WorldWideScience

Sample records for replica-based crack inspection

  1. A Parametric Study of Crack Propagation During Sonic IR Inspection

    Science.gov (United States)

    Chen, J. C.; Kephart, J.; Riddell, W. T.

    2006-03-01

    We have developed an experiment to study the propagation of synthetic cracks under various controlled conditions during sonic IR inspection. The experiment provides for good repeatability in testing. The parameters of interest include the initial crack length, load history (stress intensity and load ratio) during crack generation, geometry of the crack, material, and also the various conditions involving the ultrasonic source. In general, we find that under typical sonic IR inspection conditions, the initial crack will propagate when subjected to sonic IR testing. The crack growth after each inspection event varies and exhibits a distribution in length of propagation. The results show that the average crack propagation decreases with increasing initial crack length and increasing stress intensity.

  2. In Situ Inspection of Fasteners for Detecting Small Cracks

    Energy Technology Data Exchange (ETDEWEB)

    Good, Morris S.; Harris, Robert V.; Skorpik, James R.; Pardini, Allan F.; Smith, Christopher M.; Bowey, Robert E.; Adamson, Justus D.

    2000-01-01

    An in-situ bolting and fastener inspection system has been developed by PNNL under funding from the Department of Energy. The inspection system utilizes an ultrasonic pulse-echo technique to detect very small cracks emanating from the thread root. The primary benefits are the ability to inspect the fastener without its removal, much improved detection sensitivity to small cracks and the intuitive interpretation of the acquired images.

  3. CIRCUMFERENTIAL MFL IN-LINE INSPECTION FOR CRACKS IN PIPELINES

    Energy Technology Data Exchange (ETDEWEB)

    J.B. Nestleroth

    2003-06-01

    Circumferential MFL is a new implementation of a widely used technology that has potential to provide improved detection and quantification of axially oriented defects such as cracks, seam weld defects, mechanical damage, and groove corrosion. This implementation works by orienting the magnetic field around the pipe rather that along the axis. By orienting the magnetic field around the pipe (the circumferential direction), the axial defects that were magnetically transparent can disrupt more of the magnetic field and can be more easily detected. Initial implementations of circumferential MFL have found that flux leakage from cracks at the interior of the pipe is small, and the signals from cracks are difficult to detect. The objective of this project is to improve detection of cracks by changing the implementation along with using data from overlapping and complementary inspection techniques. Two technology enhancements were investigated: Combining high- and low-magnetization technology for stress detection; and Combining axial and circumferential MFL methods. Although a method combining high- and low-magnetization technology showed promise for characterizing gouges cause by third party excavation equipment, its commercial development was not successful for two reasons. First, the stress diminishes the crack signal, while the opening of the crack increases the signal. The stress-induced changes in flux leakage around cracks were small and any critical information on the severity of cracks and crack-like defects is difficult to distinguish from changes caused by the crack opening and other inspection variables. Second, it is difficult to magnetize pipe material in the circumferential direction. A relatively low, non-uniform magnetization level produced by the circumferential magnetizer makes detection of changes due to stress extremely difficult. This project also examined combining axial and circumferential MFL to improve crack detection and distinguish cracks for

  4. Electromagnetic pulsed thermography for natural cracks inspection

    Science.gov (United States)

    Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing

    2017-02-01

    Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF).

  5. Electromagnetic pulsed thermography for natural cracks inspection

    Science.gov (United States)

    Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing

    2017-01-01

    Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF). PMID:28169361

  6. Ultrasonic inspection reliability for intergranular stress corrosion cracks

    Energy Technology Data Exchange (ETDEWEB)

    Heasler, P G; Taylor, T T; Spanner, J C; Doctor, S R; Deffenbaugh, J D [Pacific Northwest Lab., Richland, WA (USA)

    1990-07-01

    A pipe inspection round robin entitled Mini-Round Robin'' was conducted at Pacific Northwest Laboratory from May 1985 through October 1985. The research was sponsored by the US Nuclear Regulatory Commission, Office of Nuclear Regulatory Research under a program entitled Evaluation and Improvement of NDE Reliability for Inservice Inspection of Light Water Reactors.'' The Mini-Round Robin (MRR) measured the intergranular stress corrosion (GSC) crack detection and sizing capabilities of inservice inspection (ISI) inspectors that had passed the requirements of IEB 83-02 and the Electric Power Research Institute (EPRI) sizing training course. The MRR data base was compared with an earlier Pipe Inspection Round Robin (PIRR) that had measured the performance of inservice inspection prior to 1982. Comparison of the MRR and PIRR data bases indicates no significant change in the inspection capability for detecting IGSCC. Also, when comparing detection of long and short cracks, no difference in detection capability was measured. An improvement in the ability to differentiate between shallow and deeper IGSCC was found when the MRR sizing capability was compared with an earlier sizing round robin conducted by the EPRI. In addition to the pipe inspection round robin, a human factors study was conducted in conjunction with the Mini-Round Robin. The most important result of the human factors study is that the Relative Operating Characteristics (ROC) curves provide a better methodology for describing inspector performance than only probability of detection (POD) or single-point crack/no crack data. 6 refs., 55 figs., 18 tabs.

  7. On the approximation of crack shapes found during inservice inspection

    Energy Technology Data Exchange (ETDEWEB)

    Bhate, S.R.; Chawla, D.S.; Kushwaha, H.S. [Bhabha Atomic Research Centre, Bombay (India)] [and others

    1997-04-01

    This paper addresses the characterization of axial internal flaw found during inservice inspection of a pipe. J-integral distribution for various flaw shapes is obtained using line spring finite, element method. The peak J-value and its distribution across the crack is found to be characteristic feature of each shape. The triangular shape yields peak J-value away from the center, the point of depth. The elliptic approximation results in large overestimate of J-value for unsymmetric flaws. Triangular approximation is recommended for such flaws so that further service can be obtained from the component.

  8. Crack Characterisation for In-service Inspection Planning - An Update

    Energy Technology Data Exchange (ETDEWEB)

    Waale, Jan [lnspecta Technology AB, Stockholm (Sweden)

    2006-05-15

    One important factor to optimize the NDT equipment and NDT procedure is to know the characteristics of the specific defects being sought for in each case. Thus, access is necessary to reliable morphology data of defects from all possible degradation mechanisms in all existing materials of the components that are subject to the NDT. In 1994 the Swedish Nuclear Power Inspectorate (SKI) initiated a project for compiling crack morphology data based on systematic studies of cracks that have been observed in different plants (nuclear and non-nuclear) in order to determine typical as well as more extreme values of e.g. orientation, width and surface roughness. Although, a large number of identified cracking incidents was covered by the work it was recognised that further studies were needed to increase the data base, and thereby getting more confidence in the use of different crack characteristic data for NDT development and qualification purposes. That is the major reason why the present work was initiated. A thorough review of the SKI archives was performed aiming to find useful material from the time period between 1994 and today to compile complementary data and produce an update. Furthermore, older material was collected and evaluated. Thus, the data cover cracking found within the time period 1977-2003. In addition, useful material was supplied by the Swedish nuclear power plants. The evaluation and presentation of the results are similar to the 1994 study, with a few exceptions. The base for the evaluation is failure analysis reports, where the crack morphology parameters were measured from photos on cracked surfaces or cross sections through cracks. The resulting data were divided into seven groups depending on the cracking mechanism/material group combination. The data groups are: IGSCC in austenitic stainless steels; IGSCC in nickel base alloys; IDSCC in nickel base weld metal; TGSCC in austenitic stainless steels Thermal fatigue in austenitic stainless steels

  9. Optimization of ultrasonic array inspections using an efficient hybrid model and real crack shapes

    Energy Technology Data Exchange (ETDEWEB)

    Felice, Maria V., E-mail: maria.felice@bristol.ac.uk [Department of Mechanical Engineering, University of Bristol, Bristol, U.K. and NDE Laboratory, Rolls-Royce plc., Bristol (United Kingdom); Velichko, Alexander, E-mail: p.wilcox@bristol.ac.uk; Wilcox, Paul D., E-mail: p.wilcox@bristol.ac.uk [Department of Mechanical Engineering, University of Bristol, Bristol (United Kingdom); Barden, Tim; Dunhill, Tony [NDE Laboratory, Rolls-Royce plc., Bristol (United Kingdom)

    2015-03-31

    Models which simulate the interaction of ultrasound with cracks can be used to optimize ultrasonic array inspections, but this approach can be time-consuming. To overcome this issue an efficient hybrid model is implemented which includes a finite element method that requires only a single layer of elements around the crack shape. Scattering Matrices are used to capture the scattering behavior of the individual cracks and a discussion on the angular degrees of freedom of elastodynamic scatterers is included. Real crack shapes are obtained from X-ray Computed Tomography images of cracked parts and these shapes are inputted into the hybrid model. The effect of using real crack shapes instead of straight notch shapes is demonstrated. An array optimization methodology which incorporates the hybrid model, an approximate single-scattering relative noise model and the real crack shapes is then described.

  10. Investigation of ultrasonic phased array inspection of a planar crack using finite element method

    OpenAIRE

    Mardani Kharat, Mostafa; Sodagar,Sina; Rashed, G. R.

    2012-01-01

    International audience; The characteristics of the ultrasonic field radiated by a linear phased array transducer and the echo information of the inspected area are the main basis of designing a phased array inspection system. In this paper, a theoretical investigation is accomplished on the ultrasonic wave diffraction using the ultrasonic phased array method for evaluation of the planar cracks. For this purpose, the ultrasonic wave field resulting from a phased array transducer and its intera...

  11. Study of methods for automated crack inspection of electrically poled piezoelectric ceramics.

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Pin; Hwang, Stephen C.; Jokiel, Bernhard, Jr.; Burns, George Robert

    2004-06-01

    The goal of this project was to identify a viable, non-destructive methodology for the detection of cracks in electrically poled piezoelectric ceramics used in neutron generator power supply units. The following methods were investigated: Impedance Spectroscopy, Scanning Acoustic Microscopy, Lock-in Thermography, Photo-acoustic Microscopy, and Scanned Vicinal Light. In addition to the exploration of these techniques for crack detection, special consideration was given to the feasibility of integrating these approaches to the Automatic Visual Inspection System (AVIS) that was developed for mapping defects such as chips, pits and voids in piezoelectric ceramic components. Scanned Vicinal Light was shown to be the most effective method of automatically detecting and quantifying cracks in ceramic components. This method is also very effective for crack detection in other translucent ceramics.

  12. Ultrasonic Phased Array Inspection for an Isogrid Structural Element with Cracks

    Science.gov (United States)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.; Schumacher, E. J.

    2010-01-01

    In this investigation, a T-shaped aluminum alloy isogrid stiffener element used in aerospace applications was inspected with ultrasonic phased array methods. The isogrid stiffener element had various crack configurations emanating from bolt holes. Computational simulation methods were used to mimic the experiments in order to help understand experimental results. The results of this study indicate that it is at least partly feasible to interrogate this type of geometry with the given flaw configurations using phased array ultrasonics. The simulation methods were critical in helping explain the experimental results and, with some limitation, can be used to predict inspection results.

  13. Aircraft corrosion and crack inspection using advanced magneto-optic imaging technology

    Science.gov (United States)

    Thome, David K.; Fitzpatrick, Gerald L.; Skaugset, Richard L.; Shih, William C.

    1996-11-01

    A next generation magneto-optic imaging system, the MOI 303, has recently been introduced with the ability to generate real-time, complete, 2D eddy current images of cracks and corrosion in aircraft. The new imaging system described features advanced, digital remote control operation and on- screen display of setup parameters for ease of use. This instrument gives the inspector the capability to more rapidly scan large surfaces areas. The magneto-optic/eddy current imaging technology has already been formally approved for inspection of surface cracking on an aircraft fuselage. The improved magneto-optic imager is now poised to aid rapid inspection for corrosion and subsurface cracking. Previous magneto-optic imaging systems required the inspector to scan the surface twice for complete inspection coverage: a second scan was necessary with the imager rotated about 90 degrees from the orientation of the first pass. However, by providing eddy current excitation simultaneously from two orthogonal directions, complete, filled-in magneto-optic images are now generated regardless of the orientation of the imager. THese images are considerably easier to interpret and evaluate. In addition, there is a synergism obtained in applying eddy current excitation simultaneously in multiple directions: better penetration is obtained and the resulting images have better signal to noise levels compared to those produced with eddy current excitation applied only in one direction. Examples of these improved images are presented.

  14. POD generator project: a numerical assessment of the inspection of fatigue cracks using TOFD

    NARCIS (Netherlands)

    Bloom, J.G.P.; Stelwagen, U.; Mast, A.; Volker, A.W.F.

    2009-01-01

    Risk based inspection strategies rely on detailed knowledge of the performance of inspection techniques. The objective of the "POD generator" project is to develop a numerical modeling approach to assess the effectiveness of specific inspection techniques. Simulation offers flexibility and reliabili

  15. Comparison of the Inspections of Smooth and Rough Crack-Like Defects Using Ultrasonic Arrays

    Science.gov (United States)

    Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.

    2011-06-01

    The use of ultrasonic arrays to detect crack-like defects is an important area in nondestructive evaluation. The array data, which contains scattered ultrasonic waves from a scatterer, can be used to reconstruct a high resolution image, e.g., using the total focusing method (TFM). In this paper, the TFM images from smooth and rough crack-like defects are compared. It is shown that roughness can be either beneficial or detrimental to the detectability of crack-like defects.

  16. Characterization of Delaminations and Transverse Matrix Cracks in Composite Laminates Using Multiple-Angle Ultrasonic Inspection

    Science.gov (United States)

    Johnston, Patrick H.; Appleget, Chelsea D.; Odarczenko, Michael T.

    2012-01-01

    Delaminations and transverse matrix cracks often appear concurrently in composite laminates. Normal-incidence ultrasound is excellent at detecting delaminations, but is not optimum for matrix cracks. Non-normal incidence, or polar backscattering, has been shown to optimally detect matrix cracks oriented perpendicular to the ultrasonic plane of incidence. In this work, a series of six composite laminates containing slots were loaded in tension to achieve various levels of delamination and ply cracking. Ultrasonic backscattering was measured over a range of incident polar and azimuthal angles, in order to characterize the relative degree of damage of the two types. Sweptpolar- angle measurements were taken with a curved phased array, as a step toward an array-based approach to simultaneous measurement of combined flaws.

  17. DEVELOPMENT OF AN EMAT IN-LINE INSPECTION SYSTEM FOR DETECTION, DISCRIMINATION, AND GRADING OF STRESS CORROSION CRACKING IN PIPELINES

    Energy Technology Data Exchange (ETDEWEB)

    Jeff Aron; Jon Gore, Roger Dalton; Stuart Eaton; Adrian Bowles; Owen Thomas; Tim Jarman

    2003-07-01

    This report describes progress, experiments, and results for a project to develop a pipeline inline inspection tool that uses electromagnetic acoustic transducers (EMATs) to detect and grade stress corrosion cracking (SCC). There is a brief introduction that gives background material about EMATs and relevant previous Tuboscope work toward a tool. This work left various choices about the modes and transducers for this project. The experimental section then describes the lab systems, improvements to these systems, and setups and techniques to narrow the choices. Improvements, which involved transducer matching networks, better magnetic biasing, and lower noise electronics, led to improved signal to noise (SNR) levels. The setups permitted transducer characterizations and interaction measurements in plates with man-made cracks, pipeline sections with SCC, and a full pipe with SCC. The latter were done with a moveable and compact EMAT setup, called a lab mouse, which is detailed. Next, the results section justifies the mode and transducer choices. These were for magnetostrictive EMATs and the use of EMAT launched modes: SH0 (at 2.1 MHz-mm) and SV1 (at 3.9 MHz-mm). This section then gives details of measurements on these modes. The measurements consisted of signal to noise ratio, insertion loss, magnetic biasing sensitivities crack reflection and transmission coefficients, beam width, standoff and tilt sensitivities. For most of the measurements the section presents analysis curves, such as reflection coefficient versus crack depth. Some notable results for the chosen modes are: that acceptable SNRs were generated in a pipe with magnetostrictive EMATs, that optimum bias for magnetostrictive transmitters and receivers is magnetic saturation, that crack reflection and transmission coefficients from crack interactions agree with 2 D simulations and seem workable for crack grading, and that the mouse has good waveform quality and so is ready for exhaustive measurement EMAT

  18. FAILURE ANALYSIS AND INSPECTION OF CRACKING OF IN-SERVICE CATALYTIC REGENERATOR

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The special subject"research on life prediction technology of important in-service pressure vessels" mainly analyzes the failure mechanism of large-sized important and critical in-service pressure vessels under the action of working medium and investigates safety assessment and life prediction technology with a view to enhance the operation reliability of in-service pressure vessels in China. Based on a series of accident investigation and test & measuring research, the cause of cracking of catalytic regenerator is analyzed and the in-line non-destructive examination method and failure prevention measures for the cracking of catalytic regenerator are proposed.

  19. Root crack sizing using phased array inspections and autoregressive spectral extrapolation signal processing

    Science.gov (United States)

    Caldwell, J.; Shakibi, B.; Moles, M.; Sinclair, A. N.

    2013-01-01

    Phased array inspection was conducted on a V-butt welded steel sample with multiple shallow flaws of varying depths. The inspection measurements were processed using Wiener filtering and Autoregressive Spectral Extrapolation (AS) to enhance the signals. Phased array inspections were conducted using multiple phased array probes of varying nominal central frequencies (2.25, 4, 5 and 10 MHz). This paper describes the measured results, which show high accuracy, typically in the range of 0.1-0.2 mm. The results concluded that: 1. There was no statistical difference between the calculated flaw depths from phased array inspections at different flaw tip angles. 2. There was no statistical difference in flaw depths calculated using phased array data collected from either side of the weld. 3. Flaws with depths less than the estimated probe signal shear wavelength could not be sized. 4. Finally, there was no statistical difference in the calculated flaw depths using phased array probes with different sampling frequencies and destructive measurements of the flaws.

  20. DEVELOPMENT OF AN EMAT IN-LINE INSPECTION SYSTEM FOR DETECTION, DISCRIMINATION, AND GRADING OF STRESS CORROSION CRACKING IN PIPELINES

    Energy Technology Data Exchange (ETDEWEB)

    Jeff Aron; Jeff Jia; Bruce Vance; Wen Chang; Raymond Pohler; Jon Gore; Stuart Eaton; Adrian Bowles; Tim Jarman

    2005-02-01

    This report describes prototypes, measurements, and results for a project to develop a prototype pipeline in-line inspection (ILI) tool that uses electromagnetic acoustic transducers (EMATs) to detect and grade stress corrosion cracking (SCC). The introduction briefly provides motivation and describes SCC, gives some background on EMATs and guided ultrasonic waves, and reviews promising results of a previous project using EMATs for SCC. The experimental section then describes lab measurement techniques and equipment, the lab mouse and prototypes for a mule, and scan measurements made on SCC. The mouse was a moveable and compact EMAT setup. The prototypes were even more compact circuits intended to be pulled or used in an ILI tool. The purpose of the measurements was to determine the best modes, transduction, and processing to use, to characterize the transducers, and to prove EMATs and mule components could produce useful results. Next, the results section summarizes the measurements and describes the mouse scans, processing, prototype circuit operating parameters, and performance for SH0 scans. Results are given in terms of specifications--like SNR, power, insertion loss--and parametric curves--such as signal amplitude versus magnetic bias or standoff, reflection or transmission coefficients versus crack depth. Initially, lab results indicated magnetostrictive transducers using both SH0 and SV1 modes would be worthwhile to pursue in a practical ILI system. However, work with mule components showed that SV1 would be too dispersive, so SV1 was abandoned. The results showed that reflection measurements, when normalized by the direct arrival are sensitive to and correlated with SCC. This was not true for transmission measurements. Processing yields a high data reduction, almost 60 to 1, and permits A and C scan display techniques and software already in use for pipeline inspection. An analysis of actual SH0 scan results for SCC of known dimensions showed that length

  1. Ultrasonic inspection of steam-generator tube axial cracking using Lamb wave

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae Seok

    2007-02-15

    In this study, the interaction of Lamb wave propagating thin tube structure with finite vertical discontinuity was studied using both modal decomposition method (MDM) and experimental method. For MDM, a global matrix formulation and orthogonality of Lamb mode was employed to describe the boundary condition of finite vertical discontinuity of the tube and the mode conversion phenomenon respectively. The final form of governing equation by MDM was a linear matrix equation which could be solved using a simple matrix identity. The calculation result showed that, below the cut-off frequency, reflection amplitudes of both A0 and S0 Lamb mode increase as the depth of discontinuity increased beyond the threshold value. An experimental investigation was performed using a Hertzian-contact transducer and steam-generator tubes to verify the calculation results by MDM. A0 Lamb mode was selected as a test signal considering the characteristics of the transducer and previous studies. The experiment for mode identification using half-sectioned tube verified that the Hertzian-contact transducer effectively generated A0 Lamb mode. Tests performed using steam-generator tubes with EDM (electric discharge machined) axial notches showed that the deeper notches produced the higher reflection echo. A0 Lamb mode interacted with the notch having a depth larger than 1/40 of wave length, or corresponding to 30% of the wall thickness. This finding was in good agreement with previous studies and the prediction by MDM. The experiment using real crack specimens to estimate the deviation of reflection amplitude showed that the reflection cross-section of real crack was very similar with that of EDM notch. Therefore, specimens with EDM notches can be used as reference blocks for Lamb wave UT calibration.

  2. Evidence of cracks in austenitic pipe weldings with a radiometric inspection system; Nachweis von Rissen in austenitischen Rohrleitungsnaehten mit einem radiometrischen Pruefsystem

    Energy Technology Data Exchange (ETDEWEB)

    Maier, H.J.; Wuensch, W. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt

    1999-08-01

    The paper reports the development of a radiometric prototype device and its application to inspection of austenitic weldings with intercrystalline crack defects. The device initially was intended to be used for supplemental inspection for clarification of contradictory or unclear testing results, but the results obtained justify to consider the possibility of using it as an independent, full-scope testing instrument. (orig./CB) [Deutsch] Berichtet wird ueber die Entwicklung eines Prototypes eines Radiometrie-Geraetes zur Pruefung von austenitischen Schweissnaehten mit interkristalliner Rissbildung, zunaechst als Entscheidungshilfe bei unklaren bzw. sich widersprechenden Pruefresultaten. Zwischenzeitlich wird auch daran gedacht, ein solches Geraet fuer eine vollstaendige Pruefung weiter zu entwickeln. (orig./DGE)

  3. Evidence of cracks in austenitic pipe weldings with a radiometric inspection system; Nachweis von Rissen in austenitischen Rohrleitungsnaehten mit einem radiometrischen Pruefsystem

    Energy Technology Data Exchange (ETDEWEB)

    Maier, H.J.; Wuensch, W. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt

    1999-08-01

    The paper reports the development of a radiometric prototype device and its application to inspection of austenitic weldings with intercrystalline crack defects. The device initially was intended to be used for supplemental inspection for clarification of contradictory or unclear testing results, but the results obtained justify to consider the possibility of using it as an independent, full-scope testing instrument. (orig./CB) [Deutsch] Berichtet wird ueber die Entwicklung eines Prototypes eines Radiometrie-Geraetes zur Pruefung von austenitischen Schweissnaehten mit interkristalliner Rissbildung, zunaechst als Entscheidungshilfe bei unklaren bzw. sich widersprechenden Pruefresultaten. Zwischenzeitlich wird auch daran gedacht, ein solches Geraet fuer eine vollstaendige Pruefung weiter zu entwickeln. (orig./DGE)

  4. GIS-based automated management of highway surface crack inspection system

    Science.gov (United States)

    Chung, Hung-Chi; Shinozuka, Masanobu; Soeller, Tony; Girardello, Roberto

    2004-07-01

    An automated in-situ road surface distress surveying and management system, AMPIS, has been developed on the basis of video images within the framework of GIS software. Video image processing techniques are introduced to acquire, process and analyze the road surface images obtained from a moving vehicle. ArcGIS platform is used to integrate the routines of image processing and spatial analysis in handling the full-scale metropolitan highway surface distress detection and data fusion/management. This makes it possible to present user-friendly interfaces in GIS and to provide efficient visualizations of surveyed results not only for the use of transportation engineers to manage road surveying documentations, data acquisition, analysis and management, but also for financial officials to plan maintenance and repair programs and further evaluate the socio-economic impacts of highway degradation and deterioration. A review performed in this study on fundamental principle of Pavement Management System (PMS) and its implementation indicates that the proposed approach of using GIS concept and its tools for PMS application will reshape PMS into a new information technology-based system that can provide convenient and efficient pavement inspection and management.

  5. Development of a novel non-contact inspection technique to detect micro cracks under the surface of a glass substrate by thermal stress-induced light scattering method

    Science.gov (United States)

    Sakata, Yoshitaro; Terasaki, Nao; Nonaka, Kazuhiro

    2017-05-01

    Fine polishing techniques, such as a chemical mechanical polishing treatment, are important techniques in glass substrate manufacturing. However, these techniques may cause micro cracks under the surface of glass substrates because they used mechanical friction. A stress-induced light scattering method (SILSM), which was combined with light scattering method and mechanical stress effects, was proposed for inspecting surfaces to detect polishing-induced micro cracks. However, in the conventional SILSM, samples need to be loaded with physical contact, and the loading point is invisible in transparent materials. Here, we introduced a novel non-contact SILSM using a heating device. A glass substrate was heated first, and then the light scattering intensity of micro cracks was detected by a cooled charge-couple device camera during the natural cooling process. Results clearly showed during the decreasing surface temperature of a glass substrate, appropriate thermal stress is generated for detecting micro cracks by using the SILSM and light scattering intensity from micro cracks changes. We confirmed that non-contact thermal SILSM (T-SILSM) can detect micro cracks under the surface of transparent materials.

  6. Evaluation of a Small-Crack Monitoring System

    Science.gov (United States)

    Newman, John A.; Johnston, William M.

    2010-01-01

    A new system has been developed to obtain fatigue crack growth rate data from a series of images acquired during fatigue testing of specimens containing small surface cracks that initiate at highly-polished notches. The primary benefit associated with replica-based crack growth rate data methods is preserving a record of the crack configuration during the life of the specimen. Additionally, this system has the benefits of both reducing time and labor, and not requiring introduction of surface replica media into the crack. Fatigue crack growth rate data obtained using this new system are found to be in good agreement with similar results obtained from surface replicas.

  7. Model based Inverse Methods for Sizing Cracks of Varying Shape and Location in Bolt hole Eddy Current (BHEC) Inspections (Postprint)

    Science.gov (United States)

    2016-02-10

    10.1063/1.4940557 14. ABSTRACT (Maximum 200 words) A comprehensive approach is presented to perform model-based inversion of crack characteristics ...thickness crack types, and from both standard eddy current hardware and a prototype BHEC system with z -axis position encoding. Signal processing...algorithms were developed to process and extract features from the 2D data sets, and inversion algorithms using VIC-3D generated surrogate models were used

  8. Nuclear Plant Inspection

    Science.gov (United States)

    1983-01-01

    Engineers from the Power Authority of the State of New York use a Crack Growth Analysis Program supplied by COSMIC (Computer Software Management and Information Center) in one stage of nuclear plant inspection. Welds of the nuclear steam supply system are checked for cracks; radiographs, dye penetration and visual inspections are performed to locate cracks in the metal structure and welds. The software package includes three separate crack growth analysis models and enables necessary repairs to be planned before serious problems develop.

  9. 管道裂纹远场涡流检测正演模型设计%Design on Forward Modeling of RFEC Inspection for Cracks

    Institute of Scientific and Technical Information of China (English)

    敖永才; 师奕兵; 王志刚; 李西风

    2012-01-01

    Being an inverse problem of electromagnetic fields, the quantitative inspection of pipeline cracks in remote field eddy current inspection ( RFECI) becomes an ill-posed problem for the lack of the prior constraints. The significant correlationship between the cracks and the features of the magnetic signals through the researches on the axisymmetric defects of the pipeline is demonstrated. A forward modeling, which can quantitatively map the pipeline defects to the features of the magnetic signals, based on back-propagation neural network (BPNN) is proposed. The high approximation accuracy and the good generalization ability of the forward modeling mean the effective prior knowledge and constraints for the quantitative inverse of the pipeline defects.%管道远场涡流裂纹缺陷检测的本质是电磁场反演问题,由于先验约束条件的不足,缺陷尺寸的定量检测成为一个无定解的不适定问题.提出了一种基于BP神经网络学习算法的管道远场涡流检测正演模型的设计方法,通过对轴对称缺陷管道模型的仿真研究,提取出与缺陷尺寸显著相关的关键磁场特征量,实现了从管道裂纹缺陷尺寸空间到磁场信号特征空间的非线性定量映射.经测试,正演模型对远场涡流特征信号具有良好的逼近精度和推广能力,可为管道轴对称裂纹缺陷的定量反演评估提供有效的先验知识和约束条件.

  10. Principles and Application of Magnetic Rubber Testing for Crack Detection in High-Strength Steel Components: I. Active-Field Inspection

    Science.gov (United States)

    2014-12-01

    UNCLASSIFIED UNCLASSIFIED Principles and Application of Magnetic Rubber Testing for Crack Detection in High-Strength Steel Components: I...scientific principles governing both active-field and residual-field variants of MRT were examined. The results of theoretical and experimental...investigations into active-field MRT are documented in the current report, which describes the principles of active-field MRT, and then examines both the basis

  11. Principles and Application of Magnetic Rubber Testing for Crack Detection in High-Strength Steel Components: II. Residual-Field Inspection

    Science.gov (United States)

    2014-12-01

    inspection, or for ring-shaped specimens by a toroidal cable-wrap [4]. UNCLASSIFIED DSTO-TR-3033 UNCLASSIFIED 3 Figure 1 Magnetisation in...residual-field techniques for the idealised two-dimensional (2-D) geometry where bars, rods and tubes containing a longitudinal slot are magnetised using...for active-field leakage fields all reports show that the leakage field increases with slot depth. The literature however contains contradictory

  12. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    evaluating ciack initiation time and crack propagation, prgram I was used for performing the major fatigue test with the aircraft structure. In...advantage to begin with the end of the fracture, this is especially so in the case of the quantitative evaluation of striations. The overload fracture...Select the Measuring Line for Quantitative Evaluation Actually, the fatigue fracture should be inspected completely from the point of origin to the

  13. Modelling in Optimal Inspection and Repair

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Rackwitz, R.; Faber, M.H.;

    1991-01-01

    A model for reliability based optimal inspection and repair strategies is described. The total expected costs in the lifetime is minimized with the number of inspections, the inspection times and efforts, the repair crack size limit and a design parameter as optimization variables. The equivalenc...

  14. Carburizing Inspection of Cracking Furnace Tube Using Magnetic Hysteresis Non-Destructive Evaluation Technique%磁滞无损评估技术在裂解炉管渗碳检测中的应用

    Institute of Scientific and Technical Information of China (English)

    刘德宇; 王宁辉; 张国庆; 李国瑞

    2015-01-01

    Large tube type fuel heating furnaces are important and essential equipments, with a wide range of applications in the petroleum and chemical industry, in which the failure modes of furnace tubes are mostly caused by carburizing. To estimate the effect of magnetic hysteresis non-destructive evaluation technique on carburizing inspection, both new and the three-years-service cracking furnace tubes were performed carburizing test. Different carburized depth of tubes were got and their coercivity was tested. The results showed that there is a good relationship between the coercivity and carburized case depth, which would be a great potential applications in the carburizing inspection of tube.%大型管式燃料加热炉是石油化工企业里广泛应用且必不可少的重要设备,其中炉管的失效大多由渗碳引起。为了评价磁滞无损评估技术在渗碳层厚度检测中应用的有效性,对未服役和服役3年的裂解炉炉管进行渗碳实验,得到不同渗碳层厚度的炉管,并采集磁滞参数矫顽力,结果表明,矫顽力与渗碳层厚度具有很好的对应关系,在炉管渗碳检测中具有很大的应用前景。

  15. CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART

    Directory of Open Access Journals (Sweden)

    Karin Kocúrová

    2010-03-01

    Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.

  16. Lock-in thermography, penetrant inspection, and scanning electron microscopy for quantitative evaluation of open micro-cracks at the tooth-restoration interface

    Science.gov (United States)

    Streza, M.; Hodisan, I.; Prejmerean, C.; Boue, C.; Tessier, Gilles

    2015-03-01

    The evaluation of a dental restoration in a non-invasive way is of paramount importance in clinical practice. The aim of this study was to assess the minimum detectable open crack at the cavity-restorative material interface by the lock-in thermography technique, at laser intensities which are safe for living teeth. For the analysis of the interface, 18 box-type class V standardized cavities were prepared on the facial and oral surfaces of each tooth, with coronal margins in enamel and apical margins in dentine. The preparations were restored with the Giomer Beautifil (Shofu) in combination with three different adhesive systems. Three specimens were randomly selected from each experimental group and each slice has been analysed by visible, infrared (IR), and scanning electron microscopy (SEM). Lock-in thermography showed the most promising results in detecting both marginal and internal defects. The proposed procedure leads to a diagnosis of micro-leakages having openings of 1 µm, which is close to the diffraction limit of the IR camera. Clinical use of a thermographic camera in assessing the marginal integrity of a restoration becomes possible. The method overcomes some drawbacks of standard SEM or dye penetration testing. The results support the use of an IR camera in dentistry, for the diagnosis of micro-gaps at bio-interfaces.

  17. Optimal Inspection Planning for Fatigue Damage of Offshore Structures

    DEFF Research Database (Denmark)

    Madsen, H.O.; Sørensen, John Dalsgaard; Olesen, R.

    1990-01-01

    A formulation of optimal design, inspection and maintenance against damage caused by fatigue crack growth is formulated. A stochastic model for fatigue crack growth based on linear elastic fracture mechanics Is applied. Failure is defined by crack growth beyond a critical crack size. The failure...... probability and associated sensitivity factors are computed by first-order reliability methods. Inspection reliability is included through a pod (probability of detection) curve. Optimization variables are structural design parameters, inspection times and qualities. The total expected cost of design......, inspection, repair and failure is minimized with a constraint on the life time reliability....

  18. Safety and Inspection Planning of Older Installations

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Ersdal, G.

    2008-01-01

    and a no-crack detection assumption imply that the inspection time intervals usually become longer and longer with time. For ageing platforms several small cracks should be expected to be observed according to the bath-tub curve development often assumed - implying an increased risk for crack initiation...... at the end of the expected lifetime - corresponding to a bath-tub hazard rate effect. The approach illustrated is for welded steel details in platforms. Systems effects are considered, including the use of dependence between inspection and failure events in different components for inspection planning....

  19. Knuckle Cracking

    Science.gov (United States)

    ... Ask The Expert Ask a Question Physician Corner Rheumatology Conference Rheumatology Rounds Case Rounds Radiology Rounds Pathophysiology of the ... Appointment Information Contact Us Our Faculty Our Staff Rheumatology Specialty Centers Knuckle Cracking Q & A September 10, ...

  20. FAA Fluorescent Penetrant Laboratory Inspections

    Energy Technology Data Exchange (ETDEWEB)

    WINDES,CONNOR L.; MOORE,DAVID G.

    2000-08-02

    The Federal Aviation Administration Airworthiness Assurance NDI Validation Center currently assesses the capability of various non-destructive inspection (NDI) methods used for analyzing aircraft components. The focus of one such exercise is to evaluate the sensitivity of fluorescent liquid penetrant inspection. A baseline procedure using the water-washable fluorescent penetrant method defines a foundation for comparing the brightness of low cycle fatigue cracks in titanium test panels. The analysis of deviations in the baseline procedure will determine an acceptable range of operation for the steps in the inspection process. The data also gives insight into the depth of each crack and which step(s) of the inspection process most affect penetrant sensitivities. A set of six low cycle fatigue cracks produced in 6.35-mm thick Ti-6Al-4V specimens was used to conduct the experiments to produce sensitivity data. The results will document the consistency of the crack readings and compare previous experiments to find the best parameters for water-washable penetrant.

  1. Inspection Database

    Data.gov (United States)

    U.S. Department of Health & Human Services — FDA is disclosing the final inspection classification for inspections related to currently marketed FDA-regulated products. The disclosure of this information is...

  2. Inspection Database

    Data.gov (United States)

    U.S. Department of Health & Human Services — FDA is disclosing the final inspection classification for inspections related to currently marketed FDA-regulated products. The disclosure of this information is not...

  3. Cracks assessment using ultrasonic technology

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Maria Pia; Tomasella, Marcelo [OLDELVAL S.A. Oleoductos del Valle, Rio Negro (Argentina). Pipeline Integrity Dept.

    2005-07-01

    The goal of Oldelval Integrity Program is to prevent ruptures and leaks, developing strategies for a better handling of the integrity of our pipelines. In order to achieve it we have studied and modeled each process that involved in the integrity pipeline. Those processes are mainly based on defects reported by an internal inspection tool and supplied with field inspection and monitoring data. Years of evaluation, study and the continuous effort overturned towards a phenomenon that worries to the industry, as it is the SCC. Since 1998 up to 2004 SCC was included in the integrity program with some preventive maintenance programs. The accomplishment of the inspection based on ultrasound tools, is the culmination of years of evaluation and investigations supported by field digs and materials susceptibility. This paper describes Oldelval's results with ultrasonic crack detection tool, and how it can be reliably to detect SCC. (author)

  4. Crack depth determination with inductive thermography

    Science.gov (United States)

    Oswald-Tranta, B.; Schmidt, R.

    2015-05-01

    Castings, forgings and other steel products are nowadays usually tested with magnetic particle inspection, in order to detect surface cracks. An alternative method is active thermography with inductive heating, which is quicker, it can be well automated and as in this paper presented, even the depth of a crack can be estimated. The induced eddy current, due to its very small penetration depth in ferro-magnetic materials, flows around a surface crack, heating this selectively. The surface temperature is recorded during and after the short inductive heating pulse with an infrared camera. Using Fourier transformation the whole IR image sequence is evaluated and the phase image is processed to detect surface cracks. The level and the local distribution of the phase around a crack correspond to its depth. Analytical calculations were used to model the signal distribution around cracks with different depth and a relationship has been derived between the depth of a crack and its phase value. Additionally, also the influence of the heating pulse duration has been investigated. Samples with artificial and with natural cracks have been tested. Results are presented comparing the calculated and measured phase values depending on the crack depth. Keywords: inductive heating, eddy current, infrared

  5. ANNUAL RADIOACTIVE WASTE TANK INSPECTION PROGRAM - 2011

    Energy Technology Data Exchange (ETDEWEB)

    West, B.; Waltz, R.

    2012-06-21

    Aqueous radioactive wastes from Savannah River Site (SRS) separations and vitrification processes are contained in large underground carbon steel tanks. Inspections made during 2011 to evaluate these vessels and other waste handling facilities along with evaluations based on data from previous inspections are the subject of this report. The 2011 inspection program revealed that the structural integrity and waste confinement capability of the Savannah River Site waste tanks were maintained. All inspections scheduled per SRR-LWE-2011-00026, HLW Tank Farm Inspection Plan for 2011, were completed. Ultrasonic measurements (UT) performed in 2011 met the requirements of C-ESR-G-00006, In-Service Inspection Program for High Level Waste Tanks, Rev. 3, and WSRC-TR-2002-00061, Rev.6. UT inspections were performed on Tanks 25, 26 and 34 and the findings are documented in SRNL-STI-2011-00495, Tank Inspection NDE Results for Fiscal Year 2011, Waste Tanks 25, 26, 34 and 41. A total of 5813 photographs were made and 835 visual and video inspections were performed during 2011. A potential leaksite was discovered at Tank 4 during routine annual inspections performed in 2011. The new crack, which is above the allowable fill level, resulted in no release to the environment or tank annulus. The location of the crack is documented in C-ESR-G-00003, SRS High Level Waste Tank Leaksite Information, Rev.6.

  6. Reliability-based optimum inspection and maintenance procedures. [for engines

    Science.gov (United States)

    Nanagud, S.; Uppaluri, B.

    1975-01-01

    The development of reliability-based optimum inspection and maintenance schedules for engines needs an understanding of the fatigue behavior of the engines. Critical areas of the engine structure prone to fatigue damage are usually identified beforehand or after the fleet has been put into operation. In these areas, fatigue cracks initiate after several flight hours, and these cracks grow in length until failure takes place when these cracks attain the critical lengths. Crack initiation time and its growth rate are considered to be random variables. Usually, the inspection (fatigue) or test data from similar engines are used as prior distributions. The existing state-of-the-art is to ignore the different lengths of cracks obserbed at various inspections and to consider only the fact that a crack existed (or did not exist) at the time of inspection. In this paper, a procedure has been developed to obtain the probability of finding a crack of a given size at a certain time if the probability distributions for crack initiation and rates of growth are known. Application of the developed stochastic models to devise optimum procedures for inspection and maintenance are also discussed.

  7. Reliability-based optimum inspection and maintenance procedures. [for engines

    Science.gov (United States)

    Nanagud, S.; Uppaluri, B.

    1975-01-01

    The development of reliability-based optimum inspection and maintenance schedules for engines needs an understanding of the fatigue behavior of the engines. Critical areas of the engine structure prone to fatigue damage are usually identified beforehand or after the fleet has been put into operation. In these areas, fatigue cracks initiate after several flight hours, and these cracks grow in length until failure takes place when these cracks attain the critical lengths. Crack initiation time and its growth rate are considered to be random variables. Usually, the inspection (fatigue) or test data from similar engines are used as prior distributions. The existing state-of-the-art is to ignore the different lengths of cracks obserbed at various inspections and to consider only the fact that a crack existed (or did not exist) at the time of inspection. In this paper, a procedure has been developed to obtain the probability of finding a crack of a given size at a certain time if the probability distributions for crack initiation and rates of growth are known. Application of the developed stochastic models to devise optimum procedures for inspection and maintenance are also discussed.

  8. Evaluation of creep-fatigue crack growth for large-scale FBR reactor vessel and NDE assessment

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Young Sang; Kim, Jong Bum; Kim, Seok Hun; Yoo, Bong

    2001-03-01

    Creep fatigue crack growth contributes to the failure of FRB reactor vessels in high temperature condition. In the design stage of reactor vessel, crack growth evaluation is very important to ensure the structural safety and setup the in-service inspection strategy. In this study, creep-fatigue crack growth evaluation has been performed for the semi-elliptical surface cracks subjected to thermal loading. The thermal stress analysis of a large-scale FBR reactor vessel has been carried out for the load conditions. The distributions of axial, radial, hoop, and Von Mises stresses were obtained for the loading conditions. At the maximum point of the axial and hoop stress, the longitudinal and circumferential surface cracks (i.e. PTS crack, NDE short crack and shallow long crack) were postulated. Using the maximum and minimum values of stresses, the creep-fatigue crack growth of the proposed cracks was simulated. The crack growth rate of circumferential cracks becomes greater than that of longitudinal cracks. The total crack growth of the largest PTS crack is very small after 427 cycles. The structural integrity of a large-scale reactor can be maintained for the plant life. The crack depth growth of the shallow long crack is faster than that of the NDE short crack. In the ISI of the large-scale FBR reactor vessel, the ultrasonic inspection is beneficial to detect the shallow circumferential cracks.

  9. Working session 2: Tubing inspection

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, J. [Tecnatom, S.A. San Sebastian de los Reyes, Madrid (Spain); Tapping, R.L. [AECL, Chalk River, Ontario (Canada)

    1997-02-01

    This session was attended by delegates from 10 countries, and four papers were presented. A wide range of issues was tabled for discussion. Realizing that there was limited time available for more detailed discussion, three topics were chosen for the more detailed discussion: circumferential cracking, performance demonstration (to focus on POD and sizing), and limits of methods. Two other subsessions were organized: one dealt with some challenges related to the robustness of current inspection methods, especially with respect to leaving cracked tubes in service, and the other with developing a chart of current NDE technology with recommendations for future development. These three areas are summarized in turn, along with conclusions and/or recommendations. During the discussions there were four presentations. There were two (Canada, Japan) on eddy current probe developments, both of which addressed multiarray probes that would detect a range of flaws, one (Spain) on circumferential crack detection, and one (JRC, Petten) on the recent PISC III results.

  10. Localization and characterization of fatigue cracks around fastener holes using spherically focused ultrasonic probes

    Science.gov (United States)

    Hopkins, Deborah; Datuin, Marvin; Aldrin, John; Warchol, Mark; Warchol, Lyudmila; Forsyth, David

    2017-02-01

    Results are presented from laboratory experiments and simulations that demonstrate the ability to localize fatigue cracks around fastener holes using spherically focused ultrasonic probes for shear-wave inspections. For the experiments, fatigue cracks were created in aluminum plates in a testing frame under cyclic loading. With the exceptions of one specimen with a mid-bore crack and another with a "through" crack, the remaining specimens contain surface-breaking cracks. All of the specimens were inspected for the cracks intersecting the back wall, and some were flipped over and re-inspected with the crack intersecting the front surface. Parameter and variable sensitivity studies were performed using CIVA Simulation Software. In contrast to C-scans where detection and localization of small cracks can be very difficult, modeling and initial experimental results demonstrate that cracks can be accurately located in "True" B-scans (B-scans projected in the part along the beam path). Initial results show that small-amplitude diffracted/scattered signals from the crack tips and edges are essential in obtaining clear crack traces in the True B-scans. It is important therefore that experimental data be acquired with sufficient gain to capture the diffracted/scattered signals. In all of the cases studied here, saturating the high-amplitude specular reflections from the fastener hole and crack enhanced the crack trace in the True B-scans.

  11. Creep crack growth analysis using C{sub t}-parameter for internal circumferential and external axial surface cracks in a pressurized cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Tun, Nwe Ni; Yang, Hee Seung; Yu, Jong Min; Yoon, Kee Bong [Dept. of Mechanical Engineering, Chung Ang University, Seoul (Korea, Republic of)

    2016-12-15

    Creep crack growth at elevated temperatures is a critical consideration in estimating the remaining life of high temperature structural components and in deciding their inspection interval. In this study, creep crack growth analyses for external radial-axial and internal radial-circumferential surface cracks in a pressurized cylinder were conducted by an analytical method. The effect of crack depth and crack length on the variations in Ct and remaining life predictions were investigated for surface cracks with various initial aspect ratios. It was observed that the remaining life of an internal radial-circumferential surface crack was approximately 53 times longer than that of an external radial-axial surface crack for the same crack size and loading conditions with 316 stainless steel material. It was also observed that the variations in remaining life, crack propagations, and the Ct values were considerably sensitive to the crack location and crack depth. Convergence of crack aspect ratio was not observed when the crack depth ratio was increased. Since the method is independent of material properties and location of the crack geometries, it can be extended to various material properties and various locations of the surface crack geometries.

  12. Hospital Inspections

    Data.gov (United States)

    U.S. Department of Health & Human Services — Welcome to hospitalinspections.org, a website run by the Association of Health Care Journalists (AHCJ) that aims to make federal hospital inspection reports easier...

  13. Hospital Inspections

    Data.gov (United States)

    U.S. Department of Health & Human Services — Welcome to hospitalinspections.org, a website run by the Association of Health Care Journalists (AHCJ) that aims to make federal hospital inspection reports easier...

