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Sample records for vibration fatigue specimens

  1. Experimental Research on Vibration Fatigue of CFRP and Its Influence Factors Based on Vibration Testing

    OpenAIRE

    Fan, Zhengwei; Jiang, Yu; Zhang, Shufeng; Chen, Xun

    2017-01-01

    A new research method based on vibration testing for the vibration fatigue of FRP was proposed in this paper. Through the testing on a closed-loop controlled vibration fatigue test system, the vibration fatigue phenomenon of typical carbon-fiber-reinforced plastic (CFRP) cantilevered laminate specimens was carefully studied. Moreover, a method based on the frequency response function was proposed to monitor the fatigue damage accumulation of specimens. On the basis of that, the influence fact...

  2. Fatigue Specimens for Sheet and Plate Material

    NARCIS (Netherlands)

    Schijve, J.

    1998-01-01

    The usefulness of simple sheet and plate specimens is discussed for various experimental research purposes. Specimens should be representative as much as possible for the conditions of fatigue problems in practice, which is more difficult to achieve for the fatigue crack initiation phase than for

  3. A Biaxial Fatigue Specimen for Uniaxial Loading

    OpenAIRE

    Bellett, Daniel; Morel, Franck; Morel, Anne; Lebrun, Jean-Lou

    2011-01-01

    International audience; The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the paramet...

  4. Vibration fatigue using modal decomposition

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2018-01-01

    Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.

  5. High Temperature Fatigue Life Evaluation Using Small Specimen

    National Research Council Canada - National Science Library

    NOGAMI, Shuhei; HISAKA, Chiaki; FUJIWARA, Masaharu; WAKAI, Eichi; HASEGAWA, Akira

    2017-01-01

    For developing the high temperature fatigue life evaluation method using small specimen, the effect of specimen size and test environment on the high temperature fatigue life of the reduced activation...

  6. High Frequency Vibration Based Fatigue Testing of Developmental Alloys

    Science.gov (United States)

    Holycross, Casey M.; Srinivasan, Raghavan; George, Tommy J.; Tamirisakandala, Seshacharyulu; Russ, Stephan M.

    Many fatigue test methods have been previously developed to rapidly evaluate fatigue behavior. This increased test speed can come at some expense, since these methods may require non-standard specimen geometry or increased facility and equipment capability. One such method, developed by George et al, involves a base-excited plate specimen driven into a high frequency bending resonant mode. This resonant mode is of sufficient frequency (typically 1200 to 1700 Hertz) to accumulate 107 cycles in a few hours. One of the main limitations of this test method is that fatigue cracking is almost certainly guaranteed to be surface initiated at regions of high stress. This brings into question the validity of the fatigue test results, as compared to more traditional uniaxial, smooth-bar testing, since high stresses are subjecting only a small volume to fatigue damage. This limitation also brings into question the suitability of this method to screen developmental alloys, should their initiation life be governed by subsurface flaws. However, if applicable, the rapid generation of fatigue data using this method would facilitate faster design iterations, identifying more quickly, material and manufacturing process deficiencies. The developmental alloy used in this study was a powder metallurgy boron-modified Ti-6Al-4V, a new alloy currently being considered for gas turbine engine fan blades. Plate specimens were subjected to fully reversed bending fatigue. Results are compared with existing data from commercially available Ti-6Al-4V using both vibration based and more traditional fatigue test methods.

  7. Development of fatigue life evaluation method using small specimen

    Science.gov (United States)

    Nogami, Shuhei; Nishimura, Arata; Wakai, Eichi; Tanigawa, Hiroyasu; Itoh, Takamoto; Hasegawa, Akira

    2013-10-01

    For developing the fatigue life evaluation method using small specimen, the effect of specimen size and shape on the fatigue life of the reduced activation ferritic/martensitic steels (F82H-IEA, F82H-BA07 and JLF-1) was investigated by the fatigue test at room temperature in air using round-bar and hourglass specimens with various specimen sizes (test section diameter: 0.85-10 mm). The round-bar specimen showed no specimen size and no specimen shape effects on the fatigue life, whereas the hourglass specimen showed no specimen size effect and obvious specimen shape effect on it. The shorter fatigue life of the hourglass specimen observed under low strain ranges could be attributed to the shorter micro-crack initiation life induced by the stress concentration dependent on the specimen shape. On the basis of this study, the small round-bar specimen was an acceptable candidate for evaluating the fatigue life using small specimen.

  8. Specimen edge effects on bending fatigue of carburized steel

    Science.gov (United States)

    Cohen, R. E.; Matlock, D. K.; Krauss, G.

    1992-10-01

    The effects of specimen geometry on the fatigue behavior of SAE 4320 steel carburized at 927 °C were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison to the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenite in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the square-edged samples at a location approximately 200 to 900 ώm from the square edge. The implications of this study on laboratory analyses of the bending fatigue performance of carburized gear steels are discussed.

  9. 14 CFR 23.907 - Propeller vibration and fatigue.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood... evaluation of the propeller to show that failure due to fatigue will be avoided throughout the operational...

  10. 14 CFR 25.907 - Propeller vibration and fatigue.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller vibration and fatigue. 25.907... vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a... propeller to show that failure due to fatigue will be avoided throughout the operational life of the...

  11. [Chronic fatigue syndrome in patients with vibration disease].

    Science.gov (United States)

    Kir'iakov, V A; Saarkoppel', L M; Krylova, I V; Sukhova, A V

    2013-01-01

    The article presents study results that demonstrate chronic fatigue syndrome in patients with vibration disease. Clinical manifestations of chronic fatigue syndrome are characterized by changes in the emotional-volitional and cognitive areas. Application of nootropic drug cortexin increases the efficiency of rehabilitation in patients with vibration disease with chronic fatigue syndrome.

  12. Evaluation of composite flattened tubular specimen. [fatigue tests

    Science.gov (United States)

    Liber, T.; Daniel, I. M.

    1978-01-01

    Flattened tubular specimens of graphite/epoxy, S-glass/epoxy, Kevlar-49/epoxy, and graphite/S-glass/epoxy hybrid materials were evaluated under static and cyclic uniaxial tensile loading and compared directly with flat coupon data of the same materials generated under corresponding loading conditions. Additional development for the refinement of the flattened specimen configuration and fabrication was required. Statically tested graphite/epoxy, S-glass/epoxy, and Kevlar 49/epoxy flattened tube specimens exhibit somewhat higher average strengths than their corresponding flat coupons. Flattened tube specimens of the graphite/S-glass/epoxy hybrid and the graphite/epoxy flattened tube specimens failed in parasitic modes with consequential lower strength than the corresponding flat coupons. Fatigue tested flattened tube specimens failed in parasitic modes resulting in lower fatigue strengths than the corresponding flat coupons.

  13. Design optimization of cruciform specimens for biaxial fatigue loading

    Directory of Open Access Journals (Sweden)

    R. Baptista

    2014-10-01

    Full Text Available In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.

  14. Design of Ultrasonic Fatigue Specimen of MB8 Wrought Magnesium Alloy by Analytic Method

    Directory of Open Access Journals (Sweden)

    DENG Haipeng

    2016-08-01

    Full Text Available Ultrasonic fatigue specimen of MB8 wrought magnesium alloy was designed by calculation. In order to reduce the vibration amplitude, heat and pressure of the cooling system and also to protect the phase change, the sample was designed into variable cross-section. Based on the vibration displacement equation, boundary condition and displacement continuity condition, the relationship between the resonant length and other dimensions of the sample was derived. A series of size of ultrasonic fatigue specimens was calculated, which provided reference for the research of ultrasonic fatigue test of magnesium alloy. The results show that the resonance length decreases with the increase of the length of transition section, and the arc transition radius increases with the increase of the length of arc transition section.With the decrease of the length of arc transition section, Cs and M decreases for the specimen without uniform cross section in middle. With the decrease of the length of uniform cross section in the middle, Cs and M decreased for the specimen with uniform cross section in the middle.

  15. Postural sway under muscle vibration and muscle fatigue in humans.

    Science.gov (United States)

    Vuillerme, Nicolas; Danion, Frédéric; Forestier, Nicolas; Nougier, Vincent

    2002-11-22

    Separate studies have demonstrated that vibration and fatigue of ankle muscles alter postural control. The purpose of the present experiment was to investigate the effect of ankle muscle vibration on the regulation of postural sway in bipedal stance following ankle muscle fatigue. Center of foot pressure displacements were recorded using a force platform. Results showed a similar increase in postural sway under muscle fatigue as well as under muscle vibration. Interestingly, under muscle fatigue muscle vibration did not induce a further increase in postural sway. Two hypotheses could, at least, account for this observation: (1). fatigued muscles are less sensitive to muscle vibration and (2). the central nervous system relies less upon proprioceptive information originating from fatigued muscles for regulating postural sway.

  16. The Effect of Load Magnitude on Fatigue Life and Thermal Behavior of Notched Fatigue Specimen

    Directory of Open Access Journals (Sweden)

    Laith Hussain Al Najar

    2017-11-01

    Full Text Available Fatigue failure is an important phenomenon that occurred in the mechanical and structural systems. Furthermore, the failure due to fatigue load causes losing in that system. So many researches studying the fatigue behavior and improving the design of mechanical and structural systems in order to increase the fatigue resistance of these systems.  In this work, the effects of notch position and load magnitude on fatigue behavior were studied. In order to study the fatigue life of the test specimens due to make V- notched, the rotating cantilever beam samples were used. Also, the temperature distribution along testing specimens was monitoring of IR camera during the fatigue tests. Numerical model has been done by using ANSYS Workbench 15.0.  The comparison between experimental and numerical results was made, also the hardness of the fractured surfaces was measured. The results show that, the fatigue life of the test specimens can be increased by making a notch in the appropriate position. Also, there is a similarity between experimental and numerical results. IR camera gave a good expectance to the fracture position from changing in temperature distribution along the test specimens. Finally, the area of sudden fracture of the fractured surfaces reduced directly with load magnitude and inversely with notch shifting away from edge region.

  17. Edgeless composite laminate specimen for static and fatigue testing

    Science.gov (United States)

    Liber, T.; Daniel, I. M.

    1978-01-01

    The influence of edge effects on the tensile properties of angle-ply laminate composites can be eliminated by using edgeless (round tubular) specimens. However, uniaxial tests with such specimens, static and fatigue, have been generally unsuccessful because of the differential Poisson effect between the test section and the grips. An edgeless cylindrical specimen, developed to circumvent these difficulties, is examined in the present paper. It is a flattened tube consisting of two flat sides connected by curved sections. It can be handled much like the standard flat coupon. The flat ends of the specimen are provided with crossplied fiberglass gripping tabs, the same as used for flat test coupons. As part of the tabbing, the hollow ends must be plugged with inserts to prevent crushing of the ends. A special insert design was developed to minimize detrimental Poisson effects ordinarily introduced by inserts.

  18. Fatigue and soft tissue vibration during prolonged running.

    Science.gov (United States)

    Khassetarash, Arash; Hassannejad, Reza; Ettefagh, Mir Mohammad; Sari-Sarraf, Vahid

    2015-12-01

    Muscle tuning paradigm proposes that the mechanical properties of soft tissues are tuned in such a way that its vibration amplitude become minimized. Therefore, the vibrations of soft tissue are heavily damped. However, it has been hypothesized that the ability of muscle tuning decreases with fatigue. This study investigated the changes in vibration characteristics of soft tissue with fatigue. Vibrations of the gastrocnemius muscle of 8 runners during a prolonged run protocol on a treadmill at constant velocity (4 ms(-1)) were measured using a tri-axial accelerometer. The vibration amplitude is calculated using the Fourier transform and a wavelet-based method was used to calculate the damping coefficient. The results showed that: (1) the vibration amplitude in longitudinal direction increased with fatigue, which may be interpreted as the decreased muscle function with fatigue. (2) The amplitude increase percent strongly depended on the vibration frequency. (3) The damping coefficient of the gastrocnemius increased with fatigue. A 1-DOF mass-spring-damper model was used in order to validate the wavelet based method and simulate the observed phenomena. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Tndon vibration does not alter recovery time following fatigue.

    Science.gov (United States)

    Christie, Anita D; Miller, Nick R

    2015-05-01

    Tendon vibration has been shown to enhance muscle activity and to increase muscular endurance times. The impact of vibration on recovery from fatigue, however, is not known. This study aims to determine whether tendon vibration reduces recovery time following fatiguing contractions. Eight sedentary males (22 ± 2.8 yr) performed a fatiguing protocol of ankle dorsiflexor muscles on two separate days, with a minimum of 48 h between visits. Surface EMG was recorded from the tibialis anterior muscle while participants were performing 25 maximal voluntary contractions (MVCs), each lasting 5 s and separated by 2 s. Following the fatiguing protocol, recovery was assessed with 3-s MVC each minute over a 10-min period. Recovery time was defined as the time at which force had returned to 90% of baseline values. At one visit, vibration was applied to the distal tendon of the tibialis anterior muscle between MVCs (throughout recovery). The alternate visit involved a sham condition in which no vibration was applied. MVC force (P = 0.48) and EMG amplitude (P = 0.26) were not significantly different across testing days. Both MVC force (P fatigue protocol. However, there were no significant interaction effects for MVC force (P = 0.82) or EMG amplitude (P = 0.09), indicating similar levels of fatigue across days. With tendon vibration, MVC force recovered within 4.0 ± 2.5 min, which was not different from the sham condition (5.3 ± 1.8 min; P = 0.42). Similarly, EMG recovery time was not different between vibration condition (3.9 ± 3.8 min) and sham condition (4.9 ± 2.5 min) (P = 0.41). These results suggest that activation of excitatory group Ia afferents through tendon vibration does not substantially alter recovery time following fatigue.

  20. The Vibration Based Fatigue Damage Assessment of Steel and Steel Fiber Reinforced Concrete (SFRC Composite Girder

    Directory of Open Access Journals (Sweden)

    Xu Chen

    2015-01-01

    Full Text Available The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current fatigue damage assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based fatigue damage assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the fatigue damage development. Generally, it confirmed the feasibility of executing fatigue damage assessment of composite bridge based on vibration method.

  1. Growth behavior of fatigue cracks in ultrafine grained Cu smooth specimens with a small hole

    National Research Council Canada - National Science Library

    Masahiro Goto; Kakeru Morita; Junichi Kitamura; Takaei Yamamoto; Masataka Baba; Seung-zeon Han; Sangshik Kim

    2015-01-01

      In order to study the growth mechanism of fatigue cracks in ultrafine grained copper, stresscontrolled fatigue tests of round-bar specimens with a small blind hole as a crack starter were conducted...

  2. Room temperature fatigue behavior of OFHC copper and CuAl25 specimens of two sizes

    DEFF Research Database (Denmark)

    Singhal, A.; Stubbins, J.F.; Singh, B.N.

    1994-01-01

    requiring an understanding of their fatigue behavior.This paper describes the room temperature fatigue behavior of unirradiated OFHC (oxygen-free high-conductivity) copper and CuAl25 (copper strengthened with a 0.25% atom fraction dispersion of alumina). The response of two fatigue specimen sizes to strain...... controlled fatigue loading is examined, and differences in behavior are discussed. Specimens with the smaller size are now being irradiated in several reactors...

  3. Neuromuscular fatigue induced by whole-body vibration exercise.

    Science.gov (United States)

    Maffiuletti, Nicola A; Saugy, Jonas; Cardinale, Marco; Micallef, Jean-Paul; Place, Nicolas

    2013-06-01

    The aim of this study was to examine the magnitude and the origin of neuromuscular fatigue induced by half-squat static whole-body vibration (WBV) exercise, and to compare it to a non-WBV condition. Nine healthy volunteers completed two fatiguing protocols (WBV and non-WBV, randomly presented) consisting of five 1-min bouts of static half-squat exercise with a load corresponding to 50 % of their individual body mass. Neuromuscular fatigue of knee and ankle muscles was investigated before and immediately after each fatiguing protocol. The main outcomes were maximal voluntary contraction (MVC) torque, voluntary activation, and doublet peak torque. Knee extensor MVC torque decreased significantly (P fatiguing protocols. Doublet peak torque decreased significantly and to a similar extent following WBV and non-WBV exercise, for both knee extensors (-25 %; P fatigue and did not change its causative factors compared to non-WBV half-squat resistive exercise in recreationally active subjects.

  4. A low cycle fatigue test device for micro-cantilevers based on self-excited vibration principle.

    Science.gov (United States)

    Qi, Mingjing; Liu, Zhiwei; Yan, Xiaojun

    2014-10-01

    This paper reports a low-cycle fatigue test device for micro-cantilevers, which are widely used in micro scale structures. The working principle of the device is based on the phenomenon that a micro-cantilever can be set into self-excited vibration between two electrodes under DC voltage. Compared with previous devices, this simple device can produce large strain amplitude on non-notched specimens, and allows a batch of specimens to be tested simultaneously. Forty-two micro-cantilever specimens were tested and their fatigue fracture surfaces exhibit typical low cycle fatigue characteristics. As such, the device is very attractive for future fatigue investigation for micro scale structures.

  5. Effect of groove on socket welds under the condition of vibration fatigue

    Science.gov (United States)

    Xiu, Junjie; Jing, Hongyang; Han, Yongdian; Zhao, Lei; Xu, Lianyong

    2013-02-01

    Root failures of socket welds in small bore piping caused by vibration mainly occur at nuclear power plants (NPPs). It was observed that at higher stress level failures tended to originate at the toe while for the case of lower stress failures tended to occur at the root. The groove can increase the penetration depth (PD) of root, which is beneficial to the fatigue life. The effect of groove was also investigated by finite element method (FEM). The simulation results show that groove can decline the stress distribution, stress triaxiality and maximum principal plastic strain in the weld root, and the 5 mm groove suffering σmax (the highest stress of root failure) is almost same as no groove subjecting to σf (fatigue limit). The test results show that the socket weld with groove can increase the natural frequency and damping of specimen, which make the system more difficult to vibrate. Moreover, the groove can also improve the fatigue property of specimen which do not exist the root failure even under high cycle fatigue (HCF).

  6. Online vibration-based crack detection during fatigue testing

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, B.; Vecchio, A.; Auweraer, H. van der [LMS International, Heverlee (Belgium); Mevel, L. [INRIA, Rennes (France); Vanlanduit, S.; Guillaume, P. [Dept. of Mechanical Engineering, VUB, Brussels (Belgium); Goursat, M. [Rocquencourt, INRIA, Le Chesnay (France)

    2003-07-01

    When performing fatigue tests, it is essential to monitor the degradation of the structure with an increasing number of fatigue cycles. In this article, a vibration-based damage detection method will be proposed. Such a method has the advantage that it operates online with the fatigue test. Especially for structures with very high fatigue strength, it is important that the test does not have to be interrupted. The damage detection method that will be used is based on a residual generated from a stochastic subspace identification method. The basic idea is that a model for the undamaged structure is identified and that, afterwards, vibration measurements from a possibly damaged structure are confronted with this model. A statistical local approach hypothesis testing is used to assess the deviation of the new data from the nominal model. After introducing the damage detection method, its performance will be illustrated on data from a fatigue experiment. The method will be compared to other linear and non-linear vibration-based damage detection methods. (orig.)

  7. Multiaxial vibration fatigue-A theoretical and experimental comparison

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2016-08-01

    Random vibration excitation is a common cause of failure, especially if natural dynamics is excited. The high-cycle vibration-fatigue analysis typically requires the structural dynamics analysis, the response analysis and the fatigue analysis. The material parameters (S-N curve) are obtained at uniaxial stress state. However, in real structures the stress state is rarely uniaxial and the direct application of the S-N curve is difficult. The stress tensor is reduced to a more manageable representation using a multiaxial criterion. In this study, maximum normal stress, maximum shear stress, maximum normal-and-shear stress, C-S criterion, Projection-by- Projection and the Preumont and Piéfort criterion for multiaxial stress state are compared theoretically and experimentally. The crack location and the time-to-failure were compared. The time-to-failure was found relatively accurate with all multiaxial criteria; however, the crack-location estimation was found not to be accurate enough for either of the compared criteria. The study proves the applicability of the vibration-fatigue analysis procedure on real vibrating structures with rich structural dynamics. Random vibration excitation is a common cause of failure, especially if natural dynamics is excited. The high-cycle vibration-fatigue analysis typically requires the structural dynamics analysis, the response analysis and the fatigue analysis. The material parameters (S-N curve) are obtained at uniaxial stress state. However, in real structures the stress state is rarely uniaxial and the direct application of the S-N curve is difficult. The stress tensor is reduced to a more manageable representation using a multiaxial criterion. In this study, maximum normal stress, maximum shear stress, maximum normaland-shear stress, C-S criterion, Projection-by-Projection and the Preumont and Piéfort criterion for multiaxial stress state are compared theoretically and experimentally. The crack location and the time

  8. Multiaxis Rainflow Fatigue Methods for Nonstationary Vibration

    Science.gov (United States)

    Irvine, T.

    2016-01-01

    Mechanical structures and components may be subjected to cyclical loading conditions, including sine and random vibration. Such systems must be designed and tested accordingly. Rainflow cycle counting is the standard method for reducing a stress time history to a table of amplitude-cycle pairings prior to the Palmgren-Miner cumulative damage calculation. The damage calculation is straightforward for sinusoidal stress but very complicated for random stress, particularly for nonstationary vibration. This paper evaluates candidate methods and makes a recommendation for further study of a hybrid technique.

  9. Multiaxis Rainflow Fatigue Methods for Nonstationary Vibration

    Science.gov (United States)

    Irvine, T.

    2016-09-01

    Mechanical structures and components may be subjected to cyclical loading conditions, including sine and random vibration. Such systems must be designed and tested according. Rainflow cycle counting is the standard method for reducing a stress time history to a table of amplitude-cycle pairings prior to the Palmgren-Miner cumulative damage calculation. The damage calculation is straightforward for sinusoidal stress but very complicated for random stress, particularly for nonstationary vibration. This paper evaluates candidate methods and makes a recommendation for further study of a hybrid technique.

  10. Experimental Design and Validation of an Accelerated Random Vibration Fatigue Testing Methodology

    OpenAIRE

    Yu Jiang(Center for Statistical and Theoretical Condensed Matter Physics, Zhejiang Normal University, Jinhua City, Zhejiang Province 321004, China); Gun Jin Yun; Li Zhao; Junyong Tao

    2015-01-01

    Novel accelerated random vibration fatigue test methodology and strategy are proposed, which can generate a design of the experimental test plan significantly reducing the test time and the sample size. Based on theoretical analysis and fatigue damage model, several groups of random vibration fatigue tests were designed and conducted with the aim of investigating effects of both Gaussian and non-Gaussian random excitation on the vibration fatigue. First, stress responses at a weak point of a ...

  11. Comparison between dog-bone and Gaussian specimens for size effect evaluation in gigacycle fatigue

    Directory of Open Access Journals (Sweden)

    A. Tridello

    2013-10-01

    Full Text Available Gigacycle fatigue properties of materials are strongly affected by the specimen risk volume (volume of material subjected to a stress amplitude larger than the 90% of the maximum stress. Gigacycle fatigue tests, performed with ultrasonic fatigue testing machines, are commonly carried out by using hourglass shaped specimens with a small risk volume. The adoption of traditional dog-bone specimens allows for increasing the risk volume, even if the increment is quite limited. In order to obtain larger risk volumes, a new specimen shape is proposed (Gaussian specimen. The dog-bone and the Gaussian specimens are compared through Finite Element Analyses and the numerical results are validated experimentally by means of strain gages measurements. The range of applicability of the two different specimens in terms of available risk volume and stress concentration effects due to the cross section variation is determined.

  12. Axial-torsional fatigue: A study of tubular specimen thickness effects

    Science.gov (United States)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1990-01-01

    A room-temperature experimental program was conducted on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behavior and fatigue life of thin-wall, tubular, axial-torsional fatigue specimens. The following experimental variables were examined in this study: the depth of the surface work-hardened layer produced in specimen machining, and the effects of strain range and axial-torsional strain phasing. Tubular fatigue specimens were fabricated with wall thicknesses of 1.5, 2.0, and 2.5 mm. One as-fabricated specimen from each wall thickness was sectioned for microstructural examination and microhardness measurement. A specimen of each wall thickness was tested at each of three conditions - high strain range in-phase, low strain range in-phase, and low strain range out-of-phase - for a total of nine axial-torsional fatigue experiments. The machining-induced work-hardened zone, as a percentage of the gage section material, was found to have a minimal effect on both deformation behavior and fatigue life. Also, little or no variation in fatigue life or deformation behavior as a function of wall thickness was observed. Out-of-phase fatigue tests displayed shorter fatigue lives and more cyclic hardening than in-phase tests.

  13. Rotorcraft airframe structural optimization for combined vibration and fatigue constraints

    Science.gov (United States)

    Sareen, Ashish K.; Schrage, Daniel P.; Murthy, T. S.

    1991-01-01

    This paper addresses the application of a formal optimization technique in rotorcraft airframe structural design studies to reduce the structural weight, to lower airframe vibrations, and to enhance fatigue life of the structure. Vibration and fatigue considerations in airframe design are described. An optimization methodology based on the use of a nonlinear programming technique to size airframe structural members subjected to constraints on weight, vibration response and fatigue stresses under dynamic loads, are described. The paper focuses on the development of necessary computational tools for airframe structural optimization and describes the sensitivity analysis procedure for these types of design constraints. Further, the paper describes the optimization procedure as implemented in a computer code called DYNOPT which is a unique operational combination of several newly developed Fortran codes as well as modification of existing codes consisting of the direct matrix abstraction modules of the MSC/NASTRAN Program and CONMIN optimizer. The application of the optimization procedure is demonstrated using an elastic-line model of the Bell AH-1G helicopter airframe structure and computational results are discussed.

  14. Axial-torsional fatigue - A study of tubular specimen thickness effects

    Science.gov (United States)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1993-01-01

    Experiments were carried out at room temperature on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behavior and fatigue life of thin-wall tubular axial-torsional fatigue specimens. The experimental variables examined included the depth of the surface work-hardened layer produced in specimen machining, and the effects of strain range and axial-torsional strain phasing. Tubular fatigue specimens had wall thicknesses of 1.5, 2.0, and 2.5 mm. One as-fabricated specimen from each wall thickness was sectioned for microstructural examination and microhardness measurement. A specimen of each wall thickness was tested in axial-torsional fatigue experiments for each of the three conditions: high strain range in-phase, low strain range in-phase, and low strain range out-of-phase. The machining-induced work-hardened zone, as a percentage of the gage section material, was found to have a minimal effect on both deformation behavior and fatigue life. Out-of-phase fatigue tests displayed shorter fatigue lives and more cyclic hardening than in-phase tests.

  15. Fatigue life estimation for different notched specimens based on the volumetric approach

    Science.gov (United States)

    Zehsaz, M.; Hassanifard, S.; Esmaeili, F.

    2010-06-01

    In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

  16. Fatigue life estimation for different notched specimens based on the volumetric approach

    Directory of Open Access Journals (Sweden)

    Esmaeili F.

    2010-06-01

    Full Text Available In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

  17. Fatigue Failure Results for Multi-Axial versus Uniaxial Stress Screen Vibration Testing

    Directory of Open Access Journals (Sweden)

    Wayne E. Whiteman

    2002-01-01

    Full Text Available To date, the failure potential and prediction between simultaneous multi-axial versus sequentially applied uniaxial vibration stress screen testing has been the subject of great debate. In most applications, current vibration tests are done by sequentially applying uniaxial excitation to the test specimen along three orthogonal axes. The most common standards for testing military equipment are published in MIL-STD-810F and NAVMAT P-9492. Previous research had shown that uniaxial testing may be unrealistic and inadequate. This current research effort is a continuing effort to systematically investigate the differences between fatigue damage mechanisms and the effects of uniaxial versus tri-axial testing. This includes assessing the ability of the tri-axial method in predicting the formation of damage mechanisms, specifically looking at the effects of stress or fatigue failure. Multi-axial testing achieves the synergistic effect of exciting all modes simultaneously and induces a more realistic vibration stress loading condition. As such, it better approximates real-world operating conditions. This paper provides the latest results on the differences between multi-axial and uniaxial testing of a simple notched cantilever beam.

  18. Fatigue failure of materials under narrow band random vibrations. I.

    Science.gov (United States)

    Huang, T. C.; Hubbard, R. B.; Lanz, R. W.

    1971-01-01

    A novel approach for the study of fatigue failure of materials under the multifactor influence of narrow band random vibrations is developed. The approach involves the conduction of an experiment in conjunction with various statistical techniques. Three factors including two statistical properties of the excitation or response are considered and varied simultaneously. A minimum of 6 tests for 3 variables is possible for a fractional f actorial design. The four coefficients of the predicting equation can be independently estimated. A look at 3 predicting equations shows the predominant effect of the root mean square stress of the first order equation.

  19. Crack initiation in smooth fatigue specimens of austenitic stainless steel in light water reactor environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Smith, J. L.

    1999-04-08

    The fatigue design curves for structural materials specified in Section III of the ASME Boiler and Pressure Vessel Code are based on tests of smooth polished specimens at room temperature in air. The effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves; however, recent test data illustrate the detrimental effects of LWR coolant environments on the fatigue resistance of austenitic stainless steels (SSs). Certain loading and environmental conditions have led to test specimen fatigue lives that are significantly shorter than those obtained in air. Results of fatigue tests that examine the influence of reactor environments on crack initiation and crack growth of austenitic SSs are presented. Block loading was used to mark the fracture surface to determine crack length as a function of fatigue cycles in water environments, Crack lengths were measured by scanning electron microscopy. The mechanism for decreased fatigue life in LWR environments is discussed, and crack growth rates in the smooth fatigue specimens are compared with existing data from studies of crack growth rates.

  20. Crack path for run-out specimens in fatigue tests: is it belonging to high- or very-high-cycle fatigue regime?

    Directory of Open Access Journals (Sweden)

    A. Shanyavskiy

    2015-10-01

    Full Text Available Fatigue tests run-out specimens up to 106 – 5x107 load cycles are used to determine the stress level named “fatigue limit”. Nevertheless, it is not clear what kind of fatigue cracking takes or will take place in these specimens. To discuss this problem, fatigue tests of titanium alloy VT3-1 specimens have been performed under tension with different values of R-ratio and under rotating-bending after various thermo-mechanical treatments (tempering, surface hardening and their combinations. Well-known S-N curves in High-Cycle- Fatigue regime have been plotted with run-out specimens usually used for “fatigue limit” determination. Then, after fatigue tests, run-out specimens have been tensed up to their failure, and fracture surface analyses have been performed for all tested specimens. It is found that run-out specimens in all combinations of treatments, for different R-ratio, have fracture surfaces for crack path in Very-High-Cycle-Fatigue regime. Based on this result, all S-N curves have been reconstructed in duplex curves for High- and Very-High-Cycle-Fatigue regime without using knowledge about “fatigue limit”. Detailed fracture surfaces analyses have been developed, and crack paths have been compared for various combinations of materials and surface states.

  1. Face/core debond fatigue crack growth characterization using the sandwich mixed mode bending specimen

    DEFF Research Database (Denmark)

    Manca, Marcello; Quispitupa, Amilcar; Berggreen, Christian

    2012-01-01

    Face/core fatigue crack growth in foam-cored sandwich composites is examined using the mixed mode bending (MMB) test method. The mixed mode loading at the debond crack tip is controlled by changing the load application point in the MMB test fixture. Sandwich specimens were manufactured using H45...... and H100 PVC foam cores and E-glass/polyester face sheets. All specimens were pre-cracked in order to define a sharp crack front. The static debond fracture toughness for each material configuration was measured at different mode-mixity phase angles. Fatigue tests were performed at 80% of the static...

  2. Observation of fracture behavior of 3-D printed specimens under rolling contact fatigue in water

    Directory of Open Access Journals (Sweden)

    Mizobe Koshiro

    2017-01-01

    Full Text Available Polymer bearing was widely used in the corrosive conditions because of its high corrosion durability. The polymer bearing had been formed using molding and machining until the new 3-D printing method was developed. In this study, we performed the rolling contact fatigue tests of the 3-D printed specimens in water and observed the fracture behaviour of the specimens. We found that the surface cracks are related to both the rolling direction and the lamination directions.

  3. Analysis of muscle fatigue induced by isometric vibration exercise at varying frequencies.

    Science.gov (United States)

    Mischi, M; Rabotti, C; Cardinale, M

    2012-01-01

    An increase in neuromuscular activity, measured by electromyography (EMG), is usually observed during vibration exercise. The underlying mechanisms are however unclear, limiting the possibilities to introduce and exploit vibration training in rehabilitation programs. In this study, a new training device is used to perform vibration exercise at varying frequency and force, therefore enabling the analysis of the relationship between vibration frequency and muscle fatigue. Fatigue is estimated by maximum voluntary contraction measurement, as well as by EMG mean-frequency and conduction-velocity analysis. Seven volunteers performed five isometric contractions of the biceps brachii with a load consisting of a baseline of 80% of their maximum voluntary contraction (MVC), with no vibration and with a superimposed 20, 30, 40, and 50 Hz vibrational force of 40 N. Myoelectric and mechanical fatigue were estimated by EMG analysis and by assessment of the MVC decay, respectively. A dedicated motion artifact canceler, making use of accelerometry, is proposed to enable accurate EMG analysis. Use of this canceler leads to better interpolation of myoelectric fatigue trends and to better correlation between mechanical and myoelectric fatigue. In general, our results suggest vibration at 30 Hz to be the most fatiguing exercise. These results contribute to the analysis of vibration exercise and motivate further research aiming at improved training protocols.

  4. Effect of laser shock processing on fatigue life of 2205 duplex stainless steel notched specimens

    Science.gov (United States)

    Vázquez Jiménez, César A.; Gómez Rosas, Gilberto; Rubio González, Carlos; Granados Alejo, Vignaud; Hereñú, Silvina

    2017-12-01

    The effect laser shock processing (LSP) on high cycle fatigue behavior of 2205 duplex stainless steel (DSS) notched samples was investigated. The swept direction parallel (LSP 1) and perpendicular (LSP 2) to rolling were used in order to examine the sensitivity of LSP to manufacturing process since this steel present significantly anisotropy. The Nd:YAG pulsed laser operating at 10 Hz frequency and 1064 nm wavelength was utilized. The LSP configuration was the water jet mode without protective coating. Notched specimens 4 mm thick were treated on both sides, and then fatigue loading was applied with R = 0.1. The results showed that the LSP 2 condition induces higher compressive residual stresses as well as a higher fatigue life than the LSP 1 condition. By applying LSP 2 condition, an enhancement of fatigue life up to 402% is reported. In addition, the microhardness profiles showed different depths of hardening layer for each direction, according to the anisotropy observed.

  5. Electromyographic assessment of muscle fatigue during isometric vibration training at varying frequencies.

    Science.gov (United States)

    Mischi, M; Rabotti, C; Cardinale, M

    2010-01-01

    Resistance exercise is essential to improve or maintain muscle performance. Vibration training has been suggested as an alternative option for muscle conditioning, aiming especially at improving muscle strength and power. Several studies link the effects of vibration training to enhanced neuromuscular stimulation, measured by electromyography (EMG) and typically ascribed to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear, limiting the use of vibration training. This paper proposes additional methods to analyze the mechanisms involved in vibration training. A dedicated measurement setup was realized to relate vibration parameters to muscle fatigue in the biceps brachii. Fatigue is estimated by EMG mean frequency and conduction velocity assessments as well as by maximum voluntary contraction (MVC) force measurements. A modified maximum likelihood algorithm is proposed for the conduction velocity estimation based on high-density EMG recording. Five volunteers performed four isometric contractions of 50 s at 80% MVC with no vibration (control) and with superimposed vibration at 20, 30, and 40 Hz. Fatigue was estimated from the decay of force, EMG mean frequency, and EMG conduction velocity. 30-Hz vibrations represented the most fatiguing stimulus. Our preliminary results also show a better correlation between force and conduction velocity decay than between force and mean frequency decay, indicating the former as a better EMG indicator of fatigue. The proposed methods provide important advancements for the analysis of vibration exercise and guidance towards the definition of optimal training protocols.

  6. Influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates

    DEFF Research Database (Denmark)

    Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi

    2016-01-01

    in accordance with the ISO 527-5 standard and two slightly different dog-bone shaped specimens were evaluated by means of finite element modelling. Subsequent comparative fatigue tests were performed for the laminates with the three specimen types. The results showed that the test specimen type has......It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...... specimen that fails in the gauge section. The second objective was to compare fatigue performance of two laminates, one having a newly developed UD powder-bound fabric as a reinforcement and the other having a quasi-UD stitched non-crimp fabric as a reinforcement. In the first phase, a rectangular specimen...

  7. An investigation on the fatigue behavior of DCB specimen bonded with aluminum foam at Mode III

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H.; Cho, J. U. [Kongju University, Cheonan (Korea, Republic of); Zhao, G [School of Aerospace, Xian Jiaotong University, Xian (China); Cho, C. [Dept. of Mechanical Engineering, Inha University, Incheon (Korea, Republic of)

    2016-10-15

    Aluminum foam with its excellent physical and mechanical characteristics is a lightweight metallic material used with good quality in vehicle bumpers, internal shock absorbers on planes, as materials for vessel joints etc. On the contrary, when aluminum foam is used without sufficient investigation, there is the likelihood of damage or destruction of the machine or mechanical structure, and in extreme case it may cause to human casualties. This study aims to analyze the characteristics of adhesive structures with aluminum foam for the closed-type aluminum foam used primarily as shock absorbers. The fatigue analyses of the DCB test specimens at mode III with aluminum foam are verified through a fatigue experiment. As the analysis results, test specimen models with the thicknesses (t) of 35 mm, 45 mm and 55 mm showed the peak load occurrence approximately after the progress from 0 to 50 cycles. And afterwards the load gradually decreased as the cycles increased. The peak loads for each DCB test specimens were ±0.80 kN for the specimen thickness(t) of 35 mm, ±0.98 kN for the specimen thickness(t) of 45 mm and ±1.18 kN for the specimen thickness(t) of 55 mm. It is also shown that the peak load occurring on the specimen increased as specimen thickness increased. These study results are compared with the specimen thickness of 35 mm model as the basis. When the specimen thickness is increased as much as 10 mm, the peak load is increased approximately 1.25 times. When the specimen thickness is also increased as much as 20 mm, the peak load is increased 1.5 times. The analysis data and the real experiment data showed similar results each other. Therefore, it can be thought that the analysis data is applicable in real field. And it is estimated that the mechanical characteristics of the DCB test specimen at mode III during the fatigue load conditions can be systematically and efficiently analyzed.

  8. Effects of loading sequence for notched specimens under high-low two-step fatigue loading

    Science.gov (United States)

    Crews, J. H., Jr.

    1971-01-01

    The effects of loading sequence on crack-initiation period were investigated for notched aluminum-alloy specimens under high-low two-step loading with special emphasis on local cyclic stresses and strains at the notch root. Local stress and strain were determined by a procedure based on an equation proposed by Neuber which relates elastoplastic stress and strain at a notch. Local stress and strain were also measured experimentally to verify the Neuber equation. The effects of initial high load on the crack-initiation periods were demonstrated with notched specimens and were simulated in unnotched specimens fatigue tested with local stress sequences. An analysis of the results indicated that sequence effects were not caused solely by local residual stresses, as is usually assumed; the existence of a damaging effect, resulting from the high local strain cycles, was demonstrated. The sequence effects observed with notched specimens were interpreted as the combined result of residual stresses and high local strain cycles.

  9. Fatigue failure in metal bellows due to flow-induced vibrations

    Science.gov (United States)

    Daniels, C. M.; Fargo, C. G.

    1969-01-01

    To prevent fatigue due to flow-induced vibrations in metal bellows connected to ducts carrying liquid hydrogen, a study was made which shows that the flexure lines are in general a function of the vibration coupling between the fluid and bellows structure, and the nature of the external environment.

  10. Different fatigue-resistant leg muscles and EMG response during whole-body vibration.

    Science.gov (United States)

    Simsek, Deniz

    2017-12-01

    The purpose of this study was to determine the effects of static whole-body vibration (WBV) on the Electromyograhic (EMG) responses of leg muscles, which are fatigue-resistant in different manner. The study population was divided into two groups according to the values obtained by the Fatigue Index [Group I: Less Fatigue Resistant (LFR), n=11; Group II: More Fatigue Resistant (MFR), n=11]. The repeated electromyographic (EMG) activities of four leg muscles were analyzed the following determinants: (1) frequency (30 Hz, 35 Hz and 40 Hz); (2) stance position (static squat position); (3) amplitude (2 mm and 4 mm) and (4) knee flexion angle (120°), (5) vertical vibration platform. Vibration data were analyzed using Minitab 16 (Minitab Ltd, State College, PA, USA). The significance level was set at pfatigue (pvibration exercise and can serve to guide the development of training programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Fatigue of micromachined stainless steel structural materials for vibrational energy harvesting

    Science.gov (United States)

    Shimizu, Y.; Van Minh, L.; Kitayoshi, H.; Kuwano, H.

    2016-11-01

    This work presents fatigue measurement for micromachined stainless steel (SUS304) structural substrate using resonant bending mode. Micromachined specimens for fatigue test had a cantilever structure with a proof mass. They were fabricated by FeCl3 wet etching and wire-discharged cutting. The SUS specimens had Young's modulus of 198 GPa on average. The endurance limit of micromachined specimens was 213 MPa on average after 108 cycles under our fracture definition. The large SUS specimens had the endurance limit of 229 MPa after 107 cycles.

  12. The Effect of the Laboratory Specimen on Fatigue Crack Growth Rate

    Science.gov (United States)

    Forth, S. C.; Johnston, W. M.; Seshadri, B. R.

    2006-01-01

    Over the past thirty years, laboratory experiments have been devised to develop fatigue crack growth rate data that is representative of the material response. The crack growth rate data generated in the laboratory is then used to predict the safe operating envelope of a structure. The ability to interrelate laboratory data and structural response is called similitude. In essence, a nondimensional term, called the stress intensity factor, was developed that includes the applied stresses, crack size and geometric configuration. The stress intensity factor is then directly related to the rate at which cracks propagate in a material, resulting in the material property of fatigue crack growth response. Standardized specimen configurations and experimental procedures have been developed for laboratory testing to generate crack growth rate data that supports similitude of the stress intensity factor solution. In this paper, the authors present laboratory fatigue crack growth rate test data and finite element analyses that show similitude between standard specimen configurations tested using the constant stress ratio test method is unobtainable.

  13. Material Characterization of Fatigue Specimens made from Meta-stable Austenitic Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Niffenegger, M.; Grosse, M.; Kalkhof, D.; Leber, H. [Paul Scherrer Institut Villigen (Switzerland); Vincent, A.; Pasco, L.; Morin, M. [Insa de Lyon (France)

    2003-07-01

    The main objective of the EU-project CRETE (Contract No.: FIS5-1999-00280) was to assess the capability and the reliability of innovative NDT-inspection techniques for the detection of material degradation, induced by thermal fatigue and neutron irradiation, of metastable austenitic and ferritic low-alloy steel. Several project partners tested aged or irradiated samples, using various techniques (acoustic, magnetic and thermoelectric). However, these indirect methods require a careful interpretation of the measured signal in terms of micro-structural evolutions due to ageing of the material. Therefore the material had to be characterized in its undamaged, as well as in its damaged state. The present report summarises only the material characterization of the fatigue specimens. It is issued simultaneously as an PSI Bericht and the CRETE work package 3 (WP3) report. Each partner according to their own specifications purchased three materials under investigation, namely AISI 347, AISI 321 and AISI 304L. After sending the material to PSI, all fatigue specimens were manufactured by the same Swiss company. Each partner was responsible for his fatigue tests which are documented in the report WP1, written by FANP. In order to characterize the material in its unfatigued as well as in its fatigued state and to consider microstructural changes related to fatigue damage the methods listed below were employed either by PSI or by INSA de Lyon: (1) Inductive Coupled Plasma Emission Photometry (ICP-OES) was applied to determine the chemical composition, (2) Scanning electron microscopy (SEM) for observing cracks, slip bands between grain and twin boundaries, - Ferromaster for measuring the magnetic permeability, (3) Physical Properties Measuring System (PPMS) for measuring magnetization characteristics, (4) Neutron- and advanced X-ray diffraction methods for the quantitative determination of martensite, - Transmission electron microscopy (TEM) for the observation of crystalline

  14. Quantification of fatigue cracking in CT specimens with passive and active piezoelectric sensing

    Science.gov (United States)

    Yu, Jianguo; Ziehl, Paul; Zarate, Boris; Caicedo, Juan; Yu, Lingyu; Giurgiutiu, Victor; Metrovich, Brian; Matta, Fabio

    2010-04-01

    Monitoring of fatigue cracks in steel bridges is of interest to bridge owners and agencies. Monitoring of fatigue cracks has been attempted with acoustic emission using either resonant or broadband sensors. One drawback of passive sensing is that the data is limited to that caused by growing cracks. In this work, passive emission was complemented with active sensing (piezoelectric wafer active sensors) for enhanced detection capabilities. Passive and active sensing methods were described for fatigue crack monitoring on specialized compact tension specimens. The characteristics of acoustic emission were obtained to understand the correlation of acoustic emission behavior and crack growth. Crack and noise induced signals were interpreted through Swansong II Filter and waveform-based approaches, which are appropriate for data interpretation of field tests. Upon detection of crack extension, active sensing was activated to measure the crack size. Model updating techniques were employed to minimize the difference between the numerical results and experimental data. The long term objective of this research is to develop an in-service prognostic system to monitor structural health and to assess the remaining fatigue life.

  15. Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans.

    Science.gov (United States)

    Griffin, L; Garland, S J; Ivanova, T; Gossen, E R

    2001-09-15

    1. In keeping with the 'muscular wisdom hypothesis', many studies have documented that the firing rate of the majority of motor units decreased during fatiguing isometric contractions. The present study investigated whether the application of periodic muscle vibration, which strongly activates muscle spindles, would alter the modulation of motor unit firing rate during submaximal fatiguing isometric contractions. 2. Thirty-three motor units from the lateral head of the triceps brachii muscle were recorded from 10 subjects during a sustained isometric 20 % maximal voluntary contraction (MVC) of the elbow extensors. Vibration was interposed on the contraction for 2 s every 10 s. Twenty-two motor units were recorded from the beginning of the fatigue task. The discharge rate of the majority of motor units remained constant (12/22) or increased (4/22) with fatigue. Six motor units demonstrated a reduction in discharge rate that later returned toward initial values; these motor units had higher initial discharge rates than the other 16 motor units. 3. In a second series of experiments, four subjects held a sustained isometric 20 % MVC for 2 min and then vibration was applied as above for the remainder of the contraction. In this case, motor units initially demonstrated a decrease in firing rate that increased after the vibration was applied. Thus muscle spindle disfacilitation of the motoneurone pool may be associated with the decline of motor unit discharge rate observed during the first 2 min of the contraction. 4. In a third set of experiments, seven subjects performed the main experiment on one occasion and repeated the fatigue task without vibration on a second occasion. Neither the endurance time of the fatiguing contraction nor the MVC torque following fatigue was affected by the application of vibration. This finding calls into question the applicability of the muscular wisdom hypothesis to submaximal contractions.

  16. Fatigue failure of materials under broad band random vibrations

    Science.gov (United States)

    Huang, T. C.; Lanz, R. W.

    1971-01-01

    The fatigue life of material under multifactor influence of broad band random excitations has been investigated. Parameters which affect the fatigue life are postulated to be peak stress, variance of stress and the natural frequency of the system. Experimental data were processed by the hybrid computer. Based on the experimental results and regression analysis a best predicting model has been found. All values of the experimental fatigue lives are within the 95% confidence intervals of the predicting equation.

  17. Individual Optimal Frequency in Whole-Body Vibration: Effect of Protocol, Joint Angle, and Fatiguing Exercise.

    Science.gov (United States)

    Carlucci, Flaminia; Felici, Francesco; Piccinini, Alberto; Haxhi, Jonida; Sacchetti, Massimo

    2016-12-01

    Carlucci, F, Felici, F, Piccinini, A, Haxhi, J, and Sacchetti, M. Individual optimal frequency in whole-body vibration: effect of protocol, joint angle, and fatiguing exercise. J Strength Cond Res 30(12): 3503-3511, 2016-Recent studies have shown the importance of individualizing the vibration intervention to produce greater effects on the neuromuscular system in less time. The purpose of this study was to assess the individual optimal vibration frequency (OVF) corresponding to the highest muscle activation (RMSmax) during vibration at different frequencies, comparing different protocols. Twenty-nine university students underwent 3 continuous (C) and 2 random (R) different vibrating protocols, maintaining a squat position on a vibration platform. The C protocol lasted 50 seconds and involved the succession of ascending frequencies from 20 to 55 Hz, every 5 seconds. The same protocol was performed twice, having the knee angle at 120° (C) and 90° (C90), to assess the effect of joint angle and after a fatiguing squatting exercise (CF) to evaluate the influence of fatigue on OVF assessment. In the random protocols, vibration time was 20 seconds with a 2-minute (R2) and a 4-minute (R4) pauses between tested frequencies. Muscle activation and OVF values did not differ significantly in the C, R2, and R4 protocols. RMSmax was higher in C90 (p fatiguing exercise had no effect on OVF. In conclusion, the shorter C protocol produced similar myoelectrical activity in the R2 and the R4 protocols, and therefore, it could be equally valid in identifying the OVF with considerable time efficiency. Knee joint angle and fatiguing exercise had an effect on surface electromyography response during vibration but did not affect OVF identification significantly.

  18. A Specimen Size Effect on the Fatigue Crack Growth Rate Threshold of IN 718

    Science.gov (United States)

    Garr, K. R.; Hresko, G. C., III

    1998-01-01

    Fatigue crack growth rate (FCGR) tests were conducted on IN 718 in the solution annealed and aged condition at room temperature in accordance with E647-87. As part of each test, the FCGR threshold was measured using the decreasing Delta K method. A new heat of material was being tested and some of this material was sent to a different laboratory which wanted to use a specimen with a 127 mm width. Threshold data previously had been established on specimens with a width of 50.8 mm. As a check of the laboratory, tests were conducted at room temperature and R equal to 0.1 for comparison with the earlier data. The results were a threshold significantly higher than previously observed. Interchanging of specimen sizes and laboratories showed that the results were not due to a heat-to-heat or lab-to-lab variation. The results to be presented here are those obtained at the original laboratory. Growth rates were measured using the electric potential drop technique at R values of 0.1, 0.7, and 0.9. Compact tension specimen sizes with planer dimensions of 25.4 mm, 50.8 mm, and 127 mm were used. Crack growth rates at threshold were generally below 2.5 X 10(exp -8) mm / cycle. Closure measurements were made on some of the specimens by a manual procedure using a clip gage. When the crack growth rate data for the specimens tested at R equal to 0.1 were plotted as a function of applied Delta K, the thresholds varied with specimen width. The larger the width, the higher the threshold. The thresholds varied from 6.5 MPa-m(exp 1/2) for the 25.4 mm specimen to 15.4 MPa-m(exp 1/2) for the 127 mm specimen. At R equal to 0.7, the 25.4 mm and 50.8 mm specimens had essentially the same threshold, about 2.9 MPa-m(exp 1/2)while the 127 mm specimen had a threshold of 4.5 MPa-m(exp 1/2). When plotted as a function of effective Delta K, the R equal to 0.1 data are essentially normalized. Various aspects of the test procedure will be discussed as well as the results of analysis of the data using

  19. Influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates

    DEFF Research Database (Denmark)

    Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi

    2016-01-01

    It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test spec...... a significant effect on the failure mode and measured fatigue life of the laminates. A significantly higher fatigue life was measured for the laminate with the powder-bound fabric reinforcement when compared to the laminate with the stitched reinforcement.......It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...... specimen that fails in the gauge section. The second objective was to compare fatigue performance of two laminates, one having a newly developed UD powder-bound fabric as a reinforcement and the other having a quasi-UD stitched non-crimp fabric as a reinforcement. In the first phase, a rectangular specimen...

  20. Problems Associated with Statistical Pattern Recognition of Acoustic Emission Signals in a Compact Tension Fatigue Specimen

    Science.gov (United States)

    Hinton, Yolanda L.

