroscopic failure in geologic granular media involve numerous grain scale mechanical interactions often generating high frequency (kHz) elastic waves, referred to as acoustic emissions (AE). These acoustic signals have been used primarily for monitoring and characterizing fatigue and progressive failure in engineered systems, with only a few applications concerning geologic granular media reported in the literature. Similar to the monitoring of seismic events preceding an earthquake, AE may offer a means for non-invasive, in-situ, assessment of mechanical precursors associated with imminent landslides or other types of rapid mass movements (debris flows, rock falls, snow avalanches, glacier stick-slip events). Despite diverse applications and potential usefulness, a systematic description of the AE method and its relevance to mechanical processes in Earth sciences is lacking. This review is aimed at providing a sound foundation for linking observed AE with various micro-mechanical failure events in geologic granular materials, not only for monitoring of triggering events preceding mass mobilization, but also as a non-invasive tool in its own right for probing the rich spectrum of mechanical processes at scales ranging from a single grain to a hillslope. We review first studies reporting use of AE for monitoring of failure in various geologic materials, and describe AE generating source mechanisms in mechanically stressed geologic media (e.g., frictional sliding, micro-crackling, particle collisions, rupture of water bridges, etc.) including AE statistical features, such as frequency content and occurrence probabilities. We summarize available AE sensors and measurement principles. The high sampling rates of advanced AE systems enable detection of numerous discrete failure events within a volume and thus provide access to statistical descriptions of progressive collapse of systems

  9. Experimental Study on Acoustic Emission Characteristics of Phyllite Specimens under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Z.Kui

    2015-10-01

    Full Text Available In order to obtain acoustic emission (AE characteristics of phyllite specimens, AE tests of phyllite specimens under uniaxial compression were carried out. Results indicate that there are three distinct failure modes. The main mode is an extension mode. The others are a shear mode and a coupling of the shear and extension modes. A relative quiescence period of AE may appear before the peak stress for any failure mode. The ratio of the cumulative hits and the cumulative energy (named the r value and the Ib value respectively are used for AE test results analysis. The plots of the Ib value show that the value variation is complex and usually decreases before the peak stress. Before the peak stress the r value decreases continuously and then keeps a relatively slow variation. After the peak stress the r value increases dramatically. The r value appears to be in a U-shape distribution. The Ib value usually decreases while the r value keeps a relatively low variation during the pre-peak stress stage, and the r value increases sharply after the peak stress. This can be used as a basis for determining the pre- or post-peak stress state.

  10. Practical acoustic emission testing

    CERN Document Server

    2016-01-01

    This book is intended for non-destructive testing (NDT) technicians who want to learn practical acoustic emission testing based on level 1 of ISO 9712 (Non-destructive testing – Qualification and certification of personnel) criteria. The essential aspects of ISO/DIS 18436-6 (Condition monitoring and diagnostics of machines – Requirements for training and certification of personnel, Part 6: Acoustic Emission) are explained, and readers can deepen their understanding with the help of practice exercises. This work presents the guiding principles of acoustic emission measurement, signal processing, algorithms for source location, measurement devices, applicability of testing methods, and measurement cases to support not only researchers in this field but also and especially NDT technicians.

  11. Acoustic Emission Characteristics of Gas-Containing Coal during Loading Dilation Process

    Directory of Open Access Journals (Sweden)

    Z. Q. Yin

    2015-12-01

    Full Text Available Raw coal was used as the study object in this paper to identify the evolution characteristics of acoustic emission (AE during the dilation process of gas-containing coal. The coal specimens were stored in gas seal devices filled with gas at different pressures (0, 0.5, 1.0, and 1.5 MPa for 24 h prior to testing. Then, the specimens were tested in a rock-testing machine, and the deformation and crack fracture patterns were recorded by using strain gauges and an AE system. The axial and volumetric strains–stress curves were analyzed in relation to the AE and the failure mode. Results show that as gas pressure increases, the uniaxial compression strength and elasticity modulus of gas-containing coal decreases, whereas the Poisson’s ratio increases. In all the coal specimens, the dilation initiation stress decreases, and the dilation degree increases. During the dilation process, before the loaded coal specimens reach peak stress, and as the load increases, the changes in the specimens and in the AE energy parameter of specimens can be divided into four phases: crack closure deformation, elastic deformation, stable crack propagation, and unstable crack propagation (dilation process. Across the four phases, the AE energy increases evidently during crack closure and elastic deformation but decreases during stable crack propagation. As the gas pressure increases, the AE signal frequency increases from 4.5 KHz to 8.1 KHz during the dilation process. Thus, the gas presence in coal specimens exerts a significant influence on the closure of sample cracks and dilation damage.

  12. Bridging aero-fracture evolution with the characteristics of the acoustic emissions in a porous medium

    Science.gov (United States)

    Turkaya, Semih; Toussaint, Renaud; Eriksen, Fredrik; Zecevic, Megan; Daniel, Guillaume; Flekkøy, Eirik; Måløy, Knut Jørgen

    2015-09-01

    The characterization and understanding of rock deformation processes due to fluid flow is a challenging problem with numerous applications. The signature of this problem can be found in Earth Science and Physics, notably with applications in natural hazard understanding, mitigation or forecast (e.g. earthquakes, landslides with hydrological control, volcanic eruptions), or in industrial applications such as hydraulic-fracturing, steam-assisted gravity drainage, CO sequestration operations or soil remediation. Here we investigate the link between the visual deformation and the mechanical wave signals generated due to fluid injection into porous media. In a rectangular Hele-Shaw Cell, side air injection causes burst movement and compaction of grains along with channeling (creation of high permeability channels empty of grains). During the initial compaction and emergence of the main channel, the hydraulic fracturing in the medium generates a large non-impulsive low frequency signal in the frequency range 100 Hz - 10 kHz. When the channel network is established, the relaxation of the surrounding medium causes impulsive aftershock-like events, with high frequency (above 10 kHz) acoustic emissions, the rate of which follows an Omori Law. These signals and observations are comparable to seismicity induced by fluid injection. Compared to the data obtained during hydraulic fracturing operations, low frequency seismicity with evolving spectral characteristics have also been observed. An Omori-like decay of microearthquake rates is also often observed after injection shut-in, with a similar exponent p≃0.5 as observed here, where the decay rate of aftershock follows a scaling law dN/dt ∝(t-t₀ )-p . The physical basis for this modified Omori law is explained by pore pressure diffusion affecting the stress relaxation.

  13. Bridging aero-fracture evolution with the characteristics of the acoustic emissions in a porous medium

    Directory of Open Access Journals (Sweden)

    Semih eTurkaya

    2015-09-01

    Full Text Available The characterization and understanding of rock deformation processes due to fluid flow is a challenging problem with numerous applications. The signature of this problem can be found in Earth Science and Physics, notably with applications in natural hazard understanding, mitigation or forecast (e.g. earthquakes, landslides with hydrological control, volcanic eruptions, or in industrial applications such as hydraulic-fracturing, steam-assisted gravity drainage, CO₂ sequestration operations or soil remediation. Here we investigate the link between the visual deformation and the mechanical wave signals generated due to fluid injection into porous media. In a rectangular Hele-Shaw Cell, side air injection causes burst movement and compaction of grains along with channeling (creation of high permeability channels empty of grains. During the initial compaction and emergence of the main channel, the hydraulic fracturing in the medium generates a large non-impulsive low frequency signal in the frequency range 100 Hz - 10 kHz. When the channel network is established, the relaxation of the surrounding medium causes impulsive aftershock-like events, with high frequency (above 10 kHz acoustic emissions, the rate of which follows an Omori Law. These signals and observations are comparable to seismicity induced by fluid injection. Compared to the data obtained during hydraulic fracturing operations, low frequency seismicity with evolving spectral characteristics have also been observed. An Omori-like decay of microearthquake rates is also often observed after injection shut-in, with a similar exponent p≃0.5 as observed here, where the decay rate of aftershock follows a scaling law dN/dt ∝(t-t₀-p . The physical basis for this modified Omori law is explained by pore pressure diffusion affecting the stress relaxation.

  14. Sonification of acoustic emission data

    Science.gov (United States)

    Raith, Manuel; Große, Christian

    2014-05-01

    While loading different specimens, acoustic emissions appear due to micro crack formation or friction of already existing crack edges. These acoustic emissions can be recorded using suitable ultrasonic transducers and transient recorders. The analysis of acoustic emissions can be used to investigate the mechanical behavior of different specimens under load. Our working group has undertaken several experiments, monitored with acoustic emission techniques. Different materials such as natural stone, concrete, wood, steel, carbon composites and bone were investigated. Also the experimental setup has been varied. Fire-spalling experiments on ultrahigh performance concrete and pullout experiments on bonded anchors have been carried out. Furthermore uniaxial compression tests on natural stone and animal bone had been conducted. The analysis tools include not only the counting of events but the analysis of full waveforms. Powerful localization algorithms and automatic onset picking techniques (based on Akaikes Information Criterion) were established to handle the huge amount of data. Up to several thousand events were recorded during experiments of a few minutes. More sophisticated techniques like moment tensor inversion have been established on this relatively small scale as well. Problems are related to the amount of data but also to signal-to-noise quality, boundary conditions (reflections) sensor characteristics and unknown and changing Greens functions of the media. Some of the acoustic emissions recorded during these experiments had been transferred into audio range. The transformation into the audio range was done using Matlab. It is the aim of the sonification to establish a tool that is on one hand able to help controlling the experiment in-situ and probably adjust the load parameters according to the number and intensity of the acoustic emissions. On the other hand sonification can help to improve the understanding of acoustic emission techniques for training

  15. Evoked acoustic emission

    DEFF Research Database (Denmark)

    Elberling, C; Parbo, J; Johnsen, N J;

    1985-01-01

    Stimulated acoustic emissions were recorded in response to tonal stimuli at 60 dB p.e. SPL in a small group of normal-hearing adults. Power spectral analysis reveals that the evoked activity from each ear contains energy in preferential frequency bands and the change of stimulus frequency has only...

  16. Acoustic emission source modeling

    Directory of Open Access Journals (Sweden)

    Hora P.

    2010-07-01

    Full Text Available The paper deals with the acoustic emission (AE source modeling by means of FEM system COMSOL Multiphysics. The following types of sources are used: the spatially concentrated force and the double forces (dipole. The pulse excitation is studied in both cases. As a material is used steel. The computed displacements are compared with the exact analytical solution of point sources under consideration.

  17. Acoustic emission characteristics during bending fracture process of piezoelectric composite actuators

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Sung Choong; Goo, Nam Seo [Konkuk Univeristy, Seoul (Korea, Republic of)

    2006-05-15

    The objective of this study is to investigate the damage mechanisms in a thin monolithic PZT wafer and an asymmetrically laminated piezoelectric composite actuator (PCA) under bending loading by the acoustic emission (AE) technique. Fracture surface examinations were conducted using a scanning electron microscope (SEM) and an optical microscope. Using the fabricated PCAs, correlations were established between the observed damage growth mechanisms and the AE results in terms of the AE amplitude and dominant frequency band which was processed by fast Fourier transform (FFT). These correlations can be used to monitor the damage evolution in the plate-type piezoelectric composite actuators exhibiting multiple modes of damage. Results from this study revealed that the AE technique is a powerful and effective tool for identifying damage mechanisms such as brittle fracture in the PZT, matrix cracking, fiber-matrix debonding, fiber breakage and delamination between the PZT layer and fiber composite layer in the asymmetrically laminated PCAs.

  18. Characteristics of acoustic emission during stress corrosion cracking of nickel base alloy

    International Nuclear Information System (INIS)

    The acoustic emission(AE) method has been utilized to study the detectability of crack initiation and growth during intergranular stress corrosion cracking(IGSCC) of Inconel 600 alloy and to evaluate its applicability as a non-destructive testing method by comparing the crack behavior with AE parameters and measuring the minimum detectable crack size. Variously heat-treated specimens were tensioned by use of a constant extension rate tester at various extension rates to yield different stress corrosion cracking behaviors of Inconel specimens. Significant AE responses were observed during IGSCC, ductile fracture and plastic deformation. The magnitude of AE peak amplitudes was in the decreasing order for IGSCC, ductile fracture and plastic deformation. AE also was effective means to identify the transition from small crack initiation and growth to dominant crack growth. Close correlation was found to exist between AE behaviors and electrochemical current changes, suggesting that the formation and breakdown of passive film is involved in IGSCC of Inconel 600. The minimum crack size detectable with AE was approximately 200 to 400μm in length and below 100μm in depth, indicating the possibility of detecting small IGSC cracks prior to the growth of single dominant cracks

  19. Acoustic emission testing

    CERN Document Server

    Grosse, Christian U

    2008-01-01

    Acoustic Emission (AE) techniques have been studied in civil engineering for a long time. The techniques are recently going to be more and more applied to practical applications and to be standardized in the codes. This is because the increase of aging structures and disastrous damages due to recent earthquakes urgently demand for maintenance and retrofit of civil structures in service for example. It results in the need for the development of advanced and effective inspection techniques. Thus, AE techniques draw a great attention to diagnostic applications and in material testing. The book covers all levels from the description of AE basics for AE beginners (level of a student) to sophisticated AE algorithms and applications to real large-scale structures as well as the observation of the cracking process in laboratory specimen to study fracture processes.

  20. EVAC拉伸损伤过程的声发射特性研究%STUDY ON ACOUSTIC EMISSION CHARACTERISTICS OF TENSILE DAMAGE PROCESSES IN EVAC RESIN

    Institute of Scientific and Technical Information of China (English)

    王从科; 张霞; 吕秀莲; 凡丽梅

    2011-01-01

    采用声发射(AE)参数分析和数据聚类、判别分析技术研究了乙烯-乙酸乙烯酯塑料(EVAC)拉伸损伤过程,确定了EVAC拉伸损伤过程中不同损伤阶段的AE特性,并对不同损伤类型的AE特征进行了表征.%Tensile damage processes in EVAC resin was studied by analysis of acoustic emission parameter, clustering and discriminance. The acoustic emission characteristics of different damage phases was defined, the acoustic emission parameters of different damage types were obtained.

  1. Characteristic temperatures of PbFe1/2Nb1/2O3 ferroelectrics crystals seen via acoustic emission

    International Nuclear Information System (INIS)

    PbFe1/2Nb1/2O3 ferroelectrics crystals have been investigated using an acoustic emission. All the characteristic points have been detected: the Néel antiferromagnetic–paramagnetic phase transition at 158.6 K, both the rhombohedral–tetragonal at 363–348 K and tetragonal–cubic at 382–365 K structural phase transitions, the intermediate temperature T* at 431–427.5 K and the Burns temperature T d, extending through 564–603 K. It is shown that a dielectric response is unable to locate the T d correctly, but both the thermal expansion and acoustic emission are able. Acoustic emission is found to be more powerful for T* than for T d, which is usually observed in some well known relaxor ferroelectrics. Such a phenomenon is discussed from a viewpoint of dynamics of polar nanoregions. (papers)

  2. Acoustic emission characteristics of sandstone after high temperature under uniaxial compression%单轴压缩下高温后砂岩的声发射特征

    Institute of Scientific and Technical Information of China (English)

    吴刚; 王德咏; 翟松韬

    2012-01-01

    The acoustic emission evolution process of Jiaozuo sandstone with 20 ℃-1 200 ℃ temperatures is studied using acoustic emission (AE) test under uniaxial compression. By analyzing AE parameters and the mechanical properties of sandstone after high temperature, the AE characteristics of sandstone under different temperatures and different loading stages are explored. The results show that temperature has little effect on the acoustic emission of sandstone when temperature is less than 400 ℃. The AE ring-down accumulation counts change rapidly both at about 100 °C and 600 ℃ temperatures. It is shown that 100 ℃ is the threshold of crack growth for sandstone; and the internal structure composition of sandstone changes after 600 ℃; and acoustic emission phenomenon is very obvious. From 600 ℃ to 1 200 ℃, obvious brittle-plastic transition appears in sandstone. At the same time, the emergence of acoustic emission signals is delayed and the growth rate of acoustic emission signals rises because of high temperature. Sandstone releases intensive acoustic emission signals and presents plastic failure characteristics after 1 200 ℃.%通过在单轴压缩下实施的声发射测试,研究焦作砂岩受20~1200℃温度作用后的声发射演变过程;结合不同温度下砂岩的力学性质,通过声发射参数分析研究砂岩在不同受力阶段的声发射特点.研究表明:400℃以内温度对砂岩的声发射影响不太明显,在100℃后和600℃后声发射振铃累计数均发生急剧变化,100℃是砂岩裂纹扩展发育的门槛值,600℃后砂岩内部结构成分发生了变化,声发射现象较为明显.600~1200℃时,砂岩呈现出明显的脆塑性转变现象,高温导致声发射信号的时间有所推迟,声发射信号增长率不断上升.1200℃后,砂岩释放密集的声发射信号,呈现出塑性破坏特征.

  3. Temporal Characteristics of Rock Acoustic Emission Information under Triaxial Compression%岩石三轴压缩声发射信息时序特征

    Institute of Scientific and Technical Information of China (English)

    杨睿

    2016-01-01

    The rock acoustic emission characteristics under triaxial compression shows that the evo-lution process of rock deformation and damage can be divided into five stages,they are compaction closed stage,elastic stage,elastic-plastic stage,fracture development stage and residual plastic stage.The evolu-tion process of rock samples deformation and damage can be reflected effectively by the rock acoustic e-mission characteristics.Due to the difference of internal components,structures and homogeneous degree of different types of rocks,the acoustic emission temporal characteristics of different types of rocks are also different with each other.The research results show that:①the acoustic emission time series characteris-tics of the coal rock with more internal fractures is scattered,its temporal characteristics is belongs to group shock type;②the acoustic emission events of the limestone with the characteristics of uniform and compact structure are appeared mainly before rock deformation and damage,its temporal characteristics is belongs to isolated shock type;③the sandstone with the characteristics lies between coal rock and lime-stone,its temporal characteristics is belongs to main shock type.%岩石三轴压缩变形破坏演化过程可划分为压密闭合阶段、弹性阶段、弹塑性阶段、破裂发展阶段及残余塑性阶段等5个阶段,声发射特征能够较好地反映出岩样损伤破坏的演化过程。不同类型岩石因其内部组分、结构、均质度不同,其压缩破坏过程的声发射时序特征也不尽相同。研究结果表明:①内部裂隙较多的煤岩声发射时间序列较分散,时序特征呈群震型;②结构均匀致密灰岩的声发射事件数在破坏前集中出现,时序特征呈孤震型;③均质度介于两者之间的砂岩声发射时间时序特征呈主震型。

  4. Evaluation of Wave Propagation Properties during a True-Triaxial Rock Fracture Experiment using Acoustic Emission Frequency Characteristics

    Science.gov (United States)

    Goodfellow, S. D.; Ghofrani Tabari, M.; Nasseri, M. B.; Young, R.

    2013-12-01

    A true-triaxial deformation experiment was conducted to study the evolution of wave propagation properties by using frequency characteristics of AE waveforms to diagnose the state of fracturing in a sample of sandstone. Changes in waveform frequency content has been interpreted as either the generation of progressively larger fractures or the relative attenuation of high-frequency wave components as a result of micro-crack formation. A cubic sample of Fontainebleau sandstone was initially loaded to a stress state of σ1 = σ2 = 35 MPa, σ3 = 5 MPa at which point σ1¬ was increased until failure. Acoustic emission (AE) activity was monitored by 18 PZT transducers, three embedded in each platen. The sensor amplitude response spectrum was determined by following an absolute source calibration procedure and showed a relatively constant sensitivity in the frequency range between 20 kHz and 1200 kHz. Amplified waveforms were continuously recorded at a sampling rate of 10 MHz and 12-bit resolution. Continuous acoustic emission waveforms were harvested to extract discrete events. Using a time-varying transverse isotropic velocity model, 48,502 events were locatable inside the sample volume. Prior to peak-stress, AE activity was associated with stable quasi-static growth of fractures coplanar with σ1 and σ2 located near the platen boundaries. In the post peak-stress regime, fracture growth displays unstable ¬dynamic propagation. Analysis of waveform frequency characteristics was limited to the pre peak-stress regime. Analysis of AE frequency characteristics was conducted on all 48,502 located AE events; each event file containing 18 waveforms of varied quality. If the signal to noise ratio was greater than 5, the waveforms power spectrum was estimated and the source-receiver raypath vector was calculated. The power spectrum of each waveform was divided into three frequency bands (Low: 100 - 300 kHz, Medium: 300 - 600 kHz and High: 600 - 1000 kHz) and the power in each

  5. Fault monitoring using acoustic emissions

    Science.gov (United States)

    Zhang, Danlu; Venkatesan, Gopal; Kaveh, Mostafa; Tewfik, Ahmed H.; Buckley, Kevin M.

    1999-05-01

    Automatic monitoring techniques are a means to safely relax and simplify preventive maintenance and inspection procedures that are expensive and necessitate substantial down time. Acoustic emissions (AEs), that are ultrasonic waves emanating from the formation or propagation of a crack in a material, provide a possible avenue for nondestructive evaluation. Though the characteristics of AEs have been extensively studied, most of the work has been done under controlled laboratory conditions at very low noise levels. In practice, however, the AEs are buried under a wide variety of strong interference and noise. These arise due to a number of factors that, other than vibration, may include fretting, hydraulic noise and electromagnetic interference. Most of these noise events are transient and not unlike AE signals. In consequence, the detection and isolation of AE events from the measured data is not a trivial problem. In this paper we present some signal processing techniques that we have proposed and evaluated for the above problem. We treat the AE problem as the detection of an unknown transient in additive noise followed by a robust classification of the detected transients. We address the problem of transient detection using the residual error in fitting a special linear model to the data. Our group is currently working on the transient classification using neural networks.

  6. Influence of movement regime of stick-slip process on the size distribution of accompanying acoustic emission characteristics

    Science.gov (United States)

    Matcharashvili, Teimuraz; Chelidze, Tamaz; Zhukova, Natalia; Mepharidze, Ekaterine; Sborshchikov, Alexander

    2010-05-01

    Many scientific works on dynamics of earthquake generation are devoted to qualitative and quantitative reproduction of behavior of seismic faults. Number of theoretical, numerical or physical models are already designed for this purpose. Main assumption of these works is that the correct model must be capable to reproduce power law type relation for event sizes with magnitudes greater than or equal to a some threshold value, similar to Gutenberg-Richter (GR) law for the size distribution of earthquakes. To model behavior of a seismic faults in laboratory conditions spring-block experimental systems are often used. They enable to generate stick-slip movement, intermittent behavior occurring when two solids in contact slide relative to each other driven at a constant velocity. Wide interest to such spring-block models is caused by the fact that stick-slip is recognized as a basic process underlying earthquakes generation along pre-existing faults. It is worth to mention, that in stick slip experiments reproduction of power law, in slip events size distribution, with b values close or equal to the one found for natural seismicity is possible. Stick-slip process observed in these experimental models is accompanied by a transient elastic waves propagation generated during the rapid release of stress energy in spring-block system. Oscillations of stress energy can be detected as a characteristic acoustic emission (AE). Accompanying stick slip AE is the subject of intense investigation, but many aspects of this process are still unclear. In the present research we aimed to investigate dynamics of stick slip AE in order to find whether its distributional properties obey power law. Experiments have been carried out on spring-block system consisting of fixed and sliding plates of roughly finished basalt samples. The sliding block was driven with a constant velocity. Experiments have been carried out for five different stiffness of pulling spring. Thus five different regimes

  7. ACOUSTIC EMISSION DURING STRETCHING OF POLYMERS

    Institute of Scientific and Technical Information of China (English)

    QIAN Renyuan; WANG Tiangui; SHEN Jingshu

    1983-01-01

    Acoustic emission has been studied for a wide range of polymers including amorphous glasses,semi-crystalline polymers, copolymers, polymer blends and a crosslinked rubber during the course of uni-axial stretching at room temperature. For non-crystalline polymers acoustic emission occurred in rather small number of events accompanied by crazing and micro-crack formation. Strong acoustic activity appeared during yielding and necking of crystalline polymers. Rather small number or none of acoustic bursts occurred during the initial stage of neck drawing but numerous strong bursts appeared when drawing proceeded approaching specimen break. Specimens of the same polymer but of different fabrication history may be reflected in their acoustic emission behavior. Acoustic emission during stretching crosslinked polybutadiene rubber was very weak but observable when the force-elongation curve started to deviate from the linear region. No Kaiser effect was observed for the rubber. Very strong and numerous acoustic emission was observed during stretching specimens of polymer blends.High impact resistant polymer modifications showed no sharp increase of acoustic activity before specimen break. So long as the polymer and conditions of specimen fabrication are the same quite reproducible acoustic emission behavior could be observed.

  8. 大型观览车主轴系统的声发射信号特征%Acoustic Emission Signals' Characteristics of the Giant Wheel Main Spindle

    Institute of Scientific and Technical Information of China (English)

    吴占稳; 沈功田; 袁俊

    2011-01-01

    大型观览车不仅是游乐园的标志,而且是城市的标志。针对大型观览车主轴系统难以拆卸的特点,通过试验模型,模拟了主轴运行过程,采用声发射仪器获取了主轴系统运行过程中的声发射信号。通过分析声发射信号,初步得出了主轴运行过程中声发射信号的规律特征,包括参数特征和波形频谱特征。%Giant wheel, as one type of large-scale amusement device, is not only a symbol of the amusement park, but also of the city. As one important part of the giant wheel, the main spindle is difficult to be disassembled. In this paper, the simulation model of the giant wheel was designed and manufactured, in which the operation process of the main spindle could be simulated. The acoustic emission(AE) technique was used to monitor the test process. The acoustic emission signals' characteristics were analyzed, including AE parameter distribution features and wave spectrum characteristics.

  9. An introduction to acoustic emission

    Science.gov (United States)

    Scruby, C. B.

    1987-08-01

    The technique of acoustic emission (AE) uses one or more sensors to 'listen' to a wide range of events that may take place inside a solid material. Depending on the source of this high frequency sound, there are broadly three application areas: structural testing and surveillance, process monitoring and control, and materials characterization. In the first case the source is probably a defect which radiates elastic waves as it grows. Provided these waves are detectable, AE can be used in conjunction with other NDT techniques to assess structural integrity. Advances in deterministic and statistical analysis methods now enable data to be interpreted in greater detail and with more confidence than before. In the second area the acoustic signature of processes is monitored, ranging from for instance the machining of metallic components to the mixing of foodstuffs, and changes correlated with variations in the process, with the potential for feedback and process control. In the third area, AE is used as an additional diagnostic technique for the study of, for instance, fracture, because it gives unique dynamic information on defect growth.

  10. One sensor acoustic emission localization in plates.

    Science.gov (United States)

    Ernst, R; Zwimpfer, F; Dual, J

    2016-01-01

    Acoustic emissions are elastic waves accompanying damage processes and are therefore used for monitoring the health state of structures. Most of the traditional acoustic emission techniques use a trilateration approach requiring at least three sensors on a 2D domain in order to localize sources of acoustic emission events. In this paper, we present a new approach which requires only a single sensor to identify and localize the source of acoustic emissions in a finite plate. The method proposed makes use of the time reversal principle and the dispersive nature of the flexural wave mode in a suitable frequency band. The signal shape of the transverse velocity response contains information about the propagated paths of the incoming elastic waves. This information is made accessible by a numerical time reversal simulation. The effect of dispersion is reversed and the original shape of the flexural wave is restored at the origin of the acoustic emission. The time reversal process is analyzed first for an infinite Mindlin plate, then by a 3D FEM simulation which in combination results in a novel acoustic emission localization process. The process is experimentally verified for different aluminum plates for artificially generated acoustic emissions (Hsu-Nielsen source). Good and reliable localization was achieved for a homogeneous quadratic aluminum plate with only one measurement. PMID:26372509

  11. World Conference on Acoustic Emission 2013

    CERN Document Server

    Wu, Zhanwen; Zhang, Junjiao

    2015-01-01

    This volume collects the papers from the 2013 World Conference on Acoustic Emission in Shanghai. The latest research and applications of Acoustic Emission (AE) are explored, with particular emphasis on detecting and processing of AE signals, development of AE instrument and testing standards, AE of materials, engineering structures and systems, including the processing of collected data and analytical techniques as well as experimental case studies.

  12. Acoustic emission location on aluminum alloy structure by using FBG sensors and PSO method

    Science.gov (United States)

    Lu, Shizeng; Jiang, Mingshun; Sui, Qingmei; Dong, Huijun; Sai, Yaozhang; Jia, Lei

    2016-04-01

    Acoustic emission location is important for finding the structural crack and ensuring the structural safety. In this paper, an acoustic emission location method by using fiber Bragg grating (FBG) sensors and particle swarm optimization (PSO) algorithm were investigated. Four FBG sensors were used to form a sensing network to detect the acoustic emission signals. According to the signals, the quadrilateral array location equations were established. By analyzing the acoustic emission signal propagation characteristics, the solution of location equations was converted to an optimization problem. Thus, acoustic emission location can be achieved by using an improved PSO algorithm, which was realized by using the information fusion of multiple standards PSO, to solve the optimization problem. Finally, acoustic emission location system was established and verified on an aluminum alloy plate. The experimental results showed that the average location error was 0.010 m. This paper provided a reliable method for aluminum alloy structural acoustic emission location.

  13. 基于声发射的高松矿田白云岩破坏特征分析%Analysis of Dolomite Failure Characteristics in Gaosong Ore field Based on Acoustic Emission

    Institute of Scientific and Technical Information of China (English)

    倪春中; 张世涛; 刘春学; 李雨健

    2014-01-01

    Acoustic emission is carried out dolomite which sampled from Gaosong ore field ,Gejiu tin deposit through uni-axial compressive by rigid testing machine .Characteristics of the mechanical and acoustic emission in the whole rock failure process are analyzed and so the dolomite failure mechanism .The study showed that:there exits acoustic emission activity at the beginning of loading .This is due to the original micro-fissure extrusion destruction in closing process .In the mid-term of the elastic phase ,acoustic emission events become stable and late plastic stage acoustic emission event significantly increases than before .The original crack growth is the main reason for rock acoustic emission activity and the change of the volume .%在刚性试验机上,对个旧锡矿高松矿田白云岩进行单轴受压岩石破坏全过程声发射试验,研究岩石破坏全过程力学特征和声发射特征,在此基础上分析石灰岩的破坏机理。试验研究表明:白云岩在加载初期有声发射活动,为原有微裂隙闭合过程中挤压破坏产生;弹性阶段的中期,声发射事件比较稳定;后期和塑性阶段的前期声发射事件明显增加,此时原有裂纹扩展是造成岩石声发射活动和体积变化的主要原因。

  14. 常温下16MnR板材焊接缺陷声发射特性研究%Study of Acoustic Emission Characteristics for a 16MnR Plate with Welding Defect at Normal Temperature

    Institute of Scientific and Technical Information of China (English)

    孙国豪; 张雪涛; 李建宏; 詹颖钧; 潘家祯

    2009-01-01

    Acoustic emission tests for a prepared 16 MnR rectangle plate with welding defects were carried out in laboratory. The main objective is to analyze the acoustic emission signal and the tension curve of specimen and to elaborate the acoustic emission signal distribution and corresponding stress state. Based on cracking stress calculation in fracture mechanics, the prediction of stress value corresponding large amount accoustic emission signals was made, which effectively relates the generation of acoustic emission signals with spesimen stress state. This may direct the acoustic emission inspection for vessels with defects. Selecting a suitable wavelet function, the different parameters of acoustic emission signal generated in tension test were analyzed, and the difference between different acoustic emission signals parameters in wavelet analysis was compared, finally, the signal distribution characteristics in time domain and the corresponding stress state were found out.%对预制的含有未焊透缺陷的16MnR焊接矩形试样,进行了室内声发射试验.分析了试验中记录的试样拉伸曲线和声发射信号,阐述了试样声发射信号的分布情况和相应的应力状况.通过缺陷的断裂力学计算,预测了产生大量声发射信号的应力值,将声发射信号的产生和试样所受的应力状况有效地联系起来,对含缺陷容器的声发射检测有一定的指导作用.选择合适的小波函数,分析了试验中声发射信号的不同参量,对比了声发射信号不同参量在小波分析中的差异,得出了声发射信号的时域内分布特征和相应的应力状况.

  15. Study on the characteristics of rock failure strain and acoustic emission field for two parallelling faults with the same slip direction including asperities

    Institute of Scientific and Technical Information of China (English)

    焦明若; 张国民; 马胜利; 马宏生

    2002-01-01

    By dealing with strain and acoustic emission (AE) data for two parallelling faults's instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field distribution on the asperity of parallelling faults is analyzed. Furthermore the failure process of asperities and interaction among the asperities, i.e., positive and negative seismicity are discussed. Results show that instability and failure for the parallelling faults is a kind of negative seismicity.

  16. Test Study on Acoustic Emission Evolution Characteristics in Failure Process of Plastic and Brittle Coal%塑性煤与脆性煤破坏过程的声发射演化特征试验研究

    Institute of Scientific and Technical Information of China (English)

    杨慧明

    2015-01-01

    在单轴压缩条件下,进行了塑性煤与脆性煤试件破坏过程声发射监测试验,研究两类煤破坏过程的声发射演化特征。试验结果表明:煤体破坏失稳过程中的声发射与煤体中的裂纹萌生、扩展、贯通等活动相对应,煤体的声发射演化特征与其破坏特征密切相关。塑性煤破坏过程的声发射事件率呈现“上升—峰值—下降”的演化规律;声发射事件率出现急速增大之后的稳步下降是煤体主破裂面即将贯通、煤体破坏失稳的前兆。脆性煤破坏过程的声发射事件率呈现“上升—峰值”的演化规律,声发射“下降”段不明显。研究结果可为煤体稳定性监测的声发射参数演化的解译、灾变判识准则的建立提供理论基础。%Under the condition of uniaxial compression, monitoring test of acoustic emission was carried out in the failure process of both plastic and brittle coal specimen and study was made on the evolution characteristics of acoustic emission in their failure process. The test results showed that the acoustic emission in the failure and destabilizing process of coal corresponded with the process of crack initiation,extension and interconnection in the coal,and the evolution characteristics of acoustic emission of coal were closely related to its failure characteristics. The acoustic emission event rate in the failure process of the plastic coal presented an evolution regularity of “up-peak-down”;the steady decrease of the acoustic emission event rate after its rapid increase was the precursor of the main fracture surface connection and the failure and destabilization of coal. The acoustic emission event rate of the brittle coal presented an evolution regularity of “up-peak” and the “down” stage of acoustic emission was not obvious. The study results can provide a theoretical basis for the explanations of the acoustic emission parameter evolution in coal stability

  17. Condition Monitoring and Management from Acoustic Emissions

    DEFF Research Database (Denmark)

    Pontoppidan, Niels Henrik Bohl

    2005-01-01

    In the following, I will use technical terms without explanation as it gives the freedom to describe the project in a shorter form for those who already know. The thesis is about condition monitoring of large diesel engines from acoustic emission signals. The experiments have been focused...

  18. Why and how acoustic emission in pressure vessel first hydrotest

    International Nuclear Information System (INIS)

    The main advantages obtained performing the Acoustic Emission (AE) examination during pressure vessel first hydrotest are presented. The characteristics and performance of the AE instrumentation to be used for a correct test are illustrated. The main criteria for AE source characterization (location, typical AE parameters and their correlation with pressure value), the calibration and test procedures are discussed. The ndt post-test examinations and laboratory specimen experiments are also outlined. Personnel qualification requirements are finally indicated. (Author)

  19. Spatio-temporal characteristics of acoustic emission during the deformation of rock samples with compressional and extensional en-echelon faults

    Institute of Scientific and Technical Information of China (English)

    蒋海昆; 马胜利; 张流; 侯海峰; 曹文海

    2002-01-01

    The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and extensional en-echelon faults have been studied. The results show that the pre-existing structure can significantly influence the patterns of AE spatial distribution. With increasing of differential stress, AE events firstly cluster around the two ends of pre-existing faults inside the jog and then along the line joining the two ends. The biggish AE events often occur around one end repeatedly. The image of AE clusters indicates the direction and the area of the fracture propagation. The direction of the macroscopic fracture in extensional and compressional jogs is perpendicular and parallel to the direction of axial stress, respectively. The weakening process before the fracturing of jog area is remarkable, and one of the typical precursors for the instability is that the cumulative frequency of AE events increases exponentially. After the fracturing of the jog the frequency and releasing strain energy of AE events decrease gradually. During the friction period, there is no precursory increasing of AE activity before the big stick-slip events. The change of b value in jog shows a typical change of "decreasing tendentiously →returning quickly" before the instability. The decrease of b value occurs in the process of stress increasing and sometime goes down to the weakening stage, and the quick increase b values appears in a short time just before the instability. The comparative analysis shows that the difference in b value due to the different structures is larger than b value variation caused by increase of the differential stress. For the same sample, the temporal sequence of AE is strongly affected by the mechanical state, and the high loading velocity corresponds to the high release rate of strain energy and low b value. Due to its lower failure strength, the broken area is sensitive to small changes in differential stress. Therefore, it

  20. ACOUSTIC EMISSION MODEL WITH THERMOACTIVATIVE DESTRUCTION OF COMPOSITE MATERIAL SURFACE

    Directory of Open Access Journals (Sweden)

    Sergii Filonenko

    2016-03-01

    Full Text Available Modeling of acoustic emission energy during the composite material machining for termoactivativemodel of acoustic radiation is simulated. The regularities of resultant signals energy parameters change dependingon composite materials machining speed are determined. Obtained regularities with their statistical characteristicsare described. Sensitivity of acoustic emission energy parameters to the change of composite material machiningspeed is shown.

  1. Acoustic emission monitoring of wind turbine blades

    Science.gov (United States)

    Van Dam, Jeremy; Bond, Leonard J.

    2015-03-01

    Damage to wind turbine blades can, if left uncorrected, evolve into catastrophic failures resulting in high costs and significant losses for the operator. Detection of damage, especially in real time, has the potential to mitigate the losses associated with such catastrophic failure. To address this need various forms of online monitoring are being investigated, including acoustic emission detection. In this paper, pencil lead breaks are used as a standard reference source and tests are performed on unidirectional glass-fiber-reinforced-polymer plates. The mechanical pencil break is used to simulate an acoustic emission (AE) that generates elastic waves in the plate. Piezoelectric sensors and a data acquisition system are used to detect and record the signals. The expected dispersion curves generated for Lamb waves in plates are calculated, and the Gabor wavelet transform is used to provide dispersion curves based on experimental data. AE sources using an aluminum plate are used as a reference case for the experimental system and data processing validation. The analysis of the composite material provides information concerning the wave speed, modes, and attenuation of the waveform, which can be used to estimate maximum AE event - receiver separation, in a particular geometry and materials combination. The foundational data provided in this paper help to guide improvements in online structural health monitoring of wind turbine blades using acoustic emission.

  2. Laboratory Hydraulic Fracture Characterization Using Acoustic Emission

    Science.gov (United States)

    Gutierrez, M.

    2013-05-01

    For many years Acoustic Emission (AE) testing has aided in the understanding of fracture initiation and propagation in geologic materials. AEs occur when a material emits elastic waves caused by the sudden occurrence of fractures or frictional sliding along discontinuous surfaces and grain boundaries. One important application of AE is the monitoring of hydraulic fracturing of underground formations to create functional reservoirs at sites where the permeability of the rock is too limited to allow for cost effective fluid extraction. However, several challenges remain in the use of AE to locate and characterize fractures that are created hydraulically. Chief among these challenges is the often large scatter of the AE data that are generated during the fracturing process and the difficulty of interpreting the AE data so that hydraulic fractures can be reliably characterized. To improve the understanding of the link between AE and hydraulic fracturing, laboratory scale model testing of hydraulic fracturing were performed using a cubical true triaxial device. This device consist of a loading frame capable of loading a 30x30x30 cm3 rock sample with three independent principal stresses up to 13 MPa while simultaneously providing heating up to 180 degrees C. Several laboratory scale hydraulic fracture stimulation treatments were performed on granite and rock analogue fabricated using medium strength concrete. A six sensor acoustic emission (AE) array, using wideband piezoelectric transducers, is employed to monitor the fracturing process. AE monitoring of laboratory hydraulic fracturing experiments showed multiple phenomena including winged fracture growth from a borehole, cross-field well communication, fracture reorientation, borehole casing failure and much more. AE data analysis consisted of event source location determination, fracture surface generation and validation, source mechanism determination, and determining the overall effectiveness of the induced fracture

  3. Acoustic emission during the compaction of brittle UO2 particles

    International Nuclear Information System (INIS)

    One of the options considered for recycling minor actinides is to incorporate about 10% to UO2 matrix. The presence of open pores interconnected within this fuel should allow the evacuation of helium and fission gases to prevent swelling of the pellet and ultimately its interaction with the fuel clad surrounding it. Implementation of minor actinides requires working in shielded cell, reducing their retention and outlawing additions of organic products. The use of fragmentable particles of several hundred micrometers seems a good solution to control the microstructure of the green compacts and thus control the open porosity after sintering. The goal of this study is to monitor the compaction of brittle UO2 particles by acoustic emission and to link the particle characteristics to the open porosity obtained after the compact sintering. The signals acquired during tensile strength tests on individual granules and compacts show that the acoustic emission allows the detection of the mechanism of fragmentation and enables identification of a characteristic waveform of this fragmentation. The influences of compaction stress, of the initial particle size distribution and of the internal cohesion of the granules, on the mechanical strength of the compact and on the microstructure and open porosity of the sintered pellets, are analyzed. By its ability to identify the range of fragmentation of the granules during compaction, acoustic emission appears as a promising technique for monitoring the compaction of brittle particles in the manufacture of a controlled porosity fuel. (author)

  4. Crack detection in lap-joints using acoustic emission

    International Nuclear Information System (INIS)

    Experiments have been performed to assess the feasibility of crack growth detection in an aircraft lap-joint using acoustic emission (AE). Fatigue tests were conducted in both simple geometry specimens and lap-joint specimens. A high fidelity, wide band transient recording system was used to capture the acoustic emission due to defect growth. The simple specimens were used to determine crack growth signal characteristics, while the complex lap-joint provided a more realistic specimen. Representative waveforms from these two specimens are presented, along with a discussion of wave propagnation for the particular media. A self-organizing map was investigated as a means of automatically identify crack signals. Results and suggestions for future work are presented

  5. Measuring acoustic emissions in an avalanche slope

    Science.gov (United States)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  6. Acoustic Emission Analysis Applet (AEAA) Software

    Science.gov (United States)

    Nichols, Charles T.; Roth, Don J.

    2013-01-01

    NASA Glenn Research and NASA White Sands Test Facility have developed software supporting an automated pressure vessel structural health monitoring (SHM) system based on acoustic emissions (AE). The software, referred to as the Acoustic Emission Analysis Applet (AEAA), provides analysts with a tool that can interrogate data collected on Digital Wave Corp. and Physical Acoustics Corp. software using a wide spectrum of powerful filters and charts. This software can be made to work with any data once the data format is known. The applet will compute basic AE statistics, and statistics as a function of time and pressure (see figure). AEAA provides value added beyond the analysis provided by the respective vendors' analysis software. The software can handle data sets of unlimited size. A wide variety of government and commercial applications could benefit from this technology, notably requalification and usage tests for compressed gas and hydrogen-fueled vehicles. Future enhancements will add features similar to a "check engine" light on a vehicle. Once installed, the system will ultimately be used to alert International Space Station crewmembers to critical structural instabilities, but will have little impact to missions otherwise. Diagnostic information could then be transmitted to experienced technicians on the ground in a timely manner to determine whether pressure vessels have been impacted, are structurally unsound, or can be safely used to complete the mission.

  7. Study of Acoustic Emissions from Composites

    Science.gov (United States)

    Walker, James L.; Workman, Gary L.

    1997-01-01

    The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

  8. 采动影响下突出煤体温度与声发射特性%Temperature and acoustic emission characteristics of coal in the process of outburst under the influence of mining

    Institute of Scientific and Technical Information of China (English)

    许江; 周文杰; 刘东; 李树春; 谭皓月

    2013-01-01

    Using self-developed large-scale coal and gas outburst test device and 16CHs SAMOS monitoring system of a-coustic emission, discussed the impact of coal and gas outburst on acoustic emission characteristics of coal induced by the change of stress level in distressed area. The results show that, in the process of gas adsorbing, the temperature of coal increases, and with the increase of stress in the distressed area, the increment of temperature increase of coal has the trend to reduce. In the process of outburst,the temperature of coal will experience a steep drop mutation process, but the impact of stress change in distressed area is not obvious to the plunged mutations of coal body temperature. In addition, in the coal gas filling stage, along with the increase of stress in the distressed area, Hit rate peak decreases, and the produced acoustic emission characteristics are not obvious, but in the out burst stage, along with the increase of stress in the distressed area,Hit rate peak increases,the resulting acoustic emission characteristics are more obvious. In the whole process of coal and gas outburst, through coal body acoustic emission characteristics and its temperature change rule analysis, there is a close inner link between the acoustic emission and coal temperation, and in the coal and gas outburst, coal energy is in a direct relationship with coal rupture.%利用自主研发的大型煤与瓦斯突出模拟试验装置和16CHs SAMOS System声发射测试系统,探讨采煤工作面前方卸压带应力水平对煤与瓦斯突出的孕育与发生发展过程中煤体温度及其声发射特性的影响.试验结果表明:在煤体充瓦斯阶段,煤体温度升高,且随着卸压带应力的增大,煤体温度的增量有减少的趋势;在突出发生阶段,煤体温度经历一个陡降突变的过程,但卸压带应力水平的变化对煤体温度陡降突变的影响并不明显;在煤体充瓦斯阶段,随着卸压带应力的增大,Hit率峰值

  9. An acoustic emission study of plastic deformation in polycrystalline aluminium

    Science.gov (United States)

    Bill, R. C.; Frederick, J. R.; Felbeck, D. K.

    1979-01-01

    Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminum while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.

  10. Acoustic Emissions (AE) Electrical Systems' Health Monitoring Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Acoustic Emissions (AE) are associated with physical events, such as thermal activity, dielectric breakdown, discharge inception, as well as crack nucleation and...

  11. Standard guide for acoustic emission system performance verification

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 System performance verification methods launch stress waves into the examination article on which the sensor is mounted. The resulting stress wave travels in the examination article and is detected by the sensor(s) in a manner similar to acoustic emission. 1.2 This guide describes methods which can be used to verify the response of an Acoustic Emission system including sensors, couplant, sensor mounting devices, cables and system electronic components. 1.3 Acoustic emission system performance characteristics, which may be evaluated using this document, include some waveform parameters, and source location accuracy. 1.4 Performance verification is usually conducted prior to beginning the examination. 1.5 Performance verification can be conducted during the examination if there is any suspicion that the system performance may have changed. 1.6 Performance verification may be conducted after the examination has been completed. 1.7 The values stated in SI units are to be regarded as standard. No other u...

  12. 刀具磨损声发射信号的混沌特性分析%Chaotic characteristic analysis of tool wear acoustic emission signal

    Institute of Scientific and Technical Information of China (English)

    关山; 彭昶

    2015-01-01

    In metal cutting process, surface quality and dimensional accuracy of the work piece is affected by cutting-tool wear condition. So it is important to study the cutting-tool wear, especially in automation production. Cutting-tool wear is a complex process; it is affected by various factors like cutting parameters, material characteristics and cutting environment, etc. Metal cutting is a nonlinear system; there are a lot of non-stationary signals used in condition monitoring and fault diagnosis. Vibration, force and acoustic emission (AE) are the typical signal type widely used in cutting-tool wear research. In this paper, we chose AE signal to be the carrier in analyzing cutting-tool wear. AE is the class of phenomena where transient elastic waves are generated by the rapid release of energy when the materials are distorted or under the outside load. The AE signal produced by cutting -tool wear is high-frequency and the bandwidth is nearly 50 kHz-1 MHz, so it can weaken the influence of low-frequency noise like mechanical noise and ambient noise. The measured signal sometimes contains high-frequency noise. In this paper, chaos theory was used in analyzing the nonlinear characteristics of the AE signal. Chaos theory is sensitive to noise; therefore, noise reduction was done with the method based on empirical mode decomposition and wavelet (EMD-Wavelet) before computing. The signal were decomposed into several intrinsic mode functions which was from high-frequency to low-frequency by use of EMD, then it was used to determine the noise dominated intrinsic mode functions based on consecutive mean square error (CMSE) proposed by Boudraa and then restrained them. A new signal were reconstructed by adding the rest intrinsic mode functions together and a further and last de-noising was using wavelet to processing the new one in order to get more pure signal. Before extracting the chaotic character, an important step was to reconstruct a phase space from the de

  13. A study on relation between acoustic emission and characteristic displacement field on the sample with multi en echelon structures - The theoretic and experimental explorations of strain gap

    Institute of Scientific and Technical Information of China (English)

    陈顺云; 许昭永; 杨润海; 赵晋明; 郝锦琦; 王赟赟; 王正荣; 熊秉衡

    2002-01-01

    Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographically by real-time holographic interferometry and shadow optical method of caustics, as soon as the loading process started. In the meantime, the AE (acoustic emission) signals were recorded by a micro crack information storage-analysis system. According to damage theory and location of micro fracture, we have studied the stain gap and gained: a) It is necessary that strain gap appears under the condition of linear elasticity theory, and its situation is relatively stable, corresponding to stress concentration. b) Micro fractures, which appear initially at area of high stress, occur rarely at the strain gap, and their locations are finally in the zone between the stress concentration area and the strain gap, which indicate the clusters or groups. However, the major macro fracture (final rupture) started from the shadow areas, and then grew quickly towards the strain gaps, which resulted in failure of sample.

  14. CONFINING PRESSURE EFFECT ON ACOUSTIC EMISSIONS IN ROCK FAILURE

    Institute of Scientific and Technical Information of China (English)

    陈忠辉; 唐春安; 傅宇方

    1998-01-01

    Based on the phenomenon that acoustic emissions (AE) generated by rock massincreas uddenly because of underground excavation, time sequence of AE rate in rock failurehas been discussed by using statistical damage theory. It has been demonstrated that how theinfluence of confining pressure on the deformation behavior and AE characteristics in rocks can beinferred from a simple mechanics model. The results show that loading confining pressure sharplybrings out increasing of AE. On the other hand, few AE emits when confining pressure is loadedsharply, and AE occurs again when axial pressure keeps on increasing. These results have beenwell simulated with computer and show close correspondence with directly measured curves" inexperiments.

  15. Regularities of Acoustic Emission in the Freight Car Solebar Materials

    Science.gov (United States)

    Bekher, S.

    2016-01-01

    Acoustic emission results which were obtained during tests of the samples, which were made from foundry solebars with the developing fatigue crack, are presented. The dependences of the acoustic emission event count, the force critical value during the stationary acoustic emission process, and the growth rate of the event count from the cycles number are determined. The amplitude signal distributions relating to the crack growth were received. It is offered to use the force critical value and the amplitude threshold in the rejection criteria.

  16. Experimental Investigations into the Effects of Lithology on Acoustic Emission

    Directory of Open Access Journals (Sweden)

    Baozhu Tian

    2015-11-01

    Full Text Available In order to study how lithology affects acoustic emissions (AE, a series of tunnel rock burst simulation experiments, monitored by acoustic emission instruments, were conducted on granite, marble and basalt. By analyzing the characteristic parameters, this study found that AE events occur more frequently during the rock burst process on granite and basalt. Marble remains dormant until 75% of the loading time before the peak, at which point, cracks develop rapidly and AE events dramatically increase. During the rock burst process, the AE energy release demonstrates that low energy is released in the incubation phase and robust energy is released during the later phase. Before the rock burst occurs, increased in the heterogeneity index Cv values of the AE event are subject to lithology. The Cv values of granite and basalt have an increase of about 0.2-0.4, while marble shows an increase of 1.0-1.2. The heterogeneity index Cv value of an AE event is in line with the rock burst process.

  17. Study of acoustic emission sources and signals

    Science.gov (United States)

    Pumarega, M. I. López; Armeite, M.; Oliveto, M. E.; Piotrkowski, R.; Ruzzante, J. E.

    2002-05-01

    Methods of acoustic emission (AE) signal analysis give information about material conditions, since AE generated in stressed solids can be used to indicate cracks and defect positions so as their damaging potential. We present a review of results of laboratory AE tests on metallic materials. Rings of seamless steel tubes, with and without oxide layers, were cut and then deformed by opening their ends. Seamless Zry-4 tubes were submitted to hydraulic stress tests until rupture with a purposely-constructed hydraulic system. In burst type signals, their parameters, Amplitude (A), Duration (D) and Risetime (R), were statistically studied. Amplitudes were found to follow the Log-normal distribution. This led to infer that the detected AE signal, is the complex consequence of a great number of random independent sources, which individual effects are linked. We could show, using cluster analysis for A, D and R mean values, with 5 clusters, coincidence between the clusters and the test types. A slight linear correlation was obtained for the parameters A and D. The arrival time of the AE signals was also studied, which conducted to discussing Poisson and Polya processes. The digitized signals were studied as (1/f)β noises. The general results are coherent if we consider the AE phenomena in the frame of Self Organized Criticality theory.

  18. Acoustic Emission Monitoring of Cementitious Wasteforms

    International Nuclear Information System (INIS)

    A summary is presented of the potential of non-destructive acoustic emission (AE) method to be applied for structures immobilising nuclear wastes. The use and limitations of the method are discussed with given examples of experimental configurations and results obtained from AE monitoring and data analysis of two different processes addressing particular issues related to the nuclear waste immobilisation. These are (a) corrosion of aluminium, classified as intermediate level waste (ILW) in the UK, encapsulated in cementitious structures and (b) partial melting and solidification during cooling of granite at a pressure of 0.15 GPa which simulates the conditions in a deep borehole disposal of canisters of vitrified high level waste (HLW). Methodology for analysis of the collected data and characterisation of the potential AE sources is performed at different steps including simple signals count and more complex signal parameter-based approach and advanced signal processing. The AE method has been shown as a potential tool for monitoring and inspection of structures immobilising nuclear wastes in relation to the time progress of different interactions of the waste with the encapsulating matrix or the wasteform with the hosting environment for permanent disposal. (author)

  19. Characterization of martensitic transformations using acoustic emission

    International Nuclear Information System (INIS)

    Acoustic emission (AE) is a highly sensitive technique which can reveal changes in materials not detectable by other means. The goal of this project was to obtain basic information on the AE response to martensitic transformation in steel. This information will enable the use of AE for improved quality assurance testing of rough-cut component blanks and semifinished parts. The AE response was measured as a function of temperature in four steels undergoing martensitic transformation, and the AE response was compared with martensitic start temperature M/sub s/ and finish temperature M/sub f/ obtained by other methods. As measured by AE activity, M/sub s/ occurred as much as 260C higher than previously reported using less sensitive measurement techniques. It was also found that 10 to 30% of an alloy of Fe-0.2% C-27% Ni transformed to martensite during one AE burst. These results show that AE can be used to study transformations both inside and outside the classical M/sub s/-M/sub f/ ranges. The findings will help to achieve the goal of using AE for quality assurance testing, and will add to the knowledge of the basic materials science of martensitic transformations

  20. Acoustic Emission Analysis of Prestressed Concrete Structures

    Energy Technology Data Exchange (ETDEWEB)

    Elfergani, H A; Pullin, R; Holford, K M, E-mail: ElferganiH@Cardiff.ac.uk, E-mail: PullinR@cardiff.ac.uk, E-mail: holford@Cardiff.ac.uk [Cardiff School of Engineering, Cardiff University, Queen' s Building, The Parade, Cardiff, CF24 3AA, Wales (United Kingdom)

    2011-07-19

    Corrosion is a substantial problem in numerous structures and in particular corrosion is very serious in reinforced and prestressed concrete and must, in certain applications, be given special consideration because failure may result in loss of life and high financial cost. Furthermore corrosion cannot only be considered a long term problem with many studies reporting failure of bridges and concrete pipes due to corrosion within a short period after they were constructed. The concrete pipes which transport water are examples of structures that have suffered from corrosion; for example, the pipes of The Great Man-Made River Project of Libya. Five pipe failures due to corrosion have occurred since their installation. The main reason for the damage is corrosion of prestressed wires in the pipes due to the attack of chloride ions from the surrounding soil. Detection of the corrosion in initial stages has been very important to avoid other failures and the interruption of water flow. Even though most non-destructive methods which are used in the project are able to detect wire breaks, they cannot detect the presence of corrosion. Hence in areas where no excavation has been completed, areas of serious damage can go undetected. Therefore, the major problem which faces engineers is to find the best way to detect the corrosion and prevent the pipes from deteriorating. This paper reports on the use of the Acoustic Emission (AE) technique to detect the early stages of corrosion prior to deterioration of concrete structures.

  1. Acoustic Emission Analysis of Prestressed Concrete Structures

    Science.gov (United States)

    Elfergani, H. A.; Pullin, R.; Holford, K. M.

    2011-07-01

    Corrosion is a substantial problem in numerous structures and in particular corrosion is very serious in reinforced and prestressed concrete and must, in certain applications, be given special consideration because failure may result in loss of life and high financial cost. Furthermore corrosion cannot only be considered a long term problem with many studies reporting failure of bridges and concrete pipes due to corrosion within a short period after they were constructed. The concrete pipes which transport water are examples of structures that have suffered from corrosion; for example, the pipes of The Great Man-Made River Project of Libya. Five pipe failures due to corrosion have occurred since their installation. The main reason for the damage is corrosion of prestressed wires in the pipes due to the attack of chloride ions from the surrounding soil. Detection of the corrosion in initial stages has been very important to avoid other failures and the interruption of water flow. Even though most non-destructive methods which are used in the project are able to detect wire breaks, they cannot detect the presence of corrosion. Hence in areas where no excavation has been completed, areas of serious damage can go undetected. Therefore, the major problem which faces engineers is to find the best way to detect the corrosion and prevent the pipes from deteriorating. This paper reports on the use of the Acoustic Emission (AE) technique to detect the early stages of corrosion prior to deterioration of concrete structures.

  2. EXPERIMENTAL STUDY OF ACOUSTIC EMISSION CHARACTERISTICS DURING SHEARING PROCESS OF SANDSTONE UNDER DIFFERENT WATER CONTENTS%不同含水状态下砂岩剪切过程中声发射特性试验研究

    Institute of Scientific and Technical Information of China (English)

    许江; 吴慧; 陆丽丰; 杨红伟; 谭皓月

    2012-01-01

    Based on the independent development of meso-shear test equipment for coal rock and PCI - 2 acoustic emission detection analysis system, acoustic emission features of sandstone with different saturation degrees of 0%, 50% and 100% during shearing process are studied; and the relationship between evolution law of acoustic emission signal and cracking and extension of sandstone is discussed. The results show that acoustic emission activity is associated with the whole shearing process of sandstone. The acoustic emission activity is not obvious and acoustic emission signal is comparatively small before the shear stress peak value, but after it the acoustic emission signal leaps. With the increase of water content, the shear strength reduces, and the leap point of acoustic emission signal appears in advance successively. Under different moisture states, the peak value of acoustic emission events rate always appears lag the time that the shear stress reaches its peak. With the saturation degree of 0%, the surface crack of sandstone appears after the shear stress peak and the acoustic emission activity is the most intense; the cumulative acoustic emission events at failure is the most, that is, the cumulative damage is the biggest. But with the saturation degrees of 50% and 100% the surface crack of sandstone appears before the shear stress peak, the cumulative acoustic emission events at failure is comparatively less, and the cumulative damage is smaller.%利用自主研发的煤岩细观剪切试验装置和PCI -2型声发射测试分析系统对饱和度分别为0%,50%和100%三种不同含水状态下砂岩剪切破坏过程中的声发射特性进行试验研究,探讨声发射信号随时间的演化规律及其与砂岩裂纹的开裂、扩展之间的关系.研究结果表明:声发射活动伴随着砂岩整个剪切破坏过程,表现为剪应力峰值前,声发射活动不显著,声发射信号均较小,而在剪应力峰值后声发射信号出现剧

  3. Identification of acoustic emission signal in aluminum alloys spot welding based on fractal theory

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The acoustic emission signal of aluminum alloys spot welding includes the information of forming nugget and is one of the important parameters in the quality control. Due to the nonlinearity of the signals, classic Euclidean geometry can not be applied to depict exactly. The fractal theory is implemented to quantitatively describe the characteristics of the acoustic emission signals. The experiment and calculation results show that the box counting dimension of acoustic emission signal, between 1 and 2, are distinctive from different nugget areas in AC spot welding. It is proved that box counting dimension is an effective characteristic parameter to evaluate spot welding quality. In addition, fractal theory can also be applied in other spot welding parameters, such as voltage, current, electrode force and so on, for the purpose of recognizing the spot welding quality.

  4. Acoustic characteristics of listener-constrained speech

    Science.gov (United States)

    Ashby, Simone; Cummins, Fred

    2003-04-01

    Relatively little is known about the acoustical modifications speakers employ to meet the various constraints-auditory, linguistic and otherwise-of their listeners. Similarly, the manner by which perceived listener constraints interact with speakers' adoption of specialized speech registers is poorly Hypo (H&H) theory offers a framework for examining the relationship between speech production and output-oriented goals for communication, suggesting that under certain circumstances speakers may attempt to minimize phonetic ambiguity by employing a ``hyperarticulated'' speaking style (Lindblom, 1990). It remains unclear, however, what the acoustic correlates of hyperarticulated speech are, and how, if at all, we might expect phonetic properties to change respective to different listener-constrained conditions. This paper is part of a preliminary investigation concerned with comparing the prosodic characteristics of speech produced across a range of listener constraints. Analyses are drawn from a corpus of read hyperarticulated speech data comprising eight adult, female speakers of English. Specialized registers include speech to foreigners, infant-directed speech, speech produced under noisy conditions, and human-machine interaction. The authors gratefully acknowledge financial support of the Irish Higher Education Authority, allocated to Fred Cummins for collaborative work with Media Lab Europe.

  5. Management of the Acoustic Characteristics of Jet Streams

    Directory of Open Access Journals (Sweden)

    Bulat Pavel Viktorovich

    2014-07-01

    Full Text Available The objects of research are devices, which generate and suppress the acoustic and wave pressure oscillations. Purpose of the study is the classification of oscillations generating devices, description of the physical principles of acoustic waves generation. The schemes of the most common sound generators-whistles are discussed. The gas-jet sound generators are described separately. It is shown that a simple cylindrical head at the supersonic nozzle can both enhance the acoustic emission and serve as an effective silencer. The comparison of acoustic emission of a supersonic jet and a jet, flowing into a cylindrical head is given. The results presented in the study can be recommended by the developers of whistles, sirens, other acoustic generators, installations for thermo-acoustic hardening metals, metallurgical blast devices.