  14. Model-Assisted POD for Ultrasonic Detection of Cracks at Fastener Holes

    Science.gov (United States)

    Harding, C. A.; Hugo, G. R.; Bowles, S. J.

    2006-03-01

    To reduce the cost of conducting experimental probability of detection (POD) trials, methods which utilize models to account for factors that influence the inspection reliability are being developed. This paper reports the application of POD modeling to ultrasonic detection of cracks emanating from fastener holes. The differences between ultrasonic responses from EDM notches compared to fatigue cracks are examined, including the effects of natural variation in fatigue cracks and crack closure due to residual stresses.

  15. Concrete Crack Identification Using a UAV Incorporating Hybrid Image Processing.

    Science.gov (United States)

    Kim, Hyunjun; Lee, Junhwa; Ahn, Eunjong; Cho, Soojin; Shin, Myoungsu; Sim, Sung-Han

    2017-09-07

    Crack assessment is an essential process in the maintenance of concrete structures. In general, concrete cracks are inspected by manual visual observation of the surface, which is intrinsically subjective as it depends on the experience of inspectors. Further, it is time-consuming, expensive, and often unsafe when inaccessible structural members are to be assessed. Unmanned aerial vehicle (UAV) technologies combined with digital image processing have recently been applied to crack assessment to overcome the drawbacks of manual visual inspection. However, identification of crack information in terms of width and length has not been fully explored in the UAV-based applications, because of the absence of distance measurement and tailored image processing. This paper presents a crack identification strategy that combines hybrid image processing with UAV technology. Equipped with a camera, an ultrasonic displacement sensor, and a WiFi module, the system provides the image of cracks and the associated working distance from a target structure on demand. The obtained information is subsequently processed by hybrid image binarization to estimate the crack width accurately while minimizing the loss of the crack length information. The proposed system has shown to successfully measure cracks thicker than 0.1 mm with the maximum length estimation error of 7.3%.

  16. Concrete Crack Identification Using a UAV Incorporating Hybrid Image Processing

    Directory of Open Access Journals (Sweden)

    Hyunjun Kim

    2017-09-01

    Full Text Available Crack assessment is an essential process in the maintenance of concrete structures. In general, concrete cracks are inspected by manual visual observation of the surface, which is intrinsically subjective as it depends on the experience of inspectors. Further, it is time-consuming, expensive, and often unsafe when inaccessible structural members are to be assessed. Unmanned aerial vehicle (UAV technologies combined with digital image processing have recently been applied to crack assessment to overcome the drawbacks of manual visual inspection. However, identification of crack information in terms of width and length has not been fully explored in the UAV-based applications, because of the absence of distance measurement and tailored image processing. This paper presents a crack identification strategy that combines hybrid image processing with UAV technology. Equipped with a camera, an ultrasonic displacement sensor, and a WiFi module, the system provides the image of cracks and the associated working distance from a target structure on demand. The obtained information is subsequently processed by hybrid image binarization to estimate the crack width accurately while minimizing the loss of the crack length information. The proposed system has shown to successfully measure cracks thicker than 0.1 mm with the maximum length estimation error of 7.3%.

  17. Autonomous Robotic Inspection in Tunnels

    Science.gov (United States)

    Protopapadakis, E.; Stentoumis, C.; Doulamis, N.; Doulamis, A.; Loupos, K.; Makantasis, K.; Kopsiaftis, G.; Amditis, A.

    2016-06-01

    In this paper, an automatic robotic inspector for tunnel assessment is presented. The proposed platform is able to autonomously navigate within the civil infrastructures, grab stereo images and process/analyse them, in order to identify defect types. At first, there is the crack detection via deep learning approaches. Then, a detailed 3D model of the cracked area is created, utilizing photogrammetric methods. Finally, a laser profiling of the tunnel's lining, for a narrow region close to detected crack is performed; allowing for the deduction of potential deformations. The robotic platform consists of an autonomous mobile vehicle; a crane arm, guided by the computer vision-based crack detector, carrying ultrasound sensors, the stereo cameras and the laser scanner. Visual inspection is based on convolutional neural networks, which support the creation of high-level discriminative features for complex non-linear pattern classification. Then, real-time 3D information is accurately calculated and the crack position and orientation is passed to the robotic platform. The entire system has been evaluated in railway and road tunnels, i.e. in Egnatia Highway and London underground infrastructure.

  18. 49 CFR 230.29 - Inspection and repair.

    Science.gov (United States)

    2010-10-01

    ..., DEPARTMENT OF TRANSPORTATION STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances... operator shall inspect and repair all steam locomotive boilers and appurtenances under their control. They shall immediately remove from service any boiler that has developed cracks in the barrel. The...

  19. Thermographic characterization of stress during crack growth

    Science.gov (United States)

    Cramer, K. E.; Dawicke, David S.; Welch, Christopher S.

    1992-01-01

    A full-field-thermographic technique for imaging stress patterns in dynamically loaded structures using general purpose IR imaging and image processing hardware is described. The inspection technique is based on the thermoelastic effect. A simple geometry is examined, and the experimentally determined values for the stress invariant are shown to be consistent with theoretical and numerical calculations. The application of full-field-thermographic measurement would ensure that the observed stress field has a common sampling period, thus allowing the observation of rapidly occurring stress anomalies such as the propagation of a fatigue crack. Fatigue crack propagation in two consecutive thermoelastic stress images from an aluminum sample is shown.

  20. Safety and Inspection Planning of Older Installations

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Ersdal, G.

    2007-01-01

    time intervals for ageing structures. Different approaches for updating inspection plans for older installations are proposed.The most promising method consists in increasing the rate of crack initiations at the end of the expected lifetime - corresponding to a bath-tube hazard rate effect.The approach...

  1. Point Lepreau primary heat transport pump wear ring cracking

    Energy Technology Data Exchange (ETDEWEB)

    Licina, G. [Structural Integrity Associates, Inc., San Jose, California (United States); Rankin, B. [Point Lepreau Nuclear Generating Station, Fredericton, New Brunswick (Canada)

    2011-07-01

    The number 3 Primary Heat Transport (PHT) pump from Point Lepreau Nuclear Generating Station (Point Lepreau) was disassembled after more than 30 years of service for inspection during station refurbishment. The disassembly and inspection were performed to provide assurance of continued satisfactory operation during life extension. The inspection revealed cracks in the wear ring, at and near the tack welds (Type 309 stainless steel weld metal) at the cap screws that attach the Type 420 stainless steel wear ring to the body of the pump. Investigative work consisted of on-site PT and replication of the microstructure at the surface of the wear ring, subsequent impressions of two crack faces, and hardness determinations. This paper describes the investigative work and conclusions associated with resolution of the following questions: 1. What is the most likely cause of the cracking? 2. Will the cracks propagate within the base metal of the wear ring? 3. If propagation is possible, what is the risk of cracks intersecting, such that a piece of metal could become dislodged? Question number 3 has clear ramifications with respect to foreign material entering and damaging a nuclear fuel-containing pressure tube. There are also questions associated with extent of condition, specifically, whether other PHT pumps may have similar or worse cracking and whether such cracks will grow. Results will be applied to wear rings in other PHT pumps at Point Lepreau and are likely to be applicable to similar components in other CANDU PHT pumps. (author)

  2. Crack growth monitoring at CFRP bond lines

    Science.gov (United States)

    Rahammer, M.; Adebahr, W.; Sachse, R.; Gröninger, S.; Kreutzbruck, M.

    2016-02-01

    With the growing need for lightweight technologies in aerospace and automotive industries, fibre-reinforced plastics, especially carbon-fibre (CFRP), are used with a continuously increasing annual growth rate. A promising joining technique for composites is adhesive bonding. While rivet holes destroy the fibres and cause stress concentration, adhesive bond lines distribute the load evenly. Today bonding is only used in secondary structures due to a lack of knowledge with regard to long-term predictability. In all industries, numerical simulation plays a critical part in the development process of new materials and structures, while it plays a vital role when it comes to CFRP adhesive bondings conducing the predictability of life time and damage tolerance. The critical issue with adhesive bondings is crack growth. In a dynamic tensile stress testing machine we dynamically load bonded CFRP coupon specimen and measure the growth rate of an artificially started crack in order to feed the models with the results. We also investigate the effect of mechanical crack stopping features. For observation of the bond line, we apply two non-contact NDT techniques: Air-coupled ultrasound in slanted transmission mode and active lockin-thermography evaluated at load frequencies. Both methods give promising results for detecting the current crack front location. While the ultrasonic technique provides a slightly higher accuracy, thermography has the advantage of true online monitoring, because the measurements are made while the cyclic load is being applied. The NDT methods are compared to visual inspection of the crack front at the specimen flanks and show high congruence. Furthermore, the effect of crack stopping features within the specimen on the crack growth is investigated. The results show, that not all crack fronts are perfectly horizontal, but all of them eventually come to a halt in the crack stopping feature vicinity.

  3. Ultrasonic Inspection

    Science.gov (United States)

    1976-01-01

    Automation Industries Inc. has had more than $2 million in contracts to produce innovative equipment for the Apollo program. When Marshall Space Flight Center sought a fast nondestructive way to inspect butt welds in aluminum alloys for spacecraft, the company developed a reliable ultrasonic device using multiple transducers called "delta manipulators" which detect lack of weld penetration not readily seen in radiograph automation. Industry soon adapted the ultrasonic equipment to a unique rail inspection device that saves countless man hours. Device is contained in self propelled railroad cars produced and operated by the company to check old track welds for deterioration.

  4. Gear Crack Propagation Investigation

    Science.gov (United States)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios

  5. Augmented Reality to Access Dam Cracks Information

    Directory of Open Access Journals (Sweden)

    Fabiana Frata Furlan Peres

    2016-03-01

    Full Text Available Augmented reality technology is a tool with great potential for application in several areas, including engineering. During the early phases of the enterprise life cycle, as design and construction, augmented reality has been widely used. Concrete dams, during operation and maintenance phase, require regular inspections as part of the necessary activities to keep their structural safety. Cracks are common pathology in these structures that must be detected, mapped and measured as their evolution may evidence structure compromising, need for maintenance or intervention. In this context this paper aims to present a prototype to access in situ the dam cracks information through the use of augmented reality, thus giving a contribution to the effectiveness and efficiency of inspections

  6. Fatigue crack propagation in turbine disks of EI698 superalloy

    Directory of Open Access Journals (Sweden)

    A.A. Shanyavskiy

    2013-04-01

    Full Text Available In-service fatigue cracking of turbine disks of EI698 superalloy is discussed based on crack growth analyses. In the bolt joint for disks to shaft connecting there is high level of stress-state, which directed to earlier in-disks fatigue crack origination in low-cycle-fatigue regime. Fracture surface pattern such as fatigue striations were used for their spacing measurement and crack growth duration estimating. Developed disk tests on a special bench by the equivalent program to in-service cyclic loads have allowed discovering one-to-one correlation between fatigue striation spacing and crack increment in one flight. Number of fatigue striations and beach-marks calculations permitted to estimate crack growth period for the different stages of in-service disks cracking. Equivalent stress level for in-service cracked disks was calculated and compared with stress-level in-tested disks under stress equivalent program to in-service operated cyclic loads. Based on this result non-destructive inspection intervals were discussed and recommended for in-service disks in dependence on number of their flights at the moment of developed inspection to exclude in-flight disks fast fracture.

  7. Robotic inspection technology-process an toolbox

    Energy Technology Data Exchange (ETDEWEB)

    Hermes, Markus [ROSEN Group (United States). R and D Dept.

    2005-07-01

    Pipeline deterioration grows progressively with ultimate aging of pipeline systems (on-plot and cross country). This includes both, very localized corrosion as well as increasing failure probability due to fatigue cracking. Limiting regular inspecting activities to the 'scrapable' part of the pipelines only, will ultimately result into a pipeline system with questionable integrity. The confidence level in the integrity of these systems will drop below acceptance levels. Inspection of presently un-inspectable sections of the pipeline system becomes a must. This paper provides information on ROSEN's progress on the 'robotic inspection technology' project. The robotic inspection concept developed by ROSEN is based on a modular toolbox principle. This is mandatory. A universal 'all purpose' robot would not be reliable and efficient in resolving the postulated inspection task. A preparatory Quality Function Deployment (QFD) analysis is performed prior to the decision about the adequate robotic solution. This enhances the serviceability and efficiency of the provided technology. The word 'robotic' can be understood in its full meaning of Recognition - Strategy - Motion - Control. Cooperation of different individual systems with an established communication, e.g. utilizing Bluetooth technology, support the robustness of the ROSEN robotic inspection approach. Beside the navigation strategy, the inspection strategy is also part of the QFD process. Multiple inspection technologies combined on a single carrier or distributed across interacting container must be selected with a clear vision of the particular goal. (author)

  8. Crack status analysis for concrete dams based on measured entropy

    Institute of Scientific and Technical Information of China (English)

    WU BangBin; WU ZhongRu; CHEN Bo; SU HuaiZhi; BAO TengFei; WANG ShaoWei

    2016-01-01

    The integrity and safety of concrete dams are seriously affected by the existing cracks in dam bodies,and some serious cracks may cause dam failure or disaster.The propagation of cracks in concrete dams is accompanied by changes in energy distribution,which can be represented by changes in the structure's system entropy.Therefore,the entropy theory can be used in analyzing the behavior of dam cracks.Due to the randomness and locality of crack propagation,it is difficult to predict the location of cracks by traditional monitoring methods.To solve this problem,the influence of spatial positions of monitoring points on inspection zones is represented by a weight index,and the weight index is determined by the distance measure method proposed in this paper.Through the weighted linear fusion method,the entropy of multiple monitoring points is obtained for analyzing the behavior of dam cracks in the selected zones.Meanwhile,the catastrophe theory is used as the variation criterion of an entropy sequence in order to predict the instability time of dam cracks.Case studies are put forward on a high arch dam,and the fusion entropy is calculated according to the monitoring data from strain gauges.Results show that the proposed method can effectively predict the occurrence time and location of dam cracks regardless of the layout of monitoring instruments,and it is a new way to analyze the occurrence and propagation of dam cracks.

  9. Sizing stress corrosion cracks using laser ultrasonics

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, Hamood; McNealy, Rick; Fingerhut, Martin [Applus-RTD. Houston, TX (United States); Klein, Marvin; Ansari, Homayoon [Intelligent Optical Systems, Inc. Los Angeles, CA (United States); Kania Richard [TransCanada. Calgary, AB (Canada); Rapp, Steve [Spectra Energy, Houston, TX (United States)

    2010-07-01

    Despite various efforts, no reliable tools and techniques are available to enable an operator to quantify the impact of an SCC (Stress Corrosion Cracking) colony on the safety and integrity of a pipeline. Reliable non-destructive detection and measurement tools are not available either. There is therefore a large gap between current technology and the needs of the pipeline industry. Recent developments promise that with a concentrated effort, a comprehensive solution can be devised. This paper describes technical work performed to develop and validate both the inspection tool and the time of flight diffraction (TOFD) technique for sizing the depth of SCC. It also presents preliminary results of work on a closely related project that provides, on the basis of this technology, an integrated approach and tool for mapping, sizing, and evaluating SCC, through which significant cracks are filtered from more benign cracks within an SCC colony.

  10. Multifunctional Integrated Optic Sensor for Detection of Cracks and Corrosion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Los Gatos Research proposes to develop a new nondestructive inspection sensor system, capable of simultaneously measuring strain-based load and detecting crack,...

  11. Modified Dugdale cracks and Fictitious cracks

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1998-01-01

    (displacement) respectively of material considered. The practical applicability of the two models is limited such that predicted strength sigma_CR must be less than sigma_L/3, which corresponds to an assumption that fictitious cracks are much smaller than real crack lengths considered. The reason......A number of theories are presented in the literature on crack mechanics by which the strength of damaged materials can be predicted. Among these are theories based on the well-known Dugdale model of a crack prevented from spreading by self-created constant cohesive flow stressed acting in local...... Dugdale crack is the same as if it has been weakened by the well-known Griffith crack, namely sigma_CR = (EG_CR/phi)^1/2 where E and 1 are Young's modulus and crack half-length respectively, and G_CR is the so-called critical energy release rate. The physical significance of G_CR, however, is different...

  12. 混凝土结构裂缝检测中网络算法的研究%Research on neural network algorithm in crack inspection of concrete structures

    Institute of Scientific and Technical Information of China (English)

    郑伟花

    2012-01-01

    Ultrasonic nondestructive testing method is used commonly in concrete structure defect inspection, the post-processing of traditional probabilistic method has its own disadvantages. In order to overcome these short- comings, the ant colony optimization algorithm and BP neural network fusion method is presented in this paper, the mathematical model of neural network based on ant colony optimization is established and is trained, and ver- ify the validity of the method.%检测混凝土结构缺陷一般采用超声无损检测方法,传统的概率法在后期处理时有其自身的缺点.为了克服这些缺点,提出了采用蚁群优化算法与BP神经网络融合的方法进行后期处理,建立蚁群神经网络的数学模型,实现了蚁群神经网络的训练,并通过实例验证了该方法的有效性.

  13. Crack detection and sizing technique by ultrasonic and electromagnetic methods

    Energy Technology Data Exchange (ETDEWEB)

    Komura, Ichiro E-mail: ichiro.komura@toshiba.co.jp; Hirasawa, Taiji; Nagai, Satoshi; Takabayashi, Jun-ichi; Naruse, Katsuhiko

    2001-06-01

    Improvements in defect detection and sizing capabilities for non-destructive inspection techniques have been required in order to ensure the reliable operation and life extension of nuclear power plants. For the volumetric inspection, the phased array UT technique has superior capabilities for beam steering and focusing to objective regions, and real-time B-scan imaging without mechanical scanning. In contrast to the conventional UT method, high-speed inspection is realized by the unique feature of the phased array technique. A 256-channel array system has developed for the inspection of weldment of BWR internal components such as core shrouds. The TOFD crack sizing technique also can be applied using this system. For the surface inspection, potential drop techniques and eddy current techniques have been improved, which combined the theoretical analysis. These techniques have the crack sizing capability for surface breaking cracks to which UT method is difficult to apply. This paper provides the recent progress of these phased array and electromagnetic inspection techniques.

  14. Generic Reliability-Based Inspection Planning for Fatigue Sensitive Details

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Straub, Daniel; Faber, Michael Havbro

    2005-01-01

    of fatigue sensitive details in fixed offshore steel jacket platforms and FPSO ship structures. Inspection and maintenance activities are planned such that code based requirements to the safety of personnel and environment for the considered structure are fulfilled and at the same time such that the overall......The generic approach for planning of in-service NDT inspections is extended to cover the case where the fatigue load is modified during the design lifetime of the structure. Generic reliability-based inspection planning has been developed as a practical approach to perform inspection planning...... expected costs for design, inspections, repairs and failures are minimized. The method is based on the assumption of “no-finds” of cracks during inspections. Each fatigue sensitive detail is categorized according to their type of details (SN curves), FDF values, RSR values, inspection, repair and failure...

  15. Customs Inspection

    Science.gov (United States)

    1977-05-01

    required, for the per- DASDD9-%M) ii the single point of contact for formance of customs inspection functions. customs inspecion matters .in the Office...STATUS Onfdlt dotl. member of Rr": 21 DATE if officer of corporation . slu title) ATP OoM 6A N-7s) PtavIoux MuITUONs MAY BE UN&D Figure l-9. Reld.. and...grips. Commonly called HW-4. Serial number over 300,000 denotes the in- corporation of modified hammer safety components. Model HW-5T Double Action

  16. Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

    NARCIS (Netherlands)

    Pahlavan, P.L.; De Soares Silva e Melo Mota, M.; Blacquière, G.

    2016-01-01

    Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the effe

  17. Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

    NARCIS (Netherlands)

    Pahlavan, P.L.; De Soares Silva e Melo Mota, M.; Blacquière, G.

    2016-01-01

    Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the

  18. Risk Based Inspection Planning of Ageing Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Ersdal, Gerhard

    2008-01-01

    collapse of the structure. The importance of each component can be measured by the RIF (Residual Influence Factor) for each component and is illustrated by examples. When an installation becomes older then the number of fatigue critical components can be expected to increase. If the maximum acceptable....... Different approaches for updating inspection plans for older installations are considered in order to achieve decreased inspection intervals as the structure are ageing. The most promising method consists in increasing the rate of defects / crack initiation at the end of the expected lifetime. Different...

  19. THE EXPERIMENT OF THE COMPLEX INSPECTION OF THE RAILROAD BRIDGE PIER

    Directory of Open Access Journals (Sweden)

    B. M. Usachenko

    2010-03-01

    Full Text Available The procedure and results of a visual inspection and vibrosonic diagnostics of the railroad bridge pier are described. The spatial model of the pier with an arrangement of large cracks is presented.

  20. Investigation of casing inspection through tubing with pulsed eddy current

    Science.gov (United States)

    Fu, Yuewen; Yu, Runqiao; Peng, Xuewen; Ren, Shangkun

    2012-12-01

    Corrosion and cracks of casing string in oil wells is a serious problem on which little research has been done when inspecting casing through tubing. In this study, inspecting casing through tubing with pulsed eddy current is investigated. Longitudinal and transverse probes are centred inside the tubing to detect wall thinnings and cracks in casing. A time slice of induced voltage in the receiving coil of the probe is used as the feature to recognise defects. The experimental results show that large area wall thinnings and long cracks in casing are detected successfully through the tubing with appropriate inspection parameters. The probe's orientation to the crack is important and a particular discovery is that the transverse probe should be parallel to the transverse crack and not be perpendicular to it when inspecting. A method based on linear regression is proposed to estimate flaws in casing while wall thinning in the tubing occurs at the same location. The method is effective for large area thinning in casing when tubing thinning is wide.

  1. The application of RBI-concept to ultrasonic measurement of fatigue cracks

    Energy Technology Data Exchange (ETDEWEB)

    Pitkaenen, J.; Saerkiniemi, P.; Kauppinen, P. [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    In many power plants there are problem areas, which are not included in the official inspection programs. Flaws can be induced during service due to the service conditions in components and welded joints. These can lead to failures, which cause unforeseen shutdowns during operation and unscheduled repairs have to be earned out. The basic idea of Risk Based Inspection (RBI) methodology is to include this kind of objects in the inspection program. In this presentation two possible objects for RBI are described - thermal fatigue cracking in process piping and fatigue cracking in spinning fly wheel. (orig.) 4 refs.

  2. Crack elongation and its width of large depth reinforced concrete beams

    Institute of Scientific and Technical Information of China (English)

    GUAN Jun-feng; ZHAO Shun-bo; HUANG Cheng-kui

    2010-01-01

    In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.

  3. Crack layer theory

    Science.gov (United States)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  4. Dual-frequency Eddy Current Non-destructive Detection of Fatigue Cracks in Compressor Discs of Aero Engines

    Directory of Open Access Journals (Sweden)

    B. Sasi

    2004-10-01

    Full Text Available Eddy current non-destructive testing is used to inspect the critical aircraft components. The shortcomings of the inspection method identified, based on a few accidents, necessitatethe development of high sensitive and reliable testing procedures for inspecting the critical safety related aircraft components. This paper discusses a dual-frequency eddy current testingprocedure developed for inspection of compressor discs of aero engines for detecting fatigue cracks with high sensitivity and reliability. This procedure is capable of detecting fatigue crackssmaller than 2 mm in comparison to 4 mm cracks that can be detected with the currently practiced eddy current testing procedure.

  5. Effect of crack propagation on crack tip fields

    Directory of Open Access Journals (Sweden)

    F.V. Antunes

    2013-07-01

    Full Text Available Crack closure influences fatigue crack growth rate and must be included in the design of components. Plasticity induced crack closure is intimately linked with the crack tip plastic deformation, which becomes residual as the crack propagates. The objective here is to study numerically the effect of crack propagation on crack tip fields. The transient effect observed at the beginning of crack propagation is linked to the hardening behavior of material. The effect of mesh refinement is studied, and a singular behavior is evident, which is explained by the sharp crack associated with mesh topology, composed of a regular pattern of square elements. The plastic zone size measured perpendicularly to crack flank in the residual plastic wake is quantified and compared with literature models. Finally, the removal of material at the first node behind crack tip with load cycling was observed for plane strain state and some hardening models in plane stress state.

  6. Small-crack test methods

    Science.gov (United States)

    Larsen, James M.; Allison, John E.

    This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.

  7. Effect of crack surface geometry on fatigue crack closure

    Energy Technology Data Exchange (ETDEWEB)

    Drury, W.J. [P and L Technologies, Inc., Atlanta, GA (United States); Gokhale, A.M. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering; Antolovich, S.D. [Washington State Univ., Pullman, WA (United States). School of Mechanical and Materials Engineering

    1995-10-01

    The geometry of crack faces often plays a critical role in reducing crack extension forces when crack closure occurs during fatigue crack growth. Most previous studies of fatigue crack closure are concerned with mechanical measure of closure as related to the crack growth rate; very little attention has been given to the geometry of the crack surfaces. The objective is to identify those aspects of crack surface geometry that are important in the closure process, to develop quantitative fractographic techniques to estimate such attributes in a statistically significant and robust manner, and to correlate them to the physical process of crack closure. For this purpose, fatigue crack propagation experiments were performed on a Ni-base superalloy and crack growth rates and crack closure loads were measured. Digital image profilometry and software-based analysis techniques were used for statistically reliable and detailed quantitative characterization of fatigue crack profiles. It is shown that the dimensionless, scale-independent attributes, such a height-to-width ratio of asperities, fractal dimensions, dimensionless roughness parameters, etc., do not represent the aspects of crack geometry that are of primary importance in the crack closure phenomena. Furthermore, it is shown that the scale-dependent characteristics, such as average asperity height, do represent the aspects of crack geometry that play an interactive role in the closure process. These observations have implications concerning the validity of geometry-dependent, closure-based models for fatigue crack growth.

  8. Effect of roughness on imaging and characterizing rough crack-like defect using ultrasonic arrays

    Science.gov (United States)

    Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.

    2012-05-01

    All naturally occurring crack-like defects in solid structures are rough to some degree, which can affect defect inspection and characterization. Based on the simulated array data for various rough cracks and the total focusing method imaging algorithm, the effect of roughness on defect imaging and characterization was discussed. The array data was simulated by using the forward model combining with scattering matrices for various rough cracks. The scattering matrix describes the scattering field of a scatterer from all possible incident and scattering directions. It is shown that roughness can be either beneficial or detrimental to the detectability of a crack-like defect, depending on the defect characteristics such as length, roughness, correlation length, orientation angle, and array inspection configuration. It is also shown that roughness can cause the underestimation of length of rough crack-like defects by using the image-based approach.

  9. Dual-frequency Eddy Current Non-destructive Detection of Fatigue Cracks in Compressor Discs of Aero Engines

    National Research Council Canada - National Science Library

    B. Sasi; B.P.C. Rao; T. Jayakumar

    2004-01-01

    ... related aircraft components. This paper discusses a dual-frequency eddy current testing procedure developed for inspection of compressor discs of aero engines for detecting fatigue cracks with high sensitivity and reliability...

  10. Literature Review: Theory and Application of In-Line Inspection Technologies for Oil and Gas Pipeline Girth Weld Defection

    Directory of Open Access Journals (Sweden)

    Qingshan Feng

    2016-12-01

    Full Text Available Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT inspection and remote field eddy current (RFDC inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology.

  11. Literature Review: Theory and Application of In-Line Inspection Technologies for Oil and Gas Pipeline Girth Weld Defection.

    Science.gov (United States)

    Feng, Qingshan; Li, Rui; Nie, Baohua; Liu, Shucong; Zhao, Lianyu; Zhang, Hong

    2016-12-28

    Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL) inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT) inspection and remote field eddy current (RFDC) inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology.

  12. Pavement Crack Classifiers: A Comparative Study

    Directory of Open Access Journals (Sweden)

    S. Siddharth

    2012-12-01

    Full Text Available Non Destructive Testing (NDT is an analysis technique used to inspect metal sheets and components without harming the product. NDT do not cause any change after inspection; this technique saves money and time in product evaluation, research and troubleshooting. In this study the objective is to perform NDT using soft computing techniques. Digital images are taken; Gray Level Co-occurrence Matrix (GLCM extracts features from these images. Extracted features are then fed into the classifiers which classifies them into images with and without cracks. Three major classifiers: Neural networks, Support Vector Machine (SVM and Linear classifiers are taken for the classification purpose. Performances of these classifiers are assessed and the best classifier for the given data is chosen.

  13. Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.

    Directory of Open Access Journals (Sweden)

    Jingjing Chen

    Full Text Available In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.

  14. Modelling of Corrosion Cracks

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed.......Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed....

  15. INL Review of Fueling Machine Inspection Tool Development Proposal

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, George [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    A review of a technical proposal for James Fischer Nuclear. The document describes an inspection tool to examine the graphite moderator in an AGR reactor. The system is an optical system to look at the graphite blocks for cracks. INL reviews the document for technical value.

  16. The Application of Phased Array Ultrasonic Techniques for Inspection of Railway Axles from Their End Face

    Science.gov (United States)

    Liaptsis, D.; Cooper, I.; Boyle, K.; Nicholson, P. I.

    2011-06-01

    As part of the development of a non destructive testing (NDT) system combining complementary inspection techniques, an inspection system based on phased array ultrasonic testing (PAUT) for detection of transverse cracking in solid railway axles is being developed. This paper presents the initial study, which includes the PAUT experimental setup and the initial results obtained after testing the system on railway axle blocks. The inspection of solid axles from their axle end face is investigated.

  17. Reducing uncertainty in wind turbine blade health inspection with image processing techniques

    Science.gov (United States)

    Zhang, Huiyi

    Structural health inspection has been widely applied in the operation of wind farms to find early cracks in wind turbine blades (WTBs). Increased numbers of turbines and expanded rotor diameters are driving up the workloads and safety risks for site employees. Therefore, it is important to automate the inspection process as well as minimize the uncertainties involved in routine blade health inspection. In addition, crack documentation and trending is vital to assess rotor blade and turbine reliability in the 20 year designed life span. A new crack recognition and classification algorithm is described that can support automated structural health inspection of the surface of large composite WTBs. The first part of the study investigated the feasibility of digital image processing in WTB health inspection and defined the capability of numerically detecting cracks as small as hairline thickness. The second part of the study identified and analyzed the uncertainty of the digital image processing method. A self-learning algorithm was proposed to recognize and classify cracks without comparing a blade image to a library of crack images. The last part of the research quantified the uncertainty in the field conditions and the image processing methods.

  18. Nondestructive Image Detection of Cracks for a Nuclear Fuel Plate by Using Active Thermal Phase

    Energy Technology Data Exchange (ETDEWEB)

    Park, Nak Kyu; Park, Seung Kyu; Baik, Sung Hoon; Lee, Yoon Sang; Cha, Byung Heon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kang, Young June [Chonbuk National University, Jeonju (Korea, Republic of)

    2012-05-15

    Nondestructive crack detection is a key process for the safety insurance of the nuclear fuel plates which are widely used in a nuclear research reactor. Among nondestructive detection techniques, X-ray inspection technique and ultrasonic inspection technique using high frequency are widely used to detect internal cracks of a nuclear fuel plate at present. Though X-ray inspection is fast and efficient technique by providing a crack image for whole specimen area, this technique hardly provides the delaminated crack information which should be detected. Ultrasonic inspection is also an efficient tool to detect internal cracks of materials. High frequency ultrasound based on the piezoelectric transducers is usually used to detect cracks of a nuclear fuel plate. Though it is useful technique, the inspection should be carried out by an immersion test in a water-tank and its signal is complex and it is time consuming technique because the inspection is scanned point by point in sequence for whole inspection area. A commercial scanning ultrasonic system using high frequency is usually adopted to detect cracks. An alternative inspection technique to overcome the disadvantages of the high frequency ultrasonic inspection technique is needed. Especially, nondestructive imaging techniques of the internal cracks will be useful because it can be easily used in the field. One of efficient nondestructive testing techniques is infrared thermo-graphic technique. Infrared thermographic is a contactless optical imaging technique by detecting the invisible infrared radiation. Pulsed and lock-in thermography are commonly used in thermo-graphic nondestructive evaluation techniques. The two techniques are distinctly different but are deployed in the inspection of similar components. In general, these techniques are suitable for the detection of shallow planer defects, e.g. delamination in composites or adhesion defect in surface coatings. The surface of a specimen is instantaneously heated

  19. Nonlinear ultrasonic phased array imaging of closed cracks using global preheating and local cooling

    Science.gov (United States)

    Ohara, Yoshikazu; Takahashi, Koji; Ino, Yoshihiro; Yamanaka, Kazushi

    2015-10-01

    Closed cracks are the main cause of underestimation in ultrasonic inspection, because the ultrasound transmits through the crack. Specifically, the measurement of closed-crack depth in coarse-grained materials, which are highly attenuative due to linear scatterings at the grains, is the most difficult issue. To solve this problem, we have developed a temporary crack opening method, global preheating and local cooling (GPLC), using tensile thermal stress, and a high-selectivity imaging method, load difference phased array (LDPA), based on the subtraction of phased array images between different stresses. To demonstrate our developed method, we formed a closed fatigue crack in coarse-grained stainless steel (SUS316L) specimen. As a result of applying it to the specimen, the high-selectivity imaging performance was successfully demonstrated. This will be useful in improving the measurement accuracy of closed-crack depths in coarse-grained material.

  20. Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

    Science.gov (United States)

    Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

    1987-01-01

    During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

  1. Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

    Science.gov (United States)

    Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

    1987-01-01

    During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

  2. Aspects of Inspection Planning

    DEFF Research Database (Denmark)

    Faber, M. H.; Sørensen, John Dalsgaard

    2000-01-01

    framework for updating of the reliability of components and systems on the basis of inspection results is outlined. Systems representative for inspection planning of different engineering systems subjected to typical deterioration processes are presented. Numerical simulation studies are performed......Inspection planning for systems is considered with special emphasis to the effect of the quality of inspections on the system reliability and the probability of repair. Inspection quality is described and discussed in terms of inspection reliability and inspection coverage where the latter is set...... in relation to the correlation between the failure modes of the considered system. The inspection planning problem is described in general terms taking basis in the Bayesian decision theory. Practical applicable approaches are derived from the more general but also more involving formulations. The theoretical...

  3. Aspects of Inspection Planning

    DEFF Research Database (Denmark)

    Faber, M. H.; Sørensen, John Dalsgaard

    2000-01-01

    Inspection planning for systems is considered with special emphasis to the effect of the quality of inspections on the system reliability and the probability of repair. Inspection quality is described and discussed in terms of inspection reliability and inspection coverage where the latter is set...... in relation to the correlation between the failure modes of the considered system. The inspection planning problem is described in general terms taking basis in the Bayesian decision theory. Practical applicable approaches are derived from the more general but also more involving formulations. The theoretical...... framework for updating of the reliability of components and systems on the basis of inspection results is outlined. Systems representative for inspection planning of different engineering systems subjected to typical deterioration processes are presented. Numerical simulation studies are performed...

  4. Infrastructure anchor bolt inspection program with NDE applications

    Science.gov (United States)

    Fish, Philip E.

    1996-11-01

    In 1990, Wisconsin Department of Transportation found a high mast light pole with two of six anchor bolts failed. This failure along with published reports from Michigan DOT about anchor bolt failures on cantilever sign structures, raised concern about the quality and condition of anchor bolts on the Wisconsin DOT system. Wisconsin Department of Transportation implemented an Anchor Bolt Inspection Program in 1990 for cantilever sign structures, high mast light towers, interstate light towers, and signal masts. The program requires an experienced inspection team and a practical inspection approach. Inspection preparation includes review of all background information such as design plans, design computations, construction plans, shop plans, and maintenance history. An inspection plan is developed. Special emphasis is placed on determining material type, cut or rolled threads, and type of coating for anchor bolts. Inspection emphasis are on "hands on" and Nondestructive evaluation. Special emphasis is placed on visual conditions of anchor bolts (cut or rolled threads, straightness, corrosion, nut tension etc.) along with ultrasonic inspection. This program places a strong emphasis on Non Destructive Testing (NDT), especially ultrasonic. Procedures and inspection calibrations are developed from similar anchor bolt geometry and material type. Cut notches are placed in the anchor bolts at locations of possible failure. NDT inspection calibrations are performed from these bolts. Report documentation includes all design plans, pictorial documentation of structural deficiencies, sketches, nondestructive evaluation reports, conclusions, and recommendations. This program has been successful in locating failed anchor bolts and critical cracks before failure of an entire structure.

  5. Electronic Inspection of Beef

    Science.gov (United States)

    Anselmo, Victor J.; Gammell, Paul M.; Clark, Jerry

    1987-01-01

    Two proposed methods for grading beef quality based on inspection by electronic equipment: one method uses television camera to generate image of a cut of beef as customer sees it; other uses ultrasonics to inspect live animal or unsliced carcasses. Both methods show promise for automated meat inspection.

  6. Literature Review: Theory and Application of In-Line Inspection Technologies for Oil and Gas Pipeline Girth Weld Defection

    OpenAIRE

    Qingshan Feng; Rui Li; Baohua Nie; Shucong Liu; Lianyu Zhao; Hong Zhang

    2016-01-01

    Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage...

  7. Analysis of Fatigue Crack Growth in Ship Structural Details

    Directory of Open Access Journals (Sweden)

    Leheta Heba W.

    2016-04-01

    Full Text Available Fatigue failure avoidance is a goal that can be achieved only if the fatigue design is an integral part of the original design program. The purpose of fatigue design is to ensure that the structure has adequate fatigue life. Calculated fatigue life can form the basis for meaningful and efficient inspection programs during fabrication and throughout the life of the ship. The main objective of this paper is to develop an add-on program for the analysis of fatigue crack growth in ship structural details. The developed program will be an add-on script in a pre-existing package. A crack propagation in a tanker side connection is analyzed by using the developed program based on linear elastic fracture mechanics (LEFM and finite element method (FEM. The basic idea of the developed application is that a finite element model of this side connection will be first analyzed by using ABAQUS and from the results of this analysis the location of the highest stresses will be revealed. At this location, an initial crack will be introduced to the finite element model and from the results of the new crack model the direction of the crack propagation and the values of the stress intensity factors, will be known. By using the calculated direction of propagation a new segment will be added to the crack and then the model is analyzed again. The last step will be repeated until the calculated stress intensity factors reach the critical value.

  8. Cracked lifting lug welds on ten-ton UF{sub 6} cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Dorning, R.E. [Martin Marietta Energy Systems, Inc., Piketon, OH (United States)

    1991-12-31

    Ten-ton, Type 48X, UF{sub 6} cylinders are used at the Portsmouth Gaseous Diffusion Plant to withdraw enriched uranium hexafluoride from the cascade, transfer enriched uranium hexafluoride to customer cylinders, and feed enriched product to the cascade. To accomplish these activities, the cylinders are lifted by cranes and straddle carriers which engage the cylinder lifting lugs. In August of 1988, weld cracks on two lifting lugs were discovered during preparation to lift a cylinder. The cylinder was rejected and tagged out, and an investigating committee formed to determine the cause of cracking and recommend remedial actions. Further investigation revealed the problem may be general to this class of cylinder in this use cycle. This paper discusses the actions taken at the Portsmouth site to deal with the cracked lifting lug weld problem. The actions include inspection activities, interim corrective actions, metallurgical evaluation of cracked welds, weld repairs, and current monitoring/inspection program.

  9. STAC -- a new Swedish code for statistical analysis of cracks in SG-tubes

    Energy Technology Data Exchange (ETDEWEB)

    Poern, K. [Poern Consulting, Nykoeping (Sweden)

    1997-02-01

    Steam generator (SG) tubes in pressurized water reactor plants are exposed to various types of degradation processes, among which stress corrosion cracking in particular has been observed. To be able to evaluate the safety importance of such cracking of SG-tubes one has to have a good and empirically founded knowledge about the scope and the size of the cracks as well as the rate of their continuous growth. The basis of experience is to a large extent constituted of the annually performed SG-inspections and crack sizing procedures. On the basis of this experience one can estimate the distribution of existing crack lengths, and modify this distribution with regard to maintenance (plugging) and the predicted rate of crack propagation. Finally, one can calculate the rupture probability of SG-tubes as a function of a given critical crack length. On account of the Swedish Nuclear Power Inspectorate an introductory study has been performed in order to get a survey of what has been done elsewhere in this field. The study resulted in a proposal of a computerizable model to be able to estimate the distribution of true cracks, to modify this distribution due to the crack growth and to compute the probability of tube rupture. The model has now been implemented in a compute code, called STAC (STatistical Analysis of Cracks). This paper is aimed to give a brief outline of the model to facilitate the understanding of the possibilities and limitations associated with the model.

  10. Detection of Cracks in Aluminum Structure Beneath Inconel Repair Bushings

    Science.gov (United States)

    2008-04-01

    conductivity (i.e. Inconel 718 ) – Primary challenge then becomes detecting the weak eddy current field in the structure beyond the bushing wall...was able to be selected with inspectability as a goal. – Inconel 718 • low permeability (~μ0) • low conductivity (< 2% IACS) • Combined with...Detection of Cracks in Aluminum Structure beneath Inconel Repair Bushings Mr. Kenneth J. LaCivita (USAF) AFRL/RXSA Air Force Research Laboratory

  11. Approximations in Inspection Planning

    DEFF Research Database (Denmark)

    Engelund, S.; Sørensen, John Dalsgaard; Faber, M. H.

    2000-01-01

    Planning of inspections of civil engineering structures may be performed within the framework of Bayesian decision analysis. The effort involved in a full Bayesian decision analysis is relatively large. Therefore, the actual inspection planning is usually performed using a number of approximations....... One of the more important of these approximations is the assumption that all inspections will reveal no defects. Using this approximation the optimal inspection plan may be determined on the basis of conditional probabilities, i.e. the probability of failure given no defects have been found...... by the inspection. In this paper the quality of this approximation is investigated. The inspection planning is formulated both as a full Bayesian decision problem and on the basis of the assumption that the inspection will reveal no defects....

  12. Approximations in Inspection Planning

    DEFF Research Database (Denmark)

    Engelund, S.; Sørensen, John Dalsgaard; Faber, M. H.

    2000-01-01

    Planning of inspections of civil engineering structures may be performed within the framework of Bayesian decision analysis. The effort involved in a full Bayesian decision analysis is relatively large. Therefore, the actual inspection planning is usually performed using a number of approximations....... One of the more important of these approximations is the assumption that all inspections will reveal no defects. Using this approximation the optimal inspection plan may be determined on the basis of conditional probabilities, i.e. the probability of failure given no defects have been found...... by the inspection. In this paper the quality of this approximation is investigated. The inspection planning is formulated both as a full Bayesian decision problem and on the basis of the assumption that the inspection will reveal no defects....

  13. Development of digital image correlation method to analyse crack variations of masonry wall

    Indian Academy of Sciences (India)

    Shih-Heng Tung; Ming-Hsiang Shih; Wen-Pei Sung

    2008-12-01

    The detection of crack development in a masonry wall forms an important study for investigating the earthquake resistance capability of the masonry structures. Traditionally, inspecting the structure and documenting the findings were done manually. The procedures are time-consuming, and the results are sometimes inaccurate. Therefore, the digital image correlation (DIC) technique is developed to identify the strain and crack variations. This technique is non-destructive for inspecting the whole displacement and strain field. Tests on two masonry wall samples were performed to verify the performance of the digital image correlation method. The phenomena of micro cracks, strain concentration situation and nonuniform deformation distribution which could not have been observed preciously by manual inspection are successfully identified using DIC. The crack formation tendencies on masonry wall can be observed at an earlier stage by this proposed method. These results show a great application potential of the DIC technique for various situations such as inspecting shrinkage-induced cracks in fresh concrete, masonry and reinforced concrete structures, and safety of bridges.

  14. A new methodology for non-contact accurate crack width measurement through photogrammetry for automated structural safety evaluation

    Science.gov (United States)

    Jahanshahi, Mohammad R.; Masri, Sami F.

    2013-03-01

    In mechanical, aerospace and civil structures, cracks are important defects that can cause catastrophes if neglected. Visual inspection is currently the predominant method for crack assessment. This approach is tedious, labor-intensive, subjective and highly qualitative. An inexpensive alternative to current monitoring methods is to use a robotic system that could perform autonomous crack detection and quantification. To reach this goal, several image-based crack detection approaches have been developed; however, the crack thickness quantification, which is an essential element for a reliable structural condition assessment, has not been sufficiently investigated. In this paper, a new contact-less crack quantification methodology, based on computer vision and image processing concepts, is introduced and evaluated against a crack quantification approach which was previously developed by the authors. The proposed approach in this study utilizes depth perception to quantify crack thickness and, as opposed to most previous studies, needs no scale attachment to the region under inspection, which makes this approach ideal for incorporation with autonomous or semi-autonomous mobile inspection systems. Validation tests are performed to evaluate the performance of the proposed approach, and the results show that the new proposed approach outperforms the previously developed one.

  15. On the detectability of transverse cracks in laminated composites using electrical potential change measurements

    KAUST Repository

    Selvakumaran, Lakshmi

    2015-03-01

    Real-time health monitoring of structures made of laminated composites is necessary as significant damage may occur without any visible signs on the surface. Inspection by electrical tomography (ET) seems a viable approach that relies on voltage measurements from a network of electrodes across the inspected domain to infer conductivity change within the bulk material. If conductivity decreases significantly with increasing damage, the obtained conductivity map can be correlated to the degradation state of the material. We focus here on detection of transverse cracks. As transverse cracks modify the in-plane transverse conductivity of a single ply, we expect them to be detectable by electrical measurements. Yet, the quality of detection is directly related to the sensitivity of the measurements to the presence of cracks. We use numerical experiments to demonstrate that the sensitivity depends on several material and geometrical parameters. Based on the results, the applicability of ET to detect transverse cracks is discussed. One conclusion from the study is that detecting transverse cracks using ET is more reliable in some laminate configurations than in others. Recommendations about the properties of either the pristine material or the inspected structures are provided to establish if ET is reliable in detecting transverse cracks.

  16. Development of nondestructive system for detecting the cracks in KTX brake disk using Rayleigh wave

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Soo; Lee, Ho Yong [Korea Railroad Research Institute, Uiwang (Korea, Republic of); Yeom, Yun Taek; Park, Jin Hyun; Song, Sung Jing; Kim, Hak Joon [Dept. of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kwon, Sung Duck [Dept. of Physics, Andong National University, Andong (Korea, Republic of)

    2017-02-15

    Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.

  17. The impact of instructions on aircraft visual inspection performance : a first look at the overall results.

    Energy Technology Data Exchange (ETDEWEB)

    Drury, Colin G. (State University of New York at Buffalo, Buffalo, NY); Spencer, Floyd Wayne; Wenner, Caren A.

    2003-07-01

    The purpose of this study was to investigate the impact of instructions on aircraft visual inspection performance and strategy. Forty-two inspectors from industry were asked to perform inspections of six areas of a Boeing 737. Six different instruction versions were developed for each inspection task, varying in the number and type of directed inspections. The amount of time spent inspecting, the number of calls made, and the number of the feedback calls detected all varied widely across the inspectors. However, inspectors who used instructions with a higher number of directed inspections referred to the instructions more often during and after the task, and found a higher percentage of a selected set of feedback cracks than inspectors using other instruction versions. This suggests that specific instructions can help overall inspection performance, not just performance on the defects specified. Further, instructions were shown to change the way an inspector approaches a task.