    1999-01-01

    Acoustic emission (AE) data were acquired during fatigue testing of an aluminum 2024-T4 compact tension specimen using a commercially available AE system. AE signals from crack extension were identified and separated from noise spikes, signals that reflected from the specimen edges, and signals that saturated the instrumentation. A commercially available software package was used to train a statistical pattern recognition system to classify the signals. The software trained a network to recognize signals with a 91-percent accuracy when compared with the researcher's interpretation of the data. Reasons for the discrepancies are examined and it is postulated that additional preprocessing of the AE data to focus on the extensional wave mode and eliminate other effects before training the pattern recognition system will result in increased accuracy.

  1. Fatigue Lives of Specimens Representing Critical Locations in Mirage III Spars under Australian and Swiss Test Spectra,

    Science.gov (United States)

    1985-02-01

    short life specimens (BJ tOlD and BJI 5JB) tested at a scaling factor ofŖ.2 where there were multiple initiation sites fron tlie bottom of the chamfer...specimens. the primary fatigue crack development was from multiple initiation along the bore of the bolt hole. leading to a final crack shape

  2. Analysis of Vibration Exercise at Varying Frequencies by Different Fatigue Estimators.

    Science.gov (United States)

    Xu, Lin; Rabotti, Chiara; Mischi, Massimo

    2016-12-01

    Vibration exercise (VE) has been suggested to improve muscle strength and power performance, due to enhanced neuromuscular demand. However, understanding of the most appropriate VE protocols is lacking, limiting the optimal use of VE in rehabilitation programs. In this study, the fatiguing effect of vibration at different frequencies was investigated by employing a force-modulation VE system. Twenty volunteers performed 12-s isometric contractions of the biceps brachii with a load consisting of a baseline force of 80% of their maximum voluntary contraction (MVC) and a superimposed sinusoidal force at 0 (control condition with no vibration), 20, 30, and 40 Hz. Mechanical fatigue was estimated by assessment of MVC decay after each task while myoelectric fatigue was estimated by analysis of multichannel electromyography (EMG) signals recorded during VE. EMG conduction velocity, spectral compression, power, and fractal dimension were estimated as indicators of myoelectric fatigue. Our results suggest vibration, in particular at 30 Hz, to produce a larger degree of fatigue as compared to control condition. These results motivate further research aiming at introducing VE in rehabilitation programs with improved training protocols.

  3. Growth behavior of fatigue cracks in ultrafine grained Cu smooth specimens with a small hole

    Directory of Open Access Journals (Sweden)

    Masahiro Goto

    2015-10-01

    Full Text Available In order to study the growth mechanism of fatigue cracks in ultrafine grained copper, stresscontrolled fatigue tests of round-bar specimens with a small blind hole as a crack starter were conducted. The hole was drilled on the surface where an intersection between the shear plane of the final ECAP processing and the specimen surface makes an angle of 45° or 90° with respect to the loading axis. At a low stress (  a = 90 MPa, the direction of crack paths was nearly perpendicular to the loading direction regardless of the location of the hole. Profile of crack face was examined, showing the aspect ratio (b/a of b/a = 0.82. At a high stress (  a = 240 MPa, although the growth directions inclined 45° and 90° to the loading-axis were observed depending on the location of the drilling hole, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the final ECAP shear plane. The value of aspect ratios was b/a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions, respectively. The role of deformation mode at the crack tip areas on crack growth behavior were discussed in terms of the mixed-mode stress intensity factor. The crack path formation at high stress amplitudes was affected by the in-plane shear-mode deformation at the crack tip.

  4. Fatigue limit by thermal analysis of specimen surface in mono axial traction test

    Science.gov (United States)

    Risitano, A.; Giacomo, R.; Clienti, C.

    2010-06-01

    In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest) to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported. The corresponding value of stress was a good approximation of the fatigue limit for R = - 1, determined by the conventional method. The aim of the reported examples in this paper must be interpreted as support to the basic principle of the method and not as the results of a complete experimental planning of which we will comment in an another occasion.

  5. Fatigue limit by thermal analysis of specimen surface in mono axial traction test

    Directory of Open Access Journals (Sweden)

    Clienti C.

    2010-06-01

    Full Text Available In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported. The corresponding value of stress was a good approximation of the fatigue limit for R = - 1, determined by the conventional method. The aim of the reported examples in this paper must be interpreted as support to the basic principle of the method and not as the results of a complete experimental planning of which we will comment in an another occasion.

  6. Vibration-induced muscle fatigue, a possible contribution to musculoskeletal injury.

    Science.gov (United States)

    Adamo, Diane E; Martin, Bernard J; Johnson, Peter W

    2002-11-01

    Localized muscle fatigue resulting from 30-min sustained and intermittent grip exertions of 5% maximal voluntary contraction (MVC) with and without hand-vibration exposure (10 Hz, 7 mm displacement amplitude) was investigated. Muscle fatigue was quantified by the magnitude of the twitch force elicited in the right flexor digitorum superficialis muscle of the long finger using the low-frequency fatigue (LFF) method. The influence of vibration in the sustained grip exertion condition exacerbates fatigue as seen with the reduction in twitch force 30-60 min post-work task. Intermittent low grip force exertion conditions with and without vibration exposure show negligible fatigue, suggesting the benefit of rest in the work cycle. Perception of muscle fatigue was dissociated from the objective measure of twitch force, suggesting that LFF was not perceived. The presence of LFF and the lack of perception of LFF may increase the risk for the development of musculoskeletal disorders. The findings of this study may apply to the design of the work cycles and tasks that require the use of vibratory tools.

  7. Nondestructive determination of fatigue crack damage in composites using vibration tests.

    Science.gov (United States)

    Dibenedetto, A. T.; Gauchel, J. V.; Thomas, R. L.; Barlow, J. W.

    1972-01-01

    The vibration response of glass reinforced epoxy and polyester laminates was investigated. The complex modulus and the damping capacity were measured as fatigue crack damage accumulated. Changes in the Young's modulus as well as the damping capacity correlated with the amount of crack damage. The damping was especially sensitive to debonding of the reinforcement from the resin matrix. Measurement of these vibration response changes shows promise as a means to nondestructively test the structural integrity of filament-reinforced composite structural members.

  8. High frequency vibration conditioning stimulation centrally reduces myoelectrical manifestation of fatigue in healthy subjects.

    Science.gov (United States)

    Casale, Roberto; Ring, Haim; Rainoldi, Alberto

    2009-10-01

    Vibration conditioning has been adopted as a tool to improve muscle force and reduce fatigue onset in various rehabilitation settings. This study was designed to asses if high frequency vibration can induce some conditioning effects detectable in surface EMG (sEMG) signal; and whether these effects are central or peripheral in origin. 300 Hz vibration was applied for 30 min during 5 consecutive days, to the right biceps brachii muscle of 10 healthy males aged from 25 to 50 years. sEMG was recorded with a 16 electrode linear array placed on the skin overlying the vibrated muscle. The test protocol consisted of 30% and 60% maximal voluntary contraction (MVC) as well as involuntary (electrically elicited) contractions before and after treatment. No statistically significant differences were found between PRE and POST vibration conditioning when involuntary stimulus-evoked contraction and 30% MVC were used. Significant differences in the initial values and rates of change of muscle fibre conduction velocity were found only at 60% MVC. 300 Hz vibration did not induce any peripheral changes as demonstrated by the lack of differences when fatigue was electrically induced. Differences were found only when the muscle was voluntarily fatigued at 60% MVC suggesting a modification in the centrally driven motor unit recruitment order, and interpreted as an adaptive response to the reiteration of the vibratory conditioning.

  9. The effect of fatigue on abnormal vibration induced illusion of movement in idiopathic focal dystonia.

    Science.gov (United States)

    Frima, N; Rome, S M; Grünewald, R A

    2003-08-01

    Perception of vibration induced illusionary movement (VIIM) is subnormal in dystonic patients, suggesting abnormal sensory-motor processing in patients with idiopathic focal dystonia. To examine the effects of fatigue on VIIM in patients with idiopathic torticollis. An illusionary sensation of arm extension was evoked by an 80 Hz transcutaneous vibratory stimulus applied to the biceps brachii tendon while the arm was restrained. Blindfolded patients attempted to copy the perceived movement of the vibrated arm with the opposite (tracking) arm and the change in elbow angle of the tracking arm was quantified over 45 seconds. The tasks were repeated following volitional fatigue of the vibrated arm. The subnormal perception of VIIM perceived by patients with torticollis, occurring bilaterally and remote from the location of dystonic symptoms, was corrected by fatigue of the vibrated arm compared with prefatigue values (mean (SEM): 19.04 degrees (1.76) degrees v 24.25 degrees (2.41 degrees ); p = 0.01, paired t test). While a combination of central or peripheral factors may be involved in the correction of abnormal perception of the vibration induced illusion of movement in dystonia, subnormal elasticity of muscle spindles could be implicated in the impaired perception of vibration induced illusionary movement and may predispose an individual towards developing idiopathic focal dystonia.

  10. Space Shuttle Crawler Transporter Vibration Analysis in Support of Rollout Fatigue Load Spectra Verification Program

    Science.gov (United States)

    Margasahayam, Ravi N.; Meyer, Karl A.; Nerolich, Shaun M.; Burton, Roy C.; Gosselin, Armand M.

    2004-01-01

    The Crawler Transporter (CT), designed and built for the Apollo Program in the 1960's and surpassing its initial operational life, has become an integral part of the Space Shuttle Program (SSP). The CT transports the Space Shuttle Vehicle (SSV) stack, atop the Mobile Launch Platform (MLP), from the Vehicle Assembly Building (VAB) to the launch pad. This support structure provides hydraulic jacking, leveling and load equalization for the 12 million pound stack on its 3.5-5.0 mile rollout to the launch pad. Major elements of the SSV, consisting of the orbiter, solid rocket boosters (SRB) and external tank (ET) have required fatigue analyses as part of the mission life certification. Compared to rollout vibration, the SSV sees relatively high vibration loads during launch, ascent, descent and landing phases of the mission. Although preliminary measured SRB vibration levels during rollout were of low amplitude and frequency, the duration of the rollout phase is typically high, from 5-6 hours. As part of an expanded mission life assessment, additional certification effort was initiated to define fatigue load spectra for rollout. This study addresses the CT vibration analyses in support of the rollout fatigue study. Structural models developed for modal and vibration analyses were used to identify unique CT, CT/MLP and CT/MLP/SRB vibration characteristics for comparison to instrumented rollout tests. Whereas the main structural and vibration characteristics of the SSV are well defined, minimum analytical and vibration test data on the Crawler Transporter were available. Unique vibration characteristics of the CT are attributable to the drive mechanism, hydraulic jacking system, structural framing and the CT-to-MLP support pad restraints. Initial tests performed on the CT/MLP/SRB configuration showed reasonable correlation with predicted mode shapes and frequencies.

  11. The detection of tightly closed flaws by nondestructive testing (NDT) methods. [fatigue crack formation in aluminum alloy test specimens

    Science.gov (United States)

    Rummel, W. D.; Rathke, R. A.; Todd, P. H., Jr.; Mullen, S. J.

    1975-01-01

    Liquid penetrant, ultrasonic, eddy current and X-radiographic techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens in integrally stiffened panel, and weld panel configurations. Fatigue cracks in integrally stiffened panels, lack-of-fusion in weld panels, and fatigue cracks in weld panels were the flaw types used for evaluation. A 2319 aluminum alloy weld filler rod was used for all welding to produce the test specimens. Forty seven integrally stiffened panels containing a total of 146 fatigue cracks, ninety three lack-of-penetration (LOP) specimens containing a total of 239 LOP flaws, and one-hundred seventeen welded specimens containing a total of 293 fatigue cracks were evaluated. Nondestructive test detection reliability enhancement was evaluated during separate inspection sequences in the specimens in the 'as-machined or as-welded', post etched and post proof loaded conditions. Results of the nondestructive test evaluations were compared to the actual flaw size obtained by measurement of the fracture specimens after completing all inspection sequences. Inspection data were then analyzed to provide a statistical basis for determining the flaw detection reliability.

  12. The Effects of Vibration and Muscle Fatigue on Trunk Sensorimotor Control in Low Back Pain Patients

    Science.gov (United States)

    Abboud, Jacques; Nougarou, François; Normand, Martin C.

    2015-01-01

    Introduction Changes in sensorimotor function and increased trunk muscle fatigability have been identified in patients with chronic low back pain (cLBP). This study assessed the control of trunk force production in conditions with and without local erector spinae muscle vibration and evaluated the influence of muscle fatigue on trunk sensorimotor control. Methods Twenty non-specific cLBP patients and 20 healthy participants were asked to perform submaximal isometric trunk extension torque with and without local vibration stimulation, before and after a trunk extensor muscle fatigue protocol. Constant error (CE), variable error (VE) as well as absolute error (AE) in peak torque were computed and compared across conditions. Trunk extensor muscle activation during isometric contractions and during the fatigue protocol was measured using surface electromyography (sEMG). Results Force reproduction accuracy of the trunk was significantly lower in the patient group (CE = 9.81 ± 2.23 Nm; AE = 18.16 ± 3.97 Nm) than in healthy participants (CE = 4.44 ± 1.68 Nm; AE = 12.23 ± 2.44 Nm). Local erector spinae vibration induced a significant reduction in CE (4.33 ± 2.14 Nm) and AE (13.71 ± 3.45 Nm) mean scores in the patient group. Healthy participants conversely showed a significant increase in CE (8.17 ± 2.10 Nm) and AE (16.29 ± 2.82 Nm) mean scores under vibration conditions. The fatigue protocol induced erector spinae muscle fatigue as illustrated by a significant decrease in sEMG median time-frequency slopes. Following the fatigue protocol, patients with cLBP showed significant decrease in sEMG root mean square activity at L4-5 level and responded in similar manner with and without vibration stimulation in regard to CE mean scores. Conclusions Patients with cLBP have a less accurate force reproduction sense than healthy participants. Local muscle vibration led to significant trunk neuromuscular control improvements in the cLBP patients before and after a muscle

  13. The Effects of Vibration and Muscle Fatigue on Trunk Sensorimotor Control in Low Back Pain Patients.

    Directory of Open Access Journals (Sweden)

    Jean-Alexandre Boucher

    Full Text Available Changes in sensorimotor function and increased trunk muscle fatigability have been identified in patients with chronic low back pain (cLBP. This study assessed the control of trunk force production in conditions with and without local erector spinae muscle vibration and evaluated the influence of muscle fatigue on trunk sensorimotor control.Twenty non-specific cLBP patients and 20 healthy participants were asked to perform submaximal isometric trunk extension torque with and without local vibration stimulation, before and after a trunk extensor muscle fatigue protocol. Constant error (CE, variable error (VE as well as absolute error (AE in peak torque were computed and compared across conditions. Trunk extensor muscle activation during isometric contractions and during the fatigue protocol was measured using surface electromyography (sEMG.Force reproduction accuracy of the trunk was significantly lower in the patient group (CE = 9.81 ± 2.23 Nm; AE = 18.16 ± 3.97 Nm than in healthy participants (CE = 4.44 ± 1.68 Nm; AE = 12.23 ± 2.44 Nm. Local erector spinae vibration induced a significant reduction in CE (4.33 ± 2.14 Nm and AE (13.71 ± 3.45 Nm mean scores in the patient group. Healthy participants conversely showed a significant increase in CE (8.17 ± 2.10 Nm and AE (16.29 ± 2.82 Nm mean scores under vibration conditions. The fatigue protocol induced erector spinae muscle fatigue as illustrated by a significant decrease in sEMG median time-frequency slopes. Following the fatigue protocol, patients with cLBP showed significant decrease in sEMG root mean square activity at L4-5 level and responded in similar manner with and without vibration stimulation in regard to CE mean scores.Patients with cLBP have a less accurate force reproduction sense than healthy participants. Local muscle vibration led to significant trunk neuromuscular control improvements in the cLBP patients before and after a muscle fatigue protocol. Muscle vibration

  14. The Effects of Vibration and Muscle Fatigue on Trunk Sensorimotor Control in Low Back Pain Patients.

    Science.gov (United States)

    Boucher, Jean-Alexandre; Abboud, Jacques; Nougarou, François; Normand, Martin C; Descarreaux, Martin

    2015-01-01

    Changes in sensorimotor function and increased trunk muscle fatigability have been identified in patients with chronic low back pain (cLBP). This study assessed the control of trunk force production in conditions with and without local erector spinae muscle vibration and evaluated the influence of muscle fatigue on trunk sensorimotor control. Twenty non-specific cLBP patients and 20 healthy participants were asked to perform submaximal isometric trunk extension torque with and without local vibration stimulation, before and after a trunk extensor muscle fatigue protocol. Constant error (CE), variable error (VE) as well as absolute error (AE) in peak torque were computed and compared across conditions. Trunk extensor muscle activation during isometric contractions and during the fatigue protocol was measured using surface electromyography (sEMG). Force reproduction accuracy of the trunk was significantly lower in the patient group (CE = 9.81 ± 2.23 Nm; AE = 18.16 ± 3.97 Nm) than in healthy participants (CE = 4.44 ± 1.68 Nm; AE = 12.23 ± 2.44 Nm). Local erector spinae vibration induced a significant reduction in CE (4.33 ± 2.14 Nm) and AE (13.71 ± 3.45 Nm) mean scores in the patient group. Healthy participants conversely showed a significant increase in CE (8.17 ± 2.10 Nm) and AE (16.29 ± 2.82 Nm) mean scores under vibration conditions. The fatigue protocol induced erector spinae muscle fatigue as illustrated by a significant decrease in sEMG median time-frequency slopes. Following the fatigue protocol, patients with cLBP showed significant decrease in sEMG root mean square activity at L4-5 level and responded in similar manner with and without vibration stimulation in regard to CE mean scores. Patients with cLBP have a less accurate force reproduction sense than healthy participants. Local muscle vibration led to significant trunk neuromuscular control improvements in the cLBP patients before and after a muscle fatigue protocol. Muscle vibration stimulation

  15. Study on Fatigue Crack of Supporting Plate on Sonic Vibration Head

    Directory of Open Access Journals (Sweden)

    Wang Yu

    2014-04-01

    Full Text Available The supporting plate is one of the key parts of the sonic vibration head, and the regular fatigue and fracture make the support plate be one of the most venerably damaged units, resulting in huge loss in economy and security. After analyzing the loading states of the supporting plate on sonic vibration head, the mechanical stresses of three kinds of supporting plate under different operation load cases are simulated by the method of finite element method (FEM. The effects of stress of supporting plate are studied by means of fatigue testing on actual drilling processing. The results show that the steel structures fatigue failure is caused by stress concentration and unbalance. The optimal supporting plate structure is selected by the simulation and test.

  16. Quality Factor and Microslipping of Fatigue Cracks in Thin Plates at Resonant Vibration

    Science.gov (United States)

    Wincheski, B.; Namkung, M.; Fulton, J. P.

    1993-01-01

    Resonant vibrations have been stimulated in thin metal plates using a non-contacting electromagnetic driver. A sinusoidal force was applied in a swept frequency fashion and the resulting surface displacements were monitored through the use of an acoustic microphone. It has been found that the presence of a fatigue crack in the sample causes a broadening of the second resonance peak. The Q factors of the resonance curves were determined and are directly correlated with the presence of fatigue cracks in the samples. The broadening of the curves is explained in terms of a microslipping at the crack face walls which reduces the amplitude of the resonant vibration by increasing the damping of the system. A comparison is made between the resonance characteristics of fatigue damaged and notched samples, where the stiffness of the two systems is nearly constant while the interaction between crack face walls is eliminated in the latter.

  17. Effect of different vibration frequencies on heart rate variability and driving fatigue in healthy drivers.

    Science.gov (United States)

    Jiao, Kun; Li, Zengyong; Chen, Ming; Wang, Chengtao; Qi, Shaohua

    2004-04-01

    This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV) and driving fatigue in healthy subjects during simulated driving, by the use of power spectrum analysis and subjective evaluation. Sixty healthy subjects (29.6+/-3.3 years) were randomly divided into three groups, A, B and C, and the subjects of each group participated in the simulated driving for 90 min with vertical sinusoidal vibration (acceleration 0.05 g) of 1.8 Hz (group A), 6 Hz (group B) and no vibration (group C), respectively. Low-frequency (LF) and high-frequency (HF) components of HRV, reflecting sympathetic and parasympathetic activities, and the LF:HF ratio, indicating sympathovagal balance, were measured throughout all periods. All indices of HRV were calculated in the pre-experiment period, mid-experiment period and end-experiment period, and were analyzed by repeated measures analysis of variance. Subjective responses to a questionnaire were obtained after the simulated task for the three groups. Significant differences in all indices of HRV were observed between different experiment periods and between any two groups. The ratings of subjective fatigue exhibited significant differences between any two groups. The drivers' fatigue ratings were associated with vibration frequencies in simulated driving. The study quantitatively demonstrated that different effects on autonomic nerve activities were induced by different vibration frequencies.

  18. Back muscle EMG of helicopter pilots in flight: effects of fatigue, vibration, and posture.

    Science.gov (United States)

    de Oliveira, Carlos Gomes; Nadal, Jurandir

    2004-04-01

    The high prevalence of low back pain in helicopter pilots has been attributed to back muscle fatigue due to a pilot's required posture and/or aircraft vibration. This study investigated the effect of posture and vibration on the surface electromyogram (EMG) of right and left erector spinae (ES) muscles of pilots and evaluated ES fatigue during flight. There were 12 male pilots who were monitored during helicopter flights lasting an average of 2 h. Prior to the flight, a maximal voluntary contraction (MVC) of ES was performed and the EMG was recorded. Vibration was measured at the pilot's seat through a triaxial accelerometer. The effect of posture on EMG was tested by comparing four characteristics of left and right EMG expressed as % MVC. Effect of Z vibration on EMG was investigated by coherence function and through correlation between coherently averaged EMG and Z for the frequencies of the main rotor of the helicopter (1R) and its first harmonic (2R). Fatigue was investigated through median frequencies (MF) of the EMG power spectra. No effect of posture on EMG was found for any parameter (p > 0.05). Data from one pilot suggested an effect of 1R on EMG, but statistical tests revealed this not to be significant (p > 0.05) for any pilot. No fatigue was evidenced by linear regression of MF. While the scientific literature contains the hypothesis that low back pain in helicopter pilots is mainly due to muscle fatigue caused by posture and/or vibration, the present study did not lend support to this hypothesis.

  19. Apparatus and method for fatigue testing of a material specimen in a high-pressure fluid environment

    Science.gov (United States)

    Wang, Jy-An; Feng, Zhili; Anovitz, Lawrence M; Liu, Kenneth C

    2013-06-04

    The invention provides fatigue testing of a material specimen while the specimen is disposed in a high pressure fluid environment. A specimen is placed between receivers in an end cap of a vessel and a piston that is moveable within the vessel. Pressurized fluid is provided to compression and tension chambers defined between the piston and the vessel. When the pressure in the compression chamber is greater than the pressure in the tension chamber, the specimen is subjected to a compression force. When the pressure in the tension chamber is greater than the pressure in the compression chamber, the specimen is subjected to a tension force. While the specimen is subjected to either force, it is also surrounded by the pressurized fluid in the tension chamber. In some examples, the specimen is surrounded by hydrogen.

  20. Fatigue Crack Propagation from Notched Specimens of 304 SS in elevated Temperature Aqueous Environment

    Energy Technology Data Exchange (ETDEWEB)

    Wire, G. L.; Mills, W. J.

    2002-08-01

    Fatigue crack propagation (FCP) rates for 304 stainless steel (304SS) were determined in 24 degree C and 288 degree C air and 288 degree C water using double-edged notch (DEN) specimens of 304 stainless steel (304 SS). Test performed at matched loading conditions in air and water at 288 degree C with 20-6- cc h[sub]2/kg h[sub]2O provided a direct comparison of the relative crack growth rates in air and water over a wide range of crack growth rates. The DEN crack extension ranged from short cracks (0.03-0.25 mm) to long cracks up to 4.06 mm, which are consistent with conventional deep crack tests. Crack growth rates of 304 SS in water were about 12 times the air rate. This 12X environmental enhancement persisted to crack extensions up to 4.06 mm, far outside the range associated with short crack effects. The large environmental degradation for 304 SS crack growth is consistent with the strong reduction of fatigue life in high hydrogen water. Further, very similar environmental effects w ere reported in fatigue crack growth tests in hydrogen water chemistry (HWC). Most literature data in high hydrogen water show only a mild environmental effect for 304 SS, of order 2.5 times air or less, but the tests were predominantly performed at high cyclic stress intensity or equivalently, high air rates. The environmental effect in low oxygen environments at low stress intensity depends strongly on both the stress ratio, R, and the load rise time, T[sub]r, as recently reported for austenitic stainless steel in BWR water. Fractography was performed for both tests in air and water. At 288 degree C in water, the fracture surfaces were crisply faceted with a crystallographic appearance, and showed striations under high magnification. The cleavage-like facets on the fracture surfaces suggest that hydrogen embrittlement is the primary cause of accelerated cracking.

  1. Fatigue damage observed non-destructively in fibre composite coupon test specimens by X-ray CT

    DEFF Research Database (Denmark)

    Jespersen, Kristine Munk; Mikkelsen, Lars Pilgaard

    2016-01-01

    This study presents a method for monitoring the 3D fatigue damage progression on a micro-structural level in a glass fibre/polymer coupon test specimen by means of laboratory X-ray Computed Tomography (CT). A modified mount and holder made for the standard test samples to fit into the X-ray CT...... scanner along with a tension clamp solution is presented. Initially, the same location of the test specimen is inspected by ex-situ X-ray CT during the fatigue loading history, which shows the damage progression on a micro-structural level. The openings of individual uni-directional (UD) fibre fractures...

  2. Asphalt Mixture Fatigue Testing : Influence of Test Type and Specimen Size

    NARCIS (Netherlands)

    Li, N.

    2013-01-01

    Fatigue characterization of an asphalt mixture is commonly estimated by laboratory fatigue tests. Based on the classical fatigue analysis, fatigue lives obtained from different test devices are not comparable even when they are performed at the same test conditions. It is believed that there are two

  3. Assessing the severity of fatigue crack using acoustics modulated by hysteretic vibration for a cantilever beam

    Science.gov (United States)

    He, Qingbo; Lin, Yin

    2016-05-01

    This paper investigates fatigue crack severity assessment using acoustics modulated by hysteretic vibration for a cantilever beam. In this study, a nonlinear oscillator system is constructed to induce the hysteretic frequency response of the cantilever beam in dynamics, and the hysteretic vibration is then used to modulate the acoustic waves to generate the vibro-acoustic modulation (VAM) effect. Through modulation of hysteretic vibration, the hysteretic response of the VAM can be achieved. The experimental results further validated that the VAM hysteresis phenomenon can be enhanced with the increase of crack severity owing to the change of beam's effective stiffness. Simulations in the proposed physical model explained the reason of enhancement of hysteresis phenomenon. Combined with nonlinear bistable structural model, a fatigue crack severity assessment approach was proposed by evaluating the hysteretic region (e.g., bandwidth or jumping frequency) in the vibration frequency response of the VAM effect. The reported study is valuable in building a monotonic relationship to assess the severity of fatigue crack by a nonlinear acoustics approach.

  4. Effect of NaCl Solution Spraying on Fatigue Lives of Smooth and Slit Specimens of 0.37% Carbon Steel

    Science.gov (United States)

    Makabe, Chobin; Ferdous, Md. Shafiul; Shimabukuro, Akimichi; Murdani, Anggit

    2017-07-01

    The fatigue crack initiation life and growth rate are affected by experimental conditions. A corrosive environment can be created in a laboratory by means of dropping salt water onto the specimen surface, spraying chloride mist into the experimental chamber, etc. In the case of smooth specimens of some metals, fatigue life is shortened and the fatigue limit disappears under such corrosive experimental conditions. In this study, the effects of intermittent spraying of 3% NaCl solution-mist on corrosion fatigue behavior were investigated. The material used was 0.37% carbon steel. This is called JIS S35C in Japan. Spraying of 3% NaCl solution-mist attacked the surface layer of the specimen. It is well known that the pitting, oxidation-reduction reaction, etc. affect the fatigue strength of metals in a corrosive environment. We carried out corrosion fatigue tests with smooth specimens, holed specimens and slit specimens. Then the effects of such specimen geometry on the fatigue strength were investigated when the NaCl solution-mist was sprayed onto the specimen surface. In the case of lower stress amplitude application in slit specimens, the fatigue life in a corrosive atmosphere was longer than that in the open air. It is discussed that the behavior is related to the crack closure which happens when the oxide builds up and clogs the crack or slit.

  5. Occurrence of fatigue induced by a whole-body vibration session is not frequency dependent.

    Science.gov (United States)

    Zory, Raphael F; Raphael, Zory F; Aulbrook, Wesley; Wesley, Aulbrook; Keir, Daniel A; Daniel, Keir A; Serresse, Olivier; Olivier, Serresse

    2013-09-01

    The aim of this study was to determine whether neuromuscular adaptations (magnitude and location) induced by isometric exercise performed on an oscillating platform are dependent on whole-body vibration (WBV) frequency. Eleven young men performed 4 separate fatigue sessions of static squatting exercise at 3 frequencies of WBV (V20, V40, and V60) and 1 session without vibration (V0). Isometric torque and electromyographic activity of the vastus lateralis, rectus femoris, and biceps femoris were recorded during maximal voluntary and evoked contractions of the knee extensor muscles before and after each fatigue session to examine both peripheral and central adaptations. Isometric torque decreased significantly after each of the 4 frequency sessions (V0: -9.4 ± 6.1%, p = 0.003; V20: -8.1 ± 9.9%, p = 0.010; V40: -11.9 ± 12.7%, p = 0.011; and V60: -7.8 ± 9.2%, p = 0.001, respectively), but this reduction was not significantly different between frequencies. The torque produced by evoked contraction significantly decreased from pre-exercise values after each session (V0: -14.9 ± 15.6%, p = 0.012; V20: -15.8 ± 16.4%, p = 0.010; V40: -21.0 ± 14.3%, p = 0.004; and V60: -17.3 ± 11.6%, p = 0.005, respectively); however, there was no effect of vibration frequency. In both conditions, the maximal voluntary contraction torque reduction observed was mainly attributable to peripheral fatigue and was not because of central modifications of the neuromuscular system. The present study demonstrates that the frequency of vibration does not significantly influence the magnitude and location of neuromuscular fatigue, suggesting that adding WBV to static squat exercise (on a vertically oscillating platform) does not provide an additional training stimulus.

  6. Fatigue Damage Monitoring in 304L Steel Specimens by an Acoustic Emission Method

    Directory of Open Access Journals (Sweden)

    Ould-Amer Ammar

    2014-06-01

    Full Text Available The aim of this work was to clarify fatigue crack initiation and propagation mechanisms in 304L austenitic stainless steel under different total-strain-amplitudes. A complete process from crack initiation and propagation was recorded by using the acoustic emission method in one hand, and replica method in another hand. The effect of strain amplitude on fatigue crack growth was investigated and a new representation of various fatigue curves associated to various levels of fatigue damage is proposed.

  7. Fatigue behavior of flexhoses and bellows due to flow-induced vibrations

    Science.gov (United States)

    Desai, P. V.; Thornhill, L.

    1986-01-01

    The analysis and results developed in a fresh approach to calculate flow induced vibration response of a flexible flow passage are summarized. The vibration results are further examined in the frequency domain to obtain dominant frequency information. A cumulative damage analysis due to cyclic strains is performed to obtain the number of cycles to failure for a metallic bellows of particular specifications under a variety of operational conditions. Sample plots of time and frequency domain responses are included. The complex listing of a computer program is provided. The program successively executes each of the analyses needed to calculate the vibration response, the frequency response, the cyclic strains and the number of cycles to failure. The program prompts the user for necessary input information. Sample data from the program is provided. The fatigue life results obtained by the computer model lie within an acceptable range of previously measured available data.

  8. Acute Effect of Lower-Body Vibration as a Recovery Method After Fatiguing Exercise

    Directory of Open Access Journals (Sweden)

    Svetlana Nepocatych

    2015-09-01

    Full Text Available The purpose of this study was to compare three recovery methods: control (CON, lower-body vibration (LBV and LBV+ local muscle cooling (LBVC on lower-body performance, perceived recovery, and muscle soreness. Physically active male volunteers (n=8 in a repeated-measures, counterbalanced design, completed three sets of squats to fatigue, each recovery treatment, and two Wingate Anaerobic Tests. Rating of perceived exertion (RPE, and heart rate (HR were measured after fatiguing exercise, recovery treatment and Wingate Anaerobic tests. Peak and mean power, fatigue index, Delayed Onset Muscle Soreness (DOMS, and comfort levels were compared between each treatment. In Wingate 1, no significant differences (p=0.42 were found among CON, LBV, or LBVC regarding peak power (1119±239, 1097±225, and 1146±260 W, respectively, mean power (p=0.32, or fatigue index (p=0.47. In Wingate 2, no significant (p=0.17 differences were found among CON, LBV, or LBVC regarding peak power (1042±228, 1078±233, and 1110±268 W, respectively, mean power (p=0.38, or fatigue index (p=0.15. A significantly better (p=0.01 perceived recovery was observed after LBV (6±1 and LBVC (6±1 compared to CON (4±1. The study findings support psychological but not performance enhancing benefits after the use of LBV and LBVC as recovery methods.

  9. Six weeks of whole-body vibration exercise improves pain and fatigue in women with fibromyalgia.

    Science.gov (United States)

    Alentorn-Geli, Eduard; Padilla, Jaume; Moras, Gerard; Lázaro Haro, Cristina; Fernández-Solà, Joaquim

    2008-10-01

    The aim of this study was to investigate the effectiveness of a 6-week traditional exercise program with supplementary whole-body vibration (WBV) in improving health status, physical functioning, and main symptoms of fibromyalgia (FM) in women with FM. Thirty-six (36) women with FM (mean +/- standard error of the mean age 55.97 +/- 1.55) were randomized into 3 treatment groups: exercise and vibration (EVG), exercise (EG), and control (CG). Exercise therapy, consisting of aerobic activities, stretching, and relaxation techniques, was performed twice a week (90 min/day). Following each exercise session, the EVG underwent a protocol with WBV, whereas the EG performed the same protocol without vibratory stimulus. The Fibromyalgia Impact Questionnaire (FIQ) was administered at baseline and 6 weeks following the initiation of the treatments. Estimates of pain, fatigue, stiffness, and depression were also reported using the visual analogue scale. A significant 3 x 2 (group x time)-repeated measures analysis of variance interaction was found for pain (p = 0.018) and fatigue (p = 0.002) but not for FIQ (p = 0.069), stiffness (p = 0.142), or depression (p = 0.654). Pain and fatigue scores were significantly reduced from baseline in the EVG, but not in the EG or CG. In addition, the EVG showed significantly lower pain and fatigue scores at week 6 compared to the CG, whereas no significant differences were found between the EG and CG (p > 0.05). Results suggest that a 6-week traditional exercise program with supplementary WBV safely reduces pain and fatigue, whereas exercise alone fails to induce improvements.

  10. An Analytical Solution for Predicting the Vibration-Fatigue-Life in Bimodal Random Processes

    Directory of Open Access Journals (Sweden)

    Chaoshuai Han

    2017-01-01

    Full Text Available Predicting the vibration-fatigue-life of engineering structures subjected to random loading is a critical issue for. Frequency methods are generally adopted to deal with this problem. This paper focuses on bimodal spectra methods, including Jiao-Moan method, Fu-Cebon method, and Modified Fu-Cebon method. It has been proven that these three methods can give acceptable fatigue damage results. However, these three bimodal methods do not have analytical solutions. Jiao-Moan method uses an approximate solution, Fu-Cebon method, and Modified Fu-Cebon method needed to be calculated by numerical integration which is obviously not convenient in engineering application. Thus, an analytical solution for predicting the vibration-fatigue-life in bimodal spectra is developed. The accuracy of the analytical solution is compared with numerical integration. The results show that a very good agreement between an analytical solution and numerical integration can be obtained. Finally, case study in offshore structures is conducted and a bandwidth correction factor is computed through using the proposed analytical solution.

  11. Effects of muscle fatigue on the ground reaction force and soft-tissue vibrations during running: a model study.

    Science.gov (United States)

    Nikooyan, Ali Asadi; Zadpoor, Amir Abbas

    2012-03-01

    A modeling approach is used in this paper to study the effects of fatigue on the ground reaction force (GRF) and the vibrations of the lower extremity soft tissues. A recently developed multiple degrees-of-freedom mass-spring-damper model of the human body during running is used for this purpose. The model is capable of taking the muscle activity into account by using a nonlinear controller that tunes the mechanical properties of the soft-tissue package based on two physiological hypotheses, namely, "constant force" and "constant vibration." In this study, muscle fatigue is implemented in the model as the gradual reduction of the ability of the controller to tune the mechanical properties of the lower body soft-tissue package. Simulations are carried out for various types of footwear in both pre- and postfatigue conditions. The simulation results show that the vibration amplitude of the lower body soft-tissue package may considerably increase (up to 20%) with muscle fatigue, while the effects of fatigue on the GRF are negligible. The results of this modeling study are in line with the experimental studies that found muscle fatigue does not significantly change the GRF peaks, but may increase the level of soft-tissue vibrations (particularly for hard shoes). A major contribution of the current study is the formulation of a hypothesis about how the central nervous system tunes the muscle properties after fatigue.

  12. A Demonstration using Low-kt Fatigue Specimens of a Method for Predicting the Fatigue Behaviour of Corroded Aircraft Components

    Science.gov (United States)

    2013-03-01

    measurements of crack closure were made during fatigue testing. 3. 7010-T7 FCG NASGRO model from the AFGROW material database : This is a standard...with the NASGRO data for 7010-T73651 from AFGROW’s database of NASGRO parameters [38]. 35...Conference, Florida, USA 125. Wallace, W. and Hoeppner, D. W. (1985) AGARD Corrosion Handbook Volume 1:Aircraft Corrosion: Causes and Case Histories

  13. Biaxial fatigue tests of notched specimens for AISI 304L stainless steel

    Directory of Open Access Journals (Sweden)

    G. Beretta

    2016-07-01

    Full Text Available High cycle fatigue tests were conducted for stainless steel AISI 304L. The geometry was a thin walled tube with a passing through hole. The tests were axial, torsional and in-phase axial-torsional, all of them under load control with R = −1. The S-N curves were constructed following the ASTM E739 standard and the fatigues limits were calculated following the method of maximum likelihood proposed by Bettinelli. The crack direction along the surface was analysed, with especial attention to the crack initiation zones. The notch fatigue limits for different hole diameters were compared with the predictions done with a microstructural fracture mechanics model.

  14. A Novel Method for Characterizing Fatigue Delamination Growth Under Mode I Using the Double Cantilever Beam Specimen

    Science.gov (United States)

    Carvalho, Nelson; Murri, G.

    2014-01-01

    A novel method is proposed to obtain Mode I delamination growth rate from a Double Cantilever Beam (DCB) specimen. In the proposed method, Unidirectional (UD) DCB specimens are tested in fatigue at different initial maximum energy release rates levels. The growth rate data obtained in the first increments of crack growth at each maximum energy release rate level are used to generate a Paris Law equation, which characterizes delamination growth rate without fiber-bridging, and can also be used to determine a delamination onset curve. The remaining delamination growth rate data from each test are used to determine a modified Paris law, which characterizes the delamination growth rate in a DCB specimen, explicitly accounting for fiber-bridging. The proposed expression captures well the scatter in experimental data obtained using the DCB specimens, suggesting its adequacy. The Paris Law characterizing delamination growth rate without fiber-bridging predicts higher delamination growth rates for the same maximum energy release rate applied, leading to a conservative estimate for delamination growth. This is particularly relevant, since in generic ply interfaces, fiber-bridging is less predominant than in UD DCB specimens. Failing to account for fiber-bridging in UD DCB specimens may underestimate the delamination growth rate, yielding non-conservative predictions.

  15. Fatigue Performance of Ti-6Al-4V Additively Manufactured Specimens with Integrated Capillaries of an Embedded Structural Health Monitoring System

    Science.gov (United States)

    Hinderdael, Michaël; Strantza, Maria; De Baere, Dieter; Devesse, Wim; De Graeve, Iris; Terryn, Herman; Guillaume, Patrick

    2017-01-01

    Additive manufacturing (AM) of metals offers new possibilities for the production of complex structures. Up to now, investigations on the mechanical response of AM metallic parts show a significant spread and unexpected failures cannot be excluded. In this work, we focus on the detection of fatigue cracks through the integration of a Structural Health Monitoring (SHM) system in Ti-6Al-4V specimens. The working principle of the presented system is based on the integration of small capillaries that are capable of detecting fatigue cracks. Four-point bending fatigue tests have been performed on Ti-6Al-4V specimens with integrated capillaries and compared to the reference specimenswithout capillaries. Specimens were produced by conventional subtractive manufacturing of wrought material and AM, using the laser based Directed Energy Deposition (DED) process. In this study, we investigated the effect of the presence of the capillary on the fatigue strength and fatigue initiation location. Finite element (FEM) simulations were performed to validate the experimental test results. The presence of a drilled capillary in the specimens did not alter the fatigue initiation location. However, the laser based DED production process introduced roughness on the capillary surface that altered the fatigue initiation location to the capillary surface. The fatigue performance was greatly reduced when considering a printed capillary. It is concluded that the surface quality of the integrated capillary is of primary importance in order not to influence the structural integrity of the component to be monitored. PMID:28841186

  16. Fatigue Performance of Ti-6Al-4V Additively Manufactured Specimens with Integrated Capillaries of an Embedded Structural Health Monitoring System.

    Science.gov (United States)

    Hinderdael, Michaël; Strantza, Maria; De Baere, Dieter; Devesse, Wim; De Graeve, Iris; Terryn, Herman; Guillaume, Patrick

    2017-08-25

    Additive manufacturing (AM) of metals offers new possibilities for the production of complex structures. Up to now, investigations on the mechanical response of AM metallic parts show a significant spread and unexpected failures cannot be excluded. In this work, we focus on the detection of fatigue cracks through the integration of a Structural Health Monitoring (SHM) system in Ti-6Al-4V specimens. The working principle of the presented system is based on the integration of small capillaries that are capable of detecting fatigue cracks. Four-point bending fatigue tests have been performed on Ti-6Al-4V specimens with integrated capillaries and compared to the reference specimenswithout capillaries. Specimens were produced by conventional subtractive manufacturing of wrought material and AM, using the laser based Directed Energy Deposition (DED) process. In this study, we investigated the effect of the presence of the capillary on the fatigue strength and fatigue initiation location. Finite element (FEM) simulations were performed to validate the experimental test results. The presence of a drilled capillary in the specimens did not alter the fatigue initiation location. However, the laser based DED production process introduced roughness on the capillary surface that altered the fatigue initiation location to the capillary surface. The fatigue performance was greatly reduced when considering a printed capillary. It is concluded that the surface quality of the integrated capillary is of primary importance in order not to influence the structural integrity of the component to be monitored.

  17. Fatigue fracture surface analysis in C45 steel specimens using X-Ray fractography

    NARCIS (Netherlands)

    Rajanna, K.; Kolster, B.H.; Pathiraj, B.

    1991-01-01

    X-Ray fractography is a useful technique to analyse the mechanisms operating in fracture and involves an examination of the fracture surface. In the present investigation, this technique has been employed to study the fatigue fracture behaviour of a medium carbon steel of C45 grade in different heat

  18. Fatigue damage observed non-destructively in fibre composite coupon test specimens by X-ray CT

    Science.gov (United States)

    Jespersen, K. M.; Mikkelsen, L. P.

    2016-07-01

    This study presents a method for monitoring the 3D fatigue damage progression on a micro-structural level in a glass fibre/polymer coupon test specimen by means of laboratory X-ray Computed Tomography (CT). A modified mount and holder made for the standard test samples to fit into the X-ray CT scanner along with a tension clamp solution is presented. Initially, the same location of the test specimen is inspected by ex-situ X-ray CT during the fatigue loading history, which shows the damage progression on a micro-structural level. The openings of individual uni-directional (UD) fibre fractures are seen to generally increase with the number of cycles, and new regions of UD fibre fractures also appear. There are some UD fibre fractures that are difficult to detect since their opening is small. Therefore, the effect of tension on the crack visibility is examined afterwards using a tension clamp solution. With applied tension some additional cracks become visible and the openings of fibre fractures increases, which shows the importance of applied tension during the scan.

  19. Specimen design and instrumentation for monitoring fatigue crack growth initiating at ply drops

    DEFF Research Database (Denmark)

    Goutianos, Stergios; Di Crescenzo, Leonardo; McGugan, Malcolm

    Unpredictable and excessive loads, for example caused by aerodynamic interaction between different turbines, can accelerate fatigue damage in wind turbine blades (Ghosal et. al (2000)). Fatigue damage can also initiate in the early service life of a wind turbine blade in regions of stress...... concentration, such as those caused by ply drops (Cairns et al. (1999)). Due to these issues, the design philosophy is based on conservative analysis methods and inspections at certain time intervals are required to assess the damage in the wind blades. An alternative approach is to use damage tolerant...... materials and a structural health monitoring system (McGugan et al. (2015)). In this approach, a distribution of damage types within the blades is accepted as long as they can be detected by structural health monitoring techniques and their severity evaluated by material damage models. The present work aims...

  20. Model-Based Structural Health Monitoring of Fatigue Damage Test-Bed Specimens

    Science.gov (United States)

    2011-11-15

    to it off-center. The base plate and the stiffener plate are rigidly welded by a tungsten inert gas ( TIG ) weld . Three different crack paths...shown in Figure 9(a), an 18 in long stiffener plate has been welded to each of the tested plates with 0.625 in long discrete TIG welds at 5 locations...around critical weld zones where fatigue failure is likely to initiate. Extensive numerical simulation and experimental testing has been conducted

  1. Evaluating the Impact of Whole-Body Vibration (WBV) on Fatigue and the Implications for Driver Safety.

    Science.gov (United States)

    Troxel, Wendy M; Helmus, Todd C; Tsang, Flavia; Price, Carter C

    2016-05-09

    Driver fatigue is a significant contributor to motor vehicle accidents and fatalities, although the exact share of those events attributable to fatigue is still uncertain. In 2013, accidents involving heavy trucks killed more than 3,944 people in the United States, with over 80 percent of those killed not in the truck. Numerous factors contribute to driver fatigue among commercial drivers, including shiftwork schedules; high prevalence of alcohol and substance use; extended hours; comorbid medical conditions, such as pain; and high prevalence of sleep disorders. Many of these factors have been studied extensively in the trucking industry. Whole-body vibration (WBV) is another potential factor that may contribute to driver fatigue, but it has received little attention. Beginning in January 2015, Bose Corporation and AIG commissioned the RAND Corporation to study the link between WBV and driver fatigue. This article summarizes the findings from RAND's systematic review of the literature on WBV and fatigue as well as considers appropriate study designs and methodology that will inform new areas of research focused on improving the safety of truckers and those who share the road with them. The literature review identified 24 studies examining the impact of WBV on fatigue or sleepiness. The majority of studies (n = 18) found a significant association between WBV and fatigue or sleepiness; however, there are several limitations of the existing literature that preclude definitive conclusions regarding the impact of WBV on these outcomes. This research concludes with recommendations for future studies to strengthen the evidence base.

  2. Fatigue

    Science.gov (United States)

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  3. Investigation of Effectiveness of Some Vibration-Based Techniques in Early Detection of Real-Time Fatigue Failure in Gears

    Directory of Open Access Journals (Sweden)

    Hasan Ozturk

    2010-01-01

    Full Text Available Bending fatigue crack is a dangerous and insidious mode of failure in gears. As it produces no debris in its early stages, it gives little warning during its progression, and usually results in either immediate loss of serviceability or greatly reduced power transmitting capacity. This paper presents the applications of vibration-based techniques (i.e. conventional time and frequency domain analysis, cepstrum, and continuous wavelet transform to real gear vibrations in the early detection, diagnosis and advancement monitoring of a real tooth fatigue crack and compares their detection and diagnostic capabilities on the basis of experimental results. Gear fatigue damage is achieved under heavy-loading conditions and the gearbox is allowed to run until the gears suffer badly from complete tooth breakage. It has been found that the initiation and progression of fatigue crack cannot be easily detected by conventional time and frequency domain approaches until the fault is significantly developed. On the contrary, the wavelet transform is quite sensitive to any change in gear vibration and reveals fault features earlier than other methods considered.

  4. Study of deformation evolution during failure of rock specimens using laser-based vibration measurements

    Science.gov (United States)

    Smolin, I. Yu.; Kulkov, A. S.; Makarov, P. V.; Tunda, V. A.; Krasnoveikin, V. A.; Eremin, M. O.; Bakeev, R. A.

    2017-12-01

    The aim of the paper is to analyze experimental data on the dynamic response of the marble specimen in uniaxial compression. To make it we use the methods of mathematical statistics. The lateral surface velocity evolution obtained by the laser Doppler vibrometer represents the data for analysis. The registered data were regarded as a time series that reflects deformation evolution of the specimen loaded up to failure. The revealed changes in statistical parameters were considered as precursors of failure. It is shown that before failure the deformation response is autocorrelated and reflects the states of dynamic chaos and self-organized criticality.

  5. A Randomized Controlled Pilot Study to Investigate the Effect of Whole-Body Vibration on Lower-Extremity Fatigue.

    Science.gov (United States)

    Ansari, Noureddin Nakhostin; Naghdi, Soofia; Karimi-Zarchi, Hadi; Fakhari, Zahra; Hasson, Scott

    2017-09-01

    Whole-body vibration (WBV) is a type of weight-bearing exercise used in the field of sport and rehabilitation. There is no study on the effects of WBV on muscle recovery after a fatiguing activity. To determine the effects of a single WBV session on lower-extremity fatigue. Randomized controlled pilot study. University Physiotherapy Clinic. A total of 13 healthy young men volunteered to participate in this study. Subjects were randomly assigned into the WBV group (n = 7, mean age: 21 y) or control group (CG; n = 6, mean age: 20 y). Subjects in the WBV group participated in a single-session WBV (30 Hz, amplitude 4 mm, 2 min) after lower-extremity fatigue. Peak force of quadriceps muscle, single leg hop test, and Y-test were measured before inducing muscle fatigue (T0), immediately after completing the fatigue protocol (T1), after WBV (T2), and 15 min following the application of WBV (T3). The same method was applied in the CG while the WBV machine was turned off. Repeated-measure ANOVA revealed no significant differences between groups in any of the outcomes. The findings indicated that WBV was not effective in the recovery of lower-extremity fatigue in healthy young men.

  6. The specific heat loss combined with the thermoelastic effect for an experimental analysis of the mean stress influence on axial fatigue of stainless steel plain specimens

    Directory of Open Access Journals (Sweden)

    G. Meneghetti

    2014-10-01

    Full Text Available The energy dissipated to the surroundings as heat in a unit volume of material per cycle, Q, was recently proposed by the authors as fatigue damage index and it was successfully applied to correlate fatigue data obtained by carrying out fully reversed stress- and strain-controlled fatigue tests on AISI 304L stainless steel plain and notched specimens. The use of the Q parameter to analyse the experimental results led to the definition of a scatter band having constant slope from the low- to the high-cycle fatigue regime. In this paper the energy approach is extended to analyse the influence of mean stress on the axial fatigue behaviour of unnotched cold drawn AISI 304L stainless steel bars. In view of this, stress controlled fatigue tests on plain specimens at different load ratios R (R=-1; R=0.1; R=0.5 were carried out. A new energy parameter is defined to account for the mean stress effect, which combines the specific heat loss Q and the relative temperature variation due to the thermoelastic effect corresponding to the achievement of the maximum stress level of the stress cycle. The new two-parameter approach was able to rationalise the mean stress effect observed experimentally. It is worth noting that the results found in the present contribution are meant to be specific for the material and testing condition investigated here.

  7. Effects of Phase Difference and Mean Stress on the Fatigue Strength of Small-Hole-Containing Specimens Subjected to Combined Load

    National Research Council Canada - National Science Library

    ENDO, Masahiro; ISHIMOTO, Isao

    2007-01-01

    .... Combined axial and torsional fatigue tests were conducted using annealed JIS S35C steel and quenched/tempered JIS SCM435 steel specimens containing a small hole of either 100 μm or 500 μm in diameter...

  8. Fatigue-induced changes in tonic vibration response (TVR) in humans: relationships between electromyographic and biochemical events.