  6. Application of acoustic emission to flaw detection in engineering materials

    Science.gov (United States)

    Moslehy, F. A.

    1990-01-01

    Monitoring of structures under operating loads to provide an early warning of possible failure to locate flaws in test specimens subjected to uniaxial tensile loading is presented. Test specimens used are mild steel prismatic bars with small holes at different locations. When the test specimen is loaded, acoustic emission data are automatically collected by two acoustic transducers located at opposite sides of the hole and processed by an acoustic emission analyzer. The processed information yields the difference in arrival times at the transducers, which uniquely determines the flaw location. By using this technique, flaws were located to within 8 percent of their true location. The use of acoustic emission in linear location to locate a flaw in a material is demonstrated. It is concluded that this one-dimensional application could be extended to the general flaw location problem through triangulation.

  7. Acoustic emission assessment of interface cracking in thermal barrier coatings

    Science.gov (United States)

    Yang, Li; Zhong, Zhi-Chun; Zhou, Yi-Chun; Zhu, Wang; Zhang, Zhi-Biao; Cai, Can-Ying; Lu, Chun-Sheng

    2016-04-01

    In this paper, acoustic emission (AE) and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression. The interface failure process can be identified via its AE features, including buckling, delamination incubation and spallation. According to the Fourier transformation of AE signals, there are four different failure modes: surface vertical cracks, opening and sliding interface cracks, and substrate deformation. The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz, whilst that of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. The energy released of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. Based on the energy released from cracking and the AE signals, a relationship is established between the interface crack length and AE parameters, which is in good agreement with experimental results.

  8. In situ high temperature oxidation analysis of Zircaloy-4 using acoustic emission coupled with thermogravimetry

    Science.gov (United States)

    Omar, Al Haj; Véronique, Peres; Eric, Serris; François, Grosjean; Jean, Kittel; François, Ropital; Michel, Cournil

    2015-06-01

    Zircaloy-4 oxidation behavior at high temperature (900 °C), which can be reached in case of severe accidental situations in nuclear pressurised water reactor, was studied using acoustic emission analysis coupled with thermogravimetry. Two different atmospheres were used to study the oxidation of Zircaloy-4: (a) helium and pure oxygen, (b) helium and oxygen combined with slight addition of air. The experiments with 20% of oxygen confirm the dependence on oxygen anions diffusion in the oxide scale. Under a mixture of oxygen and air in helium, an acceleration of the corrosion was observed due to the detrimental effect of nitrogen. The kinetic rate increased significantly after a kinetic transition (breakaway). This acceleration was accompanied by an acoustic emission activity. Most of the acoustic emission bursts were recorded after the kinetic transition (post-transition) or during the cooling of the sample. The characteristic features of the acoustic emission signals appear to be correlated with the different populations of cracks and their occurrence in the ZrO2 layer or in the α-Zr(O) layer. Acoustic events were recorded during the isothermal dwell time at high temperature under air. They were associated with large cracks in the zirconia porous layer. Acoustic events were also recorded during cooling after oxidation tests both under air or oxygen. For the latter, cracks were observed in the oxygen enriched zirconium metal phase and not in the dense zirconia layer after 5 h of oxidation.

  9. Measurement of acoustical characteristics of mosques in Saudi Arabia

    Science.gov (United States)

    Abdou, Adel A.

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  10. Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects

    Science.gov (United States)

    Solodov, Igor; Döring, Daniel; Busse, Gerd

    2008-06-01

    Strongly nonlinear vibrations of near-surface fractured defects driven by an elastic wave radiate acoustic energy into adjacent air in a wide frequency range. The variations of pressure in the emitted airborne waves change the refractive index of air thus providing an acoustooptic interaction with a collimated laser beam. Such an air-coupled vibrometry (ACV) is proposed for detecting and imaging of acoustic radiation of nonlinear spectral components by cracked defects. The photoelastic relation in air is used to derive induced phase modulation of laser light in the heterodyne interferometer setup. The sensitivity of the scanning ACV to different spatial components of the acoustic radiation is analyzed. The animated airborne emission patterns are visualized for the higher harmonic and frequency mixing fields radiated by planar defects. The results confirm a high localization of the nonlinear acoustic emission around the defects and complicated directivity patterns appreciably different from those observed for fundamental frequencies.

  11. Acoustic Emission from Arctic Steels and Fractographic Investigations

    OpenAIRE

    Hartwig, Cathrine Gjerstad

    2015-01-01

    There is a need for better understanding of brittle fracture due to an increased interest in exploring the undiscovered hydrocarbon resources in the arctic region. There is also a need for development of steels with better low temperature fracture toughness, as steels are experiencing a drastic decrease in toughness in the HAZ after welding. This thesis uses acoustic emission in the investigation of the brittle initiation and propagation micromechanisms for a low carbon HSLA steel. Acoust...

  12. Acoustic emission strand burning technique for motor burning rate prediction

    Science.gov (United States)

    Christensen, W. N.

    1978-01-01

    An acoustic emission (AE) method is being used to measure the burning rate of solid propellant strands. This method has a precision of 0.5% and excellent burning rate correlation with both subscale and large rocket motors. The AE procedure burns the sample under water and measures the burning rate from the acoustic output. The acoustic signal provides a continuous readout during testing, which allows complete data analysis rather than the start-stop clockwires used by the conventional method. The AE method helps eliminate such problems as inhibiting the sample, pressure increase and temperature rise, during testing.

  13. Potential of acoustic emissions from three point bending tests as rock failure precursors

    Institute of Scientific and Technical Information of China (English)

    Agioutantis Z.; Kaklis K.; Mavrigiannakis S.; Verigakis M.; Vallianatos F.; Saltas V.

    2016-01-01

    Development of failure in brittle materials is associated with microcracks, which release energy in the form of elastic waves called acoustic emissions. This paper presents results from acoustic emission mea-surements obtained during three point bending tests on Nestos marble under laboratory conditions. Acoustic emission activity was monitored using piezoelectric acoustic emission sensors, and the potential for accurate prediction of rock damage based on acoustic emission data was investigated. Damage local-ization was determined based on acoustic emissions generated from the critically stressed region as scat-tered events at stresses below and close to the strength of the material.

  14. Phonon Emission from Acoustic Black Hole

    Science.gov (United States)

    Fang, Hengzhong; Zhou, Kaihu; Song, Yuming

    2012-08-01

    We study the phonon tunneling through the horizon of an acoustic black hole by solving the Hamilton-Jacobi equation. We also make use of the closed-path integral to calculate the tunneling probability, and an improved way to determine the temporal contribution is used. Both the results from the two methods agree with Hawking's initial analysis.

  15. Wavelet analysis of acoustic emission signals from thermal barrier coatings

    Institute of Scientific and Technical Information of China (English)

    YANG Li; ZHOU Yi-chun

    2006-01-01

    The wavelet transform is applied to the analysis of acoustic emission signals collected during tensile test of the ZrO2-8% Y2O3 (YSZ) thermal barrier coatings (TBCs). The acoustic emission signals are de-noised using the Daubechies discrete wavelets,and then decomposed into different wavelet levels using the programs developed by the authors. Each level is examined for its specific frequency range. The ratio of energy in different levels to the total energy gives information on the failure modes (coating micro-failures and substrate micro-failures) associated with TBCs system.

  16. In situ high temperature oxidation analysis of Zircaloy-4 using acoustic emission coupled with thermogravimetry

    Energy Technology Data Exchange (ETDEWEB)

    Omar, Al Haj [Ecole Nationale Supérieure des Mines, SPIN-EMSE, CNRS:UMR 5307, LGF, 42023 Saint-Etienne (France); Véronique, Peres, E-mail: peres@emse.fr [Ecole Nationale Supérieure des Mines, SPIN-EMSE, CNRS:UMR 5307, LGF, 42023 Saint-Etienne (France); Eric, Serris [Ecole Nationale Supérieure des Mines, SPIN-EMSE, CNRS:UMR 5307, LGF, 42023 Saint-Etienne (France); François, Grosjean; Jean, Kittel; François, Ropital [IFP Energies nouvelles, Rond-point de l’échangeur de Solaize BP3, 69360 Solaize (France); Michel, Cournil [Ecole Nationale Supérieure des Mines, SPIN-EMSE, CNRS:UMR 5307, LGF, 42023 Saint-Etienne (France)

    2015-06-15

    Highlights: • Thermogravimetry associated to acoustic emission (AE) improves knowledge on the corrosion of metals at high temperature. • Kinetic transition is detected under air oxidation tests at 900 °C of Zircaloy-4 by a change in the rate of mass gain and by the AE activity. • AE analysis is complementary to characterizations of post mortem oxidized samples. • AE allows us to distinguish the cracks which occur during the Zircaloy-4 oxidation from the cracks which arise during the cooling of the samples. - Abstract: Zircaloy-4 oxidation behavior at high temperature (900 °C), which can be reached in case of severe accidental situations in nuclear pressurised water reactor, was studied using acoustic emission analysis coupled with thermogravimetry. Two different atmospheres were used to study the oxidation of Zircaloy-4: (a) helium and pure oxygen, (b) helium and oxygen combined with slight addition of air. The experiments with 20% of oxygen confirm the dependence on oxygen anions diffusion in the oxide scale. Under a mixture of oxygen and air in helium, an acceleration of the corrosion was observed due to the detrimental effect of nitrogen. The kinetic rate increased significantly after a kinetic transition (breakaway). This acceleration was accompanied by an acoustic emission activity. Most of the acoustic emission bursts were recorded after the kinetic transition (post-transition) or during the cooling of the sample. The characteristic features of the acoustic emission signals appear to be correlated with the different populations of cracks and their occurrence in the ZrO{sub 2} layer or in the α-Zr(O) layer. Acoustic events were recorded during the isothermal dwell time at high temperature under air. They were associated with large cracks in the zirconia porous layer. Acoustic events were also recorded during cooling after oxidation tests both under air or oxygen. For the latter, cracks were observed in the oxygen enriched zirconium metal phase and

  17. The Friction Acoustic Emission Signal Characteristics During the Plastic Forming Process of Metal%金属塑性成型过程中摩擦声发射信号特征

    Institute of Scientific and Technical Information of China (English)

    贾园; 张守茁; 席镇; 高宏; 魏盛春

    2009-01-01

    In the plastic forming process of metal, at the great pressure, the friction was produced between the deformation metal and the mold, which could made energy waste, and also so the non-uniform deformation of the metal blank. Using acoustic emission testing technique, the plastic deformation acoustic emission signals of friction were detected during the simulated metal slider and skateboards on three uniform speed and three contact pressure.Testing results showed that under certain conditions, as the pressure was increased, the counts and amplitude of acoustic emission signals would reduce.%在金属塑性成型的过程中,在较大的正压力作用下,变形金属与模具之间存在着摩擦力,导致除了浪费能源以外,还会使金属坯料的变形不均匀.采用声发射技术,检测了模拟金属滑块和滑板在三种匀速运动及三种正压力的情况下,产生的塑性变形摩擦声发射信号的变化.试验结果表明,在特定条件下,随着正压力的增加,声发射信号的计数和幅度减少.

  18. Acoustic Emissions to Measure Drought-Induced Cavitation in Plants

    Directory of Open Access Journals (Sweden)

    Linus De Roo

    2016-03-01

    Full Text Available Acoustic emissions are frequently used in material sciences and engineering applications for structural health monitoring. It is known that plants also emit acoustic emissions, and their application in plant sciences is rapidly increasing, especially to investigate drought-induced plant stress. Vulnerability to drought-induced cavitation is a key trait of plant water relations, and contains valuable information about how plants may cope with drought stress. There is, however, no consensus in literature about how this is best measured. Here, we discuss detection of acoustic emissions as a measure for drought-induced cavitation. Past research and the current state of the art are reviewed. We also discuss how the acoustic emission technique can help solve some of the main issues regarding quantification of the degree of cavitation, and how it can contribute to our knowledge about plant behavior during drought stress. So far, crossbreeding in the field of material sciences proved very successful, and we therefore recommend continuing in this direction in future research.

  19. Fatigue Damage Acoustic Emission Characteristic Parameters and Mechanism for Coating%涂层疲劳损伤声发射特征参数及损伤机理

    Institute of Scientific and Technical Information of China (English)

    李国禄; 张志强; 王海斗; 徐滨士; 朴钟宇

    2013-01-01

    使用超音速等离子喷涂设备在1045钢基体上制备了铁基合金涂层.以球盘式接触疲劳试验机为平台,研究了涂层接触疲劳损伤过程中声发射特征参数的变化规律,并分析了涂层的接触疲劳损伤机理.结果表明,在转速为2500r/min和应力水平为1.58GPa实验条件下,点蚀是涂层的主要失效形式,表现为在涂层磨痕轨迹范围内出现大量的点蚀坑,点蚀坑深度为20~30μm.涂层表面粗糙的微凸体与轴承球滚压接触产生黏着磨损,以及涂层、磨粒、滚动轴承三者形成三体磨料磨损是点蚀失效产生的主要原因.声发射幅值、有效值(Root Mean Square,RMS)、能量、计数和平均频率对涂层表面粗糙微凸体去除、弹塑性变形、裂纹萌生、裂纹稳定扩展和失稳扩展过程比较敏感,并且在不同的疲劳损伤阶段具有不同的信号反馈特点.%Fe-based alloy coating was deposited on 1045 steel by a supersonic plasma spraying device.The variation regularities of acoustic emission characteristic parameters in the process of contact fatigue damage were researched using a ball-disk contact fatigue tester,and the contact fatigue damage mechanism of as-sprayed coating was analyzed.The results show that pitting is main failure mode of the coating under the experimental conditions of the 1.58GPa contact press and 2500r/min.Many pitting pits were observed on the wear track,and depth of the pitting pits was in the range from 20μm to 30μm.The pitting failure was closely associated with adhesive wear caused by rolling contact between rough salient on coating surface and bearing balls,and three-body abrasive wear among the coating,abrasives and rolling bearings within the contact region.Acoustic emission characteristic parameters,such as amplitude,root mean square (RMS),energy,count and average frequency are sensitive for rough salient removal on coating surface,elastic and plastic deformation,crack initiation,crack stable

  20. 声发射技术对材料疲劳过程的损伤特征的研究%Study of Damage Characteristics during Fatigue by Acoustic Emission Techniques

    Institute of Scientific and Technical Information of China (English)

    王慧晶; 林哲

    2011-01-01

    文章考虑损伤效应,研究材料疲劳过程损伤特征及相对应的声发射活动性.导出的疲劳损伤演化方程具有与声发射活动相似的Paris公式形式,发展了研究裂纹声发射活动的损伤力学方法.又通过分析损伤对塑性区尺寸的影响,提出塑性区损伤修正模型.采用该修正模型的预测结果与实验结果基本吻合.并以声发射参数为损伤变量提出声发射活动中的损伤发展规律.经试验数据分析,文中提出的塑性区修正模型可以较好地反映声发射活动规律,损伤发展规律符合试验观察结果.%Damage characteristics during fatigue and acoustic emission (AE) activities accounts for damage effect on material are studied.Damage evolution equation similar to the well-known Paris'formula is derived,as well as AE activities.A damage mechanics approach is applied to investigate AE activities.According to the damage effect on the size of plastic zone,a modified model for the plastic zone with damage is presented,which shows that the results of this proposed model are in a good agreement with experiments.Considered AE parameter as damage variable,the rule of damage evolution during AE activities is developed.Predictions by the proposed model are more consistent with the test data.And the damage evolution law is coincident with the experimental results.

  1. Fracture of fiber-reinforced composites analyzed via acoustic emission.

    Science.gov (United States)

    Ereifej, Nadia S; Oweis, Yara G; Altarawneh, Sandra K

    2015-01-01

    This study investigated the fracture resistance of composite resins using a three-point bending test and acoustic emission (AE) analysis. Three groups of specimens (n=15) were prepared: non-reinforced BelleGlass HP composite (NRC), unidirectional (UFRC) and multidirectional (MFRC) fiber-reinforced groups which respectively incorporated unidirectional Stick and multidirectional StickNet fibers. Specimens were loaded to failure in a universal testing machine while an AE system was used to detect audible signals. Initial fracture strengths and AE amplitudes were significantly lower than those at final fracture in all groups (pcomposite resin materials and the monitoring of acoustic signals revealed significant information regarding the fracture process.

  2. In process acoustic emission in multirun submerged arc welding

    International Nuclear Information System (INIS)

    In order to avoid the formation of deep grooves when repairing defects in welded joints in heavy plates, an investigation was made aiming to detect and locate the defects by in-process acoustic emission in multirun submerged arc welding. Twelve defects (lack of penetration, cracks, inclusions, lack of fusion together with inclusions, blowholes) were intentionally introduced when the first plate was welded. A space-time method for processing the acoustic activity during welding allowed the detection and the location of the intentional defects as well as of the most important accidental defects evidenced by ultrasonic testing

  3. Fracture of fiber-reinforced composites analyzed via acoustic emission.

    Science.gov (United States)

    Ereifej, Nadia S; Oweis, Yara G; Altarawneh, Sandra K

    2015-01-01

    This study investigated the fracture resistance of composite resins using a three-point bending test and acoustic emission (AE) analysis. Three groups of specimens (n=15) were prepared: non-reinforced BelleGlass HP composite (NRC), unidirectional (UFRC) and multidirectional (MFRC) fiber-reinforced groups which respectively incorporated unidirectional Stick and multidirectional StickNet fibers. Specimens were loaded to failure in a universal testing machine while an AE system was used to detect audible signals. Initial fracture strengths and AE amplitudes were significantly lower than those at final fracture in all groups (pcomposite resin materials and the monitoring of acoustic signals revealed significant information regarding the fracture process. PMID:25904176

  4. Acoustic emission from gas-filled coal under triaxial compression

    Institute of Scientific and Technical Information of China (English)

    Yin; Guangzhi; Qin; Hu; Huang; Gun; Lv; Youchang; Dai; Zhixu

    2012-01-01

    Acoustic emission(AE) experiments have been performed on gas-saturated coal specimens under conventional triaxial compression.The AE characteristics were investigated for a methane gas flow through the coal specimen.One AE parameter,AE count,when normalized by the total count number was used to represent the damage evolution in the gassy coal.It is shown that this AE parameter is a reasonable indicator for damage occurring within the coal specimen since its envelope has almost the same shape as the complete stress-strain curve,except for a short time delay.In addition,the change in AE count is highly consistent with the change in coal permeability.Test results also show that methane containing coal emits a small number of AE events before entering the yield stage.AE activity gradually increases during the yield process up to the peak stress.The lowest permeability corresponds to the highest AE activity,implying failure will soon occur.An AE based constitutive model was constructed and the theoretical results agree well with those of experiments.

  5. Continuous acoustic emission monitoring of reinforced concrete under accelerated corrosion

    Science.gov (United States)

    Di Benedetti, M.; Loreto, G.; Nanni, A.; Matta, F.; Gonzalez-Nunez, M. A.

    2011-04-01

    The development of techniques capable of evaluating deterioration of reinforced concrete (RC) structures is instrumental to the advancement of techniques for the structural health monitoring (SHM) and service life estimate for constructed facilities. One of the main causes leading to degradation of RC is the corrosion of the steel reinforcement. This process can be modeled phenomenologically, while laboratory tests aimed at studying durability responses are typically accelerated in order to provide useful results within a realistic period of time. To assess the condition of damage in RC, a number of nondestructive methods have been recently studied. Acoustic emission (AE) is emerging as a nondestructive tool to detect the onset and progression of deterioration mechanisms. In this paper, the development of accelerated corrosion and continuous AE monitoring test set-up for RC specimens are presented. Relevant information are provided with regard to the characteristics of the corrosion circuit, continuous measurement and acquisition of corrosion potential, selection of AE sensors and AE parameter setting. The effectiveness of the setup in detecting and characterizing the initiation and progression of the corrosion phenomenon is discussed on the basis of preliminary results from small-scale, pre-cracked RC specimens, which are representative of areas near the clear cover in typical RC bridge members.

  6. Acoustic emission analysis of tooth-composite interfacial debonding.

    Science.gov (United States)

    Cho, N Y; Ferracane, J L; Lee, I B

    2013-01-01

    This study detected tooth-composite interfacial debonding during composite restoration by means of acoustic emission (AE) analysis and investigated the effects of composite properties and adhesives on AE characteristics. The polymerization shrinkage, peak shrinkage rate, flexural modulus, and shrinkage stress of a methacrylate-based universal hybrid, a flowable, and a silorane-based composite were measured. Class I cavities on 49 extracted premolars were restored with 1 of the 3 composites and 1 of the following adhesives: 2 etch-and-rinse adhesives, 2 self-etch adhesives, and an adhesive for the silorane-based composite. AE analysis was done for 2,000 sec during light-curing. The silorane-based composite exhibited the lowest shrinkage (rate), the longest time to peak shrinkage rate, the lowest shrinkage stress, and the fewest AE events. AE events were detected immediately after the beginning of light-curing in most composite-adhesive combinations, but not until 40 sec after light-curing began for the silorane-based composite. AE events were concentrated at the initial stage of curing in self-etch adhesives compared with etch-and-rinse adhesives. Reducing the shrinkage (rate) of composites resulted in reduced shrinkage stress and less debonding, as evidenced by fewer AE events. AE is an effective technique for monitoring, in real time, the debonding kinetics at the tooth-composite interface.

  7. Investigation of the Portevin-Le Chatelier effect by the acoustic emission

    Directory of Open Access Journals (Sweden)

    B. Grzegorczyk

    2013-09-01

    Full Text Available Purpose: The aim of this paper is to determine the relation existing between the behaviour of the signals of acoustic emissions generated in the course of plastic deformation at elevated temperature, and the shape of the work-hardening curves σ-ε and the Portevin - Le Chatelier effect. Design/methodology/approach: Single crystal was investigated applying the method of free compression at a constant strain rate and a temperature within the range from 20°C to 400°C at a strain rate of 10-5 sec-1 to 10-1 sec-1, simultaneously recording this phenomenon by means of acoustic emission. Findings: The analysis of the results of these investigations permitted to prove considerable relations between the work-hardening curve σ-ε displaying the PLC effect and the characteristics of the signals of the acoustic emission generated in the uniaxial compression. Practical implications: The AE method applied in the process of plastic deformation of single crystals of the alloy CuZn30 displays also a dependence of the activity of acoustic emissions on the stage of strain-hardening of the investigated alloy. Originality/value: In the range of the occurrence of the PLC effect during the compression test of the investigated single crystals the signal AE displays a cyclic character, distinctly correlated qualitatively with the oscillations of stresses on the curve σ-ε.

  8. Analysis of acoustic emission data for bearings subject to unbalance

    Directory of Open Access Journals (Sweden)

    Rapinder Sawhney

    2013-01-01

    Full Text Available Acoustic Emission (AE is an effective nondestructive method for investigating the behavior of materials under stress. In recent decades, AE applications in structural health monitoring have been extended to other areas such as rotating machineries and cutting tools. This research investigates the application of acoustic emission data for unbalance analysis and detection in rotary systems. The AE parameter of interest in this study is a discrete variable that covers the significance of count, duration and amplitude of AE signals. A statistical model based on Zero-Inflated Poisson (ZIP regression is proposed to handle over-dispersion and excess zeros of the counting data. The ZIP model indicates that faulty bearings can generate more transient wave in the AE waveform. Control charts can easily detect the faulty bearing using the parameters of the ZIP model. Categorical data analysis based on generalized linear models (GLM is also presented. The results demonstrate the significance of the couple unbalance.

  9. Employing Acoustic Emission for Monitoring Oil Film Regimes

    Directory of Open Access Journals (Sweden)

    David Mba

    2013-07-01

    Full Text Available The major purpose of a gear lubricant is to provide adequate oil film thickness to reduce and prevent gear tooth surface failures. Real time monitoring for gear failures is important in order to predict and prevent unexpected failures which would have a negative impact on the efficiency, performance and safety of the gearbox. This paper presents experimental results on the influence of specific oil film thickness on Acoustic Emission (AE activity for operational helical gears. Variation in film thickness during operations was achieved by spraying liquid nitrogen onto the rotating gear wheel. The experimental results demonstrated a clear relationship between the root mean square (r.m.s value of the AE signal and the specific film thickness. The findings demonstrate the potential of Acoustic Emission technology to quantify lubrication regimes on operational gears.

  10. Fault growth and acoustic emissions in confined granite

    Science.gov (United States)

    Lockner, David A.; Byerlee, James D.

    1992-01-01

    The failure process in a brittle granite was studied by using acoustic emission techniques to obtain three dimensional locations of the microfracturing events. During a creep experiment the nucleation of faulting coincided with the onset of tertiary creep, but the development of the fault could not be followed because the failure occurred catastrophically. A technique has been developed that enables the failure process to be stabilized by controlling the axial stress to maintain a constant acoustic emission rate. As a result the post-failure stress-strain curve has been followed quasi-statically, extending to hours the fault growth process that normally would occur violently in a fraction of a second. The results from the rate-controlled experiments show that the fault plane nucleated at a point on the sample surface after the stress-strain curve reached its peak. Before nucleation, the microcrack growth was distributed throughout the sample. The fault plane then grew outward from the nucleation site and was accompanied by a gradual drop in stress. Acoustic emission locations showed that the fault propagated as a fracture front (process zone) with dimensions of 1 to 3 cm. As the fracture front passed by a given fixed point on the fault plane, the subsequent acoustic emission would drop. When growth was allowed to progress until the fault bisected the sample, the stress dropped to the frictional strength. These observations are in accord with the behavior predicted by Rudnicki and Rice's bifurcation analysis but conflict with experiments used to infer that shear localization would occur in brittle rock while the material is still hardening.

  11. Smart acoustic emission system for wireless monitoring of concrete structures

    Science.gov (United States)

    Yoon, Dong-Jin; Kim, Young-Gil; Kim, Chi-Yeop; Seo, Dae-Cheol

    2008-03-01

    Acoustic emission (AE) has emerged as a powerful nondestructive tool to detect preexisting defects or to characterize failure mechanisms. Recently, this technique or this kind of principle, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures. Concrete is one of the most widely used materials for constructing civil structures. In the nondestructive evaluation point of view, a lot of AE signals are generated in concrete structures under loading whether the crack development is active or not. Also, it was required to find a symptom of damage propagation before catastrophic failure through a continuous monitoring. Therefore we have done a practical study in this work to fabricate compact wireless AE sensor and to develop diagnosis system. First, this study aims to identify the differences of AE event patterns caused by both real damage sources and the other normal sources. Secondly, it was focused to develop acoustic emission diagnosis system for assessing the deterioration of concrete structures such as a bridge, dame, building slab, tunnel etc. Thirdly, the wireless acoustic emission system was developed for the application of monitoring concrete structures. From the previous laboratory study such as AE event patterns analysis under various loading conditions, we confirmed that AE analysis provided a promising approach for estimating the condition of damage and distress in concrete structures. In this work, the algorithm for determining the damage status of concrete structures was developed and typical criteria for decision making was also suggested. For the future application of wireless monitoring, a low energy consumable, compact, and robust wireless acoustic emission sensor module was developed and applied to the concrete beam for performance test. Finally, based on the self-developed diagnosis algorithm and compact wireless AE sensor, new AE system for practical

  12. Testing of welded clad pipelines using acoustic emission method

    International Nuclear Information System (INIS)

    Recording of signals of acoustic emission (AE) on structure loading enables not only to determine the location of defects, but also to evaluate conditions, which occur in materials in defect neighbourhood, that is to approach to evaluation of a dauger degree of one or another defect. Results of AE recording and analysis on loading of pipelines sections with welded joints on 22 K steel were considered. The behaviour of preliminarily grown fatigue cracks and natural defects of welding origin was compared

  13. Acoustic emission and shape memory effect in the martensitic transformation.

    Science.gov (United States)

    Sreekala, S; Ananthakrishna, G

    2003-04-01

    Acoustic emission signals are known to exhibit a high degree of reproducibility in time and show correlations with the growth and shrinkage of martensite domains when athermal martensites are subjected to repeated thermal cycling in a restricted temperature range. We show that a recently introduced two dimensional model for the martensitic transformation mimics these features. We also show that these features are related to the shape memory effect where near full reversal of morphological features are seen under these thermal cycling conditions.

  14. Failure Mechanism of Rock Bridge Based on Acoustic Emission Technique

    OpenAIRE

    Guoqing Chen; Yan Zhang; Runqiu Huang; Fan Guo; Guofeng Zhang

    2015-01-01

    Acoustic emission (AE) technique is widely used in various fields as a reliable nondestructive examination technology. Two experimental tests were carried out in a rock mechanics laboratory, which include (1) small scale direct shear tests of rock bridge with different lengths and (2) large scale landslide model with locked section. The relationship of AE event count and record time was analyzed during the tests. The AE source location technology and comparative analysis with its actual failu...

  15. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    Science.gov (United States)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

  16. Damage Detection and Analysis in CFRPs Using Acoustic Emission Technique

    Science.gov (United States)

    Whitlow, Travis Laron

    Real time monitoring of damage is an important aspect of life management of critical structures. Acoustic emission (AE) techniques allow for measurement and assessment of damage in real time. Acoustic emission parameters such as signal amplitude and duration were monitored during the loading sequences. Criteria that can indicate the onset of critical damage to the structure were developed. Tracking the damage as it happens gives a better analysis of the failure evolution that will allow for a more accurate determination of structural life. The main challenge is distinguishing between legitimate damage signals and "false positives" which are unrelated to damage growth. Such false positives can be related to electrical noise, friction, or mechanical vibrations. This research focuses on monitoring signals of damage growth in carbon fiber reinforced polymers (CFRPs) and separating the relevant signals from the false ones. In this Dissertation, acoustic emission signals from CFRP specimens were experimentally recorded and analyzed. The objectives of this work are: (1) perform static and fatigue loading of CFRP composite specimens and measure the associated AE signals, (2) accurately determine the AE parameters (energy, frequency, duration, etc.) of signals generated during failure of such specimens, (3) use fiber optic sensors to monitor the strain distribution of the damage zone and relate these changes in strain measurements to AE data.

  17. Pen-chant: Acoustic emissions of handwriting and drawing

    Science.gov (United States)

    Seniuk, Andrew G.

    The sounds generated by a writing instrument ('pen-chant') provide a rich and underutilized source of information for pattern recognition. We examine the feasibility of recognition of handwritten cursive text, exclusively through an analysis of acoustic emissions. We design and implement a family of recognizers using a template matching approach, with templates and similarity measures derived variously from: smoothed amplitude signal with fixed resolution, discrete sequence of magnitudes obtained from peaks in the smoothed amplitude signal, and ordered tree obtained from a scale space signal representation. Test results are presented for recognition of isolated lowercase cursive characters and for whole words. We also present qualitative results for recognizing gestures such as circling, scratch-out, check-marks, and hatching. Our first set of results, using samples provided by the author, yield recognition rates of over 70% (alphabet) and 90% (26 words), with a confidence of +/-8%, based solely on acoustic emissions. Our second set of results uses data gathered from nine writers. These results demonstrate that acoustic emissions are a rich source of information, usable---on their own or in conjunction with image-based features---to solve pattern recognition problems. In future work, this approach can be applied to writer identification, handwriting and gesture-based computer input technology, emotion recognition, and temporal analysis of sketches.

  18. Effect of thermionic emission on dust-acoustic solitons

    International Nuclear Information System (INIS)

    The effect of thermionic emission on dust-acoustic solitons of very small but finite amplitude in dusty plasmas is studied taking into account the self-consistent variation of the dust charge. It is shown that thermionic emission can significantly lower the amplitude of the dust negative charge and can even make the dust charge positive. Results on the dependence of the phase velocity, amplitude and width of solitons on the dust temperature and the work function of dust material were obtained and are discussed here.

  19. Characteristics Analysis of HFM Signal over Underwater Acoustic Channels

    Directory of Open Access Journals (Sweden)

    YUAN Fei

    2013-01-01

    Full Text Available For pulse compression characteristics and not easily affected by noise, linear frequency modulation signal are widely used in underwater acoustic communication. This paper analyzes the characteristics of hyperbolic frequency modulation signal over underwater acoustic channels. Compared with linear frequency modulation signal, hyperbolic frequency modulation has the same performance of strong anti-noise and anti-multipath, what’s more, hyperbolic frequency modulation signal is better resist the influence of doppler. And discussed the influence of doppler on signal, simulation results show that the hyperbolic frequency modulation signal detection rate is better than linear frequency modulation signal in the doppler environment.

  20. Simple discrimination method between False Acoustic Emission and Acoustic Emission revealed by piezoelectric sensors, in Gran Sasso mountain measurements (L)

    Science.gov (United States)

    Diodati, Paolo; Piazza, Stefano

    2004-07-01

    Recently it was shown, studying data acquired with in-situ measurements on the Gran Sasso mountain (Italy), for about ten years, by means of a high sensitivity transducer coupled to the free-end section of a stainless steel rod fixed by cement in a rock-drill hole 10 m high, about 2500 m above sea level, that Acoustic Emission (AE) can be affected by more than 90% False Acoustic Emission (FAE) of an electromagnetic origin. A very simple method to solve the problem of the discrimination between AE events due to elastic waves, from FAE signals, due to electromagnetic noise, both coming from the same ``reception-point,'' is presented. The reliability of the obtained separation is confirmed also by the reported amplitude and time distribution of AE events, typical of fracture dynamics and those of FAE events, similar to those of noise.

  1. Acoustic waveguide characteristics of the Indian Ocean - north of equator

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Murty, T.V.R.; Somayajulu, Y.K.; Murty, C.S.

    The acoustic characteristics of the waters of the Arabian Sea and Bay of Bengal, constituting the northern Indian Ocean, are analysed based on a climatological mean sound speed field. In the upper 30-40 m in the Bay of Bengal a weak surface duct...

  2. Frequency Analysis of Acoustic Emission - Application to machining and welding

    Science.gov (United States)

    Snoussi, A.

    1987-01-01

    Ultrasonic acoustic waves were seized and exploited within a bandwidth ranging from 30 kHz to 55 kHz for non-destructive control when boring three kinds of steel with a digitally programmed drill. In addition, these waves were considered in soldering two steels and one aluminum using T.I.G. process. Spectrum analysis of acoustic emissions produced during the drill is closely related to the extraction of turnings from the metal. Because of the wick's progressive wearing out, the spectrum tends to be close to the machine's own noise spectrum. Meanwhile in the soldering operation of test-tubes of 2 mm thickness, the frequency analysis shows a particular frequency called signature corresponding to the flow of protection gas. Other frequencies associated to some internal defects in the soldering process as a delay in the fissure and a lack in the fusion were detected.

  3. Acoustic Emission Beamforming for Detection and Localization of Damage

    Science.gov (United States)

    Rivey, Joshua Callen

    The aerospace industry is a constantly evolving field with corporate manufacturers continually utilizing innovative processes and materials. These materials include advanced metallics and composite systems. The exploration and implementation of new materials and structures has prompted the development of numerous structural health monitoring and nondestructive evaluation techniques for quality assurance purposes and pre- and in-service damage detection. Exploitation of acoustic emission sensors coupled with a beamforming technique provides the potential for creating an effective non-contact and non-invasive monitoring capability for assessing structural integrity. This investigation used an acoustic emission detection device that employs helical arrays of MEMS-based microphones around a high-definition optical camera to provide real-time non-contact monitoring of inspection specimens during testing. The study assessed the feasibility of the sound camera for use in structural health monitoring of composite specimens during tensile testing for detecting onset of damage in addition to nondestructive evaluation of aluminum inspection plates for visualizing stress wave propagation in structures. During composite material monitoring, the sound camera was able to accurately identify the onset and location of damage resulting from large amplitude acoustic feedback mechanisms such as fiber breakage. Damage resulting from smaller acoustic feedback events such as matrix failure was detected but not localized to the degree of accuracy of larger feedback events. Findings suggest that beamforming technology can provide effective non-contact and non-invasive inspection of composite materials, characterizing the onset and the location of damage in an efficient manner. With regards to the nondestructive evaluation of metallic plates, this remote sensing system allows us to record wave propagation events in situ via a single-shot measurement. This is a significant improvement over

  4. Variation of solar acoustic emission and its relation to phase of the solar cycle

    Science.gov (United States)

    Chen, Ruizhu; Zhao, Junwei

    2016-05-01

    Solar acoustic emission is closely related to solar convection and photospheric magnetic field. Variation of acoustic emission and its relation to the phase of solar cycles are important to understand dynamics of solar cycles and excitation of acoustic waves. In this work we use 6 years of SDO/HMI Dopplergram data to study acoustic emissions of the whole sun and of the quiet-sun regions, respectively, in multiple acoustic frequency bands. We show the variation of acoustic emission from May 2010 to April 2016, covering half of the solar cycle 24, and analyze its correlation with the solar activity level indexed by daily sunspot number and total magnetic flux. Results show that the correlation between the whole-Sun acoustic emission and the solar activity level is strongly negative for low frequencies between 2.5 and 4.5 mHz, but strongly positive for high frequencies between 4.5 and 6.0 mHz. For high frequencies, the acoustic emission excess in sunspot halos overwhelms the emission deficiency in sunspot umbrae and penumbrae. The correlation between the acoustic emission in quiet regions and the solar activity level is negative for 2.5-4.0 mHz and positive for 4.0-5.5 mHz. This shows that the solar background acoustic power, with active regions excluded, also varies during a solar cycle, implying the excitation frequencies or depths are highly related to the solar magnetic field.

  5. Acoustic emissions correlated with hydration of Saguaro Cactus

    Science.gov (United States)

    Wardell, L. J.; Rowe, C. A.

    2013-12-01

    For some years it has been demonstrated that hardwood trees produce acoustic emissions during periods of drought, which arise from cavitation in the xylem as water is withdrawn. These emissions not only provide insights into the fluid transport behavior within these trees, but also the degree to which cavitation can proceed before inevitable tree mortality. Such studies can have significant impact on our understanding of forest die-off in the face of climate change. Plant mortality is not limited to woody trees, however, and it is not only the coniferous and deciduous forests whose response to climate and rainfall changes are important. In the desert Southwest we observe changes to survival rates of numerous species of flora. One of the most conspicuous of these plants is the iconic Saguaro Cactus (Carnegiea gigantean). These behemoths of the Sonoran Desert are very sensitive to small perturbations in their environment. Specifically, during the summer monsoon season when the cacti become well-hydrated, they can absorb hundreds of gallons of water within a very short time frame. We have obtained a juvenile saguaro on which we are conducting experiments to monitor acoustic emissions during hydration and dessication cycles. We will report on our observations obtained using piezoelectric ceramic accelerometers whose signals are digitized up to 44 Khz and recorded during hydration.

  6. STUDY OF ACOUSTIC EMISSION DURING NON- ISOTHERMAL CRYSTALLIZATION OF POLYPROPYLENE

    Institute of Scientific and Technical Information of China (English)

    SHEN Jingshu; XU Duanfu; YAO Ruigang; LIU Ruixia; LI Dawei

    1990-01-01

    In this paper we have presented the results of acoustic emission (AE) during non-isothemal crystallization of polypropylene (PP) melt with mean cooling rate 4 ℃ /min , and discussed the effects of molecular weight (MW) on AE activity. It is shown that the amount of AE ring-down counts during whole crystallization of PP depends on the MW strongly. The copious AE bursts have been observed at the late stage of PPcrystallization.AE bursts are caused by cracking ,crazing and cavitation between spherulites and inside spherulites.

  7. Acoustic emission mechanism at switching of ferroelectric crystals

    International Nuclear Information System (INIS)

    Process of acoustic emission (AE) in lead germanate (PGO) representing pure ferroelectric, and gadolinium molybdate (GMO) representing ferroelectric-ferroelastic, for which switching may be conducted both by the field and pressure, were studied. A conclusion has been drawn that piezoelectric excitation of a crystal from the surface by pulses of overpolarization current in the process of domain coalescence is the main AE source in PGO. Not only piezoresponse, but also direct sound generation in the moment of domain penetration and collapse is considered as AE mechanism in GMO

  8. Statistics of the acoustic emission signals parameters from Zircaloy-4 fuel cladding

    International Nuclear Information System (INIS)

    Statistic analysis of acoustic emission signals parameters: amplitude, duration and risetime was carried out. CANDU type Zircaloy-4 fuel claddings were pressurized up to rupture, one set of five normal pieces and six with defects included, acoustic emission was used on-line. Amplitude and duration frequency distributions were fitted with lognormal distribution functions, and risetime with an exponential one. Using analysis of variance, acoustic emission was appropriated to distinguish between defective and non-defective subsets. Clusters analysis applied on mean values of acoustic emission signal parameters were not effective to distinguish two sets of fuel claddings studied. (author)

  9. Detecting and identifying damage in sandwich polymer composite by using acoustic emission

    DEFF Research Database (Denmark)

    McGugan, M.; Sørensen, Bent F.; Østergaard, R.;

    2006-01-01

    Acoustic emission is a useful monitoring tool for extracting extra information during mechanical testing of polymer composite sandwich materials. The study of fracture mechanics within test specimens extracted from wind turbine blade material ispresented. The contribution of the acoustic emission...... monitoring technique in defining different failure modes identified during the testing is discussed. The development of in-situ structural monitoring and control systems is considered.......Acoustic emission is a useful monitoring tool for extracting extra information during mechanical testing of polymer composite sandwich materials. The study of fracture mechanics within test specimens extracted from wind turbine blade material ispresented. The contribution of the acoustic emission...

  10. Investigation on nonlinear thermo-acoustic characteristics of Rijke tube

    Institute of Scientific and Technical Information of China (English)

    DENG Kai; WU Yunfei; LI Hua; FANG Deming; ZHONG Yingjie

    2011-01-01

    Based on the energy conservation relationship, nonlinear thermo-acoustic effects of Rijke tube including instability range, saturation processes and higher harmonics modes were investigated. With coupling between the external flow and the inner space of a Rijke tube, the acoustic characteristics of self-excited oscillation were simulated. The experimental study was also carried out and the results were compared with those from simulation. The nonlinear factors which distort the acoustic waveform distortion were analyzed. From the results, it is seen that varying size of the nozzle outlet changes the acoustic impedance in the boundary, and leads to reduction of the nonlinear effects. The results show that the modes of self-excited oscillation could be influenced by the position of higher harmonics. In the large amplitude oscillation, the distortion of pressure wave within Rijke tube could be induced by the acoustic losses due to vortices on nozzle. It is found that the waveform distortion could be avoided by the shrinkage of nozzle.

  11. Deciphering acoustic emission signals in drought stressed branches: the missing link between source and sensor

    Directory of Open Access Journals (Sweden)

    Lidewei L Vergeynst

    2015-07-01

    Full Text Available When drought occurs in plants, acoustic emission signals can be detected, but the actual causes of these signals are still unknown. By analyzing the waveforms of the measured signals, it should however be possible to trace the characteristics of the acoustic emission source and get information about the underlying physiological processes. A problem encountered during this analysis is that the waveform changes significantly from source to sensor and lack of knowledge on wave propagation impedes research progress made in this field. We used finite element modeling and the well-known pencil lead break source to investigate wave propagation in a branch. A cylindrical rod of polyvinyl chloride was first used to identify the theoretical propagation modes. Two wave propagation modes could be distinguished and we used the finite element model to interpret their behavior in terms of source position for both the PVC rod and a wooden rod. Both wave propagation modes were also identified in drying-induced signals from woody branches, and we used the obtained insights to provide recommendations for further acoustic emission research in plant science.

  12. Fault diagnosis of reciprocating compressor valve with the method integrating acoustic emission signal and simulated valve motion

    Science.gov (United States)

    Wang, Yuefei; Xue, Chuang; Jia, Xiaohan; Peng, Xueyuan

    2015-05-01

    This paper proposes a method of diagnosing faults in reciprocating compressor valves using the acoustic emission signal coupled with the simulated valve motion. The actual working condition of a valve can be obtained by analyzing the acoustic emission signal in the crank angle domain and the valve movement can be predicted by simulating the valve motion. The exact opening and closing locations of a normal valve, provided by the simulated valve motion, can be used as references for the valve fault diagnosis. The typical valve faults are diagnosed to validate the feasibility and accuracy of the proposed method. The experimental results indicate that this method can easily distinguish the normal valve, valve flutter and valve delayed closing conditions. The characteristic locations of the opening and closing of the suction and discharge valves can be clearly identified in the waveform of the acoustic emission signal and the simulated valve motion.

  13. Identifying fatigue crack geometric features from acoustic emission signals

    Science.gov (United States)

    Bao, Jingjing; Poddar, Banibrata; Giurgiutiu, Victor

    2016-04-01

    Acoustic emission (AE) caused by the growth of fatigue crack were well studied by researchers. Conventional approaches predominantly are based on statistical analysis. In this study we focus on identifying geometric features of the crack from the AE signals using physics based approach. One of the main challenges of this approach is to develop a physics of materials based understanding of the generation and propagation of acoustic emissions due to the growth of a fatigue crack. As the geometry changes due to the crack growth, so does the local vibration modes around the crack. Our aim is to understand these changing local vibration modes and find possible relation between the AE signal features and the geometric features of the crack. Finite element (FE) analysis was used to model AE events due to fatigue crack growth. This was done using dipole excitation at the crack tips. Harmonic analysis was also performed on these FE models to understand the local vibration modes. Experimental study was carried out to verify these results. Piezoelectric wafer active sensors (PWAS) were used to excite cracked specimen and the local vibration modes were captured using laser Doppler vibrometry. The preliminary results show that the AE signals do carry the information related to the crack geometry.

  14. FRP/steel composite damage acoustic emission monitoring and analysis

    Science.gov (United States)

    Li, Dongsheng; Chen, Zhi

    2015-04-01

    FRP is a new material with good mechanical properties, such as high strength of extension, low density, good corrosion resistance and anti-fatigue. FRP and steel composite has gotten a wide range of applications in civil engineering because of its good performance. As the FRP/steel composite get more and more widely used, the monitor of its damage is also getting more important. To monitor this composite, acoustic emission (AE) is a good choice. In this study, we prepare four identical specimens to conduct our test. During the testing process, the AE character parameters and mechanics properties were obtained. Damaged properties of FRP/steel composite were analyzed through acoustic emission (AE) signals. By the growing trend of AE accumulated energy, the severity of the damage made on FRP/steel composite was estimated. The AE sentry function has been successfully used to study damage progression and fracture emerge release rate of composite laminates. This technique combines the cumulative AE energy with strain energy of the material rather than analyzes the AE information and mechanical separately.

  15. Acoustic characteristics of electric arc furnaces

    Science.gov (United States)

    Cherednichenko, V. S.; Bikeev, R. A.; Cherednichenko, A. V.; Ognev, A. M.

    2016-06-01

    A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115-120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.

  16. An information processing method for acoustic emission signal inspired from musical staff

    Science.gov (United States)

    Zheng, Wei; Wu, Chunxian

    2016-01-01

    This study proposes a musical-staff-inspired signal processing method for standard description expressions for discrete signals and describing the integrated characteristics of acoustic emission (AE) signals. The method maps various AE signals with complex environments into the normalized musical space. Four new indexes are proposed to comprehensively describe the signal. Several key features, such as contour, amplitude, and signal changing rate, are quantitatively expressed in a normalized musical space. The processed information requires only a small storage space to maintain high fidelity. The method is illustrated by using experiments on sandstones and computed tomography (CT) scanning to determine its validity for AE signal processing.

  17. Quantitative Acoustic Emission Fatigue Crack Characterization in Structural Steel and Weld

    Directory of Open Access Journals (Sweden)

    Adutwum Marfo

    2013-01-01

    Full Text Available The fatigue crack growth characteristics of structural steel and weld connections are analyzed using quantitative acoustic emission (AE technique. This was experimentally investigated by three-point bending testing of specimens under low cycle constant amplitude loading using the wavelet packet analysis. The crack growth sequence, that is, initiation, crack propagation, and fracture, is extracted from their corresponding frequency feature bands, respectively. The results obtained proved to be superior to qualitative AE analysis and the traditional linear elastic fracture mechanics for fatigue crack characterization in structural steel and welds.

  18. Coating adherence in galvanized steel assessed by acoustic emission wavelet analysis

    International Nuclear Information System (INIS)

    Coating-substrate adherence in galvanized steel is evaluated by acoustic emission wavelet analysis in scratch tests on hot-dip galvanized samples. The acoustic emission results are compared with optical and electron microscopy observations in order to understand coating features related to adherence and to establish criteria aimed at improving the manufacture process

  19. Longitudinal elastic wave propagation characteristics of inertant acoustic metamaterials

    Science.gov (United States)

    Kulkarni, Prateek P.; Manimala, James M.

    2016-06-01

    Longitudinal elastic wave propagation characteristics of acoustic metamaterials with various inerter configurations are investigated using their representative one-dimensional discrete element lattice models. Inerters are dynamic mass-amplifying mechanical elements that are activated by a difference in acceleration across them. They have a small device mass but can provide a relatively large dynamic mass presence depending on accelerations in systems that employ them. The effect of introducing inerters both in local attachments and in the lattice was examined vis-à-vis the propagation characteristics of locally resonant acoustic metamaterials. A simple effective model based on mass, stiffness, or their combined equivalent was used to establish dispersion behavior and quantify attenuation within bandgaps. Depending on inerter configurations in local attachments or in the lattice, both up-shift and down-shift in the bandgap frequency range and their extent are shown to be possible while retaining static mass addition to the host structure to a minimum. Further, frequency-dependent negative and even extreme effective-stiffness regimes are encountered. The feasibility of employing tuned combinations of such mass-delimited inertant configurations to engineer acoustic metamaterials that act as high-pass filters without the use of grounded elements or even as complete longitudinal wave inhibitors is shown. Potential device implications and strategies for practical applications are also discussed.

  20. Acoustic Characteristics of Advertisement Calls in Babina adenopleura

    Institute of Scientific and Technical Information of China (English)

    Xiaobin FANG; Xia QIU; Yilin ZHOU; Luyi YANG; Yi ZHAO; Weihong ZHENG; Jinsong LIU

    2015-01-01

    Acoustic communication is the most important form of communication in anuran amphibians. To understand the acoustic characteristics of male Babina adenopleura, we recorded advertisement calls and analyzed their acoustic parameters during the breeding season. Male B. adenopleura produced calls with a variable number of notes (1–5), and each note contained harmonics. Although 6%of call notes did not exhibit frequency modulation (FM), two call note FM patterns were observed:(1) upward FM;(2) upward–downward FM. With the exception of 1-and 5-note calls, the duration of successive notes decreased monotonically. With the exception of 1 note calls, the fundamental frequency of the first note was lowest, then increased; the greatest change in the fundamental frequency was always between notes 1 and 2. The dominant frequency varied between calls. For example for the ifrst call note the dominant frequency occurred in some cases in the ifrst harmonic (located in the 605.320 ± 64.533 Hz frequency band), the second harmonic (918 ± 9 Hz band), the fourth harmonic (1712 ± 333 Hz band), the sixth harmonic (the 2165 ± 152 Hz band), the seventh harmonic (the 2269 ± 140 Hz band), the eighth harmonic (the 2466 ± 15 Hz band) or the ninth harmonic (the 2636 ± 21 Hz band). Although male B. adenopleura advertisement calls have a distinctive structure, they have similar characteristics to the calls of the music frog, B. daunchina.

  1. The application of acoustic emission measurements on laboratory testpieces to large scale pressure vessel monitoring

    International Nuclear Information System (INIS)

    A test pressure vessel containing 4 artificial defects was monitored for emission whilst pressure cycling to failure. Testpieces cut from both the failed vessel and from as-rolled plate material were tested in the laboratory. A marked difference in emission characteristics was observed between plate and vessel testpieces. Activity from vessel material was virtually constant after general yield and emission amplitudes were low. Plate testpieces showed maximum activity at general yield and more frequent high amplitude emissions. An attempt has been made to compare the system sensitivities between the pressure vessel test and laboratory tests. In the absence of an absolute calibration device, system sensitivities were estimated using dummy signals generated by the excitation of an emission sensor. The measurements have shown an overall difference in sensitivity between vessel and laboratory tests of approximately 25db. The reduced sensitivity in the vessel test is attributed to a combination of differences in sensors, acoustic couplant, attenuation, and dispersion relative to laboratory tests and the relative significance of these factors is discussed. Signal amplitude analysis of the emissions monitored from laboratory testpieces showed that, whith losses of the order of 25 to 30db, few emissions would be detected from the pressure vessel test. It is concluded that no reliable prediction of acoustic behaviour of a structure may be made from laboratory test unless testpieces of the actual structural material are used. A considerable improvement in detection sensitivity, is also required for reliable detection of defects in low strength ductile materials and an absolute method of system calibration is required between tests

  2. Acoustical Characteristics of Mastication Sounds: Application of Speech Analysis Techniques

    Science.gov (United States)

    Brochetti, Denise

    Food scientists have used acoustical methods to study characteristics of mastication sounds in relation to food texture. However, a model for analysis of the sounds has not been identified, and reliability of the methods has not been reported. Therefore, speech analysis techniques were applied to mastication sounds, and variation in measures of the sounds was examined. To meet these objectives, two experiments were conducted. In the first experiment, a digital sound spectrograph generated waveforms and wideband spectrograms of sounds by 3 adult subjects (1 male, 2 females) for initial chews of food samples differing in hardness and fracturability. Acoustical characteristics were described and compared. For all sounds, formants appeared in the spectrograms, and energy occurred across a 0 to 8000-Hz range of frequencies. Bursts characterized waveforms for peanut, almond, raw carrot, ginger snap, and hard candy. Duration and amplitude of the sounds varied with the subjects. In the second experiment, the spectrograph was used to measure the duration, amplitude, and formants of sounds for the initial 2 chews of cylindrical food samples (raw carrot, teething toast) differing in diameter (1.27, 1.90, 2.54 cm). Six adult subjects (3 males, 3 females) having normal occlusions and temporomandibular joints chewed the samples between the molar teeth and with the mouth open. Ten repetitions per subject were examined for each food sample. Analysis of estimates of variation indicated an inconsistent intrasubject variation in the acoustical measures. Food type and sample diameter also affected the estimates, indicating the variable nature of mastication. Generally, intrasubject variation was greater than intersubject variation. Analysis of ranks of the data indicated that the effect of sample diameter on the acoustical measures was inconsistent and depended on the subject and type of food. If inferences are to be made concerning food texture from acoustical measures of mastication

  3. Acoustic emission monitoring of recycled aggregate concrete under bending

    Science.gov (United States)

    Tsoumani, A. A.; Barkoula, N.-M.; Matikas, T. E.

    2015-03-01

    The amount of construction and demolition waste has increased considerably over the last few years, making desirable the reuse of this waste in the concrete industry. In the present study concrete specimens are subjected at the age of 28 days to four-point bending with concurrent monitoring of their acoustic emission (AE) activity. Several concrete mixtures prepared using recycled aggregates at various percentages of the total coarse aggregate and also a reference mix using natural aggregates, were included to investigate their influence of the recycled aggregates on the load bearing capacity, as well as on the fracture mechanisms. The results reveal that for low levels of substitution the influence of using recycled aggregates on the flexural strength is negligible while higher levels of substitution lead into its deterioration. The total AE activity, as well as the AE signals emitted during failure, was related to flexural strength. The results obtained during test processing were found to be in agreement with visual observation.

  4. Acoustic emission classification for failure prediction due to mechanical fatigue

    Science.gov (United States)

    Emamian, Vahid; Kaveh, Mostafa; Tewfik, Ahmed H.

    2000-06-01

    Acoustic Emission signals (AE), generated by the formation and growth of micro-cracks in metal components, have the potential for use in mechanical fault detection in monitoring complex- shaped components in machinery including helicopters and aircraft. A major challenge for an AE-based fault detection algorithm is to distinguish crack-related AE signals from other interfering transient signals, such as fretting-related AE signals and electromagnetic transients. Although under a controlled laboratory environment we have fewer interference sources, there are other undesired sources which have to be considered. In this paper, we present some methods, which make their decision based on the features extracted from time-delay and joint time-frequency components by means of a Self- Organizing Map (SOM) neural network using experimental data collected in a laboratory by colleagues at the Georgia Institute of Technology.

  5. Analysis of concrete fracture evolution by simulation and acoustic emission

    Energy Technology Data Exchange (ETDEWEB)

    Shuhong Wang; Chun' an Tang; Wancheng Zhu; Kai Zhang [School of Racecourse and Civil Engineering, Northeastern Univ., Shenyang (China)

    2003-07-01

    According to the physical model of the three-point bending test on concrete and mortar, the numerical model of three-point bending specimen of concrete are established and a numerical code named material failure process analysis (MFPA{sup 2D}) is used to simulate the fracture process of this concrete specimen. The distribution of acoustic emission (AE), crack propagation process, and load-deflection curve of specimen are obtained for the mortar specimen and concrete specimen with and without preexisted crack. All these numerical results compare well with those experimental observations. Compared with other similar numerical model to simulate the fracture process of concrete, MFPA{sup 2D} has the advantage that the preexisted crack because the crack propagation path should not be known in advance. (orig.)

  6. Acoustic emission study on WC-Co thermal sprayed coatings

    Energy Technology Data Exchange (ETDEWEB)

    Miguel, J.M.; Guilemany, J.M.; Mellor, B.G.; Xu, Y.M

    2003-07-15

    Thermally sprayed coatings contain residual stresses that are produced in the spraying process. These may reduce the coating lifetime. In order to determine the optimum spraying conditions with respect to the residual stress level present, the acoustic emission (AE) during four-point bend tests on tungsten carbide-cobalt coatings sprayed onto mild steel substrates was investigated. Samples tested at different levels of deformation were studied by means of scanning electron microscopy and AE in order to understand the cracking mechanisms. Relationships between the number and amplitude of AE events detected and the type of cracking processes occurring were established. It has been possible to compare the residual stresses caused by the effect of different spraying parameters, such as coating thickness, spraying distance and high velocity oxy-fuel gun.

  7. Quality Testing of Gaseous Helium Pressure Vessels by Acoustic Emission

    CERN Document Server

    Barranco-Luque, M; Hervé, C; Margaroli, C; Sergo, V

    1998-01-01

    The resistance of pressure equipment is currently tested, before commissioning or at periodic maintenance, by means of normal pressure tests. Defects occurring inside materials during the execution of these tests or not seen by usual non-destructive techniques can remain as undetected potential sources of failure . The acoustic emission (AE) technique can detect and monitor the evolution of such failures. Industrial-size helium cryogenic systems employ cryogens often stored in gaseous form under pressure at ambient temperature. Standard initial and periodic pressure testing imposes operational constraints which other complementary testing methods, such as AE, could significantly alleviate. Recent reception testing of 250 m3 GHe storage vessels with a design pressure of 2.2 MPa for the LEP and LHC cryogenic systems has implemented AE with the above-mentioned aims.

  8. ANALYSIS OF CHIP FORMATION DURING HARD TURNING THROUGH ACOUSTIC EMISSION

    Directory of Open Access Journals (Sweden)

    Miroslav Neslušan

    2012-01-01

    Full Text Available The paper deals with analysis of chip formation and related aspects of the chip formation during turning hardened steel 100Cr6. The paper draws a comparison of some aspects of the chip formation between turning annealed and hardened roll bearing steel. The results of the analysis show that there is the formation of a segmented chip in the case of hard turning. Frequency of segmentation is very high. A conventional piezoelectric dynamometer limits the frequency response to about 3.5 kHz. On the other hand, the frequency of process fluctuation may by obtained by using accelerometers or acoustic emission. This paper reports about the dynamic character of cutting process when hard turning and correlation among the calculated segmentation frequencies and the experimental analysis.

  9. Fracture of Human Femur Tissue Monitored by Acoustic Emission Sensors

    Directory of Open Access Journals (Sweden)

    Dimitrios. G. Aggelis

    2015-03-01

    Full Text Available The study describes the acoustic emission (AE activity during human femur tissue fracture. The specimens were fractured in a bending-torsion loading pattern with concurrent monitoring by two AE sensors. The number of recorded signals correlates well with the applied load providing the onset of micro-fracture at approximately one sixth of the maximum load. Furthermore, waveform frequency content and rise time are related to the different modes of fracture (bending of femur neck or torsion of diaphysis. The importance of the study lies mainly in two disciplines. One is that, although femurs are typically subjects of surgical repair in humans, detailed monitoring of the fracture with AE will enrich the understanding of the process in ways that cannot be achieved using only the mechanical data. Additionally, from the point of view of monitoring techniques, applying sensors used for engineering materials and interpreting the obtained data pose additional difficulties due to the uniqueness of the bone structure.

  10. Punch stretching process monitoring using acoustic emission signal analysis. II - Application of frequency domain deconvolution

    Science.gov (United States)

    Liang, Steven Y.; Dornfeld, David A.; Nickerson, Jackson A.

    1987-01-01

    The coloring effect on the acoustic emission signal due to the frequency response of the data acquisition/processing instrumentation may bias the interpretation of AE signal characteristics. In this paper, a frequency domain deconvolution technique, which involves the identification of the instrumentation transfer functions and multiplication of the AE signal spectrum by the inverse of these system functions, has been carried out. In this way, the change in AE signal characteristics can be better interpreted as the result of the change in only the states of the process. Punch stretching process was used as an example to demonstrate the application of the technique. Results showed that, through the deconvolution, the frequency characteristics of AE signals generated during the stretching became more distinctive and can be more effectively used as tools for process monitoring.

  11. Studies of Elastic Waves in Ethylene Propylene Rubber Using Acoustic Emission Sensor

    Science.gov (United States)

    Takaoka, Masanori; Sakoda, Tatsuya; Otsubo, Masahisa; Akaiwa, Shigeru; Iki, Masatoshi; Nakano, Shigeharu

    The aim of our study is to investigate the relationship between lowering of the insulation performance of cross-linked polyethylene (CV) cable and partial discharges (PDs) followed by the dielectric breakdown and to establish a diagnostic technique using an acoustic emission (AE) sensor. In this study, we focused on characterization of AE signals detected from ethylene propylene rubbers (EPRs) used as insulating materials of CV cables. Elastic waves with various frequencies were added to the surface of the EPR, and then characteristics of the detected AE signals due to the elastic waves propagated in the EPR were evaluated. We showed characteristics of Lamb waves whose low frequency components around 100 kHz were large and their small attenuation characteristics.