  18. LiDAR-based Localization and Mapping System using Ellipse Distance Correction Models for UAV Wind Turbine Blade Inspection

    DEFF Research Database (Denmark)

    Nikolov, Ivan Adriyanov; Madsen, Claus B.

    2016-01-01

    The wind energy sector faces a constant need for annual inspections of wind turbine blades for damage, erosion and cracks. These inspections are an important part of the wind turbine life cycle and can be very constly and hazardous to specialists. This has led to the use of automated drone...

  19. Use of FBG sensors for monitoring cracks of the equestrian statue of Bartolomeo Colleoni in Venice

    Directory of Open Access Journals (Sweden)

    F. Felli

    2014-10-01

    Full Text Available The Bartolomeo Colleoni monument suffered for years damage from the local climate. The process of restoring the Colleoni equestrian statue, started in 2003, allowed to understand how the bronze statue was originally cast and manufactured and the techniques used in its construction. During this process a relevant crack on the right foreleg was investigated in correspondence of the cast-on joining the right foreleg to the front portion of the horse body. The crack was investigated experimentally by Fiber Bragg Grating (FBG sensors, avoiding any modelling because of the very complex structure of the statue. An array of FBG sensors connected in series was glued on the crack with the aim of capturing live information about the effect of applying stress on the crack opening. The monitoring system was successfully tested during repositioning of the RIDER on the horse and is available for long term inspection of the crack opening evolution.

  20. Image-based method for monitoring of crack opening on masonry and concrete using Mobile Platform

    Directory of Open Access Journals (Sweden)

    A. P. Martins

    Full Text Available This paper proposes an automatic method based on the computing vision, implemented in a mobile platform, to inspect cracks in masonry and concrete. The developed algorithm for image processing performs this task from images of the cracks evolution. The contribution of this paper is the development of a mobile tool with quick response aiming to assist technicians in periodic visits when monitoring the crack opening in masonry and concrete. The obtained results show, successfully, the dimensional alterations of cracks detected by mobile phone in a faster and accurate way compared with the conventional measurement technique. Regardless the irregular shape of the cracks, the proposed method has the advantage of producing results statistically significant in measurement repetition by decreasing the subjectivity inherent to manual measurement technique.

  1. Experimental assessment of an RFID-based crack sensor for steel structures

    Science.gov (United States)

    E Martínez-Castro, R.; Jang, S.; Nicholas, J.; Bansal, R.

    2017-08-01

    The use of welded steel cover plates had been a common design practice to increase beam section capacity in regions of high moment for decades. Many steel girder bridges with cover plates are still in service. Steel girder bridges are subject to cyclic loading, which can initiate crack formation at the toe of the weld and reduce beam capacity. Thus, timely detection of fatigue cracks is of utmost importance in steel girder bridge monitoring. To date, crack monitoring methods using in-house radio frequency identification (RFID)-based sensors have been developed to complement visual inspection and provide quantitative information of damage level. Offering similar properties at a reduced cost, commercial ultra-high frequency (UHF) passive RFID tags have been identified as a more financially viable option for pervasive crack monitoring using a dense array of sensors. This paper presents a study on damage sensitivity of low-cost commercial UHF RFID tags for crack detection and monitoring on metallic structures. Using backscatter power as a parameter for damage identification, a crack sensing system has been developed for single and multiple tag configurations for increased sensing pervasiveness. The effect on backscatter power of the existence and stage of crack propagation has been successfully characterized. For further automation of crack detection, a damage index based on the variation of backscatter power has also been established. The tested commercial RFID-based crack sensor contributes to the usage of this technology on steel girder bridges.

  2. Cracking in desiccating soils

    OpenAIRE

    Ledesma Alberto

    2016-01-01

    Soil shrinkage is produced typically under desiccating conditions. Eventually shrinkage may generate cracks in the soil mass, a phenomenon that is being studied by several researchers, because its prediction is far from being a routine in Soil Mechanics. Within this context, Unsaturated Soil Mechanics provides a promising framework to understand the mechanisms involved. In addition to that, physical modelling of desiccating soils constitutes a good tool to explore the nature of this problem. ...

  3. Utopia Cracks and Polygons

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-339, 23 April 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.

  4. Detection of Through-Deck Type Fatigue Cracks in Steel Bridges by Self-Reference Lock-in Thermography

    Directory of Open Access Journals (Sweden)

    Tamakoshi T.

    2010-06-01

    Full Text Available A new remote nondestructive inspection technique, based on thermoelastic temperature measurement by infrared thermography, is developed for detection and evaluation of fatigue cracks propagating from welded joints in steel bridges. Fatigue cracks are detected from localized high thermoelastic temperature change at crack tips due to stress singularity under variable loading from traffics on the bridge. Selfreference lock-in data processing technique is developed for the improvement of signal/noise ratio in the crack detection process. The technique makes it possible to perform correlation processing without an external reference signal. It is very difficult to detect through-deck type fatigue cracks in steel decks by the conventional NDT technique, since they are not open to the inspection. In this paper, self-reference lock-in thermography is applied for detection of through-deck type fatigue cracks. Experiments are carried out to steel deck sample, which simulates an actual steel bridge, during crack propagation test. It is found that significant stress concentration zone can be observed near the crack front, which enabled us to detect through-deck type fatigue cracks and to estimate its size.

  5. Detection of Cracks in Concrete Structure Using Microwave Imaging Technique

    Directory of Open Access Journals (Sweden)

    E. A. Jiya

    2016-01-01

    Full Text Available Cracks in concrete or cement based materials present a great threat to any civil structures; they are very dangerous and have caused a lot of destruction and damage. Even small cracks that look insignificant can grow and may eventually lead to severe structural failure. Besides manual inspection that is ineffective and time-consuming, several nondestructive evaluation techniques have been used for crack detection such as ultrasonic technique, vibration technique, and strain-based technique; however, some of the sensors used are either too large in size or limited in resolution. A high resolution microwave imaging technique with ultrawideband signal for crack detection in concrete structures is proposed. A combination of the delay-and-sum beamformer with full-view mounted antennas constitutes the image reconstruction algorithm. Various anomaly scenarios in cement bricks were simulated using FDTD, constructed, and measured in the lab. The reconstructed images showed a high similarity between the simulation and the experiment with a resolution of λ/14 which enables a detection of cracks as small as 5 mm in size.

  6. Evaluations of Structural Failure Probabilities and Candidate Inservice Inspection Programs

    Energy Technology Data Exchange (ETDEWEB)

    Khaleel, Mohammad A.; Simonen, Fredric A.

    2009-05-01

    The work described in this report applies probabilistic structural mechanics models to predict the reliability of nuclear pressure boundary components. These same models are then applied to evaluate the effectiveness of alternative programs for inservice inspection to reduce these failure probabilities. Results of the calculations support the development and implementation of risk-informed inservice inspection of piping and vessels. Studies have specifically addressed the potential benefits of ultrasonic inspections to reduce failure probabilities associated with fatigue crack growth and stress-corrosion cracking. Parametric calculations were performed with the computer code pc-PRAISE to generate an extensive set of plots to cover a wide range of pipe wall thicknesses, cyclic operating stresses, and inspection strategies. The studies have also addressed critical inputs to fracture mechanics calculations such as the parameters that characterize the number and sizes of fabrication flaws in piping welds. Other calculations quantify uncertainties associated with the inputs calculations, the uncertainties in the fracture mechanics models, and the uncertainties in the resulting calculated failure probabilities. A final set of calculations address the effects of flaw sizing errors on the effectiveness of inservice inspection programs.

  7. Evaluation of the Frequencies for Canister Inspections for SCC

    Energy Technology Data Exchange (ETDEWEB)

    Stockman, Christine [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bryan, Charles R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-02-02

    This report fulfills the M3 milestone M3FT-15SN0802042, “Evaluate the Frequencies for Canister Inspections for SCC” under Work Package FT-15SN080204, “ST Field Demonstration Support – SNL”. It reviews the current state of knowledge on the potential for stress corrosion cracking (SCC) of dry storage canisters and evaluates the implications of this state of knowledge on the establishment of an SCC inspection frequency. Models for the prediction of SCC by the Japanese Central Research Institute of Electric Power Industry (CRIEPI), the United States (U.S.) Electric Power Research Institute (EPRI), and Sandia National Laboratories (SNL) are summarized, and their limitations discussed.

  8. Eddy current system for inspection of train hollow axles

    Energy Technology Data Exchange (ETDEWEB)

    Chady, Tomasz; Psuj, Grzegorz; Sikora, Ryszard; Kowalczyk, Jacek; Spychalski, Ireneusz [Department of Electrical and Computer Engineering, Faculty of Electrical Engineering, West Pomeranian University of Technology, Szczecin (Poland)

    2014-02-18

    The structural integrity of wheelsets used in rolling stock is of great importance to the safety. In this paper, electromagnetic system with an eddy current transducer suitable for the inspection of hollow axles have been presented. The transducer was developed to detect surface braking defects having depth not smaller than 0.5 mm. Ultrasound technique can be utilized to inspect the whole axle, but it is not sufficiently sensitive to shallow defects located close to the surface. Therefore, the electromagnetic technique is proposed to detect surface breaking cracks that cannot be detected by ultrasonic technique.

  9. Focusing Automatic Code Inspections

    NARCIS (Netherlands)

    Boogerd, C.J.

    2010-01-01

    Automatic Code Inspection tools help developers in early detection of defects in software. A well-known drawback of many automatic inspection approaches is that they yield too many warnings and require a clearer focus. In this thesis, we provide such focus by proposing two methods to prioritize

  10. Crack Tip Parameters for Growing Cracks in Linear Viscoelastic Materials

    DEFF Research Database (Denmark)

    Brincker, Rune

    intensity factors. In the special case of a constant Poisson ratio only 2 deformation intensity factors are needed. Closed form solutions are given both for a slowly growing crack and for a crack that is suddenly arrested at a point at the crack extension path. Two examples are studied; a stress boundary...... value problem, and a displacement boundary value problem. The results show that the stress intensity factors and the displacement intensity factors do not depend explicitly upon the velocity of the crack tip....

  11. Development of inspection/maintenance robot for underground pipes

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ji Sup; Cho, M.W.; Kim, Y.H.; Park, B.S. [Korea Atomic Energy Research Institute, Taejon (Korea)

    1998-11-01

    A sewage inspection/maintenance robot is developed which inspects physical defects of inner walls of sewage pipes as well as effectively repairs these defects. The robot system consists of a cutting robot, a inspection robot, and a packer robot. The cutting robot removes the branch pipes extruded into a main pipe as well as grinds the surface of defected parts. Unlike other sewage cutting robots, the developed cutting robot is equipped with two cutting tools whose position can be easily changed each other by remote operations. The inspection robot is equipped with a rotary type inspection module which utilizes laser sensors and automatically inspects defects. Also, image processing technology is applied to this robot so that the identification of accurate geometry of the defects is made possible by combining the displacement data from laser sensor and a image data from the Ccd camera. The inspection robot can be autonomously navigates by utilizing a gyro compass as a navigation sensor and the velocity difference between left and right wheels. The packer robot fills the cracks or holes of inner wall by expending its rubber tube inside the pipes. 20 refs., 166 figs., 30 tabs. (Author)

  12. Mobile X-ray inspection of light weight materials

    Energy Technology Data Exchange (ETDEWEB)

    Ewert, Uwe; Redmer, Bernhard; Raedel, Christoph; Osterloh, Kurt [Federal Inst. for Materials Research and Testing (BAM), Berlin (Germany); Schnars, Ulf; Henrich, Rudolf; Schimmelmann, Olaf [Airbus, Bremen/Stade (Germany); Bavendiek, Klaus; Jahn, Mirko [YXLON International, Hamburg (Germany)

    2008-07-01

    Digital detectors such as phosphor imaging plates (IP) and digital detector arrays (DDA) allow radiographic inspection with higher efficiency and improved image quality in comparison to the classic film technique. Mobile X-ray flash tubes are used routinely for veterinarian and security applications. New high sensitive IPs and DDAs enable to apply them for inspection of light materials with low X-ray attenuation as in aluminium, plastics and composites. A versatile computed tomography (CT) system was developed for in situ inspection of large aircraft components under production conditions. A gate based planar computed tomograph was developed and tested for inspection of integrity of the stringer incorporation. Successful test trials were performed to prove the detection rate of cracks in embedded stringers. Honey comb structures of aircrafts have to be inspected for water inclusions during in-service inspections. Thermography is a powerful method for in house inspections when variations in temperature caused e.g. by sunshine can be excluded. A new X-ray diaphragm was developed for mobile back scatter measurements of large components. This method is insensitive to heat alterations in the field and thus can be applied also outdoors. (orig.)

  13. Nondestructive inspection and life determination of disc material

    Science.gov (United States)

    Craig, Hugh K.

    1991-12-01

    The prime role of nondestructive evaluation is to support development and validation of the two main processes: the materials and manufacturing method design and engineering design of the engine. The second role of nondestructive evaluation is to monitor, on a routine basis, these design processes during the manufacture and service operations. Shortcomings in the method which link the manufacturing inspection capability to the initial design life of parts are discussed. A methodology which establishes the imperfection size frequency distribution for disc materials is outlined. The data validates the disc material manufacturing process and is also used with the probabilistic lifing methods. The development of DRACULA, a program for the detection of radial-axial subsurface cracks which was brought to a generic state of service readiness and is used for disc life management, is addressed. The major points of subsurface radial-axial fatigue crack work are discussed: ultrasonic detection methods, potential sensitivity, mathematical modeling, and inspection experience.

  14. Pulsed eddy current inspection of CF-188 inner wing spar

    Science.gov (United States)

    Horan, Peter Francis

    Royal Canadian Air Force (RCAF) CF-188 Hornet aircraft engineering authorities have stated a requirement for a Non-Destructive Evaluation (NDE) technique to detect Stress Corrosion Cracking (SCC) in the inner wing spars without fastener or composite wing skin removal. Current radiographic inspections involve significant aircraft downtime, and Pulsed Eddy Current (PEC) inspection is proposed as a solution. The aluminum inner wing spars of CF-188 Hornet aircraft may undergo stress corrosion cracking (SCC) along the spar between the fasteners that secure carbon-fiber/ epoxy composite skin to the wing. Inspection of the spar through the wing skin is required to avoid wing disassembly. The thickness of the wing skin varies between 8 and 20 mm (0.3 to 0.8 inch) and fasteners may be either titanium or ferrous. PEC generated by a probe centered over a fastener, demonstrates capability of detecting simulated cracks within spars with the wing skin present. Comparison of signals from separate sensors, mounted to either side of the excitation coil, is used to detect differences in induced eddy current fields, which arise in the presence of cracks. To overcome variability in PEC signal response due to variation in 1) skin thickness, 2) fastener material and size, and 3) centering over fasteners, a large calibration data set is acquired. Multi-dimensional scores from a Modified Principal Components Analysis (PCA) of the data are reduced to one dimension (1D) using a Discriminant Analysis method. Under inspection conditions, calibrated PCA scores combined with discriminant analysis permit rapid real time go/no-go PEC detection of cracks in CF-188 inner wing spar. Probe designs using both pickup coils and Giant Magnetoresistive (GMR) sensors were tested on samples with the same ferrous and titanium fasteners found on the CF-188. Flaws were correctly detected at lift-offs of up to 21mm utilizing a variety of insulating skin materials simulating the carbon-fibre reinforced polymer

  15. Fatigue crack identification and lifetime prediction for steel bridge deck structures

    NARCIS (Netherlands)

    Pahlavan, P.L.; Pijpers, R.J.M.; Hakkesteegt, H.C.; Jansen, T.H.; Peelen, W.H.A.

    2015-01-01

    Fatigue, as the governing degradation mechanism in steel bridge decks, can lead to non-inspectable cracks under the welded intersections of stiffeners to the deck plate. As a result, estimation of the remaining service life and optimization of the maintenance program of steel bridge decks become a g

  16. Cryptography cracking codes

    CERN Document Server

    2014-01-01

    While cracking a code might seem like something few of us would encounter in our daily lives, it is actually far more prevalent than we may realize. Anyone who has had personal information taken because of a hacked email account can understand the need for cryptography and the importance of encryption-essentially the need to code information to keep it safe. This detailed volume examines the logic and science behind various ciphers, their real world uses, how codes can be broken, and the use of technology in this oft-overlooked field.

  17. DETECTION OF ODSCC IN SG TUBES DEPENDING ON THE SIZE OF THE CRACK AND ON THE PRESENCE OF SLUDGE DEPOSITS

    Directory of Open Access Journals (Sweden)

    HANSUB CHUNG

    2014-12-01

    Full Text Available It was discovered in a Korean PWR that an extensive number of very short and shallow cracks in the SG tubes were undetectable by eddy current in-service-inspection because of the masking effect of sludge deposits. Axial stress corrosion cracks at the outside diameter of the steam generator tubes near the line contacts with the tube support plates are the major concern among the six identical Korean nuclear power plants having CE-type steam generators with Alloy 600 high temperature mill annealed tubes, HU3&4 and HB3∼6. The tubes in HB3&4 have a less susceptible microstructure so that the onset of ODSCC was substantially delayed compared to HU3&4 whose tubes are most susceptible to ODSCC among the six units. The numbers of cracks detected by the eddy current inspection jumped drastically after the steam generators of HB4 were chemically cleaned. The purpose of the chemical cleaning was to mitigate stress corrosion cracking by removing the heavy sludge deposit, since a corrosive environment is formed in the occluded region under the sludge deposit. SGCC also enhances the detection capability of the eddy current inspection at the same time. Measurement of the size of each crack using the motorized rotating pancake coil probe indicated that the cracks in HB4 were shorter and substantially shallower than the cracks in HU3&4. It is believed that the cracks were shorter and shallower because the microstructure of the tubes in HB4 is less susceptible to ODSCC. It was readily understood from the size distribution of the cracks and the quantitative information available on the probability of detection that most cracks in HB4 had been undetected until the steam generators were chemically cleaned.

  18. Multiaxial mixed-mode cracking - small crack initiation and propagation

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, M. de; Reis, L.; Li Bin [Lisbon Univ. (Portugal). ICEMS - Inst. of Material and Surface Science and Engineering

    2006-07-01

    Both the fatigue crack path and fatigue life of CK45 steel and 42CrMo4 steel under various multiaxial loading paths are studied in this paper. The replica method was applied to monitor the crack initiation and small crack growth, the fractographic analyses were carried out on the fracture surface and the crack initiation angle was measured. The effects of non-proportional loading on both the crack path and fatigue life were studied, and the flattening of asperities on the crack surface due to compressive normal stress was also observed. An improved model is proposed based on correcting the strain range parameter of the ASME code approach, taking into account the additional hardening caused by the non-proportional loading path, which can improve the predictions of the fatigue lives for various non-proportional loading paths and provide an easy way to overcome the drawbacks of the current ASME code approach for non-proportional fatigue. Based on these corrected strain range parameters, a strain intensity factor range is used to correlate with the experimental results of small crack growth rates. It is concluded that the orientation of the early crack growth can be predicted well by the critical damage plane, but the fatigue life can not be predicted accurately using only the parameters on the critical plane, since the damage on all the planes contributes to fatigue damage as stated by the integral approaches. (orig.)

  19. Application of shearography to crack detection in concrete structures subjected to traffic loading

    Science.gov (United States)

    Muzet, V.; Blain, P.; Przybyla, D.

    2010-09-01

    Early detection of defects in concrete structures, such as bridges or dams, is essential to optimize the maintenance of civil engineering facilities. Optical methods constitute non-destructive means of control and measurement but they are generally confined in laboratories where both the setup and environnement are controlled. The method of shearography is especially well adapted to detect damages due to both its capacity to distinctly visualize strain concentration zones and its robustness. The experimental set-up is relatively compact, which enables to examine an extensive surface area by simply moving the shearographic head. In this paper, the application of this methodology for the detection of cracks is presented on concrete samples and circulated outside concrete structures. Due to its sensitivity to strain concentration, shearography is able to detect structural cracks, even when they were not through-cracks. Operational implementation is made on two circulated structures with experts in manual cracks detection. No stimulation device is used. In the first structure, cracks are detected on the bridge deck and on the bridge abutment. In the second structure, cracks on the intrados of the bridge deck are detected and also beginning of cracks which have not been detected by the visual inspection. Different areas are scanned and the results are in agreement with the visual inspection. This technique enables detecting cracks on structures subjected to traffic load. The natural loading of an engineering structure, i.e. the rolling traffic it bears, proves well suited for cracks detection by means of shearography, provided traffic patterns are regular enough.

  20. Reliability prediction for structures under cyclic loads and recurring inspections

    Directory of Open Access Journals (Sweden)

    Alberto W. S. Mello Jr

    2009-06-01

    Full Text Available This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA, inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a “cascade” chart. Due to the scatter, it also defines the confidence level of the “acceptable” risk. As an example, the damage tolerance analysis (DTA results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements.

  1. Catalytic cracking of lignites

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, M.; Nowak, S.; Naegler, T.; Zimmermann, J. [Hochschule Merseburg (Germany); Welscher, J.; Schwieger, W. [Erlangen-Nuernberg Univ. (Germany); Hahn, T. [Halle-Wittenberg Univ., Halle (Germany)

    2013-11-01

    A most important factor for the chemical industry is the availability of cheap raw materials. As the oil price of crude oil is rising alternative feedstocks like coal are coming into focus. This work, the catalytic cracking of lignite is part of the alliance ibi (innovative Braunkohlenintegration) to use lignite as a raw material to produce chemicals. With this new one step process without an input of external hydrogen, mostly propylene, butenes and aromatics and char are formed. The product yield depends on manifold process parameters. The use of acid catalysts (zeolites like MFI) shows the highest amount of the desired products. Hydrogen rich lignites with a molar H/C ratio of > 1 are to be favoured. Due to primary cracking and secondary reactions the ratio between catalyst and lignite, temperature and residence time are the most important parameter to control the product distribution. Experiments at 500 C in a discontinuous rotary kiln reactor show yields up to 32 wt-% of hydrocarbons per lignite (maf - moisture and ash free) and 43 wt-% char, which can be gasified. Particularly, the yields of propylene and butenes as main products can be enhanced four times to about 8 wt-% by the use of catalysts while the tar yield decreases. In order to develop this innovative process catalyst systems fixed on beads were developed for an easy separation and regeneration of the used catalyst from the formed char. (orig.)

  2. Final results of double-shell tank 241-AZ-101 ultrasonic inspection

    Energy Technology Data Exchange (ETDEWEB)

    JENSEN, C.E.

    1999-08-23

    This document presents the results and documentation of the nondestructive ultrasonic examination of tank 241-AZ-101. A tank inspection supplier was retained to provide and use an ultrasonic examination system (equipment, procedures, and inspectors) to scan a limited area of double-shell tank 241-AZ-101 primary tank wall and welds. The inspection found one reportable indication of thinning and no reportable pitting, corrosion, or cracking.

  3. Automated PCB Inspection System

    Directory of Open Access Journals (Sweden)

    Syed Usama BUKHARI

    2017-05-01

    Full Text Available Development of an automated PCB inspection system as per the need of industry is a challenging task. In this paper a case study is presented, to exhibit, a proposed system for an immigration process of a manual PCB inspection system to an automated PCB inspection system, with a minimal intervention on the existing production flow, for a leading automotive manufacturing company. A detailed design of the system, based on computer vision followed by testing and analysis was proposed, in order to aid the manufacturer in the process of automation.

  4. NDE applications in an anchor bolt and sign bridge inspection program

    Science.gov (United States)

    Fish, Philip E.

    1998-03-01

    Wisconsin Department of Transportation implemented an Anchor Bolt Inspection Program and Sign Bridge Inspection Program in 1990 for cantilever & overhead sign structures, high mast light towers, interstate light towers, and signal masts. All cantilever & overhead sign structures and high mast light towers have been inspected in-depth 'hands on' during this time period while implementation of inspection continues for interstate light towers and signal masts. The program requires an experienced inspection team and a practical inspection approach. Inspection preparation includes review of all background information such as design plans, design computations, construction plans, shop plans, and maintenance history. An inspection plan is developed. Special emphasis is placed on determining type of structure, type of material, welding details. For anchor bolts, type of material, cut or rolled threads, type of coating, and method of placement are important issues. Inspection emphasis are on 'hands on' and Nondestructive evaluation. Special emphasis is placed visual conditions of sign structures and anchor bolts (cut or rolled threads, straightness, corrosion, nut tension, etc.) along with ultrasonic inspection. This program places a strong emphasis on Non Destructive Testing (NDT), especially ultrasonic. Procedures and inspection calibrations for anchor bolts, are developed from similar anchor bolt geometry and material type. Cut notches are placed in the anchor bolts at locations of possible failure. NDT inspection calibrations are performed from these bolts. Report documentation includes all design plans, pictorial documentation of structural deficiencies, sketches, nondestructive evaluation reports, conclusions, and recommendations. This program has been successful in locating critical cracks and failed members on existing sign structures and new sign structures less than six months old. Also, failed anchor bolts and critical cracks have been located on high mast light

  5. Experiences on IGSCC crack manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Veron, P. [Equipos Nucleares, S.A., Maliano (Spain)

    1997-02-01

    The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).

  6. HYDROGEN TRANSFER IN CATALYTIC CRACKING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hydrogen transfer is an important secondary reaction of catalytic cracking reactions, which affects product yield distribution and product quality. It is an exothermic reaction with low activation energy around 43.3 kJ/mol. Catalyst properties and operation parameters in catalytic cracking greatly influence the hydrogen transfer reaction. Satisfactory results are expected through careful selection of proper catalysts and operation conditions.

  7. Signal Station Inspection Reports

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Handwritten reports resulting from detailed inspections of US Army Signal Service Stations, 1871-1889. Features reported included instrument exposure and condition,...

  8. Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA's High Temperature, High Speed Turbine Seal Test Rig

    Science.gov (United States)

    Delgado, Irebert R.; Steinetz, Bruce M.; Rimnac, Clare M.; Lewandowski, John J.

    2008-01-01

    The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA s Turbine Seal Test Facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of the NASA disk bolt holes is found to be 367 cycles at a crack depth of 0.501 mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032 cycles at a crack depth of 0.501 mm. Eddy-current inspections are suggested starting at 665 cycles since eddy current detection thresholds are currently at 0.381 mm. Inspection intervals are recommended every 50 cycles when operated at maximum operating conditions.

  9. The Characterization of Crack-Like Defects Using Ultrasonic Images

    Science.gov (United States)

    Zhang, J.; Velichko, A.; Drinkwater, B. W.; Wilcox, P. D.

    2010-02-01

    The use of ultrasonic arrays to image and size crack-like defects is an important area in non-destructive evaluation. The features in the ultrasonic data from a crack-like defect provide information about the size and orientation angle of the defect. In this paper, the characteristics of a crack-like defect were measured from its scattering coefficient matrix, when the angular coverage of measurement includes the specular regions of its scattering matrix. Alternatively, the imaged features for a large crack-like defect (its length more than two wavelengths) were directly used to characterize the defect through a rectangular box fitting approach. An efficient hybrid model was used to generate the full matrix of array data from samples with a defect and for a specified inspection configuration. This hybrid model combines far-field scattering coefficient matrix for defects with a ray based forward model. This model offers the potential to compile a look-up table through which defects can be classified and then sized. Good agreement was achieved between simulation and experimental results hence validating this model based approach.

  10. In-Service Inspection for HANARO Reactor Structure

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Sang Ik; Lee, Young Sub; Lee, Jung Hee; Jung, Hoan Sung; Cho, Yeong Garp [KAERI, Daejeon (Korea, Republic of)

    2010-12-15

    As results of the visual inspection (VT-3) on HANARO, there was no defect such as a crack, corrosion, abrasion, erosion, and physical or chemical deformation on the welded parts and other surfaces of the reactor structures and its parts. Also, the bolts and steel wire, which was tied as an indicator whether got released or not, are well being kept its integrity. Throughout this visual inspection results, it turned out that HANARO is well maintaining its integrity and initial condition after installation and assembly in 1995. This inspection was done as a second change in Sep. 2006 according to the long term inspection plan for the safety class component by ASME Sec. XI article IWB and HANARO procedure. The next five year inspection shall be done no later than the end of 2011. This inspection results such as photos taken inside the reactor pool will be helpful to find out a solution for some problem, which may cause a view point of the reactor structure and its parts during operating

  11. A consistent partly cracked XFEM element for cohesive crack growth

    DEFF Research Database (Denmark)

    Asferg, Jesper L.; Poulsen, Peter Noe; Nielsen, Leif Otto

    2007-01-01

    capable of modelling variations in the discontinuous displacement field on both sides of the crack and hence also capable of modelling the case where equal stresses are present on each side of the crack. The enrichment was implemented for the 3-node constant strain triangle (CST) and a standard algorithm...... was used to solve the non-linear equations. The performance of the element is illustrated by modelling fracture mechanical benchmark tests. Investigations were carried out on the performance of the element for different crack lengths within one element. The results are compared with previously obtained...

  12. Inspection Strategies for Concrete Bridges

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    1989-01-01

    In this paper an optimal inspection strategy for concrete bridges based on periodic routine and detailed inspections is presented. The failure mode considered is corrosion of the reinforcement due to chlorides. A simple modelling of the corrosion and of the inspection strategy is presented....... The optimal inspection strategy is determined from an optimization problem, where the design variables are time intervals between detailed inspections and the concrete cover. The strategy is illustrated on a simple structure, namely a reinforced concrete beam....

  13. Inspection Strategies for Concrete Bridges

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    1989-01-01

    In this paper an optimal inspection strategy for concrete bridges based on periodic routine and detailed inspections is presented. The failure mode considered is corrosion of the reinforcement due to chlorides. A simple modelling of the corrosion and of the inspection strategy is presented....... The optimal inspection strategy is determined from an optimization problem, where the design variables are time intervals between detailed inspections and the concrete cover. The strategy is illustrated on a simple structure, namely a reinforced concrete beam....

  14. Development of Reactor Vessel Bottom Mount Instrumentation Nozzle Routine Inspection Device

    Energy Technology Data Exchange (ETDEWEB)

    Khaled, Atya Ahmed Abdallah; Ihn, Namgung [KEPCO International Nuclear Graduate School, Ulsan (Korea, Republic of)

    2015-10-15

    The primary coolant water of pressurized water reactors has created cracks in j-weld of penetrations with Alloy 600 through a process called primary water stress corrosion cracking. On October 6, 2013, BMI nozzle number 3 at Palo Verde Unit 3 (PVNGS-3) exhibited small white de-posits around the annulus. Nozzle attachment to the RV lower head is by J-groove weld to the inside penetration of the nozzle and the weld material is of Alloy 600 material. Above two cases clearly show the necessity of routine inspection of RV lower head penetration during refueling outage. Nondestructive inspection is generally performed to detect fine cracks or defects that may develop during operation. Defects usually occur at weld regions, hence most non-destructive inspection is to scan and check any defects or crack in the weld region. BMI nozzles at the bottom head of a nuclear reactor vessel (RV) are one of such area for inspection. But BMI nozzles have not been inspected during regular refuel outage due to the relative small size of BMI nozzle and limited impact of the consequences of BMI leak. However, there is growing concern since there have been leaks at nuclear power plants (NPPs) as well as recent operating experience. In this study, we propose a system that is conveniently used for nondestructive inspection of BMI nozzles during regular refueling outage without removing all the reactor internals. A 3D model of the inspection system was also developed along with the RV and internals which permits a virtual 3D simulation to check the design concept and usability of the system.

  15. Probabilistic Analysis of Crack Width

    Directory of Open Access Journals (Sweden)

    J. Marková

    2000-01-01

    Full Text Available Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.

  16. Analysis of Crack Arrest Toughness.

    Science.gov (United States)

    1988-01-15

    vload(m) vp tn(m) Vertical Source Load (kN) on wedge HY80 Finite Element 0.0122 0.0099 3.81x10 -4 144 Steel Calculations Experiment 0.0122 --- 3.74x10-4...curve, are bona fide measures of the fracture arrest capability of tough ductile steels . The second is that the J-values represent the crack driving...fibrous mode of crack extension. (b) A new test method for studying fast fracture and arrest in tough steels . (c) Measurements of fast fracture and crack

  17. A computational algorithm for crack determination: The multiple crack case

    Science.gov (United States)

    Bryan, Kurt; Vogelius, Michael

    1992-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.

  18. A New Probability of Detection Model for Updating Crack Distribution of Offshore Structures

    Institute of Scientific and Technical Information of China (English)

    李典庆; 张圣坤; 唐文勇

    2003-01-01

    There exists model uncertainty of probability of detection for inspecting ship structures with nondestructive inspection techniques. Based on a comparison of several existing probability of detection (POD) models, a new probability of detection model is proposed for the updating of crack size distribution. Furthermore, the theoretical derivation shows that most existing probability of detection models are special cases of the new probability of detection model. The least square method is adopted for determining the values of parameters in the new POD model. This new model is also compared with other existing probability of detection models. The results indicate that the new probability of detection model can fit the inspection data better. This new probability of detection model is then applied to the analysis of the problem of crack size updating for offshore structures. The Bayesian updating method is used to analyze the effect of probability of detection models on the posterior distribution of a crack size. The results show that different probabilities of detection models generate different posterior distributions of a crack size for offshore structures.

  19. Advances in inspection automation

    Science.gov (United States)

    Weber, Walter H.; Mair, H. Douglas; Jansen, Dion; Lombardi, Luciano

    2013-01-01

    This new session at QNDE reflects the growing interest in inspection automation. Our paper describes a newly developed platform that makes the complex NDE automation possible without the need for software programmers. Inspection tasks that are tedious, error-prone or impossible for humans to perform can now be automated using a form of drag and drop visual scripting. Our work attempts to rectify the problem that NDE is not keeping pace with the rest of factory automation. Outside of NDE, robots routinely and autonomously machine parts, assemble components, weld structures and report progress to corporate databases. By contrast, components arriving in the NDT department typically require manual part handling, calibrations and analysis. The automation examples in this paper cover the development of robotic thickness gauging and the use of adaptive contour following on the NRU reactor inspection at Chalk River.

  20. Subsea infrastructure inspection

    DEFF Research Database (Denmark)

    Mai, Christian; Pedersen, Simon; Hansen, Leif

    2017-01-01

    of the offshore pipeline inspections are currently committed using Towed or Remotely Operated Vehicle (ROV) systems. It is well-known that the ROVs are very time-consuming and expensive to operate, with respect to the fact that they require a relatively large support ship to accommodate the equipment as well...... as very skilled pilot and crews. The paper examines the existing challenges related to the subsea inspection in general, the ROVs, AUVs and semi-autonomous ROVs advantages and disadvantages in different subsea inspection applications. Replacing the ROVs with Semi or fully-Autonomous Underwater Vehicle (S...... of highly autonomous (not directly supervised) systems in general, and this seems to also be the case for S-AUV technology, in part due to regulatory requirements and certifications. This study concludes that semi-autonomous upgrades to existing ROV technology is a realistic first step towards the adaption...

  1. Cracks in Utopia

    Science.gov (United States)

    1999-01-01

    Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44oN, 258oW, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  2. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  3. 21 CFR 137.190 - Cracked wheat.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested by...

  4. The crack growth mechanism in asphaltic mixes

    NARCIS (Netherlands)

    Jacobs, .M.M.J.; Hopman, P.C.; Molenaar, A.A.A.

    1995-01-01

    The crack growth mechanism in asphalt concrete (Ac) mixes is studied. In cyclic tests on several asphaltic mixes crack growth is measured, both with crack foils and with cOD-gauges. It is found that crack growth in asphaltic mixes is described by three processes which are parallel in time: cohesive

  5. Variables Affecting Probability of Detection in Bolt Hole Eddy Current Inspection

    Science.gov (United States)

    Lemire, H.; Krause, T. W.; Bunn, M.; Butcher, D. J.

    2009-03-01

    Physical variables affecting probability of detection (POD) in a bolt-hole eddy current inspection were examined. The POD study involved simulated bolt holes in 7075-T6 aluminum coupons representative of wing areas on CC-130 and CP-140 aircraft. The data were obtained from 24 inspectors who inspected 468 coupons, containing a subset of coupons with 45 electric discharge machined notches and 72 laboratory grown fatigue cracks located at the inner surface corner of the bi-layer structures. A comparison of physical features of cracks and notches in light of skin depth effects and probe geometry was used to identify length rather than depth as the significant variable producing signal variation. Probability of detection based on length produced similar results for the two discontinuity types, except at lengths less than 0.4 mm, where POD for cracks was found to be higher than that of notches.

  6. Inspection management system

    Energy Technology Data Exchange (ETDEWEB)

    Coto, L.F.M.; Alvarez, M.A.L.

    1998-07-01

    The main features of the application developed by UNION FENOSA and NorControl for inspection management are exposed. This application has been built on the basis of a Geographic Information System, whose advantages on other database systems are explained. This system, has been developed with the main objective of getting a better and easier utilization of the data collected from the inspections, in order to reduce service failures and obtain a bigger return of the effort invested in them. They are also exposed the work line and the steps followed for the implementation of the system in the Meirama steam plant, and the results obtained up to date.

  7. Computer vision barrel inspection

    Science.gov (United States)

    Wolfe, William J.; Gunderson, James; Walworth, Matthew E.

    1994-02-01

    One of the Department of Energy's (DOE) ongoing tasks is the storage and inspection of a large number of waste barrels containing a variety of hazardous substances. Martin Marietta is currently contracted to develop a robotic system -- the Intelligent Mobile Sensor System (IMSS) -- for the automatic monitoring and inspection of these barrels. The IMSS is a mobile robot with multiple sensors: video cameras, illuminators, laser ranging and barcode reader. We assisted Martin Marietta in this task, specifically in the development of image processing algorithms that recognize and classify the barrel labels. Our subsystem uses video images to detect and locate the barcode, so that the barcode reader can be pointed at the barcode.

  8. Fiber Sensing of Micro -Crack

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Optical fiber sensors are used for sensing micro-cracking in composite and metal materials in aerospace applications. The sensing mechanism is based on the detection of acoustic emission signals, which are known to emanate from micro-cracks when they grow under further loading. The sensor head consists of a fiber Bragg grating that is capable of detecting acoustic emission signals generated by pencil lead breaking, of frequencies up to 200 kHz.

  9. Enhancing pulsed eddy current for inspection of P-3 Orion lap-joint structures

    Science.gov (United States)

    Butt, D. M.; Underhill, P. R.; Krause, T. W.

    2016-02-01

    During flight, aircraft are subjected to cyclic loading. In the Lockheed P-3 Orion airframe, this cyclic loading can lead to development of fatigue cracks at steel fastener locations in the top and second layers of aluminum wing skin lap-joints. An inspection method that is capable of detecting these cracks, without fastener removal, is desirable as this can minimize aircraft downtime, while subsequently reducing the risk of collateral damage. The ability to detect second layer cracks has been demonstrated using a Pulsed Eddy Current (PEC) probe design that utilizes the ferrous fastener as a flux conduit. This allows for deeper penetration of flux into the lap-joint second layer and consequently, sensitivity to the presence of cracks. Differential pick-up coil pairs are used to sense the eddy current response due to the presence of a crack. The differential signal obtained from pick-up coils on opposing sides of the fastener is analyzed using a Modified Principal Components Analysis (MPCA). This is followed by a cluster analysis of the resulting MPCA scores to separate fastener locations with cracks from those without. Probe design features, data acquisition system parameters and signal post-processing can each have a strong impact on crack detection. Physical probe configurations and signal analysis processes, used to enhance the PEC system for detection of cracks in P-3 Orion lap-joint structures, are investigated and an enhanced probe design is identified.

  10. Fatigue Crack Length Sizing Using a Novel Flexible Eddy Current Sensor Array

    Directory of Open Access Journals (Sweden)

    Ruifang Xie

    2015-12-01

    Full Text Available The eddy current probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar eddy current sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM, the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm.

  11. Applications of infrared thermography for nondestructive testing of fatigue cracks in steel bridges

    Science.gov (United States)

    Sakagami, Takahide; Izumi, Yui; Kobayashi, Yoshihiro; Mizokami, Yoshiaki; Kawabata, Sunao

    2014-05-01

    In recent years, fatigue crack propagations in aged steel bridge which may lead to catastrophic structural failures have become a serious problem. For large-scale steel structures such as orthotropic steel decks in highway bridges, nondestructive inspection of deteriorations and fatigue damages are indispensable for securing their safety and for estimating their remaining strength. As conventional NDT techniques for steel bridges, visual testing, magnetic particle testing and ultrasonic testing have been commonly employed. However, these techniques are time- and labor- consuming techniques, because special equipment is required for inspection, such as scaffolding or a truck mount aerial work platform. In this paper, a new thermography NDT technique, which is based on temperature gap appeared on the surface of structural members due to thermal insulation effect of the crack, is developed for detection of fatigue cracks. The practicability of the developed technique is demonstrated by the field experiments for highway steel bridges in service. Detectable crack size and factors such as measurement time, season or spatial resolution which influence crack detectability are investigated.

  12. INSPECTION TECHNOLOGY, DETECTION, AND COMPLIANCE: EVIDENCE FROM FLORIDA RESTAURANT INSPECTIONS

    OpenAIRE

    Jin, Ginger Zhe; Lee, Jungmin

    2014-01-01

    In this article, we show that a small innovation in inspection technology can make substantial differences in inspection outcomes. For restaurant hygiene inspections, the state of Florida has introduced a handheld electronic device, the portable digital assistant (PDA), which reminds inspectors of 1,000 potential violations that may be checked for. Using inspection records from July 2003 to June 2009, we find that the adoption of PDA led to 11% more detected violations and subsequently restau...

  13. Development of an automatic weld surface appearance inspection system using machine vision

    Institute of Scientific and Technical Information of China (English)

    Lin Sanbao; Fu Xibin; Fan Chenglei; Yang Chunli; Luo Lu

    2009-01-01

    In this paper, an automatic inspection system for weld surface appearance using machine vision has been developed to recognize weld surface defects such as porosities, cracks, etc. It can replace conventional manual visual inspection method, which is tedious, time-consuming, subjective, experience-depended, and sometimes biased. The system consists of a CCD camera, a self-designed annular light source, a sensor controller, a frame grabbing card, a computer and so on. After acquiring weld surface appearance images using CCD, the images are preprocessed using median filtering and a series of image enhancement algorithms. Then a dynamic threshold and morphology algorithms are applied to segment defect object. Finally, defect features information is obtained by eight neighborhoods boundary chain code algorithm. Experimental results show that the developed system is capable of inspecting most surface defects such as porosities, cracks with high reliability and accuracy.

  14. Remote Inspection Challenge

    Science.gov (United States)

    Roman, Harry T.

    2013-01-01

    The ability to remotely inspect equipment of an aging infrastructure is becoming of major interest to many industries. Often the ability to just get a look at a piece of critical equipment can yield very important information. With millions of miles of piping installed throughout the United States, this vast network is critical to oil, natural…

  15. Additive Manufacturing Infrared Inspection

    Science.gov (United States)

    Gaddy, Darrell

    2014-01-01

    Additive manufacturing is a rapid prototyping technology that allows parts to be built in a series of thin layers from plastic, ceramics, and metallics. Metallic additive manufacturing is an emerging form of rapid prototyping that allows complex structures to be built using various metallic powders. Significant time and cost savings have also been observed using the metallic additive manufacturing compared with traditional techniques. Development of the metallic additive manufacturing technology has advanced significantly over the last decade, although many of the techniques to inspect parts made from these processes have not advanced significantly or have limitations. Several external geometry inspection techniques exist such as Coordinate Measurement Machines (CMM), Laser Scanners, Structured Light Scanning Systems, or even traditional calipers and gages. All of the aforementioned techniques are limited to external geometry and contours or must use a contact probe to inspect limited internal dimensions. This presentation will document the development of a process for real-time dimensional inspection technique and digital quality record of the additive manufacturing process using Infrared camera imaging and processing techniques.

  16. Ofsted Re-Inspected

    Science.gov (United States)

    Coffield, Frank

    2012-01-01

    The author never thought he would have to thank Ofsted for a change in its approach that may result in a major improvement in provision; and yet, with the introduction of the revised Common Inspection Framework (CIF), it has made teaching and learning (T&L) the first priority throughout the learning and skills sector. While he wishes to…

  17. A Study on Advanced Ultrasonic Technique for Thermal Fatigue Crack Detection of Thermal Stratification Pipeline in NPPs

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Won Geun; Lee, Min Rae; Choi, Snag Woo; Lee, Joon Hyun [Pusan National University, Busan (Korea, Republic of); Lee, Bo Young [Hankook Aviation Univ., Goyang (Korea, Republic of)

    2005-07-01

    Ultrasonic inspection techniques are widely used to ensure the reliable operation and lifetime extension of nuclear power plants. Thermal stratification typically occurs in the surge line or the main feed water lines in nuclear power plants. Thermal stratification is a flow condition in which hotter fluid flows over a colder region of fluid in pipeline. Since a change in temperature causes a change in the density of the pipe wall, these thermal conditions might lead to increased overall bending stresses in pipelines. In addition, cyclic changes in stratification height cause thermal stress. This cycling can lead to thermal fatigue crack initiation and crack growth. If thermal fatigue crack grows continuously, the leakage of water or steam will occur and this may cause serious problems on reactor cooling system. Therefore, these cracks must be detected before the crack growth reaches for leakage. In this study, an ultrasonic technique was employed for evaluation of thermal fatigue cracks due to thermal stratification in pipelines of nuclear power plants. The angle beam ultrasonic techniques(time-of-flight diffraction(TOFD) and shadow effect method) were used to detect thermal fatigue cracks which grow from the inner surface of the pipeline. The angle beam ultrasonic technique is usually used for the detection of cracks on the inside of the structures. When ultrasonic waves generated from the angle probe encounters a crack, ultrasonic waves of the shear modes are reflect or transmit from the crack wall. Also ultrasonic waves generated from the angle probe shear modes are diffracted from the tip of the crack, and the shear wave is reflected from the corner of the crack.

  18. Big Lake Dam Inspection Report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes an inspection of the Big Lake Dam that was done in September of 1983. The inspection did not reveal any conditions that constitute and...

  19. Codified Risk Based Inspection Planning

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, M.H.

    2002-01-01

    Simplified methods are described for reliability- and risk-based inspection planning of steel structures. The methods simplify the practical aspects of identifying inspection plans complying both with specific requirements to the maximum acceptable annual probability of structural collapse...

  20. Flexible mobile robot system for smart optical pipe inspection

    Science.gov (United States)

    Kampfer, Wolfram; Bartzke, Ralf; Ziehl, Wolfgang

    1998-03-01

    Damages of pipes can be inspected and graded by TV technology available on the market. Remotely controlled vehicles carry a TV-camera through pipes. Thus, depending on the experience and the capability of the operator, diagnosis failures can not be avoided. The classification of damages requires the knowledge of the exact geometrical dimensions of the damages such as width and depth of cracks, fractures and defect connections. Within the framework of a joint R&D project a sensor based pipe inspection system named RODIAS has been developed with two partners from industry and research institute. It consists of a remotely controlled mobile robot which carries intelligent sensors for on-line sewerage inspection purpose. The sensor is based on a 3D-optical sensor and a laser distance sensor. The laser distance sensor is integrated in the optical system of the camera and can measure the distance between camera and object. The angle of view can be determined from the position of the pan and tilt unit. With coordinate transformations it is possible to calculate the spatial coordinates for every point of the video image. So the geometry of an object can be described exactly. The company Optimess has developed TriScan32, a special software for pipe condition classification. The user can start complex measurements of profiles, pipe displacements or crack widths simply by pressing a push-button. The measuring results are stored together with other data like verbal damage descriptions and digitized images in a data base.