    Science.gov (United States)

    Brerro-Saby, Christelle; Delliaux, Stéphane; Steinberg, Jean Guillaume; Jammes, Yves

    2008-11-01

    Fatigue-induced changes in the proprioceptive reflex loop were explored in humans by using the tonic electromyographic (EMG) response to vibration (TVR) and relating it to lactic acidosis (LA) and oxidative stress. TVR was measured in flexor digitorum superficialis before and after sustained or intermittent handgrip at maximal voluntary contraction (MVC). TVR variations were compared with the changes in EMG power spectrum preceding contractile fatigue, the Hoffman reflex (H-reflex), and plasma concentrations of LA and thiobarbituric acid reactive substances (TBARS). After both sustained and intermittent handgrips, TVR amplitude first declined then increased, independently from the changes in EMG power spectrum and H-reflex. TVR depression and facilitation were respectively concomitant with increases in LA and TBARS. The TVR depression was proportional to the increased LA level. The origin of TVR changes after muscle fatigue is questioned because the relationship between TVR depression and LA accumulation might be temporal, not causal, and changes in muscle stiffness were not explored.

  9. Effect of specimen thickness of fatigue-crack-growth behavior and fracture toughness of 7075-T6 and 7178-T6 aluminum alloys

    Science.gov (United States)

    Hudson, C. M.; Newman, J. C., Jr.

    1973-01-01

    A study was made to determine the effects of specimen thickness on fatigue crack growth and fracture behavior of 7075-T6 and 7178-T6 aluminum alloy sheet and plate. Specimen thicknesses ranged from 5.1 to 12.7 mm (0.20 to 0.50 in.) for 7075-T6 and from 1.3 to 6.4 mm (0.05 to 0.25 in.) for 7178-T6. The stress ratios R used in the crack growth experiments were 0.02 and 0.50. For 7075-T6, specimen thickness had relatively little effect on fatigue-crack growth. However, the fracture toughness of the thickness of the thickest gage of 7075-T6 was about two-thirds of the fracture toughness of the thinner gages of 7075-T6. For 7178-T6, fatigue cracks generally grew somewhat faster in the thicker gages than in the thinnest gage. The fracture toughness of the thickest gage of 7178-T6 was about two-thirds of the fracture toughness of the thinner gages of 7178-T6. Stress intensity methods were used to analyze the experimental results. For a given thickness and value of R, the rate of fatigue crack growth was essentially a single-valued function of the stress intensity range for 7075-T6 and 7178-T6. An empirical equation developed by Forman, Kearney, and Engle fit the 7075-T6 and 7178-T6 crack growth data reasonably well.

  10. Fatigue

    Science.gov (United States)

    ... as systemic lupus erythematosus Cancer Heart failure Diabetes Fibromyalgia Infection, especially one that takes a long time ... Bennett RM. Fibromyalgia, chronic fatigue syndrome, and ... Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, ...

  11. Effect of Oil Viscosity on the Fatigue Limit of Drilled Specimens and the Small Crack Growth Law

    National Research Council Canada - National Science Library

    GOTO, Masahiro; NISITANI, Hironobu; MIYAGAWA, Hiroomi; YANAGAWA, Yasuhiro

    1989-01-01

    ... to evaluate the effect of oil viscosity on the fatigue limit and small crack growth law. The results showed that there was a limited effect from the oils on the fatigue limit, but that the small-crack growth law, dl/dN=C1σ...

  12. Progress Letter Report on Bending Fatigue Test System Development for Spent Nuclear Fuel Vibration Integrity Study (Out-of-cell fatigue testing development - Task 2.4)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Wang, Hong [ORNL; Cox, Thomas S [ORNL; Baldwin, Charles A [ORNL; Bevard, Bruce Balkcom [ORNL

    2013-08-01

    Vibration integrity of high burn-up spent nuclear fuel in transportation remains to be a critical component of US nuclear waste management system. The structural evaluation of package for spent fuel transportation eventually will need to see if the content or spent fuel is in a subcritical condition. However, a system for testing and characterizing such spent fuel is still lacking mainly due to the complication involved with dealing radioactive specimens in a hot cell environment. Apparently, the current state-of-the-art in spent fuel research and development is quite far away from the delivery of reliable mechanical property data for the assessment of spent fuels in the transport package evaluation. Under the sponsorship of US NRC, ORNL has taken the challenge in developing a robust testing system for spent fuel in hot cell. An extensive literature survey was carried out and unique requirements of such testing system were identified. The U-frame setup has come to the top among various designs examined for reverse bending fatigue test of spent fuel rod. The U-frame has many features that deserve mentioned here: Easy to install spent fuel rod in test; Less linkages than in conventional bending test setup such as three-point or four-point bending; Target the failure mode relevant to the fracture of spent fuel rod in transportation by focusing on pure bending; The continuous calibrations and modifications resulted in the third generation (3G) U-frame testing setup. Rigid arms are split along the LBB axis at rod sample ends. For each arm, this results in a large arm body and an end piece. Mating halves of bushings were modified into two V-shaped surfaces on which linear roller bearings (LRB) are embedded. The rod specimen is installed into the test fixture through opening and closing slide end-pieces. The 3G apparently has addressed major issues of setup identified in the previous stage and been proven to be eligible to be further pursued in this project. On the other

  13. An advanced tube wear and fatigue workstation to predict flow induced vibrations of steam generator tubes; Un outil de prediction de l`usure et de la fatigue des tubes de generateurs de vapeur soumis a des vibrations sous ecoulement

    Energy Technology Data Exchange (ETDEWEB)

    Gay, N. [Electricite de France (EDF), 78 - Chatou (France); Baratte, C. [Electricite de France (EDF), 69 - Villeurbanne (France); Flesch, B. [Electricite de France (EDF), 75 - Paris (France)

    1997-12-31

    Flow induced tube vibration damage is a major concern for designers and operators of nuclear power plant steam generators (SG). The operating flow-induced vibrational behaviour has to be estimated accurately to allow a precise evaluation of the new safety margins in order to optimize the maintenance policy. For this purpose, an industrial `Tube Wear and Fatigue Workstation`, called `GEVIBUS Workstation` and based on an advanced methodology for predictive analysis of flow-induced vibration of tube bundles subject to cross-flow has been developed at Electricite de France. The GEVIBUS Workstation is an interactive processor linking modules as: thermalhydraulic computation, parametric finite element builder, interface between finite element model, thermalhydraulic code and vibratory response computations, refining modelling of fluid-elastic and random forces, linear and non-linear dynamic response and the coupled fluid-structure system, evaluation of tube damage due to fatigue and wear, graphical outputs. Two practical applications are also presented in the paper; the first simulation refers to an experimental set-up consisting of a straight tube bundle subject to water cross-flow, while the second one deals with an industrial configuration which has been observed in some operating steam generators i.e., top tube support plate degradation. In the first case the GEVIBUS predictions in terms of tube displacement time histories and phase planes have been found in very good agreement with experiment. In the second application the GEVIBUS computation showed that a tube with localized degradation is much more stable than a tube located in an extended degradation zone. Important conclusions are also drawn concerning maintenance. (author). 28 refs.

  14. Characterisation of foreign object damage (FOD) and early fatigue crack growth in laser shock peened Ti-6Al-4V aerofoil specimens

    Energy Technology Data Exchange (ETDEWEB)

    Spanrad, S. [Mechanical Behaviour of Materials Laboratory, Department of Mechanical and Design Engineering, University of Portsmouth (United Kingdom); Tong, J., E-mail: jie.tong@port.ac.uk [Mechanical Behaviour of Materials Laboratory, Department of Mechanical and Design Engineering, University of Portsmouth (United Kingdom)

    2011-02-25

    Research highlights: {yields} A study of deformation in a generic LSPed aerofoil specimen subjected to high speed head-on and 45 deg. impacts, and subsequently fatigue loading. {yields} Characterisation of damage features considering geometry of the projectile, impact angle and impact velocity. {yields} Onset and early crack growth due to FOD in LSPed samples compared to those without LSP subjected to cubical impacts under simulated service loading conditions. - Abstract: Foreign object damage (FOD) has been identified as one of the primary life limiting factors for fan and compressor blades, with the leading edge of aerofoils particularly susceptible to such damage. In this study, a generic aerofoil specimen of Ti-6Al-4V alloy was used. The specimens were treated by laser shock peening (LSP) to generate compressive residual stresses in the leading edge region prior to impact. FOD was simulated by firing a cubical projectile at the leading edge using a laboratory gas gun at 200 m/s, head-on; and at 250 m/s, at an angle of 45 deg. The specimens were then subjected to 4-point bend fatigue testing under high cycle (HCF), low cycle (LCF) and combined LCF and HCF loading conditions. Scanning electron microscopy (SEM) was used to characterise the damage features due to FOD. Crack initiation and early crack growth due to FOD and subsequent fatigue growth were examined in detail. The results were compared between the two impact conditions; and with those from samples without LSP treatment as well as those impacted with spherical projectiles. The results seem to suggest that LSP has improved the crack growth resistance post FOD. Delayed onset of crack initiation was observed in LSPed samples compared to those without LSP under similar loading conditions. Damage features depend on the geometry of the projectile, the impact angle as well as the impact velocity.

  15. Demonstrating the Effect of Particle Impact Dampers on the Random Vibration Response and Fatigue Life of Printed Wiring Assemblies

    Science.gov (United States)

    Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert

    2013-01-01

    In a recent experimental study, small Particle Impact Dampers (PID) were bonded directly to the surface of printed circuit board (PCB) or printed wiring assemblies (PWA), reducing the random vibration response and increasing the fatigue life. This study provides data verifying practicality of this approach. The measured peak strain and acceleration response of the fundamental out of plane bending mode was significantly attenuated by adding a PID device. Attenuation of this mode is most relevant to the fatigue life of a PWA because the local relative displacements between the board and the supported components, which ultimately cause fatigue failures of the electrical leads of the board-mounted components are dominated by this mode. Applying PID damping at the board-level of assembly provides mitigation with a very small mass impact, especially as compared to isolation at an avionics box or shelf level of assembly. When compared with other mitigation techniques at the PWA level (board thickness, stiffeners, constrained layer damping), a compact PID device has the additional advantage of not needing to be an integral part of the design. A PID can simply be bonded to heritage or commercial off the shelf (COTS) hardware to facilitate its use in environments beyond which it was originally qualified. Finite element analysis and test results show that the beneficial effect is not localized and that the attenuation is not due to the simple addition of mass. No significant, detrimental reduction in frequency was observed. Side-by-side life testing of damped and un-damped boards at two different thicknesses (0.070" and 0.090") has shown that the addition of a PID was much more significant to the fatigue life than increasing the thickness. High speed video, accelerometer, and strain measurements have been collected to correlate with analytical results.

  16. A novel high cycle fatigue assessment of small-bore side branches: tailor-made acceptable vibration levels based on the remaining life of existing structures

    NARCIS (Netherlands)

    Beek, P.J.G. van; Pijpers, R.J.M.; Macdonald, K.; Maljaars, J.; Lunde, K.; Korst, H.J.C.; Hansen, F.

    2014-01-01

    This paper describes a novel and advanced tailor-made fatigue assessment method whereby acceptable vibration levels are based on maximum acceptable stress ranges for individual side branches. The acceptable stress ranges for each critical welded connection are based on a fracture mechanics analysis

  17. Mechanical Behavior of Lithium-Ion Batteries and Fatigue Behavior of Ultrasonic Weld-Bonded Lap-Shear Specimens of Dissimilar Magnesium and Steel Sheets

    Science.gov (United States)

    Lai, Wei-Jen

    The mechanical behaviors of LiFePO4 battery cell and module specimens under in-plane constrained compression were investigated for simulations of battery cells, modules and packs under crush conditions. The experimental stress-strain curves were correlated to the deformation patterns of battery cell and module specimens. Analytical solutions were developed to estimate the buckling stresses and to provide a theoretical basis for future design of representative volume element cell and module specimens. A physical kinematics model for formation of kinks and shear bands in battery cells was developed to explain the deformation mechanism for layered battery cells under in-plane constrained compression. A small-scale module constrained punch indentation test was also conducted to benchmark the computational results. The computational results indicate that macro homogenized material models can be used to simulate battery modules under crush conditions. Fatigue behavior and failure modes of ultrasonic spot welds in lap-shear specimens of magnesium and steel sheets with and without adhesive were investigated. For ultrasonic spot welded lap-shear specimens, the failure mode changes from the partial nugget pullout mode under low-cycle loading conditions to the kinked crack failure mode under high-cycle loading conditions. For adhesive-bonded and weld-bonded lap-shear specimens, the test results show the near interface cohesive failure mode and the kinked crack failure mode under low-cycle and high-cycle loading conditions, respectively. Next, the analytical effective stress intensity factor solutions for main cracks in lap-shear specimens of three dissimilar sheets under plane strain conditions were developed and the solutions agreed well with the computational results. The analytical effective stress intensity factor solutions for kinked cracks were compared with the computational results at small kink lengths. The results indicate that the computational results approach to

  18. On the effects of hull-girder vibration upon fatigue strength of a Post-Panamax container ship disaggregated by short-term sea state

    Directory of Open Access Journals (Sweden)

    Fukasawa Toichi

    2014-06-01

    Full Text Available The effects of hull-girder vibration on the fatigue strength of a Post-Panamax container ship are discussed in the present paper. Firstly, the short-term sea states are categorized according to the occurrence probability of each sea state. Time histories of hull-girder stress in short-term sea states are calculated by means of a nonlinear simulation code of ship response assuming that the hull-girder is rigid and flexible. Then, the calculated stress peaks are processed by the rainflow counting method, where two different counting procedures are used based on the considerations of crack propagation behaviors. Finally, the fatigue damage in life time of the ship in each categorized short-term sea state is estimated by means of Miner’s rule. Based on the calculated results, the effects of hull-girder vibrations on the fatigue damage are clarified by disaggregated damage from short-term sea state.

  19. On the effects of hull-girder vibration upon fatigue strength of a Post-Panamax container ship disaggregated by short-term sea state

    Directory of Open Access Journals (Sweden)

    Toichi Fukasawa

    2014-06-01

    Full Text Available The effects of hull-girder vibration on the fatigue strength of a Post-Panamax container ship are discussed in the present paper. Firstly, the short-term sea states are categorized according to the occurrence probability of each sea state. Time histories of hull-girder stress in short-term sea states are calculated by means of a nonlinear simulation code of ship response assuming that the hull-girder is rigid and flexible. Then, the calculated stress peaks are processed by the rainflow counting method, where two different counting procedures are used based on the considerations of crack propagation behaviors. Finally, the fatigue damage in life time of the ship in each categorized short-term sea state is estimated by means of Miner's rule. Based on the calculated results, the effects of hull-girder vibrations on the fatigue damage are clarified by disaggregated damage from short-term sea state.

  20. Very high cycle fatigue testing of concrete using ultrasonic cycling

    Energy Technology Data Exchange (ETDEWEB)

    Karr, Ulrike; Schuller, Reinhard; Fitzka, Michael; Mayer, Herwig [Univ. of Natural Resources and Life Sciences, Vienna (Austria). Inst. of Physics and Materials Science; Denk, Andreas; Strauss, Alfred [Univ. of Natural Resources and Life Sciences, Vienna (Austria)

    2017-06-01

    The ultrasonic fatigue testing method has been further developed to perform cyclic compression tests with concrete. Cylindrical specimens vibrate in resonance at a frequency of approximately 20 kHz with superimposed compressive static loads. The high testing frequency allows time-saving investigations in the very high cycle fatigue regime. Fatigue tests were carried out on ''Concrete 1'' (compressive strength f{sub c} = 80 MPa) and ''Concrete 2'' (f{sub c} = 107 MPa) under purely compressive loading conditions. Experiments at maximum compressive stresses of 0.44 f{sub c} (Concrete 1) and 0.38 f{sub c} (Concrete 2) delivered specimen failures above 109 cycles, indicating that no fatigue limit exists for concrete below one billion load cycles. Resonance frequency, power required to resonate the specimen and second order harmonics of the vibration are used to monitor fatigue damage in situ. Specimens were scanned by X-ray computed tomography prior to and after testing. Fatigue cracks were produced by ultrasonic cycling in the very high cycle fatigue regime at interfaces of grains as well as in cement. The possibilities as well as limitations of ultrasonic fatigue testing of concrete are discussed.

  1. Analysis of chemical components of shiitake polysaccharides and its anti-fatigue effect under vibration.

    Science.gov (United States)

    Li, Xiaoling; Zhang, Hongbo; Xu, Haibo

    2009-11-01

    The shiitake polysaccharides were obtained from shiitake mushroom. Four fractions were isolated from the polysaccharides using a Sephadex G-100 gel column. Chemical components of the two main fractions were determined by thin layer chromatography (TLC), and high performance liquid chromatography (HPLC). F1 was composed of rhamnose, glucose, and mannose. F3 was composed of xylose, mannose, arabinose and galactose. The obtained results still showed that administration of shiitake polysaccharides could improve muscle's comfortability of animals under a long period of vibration. The above findings might be applicable to studies of vibration ergonomics.

  2. Effect of Post-Exercise Whole Body Vibration with Stretching on Mood State, Fatigue, and Soreness in Collegiate Swimmers

    Directory of Open Access Journals (Sweden)

    Justin J. Merrigan

    2017-01-01

    Full Text Available Static stretching (SS during whole body vibration (WBV has been suggested for exercise recovery. The purpose was to compare post-exercise self-ratings of fatigue (FAT, mood state (BAM, soreness (SOR, and perceived exertion (RPE between SS and WBV+SS in swimmers (9 women, mean ± SD: 19.3 ± 1.3 year, 171 ± 5.7 cm, 67.6 ± 7.2 kg, 26.6 ± 4.1 %body fat (%BF; 10 men, mean ± SD: 19.7 ± 1.0 year, 183 ± 5.5 cm, 77.1 ± 4.2 kg, 13.1 ± 2.2 %BF. Athletes were divided by sex, event (sprint, distance, and assigned to SS or WBV+SS. Both conditions consisted of SS performed on the WBV platform with or without WBV (50 Hz, 6 mm. Sessions consisted of: pre and post measures of BAM, FAT, SOR; the condition; and RPE. Mixed factorial ANOVA were run. A significant condition by pre/post interaction was observed (p = 0.035. Post hoc analyses showed WBV+SS elicited lower post-exercise ratings of FAT (p = 0.002 and the BAM affective states, of tension (p = 0.031, and fatigue (p = 0.087. RPE did not differ between conditions. Of interest is the decrease in tension and fatigue noted by the BAM. Mood state can be indicative of how athletes adapt to training volume and intensity.

  3. Fatigue damage from random vibration pulse process of tubular structural elements subject to wind

    DEFF Research Database (Denmark)

    Christensen, Claus F.; Ditlevsen, Ove Dalager

    1997-01-01

    In a wide range of the Reynolds number an elastically suspended circular cylinder surrounded by a homogeneous wind velocity field will generate vortex shedding of a frequency that by and large is proportional to the far field wind velocity. However, if the cylinder is free to vibrate, resonance w...

  4. Experimental Investigation on the Fatigue Life of Ti-6Al-4V Treated by Vibratory Stress Relief

    Directory of Open Access Journals (Sweden)

    Han-Jun Gao

    2017-05-01

    Full Text Available Vibratory stress relief (VSR is a highly efficient and low-energy consumption method to relieve and homogenize residual stresses in materials. Thus, the effect of VSR on the fatigue life should be determined. Standard fatigue specimens are fabricated to investigate the fatigue life of Ti-6Al-4V titanium alloy treated by VSR. The dynamic stresses generated under different VSR amplitudes are measured, and then the relationship between the dynamic stress and vibration amplitude is obtained. Different specimen groups are subjected to VSRs with different amplitudes and annealing treatment with typical process parameters. Residual stresses are measured to evaluate the stress relieving effects. Finally, the fatigue behavior under different states is determined by uniaxial tension–compression fatigue experiments. Results show that VSR and annealing treatment have negative effects on the fatigue life of Ti-6Al-4V. The fatigue life is decreased with the increase in VSR amplitude. When the VSR amplitude is less than 0.1 mm, the decrease in fatigue limit is less than 2%. Compared with specimens without VSR or annealing treatment, the fatigue limit of the specimens treated by VSR with 0.2 mm amplitude and annealing treatment decreases by 10.60% and 8.52%, respectively. Although the stress relieving effect is better, high amplitude VSR will lead to the decrease of Ti-6Al-4V fatigue life due to the defects generated during vibration. Low amplitude VSR can effectively relieve the stress with little decrease in fatigue life.

  5. Effect of Neoprene Coatings on the Cyclic Fatigue of Specimens and Parts Subjected to the Action of Fretting-Corrosion

    Science.gov (United States)

    1974-10-07

    CONYRAc+’ Oa OPAV4 040 0e. omeo,.4A 11wS 1116oRT 0duhsocalso Raja CT P40FTD-HC-23-2124-74 Sb. OTNCA MILPORY #40491 (Any em.,ri numnbr* Mae mar be assigned... imar l.y a ..peclal apparatus. The contact surfaces of the specImen w.*re polihed to a zmoottinezs of V 9. Three forms of o;pecimen were tested: with

  6. A novel bending fatigue test device based on self-excited vibration principle and its application to superelastic Nitinol microwire study

    Science.gov (United States)

    Leng, Jiaming; Yan, Xiaojun; Zhang, Xiaoyong; Qi, Mingjing; Liu, Zhiwei; Huang, Dawei

    2017-10-01

    Most Nitinol-alloy-based biomedical devices are usually manufactured from straight drawn microwires or microbeams. Fatigue due to cyclic bending is interpreted as the primary failure mechanism in these devices. However, the bending fatigue performance of a Nitinol microwire is rarely studied because of the lack of test devices. Therefore, we firstly establish a bending fatigue test device based on the self-excited vibration principle. Then, we further improve and experimentally verify the device in three aspects to enlarge the strain amplitude: electrode distance optimization, electrode placement angle optimization and local stiffness enhancement. Based on these improvements, the strain amplitude is increased to 6%, successfully meeting the requirements of Nitinol microwire bending fatigue tests. Using the improved test device, a group of superelastic Nitinol (55.8% Ni-44.2% Ti) microwires with a diameter of 50.8 μm are tested. The test results show that the fatigue strain limit for the chosen life (1 × 106 cycles) is around 1.9%, and the inflexion appears at a strain amplitude of 2.3%. SEM observation shows the typical features of low-cycle and high-cycle fatigue on the fracture surfaces.

  7. Efficacy of the whole-body vibration for pain, fatigue and quality of life in women with fibromyalgia: a systematic review.

    Science.gov (United States)

    Moretti, Eduarda; Tenório, Angélica; Holanda, Laís; Campos, Adriana; Lemos, Andrea

    2017-02-10

    To determine the quality of evidence on the use of whole-body vibration (WBV) in controlling pain, fatigue and quality of life in women with fibromyalgia. The search involved MEDLINE/PubMed, LILACS, CINAHL, CENTRAL and PEDro, without temporal or language restriction. The terms "fibromyalgia" and "whole-body vibration" were used. Trials (randomized or quasi-randomized) that compared a group of women with fibromyalgia who received WBV to a control group with no intervention were included. The quality of evidence was assessed using the GRADE system. The quantitative evaluation by meta-analysis was also used, whenever possible. Three studies were included. Regarding the outcome pain, it has not been possible to assess the magnitude of effect of treatment. The result of the outcome fatigue showed no difference between the groups after the proposed intervention (Mean Difference: 0.01; 95% CI: -0.11 to 0.09). The meta-analysis for the outcome quality of life showed a small difference between groups, favoring the WBV group (Standard Mean Difference: 0.4943; p = 0.05; 95% CI: 0.0045 to 0.9841). The results, based on very low quality of evidence, were inconclusive regarding pain, and showed no clinically important effects on the control of fatigue and improvement of quality of life. Implications for rehabilitation There is no evidence to support the use of whole-body vibration for pain treatment of women with fibromyalgia. The use of whole-body vibration in women with fibromyalgia showed no clinically important effects in the control of fatigue and improvement of quality of life.

  8. Wavelet analysis of lumbar muscle oxygenation signals during whole-body vibration: implications for the development of localized muscle fatigue.

    Science.gov (United States)

    Li, Zengyong; Zhang, Ming; Chen, Guoqiang; Luo, Site; Liu, Feifei; Li, Jianping

    2012-08-01

    The objective of this study was to assess the effects of whole-body vibration (WBV) on lumbar muscle oxygenation oscillations in healthy men based on the wavelet transform of near-infrared spectroscopy signals. Twelve healthy participants were exposed to WBV at frequencies of 3, 4.5 and 6 Hz while muscle oxygenation signal was monitored before, during and recovery from WBV. With spectral analysis based on wavelet transform of NIR signal, six frequency intervals were identified (I, 0.005-0.0095 Hz; II, 0.0095-0.02 Hz; III, 0.02-0.06 Hz; IV, 0.06-0.16 Hz; V, 0.16-0.40 Hz and VI, 0.40-2.0 Hz). It was found that the muscle oxygenation oscillations at 4.5 Hz in the frequency intervals I, II and III was lower during WBV compared with that of at 3 Hz. Present results demonstrated WBV at 4.5 Hz induced lower oscillatory activities than that of at 3 Hz. The lower oscillatory activities might indicate a decrease in the efficiency of oxygen supply to the oxygenated tissue and such mechanism might contribute to the development of local muscle fatigue.

  9. Fatigue limit estimation of titanium alloy Ti-6Al-4V with infrared thermography

    Science.gov (United States)

    Akai, Atsushi; Shiozawa, Daiki; Sakagami, Takahide

    2017-05-01

    Fatigue limit estimation using infrared thermography has recently received attention as a method for reducing the time required for product design. In this study, the applicability of a method based on mean temperature and dissipated energy measurements was experimentally investigated on a titanium alloy; fatigue plate specimens were fabricated from the titanium alloy Ti-6Al-4V ELI. The fatigue limit of these specimens obtained from conventional fatigue testing was found to be 620 MPa. The estimated fatigue limit obtained from mean temperature measurements was found to be 600 MPa, although estimating the fatigue limit using dissipated energy measurements was difficult because little significant change in dissipated energy values with the stress amplitude was observed. These tendencies are probably attributed to the crystal structure displaying different deformation properties and high vibration absorption properties. The resonance components from the fatigue testing instruments (noise components) were calculated from the frequency analysis of the time-series temperature fluctuation data measured by infrared thermography. The increase in the dissipated energy values (with the noise components subtracted) against the stress amplitude changed at a certain stress amplitude and the fatigue limit could be estimated to be 565 MPa. Therefore, the relative error between the fatigue limit value obtained from conventional fatigue testing and the estimated values was within 10%. The fatigue limit could be estimated more accurately by considering the influence of different deformation properties between tensile and compressive loading due to the crystal structure differences in the dissipated energy measurement.

  10. Time-dependent leak behavior of flawed Alloy 600 tube specimens at constant pressure

    Energy Technology Data Exchange (ETDEWEB)

    Bahn, Chi Bum, E-mail: bahn@anl.gov [Argonne National Laboratory, Argonne, IL 60439 (United States); Majumdar, Saurin [Argonne National Laboratory, Argonne, IL 60439 (United States); Harris, Charles [United States Nuclear Regulatory Commission, Rockville, MD 20852 (United States)

    2011-10-15

    Leak rate testing has been performed using Alloy 600 tube specimens with throughwall flaws. Some specimens have shown time-dependent leak behavior at constant pressure conditions. Fractographic characterization was performed to identify the time-dependent crack growth mechanism. The fracture surface of the specimens showed the typical features of ductile fracture, as well as the distinct crystallographic facets, typical of fatigue crack growth at low {Delta}K level. Structural vibration appears to have been caused by the oscillation of pressure, induced by a high-pressure pump used in a test facility, and by the water jet/tube structure interaction. Analyses of the leak behaviors and crack growth indicated that both the high-pressure pump and the water jet could significantly contribute to fatigue crack growth. To determine whether the fatigue crack growth during the leak testing can occur solely by the water jet effect, leak rate tests at constant pressure without the high-pressure pump need to be performed. - Highlights: > Leak rate of flawed Alloy 600 tubing increased at constant pressure condition. > Fractography revealed two cases: ductile tearing and crystallographic facets. > Crystallographic facets are typical features of fatigue crack growth at low {Delta}K. > Fatigue source could be water jet-induced vibration and/or high-pressure pump pulsation.

  11. Microstructural Characterization Of Laser Heat Treated AISI 4140 Steel With Improved Fatigue Behavior

    Directory of Open Access Journals (Sweden)

    Oh M.C.

    2015-06-01

    Full Text Available The influence of surface heat treatment using laser radiation on the fatigue strength and corresponding microstructural evolution of AISI 4140 alloy steel was investigated in this research. The AISI 4140 alloy steel was radiated by a diode laser to give surface temperatures in the range between 600 and 800°C, and subsequently underwent vibration peening. The fatigue behavior of surface-treated specimens was examined using a giga-cycle ultrasonic fatigue test, and it was compared with that of non-treated and only-peened specimens. Fatigue fractured surfaces and microstructural evolution with respect to the laser treatment temperatures were investigated using an optical microscope. Hardness distribution was measured using Vickers micro-hardness. Higher laser temperature resulted in higher fatigue strength, attributed to the phase transformation.

  12. Intercrystalline and transcrystalline vibration fatigue failure in the inconel 718 nickel-based alloy; Inter- und transkristalliner Schwingbruch in der Nickelbasislegierung Inconel 718

    Energy Technology Data Exchange (ETDEWEB)

    Wanzek, Horst; Fruhner, Annett [Lufthansa Technik AG, Hamburg (Germany). Metallurgical Lab., HAM WR123

    2011-07-01

    The fracture of the turbine rotor disc resulted in the breakdown of the APU and high expenses. The APU is located below the vertical tailplane, at the tail of every major-sized aircraft. The vane receptacle failed in the mode of a vibration fatigue failure of an intercrystalline and transcrystalline progression. The cause of this damage is attributable to the fatigue of the material. This can result from the long service life (21 131 h) and the fact that 9 more vane receptacles exhibited a comparable damage pattern. In INCONEL 718 alloys, cracks propagate in a transcrystalline way when under an alternate bend stress and at temperatures below abt. 600 C. In contrast, cracks propagate because of grain boundary oxidation above abt. 600 C in an intercrystalline way. The phenomenon that the two crack modi occurred alternately on the same fracture area is explained from the fact that the component part was exposed to different temperatures during operation. While the crack progress was transcrystalline in the ''cooler'' starting and stopping phase crack propagation occurred along the grain boundaries (was intercrystalline) in a normal operation above 600 C. Besides a limitation of the running time in its service life, other measures could not be taken for this component part. (orig.)

  13. Analysis of acoustic emission waveforms from fatigue cracks

    Science.gov (United States)

    Bhuiyan, Md. Yeasin; Bao, Jingjing; Poddar, Banibrata; Giurgiutiu, Victor

    2017-04-01

    Acoustic emission (AE) monitoring technique is a well-known approach in the field of NDE/SHM. AE monitoring from the defect formation and failure in the materials were well studied by the researchers. However, conventional AE monitoring techniques are predominantly based on statistical analysis. In this study we focus on understanding the AE waveforms from the fatigue crack growth using physics based approach. The growth of the fatigue crack causes the acoustic emission in the material that propagates in the structure. One of the main challenges of this approach is to develop the physics based understanding of the AE source itself. The acoustic emission happens not only from the crack growth but also from the interaction of the crack lips during fatigue loading of the materials. As the waveforms are generated from the AE event, they propagate and create local vibration modes along the crack faces. Fatigue experiments were performed to generate the fatigue cracks. Several test specimens were used in the fatigue experiments and corresponding AE waveforms were captured. The AE waveforms were analyzed and distinguished into different groups based on the similar nature on both time domain and frequency domain. The experimental results are explained based on the physical observation of the specimen.

  14. CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior.

    Science.gov (United States)

    Zucuni, C P; Guilardi, L F; Fraga, S; May, L G; Pereira, G K R; Valandro, L F

    2017-07-01

    This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Tissue vibration in prolonged running.

    Science.gov (United States)

    Friesenbichler, Bernd; Stirling, Lisa M; Federolf, Peter; Nigg, Benno M

    2011-01-04

    The impact force in heel-toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior-posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Experiment investigation of laser shock peening on TC6 titanium alloy to improve high cycle fatigue performance

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Xiangfan, E-mail: skingkgd@163.com; He, Weifeng; Zhou, Liucheng; Li, Qipeng; Wang, Xuede

    2014-01-31

    Laser shock peening (LSP) is an innovative surface treatment technique, and can significantly improve the fatigue performance of metallic components. In this paper, the objective of this work was to improve the fatigue resistance of TC6 titanium alloy by laser shock peening. Firstly, the effects on the microstructure and mechanical properties with different LSP impacts were investigated, which were observed and measured by X-ray diffraction (XRD), transmission electron microscope (TEM), residual stress tester and microhardness tester. Specially, nanostructure was detected in the laser-peened surface layer with multiple LSP impacts. Whereafter, a better parameter was chosen to be applied on the standard vibration fatigue specimens. Via the high-cycle vibration fatigue tests, the high cycle fatigue limits of the specimens without and with LSP were obtained and compared. The fatigue results demonstrate that LSP can effectively improve the fatigue limit of TC6 titanium alloy. The strengthening mechanism was indicated by analyzing the effects on the microstructure and mechanical properties comprehensively.

  17. Nitinol Fatigue Life for Variable Strain Amplitude Fatigue

    Science.gov (United States)

    Lin, Z.; Pike, K.; Schlun, M.; Zipse, A.; Draper, J.

    2012-12-01

    Nitinol fatigue testing results are presented for variable strain amplitude cycling. The results indicate that cycles smaller than the constant amplitude fatigue limit may contribute to significant fatigue damage when they occur in a repeating sequence of large and small amplitude cycles. The testing utilized two specimen types: stent-like diamond specimens and Z-shaped wire specimens. The diamond specimens were made from nitinol tubing with stent-like manufacturing processes and the Z-shaped wire specimens were made from heat set nitinol wire. The study explored the hypothesis that duty cycling can have an effect on nitinol fatigue life. Stent-like structures were subjected to different in vivo loadings in order to create more complex strain amplitudes. The main focus in this study was to determine whether a combination of small and large amplitudes causes additional damage that alters the fatigue life of a component.

  18. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...

  19. Heavy-section fracture toughness screening specimen

    Science.gov (United States)

    Shannon, J. L., Jr.; Brown, W. F., Jr.; Donald, J. K.

    1977-01-01

    The reported study has the objective to fix the proportions and limits of application of a double-edge-notch specimen with one of the notches tipped with a fatigue crack (DENC). Details regarding the DENC specimen are discussed, taking into account specimen length, notch length, specimen width and thickness, and the loading pins. The influence of specimen width and thickness on the crack strenght and apparent plane-strain fracture toughness of the specimen has been determined for eight alloys. It is concluded that the DENC specimen shows promise for screening alloys with reference to their plane-strain fracture toughness in sections up to 1 in.

  20. Virtual Specimens

    Science.gov (United States)

    de Paor, D. G.

    2009-12-01

    Virtual Field Trips have been around almost as long as the Worldwide Web itself yet virtual explorers do not generally return to their desktops with folders full of virtual hand specimens. Collection of real specimens on fields trips for later analysis in the lab (or at least in the pub) has been an important part of classical field geoscience education and research for generations but concern for the landscape and for preservation of key outcrops from wanton destruction has lead to many restrictions. One of the author’s favorite outcrops was recently vandalized presumably by a geologist who felt the need to bash some of the world’s most spectacular buckle folds with a rock sledge. It is not surprising, therefore, that geologists sometimes leave fragile localities out of field trip itineraries. Once analyzed, most specimens repose in drawers or bins, never to be seen again. Some end up in teaching collections but recent pedagogical research shows that undergraduate students have difficulty relating specimens both to their collection location and ultimate provenance in the lithosphere. Virtual specimens can be created using 3D modeling software and imported into virtual globes such as Google Earth (GE) where, they may be linked to virtual field trip stops or restored to their source localities on the paleo-globe. Sensitive localities may be protected by placemark approximation. The GE application program interface (API) has a distinct advantage over the stand-alone GE application when it comes to viewing and manipulating virtual specimens. When instances of the virtual globe are embedded in web pages using the GE plug-in, Collada models of specimens can be manipulated with javascript controls residing in the enclosing HTML, permitting specimens to be magnified, rotated in 3D, and sliced. Associated analytical data may be linked into javascript and localities for comparison at various points on the globe referenced by ‘fetching’ KML. Virtual specimens open up

  1. Random Fatigue Analysis of Drill-Strings in Frequency Domain

    Directory of Open Access Journals (Sweden)

    Zheng JiaHao

    2017-01-01

    Full Text Available Predicting fatigue damage induced by vibrations is of benefit to oil and gas industry. In this paper a spectral method is developed to estimate the damage of vibration, including both deterministic and random vibration, on the fatigue life of drillstrings. The drill-string is first modeled by the continuous parameter method with two vibration modes: axial and torsional. After the vibration response is obtained, the equivalent stress spectra are calculated for any position along the drill-string, based on maximum shear stress fatigue failure criterion. The fatigue life of the drill-string at arbitrary position is then estimated by the developed spectral methods

  2. Prediction of Mean and Design Fatigue Lives of Self Compacting Concrete Beams in Flexure

    Science.gov (United States)

    Goel, S.; Singh, S. P.; Singh, P.; Kaushik, S. K.

    2012-02-01

    In this paper, result of an investigation conducted to study the flexural fatigue characteristics of self compacting concrete (SCC) beams in flexure are presented. An experimental programme was planned in which approximately 60 SCC beam specimens of size 100 × 100 × 500 mm were tested under flexural fatigue loading. Approximately 45 static flexural tests were also conducted to facilitate fatigue testing. The flexural fatigue and static flexural strength tests were conducted on a 100 kN servo-controlled actuator. The fatigue life data thus obtained have been used to establish the probability distributions of fatigue life of SCC using two-parameter Weibull distribution. The parameters of the Weibull distribution have been obtained by different methods of analysis. Using the distribution parameters, the mean and design fatigue lives of SCC have been estimated and compared with Normally vibrated concrete (NVC), the data for which have been taken from literature. It has been observed that SCC exhibits higher mean and design fatigue lives compared to NVC.

  3. Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

    OpenAIRE

    Lian, B.; Ueno, A; Iwashita, T

    2016-01-01

    To substitute for a traditional replication technique, an in-situ fatigue crack observing system for rotating bending testing machine has been newly developed. For verifying performance of this observing system, fatigue tests were carried out by using fatigue specimen having a small artificial defect. It is proved that this system can be detect a small fatigue crack and its propagation behavior.

  4. Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

    OpenAIRE

    Lian, B.; Ueno, A; Iwashita, T

    2015-01-01

    To substitute for a traditional replication technique, an in-situ fatigue crack observing system for rotating bending testing machine has been newly developed. For verifying performance of this observing system, fatigue tests were carried out by using fatigue specimen having a small artificial defect. It is proved that this system can be detect a small fatigue crack and its propagation behavior.

  5. Specimen Preparation

    Science.gov (United States)

    Williams, David B.; Carter, C. Barry

    Specimen preparation is a very broad subject; there are books devoted to this topic alone. The intention here is to summarize the techniques, suggest routes that you might follow, and above all to emphasize that there are many ways to produce a TEM specimen; the one you choose will depend on the information you need, time constraints, availability of equipment, your skill, and the material. So we’ll concentrate on the ‘principles of cooking,’ but won’t try to list all the possible ‘recipes.’ One important point to bear in mind is that your technique must not affect what you see or measure, or if it does, then you must know how. Specimen preparation artifacts may be interesting but they are not usually what you want to study. Incidentally, we’ll make ‘specimens’ from the ‘sample’ we’re investigating so we’ll look at ‘TEM specimens,’ but sometimes we, and everyone else, will interchange the two words.

  6. Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects

    Science.gov (United States)

    Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.

    2011-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.

  7. Fatigue Properties of SUS304 Stainless Steel after Ultrasonic Nanocrystal Surface Modification (unsm)

    Science.gov (United States)

    Zhang, K. Y.; Pyoun, Y. S.; Cao, X. J.; Wu, B.; Murakami, R.

    The changing of materials surface properties method always was taken into improving the fatigue strength. In this paper, an ultrasonic nanocrystal surface modification(UNSM) technique was used on the SUS 304 stainless steel to form a nanostructured surface layer with different static load(70N, 90N, 110N, 130N) and the vibration strike number was about 20,000times/mm2. The untreated and different condition specimens fatigue strength was all tested by a dual-spindle rotating bending fatigue test machine. SPring-8(a large synchrotron radiation facility) was used to test the surface nanocrystallization components. The X-ray diffraction (XRD), the scanning electron microscopy (SEM), optical microscope and a micro-Vickers hardness tester (MVK-E3, Akashi) were separately used to get the surface residual stresses, fracture surface after fatigue testing, metallographic structure and the microhardness of the nanostructured surface layer. The result showed that martensite transformation took place on the surface of specimens, the surface residual stresses had only a small increase and some cracks occurred between the martensite layer and the austenite layer, but the fatigue strength of 90N improved 81%.

  8. Fatigue Behavior of Inconel 718 TIG Welds

    Science.gov (United States)

    Alexopoulos, Nikolaos D.; Argyriou, Nikolaos; Stergiou, Vasillis; Kourkoulis, Stavros K.

    2014-08-01

    Mechanical behavior of reference and TIG-welded Inconel 718 specimens was examined in the present work. Tensile, constant amplitude fatigue, and fracture toughness tests were performed in ambient temperature for both, reference and welded specimens. Microstructure revealed the presence of coarse and fine-grained heat-affected zones. It has been shown that without any post-weld heat treatment, welded specimens maintained their tensile strength properties while their ductility decreased by more than 40%. It was found that the welded specimens had lower fatigue life and this decrease was a function of the applied fatigue maximum stress. A 30% fatigue life decrease was noticed in the high cycle fatigue regime for the welded specimens while this decrease exceeded 50% in the low cycle fatigue regime. Cyclic stress-strain curves showed that Inconel 718 experiences a short period of hardening followed by softening for all fatigue lives. Cyclic fatigue response of welded specimens' exhibited cyclically stable behavior. Finally, a marginal decrease was noticed in the Mode I fracture toughness of the welded specimens.

  9. Fatigue analysis of aluminum drill pipes

    Directory of Open Access Journals (Sweden)

    João Carlos Ribeiro Plácido

    2005-12-01

    Full Text Available An experimental program was performed to investigate the fundamental fatigue mechanisms of aluminum drill pipes. Initially, the fatigue properties were determined through small-scale tests performed in an optic-mechanical fatigue apparatus. Additionally, full-scale fatigue tests were carried out with three aluminum drill pipe specimens under combined loading of cyclic bending and constant axial tension. Finally, a finite element model was developed to simulate the stress field along the aluminum drill pipe during the fatigue tests and to estimate the stress concentration factors inside the tool joints. By this way, it was possible to estimate the stress values in regions not monitored during the fatigue tests.

  10. Optimal Design of One-Folded Leaf Spring with High Fatigue Life Applied to Horizontally Vibrating Linear Actuator in Smart Phone

    Directory of Open Access Journals (Sweden)

    Ki Bum Lee

    2014-02-01

    Full Text Available Horizontally vibrating linear actuator (HVLA instead of VVLA has been under study in a few past years and recently HVLA with thickness of 2.5 mm was developed. The one-folded leaf spring to guide the moving part is newly designed and applied in HVLA, but unfortunately it makes HVLA be wider. Accordingly, this paper presents the optimal design of one-folded leaf spring, which results in reduction of HLVA width. The commercial design optimization tool “PIAnO” was utilized based on design of experiments (DOE, approximation techniques, and optimization algorithm. In addition, for the vibration modal analysis and harmonic response analysis to generate metamodeling, the software “ANSYS” is utilized. The optimal width of leaf spring was reduced by 46% compared to the initial one, while all the design constraints were satisfied, which clearly showed the validity of the proposed design approach.

  11. The concept of fatigue fracture toughness in fatigue delamination growth behavior

    NARCIS (Netherlands)

    Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This paper provides a study on mode I fatigue delamination growth in composite laminates using energy principles. Experimental data has been obtained from fatigue tests conducted on Double Cantilever Beam (DCB) specimens at various stress ratios. A concept of fatigue fracture toughness is proposed

  12. Biaxial fatigue of metals the present understanding

    CERN Document Server

    Schijve, Jaap

    2016-01-01

    Problems of fatigue under multiaxial fatigue loads have been addressed in a very large number of research publications. The present publication is primarily a survey of biaxial fatigue under constant amplitude loading on metal specimens. It starts with the physical understanding of the fatigue phenomenon under biaxial fatigue loads. Various types of proportional and non-proportional biaxial fatigue loads and biaxial stress distributions in a material are specified. Attention is paid to the fatigue limit, crack nucleation, initial micro crack growth and subsequent macro-crack in different modes of crack growth. The interference between the upper and lower surfaces of a fatigue crack is discussed. Possibilities for predictions of biaxial fatigue properties are analysed with reference to the similarity concept. The significance of the present understanding for structural design problems is considered. The book is completed with a summary of major observations.

  13. Fatigue in tension perpendicular to the grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In order to test the predictive validity of the result from the small tension specimens, fatigue experiments...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...

  14. Fatigue In Tension Perpendicular to the Grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben

    2004-01-01

    Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In arder to test the predictive validity of the result from the small tension specimens, fatigue experiments...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...

  15. Prediction of Fatigue Life Considering Scatter

    OpenAIRE

    皮籠石, 紀雄; 西谷, 弘信; 後藤, 真宏; 豊廣, 利信; 北山, 智

    1993-01-01

    Fatigue life of a plain specimen is stochastic and consists mainly of the growth life of small cracks. Therefore, the distribution of fatigue life can be evaluated through the statistical properties in the growth of small cracks. In the present paper, rotating bending fatigue tests were carried out on specimens with two small blind holes in 0.42% carbon steel in order to investigate the distribution characteristics of the fatigue crack growth life based on the small-crack growth law, dl/dN=Cσ...

  16. Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

    Directory of Open Access Journals (Sweden)

    B. Lian

    2016-02-01

    Full Text Available To substitute for a traditional replication technique, an in-situ fatigue crack observing system for rotating bending testing machine has been newly developed. For verifying performance of this observing system, fatigue tests were carried out by using fatigue specimen having a small artificial defect. It is proved that this system can be detect a small fatigue crack and its propagation behavior.

  17. Corrosion Fatigue in District Heating Water Tanks

    DEFF Research Database (Denmark)

    Maahn, Ernst Emanuel

    1996-01-01

    Three candidate materials for construction of buffer tanks for district heating water have been tested for corrosion fatigue properties in a district heating water environment. The investigation included Slow Strain Rate Testing of plain tensile specimens, crack initiation testing by corrosion...... fatigue of plain tensile specimens and crack growth rate determination for Compact Tensile Specimens under corrosion fatigue conditions. The three materials are equal with respect to stress corrosion sensibility and crack initiation. Crack growth rate is increased with a factor of 4-6 relative to an inert...

  18. Biaxial Fatigue Cracking from Notch

    Science.gov (United States)

    2013-03-04

    of the central notch. BIAXIAL FATIGUE TEST The biaxial fatigue test was conducted in a MTS 793.10 Multiaxial Purpose Test-Ware with two pairs...of servo -hydraulic actuators and two pairs of load cells, arranged perpendicular to each other on a horizontal plane in a rigid frame, Figure A-1...TR-2009/12, of 19 Feb 2009. NAWCADPAX/TR-2013/32 15 APPENDIX A FIGURES 1. MTS Machine and Cruciform Specimen 2. Effect of Biaxiality

  19. Fatigue, Creep-Fatigue, and Thermomechanical Fatigue Life Testing of Alloys

    Science.gov (United States)

    Halford, Gary R.; Lerch, Bradley A.; McGaw, Michael A.

    2000-01-01

    The fatigue crack initiation resistance of an alloy is determined by conducting a series of tests over a range of values of stress amplitude or strain range. The observed number of cycles to failure is plotted against the stress amplitude or strain range to obtain a fatigue curve. The fatigue properties quoted for an alloy are typically the constants used in the equation(s) that describe the fatigue curve. Fatigue lives of interest may be as low as 10(exp 2) or higher than 10(exp 9) cycles. Because of the enormous scatter associated with fatigue, dozens of tests may be needed to confidently establish a fatigue curve, and the cost may run into several thousands of dollars. To further establish the effects on fatigue life of the test temperature, environment, alloy condition, mean stress effects, creep-fatigue effects, thermomechanical cycling, etc. requires an extraordinarily large and usually very costly test matrix. The total effort required to establish the fatigue resistance of an alloy should not be taken lightly. Fatigue crack initiation tests are conducted on relatively small and presumed to be initially crack-free, samples of an alloy that are intended to be representative of the alloy's metallurgical and physical condition. Generally, samples are smooth and have uniformly polished surfaces within the test section. Some may have intentionally machined notches of well-controlled geometry, but the surface at the root of the notch is usually not polished. The purpose of polishing is to attain a reproducible surface finish. This is to eliminate surface finish as an uncontrolled variable. Representative test specimen geometries will be discussed later. Test specimens are cyclically loaded until macroscopically observable cracks initiate and eventually grow to failure. Normally, the fatigue failure life of a specimen is defined as the number of cycles to separation of the specimen into two pieces. Alternative definitions are becoming more common, particularly for

  20. Effect of vibration stabilization of the process of postcritical deformation

    Science.gov (United States)

    Wildemann, V. E.; Lomakin, E. V.; Tretyakov, M. P.

    2016-03-01

    Results of the experimental study of vibration stabilization of the process of postcritical deformation during the tensile testing of solid cylindrical specimens made of 20 and 40Cr structural steels under additional vibrations are presented. The vibrations are implemented using cyclic torsion of the specimens at a small amplitude and a frequency of 10-30 Hz.

  1. Evaluation of hybrid composite materials in cylindrical specimen geometries

    Science.gov (United States)

    Liber, T.; Daniel, I. M.

    1976-01-01

    Static and fatigue properties of three composite materials and hybrids were examined. The materials investigated were graphite/epoxy, S-glass/epoxy, PRD-49 (Kevlar 49)/epoxy, and hybrids in angle-ply configurations. A new type of edgeless cylindrical specimen was developed. It is a flattened tube with two flat sides connected by curved sections and it is handled much like the standard flat coupon. Special specimen fabrication, tabbing, and tab region reinforcing techniques were developed. Axial modulus, Poisson's ratio, strength, and ultimate strain were obtained under static loading from flattened tube specimens of nine laminate configurations. In the case of graphite/epoxy the tubular specimens appeared to yield somewhat higher strength and ultimate strain values than flat specimens. Tensile fatigue tests were conducted with all nine types of specimens and S-N curves obtained. Specimens surviving 10 million cycles of tensile loading were subsequently tested statically to failure to determine residual properties.

  2. Postdialysis fatigue.

    Science.gov (United States)

    Sklar, A H; Riesenberg, L A; Silber, A K; Ahmed, W; Ali, A

    1996-11-01

    To clarify the demographic and clinicolaboratory features of postdialysis fatigue (PDF), we enrolled 85 patients on maintenance hemodialysis in a cross-sectional study using validated questionnaires and chart review. Forty-three patients complained of fatigue after dialysis. On formal testing using the Kidney Disease Questionnaire, the PDF group had statistically greater severity of fatigue and somatic complaints than the group of patients without subjective fatigue (P = 0.03 and 0.04, respectively). On a scale measuring intensity of fatigue (1 = least to 5 = worst), the PDF group average was 3.4 +/- 1.2. PDF subjects reported that 80% +/- 25% of dialysis treatments were followed by fatigue symptoms. In 28 (65%) of patients, the symptoms started with the first dialysis treatment. They reported needing an average of 4.8 hours of rest or sleep to overcome the fatigue symptoms (range, 0 to 24 hours). There were no significant differences between patients with and without PDF in the following parameters: age; sex; type of renal disease; presence of diabetes mellitus, heart disease (congestive, ischemic), or chronic obstructive lung disease; blood pressure response to dialysis; type or adequacy of dialysis regimen; hematocrit; electrolytes; blood urea nitrogen; creatinine; cholesterol; albumin; parathyroid hormone; ejection fraction; and use of antihistamines, benzodiazepines, and narcotics. In the fatigue group, there was significantly greater use of antihypertensive medications known to have fatigue as a side effect (P = 0.007). Depression was more common in the fatigue group by Beck Depression score (11.6 +/- 8.0 v 7.8 +/- 6.3; P = 0.02). We conclude that (1) postdialysis fatigue is a common, often incapacitating symptom in patients on chronic extracorporeal dialysis; (2) no routinely measured parameter of clinical or dialytic function appears to predict postdialysis fatigue; and (3) depression is highly associated with postdialysis fatigue, but the cause

  3. Probabilistic fatigue life prediction methodology for notched components based on simple smooth fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. R.; Li, Z. X. [Dept.of Engineering Mechanics, Jiangsu Key Laboratory of Engineering Mechanics, Southeast University, Nanjing (China); Hu, X. T.; Xin, P. P.; Song, Y. D. [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing (China)

    2017-01-15

    The methodology of probabilistic fatigue life prediction for notched components based on smooth specimens is presented. Weakestlink theory incorporating Walker strain model has been utilized in this approach. The effects of stress ratio and stress gradient have been considered. Weibull distribution and median rank estimator are used to describe fatigue statistics. Fatigue tests under different stress ratios were conducted on smooth and notched specimens of titanium alloy TC-1-1. The proposed procedures were checked against the test data of TC-1-1 notched specimens. Prediction results of 50 % survival rate are all within a factor of two scatter band of the test results.