  12. Use of Acoustic Emission During Scratch Testing for Understanding Adhesion Behavior of Aluminum Nitride Coatings

    Science.gov (United States)

    Choudhary, R. K.; Mishra, P.

    2016-06-01

    In this work, acoustic emission during scratch testing of the aluminum nitride coatings formed on stainless steel substrate by reactive magnetron sputtering was analyzed to assess the coating failure. The AlN coatings were formed under the variation of substrate temperature, substrate bias potential, and discharge power. The coatings deposited in the temperature range of 100 to 400 °C showed peak acoustic emission less than 1.5%, indicating ductile nature of the coating. However, for coatings formed with substrate negative bias potential of 20 to 50 V, numerous sharp acoustic bursts with maximum emission approaching 80% were observed, indicating brittle nature of the coatings with large number of defects present. The shift in the intensity of the first major acoustic peak toward higher load, with the increasing bias potential, confirmed improved adhesion of the coating. Also, the higher discharge power resulted in increased acoustic emission.

  13. Monitoring and failure analysis of corroded bridge cables under fatigue loading using acoustic emission sensors.

    Science.gov (United States)

    Li, Dongsheng; Ou, Jinping; Lan, Chengming; Li, Hui

    2012-01-01

    Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index. PMID:22666009

  14. Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors

    Directory of Open Access Journals (Sweden)

    Hui Li

    2012-03-01

    Full Text Available Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index.

  15. The Basic Study on the Method of Acoustic Emission Signal Processing for the Failure Detection in the NPP Structures

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Hyun; Kim, Jae Seong; Lee, Bo Young [Korea Aerospace University, Goyang (Korea, Republic of); Lee, Jung; Kwag, No Gwon [SAEAN, Seoul (Korea, Republic of)

    2009-10-15

    The thermal fatigue crack(TFC) is one of the life-limiting mechanisms at the nuclear power plant operating conditions. In order to evaluate the structural integrity, various non-destructive test methods such as radiographic test, ultrasonic test and eddy current are used in the industrial field. However, these methods have restrictions that defect detection is possible after the crack growth. For this reason, acoustic emission testing(AET) is becoming one of powerful inspection methods, because AET has an advantage that possible to monitor the structure continuously. Generally, every mechanism that affects the integrity of the structure or equipment is a source of acoustic emission signal. Therefore the noise filtering is one of the major works to the almost AET researchers. In this study, acoustic emission signal was collected from the pipes which were in the successive thermal fatigue cycles. The data were filtered based on the results from previous experiments. Through the data analysis, the signal characteristics to distinguish the effective signal from the noises for the TFC were proven as the waveform difference. The experiment results provide preliminary information for the acoustic emission technique to the continuous monitoring of the structure failure detection

  16. Phenomenological Description of Acoustic Emission Processes Occurring During High-Pressure Sand Compaction

    Science.gov (United States)

    Delgado-Martín, Jordi; Muñoz-Ibáñez, Andrea; Grande-García, Elisa; Rodríguez-Cedrún, Borja

    2016-04-01

    Compaction, pore collapse and grain crushing have a significant impact over the hydrodynamic properties of sand formations. The assessment of the crushing stress threshold constitutes valuable information in order to assess the behavior of these formations provided that it can be conveniently identified. Because of the inherent complexities of the direct observation of sand crushing, different authors have developed several indirect methods, being acoustic emission a promising one. However, previous researches have evidenced that there are different processes triggering acoustic emissions which need to be carefully accounted. Worth mentioning among them are grain bearing, grain to container friction, intergranular friction and crushing. The work presented here addresses this purpose. A broadband acoustic emission sensor (PA MicroHF200) connected to a high-speed data acquisition system and control software (AeWIN for PCI1 2.10) has been attached to a steel ram and used to monitor the different processes occurring during the oedometric compaction of uniform quartz sand up to an axial load of about 110 MPa and constant temperature. Load was stepwise applied using a servocontrolled hydraulic press acting at a constant load rate. Axial strain was simultaneously measured with the aid of a LDT device. Counts, energy, event duration, rise time and amplitude were recorded along each experiment and after completion selected waveforms were transformed from the time to the frequency domain via FFT transform. Additional simplified tests were performed in order to isolate the frequency characteristics of the dominant processes occurring during sand compaction. Our results show that, from simple tests, it is possible to determine process-dependent frequency components. When considering more complex experiments, many of the studied processes overlap but it is still possible to identify when a particular one dominates as well as the likely onset of crushing.

  17. Fluids and Combustion Facility Acoustic Emissions Controlled by Aggressive Low-Noise Design Process

    Science.gov (United States)

    Cooper, Beth A.; Young, Judith A.

    2004-01-01

    The Fluids and Combustion Facility (FCF) is a dual-rack microgravity research facility that is being developed by Northrop Grumman Information Technology (NGIT) for the International Space Station (ISS) at the NASA Glenn Research Center. As an on-orbit test bed, FCF will host a succession of experiments in fluid and combustion physics. The Fluids Integrated Rack (FIR) and the Combustion Integrated Rack (CIR) must meet ISS acoustic emission requirements (ref. 1), which support speech communication and hearing-loss-prevention goals for ISS crew. To meet these requirements, the NGIT acoustics team implemented an aggressive low-noise design effort that incorporated frequent acoustic emission testing for all internal noise sources, larger-scale systems, and fully integrated racks (ref. 2). Glenn's Acoustical Testing Laboratory (ref. 3) provided acoustical testing services (see the following photograph) as well as specialized acoustical engineering support as part of the low-noise design process (ref. 4).

  18. Acoustic emission measurements in petroleum-related rock mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Unander, Tor Erling

    2002-07-01

    Acoustic emission activity in rock has usually been studied in crystalline rock, which reflects that rock mechanics has also mostly been occupied with such rocks in relations to seismology, mining and tunneling. On the other hand, petroleum-related rock mechanics focuses on the behaviour of sedimentary rock. Thus, this thesis presents a general study of acoustic emission activity in sedimentary rock, primarily in sandstone. Chalk, limestone and shale have also been tested, but to much less degree because the AE activity in these materials is low. To simplify the study, pore fluids have not been used. The advent of the personal computer and computerized measuring equipment have made possible new methods both for measuring and analysing acoustic emissions. Consequently, a majority of this work is devoted to the development and implementation of new analysis techniques. A broad range of topics are treated: (1) Quantification of the AE activity level, assuming that the event rate best represents the activity. An algorithm for estimating the event rate and a methodology for objectively describing special changes in the activity e.g., onset determination, are presented. (2) Analysis of AE waveform data. A new method for determining the source energy of an AE event is presented, and it is shown how seismic source theory can be used to analyze even intermediate quality data. Based on these techniques, it is shown that a major part of the measured AE activity originates from a region close to the sensor, not necessarily representing the entire sample. (3) An improved procedure for estimating source locations is presented. The main benefit is a procedure that better handles arrival time data with large errors. Statistical simulations are used to quantify the uncertainties in the locations. The analysis techniques are developed with the application to sedimentary rock in mind, and in two articles, the techniques are used in the study of such materials. The work in the first

  19. Development of Novel Optical Fiber Interferometric Sensors with High Sensitivity for Acoustic Emission Detection

    OpenAIRE

    Deng, Jiangdong

    2004-01-01

    For the purpose of developing a new highly-sensitive and reliable fiber optical acoustic sensor capable of real-time on-line detection of acoustic emissions in power transformers, this dissertation presents the comprehensive research work on the theory, modeling, design, instrumentation, noise analysis, and performance evaluation of a diaphragm-based optical fiber acoustic (DOFIA) sensor system. The optical interference theory and the diaphragm dynamic vibration analysis form the two fou...

  20. Correlation of Acoustic Emission Signals with Kinetics of Fatigue Crack Growth in the Shock Absorber of Aircraft Landing Gear

    OpenAIRE

    Šanjavskis, A; Urbahs, A; Banov, M; Doroško, S; Hodoss, N

    2009-01-01

    In this article it is analyzed possibility of correlation between acoustic emission (AE) parameters and characteristics of fatigue crack development beginning from moment of crack initiation before didruption. A shock absorber cylinder of aircraft landing gear leg was used as object of investigation. In process of testing the fatigue crack was grew during action of periodic loading which imitates full flight cycle including take-off and landing and running at the ground. This testing was fini...

  1. Effect of A-site La and Ba doping on threshold field and characteristic temperatures of PbSc0.5Ta0.5O3 relaxor studied by acoustic emission

    Science.gov (United States)

    Dul'kin, E.; Mihailova, B.; Gospodinov, M.; Roth, M.

    2012-09-01

    The structural transitions in Pb1-xLaxSc(1+x)/2Ta(1-x)/2O3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) [E. Dul'kin et al., EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at Tn = 276 K, lying in the vicinity of dielectric temperature maximum (Tm). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of Tn previously observed for both the PST and PBST, namely, Tn initially decreases with the increase of E, attains a minimum at a threshold field Eth = 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate Ṅ = 12 s-1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to Tn, Eth, and Ṅ are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb2+ by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of Tn and Eth, whereas the latter is shown to affect the normalized Ṅ, indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.

  2. Acoustic emission analysis coupled with thermogravimetric experiments dedicated to high temperature corrosion studies on metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Serris, Eric; Al Haj, Omar; Peres, Veronique; Cournil, Michel [Ecole Nationale Superieure des Mines de Saint-Etienne (France); Kittel, Jean; Grosjean, Francois; Ropital, Francois [IFP Energies nouvelles, BP3 rond-point de l' echangeur de Solaize (France)

    2014-11-01

    High temperature corrosion of metallic alloys (like iron, nickel, zirconium alloys) can damage equipment of many industrial fields (refinery, petrochemical, nuclear..). Acoustic emission (AE) is an interesting method owing to its sensitivity and its non-destructive aspect to quantify the level of damage in use of these alloys under various environmental conditions. High temperature corrosive phenomena create stresses in the materials; the relaxation by cracks of these stresses can be recorded and analyzed using the AE system. The goal of our study is to establish an acoustic signals database which assigns the acoustic signals to the specific corrosion phenomena. For this purpose, thermogravimetric analysis (TGA) is coupled with acoustic emission (AE) devices. The oxidation of a zirconium alloy, zircaloy-4, is first studied using thermogravimetric experiment coupled to acoustic emission analysis at 900 C. An inward zirconium oxide scale, preliminary dense, then porous, grow during the isothermal isobaric step. The kinetic rate increases significantly after a kinetic transition (breakaway). This acceleration occurs with an increase of acoustic emission activity. Most of the acoustic emission bursts are recorded after the kinetic transition. Acoustic emission signals are also observed during the cooling of the sample. AE numerical treatments (using wavelet transform) completed by SEM microscopy characterizations allows us to distinguish the different populations of cracks. Metal dusting represents also a severe form of corrosive degradation of metal alloy. Iron metal dusting corrosion is studied by AE coupled with TGA at 650 C under C{sub 4}H{sub 10} + H{sub 2} + He atmosphere. Acoustic emission signals are detected after a significant increase of the sample mass.

  3. Experimental analysis of crack evolution in concrete by the acoustic emission technique

    Directory of Open Access Journals (Sweden)

    J. Saliba

    2015-10-01

    Full Text Available The fracture process zone (FPZ was investigated on unnotched and notched beams with different notch depths. Three point bending tests were realized on plain concrete under crack mouth opening displacement (CMOD control. Crack growth was monitored by applying the acoustic emission (AE technique. In order to improve our understanding of the FPZ, the width and length of the FPZ were followed based on the AE source locations maps and several AE parameters were studied during the entire loading process. The bvalue analysis, defined as the log-linear slope of the frequency-magnitude distribution of acoustic emissions, was also carried out to describe quantitatively the influence of the relative notch depth on the fracture process. The results show that the number of AE hits increased with the decrease of the relative notch depth and an important AE energy dissipation was observed at the crack initiation in unnotched beams. In addition, the relative notch depth influenced the AE characteristics, the process of crack propagation, and the brittleness of concrete.

  4. Combined optical fiber interferometric sensors for the detection of acoustic emission

    Institute of Scientific and Technical Information of China (English)

    LIANG Yi-jun; MU Lin-lin; LIU Jun-feng; YU Xiao-tao

    2008-01-01

    A type of combined optical fiber interferometric acoustic emission sensor is proposed.The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure.Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy.PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid.The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of intefferometer and using Fourier transform technique.The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.

  5. Characterisation of Damage in Composite Structures using Acoustic Emission

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, M; Featherston, C; Holford, K; Pullin, R [Cardiff School of Engineering, Cardiff University, Queens Buildings, Newport Road, Cardiff, CF24 3AA (United Kingdom); May, M [Fraunhofer Institut fuer Kurzzeitdynamik, Ernst-Mach-Institut, Eckerstr. 4, 79104 Freiburg (Germany); Hallet, S, E-mail: eatonm@cf.ac.uk, E-mail: michael.may@emi.fraunhofer.de, E-mail: featherstoncaf@cardiff.ac.uk, E-mail: holford@cardiff.ac.uk, E-mail: stephen.hallett@bristol.ac.uk, E-mail: pullinr@cf.ac.uk [Department of Aerospace Engineering, University of Bristol, Queens Building, University Walk, Bristol, BS8 1TR (United Kingdom)

    2011-07-19

    Detection and characterisation of damage in composite structures during in-service loading is highly desirable. Acoustic emission (AE) monitoring of composite components offers a highly sensitive method for detecting matrix cracking and delamination damage mechanisms in composites. AE relies on the detection of stress waves that are released during damage propagation and using an array of sensors, damage location may be determined. A methodology for damage characterisation based on measuring the amplitude ratio (MAR) of the two primary lamb wave modes; symmetric (in-plane) and asymmetric (out-of-plane) that propagate in plate like structures has been developed. This paper presents the findings of a series of tensile tests in composite coupons with large central ply blocks. The specimens were monitored using AE sensors throughout loading and once significant AE signals were observed the loading process was stopped. The specimens were removed and subjected to x-ray inspection to assess for any damage. The onset of damage was successfully detected using AE and was identified as being matrix cracking using the MAR methodology. The results were validated with x-ray inspection and a strong correlation was observed between the number of significant AE signals recorded and the number of identified matrix cracks.

  6. New methods for leaks detection and localisation using acoustic emission

    International Nuclear Information System (INIS)

    Real time monitoring of Pressurized Water nuclear Reactor secondary coolant system tends to integrate digital processing machines. In this context, the method of acoustic emission seems to exhibit good performances. Its principle is based on passive listening of noises emitted by local micro-displacements inside a material under stress which propagate as elastic waves. The lack of a priori knowledge on leak signals leads us to go deeper into understanding flow induced noise generation. Our studies are conducted using a simple leak model depending on the geometry and the king of flow inside the slit. Detection and localization problems are formulated according to the maximum likelihood principle. For detection, the methods using a indicator of similarity (correlation, higher order correlation) seems to give better results than classical ones (rms value, envelope, filter banks). For leaks location, a large panel of classical (generalized inter-correlation) and innovative (convolution, adaptative, higher order statistics) methods of time delay estimation are presented. The last part deals with the applications of higher order statistics. The analysis of higher order estimators of a non linear non Gaussian stochastic process family, the improvement of non linear prediction performances and the optimal-order choice problem are addressed in simple analytic cases. At last, possible applications to leak signals analysis are pointed out. (authors).264 refs., 7 annexes

  7. Use of Macro Fibre Composite Transducers as Acoustic Emission Sensors

    Directory of Open Access Journals (Sweden)

    Mark Eaton

    2009-04-01

    Full Text Available The need for ever lighter and more efficient aerospace structures and components has led to continuous optimization pushing the limits of structural performance. In order to ensure continued safe operation during long term service it is desirable to develop a structural health monitoring (SHM system. Acoustic emission (AE offers great potential for real time global monitoring of aerospace structures, however currently available commercial sensors have limitations in size, weight and adaptability to complex structures. This work investigates the potential use of macro-fibre composite (MFC film transducers as AE sensors. Due to the inhomogeneous make-up of MFC transducers their directional dependency was examined and found to have limited effect on signal feature data. However, signal cross-correlations revealed a strong directional dependency. The sensitivity and signal attenuation with distance of MFC sensors were compared with those of commercially available sensors. Although noticeably less sensitive than the commercial sensors, the MFC sensors still had an acceptable operating range. Furthermore, a series of compressive carbon fiber coupon tests were monitored in parallel using both an MFC sensor and a commercially available sensor for comparison. The results showed good agreement of AE trends recorded by both sensors.

  8. DETECTION OF DRUGSTORE BEETLES IN 9975 PACKAGES USING ACOUSTIC EMISSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Shull, D.

    2013-03-04

    This report documents the initial feasibility tests performed using a commercial acoustic emission instrument for the purpose of detecting beetles in Department of Energy 9975 shipping packages. The device selected for this testing was a commercial handheld instrument and probe developed for the detection of termites, weevils, beetles and other insect infestations in wooden structures, trees, plants and soil. The results of two rounds of testing are presented. The first tests were performed by the vendor using only the hand-held instrument’s indications and real-time operator analysis of the audio signal content. The second tests included hands-free positioning of the instrument probe and post-collection analysis of the recorded audio signal content including audio background comparisons. The test results indicate that the system is promising for detecting the presence of drugstore beetles, however, additional work would be needed to improve the ease of detection and to automate the signal processing to eliminate the need for human interpretation. Mechanisms for hands-free positioning of the probe and audio background discrimination are also necessary for reliable detection and to reduce potential operator dose in radiation environments.

  9. Transient cavitation and acoustic emission produced by different laser lithotripters.

    Science.gov (United States)

    Zhong, P; Tong, H L; Cocks, F H; Pearle, M S; Preminger, G M

    1998-08-01

    Transient cavitation and shockwave generation produced by pulsed-dye and holmium:YAG laser lithotripters were studied using high-speed photography and acoustic emission measurements. In addition, stone phantoms were used to compare the fragmentation efficiency of various laser and electrohydraulic lithotripters. The pulsed-dye laser, with a wavelength (504 nm) strongly absorbed by most stone materials but not by water, and a short pulse duration of approximately 1 microsec, induces plasma formation on the surface of the target calculi. Subsequently, the rapid expansion of the plasma forms a cavitation bubble, which expands spherically to a maximum size and then collapses violently, leading to strong shockwave generation and microjet impingement, which comprises the primary mechanism for stone fragmentation with short-pulse lasers. In contrast, the holmium laser, with a wavelength (2100 nm) most strongly absorbed by water as well as by all stone materials and a long pulse duration of 250 to 350 microsec, produces an elongated, pear-shaped cavitation bubble at the tip of the optical fiber that forms a vapor channel to conduct the ensuing laser energy to the target stone (Moss effect). The expansion and subsequent collapse of the elongated bubble is asymmetric, resulting in weak shockwave generation and microjet impingement. Thus, stone fragmentation in holmium laser lithotripsy is caused primarily by thermal ablation (drilling effect). PMID:9726407

  10. Analysis of Acoustic Emission Signals using WaveletTransformation Technique

    Directory of Open Access Journals (Sweden)

    S.V. Subba Rao

    2008-07-01

    Full Text Available Acoustic emission (AE monitoring is carried out during proof pressure testing of pressurevessels to find the occurrence of any crack growth-related phenomenon. While carrying out AEmonitoring, it is often found that the background noise is very high. Along with the noise, thesignal includes various phenomena related to crack growth, rubbing of fasteners, leaks, etc. Dueto the presence of noise, it becomes difficult to identify signature of the original signals related to the above phenomenon. Through various filtering/ thresholding techniques, it was found that the original signals were getting filtered out along with noise. Wavelet transformation technique is found to be more appropriate to analyse the AE signals under such situations. Wavelet transformation technique is used to de-noise the AE data. The de-noised signal is classified to identify a signature based on the type of phenomena.Defence Science Journal, 2008, 58(4, pp.559-564, DOI:http://dx.doi.org/10.14429/dsj.58.1677

  11. Acoustic emission source localization based on distance domain signal representation

    Science.gov (United States)

    Gawronski, M.; Grabowski, K.; Russek, P.; Staszewski, W. J.; Uhl, T.; Packo, P.

    2016-04-01

    Acoustic emission is a vital non-destructive testing technique and is widely used in industry for damage detection, localisation and characterization. The latter two aspects are particularly challenging, as AE data are typically noisy. What is more, elastic waves generated by an AE event, propagate through a structural path and are significantly distorted. This effect is particularly prominent for thin elastic plates. In these media the dispersion phenomenon results in severe localisation and characterization issues. Traditional Time Difference of Arrival methods for localisation techniques typically fail when signals are highly dispersive. Hence, algorithms capable of dispersion compensation are sought. This paper presents a method based on the Time - Distance Domain Transform for an accurate AE event localisation. The source localisation is found through a minimization problem. The proposed technique focuses on transforming the time signal to the distance domain response, which would be recorded at the source. Only, basic elastic material properties and plate thickness are used in the approach, avoiding arbitrary parameters tuning.

  12. Dislocation unpinning model of acoustic emission from alkali halide crystals

    Indian Academy of Sciences (India)

    B P Chandra; Anubha S Gour; Vivek K Chandra; Yuvraj Patil

    2004-06-01

    The present paper reports the dislocation unpinning model of acoustic emission (AE) from alkali halide crystals. Equations are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number of AE pulse emitted. It is found that the AE pulse rate should be maximum for a particular strain of the crystals. The peak value of the AE pulse rate should depend on the volume and strain rate of the crystals, and also on the pinning time of dislocations. Since the pinning time of dislocations decreases with increasing strain rate, the AE pulse rate should be weakly dependent on the strain rate of the crystals. The total number of AE should increase linearly with deformation and then it should attain a saturation value for the large deformation. By measuring the strain dependence of the AE pulse rate at a fixed strain rate, the time constant $_{\\text{s}}$ for surface annihilation of dislocations and the pinning time $_{\\text{p}}$ of the dislocations can be determined. A good agreement is found between the theoretical and experimental results related to the AE from alkali halide crystals.

  13. Early corrosion monitoring of prestressed concrete piles using acoustic emission

    Science.gov (United States)

    Vélez, William; Matta, Fabio; Ziehl, Paul H.

    2013-04-01

    The depassivation and corrosion of bonded prestressing steel strands in concrete bridge members may lead to major damage or collapse before visual inspections uncover evident signs of damage, and well before the end of the design life. Recognizing corrosion in its early stage is desirable to plan and prioritize remediation strategies. The Acoustic Emission (AE) technique is a rational means to develop structural health monitoring and prognosis systems for the early detection and location of corrosion in concrete. Compelling features are the sensitivity to events related to micro- and macrodamage, non-intrusiveness, and suitability for remote and wireless applications. There is little understanding of the correlation between AE and the morphology and extent of early damage on the steel surface. In this paper, the evidence collected from prestressed concrete (PC) specimens that are exposed to salt water is discussed vis-à-vis AE data from continuous monitoring. The specimens consist of PC strips that are subjected to wet/dry salt water cycles, representing portions of bridge piles that are exposed to tidal action. Evidence collected from the specimens includes: (a) values of half-cell potential and linear polarization resistance to recognize active corrosion in its early stage; and (b) scanning electron microscopy micrographs of steel areas from two specimens that were decommissioned once the electrochemical measurements indicated a high probability of active corrosion. These results are used to evaluate the AE activity resulting from early corrosion.

  14. Various numerical simulation methods for acoustic emission in rock

    International Nuclear Information System (INIS)

    Acoustic Emission (AE) or Microseismicity (MS) is a very useful method to understand fracture mechanism and to predict serious rock fracture like rockburst. This method can be applied to monitor reservoirs where water and gas are injected, for example, in underground sequestration of carbon dioxide and in Enhanced Oil Recovery (EOR) of petroleum industry. If a numerical simulation helps to interpret AE monitoring results, AE monitoring would become much more powerful tool for the rock engineering. Thus, in this paper, the authors review various methods that can simulate occurrence of AE events incorporating inhomogeneity of rock. A code of Finite Element Method (FEM) developed by Tang et al., those of Boundary Element Method (BEM) by Napier's and Stephansson's groups and those of Distinct Element Method (DEM) by Shimizu et. al., Fakhimi et al. and Cai et al. are briefly introduced as simulation methods of brittle fracture like rockburst. For simulation of AE events induced by water or gas injection, DEM incorporating Fluid Flow Algorism by Shimizu et al. are introduced, with showing their simulation results of hydraulic fracturing. (author)

  15. Acoustic emission of fire damaged fiber reinforced concrete

    Science.gov (United States)

    Mpalaskas, A. C.; Matikas, T. E.; Aggelis, D. G.

    2016-04-01

    The mechanical behavior of a fiber-reinforced concrete after extensive thermal damage is studied in this paper. Undulated steel fibers have been used for reinforcement. After being exposed to direct fire action at the temperature of 850°C, specimens were subjected to bending and compression in order to determine the loss of strength and stiffness in comparison to intact specimens and between the two types. The fire damage was assessed using nondestructive evaluation techniques, specifically ultrasonic pulse velocity (UPV) and acoustic emission (AE). Apart from the strong, well known, correlation of UPV to strength (both bending and compressive), AE parameters based mainly on the frequency and duration of the emitted signals after cracking events showed a similar or, in certain cases, better correlation with the mechanical parameters and temperature. This demonstrates the sensitivity of AE to the fracture incidents which eventually lead to failure of the material and it is encouraging for potential in-situ use of the technique, where it could provide indices with additional characterization capability concerning the mechanical performance of concrete after it subjected to fire.

  16. Acoustic Emission, b-values and Foliation Plane Anisotropy

    Science.gov (United States)

    Sehizadeh, Mahdi; Nasseri, Mohammad H.; Ye, Sheng; Young, R. Paul

    2016-04-01

    The b-value and D-value are two parameters related to size and distance distribution of earthquakes. There are many different factors affecting b-value such as stress state, thermal gradients, focal mechanism and heterogeneity. For example, the literature shows that the b-value changes systematically with respect to the focal mechanism. In laboratory experiments, foliation planes introduce a weakness in samples and can be considered as a potential for rupture or pre-existing faults, so they may exhibit similar relationships. The D-value defines the degree of clustering of earthquakes and would be expected to have a defined relationship with respect to the anisotropy. Using a unique facility in the Rock Fracture Dynamics laboratory at the University of Toronto, three sets of polyaxial experiments have been performed on cubic samples with foliation planes systematically oriented at different angles to the principal stress direction. During these tests, samples were loaded under controlled true-triaxial stress conditions until they failed or had severe damage and acoustic emission events were recorded using 18 sensors around the samples. The paper describes how the combination of stress state and foliation planes affects the b-value and D-value under laboratory conditions.

  17. Acoustic Emission Measurement with Fiber Bragg Gratings for Structure Health Monitoring

    Science.gov (United States)

    Banks, Curtis E.; Walker, James L.; Russell, Sam; Roth, Don; Mabry, Nehemiah; Wilson, Melissa

    2010-01-01

    Structural Health monitoring (SHM) is a way of detecting and assessing damage to large scale structures. Sensors used in SHM for aerospace structures provide real time data on new and propagating damage. One type of sensor that is typically used is an acoustic emission (AE) sensor that detects the acoustic emissions given off from a material cracking or breaking. The use of fiber Bragg grating (FBG) sensors to provide acoustic emission data for damage detection is studied. In this research, FBG sensors are used to detect acoustic emissions of a material during a tensile test. FBG sensors were placed as a strain sensor (oriented parallel to applied force) and as an AE sensor (oriented perpendicular to applied force). A traditional AE transducer was used to collect AE data to compare with the FBG data. Preliminary results show that AE with FBGs can be a viable alternative to traditional AE sensors.

  18. Scanning thermoelectric and acoustic emission dignostic of structural inhomogeneities of thermocouple materials

    Directory of Open Access Journals (Sweden)

    Prokhorenko V.J.

    2010-01-01

    Full Text Available New method for diagnostic of constructional and functional materials by means of thermoelectric and acoustic- emission measurements is proposed. The method allows not only to establish the defect location, but its partial temperature relaxation achieve.

  19. ?Smart COPVs? - Continued Successful Development of JSC IR&D Acoustic Emissions (AE) SHM Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop and apply promising quantitative pass/fail criteria to CPV using acoustic emission (AE) and lay the foundation for continued development of an automated...

  20. Energy monitoring and analysis during deformation of bedded-sandstone: use of acoustic emission.

    Science.gov (United States)

    Wasantha, P L P; Ranjith, P G; Shao, S S

    2014-01-01

    This paper investigates the mechanical behaviour and energy releasing characteristics of bedded-sandstone with bedding layers in different orientations, under uniaxial compression. Cylindrical sandstone specimens (54 mm diameter and 108 mm height) with bedding layers inclined at angles of 10°, 20°, 35°, 55°, and 83° to the minor principal stress direction, were produced to perform a series of Uniaxial Compressive Strength (UCS) tests. One of the two identical sample sets was fully-saturated with water before testing and the other set was tested under dry conditions. An acoustic emission system was employed in all the testing to monitor the acoustic energy release during the whole deformation process of specimens. From the test results, the critical joint orientation was observed as 55° for both dry and saturated samples and the peak-strength losses due to water were 15.56%, 20.06%, 13.5%, 13.2%, and 13.52% for the bedding orientations 10°, 20°, 35°, 55°, and 83°, respectively. The failure mechanisms for the specimens with bedding layers in 10°, 20° orientations showed splitting type failure, while the specimens with bedding layers in 55°, 83° orientations were failed by sliding along a weaker bedding layer. The failure mechanism for the specimens with bedding layers in 35° orientation showed a mixed failure mode of both splitting and sliding types. Analysis of the acoustic energy, captured from the acoustic emission detection system, revealed that the acoustic energy release is considerably higher in dry specimens than that of the saturated specimens at any bedding orientation. In addition, higher energy release was observed for specimens with bedding layers oriented in shallow angles (which were undergoing splitting type failures), whereas specimens with steeply oriented bedding layers (which were undergoing sliding type failures) showed a comparatively less energy release under both dry and saturated conditions. Moreover, a considerable amount of

  1. Way and device for estimation of constructions technical state during acoustic-emission control

    OpenAIRE

    Kosenkov, I. V.

    2007-01-01

    The search urgency of new non-destructive control methods for responsible constructions is proved. An acoustic-emission responsible structures control method is suggested which is based on invariants method and Mann-Whitney U-criterion. A generalization of analytical relations for invariants method is performed. A device for estimating the constructions destruction processes during acoustic-emission control using invariants method is described.

  2. Acoustic Emission Technique for Characterizing Deformation and Fatigue Crack Growth in Austenitic Stainless Steels

    Science.gov (United States)

    Raj, Baldev; Mukhopadhyay, C. K.; Jayakumar, T.

    2003-03-01

    Acoustic emission (AE) during tensile deformation and fatigue crack growth (FCG) of austenitic stainless steels has been studied. In AISI type 316 stainless steel (SS), AE has been used to detect micro plastic yielding occurring during macroscopic plastic deformation. In AISI type 304 SS, relation of AE with stress intensity factor and plastic zone size has been studied. In AISI type 316 SS, fatigue crack growth has been characterised using acoustic emission.

  3. Correlation of infrared thermographic patterns and acoustic emission signals with tensile deformation and fracture processes

    Science.gov (United States)

    Venkataraman, B.; Raj, Baldev; Mukhopadhyay, C. K.; Jayakumar, T.

    2001-04-01

    During tensile deformation, part of the mechanical work done on the specimen is transformed into heat and acoustic activity. The amount of acoustic activity and the thermal emissions depend on the test conditions and the deformation behavior of the specimen during loading. Authors have used thermography and acoustic emission (AE) simultaneously for monitoring tensile deformation in AISI type 316 SS. Tensile testing was carried out at 298 K at three different strain rates. It has been shown that the simultaneous use of these techniques can provide complementary information for characterizing the tensile deformation and fracture processes.

  4. Effect of aluminium in propellant composition on acoustic emission parameters (Short Communication

    Directory of Open Access Journals (Sweden)

    Rm. Muthiah

    2001-04-01

    Full Text Available The study reports the variation in acoustic emission signals acquired during combustion of typical propellants with varying aluminium and ammonium perchlorate content. It was observed that when propellant strands having the same composition undergo combustion under similar conditions, they produce consistent acoustic emission signals. To study the effect of variation of aluminium content in the propellant composition on the acoustic emission produced during combustion, the aluminium content was varied from 6 per cent to 18 per cent in a HTPB-based composite propellant with 86 per cent solid loading. Experiments were carried out with propellant strands under the same conditions for a comparative study. Acoustic emission parameters, such as peak amplitude, ring-down counts, average frequency, hits and energy were studied as functions of time. Among these parameters, only energy ring-down counts and frequency varied significantly with aluminium content. The effect of cumulative values of energy, frequency and ring-down counts, the effect of burn rate and theoretical specific impulse against the aluminium percentage variation, and the variation of specific impulse against acoustic energy can all be correlated. The clear trend is indicative of possible prediction of propellant performance parameter like specific impulse from acoustic emission parameters.

  5. Evaluation of corrosion damage of aluminum alloy using acoustic emission testing

    Institute of Scientific and Technical Information of China (English)

    GENG Rongsheng; FU Gangqiang

    2004-01-01

    Current studies are aiming at monitoring corrosion damage of aircraft main structures by using acoustic emission (AE) technique and at supplying useful data for determining calendar life of the aircraft. The characteristics of AE signals produced during accelerating corrosion process are described, and methods for evaluating corrosion damages and determining remaining life of main structures of aircraft using AE testing are outlined. Experimental results have shown that AE technique can detect corrosion damage of aluminum alloy much earlier than conventional non-destructive testing means, such as ultrasonic testing and eddy current testing. Relationship between corrosion damage and AE parameters was obtained through investigating corrosion damage extent and changes of AE signals during accelerating corrosion test, and showing that AE technique can be used to detect early corrosion, investigating corrosion developing trend, and in monitoring and evaluating corrosion damages.

  6. Acoustic emission of heat treated compared graphite iron under 873-1173 K

    International Nuclear Information System (INIS)

    CGI is gaining popularity in applications that require either greater strength, or lower weight than cast iron. Recently, compacted graphite iron has been used for diesel engine blocks, turbo housings and exhaust manifolds. This paper were assessed acoustic emission characteristics according to the mechanical properties change of degraded CGI340 during 1-24 hours at 873-1173 K. In results of pencil lead fracture test, the dominant frequency and the velocity of base metal were 97 kHz and 5490 m/sec, respectively. The base metal in a tensile test was obtained relatively high dominant frequency. However, the heat treated materials, the longer the heat treatment time, the higher the heat treatment temperature, were obtained in the area of lower frequencies. This phenomenon appears by long-term use.

  7. Evaluation of PTCa/PEKK composite sensors for acoustic emission detection

    CERN Document Server

    Marin-Franch, P

    2002-01-01

    This thesis reports for the first time the fabrication and characterisation of novel electroactive ceramic/polymer composite films of calcium modified lead titanate (PTCa) and poly (ether ketone ketone). Composite sensors with different concentrations of ceramic were fabricated using a hot pressing technique. The PTCa ceramic was treated using titanate coupling agent in order to improve sample quality. Dielectric measurements have been performed to study sample characteristics. Piezoelectric and pyroelectric properties of the composites have been measured and the mixed connectivity cube model used to determine the relative amounts of 0-3 and 1-3 connectivity. The advantages and limitations of the model have been discussed. Additionally, some mechanical properties of the composites have been assessed to study their potential ability to detect acoustic emission (AE) in carbon fibre reinforced composites (CFRC). The composite sensors were placed on and inserted into different panels in order to compare their abi...

  8. Neural Network Approach to Automated Condition Classification of a Check Valve by Acoustic Emission Signals

    International Nuclear Information System (INIS)

    This paper presents new techniques under development for monitoring the health and vibration of the active components in nuclear power plants, The purpose of this study is to develop an automated system for condition classification of a check valve one of the components being used extensively in a safety system of a nuclear power plant. Acoustic emission testing for a check valve under controlled flow loop conditions was performed to detect and evaluate disc movement for valve failure such as wear and leakage due to foreign object interference in a check valve, It is clearly demonstrated that the evaluation of different types of failure types such as disc wear and check valve leakage were successful by systematically analyzing the characteristics of various AE parameters, It is also shown that the leak size can be determined with an artificial neural network

  9. Accumulated damage process of thermal sprayed coating under rolling contact by acoustic emission technique

    Science.gov (United States)

    Xu, Jia; Zhou, Zhen-yu; Piao, Zhong-yu

    2016-09-01

    The accumulated damage process of rolling contact fatigue (RCF) of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-ondisc machine was employed to conduct RCF experiments. Acoustic emission (AE) technique was introduced to monitor the RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.

  10. Relation between welding parameter and acoustic emission information during laser deep penetration welding

    Institute of Scientific and Technical Information of China (English)

    陈彦宾; 张忠典; 王欣

    2002-01-01

    In laser non-penetration deep penetration welding process, welding material will vaporize, metal vapor and ambient gas will produce a higher degree ionization, which forms plasma of high concentration. In the case of forming a small hole, plasma will eject from the hole, and form acoustic emission (AE) signals. Because AE information has many advantages such as non-contact measuring, fast response, and high ratio of signal to noise, it can be used as a monitor variable for in-process control. By studying AE information, information of welding pool and small hole can be obtained. According to characteristic of AE information, this paper reveals the correlation between welding parameters and AE signals, and provides a good base for further quality control.

  11. Acoustic emission detection of 316L stainless steel welded joints during intergranular corrosion

    Institute of Scientific and Technical Information of China (English)

    Meng-yu Chai; Quan Duan; Wen-jie Bai; Zao-xiao Zhang; Xu-meng Xie

    2015-01-01

    This study analyzes acoustic emission (AE) signals during the intergranular corrosion (IGC) process of 316L stainless steel welded joints under different welding currents in boiling nitric acid. IGC generates several AE signals with high AE activity. The AE tech-nique could hardly distinguish IGC in stainless steel welded joints with different welding heat inputs. However, AE signals can effectively distinguish IGC characteristics in different corrosion stages. The IGC resistance of a heat-affected zone is lower than that of a weld zone. The initiation and rapid corrosion stages can be distinguished using AE results and microstructural analysis. Moreover, energy count rate and am-plitude are considered to be ideal parameters for characterizing different IGC processes. Two types of signals are detected in the rapid corro-sion stage. It can be concluded that grain boundary corrosion and grain separation are the AE sources of type 1 and type 2, respectively.

  12. Influence of attenuation on acoustic emission signals in carbon fiber reinforced polymer panels.

    Science.gov (United States)

    Asamene, Kassahun; Hudson, Larry; Sundaresan, Mannur

    2015-05-01

    Influence of attenuation on acoustic emission (AE) signals in Carbon Fiber Reinforced Polymer (CFRP) crossply and quasi-isotropic panels is examined in this paper. Attenuation coefficients of the fundamental antisymmetric (A0) and symmetric (S0) wave modes were determined experimentally along different directions for the two types of CFRP panels. In the frequency range from 100 kHz to 500 kHz, the A0 mode undergoes significantly greater changes due to material related attenuation compared to the S0 mode. Moderate to strong changes in the attenuation levels were noted with propagation directions. Such mode and frequency dependent attenuation introduces major changes in the characteristics of AE signals depending on the position of the AE sensor relative to the source. Results from finite element simulations of a microscopic damage event in the composite laminates are used to illustrate attenuation related changes in modal and frequency components of AE signals.

  13. Evaluation of fatigue damage for wind turbine blades using acoustic emission

    Energy Technology Data Exchange (ETDEWEB)

    Jee, Hyun Sup; Ju, No Hoe [Korea Institute of Materials Science, Changwon (Korea, Republic of); So, Cheal Ho [Dongshin University, Naju (Korea, Republic of); Lee, Jong Kyu [Dept. of Physics, Pukyung National University, Busan (Korea, Republic of)

    2015-06-15

    In this study, the flap fatigue test of a 48 m long wind turbine blade was performed for 1 million cycles to evaluate the characteristics of acoustic emission signals generated from fatigue damage of the wind blades. As the number of hits and total energy continued to increase during the first 0.6 million cycles, blade damage was constant. The rise-time result showed that the major aspects of damage were initiation and propagation of matrix cracks. In addition, the signal analysis of each channel showed that the most seriously damaged sections were the joint between the skin and spar, 20 m from the connection, and the spot of actual damage was observable by visual inspection. It turned out that the event source location was related to the change in each channel{sup s} total energy. It is expected that these findings will be useful for the optimal design of wind turbine blades.

  14. Relationship between geometric welding parameters and optical-acoustic emissions from electric arc in GMAW-S process

    Directory of Open Access Journals (Sweden)

    E. Huanca Cayo

    2011-05-01

    Full Text Available Purpose: Show the relationship between geometric characteristics of the weld bead and the optical-acoustic emissions from electric arc during welding in the GMAW-S process.Design/methodology/approach: Bead on plate welding experiments was carried out setting different process parameters. Every welding parameter group was set aiming to reach a high stability level what guarantee a geometrical uniformity in the weld beads. In each experiment was simultaneously acquired arc voltage, welding current, infrared and acoustic emissions; from them were computed parameters as arc power, acoustic peaks rate and infrared radiation rate. It was used a tri-dimensional LASER scanner for to acquire geometrical information from the weld beads surface as width and height of the bead. Depth penetration was measured from sectional cross cutting of weld beads.Findings: Previous analysis showed that the arc emission parameters reach a stationary state with different characteristic for each experiment group which means that there is some correlation level between them. Posterior analysis showed that from infrared parameter is possible to monitoring external weld bead geometry and principally its penetration depth. From acoustic parameter is possible to monitoring principally the external weld bead geometry. Therefore is concluded that there is a close relation between the arc emissions and the weld bead geometry and that them could be used to measuring the welding geometrical parameters.Research limitations/implications: After analysis it was noticed that the infrared sensing has a better performance than acoustic sensing in the depth penetration monitoring. Infrared sensing also sources some information about external geometric parameters that in conjunction with the acoustic sensing is possible to have reliable information about weld bead geometry. This method of sensing geometric parameters could be applied in other welding processes, but is necessary to have

  15. A Study on the Evaluation of Valve Leak Rates Using Acoustic Emission Technique

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Guk; Lee, Jun Shin; Lee, Sun Ki; Shon, Seok Man; Lee, Wook Ryun; Kim, Tae Ryong [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Lim, Yong Jae; Choo, Kee Young [Hana Evertech Co., Seongnam (Korea, Republic of)

    2005-07-01

    The objective of this study is to estimate the feasibility of acoustic emission method for the internal leak from the valves. In this study, two types of valve(a 3 1/2 inch glove valve for 600 psi steam and a 4 inch ball valve water ) leak tests using three different leak path and numerous leak rates were performed in order to analyze acoustic emission properties when leaks arise in valve seat. As a result of leak test for specimens simulated valve seat, we conformed that leak sound amplitude increased in proportion to the increase of leak rate, and leak rates were plotted versus peak acoustic amplitudes recorded within those two narrow frequency bands on each spectral plot. The resulting plots of leak rate versus peak acoustic amplitude were the primary basis for determining the feasibility of quantifying leak acoustically. The large amount of data collected also allowed a grief investigation of the effects of different leak paths, leakage rates, pressure differentials and transducers on the acoustic amplitude spectra. From the experimental results, it was suggested that the acoustic emission method for monitoring of leak was feasible.

  16. Acoustic characteristics of bubble bursting at the surface of a high-viscosity liquid

    Institute of Scientific and Technical Information of China (English)

    Liu Xiao-Bo; Zhang Jian-Run; Li Pu

    2012-01-01

    An acoustic pressure model of bubble bursting is proposed.An experiment studying the acoustic characteristics of the bursting bubble at the surface of a high-viscosity liquid is reported.It is found that the sudden bursting of a bubble at the high-viscosity liquid surface generates N-shape wave at first,then it transforms into a jet wave.The fundamental frequency of the acoustic signal caused by the bursting bubble decreases linearly as the bubble size increases.The results of the investigation can be used to understand the acoustic characteristics of bubble bursting.

  17. Fatigue and fracture assessment of cracks in steel elements using acoustic emission

    Science.gov (United States)

    Nemati, Navid; Metrovich, Brian; Nanni, Antonio

    2011-04-01

    Single edge notches provide a very well defined load and fatigue crack size and shape environment for estimation of the stress intensity factor K, which is not found in welded elements. ASTM SE(T) specimens do not appear to provide ideal boundary conditions for proper recording of acoustic wave propagation and crack growth behavior observed in steel bridges, but do provide standard fatigue crack growth rate data. A modified versions of the SE(T) specimen has been examined to provide small scale specimens with improved acoustic emission(AE) characteristics while still maintaining accuracy of fatigue crack growth rate (da/dN) versus stress intensity factor (ΔK). The specimens intend to represent a steel beam flange subjected to pure tension, with a surface crack growing transverse to a uniform stress field. Fatigue test is conducted at low R ratio. Analytical and numerical studies of stress intensity factor are developed for single edge notch test specimens consistent with the experimental program. ABAQUS finite element software is utilized for stress analysis of crack tips. Analytical, experimental and numerical analysis were compared to assess the abilities of AE to capture a growing crack.

  18. Comparative Analysis on Dynamic Split Characteristics of Natural and Water Saturated Concretes Based on Acoustic Emission%基于声发射的自然与饱水状态混凝土动态劈拉特性对比

    Institute of Scientific and Technical Information of China (English)

    邹三兵; 杨乃鑫; 罗曦; 彭刚

    2016-01-01

    Radial splitting tensile tests for natural and water saturated concrete specimens with size ofΦ150×150mm was carried out under different strain rates( 10-5 ,10-4 ,10-3 and 10-2 s-1 ) . Splitting tensile strength of concrete was analyzed in detail, and energy release characteristics and damage law of natural and water saturated concretes were researched in the whole process of splitting tensile damage by real⁃time acoustic emission data. The results show that:1) with the increase of loading rate ,splitting tensile strength of natural and water saturated concretes increa⁃ses;2 ) at low strain rates ( 10-5 , 10-4 and 10-3/s ) , the splitting tensile strength of water saturated concrete is smaller than that of natural concrete due to the wedging action of free water, whereas at the strain rate of 10-2/s, the splitting tensile strength of water saturated concrete is larger than that of natural concrete due to Stefan effect;3) dynamic enhancement factor of water saturated concrete is larger than that of natural concrete, and strain rate sensitivity of water saturated concrete is more obvious;4) acoustic emission signal characteristics is in accordance with concrete failure characteristics, and acoustic emission data can be used to accurately monitor the process of concrete splitting tensile failure.%为研究自然状态与饱水状态混凝土的动态劈拉特性,进行了不同应变速率(10-5/s ,10-4/s ,10-3/s ,10-2/s)下的径向劈拉试验,对混凝土劈拉强度进行了深入分析,并利用实时采集的声发射数据分析自然状态与饱水状态混凝土在劈拉破坏全过程中的能量释放特性及破坏规律。结果表明:自然状态和饱水状态混凝土的劈拉强度随加载速率的增加而增大。在低应变速率(10-5/s,10-4/s和10-3/s)时,由于自由水的楔入作用,饱水状态混凝土的劈拉强度比自然状态混凝土的劈拉强度小;在应变速率为10

  19. Acoustic emissions in rock deformation experiments under micro-CT

    Science.gov (United States)

    Tisato, Nicola; Goodfellow, Sebastian D.; Moulas, Evangelos; Di Toro, Giulio; Young, Paul; Grasselli, Giovanni

    2016-04-01

    The study of acoustic emissions (AE) generated by rocks undergoing deformation has become, in the last decades, one of the most powerful tools for boosting our understanding of the mechanisms which are responsible for rock failures. AE are elastic waves emitted by the local failure of micro- or milli-metric portions of the tested specimen. At the same time, X-ray micro computed tomography (micro-CT) has become an affordable, reliable and powerful tool for imaging the internal structure of rock samples. In particular, micro-CT coupled with a deformation apparatus offers the unique opportunity for observing, without perturbing, the sample while the deformation and the formation of internal structures, such as shear bands, is ongoing. Here we present some preliminary results gathered with an innovative apparatus formed by the X-ray transparent pressure vessel called ERDμ equipped with AE sensors, an AE acquisition system and a micro-CT apparatus available at the University of Toronto. The experiment was performed on a 12 mm diameter 36 mm long porous glass sample which was cut on a 60 deg inclined plane (i.e. saw-cut sample). Etna basaltic sand with size ~1 mm was placed between the two inclined faces forming an inclined fault zone with ~2 mm thickness. The sample assembly was jacketed with a polyefin shrink tube and two AE sensors were glued onto the glass samples above and below the fault zone. The sample was then enclosed in the pressure vessel and confined with compressed air up to 3 MPa. A third AE sensor was placed outside the vessel. The sample was saturated with water and AE were generated by varying the fluid and confining pressure or the vertical force, causing deformations concentrated in the fault zone. Mechanical data and AE traces were collected throughout the entire experiment which lasted ~24 hours. At the same time multiple micro-CT 3D datasets and 2D movie-radiographies were collected, allowing the 3D reconstruction of the deformed sample at

  20. Uniaxial compression CT and acoustic emission test on the coal crack propagation destruction process

    Institute of Scientific and Technical Information of China (English)

    Jing-hong LIU; Yao-dong JIANG; Yi-xin ZHAO; Jie ZHU

    2013-01-01

    Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation.A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission.The test comparison analyzes the acoustic emission load and CT images for an effective observation on the entire process,from crack propagation to the samples' destruction.The box dimension of the coal samples' acoustic emission series and the CT images were obtained through calculations by using the authors' own program.The results show that the fractal dimension of both the acoustic emission energy and CT image increase rapidly,indicating coal and rock mass has entered a dangerous condition.Hence,measures should be taken to unload the pressure of the coal and rock mass.The test results provide intuitive observation data for the coal meso-damage model.The test contributes to in-depth studies of coal or rock crack propagation mechanisms and provides a theoretical basis for rock burst mechanism.

  1. An investigation of the acoustic characteristics of a compression ignition engine operating with biodiesel blends

    International Nuclear Information System (INIS)

    In this paper, an experimental investigation has been carried out on the acoustic characteristics of a compression ignition (CI) engine running with biodiesel blends under steady state operating conditions. The experiment was conducted on a four-cylinder, four-stroke, direct injection and turbocharged diesel engine which runs with biodiesel (B50 and B100) and pure diesel. The signals of acoustic, vibration and in-cylinder pressure were measured during the experiment. To correlate the combustion process and the acoustic characteristics, both phenomena have been investigated. The acoustic analysis resulted in the sound level being increased with increasing of engine loads and speeds as well as the sound characteristics being closely correlated to the combustion process. However, acoustic signals are highly sensitive to the ambient conditions and intrusive background noise. Therefore, the spectral subtraction was employed to minimize the effects of background noise in order to enhance the signal to noise ratio. In addition, the acoustic characteristics of CI engine running with different fuels (biodiesel blends and diesel) was analysed for comparison. The results show that the sound energy level of acoustic signals is slightly higher when the engine fuelled by biodiesel and its blends than that of fuelled by normal diesel. Hence, the acoustic characteristics of the CI engine will have useful information for engine condition monitoring and fuel content estimation.

  2. Fatigue crack growth monitoring of idealized gearbox spline component using acoustic emission

    Science.gov (United States)

    Zhang, Lu; Ozevin, Didem; Hardman, William; Kessler, Seth; Timmons, Alan

    2016-04-01

    The spline component of gearbox structure is a non-redundant element that requires early detection of flaws for preventing catastrophic failures. The acoustic emission (AE) method is a direct way of detecting active flaws; however, the method suffers from the influence of background noise and location/sensor based pattern recognition method. It is important to identify the source mechanism and adapt it to different test conditions and sensors. In this paper, the fatigue crack growth of a notched and flattened gearbox spline component is monitored using the AE method in a laboratory environment. The test sample has the major details of the spline component on a flattened geometry. The AE data is continuously collected together with strain gauges strategically positions on the structure. The fatigue test characteristics are 4 Hz frequency and 0.1 as the ratio of minimum to maximum loading in tensile regime. It is observed that there are significant amount of continuous emissions released from the notch tip due to the formation of plastic deformation and slow crack growth. The frequency spectra of continuous emissions and burst emissions are compared to understand the difference of sudden crack growth and gradual crack growth. The predicted crack growth rate is compared with the AE data using the cumulative AE events at the notch tip. The source mechanism of sudden crack growth is obtained solving the inverse mathematical problem from output signal to input signal. The spline component of gearbox structure is a non-redundant element that requires early detection of flaws for preventing catastrophic failures. In this paper, the fatigue crack growth of a notched and flattened gearbox spline component is monitored using the AE method The AE data is continuously collected together with strain gauges. There are significant amount of continuous emissions released from the notch tip due to the formation of plastic deformation and slow crack growth. The source mechanism of

  3. Monitoring of pipeline hydrostatic testing with artificial flaws applying acoustic emission and ultra-sonic techniques; Monitoracao de teste hidrostatico de tubos com descontinuidades artificiais empregando as tecnicas de emissao acustica e ultra-som

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Sergio Damasceno [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

    2003-07-01

    Charts and parameters used to perform and analyzing the acoustic emission data collected during the hydrostatic test in pipe samples build in API XL 60 with 20 inches of diameter and 14 millimeters of thickness are shown. These pipes had internal and external artificial flaws done by electro-erosion process with aspect ratio 1 x 20. A relationship between acoustic emission results, ultrasound and J-Integral were established using the applied pressurization sequence. Characteristics values of acoustic emission signals were shown as a criteria of field tests. (author)

  4. Characterization by acoustic emission and electrochemical impedance spectroscopy of the cathodic disbonding of Zn coating

    Energy Technology Data Exchange (ETDEWEB)

    Amami, Souhail [Universite de Technologie de Compiegne, Departement de Genie Mecanique, Laboratoire Roberval, UMR 6066 du CNRS, B.P. 20529, 60206 Compiegne Cedex (France)], E-mail: souhail.amami@utc.fr; Lemaitre, Christian; Laksimi, Abdelouahed; Benmedakhene, Salim [Universite de Technologie de Compiegne, Departement de Genie Mecanique, Laboratoire Roberval, UMR 6066 du CNRS, B.P. 20529, 60206 Compiegne Cedex (France)

    2010-05-15

    Galvanized steel has been tested in a synthetic sea water solution under different cathodic overprotection conditions. The generated hydrogen flux caused the damage of the metal-zinc interface and led to a progressive coating detachment. Scanning electron microscopy, electrochemical impedance spectroscopy and acoustic emission technique were used to characterize the damage chronology under different cathodic potentials. A damage mechanism was proposed and the acoustic signature related to the coating degradation was statistically identified using clustering techniques.

  5. Combining Passive Thermography and Acoustic Emission for Large Area Fatigue Damage Growth Assessment of a Composite Structure

    Science.gov (United States)

    Zalameda, Joseph N.; Horne, Michael R.; Madaras, Eric I.; Burke, Eric R.

    2016-01-01

    Passive thermography and acoustic emission data were obtained for improved real time damage detection during fatigue loading. A strong positive correlation was demonstrated between acoustic energy event location and thermal heating, especially if the structure under load was nearing ultimate failure. An image processing routine was developed to map the acoustic emission data onto the thermal imagery. This required removing optical barrel distortion and angular rotation from the thermal data. The acoustic emission data were then mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. This technology provides improved real time inspections of advanced composite structures during fatigue testing.Keywords: Thermal nondestructive evaluation, fatigue damage detection, aerospace composite inspection, acoustic emission, passive thermography

  6. Aespoe Pillar Stability Experiment. Acoustic emission and ultrasonic monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Haycox, Jon; Pettitt, Will; Young, R. Paul [Applied Seismology Consultants Ltd., Shrewsbury (United Kingdom)

    2005-12-15

    This report describes the results from acoustic emission (AE) and ultrasonic monitoring of the Aespoe Pillar Stability Experiment (APSE) at SKB's Hard Rock Laboratory (HRL), Sweden. The APSE is being undertaken to demonstrate the current capability to predict spalling in a fractured rock mass using numerical modelling techniques, and to demonstrate the effect of backfill and confining pressure on the propagation of micro-cracks in rock adjacent to deposition holes within a repository. An ultrasonic acquisition system has provided acoustic emission and ultrasonic survey monitoring throughout the various phases of the experiment. Results from the entire data set are provided with this document so that they can be effectively compared to several numerical modelling studies, and to mechanical and thermal measurements conducted around the pillar volume, in an 'integrated analysis' performed by SKB staff. This document provides an in-depth summary of the AE and ultrasonic survey results for future reference. The pillar has been produced by excavating two 1.8 m diameter deposition holes 1 m apart. These were bored in 0.8 m steps using a Tunnel Boring Machine specially adapted for vertical drilling. The first deposition hole was drilled in December 2003. Preceding this a period of background monitoring was performed so as to obtain a datum for the results. The hole was then confined to 0.7 MPa internal over pressure using a specially designed water-filled bladder. The second deposition hole was excavated in March 2004. Heating of the pillar was performed over a two month period between ending in July 2004, when the confined deposition hole was slowly depressurised. Immediately after depressurisation the pillar was allowed to cool with cessation of monitoring occurring a month later. A total of 36,676 AE triggers were recorded over the reporting period between 13th October 2003 and 14th July 2004. Of these 15,198 have produced AE locations. The AE data set

  7. Acoustic emission (AE) health monitoring of diaphragm type couplings using neural network analysis

    Science.gov (United States)

    Godinez-Azcuaga, Valery F.; Shu, Fong; Finlayson, Richard D.; O'Donnell, Bruce

    2005-05-01

    This paper presents the latest results obtained from Acoustic Emission (AE) monitoring and detection of cracks and/or damage in diaphragm couplings, which are used in some aircraft and engine drive systems. Early detection of mechanical failure in aircraft drive train components is a key safety and economical issue with both military and civil sectors of aviation. One of these components is the diaphragm-type coupling, which has been evaluated as the ideal drive coupling for many application requirements such as high speed, high torque, and non-lubrication. Its flexible axial and angular displacement capabilities have made it indispensable for aircraft drive systems. However, diaphragm-type couplings may develop cracks during their operation. The ability to monitor, detect, identify, and isolate coupling cracks on an operational aircraft system is required in order to provide sufficient advance warning to preclude catastrophic failure. It is known that metallic structures generate characteristic Acoustic Emission (AE) during crack growth/propagation cycles. This phenomenon makes AE very attractive among various monitoring techniques for fault detection in diaphragm-type couplings. However, commercially available systems capable of automatic discrimination between signals from crack growth and normal mechanical noise are not readily available. Positive classification of signals requires experienced personnel and post-test data analysis, which tend to be a time-consuming, laborious, and expensive process. With further development of automated classifiers, AE can become a fully autonomous fault detection technique requiring no human intervention after implementation. AE has the potential to be fully integrated with automated query and response mechanisms for system/process monitoring and control.

  8. The application of the acoustic emission technique to stone decay by sodium sulphate in laboratory tests

    Directory of Open Access Journals (Sweden)

    Grossi, C. M.

    1997-03-01

    Full Text Available Acoustic emission was monitored during salt crystallisation cycles in order to study the mechanisms of rock deterioration by sodium sulphate in laboratory tests. Some porous carbonate stones used in Spanish monuments (Cathedral of Oviedo, Murcia and Seo Vella of Lérida were selected for this study. The acoustic emission detected during the different stages of the cycles (immersion, drying and cooling was interpreted to be the result of the salt behaviour inside the stone. The use of this technique has confirmed that this behaviour depends on salt characteristics (solubility, hydration state and polymorphism of anhydrous sodium sulphate and stone porosity and pore network.

    Para determinar los mecanismos de deterioro de las rocas debidos a la acción del sulfato de sodio, se ha registrado la emisión acústica durante ensayos de cristalización de sales en el laboratorio. Para ello, se han seleccionado tres piedras porosas carbonatadas utilizadas como materiales de construcción en monumentos españoles (Catedrales de Oviedo, Murcia y Seo Vella de Lérida. La emisión acústica detectada durante las diferentes etapas de los ciclos (inmersión, secado y enfriamiento se ha interpretado como debida al comportamiento de la sal en el interior de la piedra. Mediante esta técnica se ha confirmado que este comportamiento depende de las características de la sal (solubilidad, diferentes estados de hidratación y el polimorfismo del sulfato de sodio anhidro y de la porosidad y configuración del sistema poroso de las rocas.

  9. Initiation of acoustic emission in fluid-saturated sandstone samples

    Science.gov (United States)

    Lapshin, V. B.; Patonin, A. V.; Ponomarev, A. V.; Potanina, M. G.; Smirnov, V. B.; Stroganova, S. M.

    2016-07-01

    A rock behavior experiment with uniaxial compression revealed the effect of acoustic activity in loaded fluid-saturated Berea sandstone samples in response to an electric current. It is established that it is substantially intensified in periods of the current impact and decreases after its cut-off. The current impact also results in a growth of radial deformation indicating an increase in the sample volume. The effect of acoustic activation increases in response to increased heat emitted by the electric current during its flow through the sample, which allows the discovered effect to be explained by initiation of its destruction due to thermal expansion of the fluid in rock interstices and fissures.

  10. The application of Shuffled Frog Leaping Algorithm to Wavelet Neural Networks for acoustic emission source location

    Science.gov (United States)

    Cheng, Xinmin; Zhang, Xiaodan; Zhao, Li; Deng, Aideng; Bao, Yongqiang; Liu, Yong; Jiang, Yunliang

    2014-04-01

    When using acoustic emission to locate the friction fault source of rotating machinery, the effects of strong noise and waveform distortion make accurate locating difficult. Applying neural network for acoustic emission source location could be helpful. In the BP Wavelet Neural Network, BP is a local search algorithm, which falls into local minimum easily. The probability of successful search is low. We used Shuffled Frog Leaping Algorithm (SFLA) to optimize the parameters of the Wavelet Neural Network, and the optimized Wavelet Neural Network to locate the source. After having performed the experiments of friction acoustic emission's source location on the rotor friction test machine, the results show that the calculation of SFLA is simple and effective, and that locating is accurate with proper structure of the network and input parameters.

  11. Acoustic emission technique based rubbing identification for Rotor-bearing systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Rubbing is the frequent and dangerous fault in the rotating machine, and efficient identi-fication of the rubbing is a hot research subject in the field of fault diagnosis. In this paper, a newrubbing identification method is proposed, which is based on the acoustic emission technique. Inthis method, the acoustic emission signal of the rubbing in the multi-support rotor-bearing systemis acquired by the acoustic emission sensor, and then the continuous wavelet transform is utilizedto analyze this signal. Based on the rubbing mechanism, the frequency feature of the multiple fre-quency relation in the instantaneous frequency wave is extracted as the rubbing identification fea-ture. The experimental results prove that the proposed method is efficient and feasible.