  1. Inspection and evaluation guidelines for light water reactor internals

    Energy Technology Data Exchange (ETDEWEB)

    Iizuka, N. [Tokyo Electric Power Co., Inc. (Japan); Taniguchi, K. [Kansai Electric Power Co., Inc., Osaka (Japan); Yoshinaga, T. [Japan Atomic Power Co., Tokyo (Japan)

    2002-12-01

    On February, 2000, in the Engineering Society of Thermal and Nuclear Power Generation, the 'Investigation Group on Inspection and Evaluation Guidelines for Nuclear Reactor Internals' was established. This group was started at moments of some damage cases on reactor internals on BWRs and PWRs in Japan and foreign countries and of finding out cracks based on a number of SCC (stress corrosion cracking) at Inconel alloy weldings of a shroud support of BWR internals in Tsuruga Nuclear Power Station Unit-1 of the Japan Nuclear Power Generation Co., Ltd. on December, 1999. Under these conditions, this group made some guidelines for rational inspection with clear technical foundation, and so on as well as arrangements on structural functions, importance at safety, and so on of the reactor internals, promoted some investigations aiming at wide general proposal on how to carry out future internal inspections on LWR in Japan, and completed almost all of the investigations on March, 2002. Here were described basic indications of the guideline development and summaries of the developed guideline. (G.K.)

  2. Fatigue reliability of cracked engineering structures

    Science.gov (United States)

    Lanning, David Bruce, Jr.

    1997-12-01

    This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation

  3. From Inspection to School Improvement? Evaluating the Accelerated Inspection Programme in Waltham Forest.

    Science.gov (United States)

    Hopkins, David; Harris, Alma; Watling, Rob; Beresford, John

    1999-01-01

    Outlines the main findings from the evaluation of the Accelerated Inspection Programme (AIP) in Waltham Forest under three main phases (pre-inspection, inspection, and post inspection). Focuses on the relationship between inspection and school improvement. Discusses the recommendations. (CMK)

  4. Overview of steam generator tube-inspection technology

    Energy Technology Data Exchange (ETDEWEB)

    Obrutsky, L.; Renaud, J.; Lakhan, R., E-mail: obrutskl@aecl.ca, E-mail: renaudj@aecl.ca, E-mail: lakhanr@aecl.ca [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)

    2014-03-15

    Degradation of steam generator (SG) tubing due to both mechanical and corrosion modes has resulted in extensive repairs and replacement of SGs around the world. The variety of degradation modes challenges the integrity of SG tubing and, therefore, the stations' reliability. Inspection and monitoring aimed at timely detection and characterization of the degradation is a key element for ensuring tube integrity. Up to the early-70's, the in-service inspection of SG tubing was carried out using single-frequency eddy current testing (ET) bobbin coils, which were adequate for the detection of volumetric degradation. By the mid-80's, additional modes of degradation such as pitting, intergranular attack, and axial and circumferential inside or outside diameter stress corrosion cracking had to be addressed. The need for timely, fast detection and characterization of these diverse modes of degradation motivated the development in the 90's of inspection systems based on advanced probe technology coupled with versatile instruments operated by fast computers and remote communication systems. SG inspection systems have progressed in the new millennium to a much higher level of automation, efficiency and reliability. Also, the role of Non Destructive Evaluation (NDE) has evolved from simple detection tools to diagnostic tools that provide input into integrity assessment decisions, fitness-far-service and operational assessments. This new role was motivated by tighter regulatory requirements to assure the safety of the public and the environment, better SG life management strategies and often self-imposed regulations. It led to the development of advanced probe technologies, more reliable and versatile instruments and robotics, better training and qualification of personnel and better data management and analysis systems. This paper provides a brief historical perspective regarding the evolution of SG inspections and analyzes the motivations behind that

  5. Numerical Simulation of Nonlinear Lamb Waves Used in a Thin Plate for Detecting Buried Micro-Cracks

    Directory of Open Access Journals (Sweden)

    Xiang Wan

    2014-05-01

    Full Text Available Compared with conventional linear ultrasonic inspection methods, which are sensitive only to severe defects, nonlinear ultrasonic inspection methods are better for revealing micro-cracks in thin plates. However, most nonlinear ultrasonic inspection methods have only been experimentally investigated using bulk or Rayleigh waves. Numerical studies, especially numerical simulations of Lamb ultrasonic waves, have seldom been reported. In this paper, the interaction between nonlinear S0 mode Lamb waves and micro-cracks of various lengths and widths buried in a thin metallic plate was simulated using the finite element method (FEM. The numerical results indicate that after interacting with a micro-crack, a new wave-packet was generated in addition to the S0 mode wave-packet. The second harmonics of the S0 mode Lamb waves and the new wave-packet were caused by nonlinear acoustic effects at the micro-crack. An amplitude ratio indicator is thus proposed for the early detection of buried micro-cracks.

  6. Catastrophic Cracking Courtesy of Quiescent Cavitation

    CERN Document Server

    Daily, D Jesse; Thomson, Scott L; Truscott, Tadd T

    2012-01-01

    A popular party trick is to fill a glass bottle with water and hit the top of the bottle with an open hand, causing the bottom of the bottle to break open. We investigate the source of the catastrophic cracking through the use of high-speed video and an accelerometer attached to the bottom of a glass bottle. Upon closer inspection, it is obvious that the acceleration caused by hitting the top of the bottle is followed by the formation of bubbles near the bottom. The nearly instantaneous acceleration creates an area of low pressure on the bottom of the bottle where cavitation bubbles form. Moments later, the cavitation bubbles collapse at roughly 10 times the speed of formation, causing the bottle to break. The accelerometer data shows that the bottle is broken after the bubbles collapse and that the magnitude of the bubble collapse is greater than the initial impact. The fluid dynamics video highlights that this trick will not work if the bottle is empty nor if it is filled with a carbonated fluid because the...

  7. Overview of the software inspection process

    Energy Technology Data Exchange (ETDEWEB)

    Lane, G.L.; Dabbs, R. [Sandia National Labs., Albuquerque, NM (United States)

    1997-11-01

    This tutorial introduces attendees to the Inspection Process and teaches them how to organize and participate in a software inspection. The tutorial advocates the benefits of inspections and encourages attendees to socialize the inspection process in their organizations.

  8. 7 CFR 29.40 - Mandatory inspection.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Regulations Definitions § 29.40 Mandatory inspection. Inspection authorized or required under section 5 of the Act or Section 759 of the Appropriations Act. definitions...

  9. SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA

    Institute of Scientific and Technical Information of China (English)

    Z.X.Wu; X.C.Wu

    2001-01-01

    The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.

  10. Replica-Based High-Performance Tuple Space Computing

    DEFF Research Database (Denmark)

    Andric, Marina; De Nicola, Rocco; Lluch Lafuente, Alberto

    2015-01-01

    We present the tuple-based coordination language RepliKlaim, which enriches Klaim with primitives for replica-aware coordination. Our overall goal is to offer suitable solutions to the challenging problems of data distribution and locality in large-scale high performance computing. In particular,...

  11. Tank Inspection NDE Results for Fiscal Year 2014, Waste Tanks 26, 27, 28 and 33

    Energy Technology Data Exchange (ETDEWEB)

    Elder, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Vandekamp, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-09-29

    Ultrasonic nondestructive examinations (NDE) were performed on waste storage tanks 26, 27, 28 and 33 at the Savannah River Site as a part of the “In-Service Inspection (ISI) Program for High Level Waste Tanks.” No reportable conditions were identified during these inspections. The results indicate that the implemented corrosion control program continues to effectively mitigate corrosion in the SRS waste tanks. Ultrasonic inspection (UT) is used to detect general wall thinning, pitting and interface attack, as well as vertically oriented cracks through inspection of an 8.5 inch wide strip extending over the accessible height of the primary tank wall and accessible knuckle regions. Welds were also inspected in tanks 27, 28 and 33 with no reportable indications. In a Type III/IIIA primary tank, a complete vertical strip includes scans of five plates (including knuckles) so five “plate/strips” would be completed at each vertical strip location. In FY 2014, a combined total of 79 plate/strips were examined for thickness mapping and crack detection, equating to over 45,000 square inches of area inspected on the primary tank wall. Of the 79 plate/strips examined in FY 2014 all but three have average thicknesses that remain at or above the construction minimum thickness which is nominal thickness minus 0.010 inches. There were no service induced reportable thicknesses or cracking encountered. A total of 2 pits were documented in 2014 with the deepest being 0.032 inches deep. One pit was detected in Tank 27 and one in Tank 33. No pitting was identified in Tanks 26 or 28. The maximum depth of any pit encountered in FY 2014 is 5% of nominal thickness, which is less than the minimum reportable criteria of 25% through-wall for pitting. In Tank 26 two vertical strips were inspected, as required by the ISI Program, due to tank conditions being outside normal chemistry controls for more than 3 months. Tank 28 had an area of localized thinning on the exterior wall of the

  12. Crack stability analysis of low alloy steel primary coolant pipe

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, T.; Kameyama, M. [Kansai Electric Power Company, Osaka (Japan); Urabe, Y. [Mitsubishi Heavy Industries, Ltd., Takasago (Japan)] [and others

    1997-04-01

    At present, cast duplex stainless steel has been used for the primary coolant piping of PWRs in Japan and joints of dissimilar material have been applied for welding to reactor vessels and steam generators. For the primary coolant piping of the next APWR plants, application of low alloy steel that results in designing main loops with the same material is being studied. It means that there is no need to weld low alloy steel with stainless steel and that makes it possible to reduce the welding length. Attenuation of Ultra Sonic Wave Intensity is lower for low alloy steel than for stainless steel and they have advantageous inspection characteristics. In addition to that, the thermal expansion rate is smaller for low alloy steel than for stainless steel. In consideration of the above features of low alloy steel, the overall reliability of primary coolant piping is expected to be improved. Therefore, for the evaluation of crack stability of low alloy steel piping to be applied for primary loops, elastic-plastic future mechanics analysis was performed by means of a three-dimensioned FEM. The evaluation results for the low alloy steel pipings show that cracks will not grow into unstable fractures under maximum design load conditions, even when such a circumferential crack is assumed to be 6 times the size of the wall thickness.

  13. Inspection and teachers’ emotions: An emotional evaluation of inspection

    Directory of Open Access Journals (Sweden)

    Binali Tunç

    2015-02-01

    Full Text Available In the study, inspection is discussed in relation to the teachers’ feelings and emotions it creates before inspection, during inspection and after inspection process. Teacher’s emotions have been investigated intentionally as emotional side of education has been neglected. Education is closely related to the emotions of teachers, who are the most important producers of educational activities.Educational activities are reduced to standard activities and defined with simple explanations or single labels such as ‘good-bad’, ‘successful-unsuccessful’, ‘adequate-inadequate’. Inspection causes emotions to be neglected. Moreover, recently, it has been discussed that there are approaches and systems that suggest constant and multi-dimensional inspection instead of traditional inspection.Qualitative research model was used to understand of teacher emotions. A semi structured form was used for the 38 primary school teachers’ interviews. After teacher interviews were completed, we analyzed and compared the interviews. Participants’ expressions were checked in terms of correctness, potential validity and reliability problems such as misinterpretation.   The results of the study can be summarized as follows: There were no positive expressions related to the emotional impact of inspection on teachers. In addition, teachers felt that the inspectors were stressed, anxious, uneasy, accusatory, coercive, looking for defect and areas of unsuccessful teaching performance. Most of teachers reported that being observed and evaluated caused them to have negative emotions.Teachers’ perceptions about inspection are found to be negative. There are no statements that indicate there is a positive impression of inspection on teachers. The emotions that are experienced before inspection: pressure, hurry, stress, concern, tension, anxiety, worry, uncertainty; during inspection: stress, tension, anger, loss of strength, humiliation and lack of self

  14. IDENTIFICATION OF CRACKED ROTOR BY WAVELET TRANSFORM

    Institute of Scientific and Technical Information of China (English)

    邹剑; 陈进; 蒲亚鹏

    2002-01-01

    The dynamic equation of cracked rotor in rotational frame was modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor were obtained. By the wavelet transform, the time-frequency properties of the cracked rotor and the uncracked rotor were discussed, the difference of the time-frequency properties between the cracked rotor and the uncracked rotor was compared. A new detection algorithm using wavelet transform to identify crack was proposed. The experiments verify the availability and validity of the wavelet transform in identification of crack.

  15. Inspection tester for explosives

    Science.gov (United States)

    Haas, Jeffrey S.; Simpson, Randall L.; Satcher, Joe H.

    2007-11-13

    An inspection tester that can be used anywhere as a primary screening tool by non-technical personnel to determine whether a surface contains explosives. It includes a body with a sample pad. First and second explosives detecting reagent holders and dispensers are operatively connected to the body and the sample pad. The first and second explosives detecting reagent holders and dispensers are positioned to deliver the explosives detecting reagents to the sample pad. A is heater operatively connected to the sample pad.

  16. The effect of endodontic procedures on apical crack initiation and propagation ex vivo.

    Science.gov (United States)

    Adorno, C G; Yoshioka, T; Jindan, P; Kobayashi, C; Suda, H

    2013-08-01

    To evaluate the potential effects of endodontic procedures (instrumentation and filling) on crack initiation and propagation in apical dentine. Forty extracted single-rooted premolars with two canals were selected, 1.5 mm of the apex was ground perpendicular to the long axis of the tooth and the surface polished. The specimens were divided into 4 groups. The buccal canals of groups A, B and C were enlarged to size 40 with manual K-files. Group A was filled with gutta-percha using lateral condensation and vertical compaction without sealer. Group B was filled with the same method as group A except only lateral condensation was used. Group C was left unfilled, while group D was left unprepared and unfilled. Images of the resected surface were taken after resection (baseline), after canal preparation, after filling and after 4-week storage. The images were then inspected for cracks originating from the canal. A significant effect of preparation on crack initiation (P  0.05) or 4-week storage on crack initiation (P > 0.05) was found (logistic regression). Fisher's exact test revealed a significant effect of filling on crack propagation (P propagation (P > 0.05). Root canal procedures can potentially initiate and propagate cracks from within the root canal in the apical region. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  17. Review of Environmentally Assisted Cracking

    Science.gov (United States)

    Sadananda, K.; Vasudevan, A. K.

    2011-02-01

    Many efforts have been made in the past by several researchers to arrive at some unifying principles governing the embrittlement phenomena. An inescapable conclusion reached by all these efforts was that the behavior is very complex. Hence, recognizing the complexity of material/environment behavior, we focus our attention here only in extracting some similarities in the experimental trends to arrive at some generic principles of behavior. Crack nucleation and growth are examined under static load in the presence of internal and external environments. Stress concentration, either pre-existing or in-situ generated, appears to be a requirement for embrittlement. A chemical stress concentration factor is defined for a given material/environment system as the ratio of failure stress with and without the damaging chemical environment. All factors that affect the buildup of the required stress concentration, such as planarity of slip, stacking fault energy, etc., also affect the stress-corrosion behavior. The chemical stress concentration factor is coupled with the mechanical stress concentration factor. In addition, generic features for all systems appear to be (a) an existence of a threshold stress as a function of concentration of the damaging environment and flow properties of the material, and (b) an existence of a limiting threshold as a function of concentration, indicative of a damage saturation for that environment. Kinetics of crack growth also depends on concentration and the mode of crack growth. In general, environment appears to enhance crack tip ductility on one side by the reduction of energy for dislocation nucleation and glide, and to reduce cohesive energy for cleavage, on the other. These two opposing factors are coupled to provide environmentally induced crack nucleation and growth. The relative ratio of these two opposing factors depends on concentration and flow properties, thereby affecting limiting thresholds. The limiting concentration or

  18. Investigating the Effects of Lead Forming Parameters on Intermetallic Layer Crack Using the Finite-Element Method

    Science.gov (United States)

    Chin, J. W. C.; Kok, C. K.; Rajmohan, M. M.; Yeo, V. S. H.; Said, M. R.

    2012-04-01

    The lead trim-and-form process is important in the manufacturing of programmable logic devices, microprocessors, and memories. Normally, inspection of a chip package is performed in a lead inspection machine after the lead forming process to detect defects on the leads. One such defect is the lead intermetallic compound (IMC) crack, exhibiting itself as plating crack. In this study, IMC crack of package leads, which causes loose connection between the copper lead and the tin plating, was analyzed using the finite-element method. The simulation results were verified by matching the simulated and actual formed lead profile. Simulation results showed a strong correlation between IMC crack after forming and aging and high residual tensile strain induced during lead forming. A proposal was made to resolve the crack issue by performing design of experiment (DOE) to reduce the residual tensile strain of the lead upon forming. Three optimization parameters were chosen, namely the forming angle, the shank angle, and the pre-forming angle. It is shown that, with the optimized parameter setting, a reduction of the residual strain can be achieved, thus minimizing the risk of IMC crack.

  19. Cracking and corrosion recovery boiler

    Energy Technology Data Exchange (ETDEWEB)

    Suik, H. [Tallinn Technical University, Horizon Pulp and Paper, Tallinn (Estonia)

    1998-12-31

    The corrosion of heat surfaces and the cracking the drums are the main problems of the recovery boiler. These phenomena have been appeared during long-term operation of boiler `Mitsubishi - 315` erected at 1964. Depth of the crack is depending on the number of shutdowns and on operation time. Corrosion intensity of different heat surfaces is varying depend on the metal temperature and the conditions at place of positioning of tube. The lowest intensity of corrosion is on the bank tubes and the greatest is on the tubes of the second stage superheater and on the tubes at the openings of air ports. (orig.) 5 refs.

  20. Modified Dugdale crack models - some easy crack relations

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    are assumed to be self created by local materials flow. The strength sigma_CR predictid by the Dugdale model is sigma_CR =(E Gamma_CR/phi1)^½ where E and 1 are Young’s modulus and crack half-length respectively of the material considered. The so-called critical strain energy rate is Gamma_CR = sigma......_Ldelta_CR where sigma_L is strength, and at the same time constant flow stress, of the uncracked material while delta_CR is flow limit (displacement).Obviously predictions by the Dugdale model are most reliable for materials with stress-strain relations where flow can actually be described (or well approximated......) by a constant flow stress (sigma_L). A number of materials, however, do not at all exhibit this kind of flow. Such materials are considered in this paper by Modified Dugdale crack models which apply for any cohesive stress distribution in crack front areas. Formally modified Dugdale crack models exhibit...

  1. Technical Letter Report - Analysis of Ultrasonic Data on Piping Cracks at Ignalina Nuclear Power Plant Before and After Applying a Mechanical Stress Improvement Process, JCN-N6319, Task 2

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Michael T.; Cumblidge, Stephen E.; Crawford, Susan L.

    2008-02-26

    Pacific Northwest National Laboratory (PNNL) is assisting the United States Nuclear Regulatory Commission (NRC) in developing a position on the management of primary water stress corrosion cracking (PWSCC) in piping systems previously analyzed for leak-before-break (LBB). Part of this work involves determining whether inspections alone are sufficient or if inspections plus mitigation techniques are needed. The work described in this report addresses the reliability of ultrasonic phased-array (PA) examinations for inspection of cracks that have been subjected to the mitigation method of mechanical stress improvement process (MSIP). It is believed that stresses imparted during MSIP may make ultrasonic crack responses in piping welds more difficult to detect and accurately characterize. To explore this issue, data were acquired, both before and after applying MSIP, and analyzed from cracked areas in piping at the Ignalina Nuclear Power Plant (INPP) in Lithuania. This work was performed under NRC Project JCN-N6319, PWSCC in Leak-Before-Break Systems.

  2. Selection of Shear Horizontal Wave Transducers for Robotic Nondestructive Inspection in Harsh Environments

    Directory of Open Access Journals (Sweden)

    Sungho Choi

    2016-12-01

    Full Text Available Harsh environments and confined spaces require that nondestructive inspections be conducted with robotic systems. Ultrasonic guided waves are well suited for robotic systems because they can provide efficient volumetric coverage when inspecting for various types of damage, including cracks and corrosion. Shear horizontal guided waves are especially well suited for robotic inspection because they are sensitive to cracks oriented perpendicular or parallel to the wave propagation direction and can be generated with electromagnetic acoustic transducers (EMATs and magnetostrictive transducers (MSTs. Both types of transducers are investigated for crack detection in a stainless steel plate. The MSTs require the robot to apply a compressive normal force that creates frictional force coupling. However, the coupling is observed to be very dependent upon surface roughness and surface debris. The EMATs are coupled through the Lorentz force and are thus noncontact, although they depend on the lift off between transducer and substrate. After comparing advantages and disadvantages of each transducer for robotic inspection the EMATs are selected for application to canisters that store used nuclear fuel.

  3. FRACTAL KINEMATICS OF CRACK PROPAGATION IN GEOMATERIALS

    Institute of Scientific and Technical Information of China (English)

    谢和平

    1995-01-01

    Experimental results indicate that propagation paths of cracks in geomaterials are often irregular, producing rough fracture surfaces which are fractal. A formula is derived for the fractal kinematics of crack propagation in geomaterials. The formula correlates the dynamic and static fracture toughnesses with crack velocity, crack length and a microstructural parameter, and allows the fractal dimension to be obtained. From the equations for estimating crack velocity and fractal dimension it can be shown that the measured crack velocity, Vo , should be much smaller than the fractal crack velocity, V. It can also be shown that the fractal dimension of the crack propagation path can be calculated directly from Vo and from the fracture toughness.

  4. Interacting Cracks in an Environmentally Assisted Fracture

    Science.gov (United States)

    Levandovsky, Artem; Balazs, Anna

    2006-03-01

    We perform the study of environmentally assisted fracture within the framework of a lattice model. Formation of an ensemble of environmentally assisted microcracks, their coalescence and formation of crack ``avalanches'' lead to a very rich dynamical picture. Under specific condition crack healing can occur due to cohesive forces, which hold material together and tend to pull atoms together even if they are separated by a crack over several lattice units. We investigate the dynamical interplay between crack formation, arrest, healing and re-cracking. The goal here is to provide an understanding of the conditions leading to the phenomena of crack healing that happens along with the crack formation. We study the morphology of crack patterns with the intentions to establish a way to enhance the healing property of a material sample.

  5. On multiple crack detection in beam structures

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Shapour; Kargozarfard, Mohammad [Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)

    2013-01-15

    This study presents an inverse procedure to identify multiple cracks in beams using an evolutionary algorithm. By considering the crack detection procedure as an optimization problem, an objective function can be constructed based on the change of the eigenfrequencies and some strain energy parameters. Each crack is modeled by a rotational spring. The changes in natural frequencies due to the presence of the cracks are related to a damage index vector. Then, the bees algorithm, a swarm-based evolutionary optimization technique, is used to optimize the objective function and find the damage index vector, whose positive components show the number and position of the cracks. A second objective function is also optimized to find the crack depths. Several experimental studies on cracked cantilever beams are conducted to ensure the integrity of the proposed method. The results show that the number of cracks as well as their sizes and locations can be predicted well through this method.

  6. Crack and flip phacoemulsification technique.

    Science.gov (United States)

    Fine, I H; Maloney, W F; Dillman, D M

    1993-11-01

    The crack and flip phacoemulsification technique combines the advantages of circumferential division of the nucleus and nucleofactis techniques. As such, it adds safety and control to the procedure. We describe each of the surgical maneuvers, including machine settings, and explain the rationale for maneuvers and machine settings.

  7. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

      National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:……

  8. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:

  9. HYDROTHERMAL CRACKING OF RESIDUAL OILS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrothermal cracking of heavy oils, such as Canadian oil sand bitumen and Arabian heavy vacuum residue, as well as their model compound were performed over sulfided Ni/Al2O3 and NiMo/Al2O3 catalysts under 663~703 K and 6.0~8.0 MPa of hydrogen pressure in a batch autoclave reactor. According to the reaction mechanism of hydrothermal cracking, a small amount of free redical initiators, such as di-tert-peroxide, sulfur, etc., was added into the feed to generate free redicals at lower temperature, and obviously showed promotional effect on the conversion of hydrocarbons. The reaction mechanisms of hydrothermal cracking as well as the enhancing effect of initiators were studied by a probe reaction with 1-phenyldodecane as a model compound. The hydrothermal cracking of hydrocarbon proceeded via free redical mechanism and hydrogenating quench. The initiators might easily generate free redicals under reaction temperature, these redicals might abstract H from hydrocarbon molecule and reasonably initiate the chain reactions, therefore, promote the conversion of hydrocarbon even at lower reaction temperature.

  10. Confining crack propagation in defective graphene.

    Science.gov (United States)

    López-Polín, Guillermo; Gómez-Herrero, Julio; Gómez-Navarro, Cristina

    2015-03-11

    Crack propagation in graphene is essential to understand mechanical failure in 2D materials. We report a systematic study of crack propagation in graphene as a function of defect content. Nanoindentations and subsequent images of graphene membranes with controlled induced defects show that while tears in pristine graphene span microns length, crack propagation is strongly reduced in the presence of defects. Accordingly, graphene oxide exhibits minor crack propagation. Our work suggests controlled defect creation as an approach to avoid catastrophic failure in graphene.

  11. Shell Inspection History and Current CMM Inspection Efforts

    Energy Technology Data Exchange (ETDEWEB)

    Montano, Joshua Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-01-26

    The following report provides a review of past and current CMM Shell Inspection efforts. Calibration of the Sheffield rotary contour gauge has expired and the primary inspector, Matthew Naranjo, has retired. Efforts within the Inspection team are transitioning from maintaining and training new inspectors on Sheffield to off-the-shelf CMM technology. Although inspection of a shell has many requirements, the scope of the data presented in this report focuses on the inner contour, outer contour, radial wall thickness and mass comparisons.

  12. Eddy current monitoring of fatigue crack growth in Zr-2.5% Nb pressure tube

    Science.gov (United States)

    Krause, T. W.; Martin, A. E.; Sheppard, R. R.; Schankula, J. J.

    2000-05-01

    Zr-2.5% wt. Nb pressure tubes (PTs) form the core of the heat transport system in CANDU nuclear reactors. These 6 m long, 100 mm diameter tubes are operated at elevated temperatures (nominally 300 °C) and at pressures that produce hoop stresses that are 25% of the ultimate tensile strength of the PT (120 Mpa). Therefore, detection and characterization of flaws in these components becomes crucial for their continued pressure retaining integrity. If a flaw is detected, however, the cost of PT replacement is expensive. Periodic in-service inspection of a flaw that demonstrates no change in flaw characteristics can be used to allow a pressure tube to remain in-service. This requires confidence in the accuracy and reliability of methods used to inter flaw characteristics. Such confidence can only be developed by comparing nondestructive predictions with results from destructive examinations. In this work, eddy current testing was used to monitor the progressive stages of a fatigue crack, grown through pressure cycling from a notch on the inner surface of a PT. Results from a differential lift-off compensated eddy current probe were used to produce sizing estimates of the crack grown between 35% (base of notch) and 74% of the PT wall. A comparison with a destructive examination of the crack demonstrated sensitivity too changes in crack depth accurate to 5% of the tube wall thickness. Such results, combined with similar information obtained from ultrasonics will increase confidence in interpretation of PT inspection data.

  13. Correction to the crack extension direction in numerical modelling of mixed mode crack paths

    DEFF Research Database (Denmark)

    Lucht, Tore; Aliabadi, M.H.

    2007-01-01

    In order to avoid introduction of an error when a local crack-growth criterion is used in an incremental crack growth formulation, each straight crack extension would have to be infinitesimal or have its direction corrected. In this paper a new procedure to correct the crack extension direction i...

  14. Mesh sensitivity effects on fatigue crack growth by crack-tip blunting and re-sharpening

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2007-01-01

    Crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading is one of the basic mechanisms for fatigue crack growth in ductile metals. Based on an elastic–perfectly plastic material model, crack growth computations have been continued up to 700 full cycles by using...

  15. Fatigue crack growth from a cracked elastic particle into a ductile matrix

    NARCIS (Netherlands)

    Groh, S.; Olarnrithinun, S.; Curtin, W. A.; Needleman, A.; Deshpande, V. S.; Van der Giessen, E.

    2008-01-01

    The monotonic and cyclic crack growth rate of cracks is strongly influenced by the microstructure. Here, the growth of cracks emanating from pre-cracked micron-scale elastic particles and growing into single crystals is investigated, with a focus on the effects of (i) plastic confinement due to the

  16. Comparative study of Palito inspection and MFL Inspection

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Anne A. de; Miranda, Ivan Vicente Janvrot; Silva, Jose Augusto Pereira da [Pipeway Engenharia, Rio de Janeiro, RJ (Brazil); Guimaraes, Frederico S.; Magalhaes, Joao Alfredo P. [Minds at Work, Rio de Janeiro, RJ (Brazil); Sabino, Joao Marcos [Petroleo Brasileiro S.A. (PETROBRAS/UN-RN/CE), Natal, RN (Brazil). Unidade de Negocios Rio Grande do Norte e Ceara

    2009-07-01

    A 16 inches oil pipeline was surveyed with MFL and Palito pig in 2007. The MFL inspection was performed by Pipeway Engenharia while Palito inspection was performed by PETROBRAS. A comparison between the results of these two ILI inspections has been made to validate Palito Pig and to assess main characteristics and differences between the two techniques. The purpose of this paper is to detail the methodology applied to perform the comparison and to present a comparative study of results registered in the MFL and Palito inspections by Pipeway Engenharia, PETROBRAS/CENPES and CPTI/PUC-Rio. (author)

  17. Twisting cracks in Bouligand structures.

    Science.gov (United States)

    Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo

    2017-06-10

    The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. A Bevel Gear Quality Inspection System Based on Multi-Camera Vision Technology.

    Science.gov (United States)

    Liu, Ruiling; Zhong, Dexing; Lyu, Hongqiang; Han, Jiuqiang

    2016-08-25

    Surface defect detection and dimension measurement of automotive bevel gears by manual inspection are costly, inefficient, low speed and low accuracy. In order to solve these problems, a synthetic bevel gear quality inspection system based on multi-camera vision technology is developed. The system can detect surface defects and measure gear dimensions simultaneously. Three efficient algorithms named Neighborhood Average Difference (NAD), Circle Approximation Method (CAM) and Fast Rotation-Position (FRP) are proposed. The system can detect knock damage, cracks, scratches, dents, gibbosity or repeated cutting of the spline, etc. The smallest detectable defect is 0.4 mm × 0.4 mm and the precision of dimension measurement is about 40-50 μm. One inspection process takes no more than 1.3 s. Both precision and speed meet the requirements of real-time online inspection in bevel gear production.

  19. Complete inspection of friction stir welds in aluminum using ultrasonic and eddy current arrays

    Energy Technology Data Exchange (ETDEWEB)

    Lamarre, A.; Dupuis, O. [R/D Tech, Quebec, Quebec (Canada)]. E-mail: andre.lamarre@rd-tech.com; olivier.dupuis@rd-tech.com; Moles, M. [R/D Tech, Mississauga, Ontario (Canada)]. E-mail: Michael.moles@rd-tech.com

    2006-07-15

    Ultrasonic phased-array offers tremendous advantages for the inspection of Friction stir welds (FSW), a new method of joining metals using a solid state bonding process. Phased array ultrasonics can reliably detect all internal volumetric defects in FSW, such as cracks, inclusion, porosity and lack-of-penetration. Spot-focused beams improve detection, inspection angles can be optimized electronically and electronic scan of the beam normal to the welds gives rapid one-line scan inspection to assure full coverage. Furthermore, a technique using ultrasonic attenuation measurements shows the presence or absence of conditions for forming kissing bonds (or entrapped oxide defects). Also, eddy current arrays can be used for surface inspection, and can help to detect tight kissing bonds. Using all three approaches, the overall detection capability of kissing bonds is high. (author)

  20. Laser Safety Inspection Criteria

    Energy Technology Data Exchange (ETDEWEB)

    Barat, K

    2005-06-13

    A responsibility of the Laser Safety Officer (LSO) is to perform laser audits. The American National Standard Z136.1 Safe Use of Lasers references this requirement through several sections. One such reference is Section 1.3.2.8, Safety Features Audits, ''The LSO shall ensure that the safety features of the laser installation facilities and laser equipment are audited periodically to assure proper operation''. The composition, frequency and rigor of that inspection/audit rests in the hands of the LSO. A common practice for institutions is to develop laser audit checklists or survey forms It is common for audit findings from one inspector or inspection to the next to vary even when reviewing the same material. How often has one heard a comment, ''well this area has been inspected several times over the years and no one ever said this or that was a problem before''. A great number of audit items, and therefore findings, are subjective because they are based on the experience and interest of the auditor to particular items on the checklist. Beam block usage, to one set of eyes might be completely adequate, while to another, inadequate. In order to provide consistency, the Laser Safety Office of the National Ignition Facility Directorate has established criteria for a number of items found on the typical laser safety audit form. The criteria are distributed to laser users. It serves two broad purposes; first, it gives the user an expectation of what will be reviewed by an auditor. Second, it is an opportunity to explain audit items to the laser user and thus the reasons for some of these items, such as labelling of beam blocks.

  1. Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

    Institute of Scientific and Technical Information of China (English)

    Himanshu PATHAK[1; Akhilendra SINGH[2; I.V. SINGH[3; S. K. YADAV[3

    2015-01-01

    This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.

  2. Assessment of Partially Conductive Cracks from Eddy Current Non-Destructive Testing Signals using Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Ladislav Janousek

    2015-01-01

    Full Text Available This paper deals with a three-dimensional non-destructive evaluation of partially conductive cracks from eddy current testing signals. An SUS316L plate specimen containing a crack is non-destructively inspected by the eddy current method using numerical simulations. An extensive database of eddy current response signals is prepared while dimensional parameters of a crack together with its partial conductivity are varied in wide ranges. A Support Vector Machine classification algorithm is employed to solve the electromagnetic inverse problem. The acquired signals are employed for training the algorithm and for testing its performance. It is demonstrated that the Support Vector Machine algorithm is able to properly classify detected defects into proper classes with very high probability even the partial conductivity of a detected crack together with its width are unknown.

  3. Report on Status of Shipment of High Fluence Austenitic Steel Samples for Characterization and Stress Corrosion Crack Testing

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Scarlett R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Leonard, Keith J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    The goal of the Mechanisms of Irradiation Assisted Stress Corrosion Cracking (IASCC) task in the LWRS Program is to conduct experimental research into understanding how multiple variables influence the crack initiation and crack growth in materials subjected to stress under corrosive conditions. This includes understanding the influences of alloy composition, radiation condition, water chemistry and metallurgical starting condition (i.e., previous cold work or heat treatments and the resulting microstructure) has on the behavior of materials. Testing involves crack initiation and growth testing on irradiated specimens of single-variable alloys in simulated Light Water Reactor (LWR) environments, tensile testing, hardness testing, microstructural and microchemical analysis, and detailed efforts to characterize localized deformation. Combined, these single-variable experiments will provide mechanistic understanding that can be used to identify key operational variables to mitigate or control IASCC, optimize inspection and maintenance schedules to the most susceptible materials/locations, and, in the long-term, design IASCC-resistant materials.

  4. Weight Function Method for Stress Intensity Factor of Internal Surface Semi-elliptical Crack in Elliptical Holes

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The hatches for inspecting are usually designed with elliptical holes in airplane structures, so computation of the stress intensity factor of three dimensional crack at elliptical holes is pivotal for damage tolerance analysis of these structures. In this paper, weight function is derived for a two dimensional through cracks at elliptical holes by applying a compounding method. Stress intensity factor formulas for an internal surface semi-elliptical crack in elliptical holes are obtained using the three dimensional weight function method. Stress intensity factors for an internal surface semi-elliptical crack in elliptical holes under remote tension are computed. At the same time, research on how radius of curvature for elliptical holes affect stress intensity factors was conducted. Stress intensity factors decrease when radius of curvature increases. Some results and conclusions which are of practical value are given.

  5. PFM Analysis for Pre-Existing Cracks on Alloy 182 Weld in PWR Primary Water Environment using Monte Carlo Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae Phil; Bahn, Chi Bum [Pusan National University, Busan (Korea, Republic of)

    2015-10-15

    Probabilistic Fracture Mechanics (PFM) analysis was generally used to consider the scatter and uncertainty of parameters in complex phenomenon. Weld defects could be present in weld regions of Pressurized Water Reactors (PWRs), which cannot be considered by the typical fracture mechanics analysis. It is necessary to evaluate the effects of the pre-existing cracks in welds for the integrity of the welds. In this paper, PFM analysis for pre-existing cracks on Alloy 182 weld in PWR primary water environment was carried out using a Monte Carlo simulation. PFM analysis for pre-existing cracks on Alloy 182 weld in PWR primary water environment was carried out. It was shown that inspection decreases the gradient of the failure probability. And failure probability caused by the pre-existing cracks was stabilized after 15 years of operation time in this input condition.

  6. Photoelastic studies of crack propagation and crack arrest. [Homalite 100

    Energy Technology Data Exchange (ETDEWEB)

    Irwin, G.R.; Dally, J.W.; Kobayashi, T.; Fourney, W.L.; Etheridge, J.M.

    1977-09-01

    This report describes the third year effort on research programs dealing with the characterization of dynamic aspects of fracture. The results included in this report are (1) verification of the BCL one-dimensional computer code; (2) determination of a-dot--K relationship from modified compact-tension specimen of Homalite 100; (3) verification of the MRL procedure for K/sub Ia/ measurement with machine-loaded C-DCB specimen of Homalite 100; (4) influence of adhesive toughness, adhesive thickness, and toughness of the arrest section on crack behavior in duplex specimens of both the M-CT and R-DCB types; (5) crack propagation in a thermally stressed ring specimen; and (6) development of a two-dimensional finite-difference code to predict fracture behavior in specimens of rectangular geometry under various a-dot vs K relationships. 118 figures, 53 tables.

  7. Waste inspection tomography (WIT)

    Energy Technology Data Exchange (ETDEWEB)

    Bernardi, R.T. [Bio-Imaging Research, Inc., Lincolnshire, IL (United States)

    1995-10-01

    Waste Inspection Tomography (WIT) provides mobile semi-trailer mounted nondestructive examination (NDE) and assay (NDA) for nuclear waste drum characterization. WIT uses various computed tomography (CT) methods for both NDE and NDA of nuclear waste drums. Low level waste (LLW), transuranic (TRU), and mixed radioactive waste can be inspected and characterized without opening the drums. With externally transmitted x-ray NDE techniques, WIT has the ability to identify high density waste materials like heavy metals, define drum contents in two- and three-dimensional space, quantify free liquid volumes through density and x-ray attenuation coefficient discrimination, and measure drum wall thickness. With waste emitting gamma-ray NDA techniques, WIT can locate gamma emitting radioactive sources in two- and three-dimensional space, identify gamma emitting, isotopic species, identify the external activity levels of emitting gamma-ray sources, correct for waste matrix attenuation, provide internal activity approximations, and provide the data needed for waste classification as LLW or TRU.

  8. Inhibiting Corrosion Cracking: Crack Tip Chemistry and Physics.

    Science.gov (United States)

    1986-03-14

    5 5. Swuzary 113 Rferences 114 wl NO 4L iv . List of Figuring 1. Microipette pulling machine . 29 2. Anodic polarization of 7075-T6 Al alloy in dilute...environment has a strong effect on microplastic behavior at the tip of a fatigue crack. Stolz and Pelloux suggest that nitrate ion competes with chloride...Crystalline Na2 N 20 29H20 precipitates when the filtrate is placed in a vacunm desiccator over sulfuric acid. The filtered precipitate is washed

  9. Crack branching in carbon steel. Fracture mechanisms

    Science.gov (United States)

    Syromyatnikova, A. S.; Alekseev, A. A.; Levin, A. I.; Lyglaev, A. V.

    2010-04-01

    The fracture surfaces of pressure vessels made of carbon steel that form during crack branching propagation are examined by fractography. Crack branching is found to occur at a crack velocity higher than a certain critical value V > V c . In this case, the material volume that is involved in fracture and depends on the elastoplastic properties of the material and the sample width has no time to dissipate the energy released upon crack motion via the damage mechanisms intrinsic in the material under given deformation conditions (in our case, via cracking according to intragranular cleavage).

  10. Strength of Cracked Reinforced Concrete Disks

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...... for the shear strength of disks with initial cracks and disks suffering from isotropic cracking are presented. Furthermore, in the case of isotropicly cracked disks subjected to arbitrary in-plane loading, a general yield condition is derived....

  11. Alternating grain orientation and weld solidification cracking

    Science.gov (United States)

    Kou, S.; Le, Y.

    1985-10-01

    A new mechanism for reducing weld solidification cracking was proposed, based on the concept of the crack path and resistance to crack propagation, and its effectiveness was verified in magnetically oscillated GTA welds of a rather crack susceptible material 2014 aluminum alloy. This mechanism, i.e., alternating grain orientation, was most pronounced in welds made with transverse arc oscillation of low frequency and high amplitude, and solidification cracking was dramatically reduced in these welds. The effect of the arc oscillation pattern, amplitude, and frequency on the formation of alternating columnar grains and the reduction of solidification cracking in GTA welds of 2014 aluminum alloy was examined and explained. The present study demonstrated for the first time that columnar grains can, in fact, be very effective in reducing solidification cracking, provided that they are oriented favorably.

  12. Applicability of a Crack-Detection System for Use in Rotor Disk Spin Test Experiments Being Evaluated

    Science.gov (United States)

    Abdul-Aziz, Ali; Baaklini, George Y.; Roth, Don J.

    2004-01-01

    Engine makers and aviation safety government institutions continue to have a strong interest in monitoring the health of rotating components in aircraft engines to improve safety and to lower maintenance costs. To prevent catastrophic failure (burst) of the engine, they use nondestructive evaluation (NDE) and major overhauls for periodic inspections to discover any cracks that might have formed. The lowest cost fluorescent penetrant inspection NDE technique can fail to disclose cracks that are tightly closed during rest or that are below the surface. The NDE eddy current system is more effective at detecting both crack types, but it requires careful setup and operation and only a small portion of the disk can be practically inspected. So that sensor systems can sustain normal function in a severe environment, health-monitoring systems require the sensor system to transmit a signal if a crack detected in the component is above a predetermined length (but below the length that would lead to failure) and lastly to act neutrally upon the overall performance of the engine system and not interfere with engine maintenance operations. Therefore, more reliable diagnostic tools and high-level techniques for detecting damage and monitoring the health of rotating components are very essential in maintaining engine safety and reliability and in assessing life.

  13. Bare PCB inspection system with SV-GMR sensor eddy-current testing probe

    OpenAIRE

    Chomsuwan, K.; Yamada, Sotoshi; Iwahara, Masayoshi

    2007-01-01

    This paper describes bare printed circuit board (PCB) inspection based on eddy-current testing (ECT) technique with high scanning speed. A high-frequency ECT probe composed of a meander coil as an exciting coil and the spin-valve giant magnetoresistance (SV-GMR) sensor was fabricated and is proposed. The ECT probe was designed based on crack inspection over flat surface, especially suitable for microdefect detection on high-density bare PCB. The ECT signal detected by the SV-GMR sensor was ac...

  14. The Use of In-Service Inspection Data in the Performance Measurement of Non-Destructive Inspections (Mise en oeuvre de donn es resultant de visites d’inspection en service pour l’evaluation des performances des visites d’inspection non destructives)

    Science.gov (United States)

    2005-03-01

    Mean POD Curve for the “Hit/Miss” Data and CDF Curve for the “Hit” Data of 5-7 the Manual Eddy Current Inspection of the F-16 Fuselage Longeron Tab... Administrativo Direccao de Mecanica Aeronautica/GZE avenue dea Forca Aerea Portuguesa email: jnogueira@emfa.pt UNITED KINGDOM Dr. D. Bruce DSTL...structure. High positive g-loads cause fatigue cracking in the tab radii of the longeron. NDI of the tab radii involves a manual eddy current inspection

  15. Inspection of chimneys for Carolina Power and Light Company

    Energy Technology Data Exchange (ETDEWEB)

    Rabon, T.R. [Carolina Power and Light Co., Raleigh, NC (United States)

    1995-10-01

    Regular inspection and appropriate examination, with immediate follow-up repairs, are paramount to properly maintain chimneys. Chimneys are required to operate the units. Failure of a chimney could result in loss of life and could damage the unit(s). The previous program of performing visual inspections only, without the benefit of nondestructive testing and core examination, was unsatisfactory. The cost of examination with follow-up repairs is a sound investment compared to the cost associated with an extended outage for major repairs or replacement. The basic operating conditions for which the chimneys were designed have changed significantly. Originally, the chimneys were to operate with dry, hot gases; possess a high natural updraft and temperatures above acid dew point; and maintain negative pressure inside the liner--such that small liner cracks did not create a concern. The present conditions of operation are significantly different. These are wet, lower gas temperatures, acid saturated gases, less natural draft, and sometimes positive pressure inside the liner. There is now exfiltration of flue gas through any present liner cracks, breech seals, and open mortar joints into the annular space. The concrete sheath is not durable against exposure to flue gas.

  16. Biaxial Fatigue Cracking from Notch

    Science.gov (United States)

    2013-03-04

    Leevers (reference 11) noticed that the variation in  from 0 to 2 has little effect on the da/dN in PVC ( polyvinyl - chloride ), but reduces the da/dN...under biaxial rotating and bending. Ahmad (reference 2) formulated a model for the biaxial fatigue crack growth in aggressive environment, outlined by...1962, Vol. 90, pp. 238-239. 20. ASM Handbook , Vol. 12 Fractography: 1992, p. 430, 438. 21. Metals Handbook , Vol. 9 Fractography and Atlas of

  17. The Growth of Small Corrosion Fatigue Cracks in Alloy 7075

    Science.gov (United States)

    Piascik, Robert S.

    2015-01-01

    The corrosion fatigue crack growth characteristics of small (greater than 35 micrometers) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500×) crack length measurements in laboratory air and 1% sodium chloride (NaCl) environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K(sub max) growth rates are similar to small crack da/dN.

  18. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Science.gov (United States)

    Kruml, T.; Hutař, P.; Náhlík, L.; Seitl, S.; Polák, J.