  4. Evaluating cyclic fatigue of sealants during outdoor testing

    Science.gov (United States)

    R. Sam Williams; Steven Lacher; Corey Halpin; Christopher White

    2009-01-01

    A computer-controlled test apparatus (CCTA) and other instrumentation for subjecting sealant specimens to cyclic fatigue during outdoor exposure was developed. The CCTA enables us to use weather-induced conditions to cyclic fatigue specimens and to conduct controlled tests in-situ during the outdoor exposure. Thermally induced dimensional changes of an aluminum bar...

  5. Replacement/Refurbishment of JSC/NASA POD Specimens

    Science.gov (United States)

    Castner, Willard L.

    2010-01-01

    The NASA Special NDE certification process requires demonstration of NDE capability by test per NASA-STD-5009. This test is performed with fatigue cracked specimens containing very small cracks. The certification test results are usually based on binomial statistics and must meet a 90/95 Probability of Detection (POD). The assumption is that fatigue cracks are tightly closed, difficult to detect, and inspectors and processes passing such a test are well qualified for inspecting NASA fracture critical hardware. The JSC NDE laboratory has what may be the largest inventory that exists of such fatigue cracked NDE demonstration specimens. These specimens were produced by the hundreds in the late 1980s and early 1990s. None have been produced since that time and the condition and usability of the specimens are questionable.

  6. High Energy Vibration for Gas Piping

    Science.gov (United States)

    Lee, Gary Y. H.; Chan, K. B.; Lee, Aylwin Y. S.; Jia, ShengXiang

    2017-07-01

    In September 2016, a gas compressor in offshore Sarawak has its rotor changed out. Prior to this change-out, pipe vibration study was carried-out by the project team to evaluate any potential high energy pipe vibration problems at the compressor’s existing relief valve downstream pipes due to process condition changes after rotor change out. This paper covers high frequency acoustic excitation (HFAE) vibration also known as acoustic induced vibration (AIV) study and discusses detailed methodologies as a companion to the Energy Institute Guidelines for the avoidance of vibration induced fatigue failure, which is a common industry practice to assess and mitigate for AIV induced fatigue failure. Such detailed theoretical studies can help to minimize or totally avoid physical pipe modification, leading to reduce offshore plant shutdown days to plant shutdowns only being required to accommodate gas compressor upgrades, reducing cost without compromising process safety.

  7. Fatigue behaviour of synthetic nodular cast irons

    Directory of Open Access Journals (Sweden)

    A. Vaško

    2015-01-01

    Full Text Available The paper shows the influence of charge composition on microstructure, fatigue properties and failure micromechanisms of nodular cast irons. The additive of metallurgical silicon carbide (SiC in analysed specimens increases the content of ferrite in the matrix, decreases the size of graphite and increases the average count of graphitic nodules per unit of area. Consequently, the mechanical and fatigue properties of nodular cast iron are improved. The best fatigue properties (fatigue strength were reached in the melt which was created by 60 % of steel scrap and 40 % of pig iron in the basic charge with SiC additive.

  8. Gigacycle Fatigue Properties of Hydrogen-Charged JIS-SCM440 Low-Alloy Steel Under Ultrasonic Fatigue Testing

    Science.gov (United States)

    Furuya, Yoshiyuki; Hirukawa, Hisashi; Hayakawa, Masao

    2010-09-01

    Gigacycle fatigue tests were conducted on hydrogen-charged low-alloy steel. In this study, high- and low-strength specimens were prepared to investigate the effects of hydrogen on internal and surface fractures, respectively. The fatigue tests were conducted mainly by ultrasonic fatigue testing at 20 kHz and additionally by conventional servohydraulic fatigue testing at 50 Hz. All high-strength specimens revealed internal fractures. The fatigue strength of the hydrogen-charged specimens was much lower than that of the uncharged specimens. In the low-strength specimens, the uncharged specimens revealed surface fractures in the short-life regions in addition to internal fractures in the long-life regions. However, the hydrogen-charged specimens revealed internal fractures only that were combined with a much lower fatigue strength. The difference in fracture surfaces was small between the hydrogen-charged and the uncharged specimens, whereas the optically dark areas of the hydrogen-charged specimens seemed smaller than those of the uncharged specimens.

  9. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

    This study is centred on assessment of the fatigue strength of titanium fusion welds for deep-water riser's applications. Deep-water risers are subjected to significant fatigue loading. Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments. The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechanics modelling of fatigue crack growth. Two series of welded grade of titanium consisting of 14 specimens in each series were fatigue tested under constant amplitude loading. Prior to fatigue testing, strain gauge measurements of some specimens was conducted to enable the definition of stress range in the fatigue assessment procedure. The results were compared with finite solid element analysis and related to fatigue stresses in a riser pipe wall. Distribution and geometry of internal and surface defects both in the as-welded and in the post-weld machined conditions were assessed using fractography. This served as a tool to determine the fatigue initiation point in the welds. Fracture mechanics was applied to model fatigue strength of titanium welds with initiation from weld defects. Two different stress intensity factor formulations for embedded eccentrically placed cracks were used for analysis of elliptical cracks with the major axis parallel and close to one of the free surfaces. The methods were combined to give a satisfactory model for crack growth analysis. The model analyses crack growth of elliptical and semi-elliptical cracks in two directions, with updating of the crack geometry. Fatigue strength assessment was conducted using two crack growth models, the Paris-Erdogan relation with no threshold and the Donahue et al. relation with an implied threshold. The model was validated against experimental data, with a discussion on the choice of crack growth model. (author)

  10. A Fatigue Measuring Protocol for Wireless Body Area Sensor Networks.

    Science.gov (United States)

    Akram, Sana; Javaid, Nadeem; Ahmad, Ashfaq; Khan, Zahoor Ali; Imran, Muhammad; Guizani, Mohsen; Hayat, Amir; Ilahi, Manzoor

    2015-12-01

    As players and soldiers preform strenuous exercises and do difficult and tiring duties, they are usually the common victims of muscular fatigue. Keeping this in mind, we propose FAtigue MEasurement (FAME) protocol for soccer players and soldiers using in-vivo sensors for Wireless Body Area Sensor Networks (WBASNs). In FAME, we introduce a composite parameter for fatigue measurement by setting a threshold level for each sensor. Whenever, any sensed data exceeds its threshold level, the players or soldiers are declared to be in a state of fatigue. Moreover, we use a vibration pad for the relaxation of fatigued muscles, and then utilize the vibrational energy by means of vibration detection circuit to recharge the in-vivo sensors. The induction circuit achieves about 68 % link efficiency. Simulation results show better performance of the proposed FAME protocol, in the chosen scenarios, as compared to an existing Wireless Soccer Team Monitoring (WSTM) protocol in terms of the selected metrics.

  11. Assessment of Fatigue in Aviation Crews

    Science.gov (United States)

    1987-06-01

    metabolism, nutrition, anoxia, heat stress, sleep decrement, cognitive work capacity, vision decrement, vibration and sleep patterns. This list represents... cognitive and behavioral disorganization. These are states which most probably will deviate from a person’s internal demands. And, therefore, the concern...Mishaps and Fatigue," Aviation- Space. and Environmental Medicine, June 1983, Vol. 54, No. 6, pp. 535-538. Cameron, C.A., "Theory of Fatigue," Ergonomi

  12. Assessment of fatigue crack length via plastic deformation in compact tension specimens using magnetic Barkhausen noise; Evaluacion de la longitud de grietas por fatiga mediante la deformacion plastica en muestras compactas de traccion empleando el ruido magnetico de Barkhausen

    Energy Technology Data Exchange (ETDEWEB)

    Reyes-Rodriguez, F. de los; Diego-Velasco, G. de; Capo-Sanchez, J.; Franco-Fidalgo, E.

    2013-07-01

    In this paper the influence of different parameters on crack length is determined via plastic deformation using magnetic Barkhausen noise; the compact specimens steel used in this study were 12Cr1MoV and 11Cr1Mo, which are used for steam transportation on power plants. The main objective of this paper is to determine the crack length and its incubation time using magnetic Barkhausen noise, which lets to improve the pre-cracking process prior creep crack growth rate test simulating the real conditions of high pressure and temperature of main steam lines. Results showed that mean root square and maximum pick of voltage decrease with plastic deformation for each steel analyzed in this work, on the other hand, with the increasing of plastic deformation, a logic relationship between plastic deformation and spectrum density is observed for mid frequencies values, as well as, a variation of the amplitude, width and shape of the Barkhausen signal envelope. (Author)

  13. Urine culture - catheterized specimen

    Science.gov (United States)

    Culture - urine - catheterized specimen; Urine culture - catheterization; Catheterized urine specimen culture ... International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis . 2010;50(5): ...

  14. Fatigue (PDQ)

    Science.gov (United States)

    ... home. Depression. Anxiety. Trouble sleeping. Younger age. Being underweight. Having advanced cancer or other medical conditions. Fatigue ... detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health ...

  15. Fatigue in Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    1999-01-01

    Fatigue damage accumulation in steel structures under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series have been carried through on various...... types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel with a yield stress of ~ 360-410 MPa or high-strength steel with a yield stress of ~ 810-1010 MPa. The fatigue tests and the fracture mechanics analyses...... test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner's rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from Miner's rule will depend...

  16. EFRC guidelines for vibrations in reciprocating compressor systems

    NARCIS (Netherlands)

    Eijk, A.

    2008-01-01

    One of the disadvantages of a reciprocating compressor is that it generates pulsations and vibrations, which, without limitation and proper attention during design, manufacturing, installation and operation, can lead to fatigue failures, inefficiency, capacity limitations and unsafe situations. To

  17. Does EMG activation differ among fatigue-resistant leg muscles ...

    African Journals Online (AJOL)

    ... higher frequencies (max 40Hz) and amplitudes (4mm) (p≤0.001). The results could be useful for the optimal prescription of vibration exercise and can guide the development of training and rehabilitation programmes. Key words: Fatigue; Fatigue resistance; Isokinetic; Rehabilitation; Muscle activation; Electromyography.

  18. Wave propagation in coated cylinders with reference to fretting fatigue

    Indian Academy of Sciences (India)

    Fretting fatigue is the phenomenon of crack initiation due to dynamic contact loading, a situation which is commonly encountered in mechanical couplings subjected to vibration. The study of fretting fatigue in high frequency regime has gained importance in recent years. However the stress wave effects at high frequency y ...

  19. Abnormal vibration induced illusion of movement in essential tremor: evidence for abnormal muscle spindle afferent function

    OpenAIRE

    Frima, N; Grunewald, R

    2005-01-01

    Objectives: Vibration induced illusion of movement (VIIM) is abnormal in patients with idiopathic focal dystonia, an abnormality which corrects with fatigue of the vibrated muscle. Since dystonia and essential tremor sometimes coexist in families, we investigated the perception of VIIM and the effect of fatigue on VIIM in patients with essential tremor.

  20. [Auditory fatigue].

    Science.gov (United States)

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

    Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.

  1. VHCF Properties of A7075-T651 Al Alloy Depending on Shot Peening and Fatigue Testing Methods

    Directory of Open Access Journals (Sweden)

    Min-Soo Suh

    2015-01-01

    Full Text Available Fatigue characteristics of A7075-T651 aluminum material were studied with surface treatment of shot peening. The fatigue life was characterized by two fatigue testing methods, ultrasonic fatigue test (UFT, 20 kHz and the rotary-bending fatigue test (RFT, 53 Hz. The fatigue life improvement was confirmed by rotary bending fatigue tester. However, the surface modification effects were hardly observed by UFT method. The RFT results validate that the fatigue properties of RFT show a fine congruence regardless of the test machine types. The results of hardness, compressive residual stress, fatigue strength, and mechanical properties of specimen were improved by shot peening.

  2. Standard guide for fretting fatigue testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This guide defines terminology and covers general requirements for conducting fretting fatigue tests and reporting the results. It describes the general types of fretting fatigue tests and provides some suggestions on developing and conducting fretting fatigue test programs. 1.2 Fretting fatigue tests are designed to determine the effects of mechanical and environmental parameters on the fretting fatigue behavior of metallic materials. This guide is not intended to establish preference of one apparatus or specimen design over others, but will establish guidelines for adherence in the design, calibration, and use of fretting fatigue apparatus and recommend the means to collect, record, and reporting of the data. 1.3 The number of cycles to form a fretting fatigue crack is dependent on both the material of the fatigue specimen and fretting pad, the geometry of contact between the two, and the method by which the loading and displacement are imposed. Similar to wear behavior of materials, it is important t...

  3. Fatigue Strength and Crack Initiation Mechanism of Very-High-Cycle Fatigue for Low Alloy Steels

    Science.gov (United States)

    Hong, Youshi; Zhao, Aiguo; Qian, Guian; Zhou, Chengen

    2012-08-01

    The fatigue strength and crack initiation mechanisms of very-high-cycle fatigue (VHCF) for two low alloy steels were investigated. Rotary bending tests at 52.5 Hz with hour-glass type specimens were carried out to obtain the fatigue propensity of the test steels, for which the failure occurred up to the VHCF regime of 108 cycles with the S-N curves of stepwise tendency. Fractography observations show that the crack initiation of VHCF is at subsurface inclusion with "fish-eye" pattern. The fish-eye is of equiaxed shape and tends to tangent the specimen surface. The size of the fish-eye becomes large with the increasing depth of related inclusion from the surface. The fish-eye crack grows faster outward to the specimen surface than inward. The values of the stress intensity factor ( K I ) at different regions of fracture surface were calculated, indicating that the K I value of fish-eye crack is close to the value of relevant fatigue threshold (Δ K th ). A new parameter was proposed to interpret the competition mechanism of fatigue crack initiation at the specimen surface or at the subsurface. The simulation results indicate that large inclusion size, small grain size, and high strength of material will promote fatigue crack initiation at the specimen subsurface, which are in agreement with experimental observations.

  4. Experimental Determination of Stress Intensity in a Cracked Cylindrical Specimen,

    Science.gov (United States)

    1980-05-01

    CRACKED CYLINDRICAL SPEC IMEN 7 ABSTRACT The range of stress intensity at the tip of a fatigue crack is the major factor controlling the crack growth...of this report will be similarly clesiied): The range of stress intensity at the tip of a fatigue crack is the major factor controlling the crack...EXPERIMENTAL STRESS INTENSITY CALIBRATION 3 3. EXPERIMENTAL DETAILS 4 3.1 Specimen Geometries 4 3.2 Material 5 3.3 Fatigue Loading 5 3.4 Crack Length

  5. Chronic Fatigue Syndrome

    Science.gov (United States)

    Chronic fatigue syndrome (CFS) is a disorder that causes extreme fatigue. This fatigue is not the kind of tired feeling that ... activities. The main symptom of CFS is severe fatigue that lasts for 6 months or more. You ...

  6. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2009-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...... of the investigation, fatigue test series with a total of 540 fatigue tests have been carried through on various types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel or high-strength steel. The fatigue tests...... and variable amplitude fatigue test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner’s rule, which is normally used in the design against fatigue in steel structures, may give results, which are unconservative, and that the validity of the results obtained from...

  7. Study on Tension-Compression Fatigue Properties of Hard Machined Components

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2015-01-01

    Full Text Available Hard turning and fatigue tests are conducted to study the influence of cutting process on the fatigue properties of hard machined components in this work. The specimens are machined under various cutting speeds and tool wear condition. Tension-compression fatigue tests of the specimens are performed. The typical fatigue fracture patterns are observed and discussed. The fatigue life of the specimens is recorded and compared. The mechanism of the influence of white layer on fatigue properties is proposed, and the effects of white layer on the fatigue life are obtained. The changing process of tensile and compressive residual stresses is discussed. The effects of surface residual stress and maximum residual stress on the fatigue life are clarified.

  8. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    Science.gov (United States)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  9. Fatigue Properties of the Ultra-High Strength Steel TM210A.

    Science.gov (United States)

    Yin, Guang-Qiang; Kang, Xia; Zhao, Gui-Ping

    2017-09-09

    This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = -1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 10⁷ cycles. A double weighted least square method was then used to fit the stress-life (S-N) curve. The S-N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69.

  10. Non-traditional vibration mitigation methods for reciprocating compressor system

    NARCIS (Netherlands)

    Eijk, A.; Lange, T.J. de; Vreugd, J. de; Slis, E.J.P.

    2016-01-01

    Reciprocating compressors generate vibrations caused by pulsation-induced forces, mechanical (unbalanced) free forces and moments, crosshead guide forces and cylinder stretch forces. The traditional way of mitigating the vibration and cyclic stress levels to avoid fatigue failure of parts of the

  11. Cost-effective and detailed modelling of compressor manifold vibrations

    NARCIS (Netherlands)

    Eijk, A.; Egas, G.; Smeulers, J.P.M.

    1996-01-01

    In systems with large reciprocating compressors, so-called compressor manifold vibrations can contribute to fatigue failure of the pipe system. These vibrations are excited by pulsation-induced forces and by forces generated by the compressor. This paper describes an advanced and accurate method for

  12. Research and development studies for predicting the thermal fatigue; Etudes de R and D pour la prediction de la fatigue thermique

    Energy Technology Data Exchange (ETDEWEB)

    Moulin, D.; Garnier, J.; Fissolo, A.; Lejeail, Y. [CEA, 75 - Paris (France); Stephan, J.M.; Moinereau, D.; Masson, J. [Electricite de France, Les Renardieres, 77 - Moret sur Loing (France). Direction des Etudes et Recherches

    2001-07-01

    This paper presents some studies in development or realized in the EDF and CEA laboratories, concerning the thermal fatigue damage in nuclear reactor components. The first part presents the basic principles and the methods of lifetime prediction. The second part gives some examples on sodium loop, water loop, welded junctions resistance to thermal fatigue and tests on fatigue specimen. (A.L.B.)

  13. The fatigue life of a cobalt-chromium alloy after laser welding.

    Science.gov (United States)

    Al-Bayaa, Nabil Jalal Ahmad; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

    2011-03-01

    The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld.

  14. Fretting Fatigue with Cylindrical-On-Flat Contact: Crack Nucleation, Crack Path and Fatigue Life

    Science.gov (United States)

    Noraphaiphipaksa, Nitikorn; Manonukul, Anchalee; Kanchanomai, Chaosuan

    2017-01-01

    Fretting fatigue experiments and finite element analysis were carried out to investigate the influence of cylindrical-on-flat contact on crack nucleation, crack path and fatigue life of medium-carbon steel. The location of crack nucleation was predicted using the maximum shear stress range criterion and the maximum relative slip amplitude criterion. The prediction using the maximum relative slip amplitude criterion gave the better agreement with the experimental result, and should be used for the prediction of the location of crack nucleation. Crack openings under compressive bulk stresses were found in the fretting fatigues with flat-on-flat contact and cylindrical-on-flat contacts, i.e., fretting-contact-induced crack openings. The crack opening stress of specimen with flat-on-flat contact was lower than those of specimens with cylindrical-on-flat contacts, while that of specimen with 60-mm radius contact pad was lower than that of specimen with 15-mm radius contact pad. The fretting fatigue lives were estimated by integrating the fatigue crack growth curve from an initial propagating crack length to a critical crack length. The predictions of fretting fatigue life with consideration of crack opening were in good agreement with the experimental results. PMID:28772522

  15. Fatigue Life of High-Strength Steel Offshore Tubular Joints

    DEFF Research Database (Denmark)

    Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

    1996-01-01

    In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high......-strength steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained...

  16. Monitoring vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering

    2003-12-01

    The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.

  17. USE OF ROUND BAR SPECIMEN IN FRACTURE TOUGHNESS TEST OF METALLIC MATERIALS

    OpenAIRE

    NEELAKANTHA V LONDE,; DR. T.JAYARAJU; DR. P.R.SADANANDA RAO

    2010-01-01

    The fracture toughness of high strength metallic materials is determined by standard test methods like ASTM E 399, ASTM E-1820 using standard specimen geometries such as Compact tension (CT) or Single edge notched bend (SENB) specimens. This paper explains a simple test methodology based on fracture mechanics approach usingcircumferentially cracked round bar (CCRB) specimen. Specimen preparation and fatigue precracking is quite simple, consuming less material and machining time. This CCRB, be...

  18. Fatigue Analysis of Proton Exchange Membrane Fuel Cell Stacks Based on Structural Stress Distribution

    Science.gov (United States)

    Wu, C. W.; Liu, B.; Wei, M. Y.; Liu, L. F.

    2017-05-01

    Proton exchange membrane fuel cell (PEMFC) stack usually undergoes various vibrations during packing, transportation and serving time, in particular for those used in the automobiles and portable equipment. Based on the Miner fatigue damage theory, the fatigue lives of the fuel cell components are first assessed. Then the component fatigue life contours of the stack are obtained under four working conditions, i.e. the three single-axial (in X-, Y- and Z-axis separately) and multi-axial random vibrations. Accordingly, the component damage under various vibrations is evaluated. The stress distribution on the gasket and PEM will greatly affect their fatigue lives. Finally, we compare the fatigue lives of 4-bolt- and 6-bolt-clamping stacks under the same total clamping force, and find that increasing the bolt number could improve the bolt fatigue lives.

  19. Fatigue Analysis of Load-Carrying Fillet Welds

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tychsen, Jesper; Andersen, Jens Ulfkjær

    2006-01-01

    is a doubler plate connection, which is often applied in connection with modifications of offshore structures. As a part of the present work, fatigue tests have been performed with test specimens fabricated by the current industry standard for welded offshore steel structures. The fatigue tests show....... Using the test results, it is shown that the new definition of fatigue stress can be used for a wide range of DOB with a low standard deviation of the resulting SN curve....

  20. Stress analysis of vibrating pipelines

    Science.gov (United States)

    Zachwieja, Janusz

    2017-03-01

    The pipelines are subject to various constraints variable in time. Those vibrations, if not monitored for amplitude and frequency, may result in both the fatigue damage in the pipeline profile at high stress concentration and the damage to the pipeline supports. If the constraint forces are known, the system response may be determined with high accuracy using analytical or numerical methods. In most cases, it may be difficult to determine the constraint parameters, since the industrial pipeline vibrations occur due to the dynamic effects of the medium in the pipeline. In that case, a vibration analysis is a suitable alternative method to determine the stress strain state in the pipeline profile. Monitoring the pipeline vibration levels involves a comparison between the measured vibration parameters and the permissible values as depicted in the graphs for a specific pipeline type. Unfortunately, in most cases, the studies relate to the petrochemical industry and thus large diameter, long and straight pipelines. For a pipeline section supported on both ends, the response in any profile at the entire section length can be determined by measuring the vibration parameters at two different profiles between the pipeline supports. For a straight pipeline section, the bending moments, variable in time, at the ends of the analysed section are a source of the pipe excitation. If a straight pipe section supported on both ends is excited by the bending moments in the support profile, the starting point for the stress analysis are the strains, determined from the Euler-Bernoulli equation. In practice, it is easier to determine the displacement using the experimental methods, since the factors causing vibrations are unknown. The industrial system pipelines, unlike the transfer pipelines, are straight sections at some points only, which makes it more difficult to formulate the equation of motion. In those cases, numerical methods can be used to determine stresses using the

  1. Seafarer fatigue

    DEFF Research Database (Denmark)

    Jepsen, Jørgen Riis; Zhao, Zhiwei; van Leeuwen, Wessel M. A.

    2015-01-01

    Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating...... and metabolic pathways to the development of chronic diseases that are particularly prevalent in seafarers. Conclusions: Taking into account the frequency of seafarer fatigue and the severity of its consequences, one should look into the efficacy of the current legislative framework and the industry’s...... compliance, the manning of the international merchant fleet, and optimised working, living and sleeping conditions at sea. Considering circumstances at sea, e.g. working in shifts and crossing time zones, that cannot be altered, further assessment of the potentials of preventive interventions including...

  2. High cycle fatigue of AA6082 and AA6063 aluminum extrusions

    Science.gov (United States)

    Nanninga, Nicholas E.

    The high cycle fatigue behavior of hollow extruded AA6082 and AA6063 aluminum extrusions has been studied. Hollow extruded aluminum profiles can be processed into intricate shapes, and may be suitable replacements for fatigue critical automotive applications requiring reduced weight. There are several features inherent in hollow aluminum extrusions, such as seam welds, charge welds, microstructural variations and die lines. The effects of such extrusion variables on high cycle fatigue properties were studied by taking specimens from an actual car bumper extrusion. It appears that extrusion die lines create large anisotropy differences in fatigue properties, while welds themselves have little effect on fatigue lives. Removal of die lines greatly increased fatigue properties of AA6082 specimens taken transverse to the extrusion direction. Without die lines, anisotropy in fatigue properties between AA6082 specimens taken longitudinal and transverse to the extrusion direction, was significantly reduced, and properties associated with the orientation of the microstructure appears to be isotropic. A fibrous microstructure for AA6082 specimens showed great improvements in fatigue behavior. The effects of elevated temperatures and exposure of specimens to NaCl solutions was also studied. Exposure to the salt solution greatly reduced the fatigue lives of specimens, while elevated temperatures showed more moderate reductions in fatigue lives.

  3. Vibrational Diver

    Science.gov (United States)

    Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef

    2014-10-01

    The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

  4. Rotary bending fatigue properties of Inconel 718 alloys by ultrasonic nanocrystal surface modification technique

    Directory of Open Access Journals (Sweden)

    Jun-Hyong Kim

    2015-08-01

    Full Text Available This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM technique on fatigue properties of SAE AMS 5662 (solution treatment of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue tester. Results revealed that the UNSM-treated specimens showed longer fatigue life in comparison with those of the untreated specimens. The improvement in fatigue life of the UNSM-treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analysed using a scanning electron microscopy (SEM in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.

  5. Fatigue in Welded High-Strength Steel Plate Elements under Stochastic Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1999-01-01

    The present project is a part of an investigation on fatigue in offshore structures in high-strength steel. The fatigue life of plate elements with welded attachments is studied. The material used has a yield stress of ~ 810-840 MPa, and high weldability and toughness properties. Fatigue test...... series with constant amplitude loading and with various types of stochastic loading have been carried through on test specimens in high-strength steel, and - for a comparison - on test specimens in conventional offshore structural steel with a yield stress of ~ 400-410 MPa.A comparison between constant...... amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those...

  6. Controlled Environment Specimen Transfer

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad; Zandbergen, Henny W.; Hansen, Thomas Willum

    2014-01-01

    an environmental transmission electron microscope to an in situ X-ray diffractometer through a dedicated transmission electron microscope specimen transfer holder, capable of sealing the specimen in a gaseous environment at elevated temperatures. Two catalyst material systems have been investigated; Cu/ZnO/Al2O3...... transferred in a reactive environment to the environmental transmission electron microscope where further analysis on the local scale were conducted. The Co/Al2O3 catalyst was reduced in the environmental microscope and successfully kept reduced outside the microscope in a reactive environment. The in situ......Specimen transfer under controlled environment conditions, such as temperature, pressure, and gas composition, is necessary to conduct successive complementary in situ characterization of materials sensitive to ambient conditions. The in situ transfer concept is introduced by linking...

  7. Side Effects: Fatigue

    Science.gov (United States)

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  8. Conditioning monitoring by microstructural evaluation of cumulative fatigue damage

    Science.gov (United States)

    Fukuoka, C.; Nakagawa, Y. G.; Lance, J. J.; Pangborn, R. N.

    1996-12-01

    The objective of this work is to evaluate the damage induced below and above the fatigue limit (Δ σ t =360 MPa) in pressure vessel steels, such as SA508. Fatigue damage was induced in samples taken from an SA508 steel plate by various loading histories in order to examine the influence of prior cyclic loading below the fatigue limit. Cell-to-cell misorientation differences were measured by the selected area diffraction (SAD) method. Surface cracking was also studied by the replication method. Small cracks were observed after precycling both below and above the fatigue limit. It was, however, found that fatigue test bars had a longer lifetime after precycling below the fatigue limit, while precycling above the fatigue limit caused other specimens to fail even when subsequently cycled below the fatigue limit. Cell-to-cell misorientation usually increases with accumulation of fatigue damage, but it was found that the misorientations measured after precycling below the fatigue limit decreased again at the beginning of the subsequent cycling above the fatigue limit. It should be noted that the misorientation at failure was always about 4 to 5 deg, regardless of loading histories. Misorientation showed good correlation with the fatigue lifetime of the samples.

  9. Estimation of Corrosion Fatigue Lives Based on the Variations of the Crack Lengths Distributions During Stress Cycling

    OpenAIRE

    Ishihara, Sotomi; Maekawa, Ichiro; Shiozawa, Kazuaki; Miyao, Kazyu

    1985-01-01

    Many small distributed cracks have been observed on the specimen during corrosion fatigue process, and the damage of corrosion fatigue is related to the behaviour of these distributed cracks. The distribution of crack lengths during corrosion fatigue was approximated well by the three parameter Weibull distribution under plane-bending fatigue tests of carbon steel in salt water. A method of estimation of corrosion fatigue lives was proposed. The crack initiation, crack growth behaviour and th...

  10. Fatigue Failure of Concrete in Tension

    NARCIS (Netherlands)

    Cornelissen, H.A.W.

    1984-01-01

    Concentric tensile and flexural tensile fatigue tests were carried out on plain concrete specimens. The effects of pulsating tensile loadings as well as of alternating tensilecompressive loadings were studiep. The results of the constant-amplitude tests have been presented in S-N diagrams and a

  11. Fatigue Reliability Analysis of 6156-T6 Riveted Joints based on Detail Fatigue Rating

    Science.gov (United States)

    Chen, An; Yang, Jun; Zhang, Kan; Zhang, Haiying

    2017-11-01

    The fatigue behavior of two kinds of riveted joints 6156-T6 aluminum alloy structures was experimentally investigated. The detail fatigue rating (DFR) values of 6156-T6 is calculated based on statistical analysis of fatigue tests. The fatigue crack initiation and propagation behavior are examined using scanning electron microscopy. The results show that DFR value of 6156-T6 aluminum alloy with riveted lap joints is 97.81MPa, and the DFR value of rivet-filled countersink hole structure is 168.39MPa. The crack initiation sites occurred at the vicinity of the fastener hole in all specimens. The fatigue striations were uniformly spaced in the region of stable crack growth.

  12. Ultrasonic fatigue testing device under biaxial bending

    Directory of Open Access Journals (Sweden)

    C. Brugger

    2016-07-01

    Full Text Available A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. A flat smooth specimen with a disc geometry is placed on a torus frame and cyclically loaded at the center of its upper face. Disc bending generates a biaxial proportional stress state at the center of the lower face. Any positive loading ratio can be applied. A cast aluminum alloy (used to produce cylinder heads has been tested under biaxial bending using this device in order to determine its fatigue strength at 109 cycles under high hydrostatic pressure. Self-heating is moderate but macroscopic fatigue cracks after testing are very long. First results in VHCF regime are consistent with literature results obtained under similar stress state but in HCF regime and at 20 Hz.

  13. The Effects of Hot Corrosion Pits on the Fatigue Resistance of a Disk Superalloy

    Science.gov (United States)

    Gabb, Timothy P.; Telesman, Jack; Hazel, Brian; Mourer, David P.

    2009-01-01

    The effects of hot corrosion pits on low cycle fatigue life and failure modes of the disk superalloy ME3 were investigated. Low cycle fatigue specimens were subjected to hot corrosion exposures producing pits, then tested at low and high temperatures. Fatigue lives and failure initiation points were compared to those of specimens without corrosion pits. Several tests were interrupted to estimate the fraction of fatigue life that fatigue cracks initiated at pits. Corrosion pits significantly reduced fatigue life by 60 to 98 percent. Fatigue cracks initiated at a very small fraction of life for high temperature tests, but initiated at higher fractions in tests at low temperature. Critical pit sizes required to promote fatigue cracking were estimated, based on measurements of pits initiating cracks on fracture surfaces.

  14. Genomics and museum specimens.

    Science.gov (United States)

    Nachman, Michael W

    2013-12-01

    Nearly 25 years ago, Allan Wilson and colleagues isolated DNA sequences from museum specimens of kangaroo rats (Dipodomys panamintinus) and compared these sequences with those from freshly collected animals (Thomas et al. 1990). The museum specimens had been collected up to 78 years earlier, so the two samples provided a direct temporal comparison of patterns of genetic variation. This was not the first time DNA sequences had been isolated from preserved material, but it was the first time it had been carried out with a population sample. Population geneticists often try to make inferences about the influence of historical processes such as selection, drift, mutation and migration on patterns of genetic variation in the present. The work of Wilson and colleagues was important in part because it suggested a way in which population geneticists could actually study genetic change in natural populations through time, much the same way that experimentalists can do with artificial populations in the laboratory. Indeed, the work of Thomas et al. (1990) spawned dozens of studies in which museum specimens were used to compare historical and present-day genetic diversity (reviewed in Wandeler et al. 2007). All of these studies, however, were limited by the same fundamental problem: old DNA is degraded into short fragments. As a consequence, these studies mostly involved PCR amplification of short templates, usually short stretches of mitochondrial DNA or microsatellites. In this issue, Bi et al. (2013) report a breakthrough that should open the door to studies of genomic variation in museum specimens. They used target enrichment (exon capture) and next-generation (Illumina) sequencing to compare patterns of genetic variation in historic and present-day population samples of alpine chipmunks (Tamias alpinus) (Fig. 1). The historic samples came from specimens collected in 1915, so the temporal span of this comparison is nearly 100 years. © 2013 John Wiley & Sons Ltd.

  15. Downhole vibration causing a drill collar failure and solutions

    Directory of Open Access Journals (Sweden)

    Quanta Zhu

    2017-03-01

    Full Text Available In large borehole drilling of some blocks or formations, due to serious downhole vibration, fatigue failure of a drill collar occurs frequently and most washouts and fractures are in thread root. An analysis of the above failure shows that the drill collar fatigue failure is caused by the cyclic bending stress due to serious downhole vibration. Therefore, downhole vibration modes were theoretically analyzed in terms of axial vibration, lateral vibration, stick-slip, and the physical model established by the mechanical vibration field. Then the resonance damage caused by the actual different downhole vibrations and its theoretical basis were analyzed; and according to the downhole drill string lateral vibration and whirling law, the best area to ensure drilling parameter stability based on the given boundary conditions was figured out, and the theory was clarified that in the best area of drilling, the maximum ROP will be achieved by maintaining the drill string stable or eliminating the vibration/stick-slip, meanwhile the stress fatigue of BHA will be reduced or eliminated especially for drill collar. Finally, solutions were provided as follows: (1 According to the special BHA, drilling conditions, together with physical and mathematical models listed above, downhole resonance speed and related parameters to be avoided can be easily figured out. It was also clarified that resonance speed is exactly the vibration speed that need to be avoided; and that the resonance frequency can be avoided with software for vibration analysis in BHA design and application at well sites; (2 V-Stab is a new and efficient tool which can reduce or eliminate downhole lateral vibration and stick-slip.

  16. The effect to bending fatigue strength of 65 mn under torsion strain-hardening

    Science.gov (United States)

    Zou, Guangping; Xue, Qichao; Li, Wei

    2010-03-01

    Bending Fatigue experiments for 65Mn are carried out to study the effects of torsion strain-hardening. Firstly bending fatigue specimens are pre-twisted for torsion strain-hardening by using torsion testing machine. And specimens are divided as 8 groups and each group has 8 specimens. A series of plastic shear strains are applied to each group. Then bending fatigue experiments are carried on to estimate torsion fatigue strength by fatigue bending machine. Finally micrograms of fatigue damage are taken by stereo microscope. The test results showed that torsion strain-hardening has a certain effects that when torsion plastic strain is small, bending fatigue strength is increased. Oppositely, when torsion plastic strain is large, bending fatigue strength are all decreased in a large rate compared with specimens without torsion strain-hardening. Comparing different test results and corresponding paragraphs obtained from stereo microscope, a reasonable explanation can be deduced by using metal micromechanics theory and crystal lattice dislocation theory. A possible reason is that when torsion plastic strain is small, there will be more dislocation in crystal lattice, which can raise the fatigue strength. And when torsion plastic strain is large, dislocations are piled up in some position which can bring flaws under loads, which reduce the fatigue strength of specimen.

  17. FATIGUE PROPERTIES OF SPRING REINFORCES POLYMER GEARS

    Directory of Open Access Journals (Sweden)

    Hilal CAN

    2005-03-01

    Full Text Available Failure of gears, occur surface pressure stress and fracture at base of teeth. For steel gears, it is known that process of carburizing increases fatigue strength. Internal stress on the surface increases of fracture fatigue strength. In this study fatigue properties of polypropylene gear reinforced with 1.2 mm wire diameter metallic springs was investigated. Extension springs were used as reinforcement element and placed into the mould and stretched before injection of polypropylene material into the mould. After injection of polypropylene, stretched springs were loosened in order to obtain pre-stressing. Fatigue tests were performed on the produced gear. Reinforcement increased the strength of gears. At result of experiments, pre-stressing increase in service life 12 times more than that of specimens without reinforcement.

  18. Nodular cast iron fatigue lifetime in cyclic plane bending

    Directory of Open Access Journals (Sweden)

    Marian Kokavec

    2012-05-01

    Full Text Available The fatigue behavior of a component is strongly dependent on the material and its surface condition. Therefore, the manner in which the surface is prepared during component manufacturing (surface roughness, residual stresses etc. has a decisive role in dictating the initiation time for fatigue cracks. The fatigue behavior of the same material, a nodular cast iron, with three different surface conditions (fine ground, sand blast and as-cast has been investigated under cyclic plane bending. The results show differences in fatigue strength, which are associated with the surface conditions. The characteristics of the surface layers of the different test specimens were examined by metallography.

  19. Thermal emission in fatigue described by power laws

    Directory of Open Access Journals (Sweden)

    Gallinatti A.E.

    2010-06-01

    Full Text Available In the present work, a theoretical model proposed by the literature and focused on the relationship between microplasticizations thermal behaviour and fatigue scatter is analysed and applied to fatigue test results of standard and notched steel specimens. The same experimental data are subjected to the TCM (Two Curves Method thermographic elaboration technique, in order to quickly evaluate fatigue limit values. TCM method has been modified, aiming at interpolating thermal data referred to the region of loads upper than fatigue limit with a non linear regression law having the same mathematical structure of the theoretical model equations (power laws.

  20. Size effects on the fatigue behavior of bulk metallic glasses

    Science.gov (United States)

    Wang, G. Y.; Liaw, P. K.; Yokoyama, Y.; Inoue, A.

    2011-12-01

    Size effects on bending fatigue characteristics are investigated on Zr-based bulk-metallic glasses (BMGs). The fatigue lifetimes and endurance limits of the large-size samples are greater than those of the small-size samples. The results suggest that although a BMG exhibits good ductility due to the formation of multiple shear bands when its size decreases, the fatigue resistance of BMGs might degrade when the specimen size becomes smaller. The current study finds that small-size BMG samples under bending fatigue could fail in the flexural or fracture mode.

  1. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, Jette Andkjær

    1999-01-01

    Fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test specimens...... have been carried through. The materials that have been used are either conventional structural steel with a yield stress of f(y) similar to 400-410 MPa or high-strength steel with a yield stress of f(y) similar to 810-840 MPa. The fatigue tests have been carried out using load histories, which...

  2. Fatigue in Steel Highway Bridges under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Nielsen, J.A.; Vejrum, Tina

    1997-01-01

    In the present investigation, fatigue damage accumulation in steel highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis.In the experimental part of the investigation, fatigue test series...... on welded plate test specimens have been carried through. The materials that have been used are either conventional structural steel with a yield stress of ~ 400-410 MPa or high-strength steel with a yield stress of ~ 810-840 MPa.The fatigue tests have been carried out using load histories, which correspond...

  3. Effect of Grain Size on Ultrasonic Fatigue Properties of Ni-Base Super Alloy Inconel 718

    OpenAIRE

    皮籠石, 紀雄; 前村, 英史; 陳, 強; 後藤, 真宏; 森野, 数博

    2008-01-01

    Ultrasonic fatigue tests of plain specimens with different grain sizes were carried out for Ni-base super alloy, Inconel 718, in ambient air in order to investigate the effect of grain size on fatigue properties. Fatigue strength was increased with decrease in grain size. The increase in fatigue strength by refining grain size was mainly caused by the suppression of crack initiation. That is, the effect of grain size on crack growth rate was hardly recognized, though crack morphology was roug...

  4. 37 CFR 2.59 - Filing substitute specimen(s).

    Science.gov (United States)

    2010-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2010-07-01 2010-07-01 false Filing substitute specimen(s). 2.59 Section 2.59 Patents, Trademarks, and Copyrights UNITED STATES PATENT AND TRADEMARK OFFICE, DEPARTMENT OF COMMERCE RULES OF PRACTICE IN TRADEMARK CASES Drawing § 2.59 Filing substitute specimen(s). (a...

  5. Literature review : an analysis of laboratory fatigue tests.

    Science.gov (United States)

    1975-01-01

    This report discusses the various types of fatigue tests, grouped by the type of specimen (beam, plate, Marshall, etc.) used. The discussion under each type of specimen covers the test, and the analytical methods used in evaluating the data. The test...

  6. Monitoring of fatigue crack under complex environment using guided waves

    Science.gov (United States)

    Tang, Jianfei; Yan, Gang; Xu, Xiwu

    2012-04-01

    This paper presents an experimental study on monitoring of fatigue crack under complex environment using guided waves. An experimental set-up consisting of an electrical oven, a MTS testing machine and a monitoring system is established to perform the study. First, the combined effects of temperature, load and vibration on the propagation of guided waves in metallic structure is studied. Then, a statistical approach is proposed to detect fatigue crack under these combined effects. Damage feature is extracted after the guided wave signals are processed by Fourier transform. A Monte Carlo procedure is employed to estimate the probability density functions of the feature before and after cracking, respectively. By comparing the probability density functions, the probability of existence of fatigue crack is determined. Experimental study on a fatigue coupon under combined effects of temperature, load and vibration is conducted to demonstrate the effectiveness of the proposed method.

  7. Crack Propagation on ESE(T) Specimens Strengthened with CFRP Sheets

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Jensen, Peter Holmstrøm; Dyrelund, Jens

    2009-01-01

    In this paper fatigue tests on side notched steel test specimens strengthened with adhesive bonded fibre reinforced polymer (FRP) sheets are presented. The specimens are subject to crack growth both in the steel and bond line. Influence of the load ratio and initial crack length on the overall en...

  8. Influence on driver fatigue of vertical vibrations over long distances. Assessment in terms of stress hormones; Driver no unten hiro ni okeru joge shindo no eikyo. Stress hormone wo shiyo to shite

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, T.; Inagaki, H. [Toyota Central Research and Development Labs., Inc., Aichi (Japan)

    1998-05-01

    Driving tests are conducted to obtain some indexes that describe the cumulative effect of the sense of tiredness. The heart rate, Mayer wave related sinus arrhythmia, respiratory sinus arrhythmia, urinary adrenaline, noradrenaline, and cortisol in saliva are tested. Adrenaline and Mayer wave related sinus arrhythmia are ultimately named in view of their correlation with tiredness. It is believed that tiredness is attributable to two factors, which are increase in mental stress and decrease in vigilance. An excitation test is then conducted using a motion simulator. Upon application of 4Hz vibrations (equivalent to the chest section resonance frequency), adrenaline increases sharply, and then decreases sharply upon termination of excitation. Upon application of 1.6Hz vibrations (equivalent to the head section resonance frequency), adrenaline increases but not sharply, and the elevated level is sustained for some time after excitation. Driving tests are next conducted using a vehicle with its suspension fixed and another with 1-2Hz vibrations reduced. Rise in the adrenaline level is found inhibited aboard the latter. No difference is detected in terms of Mayer wave related sinus arrhythmia between the two vehicles. 4 refs., 7 figs., 4 tabs.

  9. Vibrating minds

    CERN Document Server

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  10. Investigation into Fretting Fatigue Under Cyclic Contact Load and in Conjunction with Plain Fatigue of Titanium Alloy

    Science.gov (United States)

    2008-03-01

    called fretting wear. In the center of contact, the surface of the specimen and the pads are welding together. Figure 2.2 shows the two zones...1000 TPF/TFF Fa tig ue L ife (C yc le s) TPF = Total Number Of Plain Fatigue Cycles, TFF = Total Number Of Fretting Fatigue Cycles Figure 5.26...PF/FF Fa tig ue L ife (C yc le s) PF =Number of Cycles in One Block of Plain Fatigue, FF = Number of Cycles in One Block of Fretting Fatigue

  11. Biaxial Creep Specimen Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    JL Bump; RF Luther

    2006-02-09

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.

  12. Creep-Fatigue Failure Diagnosis

    Directory of Open Access Journals (Sweden)

    Stuart Holdsworth

    2015-11-01

    Full Text Available Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis.

  13. Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

    Directory of Open Access Journals (Sweden)

    Xiaojian Cao

    2017-10-01

    Full Text Available The effect of ultrasonic nanocrystal surface modification (UNSM on the fatigue behavior of Ti6Al4V (TC4 in simulated body fluid (SBF was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 μm and 36,000 strikes per unit produced about 35 μm surface severe plastic deformation (SPD layers on the TC4 specimens. One group was treated with a hybrid surface treatment (UNSM + TiN film. UNSM technique improves the micro hardness and the compressive residual stress. The surface roughness is increased slightly, but it can be remarkably improved by the TiN film. The fatigue strength of TC4 is improved by about 7.9% after UNSM. Though the current density of corrosion is increased and the pitting corrosion is accelerated, UNSM still improved the fatigue strength of TC4 after pre-soaking in SBF by 10.8%. Interior cracks initiate at the deformed carbide and oxide inclusions due to the ultrasonic impacts of UNSM. Corrosion products are always observed at the edge of fracture surface to both interior cracks and surface cracks. Coating a TiN film on the UNSMed surface helps to improve the whole properties of TC4 further.

  14. TORSIONAL DEFORMATION AND FATIGUE BEHAVIOUR OF 6061 ALUMINIUM ALLOY

    Directory of Open Access Journals (Sweden)

    marini marno

    2012-02-01

    Full Text Available Torsional deformation and fatigue behaviour of both solid and thin-walled tubular specimens were made from as-received and heat treated 6061 aluminium alloy were studied. 6061 aluminium alloy have been widely used as a candidate material in automobile, aerospace, aircraft and structural application because of their superior mechanical properties such as high strength to weight ratio, good ductility and others. The differences in cyclic deformation and fatigue behaviours between round and solid specimens where a stress gradient exist, and thin-walled tubular specimens where a uniform stress state is commonly assumed, are also discussed. Von Mises and Tresca criteria has been used to predict the monotonic and cyclic deformation curve and compared to the torsional data obtained from the experiment. The S-N curve was used to present and evaluate the fatigue life of the specimens. Through fractographic analysis, failure criteria of fracture surfaces were observed and discussed. 

  15. Continuous fatigue crack monitoring of bridges: Long-Term Electrochemical Fatigue Sensor (LTEFS)

    Science.gov (United States)

    Moshier, Monty A.; Nelson, Levi; Brinkerhoff, Ryan; Miceli, Marybeth

    2016-04-01

    Fatigue cracks in steel bridges degrade the load-carrying capacity of these structures. Fatigue damage accumulation caused by the repetitive loading of everyday truck traffic can cause small fatigue cracks initiate. Understanding the growth of these fatigue cracks is critical to the safety and reliability of our transportation infrastructure. However, modeling fatigue in bridges is difficult due to the nature of the loading and variations in connection integrity. When fatigue cracks reach critical lengths failures occur causing partial or full closures, emergency repairs, and even full structural failure. Given the aging US highway and the trend towards asset management and life extension, the need for reliable, cost effective sensors and monitoring technologies to alert bridge owners when fatigue cracks are growing is higher than ever. In this study, an innovative Long-Term Electrochemical Fatigue Sensor (LTEFS) has been developed and introduced to meet the growing NDT marketplace demand for sensors that have the ability to continuously monitor fatigue cracks. The performance of the LTEFS has been studied in the laboratory and in the field. Data was collected using machined specimens with different lengths of naturally initiated fatigue cracks, applied stress levels, applied stress ratios, and for both sinusoidal and real-life bridge spectrum type loading. The laboratory data was evaluated and used to develop an empirically based algorithm used for crack detection. Additionally, beta-tests on a real bridge structure has been completed. These studies have conclusively demonstrated that LTEFS holds great potential for long-term monitoring of fatigue cracks in steel structures

  16. Standard practice for conducting force controlled constant amplitude axial fatigue tests of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice covers the procedure for the performance of axial force controlled fatigue tests to obtain the fatigue strength of metallic materials in the fatigue regime where the strains are predominately elastic, both upon initial loading and throughout the test. This practice is limited to the fatigue testing of axial unnotched and notched specimens subjected to a constant amplitude, periodic forcing function in air at room temperature. This practice is not intended for application in axial fatigue tests of components or parts. Note 1-The following documents, although not directly referenced in the text, are considered important enough to be listed in this practice: E 739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (-N) Fatigue Data STP 566 Handbook of Fatigue Testing STP 588 Manual on Statistical Planning and Analysis for Fatigue Experiments STP 731 Tables for Estimating Median Fatigue Limits

  17. Small specimen test technology and methodology of IFMIF/EVEDA and the further subjects

    Science.gov (United States)

    Wakai, E.; Nogami, S.; Kasada, R.; Kimura, A.; Kurishita, H.; Saito, M.; Ito, Y.; Takada, F.; Nakamura, K.; Molla, J.; Garin, P.

    2011-10-01

    About one thousands of small size specimens will be irradiated in the High Flux Test Module (HFTM) with a limited irradiation volume of 0.5 l in the International Fusion Materials Irradiation Facility (IFMIF). It is necessary to verify that the experimental data of these small specimens mechanical characterization can be safely extrapolated to standard specimen data, enabling a sound dimensioning of DEMO reactor. The program of small specimen test technique (SSTT) in IFMIF/EVEDA (Engineering Validation and Engineering Design Activity) phase for fatigue, fracture toughness and crack growth measurement is summarized, and recent progress and some analysis of the experiments for small size specimens have been shown.

  18. A Study on the VHCF Fatigue Behaviors of Hydrogen Attacked Inconel 718 Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang-Min [Kyungpook National Univ., DMI Senior Fellow, Daegu (Korea, Republic of); Nahm, Seung-Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Kim, Jun-Hyong; Pyun, Young-Sik [Sun Moon Univ., Chunan (Korea, Republic of)

    2016-07-15

    This study is to investigate the influence of hydrogen attack and UNSM on fatigue behaviors of the Inconel 718 alloy. The decrease of the fatigue life between the untreated and the hydrogen attacked material is 10-20%. The fatigue lives of hydrogen attacked specimen decreased without a fatigue limit, similar to those of nonferrous materials. Due to hydrogen embrittlement, about 80% of the surface cracks were smaller than the average grain size of 13 μm. Many small surface cracks caused by the embrittling effect of hydrogen attack were initiated at the grain boundaries and surface scratches. Cracks were irregularly distributed, grew, and then coalesced through tearing, leading to a reduction of fatigue life. Results revealed that the fatigue lives of UNSM-treated specimens were longer than those of the untreated specimens.

  19. NASA Biological Specimen Repository

    Science.gov (United States)

    McMonigal, K. A.; Pietrzyk, R. A.; Sams, C. F.; Johnson, M. A.