  12. Acoustic emission partial discharge detection technique applied to fault diagnosis: Case studies of generator transformers

    Directory of Open Access Journals (Sweden)

    Shanker Tangella Bhavani

    2016-01-01

    Full Text Available In power transformers, locating the partial discharge (PD source is as important as identifying it. Acoustic Emission (AE sensing offers a good solution for both PD detection and PD source location identification. In this paper the principle of the AE technique, along with in-situ findings of the online acoustic emission signals captured from partial discharges on a number of Generator Transformers (GT, is discussed. Of the two cases discussed, the first deals with Acoustic Emission Partial Discharge (AEPD tests on two identical transformers, and the second deals with the AEPD measurement of a transformer carried out on different occasions (years. These transformers are from a hydropower station and a thermal power station in India. Tests conducted in identical transformers give the provision for comparing AE signal amplitudes from the two transformers. These case studies also help in comprehending the efficacy of integrating Dissolved Gas is (DGA data with AEPD test results in detecting and locating the PD source.

  13. Surface Roughness Evaluation Based on Acoustic Emission Signals in Robot Assisted Polishing

    Directory of Open Access Journals (Sweden)

    Beatriz de Agustina

    2014-11-01

    Full Text Available The polishing process is the most common technology used in applications where a high level of surface quality is demanded. The automation of polishing processes is especially difficult due to the high level of skill and dexterity that is required. Much of this difficulty arises because of the lack of reliable data on the effect of the polishing parameters on the resulting surface roughness. An experimental study was developed to evaluate the surface roughness obtained during Robot Assisted Polishing processes by the analysis of acoustic emission signals in the frequency domain. The aim is to find out a trend of a feature or features calculated from the acoustic emission signals detected along the process. Such an evaluation was made with the objective of collecting valuable information for the establishment of the end point detection of polishing process. As a main conclusion, it can be affirmed that acoustic emission (AE signals can be considered useful to monitor the polishing process state.

  14. Acoustic characteristics of the flow over different shapes of nozzle chevrons,

    Directory of Open Access Journals (Sweden)

    Daniel CRUNTEANU

    2013-09-01

    Full Text Available The objective of this paper is to present a comparison between different types of chevrons and their influence on the acoustic power level radiated by the flow over them. The comparison was performed using a two-dimensional simulation of the flow over four different shapes of chevrons resulting propagation of the acoustic waves for each shape. Acoustic characteristics were revealed studying the main flow parameters (pressure, velocity, kinetic energy in order to be able to discover the most efficient shape of chevron regarding the acoustic power level emitted.

  15. Quantitative Analysis Of Acoustic Emission From Rock Fracture Experiments

    Science.gov (United States)

    Goodfellow, Sebastian David

    This thesis aims to advance the methods of quantitative acoustic emission (AE) analysis by calibrating sensors, characterizing sources, and applying the results to solve engi- neering problems. In the first part of this thesis, we built a calibration apparatus and successfully calibrated two commercial AE sensors. The ErgoTech sensor was found to have broadband velocity sensitivity and the Panametrics V103 was sensitive to surface normal displacement. These calibration results were applied to two AE data sets from rock fracture experiments in order to characterize the sources of AE events. The first data set was from an in situ rock fracture experiment conducted at the Underground Research Laboratory (URL). The Mine-By experiment was a large scale excavation response test where both AE (10 kHz - 1 MHz) and microseismicity (MS) (1 Hz - 10 kHz) were monitored. Using the calibration information, magnitude, stress drop, dimension and energy were successfully estimated for 21 AE events recorded in the tensile region of the tunnel wall. Magnitudes were in the range -7.5 triaxial deformation experiment, where the objectives were to characterize laboratory AE sources and identify issues related to moving the analysis from ideal in situ conditions to more complex laboratory conditions in terms of the ability to conduct quantitative AE analysis. We found AE magnitudes in the range -7.8 limited knowledge of attenuation which we proved was continuously evolving, (2) the use of a narrow frequency band for acquisition, (3) the inability to identify P and S waves given the small sample size, and (4) acquisition using a narrow amplitude range given a low signal to noise ratio. Moving forward to the final stage of this thesis, with the ability to characterize the sources of AE, we applied our method to study an engineering problem. We chose hydraulic fracturing because of its obvious importance in the future of Canadian energy production. During a hydraulic fracture treatment

  16. Application of acoustic emission testing as a non-destructive quality control of conrete

    International Nuclear Information System (INIS)

    The time dependence of texture changes in concrete is studied in short-time pressure experiments, using the method of acoustic emission testing. These investigations have been performed as a function of strength and composition of the material under study. As a result, the method of acoustic emission testing is shown to be an adequate method to evaluate the evolution and the character of the structural changes. In the case where only the time developement is of interest, a simple electronic method, the pulse-sum-method or pulse rate method can be applied. However only a signal evaluation procedure can give information on the character of the structure changes. (orig./RW)

  17. Acoustic emission localization on ship hull structures using a deep learning approach

    DEFF Research Database (Denmark)

    Georgoulas, George; Kappatos, Vassilios; Nikolakopoulos, George

    In this paper, deep belief networks were used for localization of acoustic emission events on ship hull structures. In order to avoid complex and time consuming implementations, the proposed approach uses a simple feature extraction module, which significantly reduces the extremely high dimension......In this paper, deep belief networks were used for localization of acoustic emission events on ship hull structures. In order to avoid complex and time consuming implementations, the proposed approach uses a simple feature extraction module, which significantly reduces the extremely high...

  18. Acoustic emission measurements of PWR weld material with inserted defects using advanced instrumentation

    International Nuclear Information System (INIS)

    Twenty-one steel tensile specimens containing realistic welding defects have been monitored for acoustic emission during loading to failure. A new design of broad frequency bandwidth point contact transducer was used and the resulting signal captured using a high speed transient recording system. The data was analysed using the techniques of statistical pattern recognition to separate different types of signals. The results show that it is possible to separate true acoustic emission from background noise and to distinguish between certain types of defect. (author)

  19. Transmission Characteristics in Tubular Acoustic Metamaterials Studied with Fluid Impedance Theory

    Institute of Scientific and Technical Information of China (English)

    FAN Li; ZHANG Shu-Yi; ZHANG Hui

    2011-01-01

    Tubular acoustic metamaterials with negative densities composed of periodical membranes set up along pipes are studied with the fluid impedance theory. In addition to the conventional forbidden bands induced by the Bragg-scattering due to the periodic distributions of different acoustic impedances, the low-frequency forbidden band (LFB) with the low-frequency limit of zero Hertz is studied, in which the LFB is explained with acoustic impedance matching and the Bloch theory. Furthermore, the influences of the structural parameters of the tubular acoustic metamaterials on the transmission characteristics, such as the transmission coefficients, dispersion curves, widths of forbidden and pass bands, fluctuations in pass bands, etc., are evaluated, which can be used in the optimization of the acoustic insulation ability of the metamaterials.%Tubular acoustic metamaterials with negative densities composed of periodical membranes set up along pipes are studied with the fluid impedance theory.In addition to the conventional forbidden bands induced by the Bragg-scattering due to the periodic distributions of different acoustic impedances,the low-frequency forbidden band (LFB) with the low-frequency limit of zero Hertz is studied,in which the LFB is explained with acoustic impedance matching and the Bloch theory.Furthermore,the influences of the structural parameters of the tubular acoustic metamaterials on the transmission characteristics,such as the transmission coefficients,dispersion curves,widths of forbidden and pass bands,fluctuations in pass bands,etc.,are evaluated,which can be used in the optimization of the acoustic insulation ability of the metamaterials.Like electromagnetic metamaterials,acoustic metamaterials have been presented with different structures,which have negative constitutive parameters of acoustic propagation and can realize unique acoustic characteristics and applications.[1-5] Recently,acoustic metamaterials were introduced into acoustic resonance

  20. Identifying co-located acoustic emissions with highly correlated waveforms during stick-slip experiments

    Science.gov (United States)

    Goebel, T. H.; Zechar, J. D.; Becker, T. W.; Dresen, G. H.

    2012-12-01

    Repeating earthquakes, which may result from the repeated failure of strong fault patches, could help advance the understanding of structural differences of faults. They also provide a framework to test basic assumptions in earthquake physics and to quantify earthquake predictability. Our current efforts concentrate on a broadening of the understanding of micro-seismicity characteristics and its relation to fault structure and larger magnitude seismic events. In this study, we consider the possibly smallest repeating earthquakes: those generated in a laboratory setting. We present results from stick-slip experiments conducted on saw-cut surfaces with different roughness. During these tests we identified repeating acoustic emissions (AEs), i.e, largely co-located AEs with highly similar waveforms, and relate them to the difference in roughness of a particular surfaces. For these test we used three homogeneous Westerly granite cores that were pre-cut at a 30 degree angle to the loading axis. The saw-cuts were ground to be largely parallel and to create a specific roughness using silicon-carbide abrasives with different grain-sizes. We loaded the so prepared surfaces axially at a confining pressure of 120 to 150 MPa until several (up to 7) stick-slips occurred and recorded mechanical data and AEs, including full waveforms. AE locations were determined using automatically-picked first-arrival times of a 14 channel miniature seismic array. The location uncertainty was between 1-4 mm. In identifying repeating AEs, we conducted a systematic sensitivity analysis. Initially, we only imposed constrains on waveforms similarity and tested the influence of distance-constrains on the identification process. For a more restrictive choice of cross-correlation coefficient and correlation windows, the size of clusters did not grow above twice the approximate uncertainties of acoustic emission locations. Thus, repeating AEs identified with our algorithm are representative of tectonic

  1. Experimental observation of acoustic emissions generated by a pulsed proton beam from a hospital-based clinical cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Kevin C.; Solberg, Timothy D.; Avery, Stephen, E-mail: Stephen.Avery@uphs.upenn.edu [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Vander Stappen, François; Janssens, Guillaume; Prieels, Damien [Ion Beam Applications SA, Louvain-la-Neuve 1348 (Belgium); Bawiec, Christopher R.; Lewin, Peter A. [School of Biomedical Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Sehgal, Chandra M. [Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2015-12-15

    Purpose: To measure the acoustic signal generated by a pulsed proton spill from a hospital-based clinical cyclotron. Methods: An electronic function generator modulated the IBA C230 isochronous cyclotron to create a pulsed proton beam. The acoustic emissions generated by the proton beam were measured in water using a hydrophone. The acoustic measurements were repeated with increasing proton current and increasing distance between detector and beam. Results: The cyclotron generated proton spills with rise times of 18 μs and a maximum measured instantaneous proton current of 790 nA. Acoustic emissions generated by the proton energy deposition were measured to be on the order of mPa. The origin of the acoustic wave was identified as the proton beam based on the correlation between acoustic emission arrival time and distance between the hydrophone and proton beam. The acoustic frequency spectrum peaked at 10 kHz, and the acoustic pressure amplitude increased monotonically with increasing proton current. Conclusions: The authors report the first observation of acoustic emissions generated by a proton beam from a hospital-based clinical cyclotron. When modulated by an electronic function generator, the cyclotron is capable of creating proton spills with fast rise times (18 μs) and high instantaneous currents (790 nA). Measurements of the proton-generated acoustic emissions in a clinical setting may provide a method for in vivo proton range verification and patient monitoring.

  2. Influence of a single lightning on the intensity of an air electric field and acoustic emission of near surface rocks

    Directory of Open Access Journals (Sweden)

    S. E. Smirnov

    2012-06-01

    Full Text Available The effect of a single lightning discharge on electric field intensity in the near ground atmosphere was investigated. The effect appeared as a sharp fall of electric field potential gradient from 80 V m−1 up to −21 V m−1. The process of intensity recovery is described by flat capacitor model with characteristic time of recovery of 17 c. Simultaneously with electric field, the acoustic emission response in the near surface rocks on lightning discharge was registered in the frequency range of 6.5–11 kHz.

  3. Influence of a single lightning on the intensity of an air electric field and acoustic emission of near surface rocks

    OpenAIRE

    Smirnov, S. E.; Marapulets, Y. V.

    2012-01-01

    The effect of a single lightning discharge on electric field intensity in the near ground atmosphere was investigated. The effect appeared as a sharp fall of electric field potential gradient from 80 V m−1 up to −21 V m−1. The process of intensity recovery is described by flat capacitor model with characteristic time of recovery of 17 c. Simultaneously with electric field, the acoustic emission response in the near surface rocks on lightning disch...

  4. Correlated terahertz acoustic and electromagnetic emission in dynamically screened InGaN/GaN quantum wells

    NARCIS (Netherlands)

    van Capel, P.J.S.; Turchinovich, D.; Porte, H.P.; Lahmann, S.; Rossow, U.; Dijkhuis, J.I.

    2011-01-01

    We investigate acoustic and electromagnetic emission from optically excited strained piezoelectric In0.2Ga0.8N/GaN multiple quantum wells (MQWs), using optical pump-probe spectroscopy, time-resolved Brillouin scattering, and THz emission spectroscopy. A direct comparison of detected acoustic signals

  5. Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation

    DEFF Research Database (Denmark)

    Lura, Pietro; Couch, J.; Jensen, Ole Mejlhede;

    2009-01-01

    . According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs...

  6. Analysis of Acoustic Emission Characteristics on Different Sampling Direction of Steel Plate%不同取样方向钢板试件的声发射特性分析

    Institute of Scientific and Technical Information of China (English)

    谢志龙; 闫小青; 扶名福; 樊保圣

    2011-01-01

    For tensile test,standard tensile samples were intercepted from ST 13 cold-rolled along 0 ° ,45 ° and 90 °direction, respectively. Combined with the mechanical properties of metal materials, the characterization, idenficai and differences of acoustic emissian (AE) parameters were analyzed in the tensile process of specimens. The resuits can be concluded as follows: the AE parameter, such as counting, amplitude and energy can token the damage process. The 0° direction specimen have higher intensity, elongation and fracture energy, the 90° direction specimen take second place, the 45° direction specimen have lower intensity ,elongation and fracture energy.%从ST13冷轧钢板中分别沿0.方向、45.方向和90°方向截取标准拉伸试样进行拉伸试验.结合金属材料的力学性能,分析试件在拉伸过程中声发射参数的表征和特性,以及在拉伸过程中声发射特征参数的异同性.结果表明:声发射计数、幅值和能量能较好地表征试件的整个拉伸过程,并得出0.方向钢板试件强度高,伸长率大,断裂能量大,90°方向次之,45.方向强度低,伸长率小,断裂能量小.

  7. Acoustic emission from magnetic flux tubes in the solar network

    CERN Document Server

    Vigeesh, G

    2013-01-01

    We present the results of three-dimensional numerical simulations to investigate the excitation of waves in the magnetic network of the Sun due to footpoint motions of a magnetic flux tube. We consider motions that typically mimic granular buffeting and vortex flows and implement them as driving motions at the base of the flux tube. The driving motions generates various MHD modes within the flux tube and acoustic waves in the ambient medium. The response of the upper atmosphere to the underlying photospheric motion and the role of the flux tube in channeling the waves is investigated. We compute the acoustic energy flux in the various wave modes across different boundary layers defined by the plasma and magnetic field parameters and examine the observational implications for chromospheric and coronal heating.

  8. Real-Time Source Classification with an Waveform Parameter Filtering of Acoustic Emission Signals

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seung Hyun; Park, Jae Ha; Ahn, Bong Young [Chonnam National University, Gwangju (Korea, Republic of)

    2011-04-15

    The acoustic emission(AE) technique is a well established method to carry out structural health monitoring(SHM) of large structures. However, the real-time monitoring of the crack growth in the roller coaster support structures is not easy since the vehicle operation produces very large noise as well as crack growth. In this investigation, we present the waveform parameter filtering method to classify acoustic sources in real-time. This method filtrates only the AE hits by the target acoustic source as passing hits in a specific parameter band. According to various acoustic sources, the waveform parameters were measured and analyzed to verify the present filtering method. Also, the AE system employing the waveform parameter filter was manufactured and applied to the roller coaster support structure in an actual amusement park

  9. Investigation of Material Performance Degradation for High-Strength Aluminum Alloy Using Acoustic Emission Method

    Directory of Open Access Journals (Sweden)

    Yibo Ai

    2015-02-01

    Full Text Available Structural materials damages are always in the form of micro-defects or cracks. Traditional or conventional methods such as micro and macro examination, tensile, bend, impact and hardness tests can be used to detect the micro damage or defects. However, these tests are destructive in nature and not in real-time, thus a non-destructive and real-time monitoring and characterization of the material damage is needed. This study is focused on the application of a non-destructive and real-time acoustic emission (AE method to study material performance degradation of a high-strength aluminum alloy of high-speed train gearbox shell. By applying data relative analysis and interpretation of AE signals, the characteristic parameters of materials performance were achieved and the failure criteria of the characteristic parameters for the material tensile damage process were established. The results show that the AE method and signal analysis can be used to accomplish the non-destructive and real-time detection of the material performance degradation process of the high-strength aluminum alloy. This technique can be extended to other engineering materials.

  10. Temporal characteristics of surface-acoustic-wave-driven luminescence from a lateral p-n junction

    Science.gov (United States)

    Gell, J. R.; Ward, M. B.; Shields, A. J.; Atkinson, P.; Bremner, S. P.; Anderson, D.; Kataoka, M.; Barnes, C. H. W.; Jones, G. A. C.; Ritchie, D. A.

    2007-07-01

    Short radio frequency pulses were used to study the surface-acoustic-wave-driven light emission from a molecular beam epitaxy regrown GaAs /AlGaAs lateral p-n junction. The luminescence provides a fast probe of the signals arriving at the junction allowing the authors to temporally separate the effect of the surface-acoustic-wave from pickup of the free space electromagnetic wave. Oscillations in the light intensity are resolved at the resonant frequency of the transducer, suggesting that the surface-acoustic-wave is transporting electrons across the junction in packets.

  11. Acoustic emission non-destructive testing of structures using source location techniques.

    Energy Technology Data Exchange (ETDEWEB)

    Beattie, Alan G.

    2013-09-01

    The technology of acoustic emission (AE) testing has been advanced and used at Sandia for the past 40 years. AE has been used on structures including pressure vessels, fire bottles, wind turbines, gas wells, nuclear weapons, and solar collectors. This monograph begins with background topics in acoustics and instrumentation and then focuses on current acoustic emission technology. It covers the overall design and system setups for a test, with a wind turbine blade as the object. Test analysis is discussed with an emphasis on source location. Three test examples are presented, two on experimental wind turbine blades and one on aircraft fire extinguisher bottles. Finally, the code for a FORTRAN source location program is given as an example of a working analysis program. Throughout the document, the stress is on actual testing of real structures, not on laboratory experiments.

  12. Arguments for fundamental emission by the parametric process L yields T + S in interplanetary type III bursts. [langmuir, electromagnetic, ion acoustic waves (L, T, S)

    Science.gov (United States)

    Cairns, I. H.

    1984-01-01

    Observations of low frequency ion acoustic-like waves associated with Langmuir waves present during interplanetary Type 3 bursts are used to study plasma emission mechanisms and wave processes involving ion acoustic waves. It is shown that the observed wave frequency characteristics are consistent with the processes L yields T + S (where L = Langmuir waves, T = electromagnetic waves, S = ion acoustic waves) and L yields L' + S proceeding. The usual incoherent (random phase) version of the process L yields T + S cannot explain the observed wave production time scale. The clumpy nature of the observed Langmuir waves is vital to the theory of IP Type 3 bursts. The incoherent process L yields T + S may encounter difficulties explaining the observed Type 3 brightness temperatures when Langmuir wave clumps are incorporated into the theory. The parametric process L yields T + S may be the important emission process for the fundamental radiation of interplanetary Type 3 bursts.

  13. Effect of Thermionic Emission on Dust-Acoustic Solitons in a Dust-Electron Plasma

    Institute of Scientific and Technical Information of China (English)

    REN Li-Wen; WANG Zheng-Xiong; LIU Yue; WANG Xiao-Gang

    2007-01-01

    The effects of thermionic emission on dust-acoustic solitons with a very small but finite amplitude in a dustelectron plasma are studied using the reductive perturbation technique. The self-consistent variation of dust charge is taken into account. It is shown that the thermionic emission could significantly increase the dust positive charge. The dependences of the phase velocity, amplitude, and width of such solitons on the dust temperature and the dust work function of dust material are plotted and discussed.

  14. Evoked acoustic emissions from the human ear. III. Findings in neonates

    DEFF Research Database (Denmark)

    Johnsen, N J; Bagi, P; Elberling, C

    1983-01-01

    Stimulated acoustic emissions were recorded in a consecutive series of 20 full-term and otherwise normal neonates with the equipment and method previously used in adults. One ear randomly chosen was tested in each baby, and otoscopy and tympanometry were normal in all ears. A 2 kHz click stimulus...

  15. On the possibilities of acoustic emission method using for estimation of large diameter quality tubes

    International Nuclear Information System (INIS)

    Results of investigation of acoustic emission (AE) method are given. It is shown that using the AE method for control of large diameter tubes in the process of cooling tube welded joints is possible. The comparison of results of control by AE and UST methods, which showed a good cerrelation between them, was performed

  16. Advanced Computing Methods for Knowledge Discovery and Prognosis in Acoustic Emission Monitoring

    Science.gov (United States)

    Mejia, Felipe

    2012-01-01

    Structural health monitoring (SHM) has gained significant popularity in the last decade. This growing interest, coupled with new sensing technologies, has resulted in an overwhelming amount of data in need of management and useful interpretation. Acoustic emission (AE) testing has been particularly fraught by the problem of growing data and is…

  17. Statistical fracture of E-glass fibres using a bundle tensile test and acoustic emission monitoring

    OpenAIRE

    R'Mili, M.; Moevus, M.; Godin, N.

    2009-01-01

    Statistical fracture of E-glass fibres using a bundle tensile test and acoustic emission monitoring correspondance: Corresponding author.Tel.: +33472436127; fax: +33472438528. (R?Mili, M.) (R?Mili, M.) Universite de Lyon--> , INSA-Lyon--> , MATEIS--> , 7 Avenue Jean Capelle--> , 69621 Villeurbanne Cedex--> - FRANCE (R?Mili, M.) Universite de Lyon--> , INSA-Lyo...

  18. Coupling thermogravimetric and acoustic emission measurements: its application to study the inhibition of catalytic coke deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ropital, Francois; Dascotte, Philippe; Marchand, Pierre [Institut Francais du Petrole, 1 Avenue Bois Preau, 92952 Rueil-Malmaison (France); Faure, Thierry; Lenain, Jean-Claude; Proust, Alain [Euro Physical Acoustics, 27 Rue Magellan, 94373 Sucy-en-Brie Cedex (France)

    2004-07-01

    In order to improve the knowledge on the high temperature behaviour of metallic materials, the coupling of several in situ physical analysis methods is a promising way. For this purpose a thermogravimetric balance has been equipped with a specific acoustic emission device in order to continuously measure the mass variation of the corrosion sample and the acoustic emission transient under experimental conditions of temperature and gas phase compositions that are representative of the industrial environments. The catalytic coke deposition condition that is a major problem for the refinery and petrochemical industries, has been studied with such a device. The carbon deposition on reactor walls can induce localised disruption in the process such as heat-transfer reduction and pressure drops. To prevent these perturbations, proper selections of the metallurgical or internal coating compositions of the equipment, or the injection of accurate amount of inhibitors have to be decided. The feasibility of the coupling at high temperature of thermogravimetric and acoustic emission has been demonstrated. This new technique has been applied to study the inhibition of the catalytic coke deposition on pure iron by sulphur additives in the temperature range of 650 deg. C and under different mixed atmospheres of hydrocarbon and hydrogen contents. Good correlation has been obtained between the coking rates measured by thermogravimetric measurements and the intensities of the acoustic emission parameters. (authors)

  19. Quality control of graphite mold by acoustic emission testing

    International Nuclear Information System (INIS)

    The brittleness of the graphite used for producing uranium tubes by gravity casting is monitored by acoustic test. Ancillary units, around a central data processing unit, also have a data processing function (micro-informatics) enabling the three following essential functions to be met: (1) control of the movement of integrating waves to five degrees of freedom, (2) control of the monitoring appliance and (3) pre-processing acquisition and presentation of the data. Mention is made of the facilities being used and of the progress of some research work

  20. THE ACOUSTICAL CHARACTERISTICS OF THE SAYYIDINA ABU BAKAR MOSQUE, UTeM

    Directory of Open Access Journals (Sweden)

    DG. H. KASSIM

    2015-01-01

    Full Text Available In the Muslim world, mosques are built with grandeur architectural design to depict an important house of worship in Islam. Unfortunately the acoustical performance in mosque is rarely considered at the design stage which eventually deteriorates the speech intelligibility. This includes the Sayyidina Abu Bakar Mosque in UTeM where poor subjective speech clarity is experienced during congregation. The objective of this paper is to discuss the acoustical characteristics of the mosque. The CATT indoor acoustic software was used to calculate important room acoustic parameters such as reverberation time (RT and clarity (C50. The measurement was conducted to validate the RT from the simulation where good agreement is obtained. This study finds that the Sayyidina Abu Bakar Mosque UTeM has poor acoustical performance at low frequencies below 1 kHz, i.e. the frequency range which is significantly responsible for the speech intelligibility

  1. Effects of changes in dynamic characteristics of the middle ear on transient-evoked otoacoustic emissions

    Directory of Open Access Journals (Sweden)

    Špirić Sanja

    2011-01-01

    Full Text Available Transient-evoked otoacoustic emissions are transmitted through the middle ear. The purpose of this study was to investigate the effects of dynamic properties of the transmission system on the measurability of transient otoacoustic emissions. The authors analyzed the presence of transient otoacoustic emissions in 48 children with serous otitis media regarding the tympanogram, presence and type of effusion and pure tone average findings. The results obtained in this research show the predominant absence of transient otoacoustic emissions in patients with type B tympanogram (69.1% especially if the effusion is mucoid (77.5% with the hearing loss of 15 decibel hearing level. This research shows that disorders in dynamic characteristics of the middle ear in patients with serous otitis obstruct the transmission of acoustic energy and affect the measurability of transient otoacoustic emissions, especially if the effusion is mucoid and hearing loss of 15 decibel hearing level.

  2. Experimental Research on Characteristics of Acoustic Emission Signal under Pump Cavitation Conditions%水泵空化状态下的声发射信号特征试验研究

    Institute of Scientific and Technical Information of China (English)

    谢志聪; 李录平; 邹淑云; 夏侯国伟; 高倩霞

    2012-01-01

    针对水泵空化现象较难解决的问题,在水泵试验台上进行定转速定流量的空化模拟试验,利用已设计好的监测系统对水泵的声发射信号进行了实时采集和分析处理,并分析了水泵在空化状态下的声发射信号波形频谱特征和声发射信号参数转征,获得了水泵有效汽蚀余量与声发射信号特征参数之间的关系.试验结果表明,声发射信号特征与水泵空化状态之间存在明显的对应关系,可利用此种关系判断水泵空化故障的发生,为运用声发射技术监测水泵空化提供了试验依据.%In view of thorny issue for solving pump cavitation. The cavitation experiments are simulated on a pump test-bed under the conditions of constant rotational speed and discharge. The AE signal of the pump is acquired and analyzed with the designed monitoring system. And the characteristics of AE signal waveform spectrum and parameters are obtained under the pump cavitation conditions. Then the relationship between the effective net positive suction head and the AE signal parameters is obtained. The results show that there is a close correlation between AE signal characteristics and pump cavitation conditions and it can be used to determine the occurrence of pump cavitation fault, which provides experimental references for monitoring pump cavitation.

  3. Acoustic emission testing on an F/A-18 E/F titanium bulkhead

    Science.gov (United States)

    Martin, Christopher A.; Van Way, Craig B.; Lockyer, Allen J.; Kudva, Jayanth N.; Ziola, Steve M.

    1995-04-01

    An important opportunity recently transpired at Northrop Grumman Corporation to instrument an F/A - 18 E/F titanium bulkhead with broad band acoustic emission sensors during a scheduled structural fatigue test. The overall intention of this effort was to investigate the potential for detecting crack propagation using acoustic transmission signals for a large structural component. Key areas of experimentation and experience included (1) acoustic noise characterization, (2) separation of crack signals from extraneous noise, (3) source location accuracy, and (4) methods of acoustic transducer attachment. Fatigue cracking was observed and monitored by strategically placed acoustic emission sensors. The outcome of the testing indicated that accurate source location still remains enigmatic for non-specialist engineering personnel especially at this level of structural complexity. However, contrary to preconceived expectations, crack events could be readily separated from extraneous noise. A further dividend from the investigation materialized in the form of close correspondence between frequency domain waveforms of the bulkhead test specimen tested and earlier work with thick plates.

  4. Combining passive thermography and acoustic emission for large area fatigue damage growth assessment of a composite structure

    Science.gov (United States)

    Zalameda, Joseph N.; Horne, Michael R.; Madaras, Eric I.; Burke, Eric R.

    2016-05-01

    Passive thermography and acoustic emission data were obtained for improved real time damage detection during fatigue loading. A strong positive correlation was demonstrated between acoustic energy event location and thermal heating, especially if the structure under load was nearing ultimate failure. An image processing routine was developed to map the acoustic emission data onto the thermal imagery. This required removing optical barrel distortion and angular rotation from the thermal data. The acoustic emission data were then mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. This technology provides improved real time inspections of advanced composite structures during fatigue testing.

  5. Current state of acoustic emission as an aid to the structural integrity assessment of nuclear power plants

    International Nuclear Information System (INIS)

    As an integral method permitting continuous monitoring and remote defect location, acoustic emission offers promising benefits for the nuclear industry. The potential applications relating to the integrity of the primary pressure boundary of nuclear reactors that are considered in this presentation are: detection of flaws during pre-service and requalification hydrotests and continuous monitoring for crack growth and leakage. The correlations between fracture mechanics and acoustic emission are discussed on the basis of certain fundamentals of material emission behaviour. The influence of instrumentation and wave propagation related aspects on the detectability and evaluation of acoustic emission signals is considered. A critical review is given of the application of acoustic emission to the assessment of reactor pressure vessel integrity, which demands a precise knowledge of the method's ability to distinguish different origins of acoustic emission, to detect and locate cracks and to evaluate the severity of cracks. World wide, at least 40 reactor pressure vessels and nuclear primary systems have been monitored by acoustic emission, either during acceptance pressure tests at the manufacturer's shop or during pre-service testing after installation in a plant. Together with the monitoring of requalification hydrotests after a certain period of operation, these applications of acoustic emission are currently receiving the most attention. The experience gained with continuous monitoring by acoustic emission is reported. The technique of leak detection by acoustic emission shows promising results, which permit the location and quantification of leaks. It is expected that practical experience and future research work will enhance the accuracy and detection sensitivity. (author)

  6. Controlled ultrasound-induced blood-brain barrier disruption using passive acoustic emissions monitoring.

    Directory of Open Access Journals (Sweden)

    Costas D Arvanitis

    Full Text Available The ability of ultrasonically-induced oscillations of circulating microbubbles to permeabilize vascular barriers such as the blood-brain barrier (BBB holds great promise for noninvasive targeted drug delivery. A major issue has been a lack of control over the procedure to ensure both safe and effective treatment. Here, we evaluated the use of passively-recorded acoustic emissions as a means to achieve this control. An acoustic emissions monitoring system was constructed and integrated into a clinical transcranial MRI-guided focused ultrasound system. Recordings were analyzed using a spectroscopic method that isolates the acoustic emissions caused by the microbubbles during sonication. This analysis characterized and quantified harmonic oscillations that occur when the BBB is disrupted, and broadband emissions that occur when tissue damage occurs. After validating the system's performance in pilot studies that explored a wide range of exposure levels, the measurements were used to control the ultrasound exposure level during transcranial sonications at 104 volumes over 22 weekly sessions in four macaques. We found that increasing the exposure level until a large harmonic emissions signal was observed was an effective means to ensure BBB disruption without broadband emissions. We had a success rate of 96% in inducing BBB disruption as measured by in contrast-enhanced MRI, and we detected broadband emissions in less than 0.2% of the applied bursts. The magnitude of the harmonic emissions signals was significantly (P<0.001 larger for sonications where BBB disruption was detected, and it correlated with BBB permeabilization as indicated by the magnitude of the MRI signal enhancement after MRI contrast administration (R(2 = 0.78. Overall, the results indicate that harmonic emissions can be a used to control focused ultrasound-induced BBB disruption. These results are promising for clinical translation of this technology.

  7. Acoustic emissions of digital data video projectors- Investigating noise sources and their change during product aging

    Science.gov (United States)

    White, Michael Shane

    2005-09-01

    Acoustic emission testing continues to be a growing part of IT and telecommunication product design, as product noise is increasingly becoming a differentiator in the marketplace. This is especially true for digital/video display companies, such as InFocus Corporation, considering the market shift of these products to the home entertainment consumer as retail prices drop and performance factors increase. Projectors and displays using Digital Light Processing(tm) [DLP(tm)] technology incorporate a device known as a ColorWheel(tm) to generate the colors displayed at each pixel in the image. These ColorWheel(tm) devices spin at very high speeds and can generate high-frequency tones not typically heard in liquid crystal displays and other display technologies. Also, acoustic emission testing typically occurs at the beginning of product life and is a measure of acoustic energy emitted at this point in the lifecycle. Since the product is designed to be used over a long period of time, there is concern as to whether the acoustic emissions change over the lifecycle of the product, whether these changes will result in a level of nuisance to the average customer, and does this nuisance begin to develop prior to the intended lifetime of the product.

  8. Thickness measurement of Ni thin film using dispersion characteristics of a surface acoustic wave

    International Nuclear Information System (INIS)

    In this study, we suggest a method to measure the thickness of thin films nondestructively using the dispersion characteristics of a surface acoustic wave propagating along the thin film surface. To measure the thickness of thin films, we deposited thin films with different thicknesses on a Si (100) wafer substrate by controlling the deposit time using the E-beam evaporation method. The thickness of the thin films was measured using a scanning electron microscope. Subsequently, the surface wave velocity of the thin films with different thicknesses was measured using the V(z) curve method of scanning acoustic microscopy. The correlation between the measured thickness and surface acoustic wave velocity was verified. The wave velocity of the film decreased as the film thickness increased. Therefore, thin film thickness can be determined by measuring the dispersion characteristics of the surface acoustic wave velocity.

  9. The Frequency Characteristics Simulation of Traveling Wave Thermo-Acoustic Engine

    Directory of Open Access Journals (Sweden)

    Ma Lili

    2013-04-01

    Full Text Available The frequency characteristics of thermo-acoustic engine mainly depend on the internal working medium and device structure. The linear resonant system is consisted of ironless permanent magnet linear synchronous motor and the resonant spring. Through the analysis of thermo-acoustic power generation system model, the parameters of linear resonant system are determined by building a mathematical model of linear resonant system. Combined with modern control theory and robust control theory, a robust position controller was design. The theoretical analysis and simulation proved that the controller can make the linear resonance system obtain higher frequency response and displacement accuracy. Controller response time and output is more stable, the controller meets the necessary optimal control. The controller is suitable for thermal acoustic generator control system with high reliable and robust quantitative. The designed linear resonance system can well simulate the frequency characteristics of thermo-acoustic engine.

  10. Effect of Pyramidal Dome Geometry on the Acoustical Characteristics in A Mosque

    Directory of Open Access Journals (Sweden)

    Dg. H. Kassim

    2014-12-01

    Full Text Available As an important symbol in Islam, a mosque is built with architectural grandeur. Among the characteristics is its high ceiling and it is usually constructed with a typical spherical dome shape. Some mosques, however, are influenced by the local culture and the dome can be of a different shape, such as pyramidal, as found in mosques in Malacca, Malaysia. This paper presents an assessment of the internal acoustical characteristics of a mosque having a pyramidal dome. The study is conducted by means of computer simulation using CATT indoor acoustic software. Reverberation time and clarity are taken to evaluate the intelligibility of speech. The effect of the angle and height of the dome on the acoustical parameters is discussed. It is found that a pyramidal dome with a steeper angle contributes to poor acoustic clarity.

  11. Characterization of granular collapse onto hard substrates by acoustic emissions

    Science.gov (United States)

    Farin, Maxime; Mangeney, Anne; Toussaint, Renaud; De Rosny, Julien

    2013-04-01

    Brittle deformation in granular porous media can generate gravitational instabilities such as debris flows and rock avalanches. These phenomena constitute a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and rock blocks. The elastic energy emitted by a single bouncing steel bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, two types of acoustic sensors were used to record the signals in a wide frequency range: accelerometers (1 Hz to 56 kHz) and piezoelectric sensors (100 kHz to 1 MHz). The experiments were also monitored optically using fast cameras. We developed a technique to use quantitatively both types of sensors to evaluate the elastic energy emitted by the sources. Eventually, we looked at what

  12. Acoustic Emission Behavior of Early Age Concrete Monitored by Embedded Sensors

    Directory of Open Access Journals (Sweden)

    Lei Qin

    2014-10-01

    Full Text Available Acoustic emission (AE is capable of monitoring the cracking activities inside materials. In this study, embedded sensors were employed to monitor the AE behavior of early age concrete. Type 1–3 cement-based piezoelectric composites, which had lower mechanical quality factor and acoustic impedance, were fabricated and used to make sensors. Sensors made of the composites illustrated broadband frequency response. In a laboratory, the cracking of early age concrete was monitored to recognize different hydration stages. The sensors were also embedded in a mass concrete foundation to localize the temperature gradient cracks.

  13. Experimental study of the acoustic characteristics of micro-perforated functional absorbers

    Institute of Scientific and Technical Information of China (English)

    WANG Jiqing; SONG Yongmin; SHENG Shengwo

    2005-01-01

    Micro-perforated panels have been widely used as fiber-free acoustical material for decades in the form of wall or ceiling covering with some air space behind. This paper presents the test study on the acoustical characteristics of two different types of functional absorbers,panel type and tube type, constructed with micro-perforated metal or PVC (polyvinyl chloride) sheets. Acoustical measurements of such functional absorbers in reverberation chamber demonstrate the merit of good absorption as expected. They are not only cost effective in construction and installation, but also appealing esthetically for architectural interior design.

  14. Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

    Science.gov (United States)

    Moradian, Zabihallah; Einstein, Herbert H.; Ballivy, Gerard

    2016-03-01

    Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g., hits and energy) to stress-strain plots of rocks let us detect cracking levels properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper, the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro- and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages (1) crack closure, (2) linear elastic deformation, (3) micro-crack initiation (white patch initiation), (4) micro-crack growth (stable crack growth), (5) micro-crack coalescence (macro-crack initiation), (6) macro-crack growth (unstable crack growth), (7) macro-crack coalescence and (8) failure.

  15. Study of the Tensile Damage of High-Strength Aluminum Alloy by Acoustic Emission

    Directory of Open Access Journals (Sweden)

    Chang Sun

    2015-11-01

    Full Text Available The key material of high-speed train gearbox shells is high-strength aluminum alloy. Material damage is inevitable in the process of servicing. It is of great importance to study material damage for in-service gearboxes of high-speed train. Structural health monitoring methods have been widely used to study material damage in recent years. This study focuses on the application of an acoustic emission (AE method to quantify tensile damage evolution of high-strength aluminum alloy. First, a characteristic parameter was developed to connect AE signals with tensile damage. Second, a tensile damage quantification model was presented based on the relationship between AE counts and tensile behavior to study elastic deformation of tensile damage. Then tensile tests with AE monitoring were employed to collect AE signals and tensile damage data of nine samples. The experimental data were used to quantify tensile damage of high-strength aluminum alloy A356 to demonstrate the effectiveness of the proposed method.

  16. Signal Simulation and Experimental Research on Acoustic Emission using LS-DYNA

    Directory of Open Access Journals (Sweden)

    Zhang Jianchao

    2015-09-01

    Full Text Available To calculate sound wave velocity, we performed the Hsu-Nielsen lead break experiment using the ANSYS/LS-DYNA finite element software. First, we identified the key problems in the finite element analysis, such as selecting the exciting force, dividing the grid density, and setting the calculation steps. Second, we established the finite element model of the sound wave transmission in a plate under the lead break simulation. Results revealed not only the transmission characteristics of the sound wave but also the simulation and calculation of the transmission velocity of the longitudinal and transverse waves through the time travel curve of the vibration velocity of the sound wave at various nodes. Finally, the Hsu-Nielsen lead break experiment was implemented. The results of the theoretical calculation and simulation analysis were consistent with the experimental results, thus demonstrating that the research method using the ANSYS/LS-DYNA software to simulate sound wave transmissions in acoustic emission experiments is feasible and effective.

  17. Acoustic emission monitoring of a fatigue test of an F/A-18 bulkhead

    Science.gov (United States)

    Scala, C. M.; McCardle, J. F.; Bowles, S. J.

    This paper describes the application of acoustic emission (AE) to identify cracking in several fatigue-critical regions on the port and starboard sides of an l/A-18 aircraft bulkhead undergoing fatigue testing. AE data acquisition was carried out using an array of three sensors on each side of the bulkhead. AE features stored by each array included relative arrival times of AE events at the three sensors, event rise time at the first-hit sensor, and the load level and the position on the load cycle of event occurrence. AE data processing involved a comparison between the features of those AE events stored during the fatigue testing and predicted features for cracking in the complex-shaped bulkhead. Feature prediction was based on wave propagation characteristics obtained by Pentel-lead calibration, and the known load cycle dependence of crack-related AE events. The AE processing was completed following failure of the bulkhead, and gave the correct locations of all cracks, greater than about 1 mm in depth, present in the bulkhead during the fatigue testing. The study shows that AE associated with cracking can be distinguished, even when many extraneous sources are present, and demonstrates that AE is a promising technique for nondestructive evaluation of a complex structure such as the F/A-18 bulkhead.

  18. Acoustic emission studies for characterization of fatigue crack growth behavior in HSLA steel

    Science.gov (United States)

    Kumar, Jalaj; Ahmad, S.; Mukhopadhyay, C. K.; Jayakumar, T.; Kumar, Vikas

    2016-01-01

    High strength low alloy (HSLA) steels are a group of low carbon steels and used in oil and gas pipelines, automotive components, offshore structures and shipbuilding. Fatigue crack growth (FCG) characteristics of a HSLA steel have been studied at two different stress ratios (R = 0.3 and 0.5). Acoustic emission (AE) signals generated during the FCG tests have been used to understand the FCG processes. The AE signals were captured by mounting two piezoelectric sensors on compact tension specimens in liner location configuration. The AE generated in stage II of the linear Paris region of FCG has been attributed to the presence of two sub-stages with two different slopes. The AE generated at higher values of stress intensity factor is found to be useful to identify the transition from stage II to stage III of the FCG. AE location analysis has provided support for increased damage at the crack tip for higher stress ratio. The peak stress intensity (Kmax) values at the crack tip have shown good correlation with the transitions from stage IIa to stage IIb and stage II to stage III of the FCG for the two stress ratios.

  19. Acoustic emission monitoring of medieval towers considered as sensitive earthquake receptors

    Directory of Open Access Journals (Sweden)

    A. Carpinteri

    2007-01-01

    Full Text Available Many ancient masonry towers are present in Italian territory. In some cases these structures are at risk on account of the intensity of the stresses they are subjected to due to the high level of regional seismicity. In order to preserve this inestimable cultural heritage, a sound safety assessment should take into account the evolution of damage phenomena. In this connection, acoustic emission (AE monitoring can be highly effective. This study concerns the structural stability of three medieval towers rising in the centre of Alba, a characteristic town in Piedmont (Italy. During the monitoring period a correlation between peaks of AE activity in the masonry of these towers and regional seismicity was found. Earthquakes always affect structural stability. Besides that, the towers behaved as sensitive earthquake receptors. Here a method to correlate bursts of AE activity in a masonry building and regional seismicity is proposed. In particular, this method permits to identify the premonitory signals that precede a catastrophic event on a structure, since, in most cases, these warning signs can be captured well in advance.

  20. THE ACOUSTICAL CHARACTERISTICS OF THE SAYYIDINA ABU BAKAR MOSQUE, UTeM

    OpenAIRE

    Dg. H. Kassim; A. Putra; M. J. M. NOR

    2015-01-01

    In the Muslim world, mosques are built with grandeur architectural design to depict an important house of worship in Islam. Unfortunately the acoustical performance in mosque is rarely considered at the design stage which eventually deteriorates the speech intelligibility. This includes the Sayyidina Abu Bakar Mosque in UTeM where poor subjective speech clarity is experienced during congregation. The objective of this paper is to discuss the acoustical characteristics of the mosque. The CATT ...

  1. Padé approximants for the acoustical characteristics of rigid frame porous media

    OpenAIRE

    Chandler-Wilde, S.N.

    1995-01-01

    In this paper it is shown that a number of theoretical models of the acoustical properties of rigid frame porous media, especially those involving ratios of Bessel functions of complex argument, can be accurately approximated and greatly simplified by the use of Padé approximation techniques. In the case of the model of Attenborough [J. Acoust. Soc. Am. 81, 93–102 (1987)] rational approximations are produced for the characteristic impedance, propagation constant, dynamic compressibility, and ...

  2. Stimulated emission of phonons in an acoustic cavity

    NARCIS (Netherlands)

    Tilstra, Lieuwe Gijsbert

    2002-01-01

    This thesis will present experiments on stimulated emission of phonons in dilute ruby following complete population inversion of the Zeeman-split E(2E) Kramers doublet by selective pulsed optical pumping into its upper component. The resulting phonon avalanches are detected by use of the R1 luminesc

  3. Distributed feedback fiber laser acoustic emission sensor for concrete structure health monitoring

    Science.gov (United States)

    Hao, Gengjie; Huang, Wenzhu; Zhang, Wentao; Sun, Baochen; Li, Fang

    2014-05-01

    This paper introduces a highly-sensitive fiber optical acoustic emission (AE) sensor and a parameter analysis method aiming at concrete structure health monitoring. Distributed feedback fiber-laser (DFB-FL), which is encapsulated to have a high acoustic sensitivity, is used for sensor unit of the AE sensor. The AE signal of concrete beam in different work stages, based on the four-point bending experiment of the concrete beam, is picked up, and the relationship between the concrete beam work stages and the AE parameter is found. The results indicate that DFB-FLAES can be used as sensitive transducers for recording acoustic events and forecasting the imminent failure of the concrete beam.

  4. A Novel Acoustic Emission Fiber Optic Sensor Based on a Single Mode Optical Fiber Coupler

    Institute of Scientific and Technical Information of China (English)

    CHEN Rongsheng; LIAO Yanbiao; ZHENG Gangtie; LIU Tongyu; Gerard Franklyn Fernando

    2001-01-01

    This paper reports, for the first time, on the use of a fused-taper single mode optical fiber coupler as a sensing element for the detection of acoustic emission (AE) and ultrasound. When an acoustic wave impinges on the mode-coupling region of a coupler, the coupling coefficient is modulated via the photo-elastic effect. Therefore, the transfer function of the coupler is modulated by an acoustic wave. The sensitivity of the sensor at 140 kHz was approximately 5.2 mV/Pa and the noise floor was 1 Pa. The bandwidth of the sensor was up to several hundred kHz. This AE sensor exhibits significant advantage compared with interferometer-based AE sensors.

  5. A New Fault Location Approach for Acoustic Emission Techniques in Wind Turbines

    Directory of Open Access Journals (Sweden)

    Carlos Quiterio Gómez Muñoz

    2016-01-01

    Full Text Available The renewable energy industry is undergoing continuous improvement and development worldwide, wind energy being one of the most relevant renewable energies. This industry requires high levels of reliability, availability, maintainability and safety (RAMS for wind turbines. The blades are critical components in wind turbines. The objective of this research work is focused on the fault detection and diagnosis (FDD of the wind turbine blades. The FDD approach is composed of a robust condition monitoring system (CMS and a novel signal processing method. CMS collects and analyses the data from different non-destructive tests based on acoustic emission. The acoustic emission signals are collected applying macro-fiber composite (MFC sensors to detect and locate cracks on the surface of the blades. Three MFC sensors are set in a section of a wind turbine blade. The acoustic emission signals are generated by breaking a pencil lead in the blade surface. This method is used to simulate the acoustic emission due to a breakdown of the composite fibers. The breakdown generates a set of mechanical waves that are collected by the MFC sensors. A graphical method is employed to obtain a system of non-linear equations that will be used for locating the emission source. This work demonstrates that a fiber breakage in the wind turbine blade can be detected and located by using only three low cost sensors. It allows the detection of potential failures at an early stages, and it can also reduce corrective maintenance tasks and downtimes and increase the RAMS of the wind turbine.

  6. Acoustic, electromagnetic, neutron emissions from fracture and earthquakes

    CERN Document Server

    Lacidogna, Giuseppe; Manuello, Amedeo

    2015-01-01

    This book presents the relevant consequences of recently discovered and interdisciplinary phenomena, triggered by local mechanical instabilities. In particular, it looks at emissions from nano-scale mechanical instabilities such as fracture, turbulence, buckling and cavitation, focussing on vibrations at the TeraHertz frequency and Piezonuclear reactions. Future applications for this work could include earthquake precursors, climate change, energy production, and cellular biology. A series of fracture experiments on natural rocks demonstrates that the TeraHertz vibrations are able to induce fission reactions on medium weight elements accompanied by neutron emissions. The same phenomenon appears to have occurred in several different situations, particularly in the chemical evolution of the Earth and Solar System, through seismicity (rocky planets) and storms (gaseous planets). As the authors explore, these phenomena can also explain puzzles related to the history of our planet, like the ocean formation or th...

  7. Study of focusing characteristics of ultrasound for designing acoustic lens in ultrasonic moxibustion device

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jae Hyun; Song, Sung Jin; Kim, Hak Joon [School of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kim, Ki Bok [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2015-04-15

    Traditional moxibustion therapy can cause severe pain and leave scarring burns at the moxibustion site as it relies on the practitioner's subjective and qualitative treatment. Recently, ultrasound therapy has received attention as an alternative to moxibustion therapy owing to its objectiveness and quantitative nature. However, in order to convert ultrasound energy into heat energy, there is a need to precisely understand the ultrasound-focusing characteristics of the acoustic lens. Therefore, in this study, an FEM simulation was performed for acoustic lenses with different geometries a concave lens and zone lens as the geometry critically influences ultrasound focusing. The acoustic pressure field, amplitude, and focal point were also calculated. Furthermore, the performance of the fabricated acoustic lens was verified by a sound pressure measurement experiment.

  8. Effects of Specimen Height on the Acoustic Emission Rate Value ‘a’ for Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    WANG Yan; HU Hongxiang; LU Guijuan; CHEN Shijie; LIU Shaojun; WANG Yao

    2016-01-01

    In order to study the size effect on the AE rate ‘a’ value, three kinds of mix ratios were set up by different particle sizes and water cement ratios, 45 cement mortar specimens with ifve different heights were tested under axial compression. And the whole damage processes were monitored by full-digital acoustic emission acquisition system, followed by an analysis of mechanical behavior and AE activity. The experimental results show that the height of the cement specimen has signiifcant effects on the compressive strength and the acoustic emission rate ‘a’ value, but a slight effect on the accumulated AE hits number, which is analyzed from aspects of failure process of cement mortar specimens.

  9. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    CERN Document Server

    Fernández, E; Bilmes, G M; 10.4279/PIP.040003

    2012-01-01

    Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE) produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation" triggered by the disruptive effect of cavitation inception.

  10. Experimental study of advanced continuous acoustic-emission monitoring of BWR components. Final report

    International Nuclear Information System (INIS)

    This report presents the results of a four year research program on the utilization of acoustic emission techniques on light water reactor component applications. Two techniques of the acoustic emission technology were applied to specific problems occurring within the light water reactor system. Crack detection AE monitoring was applied to thermal cycle fatigue cracking problems and stress corrosion cracking problems. Leak detection AE monitoring was applied to valve leakage in the main steam safety relief valves and incontainment packing gland valves. The report provides AE data showing how AE crack detection can be used as an on-line diagnostic monitoring tool. By having an active monitor on light water reactor components, the inservice inspection of the components is being performed during operation rather than refueling periods, thereby reducing critical path time during outages. The resultant benefit is increased plant availability and a reduction in accumulated radiation exposure

  11. Band-limited Green's Functions for Quantitative Evaluation of Acoustic Emission Using the Finite Element Method

    Science.gov (United States)

    Leser, William P.; Yuan, Fuh-Gwo; Leser, William P.

    2013-01-01

    A method of numerically estimating dynamic Green's functions using the finite element method is proposed. These Green's functions are accurate in a limited frequency range dependent on the mesh size used to generate them. This range can often match or exceed the frequency sensitivity of the traditional acoustic emission sensors. An algorithm is also developed to characterize an acoustic emission source by obtaining information about its strength and temporal dependence. This information can then be used to reproduce the source in a finite element model for further analysis. Numerical examples are presented that demonstrate the ability of the band-limited Green's functions approach to determine the moment tensor coefficients of several reference signals to within seven percent, as well as accurately reproduce the source-time function.

  12. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    Directory of Open Access Journals (Sweden)

    Gabriel Mario Bilmes

    2012-05-01

    Full Text Available Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation"' triggered by the disruptive effect of cavitation inception.

  13. Multi-scale morphology analysis of acoustic emission signal and quantitative diagnosis for bearing fault

    Science.gov (United States)

    Wang, Wen-Jing; Cui, Ling-Li; Chen, Dao-Yun

    2016-04-01

    Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains. One of the major challenges is how to differentiate relevant signals to operational conditions of bearings from noises emitted from the surrounding environment. In this work, we report a procedure for analyzing acoustic emission signals collected from rolling bearings for diagnosis of bearing health conditions by examining their morphological pattern spectrum (MPS) through a multi-scale morphology analysis procedure. The results show that acoustic emission signals resulted from a given type of bearing faults share rather similar MPS curves. Further examinations in terms of sample entropy and Lempel-Ziv complexity of MPS curves suggest that these two parameters can be utilized to determine damage modes.

  14. Acoustic Emission Based In-process Monitoring in Robot Assisted Polishing

    DEFF Research Database (Denmark)

    Pilny, Lukas; Bissacco, Giuliano; De Chiffre, Leonardo;

    The applicability of acoustic emission (AE) measurements for in-process monitoring in the Robot Assisted Polishing (RAP) process was investigated. Surface roughness measurements require interruption of the process, proper surface cleaning and measurements that sometimes necessitate removal of the...... improving the efficiency of the process. It also allows for intelligent process control and generally enhances the robustness and reliability of the automated RAP system in industrial applications.......The applicability of acoustic emission (AE) measurements for in-process monitoring in the Robot Assisted Polishing (RAP) process was investigated. Surface roughness measurements require interruption of the process, proper surface cleaning and measurements that sometimes necessitate removal...... of the part from the machine tool. In this study, development of surface roughness during polishing rotational symmetric surfaces by the RAP process was inferred from AE measurements. An AE sensor was placed on a polishing tool, and a cylindrical rod of Vanadis 4E steel having an initial turned surface...

  15. ACEMAN (II): a PDP-11 software package for acoustic emission analysis

    International Nuclear Information System (INIS)

    A powerful, but easy-to-use, software package (ACEMAN) for acoustic emission analysis has been developed at Berkeley Nuclear Laboratories. The system is based on a PDP-11 minicomputer with 24 K of memory, an RK05 DISK Drive and a Tektronix 4010 Graphics terminal. The operation of the system is described in detail in terms of the functions performed in response to the various command mnemonics. The ACEMAN software package offers many useful facilities not found on other acoustic emission monitoring systems. Its main features, many of which are unique, are summarised. The ACEMAN system automatically handles arrays of up to 12 sensors in real-time operation during which data are acquired, analysed, stored on the computer disk for future analysis and displayed on the terminal if required. (author)

  16. Study of electromagnetic and acoustic emission in creep experiments of water-containing rock samples

    Institute of Scientific and Technical Information of China (English)

    JING Hong-wen; ZHANG Zhong-yu; XU Guo-an

    2008-01-01

    Based on biaxial shear creep tests conducted on rock samples with different water contents, we present the results of our study on the regularities of electromagnetic and acoustic emission during the process of creep experiments in which we have ana-lyzed the contribution of water to the occurrence of electromagnetic radiation. The result shows that in the creep-fracturing course of rock samples, when the water content increases, the initial frequency and amplitude of electromagnetic and acoustic emission also increases, but at a decreasing growth rate caused by loading stress. This can be used as a criterion for the long-term stability of rock masses under conditions of repeated inundation and discharge of water.

  17. Remote structural health monitoring with serially multiplexed fiber optic acoustic emission sensors

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Development and testing of a serially multiplexed fiber optic sensor system is described. The sensor differs from conventional fiber optic acoustic systems, as it is capable of sensing AE emissions at several points along the length of a single fiber. Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of crack locations. Laboratory experiments on plain concrete beams and post-tensioned FRP tendons were performed to evaluate the crack detection capability of the sensor system. The acoustic emission sensor was able to detect initiation, growth and location of the cracks in concrete as well as in the FRP tendons. The AE system is potentially suitable for applications involving health monitoring of structures following an earthquake.

  18. Physiological and acoustic characteristics of the male music theatre voice.

    Science.gov (United States)

    Bourne, Tracy; Garnier, Maëva; Samson, Adeline

    2016-07-01

    Six male music theatre singers were recorded in three different voice qualities: legit and two types of belt ("chesty" and "twangy"), on two vowels ([e] and [ɔ]), at four increasing pitches in the upper limit of each singer's belt range (∼250-440 Hz). The audio signal, the electroglottographic (EGG) signal, and the vocal tract impedance were all measured simultaneously. Voice samples were analyzed and then evaluated perceptually by 16 expert listeners. The three qualities were produced with significant differences at the physiological, acoustical, and perceptual levels: Singers produced belt qualities with a higher EGG contact quotient (CQEGG) and greater contacting speed quotient (Qcs), greater sound pressure level (SPL), and energy above 1 kHz (alpha ratio), and with higher frequencies of the first two vocal tract resonances (fR1, fR2), especially in the upper pitch range when compared to legit. Singers produced the chesty belt quality with higher CQEGG, Qcs, and SPL values and lower alpha ratios over the whole belt range, and with higher fR1 at the higher pitch range when compared to twangy belt. Consistent tuning of fR1 to the second voice harmonic (2f0) was observed in all three qualities and for both vowels. Expert listeners tended to identify all qualities based on the same acoustical and physiological variations as those observed in the singers' intended qualities. PMID:27475183

  19. Monitoring of the production quality of fibre-reinforced pressure vessels using acoustic emission testing; Ueberwachung der Fertigungsqualitaet von Faserverbund-Druckbehaeltern mittels Schallemissionspruefung

    Energy Technology Data Exchange (ETDEWEB)

    Duffner, Eric; Gregor, Christian; Bohse, Juergen [BAM Bundesanstalt fuer Materialforschung und -pruefung, Berlin (Germany)

    2011-07-01

    The investigation aimed at the validation of a test method for ensuring the production quality of reinforced-fibre pressure vessels in real fabrication conditions. The method is based on characteristics and permissible limiting values derived from acoustic emission curves during the first pressure test. The method had already been tested successfully on reinforced-fibre pressure vessels with metal liners and had been patented. With the current investigations, the possibility of detection fabrication defects in carbon fibre / glass fibre hybrid pressure vessels with polymer liners was evaluated. For this, fibre-reinforced pressure vessels were monitored by acoustic emission measurement during the first hydraulic pressure test; this test is commonly used for quality assurance of this type of pressure vessel, although without acoustic emission testing. Acoustic emission curves were registered for pressure vessels of a serial production, and the mean characteristics and their scatter were determined as reference values. These were compared with the acoustic emission curves of selectively induced fabrication defects. Fabrication defects are defects that may occur in serial production and are difficult or impossible to detect by conventional quality assurance methods. All investigated pressure vessel were then subject to stress until failure (leakage, bursting). This made it possible to verify the real influence of fabrication defects on the burst pressure and/or the fatigue characteristics of the pressure vessels and to assess the validity of acoustic emission testing. [German] Ziel der Untersuchung ist die Validierung einer Pruefmethodik zur Sicherung der Fertigungsqualitaet von Faserverbund - Druckbehaeltern unter realen Fertigungsbedingungen. Das Verfahren basiert auf Merkmalen und zulaessigen Grenzwerten, die aus Schallemissionsverlaeufen bei der Erstdruckpruefung abgeleitet werden [1]. Die Methodik konnte zuvor bereits erfolgreich an Faserverbund - Druckbehaeltern

  20. Initial Evaluation of Acoustic Emission SHM of PRSEUS Multi-bay Box Tests

    Science.gov (United States)

    Horne, Michael R.; Madaras, Eric I.

    2016-01-01

    A series of tests of the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) HWB Multi-Bay Test Article were conducted during the second quarter of 2015 at NASA Langley Research Center (LaRC) in the Combined Loads Test facility (COLTS). This report documents the Acoustic Emission (AE) data collected during those tests along with an initial analysis of the data. A more detailed analysis will be presented in future publications.

  1. Large Eddy simulation of Trailing Edge Acoustic Emissions of an Airfoil

    OpenAIRE

    Wu, Jinlong; Devenport, William; Paterson, Eric; Sun, Rui; Xiao, Heng

    2015-01-01

    The present investigation of trailing edge acoustic emission of an airfoil concerns the effects of the broadband noise generated by the interaction of turbulent boundary layer and airfoil trailing edge, and the tonal noise generated by the vortex shedding of trailing edge bluntness. Large eddy simulation (LES) is performed on an NACA0012 airfoil with blunt trailing edge at a Reynolds number Rec = 400; 000 based on the airfoil chord length for three different configurations with different angl...

  2. Evaluation of Acoustic Emission NDE of Kevlar Composite Over Wrapped Pressure Vessels

    Science.gov (United States)

    Horne, Michael R.; Madaras, Eric I.

    2008-01-01

    Pressurization and failure tests of small Kevlar/epoxy COPV bottles were conducted during 2006 and 2007 by Texas Research Institute Austin, Inc., at TRI facilities. This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. Results of some of the tests indicate a possibility that AE can be used to track the stress-rupture degradation of COPV vessels.

  3. The Analysis of Efficiency of Acoustic Emission Diagnostic Method for the Determination of Defect Coordinates

    OpenAIRE

    Urbahs, A; Valberga, A; Banov, M; Carjova, K; Stelpa, I

    2014-01-01

    Acoustic emission (AE) method is widely used as a non-destructive control tool of vehicle points and construction and also as a tool for technical condition monitoring. One of the most important AE diagnostic technological operations is the determination of AE source defect coordinates. Modern defect location techniques allow detecting coordinates of developing defects with high accuracy and reliability. There are several AE source detection methods, but the most popular one is a signal arriv...