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 μm was followed in symmetrical cycling with constant strain amplitude ( R ɛ = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  19. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Kruml, T., E-mail: kruml@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic); Hutar, P.; Nahlik, L.; Seitl, S.; Polak, J. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic)

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 {mu}m was followed in symmetrical cycling with constant strain amplitude (R{sub {epsilon}} = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  20. Development of a crack growth analysis is program for reactor head penetration

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Yull; Choi, Kwang Hee; Park, Jeong Il [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Kang, Young Hwan; Park, Sung Ho; Kim, Il; Kim, Young Jong; Yoo, Young Joon; Yoo, Wan; Maeng, Wan Young; Choi, Suk Nam; Kim, Kee Suk; Yoon, Sung Won; Kim, Jee Ho; Park, Myung Kyu [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1996-12-31

    Crack growth analysis program for Reactor Head Penetration is being developed for applying to plants such as, Kori 1, Kori 2, Kori 3,4 YoungKwang 1,2 and Uljin 1,2 (1) Stress Evaluation - The stress analysis is required to evaluate the structure integrity for the RVH penetration tubes. The RVH penetration tubes are geometrically non-symmetry except center one. Thus, 3D finite element analysis should be employed for the stress analysis. The magnitude and distribution of residual stress resulted from welding can be determined analytically by simulation welding procedure. (2) Flaw Evaluation - There are two objectives of the penetration tube flaw evaluation to predict the time required for a crack to propagate to the acceptance criteria. The first objective is to perform the parametric evaluation for a postulated crack. The second objective is to develop the flaw evaluation program for the crack detected during the inspection. (3) Characterization of Material Properties of Alloy 600 - These study is to provide data which similarly represent the properties of PWR power plants in Korea. The data is used for analyzing of the stress distribution around penetration tubes. And the PWSCC data will be used for the crack growth rate of the penetration tubes. (author). 92 refs., 121 figs.

  1. Case Study and Numerical Analysis of Vibration and Runner Cracks for the Lipno I Hydroelectric Project

    Science.gov (United States)

    Zouhar, J.; Obrovsky, J.; Feilhauer, M.; Skotak, A.

    2016-11-01

    The refurbishment of the Lipno I TG2 Francis turbine, situated on River Vltava, with maximum net head of 165 m and required operational range from 0 to 67MW of turbine power was performed in 2014. The new hydraulic design of the spiral case, distributor and runner was developed for this project. After about 1000 hours of operation the site inspection was performed and the cracks were found on 8 runner blades of 17 blades altogether. The all cracks were found near runner hub beginning from the trailing edge. The dimensions of the cracks were different with maximum length of 123 mm and minimum length of 3 mm. The runner was repaired and the intensive investigation was started to define the main cause of the cracks creation and to determine the measures for their elimination. This paper presents the program of this investigation which consists of static and dynamic blade strain measurement, CFD and FEM analysis, discusses the crack causes and overview the solution how to return the turbine successfully to operation.

  2. Labor inspection in Brazil

    Directory of Open Access Journals (Sweden)

    Adalberto Cardoso

    2006-01-01

    Full Text Available One aspect the literature overlooks on the effects of labor regulation of labor market efficiency is the degree of the legislation's effectiveness, i.e., its actual enforcement in daily work relations. Even the more sophisticated econometric studies (which take into account the effects of interaction between labor market regulatory institutions in explaining its dynamics leave this central issue aside, namely enforcement versus non-enforcement of the law. Keeping this issue in mind, we seek to answer the following question in this article: given that the effectiveness of labor legislation depends on the interaction between the overall sanctions and the probability of the employer getting caught breaking the law, and given that the law's effectiveness is a decisive aspect for the real measurement of a country's labor costs, to what extent is the Brazilian labor inspection system designed to meet its objective, namely, to enforce the law?

  3. Industrial Inspection System

    Science.gov (United States)

    1993-01-01

    ACTIS+ is a smaller, personal computer version of ACTIS, a computed tomography system which finds its origins in the Apollo lunar landing research. It is used to identify imperfections in aerospace structures and components. Designed to be added to an existing real time radiography system, its components include a high precision rotation/elevation manipulator, color image monitor, graphical user interface monitor, and PC compatible workstation. Cross-sectional CT images are more detailed than radiographic images and the high speed scanning feature offers the capability for 100 percent inspection in a production environment. Bio-Imaging Research, Inc. (BIR) originally developed ACTIS for Marshall Space Flight Center (MSFC), and commercial units were sold to aerospace manufacturers. The technology was refined for ACTIS+, which is principally used in non-destructive testing.

  4. Photoelectric Inspecting of Artillery Bore

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jie; MA Hong; BAI Su-ping; YAN Yu-feng

    2008-01-01

    A photoelectric equipment for inspecting artillery bore is composed of digital display grating sensor and data processing with computer. It can replace the traditional mechanical measurer and realize the automatic inspection of artillery bore. Introduced are briefly the working principles and analysis of this device.

  5. Automated visual inspection of textile

    DEFF Research Database (Denmark)

    Jensen, Rune Fisker; Carstensen, Jens Michael

    1997-01-01

    A method for automated inspection of two types of textile is presented. The goal of the inspection is to determine defects in the textile. A prototype is constructed for simulating the textile production line. At the prototype the images of the textile are acquired by a high speed line scan camera...

  6. Applying ultrasonic in-line inspection technology in a deep water environment: exploring the challenges

    Energy Technology Data Exchange (ETDEWEB)

    Thielager, N.; Nadler, M.; Pieske, M.; Beller, M. [NDT Systems and Services AG, Stutensee (Germany)

    2009-12-19

    The demand for higher inspection accuracies of in-line inspection tools (ILI tools) is permanently growing. As integrity assessment procedures are being refined, detection performances, sizing accuracies and confidence levels regarding detection and sizing play an ever increasing role. ILI tools utilizing conventional ultrasound technology are at the forefront of technology and fulfill the market requirements regarding sizing accuracies and the ability to provide quantitative measurements of wall thickness as well as crack inspection capabilities. Data from ultrasonic tools is ideally suited for advanced integrity assessment applications and run comparisons. Making this technology available for a deep-water environment of heavy wall, high pressures and temperatures comes with a wide range of challenges which have to be addressed. This paper will introduce developments recently made in order to adapt and modify ultrasonic in-line inspection tools for the application in a heavy wall, high pressure and high temperature environment as encountered in deep offshore pipelines. The paper will describe necessary design modifications and new conceptual approaches especially regarding tool electronics, cables, connectors and the sensor carrier. A tool capable of deep-water inspection with a pressure bearing capability of 275 bar will be introduced and data from inspection runs will be presented. As an outlook, the paper will also discuss future inspection requirements for offshore pipelines with maximum pressure values of up to 500 bar. (author)

  7. Computerized fracture critical and specialized bridge inspection program with NDE applications

    Science.gov (United States)

    Fish, Philip E.

    1998-03-01

    Wisconsin Department of Transportation implemented a Fracture Critical & Specialized Inspection Program in 1987. The program has a strong emphasis on Nondestructive Testing (NDT). The program is also completely computerized, using laptop computers to gather field data, digital cameras for pictures, and testing equipment with download features. Final inspection reports with detailed information can be delivered within days of the inspection. The program requires an experienced inspection team and qualified personnel. Individuals performing testing must be licensed ASNT (American Society for Nondestructive Testing) Level III and must be licensed Certified Weld Inspectors (American Welding Society). Several critical steps have been developed to assure that each inspection identifies all possible deficiencies that may be possible on a Fracture Critical or Unique Bridge. They include; review of all existing plans and maintenance history; identification of fracture critical members, identification of critical connection details, welds, & fatigue prone details, development of visual and NDE inspection plan; field inspection procedures; and a detailed formal report. The program has found several bridges with critical fatigue conditions which have resulted in replacement or major rehabilitation. In addition, remote monitoring systems have been installed on structures with serious cracking to monitor for changing conditions.

  8. EUV blank inspection

    Science.gov (United States)

    Peters, J. H.; Tonk, C.; Spriegel, D.; Han, Hak-Seung; Cho, Wonil; Wurm, Stefan

    2008-04-01

    One of the major topics for the introduction of extreme ultraviolet (EUV) technology is the availability of defect-free masks. From the mask makers' perspective, the quality of the incoming blank material is one of the key ingredients impacting the yield of structured masks. Besides flatness and layer thickness uniformity, the number of defects determines the final quality of the mask delivered to the customer for printing. Defects within the layers of optical blanks have shown that they have a growing impact on the mask structuring process, well below the usual defect specifications of the blanks. It is expected that this finding will also hold true for material layers above the multi-layer. In addition to printing performance, EUV masks need to have a defect-free multi-layer. While this layer is easily accessible during blank production, mask makers usually acquire the complete blank stacks with or without the coated resist. Incoming blank inspection, therefore, must check the quality of the complete stack without destroying any of the functionality of these layers. Siemens and AMTC have jointly developed a blank inspection tool that has been installed in AMTC's Dresden facility and that allows the screening of an EUV blank under these boundary conditions. Previously, SEMATECH successfully installed an M7360 from Lasertec in its Mask Blank Development Center (MBDC) in Albany, NY, that shows much better sensitivity data than SEMATECH's earlier tool, the Lasertec M1350. This paper describes the early performance of the Siemens DF-40XP on programmed multi-layer defect blanks and regular blanks and compares it to that of the existing tools at the SEMATECH MBDC.

  9. AUTONOMOUS ROBOTIC INSPECTION IN TUNNELS

    OpenAIRE

    E. Protopapadakis; Stentoumis, C.; Doulamis, N.; A. Doulamis; Loupos, K.; Makantasis, K.; Kopsiaftis, G.; Amditis, A.

    2016-01-01

    In this paper, an automatic robotic inspector for tunnel assessment is presented. The proposed platform is able to autonomously navigate within the civil infrastructures, grab stereo images and process/analyse them, in order to identify defect types. At first, there is the crack detection via deep learning approaches. Then, a detailed 3D model of the cracked area is created, utilizing photogrammetric methods. Finally, a laser profiling of the tunnel’s lining, for a narrow region clos...

  10. Austenitic Biomaterial Cracks Evaluation by Advanced Nondestructive Techniques

    Directory of Open Access Journals (Sweden)

    Milan Smetana

    2017-01-01

    Full Text Available The article deals with Non-Destructive Evaluation (NDE of austenitic stainless steels. Eddy current, ultrasonic testing and non-contact magnetic field mapping methods are used for this purpose. ECA (Eddy Current Array and TOFD (Time of Flight Diffraction are methods that have become widely-used in the field of NDE and this is the reason for their utilization. Magnetic field mapping is nowadays an effective method of evaluation of surface-breaking defects mainly in ferromagnetic materials. The fluxgate sensor-based measurement is presented and discussed. The artificial fatigue and stress-corrosion material’s cracks are inspected. Experimental results are presented and discussed in this paper.

  11. Simplified Approach to Inspection Planning

    DEFF Research Database (Denmark)

    Bloch, Allan; Sørensen, John Dalsgaard; Faber, M. H.

    2000-01-01

    A simplified and practically applicable approach for risk based inspection planning of fatigue sensitive structural details is presented. The basic idea behind the approach is that the fatigue sensitive details are categorized according to their stress intensity factors and their design fatigue l...... of steel structures. The validity of the proposed approach is illustrated through a study regarding inspection planning of offshore structures....... life to service life ratio, i.e. the fatigue design factor (FDF) and SN curve. When the reserve strength ratio (RSR) and the corresponding probability of total structural failure given fatigue failure of the considered detail is known it is possible to make a generic description of fatigue sensitive...... structural details and thereby develop pre-made inspection plans in tables which depend on relative cost of inspections, repairs and failures. Due to the simplicity of the format of the developed inspection plans the proposed approach has a high potential in code making for the design and maintenance...

  12. 9 CFR 381.68 - Maximum inspection rates-New turkey inspection system.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Maximum inspection rates-New turkey inspection system. 381.68 Section 381.68 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE... Procedures § 381.68 Maximum inspection rates—New turkey inspection system. (a) The maximum inspection...

  13. Raw data based image processing algorithm for fast detection of surface breaking cracks

    Science.gov (United States)

    Sruthi Krishna K., P.; Puthiyaveetil, Nithin; Kidangan, Renil; Unnikrishnakurup, Sreedhar; Zeigler, Mathias; Myrach, Philipp; Balasubramaniam, Krishnan; Biju, P.

    2017-02-01

    The aim of this work is to illustrate the contribution of signal processing techniques in the field of Non-Destructive Evaluation. A component's life evaluation is inevitably related to the presence of flaws in it. The detection and characterization of cracks prior to damage is a technologically and economically significant task and is of very importance when it comes to safety-relevant measures. The Laser Thermography is the most effective and advanced thermography method for Non-Destructive Evaluation. High capability for the detection of surface cracks and for the characterization of the geometry of artificial surface flaws in metallic samples of laser thermography is particularly encouraging. This is one of the non-contacting, fast and real time detection method. The presence of a vertical surface breaking crack will disturb the thermal footprint. The data processing method plays vital role in fast detection of the surface and sub-surface cracks. Currently in laser thermographic inspection lacks a compromising data processing algorithm which is necessary for the fast crack detection and also the analysis of data is done as part of post processing. In this work we introduced a raw data based image processing algorithm which results precise, better and fast crack detection. The algorithm we developed gives better results in both experimental and modeling data. By applying this algorithm we carried out a detailed investigation variation of thermal contrast with crack parameters like depth and width. The algorithm we developed is applied for various surface temperature data from the 2D scanning model and also validated credibility of algorithm with experimental data.

  14. Subsidence crack closure: rate, magnitude and sequence

    Energy Technology Data Exchange (ETDEWEB)

    De Graff, J.V.; Romesburg, H.C.

    1981-06-01

    Tension cracks are a major surface disturbance resulting from subsidence and differential settlement above underground coal mines. Recent engineering studies of subsidence indicate that cracks may close where tensile stresses causing the cracks are reduced or relaxed. This stress reduction occurs as mining in the area is completed. Crack closure was confirmed by a study in the Wasatch Plateau coal field of central Utah. Cracks occurred in both exposed bedrock and regolith in an area with maximum subsidence of 3 m. Mean closure rate was 0.3 cm per week with individual crack closure rates between 0.2 cm and 1.0 cm per week. The mean crack closure magnitude was 80% with closure magnitudes varying between 31% and 100%. Actual magnitude values ranged from 0.6 cm to 6.5 cm with a mean value of 3.8 cm. Statistical analysis compared width change status among cracks over time. It was found that: 1) a 41% probability existed that a crack would exhibit decreasing width per weekly measurement, 2) closure state sequences seem random over time, and 3) real differences in closure state sequence existed among different cracks. (6 refs.) (In English)

  15. Crack propagation in fracture mechanical graded structures

    Directory of Open Access Journals (Sweden)

    B. Schramm

    2015-10-01

    Full Text Available The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the crack propagation behavior. Therefore, this paper examines how the crack propagation behavior changes when a crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values KI,th, different fracture toughness KIC. In particular, the emphasis of this paper is on the beginning of stable crack propagation, the crack velocity, the crack propagation direction as well as on the occurrence of unstable crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of crack propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the crack propagation behavior.

  16. Accurate depth measurement of small surface-breaking cracks using an ultrasonic array post-processing technique

    OpenAIRE

    Felice, Maria; Velichko, Alexander; Wilcox, Paul D.

    2014-01-01

    In this paper, the half-skip configuration of the Total Focusing Method (TFM) is used to image and size surface-breaking cracks. The TFM is an ultrasonic array post-processing technique which is used to synthetically focus at every image point in a target region. This paper considers the case of inspecting for cracks which have initiated from the far surface of a parallel-sided sample using an array on the near surface. Typically, only direct ray paths between the array and image points are i...

  17. Radiated Electromagnetic Field Signature of Cracked and Polluted Porcelain Insulators%Radiated Electromagnetic Field Signature of Cracked and Polluted Porcelain Insulators

    Institute of Scientific and Technical Information of China (English)

    Ehsan Azordegan; David R Swatek; Behzad Kordi

    2011-01-01

    Porcelain cap and pin insulators are by far the most popular suspension insulators in high voltage (HV) dis- tribution networks all around the world. Inspection and condition monitoring of HV insulators is also very important to the utility companies because of the critical and vital role that they play in distribution systems. In terms of safety, practicality and ease of use, remote detection methods are more popular among the line technicians. A new remote condition assessment method based on electromagnetic radiations from porcelain insulators is presented in this gaper. In a lab environment, a string of two porcelain insulators is energized by a 45 kV transformer. Electromagnetic radia- tions due tO the partial"discharge activities inside the porcelain insulator are captured by passive sensors and antennas. Two cases of defective insulators on a two insulator string are studied here. The first case focuses on the effect of con- taminated porcelain shells on radiation signature of partial discharges. A polluted porcelain shell with ESDD level of 0.03 mg/cmz was first tested. The second case studies the effect of cracks of an intentionally-cracked porcelain shell. The cracked insulator is also tested on a two insulator string. To compare the partial discharge radiation signature of different faulty insulators, phase resolved graphs were developed. The electromagnetic radiated signature of a polluted insulator and a cracked insulator was'calculated and compared using phase resolved graphs.

  18. Pulse-echo ultrasonic inspection system for in-situ nondestructive inspection of Space Shuttle RCC heat shields.

    Energy Technology Data Exchange (ETDEWEB)

    Roach, Dennis Patrick; Walkington, Phillip D.; Rackow, Kirk A.

    2005-06-01

    The reinforced carbon-carbon (RCC) heat shield components on the Space Shuttle's wings must withstand harsh atmospheric reentry environments where the wing leading edge can reach temperatures of 3,000 F. Potential damage includes impact damage, micro cracks, oxidation in the silicon carbide-to-carbon-carbon layers, and interlaminar disbonds. Since accumulated damage in the thick, carbon-carbon and silicon-carbide layers of the heat shields can lead to catastrophic failure of the Shuttle's heat protection system, it was essential for NASA to institute an accurate health monitoring program. NASA's goal was to obtain turnkey inspection systems that could certify the integrity of the Shuttle heat shields prior to each mission. Because of the possibility of damaging the heat shields during removal, the NDI devices must be deployed without removing the leading edge panels from the wing. Recently, NASA selected a multi-method approach for inspecting the wing leading edge which includes eddy current, thermography, and ultrasonics. The complementary superposition of these three inspection techniques produces a rigorous Orbiter certification process that can reliably detect the array of flaws expected in the Shuttle's heat shields. Sandia Labs produced an in-situ ultrasonic inspection method while NASA Langley developed the eddy current and thermographic techniques. An extensive validation process, including blind inspections monitored by NASA officials, demonstrated the ability of these inspection systems to meet the accuracy, sensitivity, and reliability requirements. This report presents the ultrasonic NDI development process and the final hardware configuration. The work included the use of flight hardware and scrap heat shield panels to discover and overcome the obstacles associated with damage detection in the RCC material. Optimum combinations of custom ultrasonic probes and data analyses were merged with the inspection procedures needed to

  19. Controlling fatigue crack paths for crack surface marking and growth investigations

    Directory of Open Access Journals (Sweden)

    S. Barter

    2016-01-01

    Full Text Available While it is well known that fatigue crack growth in metals that display confined slip, such as high strength aluminium alloys, develop crack paths that are responsive to the loading direction and the local microstructural orientation, it is less well known that such paths are also responsive to the loading history. In these materials, certain loading sequences can produce highly directional slip bands ahead of the crack tip and by adjusting the sequence of loads, distinct fracture surface features or progression marks, even at very small crack depths can result. Investigating the path a crack selects in fatigue testing when particular combinations of constant and variable amplitude load sequences are applied is providing insight into crack growth. Further, it is possible to design load sequences that allow very small amounts of crack growth to be measured, at very small crack sizes, well below the conventional crack growth threshold in the aluminium alloy discussed here. This paper reports on observations of the crack path phenomenon and a novel test loading method for measuring crack growth rates for very small crack depths in aluminium alloy 7050-T7451 (an important aircraft primary structural material. The aim of this work was to firstly generate short- crack constant amplitude growth data and secondly, through the careful manipulation of the applied loading, to achieve a greater understanding of the mechanisms of fatigue crack growth in the material being investigated. A particular focus of this work is the identification of the possible sources of crack growth retardation and closure in these small cracks. Interpreting these results suggests a possible mechanism for why small fatigue crack growth through this material under variable amplitude loading is faster than predicted from models based on constant amplitude data alone.

  20. Augmented reality graphic interface for upstream dam inspection

    Science.gov (United States)

    Cote, Jean; Lavallee, Jean

    1995-12-01

    This paper presents a 3D graphic interface for the inspection of cracks along a dam. The monitoring of concrete dams is restricted by the accessibility of the various parts of the structure. Since the upstream face of a dam is not usually exposed, as in our case at Hydro- Quebec, a systematic and even ad hoc inspection become extremely complex. The piloting of a ROV (Remotely Operated Vehicle) underwater is like driving in a snowstorm. The view from the camera is similar to the visibility a driver would have in a snowstorm. Sensor fusion has to be performed by the operator since each sensor is specialized for its task. Even with a 2D positioning system or sonar scan, the approach to the inspection area is very tedious. A new 3D interface has been developed using augmented reality since the position and orientation of the vehicle are known. The point of view of the observer can easily be changed during a manipulation of the ROV. A shared memory based server can access the position data of the ROV and update the graphics in real time. The graphic environment can be used as well to drive the ROV with computer generated trajectories. A video card will be added to the Silicon Graphics workstation to display the view of the camera fixed to the ROV. This visual feedback will only be available when the ROV is close enough to the dam. The images will be calibrated since the position of the camera is known. The operator interface also includes a set of stereoscopic camera, hydrophonic (sound) feedback and imaging tools for measuring cracks.

  1. Mobile acoustic system for the detection of surface-breaking cracks in pavement

    Science.gov (United States)

    Marzani, Alessandro; Rizzo, Piervincenzo; Lanza di Scalea, Francesco; Benzoni, Gianmario

    2004-07-01

    Monitoring the structural condition of road and airport pavement is an extremely critical task to ensure the safety and efficiency of teh transportation. The topic is relevant to both civil and military transportation infrastructure. The presence of damage in pavement, including surface cracking, depressions, swells, and wear, is inevitable due to the sever environmental and service loads that these structures must be subject to. Existing NDE techniques aimed at assessing the structural condition of pavement include Falling Weight Deflectometer, Ground Penetrating Radar, and acoustic methods based on surface waves. This paper presents improvements to the traditional surface-wave method for the detection of surface-breaking cracks in pavement. The advances include 1) the modeling of the problem as dipsersive waves propagating in a multilayer system, 2) the inclusion of post-processing algorithms based on the Wavelet Transform to improve the sensitivity and accuracy of the inspection, and 3) the use of non-contact, air-coupled acoustic detectors to enhance the mobility of the inspection unit. The crack detection procedure consists of first generating a dispersive wave with an impulse hammer, and then measuring the changes in velocity, amplitude and/or frequency content as the wave travels across the flaw with the aid of the Continuous Wavelet Transform. Multilayer wave propagation modeling provides a better understanding of the experimental results by predicting how the various frequencies interact with cracks of different depths. The results of field tests will be presented for both rigid (concrete-based) and flexible (bitumen-based) pavement with surface cracks.

  2. An unsupervised learning algorithm for fatigue crack detection in waveguides

    Science.gov (United States)

    Rizzo, Piervincenzo; Cammarata, Marcello; Dutta, Debaditya; Sohn, Hoon; Harries, Kent

    2009-02-01

    Ultrasonic guided waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges, and high sensitivity to small flaws. This paper describes an SHM method based on UGWs and outlier analysis devoted to the detection and quantification of fatigue cracks in structural waveguides. The method combines the advantages of UGWs with the outcomes of the discrete wavelet transform (DWT) to extract defect-sensitive features aimed at performing a multivariate diagnosis of damage. In particular, the DWT is exploited to generate a set of relevant wavelet coefficients to construct a uni-dimensional or multi-dimensional damage index vector. The vector is fed to an outlier analysis to detect anomalous structural states. The general framework presented in this paper is applied to the detection of fatigue cracks in a steel beam. The probing hardware consists of a National Instruments PXI platform that controls the generation and detection of the ultrasonic signals by means of piezoelectric transducers made of lead zirconate titanate. The effectiveness of the proposed approach to diagnose the presence of defects as small as a few per cent of the waveguide cross-sectional area is demonstrated.

  3. Online Bridge Crack Monitoring with Smart Film

    Directory of Open Access Journals (Sweden)

    Benniu Zhang

    2013-01-01

    Full Text Available Smart film crack monitoring method, which can be used for detecting initiation, length, width, shape, location, and propagation of cracks on real bridges, is proposed. Firstly, the fabrication of the smart film is developed. Then the feasibility of the method is analyzed and verified by the mechanical sensing character of the smart film under the two conditions of normal strain and crack initiation. Meanwhile, the coupling interference between parallel enameled wires of the smart film is discussed, and then low-frequency detecting signal and the custom communication protocol are used to decrease interference. On this basis, crack monitoring system with smart film is designed, where the collected crack data is sent to the remote monitoring center and the cracks are simulated and recurred. Finally, the monitoring system is applied to six bridges, and the effects are discussed.

  4. Crack Propagation in Bamboo's Hierarchical Cellular Structure

    Science.gov (United States)

    Habibi, Meisam K.; Lu, Yang

    2014-07-01

    Bamboo, as a natural hierarchical cellular material, exhibits remarkable mechanical properties including excellent flexibility and fracture toughness. As far as bamboo as a functionally graded bio-composite is concerned, the interactions of different constituents (bamboo fibers; parenchyma cells; and vessels.) alongside their corresponding interfacial areas with a developed crack should be of high significance. Here, by using multi-scale mechanical characterizations coupled with advanced environmental electron microscopy (ESEM), we unambiguously show that fibers' interfacial areas along with parenchyma cells' boundaries were preferred routes for crack growth in both radial and longitudinal directions. Irrespective of the honeycomb structure of fibers along with cellular configuration of parenchyma ground, the hollow vessels within bamboo culm affected the crack propagation too, by crack deflection or crack-tip energy dissipation. It is expected that the tortuous crack propagation mode exhibited in the present study could be applicable to other cellular natural materials as well.

  5. Air flow through smooth and rough cracks

    Energy Technology Data Exchange (ETDEWEB)

    Kula, H.-G.; Sharples, S. [Sheffield Univ. (United Kingdom). Dept. of Building Science

    1994-12-31

    A series of laboratory experiments are described which investigated the effect of surface roughness on the air flow characteristics of simple, straight-through, no-bend cracks with smooth and rough internal surfaces. The crack thicknesses used in the study were 1.0, 1.5 and 2.0mm. The crack lengths, in the direction of flow, were 50.8mm and 76.2mm. For the rough cracks the roughness was simulated with two different grades of commercially available energy-cloth (grade 60 and 100). The experimental results were satisfactorily fitted to a quadratic relationship between {Delta}p and Q of the form {Delta}p = AQ + BQ{sup 2} for both the smooth and rough crack data. The effect of roughness on the reduction of air flowing through a crack is also discussed. (author)

  6. Crack problem in a long cylindrical superconductor

    Science.gov (United States)

    Yong, Hua-Dong; Zhou, You-He; Zeng, Jun

    2008-12-01

    In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.

  7. Numerical Study of Corrosion Crack Opening

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Frandsen, Henrik Lund; Svensson, Staffan

    2008-01-01

    for the corrosion crack opening. Experiments and theoretical analysis by a numerical method, FEM, support that the relation between the reduction of the reinforcement bar diameter due to corrosion and the corresponding increase in crack width for a given time interval, measured on the surface of a concrete specimen...... is proportional. More recently, the constant of proportionality, the so-called crack-corrosion index, has been studied further with respect to its dependence on the diameter of the reinforcement and the concrete cover. In the present paper the above-mentioned work is presented and extended with more realistic 3D......-models of the cracked concrete beam. The crack-corrosion index is evaluated for a variation of different parameters, i.e. bar diameter, concrete cover, crack length and type of corrosion product. This paper is an extended version of a paper by Thoft-Christensen et al. (2005) presented at the IFIP WG 7.5 Conference...

  8. Portable, X-Y translating, infrared microscope for remote inspection of photovoltaic solar arrays

    Energy Technology Data Exchange (ETDEWEB)

    Forman, S.E.; Caunt, J.W.

    1980-01-01

    The prevalent physical defect found in terrestrial photovoltaic modules during manufacture and field exposure has been the cracked solar cell. Cells can become cracked during handling, because of thermal mismatch in their encapsulation packages, or due to environmental phenomena such as hail. A device is described which can be used remotely to locate cracked silicon solar cells in photovoltaic modules. This solar-cell inspection device can be used either in the laboratory for quality assurance and failure analysis evaluation or at array fields to monitor cracked-cell occurrence. It consists of: (a) an infrared microscope that operates at 1.0 micron, uses darkfield illumination, has a relatively large field of view (3.0 in.), has low system magnification (5X to 15X), and has a video display output; (b) a portable X-Y translator that is capable of moving the microscope over an 8 ft. x 8 ft. area; and (c) a console that allows remote instrument control and visual inspection of modules or arrays (up to 500 ft). This system presently is undergoing laboratory and field testing as part of the DOE-sponsored MIT Lincoln Laboratory Solar Photovoltiac Residential Project.

  9. DBEM crack propagation for nonlinear fracture problems

    Directory of Open Access Journals (Sweden)

    R. Citarella

    2015-10-01

    Full Text Available A three-dimensional crack propagation simulation is performed by the Dual Boundary Element Method (DBEM. The Stress Intensity Factors (SIFs along the front of a semi elliptical crack, initiated from the external surface of a hollow axle, are calculated for bending and press fit loading separately and for a combination of them. In correspondence of the latter loading condition, a crack propagation is also simulated, with the crack growth rates calculated using the NASGRO3 formula, calibrated for the material under analysis (steel ASTM A469. The J-integral and COD approaches are selected for SIFs calculation in DBEM environment, where the crack path is assessed by the minimum strain energy density criterion (MSED. In correspondence of the initial crack scenario, SIFs along the crack front are also calculated by the Finite Element (FE code ZENCRACK, using COD, in order to provide, by a cross comparison with DBEM, an assessment on the level of accuracy obtained. Due to the symmetry of the bending problem a pure mode I crack propagation is realised with no kinking of the propagating crack whereas for press fit loading the crack propagation becomes mixed mode. The crack growth analysis is nonlinear because of normal gap elements used to model the press fit condition with added friction, and is developed in an iterative-incremental procedure. From the analysis of the SIFs results related to the initial cracked configuration, it is possible to assess the impact of the press fit condition when superimposed to the bending load case.

  10. Transition from Multiple Macro-Cracking to Multiple Micro-Cracking in Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; LENG Bing

    2008-01-01

    This paper presents an experimental study of the possibility of transition from multiple macro-cracking to multiple micro-cracking in cementitious composites.Conventional polyvinyl alcohol fiber reinforced cementitious composites normally exhibit macroscopic strain-hardening and multiple cracking after the first cracks appear.However,the individual crack width at the saturated stage is normally 60 to 80 μm.In the current study,the effect of fine aggregate size on the cracking performance,especially the individual crack width in the strain-hardening stage was studied by bending tests.The results show that the individual crack widths can be reduced from 60-80 μm to 10-30 μm by modifying the particle size of the fine aggregates used in the composites.

  11. Codified Risk Based Inspection Planning

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, M.H.

    2002-01-01

    and member failure and at the same time minimizing overall total service life costs. Generic inspections plans can then be established for representative fatigue sensitive details in terms of characteristics such as FDF (Fatigue Design Factor), detail type, RSR (Reserve Strength Ratio) given fatigue failure......Simplified methods are described for reliability- and risk-based inspection planning of steel structures. The methods simplify the practical aspects of identifying inspection plans complying both with specific requirements to the maximum acceptable annual probability of structural collapse...

  12. Fatigue Crack Closure Analysis Using Digital Image Correlation

    Science.gov (United States)

    Leser, William P.; Newman, John A.; Johnston, William M.

    2010-01-01

    Fatigue crack closure during crack growth testing is analyzed in order to evaluate the critieria of ASTM Standard E647 for measurement of fatigue crack growth rates. Of specific concern is remote closure, which occurs away from the crack tip and is a product of the load history during crack-driving-force-reduction fatigue crack growth testing. Crack closure behavior is characterized using relative displacements determined from a series of high-magnification digital images acquired as the crack is loaded. Changes in the relative displacements of features on opposite sides of the crack are used to generate crack closure data as a function of crack wake position. For the results presented in this paper, remote closure did not affect fatigue crack growth rate measurements when ASTM Standard E647 was strictly followed and only became a problem when testing parameters (e.g., load shed rate, initial crack driving force, etc.) greatly exceeded the guidelines of the accepted standard.

  13. Crack

    Science.gov (United States)

    ... rate, breathing rate, blood pressure , and body temperature decreased appetite and less need for sleep feelings of restlessness, ... effects include: gangrene in the bowels resulting from decreased blood ... chest pain reduced appetite, plus health problems associated with not eating a ...

  14. SPIRALING CRACKS IN THIN SHEETS

    OpenAIRE

    2010-01-01

    En este trabajo de tesis presentamos dos experimentos en que trayectorias de fracturas sumamente reproducibles son obtenidas en láminas delgadas frágiles. En ambos casos, a partir de configuraciones iniciales sumamente simples y pequeñas, las trayectorias obtenidas son espirales logarítmicas de gran tamao. Nuestro primer experimento consiste en un crack que se inicia desde un corte recto hecho en una lámina delgada y que es forzado a propagarse por medio de empujar con un objeto sólido....

  15. Fatigue Crack Closure - A Review

    Science.gov (United States)

    1990-09-01

    gauge along the crack line. They used CCT speci- mens of high tensile strength steel ( HY80 ). The measured value of U was found to be a minimum at the...ultrasonic surface wave technique on 12.5mm thick specimens of 2024-T851, 2024-T351, Al 2219, Ti-6AI-4V and 17-4 PH steel . Most of the results were...medium and high strength steels . Exami- nation of the fracture surfaces suggested that raising the mean stress in low fracture toughness steels could

  16. Expansive Soil Crack Depth under Cumulative Damage

    Directory of Open Access Journals (Sweden)

    Bei-xiao Shi

    2014-01-01

    Full Text Available The crack developing depth is a key problem to slope stability of the expansive soil and its project governance and the crack appears under the roles of dry-wet cycle and gradually develops. It is believed from the analysis that, because of its own cohesion, the expansive soil will have a certain amount of deformation under pulling stress but without cracks. The soil body will crack only when the deformation exceeds the ultimate tensile strain that causes cracks. And it is also believed that, due to the combined effect of various environmental factors, particularly changes of the internal water content, the inherent basic physical properties of expansive soil are weakened, and irreversible cumulative damages are eventually formed, resulting in the development of expansive soil cracks in depth. Starting from the perspective of volumetric strain that is caused by water loss, considering the influences of water loss rate and dry-wet cycle on crack developing depth, the crack developing depth calculation model which considers the water loss rate and the cumulative damages is established. Both the proposal of water loss rate and the application of cumulative damage theory to the expansive soil crack development problems try to avoid difficulties in matrix suction measurement, which will surely play a good role in promoting and improving the research of unsaturated expansive soil.

  17. Nonlinear modal method of crack localization

    Science.gov (United States)

    Ostrovsky, Lev; Sutin, Alexander; Lebedev, Andrey

    2004-05-01

    A simple scheme for crack localization is discussed that is relevant to nonlinear modal tomography based on the cross-modulation of two signals at different frequencies. The scheme is illustrated by a theoretical model, in which a thin plate or bar with a single crack is excited by a strong low-frequency wave and a high-frequency probing wave (ultrasound). The crack is assumed to be small relative to all wavelengths. Nonlinear scattering from the crack is studied using a general matrix approach as well as simplified models allowing one to find the nonlinear part of crack volume variations under the given stress and then the combinational wave components in the tested material. The nonlinear response strongly depends on the crack position with respect to the peaks or nodes of the corresponding interacting signals which can be used for determination of the crack position. Juxtaposing various resonant modes interacting at the crack it is possible to retrieve both crack location and orientation. Some aspects of inverse problem solutions are also discussed, and preliminary experimental results are presented.

  18. Wettability Induced Crack Dynamics and Morphology

    CERN Document Server

    Ghosh, Udita Uday; Bhandari, Aditya Bikram; Chakraborty, Suman; DasGupta, Sunando

    2014-01-01

    Substrate wettability alteration induced control over crack formation process in thin colloidal films has been addressed in the present study. Colloidal nanosuspension (53nm, mean particle diameter) droplets have been subjected to natural drying to outline the effects of substrate surface energies over the dry-out characteristics with emphasis on crack dynamics, crack morphology and underlying particle arrangements. Experimental findings indicate that number of cracks formed decreases with increase in substrate hydrophobicity. These physical phenomena have been explained based on the magnitude of stress dissipation incurred by the substrate. DLVO predictions are also found to be in tune with the reported experimental investigations.

  19. Fatigue crack growth detect, assess, avoid

    CERN Document Server

    Richard, Hans Albert

    2016-01-01

    This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.

  20. Investigations of Low Temperature Time Dependent Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  1. Cracking of open traffic rigid pavement

    Directory of Open Access Journals (Sweden)

    Niken Chatarina

    2017-01-01

    Full Text Available The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken’s et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can’t accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.

  2. Crack spacing of unsaturated soils in the critical state

    Institute of Scientific and Technical Information of China (English)

    SUN JiChao; WANG GuangQian; SUN QiCheng

    2009-01-01

    The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur suc-cedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30,0.35].

  3. On the application of cohesive crack modeling in cementitious materials

    DEFF Research Database (Denmark)

    Stang, Henrik; Olesen, John Forbes; Poulsen, Peter Noe;

    2007-01-01

    Cohesive crack models-in particular the Fictitious Crack Model - are applied routinely in the analysis of crack propagation in concrete and mortar. Bridged crack models-where cohesive stresses are assumed to exist together with a stress singularity at the crack tip-on the other hand, are used....... Further, a quantitative condition is established indicating when a bridged crack model can be approximated with a cohesive crack model with smooth crack closure in terms of the ratio between the energy dissipation associated with the crack tip and the process zone....

  4. Probabilistic model for bridge structural evaluation using nondestructive inspection data

    Science.gov (United States)

    Carrion, Francisco; Lopez, Jose Alfredo; Balankin, Alexander

    2005-05-01

    A bridge management system developed for the Mexican toll highway network applies a probabilistic-reliability model to estimate load capacity and structural residual life. Basic inputs for the system are the global inspection data (visual inspections and vibration testing), and the information from the environment conditions (weather, traffic, loads, earthquakes); although, the model takes account for additional non-destructive testing or permanent monitoring data. Main outputs are the periodic maintenance, rehabilitation and replacement program, and the updated inspection program. Both programs are custom-made to available funds and scheduled according to a priority assignation criterion. The probabilistic model, tailored to typical bridges, accounts for the size, age, material and structure type. Special bridges in size or type may be included, while in these cases finite element deterministic models are also possible. Key feature is that structural qualification is given in terms of the probability of failure, calculated considering fundamental degradation mechanisms and from actual direct observations and measurements, such as crack distribution and size, materials properties, bridge dimensions, load deflections, and parameters for corrosion evaluation. Vibration measurements are basically used to infer structural resistance and to monitor long term degradation.

  5. Effect of Crack Closure on Ultrasonic Detection of Fatigue Cracks at Fastener Holes

    Science.gov (United States)

    Bowles, S. J.; Harding, C. A.; Hugo, G. R.

    2009-03-01

    The ultrasonic response from closed fatigue cracks grown in aluminium alloy specimens using a representative aircraft spectrum loading has been characterised as a function of tensile applied load using pulse-echo 45° shear-wave ultrasonic C-scans with focused immersion transducers. Observed trends with crack size and applied load are described and compared to results for artificial machined defects. The results demonstrate that crack closure significantly reduces the ultrasonic response compared to open cracks or machined defects.

  6. Mode Ⅰ Plane Crack Interacting with an Interfacial Crack Along a Circular Inhomogeneity

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; MA Jian-jun; LIU Zheng-guang

    2006-01-01

    The elastic interaction of the mode Ⅰ plane crack with an interfacial crack along a circular inhomogeneity is dealt with. The dislocation density and the stress intensity factors (SIFs) of the mode I plane crack are obtained numerically. A new kind of dislocation equilibrium equation about the plane crack is applied. The influence of some material parameters on the dislocation density and SIFs are analyzed.

  7. Extended propagation model for interfacial crack in composite material structure

    Institute of Scientific and Technical Information of China (English)

    闫相桥; 冯希金

    2002-01-01

    An interfacial crack is a common damage in a composite material structure . An extended propaga-tion model has been established for an interfacial crack to study the dependence of crack growth on the relativesizes of energy release rates at left and right crack tips and the properties of interfacial material characterize thegrowth of interfacial crack better.

  8. On the detectability of transverse cracks in laminated composites through measurements of electrical potential change

    KAUST Repository

    Selvakumaran, Lakshmi

    2015-01-07

    For structures made of laminated composites, real-time structural health monitoring is necessary as significant damage may occur without any visible signs on the surface. Inspection by electrical tomography seems a viable approach as the technique relies on voltage measurements from a network of electrodes over the boundary of the inspected domain to infer the change in conductivity within the bulk material. The change in conductivity, if significant, can be correlated to the degradation state of the material, allowing damage detection. We focus here on the detection of the transverse cracking mechanism which modifies the in-plane transverse conductivity of ply. The quality of detection is directly related to the sensitivity of the voltage measurements with respect to the presence of cracks. We demonstrate here from numerical experiments that the sensitivity depends on several parameters, such as the anisotropy in the electrical conductivity of the baseline composite ply or the geometricalparameters of the structure. Based on these results, applicability of electrical tomography to detect transverse cracks in a laminate is discussed.

  9. Chloride Penetration through Cracks in High-Performance Concrete and Surface Treatment System for Crack Healing

    Directory of Open Access Journals (Sweden)

    In-Seok Yoon

    2012-01-01

    Full Text Available For enhancing the service life of concrete structures, it is very important to minimize crack at surface. Even if these cracks are very small, the problem is to which extend these cracks may jeopardize the durability of these decks. It was proposed that crack depth corresponding with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It was necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. This study is devoted to examine the effect of high strength concrete and reinforcement of steel fiber on chloride penetration through cracks. High strength concrete is regarded as an excellent barrier to resist chloride penetration. However, durability performance of cracked high strength concrete was reduced seriously up to that of ordinary cracked concrete. Steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly. Meanwhile, surface treatment systems are put on the surface of the concrete in order to seal the concrete. The key-issue is to which extend a sealing is able to ensure that chloride-induced corrosion can be prevented. As a result, penetrant cannot cure cracks, however, coating and combined treatment can prevent chloride from flowing in concrete with maximum crack width of 0.06 mm and 0.08 mm, respectively.

  10. On fatigue crack growth in ductile materials by crack-tip blunting

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2004-01-01

    One of the basic mechanisms for fatigue crack growth in ductile metals is that depending on crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading. In a standard numerical analysis accounting for finite strains it is not possible to follow this process during...

  11. National Automated Conformity Inspection Process -

    Data.gov (United States)

    Department of Transportation — The National Automated Conformity Inspection Process (NACIP) Application is intended to expedite the workflow process as it pertains to the FAA Form 81 0-10 Request...

  12. Allegheny County Commercial Vehicle Inspections

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset lists the locations and results of all commercial vehicle inspections performed by the Allegheny County Police Motor Carrier Safety Assistance Program...

  13. Sea bed mapping and inspection

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    The conference has 24 presentations on the topics: Sea bed mapping, inspection, positioning, hydrography, marine archaeology, remote operation vehicles and computerized simulation technologies, oil field activities and plans, technological experiences and problems. (tk)

  14. Multifamily Housing Physical Inspection Scores

    Data.gov (United States)

    Department of Housing and Urban Development — HUD's Real Estate Assessment Center conducts physical property inspections of properties that are owned, insured or subsidized by HUD, including public housing and...

  15. Public Housing Physical Inspection Scores

    Data.gov (United States)

    Department of Housing and Urban Development — HUD's Real Estate Assessment Center conducts physical property inspections of properties that are owned, insured or subsidized by HUD, including public housing and...

  16. A Creaking and Cracking Comet

    Science.gov (United States)

    Faurschou Hviid, Stubbe; Hüttig, Christian; Groussin, Olivier; Mottola, Stefano; Keller, Horst Uwe; OSIRIS Team

    2016-10-01

    Since the middle of 2014 the OSIRIS cameras on the ESA Rosetta mission have been monitoring the evolution of the comet 67P/Churyumov-Gerasimenko as it passed through perihelion. During the perihelion passage several change events have been observed on the nucleus surface. For example existing large scale cracks have expanded and new large scale cracks have been created. Also several large scale "wave pattern" like change events have been observed in the Imhotep and Hapi regions. These are events not directly correlated with any normal visible cometary activity. One interpretation is that these are events likely caused by "seismic" activity. The seismic activity is created by the self-gravity stress of the non-spherical comet nucleus and stress created by the non-gravitational forces acting on the comet. The non-gravitational forces are changing the rotation period of the comet (~20min/perihelion passage) which induces a changing mechanical stress pattern through the perihelion passage. Also the diurnal cycle with its changing activity pattern is causing a periodic wobble in the stress pattern that can act as a trigger for a comet quake. The stress pattern has been modeled using a finite element model that includes self-gravity, the comet spin and the non-gravitational forces based on a cometary activity model. This paper will discuss what can be learned about the comet nucleus structure and about the cometary material properties from these events and from the FEM model.

  17. What can cracked polymer do

    Science.gov (United States)

    Jiao, Kexin; Zhou, Chuanhong; Kohli, Punit; Poudel, Anish; Chu, Tsuchin

    2015-03-01

    Buckling, delamination, and cracking are very well known phenomenon observed in most thin films. They were theoretically explained by the existence of mechanical instability due to the residue stress generated when a thin film is deposited on substrates or undergoing environmental stimulus. Buckled structures at micro- or nano-scale have been of great interests and have been used extensively in many applications including particles self-assembling, surface wettability modification, and micro-electronic device fabrication. However, peeling of a layer from a substrate due to delamination or fractures on a thin film due to cracking is mostly taken as an undesirable result. Therefore, strategies are inspired for preventing or removing these often undesired structures. We found that after being heated above its decomposition temperature and then cooled to room temperature, a PDMS thin film showed micro-fibers of 100 μm width and up to 1.5 cm in length. By studying the formation mechanism, control of the dimensions and of the growth pattern on a substrate for PDMS micro-fibers were realized. Giving credit to their high flexibility and optical transparency, a PDMS micro-fiber were utilized in high resolution near field imaging achieved by attaching a micro-lens on the fiber. Interestingly, a surface covered by PDMS micro-fibers will turn from superhydrophobic into superhydrophilic by further heating providing potential applications in surface wettability modification. In future, we will investigate and simulate the growth of PDMS micro-fiber and look for more possible applications.

  18. In-service fatigue cracking of the propeller shafts joined by a spline-pinned construction to the engines of AN-24, AN-26, and IL-18 aircrafts

    Directory of Open Access Journals (Sweden)

    A. Shanyavskiy

    2014-10-01

    Full Text Available The paper delivers a critical review of the research data on the crack initiation and crack growth patterns characteristic of the components of the spline-bolted joints between the propeller shaft and reducer shaft at An-24, An-26, and Il-18 aircrafts. Cracks in the shafts nucleated because of reduced bolt-fastening force. Actually, the bolt (bolts failed first (also by fatigue and then fatigue cracks nucleated and grew in the shafts, the spline surface fretting zones and/or sharp edges of the attachment (bolt-conducting holes making the crack origin sites. The crack growth history shows itself through the regular Macro-Beach Marks, each mark sequentially pointing to the next loading event of the propeller shaft, i.e., to each next flight. The cracks cease growing for some while in the airscrews and their shafts just replaced to another aircraft. For the airscrew shafts, the critically assessed data show the crack growth period Np ranging as five to ten percent of a total running period Nf . We recommend performing nondestructive inspection of the airscrew shafts on every 250- hour running period to ensure the safety flights.