    2010-01-01

    The NASA Biological Specimen Repository (NBSR) was established in 2006 to collect, process, preserve and distribute spaceflight-related biological specimens from long duration ISS astronauts. This repository provides unique opportunities to study longitudinal changes in human physiology spanning may missions. The NBSR collects blood and urine samples from all participating ISS crewmembers who have provided informed consent. These biological samples are collected once before flight, during flight scheduled on flight days 15, 30, 60, 120 and within 2 weeks of landing. Postflight sessions are conducted 3 and 30 days after landing. The number of in-flight sessions is dependent on the duration of the mission. Specimens are maintained under optimal storage conditions in a manner that will maximize their integrity and viability for future research The repository operates under the authority of the NASA/JSC Committee for the Protection of Human Subjects to support scientific discovery that contributes to our fundamental knowledge in the area of human physiological changes and adaptation to a microgravity environment. The NBSR will institute guidelines for the solicitation, review and sample distribution process through establishment of the NBSR Advisory Board. The Advisory Board will be composed of representatives of all participating space agencies to evaluate each request from investigators for use of the samples. This process will be consistent with ethical principles, protection of crewmember confidentiality, prevailing laws and regulations, intellectual property policies, and consent form language. Operations supporting the NBSR are scheduled to continue until the end of U.S. presence on the ISS. Sample distribution is proposed to begin with selections on investigations beginning in 2017. The availability of the NBSR will contribute to the body of knowledge about the diverse factors of spaceflight on human physiology.

  20. Seat Vibration in Military Propeller Aircraft: Characterization, Exposure Assessment, and Mitigation

    National Research Council Canada - National Science Library

    Smith, Suzanne D

    2006-01-01

    There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of military propeller aircraft, where persistent multi-axis vibration occurs at higher...

  1. Fatigue Properties and Fracture Mechanism of Aluminum Alloy with Orifice Chamfer and Pre-corrosion Damage

    Directory of Open Access Journals (Sweden)

    ZHOU Song

    2016-06-01

    Full Text Available Fatigue fracture often occurs because of the corrosion damage to aerospace structural aluminum alloy with holes. Fatigue tests of 7075 aluminum alloy of both unchamfered and chamfered double-hole specimens under uncorrosion and 24h pre-corrosion were carried out. The influence of both pre-corrosion damage and orifice chamferer on fatigue properties and the differences of fatigue fracture characteristics were analyzed. The results show that the effect on fatigue life of pre-corrosion damage is significant. Median fatigue lives of both unchamfered and chamfered double-hole specimens under 24h pre-corrosion decrease about 31.74% and 26.92% compared with uncorrosion specimens. The orifice chamferer have a certain effect on fatigue life of both uncorrosion and 24h pre-corrosion specimens, with median fatigue lives decreased about 28.02% and 15.36% compared with unchamfered specimens, the main reason is due to the stress concentration after orifice chamfered, on the other hand, cutting marks lead to pre-damage during the orifice chamfering process which will result in an increase of the fatigue crack initiation sites and the fracture probability.

  2. Changes in EMG activity in the upper trapezius muscle due to local vibration exposure.

    Science.gov (United States)

    Aström, Charlotte; Lindkvist, Markus; Burström, Lage; Sundelin, Gunnevi; Karlsson, J Stefan

    2009-06-01

    Exposure to vibration is suggested as a risk factor for developing neck and shoulder disorders in working life. Mechanical vibration applied to a muscle belly or a tendon can elicit a reflex muscle contraction, also called tonic vibration reflex, but the mechanisms behind how vibration could cause musculoskeletal disorders has not yet been described. One suggestion has been that the vibration causes muscular fatigue. This study investigates whether vibration exposure changes the development of muscular fatigue in the trapezius muscle. Thirty-seven volunteers (men and women) performed a sub-maximal isometric shoulder elevation for 3 min. This was repeated four times, two times with induced vibration and two times without. Muscle activity was measured before and after each 3-min period to look at changes in the electromyography parameters. The result showed a significantly smaller mean frequency decrease when performing the shoulder elevation with vibration (-2.51 Hz) compared to without vibration (-4.04 Hz). There was also a slightly higher increase in the root mean square when exposed to vibration (5.7% of maximal voluntary contraction) compared to without (3.8% of maximal voluntary contraction); however, this was not statistically significant. The results of the present study indicate that short-time exposure to vibration has no negative acute effects on the fatiguing of upper trapezius muscle.

  3. Effect of Environment on Fatigue Behavior of a Nicalon(TM)/Si-N-C Ceramic Matrix Composite

    Science.gov (United States)

    Kalluri, Sreeramesh; Ojard, Greg C.; Verrilli, Michael J.; Kiraly, Louis J. (Technical Monitor)

    2002-01-01

    The effect of environmental exposure on the fatigue life of Nicalon(TM) /Si-N-C composite was investigated in this study. Test specimens with arrays of 1.8 mm diameter holes and two different open areas, 25 and 35%, were machined. Three environmental conditions were studied: 1) continuous fatigue cycling in air, 2) fatigue cycling in air alternating with humidity exposure, and 3) fatigue cycling in air alternating with exposure to a salt-fog environment. All fatigue testing on specimens with holes was performed with a load ratio, R = 0.05, and at a temperature of 910 C. In general, fatigue lives were shortest for specimens subjected to salt-fog exposure and longest for specimens subjected to continuous fatigue cycling in air. The fatigue data generated on the specimens with holes were compared with fatigue data generated in air on specimens with no holes. Fatigue strength reduction factors for different environmental conditions and open areas investigated in the study were calculated for the Nicalon(TM) /Si-N-C composite.

  4. Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel

    Science.gov (United States)

    Matsunaga, Hisao; Noda, Hiroshi

    2011-09-01

    To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to a marked increase in the crack growth rate. Typical characteristics of hydrogen effect were observed in the slip band morphology and fatigue striation. To elucidate the behavior of hydrogen diffusion microscopically in the fatigue process, the hydrogen emission from the specimens was visualized using the hydrogen microprint technique (HMT). In the hydrogen-charged specimen, hydrogen emissions were mainly observed in the vicinity of the fatigue crack. Comparison between the HMT image and the etched microstructure image revealed that the slip bands worked as a pathway for hydrogen to move preferentially. Hydrogen-charging resulted in a significant change in the phase transformation behavior in the fatigue process. In the noncharged specimen, a massive type α' martensite was observed in the vicinity of the fatigue crack. On the other hand, in the hydrogen-charged specimen, large amounts of ɛ martensite and a smaller amount of α' martensite were observed along the slip bands. The results indicated that solute hydrogen facilitated the ɛ martensitic transformation in the fatigue process. Comparison between the results of HMT and EBSD inferred that martensitic transformations as well as plastic deformation itself can enhance the mobility of hydrogen.

  5. Cause elucidation of sodium leakage incident at `Monju` reactor. Vibration of thermometer due to fluid force

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, Koji; Wada, Yusaku; Morishita, Masaki; Yamaguchi, Akira; Ichimiya, Masakazu [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1997-01-01

    This is a report of summarized results of investigation and analysis on fracture of thermometer which is direct reason of sodium leakage incident at the second main cooling system of fast breeder reactor `Monju`. Various surveys such as on various damage factors, on flowing power vibrational features containing flowing power vibrational test of thermometer, on evaluation of high cycle fatigue due to flowing power vibration and details on propagation of and fracture due to fatigue crack, on why only said thermometer damaged, and so forth were executed. As results of these examinations, a decision was arrived that high cycle fatigue due to vibration formed by fluid force (fluid force vibration) was a direct cause of the thermometer damage. (G.K.)

  6. Piezoelectric Bolt Breakers and Bolt Fatigue Testers

    Science.gov (United States)

    Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Barengoltz, Jack; Heckman, Vanessa

    2008-01-01

    A proposed family of devices for inducing fatigue in bolts in order to break the bolts would incorporate piezoelectric actuators into resonant fixtures as in ultrasonic/ sonic drills/corers and similar devices described in numerous prior NASA Tech Briefs articles. These devices were originally intended primarily for use as safer, more-reliable, more-versatile alternatives to explosive bolts heretofore used to fasten spacecraft structures that must subsequently be separated from each other quickly on command during flight. On Earth, these devices could be used for accelerated fatigue testing of bolts. Fatigue theory suggests that a bolt subjected to both a constant-amplitude dynamic (that is, oscillatory) stress and a static tensile stress below the ultimate strength of the bolt material will fail faster than will a bolt subjected to only the dynamic stress. This suggestion would be applied in a device of the proposed type. The device would be designed so that the device and the bolt to be fatigue-tested or broken would be integral parts of an assembly (see figure). The static tension in the tightened bolt would apply not only the clamping force to hold the joined structures (if any) together but also the compression necessary for proper operation of the piezoelectric actuators as parts of a resonant structural assembly. The constant-amplitude dynamic stress would be applied to the bolt by driving the piezoelectric actuators with a sinusoidal voltage at the resonance frequency of longitudinal vibration of the assembly. The amplitude of the excitation would be made large enough so that the vibration would induce fatigue in the bolt within an acceptably short time. In the spacecraft applications or in similar terrestrial structural-separation applications, devices of the proposed type would offer several advantages over explosive bolts: Unlike explosive bolts, the proposed devices would be reusable, could be tested before final use, and would not be subject to

  7. Residual stress reduction and fatigue strength improvement by controlling welding pass sequences

    Energy Technology Data Exchange (ETDEWEB)

    Mochizuki, Masahito; Hattori, Toshio; Nakakado, Kimiaki

    2000-01-01

    The effects of residual stress on fatigue strength at a weld toe in a multi-pass fillet weld joint were evaluated. The residual stresses in the weld joints were varied by controlling the sequence of welding passes. The residual stress at the weld toe was 80 MPa in the specimen whose last welding pass was on the main plate side, but it was 170 MPa in the specimen whose last pass was on the attachment side. The fatigue strength was nearly the same at high stress amplitude for both specimens, but the fatigue strength of the specimen whose last weld pass on the main plate was higher than that of the other specimen at low stress amplitude. This difference is due to the magnitude of the initial residual stress and the relaxation of the residual stress under fatigue cycling. The effects of the residual stress were shown in a modified Goodman diagram, in which residual stress is treated as a mean stress.

  8. Corrosion-fatigue crack propagation of aluminum alloys for high-speed trains

    Science.gov (United States)

    Shen, Lin; Chen, Hui; Che, Xiaoli; Xu, Lidong

    2017-07-01

    A modified single-edge notch tension (SENT) specimen exposed to saline environment was utilized to investigate the corrosion-fatigue crack growth behaviors of 5083, 6005 and 7N01 aluminum alloys. The fatigue crack propagation life, corrosion-fatigue crack rate (da/dN) were tested. The microstructures and fracture surfaces of specimens were examined by optical microscopy and scanning electron microscopy (SEM). The results showed that fatigue crack propagation rate of 7N01 in 3.5% NaCl was significantly higher than 6005 and 5083 alloys. The mechanisms of anodic dissolution and hydrogen embrittlement are used to explain the results.

  9. Design Fatigue Lives of Polypropylene Fibre Reinforced Polymer Concrete Composites

    Directory of Open Access Journals (Sweden)

    Raman Bedi

    2014-09-01

    Full Text Available Flexural fatigue behavior of Poly-propylene fibre reinforced polymer concrete composites (PFRPCC has been investigated at various stress levels and the statistical analysis of the data thus obtained has been carried out. Polymer Concrete Composite (PCC samples without addition of any type of fibres were also tested for flexural fatigue.  Forty specimens of PCC and One hundred and Forty One specimens of PFRPCC containing 0.5%, 1.0% and 2.0% polypropylene fibres were tested in fatigue using a MTS servo controlled test system. Fatigue life distributions of PCC as well as PFRPCC are observed to approximately follow a two parameter Weibull distribution with correlation coefficient exceeding 0.9. The parameters of the Weibull distribution have been obtained by various methods. Failure probability, which is an important parameter in the fatigue design of materials, has been used to obtain the design fatigue lives for the material. Comparison of design fatigue life of PCC and PFRPCC has been carried out and it is observed that addition of fibres enhances the design fatigue life of PCC.

  10. Shot Peening Effect on Fatigue Crack Repaired Weldments

    Directory of Open Access Journals (Sweden)

    J. Efrain Rodriguez-Sanchez

    2017-01-01

    Full Text Available Fracture mechanics calculations are required to validate the safety level defined in design codes to prevent a fatigue failure. The periodic inspection-assessment cycle can lead to the implementation of a fatigue crack repair by crack removal. To improve the fatigue performance of the crack repair, residual compressive stresses induced by peening can be considered. This paper is in relation to the peening effect estimation on stress intensity factors in fatigue crack repaired weldments, since the stress intensity factor is a key parameter in fracture mechanics calculations. A set of T-butt specimens were experimentally fatigue tested and crack propagation data was gathered for the calculation of stress intensity factors. The experiments were designed to estimate the residual compressive stress depth layer and its effect on crack propagation inhibition. Experimental estimation of the peening effect on stress intensity factors in fatigue crack repaired weldments was validated by comparison against an analytical weight function solution. Experimental stress intensity factors determined from a set of fatigue tested T-butt specimens allowed estimating preliminarily that peening has a limited effect on fatigue crack propagation inhibition for edge repaired T-butt weldments subjected to bending loading.

  11. Urban vibrations

    DEFF Research Database (Denmark)

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

      lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  12. Measurement of Dynamic Viscoelasticity of Full-Size Wood Composite Panels Using a Vibration Testing Method

    Science.gov (United States)

    Cheng Guan; Houjiang Zhang; John F. Hunt; Lujing Zhou; Dan Feng

    2016-01-01

    The dynamic viscoelasticity of full-size wood composite panels (WCPs) under the free-free vibrational state were determined by a vibration testing method. Vibration detection tests were performed on 194 pieces of three types of full-size WCPs (particleboard, medium density fiberboard, and plywood (PW)). The dynamic viscoelasticity from smaller specimens cut from the...

  13. Fatigue Life of High Performance Grout for Wind Turbine Grouted Connection in Wet or Dry Environment

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Westhof, Luc; Yde, Elo

    Grouted connections of monopile supported offshore wind turbine structures are subjected to loads leading to very high oscillating service stresses in the grout material. The fatigue capacity of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens...... at varying levels of cyclic frequency and load. The fatigue tests were performed in two series: one with the specimens in air and one with the specimens submerged in water during the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when...... tested in water than when tested in air....

  14. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

    2011-01-01

    the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during...... the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency....

  15. Distribution of Corrosion Fatigue Crack Lengths in Carbon Steel : 1st Report, The Cracks Which Grow Individually

    OpenAIRE

    Ishihara, Sotomi; Shiozawa, Kazuaki; Miyao, Kazyu

    1985-01-01

    It has been known that very small distributed cracks can be observed on the surface of a smooth specimen subjected to corrosion fatigue. The fracture process can be characterized by the interaction and coalescence of these small distributed cracks. In order to analize this corrosion fatigue fracture process, high cycle fatigue tests were performed on carbon steel sheet specimens under completely reversed plane bending stresses in salt water (3.0%NaCl). Initiation and growth of cracks on the s...

  16. Distribution of Corrosion Fatigue Crack Lengths in Carbon Steel : 2nd Report, The Distributed Cracks which Interact and Coalesce

    OpenAIRE

    Ishihara, Sotomi; Shiozawa, Kazuaki; Miyao, Kazyu

    1985-01-01

    It has been known that very small distributed cracks can be observed on the surface of smooth specimen subjected to corrosion fatigue, and the fatigue crack growth rate is accelerated by the interaction and coalescence of them. In this report, following the previous report of the authors, the interaction and coalescence behaviour of the distributed cracks on the specimen surface were observed in detail. Based on the experimental results, distribution of corrosion fatigue crack lengths after a...

  17. Duplex S-N fatigue curves: statistical distribution of the transition fatigue life

    Directory of Open Access Journals (Sweden)

    D.S. Paolino

    2014-10-01

    Full Text Available In recent years, very-high-cycle fatigue (VHCF behavior of metallic materials has become a major point of interest for researchers and industries. The needs of specific industrial fields (aerospace, mechanical and energy industry for structural components with increasingly large fatigue lives, up to 1010 cycles (gigacycle fatigue, requested for a more detailed investigation on the experimental properties of materials in the VHCF regime. Gigacycle fatigue tests are commonly performed using resonance fatigue testing machines with a loading frequency of 20 kHz (ultrasonic tests. Experimental results showed that failure is due to cracks which nucleate at the specimen surface if the stress amplitude is above the conventional fatigue limit (surface nucleation and that failure is generally due to cracks which nucleate from inclusions or internal defects (internal nucleation when specimens are subjected to stress amplitudes below the conventional fatigue limit. Following the experimental evidence, the Authors recently proposed a new statistical model for the complete description of SN curves both in the high-cycle-fatigue (HCF and in the VHCF fatigue regions (Duplex S-N curves. The model differentiates between the two failure modes (surface and internal nucleation, according to the estimated distribution of the random transition stress (corresponding to the conventional fatigue limit. No assumption is made about the statistical distribution of the number of cycles at which the transition between surface and internal nucleation occurs (i.e., the transition fatigue life. In the present paper, the statistical distribution of the transition fatigue life is obtained, according to the statistical model proposed. The resulting distribution depends on the distance between the HCF and the VHCF regions and on the distribution of the random transition stress. The estimated distribution can be effectively used to predict, with a specified confidence level, the

  18. Chronic fatigue syndrome

    National Research Council Canada - National Science Library

    Gonthier, Ariane; Favrat, Bernard

    2015-01-01

    Chronic fatigue syndrome (CFS) is a debilitating disorder, characterized by a severe, persistant and unexplained fatigue, which can be associated with diffuse pain, sleep difficulties, neurocognitive and neurovegetative troubles...

  19. Insomnia and Fatigue

    Science.gov (United States)

    ... in turn leads to fatigue, may affect your self-esteem, mood, emotions, relationships and work. But you don’ ... Loss Insomnia and Fatigue Menopausal Symptoms Secondary Cancers Sexual Side Effects Living With HR-Positive Breast Cancer ...

  20. Thermal Acoustic Fatigue Apparatus

    Data.gov (United States)

    Federal Laboratory Consortium — The Thermal Acoustic Fatigue Apparatus (TAFA) is a progressive wave tube test facility that is used to test structures for dynamic response and sonic fatigue due to...

  1. Standard test method for creep-fatigue testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This test method covers the determination of mechanical properties pertaining to creep-fatigue deformation or crack formation in nominally homogeneous materials, or both by the use of test specimens subjected to uniaxial forces under isothermal conditions. It concerns fatigue testing at strain rates or with cycles involving sufficiently long hold times to be responsible for the cyclic deformation response and cycles to crack formation to be affected by creep (and oxidation). It is intended as a test method for fatigue testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. The cyclic conditions responsible for creep-fatigue deformation and cracking vary with material and with temperature for a given material. 1.2 The use of this test method is limited to specimens and does not cover testing of full-scale components, structures, or consumer products. 1.3 This test method is primarily ...

  2. Weibull statistical analysis of Krouse type bending fatigue of nuclear materials

    Science.gov (United States)

    Haidyrah, Ahmed S.; Newkirk, Joseph W.; Castaño, Carlos H.

    2016-03-01

    A bending fatigue mini-specimen (Krouse-type) was used to study the fatigue properties of nuclear materials. The objective of this paper is to study fatigue for Grade 91 ferritic-martensitic steel using a mini-specimen (Krouse-type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to those described in the ASTM B593 standard. The mini specimen was machined by waterjet and tested as-received. The bending fatigue machine was modified to test the mini-specimen with a specially designed adapter. The cycle bending fatigue behavior of Grade 91 was studied under constant deflection. The S-N curve was created and mean fatigue life was analyzed using mean fatigue life. In this study, the Weibull function was predicted probably for high stress to low stress at 563, 310 and 265 MPa. The commercial software Minitab 17 was used to calculate the distribution of fatigue life under different stress levels. We have used 2 and 3- parameters Weibull analysis to introduce the probability of failure. The plots indicated that the 3- parameter Weibull distribution fits the data well.

  3. Piezomagnetism and fatigue

    Science.gov (United States)

    Erber, T.; Guralnick, S. A.; Desai, R. D.; Kwok, W.

    1997-10-01

    Piezomagnetism refers to a change in the intrinsic magnetization of a material subjected to mechanical actions such as tension or compression. In a ferromagnet such as a mild steel these effects are easily measured: typically a stress of 0022-3727/30/20/008/img6 or 140 MPa induces a magnetic moment of the order of 0022-3727/30/20/008/img7 emu or 0022-3727/30/20/008/img8, resulting in flux densities in the range 10 mG or 0022-3727/30/20/008/img9T in the vicinity of the specimen. Since piezomagnetic effects are due to interactions between the mechanical and magnetic mesostructure of materials microplastic processes that alter the arrangement of the ferromagnetic domain structure affect the intensity of the associated magnetic fields. The progressive degradation of such materials under cyclic loading can therefore be tracked by following the evolution of the piezomagnetic field. Specifically, if the measurements are displayed as loci in a three-dimensional stress 0022-3727/30/20/008/img10 - strain 0022-3727/30/20/008/img11 - field (B) space, the approach to fatigue failure is paralleled by a series of conspicuous geometric transformations of these curves. Complementary information also appears in continuous-time records of B(t): these magnetograms clearly show the abrupt incidence of `infarcts' (microcracks) and the cumulation of phase shifts as the material degrades.

  4. Optimal Fatigue Testing

    DEFF Research Database (Denmark)

    Faber, Michael Havbro; Sørensen, John Dalsgaard; Kroon, I. B.

    1993-01-01

    This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue ...

  5. Investigation of the fatigue behavior of adhesive bonding of the lithium disilicate glass ceramic with three resin cements using rotating fatigue method.

    Science.gov (United States)

    Yassini, E; Mirzaei, M; Alimi, A; Rahaeifard, M

    2016-08-01

    To investigate the fatigue behavior of bonding interface of lithium disilicate ceramic with three different dual cure resin cements. Forty five bar shaped ceramic-resin-ceramic specimens were prepared and divided into 3 groups (n=15) according to the resin cement used (group1: Panavia F2.0, group 2: RelyX Ultimate, group 3: Duo-Link Universal). Three specimens of each group were tested using three point bending test and the fracture strength of the resin-ceramic bond was measured. Other specimens of each group were placed in the rotating fatigue testing machine at stresses equal to 30%, 40%, 50% and 60% of the fracture strength. The cyclic loading was continued until fracture or a maximum of 10,000 cycles. For the specimens which did not fail until 10,000 cycles, the cyclic loading was stopped and the remained fracture strength of the specimens was measured. None of the specimens with cyclic loads of 30% and 40% of the fracture strength, have failed until 10,000 cycles. After 10,000 load cycles, the fracture strength of these specimens was significantly lower than their initial fracture strength. On the other hand, all specimens with cyclic stresses equal to 50% and 60% of the fracture strength have failed before 10,000 cycles so that the numbers of load cycles of RelyX specimens were significantly higher than those of Panavia ones and the numbers of cycles of Panavia specimens were significantly higher than those of Duo-Link specimens. The fatigue resistance of the ceramic-resin interface is significantly lower than its bond strength. Furthermore, RelyX Ultimate showed the highest fatigue resistance and Duo-Link Universal exhibited the weakest fatigue resistance. Since dental restorations are under cyclic loading caused by mastication forces, the results of this research can be used to select fatigue resistant resin cements for bonding of ceramic restorations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Fatigue Failure of Sandwich Beams with Wrinkle Defects Used for Wind Turbine Blades

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Hvejsel, C.F.; Lund, Erik

    2012-01-01

    Glass fiber face sheet/balsa wood core sandwich beams with out-of-plane fiber misalignments/wrinkle defects were subjected to in-plane fully reversed fatigue loading and the failure modes were documented. A fatigue life design limit was estimated using finite element analyses and the Northwestern...... University failure theory. The presence of the wrinkle defect significantly lowered the fatigue strength, but it was found that the test specimens could reach a pre-defined fatigue life with no signs of damage, by applying a fatigue load below 80% of the estimated design limit....

  7. Influence of defects on the very high cycle fatigue behaviour of forged aeronautic titanium alloy

    Directory of Open Access Journals (Sweden)

    Nikitin Alexander

    2014-06-01

    Full Text Available This paper is focused on fatigue failure of forged aeronautic titanium alloy Ti-6Al-4Mo under VHCF loading. Continuous fatigue tests were carried out in gigacycle fatigue regime (up to on 1010 cycles on specimens machined from real aircraft compressor disk produced by forging. It has been shown, that crack initiation site shifts from surface to subsurface location with stress amplitude decreasing and fatigue life increasing. Microstructural inhomogeneities so that “hard” alpha particles, borders of large alpha lamella clusters and TiN particles are the cause of fatigue crack nucleation in forged Ti-6Al-4Mo titanium alloy under VHCF loading.

  8. Comparative fatigue behavior of different bone cements.

    Science.gov (United States)

    Gates, E I; Carter, D R; Harris, W H

    1984-10-01

    Tensile and fatigue studies were performed on four different preparations of acrylic bone cement: (1) surgical Simplex-P inserted into molds in the dough stage, (2) Zimmer Low Viscosity Cement (LVC) inserted in the liquid phase, (3) an experimental cement inserted in the dough phase, and (4) the same experimental cement inserted in the liquid phase. The void characteristics of the cements appeared to dictate their mechanical performance. While tests revealed no difference in the tensile strengths of the four cement preparations, small but statistically significant differences in mean fatigue life were observed. The experimental cement used in the dough stage exhibited superior fatigue characteristics when compared with Simplex and LVC. LVC had the poorest mechanical properties of the four cement groups. Since the specimen preparation procedures can markedly influence the cement void characteristics and, consequently, the mechanical properties, general statements about different cement types are offered with considerable reservations.

  9. Evaluation of Massey Ferguson Model 165 Tractor Drivers exposed to whole-body vibration

    Directory of Open Access Journals (Sweden)

    P. Nassiri

    2013-12-01

    Conclusion: This study shows that the need to provide intervention , controlling and managing measures to eliminate or reduce exposure to whole body vibration among tractor drivers its necessary. And, preventing main disorder Including musculoskeletal disorders, discomfort and early fatigue is of circular importance. More studies are also necessary to identify the sources of vibration among various of tractors.

  10. High cycle fatigue properties of CLAM steel at 723 K and 823 K

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yanyun; Zhai, Xiangwei; Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn; Li, Chunjing; Huang, Qunying

    2015-11-15

    Highlights: • High cycle fatigue properties of CLAM steel were investigated at 723 K and 823 K. • The condition fatigue limit at N = 10{sup 7} were 275 MPa and 235 MPa at 723 K and 823 K. • Fatigue strength decreased when stress and temperature increased at 723 K and 823 K. • Dislocation density decrease and subgrain coarsening during the test process were the possible reasons for fatigue limit decrease. - Abstract: This paper highlights the results of a study on the high cycle fatigue strength and fracture mechanism of China Low Activation Martensitic (CLAM) steel. The high cycle fatigue test results showed that the fatigue strength of CLAM steel decreased with the temperature, and the condition fatigue strengths (N = 10{sup 7}) were 275 MPa and 235 MPa at 723 K and 823 K, respectively. The fractograph results indicated that the fractures were mainly initiated from the surface of the specimen.

  11. Fatigue Testing of Abrasive Water Jet Cut Titanium

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri; Dahl, Michael E.; Williford, Ralph E.

    2009-06-08

    Battelle Memorial Institute as part of its U.S. Department of Energy (USDOE) Contract No. DE-AC05-76RL01830 to operate the Pacific Northwest National Laboratory (PNNL) provides technology assistance to qualifying small businesses in association with a Technology Assistance Program (TAP). Qualifying companies are eligible to receive a set quantity of labor associated with specific technical assistance. Having applied for a TAP agreement to assist with fatigue characterization of Abrasive Water Jet (AWJ) cut titanium specimens, the OMAX Corporation was awarded TAP agreement 09-02. This program was specified to cover dynamic testing and analysis of fatigue specimens cut from titanium alloy Ti-6%Al-4%V via AWJ technologies. In association with the TAP agreement, a best effort agreement was made to characterize fatigue specimens based on test conditions supplied by OMAX.

  12. Fatigue strength testing of LTCC and alumina ceramics bonds

    Science.gov (United States)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  13. Velocity-specific fatigue: quantifying fatigue during variable velocity cycling.

    Science.gov (United States)

    Gardner, A Scott; Martin, David T; Jenkins, David G; Dyer, Iain; Van Eiden, Jan; Barras, Martin; Martin, James C

    2009-04-01

    Previous investigators have quantified fatigue during short maximal cycling trials ( approximately 30 s) by calculating a fatigue index. Other investigators have reported a curvilinear power-pedaling rate relationship during short fatigue-free maximal cycling trials (track bicycles. Data from the initial portion of maximal acceleration were used to establish maximal power-pedaling rate relationships. Fatigue was quantified three ways: 1) traditional fatigue index, 2) fatigue index modified to account for the power-pedaling rate relationship (net fatigue index), and 3) work deficit, the difference between actual work done and work that might have been accomplished without fatigue. Fatigue index (55.4% +/- 6.4%) was significantly greater than net fatigue index (41.0% +/- 7.9%, P cycling. These measures can be used to compare fatigue during different fatigue protocols, including world-class sprint cycling competition. Precise quantification of fatigue during elite cycling competition may improve evaluation of training status, gear ratio selection, and fatigue resistance.

  14. Evaluation of corrosion fatigue and life prediction of lower arm for automotive suspension component

    Science.gov (United States)

    Kim, Yong-Sang; Kim, Jung-Gu

    2017-01-01

    Lower arm is one of the suspension components of automobile. It is suffered from driving vibration and corrosive environment, namely corrosion fatigue. In this study, corrosion fatigue property of lower arm was investigated, and a modified model based on Palmgren-Miner rule was developed to predict the lifetimes of corrosion fatigue. The corrosion fatigue life of lower arm was about 1/6 times shorter than fatigue life. Based on the results of corrosion fatigue tests and meteorological data in Seoul and Halifax, the corrosion fatigue life of lower arm was predicted. The satisfaction of 10-year and 300,000 km warranty was dominated by the climate of automobile driving. This prediction indicates that the weather condition or driving condition influences the life of automotive parts. Therefore, to determine the warranty of automotive parts, the driving condition has to be carefully considered.

  15. Theory of vibration protection

    CERN Document Server

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  16. Analyses of Fatigue and Fatigue-Crack Growth under Constant- and Variable-Amplitude Loading

    Science.gov (United States)

    Newman, J. C., Jr.

    1999-01-01

    Studies on the growth of small cracks have led to the observation that fatigue life of many engineering materials is primarily crack growth from micro-structural features, such as inclusion particles, voids, slip-bands or from manufacturing defects. This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using small-crack theory under various loading conditions. Constraint factors, to account for three-dimensional effects, were selected to correlate large-crack growth rate data as a function of the effective stress-intensity factor range (delta K(sub eff)) under constant-amplitude loading. Modifications to the delta K(sub eff)-rate relations in the near-threshold regime were needed to fit measured small-crack growth rate behavior. The model was then used to calculate small- and large-crack growth rates, and to predict total fatigue lives, for notched and un-notched specimens under constant-amplitude and spectrum loading. Fatigue lives were predicted using crack-growth relations and micro-structural features like those that initiated cracks in the fatigue specimens for most of the materials analyzed. Results from the tests and analyses agreed well.

  17. Computer simulation of fatigue under diametrical compression.

    Science.gov (United States)

    Carmona, H A; Kun, F; Andrade, J S; Herrmann, H J

    2007-04-01

    We study the fatigue fracture of disordered materials by means of computer simulations of a discrete element model. We extend a two-dimensional fracture model to capture the microscopic mechanisms relevant for fatigue and we simulate the diametric compression of a disc shape specimen under a constant external force. The model allows us to follow the development of the fracture process on the macrolevel and microlevel varying the relative influence of the mechanisms of damage accumulation over the load history and healing of microcracks. As a specific example we consider recent experimental results on the fatigue fracture of asphalt. Our numerical simulations show that for intermediate applied loads the lifetime of the specimen presents a power law behavior. Under the effect of healing, more prominent for small loads compared to the tensile strength of the material, the lifetime of the sample increases and a fatigue limit emerges below which no macroscopic failure occurs. The numerical results are in a good qualitative agreement with the experimental findings.

  18. Fatigue Crack Prognostics by Optical Quantification of Defect Frequency

    Science.gov (United States)

    Chan, K. S.; Buckner, B. D.; Earthman, J. C.

    2017-11-01

    Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks per second detected using a laser beam that is scanned across a surface at a constant predetermined frequency. In the present article, a mechanistic approach was taken to develop a methodology for deducing crack length and crack growth information from defect frequency data generated from laser scanning measurements made on fatigued surfaces. The method was developed by considering a defect frequency vs fatigue cycle curve that comprised three regions: (i) a crack initiation regime of rising defect frequency, (ii) a plateau region of a relatively constant defect frequency, and (iii) a region of rapid rising defect frequency due to crack growth. Relations between defect frequency and fatigue cycle were developed for each of these three regions and utilized to deduce crack depth information from laser scanning data of 7075-T6 notched specimens. The proposed method was validated using experimental data of crack density and crack length data from the literature for a structural steel. The proposed approach was successful in predicting the length or depth of small fatigue cracks in notched 7075-T6 specimens and in smooth fatigue specimens of a structural steel.

  19. Fatigue Damage in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1996-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Fatigue failure is found to depend both on the total time under load and on the number of cycles.Recent accelerated fatigue research on wood is reviewed, and a discrepancy between...... to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation between stiffness reduction...

  20. Damage evolution in adhesive joints subjected to impact fatigue

    Science.gov (United States)

    Casas-Rodriguez, J. P.; Ashcroft, I. A.; Silberschmidt, V. V.

    2007-12-01

    There is increasing interest in the effects of low-velocity impacts produced in components and structures by vibrating loads. This type of loading is known as impact-fatigue. The main aim of this paper is to investigate the behaviour of adhesive joints exposed to low-velocity impacting, to study the impact-fatigue life and to compare this loading regime with standard fatigue (i.e. non-impacting, constant amplitude, sinusoidal fatigue). To this effect, bonded aluminium single lap joints have been subjected to multiple impacting tensile loads and it has been shown that this is an extremely damaging load regime compared to standard fatigue. Two modifications of the accumulated time-stress model have been proposed to characterise the impact-fatigue results presented in this paper. The first model has been termed the modified load-time model and relates the total cumulative loading time of the primary tensile load wave to the mean maximum force. The second model attempts to characterise sample damage under impact-fatigue by relating the maximum force normalised with respect to initial maximum force to the accumulated loading time normalised with respect to the total accumulated loading time. This model has been termed the normalised load-time model. It is shown that both models provide a suitable characterisation of impact-fatigue in bonded joints.

  1. Innovation in Active Vibration Control Strategy of Intelligent Structures

    Directory of Open Access Journals (Sweden)

    A. Moutsopoulou

    2014-01-01

    Full Text Available Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.

  2. Fatigue Characteristics of 3D Printed Acrylonitrile Butadiene Styrene (ABS)

    Science.gov (United States)

    Padzi, M. M.; Bazin, M. M.; Muhamad, W. M. W.

    2017-11-01

    Recently, the use of 3D printer technology has become significant to industries, especially when involving the new product development. 3D printing is a technology, which produces the 3D product or prototype using a layer-by-layer technique. However, there becomes less research on the mechanical performance of the 3D printed component. In the present work, fatigue characteristics of 3D printed specimen have been studied. Acrylonitrile butadiene styrene (ABS) has been chosen as a material research due to its wide applications. Two types of specimen used, which is the 3D printing and moulding specimens. Fused deposition modelling (FDM) technique was used to produce the specimens. The dog bone shape part was produced based on ASTM D638 standard and the tensile test has been carried out to get the mechanical properties. Fatigue test was carried out at 40%, 60% and 80% of the tensile strength. The moulded part shows higher fatigue cycles compared to 3D printed part for all loading percentages. Fatigue lives for 40%, 60% and 80%, were 911, 2645 and 26948 cycles, respectively. The results indicated that 3D printed part has a lower fatigue life, which may not suitable for industrial applications. However, the 3D printed part could be improved by using various parameters and may be introduced in low strength application.

  3. The Fatigue Behavior of Steel Structures under Random Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning

    2008-01-01

    Fatigue damage accumulation in steel structures under random loading has been studied in a number of investigations at the Technical University of Denmark. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part...... of the investigation, fatigue test series with a total of 540 fatigue tests have been carried through on various types of welded plate test specimens and full-scale offshore tubular joints. The materials that have been used are either conventional structural steel or high-strength steel. The fatigue tests...... and the fracture mechanics analyses have been carried out using load histories, which are realistic in relation to the types of structures studied, i.e. primarily bridges, offshore structures and chimneys. In general, the test series carried through show a significant difference between constant amplitude...

  4. Adaptations of mouse skeletal muscle to low intensity vibration training

    Science.gov (United States)

    McKeehen, James N.; Novotny, Susan A.; Baltgalvis, Kristen A.; Call, Jarrod A.; Nuckley, David J.; Lowe, Dawn A.

    2013-01-01

    Purpose We tested the hypothesis that low intensity vibration training in mice improves contractile function of hindlimb skeletal muscles and promotes exercise-related cellular adaptations. Methods We subjected C57BL/6J mice to 6 wk, 5 d·wk−1, 15 min·d−1 of sham or low intensity vibration (45 Hz, 1.0 g) while housed in traditional cages (Sham-Active, n=8; Vibrated-Active, n=10) or in small cages to restrict physical activity (Sham-Restricted, n=8; Vibrated-Restricted, n=8). Contractile function and resistance to fatigue were tested in vivo (anterior and posterior crural muscles) and ex vivo on the soleus muscle. Tibialis anterior and soleus muscles were evaluated histologically for alterations in oxidative metabolism, capillarity, and fiber types. Epididymal fat pad and hindlimb muscle masses were measured. Two-way ANOVAs were used to determine effects of vibration and physical inactivity. Results Vibration training resulted in a 10% increase in maximal isometric torque (P=0.038) and 16% faster maximal rate of relaxation (P=0.030) of the anterior crural muscles. Posterior crural muscles were unaffected by vibration, with the exception of greater rates of contraction in Vibrated-Restricted mice compared to Vibrated-Active and Sham-Restricted mice (P=0.022). Soleus muscle maximal isometric tetanic force tended to be greater (P=0.057) and maximal relaxation was 20% faster (P=0.005) in Vibrated compared to Sham mice. Restriction of physical activity induced muscle weakness but was not required for vibration to be effective in improving strength or relaxation. Vibration training did not impact muscle fatigability or any indicator of cellular adaptation investigated (P≥0.431). Fat pad but not hindlimb muscle masses were affected by vibration training. Conclusion Vibration training in mice improved muscle contractility, specifically strength and relaxation rates, with no indication of adverse effects to muscle function or cellular adaptations. PMID:23274599

  5. Fatigue Behavior and Modeling of Additively Manufactured Ti-6Al-4V Including Interlayer Time Interval Effects

    Science.gov (United States)

    Torries, Brian; Shamsaei, Nima

    2017-12-01

    The effects of different cooling rates, as achieved by varying the interlayer time interval, on the fatigue behavior of additively manufactured Ti-6Al-4V specimens were investigated and modeled via a microstructure-sensitive fatigue model. Comparisons are made between two sets of specimens fabricated via Laser Engineered Net Shaping (LENS™), with variance in interlayer time interval accomplished by depositing either one or two specimens per print operation. Fully reversed, strain-controlled fatigue tests were conducted, with fractography following specimen failure. A microstructure-sensitive fatigue model was calibrated to model the fatigue behavior of both sets of specimens and was found to be capable of correctly predicting the longer fatigue lives of the single-built specimens and the reduced scatter of the double-built specimens; all data points fell within the predicted upper and lower bounds of fatigue life. The time interval effects and the ability to be modeled are important to consider when producing test specimens that are smaller than the production part (i.e., property-performance relationships).

  6. Fatigue Behavior and Modeling of Additively Manufactured Ti-6Al-4V Including Interlayer Time Interval Effects

    Science.gov (United States)

    Torries, Brian; Shamsaei, Nima

    2017-10-01

    The effects of different cooling rates, as achieved by varying the interlayer time interval, on the fatigue behavior of additively manufactured Ti-6Al-4V specimens were investigated and modeled via a microstructure-sensitive fatigue model. Comparisons are made between two sets of specimens fabricated via Laser Engineered Net Shaping (LENS™), with variance in interlayer time interval accomplished by depositing either one or two specimens per print operation. Fully reversed, strain-controlled fatigue tests were conducted, with fractography following specimen failure. A microstructure-sensitive fatigue model was calibrated to model the fatigue behavior of both sets of specimens and was found to be capable of correctly predicting the longer fatigue lives of the single-built specimens and the reduced scatter of the double-built specimens; all data points fell within the predicted upper and lower bounds of fatigue life. The time interval effects and the ability to be modeled are important to consider when producing test specimens that are smaller than the production part (i.e., property-performance relationships).

  7. Determinants of seafarers’ fatigue

    DEFF Research Database (Denmark)

    Bøggild Dohrmann, Solveig; Leppin, Anja

    2017-01-01

    Purpose: Fatigue jeopardizes seafarer’s health and safety. Thus, knowledge on determinants of fatigue is of great importance to facilitate its prevention. However, a systematic analysis and quality assessment of all empirical evidence specifically for fatigue are still lacking. The aim...... in the review. The main reason for exclusion was fatigue not being the outcome variable. Results: Most evidence was available for work time-related factors suggesting that working nights was most fatiguing, that fatigue levels were higher toward the end of watch or shift, and that the 6-h on–6-h off watch...... system was the most fatiguing. Specific work demands and particularly the psychosocial work environment have received little attention, but preliminary evidence suggests that stress may be an important factor. A majority of 12 studies were evaluated as potentially having a high risk of bias. Conclusions...

  8. Shot peening impact on fatigue scattered structural elements of vehicles

    Directory of Open Access Journals (Sweden)

    Sebastian KAMIŃSKI

    2015-09-01

    Full Text Available The theme of this work is to know about the current state of knowledge in the field of materials processing using a distributed circular pellet of shot peening steel surfaces. The paper presents an analysis of the issues and test their own dedicated fatigue life specimens made of steel S355 J2 + N subjected to shot peening, and to compare these results with the strength of the specimens not subjected to this treatment. The results will be presented in the fatigue characteristics S-N double logarithmic system.

  9. Devices for fatigue testing of electroplated nickel (MEMS)

    DEFF Research Database (Denmark)

    Larsen, Kristian Pontoppidan; Ravnkilde, J. T.; Ginnerup, Morten

    2002-01-01

    In-situ fatigue test devices with integrated electrostatic actuator were fabricated in electroplated nanocrystalline nickel (nano-nickel). The devices feature in-plane approximately pure bending with fixed displacement of the test specimen of the dimensions: widths from 2μm to 3.7μm, a height of 7...... after 108 cycles. The combination of high strength and toughness, which is known for nanocrystalline materials, together with very small test specimens and low surface roughness could be the explanation for the good fatigue properties....

  10. Fatigue failure of sandwich beams with face sheet wrinkle defects

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Hvejsel, C.F.; Thomsen, Ole Thybo

    2012-01-01

    and application of the Northwestern University failure criteria. The presence of a wrinkle defect reduced the fatigue life by approximately 66%, compared to that of an unnotched reference laminate. Furthermore, the results from the fatigue tests revealed that the design limit was initially overestimated......, as the specimens loaded close to the predicted design limit typically failed before reaching the target life, or reached test run-out with visible face sheet damage indicating imminent final failure in the worst case. It was found that specimens would reach target life with no visible or otherwise detectable...

  11. Fatigue Life of Postbuckled Structures with Indentation Damage

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of the stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 37 millimeters to 56 millimeters were tested in fatigue and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  12. Fatigue Life of Postbuckled Structures with Indentation Damages

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of each stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 32 millimeters to 56 millimeters were tested quasi-statically and in fatigue, and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  13. Flexure fatigue of 10 commonly used denture base resins.

    Science.gov (United States)

    Johnston, E P; Nicholls, J I; Smith, D E

    1981-11-01

    The flexure fatigue properties of 10 denture base resins (four different types) were tested. Each specimen underwent two-way testing in a water bath maintained at 37 degrees +/- 1 degree C. A load of 3,650 gm was applied a 342 flexures per minute until the specimen broke. The resin types listed in order of increasing resistance to flexure fatigue are polymethylmethacrylate (PMM) pour resins, PMM thermosetting resins, vinyl resins, and a PMM grafted resin. Although small samples size and scatter of results limit broad application of this data, it is of some significance that the grafted resin Lucitone 199 tended to withstand repeated flexure when compared to the other resins.

  14. Janka hardness using nonstandard specimens

    Science.gov (United States)

    David W. Green; Marshall Begel; William Nelson

    2006-01-01

    Janka hardness determined on 1.5- by 3.5-in. specimens (2×4s) was found to be equivalent to that determined using the 2- by 2-in. specimen specified in ASTM D 143. Data are presented on the relationship between Janka hardness and the strength of clear wood. Analysis of historical data determined using standard specimens indicated no difference between side hardness...

  15. Effect of vibration on visual display terminal work performance.

    Science.gov (United States)

    Hsieh, Yao-Hung; Lin, Chiuhsiang Joe; Chen, Hsiao-Ching

    2007-12-01

    Today electronic visual displays have dramatic use in daily life. Reading these visual displays is subject to their vibration. Using a software-simulation of a vibrated environment, the study investigated the effect of vibration on visual performance and fatigue for several numerical display design characteristics including the font size and the number of digits displayed. Both the frequency and magnitude of vibration had significant effects on the reaction time, accuracy, and visual fatigue. 10 graduate students (23-30 years old; M = 25.6), randomly tested in this experiment, were offered about 25 U.S. dollars for their participation. Numbers in vertical presentation were affected more in vertical vibration than those in horizontal presentation. Analysis showed whenever the display is used in vibration environment, an increased font size may be an effective way to compensate the adverse effect of vibration. The software design of displayed materials must be designed to take the motion effect into consideration to increase the quality of the screen display.

  16. Quantitative acoustic emission monitoring of fatigue cracks in fracture critical steel bridges.

    Science.gov (United States)

    2014-01-01

    The objective of this research is to evaluate the feasibility to employ quantitative acoustic : emission (AE) techniques for monitoring of fatigue crack initiation and propagation in steel : bridge members. Three A36 compact tension steel specimens w...

  17. An active control logic to improve the fatigue strength of smart flexible structures

    Science.gov (United States)

    Ambrosio, Pasquale; Braghin, Francesco; Resta, Ferruccio; Ripamonti, Francesco

    2013-04-01

    In general active vibration control intrinsically implies a fatigue damage reduction. Anyway, this assumption is not always verified. In these cases it is possible to deeper investigate the fatigue phenomena on smart flexible structures and their reduction from a control point of view. In this article, to identify the problem main parameters, a simplified interpretation of fatigue damage is given using the frequency analysis framework. Then, the active control logic is defined as an optimization problem with a quadratic functional taking into account the previously cited parameters. Finally, because of non-linearity of fatigue phenomenon, an adaptive approach is applied and a numerical/experimental validation is carried out.

  18. Cognitive and Physical Fatigue Tasks Enhance Pain, Cognitive Fatigue and Physical Fatigue in People with Fibromyalgia

    Science.gov (United States)

    Dailey, Dana L; Keffala, Valerie J; Sluka, Kathleen A

    2014-01-01

    Objective Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task and a dual fatigue task. Methods Twenty four people with fibromyalgia and 33 healthy controls completed pain, fatigue and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue and perceived physical fatigue were assessed during each task using visual analogue scales. Function was assessed with shoulder range of motion and grip. Results People with fibromyalgia had significantly higher increases in pain, cognitive fatigue and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (pfatigue tasks, respectively. Conclusions These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. PMID:25074583

  19. Creep, fatigue and creep-fatigue interactions in modified 9% Chromium - 1% Molybdenum (P91) steels

    Science.gov (United States)

    Kalyanasundaram, Valliappa

    Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the proposed research are to characterize the creep, fatigue and C-F behavior of grade P91 steels at 625 C and develop robust constitutive models for simulating/predicting their microstructural response under different loading conditions. This work will utilize experimental data from 16 laboratories worldwide that conducted tests (creep, fatigue and C-F) on grade P91 steel at 625°C in a round-robin (RR) program. Along with 7 creep deformation and rupture tests, 32 pure fatigue and 46 C-F tests from the RR are considered in this work. A phenomenological constitutive model formulated in this work needs just five fitting parameters to simulate/predict the monotonic, pure fatigue and C-F behavior of grade P91 at 625 C. A modified version of an existing constitutive model is also presented for particularly simulating its isothermal creep deformation and rupture behavior. Experimental results indicate that specimen C-F lives, as measured by the 2% load drop criterion, seem to decrease with increasing strain ranges and increasing hold times at 625°C. Metallographic assessment of the tested specimens shows that the damage mode in both pure fatigue and 600 seconds hold time cyclic tests is predominantly transgranular fatigue with some presence of

  20. Investigation of mistuning impact on vibration of rotor bladed disks

    Science.gov (United States)

    Repetckii, O.; Ryzhikov, I.; Quyet Nguyen, Tien

    2018-01-01

    Mistuning often reduces the fatigue life of bladed disks. The objective of this study is to determine the degree of influence of various types of mistuning on bladed disk vibration. It is also important to determine how the position of the detuned blades in the bladed disk affects the vibrations. The results of experimental and numerical analysis of mistuned bladed disk vibration are presented. The authors investigated the effect of various types of mistuning (geometry, mass, etc.) on the free vibrations of the bladed disk. The worst cases with minimum mistuning and maximum localization were identified. The developed algorithms for calculating of mistuned bladed disks vibration and obtained results can be used, when designing turbomachines rotors.

  1. Defects detection on the welded reinforcing steel with self-shielded wires by vibration tests

    Directory of Open Access Journals (Sweden)

    Crâştiu Ion

    2017-01-01

    Full Text Available The aim of this paper is the development and validation of a vibroacustic technique to welding defects detection, especially for welded reinforcing structures. In welded structures subjected to dynamic cyclic loads may appear and propagate fatigue cracks due to local structural damage. These cracks may initiate due to the technological parameters used in welding process, or due to environmental operating conditions. By the means of Finite Element Method (FEM, the natural frequencies and shape modes of more welded steel specimens are determined. The analysis is carried out in undamaged condition as well as damaged one, after artificially induced damages. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone, which is suitable for high-fidelity acoustic measurements in the frequency range of 20 – 20.000 Hz. The vibration responses of the welded specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform (FFT, and Prony's series. The results are compared to modal parameters estimated using FE Analysis.

  2. Cyclic Fracture Toughness of Railway Axle and Mechanisms of its Fatigue Fracture

    Directory of Open Access Journals (Sweden)

    Sorochak Andriy

    2015-06-01

    Full Text Available The main regularities in fatigue fracture of the railway axle material - the OSL steel - are found in this paper. Micromechanisms of fatigue crack propagation are described and systematized, and a physical-mechanical interpretation of the relief morphology at different stages of crack propagation is proposed for fatigue cracks in specimens cut out of the surface, internal and central layers of the axle.

  3. The effect of A5TB refiner on the fatigue strength of 6063AL alloy ...

    African Journals Online (AJOL)

    The study focuses on the influence of aluminium titanium boron (A5TB) master alloy on the fatigue behaviour of 6063Al alloy. Cylindrical cast rods of 6063Al alloy containing different proportions of A5TB ranging from 0 - 0.11 wt.% were produced and were machined to conform to a standard fatigue specimen. The test ...

  4. Influence de la fatigue thermique et des chocs thermiques sur la ...

    African Journals Online (AJOL)

    13 nov. 2007 ... T.I.G welding process on specimens made out of 42CD4 ferritic steel. The study concerns tree different ... of the test. Key words: thermal fatigue; thermal shocks; austenitic stainless steel; friction; wear; welding. 1. INTRODUCTION ..... Michaud, Simulation expérimentale de la fatigue thermique d'un cylindre ...

  5. Effect of stress ratio and frequency on fatigue crack growth rate of ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Effect of stress ratio and frequency on the fatigue crack propagation of 2618 aluminium alloy– silicon carbide composite were investigated at ambient temperature. With the first set of specimens, the fatigue crack growth rates were studied at three frequencies of 1 Hz, 5 Hz and 10 Hz at a stress ratio of 0⋅1 whereas.