  4. Multipoint dynamically reconfigure adaptive distributed fiber optic acoustic emission sensor (FAESense) system for condition based maintenance

    Science.gov (United States)

    Mendoza, Edgar; Prohaska, John; Kempen, Connie; Esterkin, Yan; Sun, Sunjian; Krishnaswamy, Sridhar

    2010-09-01

    This paper describes preliminary results obtained under a Navy SBIR contract by Redondo Optics Inc. (ROI), in collaboration with Northwestern University towards the development and demonstration of a next generation, stand-alone and fully integrated, dynamically reconfigurable, adaptive fiber optic acoustic emission sensor (FAESense™) system for the in-situ unattended detection and localization of shock events, impact damage, cracks, voids, and delaminations in new and aging critical infrastructures found in ships, submarines, aircraft, and in next generation weapon systems. ROI's FAESense™ system is based on the integration of proven state-of-the-art technologies: 1) distributed array of in-line fiber Bragg gratings (FBGs) sensors sensitive to strain, vibration, and acoustic emissions, 2) adaptive spectral demodulation of FBG sensor dynamic signals using two-wave mixing interferometry on photorefractive semiconductors, and 3) integration of all the sensor system passive and active optoelectronic components within a 0.5-cm x 1-cm photonic integrated circuit microchip. The adaptive TWM demodulation methodology allows the measurement of dynamic high frequnency acoustic emission events, while compensating for passive quasi-static strain and temperature drifts. It features a compact, low power, environmentally robust 1-inch x 1-inch x 4-inch small form factor (SFF) package with no moving parts. The FAESense™ interrogation system is microprocessor-controlled using high data rate signal processing electronics for the FBG sensors calibration, temperature compensation and the detection and analysis of acoustic emission signals. Its miniaturized package, low power operation, state-of-the-art data communications, and low cost makes it a very attractive solution for a large number of applications in naval and maritime industries, aerospace, civil structures, the oil and chemical industry, and for homeland security applications.

  5. Acoustic emissions for particle sizing of powders through signal processing techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bastari, A.; Cristalli, C.; Morlacchi, R.; Pomponi, E. [Loccioni Group (Italy)

    2011-04-15

    The present work introduces an innovative method for measuring particle size distribution of an airborne powder, based on the application of signal processing techniques to the acoustic emission signals produced by the impacts of the powder with specific metallic surfaces. The basic idea of the proposed methodology lies on the identification of the unknown relation between the acquired acoustic emission signals and the powder particle size distribution, by means of a multi-step procedure. In the first step, wavelet packet decomposition is used to extract useful features from the acoustic emission signals: the dimensionality of feature space is further reduced through multivariate data analysis techniques. As a final step, a neural network is properly trained to map the feature vector into the particle size distribution. The proposed solution has several advantages, such as low cost and low invasiveness which allow the system based on this technique to be easily integrated in pre-existing plants. It has been successfully applied to the PSD measurement of coal powder produced by grinding mills in a coal-fired power station, and the experimental results are reported in the paper. The measurement principle can also be applied to different particle sizing applications, whenever a solid powder is carried in air or in other gases.

  6. Health monitoring of Ceramic Matrix Composites from waveform-based analysis of Acoustic Emission

    Directory of Open Access Journals (Sweden)

    Maillet Emmanuel

    2015-01-01

    Full Text Available Ceramic Matrix Composites (CMCs are anticipated for use in the hot section of aircraft engines. Their implementation requires the understanding of the various damage modes that are involved and their relation to life expectancy. Acoustic Emission (AE has been shown to be an efficient technique for monitoring damage evolution in CMCs. However, only a waveform-based analysis of AE can offer the possibility to validate and precisely examine the recorded AE data with a view to damage localization and identification. The present work fully integrates wave initiation, propagation and acquisition in the analysis of Acoustic Emission waveforms recorded at various sensors, therefore providing more reliable information to assess the relation between Acoustic Emission and damage modes. The procedure allows selecting AE events originating from damage, accurate determination of their location as well as the characterization of effects of propagation on the recorded waveforms. This approach was developed using AE data recorded during tensile tests on carbon/carbon composites. It was then applied to melt-infiltrated SiC/SiC composites.

  7. An Approach to Acoustic Emission Technique Applications to Evaluate Damage Mechanisms in Composite Materials

    Directory of Open Access Journals (Sweden)

    Rios-Soberanis C.R.

    2015-01-01

    Full Text Available Acoustic Emission technique is a versatile method for characterization in materials science. It is considered to be a “passive” non-destructive method since damage can be only evaluated when de defects are being developed during the test which, at the end of the day, it is considered an advantage because failure mechanisms and damage process can be monitored and identified during the load history. When a failure mechanism is activated due to a discontinuity in the material such as crack propagation, part of the total strain energy is dissipated as an elastic waves that propagate from the damage source through the medium. Therefore, this released energy can be detected by piezoelectric sensors that perceive the emitted signal from the damage notation site by the surface dynamic movement and convert it in an electrical response. Acoustic emission signals can be correlated with the onset of damage process occurring in the tested materials and also to de diverse failure mechanisms such as matrix cracking, interface damage, fiber fracture, etc. This paper proposes to discuss our information and results on acoustic emission materials characterization undertaken on different types of materials.

  8. Acoustic Emission Technique, an Overview as a Characterization Tool in Materials Science

    Directory of Open Access Journals (Sweden)

    C. R. Ríos-Soberanis

    2011-12-01

    Full Text Available In order to predict the mechanical behavior of a composite during its service life, it is important to evaluate its mechanical response under different types of external stresses by studying the initiation and development of cracks and the effects induced by damage and degradation. The onset of damage is related to the structural integrity of the component and its fatigue life. For this, among other reasons, non-destructive techniques such as acoustic emission(AE have been widely used nowadays for composite materials haracterization. This method has demonstrated excellent results on detecting and identifying initiations sites, cracking propagation and fracture mechanisms of polymer matrix composite and ceramic materials. This paper focuses on commenting the importance of the acoustic emission technique as a unique tool for characterizing mechanical parameters in response to external stresses and degradation processes by reviewing previous investigations carried out by the author as participant. Acoustic emission was employed to monitor the micro-failure mechanisms in composites in relation to the stress level in real-time during the tests carried out. Some results obtained from different analysis are discussed to support the significance of using AE, technique that will be increasingly employed in the composite materials field due to its several lternatives for understanding the mechanical behavior; therefore, the objective of this manuscript is to involve the benefits andadvantages of AE in the characterization of materials.

  9. Classification Identification of Acoustic Emission Signals from Underground Metal Mine Rock by ICIMF Classifier

    Directory of Open Access Journals (Sweden)

    Hongyan Zuo

    2014-01-01

    Full Text Available To overcome the drawback that fuzzy classifier was sensitive to noises and outliers, Mamdani fuzzy classifier based on improved chaos immune algorithm was developed, in which bilateral Gaussian membership function parameters were set as constraint conditions and the indexes of fuzzy classification effectiveness and number of correct samples of fuzzy classification as the subgoal of fitness function. Moreover, Iris database was used for simulation experiment, classification, and recognition of acoustic emission signals and interference signals from stope wall rock of underground metal mines. The results showed that Mamdani fuzzy classifier based on improved chaos immune algorithm could effectively improve the prediction accuracy of classification of data sets with noises and outliers and the classification accuracy of acoustic emission signal and interference signal from stope wall rock of underground metal mines was 90.00%. It was obvious that the improved chaos immune Mamdani fuzzy (ICIMF classifier was useful for accurate diagnosis of acoustic emission signal and interference signal from stope wall rock of underground metal mines.

  10. Delayed Alumina Scale Spallation on Rene'n5+y: Moisture Effects and Acoustic Emission

    Science.gov (United States)

    Smialek, James L.; Morscher, Gregory N.

    2001-01-01

    The single crystal superalloy Rene'N5 (with or without Y-doping and hydrogen annealing) was cyclically oxidized at 1150 C for 1000 hours. After considerable scale growth (>= 500 hours), even the adherent alumina scales formed on Y-doped samples exhibited delayed interfacial spallation during subsequent water immersion tests, performed up to one year after oxidation. Spallation was characterized by weight loss, the amount of spalled area, and acoustic emission response. Hydrogen annealing (prior to oxidation) reduced spallation both before and after immersion, but without measurably reducing the bulk sulfur content of the Y-doped alloys. The duration and frequency of sequential, co-located acoustic emission events implied an interfacial crack growth rate at least 10(exp -3) m/s, but possibly higher than 10(exp 2) m/s. This is much greater than classic moisture-assisted slow crack growth rates in bulk alumina (10(exp -6) to 10(exp -3) m/s), which may still have occurred undetected by acoustic emission. An alternative failure sequence is proposed: an incubation process for preferential moisture ingress leads to a local decrease in interfacial toughness, thus allowing fast fracture driven by stored strain energy.

  11. New approaches for automatic threedimensional source localization of acoustic emissions--Applications to concrete specimens.

    Science.gov (United States)

    Kurz, Jochen H

    2015-12-01

    The task of locating a source in space by measuring travel time differences of elastic or electromagnetic waves from the source to several sensors is evident in varying fields. The new concepts of automatic acoustic emission localization presented in this article are based on developments from geodesy and seismology. A detailed description of source location determination in space is given with the focus on acoustic emission data from concrete specimens. Direct and iterative solvers are compared. A concept based on direct solvers from geodesy extended by a statistical approach is described which allows a stable source location determination even for partly erroneous onset times. The developed approach is validated with acoustic emission data from a large specimen leading to travel paths up to 1m and therefore to noisy data with errors in the determined onsets. The adaption of the algorithms from geodesy to the localization procedure of sources of elastic waves offers new possibilities concerning stability, automation and performance of localization results. Fracture processes can be assessed more accurately. PMID:26233938

  12. Localization of acoustic emission sources. Possibilities and limits

    International Nuclear Information System (INIS)

    It is necessary to dispose of a system capable of data acquisition and processing in real time. The coordinates of emissive sources must be calculated either immediately after the detection of information or after a brief storage time. Emphasis is laid on the various parameters liable to affect the measurement precision: transducers (type, selectivity, form of signal), threshold device (dynamics, influence on the precision), screening device (influence on the number of data received). Four-transducer patterns are now in common use: square, centred equilateral triangle, lozenge mesh ... Each geometry possesses zones of indetermination. The accuracy on the coordinates of the source varies according to the position of this source with respect to the four-transducer mesh, which leads to a case-by-case study of the arrangement and dimensions of the meshes placed on the structure to be observed. Detection and localization equipment must be designed as a whole system flexible and easy to adapt to any structure

  13. Development of Acoustic Emission Technology for Condition Monitoring and Diagnosis of Rotating Machines; Bearings, Pumps, Gearboxes, Engines and Rotating Structures.

    OpenAIRE

    Mba, David; Rao, Raj B. K. N.

    2006-01-01

    One of the earliest documented applications of Acoustic Emission Technology (AET) to rotating machinery monitoring was in the late 1960s. Since then there has been an explosion in research and application based studies covering bearings, pumps, gearboxes, engines and rotating structures. This paper presents a comprehensive and critical review to date on the application of Acoustic Emission Technology to condition monitoring and diagnostics of rotating machinery.

  14. Experimental study of acoustical characteristics of honeycomb sandwich structures

    Science.gov (United States)

    Peters, Portia Renee

    Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material

  15. 3D Characteristic Diagram of Acoustically Induced Surface Vibration with Different Landmines Buried

    Institute of Scientific and Technical Information of China (English)

    吴智强; 张燕丽; 王驰; 朱俊; 徐文文; 袁志文

    2016-01-01

    The 3Dcharacteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vi-bration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried land-mines.

  16. Correlation of acoustic emissions associated with effects from diagnostic and therapeutic ultrasound

    Science.gov (United States)

    Samuel, Stanley

    2007-12-01

    This research has investigated the correlation of acoustic emissions with associated contrast-mediated ultrasound bio-effects. The hypothesis that motivated this study was that during exposure with ultrasound, the cavitation occurring in tissue emits acoustical signals, which if correlated with specific bio-effects, could provide a way to monitor the potential bio-effects of exposure. A good bio-effects indicator would find immediate use in research on drug and gene delivery, and could have clinical application in avoiding bio-effects in diagnosis. Studies conducted to test the hypothesis involved investigation of (i) the influence of pulse repetition frequency (PRF) and number of exposures on cell damage, (ii) the effect of total exposure duration and pulse-to-pulse bubble distribution on acoustic emissions and corresponding cell damage, and (iii) the translation of in vitro effects to an in situ environment. Exposures were primarily conducted at a peak rarefactional pressure of 2 MPa, 2.25 MHz insonating frequency and pulse length of 46 cycles. PRFs of 1-, 10-, 100-, 500-, and 1000 Hz were compared. High speed photography (2000 fps) was employed for the investigation of pulse-to-pulse bubble distribution while intravital microscopy was used for in situ studies. A strong correlation was observed between acoustic emissions and bio-effects with the availability of bubbles of resonant size serving as a key link between the two. It was observed that total exposure duration may play an important role in cell damage. Damage increased with increasing total exposure duration from 0 ms to 100 ms with a plateau at above 100 ms. These results were consistent for all studies. There is, therefore, an implication that manipulating these parameters may allow for measurement and control of the extent of bioeffects. Moreover, the correlation of acoustic emission and extravasation observed in in situ studies reveals that cumulative function of the relative integrated power spectrum

  17. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, Alexey V., E-mail: a-bulanov@me.com [Far Eastern Federal University, Vladivostok, Russia 690950 (Russian Federation); V.I. Il’ichev Pacific Oceanological Institute, Vladivostok, Russia 690041 (Russian Federation); Nagorny, Ivan G., E-mail: ngrn@mail.ru [Far Eastern Federal University, Vladivostok, Russia 690950 (Russian Federation); Institute for automation and control processes, Vladivostok, Russia 690041 (Russian Federation)

    2015-10-28

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained.

  18. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    International Nuclear Information System (INIS)

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained

  19. Comparison of Medical and Voice Therapy for reflux Laryngitis Based on Acoustic and Laryngeal Characteristics

    Directory of Open Access Journals (Sweden)

    Abbas Dehestani Ardakani

    2011-12-01

    Full Text Available Background and Aim: Reflux laryngitis is extremely common among patients with voice disorder. Medical therapy approaches are not efficient enough. The main goal of this study is to assess the acoustic and laryngeal characteristics of patients with dysphonia before and after medical or voice therapy, and to evaluate the effectiveness of each.Methods: In this retrospective study, 16 reflux laryngitis patients were assessed. Five received complete voice therapy, tow ceased voice therapy and nine received medication. Perceptual voice evaluation was performed by a speech-language pathologist, the severity of voice problem was calculated, based on the affected acoustic and laryngeal characteristics pre- and post-treatment.Results: Post-treatment evaluation in patients who received complete voice therapy indicates 80 percent improvement in the severity of disorder and 100 percent improvement in the perceptual voice evaluation. After medical therapy, we observed that voice disorder and perceptual voice evaluation are improved 44 and 66 percent respectively. The improvement was statistically significant in both treatment approaches: complete voice therapy (P=0.039 and medical therapy (p=0.017.Conclusion: In patients with reflux laryngitis, most acoustic and laryngeal characteristics were normal and satisfying after the treatment. It can be concluded that the proficiency of voice therapy in improving the acoustic and laryngeal characteristics is comparable to medical therapy

  20. A study on the condition monitoring of check valve at nuclear power plants using the acoustic emission and a neural network technique

    International Nuclear Information System (INIS)

    The analysis of Acoustic Emission (AE) signals produced during object leakage is promising for condition monitoring of the components. In this study, an advanced condition monitoring technique based on acoustic emission detection and artificial neural networks was applied to a check valve, one of the components being used extensively in a safety system of a nuclear power plant. AE testing for a check valve under controlled flow loop conditions was performed to detect and evaluate disk movement for valve degradation such as wear and leakage due to foreign object interference in a check valve. It is clearly demonstrated that the evaluation of different types of failure modes such as disk wear and check valve leakage were successful by systematically analyzing the characteristics of various AE parameters. It is also shown that the leak size can be determined with an artificial neural network

  1. Time-distance domain transformation for Acoustic Emission source localization in thin metallic plates.

    Science.gov (United States)

    Grabowski, Krzysztof; Gawronski, Mateusz; Baran, Ireneusz; Spychalski, Wojciech; Staszewski, Wieslaw J; Uhl, Tadeusz; Kundu, Tribikram; Packo, Pawel

    2016-05-01

    Acoustic Emission used in Non-Destructive Testing is focused on analysis of elastic waves propagating in mechanical structures. Then any information carried by generated acoustic waves, further recorded by a set of transducers, allow to determine integrity of these structures. It is clear that material properties and geometry strongly impacts the result. In this paper a method for Acoustic Emission source localization in thin plates is presented. The approach is based on the Time-Distance Domain Transform, that is a wavenumber-frequency mapping technique for precise event localization. The major advantage of the technique is dispersion compensation through a phase-shifting of investigated waveforms in order to acquire the most accurate output, allowing for source-sensor distance estimation using a single transducer. The accuracy and robustness of the above process are also investigated. This includes the study of Young's modulus value and numerical parameters influence on damage detection. By merging the Time-Distance Domain Transform with an optimal distance selection technique, an identification-localization algorithm is achieved. The method is investigated analytically, numerically and experimentally. The latter involves both laboratory and large scale industrial tests. PMID:26950889

  2. Co-detection of acoustic emissions during failure of heterogeneous media: new perspectives for natural hazard early warning

    CERN Document Server

    Faillettaz, J; Reiweger, I

    2015-01-01

    A promising method for real time early warning of gravity driven rupture that considers both the heterogeneity of natural media and characteristics of acoustic emissions attenuation is proposed. The method capitalizes on co-detection of elastic waves emanating from micro-cracks by multiple and spatially separated sensors. Event co-detection is considered as surrogate for large event size with more frequent co-detected events marking imminence of catastrophic failure. Using a spatially explicit fiber bundle numerical model with spatially correlated mechanical strength and two load redistribution rules, we constructed a range of mechanical failure scenarios and associated failure events (mapped into AE) in space and time. Analysis considering hypothetical arrays of sensors and consideration of signal attenuation demonstrate the potential of the co-detection principles even for insensitive sensors to provide early warning for imminent global failure.

  3. Effect of Pyramidal Dome Geometry on the Acoustical Characteristics in A Mosque

    OpenAIRE

    Dg. H. Kassim; A. Putra; M. J. M. NOR; N.S. Muhammad

    2014-01-01

    As an important symbol in Islam, a mosque is built with architectural grandeur. Among the characteristics is its high ceiling and it is usually constructed with a typical spherical dome shape. Some mosques, however, are influenced by the local culture and the dome can be of a different shape, such as pyramidal, as found in mosques in Malacca, Malaysia. This paper presents an assessment of the internal acoustical characteristics of a mosque having a pyramidal dome. The study is conducted by me...

  4. Comparison of Acoustic Characteristics of Date Palm Fibre and Oil Palm Fibre

    OpenAIRE

    Lamyaa Abd ALRahman; Raja Ishak Raja; Roslan Abdul Rahman; Zawawi Ibrahim

    2014-01-01

    This study investigated and compared the acoustic characteristics of two natural organic fibres: date palm fibre and oil palm fibre, these materials eligible for acoustical absorption. During the processing stage, both fibre sheets are treated with latex. The two fibres are compressed after latex treatment Circular samples (100 mm in diameter and 28 mm, based on the measurement tube requirements) are cut out of the sheets. The density of the date palm fibre sheet is 150 kg/m3 for a 50 mm thic...

  5. Surface acoustic wave regulated single photon emission from a coupled quantum dot-nanocavity system

    CERN Document Server

    Weiß, Matthias; Reichert, Thorsten; Finley, Jonathan J; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J

    2016-01-01

    A coupled quantum dot--nanocavity system in the weak coupling regime of cavity quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a $f_{\\rm SAW}\\simeq800\\,\\mathrm{MHz}$ surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function $g^{(2)}$. All relevant frequencies of our experiment are faithfully identified in the Fourier transform of $g^{(2)}$, demonstrating high fidelity regulation of the stream of single photons emitted by the system. The implemented scheme can be directly extended to strongly coupled systems and acoustically drives non-adiabatic entangling quantum gates based on Landau-Zener transitions.

  6. Online monitoring of Accessories for Underground Electrical Installations through Acoustics Emissions

    Directory of Open Access Journals (Sweden)

    Casals-Torrens P.

    2012-04-01

    Full Text Available The acoustic waves caused by Partial Discharges inside the dielectric materials, can be detected by acoustic emission (AE sensors and analyzed in the time domain. The experimental results presented, show the online detection capability of these sensors in the environment near a cable accessory, such as a splice or terminal. The AE sensors are immune to electromagnetic interference and constitute a detection method non-intrusive and non-destructive, which ensures a galvanic decoupling with respect to electric networks, this technique of partial discharge detection can be applied as a test method for preventive or predictive maintenance (condition-based maintenance to equipments or facilities of medium and high voltage in service and represents an alternative method to electrical detection systems, conventional or not, that continue to rely on the detection of current pulses. This paper presents characterization tests of the sensors AE through comparative tests of partial discharge on accessories for underground power cables.

  7. Separating medial olivocochlear from acoustic reflex effects on transient evoked otoacoustic emissions in unanesthetized mice

    Science.gov (United States)

    Xu, Yingyue; Cheatham, Mary Ann; Siegel, Jonathan

    2015-12-01

    Descending neural pathways in the mammalian auditory system are believed to modulate the function of the peripheral auditory system [3, 8, 10]. These pathways include the medial olivocochlear (MOC) efferent innervation to the cochlear outer hair cells (OHCs) and the acoustic reflex pathways mediating middle ear muscle (MEM) contractions. The MOC effects can be monitored noninvasively using otoacoustic emissions (OAEs) [5, 6], which are acoustic byproducts of cochlear function [7]. In this study, we applied a sensitive method to determine when and to what degree contralateral MEM suppression contaminated MOC efferent effects on TEOAEs in unanesthetized mice. The lowest contralateral broadband noise evoking MEM contractions varied across animals. Examples of potential MOC-mediated TEOAE suppression with contralateral noise below MEM contraction thresholds were seen, but this behavior did not occur in the majority of cases.

  8. Effects of Inlet/Outlet Ducts on Acoustic Attenuation Characteristics of Circular Expansion Chambers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-bo; GE Yun-shan; JI Zhen-lin; ZHANG Wen-ping; SONG Yan-rong; HAN Xiu-kun; ZHANG Xue-min

    2006-01-01

    The effect of coaxial, offset and extended inlet/outlet on the acoustic attenuation characteristics of circular expansion chambers are studied by the three-dimensional finite element method. The numerical results of transmission loss are compared with experiment results to verify the necessary of using three-dimensional methods. Maps of acoustic pressure level distribution inside of chambers and inlet/outlet ducts are given at a frequency to demonstrate the difference of acoustic wave propagation behavior caused by locations of inlet/outlet ducts. For the chambers of the same length, the chamber with extended inlet/outlet duct has higher attenuation ability than coaxial and offset inlet/outlet duct over middle frequencies.

  9. Statistical analysis of acoustic characteristics of Tibetan Lhasa dialect speech emotion

    Directory of Open Access Journals (Sweden)

    Guo Dandan

    2016-01-01

    Full Text Available The paper makes a quantitative analysis and comparison on the continuous speech emotion of Lhasa Tibetan in the four basic emotional patterns (happy, surprise, sad, neutral pitch, energy and time length by experimental phonetics and the linear statistical research methods, found that there is a positive correlation between the Lhasa Tibetan emotional speech and pitch, energy and duration, etc. And the pitch, energy and duration of negative emotion acoustic parameters are bigger than positive emotion, on this basis, drawing the Lhasa Tibetan speech emotion acoustic feature patterns. Compared with the Chinese language and the Tibetan, even though both have the tone prosodic features, they also have significant differences in the acoustic characteristics of the speech emotion.

  10. Correlated terahertz acoustic and electromagnetic emission in dynamically screened InGaN/GaN quantum wells

    DEFF Research Database (Denmark)

    van Capel, P. J. S.; Turchinovich, Dmitry; Porte, Henrik;

    2011-01-01

    signals and THz electromagnetic radiation signals demonstrates that transient strain generation in InGaN/GaN MQWs is correlatedwith electromagnetic THz generation, and both types of emission find their origin in ultrafast dynamical screening of the built-in piezoelectric field in the MQWs. The measured......We investigate acoustic and electromagnetic emission from optically excited strained piezoelectric In0.2Ga0.8N/GaN multiple quantum wells (MQWs), using optical pump-probe spectroscopy, time-resolved Brillouin scattering, and THz emission spectroscopy. A direct comparison of detected acoustic...

  11. Waves on a Hele-Shaw Cell: Simulations of Acoustic Emissions During Aerofracture

    Science.gov (United States)

    Turkaya, Semih; Toussaint, Renaud; Kvalheim Eriksen, Fredrik; Daniel, Guillaume; Grude Flekkøy, Eirik; Jørgen Måløy, Knut

    2016-04-01

    In this work, we develop a numerical model to explain the lab scale experimental setup [1] modeling the aerofractures in a porous medium. The mentioned experimental setup consists in a rectangular Hele-Shaw cell with three closed boundaries and one semi-permeable boundary which enables the flow of the fluid but not the solid particles. During the experiments, the fluid (pressurized air) is injected into the system with a constant injection pressure from the point opposite to the semi-permeable boundary. At the large enough injection pressures, the fluid also displaces grains (80 μm grain size) and creates channels and fractures towards the semi-permeable boundary. This analogue model is developed in a linear geometry, with confinement and at a lower porosity to study the instabilities developing during the fast motion of a fluid in dense porous materials: fracturing, fingering, and channeling. Different sources of the signal (air vibration in the carved area, changes in the effective stress due to fluid-solid interactions [2]) are separately analyzed and are investigated further using a far field approximation of Lamb waves presented by Goyder & White [3]. In the analysis phase, power spectrum of different timewindows (5 ms) obtained from the recorded signal are computed. Then, the evolution of this power spectrum is compared with the experimental findings. In the power spectrum, it is possible to see some characteristic structure like peaks in specific frequency ranges. These "peaks" are strongly influenced by the size and branching of the channels, compaction of the medium, vibration of air in the pores and the fundamental frequency of the plate. We found that, in the synthetic dataset, the peaks in the low frequency range (f Bridging aero-fracture evolution with the characteristics of the acoustic emissions in a porous medium." Front. Phys., 3 (2015): 70. doi: 10.3389/fphy.2015.00070 2. Niebling MJ, Toussaint R, Flekkøy EG, Maløy KJ. "Dynamic aerofracture of

  12. Standard practice for examination of fiberglass reinforced plastic fan blades using acoustic emission

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice provides guidelines for acoustic emission (AE) examinations of fiberglass reinforced plastic (FRP) fan blades of the type used in industrial cooling towers and heat exchangers. 1.2 This practice uses simulated service loading to determine structural integrity. 1.3 This practice will detect sources of acoustic emission in areas of sensor coverage that are stressed during the course of the examination. 1.4 This practice applies to examinations of new and in-service fan blades. 1.5 This practice is limited to fan blades of FRP construction, with length (hub centerline to tip) of less than 3 m [10 ft], and with fiberglass content greater than 15 % by weight. 1.6 AE measurements are used to detect emission sources. Other nondestructive examination (NDE) methods may be used to evaluate the significance of AE sources. Procedures for other NDE methods are beyond the scope of this practice. 1.7 Units—The values stated in either SI units or inch-pound units are to be regarded separately as sta...

  13. Quantitative evaluation of rejuvenators to restore embrittlement temperatures in oxidized asphalt mixtures using acoustic emission

    Science.gov (United States)

    Sun, Zhe; Farace, Nicholas; Arnold, Jacob; Behnia, Behzad; Buttlar, William G.; Reis, Henrique

    2015-03-01

    Towards developing a method capable to assess the efficiency of rejuvenators to restore embrittlement temperatures of oxidized asphalt binders towards their original, i.e., unaged values, three gyratory compacted specimens were manufactured with mixtures oven-aged for 36 hours at 135 °C. In addition, one gyratory compacted specimen manufactured using a short-term oven-aged mixture for two hours at 155 °C was used for control to simulate aging during plant production. Each of these four gyratory compacted specimens was then cut into two cylindrical specimen 5 cm thick for a total of six 36-hour oven-aged specimens and two short term aging specimens. Two specimens aged for 36 hours and the two short-term specimens were then tested using an acoustic emission approach to obtain base acoustic emission response of short-term and severely-aged specimens. The remaining four specimens oven-aged for 36 hours were then treated by spreading their top surface with rejuvenator in the amount of 10% of the binder by weight. These four specimens were then tested using the same acoustic emission approach after two, four, six, and eight weeks of dwell time. It was observed that the embrittlement temperatures of the short-term aged and severely oven-aged specimens were -25 °C and - 15 °C, respectively. It was also observed that after four weeks of dwell time, the rejuvenator-treated samples had recuperated the original embrittlement temperatures. In addition, it was also observed that the rejuvenator kept acting upon the binder after four weeks of dwell time; at eight weeks of dwell time, the specimens had an embrittlement temperature about one grade cooler than the embrittlement temperature corresponding to the short-term aged specimen.

  14. STUDY ON STABILITY OF UNDERGROUND STRUCTURAL ENGINEERING BY ACOUSTIC EMISSION MONITORING SYSTEM

    Institute of Scientific and Technical Information of China (English)

    来兴平; 张冰川; 蔡美峰

    2000-01-01

    A simulation acoustic emission (AE) signal was processed. And an effective algorithm was presented to obtain the useful signal about the place information from the simulation signal. This paper introduces the artificial monitoring system, its application at underground roadway and its monitoring results, and tries to explore theoretically analyzing method of stability of underground concrete roadway by AE parameters. A simulation AE signal was processed. And an effective algorithm was presented to obtain the useful signal about the place information from the simulation signal It shows the nice future of the application in the active damage detection of composite material.

  15. Time reverse modeling of acoustic emissions in a reinforced concrete beam.

    Science.gov (United States)

    Kocur, Georg Karl; Saenger, Erik H; Grosse, Christian U; Vogel, Thomas

    2016-02-01

    The time reverse modeling (TRM) is applied for signal-based acoustic emission (AE) analysis of reinforced concrete (RC) specimens. TRM uses signals obtained from physical experiments as input. The signals are re-emitted numerically into a structure in a time-reversed manner, where the wavefronts interfere and appear as dominant concentrations of energy at the origin of the AE. The experimental and numerical results presented for selected AE signals confirm that TRM is capable of localizing AE activity in RC caused by concrete cracking. The accuracy of the TRM results is corroborated by three-dimensional crack distributions obtained from X-ray computed tomography images.

  16. Couple analyzing the acoustic emission characters from hard composite rock fracture

    Institute of Scientific and Technical Information of China (English)

    Xingping Lai; Linhai Wang; Meifeng Cai

    2004-01-01

    Rock mass is fractured media. Its fracture is a nonlinear process. The accumulation of acoustic emission (AE) is closely related to the degree of damage. The dynamics problem is simply described based on the non-equilibrium statistical theory of crack evolvement, trying to use the hybrid analysis of the statistical theory and scan electron microscopy (SEM), the characters of AE sig nals from rock damage in a mined-out area is synthetically analyzed and evaluated. These provide an evidence to reverse deduce and accurately infer the position of rock fracture for dynamical hazard control.

  17. An efficient closed-form solution for acoustic emission source location in three-dimensional structures

    Directory of Open Access Journals (Sweden)

    Xibing Li

    2014-02-01

    Full Text Available This paper presents an efficient closed-form solution (ECS for acoustic emission(AE source location in three-dimensional structures using time difference of arrival (TDOA measurements from N receivers, N ≥ 6. The nonlinear location equations of TDOA are simplified to linear equations. The unique analytical solution of AE sources for unknown velocity system is obtained by solving the linear equations. The proposed ECS method successfully solved the problems of location errors resulting from measured deviations of velocity as well as the existence and multiplicity of solutions induced by calculations of square roots in existed close-form methods.

  18. Damage Accumulation in Cyclically-Loaded Glass-Ceramic Matrix Composites Monitored by Acoustic Emission

    Science.gov (United States)

    Aggelis, D. G.; Dassios, K. G.; Kordatos, E. Z.; Matikas, T. E.

    2013-01-01

    Barium osumilite (BMAS) ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE) sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism. PMID:24381524

  19. Acoustic emission of a passenger car.Effect of road gradient

    OpenAIRE

    HAMET, JF; Lelong, J.

    2005-01-01

    The effect of a road gradient on the acoustic emission of a passenger car is ad-dressed on a theoretical and an experimental ground. The work is based on an engine rpm/engine torque/engine noise relation, given through an abacus in an Internoise communication [1]. The increase of the total running resistance due to the occurrence of a climbing resistance results in an increase of the engine noise. The increase is higher gear shift k+1 than in gear shift k. The consequences on the total emissi...

  20. An Analytical Solution for Acoustic Emission Source Location for Known P Wave Velocity System

    Directory of Open Access Journals (Sweden)

    Longjun Dong

    2014-01-01

    Full Text Available This paper presents a three-dimensional analytical solution for acoustic emission source location using time difference of arrival (TDOA measurements from N receivers, N⩾5. The nonlinear location equations for TDOA are simplified to linear equations, and the direct analytical solution is obtained by solving the linear equations. There are not calculations of square roots in solution equations. The method solved the problems of the existence and multiplicity of solutions induced by the calculations of square roots in existed close-form methods. Simulations are included to study the algorithms' performance and compare with the existing technique.

  1. An efficient closed-form solution for acoustic emission source location in three-dimensional structures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xibing [School of Resources and Safety Engineering, Central South University, Changsha, 410083 (China); Dong, Longjun, E-mail: csudlj@163.com [School of Resources and Safety Engineering, Central South University, Changsha, 410083 (China); Australian Centre for Geomechanics, The University of Western Australia, Crawley, 6009 (Australia)

    2014-02-15

    This paper presents an efficient closed-form solution (ECS) for acoustic emission(AE) source location in three-dimensional structures using time difference of arrival (TDOA) measurements from N receivers, N ≥ 6. The nonlinear location equations of TDOA are simplified to linear equations. The unique analytical solution of AE sources for unknown velocity system is obtained by solving the linear equations. The proposed ECS method successfully solved the problems of location errors resulting from measured deviations of velocity as well as the existence and multiplicity of solutions induced by calculations of square roots in existed close-form methods.

  2. Time reverse modeling of acoustic emissions in a reinforced concrete beam.

    Science.gov (United States)

    Kocur, Georg Karl; Saenger, Erik H; Grosse, Christian U; Vogel, Thomas

    2016-02-01

    The time reverse modeling (TRM) is applied for signal-based acoustic emission (AE) analysis of reinforced concrete (RC) specimens. TRM uses signals obtained from physical experiments as input. The signals are re-emitted numerically into a structure in a time-reversed manner, where the wavefronts interfere and appear as dominant concentrations of energy at the origin of the AE. The experimental and numerical results presented for selected AE signals confirm that TRM is capable of localizing AE activity in RC caused by concrete cracking. The accuracy of the TRM results is corroborated by three-dimensional crack distributions obtained from X-ray computed tomography images. PMID:26518525

  3. Acoustic emission-based in-process monitoring of surface generation in robot-assisted polishing

    DEFF Research Database (Denmark)

    Pilny, Lukas; Bissacco, Giuliano; De Chiffre, Leonardo;

    2015-01-01

    The applicability of acoustic emission (AE) measurements for in-process monitoring of surface generation in the robot-assisted polishing (RAP) was investigated. Surface roughness measurements require interruption of the process, proper surface cleaning and measurements that sometimes necessitate...... removal of the part from the machine tool. In this study, stabilisation of surface roughness during polishing rotational symmetric surfaces by the RAP process was monitored by AE measurements. An AE sensor was placed on a polishing arm in direct contact with a bonded abrasive polishing tool...

  4. Mechanical degradation of cross-ply laminates monitored by acoustic emission

    Science.gov (United States)

    Paipetis, A.; Xyrafa, M.; Barkoula, N. M.; Matikas, T. E.; Aggelis, D. G.

    2011-04-01

    This study deals with the investigation of cross ply composites failure by acoustic emission (AE). Broadband AE sensors monitor the different sources of failure in coupons of this material during a tensile loading-unloading test. The cumulative number of AE activity, and other qualitative indices based on the shape of the waves, were well correlated to the sustained load. AE parameters indicate the shift of failure mechanisms within the composite as the load increases. The ultimate goal is a methodology based on NDT techniques for real time characterization of the degradation and identification of the fracture stage of advanced composite materials.

  5. Electron Beam Emission Characteristics from Plasma Focus Devices

    Science.gov (United States)

    Zhang, T.; Patran, A.; Wong, D.; Hassan, S. M.; Springham, S. V.; Tan, T. L.; Lee, P.; Lee, S.; Rawat, R. S.

    2006-01-01

    In this paper we observed the characteristics of the electron beam emission from our plasma focus machine filling neon, argon, helium and hydrogen. Rogowski coil and CCD based magnetic spectrometer were used to obtain temporal and energy distribution of electron emission. And the preliminary results of deposited FeCo thin film using electron beam from our plasma focus device were presented.

  6. Acoustic emission generated during the gas sorption-desorption process in coal

    Institute of Scientific and Technical Information of China (English)

    Ma Yankun; Wang Enyuan; Xiao Dong; Li Zhonghui; Liu Jie; Gan Lijia

    2012-01-01

    An experimental system for monitoring the acoustic signals generated in coal during gas sorption and/or desorption was designed and the acoustic signals were observed under different gas pressures.The experimental results show that signals generated by the coal during gas adsorption are attenuated over time.Also,the signals are not continuous but are impulsive.The intensity of the signals generated during gas desorption is far smaller than that observed during adsorption.The signal seen during desorption remains essentially stable.Cycles of sorption and desorption cause acoustic emission signals that exhibit a memory effect,which depends upon the maximum gas pressure the sample was exposed to in earlier cycles.Lower pressures in subsequent cycles,compared to the maximum adsorption pressure in previous cycles,cause both the energy and impulse frequency to be lower than previously.On the contrary,a gas adsorption pressure that exceeds the maximum pressure seen by the sample during earlier cycles causes both the energy and impulse frequency to be high.

  7. Nanodiamond vacuum field emission device with gate modulated triode characteristics

    Science.gov (United States)

    Hsu, S. H.; Kang, W. P.; Raina, S.; Huang, J. H.

    2013-05-01

    A three-electrode nanodiamond vacuum field emission (VFE) device with gate modulated triode characteristics is developed by integrating nanodiamond emitter with self-aligned silicon gate and anode, employing a mold transfer technique in conjunction with chemical vapor deposition of nanodiamond. Triode behavior showing emission current modulation with high current density at low operating voltages is achieved. A systematic analysis based on modified Fowler-Nordheim theory is used to analyze gate modulated VFE characteristics, confirming the triode field emission mechanism and operating principle. The realization of an efficient VFE microtriode has achieved the fundamental step for further development of vacuum integrated microelectronics.

  8. Contralateral acoustic suppression of transient evoked otoacoustic emissions: Activation of the medial olivocochlear system

    Directory of Open Access Journals (Sweden)

    Komazec Zoran

    2003-01-01

    Full Text Available Medial olivocochlear pathway represents the final part of efferent acoustic pathway which comes from the superior olivary complex ending at outer hair cells. Activation of medial olivocochlear system (MOCS alters the cochlear output decreasing the travelling wave within cochlea. Stimulation of MOCS provides protection against moderate levels of noise, encoding noise signals as well as selecting hearing attention. Activation of MOCS can be performed using contralateral acoustic stimulation. The principal result of presentation of contralateral acoustic stimulation during screening of transient evoked otoacoustic emission (TEOAE is an attenuation of the TEOAE amplitude. Thirty-eight ears were examined in this study: twenty-eight ears from 14 normal-hearing adults and 10 patients with unilateral deafness. Healthy subjects were exposed to contralateral broad-band noise of various intensities (40, 30, 20 and 10 dB SL, as well as 30 dB SL pure tone stimulation (1 kHz and 4 kHz. A decrease of TEOAE amplitudes during contralateral stimulation with 40 and 30 dB SL broad-band noise and pure tones was established. This effect was a result of MOCS activation. A greater intensity of contralateral stimulation evoked greater decrease of TEOAE amplitude; stimulation with broad-band noise caused greater attenuation than with pure tone stimulation. Contralateral stimulation of deaf ears in the group with unilateral deafness was also performed. Statistically significant difference between TEOAE amplitude before and during contralateral stimulation was not established. This circumstance explains that activation of MOCS and consequent reduction of outer hair cells motility is very possibly caused by contralateral acoustic stimulation. Apart from studying physiological significance of efferent auditory system, results of this and similar studies can be used for production of hearing aids improving speech discrimination in noisy environment.

  9. EMISSION CHARACTERISTICS OF LIQUID METAL ION SOURCE

    OpenAIRE

    Arimoto, H.; Komuro, M.

    1989-01-01

    Energy distributions of Au-Si-Be, Au-Si, Pd-Ni-Si-Be-B, and Pt-Si liquid metal alloy ion sources were investigated, being focused on behaviors of Si++ and Si+. We found that the energy spreads of the Si++ and Si+ were kept constant at 6 to 7.5 eV, even at an extremely low emission current (50 nA). This saturation results in a decrease in the figure of merit, (dI/dΩ)/ (ƊE)2, for an ion probe forming. (dI/dΩ : angular current density, ƊE : energy spread) The energy distribution profiles suggest...

  10. Extraction of internal emission characteristics from printed OLEDs

    Science.gov (United States)

    Hildner, Mark L.; Ziebarth, Jonathan M.

    2012-09-01

    Accurate optical modeling of OLED device performance is beneficial to OLED manufacturing because as materials and architectures are modified, experimental effort and resources are saved in the search for optimal structures. The success of such modeling depends crucially on model inputs, which include, along with layer thicknesses and optical constants, internal emission characteristics such as the internal emission spectrum (IES) of the emitter and the location and profile of emission in the emissive layer (EML). This presentation will describe two methods we have used to extract the internal emission characteristics of our printed bottom emitting OLEDs. The first method, which we devised and implemented with assumptions specific to our devices, is a simpler one for both modeling and data collection: we collected spectra at normal viewing angle for a series of devices with different architectures, and extracted a normalized IES common to all these devices. We will show how an emission location was obtained from this method with some simple model assumptions. In the more rigorous second method - one presented by van Mensfoort et al 1 - internal emission characteristics were extracted independently for each device: spectra at multiple angles were collected, which allowed the extraction of an individual IES and emission profile. We will compare the findings of the two methods and assess the validity of the assumptions used in the first method.

  11. Electrical Resistance and Acoustic Emission Measurements for Monitoring the Structural Behavior of CFRP Laminate

    KAUST Repository

    Zhou, Wei

    2015-07-12

    Electrical resistance and acoustic emission (AE) measurement are jointly used to monitor the degradation in CFRP laminates subjected to tensile tests. The objective of this thesis is to perform a synergertic analysis between a passive and an active methods to better access how these perform when used for Structural Health Moni- toring (SHM). Laminates with three different stacking sequences: [0]4, [02/902]s and [+45/ − 45]2s are subjected to monotonic and cyclic tensile tests. In each laminate, we carefully investigate which mechanisms of degradation can or cannot be detect- ed by each technique. It is shown that most often, that acoustic emission signals start before any electrical detection is possible. This is is explained based on the redundance of the electrical network that makes it less sensitive to localized damages. Based on in depth study of AE signals clustering, a new classification is proposed to recognize the different damage mechanims based on only two parameters: the RA (rise time/amplitude) and the duration of the signal.

  12. Robust Clustering of Acoustic Emission Signals Using Neural Networks and Signal Subspace Projections

    Directory of Open Access Journals (Sweden)

    Shi Zhiqiang

    2003-01-01

    Full Text Available Acoustic emission-based techniques are being used for the nondestructive inspection of mechanical systems. For reliable automatic fault monitoring related to the generation and propagation of cracks, it is important to identify the transient crack-related signals in the presence of strong time-varying noise and other interference. A prominent difficulty is the inability to differentiate events due to crack growth from noise of various origins. This work presents a novel algorithm for automatic clustering and separation of acoustic emission (AE events based on multiple features extracted from the experimental data. The algorithm consists of two steps. In the first step, the noise is separated from the events of interest and subsequently removed using a combination of covariance analysis, principal component analysis (PCA, and differential time delay estimates. The second step processes the remaining data using a self-organizing map (SOM neural network, which outputs the noise and AE signals into separate neurons. To improve the efficiency of classification, the short-time Fourier transform (STFT is applied to retain the time-frequency features of the remaining events, reducing the dimension of the data. The algorithm is verified with two sets of data, and a correct classification ratio over 95% is achieved.

  13. Damage Modes Recognition and Hilbert-Huang Transform Analyses of CFRP Laminates Utilizing Acoustic Emission Technique

    Science.gov (United States)

    WenQin, Han; Ying, Luo; AiJun, Gu; Yuan, Fuh-Gwo

    2016-04-01

    Discrimination of acoustic emission (AE) signals related to different damage modes is of great importance in carbon fiber-reinforced plastic (CFRP) composite materials. To gain a deeper understanding of the initiation, growth and evolution of the different types of damage, four types of specimens for different lay-ups and orientations and three types of specimens for interlaminar toughness tests are subjected to tensile test along with acoustic emission monitoring. AE signals have been collected and post-processed, the statistical results show that the peak frequency of AE signal can distinguish various damage modes effectively. After a AE signal were decomposed by Empirical Mode Decomposition (EMD) method, it may separate and extract all damage modes included in this AE signal apart from damage mode corresponding to the peak frequency. Hilbert-Huang Transform (HHT) of AE signals can clearly illustrate the frequency distribution of Intrinsic Mode Functions (IMF) components in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition to help understanding the damage process.

  14. Determination of bearing steel heat treatment with the use of the acoustic emission method

    Directory of Open Access Journals (Sweden)

    T.Z. Woźniak

    2010-07-01

    Full Text Available A study on the control of an extremely important stage of the martensitic-bainitic austempering and obtaining the M-B structure in the 100CrMnSi6-4 steel with the use of the acoustic emission (AE has been undertaken. In order to enrich retained austenite with carbon,steels are austempered at appropriately low temperatures. A martensitic transformation, resulting from diffusionless and displacive transformation is associated with significant AE signs. The strain energy produced during growth due to the shape change is reduced by plastic deformation. Predominant source of (AE is the movement of dislocations in order to relieve internal stresses.The heat treatment was performed in a modern, purpose-constructed device which simultaneously records acoustic emission effects. The signals were recorded with the use of an AE analyzer 20–800 kHz, and they were received by means of a broadband piezoelectric transducer with the use of a specialist card with a sampling frequency of 1200 kHz. The results regarding a correlation of austempering temperature and the maximum number of AE events and dilatometric results have been presented. This parameter can be used for precise Ms temperatureestimation. Basing on microstructural investigations, it has been found that previously formed martensite with midrib morphology alsoaccelerates the bainitic transformation.

  15. Determination of bearing steel heat treatment with the use of the acoustic emission method

    Directory of Open Access Journals (Sweden)

    T. Z. Wozniak

    2010-10-01

    Full Text Available A study on the control of an extremely important stage of the martensitic-bainitic austempering and obtaining the M-B structure in the 100CrMnSi6-4 steel with the use of the acoustic emission (AE has been undertaken. In order to enrich retained austenite with carbon, steels are austempered at appropriately low temperatures. A martensitic transformation, resulting from diffusionless and displacive transformation is associated with significant AE signs. The strain energy produced during growth due to the shape change is reduced by plastic deformation. Predominant source of (AE is the movement of dislocations in order to relieve internal stresses.The heat treatment was performed in a modern, purpose-constructed device which simultaneously records acoustic emission effects. The signals were recorded with the use of an AE analyzer 20–800 kHz, and they were received by means of a broadband piezoelectric transducer with the use of a specialist card with a sampling frequency of 1200 kHz. The results regarding a correlation of austempering temperature and the maximum number of AE events and dilatometric results have been presented. This parameter can be used for precise Ms temperature estimation. Basing on microstructural investigations, it has been found that previously formed martensite with midrib morphology also accelerates the bainitic transformation.

  16. A combined complex electrical impedance and acoustic emission study in limestone samples under uniaxial loading

    Science.gov (United States)

    Saltas, V.; Fitilis, I.; Vallianatos, F.

    2014-12-01

    In the present work, complex electrical impedance measurements in the frequency range of 10 mHz to 1 MHz were carried out in conjunction with acoustic emission monitoring in limestone samples subjected to linear and stepped-like uniaxial loading, up to ultimate failure. Cole-Cole plots of the complex impedance during the stepped loading of limestone have been used to discriminate the contributions of grains interior, grain boundaries and electrode polarization effects to the overall electrical behavior. The latter is well-described with an equivalent-circuit model which comprises components of constant phase elements and resistances in parallel connection. Electrical conductivity increases upon uniaxial loading giving rise to negative values of effective activation volume. This is a strong experimental evidence for the generation of transient electric signals recorded prior to seismic events and may be attributed to charge transfer (proton conduction) due to cracks generation and propagation as a result of the applied stress. The time-series of ac-conductivity at two distinct frequencies (10 kHz, 200 kHz) during linear loading of limestone samples exhibits a strong correlation with the acoustic emission activity obeying the same general self-similar law for critical phenomena that has been reported for the energy release before materials fracture.

  17. Can acoustic emissions patterns signal imminence of avalanche events in a growing sand pile?

    Science.gov (United States)

    Vögtli, Melanie; Lehmann, Peter; Breitenstein, Daniel; Or, Dani

    2014-05-01

    Gravity driven mass release is often triggered abruptly with limited precursory cues to indicate imminent failure and thus limiting early warning. Evidence suggests that with increased mechanical loading of a slope, numerous local damage events marking friction between rearranged particles or breakage of roots release strain energy as elastic waves measurable as acoustic emissions. We examined the potential predictability of mass release events from preceding acoustic emission (AE) signatures in a well-known and simple model system of a growing sand pile. We installed four AE-sensors within the core of a 30 cm (diameter) sand pile fed by a constant input of grains and mounted on a balance. Subsequent to the convergence of the slope to dynamic angle of repose, sand avalanche across the bottom boundary were monitored by abrupt mass change and by the amplitudes and number of AE events (recorded at high frequency and averaged to 0.2 s). We detected a systematic change of AE-patterns characterized by systematically decreasing AE standard deviation prior to each mass release. Although the lead time following minimum AE standard deviation was relatively short (10s of seconds), the AE signature already started to change minutes before the mass release. Accordingly the information embedded in AE signal dynamics could potentially offer larger lead times for systems of practical interest.

  18. The Sound Emission Board of the KM3NeT Acoustic Positioning System

    CERN Document Server

    Llorens, C D; Sogorb, T; Bou--Cabo, M; Martínez-Mora, J A; Larosa, G; Adrián-Martínez, S

    2012-01-01

    We describe the sound emission board proposed for installation in the acoustic positioning system of the future KM3NeT underwater neutrino telescope. The KM3NeT European consortium aims to build a multi-cubic kilometre underwater neutrino telescope in the deep Mediterranean Sea. In this kind of telescope the mechanical structures holding the optical sensors, which detect the Cherenkov radiation produced by muons emanating from neutrino interactions, are not completely rigid and can move up to dozens of meters in undersea currents. Knowledge of the position of the optical sensors to an accuracy of about 10 cm is needed for adequate muon track reconstruction. A positioning system based on the acoustic triangulation of sound transit time differences between fixed seabed emitters and receiving hydrophones attached to the kilometre-scale vertical flexible structures carrying the optical sensors is being developed. In this paper, we describe the sound emission board developed in the framework of KM3NeT project, whi...

  19. [Characteristic of Particulate Emissions from Concrete Batching in Beijing].

    Science.gov (United States)

    Xue, Yi-feng; Zhou, Zhen; Zhong, Lian-hong; Yan, Jing; Qu, Song; Huang, Yu-hu; Tian, He- zhong; Pan, Tao

    2016-01-15

    With the economic development and population growth in Beijing, there is a strong need for construction and housing, which leads to the increase of the construction areas. Meanwhile, as a local provided material, the production of concrete has been raised. In the process of concrete production by concrete batching, there are numerous particulates emitted, which have large effect on the atmospheric environment, however, systematic study about the tempo-spatial characteristics of pollutant emission from concrete batching is still rare. In this study, we estimated the emission of particulates from concrete batching from 1991 to 2012 using emission factor method, analyzed the tempo-spatial characteristics of pollutant emission, established the uncertainty range by adopting Monte-Carlo method, and predicted the future emission in 2020 based on the relative environmental and economical policies. The results showed that: (1) the emissions of particulates from concrete batching showed a trend of "first increase and then decrease", reaching the maximum in 2005, and then decreased due to stricter emission standard and enhanced environmental management. (2) according to spatial distribution, the emission of particulates from concrete batch mainly concentrated in the urban area with more human activities, and the area between the fifth ring and the sixth ring contributed the most. (3) through scenarios analysis, for further reducing the emission from concrete batching in 2020, more stricter standard for green production as well as powerful supervision is needed.

  20. Experimental study of ultra-thin films mechanical integrity by combined nanoindentation and nano-acoustic emission

    Science.gov (United States)

    Zhang, Zihou

    Advancement of interconnect technology has imposed significant challenge on interface characterization and reliability for blurred interfaces between layers. There is a need for material properties and these miniaturized length scales and assessment of reliability; including the intrinsic film fracture toughness and the interfacial fracture toughness. The nano-meter range of film thicknesses currently employed, impose significant challenges on evaluating these physical quantities and thereby impose significant challenge on the design cycle. In this study we attempted to use a combined nano-indentation and nano-acoustic emission to qualitatively and quantitatively characterize the failure modes in ultra-thin blanket films on Si substrates or stakes of different characteristics. We have performed and analyzed an exhaustive group of testes that cove many diverge combination of film-substrate combination, provided by both Intel and IBM. When the force-indentation depth curve shows excursion, a direct measure of the total energy release rate is estimated. The collected acoustic emission signal is then used to partition the total energy into two segments, one associated with the cohesive fracture toughness of the film and the other is for the adhesive fracture toughness of the interface. The acoustic emission signal is analyzed in both the time and frequency domain to achieve such energy division. In particular, the signal time domain analysis for signal skewness, time of arrival and total energy content are employed with the proper signal to noise ratio. In the frequency domain, an expansive group of acoustic emission signals are utilized to construct the details of the power spectral density. A bank of band-pass filters are designed to sort the individual signals to those associated with adhesive interlayer cracking, cohesive channel cracking, or other system induced noise. The attenuation time and the energy content within each spectral frequency were the key elements

  1. Study of the microwave emissivity characteristics over Gobi Desert

    International Nuclear Information System (INIS)

    The microwave emissivity represents the capacity of the thermal radiation of the surface, and it is the significant parameter for understanding the geophysical processes such as surface energy budget and surface radiation. Different land covers have different emissivity properties, and the Gobi Desert in Central Asia seriously impact the sandstorms occur and develop in China, because of its special geographical environment and surface soil characteristics. In this study half-month averaged microwave emissivity from March 2003 to February 2004 over the Gobi Desert has been estimated. Emissivities in this area at different frequencies, polarization and their seasonal variations are discussed respectively. The results showed that emissivity polarization difference decrease as the frequency increases, and the polarization difference is large (0.03–0.127). The H polarization emissivity increases with increasing frequency, but the V-polarized microwave emissivity is reduced with increasing frequency because of the body scattering. In winter, emissivity decreases sharply in snow covered area, especially for higher frequencies (such as 89GHz). In addition, we compared emissivity with MODIS NDVI data at the same time in the Gobi Desert, and the results indicate that NDVI derived the good negative correlation with microwave emissivity polarization difference at 37GHz

  2. Study of the microwave emissivity characteristics over Gobi Desert

    Science.gov (United States)

    Yubao, Qiu; Lijuan, Shi; Wenbo, Wu

    2014-03-01

    The microwave emissivity represents the capacity of the thermal radiation of the surface, and it is the significant parameter for understanding the geophysical processes such as surface energy budget and surface radiation. Different land covers have different emissivity properties, and the Gobi Desert in Central Asia seriously impact the sandstorms occur and develop in China, because of its special geographical environment and surface soil characteristics. In this study half-month averaged microwave emissivity from March 2003 to February 2004 over the Gobi Desert has been estimated. Emissivities in this area at different frequencies, polarization and their seasonal variations are discussed respectively. The results showed that emissivity polarization difference decrease as the frequency increases, and the polarization difference is large (0.03-0.127). The H polarization emissivity increases with increasing frequency, but the V-polarized microwave emissivity is reduced with increasing frequency because of the body scattering. In winter, emissivity decreases sharply in snow covered area, especially for higher frequencies (such as 89GHz). In addition, we compared emissivity with MODIS NDVI data at the same time in the Gobi Desert, and the results indicate that NDVI derived the good negative correlation with microwave emissivity polarization difference at 37GHz.

  3. Influence of a single lightning discharge on the intensity of an air electric field and acoustic emission of near-surface rocks

    Directory of Open Access Journals (Sweden)

    S. E. Smirnov

    2012-10-01

    Full Text Available The effect was observed as a sharp fall of the electric potential gradient from +80 V m−1 down to –21 V m−1. After that the field returned to its normal level according to the formula of the capacitor discharge with 17 s characteristic time. Simultaneously, the response of the acoustic emission of surface rocks in the range of frequencies between 6.5 kHz and 11 kHz was evaluated.

  4. Comparison of Acoustic Characteristics of Date Palm Fibre and Oil Palm Fibre

    Directory of Open Access Journals (Sweden)

    Lamyaa Abd ALRahman

    2014-02-01

    Full Text Available This study investigated and compared the acoustic characteristics of two natural organic fibres: date palm fibre and oil palm fibre, these materials eligible for acoustical absorption. During the processing stage, both fibre sheets are treated with latex. The two fibres are compressed after latex treatment Circular samples (100 mm in diameter and 28 mm, based on the measurement tube requirements are cut out of the sheets. The density of the date palm fibre sheet is 150 kg/m3 for a 50 mm thickness and 130 kg/m3 for a 30 mm thickness. In contrast, the density of oil palm fibre is 75 kg/m3 for a 50 mm thickness and 65 kg/m3 for a 30 mm thickness. An impedance tube was used to test the thicknesses of both samples based on international standards. The results show that the date palm fibre exhibits two Acoustic Absorption Coefficient (AAC peaks: 0.93 at 1356 Hz and 0.99 at 4200-4353 Hz for the 50-mm-thick sample. In contrast, the 30-mm-thick sample has a single AAC peak of 0.83 at 2381.38-2809.38 Hz. However, the 50-mm-thick oil palm fibre has an AAC peak of 0.75 at 1946.88-2178.13 Hz and the 30-mm-thick oil palm fibre has an acoustic absorption coefficient peak 0.59 at 3225-3712.5 Hz. Thus, the date palm fibre has a higher acoustic absorption coefficient for high and low frequencies than does oil palm fibre. Both fibres are promising for use as sound absorber materials to protect against environmental noise pollution.

  5. Avalanche dynamics of structural phase transitions in shape memory alloys by acoustic emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Benno

    2009-09-24

    In this work the avalanche dynamics of five shape memory samples has been analyzed by acoustic emission spectroscopy. The acoustic emission spectroscopy is particularly suitable for this analysis as it couples with high sensitivity to small structural changes caused by nucleation processes, interface movements, or variant rearrangements [91]. Owing to its high time resolution it provides a statistical approach to describe the jerky and intermittent character of the avalanche dynamics [20]. Rate-dependent cooling and heating runs have been conducted in order to study time-dependent aspects of the transition dynamics of the single crystals Ni{sub 63}Al{sub 37}, Au{sub 50.5}Cd{sub 49.5}, and Fe{sub 68.8}Pd{sup single}{sub 31.2}, and the polycrystalline sample Fe{sub 68.8}Pd{sup poly}{sub 31.2}. Moreover, a ferromagnetic Ni{sub 52}Mn{sub 23}Ga{sub 25} single crystal has been studied by temperature cycles under an applied magnetic field and additionally by magnetic-field cycles at a constant temperature in the martensitic phase. All samples analyzed in this work show power law behavior in the acoustic emission features amplitude, energy, and duration, which indicates scale-free behavior. The access to these power law spectra allows an investigation of energy barriers separating the metastable states, which give rise to avalanche transition dynamics. By performing rate-dependent experiments the importance of thermal fluctuations and the impact of martensite respectively twin stabilization processes have been examined. In the case of the Ni{sub 52}Mn{sub 23}Ga{sub 25} sample, the magnetic-field-induced variant rearrangement at slow field cycles leads to stronger signals than the rearrangement at quick cycles. This behavior can be explained by twin stabilization processes, which are accompanied by a reduction of the twin boundary mobility. For Ni{sub 63}Al{sub 37}, the combination of relevant thermal fluctuations, different involved time scales, and a high degree of

  6. Avalanche dynamics of structural phase transitions in shape memory alloys by acoustic emission spectroscopy

    International Nuclear Information System (INIS)

    In this work the avalanche dynamics of five shape memory samples has been analyzed by acoustic emission spectroscopy. The acoustic emission spectroscopy is particularly suitable for this analysis as it couples with high sensitivity to small structural changes caused by nucleation processes, interface movements, or variant rearrangements [91]. Owing to its high time resolution it provides a statistical approach to describe the jerky and intermittent character of the avalanche dynamics [20]. Rate-dependent cooling and heating runs have been conducted in order to study time-dependent aspects of the transition dynamics of the single crystals Ni63Al37, Au50.5Cd49.5, and Fe68.8Pdsingle31.2, and the polycrystalline sample Fe68.8Pdpoly31.2. Moreover, a ferromagnetic Ni52Mn23Ga25 single crystal has been studied by temperature cycles under an applied magnetic field and additionally by magnetic-field cycles at a constant temperature in the martensitic phase. All samples analyzed in this work show power law behavior in the acoustic emission features amplitude, energy, and duration, which indicates scale-free behavior. The access to these power law spectra allows an investigation of energy barriers separating the metastable states, which give rise to avalanche transition dynamics. By performing rate-dependent experiments the importance of thermal fluctuations and the impact of martensite respectively twin stabilization processes have been examined. In the case of the Ni52Mn23Ga25 sample, the magnetic-field-induced variant rearrangement at slow field cycles leads to stronger signals than the rearrangement at quick cycles. This behavior can be explained by twin stabilization processes, which are accompanied by a reduction of the twin boundary mobility. For Ni63Al37, the combination of relevant thermal fluctuations, different involved time scales, and a high degree of intrinsic disorder leads to a lower acoustic activity and weaker signals under decreasing cooling rates. In the

  7. Impact Of Real-World Driving Characteristics On Vehicular Emissions

    OpenAIRE

    Nesamani, K S; Subramanian, K. P.