  19. Development and field application of a nonlinear ultrasonic modulation technique for fatigue crack detection without reference data from an intact condition

    Science.gov (United States)

    Lim, Hyung Jin; Kim, Yongtak; Koo, Gunhee; Yang, Suyoung; Sohn, Hoon; Bae, In-hwan; Jang, Jeong-Hwan

    2016-09-01

    In this study, a fatigue crack detection technique, which detects a fatigue crack without relying on any reference data obtained from the intact condition of a target structure, is developed using nonlinear ultrasonic modulation and applied to a real bridge structure. Using two wafer-type lead zirconate titanate (PZT) transducers, ultrasonic excitations at two distinctive frequencies are applied to a target inspection spot and the corresponding ultrasonic response is measured by another PZT transducer. Then, the nonlinear modulation components produced by a breathing-crack are extracted from the measured ultrasonic response, and a statistical classifier, which can determine if the nonlinear modulation components are statistically significant in comparison with the background noise level, is proposed. The effectiveness of the proposed fatigue crack detection technique is experimentally validated using the data obtained from aluminum plates and aircraft fitting-lug specimens under varying temperature and loading conditions, and through a field testing of Yeongjong Grand Bridge in South Korea. The uniqueness of this study lies in that (1) detection of a micro fatigue crack with less than 1 μm width and fatigue cracks in the range of 10-20 μm in width using nonlinear ultrasonic modulation, (2) automated detection of fatigue crack formation without using reference data obtained from an intact condition, (3) reliable and robust diagnosis under varying temperature and loading conditions, (4) application of a local fatigue crack detection technique to online monitoring of a real bridge.

  20. Analysis of cracked core spray injection line piping from the Quad Cities Units 1 and 2 boiling water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Diercks, D.R.

    1983-12-01

    Elbow assemblies and adjacent piping from the loops A and B core spray injection lines of Quad Cities Units 1 and 2 Boiling Water Reactors have been examined in order to determine the nature and causes of coolant leakages and flaw indications detected during hydrostatic tests and subsequent ultrasonic inspections. The elbow assemblies were found to contain multiple intergranular cracks in the weld heat-affected zones. The cracking was predominantly axial in orientation in the forged elbow and wedge components, whereas mixed axial and circumferential cracking was seen in the wrought piping pieces. In at least two instances, axial cracks completely penetrated the circumferential weld joining adjacent components. Based upon the observations made in the present study, the failures were attributed to intergranular stress corrosion cracking caused by the weld-induced sensitized microstructure and residual stresses present; dissolved oxygen in the reactor coolant apparently served as the corrosive species. The predominantly axial orientation of the cracks present in the forged components is believed to be related to the banded microstructure present in these components. The metallographic studies reported are supplemented by x-radiography, chemical analysis and mechanical test results, determinations of the degree of sensitization present, and measurements of weld metal delta ferrite content.

  1. Nondestructive inspection of plasma-sprayed metallic coatings for coal conversion equipment

    Energy Technology Data Exchange (ETDEWEB)

    Scott, G.W.; Snyder, S.D.; Simpson, W.A. Jr.

    1979-12-01

    This report describes the results of a project to develop nondestructive inspection techniques for metallic wear- and process-resistant coatings used in coal system components. Physical properties, especially porosity, and the nominal 0.25 mm (0.010 in.) thickness complicate the inspection of these coatings. The class of coatings selected for laboratory evaluation were CoCrAlY (cobalt-chromium-aluminum-yttrium) types; the specific material used was a Union Carbide spray powder, UCAR LCO-7, which is Co-22.8% Cr-12.9% Al-0.6% Y, sprayed onto alloy 800 substrates. The desired inspection techniques were to: (1) detect cracks or holes in the coating; (2) measure the coating thickness from the coated side; and (3) detect lamellar flaws or separations within the coating layer or between the coating and the substrate. Surface methods (such as liquid penetrant), eddy currents, and radiography were investigated for crack and hole detection; eddy currents, x-ray fluorescence, and ultrasonics were investigated for thickness measurement; and ultrasonics and infrared thermography were investigated for lamellar flaw detection. In general, we determined that significant development effort was required to adapt even the more common and highly developed techniques to the coating inspection problems. Significant progress was made in a number of the investigations undertaken, but financial restraints prevented completion of the planned work.

  2. Virtual World Security Inspection

    Directory of Open Access Journals (Sweden)

    Nicholas Charles Patterson

    2012-06-01

    Full Text Available Virtual property theft is a serious problem that exists in virtual worlds. Legitimate users of these worlds invest considerable amounts of time, effort and real-world money into obtaining virtual property, but unfortunately, are becoming victims of theft in high numbers. It is reported that there are over 1 billion registered users of virtual worlds containing virtual property items worth an estimated US$50 billion dollars. The problem of virtual property theft is complex, involving many legal, social and technological issues. The software used to access virtual worlds is of great importance as they form the primary interface to these worlds and as such the primary interface to conduct virtual property theft. The security vulnerabilities of virtual world applications have not, to date, been examined. This study aims to use the process of software inspection to discover security vulnerabilities that may exist within virtual world software – vulnerabilities that enable virtual property theft to occur. Analyzing three well know virtual world applications World of Warcraft, Guild Wars and Entropia Universe, this research utilized security analysis tools and scenario testing with focus on authentication, trading, intruder detection and virtual property recovery. It was discovered that all three examples were susceptible to keylogging, mail and direct trade methods were the most likely method for transferring stolen items, intrusion detection is of critical concern to all VWEs tested, stolen items were unable to be recovered in all cases and lastly occurrences of theft were undetectable in all cases. The results gained in this study present the key problem areas which need to be addressed to improve security and reduce the occurrence of virtual property theft.

  3. Ultrasonic in-line inspection of pipelines, new generation of tools

    Energy Technology Data Exchange (ETDEWEB)

    Uzelac, Neb I.; Reber, Konrad; Beller, Michael; Barbian, Otto Alfred [NDT Systems and Services (Germany)

    2003-07-01

    In-line inspection (ILI) of pipelines has established itself as the most efficient tool for evaluating the condition of a pipeline and an indispensable part of pipeline integrity management. Historically, there have been two major technologies used in in-line inspection for corrosion, the magnetic flux leakage (MFL) and ultrasonics (UT), each having their distinct properties and fields of application. Ultrasonic (UT) ILI has always provided unique quality of information about the pipelines, rendering highest accuracy and tightest measurement tolerances. In the 1990s ultrasonic tools for detection of cracks have become available. This paper describes the new generation of ultrasonic ILI tools, both for metal loss (corrosion) and crack detection. It has been developed based on the expertise gained utilizing the first generation of UT tools combined with the advancements in electronic, hardware and software components available today. Properties of the new tools are presented. Tool specifications and their defect detection capabilities are discussed, as well as the characteristics that make them unique. The performance of these new tools offers advantages in detection and sizing performance, increased operational convenience and improved reporting. Based on examples from tests and inspection runs, it can be seen that the new tool technology can successfully operate in situations and pipe configurations that UT technology has historically had problems with. Examples of this are shown and it is discussed what kind of applications this technology is best suited for. Also, assessment of defects regarding the remaining strength of the pipe is being discussed and demonstrations shown of how the new UT metal loss tools provide superior results over others in fully using the most advanced defect assessment algorithms. Inspection of pipelines for crack and crack-like defect is another aspect where this technology offers the highest standards within the industry. Examples are

  4. 46 CFR 61.30-15 - Visual inspection.

    Science.gov (United States)

    2010-10-01

    ... INSPECTIONS Tests and Inspections of Fired Thermal Fluid Heaters § 61.30-15 Visual inspection. Thermal fluid heaters are examined by a marine inspector at the inspection for certification, periodic inspection...

  5. 75 FR 81965 - Grain Inspection Advisory Committee Reestablishment

    Science.gov (United States)

    2010-12-29

    ... Grain Inspection, Packers and Stockyards Administration Grain Inspection Advisory Committee Reestablishment AGENCY: Grain Inspection, Packers and Stockyards Administration, USDA. ACTION: Notice to... Grain Inspection, Packers and Stockyards Administration (GIPSA) Grain Inspection Advisory Committee...

  6. Development of automated nondestructive inspection system for BMI nozzles in nuclear vessel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Joon Soo; Lee, Won Kun; Han, Won Jin; Lee, Sun Ho; Seong, Un Hak [Doosan Heavy Industries and Construction Co., Ltd., Changwon (Korea, Republic of)

    2013-02-15

    BMI nozzles in bottom head of the nuclear vessel are one of major components in nuclear power plants. The BMI nozzles have high possibility to generate PWSCC(primary water stress corrosion crack) according to recent foreign case although operation temperature is lower then the upper head of the nuclear vessel. Thus, nondestructive inspection of the BMI nozzles is required. But, inspection of BMI nozzles is not easy since the BMI nozzles placed in high radiated area and inside the nozzles filled with boric acid. Thus, in this study, a TOFD transducer for inspection of BMI and automated scanner system with water were developed. Also, validation of performance of the developed transducer and system are performed using specimens with artificial defects.

  7. Development of crack shape: LBB methodology for cracked pipes

    Energy Technology Data Exchange (ETDEWEB)

    Moulin, D.; Chapuliot, S.; Drubay, B. [Commissariat a l Energie Atomique, Gif sur Yvette (France)

    1997-04-01

    For structures like vessels or pipes containing a fluid, the Leak-Before-Break (LBB) assessment requires to demonstrate that it is possible, during the lifetime of the component, to detect a rate of leakage due to a possible defect, the growth of which would result in a leak before-break of the component. This LBB assessment could be an important contribution to the overall structural integrity argument for many components. The aim of this paper is to review some practices used for LBB assessment and to describe how some new R & D results have been used to provide a simplified approach of fracture mechanics analysis and especially the evaluation of crack shape and size during the lifetime of the component.

  8. 23 CFR 650.311 - Inspection frequency.

    Science.gov (United States)

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false Inspection frequency. 650.311 Section 650.311 Highways..., STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine... level and frequency to which these bridges are inspected considering such factors as age,...

  9. Microscopic study of stress effects around micro-crack tips using a non-contact stress-induced light scattering method

    Science.gov (United States)

    Sakata, Y.; Terasaki, N.; Nonaka, K.

    2016-09-01

    Fine-polishing techniques may cause micro-cracks under glass substrate surfaces. According to highly requirement from production field, a thermal stress-induced light scattering method (T-SILSM) was successfully developed for a non-contact inspection to detect the micro-cracks through changing in the intensity of light scattering accompanied by applying thermal stress at the responding position of the micro-cracks. In this study, in order to investigate that the origin of the measuring principle in microscopic order, a newly developed microscopic T-SILSM system with a rotation stage and a numerical simulation analysis were used to investigate the following; (1) the scattering points and surface in the micro-crack, (2) the stress concentration points in the micro-crack, and (3) the relationship between these information and the point in which intensity of the light scattering changes in the micro-crack through T-SILSM. Light scattering was observed at the responding position of the micro-crack with selectivity in the direction of laser irradiation even in the microscopic order. In addition, the position of the changes in the light scattering in was at both tips in the micro-crack, and it was consistent with the stress concentration point in the micro-crack. Therefore, it can be concluded that the intentional change in light scattering though T-SILSM is originated from light scattering at micro-crack and also from stress concentration and consecutive change in refractive index at both tips in micro-crack.

  10. A study of defects on EUV mask using blank inspection, patterned mask inspection, and wafer inspection

    Energy Technology Data Exchange (ETDEWEB)

    Huh, S.; Ren, L.; Chan, D.; Wurm, S.; Goldberg, K. A.; Mochi, I.; Nakajima, T.; Kishimoto, M.; Ahn, B.; Kang, I.; Park, J.-O.; Cho, K.; Han, S.-I.; Laursen, T.

    2010-03-12

    The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography (EUVL) into high volume manufacturing. yet link data is available for understanding native defects on real masks. In this paper, a full-field EUV mask is fabricated to investigate the printability of various defects on the mask. The printability of defects and identification of their source from mask fabrication to handling were studied using wafer inspection. The printable blank defect density excluding particles and patterns is 0.63 cm{sup 2}. Mask inspection is shown to have better sensitivity than wafer inspection. The sensitivity of wafer inspection must be improved using through-focus analysis and a different wafer stack.

  11. Characterization of crack growth under combined loading

    Science.gov (United States)

    Feldman, A.; Smith, F. W.; Holston, A., Jr.

    1977-01-01

    Room-temperature static and cyclic tests were made on 21 aluminum plates in the shape of a 91.4x91.4-cm Maltese cross with 45 deg flaws to develop crack growth and fracture toughness data under mixed-mode conditions. During cyclic testing, it was impossible to maintain a high proportion of shear-mode deformation on the crack tips. Cracks either branched or turned. Under static loading, cracks remained straight if shear stress intensity exceeded normal stress intensity. Mixed-mode crack growth rate data compared reasonably well with published single-mode data, and measured crack displacements agreed with the straight and branched crack analyses. Values of critical strain energy release rate at fracture for pure shear were approximately 50% higher than for pure normal opening, and there was a large reduction in normal stress intensity at fracture in the presence of high shear stress intensity. Net section stresses were well into the inelastic range when fracture occurred under high shear on the cracks.

  12. Locating a leaking crack by safe stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Coleman, C.E.; Sagat, S. (Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.); Shek, G.K.; Graham, D.B.; Durand, M.A. (Ontario Hydro, Toronto, ON (Canada))

    1990-01-01

    A few Zr-2.5 Nb alloy pressure tubes in CANDU nuclear reactors have leaked through cracks that have grown by delayed hydride cracking (DHC). In some instances, tubes contained confirmed leaks that were leaking at a rate too low for precise identification of the leaking channel. Controlled stimulation of DHC can be used to help locate these leaks by extending the crack and increasing the leak rate without approaching crack instability. In the event of a leak being detected, a plant operator can gain time for leak location by a heating and unloading manoeuvre that will arrest crack growth and increase the critical crack length. This manoeuvre increases the safety margin against tube rupture. If required, the operator can then stimulate cracking in a controlled manner to aid in leak identification. Sequences of temperature and load manoeuvres for safe crack stimulation have been found by laboratory tests on dry specimens and the efficacy of the process has been demonstrated, partly in a power reactor, and partly in a full-scale simulation of a leaking pressure tube. (author).

  13. Entering a Crack: An Encounter with Gossip

    Science.gov (United States)

    Henderson, Linda

    2014-01-01

    In this paper, I enter a crack to think otherwise about the concept "gossip". Drawing on previous scholarship engaging with Deleuzian concepts to inform research methodologies, this paper builds on this body of work. Following Deleuze and Guattari, the paper undertakes a mapping of gossip, subsequent to an encounter with a crack.…

  14. Crack propagation directions in unfilled resins.

    Science.gov (United States)

    Baran, G; Sadeghipour, K; Jayaraman, S; Silage, D; Paul, D; Boberick, K

    1998-11-01

    Posterior composite restorative materials undergo accelerated wear in the occlusal contact area, primarily through a fatigue mechanism. To facilitate the timely development of new and improved materials, a predictive wear model is desirable. The objective of this study was to develop a finite element model enabling investigators to predict crack propagation directions in resins used as the matrix material in composites, and to verify these predictions by observing cracks formed during the pin-on-disc wear of a 60:40 BISGMA:TEGDMA resin and an EBPADMA resin. Laser confocal scanning microscopy was used to measure crack locations. Finite element studies were done by means of ABAQUS software, modeling a cylinder sliding on a material with pre-existing surface-breaking cracks. Variables included modulus, cylinder/material friction coefficient, crack face friction, and yield behavior. Experimental results were surprising, since most crack directions were opposite previously published observations. The majority of surface cracks, though initially orthogonal to the surface, changed direction to run 20 to 30 degrees from the horizontal in the direction of indenter movement. Finite element modeling established the importance of subsurface shear stresses, since calculations provided evidence that cracks propagate in the direction of maximum K(II)(theta), in the same direction as the motion of the indenter, and at an angle of approximately 20 degrees. These findings provide the foundation for a predictive model of sliding wear in unfilled glassy resins.

  15. Uncertainty Quantification in Fatigue Crack Growth Prognosis

    Directory of Open Access Journals (Sweden)

    Shankar Sankararaman

    2011-01-01

    Full Text Available This paper presents a methodology to quantify the uncertainty in fatigue crack growth prognosis, applied to structures with complicated geometry and subjected to variable amplitude multi-axial loading. Finite element analysis is used to address the complicated geometry and calculate the stress intensity factors. Multi-modal stress intensity factors due to multi-axial loading are combined to calculate an equivalent stress intensity factor using a characteristic plane approach. Crack growth under variable amplitude loading is modeled using a modified Paris law that includes retardation effects. During cycle-by-cycle integration of the crack growth law, a Gaussian process surrogate model is used to replace the expensive finite element analysis. The effect of different types of uncertainty – physical variability, data uncertainty and modeling errors – on crack growth prediction is investigated. The various sources of uncertainty include, but not limited to, variability in loading conditions, material parameters, experimental data, model uncertainty, etc. Three different types of modeling errors – crack growth model error, discretization error and surrogate model error – are included in analysis. The different types of uncertainty are incorporated into the crack growth prediction methodology to predict the probability distribution of crack size as a function of number of load cycles. The proposed method is illustrated using an application problem, surface cracking in a cylindrical structure.

  16. Entering a Crack: An Encounter with Gossip

    Science.gov (United States)

    Henderson, Linda

    2014-01-01

    In this paper, I enter a crack to think otherwise about the concept "gossip". Drawing on previous scholarship engaging with Deleuzian concepts to inform research methodologies, this paper builds on this body of work. Following Deleuze and Guattari, the paper undertakes a mapping of gossip, subsequent to an encounter with a crack.…

  17. Investigation of Cracked Lithium Hydride Reactor Vessels

    Energy Technology Data Exchange (ETDEWEB)

    bird, e.l.; mustaleski, t.m.

    1999-06-01

    Visual examination of lithium hydride reactor vessels revealed cracks that were adjacent to welds, most of which were circumferentially located in the bottom portion of the vessels. Sections were cut from the vessels containing these cracks and examined by use of the metallograph, scanning electron microscope, and microprobe to determine the cause of cracking. Most of the cracks originated on the outer surface just outside the weld fusion line in the base material and propagated along grain boundaries. Crack depths of those examined sections ranged from {approximately}300 to 500 {micro}m. Other cracks were reported to have reached a maximum depth of 1/8 in. The primary cause of cracking was the creation of high tensile stresses associated with the differences in the coefficients of thermal expansion between the filler metal and the base metal during operation of the vessel in a thermally cyclic environment. This failure mechanism could be described as creep-type fatigue, whereby crack propagation may have been aided by the presence of brittle chromium carbides along the grain boundaries, which indicates a slightly sensitized microstructure.

  18. Fracture Mechanical Markov Chain Crack Growth Model

    DEFF Research Database (Denmark)

    Gansted, L.; Brincker, Rune; Hansen, Lars Pilegaard

    1991-01-01

    On the basis of the B-model developed in [J. L. Bogdanoff and F. Kozin, Probabilistic Models of Cumulative Damage. John Wiley, New York (1985)] a new numerical model incorporating the physical knowledge of fatigue crack propagation is developed. The model is based on the assumption that the crack...

  19. Solute transport in cracking clay soils

    NARCIS (Netherlands)

    Bronswijk, J.J.B.; Ritsema, C.J.; Oostindie, K.; Hamminga, P.

    1996-01-01

    A bromide tracer applied to a cracked clay soil was adsorbed in the soil matrix close to the soil surface. Upon subsequent precipitation, a small part of the bromide dissolved and flowed rapidly through cracks to the subsoil and the groundwater. As a result, the groundwater and the drain discharge

  20. Strength of Cracked Reinforced Concrete Disks

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...

  1. Corrosion and Cracking of Reinforced Concrete

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Modelling of the deterioration of reinforced concrete has in recent years changed from being a deterministic modelling based on experience to be stochastic modelling based on sound and consistent physical, chemical and mechanical principles. In this paper is presented a brief review of modern mod...... for time to initial corrosion, time to initial cracking, and time to a given crack width may be obtained....

  2. Analysis of internal crack in a six-ton P91 ingot

    Directory of Open Access Journals (Sweden)

    Jing-an Yang

    2016-05-01

    Full Text Available P91 is a new kind of heat-resistant and high-tensile steel. It can be extruded after ingot casting and can be widely used for different pipes in power plants. However, due to its mushy freezing characteristics, a lack of feeding in the ingot center often generates many defects, such as porosity and crack. A six-ton P91 ingot was cast and sliced, and a representative part of the longitudinal section was inspected in more detail. The morphology of crack-like defects was examined by X-ray high energy industrial CT and reconstructed by 3D software. There are five main portions of defects larger than 200 mm3, four of which are interconnected. These initiated from continuous liquid film, and then were torn apart by excessive tensile stress within the brittle temperature range (BTR. The 3D FEM analysis of thermo-mechanical simulation was carried out to analyze the formation of porosity and internal crack defects. The results of shrinkage porosity and Niyama values revealed that the center of the ingot suffers from inadequate feeding. Several criteria based on thermal and mechanical models were used to evaluate the susceptibility of hot crack formation. The Clyne and Davies’ criterion and Katgerman’s criterion successfully predicted the high hot crack susceptibility in the ingot center. Six typical locations in the longitudinal section had been chosen for analysis of the stresses and strains evolution during the BTR. Locations in the defects region showed the highest tensile stresses and relative high strain values, while other locations showed either low tensile stresses or low strain values. In conclusion, hot crack develops only when stress and strain exceed a threshold value at the same time during the BTR.

  3. Effects of surface roughness on magnetic flux leakage testing of micro-cracks

    Science.gov (United States)

    Deng, Zhiyang; Sun, Yanhua; Yang, Yun; Kang, Yihua

    2017-04-01

    Magnetic flux leakage (MFL) testing owns the advantages of high inspection sensitivity and stability, but its testing results are always affected by surface roughness. The relationship between the surface roughness ({{R}a} ) and detection signals for surface-breaking cracks is mainly discussed. The existence of roughness magnetic compression effect (RMCE) in present MFL testing is specially pointed out and its relevant theory is also analyzed, which manifest themselves in the compression of MFL signal in its peak value and the baseline drifts mixed with noise. An experimental investigation on surface comparators with different arithmetic average height ({{R}a} ) and artificial notch size, is performed to analyze the effects of surface roughness on detection signals of cracks. The detection limit (DL) of micro-crack is analyzed by comparing the {{B}y} noise-signal ratio ({{S}y} ) and peak-peak signals of the cracks. Meanwhile, {{S}y} increases with the {{R}a} and R{{S}m} , in this case, relatively shallow defects cannot be clearly distinguished at determined rough surface. Afterwards, a series of simulations are designed and performed to verify the effects of surface roughness on characteristic {{B}y} of the electromagnetic field, and a theoretical DL of micro-crack is presented as: DL=2.88{{R}a}+7.00 . Furthermore, the optimal lift-off value is selected for the micro-cracks’ detection to weaken the negative magnetic compression effect. MFL signals cannot reflect the accurate sizes of the cracks on rough surface due to the RMCE and its relevant phenomenon. The discovery and results will benefit the quantitative evaluation of the MFL testing.

  4. Challenges Faced in Modern Quality Inspection

    Directory of Open Access Journals (Sweden)

    Borkowski Stanisław

    2016-09-01

    Full Text Available Point of view, preferences and priorities of quality inspection in modern production systems have changed. Quality inspection in its activities is no longer limited only to the documentation of the past, nor is it seen solely as a tool for the detection of nonconformity. Nowadays, the most important quality inspection function is prevention, whose most important goal is to make it before nonconformity. What is expected from modern quality inspection is that it actively improves the production and quality as well as reduces the costs. The aim of the article is to present requirements, guidelines and challenges in the organization of modern quality inspection in a manufacturing company. The role of quality inspection in the classical model and modern model of quality improvement was presented. Determinants of effective quality inspection were presented, as well. The quality inspection methods that best fit into the paradigm of modern quality inspection, that is source inspection, together with visual management were pointed out.

  5. ROBOTIC TANK INSPECTION END EFFECTOR

    Energy Technology Data Exchange (ETDEWEB)

    Rachel Landry

    1999-10-01

    The objective of this contract between Oceaneering Space Systems (OSS) and the Department of Energy (DOE) was to provide a tool for the DOE to inspect the inside tank walls of underground radioactive waste storage tanks in their tank farms. Some of these tanks are suspected to have leaks, but the harsh nature of the environment within the tanks precludes human inspection of tank walls. As a result of these conditions only a few inspection methods can fulfill this task. Of the methods available, OSS chose to pursue Alternating Current Field Measurement (ACFM), because it does not require clean surfaces for inspection, nor any contact with the Surface being inspected, and introduces no extra by-products in the inspection process (no coupling fluids or residues are left behind). The tool produced by OSS is the Robotic Tank Inspection End Effector (RTIEE), which is initially deployed on the tip of the Light Duty Utility Arm (LDUA). The RTEE combines ACFM with a color video camera for both electromagnetic and visual inspection The complete package consists of an end effector, its corresponding electronics and software, and a user's manual to guide the operator through an inspection. The system has both coarse and fine inspection modes and allows the user to catalog defects and suspected areas of leakage in a database for further examination, which may lead to emptying the tank for repair, decommissioning, etc.. The following is an updated report to OSS document OSS-21100-7002, which was submitted in 1995. During the course of the contract, two related subtasks arose, the Wall and Coating Thickness Sensor and the Vacuum Scarifying and Sampling Tool Assembly. The first of these subtasks was intended to evaluate the corrosion and wall thinning of 55-gallon steel drums. The second was retrieved and characterized the waste material trapped inside the annulus region of the underground tanks on the DOE's tank farms. While these subtasks were derived from the original

  6. Crack spacing threshold of double cracks propagation for large-module rack

    Institute of Scientific and Technical Information of China (English)

    赵铁柱; 石端伟; 姚哲皓; 毛宏勇; 程术潇; 彭惠

    2015-01-01

    Large-module rack of the Three Gorges shiplift is manufactured by casting and machining, which is unable to avoid slag inclusions and surface cracks. To ensure its safety in the future service, studying on crack propagation rule and the residual life estimation method of large-module rack is of great significance. The possible crack distribution forms of the rack in the Three Gorges shiplift were studied. By applying moving load on the model in FRANC3D and ANSYS, quantitative analyses of interference effects on double cracks in both collinear and offset conditions were conducted. The variation rule of the stress intensity factor (SIF) influence factor,RK, of double collinear cracks changing with crack spacing ratio,RS, was researched. The horizontal and vertical crack spacing threshold of double cracks within the design life of the shiplift were obtained, which are 24 and 4 times as large as half of initial crack length,c0, respectively. The crack growth rates along the length and depth directions in the process of coalescence on double collinear cracks were also studied.

  7. Unsaturated Seepage Analysis of Cracked Soil including Development Process of Cracks

    Directory of Open Access Journals (Sweden)

    Ling Cao

    2016-01-01

    Full Text Available Cracks in soil provide preferential pathways for water flow and their morphological parameters significantly affect the hydraulic conductivity of the soil. To study the hydraulic properties of cracks, the dynamic development of cracks in the expansive soil during drying and wetting has been measured in the laboratory. The test results enable the development of the relationships between the cracks morphological parameters and the water content. In this study, the fractal model has been used to predict the soil-water characteristic curve (SWCC of the cracked soil, including the developmental process of the cracks. The cracked expansive soil has been considered as a crack-pore medium. A dual media flow model has been developed to simulate the seepage characteristics of the cracked expansive soil. The variations in pore water pressure at different part of the model are quite different due to the impact of the cracks. This study proves that seepage characteristics can be better predicted if the impact of cracks is taken into account.

  8. Probabilistic analysis of linear elastic cracked structures

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper presents a probabilistic methodology for linear fracture mechanics analysis of cracked structures. The main focus is on probabilistic aspect related to the nature of crack in material. The methodology involves finite element analysis; statistical models for uncertainty in material properties, crack size, fracture toughness and loads; and standard reliability methods for evaluating probabilistic characteristics of linear elastic fracture parameter. The uncertainty in the crack size can have a significant effect on the probability of failure, particularly when the crack size has a large coefficient of variation. Numerical example is presented to show that probabilistic methodology based on Monte Carlo simulation provides accurate estimates of failure probability for use in linear elastic fracture mechanics.

  9. Strain rate effects in stress corrosion cracking

    Energy Technology Data Exchange (ETDEWEB)

    Parkins, R.N. (Newcastle upon Tyne Univ. (UK). Dept. of Metallurgy and Engineering Materials)

    1990-03-01

    Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.

  10. Crack front propagation by kink formation

    Energy Technology Data Exchange (ETDEWEB)

    Roesch, Frohmut; Trebin, Hans-Rainer [Universitaet Stuttgart, Institut fuer Theoretische und Angewandte Physik, 70550 Stuttgart (Germany)

    2010-07-01

    In a brittle material a travelling crack generates an upper and a lower fracture surface, which meet at a one-dimensional crack front. From a macroscopic point of view there is no reason why this curve should deviate from a straight line, contrary to the atomistic point of view, where a crack propagates by successive rupture of cohesive bonds. We investigate fracture of the C15 NbCr{sub 2} Friauf-laves phase on an atomic level by means of molecular dynamics simulations. The numerical experiments highlight that crack fronts in general do not form a straight line and propagate by kink-pair formation at low loads (EPL 87 (2009) 66004). This mechanism should be relevant for crack propagation in any ordered brittle solid.

  11. XFEM for Thermal Crack of Massive Concrete

    Directory of Open Access Journals (Sweden)

    Guowei Liu

    2013-01-01

    Full Text Available Thermal cracking of massive concrete structures occurs as a result of stresses caused by hydration in real environment conditions. The extended finite element method that combines thermal fields and creep is used in this study to analyze the thermal cracking of massive concrete structures. The temperature field is accurately simulated through an equivalent equation of heat conduction that considers the effect of a cooling pipe system. The time-dependent creep behavior of massive concrete is determined by the viscoelastic constitutive model with Prony series. Based on the degree of hydration, we consider the main properties related to cracking evolving with time. Numerical simulations of a real massive concrete structure are conducted. Results show that the developed method is efficient for numerical calculations of thermal cracks on massive concrete. Further analyses indicate that a cooling system and appropriate heat preservation measures can efficiently prevent the occurrence of thermal cracks.

  12. The geometry of soil crack networks

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    The subject of this work is the modification and specification of an approach to detail the estimation of soil crack network characteristics. The modification aims at accounting for the corrected soil crack volume based on the corrected shrinkage geometry factor compared to known estimates of crack volume and shrinkage geometry factor. The mode of the correction relies on recent results of the soil reference shrinkage curve. The main exposition follows the preliminary brief review of available approaches to dealing with the geometry of soil crack networks and gives a preliminary brief summary of the approach to be modified and specified. To validate and illustrate the modified approach the latter is used in the analysis of available data on soil cracking in a lysimeter.

  13. Field cracking performance of airfield rigid pavements

    Directory of Open Access Journals (Sweden)

    Yusuf Mehta

    2017-08-01

    Full Text Available This paper discusses cracking in airport pavements as studied in Construction Cycle 6 of testing carried out at the National Airport Pavement Testing Facility by the Federal Aviation Administration. Pavements of three different flexural strengths as well as two different subgrades, a soft bituminous layer and a more rigid layer known as econocrete, were tested. In addition to this, cracking near two types of isolated transition joints, a reinforced edge joint and a thickened edge joint, was considered. The pavement sections were tested using a moving load simulating that of an aircraft. It has been determined that the degree of cracking was reduced as the flexural strength of the pavement was increased and that fewer cracks formed over the econocrete base than over the bituminous base. In addition, the thickened edge transition joint was more effective in preventing cracking at the edges compared to the reinforced edge joint.

  14. Crack Growth in Concrete Gravity Dams Based on Discrete Crack Method

    Directory of Open Access Journals (Sweden)

    A. R. Lohrasbi

    2008-01-01

    Full Text Available Seepage is the most parameter in water management safety and in stable agricultural. This seepage is passed through the cracks that are present to some degree in hydraulic structures. They may exist as basic defects in the constituent materials or may be induced in construction or during service life. To avoid such failure in concrete dams, safety would be an important factor. Over-design carries heavy penalty in terms of excess weight. So the fracture mechanics theory is a principal necessity of evaluating the stability of such crack propagation. For the process of crack propagation analysis in concrete structures, there are two general models: discrete crack and smeared crack. This study surveys the crack propagation in concrete gravity dams based on discrete crack methods. Moreover, we use a program provided specifically for this purpose.

  15. Crack shape developments and leak rates for circumferential complex-cracked pipes

    Energy Technology Data Exchange (ETDEWEB)

    Brickstad, B.; Bergman, M. [SAQ Inspection Ltd., Stockholm (Sweden)

    1997-04-01

    A computerized procedure has been developed that predicts the growth of an initial circumferential surface crack through a pipe and further on to failure. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes and for the through-wall cracks, crack opening areas and leak rates are also calculated. The procedure is based on a large number of three-dimensional finite element calculations of cracked pipes. The results from these calculations are stored in a database from which the PC-program, denoted LBBPIPE, reads all necessary information. In this paper, a sensitivity analysis is presented for cracked pipes subjected to both stress corrosion and vibration fatigue.

  16. Fully plastic crack opening analyses of complex-cracked pipes for Ramberg-Osgood materials

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jae Uk; Choi, Jae Boong [Sungkyunkwan University, Suwon (Korea, Republic of); Huh, Nam Su [Seoul National University, Seoul (Korea, Republic of); Kim, Yun Jae [Korea University, Seoul (Korea, Republic of)

    2016-04-15

    The plastic influence functions for calculating fully plastic Crack opening displacement (COD) of complex-cracked pipes were newly proposed based on systematic 3-dimensional (3-D) elastic-plastic Finite element (FE) analyses using Ramberg-Osgood (R-O) relation, where global bending moment, axial tension and internal pressure are considered separately as a loading condition. Then, crack opening analyses were performed based on GE/EPRI concept by using the new plastic influence functions for complex-cracked pipes made of SA376 TP304 stainless steel, and the predicted CODs were compared with FE results based on deformation plasticity theory of tensile material behavior. From the comparison, the confidence of the proposed fully plastic crack opening solutions for complex-cracked pipes was gained. Therefore, the proposed engineering scheme for COD estimation using the new plastic influence functions can be utilized to estimate leak rate of a complex-cracked pipe for R-O material.

  17. General forms of elastic-plastic matching equations for mode-Ⅲ cracks near crack line

    Institute of Scientific and Technical Information of China (English)

    Zhi-jian YI; Chao-hua ZHAO; Qing-guo YANG; Kai PENG; Zong-ming HUANG

    2009-01-01

    Crack line analysis is an effective way to solve elastic-plastic crack problems.Application of the method does not need the traditional small-scale yielding conditions and can obtain sufficiently accurate solutions near the crack line. To address mode-Ⅲ crack problems under the perfect elastic-plastic condition,matching procedures of the crack line analysis method are summarized and refined to give general forms and formulation steps of plastic field,elastic-plastic boundary,and elastic-plastic matching equations near the crack line. The research unifies mode-Ⅲ crack problems under different conditions into a problem of determining four integral constants with four matching equations.An example is given to verify correctness,conciseness,and generality of the procedure.

  18. Nitrile O-ring Cracking: A Case of Vacuum Flange O-ring Failures

    Energy Technology Data Exchange (ETDEWEB)

    Dees, Craig

    2016-07-01

    A review of recent nitrile O-ring failures in ISO-KF vacuum flange connections in glovebox applications is presented. An investigation of a single “isolated” o-ring failure leads to the discovery of cracked nitrile o-rings in a glovebox atmospheric control unit. The initial cause of the o-ring failure is attributed to ozone degradation. However, additional investigation reveals nitrile o-ring cracking on multiple gloveboxes and general purpose piping, roughly 85% of the nitrile o-rings removed for inspection show evidence of visible cracking after being in service for 18 months or less. The results of material testing and ambient air testing is presented, elevated ozone levels are not found. The contributing factors of o-ring failure, including nitrile air sensitivity, inadequate storage practices, and poor installation techniques, are discussed. A discussion of nitrile o-ring material properties, the benefits and limitations, and alternate materials are discussed. Considerations for o-ring material selection, purchasing, storage, and installation are presented in the context of lessons learned from the nitrile o-ring cracking investigation. This paper can be presented in 20 minutes and does not require special accommodations or special audio visual devices.

  19. Crack Propagation Analysis Using Acoustic Emission Sensors for Structural Health Monitoring Systems

    Science.gov (United States)

    Horn, Walter; Steck, James

    2013-01-01

    Aerospace systems are expected to remain in service well beyond their designed life. Consequently, maintenance is an important issue. A novel method of implementing artificial neural networks and acoustic emission sensors to form a structural health monitoring (SHM) system for aerospace inspection routines was the focus of this research. Simple structural elements, consisting of flat aluminum plates of AL 2024-T3, were subjected to increasing static tensile loading. As the loading increased, designed cracks extended in length, releasing strain waves in the process. Strain wave signals, measured by acoustic emission sensors, were further analyzed in post-processing by artificial neural networks (ANN). Several experiments were performed to determine the severity and location of the crack extensions in the structure. ANNs were trained on a portion of the data acquired by the sensors and the ANNs were then validated with the remaining data. The combination of a system of acoustic emission sensors, and an ANN could determine crack extension accurately. The difference between predicted and actual crack extensions was determined to be between 0.004 in. and 0.015 in. with 95% confidence. These ANNs, coupled with acoustic emission sensors, showed promise for the creation of an SHM system for aerospace systems. PMID:24023536

  20. Investigating Reaction-Driven Cracking

    Science.gov (United States)

    Kelemen, P. B.; Hirth, G.; Savage, H. M.

    2013-12-01

    Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required

  1. LiDAR-based 2D Localization and Mapping System using Elliptical Distance Correction Models for UAV Wind Turbine Blade Inspection

    DEFF Research Database (Denmark)

    Nikolov, Ivan Adriyanov; Madsen, Claus B.

    2017-01-01

    The wind energy sector faces a constant need for annual inspections of wind turbine blades for damage, erosion and cracks. These inspections are an important part of the wind turbine life cycle and can be very costly and hazardous to specialists. This has led to the use of automated drone...... inspections and the need for accurate, robust and inexpensive systems for localization of drones relative to the wing. Due to the lack of visual and geometrical features on the wind turbine blade, conventional SLAM algorithms have a limited use. We propose a cost-effective, easy to implement and extend system...

  2. The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components Delayed Hydride Cracking

    CERN Document Server

    Puls, Manfred P

    2012-01-01

    By drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the focus lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals.   This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing that our understanding of DHC is supported by progress across a broad range of fields. These include hysteresis associated with first-order phase transformations; phase relationships in coherent crystalline metallic...

  3. Welding overlay analysis of dissimilar metal weld cracking of feedwater nozzle

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Y.L., E-mail: YLTsai@itri.org.t [National Chiao Tung University, Mechanical Engineering Department, 1001 TaHsueh Road, HsinChu, Taiwan 30010 (China); Industrial Technology Research Institute (ITRI), 195 Chung Hsing Rd., Sec.4 Chu Tung, HsinChu, Taiwan 310 (China); Wang, Li. H. [Industrial Technology Research Institute (ITRI), 195 Chung Hsing Rd., Sec.4 Chu Tung, HsinChu, Taiwan 310 (China); Fan, T.W. [Industrial Technology Research Institute (ITRI), 195 Chung Hsing Rd., Sec.4 Chu Tung, HsinChu, Taiwan 310 (China); Chung Hua University, Department of Civil Engineering and Engineering Informatics, 707, Sec.2, WuFu Rd., HsinChu, Taiwan 300 (China); Ranganath, Sam [Industrial Technology Research Institute (ITRI), 195 Chung Hsing Rd., Sec.4 Chu Tung, HsinChu, Taiwan 310 (China); Wang, C.K. [Taiwan Power Company (TPC), No.242, Sec. 3, Roosevelt Rd., Zhongzheng District, Taipei City 100, Taiwan (China); Chou, C.P. [National Chiao Tung University, Mechanical Engineering Department, 1001 TaHsueh Road, HsinChu, Taiwan 30010 (China)

    2010-01-15

    Inspection of the weld between the feedwater nozzle and the safe end at one Taiwan BWR showed axial indications in the Alloy 182 weld. The indication was sufficiently deep that continued operation could not be justified considering the crack growth for one cycle. A weld overlay was decided to implement for restoring the structural margin. This study reviews the cracking cases of feedwater nozzle welds in other nuclear plants, and reports the lesson learned in the engineering project of this weld overlay repair. The overlay design, the FCG calculation and the stress analysis by FEM are presented to confirm that the Code Case structural margins are met. The evaluations of the effect of weld shrinkage on the attached feedwater piping are also included. A number of challenges encountered in the engineering and analysis period are proposed for future study.

  4. Reliability Of Inspection By SLAM

    Science.gov (United States)

    Roth, Don J.; Klima, Stanley J.; Kiser, James D.; Baaklini, George Y.

    1988-01-01

    Scanning laser acoustic microscopy finds flaws in ceramic specimens. Laser light used to detect distortions, on angstrom scale, produced on surface of specimen by ultrasonic waves transmitted through specimen. From distortion, SLAM creates picture on video monitor of such defects as voids, inclusions, and cracks.

  5. Three-Dimensional Gear Crack Propagation Studied

    Science.gov (United States)

    Lewicki, David G.

    1999-01-01

    Gears used in current helicopters and turboprops are designed for light weight, high margins of safety, and high reliability. However, unexpected gear failures may occur even with adequate tooth design. To design an extremely safe system, the designer must ask and address the question, "What happens when a failure occurs?" With gear-tooth bending fatigue, tooth or rim fractures may occur. A crack that propagates through a rim will be catastrophic, leading to disengagement of the rotor or propeller, loss of an aircraft, and possible fatalities. This failure mode should be avoided. A crack that propagates through a tooth may or may not be catastrophic, depending on the design and operating conditions. Also, early warning of this failure mode may be possible because of advances in modern diagnostic systems. One concept proposed to address bending fatigue fracture from a safety aspect is a splittooth gear design. The prime objective of this design would be to control crack propagation in a desired direction such that at least half of the tooth would remain operational should a bending failure occur. A study at the NASA Lewis Research Center analytically validated the crack-propagation failsafe characteristics of a split-tooth gear. It used a specially developed three-dimensional crack analysis program that was based on boundary element modeling and principles of linear elastic fracture mechanics. Crack shapes as well as the crack-propagation life were predicted on the basis of the calculated stress intensity factors, mixed-mode crack-propagation trajectory theories, and fatigue crack-growth theories. The preceding figures show the effect of the location of initial cracks on crack propagation. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth was simulated in a case study to evaluate crack-propagation paths. Tooth

  6. Last experiences on ID BWR shroud inspection and the new developments to examine the below core plate areas

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, R.; Gonzalez, E.; Willke, A.; Yague, L. [TECNATOM SA, Madrid (Spain)

    2001-07-01

    In recent years, the owners of BWR type nuclear power plants have had to address new inspection requirements relating to the core shroud inside the reactor vessel, the aim of which is to contain the fuel assemblies and provide support for the structures located in the upper part of the reactor. The shroud consists of a cylinder measuring some 40-50 mm in thickness, manufactured from various sections of AISI-304 stainless steel and INCONEL, joined by vertical and circumferential welds. The appearance of unstable cracks in these welds would directly affect the structural integrity of the component and the safety of the plant. As regards access to the core shroud and to the surface to be examined, two alternatives might be considered: inspection from outside the component, moving along the so-called annulus between the reactor vessel wall and the component (OD inspection), or from the interior (ID inspection). With a view to addressing this problem, Tecnatom has in recent years launched several projects, grouped under the generic name TEIDE, in order to develop scanners and NDT techniques achieving the maximum inspection coverage of this component. The decision was taken to perform ID inspections, mainly because this type of scanners were not available at that time, and which provide the 4 following advantages. 1) Maximum inspected weld length. This avoids interference with the jet pumps and the systems present in the annulus and affecting OD inspections. Besides, the repairs performed on in-service core shrouds in all cases imply the addition of new fixed elements on their outer surface, since the fuel assembly space must be left free. 2) Reduction of inspection times and of unforeseen events: maintenance of planning schedules, reduction of personnel doses, reduced critical path time. 3) High inspection accuracy and repeatability. 4) Simplification of equipment positioning work (similar to the installation of fuel assemblies). As regards inspection techniques, the

  7. TANK INSPECTION NDE RESULTS FOR FISCAL YEAR 2007INCLUDING WASTE TANKS 35, 36, 37, 38 AND 15

    Energy Technology Data Exchange (ETDEWEB)

    Elder, J

    2007-09-27

    Ultrasonic (UT) nondestructive examinations (NDE) were performed on waste storage tanks 35, 36, 37, 38 and 15 at the Savannah River Site as a part of the 'In-Service Inspection (ISI) Program for High Level Waste Tanks.' 1 The inspections were performed from the annular space of the waste storage tanks. The inspections included thickness mapping and crack detection scans on specified areas of the tanks covering all present and historic interface levels and selected welds with particular emphasis on the vapor space regions. Including the tanks in this report, all of the 27 Type III tanks at SRS have been inspected in accordance with the ISI plan. Of the four Type III tanks examined this year, all had areas of reportable thickness in either the Primary or Secondary tank. All of these areas on the primary tank are attributed to fabrication artifacts. None of the four Type III tanks examined this year showed evidence of service induced thinning on the primary wall. All four tanks had secondary wall and/or floor plates where the remaining thickness measured below the 10% wall loss criteria. Tank 15, a Type II, non-stress relieved, waste tank was also inspected this fiscal year as part of the ISI program. The same examination techniques were used on Tank 15 as on the Type III tanks. Tank 15 has been out of service due to leakage from stress corrosion cracking (SCC). Inspections were performed to validate known corrosion models and determine if crack growth occurred since the previous examination five years ago. Several cracks were found to have increased in length perpendicular to the weld seam. In the areas of the 27 Type III tanks inspected to date, ten tanks have reportable thickness in the primary wall and 17 have reportable thickness in the secondary tank walls or floor. All of the reportable thickness areas in the primary walls are from fabrication artifacts. Incipient pitting has been detected in five of the 27 Type III primary tanks. No cracking was

  8. Inspection relief for BWR internal components with noble metal chemical application (NMCA)

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, J.A. [Exelom Corp., Clinton Power Station, Clinton, IL (United States); Pathania, R.S. [EPRI, Palo Alto, CA (United States)

    2001-07-01

    The BWRVIP has developed methods to verify effectiveness of NMCA for mitigation of intergranular stress corrosion cracking (IGSCC). One of the major problems in demonstrating the effectiveness of NMCA inside the reactor vessel is the difficulty of measuring the electrochemical driving force of IGSCC of the various reactor internal components. Many plants do not have direct ECP measurements available at pertinent locations such as the lower plenum. Even those plants that do have direct measurements available recognize that such local measurements may not be representative of all potentially susceptible component surfaces. Therefore, it is desirable to develop valid supplementary techniques that do not depend exclusively on direct measurements of the ECP at specific locations to reliably demonstrate NMCA effectiveness. This paper describes the verification methods developed by the BWRVIP and reports on an industry survey which shows how extensively these recommendations are being implemented. Furthermore, the effectiveness of NMCA is dependent upon the uniform application and the durability of the catalytic surface. Results are provided from the durability monitor at the Duane Arnold Energy Center (DAEC) NMCA demonstration project. Based on the crack growth modeling and radiolysis results, a vessel internals inspection program can be developed based on Factors of Improvement (FOIs) for plants that have implemented NMCA. The FOI calculated for each internal component based on crack growth modeling results can be applied to revise the internals inspection interval established in the various BWRVIP inspection and evaluation (I and E) documents. For an example, this paper discusses revisions to the inspection intervals for recirculation piping welds. (author)

  9. BRIDGE CRACK DETECTION USING MULTI-ROTARY UAV AND OBJECT-BASE IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    J. Y. Rau

    2017-08-01

    Full Text Available Bridge is an important infrastructure for human life. Thus, the bridge safety monitoring and maintaining is an important issue to the government. Conventionally, bridge inspection were conducted by human in-situ visual examination. This procedure sometimes require under bridge inspection vehicle or climbing under the bridge personally. Thus, its cost and risk is high as well as labor intensive and time consuming. Particularly, its documentation procedure is subjective without 3D spatial information. In order cope with these challenges, this paper propose the use of a multi-rotary UAV that equipped with a SONY A7r2 high resolution digital camera, 50 mm fixed focus length lens, 135 degrees up-down rotating gimbal. The target bridge contains three spans with a total of 60 meters long, 20 meters width and 8 meters height above the water level. In the end, we took about 10,000 images, but some of them were acquired by hand held method taken on the ground using a pole with 2–8 meters long. Those images were processed by Agisoft PhotoscanPro to obtain exterior and interior orientation parameters. A local coordinate system was defined by using 12 ground control points measured by a total station. After triangulation and camera self-calibration, the RMS of control points is less than 3 cm. A 3D CAD model that describe the bridge surface geometry was manually measured by PhotoscanPro. They were composed of planar polygons and will be used for searching related UAV images. Additionally, a photorealistic 3D model can be produced for 3D visualization. In order to detect cracks on the bridge surface, we utilize object-based image analysis (OBIA technique to segment the image into objects. Later, we derive several object features, such as density, area/bounding box ratio, length/width ratio, length, etc. Then, we can setup a classification rule set to distinguish cracks. Further, we apply semi-global-matching (SGM to obtain 3D crack information and based

  10. Bridge Crack Detection Using Multi-Rotary Uav and Object-Base Image Analysis

    Science.gov (United States)

    Rau, J. Y.; Hsiao, K. W.; Jhan, J. P.; Wang, S. H.; Fang, W. C.; Wang, J. L.