  6. Effect of stress ratio and frequency on fatigue crack growth rate of ...

    Indian Academy of Sciences (India)

    Effect of stress ratio and frequency on the fatigue crack propagation of 2618 aluminium alloy–silicon carbide composite were investigated at ambient temperature. With the first set of specimens, the fatigue crack growth rates were studied at three frequencies of 1 Hz, 5 Hz and 10 Hz at a stress ratio of 0.1 whereas the effects ...

  7. Page 1 X-ray Study of fatigue-cycled aluminium 209 of cases, the ...

    Indian Academy of Sciences (India)

    the single line method, it is assumed that the Cauchy and the Gaussian components represent respectively the contribution from crystallite size and the microstrains. The f profile which only includes the effect of fatigue cycling was calculated from the profile obtained on fatigue-cycled specimens by removing the contribution ...

  8. Inconel 718 and UNSM Treated Alloy Study on the Rotary Bending High Temperature Fatigue Characteristics under a Light Concentrating System

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of); Nahm, Seung Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Woo, Young Han; Hur, Kwang Ho; Hong, Sang Hwui [Gyeongbuk Hybrid Technology Institute, Daegu (Korea, Republic of); Kim, Jun Hyong; Pyun, Young Sik [Sun Moon Univ., Asan (Korea, Republic of)

    2016-11-15

    This study investigated the influence of high temperature and UNSM on the fatigue behavior of Inconel 718 alloy at RT, 300, 500, and 600℃. Fatigue properties of Inconel 718 were reduced at high temperatures compared to those at room temperature. However, the endurance limit was similar to that of the room temperature sample at the design stress level. High-temperature fatigue characteristics of the UNSM-treated specimen were significantly improved at the design stress level as compared to the untreated specimens. Specifically, the influence of temperature on the S-N curves at the design stress level of the UNSM-treated specimen showed the tendency of longer fatigue lives than those of untreated ones. Researchers can obtain rotary fatigue test results simply by heating specimens with a halogen lamp to precise temperatures during specific operations.

  9. Effect of Cold Expansion on Fatigue Life of Hole Structure of TC17 Titanium Alloy

    Directory of Open Access Journals (Sweden)

    AI Yingjun

    2017-12-01

    Full Text Available In order to improve the fatigue performance of TC17 central hole specimen, the hole wall surface integrity was characterized by scanning electron microscopy (SEM, roughness meter, X-ray diffraction, and the influence of hole cold expansion(HCE parameter on the fatigue performance of the hole specimens was investigated. The results show that the minimum fatigue life (14718 cycle of the HCE specimens with an expansion value of 0.18 mm is higher than the original specimen (13965 cycle. Compared to the specimens with the expansion values of 0.28 mm and 0.38 mm, the fatigue life dispersion is less, no obvious stress concentration phenomenon is found, and it has the best fatigue performance than the other two. The surface roughness value of hole wall is the lowest after the HCE with 0.18 mm, the inner hole wall forms a certain depth of strengthened layer, the residual compressive stress produced in the hole side effectively suppresses the produce of fatigue cracks in the inner hole wall, so the fatigue performance of hole structure is improved.

  10. Histopathologic Analysis of Pancreaticoduodenectomy Specimen

    Directory of Open Access Journals (Sweden)

    Ramesh Dhakhwa

    2016-12-01

    Conclusions: Pancreaticoduodenectomy specimen requires thorough histopathological evaluation. Pathologists should also be aware of possibility of a benign diagnosis in PD specimens which have been resected presuming malignancy based on clinical judgement and radiological data. Keywords: histopathologic evaluation, pancreaticoduodenectomy, periampullary carcinoma. | PubMed

  11. Effect of Microstructure on Fatigue Crack Propagation and S-N Fatigue Behaviors of TMCP Steels with Yield Strengths of Approximately 450 MPa

    Science.gov (United States)

    Kim, Youngju; Kwon, Jaeki; Lee, Hyunjung; Jang, Wookil; Choi, Jongkyo; Kim, Sangshik

    2011-04-01

    In the present study, stress (S) - number of cycles to failure (N) (S-N) fatigue and fatigue crack propagation behaviors of three thermomechanical control process steels with different microstructures but similar yield strengths of approximately 450 MPa were investigated. The P + F steel was predominately pearlite plus ferrite, whereas B1 and B2 steels were both bainitic steels with martensite-austenite and pearlitic islands. Despite the significant difference in microstructural features, the resulting fatigue crack propagation rates and near-threshold Δ K values were comparable with each other. The hard phases, such as pearlite colonies in the P + F specimen, tended to affect fatigue crack propagation behavior in a similar manner, and severe crack branching was observed in intermediate and high Δ K regimes. Despite similar fatigue crack propagation rates and near-threshold Δ K values, the resistance to S-N fatigue was substantially different for each steel specimen. Depending on fatigue crack initiators, such as the ferrite/pearlite phase boundaries for the P + F specimens and the cracked martensite-austenite and/or small pearlitic islands for the bainitic specimens, the cycles for crack initiation varied greatly.

  12. High-Cycle Fatigue of High-Strength Low Alloy Steel Q345 Subjected to Immersion Corrosion for Mining Wheel Applications

    Science.gov (United States)

    Dicecco, Sante; Altenhof, William; Hu, Henry; Banting, Richard

    2017-04-01

    In an effort to better understand the impact of material degradation on the fatigue life of mining wheels made of a high-strength low alloy carbon steel (Q345), this study seeks to evaluate the effect of surface corrosion on the high-cycle fatigue behavior of the Q345 alloy. The fatigue behavior of the polished and corroded alloy was investigated. Following exposure to a 3.5 wt.% NaCl saltwater solution, polished and corroded fatigue specimens were tested using an R.R. Moore rotating-bending fatigue apparatus. Microstructural analyses via both optical microscopy and scanning electron microscopy (SEM) revealed that one major phase, α-iron phase, ferrite, and one minor phase, colony pearlite, existed in the extracted Q345 alloy. The results of the fatigue testing showed that the polished and corroded specimens had an endurance strength of approximately 295 and 222 MPa, respectively, at 5,000,000 cycles. The corroded surface condition resulted in a decrease in the fatigue strength of the Q345 alloy by 24.6%. Scanning electron microscope fractography indicated that failure modes for polished and corroded fatigue specimens were consistent in the high-cycle low loading fatigue regime. Conversely, SEM fractography of low-cycle high-loading fatigue specimens found considerable differences in fracture surfaces between the corroded and polished fatigue specimens.

  13. Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF range based on inclusion population

    Directory of Open Access Journals (Sweden)

    Kolyshkin A.

    2014-06-01

    Full Text Available The VHCF behaviour of metallic materials containing microstructural defects such as non-metallic inclusions is determined by the size and distribution of the damage dominating defects. In the present paper, the size and location of about 60.000 inclusions measured on the longitudinal and transversal cross sections of AISI 304 sheet form a database for the probabilistic determination of failure-relevant inclusion distribution in fatigue specimens and their corresponding fatigue lifes. By applying the method of Murakami et al. the biggest measured inclusions were used in order to predict the size of failure-relevant inclusions in the fatigue specimens. The location of the crack initiating inclusions was defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. Reasonable agreement was obtained between modeling and experimental results.

  14. Deformation Properties and Fatigue of Bituminous Mixtures

    Directory of Open Access Journals (Sweden)

    Frantisek Schlosser

    2013-01-01

    Full Text Available Deformation properties and fatigue performance are important characteristics of asphalt bound materials which are used for construction of pavement layers. Viscoelastic asphalt mixtures are better characterized via dynamic tests. This type of tests allows us to collate materials with regard to axle vibrations which lie usually in the range of 6 Hz–25 Hz for standard conditions. Asphalt modified for heat sensitivity in the range from −20°C to +60°C has significant impact on the overall characteristics of the mixture. Deformation properties are used as inputs for empirical mixture design, and fatigue performance of asphalt mixtures reflects the parameters of functional tests. Master curves convey properties of asphalt mixtures for various conditions and allow us to evaluate them without the need of time expensive testing.

  15. Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

    Directory of Open Access Journals (Sweden)

    Hitoshi Soyama

    2015-08-01

    Full Text Available It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening.

  16. Fatigue characteristics of dual-phase steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Onn, Irwan Herman; Ahmad, Norhayati; Tamin, Mohd Nasir [Universiti Teknologi Malaysia, Skudai (Malaysia)

    2015-01-15

    Fatigue characteristics of dual-phase steel sheets, commonly used in automobile body construction were established. For this purpose, a series of fatigue tests, each at constant stress amplitude were conducted on 1.2 mm-thick, dual-phase DP600 steel sheet specimens with two different load ratios of minimum-to-maximum stress, R = 0.1 and -1. The resulting fatigue behavior is expressed in terms of fatigue strength-life (S-N) curves. Fatigue behavior of the steel sheets in the high-cycle fatigue region can be represented by Basquin's equation with coefficient and exponent value of 921.2 and 0.093, respectively. An endurance limit of 255 MPa is observed. In addition, fatigue strengths of the dual-phase steel sheets display lower magnitude than their bulk counterparts. Effect of mean stress on fatigue behavior of the steel sheets is well predicted by Walker's model. Exponential calibration factor is introduced to the models by SWT, Goodman and Morrow with comparable prediction to the Walker's model.

  17. Characterizing the magnetic memory signals on the surface of plasma transferred arc cladding coating under fatigue loads

    Science.gov (United States)

    Huang, Haihong; Han, Gang; Qian, Zhengchun; Liu, Zhifeng

    2017-12-01

    The metal magnetic memory signals were measured during dynamic tension tests on the surfaces of the cladding coatings by plasma transferred arc (PTA) welding and the 0.45% C steel. Results showed that the slope of the normal component Hp(y) of magnetic signal and the average value of the tangential component Hp(x) reflect the magnetization of the specimens. The signals increased sharply in the few initial cycles; and then fluctuated around a constant value during fatigue process until fracture. For the PTA cladding coating, the slope of Hp(y) was steeper and the average of Hp(x) was smaller, compared with the 0.45% C steel. The hysteresis curves of cladding layer, bonding layer and substrate were measured by vibrating sample magnetometer testing, and then saturation magnetization, initial susceptibility and coercivity were further calculated. The stress-magnetization curves were also plotted based on the J-A model, which showed that the PTA cladding coating has smaller remanence and coercivity compared with the 0.45% C steel. The microstructures of cladding coating confirmed that the dendritic structure and second-phase of alloy hinder the magnetic domain motion, which was the main factor influencing the variation of magnetic signal during the fatigue tests.

  18. Ex-situ X-ray computed tomography data for a non-crimp fabric based glass fibre composite under fatigue loading

    Directory of Open Access Journals (Sweden)

    Kristine M. Jespersen

    2017-12-01

    Full Text Available The data published with this article are high resolution X-ray computed tomography (CT data obtained during an ex-situ fatigue test of a coupon test specimen made from a non-crimp fabric based glass fibre composite similar to those used for wind turbine blades. The fatigue test was interrupted four times for X-ray CT examination during the fatigue life of the considered specimen. All the X-ray CT experiments were performed in the region where unidirectional fibre fractures first became visible, and thereby include the damage progression in 3D in this specific region during fatigue loading of the specimen.

  19. Effect of the Machining Processes on Low Cycle Fatigue Behavior of a Powder Metallurgy Disk

    Science.gov (United States)

    Telesman, J.; Kantzos, P.; Gabb, T. P.; Ghosn, L. J.

    2010-01-01

    A study has been performed to investigate the effect of various machining processes on fatigue life of configured low cycle fatigue specimens machined out of a NASA developed LSHR P/M nickel based disk alloy. Two types of configured specimen geometries were employed in the study. To evaluate a broach machining processes a double notch geometry was used with both notches machined using broach tooling. EDM machined notched specimens of the same configuration were tested for comparison purposes. Honing finishing process was evaluated by using a center hole specimen geometry. Comparison testing was again done using EDM machined specimens of the same geometry. The effect of these machining processes on the resulting surface roughness, residual stress distribution and microstructural damage were characterized and used in attempt to explain the low cycle fatigue results.

  20. Comparative Physiology of Fatigue

    National Research Council Canada - National Science Library

    JONES, JAMES H

    2016-01-01

    ABSTRACTThis review attempts to provide insights into factors associated with fatigue in human and nonhuman animals by using the two fundamental approaches of comparative physiologydetermining common...

  1. Neurobiological studies of fatigue

    Science.gov (United States)

    Harrington, Mary E.

    2012-01-01

    Fatigue is a symptom associated with many disorders, is especially common in women and in older adults, and can have a huge negative influence on quality of life. Although most past research on fatigue uses human subjects instead of animal models, the use of appropriate animal models has recently begun to advance our understanding of the neurobiology of fatigue. In this review, results from animal models using immunological, developmental, or physical approaches to study fatigue are described and compared. Common across these animal models is that fatigue arises when a stimulus induces activation of microglia and/or increased cytokines and chemokines in the brain. Neurobiological studies implicate structures in the ascending arousal system, sleep executive control areas, and areas important in reward. In addition, the suprachiasmatic nucleus clearly plays an important role in homeostatic regulation of the neural network mediating fatigue. This nucleus responds to cytokines, shows decreased amplitude firing rate output in models of fatigue, and responds to exercise, one of our few treatments for fatigue. This is a young field but very important as the symptom of fatigue is common across many disorders and we do not have effective treatments. PMID:22841649

  2. Laser thermal shock and fatigue testing system

    Science.gov (United States)

    Fantini, Vincenzo; Serri, Laura; Bianchi, P.

    1997-08-01

    Thermal fatigue consists in repeatedly cycling the temperature of a specimen under test without any other constraint and stopping the test when predefined damage aspects. The result is a lifetime in terms of number of cycles. The parameters of the thermal cycle are the following: minimum and maximum temperature, time of heating, of cooling and time at high or at low temperature. When the temperature jump is very big and fast, phenomena of thermal shock can be induced. Among the numerous techniques used to perform these tests, the laser thermal fatigue cycling is very effective when fast heating of small and localized zones is required. That's the case of test performed to compare new and repaired blades of turbogas machines or components of combustion chambers of energy power plants. In order to perform these tests a thermal fatigue system, based on 1 kW Nd-YAG laser as source of heating, has been developed. The diameter of the heated zone of the specimen irradiated by the laser is in the range 0.5 - 20 mm. The temperatures can be chosen between 200 degree(s)C and 1500 degree(s)C and the piece can be maintained at high and/or low temperature from 0 s to 300 s. Temperature are measured by two sensors: a pyrometer for the high range (550 - 1500 degree(s)C) and a contactless thermocouple for the low range (200 - 550 degree(s)C). Two different gases can be blown on the specimen in the irradiated spot or in sample backside to speed up cooling phase. A PC-based control unit with a specially developed software performs PID control of the temperature cycle by fast laser power modulation. A high resolution vision system of suitable magnification is connected to the control unit to detect surface damages on the specimen, allowing real time monitoring of the tested zone as well as recording and reviewing the images of the sample during the test. Preliminary thermal fatigue tests on flat specimens of INCONEL 738 and HAYNES 230 are presented. IN738 samples, laser cladded by

  3. Influence of Hole Cold Expansion on Microstructure and Fatigue Life of 2124 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    YI Linna

    2016-10-01

    Full Text Available The change of fatigue life and microstructure of 2124-T851 thick plate after cold expanded with different deformation was studied by fatigue test, TEM, SEM and X-ray diffraction apparatus. The results show that the fatigue life increases with the increase of expanded deformation until the maximum value is reached, and then decreased rapidly with the increase of expanded deformation. At 0.4 mm expanded deformation, fatigue life reach peak value, which is 12.66 times of the non-cold-worked specimens. The microstructure research results show that the residual compressive stress and dislocation cell structure form around the cold-worked holes during the cold expansion, and increase quickly with the expanded deformation. The strengthened layer retarded the fatigue crack growth rate. The appropriate cold expanded deformation can improve the surface roughness of hole, and retard the initiation of fatigue crack, consequently improving the whole fatigue life.

  4. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

    Science.gov (United States)

    Özdeş, Hüseyin; Tiryakioğlu, Murat

    2017-02-01

    Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengths at 104 and 106 cycles have been found increase with quality index, providing further evidence about the relationship observed between structural quality and fatigue performance. Empirical equations between Basquin parameters and structural quality index have been developed. The use of the comprehensive methodology to estimate fatigue life is demonstrated with an example.

  5. Fatigue life investigation of UIC 54 rail profile for high speed rail

    Science.gov (United States)

    Gurubaran, P.; Afendi, M.; Nur Fareisha, M. A.; Majid, M. S. Abdul; Haftirman, I.; Rahman, M. T. A.

    2017-10-01

    This study is to investigate the fatigue life of high speed rail in Malaysia. This paper describes about the experimental and simulation analysis investigation on fatigue life of rail profile UIC 54 using bulk specimen according to ASTM E 466-15 standard. The Fatigue life testing was performed in the fatigue testing machine (Instron 8800) 100 kN. Meanwhile, the fatigue life analysis was performed in ANSYS Workbench 14.5. Furthermore, the stress levels for experimental testing were applied as 16.7%, 25%, 35%, 50%, 58.3%, 66.77% and 75% with machine frequency of 20 Hz. Apart from that, the total fatigue life cycles for rail profile UIC 54 were acquired from both experimental and simulation. The fatigue life S-N curves were plotted and validated with the results of the simulation analysis with experimental results.

  6. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

    DEFF Research Database (Denmark)

    Ibsø, Jan Behrend; Agerskov, Henning

    1996-01-01

    test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination...... of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied....

  7. A Modified Fatigue Damage Model for High-Cycle Fatigue Life Prediction

    Directory of Open Access Journals (Sweden)

    Meng Wang

    2016-01-01

    Full Text Available Based on the assumption of quasibrittle failure under high-cycle fatigue for the metal material, the damage constitutive equation and the modified damage evolution equation are obtained with continuum damage mechanics. Then, finite element method (FEM is used to describe the failure process of metal material. The increment of specimen’s life and damage state can be researched using damage mechanics-FEM. Finally, the lifetime of the specimen is got at the given stress level. The damage mechanics-FEM is inserted into ABAQUS with subroutine USDFLD and the Python language is used to simulate the fatigue process of titanium alloy specimens. The simulation results have a good agreement with the testing results under constant amplitude loading, which proves the accuracy of the method.

  8. Fatigue properties of X80 pipeline steels with ferrite/bainite dual-phase microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Zuo-peng [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Qiao, Gui-ying [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Key Lab of Applied Chemistry of Hebei Province and School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Tang, Lei [Key Lab of Applied Chemistry of Hebei Province and School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Zhu, Hong-wei; Liao, Bo [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China); Xiao, Fu-ren, E-mail: frxiao@ysu.edu.cn [Key Lab of Metastable Materials Science & Technology and College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2016-03-07

    Fatigue properties are important parameters for the safety design and security evaluation of gas transmission pipelines. In this work, the fatigue life at different stresses of full-thickness X80 pipeline steel plates with a ferrite/bainite dual-phase microstructure was investigated using a MTS servo-hydraulic universal testing machine; the fatigue crack propagation rate was examined with CT specimens by using an INSTRON 8874 testing machine. Results indicate that fatigue life increases as maximum stress decreases; as the maximum stress decreases to the maximum operating stress (440 MPa), the fatigue life is approximately 4.2×10{sup 5} cycles. The fatigue crack of the full-thickness fatigue life specimens is generated at the surface of rolled steel plates and then the crack propagates and grows inward until a fracture is formed. During fatigue crack growth, a transitional turning point appears in the curve of da/dN with ΔK in the Paris region. The transitional turning point that divides the Paris region to two stages is approximately ΔK≅30 MPa m{sup 1/2}. The change in the growth rate (da/dN) is related to the variation of the crack path and in the fracture mode because of the possible microstructural sensitivity of fatigue crack propagation behavior. This study also discussed the effect of duple phase ferrite/bainite microstructure on fatigue crack initiation and propagation.

  9. Fatigue strength of Co-Cr-Mo alloy clasps prepared by selective laser melting.

    Science.gov (United States)

    Kajima, Yuka; Takaichi, Atsushi; Nakamoto, Takayuki; Kimura, Takahiro; Yogo, Yoshiaki; Ashida, Maki; Doi, Hisashi; Nomura, Naoyuki; Takahashi, Hidekazu; Hanawa, Takao; Wakabayashi, Noriyuki

    2016-06-01

    We aimed to investigate the fatigue strength of Co-Cr-Mo clasps for removable partial dentures prepared by selective laser melting (SLM). The Co-Cr-Mo alloy specimens for tensile tests (dumbbell specimens) and fatigue tests (clasp specimens) were prepared by SLM with varying angles between the building and longitudinal directions (i.e., 0° (TL0, FL0), 45° (TL45, FL45), and 90° (TL90, FL90)). The clasp specimens were subjected to cyclic deformations of 0.25mm and 0.50mm for 10(6) cycles. The SLM specimens showed no obvious mechanical anisotropy in tensile tests and exhibited significantly higher yield strength and ultimate tensile strength than the cast specimens under all conditions. In contrast, a high degree of anisotropy in fatigue performance associated with the build orientation was found. For specimens under the 0.50mm deflection, FL90 exhibited significantly longer fatigue life (205,418 cycles) than the cast specimens (112,770 cycles). In contrast, the fatigue lives of FL0 (28,484 cycles) and FL45 (43,465 cycles) were significantly shorter. The surface roughnesses of FL0 and FL45 were considerably higher than those of the cast specimens, whereas there were no significant differences between FL90 and the cast specimens. Electron backscatter diffraction (EBSD) analysis indicated the grains of FL0 showed preferential close to orientation of the γ phase along the normal direction to the fracture surface. In contrast, the FL45 and FL90 grains showed no significant preferential orientation. Fatigue strength may therefore be affected by a number of factors, including surface roughness and crystal orientation. The SLM process is a promising candidate for preparing tough removable partial denture frameworks, as long as the appropriate build direction is adopted. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades

    Science.gov (United States)

    Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

    2012-01-01

    Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

  11. Detection of localized fatigue damage in steel by thermography

    Science.gov (United States)

    Medgenberg, Justus; Ummenhofer, Thomas

    2007-04-01

    Fatigue damage of unalloyed steels in the high cycle regime is governed by localized cyclic plastic deformations and subsequent crack initiation. The extent of early microplastic deformations depends on the applied stress level, stress concentration at macroscopic notches, surface treatment, residual stresses etc. The onset of a nonlinear material response can be regarded as an early indicator of fatigue damage. During fatigue loading thermoelastic coupling and thermoplastic dissipation cause characteristic temperature variations in tested specimens which have been assessed by a highly sensitive infrared camera. A specialized data processing method in the time domain has been developed which allows to separate the different contributions to the measured temperature signal. In contrast to other methods - as e.g. measuring the rise of mean temperature during fatigue loading - the proposed methodology is based on measurements during the stabilized temperature regimen and offers very high spatial resolution of localized phenomena. Investigations have been made on mildly notched cylindrical and also on welded specimens. The results confirm the close relation between the local temperature signal and typical fatigue phenomena. The new methodology allows for a much better localization and quantification of effects as cyclic plasticity, crack initiation, crack growth etc. The following paper presents considerations and experimental results of an application of thermography to the local assessment of fatigue damage.

  12. 2003 Dead Bald Eagle Specimen

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The specimen report states the Bald Eagle was found along the side of the I-95 by a motorist who contacted Santee National Wildlife Refuge. The Bald Eagle was taken...

  13. Fatigue Debond Growth in Sandwich Structures Loaded in Mixed Mode Bending (MMB)

    DEFF Research Database (Denmark)

    Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.

    2008-01-01

    the fracture toughness of the debonded sandwich specimens at different mixed mode loadings. The mixed mode ratio (mode I to mode II) was controlled by changing the lever arm distance of the MMB test rig. Compliance technique and visual inspection was employed to measure the crack length during fatigue. Fatigue...... tests were performed at 90% of the static fracture toughness at a loading ratio of R=0.1. Fatigue results revealed higher debond crack growth rates when the lever arm distance was increased. For some specimens, the crack propagated just below the face/core interface in the foam core and for others...... the crack kinked into the face sheet....

  14. Fatigue crack growth retardation in spot heated mild steel sheet

    Indian Academy of Sciences (India)

    A fatigue crack can be effectively retarded by heating a spot near the crack tip under nil remote stress condition. The subcritical spot heating at a proper position modifies the crack growth behaviour in a way, more or less, similar to specimen subjected to overload spike. It is observed that the extent of crack growth retardation ...

  15. Fatigue Crack Propagation Simulation in Plane Stress Constraint

    DEFF Research Database (Denmark)

    Ricardo, Luiz Carlos Hernandes; Spinelli, Dirceu

    2010-01-01

    Nowadays, structural and materials engineers develop structures and materials properties using finite element method. This work presents a numerical determination of fatigue crack opening and closure stress intensity factors of a C(T) specimen. Two different standard variable spectrum loadings ar...

  16. Microstructural Effects on Creep-Fatigue Life of Alloy 709

    Energy Technology Data Exchange (ETDEWEB)

    McMurtrey, Michael [Idaho National Lab. (INL), Idaho Falls, ID (United States); Carroll, Laura [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wright, Jill [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-08-01

    Creep-fatigue tests were performed on plates of Alloy 709 from various heats and processing conditions, but often with inhomogeneous microstructures. After testing, metallographic analysis was performed and the specimens were generally found to either have a uniform grain size or a bimodal grain size distribution with either isolated or groups (bands) of large grains. Creep-fatigue life was characterized with respect to the length of the grain boundary perpendicular to the stress axis, and it was found that large grains (>400 μm) tended to be detrimental to creep-fatigue life, with the exception of elongated (parallel to the stress axis) grains and some specimens that underwent additional annealing.

  17. DNA extraction from herbarium specimens.

    Science.gov (United States)

    Drábková, Lenka Záveská

    2014-01-01

    With the expansion of molecular techniques, the historical collections have become widely used. Studying plant DNA using modern molecular techniques such as DNA sequencing plays an important role in understanding evolutionary relationships, identification through DNA barcoding, conservation status, and many other aspects of plant biology. Enormous herbarium collections are an important source of material especially for specimens from areas difficult to access or from taxa that are now extinct. The ability to utilize these specimens greatly enhances the research. However, the process of extracting DNA from herbarium specimens is often fraught with difficulty related to such variables as plant chemistry, drying method of the specimen, and chemical treatment of the specimen. Although many methods have been developed for extraction of DNA from herbarium specimens, the most frequently used are modified CTAB and DNeasy Plant Mini Kit protocols. Nine selected protocols in this chapter have been successfully used for high-quality DNA extraction from different kinds of plant herbarium tissues. These methods differ primarily with respect to their requirements for input material (from algae to vascular plants), type of the plant tissue (leaves with incrustations, sclerenchyma strands, mucilaginous tissues, needles, seeds), and further possible applications (PCR-based methods or microsatellites, AFLP).

  18. Fatigue Evaluation Algorithms: Review

    DEFF Research Database (Denmark)

    Passipoularidis, Vaggelis; Brøndsted, Povl

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Pu...

  19. Relationship between static chemical and cyclic mechanical fatigue in a feldspathic porcelain.

    Science.gov (United States)

    White, S N; Li, Z C; Yu, Z; Kipnis, V

    1997-03-01

    The goal of this study was to determine if static chemical and cyclic mechanical fatigue are independent, or if they interact to produce greater than additive strength loss in a feldspathic porcelain. A blunt indentation technique was used to investigate the response of a feldspathic dental porcelain to cyclic mechanical fatigue and static chemical fatigue. All specimens were fabricated in a dry inert environment and then mechanically fatigued by cyclic loading and strength-tested in dry inert nitrogenous, ambient or wet environments. A series of experiments were performed to evaluate the effects of chemical and mechanical fatigue, and their interaction on strength loss; to determine the effects of, and interaction between, the factors of cyclic fatigue environment and strength test environment on strength; to ascertain if the type of environment during strength testing influenced specimen strength; and to distinguish between chemical damage caused by exposure to moisture alone and stress corrosion damage resulting from the strength testing environment, using a pair of two-way analysis of variance, a single one-way analysis of variance and a t-test (p fatigue and cyclic mechanical fatigue significantly reduced specimen strength, but they did not interact to produce greater than summative effects. It was also learned that chemical fatigue was not detected on initial exposure to moisture and that it occurred to a small extent during mechanical fatigue cycling, and primarily occurred during strength testing through a stress-corrosion phenomenon. Micrographs visually evaluated the effects of mechanical and chemical fatigue on surface contact damage. As both static chemical and cyclic mechanical fatigue influenced porcelain strength, they should both be considered in future evaluations. However, because they largely acted independently, they can be studied separately.

  20. Experimental Investigation on the Fatigue Mechanical Properties of Intermittently Jointed Rock Models Under Cyclic Uniaxial Compression with Different Loading Parameters

    Science.gov (United States)

    Liu, Yi; Dai, Feng; Dong, Lu; Xu, Nuwen; Feng, Peng

    2018-01-01

    Intermittently jointed rocks, widely existing in many mining and civil engineering structures, are quite susceptible to cyclic loading. Understanding the fatigue mechanism of jointed rocks is vital to the rational design and the long-term stability analysis of rock structures. In this study, the fatigue mechanical properties of synthetic jointed rock models under different cyclic conditions are systematically investigated in the laboratory, including four loading frequencies, four maximum stresses, and four amplitudes. Our experimental results reveal the influence of the three cyclic loading parameters on the mechanical properties of jointed rock models, regarding the fatigue deformation characteristics, the fatigue energy and damage evolution, and the fatigue failure and progressive failure behavior. Under lower loading frequency or higher maximum stress and amplitude, the jointed specimen is characterized by higher fatigue deformation moduli and higher dissipated hysteresis energy, resulting in higher cumulative damage and lower fatigue life. However, the fatigue failure modes of jointed specimens are independent of cyclic loading parameters; all tested jointed specimens exhibit a prominent tensile splitting failure mode. Three different crack coalescence patterns are classified between two adjacent joints. Furthermore, different from the progressive failure under static monotonic loading, the jointed rock specimens under cyclic compression fail more abruptly without evident preceding signs. The tensile cracks on the front surface of jointed specimens always initiate from the joint tips and then propagate at a certain angle with the joints toward the direction of maximum compression.

  1. Examining fatigue in COPD

    DEFF Research Database (Denmark)

    Al-Shair, Khaled; Muellerova, Hana; Yorke, Janelle

    2012-01-01

    ABSTRACT: INTRODUCTION: Fatigue is a disruptive symptom that inhibits normal functional performance of COPD patients in daily activities. The availability of a short, simple, reliable and valid scale would improve assessment of the characteristics and influence of fatigue in COPD. METHODS......: At baseline, 2107 COPD patients from the ECLIPSE cohort completed the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) scale. We used well-structured classic method, the principal components analysis (PCA) and Rasch analysis for structurally examining the 13-item FACIT-F. RESULTS: Four items...... were less able to capture fatigue characteristics in COPD and were deleted. PCA was applied to the remaining 9 items of the modified FACIT-F and resulted in three interpretable dimensions: i) general (5 items); ii) functional ability (2 items); and iii) psychosocial fatigue (2 items). The modified...

  2. A preliminary probabilistic framework of the assessment of bridge cable fatigue

    DEFF Research Database (Denmark)

    Roldsgaard, Joan Hee; Georgakis, Christos T.; Faber, Michael Havbro

    In this paper, a basic and preliminary framework for the assessment of cumulative bridge cable fatigue damage due to wind-induced vibrations is presented. The damage assessment is performed using a probabilistic approach, based on a Bayesian Probabilistic Network, where the wind environment...... to meteorological and site-specific condi-tions can be utilized to assess the probability of occurrence of ice-induced vibrations. The fatigue stress in the cable bending mode is evaluated together with the corresponding fatigue lifetime. The modeling scheme shows flexibility in the sense that the individual......, traffic load-ing, bridge specific parameters and the mechanisms that induce significant cable vibrations are the main input parameters. The suggested framework is illustrated on a case study considering the second longest hanger ca-ble of the Great Belt Bridge outlining how information with respect...

  3. Vibration Characteristics of Roundabout Swing of HAWT Wind Wheel

    Directory of Open Access Journals (Sweden)

    Jian-long Ma

    2016-01-01

    Full Text Available Modal testing was used to show that the roundabout swing was a natural vibration mode of the wind wheel of a horizontal-axis wind turbine (HAWT. During the vibration, the blade root was simultaneously subjected to bending and rotary shear stresses. A method for indirect testing and determination of the dynamic frequencies of the typical vibrations of the wind wheel was developed, based on the frequency-holding characteristic of each subsignal during the transmission of the multiple mixed-vibration signals. The developed method enabled simple and accurate acquisition of the dynamic frequencies without destruction of the flow and structural fields. The dynamic vibration stress of the roundabout swing was found to be significantly stronger than those of the first- and second-order flexural vibrations of the blades. By a combination of numerical simulations and tests, it was determined that the pneumatic circumferential force was the primary determinant of the roundabout swing vibration frequencies, the relationship being quadratic. The roundabout swing vibration potentially offers new explanations and analytical pathways regarding the behavior of horizontal-axis wind turbines, which have been found to be frequently involved in fatigue-damage accidents within periods shorter than their design lives.

  4. Tunable Passive Vibration Suppressor

    Science.gov (United States)

    Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)

    2016-01-01

    An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.

  5. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.

  6. Monitoring fatigue crack growth using nonlinear ultrasonic phased array imaging

    Science.gov (United States)

    Cheng, Jingwei; Potter, Jack N.; Croxford, Anthony J.; Drinkwater, Bruce W.

    2017-05-01

    Nonlinear imaging techniques have recently emerged which have the potential to detect material degradation and challenging defects, such as closed cracks. This paper describes an investigation into the performance of nonlinear ultrasonic imaging (NUI) for the monitoring of the early stages of fatigue crack growth. This technique, in conjunction with conventional array imaging, is applied to the periodic monitoring of steel compact tension specimens subjected to high cycle fatigue loading. The detection limits of these techniques are investigated. Their abilities to localise and detect small cracks are further quantified with the aid of micrography. The results suggest that NUI is more sensitive than conventional ultrasonic imaging to the microscale changes occurring at the early stages of failure, i.e. detectability starts c. 15% of fatigue life. In addition to early detection, the potential for NUI to deliver accurate sizing of fatigue cracks and monitor crack propagation is also presented.

  7. High Cycle Fatigue Behavior of Shot-Peened Steels

    Science.gov (United States)

    Mirzazadeh, M. M.; Plumtree, A.

    2012-08-01

    The uniaxial fully reversed (R = -1) long life fatigue behavior of four shot-peened engineering steels with approximately the same hardness was investigated. Shot-peening, air-cooled forged AISI 1141 and crackable AISI 1070 steels had little effect on their fatigue limits (+2.5 and -2.0 pct, respectively). In the case of a powder forged 0.5 pct C steel, an increase in the fatigue limit of 10.4 pct was observed, albeit with a large standard deviation. Shot-peening quench and tempered AISI 1151 steel decreased its fatigue limit 12.0 pct, as a result of cyclic softening. In general, the beneficial effects of shot-peening these smooth specimens were relatively small. Neither cyclic softening nor hardening occurred in the non-shot-peened steels cycled under the same conditions.

  8. Micromechanisms in tension-compression fatigue of composite laminates containing transverse plies

    DEFF Research Database (Denmark)

    Gamstedt, E.K.; Sjögren, B.A.

    1999-01-01

    to optimise fatigue resistance. In this study, glass-fibre-reinforced vinyl-ester was used. The adverse effect of compressive load excursions was verified by counting the transverse cracks in cross-ply laminates. The mechanisms were studied in low-cycle fatigue of a specimen containing a single transverse......-tension fatigue to transverse and multidirectional laminates. By analysing the debonding mechanisms and modelling thereof, the macroscopic fatigue behaviour can be better understood. Also, the dominant crack-propagation mode can be identified which may be of use in selection of constituent material properties...

  9. Progress in the Research of Fatigue of Weathering Steel after Corrosion

    Science.gov (United States)

    Jianyu, Liang; Jian, Yao; Youwu, Xu

    2017-12-01

    Weathering steel has a good corrosion resistance in the atmosphere, and the application of weathering steel in civil structure also reduces the cost of painting and maintenance. It is also possible for the bare weathering steel to bear the fatigue load with a rust layer. This paper summarizes the fatigue researches after corrosion of weathering steel, including the shape of specimens, failure modes of fatigue and the conclusions obtained through experimental investigations. It is also introduced the fatigue model of weathering steel after corrosion, which can be useful for the engineering application or further researches.

  10. Fatigue cracks in Eurofer 97 steel: Part I. Nucleation and small crack growth kinetics

    Science.gov (United States)

    Kruml, T.; Polák, J.

    2011-05-01

    Fatigue crack nucleation and growth were studied in the Eurofer 97 ferritic-martensitic steel at room temperature. Cylindrical specimens with a shallow notch and no artificial crack starters were used. The constant strain amplitude cycling was adopted. First fatigue cracks nucleate at about 5% of the fatigue life along the surface slip bands. If a crack overcome the barrier of the first high angle boundary, its growth is regular and an exponential growth law is observed. This law may be used for the residual fatigue life prediction based on the small crack growth kinetics.

  11. Effect of electric discharge machining on the fatigue life of Inconel 718

    Science.gov (United States)

    Jeelani, S.; Collins, M. R.

    1988-01-01

    The effect of electric discharge machining on the fatigue life of Inconel 718 alloy at room temperature was investigated. Data were generated in the uniaxial tension fatigue mode at ambient temperature using flat 3.175 mm thick specimens. The specimens were machined on a wire-cut electric discharge machine at cutting speeds ranging from 0.5 to 2 mm per minute. The specimens were fatigued at a selected stress, and the resulting fatigue lives compared with that of the virgin material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. From the results of the investigation, it was concluded that the fatigue life of the specimens machined using EDM decreased slightly as compared with that of the virgin material, but remained unchanged as the cutting speed was changed. The results are explained using data produced employing microhardness measurements, profilometry, and optical and scanning microscopy.

  12. Influence of the crystalline orientations on microcrack initiation in low-cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Mu, P. [Univ Lille Nord de France, F-59000 Lille (France); ECLille, LML, F-59650 Villeneuve d’Ascq (France); CNRS, UMR 8107, UMR 8579 (France); Aubin, V., E-mail: veronique.aubin@ecp.fr [ECP, MSSMat, F-92295 Châtenay-Malabry (France); CNRS, UMR 8107, UMR 8579 (France); Alvarez-Armas, I.; Armas, A. [IFIR, CONICET, Universidad Nacional de Rosario (Argentina)

    2013-06-20

    Present study aims at analyzing the crack initiation in an austenitic stainless steel in low-cycle fatigue. A fatigue test was carried out using a polished specimen. The surface of the specimen was observed in situ during the fatigue test, in order to establish the time of slip activity or crack initiation. After a number of cycles sufficient to initiate small cracks, the test was stopped and the surface observed by scanning electron microscopy. The electron backscattered diffraction technique (EBSD) was used to identify the orientations of surface grains in the central zone of the fatigue specimen. Crack-initiation sites and slip systems associated to the initiated microcracks were identified. The criterion of the maximum Schmid factor explains two-thirds of the cracks initiated in slip systems; however if the favorably oriented slip band with respect to this criterion makes an angle of around 45° to the loading direction, a crack may initiate in another slip system.

  13. Fatigue damage of steam turbine shaft at asynchronous connections of turbine generator to electrical network

    Science.gov (United States)

    Bovsunovsky, A. P.

    2015-07-01

    The investigations of cracks growth in the fractured turbine rotors point out at theirs fatigue nature. The main reason of turbine shafts fatigue damage is theirs periodical startups which are typical for steam turbines. Each startup of a turbine is accompanied by the connection of turbine generator to electrical network. During the connection because of the phase shift between the vector of electromotive force of turbine generator and the vector of supply-line voltage the short-term but powerful reactive shaft torque arises. This torque causes torsional vibrations and fatigue damage of turbine shafts of different intensity. Based on the 3D finite element model of turbine shaft of the steam turbine K-200-130 and the mechanical properties of rotor steel there was estimated the fatigue damage of the shaft at its torsional vibrations arising as a result of connection of turbine generator to electric network.

  14. Probabilistic fatigue life prediction of metallic and composite materials

    Science.gov (United States)

    Xiang, Yibing

    Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

  15. Research overview on vibration damping of mistuned bladed disk assemblies

    Directory of Open Access Journals (Sweden)

    Liang ZHANG

    2016-04-01

    Full Text Available Bladed disk assemblies are very important parts in auto engine and gas turbine, and is widely used in practical engineering. The mistuning existing commonly in the bladed disk assemblies can destroy the vibration characteristics of the bladed disk assemblies, which is one of the reasons for the high cycle fatigue failure of bladed disk assemblies, so it is necessary to research how to reduce the vibration of the bladed disk assemblies. On the basis of the review of relevant research at home and abroad, the mistuning vibration mechanism of the bladed disk assemblies is introduced, and the main technical methods of the vibration damping of bladed disk assemblies are reviewed, such as artificially active mistuning, collision damping, friction damping and optimization of the blade position. Some future research directions are presented.

  16. Vibration Analysis Of a Self-Excited Elastic Beam

    Directory of Open Access Journals (Sweden)

    M. A. Barrón-M

    2010-08-01

    Full Text Available The vibration behavior and the energy exchange among the normal modes of a clamped-free self-excited elasticbeam are analyzed in this work. To model this kind of beam, the damping term of a van der Pol oscillator is directlyadded to the equation of a linear elastic beam, yielding a single nonlinear partial differential equation. To solve thisequation, a spectral method is employed. Three vibration modes are considered in the analysis, and the values of theself-exciting constant are varied in order to cover from linear to nonlinear vibration behavior. Multiple frequencies ofthe nonlinear beam are determined through the power spectral density of the beam free-end time series. Given thatthis relatively simple model mimics at least in a qualitative way some key issues of the fluid-structure problem, it couldbe potentially useful for fatigue studies and vibration analysis of rotating blades in turbomachinery.

  17. Biomechanical evaluation of a corporectomy in porcine lumbar specimens using flexible polymer belts

    Energy Technology Data Exchange (ETDEWEB)

    Beltran-Fernandez, J A; Hernandez-Gomez, L H; Ruiz-Munoz, E; Urriolagoitia-Calderon, G; Urriolagoitia-Sosa, G [Escuela Superior de IngenierIa Mecanica y Electrica (ESIME) Unidad Zacatenco, Edificio 5, 3er Piso, 07738, D.F., Mexico, Tel.: 52(55)57296000, ext. 54691 (Mexico); Gonzalez-Rebattu, A [Hospital Regional ISSSTE 10 de Octubre, Av. Instituto Politecnico Nacional, Num. 1669, Col. Magdalena de las Salinas, 07760 (Mexico); RodrIguez-Canizo, R G [Escuela Superior de IngenierIa Mecanica y Electrica (ESIME) Unidad Azcapotzalco, Av. Granjas No. 682 Col. Sta. Catarina, 02550 (Mexico); Hernandez-Moreno, H, E-mail: jbeltran@ipn.m, E-mail: luishector56@hotmail.co, E-mail: edrm_ipn@hotmail.co, E-mail: janosclub@hotmail.co, E-mail: ricname@hotmail.co, E-mail: guiurri@hotmail.co, E-mail: hihernandezm@ipn.m

    2009-08-01

    This paper presents the experimental results of a biomechanical evaluation in lumbar porcine specimens (L2-L4), instrumented with flexible polymer belts, under fatigue and tensile loading. The clinical effect called facetary arthrosis is evaluated. An experimental analysis was carried on 3 lumbar porcine specimens. In two of them, polyamide belts are fixed on the interspinous ligament from L2 to L4. Specimens are taken from pigs which are 6 month old. For the present work, the stiffness reduction of the spine and the biomechanical behaviour of the belts in conjunction with the interspinous ligament are evaluated. The purpose is to determine the failure conditions for the elements of the specimen (vertebral disk, supra and intraspinous ligament and vertebral body). Under static loading, which is the base line case, the elements of the specimen failed as a typical healthy structure. While in the fatigue combined with static loading, the element failed in different order. Additionally, the stiffness changed in accordance with the fatigue loading conditions. Because of the simplicity of this alternative technique, a high level of the structural integrity is preserved, as no holes are made on the spinous process in order to insert the fixation screws. Furthermore, there is a cost reduction.

  18. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The fati......Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations....... The fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the deck structure of the Farø Bridges...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  19. Biaxial fatigue behavior of a powder metallurgical TRIP steel

    Directory of Open Access Journals (Sweden)

    S. Ackermann

    2015-10-01

    Full Text Available Multiaxial fatigue behavior is an important topic in critical structural components. In the present study the biaxial-planar fatigue behavior of a powder metallurgical TRIP steel (Transformation Induced Plasticity was studied by taking into account martensitic phase transformation and crack growth behavior. Biaxial cyclic deformation tests were carried out on a servo hydraulic biaxial tension-compression test rig using cruciform specimens. Different states of strain were studied by varying the strain ratio between the axial strain amplitudes in the range of -1 (shear loading to 1 (equibiaxial loading. The investigated loading conditions were proportional due to fixed directions of principal strains. The studied TRIP steel exhibits martensitic phase transformation from -austenite via ε-martensite into α‘- martensite which causes pronounced cyclic hardening. The α‘-martensite formation increased with increasing plastic strain amplitude. Shear loading promoted martensite formation and caused the highest α‘-martensite volume fractions at fatigue failure in comparison to uniaxial and other biaxial states of strain. Moreover, the fatigue lives of shear tests were higher than those of uniaxial and other biaxial tests. The von Mises equivalent strain hypothesis was found to be appropriate for uniaxial and biaxial fatigue, but too conservative for shear fatigue, according to literature for torsional fatigue. The COD strain amplitude which is based on crack opening displacement gave a better correlation of the investigated fatigue lives, especially those for shear loading. Different types of major cracks were observed on the sample surfaces after biaxial cyclic deformation by using electron monitoring in an electron beam universal system and scanning electron microscopy (SEM. Specimens with strain ratios of 1, 0.5, -0.1 and -0.5 showed mode I major cracks (perpendicular to the axis of maximum principal strain. Major cracks after shear fatigue

  20. Fatigue evaluation algorithms: Review

    Energy Technology Data Exchange (ETDEWEB)

    Passipoularidis, V.A.; Broendsted, P.

    2009-11-15

    A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Puck, to model the degradation caused by failure events in ply level. Residual strength is incorporated as fatigue damage accumulation metric. Once the typical fatigue and static properties of the constitutive ply are determined,the performance of an arbitrary lay-up under uniaxial and/or multiaxial load time series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a wind turbine rotor blade construction. Two versions of the algorithm, the one using single-step and the other using incremental application of each load cycle (in case of ply failure) are implemented and compared. Simulation results confirm the ability of the algorithm to take into account load sequence effects. In general, FADAS performs well in predicting life under both spectral and block loading fatigue. (author)

  1. Fatigue Durability Analysis of Collecting Rapping System in Electrostatic Precipitators under Impact Loading

    OpenAIRE

    Ali Akbar Lotfi Neyestanak; Saeed Adib Nazari; Ali Imam; Cyrus Aghanajafi

    2014-01-01

    Due to the importance of collecting rapping system in electrostatic precipitators (ESP) and controlling the relevant damage under impact loading, fatigue durability of this system is analyzed in the present study based on the numerical and experimental results considering fatigue damage growth and vibration acceleration in the collecting system because of the successive impact of rapping hammers. By microscopic examination of the fracture surface of rapping hammer, beach marks obviously show ...

  2. Effect of adding support structures for overhanging part on fatigue strength in selective laser melting.

    Science.gov (United States)

    Kajima, Yuka; Takaichi, Atsushi; Nakamoto, Takayuki; Kimura, Takahiro; Kittikundecha, Nuttaphon; Tsutsumi, Yusuke; Nomura, Naoyuki; Kawasaki, Akira; Takahashi, Hidekazu; Hanawa, Takao; Wakabayashi, Noriyuki

    2017-11-06

    Selective laser melting (SLM) technology was recently introduced to fabricate dental prostheses. However, the fatigue strength of clasps in removable partial dentures prepared by SLM still requires improvement. In this study, we attempted to improve the fatigue strength of clasps by adding support structures for overhanging parts, which can generally be manufactured at an angle to be self-supporting. The results show that the fatigue strength of the supported specimens was more than twice that of unsupported specimens. Electron back-scattered diffraction analysis revealed that the supported specimens exhibited lower kernel average misorientation values than the unsupported specimens, which suggested that the support structure reduced the residual strain during the SLM process and helped to prevent micro-cracks led by thermal distortion. In addition, the supported specimens cooled more rapidly, thereby forming a finer grain size compared to that of the unsupported specimens, which contributed to improving the fatigue strength. The results of this study suggest that the fatigue strength of overhanging parts can be improved by intentionally adding support structures. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Effects of aerodynamic fairing on full scale blade fatigue test

    Science.gov (United States)

    Pan, Zujin; Wu, Jianzhong; Sun, Yuanrong; Jian, Liu

    2017-06-01

    The reliability of large blades should be verified by means of full scale fatigue test. In order to solve the problem of lack of exciting force during fatigue test in the flap wise direction, the program that aerodynamic fairing is installed in the tip of blade to reduce the air resistance is proposed. The numerical model of blade vibration and damping ratio calculation is established. The relationship between damping ratio, exciting force and amplitude is constructed by finite element method respectively. The difference of the exciting bending moment of blade and the damping ratio before and after the installation of aerodynamic fairing is compared respectively. The results show that damping ratio decreased by 27.9%. When the vibration of the blade reaches the target bending moment, the exciting force of the equipment decreases by 45.4%. It is an effective way to reduce the exciting force.

  4. Fatigue-induced damage in Zr-based bulk metallic glasses.

    Science.gov (United States)

    Chuang, Chih-Pin; Yuan, Tao; Dmowski, Wojciech; Wang, Gong-Yao; Freels, Matt; Liaw, Peter K; Li, Ran; Zhang, Tao

    2013-01-01

    In the present work, we investigate the effect of "fatigue" on the fatigue behavior and atomic structure of Zr-based BMGs. Fatigue experiments on the failed-by-fatigue samples indicate that the remnants generally have similar or longer fatigue life than the as-cast samples. Meanwhile, the pair-distribution-function (PDF) analysis of the as-cast and post-fatigue samples showed very small changes of local atomic structures. These observations suggest that the fatigue life of the 6-mm in-diameter Zr-based BMG is dominated by the number of pre-existing crack-initiation sites in the sample. Once the crack initiates in the specimen, the fatigue-induced damage is accumulated locally on these initiated sites, while the rest of the region deforms elastically. The results suggest that the fatigue failure of BMGs under compression-compression fatigue experiments is a defect-controlled process. The present work indicates the significance of the improved fatigue resistance with decreasing the sample size.

  5. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

    Akkerman, Moniek; Mouton, Leonora J.; Dijkstra, Froukje; Niemeijer, Anuschka S.; van Brussel, Marco; van der Woude, Lucas H. V.; Disseldorp, Laurien M.; Nieuwenhuis, Marianne K.

    2017-01-01

    Purpose: Fatigue is a common consequence of numerous pediatric health conditions. In adult burn survivors, fatigue was found to be a major problem. The current cross-sectional study is aimed at determining the levels of perceived fatigue in pediatric burn survivors. Methods: Perceived fatigue was

  6. Perceived fatigue following pediatric burns

    NARCIS (Netherlands)

    Akkerman, Moniek; Mouton, Leonora J.; Dijkstra, Froukje; Niemeijer, Anuschka S.; van Brussel, Marco|info:eu-repo/dai/nl/30481962X; Van der Woude, Lucas H. V.; Disseldorp, Laurien M.; Nieuwenhuis, Marianne K.

    2017-01-01

    Purpose Fatigue is a common consequence of numerous pediatric health conditions. In adult burn survivors, fatigue was found to be a major problem. The current cross-sectional study is aimed at determining the levels of perceived fatigue in pediatric burn survivors. Methods Perceived fatigue was

  7. Prolonged unexplained fatigue in paediatrics

    NARCIS (Netherlands)

    Bakker, R.J.

    2010-01-01

    Prolonged Unexplained Fatigue in Paediatrics. Fatigue, as the result of mental or physical exertion, will disappear after rest, drinks and food. Fatigue as a symptom of illness will recover with the recovering of the illness. But when fatigue is ongoing for a long time, and not the result of

  8. Experiences of Fatigue at Sea

    DEFF Research Database (Denmark)

    Zhao, Zhiwei; Jepsen, Jørgen Riis; Chen, Zhonglong

    2016-01-01

    Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T...