    2005-01-01

    With increase in traffic volume and change in travel related characteristics, vehicular emissions and energy consumption have increased significantly since two decades in India. Current models are not capable of estimating vehicular emissions accurately due to inadequate representation of real-world driving. The focus of this paper is to understand the level of Indian Driving cycle (IDC) in representing the real-world driving and to assess the impact of real-world driving on vehicular emissio...

  8. Investigations on the acoustic transmission characteristics of underwater perforated panel structures

    Institute of Scientific and Technical Information of China (English)

    WANG Zefeng; HU Yongming

    2009-01-01

    Perforated panel structures have a wide potential in underwater applications. However, up to now there has been little related research. The acoustic impedance of an underwater perforated panel is obtained based on the theories for air perforated panel sound absorption.In this paper sound transmission characteristics of underwater perforated panel structures are theoretically analyzed by the transfer matrix method. A formula for normal incidence sound transmission coefficients is given. The main factors that have effects on the acoustic transmission coefficient are analyzed by numerical simulations. The perforated panel structures made by ourselves are tested in a standing-wave tube by the four-sensor transfer-function method.The experimental results are well in accord with the results obtained by the numerical method,which proves that the theoretical analysis is correct. This paper has provided theoretical and experimental bases for the design of underwater perforated panel structures.

  9. Study on vibro-acoustical characteristics of damped composite boxlike shells in water

    Institute of Scientific and Technical Information of China (English)

    ZOU Yuanjie; ZHAO Deyou

    2006-01-01

    Based on the structural FEM and the acoustic BEM, a numerical model of coupled elastic layer and viscoelastic layer and outside sound field is established and the vibro-acoustical characteristics of damped composite boxlike shells are studied systematically. It can be concluded that the structural vibration responses and the sound radiation are reduced significantly due to the viscoelastic layer and its effects are dependent on the geometric, physical parameters of the layer and the excitation frequency. It is also shown that compared with the bare elastic shells, the influence of the fluid compressibility on the vibration responses of shells covered with a damping layer is not evident and the effects of the free surface and the rigid plane are weakened.

  10. Stochastic dislocation kinetics and fractal structures in deforming metals probed by acoustic emission and surface topography measurements

    Energy Technology Data Exchange (ETDEWEB)

    Vinogradov, A. [Laboratory for the Physics of Strength of Materials and Intelligent Diagnostic Systems, Togliatti State University, Togliatti 445667 (Russian Federation); Laboratory of Hybrid Nanostructured Materials, NITU MISiS, Moscow 119490 (Russian Federation); Yasnikov, I. S. [Laboratory for the Physics of Strength of Materials and Intelligent Diagnostic Systems, Togliatti State University, Togliatti 445667 (Russian Federation); Estrin, Y. [Laboratory of Hybrid Nanostructured Materials, NITU MISiS, Moscow 119490 (Russian Federation); Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, VIC 3800 (Australia)

    2014-06-21

    We demonstrate that the fractal dimension (FD) of the dislocation population in a deforming material is an important quantitative characteristic of the evolution of the dislocation structure. Thus, we show that peaking of FD signifies a nearing loss of uniformity of plastic flow and the onset of strain localization. Two techniques were employed to determine FD: (i) inspection of surface morphology of the deforming crystal by white light interferometry and (ii) monitoring of acoustic emission (AE) during uniaxial tensile deformation. A connection between the AE characteristics and the fractal dimension determined from surface topography measurements was established. As a common platform for the two methods, the dislocation density evolution in the bulk was used. The relations found made it possible to identify the occurrence of a peak in the median frequency of AE as a harbinger of plastic instability leading to necking. It is suggested that access to the fractal dimension provided by AE measurements and by surface topography analysis makes these techniques important tools for monitoring the evolution of the dislocation structure during plastic deformation—both as stand-alone methods and especially when used in tandem.

  11. 基于周期性声发射撞击计数的滚动轴承故障诊断%Fault Diagnosis of Rolling Bearings Based on Cyclical Impact Count of Acoustic Emission

    Institute of Scientific and Technical Information of China (English)

    张颖; 苏宪章; 刘占生

    2011-01-01

    分析滚动轴承不同类型故障特征频率与声发射累积撞击计数间的内在联系,建立基于周期性声发射累积撞击计数的滚动轴承故障诊断方法.采用非接触式声发射测试技术,对工作状态下滚动体、外圈和内圈故障分别进行测试及分析,试验结果证明了周期性声发射撞击计数与滚动轴承故障特征频率间的定量关系.依据此方法可对滚动轴承故障进行早期诊断.%The internal relations are analyzed between characteristic frequency and cumulative impact count of acoustic emission for rolling bearing with different types of surface defects, and the fault diagnosis method is established based on cyclical cumulative impact count of acoustic emission. The non - contact acoustic emission testing technology is used to test and analyze the faults of rolling element, outer ring and inner ring for rolling bearing under working state respectively. The experimental results show that there is quantitative relation between cumulative impact count of acoustic emission and fault characteristic frequency. The rolling bearing faults can be diagnosed early according to this method.

  12. [Acoustic emission diagnostic techniques for high-field high current-density super inducting poles

    International Nuclear Information System (INIS)

    Acoustic emission technology was introduced in the late 1970's to monitor superconducting magnets. It has now been firmly established that acoustic signals in superconducting magnets are emitted principally by mechanical events such as conductor strain, conductor motion, frictional motion, and epoxy cracking. Despite earlier suggestions, flux motion, except during flux jumping, does not appear to be an important source of AE signals in superconducting magnets. Of these several potential sources of AE signals in superconducting magnets, mechanical disturbances have been identified to be most important in high-performance, ''adiabatic'' magnets such as the dipoles used in accelerators. These mechanical disturbances are transitory, each generating a packet of AE signals that can be located with sensors. Source identification and location has been achieved with a number of superconducting magnets. In this section, the basic principle for the operation of adiabatic magnets is discussed, followed by presentation of some of the important experimental results relevant to the question of premature quench obtained at MIT

  13. Preliminary studies for monitoring erosion in pipelines by the acoustic emission technique

    Energy Technology Data Exchange (ETDEWEB)

    Tiboni, G.B. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Programa de Pos-graduacao em Engenharia Mecanica e de Materiais; Marquardt, T.A.S; SantaMaria, V.A.R.; Silva, C.H. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil)

    2009-07-01

    The aim of this work is to present some applications of Acoustic Emission (AE), which is a powerful technique for nondestructive testing in Tribology, treated here as tests of friction, wear by contact fatigue, wear by slip and wear by erosion. In this work a special attention is given to solid particle erosion and hydro-abrasive erosion, problems found in almost every pipeline that lead to local loss of material and eventually rupture of the line. The technique of AE can be used as an efficient online tool when, primarily, to monitor tribological aspects such as the rate of wear of materials, as well as detect the spread of flaws in them. In wear by erosion, specifically, the parameters of RMS and acoustic energy are capable of correlation with the type of mechanism for removal of material. As a preliminary goal, erosive tests were performed with gas (air) without erosive particles, monitored by AE, varying the surface of the samples and the internal diameter the nozzle, taking the differences in signs of AE. Correlation between parameters of RMS and amplitude were noticed with the variables of the tests, such as roughness and fluid velocity. The RMS parameter showed a exponential correction with the fluid velocity, however the amplitude signals had a linear behavior. The knowledge of these parameters is essential for the development of a system that is able to quantify the wear rate of a pipeline without taking it out of operation. (author)

  14. Acoustic emission of the Syracuse Athena temple: timescale invariance from microcracking to earthquakes

    International Nuclear Information System (INIS)

    We show the results of acoustic-emission (AE) monitoring of the Cathedral of Syracuse in Sicily (Southern Italy), built around the surviving elements of a Doric temple dedicated to Athena from the 5th century BC. We wired up a single pillar of the 2500-year-old cathedral for four months and then compared the AE data with earthquake records, observing a time correlation between the AE bursts and the sequence of nearby earthquakes and a similar scaling for the related magnitude distributions. We found that the distribution of times between events—whether earthquakes or acoustic emissions—fell onto the same curve, over a wide range of timescales and energies, when scaled appropriately. A similar 'universal scaling law' has been shown for collections of earthquakes of a range of sizes in different regions, so the new results appear to extend the law to the much smaller energy scales of a single pillar. These pieces of evidence suggest a correlation between the aging process and the local seismic activity, and that more careful monitoring of the cathedral is warranted

  15. Effect of secondary electron emission on the propagation of dust acoustic waves in a dusty plasma

    International Nuclear Information System (INIS)

    The effect of secondary electron emission on dust acoustic wave (DA) propagation has been investigated based on orbit motion limited theory of dust grain charging. The emitted secondaries are assumed to have the same temperature as that of the ambient plasma electrons so that the plasma effectively consists of three components: the ions, electrons, and the variable charge dusts. Together with the effect of secondary emission, the effect of ion and electron capture and ionization of neutral atoms and recombination have been included in the ion and electron fluid equations. Small amplitude perturbation is considered about a charge neutral steady state. It is seen that if the dust charge is positive there may occur under certain conditions zero frequency exponentially growing perturbation about the equilibrium. The possibility of the occurrence of such purely growing mode in a dusty plasma was not noted earlier. The frequency and damping decrement of DA waves in dusty plasmas with negatively charged dust and also of DA waves with positively charged dust, when they exist, are determined. Comparisons with corresponding results of DA waves in the absence of secondary emission are exhibited graphically

  16. Detection of simulated pitting corrosion and noises in crude oil storage tank by acoustic emission

    International Nuclear Information System (INIS)

    The damage mechanisms associated with crude oil storage tanks can be complex and varied and include pitting corrosion due to presence of species such as sulphate reducing bacteria. Acoustic Emission (AE) could be used to characterise the pitting corrosion signal in crude oil storage tanks but it is extremely difficult to simulate the pitting corrosion in the laboratory using crude oil as electrolyte because crude oil is considered as non corrosive medium. In this study, induced current have been introduced onto a surface ASTM 516 steel as an electrical source to simulate the electrical noise produced during pitting corrosion process and AE sensor have been used to detect this current. It is found that AE system could detect AE signal release during current induction this current and is expected that if the exact simulation of the current magnitude produced during pitting corrosion process is made available, AE characterisation of pitting corrosion in such tank could be made possible. (Author)

  17. Localization of acoustic emission sources in tensile and ct specimens using a broadband acquisition technique.

    Science.gov (United States)

    Fleischmann, P; Rouby, D; Malaprade, G; Lanchon, I

    1981-11-01

    The acoustic emission sources in a conventional cylindrical tensile test sample of short transversely-cut carbon manganese steel are localized. There is not always a good correlation between the localization of the first signals and the zone which eventually fractures. During the Lüder's plateau, the ae signals are emitted in the deformation band and, in the hardening range, there is no significant ae in the gauge length of the sample. In ct samples precracked by fatigue, the signals are due to the growth of the plastic zone around the crack tip, and the plastic zone size, measured by source localization, agrees with those provided by models derived from fracture mechanics. PMID:7292774

  18. Extensive characterization of seismic laws in acoustic emissions of crumpled plastic sheets

    Science.gov (United States)

    Costa, Leandro S.; Lenzi, Ervin K.; Mendes, Renio S.; Ribeiro, Haroldo V.

    2016-06-01

    Statistical similarities between earthquakes and other systems that emit cracking noises have been explored in diverse contexts, ranging from materials science to financial and social systems. Such analogies give promise of a unified and universal theory for describing the complex responses of those systems. There are, however, very few attempts to simultaneously characterize the most fundamental seismic laws in such systems. Here we present a complete description of the Gutenberg-Richter law, the recurrence times, Omori's law, the productivity law, and Båth's law for the acoustic emissions that occur in the relaxation process of uncrumpling thin plastic sheets. Our results show that these laws also appear in this phenomenon, but (for most cases) with different parameters from those reported for earthquakes and fracture experiments. This study thus contributes to elucidate the parallel between seismic laws and cracking noises in uncrumpling processes, revealing striking qualitative similarities but also showing that these processes display unique features.

  19. FBG-based ultrasonic wave detection and acoustic emission linear location system

    Institute of Scientific and Technical Information of China (English)

    JIANG Ming-shun; SUI Qing-mei; JIA Lei; PENG Peng; CAO Yu-qiang

    2012-01-01

    The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed,which employ fiber Bragg gratings (FBGs) as US wave sensors.In the theoretical analysis,the FBG sensor response to longitudinal US wave is investigated.The result indicates that the FBG wavelength can be modulated as static case when the grating length is much shorter than US wavelength.The experimental results of standard sinusoidal and spindle wave test agree well with the generated signal.Further research using two FBGs for realizing linear location is also achieved.The maximumlinear location error is obtained as less than 5 mm.FBG-based US wave sensor and AE linear location provide useful tools for specific requirements.

  20. A framework for the damage evaluation of acoustic emission signals through Hilbert-Huang transform

    Science.gov (United States)

    Siracusano, Giulio; Lamonaca, Francesco; Tomasello, Riccardo; Garescì, Francesca; Corte, Aurelio La; Carnì, Domenico Luca; Carpentieri, Mario; Grimaldi, Domenico; Finocchio, Giovanni

    2016-06-01

    The acoustic emission (AE) is a powerful and potential nondestructive testing method for structural monitoring in civil engineering. Here, we show how systematic investigation of crack phenomena based on AE data can be significantly improved by the use of advanced signal processing techniques. Such data are a fundamental source of information that can be used as the basis for evaluating the status of the material, thereby paving the way for a new frontier of innovation made by data-enabled analytics. In this article, we propose a framework based on the Hilbert-Huang Transform for the evaluation of material damages that (i) facilitates the systematic employment of both established and promising analysis criteria, and (ii) provides unsupervised tools to achieve an accurate classification of the fracture type, the discrimination between longitudinal (P-) and traversal (S-) waves related to an AE event. The experimental validation shows promising results for a reliable assessment of the health status through the monitoring of civil infrastructures.

  1. Moment tensor analysis of the acoustic emission source in the rock damage process

    Institute of Scientific and Technical Information of China (English)

    YU Huaizhong; ZHU Qingyong; YIN Xiangchu; WANG Yucang

    2005-01-01

    To further investigate the mechanism of acoustic emission (AE) in the rock fracture experiment, moment tensor analysis was carried out. The AE sources characterized by crack sizes, orientations and fracture modes, are represented by a time-dependent moment tensor. Since the waveforms recorded by AE monitors correlate to the moment tensors, we prefer to select the P wave amplitude from the full-space Green's function of homogeneous and isotropic materials to determine the six independent components of the moment tensor. The moment tensor analysis was used to investigate the AE sources recorded in the experiment, and three types of micro-cracks were found, which are tensile mode, shear mode and mixture of the tensile and shear mode. In addition, the motion of micro-cracks was decided by eigenvectors of moment tensor. Results indicate that the moment tensor analysis may be used as a measurement to reflect the damage evolution of rock specimen.

  2. Deformation, acoustic emission and ultrasound velocity during fatigue tests on paper

    Directory of Open Access Journals (Sweden)

    Hæggström E.

    2010-06-01

    Full Text Available We study the evolution of mechanical properties of paper samples during cyclic experiments. The issue is to look at the sample-to-sample variation, and we try to predict the number of loading cycles to failure. We used two concurrent methods to obtain the deformation: the strain was calculated from vertical displacement measured by laser interferometer sensor, as well as, computed by digital image correlation technique from pictures taken each 2s by a camera. Acoustic emission of fracture was also recorded, and an active ultrasonic wave method using piezoelectric transducers is used to follow the viscoelastic behaviour of each sample. We found that a sharp final increase of different variables like deformation, strain rate and fluctuations, are signs of an imminent rupture of the paper. Moreover looking at the evolution of these quantities during the first cycle only is already an indicator about the lifetime of the sample.

  3. Use of Acoustic Emission to Monitor Progressive Damage Accumulation in Kevlar (R) 49 Composites

    Science.gov (United States)

    Waller, Jess M.; Saulsberry, Regor L.; Andrade, Eduardo

    2009-01-01

    Acoustic emission (AE) data acquired during intermittent load hold tensile testing of epoxy impregnated Kevlar(Registeres TradeMark) 49 (K/Ep) composite strands were analyzed to monitor progressive damage during the approach to tensile failure. Insight into the progressive damage of K/Ep strands was gained by monitoring AE event rate and energy. Source location based on energy attenuation and arrival time data was used to discern between significant AE attributable to microstructural damage and spurious AE attributable to noise. One of the significant findings was the observation of increasing violation of the Kaiser effect (Felicity ratio < 1.0) with damage accumulation. The efficacy of three different intermittent load hold stress schedules that allowed the Felicity ratio to be determined analytically is discussed.

  4. Microstructure-Sensitive Investigation of Fracture Using Acoustic Emission Coupled With Electron Microscopy

    Science.gov (United States)

    Wisner, Brian; Cabal, Mike; Vanniamparambiland, Prashanth A.; Leser, William; Hochhalter, Jacob; Kontsos, Antonios

    2015-01-01

    A novel technique using Scanning Electron Microscopy (SEM) in conjunction with Acoustic Emission (AE) monitoring is proposed to investigate microstructure-sensitive fatigue and fracture of metals. The coupling between quasi in situ microscopy with actual in situ nondestructive evaluation falls into the ICME framework and the idea of quantitative data-driven characterization of material behavior. To validate the use of AE monitoring inside the SEM chamber, Aluminum 2024-B sharp notch specimen were tested both inside and outside the microscope using a small scale mechanical testing device. Subsequently, the same type of specimen was tested inside the SEM chamber. Load data were correlated with both AE information and observations of microcracks around grain boundaries as well as secondary cracks, voids, and slip bands. The preliminary results are in excellent agreement with similar findings at the mesoscale. Extensions of the application of this novel technique are discussed.

  5. Laser cleaning of steam generator tubing based on acoustic emission technology

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Su-xia; Luo, Ji-jun; Shen, Tao; Li, Ru-song [Xi' an Hi-Tech Institute, Xi' an (China)

    2015-12-15

    As a physical method, laser cleaning technology in equipment maintenance will be a good prospect. The experimental apparatus for laser cleaning of heat tubes in the steam generator was designed according to the results of theoretical analysis. There are two conclusions; one is that laser cleaning technology is attached importance to traditional methods. Which has advantages in saving on much manpower and material resource and it is a good cleaning method for heat tubes. The other is that the acoustic emission signal includes lots of information on the laser cleaning process, which can be used as real-time monitoring in laser cleaning processes. When the laser acts for 350 s, 100 % contaminants of heat tubes is cleaned off, and the sensor only receives weak AE signal at that time.

  6. Extensive Characterization of Seismic Laws in Acoustic Emissions of Crumpled Plastic Sheets

    CERN Document Server

    Costa, Leandro S; Mendes, Renio S; Ribeiro, Haroldo V

    2016-01-01

    Statistical similarities between earthquakes and other systems that emit cracking noises have been explored in diverse contexts, ranging from materials science to financial and social systems. Such analogies give promise of a unified and universal theory for describing the complex responses of those systems. There are, however, very few attempts to simultaneously characterize the most fundamental seismic laws in such systems. Here we present a complete description of the Gutenberg-Richter law, the recurrence times, Omori's law, the productivity law, and Bath's law for the acoustic emissions that happen in the relaxation process of uncrumpling thin plastic sheets. Our results show that these laws also appear in this phenomenon, but (for most cases) with different parameters from those reported for earthquakes and fracture experiments. This study thus contributes to elucidate the parallel between seismic laws and cracking noises in uncrumpling processes, revealing striking qualitative similarities but also show...

  7. Effect of hydrogen attack on acoustic emission behavior of low carbon steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to investigate the effect of hydrogen attack degree on acoustic emission (AE) behavior of low carbon steel during tensiling, specimens made of low carbon steel was exposed to hydrogen gas of 18 MPa at 450 and 500℃ for 240, 480 and 720 h respectively. Experimental results show that with increase of the hydrogen attack degree, the totally AE activity decreases during tensiling. In addition, the count of AE signals with high amplitude for the specimens with hydrogen attack keeps a constant which is less than that without hydrogen attack. It is concluded that AE signals originate in the specimens with hydrogen attack from intergranular fracture induced by methane blisterings or/and microcracks on grain boundaries.

  8. Development of Generic Methodology for Designing a Structural Health Monitoring Installation Based on the Acoustic Emission Technique

    NARCIS (Netherlands)

    Gagar, D.; Martinez, M.J.; Foote, P.

    2014-01-01

    The Acoustic Emission (AE) technique can be used to perform damage detection and localisation for structural health monitoring purposes. Implementation in aircraft structures however poses a significant challenge as its performance in terms of damage detection and localisation is not well understood

  9. A robust calibration technique for acoustic emission systems based on momentum transfer from a ball drop

    Science.gov (United States)

    McLaskey, Gregory C.; Lockner, David A.; Kilgore, Brian D.; Beeler, Nicholas M.

    2015-01-01

    We describe a technique to estimate the seismic moment of acoustic emissions and other extremely small seismic events. Unlike previous calibration techniques, it does not require modeling of the wave propagation, sensor response, or signal conditioning. Rather, this technique calibrates the recording system as a whole and uses a ball impact as a reference source or empirical Green’s function. To correctly apply this technique, we develop mathematical expressions that link the seismic moment $M_{0}$ of internal seismic sources (i.e., earthquakes and acoustic emissions) to the impulse, or change in momentum $\\Delta p $, of externally applied seismic sources (i.e., meteor impacts or, in this case, ball impact). We find that, at low frequencies, moment and impulse are linked by a constant, which we call the force‐moment‐rate scale factor $C_{F\\dot{M}} = M_{0}/\\Delta p$. This constant is equal to twice the speed of sound in the material from which the seismic sources were generated. Next, we demonstrate the calibration technique on two different experimental rock mechanics facilities. The first example is a saw‐cut cylindrical granite sample that is loaded in a triaxial apparatus at 40 MPa confining pressure. The second example is a 2 m long fault cut in a granite sample and deformed in a large biaxial apparatus at lower stress levels. Using the empirical calibration technique, we are able to determine absolute source parameters including the seismic moment, corner frequency, stress drop, and radiated energy of these magnitude −2.5 to −7 seismic events.

  10. Acoustic characteristics of the vowel systems of six regional varieties of American English

    Science.gov (United States)

    Clopper, Cynthia G.; Pisoni, David B.; de Jong, Kenneth

    2005-09-01

    Previous research by speech scientists on the acoustic characteristics of American English vowel systems has typically focused on a single regional variety, despite decades of sociolinguistic research demonstrating the extent of regional phonological variation in the United States. In the present study, acoustic measures of duration and first and second formant frequencies were obtained from five repetitions of 11 different vowels produced by 48 talkers representing both genders and six regional varieties of American English. Results revealed consistent variation due to region of origin, particularly with respect to the production of low vowels and high back vowels. The Northern talkers produced shifted low vowels consistent with the Northern Cities Chain Shift, the Southern talkers produced fronted back vowels consistent with the Southern Vowel Shift, and the New England, Midland, and Western talkers produced the low back vowel merger. These findings indicate that the vowel systems of American English are better characterized in terms of the region of origin of the talkers than in terms of a single set of idealized acoustic-phonetic baselines of ``General'' American English and provide benchmark data for six regional varieties.

  11. Avalanche dynamics of structural phase transitions in shape memory alloys by acoustic emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Benno

    2009-09-24

    In this work the avalanche dynamics of five shape memory samples has been analyzed by acoustic emission spectroscopy. The acoustic emission spectroscopy is particularly suitable for this analysis as it couples with high sensitivity to small structural changes caused by nucleation processes, interface movements, or variant rearrangements [91]. Owing to its high time resolution it provides a statistical approach to describe the jerky and intermittent character of the avalanche dynamics [20]. Rate-dependent cooling and heating runs have been conducted in order to study time-dependent aspects of the transition dynamics of the single crystals Ni{sub 63}Al{sub 37}, Au{sub 50.5}Cd{sub 49.5}, and Fe{sub 68.8}Pd{sup single}{sub 31.2}, and the polycrystalline sample Fe{sub 68.8}Pd{sup poly}{sub 31.2}. Moreover, a ferromagnetic Ni{sub 52}Mn{sub 23}Ga{sub 25} single crystal has been studied by temperature cycles under an applied magnetic field and additionally by magnetic-field cycles at a constant temperature in the martensitic phase. All samples analyzed in this work show power law behavior in the acoustic emission features amplitude, energy, and duration, which indicates scale-free behavior. The access to these power law spectra allows an investigation of energy barriers separating the metastable states, which give rise to avalanche transition dynamics. By performing rate-dependent experiments the importance of thermal fluctuations and the impact of martensite respectively twin stabilization processes have been examined. In the case of the Ni{sub 52}Mn{sub 23}Ga{sub 25} sample, the magnetic-field-induced variant rearrangement at slow field cycles leads to stronger signals than the rearrangement at quick cycles. This behavior can be explained by twin stabilization processes, which are accompanied by a reduction of the twin boundary mobility. For Ni{sub 63}Al{sub 37}, the combination of relevant thermal fluctuations, different involved time scales, and a high degree of

  12. Test emission characteristics of motorcycles in Central Taiwan.

    Science.gov (United States)

    Lin, Chi-Wen; Lu, San-Ju; Lin, Kuo-Shian

    2006-09-15

    Due to the large population and high levels of motorized-vehicle exhaust emissions, motorcycle emissions make an important contribution to total emissions in Taiwan, ROC. Aiming to reduce the air pollution generated by these motorcycles, the Taiwan Environmental Protection Administration (TEPA) has maintained an enforced inspection and maintenance (I/M) program for in-use motorcycles since 1996. This report explores the effects of engine type, engine size, engine age, and manufacturers of in-use motorcycles on CO/HC emissions in I/M testing data during the period of 1996-2002 in the Central Air Quality Basin of Taiwan. Additionally, geographical characteristics and failure rates of motorcycles are analyzed. The results indicate that the age, size, and type of engine, and the manufacturers of motorcycles all play a significant role in determining I/M emission test results. The findings also show that two-stroke motorcycles emitted approximately ten times greater HC than those of four-stroke motorcycles. CO/HC test emissions increase with a decrease in engine size, HC test emissions contributed by Yamaha and other manufacturers being the highest. Although CO/HC test emissions generally increase with the age of the motorcycle, older motorcycles do not contribute significantly to total emissions due to the small number of older motorcycles. It was observed that CO/HC test emissions depend on driving patterns, geographical location, and inspection rates of motorcycles. The failure rate due to CO is nearly four times greater than that of HC, and the older and smaller-engine-size motorcycles obtain greater failure rates. These statistical findings can also provide the EPA of Taiwan or other Asian countries with useful information for formulating better environmental strategies to manage motorcycles effectively.

  13. Emission characteristics of light-emitting diodes by confocal microscopy

    Science.gov (United States)

    Cheung, W. S.; Choi, H. W.

    2016-03-01

    The emission profiles of light-emitting diodes have typically be measured by goniophotometry. However this technique suffers from several drawbacks, including the inability to generate three-dimensional intensity profiles as well as poor spatial resolution. These limitations are particularly pronounced when the technique is used to compared devices whose emission patterns have been modified through surface texturing at the micrometer and nanometer scales,. In view of such limitations, confocal microscopy has been adopted for the study of emission characteristics of LEDs. This enables three-dimensional emission maps to be collected, from which two-dimensional cross-sectional emission profiles can be generated. Of course, there are limitations associated with confocal microscopy, including the range of emission angles that can be measured due to the limited acceptance angle of the objective. As an illustration, the technique has been adopted to compare the emission profiles of LEDs with different divergence angles using an objective with a numerical aperture of 0.8. It is found that the results are consistent with those obtained by goniophotometry when the divergence angle is less that the acceptance angle of the objective.

  14. Failure Progress of 3D Reinforced GFRP Laminate during Static Bending, Evaluated by Means of Acoustic Emission and Vibrations Analysis

    Directory of Open Access Journals (Sweden)

    Mateusz Koziol

    2015-12-01

    Full Text Available The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber fracture and the one coming from the matrix fracture with the use of the acoustic event’s energy as a criterion was applied. The failure progress during static bending was alternatively analyzed by evaluation of the vibration signal. It gave a possibility to validate the results of the acoustic emission. Acoustic emission, as well as vibration signal analysis proved to be good and effective tools for the registration of failure effects in composite laminates. Vibration analysis is more complicated methodologically, yet it is more precise. The failure progress of the 3D laminate is “safer” and more beneficial than that of the plain-woven laminate. It exhibits less rapid load capacity drops and a higher fiber effort contribution at the moment of the main laminate failure.

  15. Temperature Frequency Characteristics of Hexamethyldisiloxane (HMDSO) Polymer Coated Rayleigh Surface Acoustic Wave (SAW) Resonators for Gas-Phase Sensor Applications

    OpenAIRE

    Radeva, Ekaterina I.; Esmeryan, Karekin D.; Ivan D. Avramov

    2012-01-01

    Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs) of solid hexamethyldisiloxane (HMDSO) polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW) mode on ST-cut quartz. Using ...

  16. An effective sensor for tool wear monitoring in face milling: Acoustic emission

    Indian Academy of Sciences (India)

    M T Mathew; P Srinivasa Pai; L A Rocha

    2008-06-01

    Acoustic Emission (AE) has been widely used for monitoring manufacturing processes particularly those involving metal cutting. Monitoring the condition of the cutting tool in the machining process is very important since tool condition will affect the part size, quality and an unexpected tool failure may damage the tool, work-piece and sometimes the machine tool itself. AE can be effectively used for tool condition monitoring applications because the emissions from process changes like tool wear, chip formation i.e. plastic deformation, etc. can be directly related to the mechanics of the process. Also AE can very effectively respond to changes like tool fracture, tool chipping, etc. when compared to cutting force and since the frequency range is much higher than that of machine vibrations and environmental noises, a relatively uncontaminated signal can be obtained. AE signal analysis was applied for sensing tool wear in face milling operations. Cutting tests were carried out on a vertical milling machine. Tests were carried out for a given cutting condition, using single insert, two inserts (adjacent and opposite) and three inserts in the cutter. AE signal parameters like ring down count and rms voltage were measured and were correlated with flank wear values (VB max). The results of this investigation indicate that AE can be effectively used for monitoring tool wear in face milling operations.

  17. Standard practice for examination of seamless, Gas-Filled, pressure vessels using acoustic emission

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This practice provides guidelines for acoustic emission (AE) examinations of seamless pressure vessels (tubes) of the type used for distribution or storage of industrial gases. 1.2 This practice requires pressurization to a level greater than normal use. Pressurization medium may be gas or liquid. 1.3 This practice does not apply to vessels in cryogenic service. 1.4 The AE measurements are used to detect and locate emission sources. Other nondestructive test (NDT) methods must be used to evaluate the significance of AE sources. Procedures for other NDT techniques are beyond the scope of this practice. See Note 1. Note 1—Shear wave, angle beam ultrasonic examination is commonly used to establish circumferential position and dimensions of flaws that produce AE. Time of Flight Diffraction (TOFD), ultrasonic examination is also commonly used for flaw sizing. 1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only. 1.6 This standa...

  18. Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates

    Institute of Scientific and Technical Information of China (English)

    Ai Ting; Zhang Ru; Liu Jianfeng; Ren Li

    2012-01-01

    By using MTS815 rock mechanics test system,a series of acoustic emission (AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE tinging counting rate increases largely and the AE energy curves appear an obvious "step",which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.

  19. Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates

    Institute of Scientific and Technical Information of China (English)

    Ai; Ting; Zhang; Ru; Liu; Jianfeng; Ren; Li

    2012-01-01

    By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.

  20. Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jun-Lin; Zhou, Ke-Yi, E-mail: boiler@seu.edu.cn; Xu, Jian-Qun [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, Jiangsu Province (China); Wang, Xin-Meng; Tu, Yi-You [School of Materials Science and Engineering, Southeast University, Nanjing 210096, Jiangsu Province (China)

    2014-07-28

    Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

  1. Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

    International Nuclear Information System (INIS)

    Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

  2. Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

    Science.gov (United States)

    Huang, Jun-Lin; Zhou, Ke-Yi; Wang, Xin-Meng; Tu, Yi-You; Xu, Jian-Qun

    2014-07-01

    Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

  3. Detection of multiple AE signal by triaxial hodogram analysis; Sanjiku hodogram ho ni yoru taju acoustic emission no kenshutsu

    Energy Technology Data Exchange (ETDEWEB)

    Nagano, K.; Yamashita, T. [Muroran Institute of Technology, Hokkaido (Japan)

    1997-05-27

    In order to evaluate dynamic behavior of underground cracks, analysis and detection were attempted on multiple acoustic emission (AE) events. The multiple AE is a phenomenon in which multiple AE signals generated by underground cracks developed in an extremely short time interval are superimposed, and observed as one AE event. The multiple AE signal consists of two AE signals, whereas the second P-wave is supposed to have been inputted before the first S-wave is inputted. The first P-wave is inputted first, where linear three-dimensional particle movements are observed, but the movements are made random due to scattering and sensor characteristics. When the second P-wave is inputted, the linear particle movements are observed again, but are superimposed with the existing input signals and become multiple AE, which creates poor S/N ratio. The multiple AE detection determines it a multiple AE event when three conditions are met, i. e. a condition of equivalent time interval of a maximum value in a scalogram analysis, a condition of P-wave vibrating direction, and a condition of the linear particle movement. Seventy AE signals observed in the Kakkonda geothermal field were analyzed and AE signals that satisfy the multiple AE were detected. However, further development is required on an analysis method with high resolution for the time. 4 refs., 4 figs.

  4. Identification of a Critical Time with Acoustic Emission Monitoring during Static Fatigue Tests on Ceramic Matrix Composites: Towards Lifetime Prediction

    Directory of Open Access Journals (Sweden)

    Nathalie Godin

    2016-02-01

    Full Text Available Non-oxide fiber-reinforced ceramic-matrix composites are promising candidates for some aeronautic applications that require good thermomechanical behavior over long periods of time. This study focuses on the behavior of a SiCf/[Si-B-C] composite with a self-healing matrix at intermediate temperature under air. Static fatigue experiments were performed below 600 °C and a lifetime diagram is presented. Damage is monitored both by strain measurement and acoustic emission during the static fatigue experiments. Two methods of real-time analysis of associated energy release have been developed. They allow for the identification of a characteristic time that was found to be close to 55% of the measured rupture time. This critical time reflects a critical local energy release assessed by the applicability of the Benioff law. This critical aspect is linked to a damage phase where slow crack growth in fibers is prevailing leading to ultimate fracture of the composite.

  5. The acoustic characteristics of clause, sentence and paragraph boundaries in Chinese Putonghua

    Institute of Scientific and Technical Information of China (English)

    WANG Bei; YANG Yufang; L(U) Shinan

    2006-01-01

    The acoustic and perceptive characteristics of discourse units, including clauses,simple sentences, compound sentences and paragraphs, were studied. The acoustic characteristics were based on the analysis of a speech corpus consisted of ten monologues. The Perceived Boundary Strength (PBS) of the monologues was labeled on a five-point scale by 25 participants. The main results are as follows: (1) There is a significant difference in the PBS of clauses (corresponding to intonational phrase), sentences (including simple sentences and compound sentences) and paragraphs. But the PBS of simple sentences and compound sentences is the same, and the pitch reset and pause are also not significantly different between these two kinds of boundaries. (2) The pitch-based cue used to distinguish clauses, sentences and paragraphs appears to be the difference between pre- and post-boundary syllables, but not simply the pitch value of either syllable alone. (3) Declination mainly occurs within intonational phrases,whereas there is no consistent global declination in sentences or in paragraphs. (4) Pauses are longer and more varied at the boundary of larger discourse units. Moreover, there is a significant positive correlation between pause duration and degree of pitch reset at clause boundaries,but not at sentence or paragraph boundaries.

  6. Fresnel Number Concept and Revision of some Characteristics in the Linear Theory of Focused Acoustic Beams

    CERN Document Server

    Makov, Yu N

    2008-01-01

    The advisability of the use of the Fresnel number as the measure (characteristic) of the ratio of diffraction and focusing properties for ultrasonic transducers and its radiated beams is proposed and demonstrated. Althought this characteristic is more habitual in optics, in acoustics the equivalent (mathematically although not fully in its physical meaning) parameter of linear gain is used as a rule. However, the preference and the more accuracy of the Fresnel number use is demonstrated here on the basis that the usual determination of the linear gain parameter ceases to correspond to the real value of the gain for low Fresnel number acoustic beams. It connects with the linear effect of axial maximum pressure shift from the geometrical focus towards the transducer. This effect is known for a long time, but here the analytical formulas describing this shift with a high accuracy for arbitrary Fresnel numbers are presented. As a consequence, also the analytical dependence of the real gain on the Fresnel number i...

  7. Identification of the fragmentation of brittle particles during compaction process by the acoustic emission technique.

    Science.gov (United States)

    Favretto-Cristini, Nathalie; Hégron, Lise; Sornay, Philippe

    2016-04-01

    Some nuclear fuels are currently manufactured by a powder metallurgy process that consists of three main steps, namely preparation of the powders, powder compaction, and sintering of the compact. An optimum between size, shape and cohesion of the particles of the nuclear fuels must be sought in order to obtain a compact with a sufficient mechanical strength, and to facilitate the release of helium and fission gases during irradiation through pores connected to the outside of the pellet after sintering. Being simple to adapt to nuclear-oriented purposes, the Acoustic Emission (AE) technique is used to control the microstructure of the compact by monitoring the compaction of brittle Uranium Dioxide (UO2) particles of a few hundred micrometers. The objective is to identify in situ the mechanisms that occur during the UO2 compaction, and more specifically the particle fragmentation that is linked to the open porosity of the nuclear matter. Three zones of acoustic activity, strongly related to the applied stress, can be clearly defined from analysis of the continuous signals recorded during the compaction process. They correspond to particle rearrangement and/or fragmentation. The end of the noteworthy fragmentation process is clearly defined as the end of the significant process that increases the compactness of the material. Despite the fact that the wave propagation strongly evolves during the compaction process, the acoustic signature of the fragmentation of a single UO2 particle and a bed of UO2 particles under compaction is well identified. The waveform, with a short rise time and an exponential-like decay of the signal envelope, is the most reliable descriptor. The impact of the particle size and cohesion on the AE activity, and then on the fragmentation domain, is analyzed through the discrete AE signals. The maximum amplitude of the burst signals, as well as the mean stress corresponding to the end of the recorded AE, increase with increasing mean diameter of

  8. Topography of acoustic response characteristics in the midbrain inferior colliculus of Kunming mouse

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Topography of acoustic response characteristics of the midbrain inferior colliculus (IC) of the Kunming mouse was studied by using extracellular recording techniques. The characteristic frequency (CF) range represented in the different divisions of the IC differed markedly: 4-15 kHz in the dorsal cortex (DC), 10-70 kHz in the central nucleus (CN), and 4-35 kHz in the external cortex (EC). The CF in the CN increased from dorsal and lateral to ventral and medial, higher CFs represented at its ventromedial part and lower CFs at its dorsal part. The isofrequency contours of CFs were incurvate. Minimum thresholds (MT) of the auditory neurons in DC and the central part of CN were lower (about 10 dB SPL), but considerably higher in the dorsal and ventral region of EC. Results suggest that each of the divisions in the mouse IC may have different auditory functions.

  9. Acoustic characteristics of eight common Chinese anurans during the breeding season.

    Science.gov (United States)

    Zhou, Yi-Lin; Qiu, Xia; Fang, Xiao-Bin; Yang, Lu-Yi; Zhao, Yi; Fang, Teng; Zheng, Wei-Hong; Liu, Jin-Song

    2014-01-01

    Anurans often have species-specific vocalizations. To quantify and compare the characteristics of anuran calls in Gutianshan National Nature Reserve, Zhejiang Province, we recorded the advertisement calls of eight species belonging to four families (Ranidae, Microhylidae, Megophryidae and Bufonidae) from June to September 2012 using Sony ICD-FX8 IC recorders. All recordings were analyzed using the "Praat" software. Five acoustics parameters were measured, including temporal traits (call duration, number of notes or pulse number/call) and spectral traits (fundamental frequency, the first three formants and dominant frequency). The characteristic parameters of Microhyla ornate and Fejervarya limnocharis calls were different as were the calls of some populations of the same species recorded in different regions. The advertisement calls of the eight species were specific. Our study has provided a useful reference for identifying the calls of some common Chinese anurans.

  10. Testing of containers made of glass-fiber reinforced plastic with the aid of acoustic emission analysis

    Science.gov (United States)

    Wolitz, K.; Brockmann, W.; Fischer, T.

    1979-01-01

    Acoustic emission analysis as a quasi-nondestructive test method makes it possible to differentiate clearly, in judging the total behavior of fiber-reinforced plastic composites, between critical failure modes (in the case of unidirectional composites fiber fractures) and non-critical failure modes (delamination processes or matrix fractures). A particular advantage is that, for varying pressure demands on the composites, the emitted acoustic pulses can be analyzed with regard to their amplitude distribution. In addition, definite indications as to how the damages occurred can be obtained from the time curves of the emitted acoustic pulses as well as from the particular frequency spectrum. Distinct analogies can be drawn between the various analytical methods with respect to whether the failure modes can be classified as critical or non-critical.

  11. Detecting Acoustic Emissions With/Without Dehydration of Serpentine Outside P-T Field of Conventional Brittle Failure

    Science.gov (United States)

    Jung, H.; Fei, Y.; Silver, P. G.; Green, H. W.

    2005-12-01

    It is currently thought that earthquakes cannot be triggered at depths greater than ~60 km by unassisted brittle failure or frictional sliding, but could be triggered by dehydration embrittlement of hydrous minerals (Raleigh and Paterson, 1965; Green and Houston, 1995; Kirby, 1995; Jung et al., 2004). Using a new multianvil-based system for detecting acoustic emissions with four channels at high pressure and high temperature that was recently developed (Jung et al., 2005), we tested this hypothesis by deforming samples of serpentine. We found that acoustic emissions were detected not only during/after the dehydration of serpentine, but even in the absence of dehydration. These emissions occurred at high pressure and high temperature, and thus outside pressure-temperature field of conventional brittle failure. Backscattered-electron images of microstructures of the post-run specimen revealed fault slip at elevated pressure, with offsets of up to ~500 μm, even without dehydration. Analysis of P-wave travel times from the four sensors confirmed that the acoustic emissions originated from within the specimen during fault slip. These observations suggest that earthquakes can be triggered by slip along a fault containing serpentine at significantly higher pressure and temperature conditions than that previously thought, even without dehydration. They are thus consistent with faulting mechanisms that appeal to dehydration embrittlement, as well as those that rely solely on the rheology of non-dehydrated serpentine.

  12. Understanding the mechanical and acoustical characteristics of sand aggregates compacting under triaxial conditions

    Science.gov (United States)

    Hangx, Suzanne; Brantut, Nicolas

    2016-04-01

    Mechanisms such as grain rearrangement, coupled with elastic deformation, grain breakage, grain rearrangement, grain rotation, and intergranular sliding, play a key role in determining porosity and permeability reduction during burial of clastic sediments. Similarly, in poorly consolidated, highly porous sands and sandstones, grain rotation, intergranular sliding, grain failure, and pore collapse often lead to significant reduction in porosity through the development of compaction bands, with the reduced porosity and permeability of such bands producing natural barriers to flow within reservoir rocks. Such time-independent compaction processes operating in highly porous water- and hydrocarbon-bearing clastic reservoirs can exert important controls on production-related reservoir deformation, subsidence, and induced seismicity. We performed triaxial compression experiments on sand aggregates consisting of well-rounded Ottawa sand (d = 300-400 μm; φ = 36.1-36.4%) at room temperature, to systematically investigate the effect of confining pressure (Pceff = 5-100 MPa), strain rate (10‑6-10‑4 s‑1) and chemical environment (decane vs. water; Pf = 5 MPa) on compaction. For a limited number of experiments grain size distribution (d = 180-500 μm) and grain shape (subangular Beaujean sand; d = 180-300 μm) were varied to study their effect. Acoustic emission statistics and location, combined with microstructural and grain size analysis, were used to verify the operating microphysical compaction mechanisms. All tests showed significant pre-compaction during the initial hydrostatic (set-up) phase, with quasi-elastic loading behaviour accompanied by permanent deformation during the differential loading stage. This permanent volumetric strain involved elastic grain contact distortion, particle rearrangement, and grain failure. From the acoustic data and grain size analysis, it was evident that at low confining pressure grain rearrangement controlled compaction, with

  13. Correlation between calcium carbonate content and emission characteristics of incense.

    Science.gov (United States)

    Yang, Chi-Ru; Lin, Ta-Chang; Chang, Feng-Hsiang

    2006-12-01

    In Taiwan and China, calcium carbonate is commonly added as a filler during incense production to lower the cost. This study has found an unexpected benefit for this practice: it reduces particulate emission. Nine types of the popular incense on the local market were chosen for this study. The calcium content in raw material incense was analyzed by inductively coupled plasma atomic emission spectrometry, followed by X-ray diffraction (XRD) spectroscopy. The correlation between the calcium content and emission characteristics of incense was investigated. The calcium content varied from 1.8 to 60 mg/g (incense burned) among those nine different types of incense. Very little calcium (incense. Instead, most calcium was artificially added in the form of CaCO3 during manufacturing. The combustion characteristics, including burning rate, emission factors of particulate, ash, and solid-phase polycyclic aromatic hydrocarbons (S-PAHs), varied significantly among the nine types of incense. Incense containing 2% calcium would emit 30% less S-PAHs, compared with those with little (incense by approximately 50%.

  14. Preparation and emission characteristics of ethanol-diesel fuel blends

    Institute of Scientific and Technical Information of China (English)

    ZHANG Run-duo; HE Hong; SHI Xiao-yan; ZHANG Chang-bin; HE Bang-quan; WANG Jian-xin

    2004-01-01

    The preparation of ethanol-diesel fuel blends and their emission characteristics were investigated. Results showed the absolute ethanol can dissolve in diesel fuel at an arbitrary ratio and a small quantity of water(0.2%) addition can lead to the phase separation of blends. An organic additive was synthesized and it can develop the ability of resistance to water and maintain the stability of ethanol-diesel-trace amounts of water system. The emission characteristics of 10%, 20%, and 30% ethanol-diesel fuel blends, with or without additives, were compared with those of diesel fuel in a direct injection(DI) diesel engine. The experimental results indicated that the blend of ethanol with diesel fuel significantly reduced the concentrations of smoke, hydrocarbon(HC), and carbon monoxide(CO) in exhaust gas. Using 20% ethanol-diesel fuel blend with the additive of 2% of the total volume, the optimum mixing ratio was achieved, at which the bench diesel engine testing showed a significant decrease in exhaust gas. Bosch smoke number was reduced by 55%, HC emission by 70%, and CO emission by 45%, at 13 kW/1540 r/min. However, ethanol-diesel fuel blends produced a few ppm acetaldehydes and more ethanol in exhaust gas.

  15. Emission spectra and stimulated emission characteristics of [N2]2--N2 molecular dimer

    Institute of Scientific and Technical Information of China (English)

    SHEN; Zuochun(申作春); LU; Jianye(鲁建业); Ajmal; H.; Hamdani; GAO; Huide(高惠德); MA; Zuguang(马祖光)

    2003-01-01

    It has been proved by ab initio calculation and theoretical analysis that there exist [N2]2--N2 molecular dimers with D2h symmetry group, and there also exists an electric dipole excimer-like transition a1B2g→a1B3u. The theoretical spectra accord with the experimental results for transition a1B2g→a1B3u. The stimulated emission characteristic of N2 molecular dimer was researched through the microwave excited highly pure nitrogen and the method of amplified spontaneous emission. The experimental results show that N2 molecular dimer has stimulated emission characteristics when the microwave power is more than 100 W and the N2 pressure is in the range from 260 Pa to 2200 Pa.

  16. Comparison between sensitivities of quality control methods using ultrasonic waves, radiography and acoustic emission for the thick welded joint testing

    International Nuclear Information System (INIS)

    The testing of the thick welded joints of the nuclear industry is carried out by radiography and ultrasonics on completion of welding. When a fault is found, its repair requires a sometimes deep cut down to the position of the fault, then filling in of the cut by hand welding with a coated electrode. This very costly operation also involves the risk of causing new defects when building up by hand. Listening to the acoustic emission during the welding has been considered in order to seek the possibility of detecting defects when they appear, or soon after. The industrial use of this method would make an instant repair of the defective areas possible at less cost and with greater reliability. The study presented concerns the comparison between the results of the various non-destructive testing methods: radiography, ultrasonics and acoustic emission, for a thick welded joint in which the defects have been brought about

  17. Monotonic tensile behavior analysis of three-dimensional needle-punched woven C/SiC composites by acoustic emission

    Institute of Scientific and Technical Information of China (English)

    Peng Fang; Laifei Cheng; Litong Zhang; Jingjiang Nie

    2008-01-01

    High toughness and reliable three-dimensional needled C/SiC composites were fabricated by chemical vapor infiltration (CVI). An approach to analyze the tensile behaviors at room temperature and the damage accumulation of the composites by means of acoustic emission was researched. Also the fracture morphology was examined by S-4700 SEM after tensile tests to prove the damage mechanism. The results indicate that the cumulative energy of acoustic emission (AE) signals can be used to monitor and evaluate the damage evolution in ceramic-matrix composites. The initiation of room-temperature tensile damage in C/SiC composites occurred with the growth of micro-cracks in the matrix at the stress level about 40% of the ultimate fracture stress. The level 70% of the fracture stress could be defined as the critical damage strength.

  18. Coupling creep and damage in concrete under high sustained loading: Experimental investigation on bending beams and application of Acoustic Emission technique

    Science.gov (United States)

    Saliba, J.; Loukili, A.; Grondin, F.

    2010-06-01

    effect on concrete, probably because of the consolidation of the hardened cement paste. The influence of creep on fracture energy, fracture toughness, and characteristic length of concrete is also studied. The fracture energy and the characteristic length of concrete increases slightly when creep occurs prior to failure and the size of the fracture process zone increases too. The load-CMOD relationship is linear in the ascending portion and gradually drops off after the peak value in the descending portion. The length of the tail end portion of the softening curve increases with beams subjected to creep. Relatively more ductile fracture behavior was observed with beams subjected to creep. The contribution of non-destructive and instrumental investigation methods is currently exploited to check and measure the evolution of some negative structural phenomena, such as micro-and macro-cracking, finally resulting in a creep-like behaviour. Among these methods, the non-destructive technique based on acoustic Emission proves to be very effective, especially to check and measure micro-cracking that takes place inside a structure under mechanical loading. Thus as a part of the investigation quantitative acoustic emission techniques were applied to investigate microcracking and damage localization in concrete beams. The AE signals were captured with the AE WIN software and further analyzed with Noesis software analysis of acoustic emission data. AE waveforms were generated as elastic waves in concrete due to crack nucleation. And a multichannel data acquisition system was used to record the AE waveforms. During the three point bending tests, quantitative acoustic emission (AE) techniques were used to monitor crack growth and to deduce micro fracture mechanics in concrete beams before and after creep. Several specimens are experimented in order to match each cluster with corresponding damage mechanism of the material under loading. At the same time acoustic emission was used to

  19. Failure of compression molded all-polyolefin composites studied by acoustic emission

    Directory of Open Access Journals (Sweden)

    I. Z. Halasz

    2015-03-01

    Full Text Available This paper is aimed at studying the failure behavior of polyolefin-based self-reinforced polymer composites (SRPCs via acoustic emission (AE. Three matrix materials (ethylene octene copolymer (EOC, polypropylene-based thermoplastic elastomer (ePP, random polypropylene copolymer (rPP, and three kinds of reinforcing structures of PP homopolymer (unidirectional (UD, cross-ply (CP and woven fabric (WF were used. SRPCs were produced by compression molding using the film-stacking method. The composites were characterized by mechanical tests combined with in situ assessment of the burst-type AE events. The results showed that rPP matrix and UD reinforcement produced the greatest reinforcement, with a tensile strength more than six times as high as that of the matrix and a Young’s modulus nearly doubled compared to the neat matrix. The number of the detected AE events increased with increasing Young’s modulus of the applied matrices being associated with reduced sound damping. The AE amplitude distributions shows that failure of the SRPC structure produces AE signals in a broad amplitude range, but the highest detected amplitude range can be clearly linked to fiber fractures.

  20. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    International Nuclear Information System (INIS)

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage

  1. Analysis and Classification of Acoustic Emission Signals During Wood Drying Using the Principal Component Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Ho Yang [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Kim, Ki Bok [Chungnam National University, Daejeon (Korea, Republic of)

    2003-06-15

    In this study, acoustic emission (AE) signals due to surface cracking and moisture movement in the flat-sawn boards of oak (Quercus Variablilis) during drying under the ambient conditions were analyzed and classified using the principal component analysis. The AE signals corresponding to surface cracking showed higher in peak amplitude and peak frequency, and shorter in rise time than those corresponding to moisture movement. To reduce the multicollinearity among AE features and to extract the significant AE parameters, correlation analysis was performed. Over 99% of the variance of AE parameters could be accounted for by the first to the fourth principal components. The classification feasibility and success rate were investigated in terms of two statistical classifiers having six independent variables (AE parameters) and six principal components. As a result, the statistical classifier having AE parameters showed the success rate of 70.0%. The statistical classifier having principal components showed the success rate of 87.5% which was considerably than that of the statistical classifier having AE parameters

  2. Detecting crack profile in concrete using digital image correlation and acoustic emission

    Directory of Open Access Journals (Sweden)

    Loukili A.

    2010-06-01

    Full Text Available Failure process in concrete structures is usually accompanied by cracking of concrete. Understanding the cracking pattern is very important while studying the failure governing criteria of concrete. The cracking phenomenon in concrete structures is usually complex and involves many microscopic mechanisms caused by material heterogeneity. Since last many years, fracture or damage analysis by experimental examinations of the cement based composites has shown importance to evaluate the cracking and damage behavior of those heterogeneous materials with damage accumulation due to microcracks development ahead of the propagating crack tip; and energy dissipation resulted during the evolution of damage in the structure. The techniques used in those experiments may be the holographic interferometry, the dye penetration, the scanning electron microscopy, the acoustic emission etc. Those methods offer either the images of the material surface to observe micro-features of the concrete with qualitative analysis, or the black-white fringe patterns of the deformation on the specimen surface, from which it is difficult to observe profiles of the damaged materials.

  3. Effect of fiber orientation in uni-directional glass epoxy laminate using acoustic emission monitoring

    Institute of Scientific and Technical Information of China (English)

    V. Arumugam; S. Barath Kumar; C. Santulli; A. Joseph Stanley

    2011-01-01

    Acoustic emission (AE) can be used for in situ structural health monitoring of the composite laminates.One of the main issues of AE is to characterize different damage mechanisms from the detected AE signals.In the present work,pure resin and GFRP composites laminates with different stacking sequences such as 0°,90°,angle ply[±45°],cross-ply [0°/90°] are used to trigger different failure mechanisms when subjected to tensile test with AE monitoring.The study of failure mechanisms is facilitated by the choice of different oriented specimens in which one or two such mechanisms predominate.Range of peak frequencies in each orientation is investigated using FFT analysis.Fast Fourier Transform (FFT) enabled calculating the frequency content of each damage mechanism.Randomly selected hits from each range of peak frequencies for the specimens with different orientations subjected to tensile test with AE monitoring are analyzed using short time FFT (STFFT) analysis.STFFT analysis is used to highlight the possible failure mechanism associated with each signal.The predominance of failure modes in each orientation is useful in the study of discrimination of failure modes in composite laminates from AE data.

  4. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    Energy Technology Data Exchange (ETDEWEB)

    Paul, S.C. [Department of Civil Engineering, Stellenbosch University (South Africa); Pirskawetz, S. [BAM Federal Institute for Materials Research and Testing (Germany); Zijl, G.P.A.G. van, E-mail: gvanzijl@sun.ac.za [Department of Civil Engineering, Stellenbosch University (South Africa); Schmidt, W. [BAM Federal Institute for Materials Research and Testing (Germany)

    2015-03-15

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage.

  5. A novel technique for acoustic emission monitoring in civil structures with global fiber optic sensors

    Science.gov (United States)

    Verstrynge, E.; Pfeiffer, H.; Wevers, M.

    2014-06-01

    The application of acoustic emission (AE)-based damage detection is gaining interest in the field of civil structural health monitoring. Damage progress can be detected and located in real time and the recorded AEs hold information on the fracture process which produced them. One of the drawbacks for on-site application in large-scale concrete and masonry structures is the relatively high attenuation of the ultrasonic signal, which limits the detection range of the AE sensors. Consequently, a large number of point sensors are required to cover a certain area. To tackle this issue, a global damage detection system, based on AE detection with a polarization-modulated, single mode fiber optic sensor (FOS), has been developed. The sensing principle, data acquisition and analysis in time and frequency domain are presented. During experimental investigations, this AE-FOS is applied for the first time as a global sensor for the detection of crack-induced AEs in a full-scale concrete beam. Damage progress is monitored during a cyclic four-point bending test and the AE activity, detected with the FOS, is related to the subsequent stages of damage progress in the concrete element. The results obtained with the AE-FOS are successfully linked to the mechanical behavior of the concrete beam and a qualitative correspondence is found with AE data obtained by a commercial system.

  6. Application of acoustic emission technique and friction welding for excavator hose nipple

    International Nuclear Information System (INIS)

    Friction welding is a very useful joining process to weld metals which have axially symmetric cross section. In this paper, the feasibility of industry application was determined by analyzing the mechanical properties of weld region for a specimen of tube-to-tube shape for excavator hose nipple with friction welding, and optimized welding variables were suggested. In order to accomplish this object, friction heating pressure and friction heating time were selected as the major process variables and the experiment was performed in three levels of each parameter. An acoustic emission(AE) technique was applied to evaluate the optimal friction welding conditions nondestructively. AE parameters of accumulative count and event were analyzed in terms of generating trend of AE signals across the full range of friction weld. The typical waveform and frequency spectrum of AE signals which is generated by friction weld were discussed. From this study the optimal welding variables could be suggested as rotating speed of 1300 rpm, friction heating pressure of 15 MPa, and friction heating time of 10 sec. AE event was a useful parameter to estimate the tensile strength of tube-to tube specimen with friction weld.

  7. Classification of alkali-silica reaction and corrosion distress using acoustic emission

    Science.gov (United States)

    Abdelrahman, Marwa; ElBatanouny, Mohamed; Serrato, Michael; Dixon, Kenneth; Larosche, Carl; Ziehl, Paul

    2016-02-01

    The Nuclear Regulatory Commission regulates approximately 100 commercial nuclear power reactor facilities that contribute about 20% of the total electric energy produced in the United States. Half of these reactor facilities are over 30 years old and are approaching their original design service life. Due to economic and durability considerations, significant portions of many of the facilities were constructed with reinforced concrete, including the containment facilities, cooling towers, and foundations. While most of these concrete facilities have performed exceptionally well throughout their initial expected service life, some are beginning to exhibit different forms of concrete deterioration. In this study, acoustic emission (AE) is used to monitor two main concrete deterioration mechanisms; alkali-silica reaction (ASR) distress and corrosion of reinforcing steel. An accelerated ASR test was conducted where specimens were continuously monitored with AE. The results show that AE can detect and classify damage due to ASR distress in the specimens. AE was also used to remotely monitor active corrosion regions in a reactor facility. AE monitoring of accelerated corrosion testing was also conducted on a concrete block specimen cut from a similar reactor building. Electrochemical measurements were conducted to correlate AE activity to quantifiable corrosion measurements and to enhance capabilities for service life prediction.

  8. The Contact State Monitoring for Seal End Faces Based on Acoustic Emission Detection

    Directory of Open Access Journals (Sweden)

    Xiaohui Li

    2016-01-01

    Full Text Available Monitoring the contact state of seal end faces would help the early warning of the seal failure. In the acoustic emission (AE detection for mechanical seal, the main difficulty is to reduce the background noise and to classify the dispersed features. To solve these problems and achieve higher detection rates, a new approach based on genetic particle filter with autoregression (AR-GPF and hypersphere support vector machine (HSSVM is presented. First, AR model is used to build the dynamic state space (DSS of the AE signal, and GPF is used for signal filtering. Then, multiple features are extracted, and a classification model based on HSSVM is constructed for state recognition. In this approach, AR-GPF is an excellent time-domain method for noise reduction, and HSSVM has advantage on those dispersed features. Finally experimental data shows that the proposed method can effectively detect the contact state of the seal end faces and has higher accuracy rates than some other existing methods.

  9. Source location of artificial acoustic emission in elbow-pipe joint using neural network

    International Nuclear Information System (INIS)

    A new technique to locate a defect, combining acoustic emission (AE) and neural network, is proposed to assess the structural integrity of a pipeline in operation. Computer simulations and experiments to locate the defect using artificial AE by means of a pencil lead break are conducted at an elbow-pipe joint. Arrival time differences of the AE wave from the AE source to four sensors with 150kHz resonance frequency are measured using an AE digital measuring system with four channel devices. Half the data and all data are used for leaning of the neural network and for estimating the locations, respectively. Source location error of the elbow-pipe joint in the experiment, as well as the simulation, was less than 1%. To confirm the detection of a crack extension in a pipe joint by the system, crack tip locations due to extension are obtained from a welded defect of a tensile specimen are determined. Results are obtained for the detection of the crack extension. (author)

  10. Research on the Monitoring System of CNC Grinding Process Based on Acoustic Emission

    Institute of Scientific and Technical Information of China (English)

    HU Zhongxiang; TENG Jiaxu; YANG Junwei; HUO Xiaojing; SHI Xiaojun

    2006-01-01

    Using on-line monitoring during the CNC grinding process, the hazard case such as the crushing of grinding wheel and various safety accidents could be avoided, and the optimum time for dressing and replacing grinding wheel could also be determined, and hence, the service life of the grinding wheel could be prolonged and grinding quality could be improved. To overcome the limitation of some traditional techniques in which some parameters including the grinding power and force, torque and so on were monitored, the acoustic emission (AE) technique, which provides high sensitivity and responding speed, were developed in the present paper. The mechanism of AE during grinding was reviewed. Moreover, a virtual AE monitoring system, which could monitor the grinding state under different working conditions during the grinding, has been developed based on the Virtual Instruments technique. Some experiments were also performed on the internal grinder. The results showed that the AE signals became stronger with increasing the main shaft speed and grinding depth or decreasing the distance between the AE sensor and grinding area.