    2017-08-01

    Bridge is an important infrastructure for human life. Thus, the bridge safety monitoring and maintaining is an important issue to the government. Conventionally, bridge inspection were conducted by human in-situ visual examination. This procedure sometimes require under bridge inspection vehicle or climbing under the bridge personally. Thus, its cost and risk is high as well as labor intensive and time consuming. Particularly, its documentation procedure is subjective without 3D spatial information. In order cope with these challenges, this paper propose the use of a multi-rotary UAV that equipped with a SONY A7r2 high resolution digital camera, 50 mm fixed focus length lens, 135 degrees up-down rotating gimbal. The target bridge contains three spans with a total of 60 meters long, 20 meters width and 8 meters height above the water level. In the end, we took about 10,000 images, but some of them were acquired by hand held method taken on the ground using a pole with 2-8 meters long. Those images were processed by Agisoft PhotoscanPro to obtain exterior and interior orientation parameters. A local coordinate system was defined by using 12 ground control points measured by a total station. After triangulation and camera self-calibration, the RMS of control points is less than 3 cm. A 3D CAD model that describe the bridge surface geometry was manually measured by PhotoscanPro. They were composed of planar polygons and will be used for searching related UAV images. Additionally, a photorealistic 3D model can be produced for 3D visualization. In order to detect cracks on the bridge surface, we utilize object-based image analysis (OBIA) technique to segment the image into objects. Later, we derive several object features, such as density, area/bounding box ratio, length/width ratio, length, etc. Then, we can setup a classification rule set to distinguish cracks. Further, we apply semi-global-matching (SGM) to obtain 3D crack information and based on image scale we

  11. Crack detection in a beam with an arbitrary number of transverse cracks using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Khaji, N. [Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mehrjoo, M. [Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2014-03-15

    In this paper, a crack detection approach is presented for detecting depth and location of cracks in beam-like structures. For this purpose, a new beam element with an arbitrary number of embedded transverse edge cracks, in arbitrary positions of beam element with any depth, is derived. The components of the stiffness matrix for the cracked element are computed using the conjugate beam concept and Betti's theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain precise natural frequencies and mode shapes of the beam knowing the cracks' characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results and available experimental measurements. Moreover, by knowing the natural frequencies and mode shapes, an inverse problem is established in which the location and depth of cracks are determined. In the inverse approach, an optimization problem based on the new finite element and genetic algorithms (GAs) is solved to search the solution. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. The proposed approach is verified through a cracked beam containing various cracks with different depths.

  12. Identification of cracks in thick beams with a cracked beam element model

    Science.gov (United States)

    Hou, Chuanchuan; Lu, Yong

    2016-12-01

    The effect of a crack on the vibration of a beam is a classical problem, and various models have been proposed, ranging from the basic stiffness reduction method to the more sophisticated model involving formulation based on the additional flexibility due to a crack. However, in the damage identification or finite element model updating applications, it is still common practice to employ a simple stiffness reduction factor to represent a crack in the identification process, whereas the use of a more realistic crack model is rather limited. In this paper, the issues with the simple stiffness reduction method, particularly concerning thick beams, are highlighted along with a review of several other crack models. A robust finite element model updating procedure is then presented for the detection of cracks in beams. The description of the crack parameters is based on the cracked beam flexibility formulated by means of the fracture mechanics, and it takes into consideration of shear deformation and coupling between translational and longitudinal vibrations, and thus is particularly suitable for thick beams. The identification procedure employs a global searching technique using Genetic Algorithms, and there is no restriction on the location, severity and the number of cracks to be identified. The procedure is verified to yield satisfactory identification for practically any configurations of cracks in a beam.

  13. Subcritical crack growth in two titanium alloys.

    Science.gov (United States)

    Williams, D. N.

    1973-01-01

    Measurement of subcritical crack growth during static loading of precracked titanium alloys in salt water using samples too thin for plane strain loading to predominate was examined as a method for determining the critical stress intensity for crack propagation in salt water. Significant internal crack growth followed by arrest was found at quite low stress intensities, but crack growth rates were relatively low. Assuming these techniques provided a reliable measurement of the critical stress intensity, the value for annealed Ti-4Al-1.5Mo-0.5V alloy was apparently about 35 ksi-in. to the 1/2 power, while that for annealed Ti-4Al-3Mo-1V was below 45 ksi-in. to the 1/2 power. Crack growth was also observed in tests conducted in both alloys in an air environment. At 65 ksi-in. to the 1/2 power, the extent of crack growth was greater in air than in salt water. Ti-4Al-3Mo-1V showed arrested crack growth in air at a stress intensity of 45 ksi-in. to the 1/2 power.

  14. Autonomous underwater riser inspection tool

    Energy Technology Data Exchange (ETDEWEB)

    Camerini, Claudio; Marnet, Robson [Petrobras SA, (Brazil); Freitas, Miguel; Von der Weid, Jean Pierre [CPTI/PUC-Rio, Rio de Janeiro, (Brazil); Artigas Lander, Ricardo [EngeMOVI, Curitiba, (Brazil)

    2010-07-01

    The detection of damage on the riser is a serious concern for pipeline companies. Visual examinations by remotely operated vehicle (ROV) are presently carried out to detect the defects but this process has limitations and is expensive. This paper presents the development of a new tool to ensure autonomous underwater riser inspection (AURI) that uses the riser itself for guidance. The AURI, which is autonomous in terms of control and power supply, is equipped with several cameras that perform a complete visual inspection of the riser with 100 % coverage of the external surface of the riser. The paper presents the detailed characteristics of the first AURI prototype, describes its launching procedure and provides the preliminary test results from pool testing. The results showed that the AURI is a viable system for autonomous riser inspection. Offshore tests on riser pipelines are scheduled to be performed shortly.

  15. Post-Closure Inspection Report for the Tonopah Test Range, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    NSTec Environmental Restoration

    2007-06-01

    burrows observed at CAU 453 were backfilled. Cracking observed in three monuments at CAU 487 was repaired using sealant during the May 9, 2006, inspection. At this time, the TTR post-closure site inspections should continue as scheduled. Any potential problem areas previously identified (e.g., areas of erosion, subsidence) should be monitored closely, and periodic vegetation surveys of the vegetated covers should continue.

  16. Slow crack growth in spinel in water

    Science.gov (United States)

    Schwantes, S.; Elber, W.

    1983-01-01

    Magnesium aluminate spinel was tested in a water environment at room temperature to establish its slow crack-growth behavior. Ring specimens with artificial flaws on the outside surface were loaded hydraulically on the inside surface. The time to failure was measured. Various precracking techniques were evaluated and multiple precracks were used to minimize the scatter in the static fatigue tests. Statistical analysis techniques were developed to determine the strength and crack velocities for a single flaw. Slow crack-growth rupture was observed at stress intensities as low as 70 percent of K sub c. A strengthening effect was observed in specimens that had survived long-time static fatigue tests.

  17. Mitigation strategies for autogenous shrinkage cracking

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede

    2004-01-01

    , the fundamental parameters contributing to the autogenous shrinkage and resultant early-age cracking of concrete are presented. Basic characteristics of the cement paste that contribute to or control the autogenous shrinkage response include the surface tension of the pore solution, the geometry of the pore...... of early-age cracking due to autogenous shrinkage. Mitigation strategies discussed in this paper include: the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition......, it should be possible to minimize cracking due to autogenous shrinkage via some combination of the presented approaches....

  18. Prediction of Crack Growth in Aqueous Environments.

    Science.gov (United States)

    1986-07-01

    Impedance for the Propagation of a Crack Through HY80 Steel in 3.5Z NaCl Solution at 25*C Under Sinusoidal Loading Condi t ions...THE PROPAGATION OF A CRACK THROUGH HY80 STEEL IN 3.5% NaCI SOLUTION AT 25°C UNDER SINUSOIDAL LOADING CONDITIONS 49 and the properties of greatest...VELOCITY AS A FUNCTION OF TIME FOR A CRACK GROWN AT CONSTANT CURRENT IN HY80 STEEL Initial conditions CI in Table 5. 66 400 UJ x v> l/> L. 0

  19. Evaluation of inservice inspection examinatiions

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, D.A.; Cook, J.F.

    1990-05-01

    In order to evaluate the effectiveness of Section 11, Division 1, Rules for Inservice Inspection of Nuclear Power Plant Components,'' of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code examinations, 26 inservice inspection (ISI) summary reports from 24 facilities were reviewed. It was found that these ASME Code examinations and tests are instrumental in revealing indications and defects in welds and plant components. In addition, this study uncovered that fact that some of the Section 11 requirements are apparently not clear and are misunderstood by some of the facilities. Also, the need for more stringent requirements was evaluated and some Code changes are recommended.

  20. Evaluation of inservice inspection examinatiions

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, D.A.; Cook, J.F.

    1990-05-01

    In order to evaluate the effectiveness of Section 11, Division 1, ``Rules for Inservice Inspection of Nuclear Power Plant Components,`` of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code examinations, 26 inservice inspection (ISI) summary reports from 24 facilities were reviewed. It was found that these ASME Code examinations and tests are instrumental in revealing indications and defects in welds and plant components. In addition, this study uncovered that fact that some of the Section 11 requirements are apparently not clear and are misunderstood by some of the facilities. Also, the need for more stringent requirements was evaluated and some Code changes are recommended.

  1. Planning Annual Shutdown Inspection for BFB Boiler

    OpenAIRE

    Sorsa, Tatu

    2014-01-01

    The goal of this thesis was to create an illustrative guidebook of annual inspection planning for BFB boiler to help power plant operator when planning of annual inspection is topical. This thesis was made for Andritz Oy and it is based on inspection reports and experiences of BFB boiler’s maintenance and inspection staff. In this thesis it is shown how to plan an annual inspection for BFB boiler and thesis gives good tools and hints for operator to manage inspection from the beginning ...

  2. Bayesian reliability analysis for non-periodic inspection with estimation of uncertain parameters; Bayesian shinraisei kaiseki wo tekiyoshita hiteiki kozo kensa ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Itagaki, H. [Yokohama National University, Yokohama (Japan). Faculty of Engineering; Asada, H.; Ito, S. [National Aerospace Laboratory, Tokyo (Japan); Shinozuka, M.

    1996-12-31

    Risk assessed structural positions in a pressurized fuselage of a transport-type aircraft applied with damage tolerance design are taken up as the subject of discussion. A small number of data obtained from inspections on the positions was used to discuss the Bayesian reliability analysis that can estimate also a proper non-periodic inspection schedule, while estimating proper values for uncertain factors. As a result, time period of generating fatigue cracks was determined according to procedure of detailed visual inspections. The analysis method was found capable of estimating values that are thought reasonable and the proper inspection schedule using these values, in spite of placing the fatigue crack progress expression in a very simple form and estimating both factors as the uncertain factors. Thus, the present analysis method was verified of its effectiveness. This study has discussed at the same time the structural positions, modeling of fatigue cracks generated and develop in the positions, conditions for destruction, damage factors, and capability of the inspection from different viewpoints. This reliability analysis method is thought effective also on such other structures as offshore structures. 18 refs., 8 figs., 1 tab.

  3. Proof of Concept of Crack Localization Using Negative Pressure Waves in Closed Tubes for Later Application in Effective SHM System for Additive Manufactured Components

    Directory of Open Access Journals (Sweden)

    Michaël F. Hinderdael

    2016-01-01

    Full Text Available Additive manufactured components have a different metallurgic structure and are more prone to fatigue cracks than conventionally produced metals. In earlier papers, an effective Structural Health Monitoring solution was presented to detect fatigue cracks in additive manufactured components. Small subsurface capillaries are embedded in the structure and pressurized (vacuum or overpressure. A crack that initiated at the component’s surface will propagate towards the capillary and finally breach it. One capillary suffices to inspect a large area of the component, which makes it interesting to locate the crack on the basis of the pressure measurements. Negative pressure waves (NPW arise from the abrupt encounter of high pressure fluid with low pressure fluid and can serve as a basis to locate the crack. A test set-up with a controllable leak valve was built to investigate the feasibility of using NPW to localize a leak in closed tubes with small lengths. Reflections are expected to occur at the ends of the tube, possibly limiting the localization accuracy. In this paper, the results of the tests on the test set-up are reported. It will be shown that the crack could be localized with high accuracy (millimeter accuracy which proves the concept of crack localization on basis of NPW in a closed tube of small length.

  4. Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

    Science.gov (United States)

    Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.

    2017-02-01

    A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.

  5. Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

    Science.gov (United States)

    Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.

    2016-08-01

    A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.

  6. a Holistic Approach for Inspection of Civil Infrastructures Based on Computer Vision Techniques

    Science.gov (United States)

    Stentoumis, C.; Protopapadakis, E.; Doulamis, A.; Doulamis, N.

    2016-06-01

    In this work, it is examined the 2D recognition and 3D modelling of concrete tunnel cracks, through visual cues. At the time being, the structural integrity inspection of large-scale infrastructures is mainly performed through visual observations by human inspectors, who identify structural defects, rate them and, then, categorize their severity. The described approach targets at minimum human intervention, for autonomous inspection of civil infrastructures. The shortfalls of existing approaches in crack assessment are being addressed by proposing a novel detection scheme. Although efforts have been made in the field, synergies among proposed techniques are still missing. The holistic approach of this paper exploits the state of the art techniques of pattern recognition and stereo-matching, in order to build accurate 3D crack models. The innovation lies in the hybrid approach for the CNN detector initialization, and the use of the modified census transformation for stereo matching along with a binary fusion of two state-of-the-art optimization schemes. The described approach manages to deal with images of harsh radiometry, along with severe radiometric differences in the stereo pair. The effectiveness of this workflow is evaluated on a real dataset gathered in highway and railway tunnels. What is promising is that the computer vision workflow described in this work can be transferred, with adaptations of course, to other infrastructure such as pipelines, bridges and large industrial facilities that are in the need of continuous state assessment during their operational life cycle.

  7. On Cracking of Charged Anisotropic Polytropes

    CERN Document Server

    Azam, M

    2016-01-01

    Recently in \\cite{34}, the role of electromagnetic field on the cracking of spherical polytropes has been investigated without perturbing charge parameter explicitly. In this study, we have examined the occurrence of cracking of anisotropic spherical polytropes through perturbing parameters like anisotropic pressure, energy density and charge. We consider two different types of polytropes in this study. We discuss the occurrence of cracking in two different ways $(i)$ by perturbing polytropic constant, anisotropy and charge parameter $(ii)$ by perturbing polytropic index, anisotropy and charge parameter for each case. We conclude that cracking appears for a wide range of parameters in both cases. Also, our results are reduced to \\cite{33} in the absence of charge.

  8. Struggling with Fitzgerald's "Crack-Up" Essays.

    Science.gov (United States)

    Fulcher, James

    1998-01-01

    Ponders F. Scott Fitzgerald's essays about his "crack-up" and relates them to the many complex aspects of the struggles of a teacher using post-structural literary theory and teaching two-year college students. (SR)

  9. The Effect of Water on Crack Interaction

    Science.gov (United States)

    Gaede, O.; Regenauer-Lieb, K.

    2009-04-01

    While the mechanical coupling between pore fluid and solid phase is relatively well understood, quantitative studies dealing with chemical-mechanical weakening in geological materials are rare. Many classical poroelastic problems can be addressed with the simple law of effective stress. Experimental studies show that the presence of a chemically active fluid can have effects that exceed the predictions of the law of effective stress. These chemical fluid-rock interactions alter the mechanical properties of the solid phase. Especially chemical-mechanical weakening has important ramifications for many areas of applied geosciences ranging from nuclear waste disposal over reservoir enhancement to fault stability. In this study, we model chemically induced changes of the size of the process zone around a crack tip. The knowledge of the process zone size is used to extend existing effective medium approximations of cracked solids. The stress distribution around a crack leads to a chemical potential gradient. This gradient will be a driver for mass diffusion through the solid phase. As an example, mass diffusion is towards the crack tip for a mode I crack. In this case a chemical reaction, that weakens the solid phase, will increase the size of the process zone around the crack tip. We apply our model to the prominent hydrolytic weakening effect observed in the quartz-water system (Griggs and Blacic, 1965). Hydrolytic weakening is generally attributed to water hydrolyzing the strong Si-O bonds of the quartz crystal. The hydrolysis replaces a Si-O-Si bridge with a relatively weak hydrogen bridge between two silanol groups. This enhances dislocation mobility and hence the yield stress is reduced. The plastic process zone around a crack tip is therefore larger in a wet crystal than in a dry crystal. We calculate the size of the process zone by solving this coupled mechanical-chemical problem with the Finite Element code ABAQUS. We consider single crack, collinear crack and

  10. Inner Crack Detection Method for Cantilever Beams

    Science.gov (United States)

    Li, Zheng; Zhang, Wei; Li, Yixuan; Su, Xianyue

    2008-02-01

    In this paper, continuous wavelet transform has been performed to extract the inner crack information from the guided waves in cantilever beams, and the location and size of crack can be detected exactly. Considering its best time-frequency property, Gabor continuous wavelet transform is employed to analyze the complicated flexible wave signals in cantilever beam, which is inspirited by an impact on the free end. Otherwise, in order to enhance the sensitivity of detection for some small cracks, an improved method is discussed. Here, both computational and experimental methods are carried out for comparing the influence of different crack location in beam. Therefore, the method proposed can be expected to expand to a powerful damage detection method in a broad engineering application.

  11. Initiating, growing and cracking of hydrogen blisters

    Institute of Scientific and Technical Information of China (English)

    REN Xuechong; SHAN Guangbin; CHU Wuyang; SU Yanjing; GAO Kewei; QIAO Lijie; JIANG Bo; CHEN Gang; CUI Yinhui

    2005-01-01

    The growing process of a hydrogen blister in a wheel steel was observed in situ with an optical microscope, and the fracture surfaces formed from broken blisters on a wheel steel and bulk metallic glass were investigated. The initiating, growing, cracking and breaking of hydrogen blisters are as follows. Supersaturated vacancies can increase greatly during charging and gather together into a vacancy cluster (small cavity). Hydrogen atoms become hydrogen molecules in the vacancy cluster and hydrogen molecules can stabilize the vacancy cluster. The small cavity becomes the nucleus of hydrogen blister. The blister will grow with entering of vacancies and hydrogen atoms. With increasing hydrogen pressure, plastic deformation occurs first, the hydrogen blister near the surface extrudes, and then cracks initiate along the wall of the blister with further increasing hydrogen pressure. A cracked blister can grow further through propagating of cracks until it breaks.

  12. Dynamic Strain and Crack Monitoring Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Los Gatos Research proposes to develop a new automated vehicle health monitoring sensor system capable of measuring loads and detecting crack, corrosion, and...

  13. Decision making for stable inspection planning of deteriorating structures based on constraint reliability and uncertainties

    Directory of Open Access Journals (Sweden)

    Jalal alsarraf

    2014-06-01

    Full Text Available Life-time cost minimization is considered as the optimal criterion for planning of inspection, repair and maintenance of structures. However, most of the probabilities and the cost items related to the cost analysis generally contain inevitable uncertainties in actual cases. The appropriateness of inspection planning may be lost by several errors induced by such uncertainties. In this study, a cost minimization method with the constraint of reliability is developed in order to obtain stable inspection planning against the estimation errors of the parameters. In the analysis, the life-time cost optimization is carried out under the constraint that the failure probabilities of the members are controlled below the respective target values allowed for the members. First, initial target failure probabilities are assumed for each member. Then, the robustness of the inspection planning is investigated by adjusting the parameters within the range of uncertainties. The initial values of the target failure probabilities are altered until an acceptable result is obtained. The applicability of the proposed method is examined for a structure with several uncertain parameters. A sequential cost minimization method is employed to optimize the life-time cost. It is made clear that by using this approach, the stability of the life-time cost is maintained without losing the benefit of the cost minimization method. Keywords: Crack, Fatigue, Inspection, Numerical Model, Reliability, Structure.

  14. Artificial Intelligence Assists Ultrasonic Inspection

    Science.gov (United States)

    Schaefer, Lloyd A.; Willenberg, James D.

    1992-01-01

    Subtle indications of flaws extracted from ultrasonic waveforms. Ultrasonic-inspection system uses artificial intelligence to help in identification of hidden flaws in electron-beam-welded castings. System involves application of flaw-classification logic to analysis of ultrasonic waveforms.

  15. Artificial Intelligence Assists Ultrasonic Inspection

    Science.gov (United States)

    Schaefer, Lloyd A.; Willenberg, James D.

    1992-01-01

    Subtle indications of flaws extracted from ultrasonic waveforms. Ultrasonic-inspection system uses artificial intelligence to help in identification of hidden flaws in electron-beam-welded castings. System involves application of flaw-classification logic to analysis of ultrasonic waveforms.

  16. Finite Element Analysis of the Effect of Crack Depth and Crack Opening On the Girder

    Directory of Open Access Journals (Sweden)

    Md. Kamrul Hassan

    2011-01-01

    Full Text Available In order to identify the effect of crack depth and opening on the girder, finite element method (FEM has been used in this paper. In FE analysis, six nodded two dimensional plane elements (PLANE-2 are considered. Each node has two degree of freedom such as UX and UY. For the plane elements, a plane stress width/thickness option is chosen. For analytical model of crack of the concrete bridge girder, crack opening was increased from 0.2 mm to 1mm at an interval 0.2 mm and crack depth also increased from 30 mm to 150 mm at an interval 30 mm. The models were discreatized by a triangular mesh and convergence test was executed to obtain satisfactory results from the Plane-2 element. From the numerical result, it is seen that the principal stress become a higher with increased the crack depth and also crack opening with respect to load increasing. But the crack depth at 90 mm and crack opening at 0.6 mm, it has more effect on the girder because the stress concentration is higher than other crack depth and opening.

  17. Calculation of the crack tip opening displacement of a crack lying in a subsurface layer

    Science.gov (United States)

    Higashida, Y.; Kamada, K.

    1985-11-01

    Crack tip opening displacement of a crack lying parallel to a free surface is calculated by counting the number of dislocations emitted into the plastic zone from a crack tip. A discrete dislocation model was used to simulate the crack, while varying the strength of dislocations so as to satisfy the boundary condition. The result coincides numerically with the predictions made in a previous paper, in which the stress intensity factor appearing in a theory of bulk materials was replaced with the one which includes the surface correction.

  18. Crack Closure Effects on Fatigue Crack Propagation Rates: Application of a Proposed Theoretical Model

    Directory of Open Access Journals (Sweden)

    José A. F. O. Correia

    2016-01-01

    Full Text Available Structural design taking into account fatigue damage requires a thorough knowledge of the behaviour of materials. In addition to the monotonic behaviour of the materials, it is also important to assess their cyclic response and fatigue crack propagation behaviour under constant and variable amplitude loading. Materials whenever subjected to fatigue cracking may exhibit mean stress effects as well as crack closure effects. In this paper, a theoretical model based on the same initial assumptions of the analytical models proposed by Hudak and Davidson and Ellyin is proposed to estimate the influence of the crack closure effects. This proposal based further on Walker’s propagation law was applied to the P355NL1 steel using an inverse analysis (back-extrapolation of experimental fatigue crack propagation results. Based on this proposed model it is possible to estimate the crack opening stress intensity factor, Kop, the relationship between U=ΔKeff/ΔK quantity and the stress intensity factor, the crack length, and the stress ratio. This allows the evaluation of the influence of the crack closure effects for different stress ratio levels, in the fatigue crack propagation rates. Finally, a good agreement is found between the proposed theoretical model and the analytical models presented in the literature.

  19. Hydration Process and Crack Tendency of Concrete Based on Resistivity and Restrained Shrinkage Crack

    Institute of Scientific and Technical Information of China (English)

    MUAZU Bawa Samaila; WEI Xiaosheng; WANG Lei

    2016-01-01

    Hydration process, crack potential and setting time of concrete grade C30, C40 and C50 were monitored by using a non-contact electrical resistivity apparatus, a novel plastic ring mould and penetration resistance methods, respectively. The results show the highest resistivity of C30 at the early stage until a point when C50 accelerated and overtook the others. It has been experimentally conifrmed that the crossing point of C30 and C50 corresponds to the ifnal setting time of C50. From resistivity derivative curve, four different stages were observed upon which the hydration process is classiifed; these are dissolution, induction, acceleration and deceleration periods. Consequently, restrained shrinkage crack and setting time results demonstrated that C50 set and cracked the earliest. The cracking time of all the samples occurred within a reasonable experimental period thus the novel plastic ring is a convenient method for predicting concrete’s crack potential. The highest inlfection time (ti) obtained from resistivity curve and the ifnal setting time (tf) were used with crack time (tc) in coming up with mathematical models for the prediction of concrete’s cracking age for the range of concrete grade considered. Finally, an ANSYS numerical simulation supports the experimental ifndings in terms of the earliest crack age of C50 and the crack location.

  20. Molecular dynamics simulation of propagating cracks

    Science.gov (United States)

    Mullins, M.

    1982-01-01

    Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.

  1. Fatigue Crack Initiation Analysis in 1060 Steel

    Directory of Open Access Journals (Sweden)

    L. Gyansah

    2010-07-01

    Full Text Available This study investigates initiation of small cracks on dumble-shaped plate type specimens of 1060steel at the load ratio of R = 0 under varied cyclic stress amplitudes between 0.6 and 1.0 of yield stress usingthe Instron machine (model: 8501. Sinusoidal wave of a frequency of 10 Hz was used in the experiment. Theexperiment was conducted at a room temperature of 23ºC. Each test for different applied stress ranges wascarried out for 2×104 cycles. Microstructure and fractography of the fractured specimen were also analyzed.Nucleations of cracks were observed at Ferrite-Ferrite G rain Boundary (FFGB as well as inside Ferrite GrainBody (FGB, but the FFGB location was preferred. Results show that the average length of FFGB cracks isfound larger than that of the average length of cracks initiated inside FGB at the same cyclic loading conditions.The formation of slip band inside grain body, slip band impingement at grain boundary and elastic-plasticincompatibility synergistically have significant influence on fatigue crack initiation in 1060 steel. Additionally,the formation of irregular voids inside slip bands, initiation and growth of small voids at grain boundary andthe subsequent joining of these with other voids were seen as specific characteristics of 1060 steel. It was alsoestablished that cracks nucleate both at grain boundary and inside grain body in 1060 steel in the investigateddomain of 0.6 to 1.0Fy.It was further established that the orientation of the grain body cracks at low stress levelis greater than 45º and the average angle of orientation of these cracks increases like that of grain boundarycracks with increased magnitude of stress range.

  2. Molecular dynamics simulation of propagating cracks

    Science.gov (United States)

    Mullins, M.

    1982-01-01

    Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.

  3. Atomistic observation of a crack tip approaching coherent twin boundaries.

    Science.gov (United States)

    Liu, L; Wang, J; Gong, S K; Mao, S X

    2014-03-18

    Coherent twin boundaries (CTBs) in nano-twinned materials could improve crack resistance. However, the role of the CTBs during crack penetration has never been explored at atomic scale. Our in situ observation on nano-twinned Ag under a high resolution transmission electron microscope (HRTEM) reveals the dynamic processes of a crack penetration across the CTBs, which involve alternated crack tip blunting, crack deflection, twinning/detwinning and slip transmission across the CTBs. The alternated blunting processes are related to the emission of different types of dislocations at the crack tip and vary with the distance of the crack tip from the CTBs.

  4. Crack shape analysis of PWSCC in S/G tubings

    Energy Technology Data Exchange (ETDEWEB)

    Park, I. K. [Sunmon Univ., Chonan (Korea, Republic of)

    2000-10-01

    Crack shape of PWSCC was analyzed, based on the fractured pulled-out S/G tubings of Ulchin-1 steam generator. The shape of the cracks in kiss roll transitions was elliptical shape for short cracks, and car shape for long cracks with flat crack front. The bulging was observed under the inner wall after shot-peening. Crack shape change after shot-peening was resulted from the crack growth restraint in axial direction due to compressive residual stresses on the primary side surface.

  5. Thermally activated processes of fatigue crack growth in steels

    Science.gov (United States)

    Tanaka, Masaki; Fujii, Atsushi; Noguchi, Hiroshi; Higashida, Kenji

    2014-02-01

    Fatigue crack growth rates in steels at high and low temperatures have been investigated using Paris curves. The fatigue crack growth rates at high temperatures are quite different from those at low temperatures. Arrhenius plots between fatigue crack growth rate (da/dN) and test temperatures at constant stress intensity factor range (ΔKI) indicate a difference of the rate-controlling process for fatigue crack growth with temperature. Slip deformation at the crack tip governs fatigue crack growth at high temperatures, while hydrogen diffusion is associated with crack growth at low temperatures.

  6. Hierarchical Formation of Intrasplat Cracks in Thermal Spray Ceramic Coatings

    Science.gov (United States)

    Chen, Lin; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2016-06-01

    Intrasplat cracks, an essential feature of thermally sprayed ceramic coatings, play important roles in determining coating properties. However, final intrasplat crack patterns are always considered to be disordered and irregular, resulting from random cracking during splat cooling, since the detailed formation process of intrasplat cracks has scarcely been considered. In the present study, the primary formation mechanism for intrasplat cracking was explored based on both experimental observations and mechanical analysis. The results show that the intrasplat crack pattern in thermally sprayed ceramic splats presents a hierarchical structure with four sides and six neighbors, indicating that intrasplat crack patterns arise from successive domain divisions due to sequential cracking during splat cooling. The driving forces for intrasplat cracking are discussed, and the experimental data quantitatively agree well with theoretical results. This will provide insight for further coating structure designs and tailoring by tuning of intrasplat cracks.

  7. A combined deterministic and probabilistic procedure for safety assessment of components with cracks - Handbook.

    Energy Technology Data Exchange (ETDEWEB)

    Dillstroem, Peter; Bergman, Mats; Brickstad, Bjoern; Weilin Zang; Sattari-Far, Iradj; Andersson, Peder; Sund, Goeran; Dahlberg, Lars; Nilsson, Fred (Inspecta Technology AB, Stockholm (Sweden))

    2008-07-01

    SSM has supported research work for the further development of a previously developed procedure/handbook (SKI Report 99:49) for assessment of detected cracks and tolerance for defect analysis. During the operative use of the handbook it was identified needs to update the deterministic part of the procedure and to introduce a new probabilistic flaw evaluation procedure. Another identified need was a better description of the theoretical basis to the computer program. The principal aim of the project has been to update the deterministic part of the recently developed procedure and to introduce a new probabilistic flaw evaluation procedure. Other objectives of the project have been to validate the conservatism of the procedure, make the procedure well defined and easy to use and make the handbook that documents the procedure as complete as possible. The procedure/handbook and computer program ProSACC, Probabilistic Safety Assessment of Components with Cracks, has been extensively revised within this project. The major differences compared to the last revision are within the following areas: It is now possible to deal with a combination of deterministic and probabilistic data. It is possible to include J-controlled stable crack growth. The appendices on material data to be used for nuclear applications and on residual stresses are revised. A new deterministic safety evaluation system is included. The conservatism in the method for evaluation of the secondary stresses for ductile materials is reduced. A new geometry, a circular bar with a circumferential surface crack has been introduced. The results of this project will be of use to SSM in safety assessments of components with cracks and in assessments of the interval between the inspections of components in nuclear power plants

  8. Automated Ply Inspection (API) for AFP Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Automated Ply Inspection (API) system autonomously inspects layups created by high speed automated fiber placement (AFP) machines. API comprises a high accuracy...

  9. Piping inspection carriage having axially displaceable sensor

    Science.gov (United States)

    Zollinger, William T.; Treanor, Richard C.

    1994-01-01

    A pipe inspection instrument carriage for use with a pipe crawler for performing internal inspections of piping surfaces. The carriage has a front leg assembly, a rear leg assembly and a central support connecting the two assemblies and for mounting an instrument arm having inspection instruments. The instrument arm has a y-arm mounted distally thereon for axially aligning the inspection instrumentation and a mounting block, a linear actuator and axial movement arm for extending the inspection instruments radially outward to operably position the inspection instruments on the piping interior. Also, the carriage has a rotation motor and gear assembly for rotating the central support and the front leg assembly with respect to the rear leg assembly so that the inspection instruments azimuthally scan the piping interior. The instrument carriage allows performance of all piping inspection operations with a minimum of moving parts, thus decreasing the likelihood of performance failure.

  10. Advanced robotics for inspection and maintenance applications

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, B. [Intech Inc., Chattanooga, Tennessee (United States)

    2008-07-01

    The BOP inspection market provides unique and challenging environments for inspection. Intech has developed a flexible manipulator platform that supports these needs, namely accuracy and environmental hazards in a cost effective package. (author)

  11. Allegheny County Weights and Measures Inspections

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Inspections conducted by the Allegheny County Bureau of Weights and Measures. The Bureau inspects weighing and timing devices such as gas pumps, laundromat timers,...

  12. Formal Inspection: A Tool for TQM

    Science.gov (United States)

    Welz, L.; Kelly, J.

    1995-01-01

    The goal of the Formal Inspection Program at the Jet Propulsion Laboratory (JPL) is to support projects wishing to use Formal Inspections to improve the quality of software and system level engineering products.

  13. Automated visual inspection of moving custom parts

    CSIR Research Space (South Africa)

    Davrajh, S

    2008-01-01

    Full Text Available to integrate vision, sensor articulation, and control systems. The apparatus was tested in a Computer Integrated Manufacturing (CIM) cell to quantify system performance. Intelligence was incorporated into the inspection routine by performing visual inspection...

  14. Allegheny County Housing and Community Environment Inspections

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Residential housing inspections and inspections in response to complaints for community environment problems, such as open vacant structures, vacant lots with...

  15. Nonlinear modal methods for crack localization

    Science.gov (United States)

    Sutin, Alexander; Ostrovsky, Lev; Lebedev, Andrey

    2003-10-01

    A nonlinear method for locating defects in solid materials is discussed that is relevant to nonlinear modal tomography based on the signal cross-modulation. The scheme is illustrated by a theoretical model in which a thin plate or bar with a single crack is excited by a strong low-frequency wave and a high-frequency probing wave (ultrasound). A crack is considered as a small contact-type defect which does not perturb the modal structure of sound in linear approximation but creates combinational-frequency components whose amplitudes depend on their closeness to a resonance and crack position. Using different crack models, including the hysteretic ones, the nonlinear part of its volume variations under the given stress and then the combinational wave components in the bar can be determined. Evidently, their amplitude depends strongly on the crack position with respect to the peaks or nodes of the corresponding linear signals which can be used for localization of the crack position. Exciting the sample by sweeping ultrasound frequencies through several resonances (modes) reduces the ambiguity in the localization. Some aspects of inverse problem solution are also discussed, and preliminary experimental results are presented.

  16. Dynamic behaviour of a rotating cracked beam

    Science.gov (United States)

    Yashar, Ahmed; Ghandchi-Tehrani, Maryam; Ferguson, Neil

    2016-09-01

    This paper presents a new approach to investigate and analyse the vibrational behaviour of cracked rotating cantilever beams, which can for example represent helicopter or wind turbine blades. The analytical Hamiltonian method is used in modelling the rotating beam and two numerical methods, the Rayleigh-Ritz and FEM, are used to study the natural frequencies and the mode shapes of the intact rotating beams. Subsequently, a crack is introduced into the FE model and simulations are performed to identify the modal characteristics for an open cracked rotating beam. The effect of various parameters such as non-dimensional rotating speed, hub ratio and slenderness ratio are investigated for both the intact and the cracked rotating beam, and in both directions of chordwise and flapwise motion. The veering phenomena in the natural frequencies as a function of the rotational speed and the buckling speed are considered with respect to the slenderness ratio. In addition, the mode shapes obtained for the flapwise vibration are compared using the modal assurance criterion (MAC). Finally, a new three dimensional design chart is produced, showing the effect of crack location and depth on the natural frequencies of the rotating beam. This chart will be subsequently important in identifying crack defects in rotating blades.

  17. Protection of brittle film against cracking

    Science.gov (United States)

    Musil, J.; Sklenka, J.; Čerstvý, R.

    2016-05-01

    This article reports on the protection of the brittle Zrsbnd Sisbnd O film against cracking in bending by the highly elastic top film (over-layer). In experiments the Zrsbnd Sisbnd O films with different elemental composition and structure were used. Both the brittle and highly elastic films were prepared by magnetron sputtering using a dual magnetron. The brittle film easily cracks in bending. On the other hand, the highly elastic film exhibits enhanced resistance to cracking in bending. Main characteristic parameters of both the brittle and highly elastic films are given. Special attention is devoted to the effect of the structure (crystalline, amorphous) of both the brittle and highly elastic top film on the resistance of cracking of the brittle film. It was found that (1) both the X-ray amorphous and crystalline brittle films easily crack in bending, (2) the highly elastic film can have either X-ray amorphous or crystalline structure and (3) both the X-ray amorphous and crystalline, highly elastic top films perfectly protect the brittle films against cracking in bending. The structure, mechanical properties and optical transparency of the brittle and highly elastic sputtered Zrsbnd Sisbnd O films are described in detail. At the end of this article, the principle of the low-temperature formation of the highly elastic films is also explained.

  18. Fatigue crack propagation analysis of plaque rupture.

    Science.gov (United States)

    Pei, Xuan; Wu, Baijian; Li, Zhi-Yong

    2013-10-01

    Rupture of atheromatous plaque is the major cause of stroke or heart attack. Considering that the cardiovascular system is a classic fatigue environment, plaque rupture was treated as a chronic fatigue crack growth process in this study. Fracture mechanics theory was introduced to describe the stress status at the crack tip and Paris' law was used to calculate the crack growth rate. The effect of anatomical variation of an idealized plaque cross-section model was investigated. The crack initiation was considered to be either at the maximum circumferential stress location or at any other possible locations around the lumen. Although the crack automatically initialized at the maximum circumferential stress location usually propagated faster than others, it was not necessarily the most critical location where the fatigue life reached its minimum. We found that the fatigue life was minimum for cracks initialized in the following three regions: the midcap zone, the shoulder zone, and the backside zone. The anatomical variation has a significant influence on the fatigue life. Either a decrease in cap thickness or an increase in lipid pool size resulted in a significant decrease in fatigue life. Comparing to the previously used stress analysis, this fatigue model provides some possible explanations of plaque rupture at a low stress level in a pulsatile cardiovascular environment, and the method proposed here may be useful for further investigation of the mechanism of plaque rupture based on in vivo patient data.

  19. Thermodynamic inspection of concrete using a controlled heat source

    Science.gov (United States)

    Milne, James M.

    1990-10-01

    Concrete is not quite such a non-destructable material as many are led to believe. It can deteriorate with time due to changes in the chemistry, the effect of moisture penetration and the corrosion of reinforcing steel bars. Much of this damage occurs relatively close to the surface, sometimes revealed by discolourations or the presence of cracks and sometimes as spallation when the corrosion products of steel cause delamination of the near surface concrete. These effects may occur in good quality concrete but their severity and rapidity of onset may be enhanced by fabrication defects when aggregates may not be to specification or the packing conditions cause porosity. It may thus be months or even years afterwards that these defects come to light. As a consequence a new industry has been formed to inspect concrete structures which may include X-ray equipment, linac accelerators, gamma isotope sources, ultrasonics, radar and of course thermography. Each of these nethods will have their own particular attractive features and merits. But most of these activities tend to be used more as a "fire fighting" service than as one ensuring regular maintenance of critical structures or even as quality control of structures during building. Quite often it seems that Non-destructive Testing is turned into a litigation service for dissatisfied customers and thermography is no stranger to this topic. It is heartening to see that the ASTM organisation in the USA and British Standards are encouraging and developing suitable standards for the inspection of concrete by thermographic techniques.

  20. Stress corrosion cracking of copper canisters

    Energy Technology Data Exchange (ETDEWEB)

    King, Fraser (Integrity Corrosion Consulting Limited (Canada)); Newman, Roger (Univ. of Toronto (Canada))

    2010-12-15

    A critical review is presented of the possibility of stress corrosion cracking (SCC) of copper canisters in a deep geological repository in the Fennoscandian Shield. Each of the four main mechanisms proposed for the SCC of pure copper are reviewed and the required conditions for cracking compared with the expected environmental and mechanical loading conditions within the repository. Other possible mechanisms are also considered, as are recent studies specifically directed towards the SCC of copper canisters. The aim of the review is to determine if and when during the evolution of the repository environment copper canisters might be susceptible to SCC. Mechanisms that require a degree of oxidation or dissolution are only possible whilst oxidant is present in the repository and then only if other environmental and mechanical loading conditions are satisfied. These constraints are found to limit the period during which the canisters could be susceptible to cracking via film rupture (slip dissolution) or tarnish rupture mechanisms to the first few years after deposition of the canisters, at which time there will be insufficient SCC agent (ammonia, acetate, or nitrite) to support cracking. During the anaerobic phase, the supply of sulphide ions to the free surface will be transport limited by diffusion through the highly compacted bentonite. Therefore, no HS. will enter the crack and cracking by either of these mechanisms during the long term anaerobic phase is not feasible. Cracking via the film-induced cleavage mechanism requires a surface film of specific properties, most often associated with a nano porous structure. Slow rates of dissolution characteristic of processes in the repository will tend to coarsen any nano porous layer. Under some circumstances, a cuprous oxide film could support film-induced cleavage, but there is no evidence that this mechanism would operate in the presence of sulphide during the long-term anaerobic period because copper sulphide

  1. Experimental Stress Analysis at Railway Inspection Pit

    Directory of Open Access Journals (Sweden)

    Nicuşor Laurentiu Zaharia

    2008-10-01

    Full Text Available Railway inspection pits are used in railway halls. The purpose of inspection pits is to allow the working under the vehicle. Inspection pits can be found in locomotive depots, factories etc. The new design for a inspection pit in a railway hall involve tests in purpose of homologations the railway infrastructure. Before the homologation committee meeting, tests are made; after the test, a testing report is made which it will be part at homologation documents.

  2. Biogenic Cracks in Porous Rock

    Science.gov (United States)

    Hemmerle, A.; Hartung, J.; Hallatschek, O.; Goehring, L.; Herminghaus, S.

    2014-12-01

    Microorganisms growing on and inside porous rock may fracture it by various processes. Some of the mechanisms of biofouling and bioweathering are today identified and partially understood but most emphasis is on chemical weathering, while mechanical contributions have been neglected. However, as demonstrated by the perseverance of a seed germinating and cracking up a concrete block, the turgor pressure of living organisms can be very significant. Here, we present results of a systematic study of the effects of the mechanical forces of growing microbial populations on the weathering of porous media. We designed a model porous medium made of glass beads held together by polydimethylsiloxane (PDMS), a curable polymer. The rheological properties of the porous medium, whose shape and size are tunable, can be controlled by the ratio of crosslinker to base used in the PDMS (see Fig. 1). Glass and PDMS being inert to most chemicals, we are able to focus on the mechanical processes of biodeterioration, excluding any chemical weathering. Inspired by recent measurements of the high pressure (~0.5 Mpa) exerted by a growing population of yeasts trapped in a microfluidic device, we show that yeast cells can be cultured homogeneously within porous medium until saturation of the porous space. We investigate then the effects of such an inner pressure on the mechanical properties of the sample. Using the same model system, we study also the complex interplay between biofilms and porous media. We focus in particular on the effects of pore size on the penetration of the biofilm within the porous sample, and on the resulting deformations of the matrix, opening new perspectives into the understanding of life in complex geometry. Figure 1. Left : cell culture growing in a model porous medium. The white spheres represent the grains, bonds are displayed in grey, and microbes in green. Right: microscopy picture of glass beads linked by PDMS bridges, scale bar: 100 μm.

  3. Examination of pulsed eddy current for inspection of second layer aircraft wing lap-joint structures using outlier detection methods

    Energy Technology Data Exchange (ETDEWEB)

    Butt, D.M., E-mail: Dennis.Butt@forces.gc.ca [Royal Military College of Canada, Dept. of Chemistry and Chemical Engineering, Kingston, Ontario (Canada); Underhill, P.R.; Krause, T.W., E-mail: Thomas.Krause@rmc.ca [Royal Military College of Canada, Dept. of Physics, Kingston, Ontario (Canada)

    2016-09-15

    Ageing aircraft are susceptible to fatigue cracks at bolt hole locations in multi-layer aluminum wing lap-joints due to cyclic loading conditions experienced during typical aircraft operation, Current inspection techniques require removal of fasteners to permit inspection of the second layer from within the bolt hole. Inspection from the top layer without fastener removal is desirable in order to minimize aircraft downtime while reducing the risk of collateral damage. The ability to detect second layer cracks without fastener removal has been demonstrated using a pulsed eddy current (PEC) technique. The technique utilizes a breakdown of the measured signal response into its principal components, each of which is multiplied by a representative factor known as a score. The reduced data set of scores, which represent the measured signal, are examined for outliers using cluster analysis methods in order to detect the presence of defects. However, the cluster analysis methodology is limited by the fact that a number of representative signals, obtained from fasteners where defects are not present, are required in order to perform classification of the data. Alternatively, blind outlier detection can be achieved without having to obtain representative defect-free signals, by using a modified smallest half-volume (MSHV) approach. Results obtained using this approach suggest that self-calibrating blind detection of cyclic fatigue cracks in second layer wing structures in the presence of ferrous fasteners is possible without prior knowledge of the sample under test and without the use of costly calibration standards. (author)

  4. Environmentally assisted cracking in light water reactors.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Chung, H. M.; Clark, R. W.; Gruber, E. E.; Shack, W. J.; Soppet, W. K.; Strain, R. V.