  9. Influence of shear cutting parameters on the fatigue behavior of a dual-phase steel

    Science.gov (United States)

    Paetzold, I.; Dittmann, F.; Feistle, M.; Golle, R.; Haefele, P.; Hoffmann, H.; Volk, W.

    2017-09-01

    The influence of the edge condition of car body and chassis components made of steel sheet on fatigue behavior under dynamic loading presents a major challenge for automotive manufacturers and suppliers. The calculated lifetime is based on material data determined by the fatigue testing of specimens with polished edges. Prototype components are often manufactured by milling or laser cutting, whereby in practice, the series components are produced by shear cutting due to its cost-efficiency. Since the fatigue crack in such components usually starts from a shear cut edge, the calculated and experimental determined lifetime will vary due to the different conditions at the shear cut edges. Therefore, the material data determined with polished edges can result in a non-conservative component design. The aim of this study is to understand the relationship between the shear cutting process and the fatigue behavior of a dual-phase steel sheet. The geometry of the shear cut edge as well as the depth and degree of work hardening in the shear affected zone can be adjusted by using specific shear cutting parameters, such as die clearance and cutting edge radius. Stress-controlled fatigue tests of unnotched specimens were carried out to compare the fatigue behavior of different edge conditions. By evaluating the results of the fatigue experiments, influential shear cutting parameters on fatigue behavior were identified. It was possible to assess investigated shear cutting strategies regarding the fatigue behavior of a high-strength steel DP800.

  10. Microstructural changes induced near crack tip during corrosion fatigue tests in austenitic-ferritic steel.

    Science.gov (United States)

    Gołebiowski, B; Swiatnicki, W A; Gaspérini, M

    2010-03-01

    Microstructural changes occurring during fatigue tests of austenitic-ferritic duplex stainless steel (DSS) in air and in hydrogen-generating environment have been investigated. Hydrogen charging of steel samples during fatigue crack growth (FCG) tests was performed by cathodic polarization of specimens in 0.1M H(2)SO(4) aqueous solution. Microstructural investigations of specimens after FCG tests were carried out using transmission electron microscopy to reveal the density and arrangement of dislocations formed near crack tip. To determine the way of crack propagation in the microstructure, electron backscatter diffraction investigations were performed on fatigue-tested samples in both kinds of environment. To reveal hydrogen-induced phase transformations the atomic force microscopy was used. The above investigations allowed us to define the character of fatigue crack propagation and microstructural changes near the crack tip. It was found that crack propagation after fatigue tests in air is accompanied with plastic deformation; a high density of dislocations is observed at large distance from the crack. After fatigue tests performed during hydrogen charging the deformed zone containing high density of dislocations is narrow compared to that after fatigue tests in air. It means that hydrogenation leads to brittle character of fatigue crack propagation. In air, fatigue cracks propagate mostly transgranularly, whereas in hydrogen-generating environment the cracks have mixed transgranular/interfacial character.

  11. Vibration analysis of cryocoolers

    Science.gov (United States)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira; Koyama, Tomohiro; Li, Rui

    2004-05-01

    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.

  12. Vibration analysis of cryocoolers

    Energy Technology Data Exchange (ETDEWEB)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Koyama, Tomohiro; Rui Li [Sumitomo Heavy Industries Ltd., Tokyo (Japan)

    2004-05-01

    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. (Author)

  13. Vibration of hydraulic machinery

    CERN Document Server

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong

    2013-01-01

    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  14. Fatigue 󈨛. Volume 2,

    Science.gov (United States)

    1987-06-01

    boundary. 638 FATIGUE 87 The bulk bismuth concentrations of the bicrystals were measured by Chicago Spectro Laboratory and Charles C. Kawin Company both...645. B.M. Strauss and W.H. Cullen , Jr., editors, ASTM, Philadelphia, 1978, pp. 164-175. (4) Meakin. J.D. and Wilsdorf, H.G.F.. Trans. TMS-AIME, Vol... Edmunds , 1986. 785 FATIGUE 87 (7) James, M.N. and Knott, J.F., Fatigue Fract. Engng Mater. Struct., Vol.8, 1985, pp.177-191. (8) Breat, J.L., Mudry, F

  15. The Effects of Local Vibration on Balance, Power, and Self-Reported Pain After Exercise.

    Science.gov (United States)

    Custer, Lisa; Peer, Kimberly S; Miller, Lauren

    2017-05-01

    Muscle fatigue and acute muscle soreness occur after exercise. Application of a local vibration intervention may reduce the consequences of fatigue and soreness. To examine the effects of a local vibration intervention after a bout of exercise on balance, power, and self-reported pain. Single-blind crossover study. Laboratory. 19 healthy, moderately active subjects. After a 30-min bout of full-body exercise, subjects received either an active or a sham vibration intervention. The active vibration intervention was performed bilaterally over the muscle bellies of the triceps surae, quadriceps, hamstrings, and gluteals. At least 1 wk later, subjects repeated the bout, receiving the other vibration intervention. Static balance, dynamic balance, power, and self-reported pain were measured at baseline, after the vibration intervention, and 24 h postexercise. After the bout of exercise, subjects had reduced static and dynamic balance and increased self-reported pain regardless of vibration intervention. There were no differences between outcome measures between the active and sham vibration conditions. The local vibration intervention did not affect balance, power, or self-reported pain.

  16. Modeling and Mechanism of Rain-Wind Induced Vibration of Bundled Conductors

    Directory of Open Access Journals (Sweden)

    Chao Zhou

    2016-01-01

    Full Text Available Under the certain rain-wind conditions, bundled conductors exhibit a rain-wind induced large-amplitude vibration. This type of vibration can cause the fatigue fractures of conductors and fatigue failures of spacers, which threaten the safety operation and serviceability of high-voltage transmission line. To reveal the mechanism of rain-wind induced vibration of bundled conductors, a series of 2-dimensional CFD models about the twin bundled conductors with rivulets are developed to obtain the curves of aerodynamic coefficients with the upper rivulet angle. The influences of the forward conductor’s aerodynamic shielding and the upper rivulet’s aerodynamic characteristics on the leeward conductor are discussed. Furthermore, a 2-dimensional 3DOF model for the rain-wind induced vibration of the leeward conductor is established. The model is solved by finite element method and Newmark method, and the effects of the wind velocity and the upper rivulet’s motion on vibration amplitude of the leeward conductor are analyzed. By contrast with the wake-induced vibration, it can easily find that the characteristics of rain-wind vibration are obviously different from those of the wake-induced vibration, and the main reason of the rain-induced vibration may be due to the upper rivulet’s motion.

  17. Chronic Fatigue Syndrome

    Science.gov (United States)

    ... light, eye pain) Psychological symptoms (irritability, mood swings, panic attacks, anxiety) Chills and night sweats Low grade ... Research Phone Number: 775-682-8250 Chronic fatigue syndrome > A-Z Health Topics The Office on Women's ...

  18. Hyperthermia and fatigue

    DEFF Research Database (Denmark)

    Nybo, Lars

    2008-01-01

    of the cardiovascular function, which eventually reduces arterial oxygen delivery to the exercising muscles. Accordingly, aerobic energy turnover is impaired and anaerobic metabolism provokes peripheral fatigue. In contrast, metabolic disturbances of muscle homeostasis are less important during prolonged exercise......The present review addresses mechanisms of importance for hyperthermia-induced fatigue during short intense activities and prolonged exercise in the heat. Inferior performance during physical activities with intensities that elicit maximal oxygen uptake is to a large extent related to perturbation...... in the heat, because increased oxygen extraction compensates for the reduction in systemic blood flow. The decrease in endurance seems to involve changes in the function of the central nervous system (CNS) that lead to fatigue. The CNS fatigue appears to be influenced by neurotransmitter activity...

  19. Chronic Fatigue Syndrome

    Science.gov (United States)

    ... people with CFS should avoid heavy meals, alcohol, caffeine, and large quantities of junk food. Some people ... to address problems. Write it down. If your memory and concentration are affected by chronic fatigue, it ...

  20. Specimen Collection and Submission Manual

    Science.gov (United States)

    2016-06-01

    local, approved medical treatment facility collection procedures. Superficial wounds and abscesses Sterile swab Follow local, approved medical...Tests May Include: West Nile virus (WNV), Eastern equine encephalitis virus, Venezuelan equine encephalitis virus, yellow fever virus, dengue virus... Wound Botulism Acceptable Specimens Required Volume/Comments Toxin Assay (T) or Culture (C) Performed Serum (priority sample type) 5 ml (less

  1. The Shock and Vibration Bulletin. Part 3. Structural Analysis, Fatigue.

    Science.gov (United States)

    1978-09-01

    PA PREDICTION OF CONSTRAINED SECONDARY FRAGMENT VELOCITIES P.S. Westine , Southwest Research Institute, Sn Antonio, TX J.H. Kineke, Jr., Ballistic...G k boAicraft," 1977 Nratioal spa e l.eC- tra ic Coference, yton, H 17-19. 6 - variatdial operator 1977. 6(x-xo ) - dirac delta fnctfon 2. Forray, N...computer code cannot When resorting to numerical analysis one %I model the behavior of the propellant (except must naturally assign values to all

  2. Rotating bending fatigue property of the Ni3Al-based single crystal superalloy IC6SX at 900°C

    Science.gov (United States)

    Jiang, Liwu; Li, Shusuo; Han, Yafang

    2017-03-01

    The high cycle fatigue behavior of a Ni3Al base single crystal superalloy IC6SX has been investigated at 900°C in this work. The specimens used for the fatigue tests were prepared by screw selection crystal method in a directional solidification furnace. The rotating bending fatigue tests were carried out at 900°Cin air, the stress ratio of R(σmax/σmin) was -1, and the rotating speed of the fatigue tests was 6500r/min(108Hz). The stress-fatigue cycle life (S-Nf) curve was obtained based on the fatigue tests, and the fracture surfaces were examined using scanning electron microscopy (SEM). It has been found that the median fatigue strength is 457.5MPa and the safety fatigue strength is 413.93MPa. And the fatigue fracture was composed of three different characteristic regions.

  3. Challenges in experimental fatigue testing of glassfibre reinforced polymer matrix composites for wind turbine industry

    DEFF Research Database (Denmark)

    Sjøgreen, Freja Naima; Goutianos, Stergios

    The wind turbine industry always strives to increase the performance of wind turbines. To design longer and lighter wind turbine blades, one of the key factors is the fatigue design limit of the composite materials used in the load carrying structures. The fatigue design limits are based...... on the variance of the fatigue test results on composite materials specimens. Options to improve the design limits of the composite materials are either to improve the material quality, or to decrease the variance of the fatigue test results by improving the fatigue test methods. In recent years, extensive work...... has been done to improve the quality of the composite materials used in wind turbine blades. This improvement has been achieved by incorporating high performance glass fibres with improved sizing and exploring new resin formulations. However, the current standardised fatigue test methods still show...

  4. Damage development in woven fabric composites during tension-tension fatigue

    DEFF Research Database (Denmark)

    Hansen, U.

    1999-01-01

    Impacted woven fabric composites were tested in tension-tension fatigue. In contrast to results from static testing, the effects of low energy impact damage in a fatigue environment were found to be the critical element leading to failure of the specimen. This difference emphasizes the need...... to identify and understand the fatigue damage mechanism. A relatively new non-destructive inspection technique using infrared thermography was found to be a very useful tool in detecting damage initiation and growth. Furthermore, this technique supplies valuable information to the characterization...... of the operating fatigue damage mechanism(s). Fatigue leads to a degradation of material properties. Consequently, in connection with impact induced local stress raisers, fatigue produces continuously changing non-uniform stress fields because of stress redistribution effects. Other models addressing evolution...

  5. High cycle fatigue of weld repaired cast Ti-6AI-4V

    Science.gov (United States)

    Hunter, G. B.; Hodi, F. S.; Eagar, T. W.

    1982-09-01

    In order to determine the effects of weld repair on fatigue life of titanium-6Al-4V castings, a series of specimens was exposed to variations in heat treatment, weld procedure, HIP cycle, cooling rate, and surface finish. The results indicate that weld repair is not detrimental to HCF properties as fatigue cracks were located primarily in the base metal. Fine surface finish and large colony size are the primary variables improving the fatigue life. The fusion zone resisted fatigue crack initiation due to a basketweave morphology and thin grain boundary alpha. Multipass welds were shown not to affect fatigue life when compared with single pass welds. A secondary HIP treatment was not detrimental to fatigue properties, but was found to be unnecessary.

  6. Normalizing effect on fatigue crack propagation at the heat-affected zone of AISI 4140 steel shielded metal arc weldings

    OpenAIRE

    B. Vargas-Arista; J. Teran-Guillen; Solis, J.; García-Cerecero,G.; Martínez-Madrid,M.

    2013-01-01

    The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ) of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughne...

  7. Wave-induced fatigue of multi-span pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Tao Xu [Marine Engineers and Consultants, Freemont, CA (United States); Lauridsen, B. [Danish Maritime Institute, Copenhagen (Denmark); Yong Bai [J P Kenny A/S, Forus (Norway)

    1999-02-01

    Free spanning of the multi-span pipeline is an important subject for design of pipeline in uneven seabed. The seabed intervention costs are largely influenced by pipeline spanning design, which includes assessment of trawl pullover response, vortex-induced vibrations and wave-induced fatigue. The objective of this paper is to develop a rational design methodology for the determination of the free span lengths based on the multi-span pipeline in-line fatigue assessment. Following the summary of the procedure, a detailed mathematical model for the free span movement and its analytical closed form solution are developed. The fatigue damage models are detailed both in time domain and frequency domain approaches. A numerical example is presented to illustrate the technical models. (author)

  8. The Recognition Of Fatigue

    DEFF Research Database (Denmark)

    Elsass, Peter; Jensen, Bodil; Mørup, Rikke

    2007-01-01

    Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87......Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87...

  9. Very High Cycle Fatigue Behavior of TA11 Titanium Alloy

    Directory of Open Access Journals (Sweden)

    JIAO Zehui

    2017-06-01

    Full Text Available The conventional fatigue test method was used to obtain the very high cycle fatigue (VHCF limits of 3×107 and 1×108 cycles for TA11 titanium alloy in different temperatures and stress ratios. Three parameter power function method was used to obtain the VHCF median S-N curves and equations. The results show that the VHCF strength of 3×107 and 1×108 cycles presented a continue reducing trend compared with the traditional 1 x 107 fatigue limit. This trend is not obvious in negative stress ratio (R=-1, but significant in normal stress ratio (R=0.1 and 0.5, and the reduction amplitude of room temperature tests was greater than that of elevated temperature tests. The fracture morphologies showed that the VHCF cracks initiat at the specimen surface of TA11 alloy in room temperature tests, and the VHCF cracks initiation ways in elevated temperature tests relate to the stress ratio. The cracks initiate at the specimen surface when R=0.1 and 0.5 but in the internal when R=0.5; The surface state of TA11 alloy specimens is the main cause of its fatigue life dispersion.

  10. Fatigue susceptibility of an endodontic fibre post material.

    Science.gov (United States)

    Barbizam, J V B; White, S N

    2014-02-01

    To evaluate effects of ageing and fatigue on the elastic modulus and short-beam shear strength of a quartz fibre/epoxy resin post material. Cylindrical specimens (25 × 2.2 mm) were made. Elastic moduli were dynamically measured before immersion in water; after immersion in water; periodically during storage in water for up to 7 years; periodically during thermal cycling in water for up to 10 000 cycles to produce thermo-mechanical fatigue; and periodically during boiling in water for up to 100 h. After ageing, the specimens underwent short-beam shear strength testing. Elastic modulus was significantly decreased by thermal cycling and by immersion in boiling water, but not by water storage. Short-beam shear strength was profoundly decreased by all three ageing processes. Short-beam shear strength was much more sensitive than elastic modulus to the ageing or fatigue processes applied in this study. A representative endodontic fibre post material was susceptible to a variety of ageing and fatigue processes. The effects of ageing and fatigue had a more pronounced impact on short-beam shear strength than on elastic modulus. The effects of boiling in water and thermal cycling in water were considerably larger than those of simple storage in water. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  11. Fatigue-Life Prediction Methodology Using Small-Crack Theory

    Science.gov (United States)

    Newmann, James C., Jr.; Phillips, Edward P.; Swain, M. H.

    1997-01-01

    This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using 'small-crack theory' for various materials and loading conditions. Crack-tip constraint factors, to account for three-dimensional state-of-stress effects, were selected to correlate large-crack growth rate data as a function of the effective-stress-intensity factor range (delta K(eff)) under constant-amplitude loading. Some modifications to the delta k(eff)-rate relations were needed in the near-threshold regime to fit measured small-crack growth rate behavior and fatigue endurance limits. The model was then used to calculate small- and large-crack growth rates, and to predict total fatigue lives, for notched and un-notched specimens made of two aluminum alloys and a steel under constant-amplitude and spectrum loading. Fatigue lives were calculated using the crack-growth relations and microstructural features like those that initiated cracks for the aluminum alloys and steel for edge-notched specimens. An equivalent-initial-flaw-size concept was used to calculate fatigue lives in other cases. Results from the tests and analyses agreed well.

  12. Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 Under Biaxial and Uniaxial Fatigue

    Science.gov (United States)

    2014-06-19

    experiment they used dog -bone specimens 18 Figure 2.5: Examples of corrosion damage in fatigue coupons, (a) mild, (b) medium, (c) severe [14...initiation and propagation behavior of aluminum alloy [51]. They used 45 mm long 12 mm wide dog -bone shaped specimens made of 6151-T6 aluminum alloy...Chlistovsky, R.M., P.J. Heffernan, and D.L. DuQuesnay. "Corrosion-fatigue behaviour of 7075-T651 aluminum alloy subjected to periodic overloads

  13. Fatigue creep damage at the cement–bone interface: An experimental and a micro-mechanical finite element study

    NARCIS (Netherlands)

    Waanders, Daan; Janssen, Dennis; Miller, Mark A.; Mann, Kenneth A.; Verdonschot, Nicolaas Jacobus Joseph

    2009-01-01

    The goal of this study was to quantify the micromechanics of the cement–bone interface under tensile fatigue loading using finite element analysis (FEA) and to understand the underlying mechanisms that play a role in the fatigue behavior of this interface. Laboratory cement–bone specimens were

  14. Experimental investigation on the effect of creep on the damage evolution of CFRP structures during fatigue loading

    NARCIS (Netherlands)

    Zarouchas, D.; Eleftheroglou, N.; Gdoutos, Emmanuel E.

    2016-01-01

    This paper presents an experimental investigation on the effect of creep on the damage evolution of Carbon Fiber Reinforced Polymer structures during fatigue loading. A new experimental campaign is proposed where unidirectional CFRP specimens are tested under the combination of fatigue and constant

  15. The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium-Aluminium Alloys

    Science.gov (United States)

    1990-02-01

    lyyer and Dowling [203] used acetate replicas to monitor small-crack closure in 4340 steel specimens tested in strain-controlled fatigue at high strain...M. Ward-Close and C. J. Beevers, "The Influence of Grain Orientation on the Mode and Rate of Fatigue Crack Growth in ax-Titanium," Metill , Trans

  16. Biomarkers for chronic fatigue.

    Science.gov (United States)

    Klimas, Nancy G; Broderick, Gordon; Fletcher, Mary Ann

    2012-11-01

    Fatigue that persists for 6 months or more is termed chronic fatigue. Chronic fatigue (CF) in combination with a minimum of 4 of 8 symptoms and the absence of diseases that could explain these symptoms, constitute the case definition for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Inflammation, immune system activation, autonomic dysfunction, impaired functioning in the hypothalamic-pituitary-adrenal axis, and neuroendocrine dysregulation have all been suggested as root causes of fatigue. The identification of objective markers consistently associated with CFS/ME is an important goal in relation to diagnosis and treatment, as the current case definitions are based entirely on physical signs and symptoms. This review is focused on the recent literature related to biomarkers for fatigue associated with CFS/ME and, for comparison, those associated with other diseases. These markers are distributed across several of the body's core regulatory systems. A complex construct of symptoms emerges from alterations and/or dysfunctions in the nervous, endocrine and immune systems. We propose that new insight will depend on our ability to develop and deploy an integrative profiling of CFS/ME pathogenesis at the molecular level. Until such a molecular signature is obtained efforts to develop effective treatments will continue to be severely limited. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. BIOMARKERS for CHRONIC FATIGUE

    Science.gov (United States)

    Broderick, Gordon; Fletcher, Mary Ann

    2012-01-01

    Fatigue that persists for 6 months or more is termed chronic fatigue. Chronic fatigue (CF) in combination with a minimum of 4 of 8 symptoms and the absence of diseases that could explain these symptoms, constitute the case definition for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Inflammation, immune system activation, autonomic dysfunction, impaired functioning in the hypothalamic-pituitary-adrenal axis, and neuroendocrine dysregulation have all been suggested as root causes of fatigue. The identification of objective markers consistently associated with CFS/ME is an important goal in relation to diagnosis and treatment, as the current case definitions are based entirely on physical signs and symptoms. This review is focused on the recent literature related to biomarkers for fatigue associated with CFS/ME and, for comparison, those associated with other diseases. These markers are distributed across several of the body’s core regulatory systems. A complex construct of symptoms emerges from alterations and/or dysfunctions in the nervous, endocrine and immune systems. We propose that new insight will depend on our ability to develop and deploy an integrative profiling of CFS/ME pathogenesis at the molecular level. Until such a molecular signature is obtained efforts to develop effective treatments will continue to be severely limited. PMID:22732129

  18. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    Science.gov (United States)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-10-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  19. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    Science.gov (United States)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-09-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  20. Kappa Delta Award. Low back pain and whole body vibration.

    Science.gov (United States)

    Pope, M H; Magnusson, M; Wilder, D G

    1998-09-01

    The investigators describe their multifaceted approach to the study of the relationship between whole body vibration and low back pain. The epidemiologic study was a two center study of drivers and sedentary workers in the United States and Sweden. The vibration exposure was measured in the vehicles. It was found that the career vibration exposure was related to low back, neck, and shoulder pain. However, disability was related to job satisfaction. In vivo experiments, using percutaneous pin mounted accelerometers have shown that the natural frequency is at 4.5 Hz. The frequency response is affected by posture, seating, and seat back inclination. The response appears to be determined largely by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration, should be reduced for those recovering from these problems. Vibration attenuating seats and correct ergonomic layout of the cabs may reduce the risks of recurrence.

  1. Simulation of Voltage Dip Event in Fixed-Speed Wind Turbines: Fatigue Evaluation

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2012-01-01

    Grid code modifications require the in service fixed speed wind turbines to ride-trough grid faults. Voltage dips due to electrical grid faults generate transients of the generator electromagnetic torque. These transients result in significant stresses and vibrations affecting the fatigue life...... transients affecting the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method was developed to evaluate the fatigue life of the mechanical system. The methodology analyses the stress history and estimates the mean and amplitudes of the counted cycles, and time of duration...

  2. Biomarkers of Fatigue: Ranking Mental Fatigue Susceptibility

    Science.gov (United States)

    2010-12-10

    Effectiveness ( SAFTE ), described in Hursh et al. 2004) holds that performance declines steeply after midnight until mid-morning where it levels off to...Meals occurred during the daylight portion of the protocol with greater frequency than the night time portion; however, participants were allowed...Vigilance Task) SAFTE (Sleep Activity Fatigue Task Effectiveness) SD (standard deviation) T (training) 28 Distribution A: Approved for

  3. Fracture mechanics parameters for small fatigue cracks

    Science.gov (United States)

    Newman, J. C., Jr.

    1992-01-01

    This paper presents a review of some common small-crack test specimens, the underlying causes of the small-crack effect, and the fracture-mechanics parameters that have been used to correlate or predict their growth behavior. This review concentrates on continuum mechanics concepts and on the nonlinear behavior of small cracks. The paper reviews some stress-intensity factor solutions for small-crack test specimens and develops some simple elastic-plastic J integral and cyclic J integral expressions that include the influence of crack-closure. These parameters were applied to small-crack growth data on two aluminum alloys, and a fatigue life prediction methodology is demonstrated. For these materials, the crack-closure transient from the plastic wake was found to be the major factor in causing the small-crack effect.

  4. Semiactive Vibration Control of a Wind Turbine Tower using an MR Damper

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Nielsen, Søren R. K.; Poulsen, B. L.

    2002-01-01

    For fatigue vibration reduction modern wind turbines are installed with different kind of passive systems such as a tuned mass damper or a tuned liquid damper. However, passive control systems are limited because they cannot adapt to broadbanded loading conditions, i.e. they perform well...... or semiactive system for reducing the fatigue will be more optimal than a passive control system. This paper presents a numerically and experimentally investigation of semiactive vibration control of wind turbine tower vibrations by using a magnetorheological (MR) fluid damper. Numerical simulations as well...... as experimental laboratory results indicate that the MR damper approach is superior to a traditional tuned mass damper for reducing the vibration of wind turbine towers....

  5. Effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK).

    Science.gov (United States)

    Simsiriwong, Jutima; Shrestha, Rakish; Shamsaei, Nima; Lugo, Marcos; Moser, Robert D

    2015-11-01

    In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semi-crystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strain-life results and the observed microstructure of fatigue specimens, a microstructure-sensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

  7. Fatigue behavior and failure mechanisms of direct laser deposited Ti–6Al–4V

    Energy Technology Data Exchange (ETDEWEB)

    Sterling, Amanda J.; Torries, Brian [Department of Mechanical Engineering, Mississippi State University, Box 9552, Mississippi State, MS 39762 (United States); Shamsaei, Nima, E-mail: shamsaei@me.msstate.edu [Department of Mechanical Engineering, Mississippi State University, Box 9552, Mississippi State, MS 39762 (United States); Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Box 5405, , Mississippi State, MS 39762 (United States); Thompson, Scott M. [Department of Mechanical Engineering, Mississippi State University, Box 9552, Mississippi State, MS 39762 (United States); Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Box 5405, , Mississippi State, MS 39762 (United States); Seely, Denver W. [Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Box 5405, , Mississippi State, MS 39762 (United States)

    2016-02-08

    In order for additive-manufactured parts to become more widely utilized and trusted in application, it is important to have their mechanical properties well-characterized and certified. The fatigue behavior and failure mechanisms of Ti–6Al–4V specimens fabricated using Laser Engineered Net Shaping (LENS), a Direct Laser Deposition (DLD) additive manufacturing (AM) process, are investigated in this study. A series of fully-reversed strain-controlled fatigue tests is conducted on Ti–6Al–4V specimens manufactured via LENS in their as-built and heat-treated conditions. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces of fatigue specimens to qualify the failure mechanism, crack initiation sites, and defects such as porosity. Due to the relatively high localized heating and cooling rates experienced during DLD, fabricated parts are observed to possess anisotropic microstructures, and thus, different mechanical properties than those of their traditionally-manufactured wrought counterparts. The fatigue lives of the investigated LENS specimens were found to be shorter than those of wrought specimens, and porosity was found to be the primary contributor to these shorter fatigue lives, with the exception of the heat-treated LENS samples. The presence of pores promotes more unpredictable fatigue behavior, as evidenced by data scatter. Pore shape, size, location, and number were found to impact the fatigue behavior of the as-built and annealed DLD parts. As porosity seems to be the main contributor to the fatigue behavior of DLD parts, it is important to optimize the manufacturing process and design parameters to minimize and control pore generation during the build.

  8. Prognostic and Remaining Life Prediction of Electronic Device under Vibration Condition Based on CPSD of MPI

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2016-01-01

    Full Text Available Prognostic of electronic device under vibration condition can help to get information to assist in condition-based maintenance and reduce life-cycle cost. A prognostic and remaining life prediction method for electronic devices under random vibration condition is proposed. Vibration response is measured and monitored with acceleration sensor and OMA parameters, including vibration resonance frequency, especially first-order resonance frequency, and damping ratio is calculated with cross-power spectrum density (CPSD method and modal parameter identification (MPI algorithm. Steinberg vibration fatigue model which considers transmissibility factor is used to predict the remaining life of electronic component. Case study with a test board is carried out and remaining life is predicted. Results show that with this method the vibration response characteristic can be monitored and predicted.

  9. Neuromuscular response of the trunk to inertial based sudden perturbations following whole body vibration exposure.

    Science.gov (United States)

    MacIntyre, Danielle; Cort, Joel A

    2014-12-01

    The effects of whole body vibration exposure on the neuromuscular responses following inertial-based trunk perturbations were examined. Kinematic and surface EMG (sEMG) data were collected while subjects were securely seated on a robotic platform. Participants were either exposed to 10 min of vibration or not, which was followed by sudden inertial trunk perturbations with and without timing and direction knowledge. Amplitude of sEMG was analyzed for data collected during the vibration protocol, whereas the onset of sEMG activity and lumbar spine angle were analyzed for the perturbation protocol. Data from the vibration protocol did not show a difference in amplitude of sEMG for participants exposed to vibration and those not. The perturbation protocol data showed that those not exposed to vibration had a 14% faster muscle onset, despite data showing no difference in fatigue level. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Effect of shot peening using ultra-fine particles on fatigue properties of 5056 aluminum alloy under rotating bending

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Shoichi, E-mail: kikuchi@mech.kobe-u.ac.jp [Department of Mechanical Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe-shi, Hyogo 657-8501 (Japan); Nakamura, Yuki [Department of Mechanical Engineering, National Institute of Technology, Toyota College, 2-1 Eisei-cho, Toyota-shi, Aichi 471-8525 (Japan); Nambu, Koichiro [Department of Mechanical Engineering, National Institute of Technology, Suzuka College, Shiroko-cho, Suzuka-shi, Mie 510-0294 (Japan); Ando, Masafumi [Innovation Team, IKK SHOT Co. Ltd., 412-4, Nunowari, Minami-Shibata-machi, Tokai-shi, Aichi 476-0001 (Japan)

    2016-01-15

    Shot peening using particles 10 μm in diameter (ultra-fine particle peening: Ultra-FPP) was introduced to improve the fatigue properties of 5056 aluminum alloy. The surface microstructures of the Ultra-FPP treated specimens were characterized using a micro-Vickers hardness tester, scanning electron microscopy (SEM), X-ray diffraction (XRD), non-contact scanning white light interferometry, and electron backscatter diffraction (EBSD). The Ultra-FPP treated specimen had higher hardness than the conventional FPP treated specimen with a short nozzle distance due to the high velocity of the ultra-fine particles. Furthermore, the surface hardness of the Ultra-FPP treated specimen tended to increase as the peening time decreased. Fatigue tests were performed in air at room temperature using a cantilever-type rotating bending fatigue testing machine. It was found that the fatigue life of the Ultra-FPP treated specimen tended to increase with decreasing peening time. Mainly, the Ultra-FPP improved the fatigue properties of 5056 aluminum alloy in the very high cycle regime of more than 10{sup 7} cycles compared with the un-peened specimens. This is because the release of the compressive residual stress is small during fatigue tests at low stress amplitudes.

  11. Fatigue crack propagation and cyclic deformation at a crack tip

    Science.gov (United States)

    Kang, T. S.; Liu, H. W.

    1974-01-01

    The fatigue crack propagation relation da/dN = f(R) Delta K squared can be derived with three assumptions: small-scale yielding, material homogeneity, and that crack tip stresses and strains are not strongly affected by plate thickness. The function f(R) is a constant at a given stress ratio, R. The effects of plate thickness and stress ratio on crack tip deformation and fatigue crack growth in 2024-T351 aluminum alloy were studied. High Delta K level in a thin specimen causes crack tip necking. Necking is more pronounced at high stress ratio. Necking causes high maximum strain near a crack tip and fast crack growth rate.

  12. Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys

    Science.gov (United States)

    Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

    2011-01-01

    The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

  13. Investigation into the fatigue behavior of wood laminates for Wind Energy Converter blade design

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, K.T.

    1987-01-01

    This work sets out to improve the understanding of the fatigue properties of wood and fatigue failure mechanisms. Three important areas were identified for research: (a) effect of R ratio on fatigue life, (b) effect of moisture on fatigue life, and (c) development of cumulative damage laws. In order to understand fatigue-damage mechanisms, a computer control and monitoring system called SArGen was developed. The computer system is designed to accurately control a fatigue machine and simultaneously monitor load, deflections and/or strains for every cycle in a fatigue tests. It is also capable of block loading a specimen with a load history consisting of up to 200 changes in load level. The systems includes a load-level correction routine to compensate for drift in load levels and can be used for static tests, monitoring load and deflection or strain at high rates of loading. Constant-load flexural fatigue tests were conducted. Most of the tests were on 4-ply laminates of 4mm-thick sliced Khaya ivorensis veneers glued with epoxy resin. For comparison, fatigue tests were also performed on rotary cut Khaya ivorensis laminates, solid Sitka spruce and unidirectional and 0/90 compressed Beech laminates. The tests on the effect of R ratio showed clearly the severity of reversed fatigue stress application at negative R ratios.

  14. Evaluation of Mechanical Properties and Fatigue Behavior of STS 304L due to Plastic Working

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyun-Bo [Yeungnam Univ., Daegu (Korea, Republic of); Kim, Young-Kyun [KOGAS Research Institute, Seoul (Korea, Republic of); Suh, Chang-Min [Kyungpook Nat’l Univ., Daegu (Korea, Republic of)

    2017-07-15

    The purpose of this study is to investigate the influence of the cold reduction rate and an ultrasonic fatigue test (UFT) on the fatigue behaviors of STS 304L. The tensile strength, yield strength, hardness value and fatigue limit in the UFT fatigue test linearly increased as thickness decreased from 1.5 mm to 1.1 mm, as the cold reduction rate of STS 304L increased. As a result of the UFT fatigue test (R = -1) of four specimens, the fatigue limit of the S-N curve formed a knee point in the region of 10{sup 6}, and the 2nd fatigue limit caused by giga cycle fatigue did not appeared. In the case of t = 1.1 mm, the highest fatigue limit was 345 MPa, which was 64.3% higher than the original material (t = 1.5 mm). As a result of the UFT fatigue test of STS 304L, many small surface cracks occurred, grown, coalesced while tearing.

  15. Influence of Quality of Rolling Surfaces of Roller Bearings on Their Vibrational Behaviour

    Directory of Open Access Journals (Sweden)

    Jevgenij Kurec

    2014-02-01

    Full Text Available The paper investigates vibrational behaviour of widely used rollerbearings No. NU207 which have different roughness of rollingsurfaces. Fatigue damage is one of the main factors that limitthe life of bearings of such type. The aims of present work wereto establish dependence of roughness parameter Ra of rollingsurfaces of bearings on their vibration velocity and investigatevibrational behaviour of roller bearings with different roughnessof rolling surfaces.

  16. AGC-2 Specimen Post Irradiation Data Package Report

    Energy Technology Data Exchange (ETDEWEB)

    Windes, William Enoch [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rohrbaugh, David T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David L. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-08-01

    This report documents results of the post-irradiation examination material property testing of the creep, control, and piggyback specimens from the irradiation creep capsule Advanced Graphite Creep (AGC)-2 are reported. This is the second of a series of six irradiation test trains planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphite grades. The AGC-2 capsule was irradiated in the Idaho National Laboratory Advanced Test Reactor at a nominal temperature of 600°C and to a peak dose of 5 dpa (displacements per atom). One-half of the creep specimens were subjected to mechanical stresses (an applied stress of either 13.8, 17.2, or 20.7 MPa) to induce irradiation creep. All post-irradiation testing and measurement results are reported with the exception of the irradiation mechanical strength testing, which is the last destructive testing stage of the irradiation testing program. Material property tests were conducted on specimens from 15 nuclear graphite grades using a similar loading configuration as the first AGC capsule (AGC-1) to provide easy comparison between the two capsules. However, AGC-2 contained an increased number of specimens (i.e., 487 total specimens irradiated) and replaced specimens of the minor grade 2020 with the newer grade 2114. The data reported include specimen dimensions for both stressed and unstressed specimens to establish the irradiation creep rates, mass and volume data necessary to derive density, elastic constants (Young’s modulus, shear modulus, and Poisson’s ratio) from ultrasonic time-of-flight velocity measurements, Young’s modulus from the fundamental frequency of vibration, electrical resistivity, and thermal diffusivity and thermal expansion data from 100–500°C. No data outliers were determined after all measurements were completed. A brief statistical analysis was performed on the irradiated data and a limited comparison between

  17. Ex-situ X-ray computed tomography data for a non-crimp fabric based glass fibre composite under fatigue loading

    DEFF Research Database (Denmark)

    Jespersen, Kristine Munk; Mikkelsen, Lars Pilgaard

    2017-01-01

    The data published with this article are high resolution X-ray computed tomography (CT) data obtained during an ex-situ fatigue test of a coupon test specimen made from a non-crimp fabric based glass fibre composite similar to those used for wind turbine blades. The fatigue test was interrupted...... four times for X-ray CT examination during the fatigue life of the considered specimen. All the X-ray CT experiments were performed in the region where unidirectional fibre fractures first became visible, and thereby include the damage progression in 3D in this specific region during fatigue loading...

  18. Low cycle fatigue and creep-fatigue interaction behavior of nickel-base superalloy GH4169 at elevated temperature of 650 °C

    Energy Technology Data Exchange (ETDEWEB)

    Chen, G., E-mail: agang@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Zhang, Y. [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Xu, D.K. [Environmental Corrosion Center, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Lin, Y.C. [School of Mechanical and Electrical Engineering, Central South University, Changsha 410083 (China); Chen, X. [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2016-02-08

    Total strain-controlled low cycle fatigue (LCF) tests of a nickel based superalloy were performed at 650 °C. Various hold times were introduced at the peak tensile strain to investigate the high-temperature creep-fatigue interaction (CFI) effects under the same temperature. A substantial decrease in fatigue life occurred as the total strain amplitude increased. Moreover, tensile strain holding further reduced fatigue life. The saturation phenomenon of holding effect was found when the holding period reached 120 s. Cyclic softening occurred during the LCF and CFI process and it was related to the total strain amplitude and the holding period. The relationship between life-time and total strain amplitude was obtained by combining Basquin equation and Coffin-Manson equation. The surface and fracture section of the fatigued specimens were observed via scanning electronic microscope (SEM) to determine the failure mechanism.

  19. Fatigue Evaluation of Recycled Asphalt Mixture Based on Energy-Controlled Mode

    Directory of Open Access Journals (Sweden)

    Tao Ma

    2017-01-01

    Full Text Available The fatigue properties of asphalt mixtures are important inputs for mechanistic-empirical pavement design. To understand the fatigue properties of asphalt mixtures better and to predict the fatigue life of asphalt mixtures more precisely, the energy-controlled test mode was introduced. Based on the implementation theory, the laboratory practice for the energy-controlled mode was realized using a four-point-bending fatigue test with multiple-step loading. In this mode, the fatigue performance of typical AC-20 asphalt specimens with various reclaimed asphalt pavement (RAP contents was tested and evaluated. Results show that the variation regulation of the dissipated energy and accumulative energy is compatible with the loading control principle, which proves the feasibility of the method. In addition, the fatigue life of the asphalt mixture in the energy-controlled mode was between that for the stress-controlled and strain-controlled modes. The specimen with a higher RAP content has a longer fatigue life and better fatigue performance.

  20. Sliding Contact Fatigue Damage in Layered Ceramic Structures

    Science.gov (United States)

    Kim, Jae-Won; Kim, Joo-Hyung; Thompson, Van P.; Zhang, Yu

    2016-01-01

    Porcelain veneered restorations often chip and fracture from repeated occlusal loading, making fatigue studies relevant. Most fatigue studies are limited to uniaxial loading without sliding motion. We hypothesize that biaxial loading (contact-load-slide-liftoff, simulating a masticatory cycle) as compared to uniaxial loading accelerates the fatigue of layered ceramics. Monolithic glass plates were epoxy joined to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Uniaxial and biaxial cyclic contact was applied through a hard sphere in water with a mouth-motion machine. The uniaxial (contact-load-hold-liftoff) and traditional R-ratio fatigue (indenter never leaves the specimen surface) produced a similar lifespan, while biaxial fatigue was more severe. The accelerated crack growth rate in biaxial fatigue is attributed to enhanced tensile stresses at the trailing edges of a moving indenter. Fracture mechanics descriptions for damage evolution in brittle materials loaded repeatedly with a sliding sphere are provided. Clinical relevance is addressed. PMID:17959894

  1. Estimation of Fatigue Life of Laser Welded AISI304 Stainless Steel T-Joint Based on Experiments and Recommendations in Design Codes

    DEFF Research Database (Denmark)

    Lambertsen, Søren Heide; Damkilde, Lars; Kristensen, Anders Schmidt

    2013-01-01

    of specimens are used, two of these are non-welded and the third is welded with a transverse welding (T-Joint). The 13 laser welded specimens are cut out with a milling cutter. The non-welded specimens are divided in 13 specimens cut out with a milling cutter and 10 specimens cut out by a plasma cutter......In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups....... The non-welded specimens are used to study the influence of heat and surface effects on the fatigue life. The fatigue life from the experiments is compared to fatigue life calculated from the guidelines in the standards DNV-RP-C203 and EUROCODE 3 EN-1993-1-9. Insignificant differences in fatigue life...

  2. Thermal fatigue of beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Deksnis, E.; Ciric, D.; Falter, H. [JET Joint undertaking, Abingdon (United Kingdom)] [and others

    1995-09-01

    Thermal fatigue life of S65c beryllium castellated to a geometry 6 x 6 x (8-10)mm deep has been tested for steady heat fluxes of 3 MW/m{sup 2} to 5 MW/m{sup 2} and under pulsed heat fluxes (10-20 MW/m{sup 2}) for which the time averaged heat flux is 5 MW/m{sup 2}. These tests were carried out in the JET neutral beam test facility A test sequence with peak surface temperatures {le} 600{degrees}C produced no visible fatigue cracks. In the second series of tests, with T{sub max} {le} 750{degrees}C evidence for fatigue appeared after a minimum of 1350 stress cycles. These fatigue data are discussed in view of the observed lack of thermal fatigue in JET plasma operations with beryllium PFC. JET experience with S65b and S65c is reviewed; recent operations with {Phi} = 25 MW/m{sup 2} and sustained melting/resolidification are also presented. The need for a failure criterion for finite element analyses of Be PFC lifetimes is discussed.

  3. The Identification of Fatigue Resistant and Fatigue Susceptible Individuals

    Science.gov (United States)

    2008-05-01

    normalized and compared 38 to normalized SAFTE predictions. See text for details. Figure 3 Fatigue plots for fatigue susceptible vs. fatigue...has 5 seconds to press the button to get points for successful signal detections. Lower tones are given with greater frequency and responses to...address the first question, and we use predictions of the Sleep Activity Fatigue Task Effectiveness, or SAFTE model (Hursh, Redmond, Johnson, Thorne

  4. Competing fatigue mechanisms in Nickel-base superalloy Rene 88DT

    Science.gov (United States)

    Chang, Paul N.

    Nickel base superalloys exhibit superior high temperature mechanical properties required for aircraft engine components. It has been known that the processing of these alloys by the powder metallurgy route introduces inclusions inside the material. The presence of such inclusions often leads to competing failure modes in fatigue that is described by a step-wise or two distinct S-N curves involving both the surface and internally-initiated cracks, resulting in large uncertainties of fatigue life. A clear understanding of such behavior is yet to be established. The principal objective of this research is to examine the effect of inclusions on the extent of fatigue failure competition from surface and internal initiators at two different specimen test volumes. Experimental fatigue testing has been performed to explore how the presence of inclusions affects the competing fatigue failure modes. In addition, how the competing failure modes will behave with changes in the specimen size was also studied. Two groups of material each with two different specimen sizes were used in this study. It has been shown that the two crack initiation mechanisms occurred in the small unseeded Rene 88DT specimens tested at 650ºC over the stress range tested. Additionally, the fatigue lives were reduced with increase in specimen volume. All fatigue failures in seeded material occurred due to crack initiations from the seeded inclusions. In the fatigue life of seeded material, two competing and separate S-N curves were found in small test volume, whereas, in the large test volume, the regions were separated by a "step" in S-N curve. It has been found that the largest inclusion size observed in metallographic surfaces was smaller than the size determined from the fatigue failure origin. An analysis method based on extreme value statistics developed by Murakami was used to predict the largest size of inclusion in the test volume. The results of this study clearly show that competition for

  5. SIZE DEPENDENCE OF FLEXURAL STRENGTH AND FATIGUE STRENGTH OF PAVEMENT CONCRETE

    Science.gov (United States)

    Yoshimoto, Toru; Sato, Ryoichi

    The size effect on flexural fatigue strength of concrete was experime ntally investigated. For this purpose, specimens of two sizes were prepared: 150mm x 150mm x 530mm (span=450mm) and 200mm x 450mm x 1800mm (span=1350mm). The stress levels were set at 70%, 80% and 90% of the compressive strength. Experimental results showed that the number of loading cycles at failure increased with the enlargement of specimens. Based on a fracture mechanics approach, with a stress level of 70%, this dependence of flexural fatigue strength on size was explained by the difference in the stress distributions in the sections of small and large sized specimens. A te nsion softening stress region was formed in the section of the small specimen, whereas elastic stress was produced over the full section in the large specimen.

  6. Effects of irradiation on low cycle fatigue properties for reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.W. [Kyoto Univ., Graduate School of Energy Science (Japan); Tanigawa, H. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Kohyama, A. [Kyoto Univ., lnstitute of Advanced Energy (Japan)

    2007-07-01

    Full text of publication follows: In materials life decision for a commercial blanket, thermal fatigue property of materials is a particularly important. The loading of structural materials in fusion reactor is, besides the plasma surface interactions, a combined effect of high heat fluxes and neutron irradiation. Depending on the pulse lengths, the operating conditions, and the thermal conductivity, these oscillating temperature gradients will cause elastic and elastic-plastic cyclic deformation giving rise to (creep-) fatigue in structural first wall and blanket components. Especially, investigation of the fatigue property in Reduced Activation Ferritic/Martensitic (RAF/M) steel and establishment of the evaluation technology are demanded in particular immediately for design/manufacturing of ITER-TBM. And also, fatigue testing after irradiation will be carried out in hot cells with remote control system. Considering limited ability of specimen manipulation in the cells, the specimen and the test method need to be simple for operation. The existing data bases of RAF/M steel provide baseline data set including post-irradiation fatigue data. However, to perform the accurate fatigue lifetime assessment for ITER-TBM and beyond utilizing the existing data base, the mechanical understanding of fatigue fracture is mandatory. It has been previously reported by co-authors that dislocation cell structure was developed on low cycle fatigued RAF/M steel, and led the fatigue crack to develop along prior austenitic grain boundary. In this work, the effects of nuclear irradiation on low cycle fatigue properties for RAF/M steels and its fracture mechanisms were examined based on the flow stress analysis and detailed microstructure analysis. Fracture surfaces and crack initiation site were investigated by scanning electron microscope (SEM). Transmission electron microscopy (TEM) was also applied to clarify the microstructural features of fatigue behavior. It is also important to

  7. Possible association between phantom vibration syndrome and occupational burnout.

    Science.gov (United States)

    Chen, Chao-Pen; Wu, Chi-Cheng; Chang, Li-Ren; Lin, Yu-Hsuan

    2014-01-01

    Phantom vibration syndrome (PVS) and phantom ringing syndrome (PRS) occur in many cell phone users. Previous studies have indicated an association between PVS/PRS and job stress. The aim of this study was to determine if PVS/PRS were also associated with occupational burnout. This was a cross-sectional study of 384 employees of a high-tech company in northern Taiwan. They all completed a phantom vibration and ringing questionnaire, the Hospital Anxiety and Depression Scale, and the Chinese version of the Occupational Burnout Inventory. Significantly more women and people with at least a college education were in the population with PRS and PVS, respectively. Anxiety and depression had no associations with PVS/PRS. Higher scores for personal fatigue, job fatigue, and service target fatigue had an independent impact on the presence of PVS, but only a higher score for service target fatigue had an independent impact on the presence of PRS. The independent association between work-related burnout and PVS/PRS suggests that PVS/PRS may be a harbinger of mental stress or a component of the clinical burnout syndrome, and may even be a more convenient and accurate predictor of occupational burnout.

  8. Optimizing specimen processing for ancient soft tissue specimens.

    Science.gov (United States)

    Prats-Muñoz, G; Malgosa, A; Isidro, A; Galtés, I

    2015-05-01

    Despite many reports concerning processing of ancient soft tissues, scant attention has been paid to optimizing procedures for processing soft tissues that have been altered by taphonomic processes. To determine the best procedures, we investigated the rehydration solution, time of exposure to the solutions, fixative solution and exposure to heat. Processes were evaluated based on the minimum section thickness, degree of tissue fragmentation, definition of tissue architecture and penetration of stains. We found that in desiccated samples, tissue architecture was optimized by using Ruffer's solution for rehydration and Schaffer's solution as fixative, because these tissues require water restoration within the tissues due to their compacted character. Heating enhanced penetration of dyes in these specimens, which improved diagnosis. Saponified tissues that had suffered extensive decomposition were more labile and required slow water uptake. The best histological sections were obtained using Sandison's solution followed by fixation with formaldehyde and avoiding heat. To obtain the best results with paleohistological specimens, the procedure must be determined by the condition of the sample and by accounting for the nature of its damage.

  9. Model Indepedent Vibration Control

    OpenAIRE

    Yuan, Jing

    2010-01-01

    A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is

  10. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...

  11. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration...

  12. Hydroelastic Vibrations of Ships

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher; Folsø, Rasmus

    2002-01-01

    A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...

  13. Gearbox vibration diagnostic analyzer

    Science.gov (United States)

    1992-01-01

    This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.

  14. Mechanical vibration and shock analysis, sinusoidal vibration

    CERN Document Server

    Lalanne, Christian

    2014-01-01

    Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m

  15. The Role of Local Microstructure on Small Fatigue Crack Propagation in an α + β Titanium Alloy, Ti-6Al-2Sn-4Zr-6Mo

    Science.gov (United States)

    Szczepanski, C. J.; Jha, S. K.; Larsen, J. M.; Jones, J. W.

    2012-11-01

    Microstructural origins of the variability in fatigue lifetime observed in the high- and very-high-cycle fatigue regimes in titanium alloys were explored by examining the role of microstructural heterogeneity (neighborhoods of grains with similar crystallographic orientations or microtexture) on the initiation and early growth of fatigue cracks in Ti-6246. Ultrasonic fatigue of focused ion beam (FIB) micronotched samples was used to investigate long lifetime (107 to 109) behavior for two microstructural conditions: one with microtexture and one without microtexture. For specimens containing notches of nominally 20 μm in length, fatigue crack initiation in the microtextured material was most likely to occur from notches placed in neighborhoods with a microtexture favorably oriented for easy basal slip. Initiation lifetimes in the untextured material with similar sized notches were, on average, slightly greater than those for the microtextured condition. In both materials, the crack-initiation lifetime from micronotches of length 2c > 20 μm was a very small fraction (fatigue lifetime for unnotched specimens. Furthermore, in the microtextured condition, small fatigue crack propagation rates did not correlate with the microtextured regions and did not statistically differ from average small crack growth rates in the untextured material. As the micronotch size was reduced below 20 μm, fatigue crack initiation was controlled by microstructure rather than by FIB-machined defects. Finally, predictions of the fraction of life consumed in small and long fatigue crack growth from preexisting cracks nominally equivalent in size to the micronotches was compared with the measured fatigue life of unnotched specimens. The predicted range of lifetimes when factoring in the experimentally observed variability in small fatigue crack growth, only accounted for 0.1 pct of the observed fatigue lifetime variability. These findings indicate that in the high-and very-high-cycle fatigue

  16. Fatigue design 1998

    Energy Technology Data Exchange (ETDEWEB)

    Marquis, G.; Solin, J. [eds.] [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    These preprints contain the presentations to be delivered at the Fatigue Design 1998 symposium held on May 26-29, 1998 in Espoo. Fatigue Design 1998 is the tenth in a series of VTT symposia addressing the challenge of fatigue of materials, components and structures. Previous international events were in 1992 and 1995. The key theme of the current meeting is `RELIABILITY`. The two volumes (VTT symposium 181-182) represent 56 contributions by authors representing 26 countries. Emphasis has been given to application oriented research topics that report new technologies, new uses of existing methods and case studies. The objective of the symposium is to bring together researchers and engineers to share experiences and new innovations in designing reliable components to resist alternating loads. (orig.)