  11. Analytical modelling of acoustic emission from buried or surface-breaking cracks under stress

    International Nuclear Information System (INIS)

    Acoustic emission (AE) is a non-destructive testing method used in various industries (aerospace, petrochemical and pressure-vessel industries in general, power generation, civil engineering, mechanical engineering, etc...) for the examination of large structures subjected to various stresses (e.g. mechanical loading).The energy released by a defect under stress (the AE phenomenon) can propagate as guided waves in thin structures or as surface Rayleigh waves in thick ones. Sensors (possibly permanently) are positioned at various locations on the structure under examination and are assumed to be sensitive to these waves. Then, post-processing tools typically based on signal processing and triangulation algorithms can be used to inverse these data, allowing one to estimate the position of the defect from which emanates the waves measured. The French Atomic Energy Commission is engaged in the development of tools for simulating AE examinations. These tools are based on specific models for the AE sources, for the propagation of guided or Rayleigh waves and for the behaviour of AE sensors. Here, the coupling of a fracture mechanics based model for AE source and surface/guided wave propagation models is achieved through an integral formulation relying on the elastodynamic reciprocity principle. As a first approximation, a simple piston-like model is used to predict the sensitivity of AE sensors. Predictions computed by our simulation tool are compared to results from the literature for validation purpose.

  12. Nonlinear Kalman Filtering for acoustic emission source localization in anisotropic panels.

    Science.gov (United States)

    Dehghan Niri, E; Farhidzadeh, A; Salamone, S

    2014-02-01

    Nonlinear Kalman Filtering is an established field in applied probability and control systems, which plays an important role in many practical applications from target tracking to weather and climate prediction. However, its application for acoustic emission (AE) source localization has been very limited. In this paper, two well-known nonlinear Kalman Filtering algorithms are presented to estimate the location of AE sources in anisotropic panels: the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). These algorithms are applied to two cases: velocity profile known (CASE I) and velocity profile unknown (CASE II). The algorithms are compared with a more traditional nonlinear least squares method. Experimental tests are carried out on a carbon-fiber reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers to validate the proposed approaches. AE sources are simulated using an instrumented miniature impulse hammer. In order to evaluate the performance of the algorithms, two metrics are used: (1) accuracy of the AE source localization and (2) computational cost. Furthermore, it is shown that both EKF and UKF can provide a confidence interval of the estimated AE source location and can account for uncertainty in time of flight measurements.

  13. Fatigue features study on the crankshaft material of 42CrMo steel using acoustic emission

    Science.gov (United States)

    Shi, Yue; Dong, Lihong; Wang, Haidou; Li, Guolu; Liu, Shenshui

    2016-09-01

    Crankshaft is regarded as an important component of engines, and it is an important application of remanufacturing because of its high added value. However, the fatigue failure research of remanufactured crankshaft is still in its primary stage. Thus, monitoring and investigating the fatigue failure of the remanufacturing crankshaft is crucial. In this paper, acoustic emission (AE) technology and machine vision are used to monitor the four-point bending fatigue of 42CrMo, which is the material of crankshaft. The specimens are divided into two categories, namely, pre-existing crack and non-preexisting crack, which simulate the crankshaft and crankshaft blank, respectively. The analysis methods of parameter-based AE techniques, wavelet transform (WT) and SEM analysis are combined to identify the stage of fatigue failure. The stage of fatigue failure is the basis of using AE technology in the field of remanufacturing crankshafts. The experiment results show that the fatigue crack propagation style is a transgranular fracture and the fracture is a brittle fracture. The difference mainly depends on the form of crack initiation. Various AE signals are detected by parameter analysis method. Wavelet threshold denoising and WT are combined to extract the spectral features of AE signals at different fatigue failure stages.

  14. Source location of artificial acoustic emission in elbow-pipe joint using neural network

    Energy Technology Data Exchange (ETDEWEB)

    Homma, Kyoji; Okamura, Yuka [The Univ. of Electro-communications, Chofu, Tokyo (Japan)

    2002-11-01

    A new technique to locate a defect, combining acoustic emission (AE) and neural network, is proposed to assess the structural integrity of a pipeline in operation. Computer simulations and experiments to locate the defect using artificial AE by means of a pencil lead break are conducted at an elbow-pipe joint. Arrival time differences of the AE wave from the AE source to four sensors with 150kHz resonance frequency are measured using an AE digital measuring system with four channel devices. Half the data and all data are used for leaning of the neural network and for estimating the locations, respectively. Source location error of the elbow-pipe joint in the experiment, as well as the simulation, was less than 1%. To confirm the detection of a crack extension in a pipe joint by the system, crack tip locations due to extension are obtained from a welded defect of a tensile specimen are determined. Results are obtained for the detection of the crack extension. (author)

  15. Development of Methodology to Assess the Failure Behaviour of Bamboo Single Fibre by Acoustic Emission Technique

    Science.gov (United States)

    Alam, Md. Saiful; Gulshan, Fahmida; Ahsan, Qumrul; Wevers, Martine; Pfeiffer, Helge; van Vuure, Aart-Willem; Osorio, Lina; Verpoest, Ignaas

    2016-06-01

    Acoustic emission (AE) was used as a tool for detecting, evaluating and for better understanding of the damage mechanism and failure behavior in composites during mechanical loading. Methodology was developed for tensile test of natural fibres (bamboo single fibre). A series of experiments were performed and load drops (one or two) were observed in the load versus time graphs. From the observed AE parameters such as amplitude, energy, duration etc. significant information corresponding to the load drops were found. These AE signals from the load drop occurred from such failure as debonding between two elementary fibre or from join of elementary fibre at edge. The various sources of load at first load drop was not consistent for the different samples (for a particular sample the value is 8 N, stress: 517.51 MPa). Final breaking of fibre corresponded to saturated level AE amplitude of preamplifier (99.9 dB) for all samples. Therefore, it was not possible to determine the exact AE energy value for final breaking. Same methodology was used for tensile test of three single fibres, which gave clear indication of load drop before the final breaking of first and second fibre.

  16. Acoustic emission signature analysis. Technical progress report No. 2, 1 March 1979-29 February 1980

    International Nuclear Information System (INIS)

    Acoustic emission in plate glass and steel has been studied as a function of angle. The low frequency AE in glass (< 1 MHz) was studied in detail, and contributions from P, S and Rayleigh waves identified. These results are isotropic, as expected theoretically. Limited high frequency (5-20 MHz) results have been obtained in glass. This is the first time, that AE energy has been measured above 3 MHz. The measurement of AE on transgranular crack growth in steel during fatigue crack growth was accomplished by use of a low noise manual hydraulic loading system and an electronic gate to reject grip noise. The signals are complex, and not yet understood in detail. The concept of the wave momentum of an AE, first introduced during the previous year, was elaboratored and a measurement technique suggested. The theoretical study of this problem led to the discovery of an infinite, previously unknown, family of elastic surface (Rayleigh-like) waves, and to further cylindrical, radially propagating plate waves. It appears these waves may be useful in other areas of ultrasonics

  17. Acoustic emission detection with fiber optical sensors for dry cask storage health monitoring

    Science.gov (United States)

    Lin, Bin; Bao, Jingjing; Yu, Lingyu; Giurgiutiu, Victor

    2016-04-01

    The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS). In the past two decades, an extensive sensor technology development has been used for structural health monitoring (SHM). Technologies for the diagnosis and prognosis of a nuclear system, such as dry cask storage system (DCSS), can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component. Fiber optical sensors have emerged as one of the major SHM technologies developed particularly for temperature and strain measurements. This paper presents the development of optical equipment that is suitable for ultrasonic guided wave detection for active SHM in the MHz range. An experimental study of using fiber Bragg grating (FBG) as acoustic emission (AE) sensors was performed on steel blocks. FBG have the advantage of being durable, lightweight, and easily embeddable into composite structures as well as being immune to electromagnetic interference and optically multiplexed. The temperature effect on the FBG sensors was also studied. A multi-channel FBG system was developed and compared with piezoelectric based AE system. The paper ends with conclusions and suggestions for further work.

  18. The design and calibration of particular geometry piezoelectric acoustic emission transducer for leak detection and localization

    Science.gov (United States)

    Yalcinkaya, Hazim; Ozevin, Didem

    2013-09-01

    Pipeline leak detection using an acoustic emission (AE) method requires highly sensitive transducers responding to less attenuative and dispersive wave motion in order to place the discrete transducer spacing in an acceptable approach. In this paper, a new piezoelectric transducer geometry made of PZT-5A is introduced to increase the transducer sensitivity to the tangential direction. The finite element analysis of the transducer geometry is modeled in the frequency domain to identify the resonant frequency, targeting 60 kHz, and the loss factor. The numerical results are compared with the electromechanical characterization tests. The transducer response to wave motion generated in different directions is studied using a multiphysics model that couples mechanical and electrical responses of structural and piezoelectric properties. The directional dependence and the sensitivity of the transducer response are identified using the laser-induced load function. The transducer response is compared with a conventional thickness mode AE transducer under simulations and leak localization in a laboratory scale steel pipe.

  19. Fiber-optic sensor-based remote acoustic emission measurement of composites

    Science.gov (United States)

    Yu, Fengming; Okabe, Yoji; Wu, Qi; Shigeta, Naoki

    2016-10-01

    Acoustic emission (AE) detection functioning at high temperatures could clarify the damage process in high heat-resistant composites. To achieve the high-temperature AE detection, a remote AE measurement based on a phase-shifted fiber Bragg grating (PS-FBG) sensor with a high sensitivity over a broad bandwidth was proposed. The common optical fibers were made from glass with good heat resistance. Hence, in this method, optical fiber was used as the waveguide to propagate the AE in the composite from a high-temperature environment to the room-temperature environment wherein the PS-FBG was located. Owing to the special AE detection configuration, this method was a new adhesive method for remote measurement (ADRM). The experiment and numerical simulation revealed that the PS-FBG sensor in the ADRM configuration demonstrated accurate remote sensing for the AE signals. This was because of the good waveguide system provided by the thin optical fiber and the sensitivity of the PS-FBG sensor to the axial strain in the core of the fiber. Consequently, the remote measurement utilizing the PS-FBG sensor in the ADRM configuration has a high potential for AE detection in high-temperature conditions.

  20. A New Method to Identify Quaternary Moraine:Acoustic Emission Stress Measurement

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhizhong; QIAO Yansong; TIAN Jiaorong; WANG Min; LI Mingze; HE Peiyuan; QIAN Fang

    2006-01-01

    How to effectively identify glacial sediments, especially Quaternary moraine, has been in dispute for decades. The traditional methods, e.g., sedimentary and geomorphologic ones, are facing challenge in eastern China where controversial moraine deposits are dominatingly distributed. Here,for the first time, we introduce the acoustic emission (AE) stress measurement, a kind of historical stress measurement, to identify Quaternary moraine. The results demonstrate that it can be employed to reconstruct stress information of glaciation remaining in gravels, and may shed light on the identification of Quaternary moraine in eastern China. First, we measured the AE stress of gravels of glacial origin that are underlying the Xidatan Glacier, eastern Kunlun Mountains in western China.Second, we calculated the stress according to the actual thickness of the glacier. The almost identical stress values suggest that the glacial gravels can memorize and preserve the overlying glacier-derived aplomb stress. And then we introduce this new approach to the controversial moraine in Mount Lushan, eastern China. The results indicate that the stress is attributed to the Quaternary glacier, and the muddy gravels in the controversial moraine in Mount Lushan are moraine deposits but not others.

  1. Clustering reveals cavitation-related acoustic emission signals from dehydrating branches.

    Science.gov (United States)

    Vergeynst, Lidewei L; Sause, Markus G R; De Baerdemaeker, Niels J F; De Roo, Linus; Steppe, Kathy

    2016-06-01

    The formation of air emboli in the xylem during drought is one of the key processes leading to plant mortality due to loss in hydraulic conductivity, and strongly fuels the interest in quantifying vulnerability to cavitation. The acoustic emission (AE) technique can be used to measure hydraulic conductivity losses and construct vulnerability curves. For years, it has been believed that all the AE signals are produced by the formation of gas emboli in the xylem sap under tension. More recent experiments, however, demonstrate that gas emboli formation cannot explain all the signals detected during drought, suggesting that different sources of AE exist. This complicates the use of the AE technique to measure emboli formation in plants. We therefore analysed AE waveforms measured on branches of grapevine (Vitis vinifera L. 'Chardonnay') during bench dehydration with broadband sensors, and applied an automated clustering algorithm in order to find natural clusters of AE signals. We used AE features and AE activity patterns during consecutive dehydration phases to identify the different AE sources. Based on the frequency spectrum of the signals, we distinguished three different types of AE signals, of which the frequency cluster with high 100-200 kHz frequency content was strongly correlated with cavitation. Our results indicate that cavitation-related AE signals can be filtered from other AE sources, which presents a promising avenue into quantifying xylem embolism in plants in laboratory and field conditions. PMID:27095256

  2. A Bayesian Approach for Localization of Acoustic Emission Source in Plate-Like Structures

    Directory of Open Access Journals (Sweden)

    Gang Yan

    2015-01-01

    Full Text Available This paper presents a Bayesian approach for localizing acoustic emission (AE source in plate-like structures with consideration of uncertainties from modeling error and measurement noise. A PZT sensor network is deployed to monitor and acquire AE wave signals released by possible damage. By using continuous wavelet transform (CWT, the time-of-flight (TOF information of the AE wave signals is extracted and measured. With a theoretical TOF model, a Bayesian parameter identification procedure is developed to obtain the AE source location and the wave velocity at a specific frequency simultaneously and meanwhile quantify their uncertainties. It is based on Bayes’ theorem that the posterior distributions of the parameters about the AE source location and the wave velocity are obtained by relating their priors and the likelihood of the measured time difference data. A Markov chain Monte Carlo (MCMC algorithm is employed to draw samples to approximate the posteriors. Also, a data fusion scheme is performed to fuse results identified at multiple frequencies to increase accuracy and reduce uncertainty of the final localization results. Experimental studies on a stiffened aluminum panel with simulated AE events by pensile lead breaks (PLBs are conducted to validate the proposed Bayesian AE source localization approach.

  3. MODELLING OF ACOUSTIC EMISSION SOURCE AND WAVE RESPONSE IN LAYERED MATERIALS

    Directory of Open Access Journals (Sweden)

    Alamin A.

    2014-03-01

    Full Text Available This study proposes a model of wave propagation in layered media for the use in acoustic emission (AE studies. This model aims to find an AE response at a free surface to the propagating waves originating at a dislocation source either in one layer medium or a layer-to-layer interface. Each of the layered media is assumed to be homogenous, linear elastic and isotropic. An integral transformation method has been applied to determine the wave response in frequency-wave number domain, which is then converted to time-space domain. In the numerical examples, we first select truncated values with the finite integral transformation, so that no wave interference happens in the responses from wave reflection at truncated boundaries. Next, we simulate wave propagation in an elastic half space, and compare results obtained with that from other kind bottom boundary. Next, we introduce a dis- location source in interface and compare a simulated AE wave response obtained with that computed in the layered medium to demonstrate the performance of the model. In each simulation, the results show good agreement with the reference solutions.

  4. A novel technique for acoustic emission monitoring in civil structures with global fiber optic sensors

    International Nuclear Information System (INIS)

    The application of acoustic emission (AE)-based damage detection is gaining interest in the field of civil structural health monitoring. Damage progress can be detected and located in real time and the recorded AEs hold information on the fracture process which produced them. One of the drawbacks for on-site application in large-scale concrete and masonry structures is the relatively high attenuation of the ultrasonic signal, which limits the detection range of the AE sensors. Consequently, a large number of point sensors are required to cover a certain area. To tackle this issue, a global damage detection system, based on AE detection with a polarization-modulated, single mode fiber optic sensor (FOS), has been developed. The sensing principle, data acquisition and analysis in time and frequency domain are presented. During experimental investigations, this AE-FOS is applied for the first time as a global sensor for the detection of crack-induced AEs in a full-scale concrete beam. Damage progress is monitored during a cyclic four-point bending test and the AE activity, detected with the FOS, is related to the subsequent stages of damage progress in the concrete element. The results obtained with the AE-FOS are successfully linked to the mechanical behavior of the concrete beam and a qualitative correspondence is found with AE data obtained by a commercial system. (papers)

  5. Evaluating damage potential of cryogenic concrete using acoustic emission sensors and permeability testing

    Science.gov (United States)

    Kogbara, Reginald B.; Parsaei, Boback; Iyengar, Srinath R.; Grasley, Zachary C.; Masad, Eyad A.; Zollinger, Dan G.

    2014-04-01

    This study evaluates the damage potential of concrete of different mix designs subjected to cryogenic temperatures, using acoustic emission (AE) and permeability testing. The aim is to investigate design methodologies that might be employed to produce concrete that resists damage when cooled to cryogenic temperatures. Such concrete would be suitable for primary containment of liquefied natural gas (LNG) and could replace currently used 9% Ni steel, thereby leading to huge cost savings. In the experiments described, concrete cubes, 150 mm x 150 mm x 150 mm, were cast using four different mix designs. The four mixes employed siliceous river sand as fine aggregate. Moreover, limestone, sandstone, trap rock and lightweight aggregate were individually used as coarse aggregates in the mixes. The concrete samples were then cooled from room temperature (20°C) to cryogenic temperature (-165°C) in a temperature chamber. AE sensors were placed on the concrete cubes during the cryogenic freezing process. The damage potential was evaluated in terms of the growth of damage as determined from AE, as a function of temperature and concrete mixture design. The damage potential observed was validated with water permeability testing. Initial results demonstrate the effects of the coefficient of thermal expansion (CTE) of the aggregates on damage growth. Concrete damage (cracking) resistance generally decreased with increasing coarse aggregate CTE, and was in the order, limestone ≥ trap rock concrete due to differential CTE of its components.

  6. Gearbox Tooth Cut Fault Diagnostics Using Acoustic Emission and Vibration Sensors — A Comparative Study

    Directory of Open Access Journals (Sweden)

    Yongzhi Qu

    2014-01-01

    Full Text Available In recent years, acoustic emission (AE sensors and AE-based techniques have been developed and tested for gearbox fault diagnosis. In general, AE-based techniques require much higher sampling rates than vibration analysis-based techniques for gearbox fault diagnosis. Therefore, it is questionable whether an AE-based technique would give a better or at least the same performance as the vibration analysis-based techniques using the same sampling rate. To answer the question, this paper presents a comparative study for gearbox tooth damage level diagnostics using AE and vibration measurements, the first known attempt to compare the gearbox fault diagnostic performance of AE- and vibration analysis-based approaches using the same sampling rate. Partial tooth cut faults are seeded in a gearbox test rig and experimentally tested in a laboratory. Results have shown that the AE-based approach has the potential to differentiate gear tooth damage levels in comparison with the vibration-based approach. While vibration signals are easily affected by mechanical resonance, the AE signals show more stable performance.

  7. Non-destructive evaluation of laboratory scale hydraulic fracturing using acoustic emission

    Science.gov (United States)

    Hampton, Jesse Clay

    The primary objective of this research is to develop techniques to characterize hydraulic fractures and fracturing processes using acoustic emission monitoring based on laboratory scale hydraulic fracturing experiments. Individual microcrack AE source characterization is performed to understand the failure mechanisms associated with small failures along pre-existing discontinuities and grain boundaries. Individual microcrack analysis methods include moment tensor inversion techniques to elucidate the mode of failure, crack slip and crack normal direction vectors, and relative volumetric deformation of an individual microcrack. Differentiation between individual microcrack analysis and AE cloud based techniques is studied in efforts to refine discrete fracture network (DFN) creation and regional damage quantification of densely fractured media. Regional damage estimations from combinations of individual microcrack analyses and AE cloud density plotting are used to investigate the usefulness of weighting cloud based AE analysis techniques with microcrack source data. Two granite types were used in several sample configurations including multi-block systems. Laboratory hydraulic fracturing was performed with sample sizes ranging from 15 x 15 x 25 cm3 to 30 x 30 x 25 cm 3 in both unconfined and true-triaxially confined stress states using different types of materials. Hydraulic fracture testing in rock block systems containing a large natural fracture was investigated in terms of AE response throughout fracture interactions. Investigations of differing scale analyses showed the usefulness of individual microcrack characterization as well as DFN and cloud based techniques. Individual microcrack characterization weighting cloud based techniques correlated well with post-test damage evaluations.

  8. Acoustic Emission Monitoring of Lightning-Damaged CFRP Laminates during Compression-after-Impact Test

    International Nuclear Information System (INIS)

    Carbon-fiber reinforced plastic(CFRP) laminates made of nano-particle-coated carbon fibers and damaged by a simulated lightning strike were tested under compression-after-impact(CAI) mode, during which the damage progress due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. Conductive nano-particles were coated directly on the fibers, from which CFRP coupons were made. The coupon were subjected to the strikes with a high voltage/current impulse of 10-40 kA within a few . The effects of nano-particle coating and the degree of damage induced by the simulated lightning strikes on AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. The assessment during the CAI tests of damaged CFRP showed that AE monitoring appeared to be useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.

  9. Final developments, validation and technology transfer for AE (acoustic emission) and SAFT-UT (Synthetic Aperture Focusing of Ultrasonic Testing)

    International Nuclear Information System (INIS)

    The program for validation and technology transfer for acoustic emission (AE) and Synthetic Aperture Focusing of Ultrasonic Testing (SAFT-UT) is designed to accomplish the final step of moving research results into beneficial application. Accomplishments for FY88 in the areas of AE and SAFT-UT data under this program are discussed in this paper. the information is treated under the topics of code activities, field validation, and seminars. Projected FY89 activities will continue to focus on these three areas

  10. Development of Generic Methodology for Designing a Structural Health Monitoring Installation Based on the Acoustic Emission Technique

    OpenAIRE

    Gagar, D.; Martinez, M.J.; Foote, P.

    2014-01-01

    The Acoustic Emission (AE) technique can be used to perform damage detection and localisation for structural health monitoring purposes. Implementation in aircraft structures however poses a significant challenge as its performance in terms of damage detection and localisation is not well understood when used with complex structural geometries and variable operational service environments. This paper presents initial developments towards a generic methodology for optimal design of a structura...

  11. The Sacred Mountain of Varallo in Italy: Seismic risk assessment by Acoustic Emission and structural numerical models

    OpenAIRE

    Alberto Carpinteri; Giuseppe Lacidogna; Stefano Invernizzi; Federico Accornero

    2013-01-01

    In this work, we examine an application of Acoustic Emission (AE) technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named "The Sacred Mountain of Varallo". Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular concern due to its uncertain structural condition and due to the level of stress caused by the regional seismicity. Therefore, lifetime...

  12. Examination of ceramic restoration adhesive coverage in cusp-replacement premolar using acoustic emission under fatigue testing

    OpenAIRE

    Chang, Yen-Hsiang; Yu, Jin-Jie; Lin, Chun-Li

    2014-01-01

    Background This study investigates CAD/CAM ceramic cusp-replacing restoration resistance with and without buccal cusp replacement under static and dynamic cyclic loads, monitored using the acoustic emission (AE) technique. Method The cavity was designed in a typical MODP (mesial-occlusal-distal-palatal) restoration failure shape when the palatal cusp has been lost. Two ceramic restorations [without coverage (WOC) and with (WC) buccal cuspal coverage with 2.0 mm reduction in cuspal height] wer...

  13. An Investigation of Vocal Tract Characteristics for Acoustic Discrimination of Pathological Voices

    Directory of Open Access Journals (Sweden)

    Jung-Won Lee

    2013-01-01

    Full Text Available This paper investigates the effectiveness of measures related to vocal tract characteristics in classifying normal and pathological speech. Unlike conventional approaches that mainly focus on features related to the vocal source, vocal tract characteristics are examined to determine if interaction effects between vocal folds and the vocal tract can be used to detect pathological speech. Especially, this paper examines features related to formant frequencies to see if vocal tract characteristics are affected by the nature of the vocal fold-related pathology. To test this hypothesis, stationary fragments of vowel /aa/ produced by 223 normal subjects, 472 vocal fold polyp subjects, and 195 unilateral vocal cord paralysis subjects are analyzed. Based on the acoustic-articulatory relationships, phonation for pathological subjects is found to be associated with measures correlated with a raised tongue body or an advanced tongue root. Vocal tract-related features are also found to be statistically significant from the Kruskal-Wallis test in distinguishing normal and pathological speech. Classification results demonstrate that combining the formant measurements with vocal fold-related features results in improved performance in differentiating vocal pathologies including vocal polyps and unilateral vocal cord paralysis, which suggests that measures related to vocal tract characteristics may provide additional information in diagnosing vocal disorders.

  14. Use of Modal Acoustic Emission to Monitor Damage Progression in Carbon Fiber/Epoxy and Implications for Composite Structures

    Science.gov (United States)

    Waller, J. M.; Nichols, C. T.; Wentzel, D. J.; Saulsberry R. L.

    2010-01-01

    Broad-band modal acoustic emission (AE) data was used to characterize micromechanical damage progression in uniaxial IM7 and T1000 carbon fiber-epoxy tows and an IM7 composite overwrapped pressure vessel (COPV) subjected to an intermittent load hold tensile stress profile known to activate the Felicity ratio (FR). Damage progression was followed by inspecting the Fast Fourier Transforms (FFTs) associated with acoustic emission events. FFT analysis revealed the occurrence of cooperative micromechanical damage events in a frequency range between 100 kHz and 1 MHz. Evidence was found for the existence of a universal damage parameter, referred to here as the critical Felicity ratio, or Felicity ratio at rupture (FR*), which had a value close to 0.96 for the tows and the COPV tested. The implications of using FR* to predict failure in carbon/epoxy composite materials and related composite components such as COPVs are discussed. Trends in the FFT data are also discussed; namely, the difference between the low and high energy events, the difference between early and late-life events, comparison of IM7 and T1000 damage progression, and lastly, the similarity of events occurring at the onset of significant acoustic emission used to calculate the FR.

  15. Dynamic control of the optical emission from GaN/InGaN nanowire quantum dots by surface acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Lazić, S., E-mail: lazic.snezana@uam.es; Chernysheva, E.; Meulen, H. P. van der; Calleja Pardo, J. M. [Departamento de Física de Materiales, Instituto “Nicolás Cabrera” and Instituto de Física de Materia Condensada (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid (Spain); Gačević, Ž.; Calleja, E. [ISOM-DIE, Universidad Politécnica de Madrid, 28040 Madrid (Spain)

    2015-09-15

    The optical emission of InGaN quantum dots embedded in GaN nanowires is dynamically controlled by a surface acoustic wave (SAW). The emission energy of both the exciton and biexciton lines is modulated over a 1.5 meV range at ∼330 MHz. A small but systematic difference in the exciton and biexciton spectral modulation reveals a linear change of the biexciton binding energy with the SAW amplitude. The present results are relevant for the dynamic control of individual single photon emitters based on nitride semiconductors.

  16. Dynamic control of the optical emission from GaN/InGaN nanowire quantum dots by surface acoustic waves

    Directory of Open Access Journals (Sweden)

    S. Lazić

    2015-09-01

    Full Text Available The optical emission of InGaN quantum dots embedded in GaN nanowires is dynamically controlled by a surface acoustic wave (SAW. The emission energy of both the exciton and biexciton lines is modulated over a 1.5 meV range at ∼330 MHz. A small but systematic difference in the exciton and biexciton spectral modulation reveals a linear change of the biexciton binding energy with the SAW amplitude. The present results are relevant for the dynamic control of individual single photon emitters based on nitride semiconductors.

  17. Resonance Spectrum Characteristics of Effective Electromechanical Coupling Coefficient of High-Overtone Bulk Acoustic Resonator

    Directory of Open Access Journals (Sweden)

    Jian Li

    2016-09-01

    Full Text Available A high-overtone bulk acoustic resonator (HBAR consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q and multi-mode resonance spectrum. By analyzing the influences of each layer’s material and structure (thickness parameters on the effective electromechanical coupling coefficient (Keff2, the resonance spectrum characteristics of Keff2 have been investigated systematically, and the optimal design of HBAR has been provided. Besides, a device, corresponding to one of the theoretical cases studied, is fabricated and evaluated. The experimental results are basically consistent with the theoretical results. Finally, the effects of Keff2 on the function of the crystal oscillators constructed with HBARs are proposed. The crystal oscillators can operate in more modes and have a larger frequency hopping bandwidth by using the HBARs with a larger Keff2·Q.

  18. The role of acoustic emission in the study of rock fracture

    Science.gov (United States)

    Lockner, D.

    1993-01-01

    The development of faults and shear fracture systems over a broad range of temperature and pressure and for a variety of rock types involves the growth and interaction of microcracks. Acoustic emission (AE), which is produced by rapid microcrack growth, is a ubiquitous phenomenon associated with brittle fracture and has provided a wealth of information regarding the failure process in rock. This paper reviews the successes and limitations of AE studies as applied to the fracture process in rock with emphasis on our ability to predict rock failure. Application of laboratory AE studies to larger scale problems related to the understanding of earthquake processes is also discussed. In this context, laboratory studies can be divided into the following categories. 1) Simple counting of the number of AE events prior to sample failure shows a correlation between AE rate and inelastic strain rate. Additional sorting of events by amplitude has shown that AE events obey the power law frequency-magnitude relation observed for earthquakes. These cumulative event count techniques are being used in conjunction with damage mechanics models to determine how damage accumulates during loading and to predict failure. 2) A second area of research involves the location of hypocenters of AE source events. This technique requires precise arrival time data of AE signals recorded over an array of sensors that are essentially a miniature seismic net. Analysis of the spatial and temporal variation of event hypocenters has improved our understanding of the progression of microcrack growth and clustering leading to rock failure. Recently, fracture nucleation and growth have been studied under conditions of quasi-static fault propagation by controlling stress to maintain constant AE rate. 3) A third area of study involves the analysis of full waveform data as recorded at receiver sites. One aspect of this research has been to determine fault plane solutions of AE source events from first motion

  19. Acoustic Emission and Ultrasonic Characterization of Jurassic Navajo Formation Deformation During Axisymmetric Compression Testing

    Science.gov (United States)

    Rinehart, A. J.; Dewers, T. A.; Holcomb, D. J.; Broome, S. T.

    2011-12-01

    Linking continuum-scale and microscale brittle damage in rock remains a challenge impacting CO2 sequestration, secondary recovery, structural monitoring, and other geotechnical engineering applications. We examine if the mode of micromechanical failure scales directly up to continuum-scale damage-induced velocity anisotropy. Axisymmetric drained lab-dry compression experiments are performed on facies of moderately cemented finely laminated quartz arenite from the Jurassic Navajo Formation, a target reservoir rock for CO2 sequestration in Utah. The tests are 1 unconfined uniaxial compression test, 1 hydrostatic compression test, and 3 triaxial compression tests. Microscale damage is monitored using acoustic emissions (AE) and continuum scale damage is monitored with ultrasonic velocity scans. During the non-hydrostatic tests, three to five unload loops are performed pre-failure, with one unload loop performed post-failure. While stresses are increasing, AEs are monitored continuously using 1.6-mm diameter, 0.5-mm thick PZT-5A pins attached circumferentially around the cylindrical sample, and with 6-mm diameter, 2-mm thick PZT-5A discs at the ends of the sample. Before and after each unload loop, the test is paused and the AE transducers sequentially emit an ultrasonic pulse to measure wave speeds. The resulting elastic wave is detected by the other AE transducers. Post-test, the changing anisotropic velocity structure of the rock during compression and failure is compared to the locations, frequency, and relative moment tensors of the AEs measured between ultrasonic scans. Pre- and post-test visual and x-ray CT scan observations of the sample are compared to the acoustic metrics. These tiered observations of rock damage will further elucidate the scaling of microscale brittle failure to the continuum-scale This work was supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of

  20. A signal processing approach for enhanced Acoustic Emission data analysis in high activity systems: Application to organic matrix composites

    Science.gov (United States)

    Kharrat, M.; Ramasso, E.; Placet, V.; Boubakar, M. L.

    2016-03-01

    Structural elements made of Organic Matrix Composites (OMC) under complex loading may suffer from high Acoustic Emission (AE) activity caused by the emergence of different emission sources at high rates with high noise level, which finally engender continuous emissions. The detection of hits in this situation becomes a challenge particularly during fatigue tests. This work suggests an approach based on the Discrete Wavelet Transform (DWT) denoising applied on signal segments. A particular attention is paid to the adjustment of the denoising parameters based on pencil lead breaks and their influence on the quality of the denoised AE signals. The validation of the proposed approach is performed on a ring-shaped Carbon Fiber Reinforced Plastics (CFRP) under in-service-like conditions involving continuous emissions with superimposed damage-related transients. It is demonstrated that errors in hit detection are greatly reduced leading to a better identification of the natural damage scenario based on AE signals.

  1. Application of dual reciprocity boundary element method to predict acoustic attenuation characteristics of marine engine exhaust silencers

    Institute of Scientific and Technical Information of China (English)

    JI Zhen-lin; WANG Xue-ren

    2008-01-01

    In marine engine exhaust silencing systems,the presence of exhaust gas flow influences the sound propagation inside the systems and the acoustic attenuation performance of silencers.In order to investigate the effects of three-dimensional gas flow and acoustic damping on the acoustic attenuation characteristics of marine engine exhaust silencers,a dual reciprocity boundary element method (DRBEM)was developed.The acoustic governing equation in three-dimensional potential flow was derived first,and then the DRBEM numerical procedure is given.Compared to the conventional boundary elementmethod (CBEM),the DRBEM considers the second order terms of flow Mach number in the acoustic governing equation,so it is suitable for the cases with higher Mach number subsonic flow.For complex exhaust silencers,it is difficult to apply the single-domain boundary element method,so a substructure approach based on the dual reciprocity boundary element method is presented.The experiments for measuring transmission loss of silencers are conducted,and the experimental setup and measurements are explained.The transmission loss of a single expansion chamber silencer with extended inlet and outlet were predicted by DRBEM and compared with the measurements.The good agreements between predictions and measurements are observed,which demonstrated that the derived acoustic governing equation and the DRBEM numerical procedure in the present study are correct.

  2. An under-water experiment on the acoustic characteristic of high temperature ultrasonic transducers

    International Nuclear Information System (INIS)

    We have boon developing an Ultrasound Doppler Velocimetry technique (UDV), in order to apply thermo-hydraulic measurement in sodium. A feasibility study had been conducted to identify development subjects of sensor and signal processing. Thus, high temperature ultrasonic transducers were manufactured to use in water and sodium tests, which will be scheduled to optimize an algorithm of signal processing and to improve the characteristic of the transducer. In this report, we described the results of an experiment on the acoustic characteristic of transducer in water. The results are as follows: (1) The ultrasound beam profile of the transducer relating to the characteristic of velocity profile measurement using scattering ultrasound wave was obtained. The estimation of ultrasound beam profile in liquid and an ultrasound near-field region were introduced from those experimental data. (2) It was confirmed that the frequency 's spectrum of transducers are adequate for the design requirement of flow velocity range. The specifications of a transmitter and receiver for a transducer were identified, such as the amplitude gain for scattered ultrasound signal and the frequency resolution for Doppler sift signal. (3) The spatial resolution of the ultrasound beam was estimated to evaluate the accuracy of flow profile measurement on UDV system. (author)

  3. In-situ Observation of Boiling Dynamics on Fuel Cladding Surface in Non-pressurized Water Using Acoustic Emission Method

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Kaige; Baek, Seung Heon; Shim, Hee-Sang; Hur, Do Haeng; Lee, Deok Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    In the PWR primary coolant system, a phenomenon of axial offset anomaly (AOA) can be caused due to accumulated boron hide out in porous CRUD deposition on the fuel cladding surface. Up to now, the CRUD deposition has been well known to be driven by subcooled nucleate boiling (SNB) on the cladding surface based on large scale experimental work. Therefore, monitoring and evaluation of the SNB-phenomenon is an important approach to study the CRUD deposition. Many attempts have been made to study the SNB and CRUD deposition using thermal hydraulic or model calculation. However, a comprehensive understanding of the SNB during CRUD deposition is still far from being realized. Acoustic emission (AE) technique, as an in-situ nondestructive evaluation (NDE) method, has been widely used to monitor the boiling activity in containers and pipes. Accordingly, this work aimed to investigate the exact AE characteristics of SNB-phenomenon on the fuel cladding surface at atmospheric pressure, with the purpose of providing an experimental groundwork for the AE investigation on SNB in high-temperature pressurized coolant system. In this study, we conducted an in-situ experimental observation of the bubble dynamic of SNB in non-pressurized water at atmospheric pressure using AE method. The AE of heater noise was confirmed to cluster between 8 and 26 khz. Three AE groups were detected during the boiling process in the Snob zones. AE group 1 and 3 seemed to be the results of bubble growth and collapse, while bubble departure from the cladding surface was reasonably associated with an isolated AE group 2.

  4. A methodology to condition distorted acoustic emission signals to identify fracture timing from human cadaver spine impact tests.

    Science.gov (United States)

    Arun, Mike W J; Yoganandan, Narayan; Stemper, Brian D; Pintar, Frank A

    2014-12-01

    While studies have used acoustic sensors to determine fracture initiation time in biomechanical studies, a systematic procedure is not established to process acoustic signals. The objective of the study was to develop a methodology to condition distorted acoustic emission data using signal processing techniques to identify fracture initiation time. The methodology was developed from testing a human cadaver lumbar spine column. Acoustic sensors were glued to all vertebrae, high-rate impact loading was applied, load-time histories were recorded (load cell), and fracture was documented using CT. Compression fracture occurred to L1 while other vertebrae were intact. FFT of raw voltage-time traces were used to determine an optimum frequency range associated with high decibel levels. Signals were bandpass filtered in this range. Bursting pattern was found in the fractured vertebra while signals from other vertebrae were silent. Bursting time was associated with time of fracture initiation. Force at fracture was determined using this time and force-time data. The methodology is independent of selecting parameters a priori such as fixing a voltage level(s), bandpass frequency and/or using force-time signal, and allows determination of force based on time identified during signal processing. The methodology can be used for different body regions in cadaver experiments.

  5. Investigation of correlation of LF power modulation of light in natural and artificial illumination situations and acoustic emission

    Science.gov (United States)

    Kleeberg, Florian P.; Gutzmann, Holger L.; Weyer, Cornelia; Weiß, Jürgen; Dörfler, Joachim; Hahlweg, Cornelius F.

    2014-09-01

    The present paper is a follow up of a paper presented in 2013 at the Novel Optical Systems conference in the session on Optics and Music. It is derived from an ongoing study on the human perception of combined optical and acoustical periodical stimuli. Originating from problems concerning artificial illumination and certain machinery with coherent optical and acoustical emissions there are effects to be observed which are interesting in the context of occupational medicine. It seems, that acoustic stimuli in the frequency range of the flicker fusion and below might lead to unexpected perceptible effects beyond those of the single stimuli. The effect of infrasound stimuli as a whole body perception seems to be boosted. Because of the difficulties in evaluation of physical and psychological effects of such coherent stimuli in a first step we question if such coherence is perceivable at all. Further, the problem of modulation of optical signals by acoustical signal is concerned. A catalogue of scenarios and 'effects to look for' including measurement concepts is presented and discussed.

  6. Sensoring Fusion Data from the Optic and Acoustic Emissions of Electric Arcs in the GMAW-S Process for Welding Quality Assessment

    Directory of Open Access Journals (Sweden)

    Eber Huanca Cayo

    2012-05-01

    Full Text Available The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms.

  7. Sensoring fusion data from the optic and acoustic emissions of electric arcs in the GMAW-S process for welding quality assessment.

    Science.gov (United States)

    Alfaro, Sadek Crisóstomo Absi; Cayo, Eber Huanca

    2012-01-01

    The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms.

  8. Chaotic characteristics of electromagnetic emission signals during deformation and fracture of coal

    Institute of Scientific and Technical Information of China (English)

    NIE Bai-sheng; HE Xue-qiu; LIU Fang-bin; ZHU Cheng-wei; WANG Ping

    2009-01-01

    Electromagnetic emission (EME) is a kind of physical phenomenon accompanying the process of deformation and frac-ture of loaded coal and rock and it is of importance in quantitatively analyzing its characteristics. This will reveal the process of deformation and fracture of coal and predicting dynamic disasters in coal mines. In this study, the G-P (Grassberger and Procaccia) algorithm, calculation steps of the (if only 1 dimension) correlation dimension of time series and the identification standards of chaotic signals are introduced. Furthermore, the correlation dimensions of EME and the acoustic emission (AE) signals of time series during deformation and fracture of coal bodies are calculated and analyzed. The results show that the time series of pulses number of EME and the time series of AE count rate are chaotic and that the saturation embedding dimensions of a K3 coal sample are, respectively, 5 and 6. The results can be used to provide basic parameters for predicting of EME and AE time series.

  9. Influence of social and behavioural characteristics of users on their evaluation of subjective loudness and acoustic comfort in shopping malls.

    Directory of Open Access Journals (Sweden)

    Qi Meng

    Full Text Available A large-scale subjective survey was conducted in six shopping malls in Harbin City, China, to determine the influence of social and behavioural characteristics of users on their evaluation of subjective loudness and acoustic comfort. The analysis of social characteristics shows that evaluation of subjective loudness is influenced by income and occupation, with correlation coefficients or contingency coefficients of 0.10 to 0.40 (p<0.05 or p<0.01. Meanwhile, evaluation of acoustic comfort evaluation is influenced by income, education level, and occupation, with correlation coefficients or contingency coefficients of 0.10 to 0.60 (p<0.05 or p<0.01. The effect of gender and age on evaluation of subjective loudness and acoustic comfort is statistically insignificant. The effects of occupation are mainly caused by the differences in income and education level, in which the effects of income are greater than that of education level. In terms of behavioural characteristics, evaluation of subjective loudness is influenced by the reason for visit, frequency of visit, and length of stay, with correlation coefficients or contingency coefficients of 0.10 to 0.40 (p<0.05 or p<0.01. Evaluation of acoustic comfort is influenced by the reason for visit to the site, the frequency of visit, length of stay, and also season of visit, with correlation coefficients of 0.10 to 0.30 (p<0.05 or p<0.01. In particular, users who are waiting for someone show lower evaluation of acoustic comfort, whereas users who go to shopping malls more than once a month show higher evaluation of acoustic comfort. On the contrary, the influence of the period of visit and the accompanying persons are found insignificant.

  10. Indirect measurement of cylinder pressure from diesel engines using acoustic emission

    Science.gov (United States)

    El-Ghamry, M.; Steel, J. A.; Reuben, R. L.; Fog, T. L.

    2005-07-01

    Indirect measurement of the cylinder pressure from diesel engines is possible using acoustic emission (AE). A method is demonstrated for a large two-stroke marine diesel engine and a small four-stroke diesel engine, which involves reconstructing the cylinder crank angle domain diagram from the AE generated during the combustion phase. Raw AE was used for modelling and reconstructing the pressure waveform in the time domain but this could not be used to model the pressure rise (compression). To overcome this problem the signal was divided into two sections representing the compression part of the signal and the fuel injection/expansion stroke. The compression part of the pressure signal was reconstructed by using polynomial fitting. An auto-regressive technique was used during the injection/expansion stroke. The rms AE signal is well correlated with the pressure signal in the time and frequency domain and complex cepstrum analysis was used to model the pressure signal for the complete combustion phase (compression, injection and expansion). The main advantage of using cepstral analysis is that the model uses the frequency content of the rms AE signal rather than the energy content of the rms AE signal, which gives an advantage when the signal has lower energy content, during the compression process. By calculating the engine running speed from the rms AE signal and selecting the proper cepstrum model correlated to the combustion rms AE energy content, an analytical algorithm was developed to give a wide range of applicability over the different conditions of engine speed, engine type and load. The pressure reconstructed from both AE and acceleration data are compared. AE has the advantage of a much higher signal-to-noise ratio and improved time resolution and is shown to be better than the acceleration.

  11. Evolutions of friction properties and acoustic emission source parameters associated with large sliding

    Science.gov (United States)

    Yabe, Y.; Tsuda, H.; Iida, T.

    2015-12-01

    It was demonstrated by Yabe (2002) that friction properties and AE (acoustic emission) activities evolve with accumulation of sliding. However, large sliding distances of ~65 mm in his experiments were achieved by recurring ~10 mm sliding on the same fault. The evolution of friction coefficient was discontinuous, when rock samples were reset. Further, normal stress was not kept constant. To overcome these problems and to reexamine the evolutions of friction properties and AE activities with continuous large sliding under a constant normal stress, we developed a rotary shear apparatus. The evolutions of friction and AE up to ~80 mm sliding under a normal stress of 5 MPa were investigated. Rate dependence of friction was the velocity strengthening (a-b>0 in rate and state friction law) at the beginning. The value of a-b gradually decreased with sliding to negative (velocity weakening). Then, it took a constant negative value, when the sliding reached a critical distance. The m-value of Ishimoto-Iida's relation of AE activity increased with sliding at the beginning and converged to a constant value at the critical sliding distance. The m-value showed a negative rate dependence at the beginning, but became neutral after sliding of the critical distance. The sliding distances required to converge the a-b value, the m-value and the rate dependence of the m-value are almost identical to one another. These results are the same as those by Yabe (2002), suggesting the intermission of sliding little affected the evolutions. We, then, examined evolutions of AE source parameters such as source radii and stress drops. The average source radius was constant over the whole sliding distance, while the average stress drop decreased at the beginning of sliding, and converged to a constant value. The sliding distance required to the conversion was the same as that for the above mentioned evolutions of friction property or AE activity.

  12. A hybrid wireless sensor network for acoustic emission testing in SHM

    Science.gov (United States)

    Grosse, Christian; McLaskey, Greg; Bachmaier, Sebastian; Glaser, Steven D.; Krüger, Markus

    2008-03-01

    Acoustic emission techniques (AET) have a lot of potential in structural health monitoring for example to detect cracks or wire breaks. However, the number of actual applications of conventional wired AET on structures is limited due to the expensive and time consuming installation process. Wires are also vulnerable to damage and vandalisms. Wireless systems instead are easy to be attached to structures, scalable and cost efficient. A hybrid sensor network system is presented being able to use any kind of commercial available AE sensor controlled by a sensor node. In addition micro-electro-mechanical systems (MEMS) can be used as sensors measuring for example temperature, humidity or strain. The network combines multi-hop data transmission techniques with efficient data pre-processing in the nodes. The data processing of different sensor data prior to energy consuming radio transmission is an important feature to enable wireless networking. Moreover, clusters of sensor nodes are formed within the network to compare the pre-processed data. In this way it is possible to limit the data transfer through the network and to the sink as well as the amount of data to be reviewed by the owner. In particular, this paper deals with the optimization of the network to record different type of data including AE data. The basic principles of a wireless monitoring system equipped with MEMS sensors is presented along with a first prototype able to record temperature, moisture, strain and other data continuously. The extraction of relevant information out of the recorded AE data in terms of array data processing is presented in a second paper by McLaskey et al. in these proceedings. Using these two techniques, monitoring of large structures in civil engineering becomes very efficient.

  13. Acoustic emission source location in complex structures using full automatic delta T mapping technique

    Science.gov (United States)

    Al-Jumaili, Safaa Kh.; Pearson, Matthew R.; Holford, Karen M.; Eaton, Mark J.; Pullin, Rhys

    2016-05-01

    An easy to use, fast to apply, cost-effective, and very accurate non-destructive testing (NDT) technique for damage localisation in complex structures is key for the uptake of structural health monitoring systems (SHM). Acoustic emission (AE) is a viable technique that can be used for SHM and one of the most attractive features is the ability to locate AE sources. The time of arrival (TOA) technique is traditionally used to locate AE sources, and relies on the assumption of constant wave speed within the material and uninterrupted propagation path between the source and the sensor. In complex structural geometries and complex materials such as composites, this assumption is no longer valid. Delta T mapping was developed in Cardiff in order to overcome these limitations; this technique uses artificial sources on an area of interest to create training maps. These are used to locate subsequent AE sources. However operator expertise is required to select the best data from the training maps and to choose the correct parameter to locate the sources, which can be a time consuming process. This paper presents a new and improved fully automatic delta T mapping technique where a clustering algorithm is used to automatically identify and select the highly correlated events at each grid point whilst the "Minimum Difference" approach is used to determine the source location. This removes the requirement for operator expertise, saving time and preventing human errors. A thorough assessment is conducted to evaluate the performance and the robustness of the new technique. In the initial test, the results showed excellent reduction in running time as well as improved accuracy of locating AE sources, as a result of the automatic selection of the training data. Furthermore, because the process is performed automatically, this is now a very simple and reliable technique due to the prevention of the potential source of error related to manual manipulation.

  14. Acoustic emission in ITER CS model coil and CS insert coil

    International Nuclear Information System (INIS)

    Acoustic emission (AE) signals induced from the Central Solenoid Model Coil (CSMC) and the Central Solenoid Insert Coil (CSIC) of the International Thermonuclear Experimental Reactor (ITER) are described. Two kinds of AE data acquisition methods for the AE signals are adopted during series of energizing, i.e., one is the whole waveform recording, and the other is the AE envelope recording. It can be estimated that the AE signals are mainly induced by motion of a superconductor because the AE signals synchronize with the voltage spikes, especially in the virgin current region. The multi channel measurement provided us with information about the spatial distribution of disturbances by the AE sensors at each installed point in CSMC. The observation of AE with high-time resolution shows that the disturbances in CSMC decrease with the iteration number of excitation, judging from instantaneous AE levels, AE energies, and AE event count. Meanwhile, under the background field of 13 T by CSMC, charging and discharging tests of the CSIC at the rate of 5 kA/s from 0 kA to 40 kA were repeated 10,003 times. We monitored the disturbances in CSIC and in CSMC during this cyclic test by using envelope signals of an AE sensor installed near the bottom of the innermost layer of CSMC. The detected AE signals were large, in the range of 1,000 to 2,000 times and 3,000 to 4,000 times. And after that, the AE signals were very small, until 10,003 times. From 3,000 through 4,000 times, we monitored strange AE behaviours that can be attributed to the loosening of bolts. (author)

  15. Detection of bond failure in the anchorage zone of reinforced concrete beams via acoustic emission monitoring

    Science.gov (United States)

    Abouhussien, Ahmed A.; Hassan, Assem A. A.

    2016-07-01

    In this study, acoustic emission (AE) monitoring was utilised to identify the onset of bond failure in reinforced concrete beams. Beam anchorage specimens were designed and tested to fail in bond in the anchorage zone. The specimens included four 250 × 250 × 1500 mm beams with four variable bonded lengths (100, 200, 300, and 400 mm). Meanwhile, an additional 250 × 250 × 2440 mm beam, with 200 mm bonded length, was tested to investigate the influence of sensor location on the identification of bond damage. All beams were tested under four-point loading setup and continuously monitored using three distributed AE sensors. These attached sensors were exploited to record AE signals resulting from both cracking and bond deterioration until failure. The variations in the number of AE hits and cumulative signal strength (CSS) versus test time were evaluated to achieve early detection of crack growth and bar slippage. In addition, AE intensity analysis was performed on signal strength of collected AE signals to develop two additional parameters: historic index (H (t)) and severity (S r). The analysis of these AE parameters enabled an early detection of both first cracks (at almost the mid-span of the beam) and bar slip in either of the anchorage zones at the beams’ end before their visual observation, regardless of sensor location. The results also demonstrated a clear correlation between the damage level in terms of crack development/measured free end bar slip and AE parameters (number of hits, CSS, H(t), and S r).

  16. Evaluation of SHM System Produced by Additive Manufacturing via Acoustic Emission and Other NDT Methods

    Directory of Open Access Journals (Sweden)

    Maria Strantza

    2015-10-01

    Full Text Available During the last decades, structural health monitoring (SHM systems are used in order to detect damage in structures. We have developed a novel structural health monitoring approach, the so-called “effective structural health monitoring” (eSHM system. The current SHM system is incorporated into a metallic structure by means of additive manufacturing (AM and has the possibility to advance life safety and reduce direct operative costs. It operates based on a network of capillaries that are integrated into an AM structure. The internal pressure of the capillaries is continuously monitored by a pressure sensor. When a crack nucleates and reaches the capillary, the internal pressure changes signifying the existence of the flaw. The main objective of this paper is to evaluate the crack detection capacity of the eSHM system and crack location accuracy by means of various non-destructive testing (NDT techniques. During this study, detailed acoustic emission (AE analysis was applied in AM materials for the first time in order to investigate if phenomena like the Kaiser effect and waveform parameters used in conventional metals can offer valuable insight into the damage accumulation of the AM structure as well. Liquid penetrant inspection, eddy current and radiography were also used in order to confirm the fatigue damage and indicate the damage location on un-notched four-point bending AM metallic specimens with an integrated eSHM system. It is shown that the eSHM system in combination with NDT can provide correct information on the damage condition of additive manufactured metals.

  17. Acoustic emission analysis for structural health monitoring of hot metal components; Schallemissionsanalyse zur Zustandsueberwachung von heissen Metallkomponenten

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, Eberhard [Fraunhofer-Institut fuer Keramische Technologien und Systeme, Dresden (Germany). Institutsteil Materialdiagnostik

    2015-07-01

    For the application of acoustic emission analysis on hot components such as pipes special application techniques are necessary to protect the sensor from the heat. The Fraunhofer IKTS-MD has developed a waveguide solution that meets these requirements. Major challenges in the application of acoustic emission analysis in an industrial environment is the strong ambient noise. This requirement meets the developed acoustic measurement system at the Fraunhofer Institute by a high measurement dynamics, storage and assessment of the complete waveforms and by special algorithms. The attractiveness of the method lies in the relatively low number of sensors with which the integrity of large plant areas (e.g. several meters under high alternating load standing superheated steam pipe) can be permanently monitored. [German] Fuer die Anwendung der Schallemissionsanalyse an heissen Komponenten wie Rohrleitungen sind besondere Applikationstechniken notwendig, um den Sensor vor der Hitze zu schuetzen. Das Fraunhofer IKTS-MD hat dafuer eine Wellenleiterloesung entwickelt, die diese Anforderungen erfuellt. Wesentliche Herausforderung bei der Anwendung der Schallemissionsanalyse in industrieller Umgebung ist das starke Umgebungsrauschen. Dieser Anforderung begegnet das am Fraunhofer-Institut entwickelte akustische Messsystem durch eine hohe Messwertdynamik, Speicherung und Bewertung der vollstaendigen Wellenformen sowie durch spezielle Auswertealgorithmen. Die Attraktivitaet des Verfahrens liegt in der vergleichsweise geringen Anzahl von Sensoren, mit denen die Integritaet grosser Anlagenbereiche (z.B. mehrere Meter unter hoher Wechsellast stehender Heissdampfleitung) dauerhaft ueberwacht werden kann.

  18. Characteristic Scales of Baryon Acoustic Oscillations from Perturbation Theory: Non-linearity and Redshift-Space Distortion Effects

    OpenAIRE

    Nishimichi, Takahiro; Ohmuro, Hiroshi; Nakamichi, Masashi; Taruya, Atsushi; Yahata, Kazuhiro; Shirata, Akihito; Saito, Shun; Nomura, Hidenori; Yamamoto, Kazuhiro; Suto, Yasushi

    2007-01-01

    An acoustic oscillation of the primeval photon-baryon fluid around the decoupling time imprints a characteristic scale in the galaxy distribution today, known as the baryon acoustic oscillation (BAO) scale. Several on-going and/or future galaxy surveys aim at detecting and precisely determining the BAO scale so as to trace the expansion history of the universe. We consider nonlinear and redshift-space distortion effects on the shifts of the BAO scale in $k$-space using perturbation theory. Th...

  19. Flow and mixing characteristics of swirling double-concentric jets subject to acoustic excitation

    Science.gov (United States)

    Huang, R. F.; Jufar, S. R.; Hsu, C. M.

    2013-01-01

    Characteristic flow modes, flow evolution processes, jet spread width, turbulence properties, and dispersion characteristics of swirling double-concentric jets were studied experimentally. Jet pulsations were induced by means of acoustic excitation. Streak pictures of smoke flow patterns, illuminated by a laser-light sheet, were recorded by a high-speed digital camera. A hot-wire anemometer was used to digitize instantaneous velocity instabilities in the flow. Jet spread width was obtained through a binary edge identification technique. Tracer-gas concentrations were measured for information on jet dispersions. Two characteristic flow patterns were observed: (1) synchronized vortex rings appeared in the low excitation intensity regime (the excitation intensity less than one) and (2) synchronized puffing turbulent jets appeared in the high excitation intensity regime (the excitation intensity greater than one). In the high excitation intensity regime, the "suction back" phenomenon occurred and therefore induced in-tube mixing. The jet spread width and turbulent fluctuation intensity exhibited particularly large values in the high excitation intensity regime at the excitation Strouhal numbers smaller than 0.85. At the excitation Strouhal numbers >0.85, the high-frequency effect caused significant decay of jet breakup and dispersion—the jet spread width and fluctuation intensity decreased sharply and may, at very high Strouhal numbers, asymptotically approach values almost the same as the values associated with unexcited jets. Exciting the jets at the high excitation intensity regime, the effects of puffing motion and in-tube mixing caused breakup of the jet in the near field and therefore resulted in a small Lagrangian integral time and small length scales of fluctuating eddies. This effect, in turn, caused drastic dispersion of the central jet fluids. It is possible that the excited jets can attain 90 % more improvements than the unexcited jets. We provide a

  20. Acoustic and aerodynamic characteristics of Country-Western, Operatic and Broadway singing styles compared to speech

    Science.gov (United States)

    Stone, Robert E.; Cleveland, Thomas F.; Sundberg, P. Johan

    2003-04-01

    Acoustic and aerodynamic measures were used to objectively describe characteristics of Country-Western (C-W) singing in a group of six premier performers in a series of studies and of operatic and Broadway singing in a female subject with professional experience in both styles of singing. For comparison purposes the same measures also were applied to individuals while speaking the same material as sung. Changes in pitch and vocal loudness were investigated for various dependent variables, including subglottal pressure, closed quotient, glottal leakage, H1-H2 difference [the level difference between the two lowest partials of the source spectrum and glottal compliance (the ratio between the air volume displaced in a glottal pulse and the subglottal pressure)], formant frequencies, long-term-average spectrum and vibrato characteristics (in operatic versus Broadway singing). Data from C-W singers suggest they use higher sub-glottal pressures in singing than in speaking. Changes in vocal intensity for doubling sub-glottal pressure is less than reported for classical singers. Several measures were similar for both speaking and C-W singing. Whereas results provide objective specification of differences between operatic and Broadway styles of singing, the latter seems similar to features of conversational speaking style.

  1. Flow and Emissions Characteristics of Multi-Swirler Combustor

    Science.gov (United States)

    Gutmark, Ephraim; Li, Guoqiang

    2003-11-01

    Modern industrial gas-turbine spray combustors feature multiple swirlers and distributed fuel injection for rapid mixing and stabilization. The flow field of this combustor, the related combustion characteristics and their control are discussed. The velocity flow field downstream of a Triple Annular Research Swirler (TARS) was characterized. Multiple combinations of swirlers were tested in cold flow under atmospheric conditions with and without confining combustion chamber. The experiments showed that a central recirculation zone (CTRZ), an annular jet with internal and external shear layers dominated the flow field downstream of TARS. Compared to unconfined case, flow with confined tube showed an enlarged CTRZ region and a recirculation region in the expansion corner with reduced concentration of turbulence intensity in the jet region. TARS also produced low emissions of NOx and CO. Measurements were performed to study the effects of several factors, including swirler combinations, exhaust nozzle size, air assist for fuel atomization and mixing length on NOx and CO emissions and combustion instability. The data showed that emissions and stability depend on the combination of several of these factors.

  2. Mode characteristics and directional emission for square microcavity lasers

    Science.gov (United States)

    Yang, Yue-De; Huang, Yong-Zhen

    2016-06-01

    Square microcavities with high quality factor whispering-gallery-like modes have a series of novel optical properties and can be employed as compact-size laser resonators. In this paper, the mode characteristics of square optical microcavities and the lasing properties of directional-emission square semiconductor microlasers are reviewed for the realization of potential light sources in the photonic integrated circuits and optical interconnects. A quasi-analytical model is introduced to describe the confined modes in square microcavities, and high quality factor whispering-gallery-like modes are predicted by the mode-coupling theory and confirmed by the numerical simulation. An output waveguide directly coupled to the position with weak mode field is used to achieve directional emission and control the lasing mode. Electrically-pumped InP-based directional-emission square microlasers are realized at room temperature, and the lasing spectra agree well with the mode analysis. Different kinds of square microcavity lasers, including dual-mode laser with a tunable interval, single-mode laser with a wide tunable wavelength range, and high-speed direct-modulated laser are also demonstrated experimentally.

  3. Acoustic Emission Detection of Macro-Cracks on Engraving Tool Steel Inserts during the Injection Molding Cycle Using PZT Sensors

    Directory of Open Access Journals (Sweden)

    Aleš Hančič

    2013-05-01

    Full Text Available This paper presents an improved monitoring system for the failure detection of engraving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signals’ peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process.

  4. Detection of stress corrosion cracking of high-strength steel used in prestressed concrete structures by acoustic emission technique

    Science.gov (United States)

    Ramadan, S.; Gaillet, L.; Tessier, C.; Idrissi, H.

    2008-02-01

    The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures.

  5. Development of additional module to neutron-physic and thermal-hydraulic computer codes for coolant acoustical characteristics calculation

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, K.N.; Bogomazov, D.N.; Poliakov, N. [Moscow Power Engineering Institute (Technical University), Moscow (Russian Federation)

    2007-07-01

    The new special module to neutron-physic and thermal-hydraulic computer codes for coolant acoustical characteristics calculation is worked out. The Russian computer code Rainbow has been selected for joint use with a developed module. This code system provides the possibility of EFOCP (Eigen Frequencies of Oscillations of the Coolant Pressure) calculations in any coolant acoustical elements of primary circuits of NPP. EFOCP values have been calculated for transient and for stationary operating. The calculated results for nominal operating were compared with results of measured EFOCP. For example, this comparison was provided for the system: 'pressurizer + surge line' of a WWER-1000 reactor. The calculated result 0.58 Hz practically coincides with the result of measurement (0.6 Hz). The EFOCP variations in transients are also shown. The presented results are intended to be useful for NPP vibration-acoustical certification. There are no serious difficulties for using this module with other computer codes.

  6. Field emission characteristics of the scanning tunneling microscope for nanolithography

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, T.M.; Adams, D.P.; Marder, B.M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1413 (United States)

    1996-07-01

    We present a systematic study of the performance of scanning tunneling microscope (STM)-based, low energy electron beam lithography, using simulations of field emission from STM tips, emphasizing realistic conditions of tip geometry and operation. We calculate the potentials and electric field for a hemispherical model emitter in an axially symmetric system. Emission current density at the tip is calculated using the Fowler{endash}Nordheim equation, and current density at the sample is obtained by calculating trajectories of emitted electrons. We characterize the beam diameter at the sample as a function of emitter radius, tip{endash}sample bias, emission current, resist thickness, and tip work function. The beam diameter is primarily affected by the tip{endash}sample gap, increasing at larger gaps, characteristic of high bias and large tip curvature. For optimal tip radius the beam diameter increases linearly with bias from approximately 2 nm at 5 V to 25 nm at 50 V. Beam diameter is nearly independent of emission current over the range 0.05{endash}50 nA. Dielectric resist films cause an increase in beam diameter due to increased tip{endash}substrate gap. Beam diameter is very sensitive to tip work function, increasing dramatically for low work function tips. Tips comprised of asperities on flat surfaces produce significantly smaller beams compared to {open_quote}{open_quote}standard{close_quote}{close_quote} tips of the same emitter radius. However, for low bias ({lt}15 V) beam diameter becomes insensitive to tip geometry. We compare these simulations to selected experimental results to evaluate the limitations to performance and assess the feasibility of routine sub-10 nm structure fabrication using STM-based low energy electron beam lithography. {copyright} {ital 1996 American Vacuum Society}

  7. Field observation of low-to-mid-frequency acoustic propagation characteristics of an estuarine salt wedge.

    Science.gov (United States)

    Reeder, D Benjamin

    2016-01-01

    The estuarine environment often hosts a salt wedge, the stratification of which is a function of the tide's range and speed of advance, river discharge volumetric flow rate, and river mouth morphology. Competing effects of temperature and salinity on sound speed in this stratified environment control the degree of acoustic refraction occurring along an acoustic path. A field experiment was carried out in the Columbia River Estuary to test the hypothesis: the estuarine salt wedge is acoustically observable in terms of low-to-mid-frequency acoustic propagation. Linear frequency-modulated acoustic signals in the 500-2000 Hz band were transmitted during the advance and retreat of the salt wedge during May 27-29, 2013. Results demonstrate that the salt wedge front is the dominant physical mechanism controlling acoustic propagation in this environment: received signal energy is relatively stable before and after the passage of the salt wedge front when the acoustic path consists of a single medium (either entirely fresh water or entirely salt water), and suffers a 10-15 dB loss and increased variability during salt wedge front passage. Physical parameters and acoustic propagation modeling corroborate and inform the acoustic observations. PMID:26827001

  8. Experimental Research of the Acoustic Emission(AE) Characteristics during the Tensile Process of the Shell Material of Blowout Preventer%防喷器壳体材料拉伸过程的声发射特性试验

    Institute of Scientific and Technical Information of China (English)

    赵俊茹; 戴光; 姚鸿滨

    2011-01-01

    In this paper, the tensile damage process of the shell material ZG25GrNiMo of blowout preventer were researched using acoustic emission technique. Analyzed the acoustic emission characteristics in different damage phases of this material were analyzed using parameter analysis and waveform analysis. The result indicated that the acoustic emission characteristics were different in yielding, plastic distortion and rupture process. The differences of frequency spectrums of different damage modes were evident.%采用声发射技术研究了防喷器主壳体材料ZG25GrNiMo的拉伸破坏过程。运用声发射参数分析方法分析了该材料在不同破坏阶段的声发射特性。分析结果表明,在材料屈服、塑性变形及断裂过程中的声发射特性具有明显的不同,且不同损伤模式的信号频谱存在明显的差异。

  9. Quadratic Time-Frequency Analysis of Hydroacoustic Signals as Applied to Acoustic Emissions of Large Whales

    Science.gov (United States)

    Le Bras, Ronan; Victor, Sucic; Damir, Malnar; Götz, Bokelmann

    2014-05-01

    In order to enrich the set of attributes in setting up a large database of whale signals, as envisioned in the Baleakanta project, we investigate methods of time-frequency analysis. The purpose of establishing the database is to increase and refine knowledge of the emitted signal and of its propagation characteristics, leading to a better understanding of the animal migrations in a non-invasive manner and to characterize acoustic propagation in oceanic media. The higher resolution for signal extraction and a better separation from other signals and noise will be used for various purposes, including improved signal detection and individual animal identification. The quadratic class of time-frequency distributions (TFDs) is the most popular set of time-frequency tools for analysis and processing of non-stationary signals. Two best known and most studied members of this class are the spectrogram and the Wigner-Ville distribution. However, to be used efficiently, i.e. to have highly concentrated signal components while significantly suppressing interference and noise simultaneously, TFDs need to be optimized first. The optimization method used in this paper is based on the Cross-Wigner-Ville distribution, and unlike similar approaches it does not require prior information on the analysed signal. The method is applied to whale signals, which, just like the majority of other real-life signals, can generally be classified as multicomponent non-stationary signals, and hence time-frequency techniques are a natural choice for their representation, analysis, and processing. We present processed data from a set containing hundreds of individual calls. The TFD optimization method results into a high resolution time-frequency representation of the signals. It allows for a simple extraction of signal components from the TFD's dominant ridges. The local peaks of those ridges can then be used for the signal components instantaneous frequency estimation, which in turn can be used as

  10. Characterization of blocks impacts from acoustic emissions: insights from laboratory experiments

    Science.gov (United States)

    Farin, Maxime; Mangeney, Anne; de Rosny, Julien; Toussaint, Renaud; Shapiro, Nikolaï

    2014-05-01

    Rockfalls, debris flows and rock avalanches represent a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and glass and over rock blocks. The elastic energy emitted by a single bouncing bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. We obtained simple scaling laws relating the impactor characteristics (size, height of fall, material,...) to the elastic energy and spectral content. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, accelerometers (1 Hz to 56 kHz) were used to record the signals in a wide frequency range. The experiments were also monitored optically using fast cameras. Eventually, we looked at what types of features in the signal are affected by individual impacts, rolling of beads or by the large scale geometry of the avalanche.

  11. Wear monitoring of single point cutting tool using acoustic emission techniques

    Indian Academy of Sciences (India)

    P Kulandaivelu; P Senthil Kumar; S Sundaram

    2013-04-01

    This paper examines the flank and crater wear characteristics of coated carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates. Among these methods, tool condition monitoring using Acoustic Techniques (AET) is an emerging one. Hence, the present work was carried out to study the stability, applicability and relative sensitivity of AET in tool condition monitoring in turning.

  12. Standard practice for determining damage-Based design Stress for fiberglass reinforced plastic (FRP) materials using acoustic emission

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This practice details procedures for establishing the direct stress and shear stress damage-based design values for use in the damage-based design criterion for materials to be used in FRP vessels and other composite structures. The practice uses data derived from acoustic emission examination of four-point beam bending tests and in-plane shear tests (see ASME Section X, Article RT-8). 1.2 The onset of lamina damage is indicated by the presence of significant acoustic emission during the reload portion of load/reload cycles. "Significant emission" is defined with historic index. 1.3 Units - The values stated in inch-pound units are to be regarded as standard. The values given in brackets are mathematical conversions to SI units which are provided for information only and are not considered standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health pr...

  13. Effect of Anisotropic Velocity Structure on Acoustic Emission Source Location during True-Triaxial Deformation Experiments

    Science.gov (United States)

    Ghofrani Tabari, Mehdi; Goodfellow, Sebastian; Young, R. Paul

    2016-04-01

    Although true-triaxial testing (TTT) of rocks is now more extensive worldwide, stress-induced heterogeneity due to the existence of several loading boundary effects is not usually accounted for and simplified anisotropic models are used. This study focuses on the enhanced anisotropic velocity structure to improve acoustic emission (AE) analysis for an enhanced interpretation of induced fracturing. Data from a TTT on a cubic sample of Fontainebleau sandstone is used in this study to evaluate the methodology. At different stages of the experiment the True-Triaxial Geophysical Imaging Cell (TTGIC), armed with an ultrasonic and AE monitoring system, performed several velocity surveys to image velocity structure of the sample. Going beyond a hydrostatic stress state (poro-elastic phase), the rock sample went through a non-dilatational elastic phase, a dilatational non-damaging elasto-plastic phase containing initial AE activity and finally a dilatational and damaging elasto-plastic phase up to the failure point. The experiment was divided into these phases based on the information obtained from strain, velocity and AE streaming data. Analysis of the ultrasonic velocity survey data discovered that a homogeneous anisotropic core in the center of the sample is formed with ellipsoidal symmetry under the standard polyaxial setup. Location of the transducer shots were improved by implementation of different velocity models for the sample starting from isotropic and homogeneous models going toward anisotropic and heterogeneous models. The transducer shot locations showed a major improvement after the velocity model corrections had been applied especially at the final phase of the experiment. This location improvement validated our velocity model at the final phase of the experiment consisting lower-velocity zones bearing partially saturated fractures. The ellipsoidal anisotropic velocity model was also verified at the core of the cubic rock specimen by AE event location of

  14. Stress Corrosion Cracking—Crevice Interaction in Austenitic Stainless Steels Characterized By Acoustic Emission

    Science.gov (United States)

    Leinonen, H.; Schildt, T.; Hänninen, H.

    2011-02-01

    Stress corrosion cracking (SCC) susceptibility of austenitic EN1.4301 (AISI 304) and EN1.4404 (AISI 316L) stainless steels was studied using the constant load method and polymer (PTFE) crevice former in order to study the effects of crevice on SCC susceptibility. The uniaxial active loading tests were performed in 50 pct CaCl2 at 373 K (100 °C) and in 0.1 M NaCl at 353 K (80 °C) under open-circuit corrosion potential (OCP) and electrochemical polarization. Pitting, crevice, and SCC corrosion were characterized and identified by acoustic emission (AE) analysis using ∆ t filtering and the linear locationing technique. The correlation of AE parameters including amplitude, duration, rise time, counts, and energy were used to identify the different types of corrosion. The stages of crevice corrosion and SCC induced by constant active load/crevice former were monitored by AE. In the early phase of the tests, some low amplitude AE activity was detected. In the steady-state phase, the AE activity was low, and toward the end of the test, it increased with the increasing amplitude of the impulses. AE allowed a good correlation between AE signals and corrosion damage. Although crevice corrosion and SCC induced AE signals overlapped slightly, a good correlation between them and microscopical characterization and stress-strain data was found. Especially, the activity of AE signals increased in the early and final stages of the SCC experiment under constant active load conditions corresponding to the changes in the measured steady-state creep strain rate of the specimen. The results of the constant active load/crevice former test indicate that a crevice can initiate SCC even in the mild chloride solution at low temperatures. Based on the mechanistic model of SCC, the rate determining step in SCC is thought to be the generation of vacancies by selective dissolution, which is supported by the low activity phase of AE during the steady-state creep strain rate region.

  15. A new setup for studying thermal microcracking through acoustic emission monitoring

    Science.gov (United States)

    Griffiths, Luke; Heap, Michael; Baud, Patrick; Schmittbuhl, Jean

    2016-04-01

    Thermal stressing is common in geothermal environments and has been shown in the laboratory to induce changes in the physical and mechanical properties of rocks. These changes are generally considered to be a consequence of the generation of thermal microcracks and debilitating chemical reactions. Thermal microcracks form as a result of the build-up of internal stresses due to: (1) the thermal expansion mismatch between the different phases present in the material, (2) thermal expansion anisotropy within individual minerals, and (3) thermal gradients. The generation of cracks during thermal stressing has been monitored in previous studies using the output of acoustic emissions (AE), a common proxy for microcrack damage, and through microstructural observations. Here we present a new experimental setup which is optimised to record AE from a rock sample at high temperatures and under a servo-controlled uniaxial stress. The design is such that the AE transducer is embedded in the top of the piston, which acts as a continuous wave guide to the sample. In this way, we simplify the ray path geometry whilst minimising the number of interfaces between the microcrack and the transducer, maximising the quality of the signal. This allows for an in-depth study of waveform attributes such as energy, amplitude, counts and duration. Furthermore, the capability of this device to apply a servo-controlled load on the sample, whilst measuring strain in real time, leads to a spectrum of possible tests combining mechanical and thermal stress. It is also an essential feature to eliminate the build-up of stresses through thermal expansion of the pistons and the sample. We plan a systematic experimental study of the AE of thermally stressed rock during heating and cooling cycles. We present results from pilot tests performed on Darley Dale sandstone and Westerly granite. Understanding the effects of thermal stressing in rock is of particular interest at a geothermal site, where

  16. Evidence of frost-cracking inferred from acoustic emissions in a high-alpine rock-wall

    OpenAIRE

    Amitrano, David; Gruber, Stephan; Girard, Lucas

    2012-01-01

    Ice formation within rock is known to be an important driver of near-surface frost weathering as well as of rock damage at the depth of several meters, which may play a crucial role for the slow preconditioning of rock fall in steep permafrost areas. This letter reports results from an experiment where acoustic emission monitoring was used to investigate rock damage in a high-alpine rock-wall induced by natural thermal cycling and freezing/thawing. The analysis of the large catalog of events ...

  17. Acoustic Characteristics of Ataxic Speech in Japanese Patients with Spinocerebellar Degeneration (SCD)

    Science.gov (United States)

    Ikui, Yukiko; Tsukuda, Mamoru; Kuroiwa, Yoshiyuki; Koyano, Shigeru; Hirose, Hajime; Taguchi, Takahide

    2012-01-01

    Background: In English- and German-speaking countries, ataxic speech is often described as showing scanning based on acoustic impressions. Although the term "scanning" is generally considered to represent abnormal speech features including prosodic excess or insufficiency, any precise acoustic analysis of ataxic speech has not been performed in…

  18. Study on After Peak Acoustic Emission Features of Rock Type Material%峰后岩石类材料的声发射特性研究

    Institute of Scientific and Technical Information of China (English)

    唐珺; 刘卫群; 费晓东

    2011-01-01

    Based on the acoustic emission test system and the rock acoustic emission theory, the uniaxial compressive tests were made on two different property rock and cement-sand grouts.The mechanics feature curve, the acoustic emission ringing numbers and the acoustic emission accumulated ringing number curve of full three sample failures' processes were obtained.A study in sections on the relationship between the deformation features and stress as well as the tinging number and time was conducted.The study showed that the acoustic emission of the rock type material would be affected by the rock strength, joint fissure and crystal grain hardness.The acoustic emission ringing number of the partial soft rock material at the elasticity and the elastic-plastic stage would be steadily increased in unit time and but when the rock material was near the peak strength, the acoustic emission occurred would be in a relative quiet phenomenon.The activity of the after peak acoustic emission would be mainly affected by the rock strength.The comparison on the acoustic emission features of the different rock failures could provide referen to evealuate the stability of natural and artificial rock projects.%基于声发射试验系统和岩石声发射理论,对2种不同性质的岩石和水泥砂浆进行了单轴压缩试验,得到了3种试样破坏全过程的力学特性曲线、声发射振铃数和累计振铃数曲线,针对其变形特征及应力、振铃数与时间的关系分阶段进行了研究.研究表明:岩石类材料声发射受岩石强度、节理裂隙和晶粒软硬大小等的影响;部分质软岩石类材料在弹性、弹塑性阶段,其单位时间声发射振铃数逐步增加,但在接近强度峰值时出现声发射相对平静现象;峰后声发射活性主要受岩石的强度影响.对比不同岩石的破坏声发射特性,可为天然和人工岩土工程稳定性评估提供参数.

  19. A Statistical Study of Mid-latitude Thunderstorm Characteristics associated with Acoustic and Gravity Waves

    Science.gov (United States)

    Lay, E. H.; Shao, X. M.; Kendrick, A.

    2014-12-01

    Gravity waves with periods greater than 5 minutes and acoustic waves with periods between 3 and 5 minutes have been detected at ionospheric heights (250-350 km) and associated with severe thunderstorms. Modeling results support these findings, indicating that acoustic waves should be able to reach 250-350 km within ~250 km horizontally of the source, and gravity waves should be able to propagate significantly further. However, the mechanism by which the acoustic waves are generated and the ubiquity of occurrence of both types of wave is unknown. We use GPS total electron content measurements to detect gravity and acoustic waves in the ionosphere. We perform a statistical study from 2005 May - July to compare the occurrence rate and horizontal extent of the waves to storm size and convective height from NEXRAD radar measurements. It is found that both gravity waves and acoustic wave horizontal extent is primarily associated with storm size and not convective height.

  20. AE (Acoustic Emission) for Flip-Chip CGA/FCBGA Defect Detection

    Science.gov (United States)

    Ghaffarian, Reza

    2014-01-01

    C-mode scanning acoustic microscopy (C-SAM) is a nondestructive inspection technique that uses ultrasound to show the internal feature of a specimen. A very high or ultra-high-frequency ultrasound passes through a specimen to produce a visible acoustic microimage (AMI) of its inner features. As ultrasound travels into a specimen, the wave is absorbed, scattered or reflected. The response is highly sensitive to the elastic properties of the materials and is especially sensitive to air gaps. This specific characteristic makes AMI the preferred method for finding "air gaps" such as delamination, cracks, voids, and porosity. C-SAM analysis, which is a type of AMI, was widely used in the past for evaluation of plastic microelectronic circuits, especially for detecting delamination of direct die bonding. With the introduction of the flip-chip die attachment in a package; its use has been expanded to nondestructive characterization of the flip-chip solder bumps and underfill. Figure 1.1 compares visual and C-SAM inspection approaches for defect detection, especially for solder joint interconnections and hidden defects. C-SAM is specifically useful for package features like internal cracks and delamination. C-SAM not only allows for the visualization of the interior features, it has the ability to produce images on layer-by-layer basis. Visual inspection; however, is only superior to C-SAM for the exposed features including solder dewetting, microcracks, and contamination. Ideally, a combination of various inspection techniques - visual, optical and SEM microscopy, C-SAM, and X-ray - need to be performed in order to assure quality at part, package, and system levels. This reports presents evaluations performed on various advanced packages/assemblies, especially the flip-chip die version of ball grid array/column grid array (BGA/CGA) using C-SAM equipment. Both external and internal equipment was used for evaluation. The outside facility provided images of the key features

  1. Acoustical Survey of Methane Plumes on North Hydrate Ridge: Constraining Temporal and Spatial Characteristics.

    Science.gov (United States)

    Kannberg, P. K.; Trehu, A. M.

    2008-12-01

    While methane plumes associated with hydrate formations have been acoustically imaged before, little is known about their temporal characteristics. Previous acoustic surveys have focused on determining plume location, but as far as we know, multiple, repeated surveys of the same plume have not been done prior to the survey presented here. In July 2008, we acquired sixteen identical surveys within 19 hours over the northern summit of Hydrate Ridge in the Cascadia accretionary complex using the onboard 3.5 and 12 kHz echosounders. As in previous studies, the plumes were invisible to the 3.5 kHz echosounder and clearly imaged with 12 kHz. Seafloor depth in this region is ~600 m. Three distinct plumes were detected close to where plumes were located by Heeschen et al. (2003) a decade ago. Two of the plumes disappeared at ~520 m water depth, which is the depth of the top of the gas hydrate stability as determined from CTD casts obtained during the cruise. This supports the conclusion of Heeschen et al. (2003) that the bubbles are armored by gas hydrate and that they dissolve in the water column when they leave the hydrate stability zone. One of the plumes near the northern summit, however, extended through this boundary to at least 400 m (the shallowest depth recorded). A similar phenomenon was observed in methane plumes in the Gulf of Mexico, where the methane was found to be armored by an oil skin. In addition to the steady plumes, two discrete "burps" were observed. One "burp" occurred approximately 600 m to the SSW of the northern summit. This was followed by a second strong event 300m to the north an hour later. To evaluate temporal and spatial patterns, we summed the power of the backscattered signal in different depth windows for each survey. We present the results as a movie in which the backscatter power is shown in map view as a function of time. The surveys encompassed two complete tidal cycles, but no correlation between plume location or intensity and tides

  2. Liturgical conditions of Catholic and Reformed celebrations and their relationships with architectural and acoustic characteristics of churches

    OpenAIRE

    Victor Desarnaulds; Carvalho, A

    2002-01-01

    Liturgical differences between Catholic and Reformed celebrations in Switzerland were studied by a temporal analysis of 16 worships. The importance of speech, music, and silence and the participation of the priest, assembly and organist are analysed. Data from 190 churches show that Reformed churches present a smaller average volume, a denser occupation of space and a shorter reverberation time than Catholic churches. The geometrical and acoustical characteristics of Reformed churches favour ...

  3. Relationship between electromagnetic and acoustic emissions during plastic deformation of gamma-irradiated LiF monocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hadjicontis, V.; Mavromatou, C.; Mastrogiannis, D. [Department of Solid State Physics, University of Athens, Panepistimiopolis, Zografos, TK 157 84, Athens (Greece); Antsygina, T. N.; Chishko, K. A. [B. Verkin Institute for Low Temperature Physics and Engineering, 47 Lenin Ave., 61103 Kharkov (Ukraine)

    2011-07-15

    Simultaneous measurements of acoustic emissions (AE) and electromagnetic emissions (EME) during plastic deformation and destruction under uniaxial compression along <001> direction are made on LiF monocrystals after gamma irradiation by {sup 60}Co source. The irradiation doses are 1, 2, and 10 Mrad. The EME measurements in the radio-frequency range are carried out using two types of electromagnetic sensors: (i) a simple electrical stub antenna and (ii) a toroidal inductance coil. Two checking experiments on unirradiated crystals are performed as the starting point to discover the effect of gamma irradiation on acoustic and electromagnetic emissive ability of plastically deformed ionic crystals. Unirradiated LiF monocrystals demonstrate high-intensive EME at easy glide and work hardening stages, as well as at the fracture during destruction of the sample. At radiation doses more than {approx}1 Mrad, in the active loading stage the EME of LiF monocrystals vanishes, except few individual electromagnetic pulses (only at 1 and 2 Mrad doses), which are time correlated with well-defined drop-jumps on the loading diagram and therefore can be associated with macroscopic crack openings. Moderate electromagnetic activity in irradiated crystals occurs only in the final stage of deformation at the complete fracture of the sample. Thus, after gamma irradiation the formation of polarization currents due to dynamic interaction between charged vacancies and moving dislocations is suppressed, and only EME connected with the redistribution of the free charge on the crack branches is observed. Acoustic emission diagrams of low-irradiated LiF are typical for the work hardening stage in crystals containing a great amount of strong point stoppers. At larger irradiation doses the AE diagram displays quite different behavior at low- and high-loading regions with a sharp boundary between them. The low-loading region shows poor AE activity, which changes sharply into high-active burst

  4. Characteristics of phenomenon and sound in microbubble emission boiling

    International Nuclear Information System (INIS)

    Background: Nowadays, the efficient heat transfer technology is required in nuclear energy. Therefore, micro-bubble emission boiling (MEB) is getting more attentions from many researchers due to its extremely high heat-transfer dissipation capability. Purpose: An experimental setup was built up to study the correspondences between the characteristics on the amplitude spectrum of boiling sound in different boiling modes. Methods: The heat element was a copper block heated by four Si-C heaters. The upper of the copper block was a cylinder with the diameter of 10 mm and height of 10 mm. Temperature data were measured by three T-type sheathed thermocouples fitted on the upper of the copper block and recorded by NI acquisition system. The temperature of the heating surface was estimated by extrapolating the temperature distribution. Boiling sound data were acquired by hydrophone and processed by Fourier transform. Bubble behaviors were captured by high-speed video camera with light system. Results: In nucleate boiling region, the boiling was not intensive and as a result, the spectra didn't present any peak. While the MEB fully developed on the heating surface, an obvious peak came into being around the frequency of 300 Hz. This could be explained by analyzing the video data. The periodic expansion and collapse into many extremely small bubbles of the vapor film lead to MEB presenting an obvious characteristic peak in its amplitude spectrum. Conclusion: The boiling mode can be distinguished by its amplitude spectrum. When the MEB fully developed, it presented a characteristic peak in its amplitude spectrum around the frequency between 300-400 Hz. This proved that boiling sound of MEB has a close relation with the behavior of vapor film. (authors)

  5. Welding stability assessment in the GMAW-S process based on fuzzy logic by acoustic sensing from arc emissions

    Directory of Open Access Journals (Sweden)

    E. Huanca Cayo

    2012-11-01

    Full Text Available Purpose: The present research work has as purpose detecting perturbations, measuring and assessing the welding stability in GMAW process in short circuit mode named hereafter as GMAW-S process.Design/methodology/approach: Welding trials were performed with a set of optimal input welding parameters. During experiments were induced some perturbations on the welding trajectory. It causes alteration on the stability of welding resulting as consequence geometrical shape deformations. During each experiments, acoustic emission signal coming from electric arc as well as arc voltage and welding current were acquired aided by a card acquisition and virtual instrumentation software. A heuristic model was performed as knowledge base rules of a fuzzy logic system. This system has two inputs and one output. Some additional welding trials were performed for assessing its performance.Findings: It was performed a welding stability assessment system based on fuzzy logic. As well as, this system is based on non-contact sensing what reduces the loading effects on the welding process.Research limitations/implications: In the present work was monitored just the acoustic emissions coming from arc. Although that, the results were satisfactory, an approach on data fusion of sensors including electromagnetic emission sensors could improve the quality assessments system.Originality/value: The non-contact welding stability assessment methods have reduces loading effects and a heuristic approach on the relations between arc emissions and welding stability allows quantifying nonlinear variables such as knowledge and experience of skilled welders, such that, it is possible to represent linguistic terms numerically what could be used as an on-line monitoring system of welding processes.

  6. Detecting the Activation of a Self-Healing Mechanism in Concrete by Acoustic Emission and Digital Image Correlation

    Directory of Open Access Journals (Sweden)

    E. Tsangouri

    2013-01-01

    Full Text Available Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process.

  7. Standard practice for examination of liquid-Filled atmospheric and Low-pressure metal storage tanks using acoustic emission

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice covers guidelines for acoustic emission (AE) examinations of new and in-service aboveground storage tanks of the type used for storage of liquids. 1.2 This practice will detect acoustic emission in areas of sensor coverage that are stressed during the course of the examination. For flat-bottom tanks these areas will generally include the sidewalls (and roof if pressure is applied above the liquid level). The examination may not detect flaws on the bottom of flat-bottom tanks unless sensors are located on the bottom. 1.3 This practice may require that the tank experience a load that is greater than that encountered in normal use. The normal contents of the tank can usually be used for applying this load. 1.4 This practice is not valid for tanks that will be operated at a pressure greater than the examination pressure. 1.5 It is not necessary to drain or clean the tank before performing this examination. 1.6 This practice applies to tanks made of carbon steel, stainless steel, aluminum and oth...

  8. Analysis of Precursors Prior to Rock Burst in Granite Tunnel Using Acoustic Emission and Far Infrared Monitoring

    Directory of Open Access Journals (Sweden)

    Zhengzhao Liang

    2013-01-01

    Full Text Available To understand the physical mechanism of the anomalous behaviors observed prior to rock burst, the acoustic emission (AE and far infrared (FIR techniques were applied to monitor the progressive failure of a rock tunnel model subjected to biaxial stresses. Images of fracturing process, temperature changes of the tunnel, and spatiotemporal serials of acoustic emission were simultaneously recorded during deformation of the model. The b-value derived from the amplitude distribution data of AE was calculated to predict the tunnel rock burst. The results showed that the vertical stress enhanced the stability of the tunnel, and the tunnels with higher confining pressure demonstrated a more abrupt and strong rock burst. Abnormal temperature changes around the wall were observed prior to the rock burst of the tunnel. Analysis of the AE events showed that a sudden drop and then a quiet period could be considered as the precursors to forecast the rock burst hazard. Statistical analysis indicated that rock fragment spalling occurred earlier than the abnormal temperature changes, and the abnormal temperature occurred earlier than the descent of the AE b-value. The analysis indicated that the temperature changes were more sensitive than the AE b-value changes to predict the tunnel rock bursts.

  9. Theoretical and experimental analysis on the mechanism of the Kaiser effect of acoustic emission in brittle rocks

    Institute of Scientific and Technical Information of China (English)

    Ruifu Yuan; Yuanhui Li

    2008-01-01

    The Kaiser effect is formally described as the absence of detectable acoustic emission (AE) events until the load imposed on the material exceeds the previous applied level and is usually used to estimate geostress. By focusing on the heterogeneity of rock material, the mechanism of the Kaiser effect under cyclic loading is analyzed based on statistic damage mechanics. Two groups of granite specimens have been cyclically loaded with two different loading paths to verify the theoretical results. The heterogeneity of rock is the real reason that causes irrecoverable damage on the Kaiser effect of acoustic emission in cyclic loading. The Kaiser effect reflects the damaged state in rocks rather than the previous stress imposed on it. Applications for using the Kaiser effect to estimate geostress were discussed here. It is shown that the commonly used uniaxial loading method for estimating geostress is not in accor-dance with the theoretical and experimental results. The analysis is of importance to use the Kaiser effect correctly for estimating geostress or in other fields.

  10. [Physiological-occupational assessment of acoustic load with equal energy but different time and informational characteristics].

    Science.gov (United States)

    Suvorov, G A; Shkarinov, L N; Kravchenko, O K; Kur'erov, N N

    1999-01-01

    The article deals with results of experimental study comparing effects of 4 types of acoustic load--noise (constant and impulse) and music (electronic symphonic one and rap)--on hearing sensitivity, processes in nervous system and subjective evaluation. All types of acoustic load were equal in energy (on evaluation according to equivalent level during the experiment). The study included 2 levels of load--90 and 95 dB. The differences revealed demonstrate importance of impulse parameters of noise and musical load for reactions of acoustic analyzer and central nervous system. The experiments show that evaluation of harm caused by temporary and impulse noises should be based not only on assessment of specific (hearing) function, but also on parameters of central nervous system state. The authors found that music of certain acoustic and informational parameters may harm hearing function. PMID:10420710

  11. Characteristics and realization of the second generation surface acoustic wave's wavelet device

    Institute of Scientific and Technical Information of China (English)

    Wen Changbao; Zhu Changchun; Lu Wenke; Liu Qinghong; Liu Junhua

    2006-01-01

    To overcome the bulk acoustic wave (BAW), the triple transit signals and the discontinuous frequency band in the first generation surface acoustic wave's (FGSAW's) wavelet device, the full transfer multistrip coupler (MSC) is applied to implement wavelet device, and a novel structure of the second generation surface acoustic wave's (SGSAW's) wavelet device is proposed. In the SGSAW's wavelet device, the BAW is separated and eliminated in different acoustic propagating tracks, and the triple transit signal is suppressed. For arbitrary wavelet scale device, the center frequency is three times the radius of frequency band, which ensures that the frequency band of the SGSAW's wavelet device is continuous, and avoids losing signals caused by the discontinuation of frequency band. Experimental result confirms that the BAW suppression, ripples in band, receiving loss and insertion loss of the SGSAW's wavelet device are remarkably improved compared with those of the FGSAW's wavelet device.

  12. Acoustic propagational characteristics and tomography studies of the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Somayajulu, Y.K.; Murty, T.V.R.

    duration acoustic tomography experiment in the eastern Arabian Sea during summer 1993 are presented in section 5. The Heard Island experiment, and India's contribution to this joint programme is outlined in section....

  13. GMAW process stability evaluation through acoustic emission by time and frequency domain analysis

    Directory of Open Access Journals (Sweden)

    E. Huanca Cayo

    2009-06-01

    Full Text Available Purpose: In the present work was made the comparative analysis in time domain and frequency domain to the acoustical pressure generate by the electric arc to determinate which of the two analysis methods is better to evaluates the stability in GMAW process.Design/methodology/approach: Welds had been made with the parameters adjusted to get the highest stability. In these conditions, were simulated instabilities that had been generated by the grease presence in the weld trajectory. In both experimental groups was acquired the acoustical pressure signal produced by electric arc to made analysis based in time domain and frequency domain.Findings: After this comparative study we conclude that the acoustical evaluation of the stability on the GMAW process presents more clarity for the analysis based in the time domain that the frequency domain.Research limitations/implications: In the gotten results, the time domain analysis method could represent adequately the stability and the instability of the process. The stability characterizes for the continuity and minim variation of the statistical parameters, but in the presence of instabilities, these parameters present chaotic changes. In the frequency domain method the variations are imperceptible for steady and unstable regions, but it presents little definite variations in the amplitude of determined bands of frequencies.Originality/value: The stability evaluation in welding is crucial because it is responsible in the weld quality. The non contact methods as the acoustical method have a potentiality extraordinary to monitoring and detect instabilities in welding. The acoustical sensing has the capacity to make an on-line monitoring of the weld process.

  14. Acoustic emission analysis of Vickers indentation fracture of cermet and ceramic coatings

    International Nuclear Information System (INIS)

    The aim of this work was to develop an instrumented experimental methodology of quantitative material evaluation based on the acoustic emission (AE) monitoring of a dead-weight Vickers indentation. This was to assess the degree of cracking and hence the toughness of thermally sprayed coatings. AE data were acquired during indentation tests on samples of coatings of nominal thickness 250–325 µm at a variety of indentation loads ranging from 49 to 490 N. Measurements were carried out on five different carbide and ceramic coatings (HVOF as-sprayed WC-12%Co (JP5000 and JetKote), HIPed WC-12%Co (JetKote) and as-sprayed Al2O3 (APS/Metco and HVOF/theta-gun)). The raw AE signals recorded during indentation were analysed and the total surface crack length around the indent determined. The results showed that the total surface crack length measured gave fracture toughness (K1c) values which were consistent with the published literature for similar coatings but evaluated using the classical approach (Palmqvist/half-penny model). Hence, the total surface crack length criteria can be applied to ceramic and cermet coatings which may or may not exhibit fracture via radial cracks. The values of K1c measured were 3.4 ± 0.1 MPa m1/2 for high-velocity oxygen fuel (HVOF) (theta-gun) Al2O3, 4.6 ± 0.3 MPa m1/2 for as-sprayed HVOF (JetKote) WC-12%Co, 7.1±0.1 MPa m1/2 for as-sprayed HVOF (JP5000) WC-12%Co and 7.4 ± 0.2 MPa m1/2 for HIPed HVOF (JetKote) WC-12%Co coatings. The crack lengths were then calibrated against the AE response and correlation coefficients evaluated. The values of K1c measured using AE correlations were 3.3 MPa m1/2 for HVOF (theta-gun) Al2O3, 2.6 MPa m1/2 for APS (Metco) Al2O3, 2.5 MPa m1/2 for as-sprayed HVOF (JetKote) WC-12%Co, 6.3 MPa m1/2 for as-sprayed HVOF (JP5000) WC-12%Co and 8.6 MPa m1/2 for HIPed HVOF (JetKote) WC-12%Co coatings. It is concluded that within each category of coating type, AE can be used as a suitable surrogate for crack length

  15. Pulsating combustion - Combustion characteristics and reduction of emissions

    Energy Technology Data Exchange (ETDEWEB)

    Lindholm, Annika

    1999-11-01

    In the search for high efficiency combustion systems pulsating combustion has been identified as one of the technologies that potentially can meet the objectives of clean combustion and good fuel economy. Pulsating combustion offers low emissions of pollutants, high heat transfer and efficient combustion. Although it is an old technology, the interest in pulsating combustion has been renewed in recent years, due to its unique features. Various applications of pulsating combustion can be found, mainly as drying and heating devices, of which the latter also have had commercial success. It is, however, in the design process of a pulse combustor, difficult to predict the operating frequency, the heat release etc., due to the lack of a well founded theory of the phenomenon. Research concerning control over the combustion process is essential for developing high efficiency pulse combustors with low emissions. Natural gas fired Helmholtz type pulse combustors have been the experimental objects of this study. In order to investigate the interaction between the fluid dynamics and the chemistry in pulse combustors, laser based measuring techniques as well as other conventional measuring techniques have been used. The experimental results shows the possibilities to control the combustion characteristics of pulsating combustion. It is shown that the time scales in the large vortices created at the inlet to the combustion chamber are very important for the operation of the pulse combustor. By increasing/decreasing the time scale for the large scale mixing the timing of the heat release is changed and the operating characteristics of the pulse combustor changes. Three different means for NO{sub x} reduction in Helmholtz type pulse combustors have been investigated. These include exhaust gas recirculation, alteration of air/fuel ratio and changed inlet geometry in the combustion chamber. All used methods achieved less than 10 ppm NO{sub x} emitted (referred to stoichiometric

  16. Performance and emission characteristics of QHCCI dimethyl ether engine

    Institute of Scientific and Technical Information of China (English)

    Ying WANG; Wei LI; Tiegang HU; Longbao ZHOU; Shenghua LIU

    2008-01-01

    Experimental investigation into the effects of different pilot amounts of dimethyl ether (DME) on the performance and emission of a single-cylinder direct-injection DME engine is conducted. The results show that a DME engine can operate at a wider range of speeds and loads at quasi-homogenous charge compression ignition (QHCCI) mode. The brake thermal efficiency increases while the exhaust temperature decreases. NOx emission decreases by about 30%-50% although there is a slight increase in HC and CO emissions. NOx, HC and CO emissions increase with an increase in the amount of DME pilot. QHCCI is a good way to increase thermal efficiency and decrease NOx emission.

  17. Acoustic and spectral characteristics of young children's fricative productions: A developmental perspective

    Science.gov (United States)

    Nissen, Shawn L.; Fox, Robert Allen

    2005-10-01

    Scientists have made great strides toward understanding the mechanisms of speech production and perception. However, the complex relationships between the acoustic structures of speech and the resulting psychological percepts have yet to be fully and adequately explained, especially in speech produced by younger children. Thus, this study examined the acoustic structure of voiceless fricatives (/f, θ, s, /sh/) produced by adults and typically developing children from 3 to 6 years of age in terms of multiple acoustic parameters (durations, normalized amplitude, spectral slope, and spectral moments). It was found that the acoustic parameters of spectral slope and variance (commonly excluded from previous studies of child speech) were important acoustic parameters in the differentiation and classification of the voiceless fricatives, with spectral variance being the only measure to separate all four places of articulation. It was further shown that the sibilant contrast between /s/ and /sh/ was less distinguished in children than adults, characterized by a dramatic change in several spectral parameters at approximately five years of age. Discriminant analysis revealed evidence that classification models based on adult data were sensitive to these spectral differences in the five-year-old age group.

  18. Research on Fatigue and Acoustic Emission of Cement%混凝土疲劳试验的AE特性研究

    Institute of Scientific and Technical Information of China (English)

    杜云; 张春明; 尾崎訒

    2001-01-01

    AE检测是对混凝土的疲劳破坏进行监测与预报的有效方法,它作为一种动态无损检测方法几乎不受材料的限制,。本研究对水泥砂浆试件(φ10cm×20cm)进行等幅低频部分片振压缩疲劳实验,结合应变进行AE测试,从而阐明混凝土在疲劳损伤中的AE特性, 为在实践中应用推广AE技术奠定试验基础。%Being a kind of dynamic un-damaging detecting method, AcousticEmission is almost applicable of all materials. Based on the const-amplitude partly low-frequency compress fatigue test carried out on cement mortar samples (φ10cm×20cm), some analysis and inspections on its strain and AE test results have been performed to explain the basic fatigue characteristics of concrete and the AE characteristics of concrete during the fatigue damaging process. Thus, a test foundation has been laid for the application of AE un-damaging test technique.

  19. Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

    Directory of Open Access Journals (Sweden)

    Pawełek A.

    2016-06-01

    Full Text Available The results of the investigation of both mechanical and acoustic emission (AE behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical, TEM and SEM images.

  20. Chemical characteristics of Siberian boreal forest fire emissions

    Science.gov (United States)

    Engling, G.; Popovicheva, O.; Fan, T. S.; Eleftheriadis, K.; Diapouli, E.; Kozlov, V.

    2014-12-01

    Smoke emissions from Siberian boreal forest fires exert critical impacts on the aerosol/climate system of subarctic regions and the Arctic. It is, therefore, crucial to assess the ability of such particles to absorb/scatter incoming solar radiation as well as act as cloud condensation nuclei, which is closely linked to the physical and chemical aerosol properties. However, observations of Siberian wildfire emissions are limited, and no systematic database of smoke particle properties is available for this region to date. As part of this study, ambient aerosol samples were collected during two smoke episodes in Tomsk, Siberia, in the summers of 2012 and 2013. In addition, the chemical composition and optical properties of smoke particles derived from the combustion of typical Siberian fuels, including pine wood and debris, were determined during chamber burn experiments in a large aerosol/combustion chamber under controlled combustion conditions representative of wildfires and prescribed burns. Detailed multi-component characterization of individual particles and bulk properties was accomplished with a suite of techniques, including various types of chromatography, microscopy, spectroscopy, and thermo-optical analysis. Individual particle analysis by SEM-EDX combined with cluster analysis revealed characteristic smoke structural components and major types of particles, which allowed to discriminate between flaming and smoldering regimes, reflected in specific morphological and chemical microstructure. The physicochemical properties representing the combustion phase (smoldering versus flaming) and the degree of processing (fresh versus aged) were assessed in the ambient aerosol based on the chamber burn results. For instance, some chemical transformation (aging of smoke particles) was noticed over a period of two days in the absence of sun light in the combustion chamber for certain chemical species, while the molecular tracer levoglucosan appeared to be rather

  1. Generation of surface acoustic wave by laser line array and its frequency characteristics

    International Nuclear Information System (INIS)

    Surface acoustic waves are very effective for the inspection of cracks and other defects in near-field region of the sample. Surface acoustic waves were generated by illumination of a sample surface with a Q-switched Nd:YAG laser pulse. A multiple slit and a cylindrical lens were used to generate the tone-burst like surface waves. Non contact detection of laser-generated surface acoustic waves was performed with the fiber optic Sagnac interferometer on a carbon steel specimen. Rayleigh wave velocity was obtained by the cross correlation of the signals recorded at different location, and was used to estimate the predominant frequency of the surface wave. Adjustment of the center frequency of the surface wave was performed by changing the distance between the sample and the lens, and the proper range for narrowband frequency was discussed.

  2. Continuous wavelet transform analysis and modal location analysis acoustic emission source location for nuclear piping crack growth monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Mohd, Shukri [Nondestructive Testing Group, Industrial Technology Division, Malaysian Nuclear Agency, 43000, Bangi, Selangor (Malaysia); Holford, Karen M.; Pullin, Rhys [Cardiff School of Engineering, Cardiff University, Queen' s Buildings, The Parade, CARDIFF CF24 3AA (United Kingdom)

    2014-02-12

    Source location is an important feature of acoustic emission (AE) damage monitoring in nuclear piping. The ability to accurately locate sources can assist in source characterisation and early warning of failure. This paper describe the development of a novelAE source location technique termed 'Wavelet Transform analysis and Modal Location (WTML)' based on Lamb wave theory and time-frequency analysis that can be used for global monitoring of plate like steel structures. Source location was performed on a steel pipe of 1500 mm long and 220 mm outer diameter with nominal thickness of 5 mm under a planar location test setup using H-N sources. The accuracy of the new technique was compared with other AE source location methods such as the time of arrival (TOA) techniqueand DeltaTlocation. Theresults of the study show that the WTML method produces more accurate location resultscompared with TOA and triple point filtering location methods. The accuracy of the WTML approach is comparable with the deltaT location method but requires no initial acoustic calibration of the structure.

  3. A comparative evaluation of piezoelectric sensors for acoustic emission-based impact location estimation and damage classification in composite structures

    Science.gov (United States)

    Uprety, Bibhisha; Kim, Sungwon; Mathews, V. John; Adams, Daniel O.

    2015-03-01

    Acoustic Emission (AE) based Structural Health Monitoring (SHM) is of great interest for detecting impact damage in composite structures. Within the aerospace industry the need to detect and locate these events, even when no visible damage is present, is important both from the maintenance and design perspectives. In this investigation, four commercially available piezoelectric sensors were evaluated for usage in an AE-based SHM system. Of particular interest was comparing the acoustic response of the candidate piezoelectric sensors for impact location estimations as well as damage classification resulting from the impact in fiber-reinforced composite structures. Sensor assessment was performed based on response signal characterization and performance for active testing at 300 kHz and steel-ball drop testing using both aluminum and carbon/epoxy composite plates. Wave mode velocities calculated from the measured arrival times were found to be in good agreement with predictions obtained using both the Disperse code and finite element analysis. Differences in the relative strength of the received wave modes, the overall signal strengths and signal-to-noise ratios were observed through the use of both active testing as well as passive steel-ball drop testing. Further comparative is focusing on assessing AE sensor performance for use in impact location estimation algorithms as well as detecting and classifying damage produced in composite structures due to impact events.

  4. Contribution of acoustic emission to monitor the effect of phosphate based inhibitor on the corrosion behavior of steel reinforcement

    Energy Technology Data Exchange (ETDEWEB)

    Nahali, Haifa [Laboratoire MATEIS CNRS UMR5511 (Equipe CorrIS), INSA-Lyon, Villeurbanne (France); Univ. de Tunis El Manar, Belvedere (Tunisia). Unite de Recherche ' ' Mecanique-Energetique' ' ; Dhouibi, Leila [Univ. de Tunis El Manar, Belvedere (Tunisia). Unite de Recherche ' ' Mecanique-Energetique' ' ; Idrissi, Hassane [Laboratoire MATEIS CNRS UMR5511 (Equipe CorrIS), INSA-Lyon, Villeurbanne (France)

    2014-11-01

    One of the most important causes of reinforced concrete structures deterioration is the corrosion of the reinforcement steel. This corrosion depends on the presence of aggressive agents such as chlorides in the surrounding medium. Numerous protection techniques have been employed to mitigate this corrosion. Among them, the use of corrosion inhibitors has been considered as one of the most effective solutions. In the present work, the influence of phosphate based inhibitor on the corrosion of reinforcing steels embedded in mortar, and immersed in sodium chloride solution, was investigated by acoustic emission technique. The monitoring of specimens shows that the phosphate based inhibitor addition in the mortar increase the threshold of chloride concentrations, causing the breakdown of steel passivation layer. Thus, the acoustic signatures of concrete fracture and of structure degradation during the corrosion of these specimens have been highlighted. Similarly, the mechanism of phosphate action in terms of preventing steel from corrosion in mortar specimens was analysed by characterization methods (SEM, XRD) of the steel-mortar interface.

  5. Continuous wavelet transform analysis and modal location analysis acoustic emission source location for nuclear piping crack growth monitoring

    International Nuclear Information System (INIS)

    Full-text: Source location is an important feature of acoustic emission (AE) damage monitoring in nuclear piping. The ability to accurately locate sources can assist in source characterisation and early warning of failure. This paper describe the development of a novelAE source location technique termed Wavelet Transform analysis and Modal Location (WTML) based on Lamb wave theory and time-frequency analysis that can be used for global monitoring of plate like steel structures. Source location was performed on a steel pipe of 1500 mm long and 220 mm outer diameter with nominal thickness of 5 mm under a planar location test setup using H-N sources. The accuracy of the new technique was compared with other AE source location methods such as the time of arrival (TOA) technique and DeltaTlocation. The results of the study show that the WTML method produces more accurate location results compared with TOA and triple point filtering location methods. The accuracy of the WTML approach is comparable with the deltaT location method but requires no initial acoustic calibration of the structure. (author)

  6. A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock-walls

    Directory of Open Access Journals (Sweden)

    L. Girard

    2012-06-01

    Full Text Available We present a custom acoustic emission (AE monitoring system designed to perform long-term measurements on high-alpine rock-walls. AE monitoring is a common technique for characterizing damage evolution in solid materials. The system is based on a two-channel AE sensor node (AE-node integrated into a Wireless Sensor Network (WSN customized for operation in harsh environments. This wireless architecture offers flexibility in the deployment of AE-nodes at any position of the rock-wall that needs to be monitored, within a range of a few hundred meters from a core station connected to the internet. The system achieves near real-time data delivery and allows the user to remotely control the AE detection threshold. In order to protect AE sensors and capture acoustic signals from specific depths of the rock-wall, a special casing was developed. The monitoring system is completed by two probes that measure rock temperature and liquid water content, both probes being also integrated into the WSN. We report a first deployment of the monitoring system on a rock-wall at Jungfraujoch, 3500 m a.s.l., Switzerland. While this first deployment of the monitoring system aims to support fundamental research on processes that damage rock under cold climate, the system could serve a number of other applications, including rock-fall hazard surveillance or structural monitoring of concrete structures.

  7. A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock walls

    Directory of Open Access Journals (Sweden)

    L. Girard

    2012-11-01

    Full Text Available We present a custom acoustic emission (AE monitoring system designed to perform long-term measurements on high-alpine rock walls. AE monitoring is a common technique for characterizing damage evolution in solid materials. The system is based on a two-channel AE sensor node (AE-node integrated into a wireless sensor network (WSN customized for operation in harsh environments. This wireless architecture offers flexibility in the deployment of AE-nodes at any position of the rock wall that needs to be monitored, within a range of a few hundred meters from a core station connected to the internet. The system achieves near real-time data delivery and allows the user to remotely control the AE detection threshold. In order to protect AE sensors and capture acoustic signals from specific depths of the rock wall, a special casing was developed. The monitoring system is completed by two probes that measure rock temperature and liquid water content, both probes being also integrated into the WSN. We report a first deployment of the monitoring system on a rock wall at Jungfraujoch, 3500 m a.s.l., Switzerland. While this first deployment of the monitoring system aims to support fundamental research on processes that damage rock under cold climate, the system could serve a number of other applications, including rock fall hazard surveillance or structural monitoring of concrete structures.

  8. Contribution of acoustic emission to monitor the effect of phosphate based inhibitor on the corrosion behavior of steel reinforcement

    International Nuclear Information System (INIS)

    One of the most important causes of reinforced concrete structures deterioration is the corrosion of the reinforcement steel. This corrosion depends on the presence of aggressive agents such as chlorides in the surrounding medium. Numerous protection techniques have been employed to mitigate this corrosion. Among them, the use of corrosion inhibitors has been considered as one of the most effective solutions. In the present work, the influence of phosphate based inhibitor on the corrosion of reinforcing steels embedded in mortar, and immersed in sodium chloride solution, was investigated by acoustic emission technique. The monitoring of specimens shows that the phosphate based inhibitor addition in the mortar increase the threshold of chloride concentrations, causing the breakdown of steel passivation layer. Thus, the acoustic signatures of concrete fracture and of structure degradation during the corrosion of these specimens have been highlighted. Similarly, the mechanism of phosphate action in terms of preventing steel from corrosion in mortar specimens was analysed by characterization methods (SEM, XRD) of the steel-mortar interface.

  9. Standard practice for acoustic emission examination of plate-like and flat panel composite structures used in aerospace applications

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice covers acoustic emission (AE) examination or monitoring of panel and plate-like composite structures made entirely of fiber/polymer composites. 1.2 The AE examination detects emission sources and locates the region(s) within the composite structure where the emission originated. When properly developed AE-based criteria for the composite item are in place, the AE data can be used for nondestructive examination (NDE), characterization of proof testing, documentation of quality control or for decisions relative to structural-test termination prior to completion of a planned test. Other NDE methods may be used to provide additional information about located damage regions. For additional information see Appendix X1. 1.3 This practice can be applied to aerospace composite panels and plate-like elements as a part of incoming inspection, during manufacturing, after assembly, continuously (during structural health monitoring) and at periodic intervals during the life of a structure. 1.4 This pra...

  10. Standard practice for examination of Gas-Filled filament-wound composite pressure vessels using acoustic emission

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice provides guidelines for acoustic emission (AE) examination of filament-wound composite pressure vessels, for example, the type used for fuel tanks in vehicles which use natural gas fuel. 1.2 This practice requires pressurization to a level equal to or greater than what is encountered in normal use. The tanks' pressurization history must be known in order to use this practice. Pressurization medium may be gas or liquid. 1.3 This practice is limited to vessels designed for less than 690 bar [10,000 psi] maximum allowable working pressure and water volume less than 1 m3 or 1000 L [35.4 ft3]. 1.4 AE measurements are used to detect emission sources. Other nondestructive examination (NDE) methods may be used to gain additional insight into the emission source. Procedures for other NDE methods are beyond the scope of this practice. 1.5 This practice applies to examination of new and in-service filament-wound composite pressure vessels. 1.6 This practice applies to examinations conducted at amb...

  11. X-ray Emission Characteristics of Flares Associated with CMEs

    Indian Academy of Sciences (India)

    Malini Aggarwal; Rajmal Jain; A. P. Mishra; P. G. Kulkarni; Chintan Vyas; R. Sharma; Meera Gupta

    2008-03-01

    We present the study of 20 solar flares observed by ``Solar X-ray Spectrometer (SOXS)” mission during November 2003 to December 2006 and found associated with coronal mass ejections (CMEs) seen by LASCO/SOHO mission. In this investigation, X-ray emission characteristics of solar flares and their relationship with the dynamics of CMEs have been presented.We found that the fast moving CMEs, i.e., positive acceleration are better associated with short rise time (< 150 s) flares. However, the velocity of CMEs increases as a function of duration of the flares in both 4.1–10 and 10–20 keV bands. This indicates that the possibility of association of CMEs with larger speeds exists with long duration flare events. We observed that CMEs decelerate with increasing rise time, decay time and duration of the associated X-ray flares. A total 10 out of 20 CMEs under current investigation showed positive acceleration, and 5 of them whose speed did not exceed 589 km/s were associated with short rise time (< 150 s) and short duration (< 1300 s) flares. The other 5 CMEs were associated with long duration or large rise time flare events. The unusual feature of all these positive accelerating CMEs was their low linear speed ranging between 176 and 775 km/s. We do not find any significant correlation between X-ray peak intensity of the flares with linear speed as well as acceleration of the associated CMEs. Based on the onset time of flares and associated CMEs within the observing cadence of CMEs by LASCO, we found that in 16 cases CME preceded the flare by 23 to 1786 s, while in 4 cases flare occurred before the CME by 47 to 685 s. We argue that both events are closely associated with each other and are integral parts of one energy release system.

  12. Acoustic emission analysis and ultrasonic backscattering analysis for characterisation of fissure systems in saline rock; Akustische Emission und Ultraschall-Rueckstreuung zur Charakterisierung von Rissgeflechten im Salzgestein

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnicke, Horst; Schulze, Eberhard [Fraunhofer-Institut fuer Zerstoerungsfreie Pruefverfahren, Institutsteil Dresden (Germany)

    2010-07-01

    For long-lived toxic or radioactive wastes, underground storage in geologically stable and near non-permeable saline rock strata is a relatively safe storage option. Correct characterisation of the so-called loosening zone of the saline bedrock is very important as the stresses around man-made caverns will cause extensive systems of microcracks that enhance the permeability for liquid and solid hazardous materials. Non-destructive characterisation of the loosening zone has the advantage of detailed 3D imaging without additional damage to the rock. The methods employed are microseismic (acoustic emission testing) and geosonar (ultrasonic backscattering). With acoustic emission testing, the temporal and spatial variations in the loosening zone can be observed without complex instrumentation. The ultrasonic method has a mean frequency of 200 kHz; it measures the backscattering of the microcrack systems and is well suited for determining the state of loosening at a given moment. Validations in a 35 year-old cavern with a circular cross section of about 3 m and in two more recent caverns with rectangular cross sections of 3 x 9 m were positive. The loosening zones had a thickness of about 0.5 m. Cracks were oriented parallel to the cavern surface; most of them were normal stress fractures. Permeabilities were 10{sup -16} m at the edge and 10{sup -23} m{sup 2}. The good results wre mostly due to the application of signal shape based techniques, e.g. conditioned signals or moment sensor analysis. The measuring system is protected against dust and water. Both the measuring systems and the evaluation algorithms can also be used in other materials with coarse structures, e.g. concrete or fibre-reinforced polymers. (orig.)

  13. Field emission characteristics from graphene on hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Takatoshi, E-mail: takatoshi-yamada@aist.go.jp [National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Masuzawa, Tomoaki; Ebisudani, Taishi; Okano, Ken [International Christian University, 3-10-2 Osawa, Mitaka, Tokyo 181-8585 (Japan); Taniguchi, Takashi [National Institute for Material Science (NIMS), 1-1-1 Namiki, Tsukuba 305-0044 (Japan)

    2014-06-02

    An attempt has been made to utilize uniquely high electron mobility of graphene on hexagonal boron nitride (h-BN) to electron emitter. The field emission property of graphene/h-BN/Si structure has shown enhanced threshold voltage and emission current, both of which are key to develop novel vacuum nanoelectronics devices. The field emission property was discussed along with the electronic structure of graphene investigated by Fowler-Nordheim plot and ultraviolet photoelectron spectroscopy. The result suggested that transferring graphene on h-BN modified its work function, which changed field emission mechanism. Our report opens up a possibility of graphene-based vacuum nanoelectronics devices with tuned work function.

  14. Multi scale analysis by acoustic emission of damage mechanisms in natural fibre woven fabrics/epoxy composites.

    Directory of Open Access Journals (Sweden)

    Touchard F.

    2010-06-01

    Full Text Available This paper proposes to develop an experimental program to characterize the type and the development of damage in composite with complex microstructure. A multi-scale analysis by acoustic emission has been developed and applied to hemp fibre woven fabrics/epoxy composite. The experimental program consists of tensile tests performed on single yarn, neat epoxy resin and composite materials to identify their AE amplitude signatures. A statistical analysis of AE amplitude signals has been realised and correlated with microscopic observations. Results have enabled to identify three types of damage in composites and their associated AE amplitudes: matrix cracking, interfacial debonding and reinforcement damage and fracture. Tracking of these damage mechanisms in hemp/epoxy composites has been performed to show the process of damage development in natural fibre reinforced composites.

  15. Acoustic emission study of the plastic deformation of quenched and partitioned 35CrMnSiA steel

    Institute of Scientific and Technical Information of China (English)

    Yang Li; Gui-yong Xiao; Lu-bin Chen; Yu-peng Lu

    2014-01-01

    Acoustic emission (AE) monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning (Q−P) heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering (Q−T) and austempering (AT). AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite (RA) in the microstructure (obtained via Q−P and AT heat treatments) due to an austenite-to-martensite phase transforma-tion. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA de-generated by tempering for the Q−P treated steel.

  16. Application of a novel optical fiber sensor to detection of acoustic emissions by various damages in CFRP laminates

    Science.gov (United States)

    Wu, Qi; Yu, Fengming; Okabe, Yoji; Kobayashi, Satoshi

    2015-01-01

    In this research, we applied a novel optical fiber sensor, phase-shifted fiber Bragg grating balanced sensor with high sensitivity and broad bandwidth, to acoustic emission (AE) detection in carbon fiber reinforced plastics (CFRPs). AE signals generated in the tensile testing of angle-ply and cross-ply CFRP laminates were both detected by the novel optical fiber sensor and traditional PZT sensors. The cumulative hits detected by both sensors coincided after applying simple data processing to eliminate the noise, and clearly exhibited Kaiser effect and Felicity effect. Typical AE signals detected by both sensors were discussed and were tried to relate to micro CFRP damages observed via microscope. These results demonstrate that this novel optical fiber sensor can reliably detect AE signals from various damages. It has the potential to be used in practical AE detection, as an alternative to the piezoelectric PZT sensor.

  17. Application of a novel optical fiber sensor to detection of acoustic emissions by various damages in CFRP laminates

    International Nuclear Information System (INIS)

    In this research, we applied a novel optical fiber sensor, phase-shifted fiber Bragg grating balanced sensor with high sensitivity and broad bandwidth, to acoustic emission (AE) detection in carbon fiber reinforced plastics (CFRPs). AE signals generated in the tensile testing of angle-ply and cross-ply CFRP laminates were both detected by the novel optical fiber sensor and traditional PZT sensors. The cumulative hits detected by both sensors coincided after applying simple data processing to eliminate the noise, and clearly exhibited Kaiser effect and Felicity effect. Typical AE signals detected by both sensors were discussed and were tried to relate to micro CFRP damages observed via microscope. These results demonstrate that this novel optical fiber sensor can reliably detect AE signals from various damages. It has the potential to be used in practical AE detection, as an alternative to the piezoelectric PZT sensor. (paper)

  18. Acoustic Emission Investigation of Rolling/Sliding Contact Fatigue Failure of NiCr-Cr3C2 Coating

    Science.gov (United States)

    Guolu, Li; Zhonglin, Xu; Tianshun, Dong; Haidou, Wang; Jinhai, Liu; Jiajie, Kang

    2016-08-01

    NiCr-Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.

  19. Acoustic emission study of the plastic deformation of quenched and partitioned 35CrMnSiA steel

    Science.gov (United States)

    Li, Yang; Xiao, Gui-yong; Chen, Lu-bin; Lu, Yu-peng

    2014-12-01

    Acoustic emission (AE) monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning (Q-P) heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering (Q-T) and austempering (AT). AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite (RA) in the microstructure (obtained via Q-P and AT heat treatments) due to an austenite-to-martensite phase transformation. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA degenerated by tempering for the Q-P treated steel.

  20. Artificial Neural Network Model for Monitoring Oil Film Regime in Spur Gear Based on Acoustic Emission Data

    Directory of Open Access Journals (Sweden)

    Yasir Hassan Ali

    2015-01-01

    Full Text Available The thickness of an oil film lubricant can contribute to less gear tooth wear and surface failure. The purpose of this research is to use artificial neural network (ANN computational modelling to correlate spur gear data from acoustic emissions, lubricant temperature, and specific film thickness (λ. The approach is using an algorithm to monitor the oil film thickness and to detect which lubrication regime the gearbox is running either hydrodynamic, elastohydrodynamic, or boundary. This monitoring can aid identification of fault development. Feed-forward and recurrent Elman neural network algorithms were used to develop ANN models, which are subjected to training, testing, and validation process. The Levenberg-Marquardt back-propagation algorithm was applied to reduce errors. Log-sigmoid and Purelin were identified as suitable transfer functions for hidden and output nodes. The methods used in this paper shows accurate predictions from ANN and the feed-forward network performance is superior to the Elman neural network.