  17. Fatigue in soccer

    DEFF Research Database (Denmark)

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-01-01

    in the game: (1) after short-term intense periods in both halves; (2) in the initial phase of the second half; and (3) towards the end of the game. Temporary fatigue after periods of intense exercise in the game does not appear to be linked directly to muscle glycogen concentration, lactate accumulation...... temperatures compared with the end of the first half. Thus, when players perform low-intensity activities in the interval between the two halves, both muscle temperature and performance are preserved. Several studies have shown that fatigue sets in towards the end of a game, which may be caused by low glycogen...... concentrations in a considerable number of individual muscle fibres. In a hot and humid environment, dehydration and a reduced cerebral function may also contribute to the deterioration in performance. In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different...

  18. Myth vs. Fact: Adrenal Fatigue

    Science.gov (United States)

    ... Endocrinologist Search Featured Resource New Mobile App DOWNLOAD Adrenal Fatigue October 2017 Download PDFs English Editors Irina Bancos, MD Additional Resources Mayo Clinic What is adrenal fatigue? The term “adrenal fatigue” has been used ...

  19. Modafinil May Alleviate Poststroke Fatigue

    DEFF Research Database (Denmark)

    Poulsen, Mai Bang; Damgaard, Bodil; Zerahn, Bo

    2015-01-01

    was randomized, double-blinded, and placebo-controlled. Patients were treated with 400-mg modafinil or placebo for 90 days. Assessments were done at inclusion, 30, 90, and 180 days. The primary end point was fatigue at 90 days measured by the Multidimensional Fatigue Inventory-20 general fatigue domain......BACKGROUND AND PURPOSE: Poststroke fatigue is common and reduces quality of life. Current evidence for intervention is limited, and this is the first placebo-controlled trial to investigate treatment of poststroke fatigue with the wakefulness promoting drug modafinil. METHODS: The trial....... Secondary end points included the Fatigue Severity Scale, the Montreal Cognitive Assessment, the modified Rankin Scale and the Stroke-specific quality of Life questionnaire. Adult patients with a recent stroke achieving a score of ≥12 on the Multidimensional Fatigue Inventory-20 general fatigue domain were...

  20. Coping with cancer -- managing fatigue

    Science.gov (United States)

    ... Fatigue is a feeling of tiredness, weakness, or exhaustion. It is different from drowsiness, which can be ... chap 45. National Cancer Institute. Fatigue (PDQ) - Health professional version. Cancer.gov Web site. Updated January 13, ...

  1. Treatments for chronic fatigue syndrome

    National Research Council Canada - National Science Library

    Rimes, K A; Chalder, T

    2005-01-01

    To review studies evaluating the treatment of chronic fatigue and chronic fatigue syndrome, to describe predictors of response to treatment and to discuss the role of the occupational health physician...

  2. Determinants of fatigue and stress.

    Science.gov (United States)

    Kocalevent, Rüya D; Hinz, Andreas; Brähler, Elmar; Klapp, Burghard F

    2011-07-20

    Fatigue can be triggered by previous perceived stress which may lead to impairment of performance and function. The purpose of the study was to investigate the relationship between fatigue and perceived stress. Health determinants including sociodemographic factors for associations between fatigue and perceived stress in the general population (N = 2,483) are outlined. Fatigue and stress were assessed with the Chalder Fatigue Scale (CFS) and the Perceived Stress Questionnaire (PSQ). Within the general population, 25.9% of male and 34.5% of female respondents reported moderate fatigue during the last six months; 9.7% of subjects reported substantial fatigue lasting six months or longer. An adjusted regression analysis (R2corr = .28, p rates of fatigue and perceived stress: female gender, divorce/separation, low social class and poor health status. We conclude that the two conditions overlap most in terms of socio-economic status and self-perceived health status.

  3. Cyclic flattened Brazilian disc tests for measuring the tensile fatigue properties of brittle rocks

    Science.gov (United States)

    Liu, Yi; Dai, Feng; Xu, Nuwen; Zhao, Tao

    2017-08-01

    We propose a cyclic flattened Brazilian disc (FBD) testing method to measure the tensile fatigue properties of brittle rocks. Our method has obvious merits in its specimen preparation and experimental operation. Two parallel flattens are introduced in the disc specimen, which facilitate easily and uniformly loading the specimen without special loading devices required. Moreover, the contact regions between two flattens and loading planes barely change during the entire loading and unloading process, ensuring a consistent contact condition. With certain appropriate loading angles, this method guarantees that the very first breakage of the specimen occurs at the center of the disc, which is the prerequisite of the Brazilian-type indirect tensile tests. To demonstrate our new method, nine cyclic FBD tensile tests are conducted. The fatigue load-deformation characteristics of FBD specimens are revealed. The tensile fatigue lives of tested specimens are observed to increase with the increase in cyclic loading frequency. Our proposed method provides a convenient and reliable approach to indirectly measure the fatigue tensile properties of brittle rocks and other brittle solids subjected to cyclic tensile loadings.

  4. Ageing and temperature effect on the fatigue performance of bituminous mixtures

    Directory of Open Access Journals (Sweden)

    T. López-Montero

    2017-06-01

    Full Text Available The ageing of asphalt mixes, together with their exposure to low temperatures, causes a progressive increase of cracking. In this paper, the effect of ageing and temperature on the fatigue of asphalt concretes made with two types of binders, conventional (50/70 and polymer modified bitumen (PMB, is studied. For this purpose, specimens previously subjected to an accelerated laboratory ageing process were tested by a strain sweep test at different temperatures (-5ºC, 5ºC and 20°C. Results were compared with the obtained from the unaged specimens showing the relative importance of ageing, temperature and type of bitumen on the parameters that determine the fatigue life of the mixture. The mixtures behaviour becomes more brittle with ageing and the decrease of temperature. However, ageing hardly has an effect on fatigue at lower temperatures. In general, mixtures made with polymer modified bitumen have a better fatigue performance to ageing and temperature.

  5. Influence of laser cutting on the fatigue limit of two high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Mateo, Antonio; Fargas, Gemma; Calvo, Jessica; Roa, Joan Josep [Univ. Politecnica de Catalunya, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering

    2015-02-01

    Laser cutting is widely used in the metal industry, particularly when components of high strength steel sheets are produced. However, the roughness of cut edges produced by laser differs from that obtained by other methods, such as mechanical blanking, and this fact influences the fatigue performance. In the present investigation, specimens of two grades of high strength austenitic steels, i.e. AISI 301LN and TWIP17Mn, were cut by laser and tested in the high cycle fatigue regime to determine their corresponding fatigue limits. A series of fatigue specimens were tested without polishing and other series after a careful polishing of the cut edges, in order to assess the influence of the cut edges condition. Results indicate a significant influence of the edge roughness, more distinctive for AISI 301LN than for TWIP steel.

  6. Experimental and numerical evaluation of the fatigue behaviour in a welded joint

    Science.gov (United States)

    Almaguer, P.; Estrada, R.

    2014-07-01

    Welded joints are an important part in structures. For this reason, it is always necessary to know the behaviour of them under cyclic loads. In this paper a S - N curve of a butt welded joint of the AISI 1015 steel and Cuban manufacturing E6013 electrode is showed. Fatigue tests were made in an universal testing machine MTS810. The stress ratio used in the test was 0,1. Flaws in the fatigue specimens were characterized by means of optical and scanning electron microscopy. SolidWorks 2013 software was used to modeling the specimens geometry, while to simulate the fatigue behaviour Simulation was used. The joint fatigue limit is 178 MPa, and a cut point at 2 039 093 cycles. Some points of the simulations are inside of the 95% confidence band.

  7. FATIGUE LIFE PREDICTION OF COMMERCIALLY PURE TITANIUM AFTER NITROGEN ION IMPLANTATION

    Directory of Open Access Journals (Sweden)

    Nurdin Ali

    2013-06-01

    Full Text Available Prediction of fatigue life has become an interesting issue in biomaterial engineering and design for reliability and quality purposes, particularly for biometallic material with modified surfaces. Commercially pure titanium (Cp-Ti implanted with nitrogen ions is a potential metallic biomaterial of the future. The effect of nitrogen ion implantation on fatigue behavior of Cp-Ti was investigated by means of axial loading conditions. The as-received and nitrogen-ion implanted specimens with the energy of 100 keV and dose of 2 × 1017 ions cm-2, were used to determine the fatigue properties and to predict the life cycle of the specimens. The effect of nitrogen ion implantation indicated revealed improved the tensile strength due to the formation of nitride phases, TiN and Ti2N. The fatigue strength of Cp-Ti and Nii-Ti was 250 and 260 MPa, respectively. The analytical results show good agreement with experimental results.

  8. An Investigation on Fatigue in High-Strength Steel Offshore Structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Lopez Martinez, L.

    1997-01-01

    In the present investigation, the fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa, and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading....... In the experimental part of the investigation, fatigue test series have been carried through on both full-scale tubular joints and smaller welded plate test specimens, in high-strength steel as well as in conventional offshore structural steel. The present document gives a summary of the main results presented in two......, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  9. Vibrations of rotating machinery

    CERN Document Server

    Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick

    2017-01-01

    This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...

  10. Elimination of flow-induced pulsations and vibrations in a process installation: a combination of on site measurements, calculations and scale modeling

    NARCIS (Netherlands)

    Bokhorst, E. van; Peters, M.C.A.M.

    2008-01-01

    The aim of the work described in this paper was to trace and eliminate vibration sources in a low pressure system with high flow velocities. Considerable vibration on the pipe system between a flashing vessel (6.5 m diameter) and heat-exchangers resulted in fatigue failure, leakage and subsequent

  11. Obtaining and analysis of results of fatigue and corrosion-fatigue in steel API 5L X60; Obtencao e analise de resultados de fadiga e corrosao-fadiga em aco API 5L X60

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Bruno Allison [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Silva, Antonio Almeida; Santos, Fabio Gualberto Chagas [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2008-07-01

    The corrosion process allied to the fatigue, due to repetitive efforts of several natures, is the main responsible for the damages in pipeline and offshore structures that results in the appears of located faults, and by the way can results in leaks and financial and environmental loss. This phenomenon calls corrosion-fatigue, however, it is very complex, and mainly, in what it concerns the form as this it develops in the structure. The objective of this work is to present some results of experimental fatigue tests and corrosion-fatigue accomplished with specimen that the material originated a pipeline steel API 5L X60. The tests developed in a machine which could test until 12 specimens per time. For test of corrosion-fatigue was used a cell-of-corrosion especially projected, in this way simulated an aggressive environmental condition in a corrosion conditions. With the results of tests, was possible estimate the fatigue limits of the specimen when submitted to the repeated flexing, and compare it with evaluate corrosion-fatigue graphs, that as the literature comes moved down of the curve, in relation to the fatigue curve. (author)

  12. INVESTIGATIONS TO IMPROVE THE TRANSFERABILITY OF SPECIMEN RESULTS BY REAL COMPONENT

    Directory of Open Access Journals (Sweden)

    Martin Riedler

    2010-12-01

    Full Text Available For the improvement of the lifetime calculation of components made of the titanium alloy Ti-6-4, a closed loop methodology from specimen to the component is presented. Based on forged pre-material specimens fatigue tests are done as a basic research, which are presented as S/N-curves. With the determined material data a lifetime calculation with the program FEMFAT is done on a typically fitting element. Finally the results of the lifetime calculation are compared to real component tests, which are done to evaluate the results of the lifetime calculation. The component tests are performed with constant and variable load. Therewith the transferability of specimen results to real components is shown. Additional fracture analysis by light microscope and scanning electron microscope is carried out to give further information of the influence factor of the lifetime and a further description between fracture behaviour of specimen and components.

  13. Fatigue-propagation du melange polymere polystyrene/polyethylene

    Science.gov (United States)

    Bureau, Martin N.

    The interrelations between the morphology of PS/HDPE and PS/SEBS/HDPE immiscible polymer blends and their mechanical behavior, namely in monotonic loading and in cyclic loading, were studied. As predicted by theory, high shear rates encountered during extrusion blending led to efficient minor phase emulsification in PS/HDPE blends for which the viscosity ratio approaches unity. Consequently, the emulsifying effect of an SEBS triblock copolymer employed as a compatibilizer was found to be negligible. In subsequent molding process, disintegration, shape relaxation and coarsening of the minor phase domains were responsible for the morphological evolution of the blends. In the compression molding process, morphological observations showed that the rate of minor phase coarsening followed the predictions of the Ostwald ripening theory, in agreement with the rheological analysis. In the injection molding process, minor phase coarsening was attributed to shear coalescence. The fatigue crack propagation behavior of injection-molded specimens of pure PS as well as of 95/5, 85/15 and 70/30 PS/HDPE blends and of 95/(0.5/4.5), 85/(1.5/13.5) and 70/(3/27) PS/(SEBS/HDPE) blends was then studied. The fatigue fracture surface features of specimens of pure PS as well as of PS/HDPE and PS/SEBS/HDPE blends were analyzed in detail in order to interpret their fatigue crack propagation behavior. In pure PS specimens, discontinuous growth bands, associated with the fracture of crazes in the plastic zone, formed at low fatigue crack growth rates, large dimple-like features at intermediate fatigue crack growth rates and fatigue striations at high fatigue crack growth rates. The fracture toughness of injection-molded specimens of pure PS as well as of 95/5, 85/15 and 70/30 PS/HDPE blends and of 95/(0.5/4.5) PS/(SEBS/HDPE), 85/(1.5/13.5) and 70/(3/27) PS/(SEBS/HDPE) was finally studied. The results showed that the addition of HDPE to PS led to a reduction of the fracture toughness KQ

  14. [Chronic fatigue syndrome: more than fatigue].

    Science.gov (United States)

    Royes, Badía; Alvarez, Carballo; Lalinde, Sevillano; Vidal, Llinas; Martín, Alegre

    2010-12-01

    Chronic fatigue syndrome (CFS) is a disease recognized by all international medical organizations and WHO, and is classified under the code G93.3 of the International Classification of Diseases. Its prevalence is estimated around 2.54% being more common in women than in men (8/2) aged between 20 and 40 Is defined as a chronic new description characterized by the presence of subjective feeling of fatigue and exhaustion long disabling of more than 6 months duration that is not relieved by rest. It is a multisystem disorder that often presents a significant number of comorbid phenomena. Not known until specific tests to confirm the diagnosis, nor is there a cure to solve this health problem definitively The strongest evidence is based on the multidisciplinary approach for the symptomatic treatment of pain, sleep disorders, neurocognitive dysfunction, autonomic and control of depression and anxiety. The specific contribution of nursing to care for the person who lives and live with the SFC should be developed primarily in the field of health education and supportive care, support and assistance to help the patient and their relatives are an adaptive response to changes in health.

  15. Modal and Vibration Analysis of Filter System in Petrochemical Plant

    Directory of Open Access Journals (Sweden)

    Zhongchi Liu

    2017-01-01

    Full Text Available Filter systems are widely used in petrochemical plants for removing solid impurities from hydrocarbon oils. The backwash is the cleaning process used to remove the impurities on the sieves of the filters without a need to interrupt the operation of the entire system. This paper presents a case study based on the actual project of a filter system in a petrochemical plant, to demonstrate the significant effect of vibration on the structural integrity of piping. The induced vibration had led to the structural fatigue failure of the pipes connecting the filter system. A preliminary assessment suggested that the vibrations are caused by the operation of backwashing of the filter system. A process for solving the vibration problem based on the modal analysis of the filter system using the commercial finite element software for simulation is therefore proposed. The computed natural frequencies of the system and the vibration data measured on site are assessed based on the resonance effect of the complete system including the piping connected to the filters. Several approaches are proposed to adjust the natural frequencies of the system in such a way that an optimal and a reasonable solution for solving the vibration problem is obtained.

  16. Multiaxial fatigue of aluminium friction stir welded joints: preliminary results

    Directory of Open Access Journals (Sweden)

    D. G. Hattingh

    2015-07-01

    Full Text Available The aim of the present research is to check the accuracy of the Modified Wöhler Curve Method (MWCM in estimating the fatigue strength of friction stir (FS welded tubular joints of Al 6082-T6 subjected to in-phase and out-of-phase multiaxial fatigue loading. The welded samples being investigated were manufactured by equipping an MTS I-STIR process development system with a retracting tool that was specifically designed and optimised for this purpose. These specimens were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out by using the generated experimental results allowed us to prove that the MWCM (applied in terms of nominal stresses is highly accurate in predicting the fatigue strength of the tested FS welded joints, its usage resulting in estimates falling with the uniaxial and torsional calibration scatter bands.

  17. Improving fatigue damage resistance of alumina through surface grading.

    Science.gov (United States)

    Ren, L; Liu, L; Bhowmick, S; Gerbig, Y B; Janal, M N; Thompson, V P; Zhang, Y

    2011-08-01

    Porcelain-veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesized that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, we fabricated graded structures by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture-resistant alumina crowns.

  18. Fatigue Damage Evolution in Fibre Composites for Wind Turbine Blades

    DEFF Research Database (Denmark)

    Jespersen, Kristine Munk

    One of the largest challenges in wind turbine design, is realistically predicting the lifetime of the blades. Wind turbine blades experience a high number of fatigue load cycles during their life-time, and the fatigue damage mechanisms of the non-crimp fabric based glass fibre composites used...... for the load carrying parts of wind turbine blades are not well understood. This PhD project establishes experimental methods making it possible to monitor the damage initiation and progression of fibre composites in 3D using X-ray CT. To overcome the resolution challenges of X-ray CT, a tension clamp solution...... that applies load to the specimen during X-ray CT examination is presented, and the advantage of combining X-ray CT with other techniques such as transilluminated white light imaging is demonstrated. The established methods are used to monitor the damage initiation and progression of fatigue damage...

  19. Analysis of Fatigue Crack Paths in Cold Drawn Pearlitic Steel

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2015-11-01

    Full Text Available In this paper, a fracto-metallographic analysis was performed on the cracked specimens of cold drawn pearlitic steel subjected to fatigue tests. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and frequent local deflections that create microstructural roughness. At the micro-level, the cold drawn pearlitic steel exhibits higher micro-roughness than the hot rolled bar (this is a consequence of the manufacturing process by cold drawing, so that the actual fractured surface in the cold drawn wire is greater than that in the hot rolled bar, due to the fact that the crack deflection events are more frequent and with higher angle in the former (the heavily drawn prestressing steel wire. These findings show the relevant role on the manufacturing process by cold drawing in the fatigue crack propagation in pearlitic steel.

  20. Improving Fatigue Damage Resistance of Alumina through Surface Grading

    Science.gov (United States)

    Ren, L.; Liu, L.; Bhowmick, S.; Gerbig, Y.B.; Janal, M.N.; Thompson, V.P.; Zhang, Y.

    2011-01-01

    Porcelain-veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesized that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, we fabricated graded structures by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture-resistant alumina crowns. PMID:21555776

  1. Fatigue Crack Growth Rate of Inconel 718 Sheet at Cryogenic Temperatures

    Science.gov (United States)

    Wells, Douglas; Wright, Jonathan; Hastings, Keith

    2005-01-01

    Inconel 718 sheet material was tested to determine fatigue crack growth rate (FCGR) at cryogenic conditions representative of a liquid hydrogen (LH2) environment at -423 degree F. Tests utilized M(T) and ESE(T) specimen geometries and environments were either cold gaseous helium or submersion in LH2. The test results support a significant improvement in the fatigue crack growth threshold at -423 degree F compared to -320 degree F or 70 degree F.

  2. Predicting the residual strength of open-hole (OH) composite specimens subjected to cyclic loading

    Science.gov (United States)

    Ceparano, Angelo; Dell'Aversano, Raffaella

    2016-05-01

    A procedure is reported that allows the prediction of the fatigue life and the residual strength of "open hole" composite specimens subjected to constant amplitude cyclic loadings. Based on a two-parameter phenomenological model explicitly accounting for the maximum applied stress, σmax, and the stress ratio, R, the procedure relies on a relatively small set of experimental fatigue life data. The approach reliability is checked in predicting the fatigue life and residual strength of AS4 carbon/epoxy 3k/E7K8 Plain Weave Fabric "open-hole" (OH) samples subjected to a very broad loading conditions from prevailing tension (R=0 and R=-0.2) to compression (R=5) to mixed tension/compression (R=-1) loadings.

  3. Effect of Pre-Fatigue on the Monotonic Deformation Behavior of a Coplanar Double-Slip-Oriented Cu Single Crystal

    Directory of Open Access Journals (Sweden)

    Xiao-Wu Li

    2016-11-01

    Full Text Available The [ 2 ¯ 33 ] coplanar double-slip-oriented Cu single crystals were pre-fatigued up to a saturation stage and then uniaxially tensioned or compressed to fracture. The results show that for the specimen pre-fatigued at a plastic strain amplitude γpl of 9.2 × 10−4, which is located within the quasi-plateau of the cyclic stress-strain (CSS curve, its tensile strength and elongation are coincidently improved, showing an obvious strengthening effect by low-cycle fatigue (LCF training. However, for the crystal specimens pre-fatigued at a γpl lower or higher than the quasi-plateau region, due to a low pre-cyclic hardening or the pre-induction of fatigue damage, no marked strengthening effect by LCF training occurs, and even a weakening effect by LCF damage takes place instead. In contrast, the effect of pre-fatigue deformation on the uniaxial compressive behavior is not so significant, since the compressive deformation is in a stress state more beneficial to the ongoing plastic deformation and it is insensitive to the damage induced by pre-cycling. Based on the observations and comparisons of deformation features and dislocation structures in the uniaxially deformed [ 2 ¯ 33 ] crystal specimens which have been pre-fatigued at different γpl, the micro-mechanisms for the effect of pre-fatigue on the static mechanical behavior are discussed.

  4. The influence of seat backrest angle on human performance during whole-body vibration.

    Science.gov (United States)

    Paddan, G S; Holmes, S R; Mansfield, N J; Hutchinson, H; Arrowsmith, C I; King, S K; Jones, R J M; Rimell, A N

    2012-01-01

    This study investigated the effects of reclined backrest angles on cognitive and psycho-motor tasks during exposure to vertical whole-body vibration. Twenty participants were each exposed to three test stimuli of vertical vibration: 2-8 Hz; 8-14 Hz and 14-20 Hz, plus a stationary control condition whilst seated on a vibration platform at five backrest angles: 0° (recumbent, supine) to 90° (upright). The vibration magnitude was 2.0 ms(-2) root-mean-square. The participants were seated at one of the backrest angles and exposed to each of the three vibration stimuli while performing a tracking and choice reaction time tasks; then they completed the NASA-TLX workload scales. Apart from 22.5° seat backrest angle for the tracking task, backrest angle did not adversely affect the performance during vibration. However, participants required increased effort to maintain performance during vibration relative to the stationary condition. These results suggest that undertaking tasks in an environment with vibration could increase workload and risk earlier onset of fatigue. Current vibration standards provide guidance for assessing exposures for seated, standing and recumbent positions, but not for semi-recumbent postures. This paper reports new experimental data systematically investigating the effect of backrest angle on human performance. It demonstrates how workload is elevated with whole-body vibration, without getting affected by backrest angle.

  5. Fatigue Life of Cast Titanium Alloys Under Simulated Denture Framework Displacements

    Science.gov (United States)

    Koike, Mari; Chan, Kwai S.; Hummel, Susan K.; Mason, Robert L.; Okabe, Toru

    2013-02-01

    The objective of the study was to evaluate the hypothesis that the mechanical properties and fatigue behavior of removable partial dentures (RPD) made from cast titanium alloys can be improved by alloying with low-cost, low-melting elements such as Cu, Al, and Fe using commercially pure Ti (CP-Ti) and Ti-6Al-4V as controls. RPD specimens in the form of rest-shaped, clasp, rectangular-shaped specimens and round-bar tensile specimens were cast using an experimental Ti-5Al-5Cu alloy, Ti-5Al-1Fe, and Ti-1Fe in an Al2O3-based investment with a centrifugal-casting machine. The mechanical properties of the alloys were determined by performing tensile tests under a controlled displacement rate. The fatigue life of the RPD specimens was tested by the three-point bending in an MTS testing machine under a cyclic displacement of 0.5 mm. Fatigue tests were performed at 10 Hz at ambient temperature until the specimens failed into two pieces. The tensile data were statistically analyzed using one-way ANOVA (α = 0.05) and the fatigue life data were analyzed using the Kaplan-Meier survival analysis (α = 0.05). The experimental Ti-5Al-5Cu alloy showed a significantly higher average fatigue life than that of either CP-Ti or Ti-5Al-1Fe alloy ( p < 0.05). SEM fractography showed that the fatigue cracks initiated from surface grains, surface pores, or hard particles in surface grains instead of the internal casting pores. Among the alloys tested, the Ti-5Al-5Cu alloy exhibited favorable results in fabricating dental appliances with an excellent fatigue behavior compared with other commercial alloys.

  6. Comparison of Mode II and III Monotonic and Fatigue Delamination Onset Behavior for Carbon/Toughened Epoxy Composites

    Science.gov (United States)

    Li, Jian; OBrien, T. Kevin; Lee, Shaw Ming

    1997-01-01

    Monotonic and fatigue tests were performed to compare the Mode II and III interlaminar fracture toughness and fatigue delamination onset for Tenax-HTA/R6376 carbon/toughened epoxy composites. The Mode II interlaminar fracture toughness and fatigue delamination onset were characterized using the end-notched flexure (ENF) test while the Mode III interlaminar fracture toughness and fatigue delamination onset were characterized by using the edge crack torsion (ECT) test. Monotonic tests show that the Mode III fracture toughness is higher than the Mode II fracture toughness. Both Mode II and III cyclic loading greatly increases the tendency for a delamination to grow relative to a single monotonically increasing load. Under fatigue loading, the Mode III specimen also has a longer life than the Mode II specimen.

  7. Design features and results from fatigue reliability research machines.

    Science.gov (United States)

    Lalli, V. R.; Kececioglu, D.; Mcconnell, J. B.

    1971-01-01

    The design, fabrication, development, operation, calibration and results from reversed bending combined with steady torque fatigue research machines are presented. Fifteen-centimeter long, notched, SAE 4340 steel specimens are subjected to various combinations of these stresses and cycled to failure. Failure occurs when the crack in the notch passes through the specimen automatically shutting down the test machine. These cycles-to-failure data are statistically analyzed to develop a probabilistic S-N diagram. These diagrams have many uses; a rotating component design example given in the literature shows that minimum size and weight for a specified number of cycles and reliability can be calculated using these diagrams.

  8. Standard test method for measurement of fatigue crack growth rates

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    1.1 This test method covers the determination of fatigue crack growth rates from near-threshold to Kmax controlled instability. Results are expressed in terms of the crack-tip stress-intensity factor range (ΔK), defined by the theory of linear elasticity. 1.2 Several different test procedures are provided, the optimum test procedure being primarily dependent on the magnitude of the fatigue crack growth rate to be measured. 1.3 Materials that can be tested by this test method are not limited by thickness or by strength so long as specimens are of sufficient thickness to preclude buckling and of sufficient planar size to remain predominantly elastic during testing. 1.4 A range of specimen sizes with proportional planar dimensions is provided, but size is variable to be adjusted for yield strength and applied force. Specimen thickness may be varied independent of planar size. 1.5 The details of the various specimens and test configurations are shown in Annex A1-Annex A3. Specimen configurations other than t...

  9. Research on Fatigue Strain and Fatigue Modulus of Concrete

    Directory of Open Access Journals (Sweden)

    Fangping Liu

    2017-01-01

    Full Text Available Concrete fatigue strain and fatigue modulus evolution play a vital role in the evaluation of the material properties. In this paper, by analyzing the advantages and disadvantages of existing concrete strain analysis methods, the level-S nonlinear fatigue strain model was proposed. The parameters’ physical meaning, the ranges, and the impact on the shape of the curve were all discussed. Then, the evolution model of fatigue modulus was established based on the fatigue strain evolution model and the hypothesis of fatigue modulus inversely related fatigue strain amplitude. The results indicate that the level-S model covered all types of fatigue strain evolution. It is very suitable for the description of strain evolution of concrete for its strong adaptability and high accuracy. It was found that the fitting curves coincided with the experimental curves very well, and the correlation coefficients were all above 0.98. The evolution curves of fatigue strain modulus both have three stages, namely, variation phase, linear change stage, and convergence stage. The difference is that the fatigue strain evolution curve is from the lower left corner to the upper right corner, but the fatigue modulus evolution curve is from the upper left corner to the right lower corner.

  10. The Nature of Fatigue in Chronic Fatigue Syndrome.

    Science.gov (United States)

    Olson, Karin; Zimka, Oksana; Stein, Eleanor

    2015-10-01

    In this article, we report the findings of our study on the nature of fatigue in patients diagnosed with chronic fatigue syndrome. Using ethnoscience as a design, we conducted a series of unstructured interviews and card sorts to learn more about how people with chronic fatigue syndrome describe fatigue. Participants (N = 14) described three distinct domains: tiredness, fatigue, and exhaustion. Most participants experienced tiredness prior to diagnosis, fatigue during daily life, and exhaustion after overexertion. We also discuss participants' ability to adapt to a variety of stressors and prevent shifts to exhaustion, and relate our findings to stress theory and other current research. Primary strategies that promoted adaptation to stressors included pacing and extended rest periods. These findings can aid health care professionals in detecting impending shifts between tiredness, fatigue, and exhaustion and in improving adaptive strategies, thereby improving quality of life. © The Author(s) 2015.

  11. Fatigue approach for addressing environmental effects in fatigue usage calculation

    Energy Technology Data Exchange (ETDEWEB)

    Wilhelm, Paul; Rudolph, Juergen [AREVA GmbH, Erlangen (Germany); Steinmann, Paul [Erlangen-Nuremberg Univ., erlangen (Germany). Chair of Applied Mechanics

    2015-04-15

    Laboratory tests consider simple trapezoidal, triangle, and sinusoidal signals. However, actual plant components are characterized by complex loading patterns and periods of holds. Fatigue tests in water environment show, that the damage from a realistic strain variation or the presence of hold-times within cyclic loading results in an environmental reduction factor (Fen) only half that of a simple waveform. This study proposes a new fatigue approach for addressing environmental effects in fatigue usage calculation for class 1 boiler and pressure vessel reactor components. The currently accepted method of fatigue assessment has been used as a base model and all cycles, which have been comparable with realistic fatigue tests, have been excluded from the code-based fatigue calculation and evaluated directly with the test data. The results presented show that the engineering approach can successfully be integrated in the code-based fatigue assessment. The cumulative usage factor can be reduced considerably.

  12. Adaptations of mouse skeletal muscle to low-intensity vibration training.

    Science.gov (United States)

    McKeehen, James N; Novotny, Susan A; Baltgalvis, Kristen A; Call, Jarrod A; Nuckley, David J; Lowe, Dawn A

    2013-06-01

    We tested the hypothesis that low-intensity vibration training in mice improves contractile function of hindlimb skeletal muscles and promotes exercise-related cellular adaptations. We subjected C57BL/6J mice to 6 wk, 5 d·wk, 15 min·d of sham or low-intensity vibration (45 Hz, 1.0g) while housed in traditional cages (Sham-Active, n = 8; Vibrated-Active, n = 10) or in small cages to restrict physical activity (Sham-Restricted, n = 8; Vibrated-Restricted, n = 8). Contractile function and resistance to fatigue were tested in vivo (anterior and posterior crural muscles) and ex vivo on the soleus muscle. Tibialis anterior and soleus muscles were evaluated histologically for alterations in oxidative metabolism, capillarity, and fiber types. Epididymal fat pad and hindlimb muscle masses were measured. Two-way ANOVAs were used to determine the effects of vibration and physical inactivity. Vibration training resulted in a 10% increase in maximal isometric torque (P = 0.038) and 16% faster maximal rate of relaxation (P = 0.030) of the anterior crural muscles. Posterior crural muscles were unaffected by vibration, except greater rates of contraction in Vibrated-Restricted mice compared with Vibrated-Active and Sham-Restricted mice (P = 0.022). Soleus muscle maximal isometric tetanic force tended to be greater (P = 0.057), and maximal relaxation was 20% faster (P = 0.005) in vibrated compared with sham mice. The restriction of physical activity induced muscle weakness but was not required for vibration to be effective in improving strength or relaxation. Vibration training did not affect muscle fatigability or any indicator of cellular adaptation investigated (P ≥ 0.431). Fat pad but not hindlimb muscle masses were affected by vibration training. Vibration training in mice improved muscle contractility, specifically strength and relaxation rates, with no indication of adverse effects to muscle function or cellular adaptations.

  13. Effect of combining traction and vibration on back muscles, heart rate and blood pressure.

    Science.gov (United States)

    Wang, Lizhen; Zhao, Meiya; Ma, Jian; Tian, Shan; Xiang, Pin; Yao, Wei; Fan, Yubo

    2014-11-01

    Eighty-five percent of the population has experienced low back pain (LBP), which may result in decreasing muscle strength and endurance, functional capacity of the spine, and so on. Traction and vibration are commonly used to relieve the low back pain. The effect of the combing traction and vibration on back muscles, heart rate (HR) and blood pressure (BP) was investigated in this study. Thirty healthy subjects participated in 12 trials lying supine on the spine-combing bed with different tilt angle (0°, 10°, 20° and 30°) and vibration modes (along with the sagittal and coronal axis with 0 Hz, 2 Hz and 12 Hz separately). EMG was recorded during each trial. Power spectral frequency analysis was applied to evaluate muscle fatigue by the shift of median power frequency (MPF). Pulse pressure (PP) was calculated from BP. HR and PP were used to estimate the effect of the combination of traction and vibration on the cardio-vascular system. It was shown that vibration could increase HR and decrease PP. The combination of traction and vibration (2 Hz vibration along Z-axis and 12 Hz vibration along Y-axis) had no significant effect on the cardio-vascular system. The MPF of lumbar erector spinae (LES) and upper trapezius (UT) decreased significantly when the angle reached 20° under the condition of 2 Hz vibration along Z-axis compared with it of 0°. Furthermore, the MPF also decreased significantly compared with it of static mode at 20° for LES and at 30° for UT. However at 12 Hz vibration along Y-axis, the MPF had significant increase when the angle reached 20° in LES and 30° in UT compared to 0°. For LES, the MPF also had significant difference when the angle was increased from 10° to 20°. Therefore, combining 2 Hz vibration along Z-axis and traction (tilt angles that less than 20°) may to reduce muscle fatigue both for LES and UT compared with either vibration or traction alone. The combination of 12 Hz vibration along Y-axis and traction (tilt angles

  14. Fatigue in Multidirectional Composites

    Science.gov (United States)

    Ramani, S. V.; Williams, D. P.

    1982-01-01

    Data in new report on fatique properties of graphite/epoxy composites prove valuable to designers of aircraft, space vehicles, and automobiles. Graphite/epoxy composites are being used increasingly in lightweight load-bearing structures, and fatigue of such structures is always major concern of designers.

  15. Control of Fretting Fatigue

    Science.gov (United States)

    1977-07-01

    Effect of Room Temperature Pre-Strain on Grain Boundary Cavitation in Nimonic 80A," J. Microscopy, 97, pp. 165-170, 1973. 48. Eden, E. M., W. N. Rose...Academic Press, New York, 1971. ♦ 115 . Milestone, W. D., An Investigation of the Basic Mechanisms of Mechanical Fretting and Fretting-Fatigue at

  16. Incompatibility and Mental Fatigue

    Science.gov (United States)

    Herzog, Thomas R.; Hayes, Lauren J.; Applin, Rebecca C.; Weatherly, Anna M.

    2011-01-01

    A straightforward prediction from attention restoration theory is that the level of incompatibility in a person's life should be positively correlated with that person's level of mental (or directed attention) fatigue. The authors tested this prediction by developing a new self-report measure of incompatibility in which they attempted to isolate…

  17. Fatigue 󈨛. Volume 1,

    Science.gov (United States)

    1987-06-01

    are constants in the cyclic Ramberg Osgood represen- tation of material stress-strain curve as in (14), Po is the re- ference load of EPRI limit load...MPa) ci, n = Ramberg -Osgood’s coefficient and strain exponent = Strain rate (s - 1) Tend = Fatigue endurance limit (MPa) &LtdlD = Total and plastic

  18. Caffeine, fatigue, and cognition

    NARCIS (Netherlands)

    Lorist, M.M.; Tops, M.

    2003-01-01

    Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support

  19. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Committee for Science and Education, Medical. Association of South Africa. Objective. To acknowledge the dinical syndrome chronic fatigue syndrome (CFS) and outline the diagnostic criteria and reasonable management. Outcomes. Attempt at containment of treatmentcost and improvement of the quality of care of patients ...

  20. Chronic fatigue syndrome

    African Journals Online (AJOL)

    Unexplained generalised muscle weakness. 5. Muscle discomfort or myalgia. 6. Prolonged (24 hours or more) generalised fatigue after levels of exercise that would have been tolerated easily in the patient's premorbid state. "7. Generalised headaches (or a type, severity or pattern different from headaches in the premorbid ...

  1. Device Design and Test of Fatigue Behaviour of Expansion Anchor Subjected to Tensile Loads

    Directory of Open Access Journals (Sweden)

    Zhang Jinfeng

    2016-01-01

    Full Text Available In order to study on the fatigue behaviour of expansion anchor (M16, grade 8.8 for overhead contact system in electrification railways, a set of safe, practical loading device is designed and a fatigue test campaign was carried out at structural laboratory of China Academy of Building Research on expansion anchor embedded in concrete block. The mobile frame of the loading device was designed well by finite-element simulation. According to some fatigue performance test of expansion anchor with different size and form, the device have been assessed experimentally its dependability. The results were found that no fatigue damage phenomenon occurred in all specimens after 2×106 cycles tensile fatigue test in this specific series. It shows that in the condition of medium level or slightly lower maximum stress limit and nominal stress range, expansion bolt has good fatigue resistance. The biggest relative displacement and the residual relative displacement after test (Δδ = δ2-δ1 was also strongly lower than the symbol of the fatigue test failure index of this specific series (0.5mm in the high cycle fatigue regime. The ultimate tension failures mode after fatigue tests in all tested samples take place in the concrete anchorage zone. The reduction range of the ultimate tensile strength properties of the anchorage system was not obvious, and the concrete was seen to be the weakest link of the system.

  2. Fatigue Life Prediction of High Modulus Asphalt Concrete Based on the Local Stress-Strain Method

    Directory of Open Access Journals (Sweden)

    Mulian Zheng

    2017-03-01

    Full Text Available Previously published studies have proposed fatigue life prediction models for dense graded asphalt pavement based on flexural fatigue test. This study focused on the fatigue life prediction of High Modulus Asphalt Concrete (HMAC pavement using the local strain-stress method and direct tension fatigue test. First, the direct tension fatigue test at various strain levels was conducted on HMAC prism samples cut from plate specimens. Afterwards, their true stress-strain loop curves were obtained and modified to develop the strain-fatigue life equation. Then the nominal strain of HMAC course determined using finite element method was converted into local strain using the Neuber method. Finally, based on the established fatigue equation and converted local strain, a method to predict the pavement fatigue crack initiation life was proposed and the fatigue life of a typical HMAC overlay pavement which runs a risk of bottom-up cracking was predicted and validated. Results show that the proposed method was able to produce satisfactory crack initiation life.

  3. Are nurses able to assess fatigue, exertion fatigue and types of fatigue in residential home patients?

    NARCIS (Netherlands)

    Tiesinga, L.J.; Dijkstra, Ate; Dassen, T.W.N.; Halfens, R.J.G.; van den Heuvel, W.J.A.

    Although fatigue is recognized as a subjective, generalized, extensive and disabling health care problem with a relatively high prevalence among the chronically ill, there have been no studies to show whether nurses caring for fatigued subjects are able to accurately assess the level of fatigue that

  4. Multi-parameter approximation of stress field in a cracked specimen using purpose-built Java applications

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sopek, J.; Tesař, D.; Frantík, P.; Pail, T.; Seitl, Stanislav

    2015-01-01

    Roč. 9, č. 33 (2015), s. 120-133 ISSN 1971-8993 Institutional support: RVO:68081723 Keywords : Cracked specimen * Near-crack-tip fields * Williams expansion * Higher order terms * Stress field reconstruction * Finite element analysis * Java application Subject RIV: JL - Materials Fatigue, Friction Mechanics

  5. Standard test method for creep-fatigue crack growth testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This test method covers the determination of creep-fatigue crack growth properties of nominally homogeneous materials by use of pre-cracked compact type, C(T), test specimens subjected to uniaxial cyclic forces. It concerns fatigue cycling with sufficiently long loading/unloading rates or hold-times, or both, to cause creep deformation at the crack tip and the creep deformation be responsible for enhanced crack growth per loading cycle. It is intended as a guide for creep-fatigue testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. Therefore, this method requires testing of at least two specimens that yield overlapping crack growth rate data. The cyclic conditions responsible for creep-fatigue deformation and enhanced crack growth vary with material and with temperature for a given material. The effects of environment such as time-dependent oxidation in enhancing the crack growth ra...

  6. The Effect of Hole Quality on the Fatigue Life of 2024-T3 Aluminum Alloy Sheet

    Science.gov (United States)

    Everett, Richard A., Jr.

    2004-01-01

    This paper presents the results of a study whose main objective was to determine which type of fabrication process would least affect the fatigue life of an open-hole structural detail. Since the open-hole detail is often the fundamental building block for determining the stress concentration of built-up structural parts, it is important to understand any factor that can affect the fatigue life of an open hole. A test program of constant-amplitude fatigue tests was conducted on five different sets of test specimens each made using a different hole fabrication process. Three of the sets used different mechanical drilling procedures while a fourth and fifth set were mechanically drilled and then chemically polished. Two sets of specimens were also tested under spectrum loading to aid in understanding the effects of residual compressive stresses on fatigue life. Three conclusions were made from this study. One, the residual compressive stresses caused by the hole-drilling process increased the fatigue life by two to three times over specimens that were chemically polished after the holes were drilled. Second, the chemical polishing process does not appear to adversely affect the fatigue life. Third, the chemical polishing process will produce a stress-state adjacent to the hole that has insignificant machining residual stresses.

  7. Microstructure, Fatigue Behavior, and Failure Mechanisms of Direct Laser-Deposited Inconel 718

    Science.gov (United States)

    Johnson, Alex S.; Shao, Shuai; Shamsaei, Nima; Thompson, Scott M.; Bian, Linkan

    2017-03-01

    Inconel 718 is considered to be a superalloy with a series of superior properties such as high strength, creep resistance, and corrosion resistance at room and elevated temperatures. Additive manufacturing (AM) is particularly appealing to Inconel 718 because of its near-net-shape production capability for circumventing the poor machinability of this superalloy. Nevertheless, AM parts are prone to porosity, which is detrimental to their fatigue resistance. Thus, further understanding of their fatigue behavior is required before their widespread use in load-bearing applications. In this work, the microstructure and fatigue properties of AM Inconel 718, produced in a Laser Engineered Net Shaping (LENS™) system and heat treated with a standard heat treatment schedule, are evaluated at room temperature. Fully reversed strain controlled fatigue tests were performed on cylindrical specimens with straight gage sections at strain amplitudes ranging from 0.001 mm/mm to 0.01 mm/mm. The fracture surfaces of fatigue specimens were inspected with a scanning electron microscope. The results indicate that the employed heat treatment allowed the large, elongated grains and dendritic structure of the as-built material to break down into smaller, equiaxed grains, with some dendritic structures remaining between layers. The AM specimens were found to possess lower fatigue resistance than wrought Inconel 718, and this is primarily attributed to the presence of brittle metal-carbide/oxide inclusions or pores near their surface.

  8. The influence of cyclic shear fatigue on the bracket-adhesive-enamel complex: an in vitro study.

    Science.gov (United States)

    Daratsianos, Nikolaos; Musabegovic, Ena; Reimann, Susanne; Grüner, Manfred; Jäger, Andreas; Bourauel, Christoph

    2013-05-01

    To describe the effect of fatigue on the strength of the bracket-adhesive-enamel complex and characterize the fatigue behavior of the materials tested. Upper central incisor brackets (Discovery(®), Dentaurum) were bonded with a light-curing (Transbond XT™, 3M Unitek) and a chemically-curing adhesive (Concise™, 3M Unitek) on bovine teeth embedded in cylindrical resign bases and stored in water at 37(±2)°C for 24 (±2)h. The first 15 specimens were tested with a universal testing machine ZMART.PRO(®) (Zwick GmbH & Co. KG, Ulm, Germany) for ultimate shear bond strength according to the DIN-13990-2-standard. The remaining three groups of 20 specimens underwent fatigue staircase testing of 100, 1000 and 3000 cycles at 1Hz with a self-made testing machine. The survived specimens were subjected to shear strength testing. The fatigued specimens showed decreased shear strength with both adhesives at all cycle levels. The shear strength after fatigue for 100, 1000 and 3000 cycles was in the Concise™-groups 34.8%, 59.0%, 47.3% and in the Transbond™ XT-groups 33.6%, 23.1%, 27.3% relative to the ultimate shear strength. The fatigue life of the Concise™-groups decreased with increasing stress and Transbond™ XT showed lower fatigue ratio with no obvious trend. The specimens bonded with Transbond™ XT showed typically favorable fracture modes in contrary to Concise™. Fatigue of the bracket-adhesive-enamel complex decreased its shear strength. The staircase method can provide a standardized experimental protocol for fatigue studies, however testing at various cycle numbers is recommended. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Muscle Deoxygenation Causes Muscle Fatigue

    Science.gov (United States)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D.

    1999-01-01

    Muscle fatigue is a common musculoskeletal disorder in the work place, and may be a harbinger for more disabling cumulative trauma disorders. Although the cause of fatigue is multifactorial, reduced blood flow and muscle oxygenation may be the primary factor in causing muscle fatigue during low intensity muscle exertion. Muscle fatigue is defined as a reduction in muscle force production, and also occurs among astronauts who are subjected to postural constraints while performing lengthy, repetitive tasks. The objectives of this research are to: 1) develop an objective tool to study the role of decreased muscle oxygenation on muscle force production, and 2) to evaluate muscle fatigue during prolonged glovebox work.

  10. Prediction of three-dimensional crack propagation paths taking high cycle fatigue into account

    Directory of Open Access Journals (Sweden)

    Guido Dhondt

    2016-01-01

    Full Text Available Engine components are usually subject to complex loading patterns such as mixed-mode Low Cycle Fatigue Loading due to maneuvering. In practice, this LCF Loading has to be superimposed by High Cyclic Fatigue Loading caused by vibrations. The changes brought along by HCF are twofold: first, the vibrational cycles which are superposed on the LCF mission increase the maximum loading of the mission and may alter the principal stress planes. Secondly, the HCF cycles themselves have to be evaluated on their own, assuring that no crack propagation occurs. Indeed, the vibrational frequency is usually so high that propagation leads to immediate failure. In the present paper it is explained how these two effects can be taken care of in a standard LCF crack propagation procedure. The method is illustrated by applying the Finite Element based crack propagation software CRACKTRACER3D on an engine blade.

  11. Structural Stability and Vibration

    DEFF Research Database (Denmark)

    Wiggers, Sine Leergaard; Pedersen, Pauli

    This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni......This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

  12. Comparative Study of Fatigue Damage Models Using Different Number of Classes Combined with the Rainflow Method

    Directory of Open Access Journals (Sweden)

    S. Zengah

    2013-06-01

    Full Text Available Fatigue damage increases with applied load cycles in a cumulative manner. Fatigue damage models play a key role in life prediction of components and structures subjected to random loading. The aim of this paper is the examination of the performance of the “Damaged Stress Model”, proposed and validated, against other fatigue models under random loading before and after reconstruction of the load histories. To achieve this objective, some linear and nonlinear models proposed for fatigue life estimation and a batch of specimens made of 6082T6 aluminum alloy is subjected to random loading. The damage was cumulated by Miner’s rule, Damaged Stress Model (DSM, Henry model and Unified Theory (UT and random cycles were counted with a rain-flow algorithm. Experimental data on high-cycle fatigue by complex loading histories with different mean and amplitude stress values are analyzed for life calculation and model predictions are compared.

  13. Numerical Study of Structural Vibration Induced by Combustion Noise - One Way Interaction

    NARCIS (Netherlands)

    Pozarlik, Artur Krzysztof; Kok, Jacobus B.W.

    2007-01-01

    The turbulent flame in the lean combustion regime in a gas turbine combustor generates significant thermo-acoustic noise. The thermo-acoustic noise induces liner vibrations that may lead to fatigue damage of the combustion system. This phenomenon is investigated in the project FLUISTCOM using both

  14. Comparison of load-fatigue testing of ceramic veneers with two different preparation designs.

    Science.gov (United States)

    Chaiyabutr, Yada; Phillips, Keith M; Ma, Polly S; Chitswe, Kinsey

    2009-01-01

    The concept of tooth preparation for ceramic veneers remains controversial regarding whether the use of a palatal chamfer would affect the longevity of restorations. This study aimed to evaluate the load-fatigue testing of ceramic veneers using two different preparation designs-an incisal shoulder finish line with or without a palatal chamfer. A pressable ceramic veneer was bonded to the prepared maxillary central incisor using resin cement. The number of cycles until fatigue failure for each tooth-veneer specimen was recorded. Results revealed that using a palatal chamfer margin design significantly increased the fatigue failure cycle count.

  15. Fatigue and Fracture Characterization of HPDC AM6OB Magnesium Alloy at Cold Temperature

    Science.gov (United States)

    Nur Hossain, Md.; Taheri, Farid

    2011-12-01

    An investigation of the fatigue and fracture characterization of the high pressure die cast (HPDC) AM60B magnesium alloy at -40 °C temperature was conducted by means of the constant load amplitude fatigue test. The results demonstrated that low temperature had a significant influence on alloy's fatigue life; the life increased at -40 °C temperature as compared to that at room temperature. The fracture surfaces of the tested specimens were observed under a scanning electron microscope (SEM) to further understand the fracture phenomenon at low temperature.

  16. The Effect of the Free Surface on the Singular Stress Field at the Fatigue Crack Front

    Directory of Open Access Journals (Sweden)

    Oplt Tomáš

    2017-11-01

    Full Text Available Description of stress singularity in the vicinity of a free surface is presented. Its presence causes the retardation of the fatigue crack growth in that region and fatigue crack is being curved. Numerical model is used to study dependence of the stress singularity exponent on Poisson’s ratio. Estimated values are compared to those already published. Experimentally measured angles of fatigue crack on SENB specimens confirm the relation between Poisson’s ratio and the angle between crack front and free surface.

  17. A study on the fatigue strength characteristics of ship structural steel with gusset welds

    Directory of Open Access Journals (Sweden)

    Sung-Jo Park

    2012-06-01

    Full Text Available This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.

  18. A study on the fatigue strength characteristics of ship structural steel with gusset welds

    Science.gov (United States)

    Park, Sung-Jo; Lee, Hyun-Woo

    2012-06-01

    This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.

  19. Fracture resistance of Zr-Nb alloys under low-cycle fatigue tests

    Science.gov (United States)

    Nikulin, S. A.; Rozhnov, A. B.; Gusev, A. Yu.; Nechaykina, T. A.; Rogachev, S. O.; Zadorozhnyy, M. Yu.

    2014-03-01

    Comparative low-cycle fatigue tests of small-scale specimens cut from the cladding tubes of E110, E125, E110opt zirconium alloys at temperatures of 25 and 350 °C using a dynamic mechanical analyzer have been carried out. It is shown that the limited cycles fatigue stress for all alloys is 50% less at temperature of 350 °C comparing to 25 °C. Besides it has been revealed that the limited cycles fatigue stress increases with increasing the strength of zirconium alloy.

  20. Determinants of fatigue and stress

    Directory of Open Access Journals (Sweden)

    Brähler Elmar

    2011-07-01

    Full Text Available Abstract Background Fatigue can be triggered by previous perceived stress which may lead to impairment of performance and function. The purpose of the study was to investigate the relationship between fatigue and perceived stress. Method Health determinants including sociodemographic factors for associations between fatigue and perceived stress in the general population (N = 2,483 are outlined. Fatigue and stress were assessed with the Chalder Fatigue Scale (CFS and the Perceived Stress Questionnaire (PSQ. Results Within the general population, 25.9% of male and 34.5% of female respondents reported moderate fatigue during the last six months; 9.7% of subjects reported substantial fatigue lasting six months or longer. An adjusted regression analysis (R2corr = .28, p Conclusion We conclude that the two conditions overlap most in terms of socio-economic status and self-perceived health status.