    2007-11-06

    This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from January to December 2002. Topics that have been investigated include: (a) environmental effects on fatigue crack initiation in carbon and low-alloy steels and austenitic stainless steels (SSs), (b) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs in BWRs, (c) evaluation of causes and mechanisms of irradiation-assisted cracking of austenitic SS in PWRs, and (d) cracking in Ni-alloys and welds. A critical review of the ASME Code fatigue design margins and an assessment of the conservation in the current choice of design margins are presented. The existing fatigue {var_epsilon}-N data have been evaluated to define the effects of key material, loading, and environmental parameters on the fatigue lives of carbon and low-alloy steels and austenitic SSs. Experimental data are presented on the effects of surface roughness on fatigue crack initiation in these materials in air and LWR environments. Crack growth tests were performed in BWR environments on SSs irradiated to 0.9 and 2.0 x 10{sup 21} n x cm{sup -2}. The crack growth rates (CGRs) of the irradiated steels are a factor of {approx}5 higher than the disposition curve proposed in NUREG-0313 for thermally sensitized materials. The CGRs decreased by an order of magnitude in low-dissolved oxygen (DO) environments. Slow-strain-rate tensile (SSRT) tests were conducted in high-purity 289 C water on steels irradiated to {approx}3 dpa. The bulk S content correlated well with the susceptibility to intergranular SCC in 289 C water. The IASCC susceptibility of SSs that contain >0.003 wt. % S increased drastically. bend tests in inert environments at 23 C were conducted on broken pieces of SSRT specimens and on unirradiated specimens of the same materials after hydrogen charging. The results of the tests and a review of other data in the literature

  5. Evaluation method of cracking resistance of lightweight aggregate concrete

    Institute of Scientific and Technical Information of China (English)

    季韬; 张彬彬; 陈永波; 庄一舟

    2014-01-01

    The cracking behavior of lightweight aggregate concrete (LWAC) was investigated by mechanical analysis, SEM and cracking-resistant test where a shrinkage-restrained ring with a clapboard was used. The relationship between the ceramsite type and the cracking resistance of LWAC was built up and compared with that of normal-weight coarse aggregate concrete (NWAC). A new method was proposed to evaluate the cracking resistance of concrete, where the concepts of cracking coefficient ζt(t) and the evaluation index Acr(t) were proposed, and the development of micro-cracks and damage accumulation were recognized. For the concrete with an ascending cracking coefficient curve, the larger Acr(t) is, the lower cracking resistance of concrete is. For the concrete with a descending cracking coefficient curve, the larger Acr(t) is, the stronger the cracking resistance of concrete is. The evaluation results show that in the case of that all the three types of coarse aggregates in concrete are pre-soaked for 24 h, NWAC has the lowest cracking resistance, followed by the LWAC with lower water absorption capacity ceramsite and the LWAC with higher water absorption capacity ceramsite has the strongest cracking resistance. The proposed method has obvious advantages over the cracking age method, because it can evaluate the cracking behavior of concrete even if the concrete has not an observable crack.

  6. Creep and Creep-Fatigue Crack Growth at Structural Discontinuities and Welds

    Energy Technology Data Exchange (ETDEWEB)

    Dr. F. W. Brust; Dr. G. M. Wilkowski; Dr. P. Krishnaswamy; Mr. Keith Wichman

    2010-01-27

    The subsection ASME NH high temperature design procedure does not admit crack-like defects into the structural components. The US NRC identified the lack of treatment of crack growth within NH as a limitation of the code and thus this effort was undertaken. This effort is broken into two parts. Part 1, summarized here, involved examining all high temperature creep-fatigue crack growth codes being used today and from these, the task objective was to choose a methodology that is appropriate for possible implementation within NH. The second part of this task, which has just started, is to develop design rules for possible implementation within NH. This second part is a challenge since all codes require step-by-step analysis procedures to be undertaken in order to assess the crack growth and life of the component. Simple rules for design do not exist in any code at present. The codes examined in this effort included R5, RCC-MR (A16), BS 7910, API 579, and ATK (and some lesser known codes). There are several reasons that the capability for assessing cracks in high temperature nuclear components is desirable. These include: (1) Some components that are part of GEN IV reactors may have geometries that have sharp corners - which are essentially cracks. Design of these components within the traditional ASME NH procedure is quite challenging. It is natural to ensure adequate life design by modeling these features as cracks within a creep-fatigue crack growth procedure. (2) Workmanship flaws in welds sometimes occur and are accepted in some ASME code sections. It can be convenient to consider these as flaws when making a design life assessment. (3) Non-destructive Evaluation (NDE) and inspection methods after fabrication are limited in the size of the crack or flaw that can be detected. It is often convenient to perform a life assessment using a flaw of a size that represents the maximum size that can elude detection. (4) Flaws that are observed using in-service detection

  7. 77 FR 76452 - Grain Inspection Advisory Committee Reestablishment

    Science.gov (United States)

    2012-12-28

    ... Doc No: 2012-31281] DEPARTMENT OF AGRICULTURE Grain Inspection, Packers and Stockyards Administration Grain Inspection Advisory Committee Reestablishment AGENCY: Grain Inspection, Packers and Stockyards... of Agriculture has reestablished the Grain Inspection, Packers and Stockyards Administration (GIPSA...

  8. Assessment of NDE Technologies for Detection and Characterization of Stress Corrosion Cracking in LWRs

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Ryan M.; Ramuhalli, Pradeep; Toloczko, Mychailo B.; Bond, Leonard J.; Montgomery, Robert O.

    2012-12-31

    Stress corrosion cracking (SCC) in light water reactors (LWRs) has been a persistent form of degradation in the nuclear industry. Examples of SCC can be found for a range of materials in boiling and pressurized water reactor environments, including carbon steels, stainless steels, and nickel-base stainless alloys. The evolution of SCC is often characterized by a long initiation stage followed by a phase of more rapid crack growth to failure. This provides a relatively short window of opportunity to detect the start of observable SCC, and it is conceivable that SCC could progress from initiation to failure between subsequent examinations when managed by applying periodic in-service inspection techniques. Implementation of advanced aging management paradigms in the current fleet of LWRs will require adaptation of existing measurement technologies and development of new technologies to perform on-line measurements during reactor operation to ensure timely detection of material degradation and to support the implementation of advanced diagnostics and prognostics. This paper considers several non-destructive examination (NDE) technologies with known sensitivity to detection of indicators for SCC initiation and/or propagation, and assesses these technologies with respect to their ability to detect and accurately characterize the significance of an SCC flaw. Potential strategies to improve SCC inspection or monitoring performance are offered to benefit management of SCC degradation in LWRs.

  9. Firebox modeling of SRT cracking heaters

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, K.M.; Albano, J.V. [ABB Lummus Crest Inc., Bloomfield, NJ (United States)

    1994-12-31

    Thermal cracking of hydrocarbons remains the most economically attractive route for the production of ethylene. The heat for the endothermic cracking reaction is supplied in high capacity fired heaters which are designed specifically to have high selectivity to olefins. In the cracking process, coke is deposited within the tubes of the radiant coil. The rate of coke deposition in a cracking furnace is a function not only of process conditions but of other factors as well. High tube metal temperatures in certain areas of the coil or hot spots can cause locally high coking rate leading to partial blockage of the tubes and consequently, short runs. The small diameter tubes used in modern high selectivity heaters are more sensitive than older large tube designs. The occurrence of these hot zones is a strong function of fireside conditions. For satisfactory performance, the heat flux profile in a cracking heater must be maintained as uniform as possible. In addition, it is important to minimize the variation of process temperatures entering the various cracking coils. These fireside variables are not only a function of the type of burners, excess air, type of fuel(s) and distribution of air and fuel but depend significantly on the air and flue gas flow patterns associated with the firebox, i.e., the firebox aerodynamics. Poor aerodynamics can adversely affect firing patterns and hence heat flux profiles in commercial furnaces. A variety of modeling techniques have been used to evaluate the firebox aerodynamics of Lummus, Short Residence Time, cracking heaters. These include flow visualization, physical cold flow modeling, and computational techniques. These approaches are discussed in this paper.

  10. Crack propagation modeling using Peridynamic theory

    Science.gov (United States)

    Hafezi, M. H.; Alebrahim, R.; Kundu, T.

    2016-04-01

    Crack propagation and branching are modeled using nonlocal peridynamic theory. One major advantage of this nonlocal theory based analysis tool is the unifying approach towards material behavior modeling - irrespective of whether the crack is formed in the material or not. No separate damage law is needed for crack initiation and propagation. This theory overcomes the weaknesses of existing continuum mechanics based numerical tools (e.g. FEM, XFEM etc.) for identifying fracture modes and does not require any simplifying assumptions. Cracks grow autonomously and not necessarily along a prescribed path. However, in some special situations such as in case of ductile fracture, the damage evolution and failure depend on parameters characterizing the local stress state instead of peridynamic damage modeling technique developed for brittle fracture. For brittle fracture modeling the bond is simply broken when the failure criterion is satisfied. This simulation helps us to design more reliable modeling tool for crack propagation and branching in both brittle and ductile materials. Peridynamic analysis has been found to be very demanding computationally, particularly for real-world structures (e.g. vehicles, aircrafts, etc.). It also requires a very expensive visualization process. The goal of this paper is to bring awareness to researchers the impact of this cutting-edge simulation tool for a better understanding of the cracked material response. A computer code has been developed to implement the peridynamic theory based modeling tool for two-dimensional analysis. A good agreement between our predictions and previously published results is observed. Some interesting new results that have not been reported earlier by others are also obtained and presented in this paper. The final objective of this investigation is to increase the mechanics knowledge of self-similar and self-affine cracks.

  11. ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH

    Institute of Scientific and Technical Information of China (English)

    C.F.Lee; L.T.Hsiao

    2002-01-01

    In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the rc controlled node-released strategy are employed to study the fatigue crack opened/closed load (Pop) of A1 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed Pop values and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (Pmax) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of Pop/Pmax vs. Kmax and R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔKeff, the A1 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔKeff and R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves. According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.

  12. TRANSPORT THROUGH CRACKED CONCRETE: LITERATURE REVIEW

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.

    2012-05-11

    Concrete containment structures and cement-based fills and waste forms are used at the Savannah River Site to enhance the performance of shallow land disposal systems designed for containment of low-level radioactive waste. Understanding and measuring transport through cracked concrete is important for describing the initial condition of radioactive waste containment structures at the Savannah River Site (SRS) and for predicting performance of these structures over time. This report transmits the results of a literature review on transport through cracked concrete which was performed by Professor Jason Weiss, Purdue University per SRR0000678 (RFP-RQ00001029-WY). This review complements the NRC-sponsored literature review and assessment of factors relevant to performance of grouted systems for radioactive waste disposal. This review was performed by The Center for Nuclear Waste Regulatory Analyses, San Antonio, TX, and The University of Aberdeen, Aberdeen Scotland and was focused on tank closure. The objective of the literature review on transport through cracked concrete was to identify information in the open literature which can be applied to SRS transport models for cementitious containment structures, fills, and waste forms. In addition, the literature review was intended to: (1) Provide a framework for describing and classifying cracks in containment structures and cementitious materials used in radioactive waste disposal, (2) Document the state of knowledge and research related to transport through cracks in concrete for various exposure conditions, (3) Provide information or methodology for answering several specific questions related to cracking and transport in concrete, and (4) Provide information that can be used to design experiments on transport through cracked samples and actual structures.

  13. Recent evaluations of crack-opening-area in circumferentially cracked pipes

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, S.; Brust, F.; Ghadiali, N.; Wilkowski, G.; Miura, N.

    1997-04-01

    Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. The leak rates depend on the crack-opening area of the through-wall crack in the pipe. In addition to LBB analyses which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section XI. The objectives of this study were to review, evaluate, and refine current predictive models for performing crack-opening-area analyses of circumferentially cracked pipes. The results from twenty-five full-scale pipe fracture experiments, conducted in the Degraded Piping Program, the International Piping Integrity Research Group Program, and the Short Cracks in Piping and Piping Welds Program, were used to verify the analytical models. Standard statistical analyses were performed to assess used to verify the analytical models. Standard statistical analyses were performed to assess quantitatively the accuracy of the predictive models. The evaluation also involved finite element analyses for determining the crack-opening profile often needed to perform leak-rate calculations.

  14. Crack Growth Monitoring by Embedded Optical Fibre Bragg Grating Sensors: Fibre Reinforced Plastic Crack Growing Detection

    DEFF Research Database (Denmark)

    Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

    2015-01-01

    This article presents a novel method to asses a crack growing/damage event in fibre reinforced plastic, or adhesive using Fibre Bragg Grating (FBG) sensors embedded in a host material. Different features of the crack mechanism that induce a change in the FBG response were identified. Double Canti...

  15. Hydrocarbon cracking selectivities with a dual zeolite fluid cracking catalyst containing REY and ZSM-5

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopalan, K.; Young, G.W. (W.R. Grace and Company, Columbia, MD (USA))

    1987-08-01

    Synthetic Y faujasite zeolites have been used commercially as cracking catalysts for the past two decades, and more recently dual zeolite fluid cracking catalysts, containing faujasite and ZSM-5 were discovered to increase the octane number of the gasoline during catalytic cracking of gas oil. This concept, where ZSM-5 constitutes only a small fraction (about 1 wt %) of the cracking catalyst, has been tested commercially in Europe and in the United States. Cracking of paraffinic and olefinic hydrocarbons by ZSM-5 catalysts has been studied by several investigators over a range of temperatures (350 to 540{degree}C) and using nearly pure ZSM-5 as the catalyst. The mechanism of octane number enhancement with the dual zeolite catalyst was investigated by examining the effect on product selectivity of addition of 1 wt % ZSM-5 to a cracking catalyst composition during catalytic cracking of a commercial gas oil at 500{degree}C. Changes in composition of the product gasoline (paraffins, olefins, naphthenes and aromatics) caused by ZSM-5 were measured. Since commercial cracking catalysts undergo continuous high temperature regeneration in the presence of steam, the effect of hydrothermal treatment of ZSM-5 was also investigated.

  16. Evolving fracture patterns: columnar joints, mud cracks, and polygonal terrain

    Science.gov (United States)

    Goehring, L.

    2012-12-01

    Contraction cracks can form captivating patterns, such as the artistic craquelure sometimes found in pottery glazes, to the cracks in dried mud, or the polygonal networks covering the polar regions of Earth and Mars. Two types are frequently encountered: those with irregular rectilinear patterns, such as that formed by an homogeneous slurry when dried (or cooled) uniformly, and more regular hexagonal patterns, such as those typified by columnar joints. Once cracks start to form in a thin contracting layer, they will sequentially break the layer into smaller and smaller pieces. A rectilinear crack pattern encodes information about the order of cracks, as later cracks tend to intersect with earlier cracks at right angles. In this manner they relieve the stresses perpendicular to the pre-existing crack. In a hexagonal pattern, in contrast, the angles between all cracks at a vertex are near 120°. In this presentation it will be shown how both types of pattern can arise from identical forces, and that a rectilinear, T-junction dominated pattern will develop into to a hexagonal pattern, with Y-junctions, if allowed to. Such an evolution can be explained as the result of three conditions: (1) if cracks advance through space, or heal and recur, that the previous positions of a crack tip acts as a line of weakness, guiding the next iteration of cracking; (2) that the order of opening of cracks can change in each iteration; and (3) that crack tips curve to maximise the local strain energy release rate. The ordering of crack patterns are seen in a number of systems: columnar joints in starch and lava; desiccation cracks in clays that are repeatedly wetted and dried; cracks in eroding gypsum-cemented sand layers; and the cracks in permafrost known as polygonal terrain. These patterns will each be briefly explored, in turn, and shown to obey the above principles of crack pattern evolution.

  17. VALIDATION OF CRACK INTERACTION LIMIT MODEL FOR PARALLEL EDGE CRACKS USING TWO-DIMENSIONAL FINITE ELEMENT ANALYSIS

    Directory of Open Access Journals (Sweden)

    R. Daud

    2013-06-01

    Full Text Available Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b > a. Crack interaction factors are evaluated based on stress intensity factors (SIFs for Mode I SIFs using a displacement extrapolation technique. Parametric studies involved a wide range of crack-to-width (0.05 ≤ a/W ≤ 0.5 and crack interval ratios (b/a > 1. For validation, crack interaction factors are compared with single edge crack SIFs as a state of zero interaction. Within the considered range of parameters, the proposed numerical evaluation used to predict the crack interaction factor reduces the error of existing analytical solution from 1.92% to 0.97% at higher a/W. In reference to FFS codes, the small discrepancy in the prediction of the crack interaction factor validates the reliability of the numerical model to predict crack interaction limits under shielding interaction effects. In conclusion, the numerical model gave a successful prediction in estimating the crack interaction limit, which can be used as a reference for the shielding orientation of other cracks.

  18. Visual inspection submersible for nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Motohiko; Okano, Hideharu; Ozaki, Osamu [Toshiba Corp., Kawasaki, Kanagawa (Japan). Nuclear Engineering Lab.; Ishikawa, Masaaki

    1996-10-01

    Remote Operated Vehicle (ROV) is currently applied for visual inspection inside the reactor pressure vessel (RPV). To inspect wide area of the RPV and structures, compactness is required for the inspection vehicle as well as good driveability. This report describes the development of visual inspection submersible which was manufactured based on the gap between structures inside RPV and applied with the support system. It was proved to be very efficient measure to make the inspection period short. Also, radiation tolerant camera and manipulator for the vehicle has been developed. (author)

  19. Evaluation of Stress Intensity Factors for Multiple Cracked Circular Disks Under Crack Surface Tractions with SBFEM

    Institute of Scientific and Technical Information of China (English)

    LIU Jun-yu; LIN Gao; LI Xiao-chuan; XU Feng-lin

    2013-01-01

    Stress intensity factors (SIFs) for the cracked circular disks under different distributing surface tractions are evaluated with the scaled boundary finite element method (SBFEM).In the SBFEM,the analytical advantage of the solution in the radial direction allows SIFs to be directly determined from its definition,therefore no special crack-tip treatment is necessary.Furthermore anisotropic material behavior can be treated easily.Different distributions of surface tractions are considered for the center and double-edge-cracked disks.The benchmark examples are modeled and an excellent agreement between the results in the present study and those in published literature is found.It shows that SBFEM is effective and possesses high accuracy.The SIFs of the cracked orthotropic material circular disks subjected to different surface tractions are also evaluated.The technique of substructure is applied to handle the multiple cracks problem.

  20. Failure analysis of corrosion cracking and simulated testing for a fluid catalytic cracking unit

    Institute of Scientific and Technical Information of China (English)

    Hua Chen; Xiaogang Li; Chaofang Dong; Ming Li; Jinwen Yang

    2005-01-01

    The failure of a fluid catalysis and cracking unit (FCCU) in a Chinese refinery was investigated by using nondestructive detection methods, fracture surface examination, hardness measurement, chemical composition and corrosion products analysis. The results showed that the failure was caused by the dew point nitrate stress corrosion cracking. For a long operation period, the wall temperature of the regenerator in the FCCU was below the fume dew point. As a result, an acid fume NOx-SOx-H2O medium presented on the surface, resulting in stress corrosion cracking of the component with high residual stress. In order to confirm the relative conclusion, simulated testing was conducted in laboratory, and the results showed similar cracking characteristics. Finally, some suggestions have been made to prevent the stress corrosion cracking of an FCCU from re-occurring in the future.

  1. Generative inspection process planner for integrated production

    Energy Technology Data Exchange (ETDEWEB)

    Brown, C.W. (Allied-Signal Aerospace Co., Kansas City, MO (USA). Kansas City Div.); Gyorog, D.A. (Kansas Univ., Lawrence, KS (USA). Dept. of Mechanical Engineering)

    1990-04-01

    This work describes the design prototype development of a generative process planning system for dimensional inspection. The system, IPPEX (Inspection Process Planning EXpert), is a rule-based expert system for integrated production. Using as advanced product modeler, relational databases, and artificial intelligence techniques, IPPEX generates the process plan and part program for the dimensional inspection of products using CMMs. Through an application interface, the IPPEX system software accesses product definition from the product modeler. The modeler is a solid geometric modeler coupled with a dimension and tolerance modeler. Resource data regarding the machines, probes, and fixtures are queried from databases. IPPEX represents inspection process knowledge as production rules and incorporates an embedded inference engine to perform decision making. The IPPEX system, its functional architecture, system architecture, system approach, product modeling environment, inspection features, inspection knowledge, hierarchical planning strategy, user interface formats, and other fundamental issues related to inspection planning and part programming for CMMs are described. 27 refs., 16 figs., 4 tabs.

  2. Shaft Crack Identification Based on Vibration and AE Signals

    Directory of Open Access Journals (Sweden)

    Wenxiu Lu

    2011-01-01

    Full Text Available The shaft crack is one of the main serious malfunctions that often occur in rotating machinery. However, it is difficult to locate the crack and determine the depth of the crack. In this paper, the acoustic emission (AE signal and vibration response are used to diagnose the crack. The wavelet transform is applied to AE signal to decompose into a series of time-domain signals, each of which covers a specific octave frequency band. Then an improved union method based on threshold and cross-correlation method is applied to detect the location of the shaft crack. The finite element method is used to build the model of the cracked rotor, and the crack depth is identified by comparing the vibration response of experiment and simulation. The experimental results show that the AE signal is effective and convenient to locate the shaft crack, and the vibration signal is feasible to determine the depth of shaft crack.

  3. Virtual restoration of cracks in digitized image of paintings

    Energy Technology Data Exchange (ETDEWEB)

    Spagnolo, G Schirripa; Somma, F

    2010-11-01

    An integrated methodology for the detection and removal of cracks on digitized image is presented in this paper. Crack-like pattern detection have been a matter of high concern among researchers mostly for its useful contribution to a variety of applications. The results presented here regard the craquelure of old paintings, however, the same methodology can be used for a much wider set of application. Many images contain similar patterns: crack in protective coating for polymers and other surfaces; fatigue crack in MEMS/NEMS; crack in epoxies used for underfill and encapsulation microelectronics components; etc. In this paper the cracks are detected by thresholding the output of the morphological top-hat transform. Afterwards, the thin dark brush strokes which have been misidentified as cracks are removed using automatic procedure. Finally, crack filling using texture synthesis algorithms. The methodology has been shown to perform very well on digitized images suffering from cracks.

  4. Fracture mechanics of piezoelectric solids with interface cracks

    CERN Document Server

    Govorukha, Volodymyr; Loboda, Volodymyr; Lapusta, Yuri

    2017-01-01

    This book provides a comprehensive study of cracks situated at the interface of two piezoelectric materials. It discusses different electric boundary conditions along the crack faces, in particular the cases of electrically permeable, impermeable, partially permeable, and conducting cracks. The book also elaborates on a new technique for the determination of electromechanical fields at the tips of interface cracks in finite sized piezoceramic bodies of arbitrary shape under different load types. It solves scientific problems of solid mechanics in connection with the investigation of electromechanical fields in piezoceramic bodies with interface cracks, and develops calculation models and solution methods for plane fracture mechanical problems for piecewise homogeneous piezoceramic bodies with cracks at the interfaces. It discusses the “open” crack model, which leads to a physically unrealistic oscillating singularity at the crack tips, and the contact zone model for in-plane straight interface cracks betw...

  5. Automatic quantification of crack patterns by image processing

    Science.gov (United States)

    Liu, Chun; Tang, Chao-Sheng; Shi, Bin; Suo, Wen-Bin

    2013-08-01

    Image processing technologies are proposed to quantify crack patterns. On the basis of the technologies, a software "Crack Image Analysis System" (CIAS) has been developed. An image of soil crack network is used as an example to illustrate the image processing technologies and the operations of the CIAS. The quantification of the crack image involves the following three steps: image segmentation, crack identification and measurement. First, the image is converted to a binary image using a cluster analysis method; noise in the binary image is removed; and crack spaces are fused. Then, the medial axis of the crack network is extracted from the binary image, with which nodes and crack segments can be identified. Finally, various geometric parameters of the crack network can be calculated automatically, such as node number, crack number, clod area, clod perimeter, crack area, width, length, and direction. The thresholds used in the operations are specified by cluster analysis and other innovative methods. As a result, the objects (nodes, cracks and clods) in the crack network can be quantified automatically. The software may be used to study the generation and development of soil crack patterns and rock fractures.

  6. Crack Detection with Lamb Wave Wavenumber Analysis

    Science.gov (United States)

    Tian, Zhenhua; Leckey, Cara; Rogge, Matt; Yu, Lingyu

    2013-01-01

    In this work, we present our study of Lamb wave crack detection using wavenumber analysis. The aim is to demonstrate the application of wavenumber analysis to 3D Lamb wave data to enable damage detection. The 3D wavefields (including vx, vy and vz components) in time-space domain contain a wealth of information regarding the propagating waves in a damaged plate. For crack detection, three wavenumber analysis techniques are used: (i) two dimensional Fourier transform (2D-FT) which can transform the time-space wavefield into frequency-wavenumber representation while losing the spatial information; (ii) short space 2D-FT which can obtain the frequency-wavenumber spectra at various spatial locations, resulting in a space-frequency-wavenumber representation; (iii) local wavenumber analysis which can provide the distribution of the effective wavenumbers at different locations. All of these concepts are demonstrated through a numerical simulation example of an aluminum plate with a crack. The 3D elastodynamic finite integration technique (EFIT) was used to obtain the 3D wavefields, of which the vz (out-of-plane) wave component is compared with the experimental measurement obtained from a scanning laser Doppler vibrometer (SLDV) for verification purposes. The experimental and simulated results are found to be in close agreement. The application of wavenumber analysis on 3D EFIT simulation data shows the effectiveness of the analysis for crack detection. Keywords: : Lamb wave, crack detection, wavenumber analysis, EFIT modeling

  7. Applied Stress Affecting the Environmentally Assisted Cracking

    Science.gov (United States)

    Vasudevan, A. K.

    2013-03-01

    Stress corrosion cracking (SCC) is affected by the mode of applied stress, i.e., tension, compression, or torsion. The cracking is measured in terms of initiation time to nucleate a crack or time to failure. In a simple uniaxial loading under tension or compression, it is observed that the initiation time can vary in orders of magnitude depending on the alloy and the environment. Fracture can be intergranular or transgranular or mixed mode. Factors that affect SCC are solubility of the metal into surrounding chemical solution, and diffusion rate (like hydrogen into a tensile region) of an aggressive element into the metal and liquid metallic elements in the grain boundaries. Strain hardening exponent that affects the local internal stresses and their gradients can affect the diffusion kinetics. We examine two environments (Ga and 3.5 pct NaCl) for the same alloy 7075-T651, under constant uniaxial tension and compression load. These two cases provide us application to two different governing mechanisms namely liquid metal embrittlement (7075-Ga) and hydrogen-assisted cracking (7075-NaCl). We note that, in spite of the differences in their mechanisms, both systems show similar behavior in the applied K vs crack initiation time plots. One common theme among them is the transport mechanism of a solute element to a tensile-stress region to initiate fracture.

  8. Crack buckling in soft gels under compression

    Institute of Scientific and Technical Information of China (English)

    Rong Long; Chung-Yuen Hui

    2012-01-01

    Recent interest in designing soft gels with high fracture toughness has called for simple and robust methods to test fracture behavior.The conventional method of applying tension to a gel sample suffers from a difficulty of sample gripping.In this paper,we study a possible fracture mechanism of soft gels under uni-axial compression.We show that the surfaces of a pre-existing crack,oriented parallel to the loading axis,can buckle at a critical compressive stress.This buckling instability can open the crack surfaces and create highly concentrated stress fields near the crack tip,which can lead to crack growth.We show that the onset of crack buckling can be deduced by a dimensional argument combined with an analysis to determine the critical compression needed to induce surface instabilities of an elastic half space.The critical compression for buckling was verified for a neoHookean material model using finite element simulations.

  9. Imaging Cracks by Laser Excited Thermography

    Science.gov (United States)

    Schlichting, J.; Kervalishvili, G. N.; Maierhofer, Ch.; Kreutzbruck, M.

    2010-02-01

    During the last years active thermography is increasingly used in a number of NDT problems in production and maintenance. In this work we focus on the detection of vertical cracks starting at the surface, which is an important indication of structural failure. By using local thermal excitation it is possible to image anisotropies in the lateral diffusivity by recording the temporal temperature data with an infrared camera. The regional transient behaviour of temperature distribution then can provide quantitative information of the crack parameter. In doing so, we present an advanced technique for the determination of the crack depth. The experimental set-up is based on an Nd:YAG laser. The beam is focused on the test sample by using an optical scanner to create the required lateral heat flow. The time resolved temperature distribution is recorded with an infrared camera (InSb FPA, 3 to 5 μm) providing a frame rate of up to 500 Hz. In addition we report on numerical simulation to investigate the concept of local heat excitation for a quantitative estimation of crack parameters. The modeling also includes the influence of surface to surface radiation inside the crack. We obtained a good consistency between experimental and theoretical data.

  10. Hot Rolling Scrap Reduction through Edge Cracking and Surface Defects Control

    Energy Technology Data Exchange (ETDEWEB)

    Beaudoin, Armand [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2016-05-29

    The design of future aircraft must address the combined demands for fuel efficiency, reduced emissions and lower operating costs. One contribution to these goals is weight savings through the development of new alloys and design techniques for airframe structures. This research contributes to the light-weighting through fabrication of monolithic components from advanced aluminum alloys by making a link between alloy processing history and in-service performance. Specifically, this research demonstrates the link between growing cracks with features of the alloy microstructure that follow from thermo-mechanical processing. This is achieved through a computer model of crack deviation. The model is validated against experimental data from production scale aluminum alloy plate, and demonstration of the effect of changes in processing history on crack growth is made. The model is cast in the open-source finite element code WARP3D, which is freely downloadable and well documented. This project provides benefit along several avenues. First, the technical contribution of the computer model offers the materials engineer a critical means of providing guidance both upstream, to process tuning to achieve optimal properties, and downstream, to enhance fault tolerance. Beyond the fuel savings and emissions reduction inherent in the light-weighting of aircraft structures, improved fault tolerance addresses demands for longer inspection intervals over baseline, and a lower life cycle cost.

  11. Study of transverse crack formation on surface area of UO{sub 2} pellet circumference

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Dionisia S.; Paneto, Lelia F.P.C.; Souza, Patricia O. de, E-mail: dionisia@inb.gov.br, E-mail: lelia@inb.gov.br, E-mail: patriciasouza@inb.gov.br [Industrias Nucleares do Brasil (INB), Resende, RJ (Brazil). Gerencia de Analise Tecnica do Combustivel Nuclear

    2013-07-01

    Microstructure of a polycrystalline material has a considerable influence on particular properties, such as mechanical strength, electrical conductivity, optical transmission and magnetic susceptibility. The uranium dioxide (UO{sub 2}) is used in water-cooled nuclear reactors, due to its desirable ceramics characteristics as a nuclear fuel. The UO{sub 2} is used in the form of pellets manufactured by wet route by INB, where they are loaded into fuel rods to build the fuel assemblies used in pressurized water reactors of Angra 1, Angra 2 and future Angra 3 nuclear power plants, for electric energy generated from nuclear power in Brazil. The geometric and structural integrity of these pellets cause direct influence on their performance during the reactor core operating cycle, so pellets presenting surface cracks leading to the phenomenon of pellet cladding interaction-PCI, resulting in failures in the fuel rod and subsequently release of fission products in the reactor coolant. Transverse cracks on surface area of pellet circumference are detected by visual inspection during the manufacturing process. This paper presents the study of these cracks formation by content analysis conducted with the support of electron microscopy. These results here are analyzed from the point of view of materials science through observation of the microstructure, and the pressing process where the defect was probably generated. (author)

  12. Identification of cracks in thin-walled structures by means of wavenumber filtering

    Science.gov (United States)

    Kudela, Paweł; Radzieński, Maciej; Ostachowicz, Wiesław

    2015-01-01

    This research is related to a signal processing of full wavefield data as an effective tool for detection, localization and visualization of a crack growth in thin-walled structures. Full wavefield data of propagating Lamb waves in structures such as plates and shells made out of metallic alloys and composite laminates contain a wealth of information about wave pattern anomalies due to occurrence of a damage. The aim is to demonstrate a method for enhancing damage visualization in structures such that estimation of the length and orientation of the crack can be easily obtained. The proposed signal processing involves application of discrete fast Fourier transform, wavenumber domain filtering and inverse discrete Fourier transform. The method is further enhanced by a technique for compensation of the wave attenuation so that the effects of structural damage have the same influence regardless of the location. The concept is first illustrated on numerically simulated data, and then tested on experimental results. In the experiments, full wavefield measurements are obtained using a scanning laser Doppler vibrometer, which allows the measurement of displacements and/or velocities along three axes over a user-defined grid. In the proposed method only out-of-plane velocities are used. Tests performed on simple aluminum and composite plates with artificially introduced longitudinal cracks confirm the effectiveness of the method and its potential for application to the inspection of a variety of structural components.

  13. Propagation of stress corrosion cracks in alpha-brasses

    Energy Technology Data Exchange (ETDEWEB)

    Beggs, Dennis Vinton [Univ. of Illinois, Urbana-Champaign, IL (United States)

    1981-01-01

    Transgranular and intergranular stress corrosion cracks were investigated in alpha-brasses in a tarnishing ammoniacal solution. Surface observation indicated that the transgranular cracks propagated discontinuously by the sudden appearance of a fine crack extending several microns ahead of the previous crack tip, often associated with the detection of a discrete acoustic emission (AE). By periodically increasing the deflection, crack front markings were produced on the resulting fracture surfaces, showing that the discontinuous propagation of the crack trace was representative of the subsurface cracking. The intergranular crack trace appeared to propagate continuously at a relatively blunt crack tip and was not associated with discrete AE. Under load pulsing tests with a time between pulses, Δt greater than or equal to 3 s, the transgranular fracture surfaces always exhibited crack front markings which corresponded with the applied pulses. The spacing between crack front markings, Δx, decreased linearly with Δt. With Δt less than or equal to 1.5 s, the crack front markings were in a one-to-one correspondence with applied pulses only at relatively long crack lengths. In this case, Δx = Δx* which approached a limiting value of 1 μm. No crack front markings were observed on intergranular fracture surfaces produced during these tests. It is concluded that transgranular cracking occurs by discontinuous mechanical fracture of an embrittled region around the crack tip, while intergranular cracking results from a different mechanism with cracking occurring via the film-rupture mechanism.

  14. Developing the information management system for safeguards national inspection

    Energy Technology Data Exchange (ETDEWEB)

    Park, S. J.; Jeon, I.; Park, W. S.; Min, K. S. [KAERI, Taejon (Korea, Republic of)

    2003-10-01

    The inspection information management system for safeguards national inspection is aimed to do the national safeguards inspection with efficiency, and to decrease the inspector's load to write inspection report by systematizing the inspection jobs and sharing the inspection data. National safeguards inspection is consisted two large jobs. The first is the national safeguards supporting job of managing to support the national inspection mission. The other is the writing a national inspection report after completing the national inspection. Before the developing of inspection information management system, the official tools(spread sheet, word processor) are usually used. But there is problem to share the data, to produce the statistics data. To solve the these problem, we developed the inspection information management system that process the job from initial to final inspection work, and opened user education. This paper explain the procedure of developing the inspection information management system for safeguards national inspection.

  15. New tools for steel catenary risers inspection; Novas ferramentas para inspecao de risers tipo SCR

    Energy Technology Data Exchange (ETDEWEB)

    Camerini, Claudio Soligo; Marinho, Carla Alves; Raphael, Fabiana N.; Maia, Carlos [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Freitas, Miguel [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil); Lopes, Ricardo Tadeu; Rocha, Henrique [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

    2005-07-01

    The Research Center of PETROBRAS and two of the Federal Brazilian Universities, PUC-Rio and UFRJ, have been developing two new projects in order to inspect risers of petroleum production. The first tool is an instrumented pig for profiling internal corrosion, having flexibility under diameter variations and independence related to thickness wall pipeline. The second one is a gammagraphy system remotely operated by ROVs, to be employed in alveoli corrosion and fatigue cracks detection in underwater pipelines. This work shows the trajectory of these two tools, describing laboratory and field tests and the future activities. (author)

  16. Nondestructive Evaluation Technology Initiatives II. Delivery Order 0002: Whole Field Turbine Disk Inspection

    Science.gov (United States)

    2007-04-01

    5.2 FPI PoD samples A set of Inconel 718 samples with artificial fatigue cracks that was used as a fluorescent penetrant inspection (FPI) PoD...No None N/A 11N E 0.029 Yes No Yes Anti-gallant No 12N E 0.028 Yes No Yes Lubricant No Notes: A = Aluminum 7075-T6 N = Inconel 718 S...contaminants on the performance of Sonic IR testing of engine components. The specimens were comprised of nine Inconel 718 and six 7075-T6 aluminum plates

  17. Crack tip shielding and anti-shielding effects of parallel cracks for a superconductor slab under an electromagnetic force

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhi Wen; Zhou, You He [Ministry of Education, Singapore (China); Lee, Kang Yong [Yonsei University, Seoul (Korea, Republic of)

    2012-02-15

    In this letter, the shielding or anti-shielding effect is firstly applied to obtain the behavior of two parallel cracks in a two-dimensional type-II superconducting under electromagnetic force. Fracture analysis is performed by the finite element method and the magnetic behavior of superconductor is described by the critical state Bean model. The stress intensity factors at the crack tips can be obtained and discussed for decreasing field after zero-field cooling. The shielding or anti-shielding effect at the crack tips depend on the distance between two parallel cracks and the crack length. The results indicate that the shielding effects of the two parallel cracks increase when the distance between the two parallel cracks decreases. It can be also obtained that the superconductors with shorter cracks has more remarkable shielding effect than those with longer cracks.

  18. Effects of plastic anisotropy on crack-tip behaviour

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo; Kuroda, Mitsutoshi

    2002-01-01

    loading remote from the crack-tip. In cases where the principal axes of the anisotropy are inclined to the plane of the crack it is found that the plastic zones as well as the stress and strain fields just around the blunted tip of the crack become non-symmetric. In these cases the peak strain...... on the blunted tip occurs off the center line of the crack, thus indicating that the crack may want to grow in a different direction. When the anisotropic axes are parallel to the crack symmetry is retained, but the plastic zones and the near-tip fields still differ from those predicted by standard isotropic...

  19. A Fast Guide Tube Position Estimation Algorithm for a Control Rod Support Pin Inspection Robot

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae C.; Jeon, Hyeong S.; Choi, Yu R.; Kim, Jae H. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2005-07-01

    The risk that PWR guide tube support pins will crack has increased the necessity for the development of inspection methods and equipment. A special remote-controlled manipulator has been widely used to inspect the guide tube support pins. We presented a matched filter algorithm for detecting the existence and estimating the position of the guide tube support pins. But, the matched filter algorithm requires numbers of complex floating point calculations for the 2-D FFT and therefore it can not be fitted in to the small-sized embedded processors. We proposed a new simplified method for estimating the position of the guide tube support pins. It uses most of the operations with integers. We ported the proposed method in intel's xscale processor running at 400 mhz. We used gnu C language in embedded linux operating system. We can calculate the algorithm at a rate of 20 frames/sec. in a 160x120 image size.

  20. A Versatile Inspection System for Pipe Structure Using Ultrasonic Waves Propagation Imager

    Science.gov (United States)

    Truong, T. C.; Lee, J. R.

    2015-07-01

    Pipe structure is vulnerable to many types of damage, such as flow-accelerated corrosion, crack, and in the case of multi-layers pipe, debonding damage. A versatile damage inspection system is needed, where it must be easily used for variety types of pipeline, must have the capability to detect many types of damage, as well as must be able to carry out inspection in the working condition of the pipe system. In this paper, we present the Ultrasonic Propagation Imager (UPI) that demonstrated to meet those demands. The UPI system consists of a high speed Q-switched laser, a high speed scanning mirror, a DAQ system, and a changeable sensing system depends on applications. Advanced signal processing using ultrasonic wavenumber imaging algorithm and energy mapping were applied for damage detection of the pipe structures.

  1. GB/T 21085-2007 Automotive Vehicle Certificate of Inspection

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    1.Background Automotive Vehicle Certificate of Inspection (hereinafter referred to certificate) is a statutory certificate for automotive vehicle registration in China and also an important content of consistency management of vehicle manufacturers.In order to strengthen the management of automotive vehicle manufacturers and their products,prevent stealing,smuggling and illegal assembling,crack down the illegal acts of forging and reselling and improve the efficiency of automotive vehicle registration,National Development and Reform Commission (NDRC) and MPS jointly put forward a solution that is to standardize the certificate and its content and build up information management system of certificates.The development of GB/T 21085-2007 Automotive Vehicle Certificate of Inspection was taken by the National Technical Committee of Auto Standardization (SAC/TC 114).

  2. Environmentally assisted cracking in LWR materials

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Chung, H.M.; Kassner, T.F.; Park, J.H.; Shack, W.J. [Argonne National Lab., IL (United States); Zhang, J.; Brust, F.W.; Dong, P. [Battelle Columbus Labs., Columbus, OH (United States)

    1998-03-01

    The effect of dissolved oxygen level on fatigue life of austenitic stainless steels is discussed and the results of a detailed study of the effect of the environment on the growth of cracks during fatigue initiation are presented. Initial test results are given for specimens irradiated in the Halden reactor. Impurities introduced by shielded metal arc welding that may affect susceptibility to stress corrosion cracking are described. Results of calculations of residual stresses in core shroud weldments are summarized. Crack growth rates of high-nickel alloys under cyclic loading with R ratios from 0.2--0.95 in water that contains a wide range of dissolved oxygen and hydrogen concentrations at 289 and 320 C are summarized.

  3. Fatigue, Wear and Cracking of Dental Materials

    Directory of Open Access Journals (Sweden)

    Traian Eugen Bolfa

    2015-07-01

    Full Text Available Evaluation of the method of failure and crack propagation in dental metals, ceramics and polymer composite materials associated with occlusal activity are associated with contact, twisting and sliding modes. Such loads can result in various combinations of damage due to fatigue and wear. In order to increase sustainability and longevity the dental materials must demonstrate sufficient strength to dynamic stresses. In the case of masticatory forces associated with high contact tensions, the contact area of the superficial layer is under a state of specialcomplex voltage. Variations in the material or the structure, impurities, scratches and voids can directly influence the structural integrity of the material and result in microscopic cracks. These cracks propagate under repeated cyclic loading leading to dental restoration failure.

  4. Inverse Crack Problems in Piezoelectric Solids

    Science.gov (United States)

    Sladek, Jan; Sladek, Vladimir; Zhang, Chuanzeng

    2010-05-01

    In the present paper, the meshless local Petrov-Galerkin (MLPG) method is applied to cracked piezoelectric solids under a stationary or transient dynamic load and unspecified electrical conditions on the crack surfaces. On the outer surface of the cracked solid the electrical boundary conditions are over-specified. The coupled governing partial differential equations are satisfied in a weak-form on small fictitious sub-domains. Nodal points are introduced and spread on the analyzed domain and each node is surrounded by a small circle for simplicity, but without loss of generality. The spatial variations of the displacements and the electric potential are approximated by the Moving Least-Squares (MLS) scheme. After performing the spatial integrations, a system of linear algebraic equations for unknown nodal values is obtained. Singular value decomposition (SVD) is applied to solve the ill-conditioned linear system of algebraic equations obtained from the local integral equations (LIEs) after the MLS approximation.

  5. Computer Simulations of the Fatigue Crack Propagation

    Directory of Open Access Journals (Sweden)

    A. Materna

    2000-01-01

    Full Text Available The following hypothesis for design of structures based on the damage tolerance philosophy is laid down: the perpendicular fatigue crack growth rate v in a certain point of a curved crack front is given by the local value of stress intensity factor per unit of nominal stress K' and the local triaxiality T which describes the constraint. The relationship v = f (K', T is supposed to be typical for a given loading spectrum and material. Such relationship for a 2024 Al alloy and the flight-simulation spectrum was derived from the fatigue test of the rectangular panel with the central hole and used for three-dimensional simulation of the corner fatigue crack propagation in the model of the wing spar flangeplate. Finite element and boundary element methods were used for these computations. The results of the simulation are in good agreement with the experiment.

  6. Crack initiation and crack growth behavior of carbon and low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Gavenda, D.J.; Luebbers, P.R.; Chopra, O.K. [Argonne National Lab., IL (United States). Energy Technology Div.

    1997-01-01

    Section III of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. These curves were based on tests of smooth polished specimens at room temperature in air. The effects of reactor coolant environments are not explicitly addressed by the Code design curves, but recent test data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be a factor of {approx}70 shorter than in air. Results of fatigue tests that examine the influence of reactor environment on crack imitation and crack growth of carbon and low-alloy steels are presented. Crack lengths as a function of fatigue cycles were determined in air by a surface replication technique, and in water by block loading that leaves marks on the fracture surface. Decreases in fatigue life of low-alloy steels in high-dissolved-oxygen (DO) water are primarily caused by the effects of environment during early stages of fatigue damage, i.e., growth of short cracks <100 {micro}m in depth. For crack sizes of >100 {micro}m, crack growth rates in high-DO water are higher than in air by one order of magnitude. The effects of LWR environments on growth of short cracks are discussed.

  7. Production of steam cracking feedstocks by mild cracking of plastic wastes

    Energy Technology Data Exchange (ETDEWEB)

    Angyal, Andras; Miskolczi, Norbert; Bartha, Laszlo; Tungler, Antal; Nagy, Lajos; Vida, Laszlo; Nagy, Gabor

    2010-11-15

    In this work the utility of new possible petrochemical feedstocks obtained by plastic waste cracking has been studied. The cracking process of polyethylene (PE), polyethylene-polypropylene (PEPP) and polyethylene-polystyrene (PEPS) has been carried out in a pilot scale tubular reactor. In this process mild reaction parameters has been applied, with the temperature of 530 C and the residence time of 15 min. The produced hydrocarbon fractions as light- and middle distillates were tested by using a laboratory steam cracking unit. It was concluded that the products of the mild cracking of plastic wastes could be applied as petrochemical feedstocks. Based on the analytical data it was determined that these liquid products contained in significant concentration (25-50 wt.%) of olefin hydrocarbons. Moreover the cracking of polystyrene containing raw material resulted in liquid products with significant amounts of aromatic hydrocarbons too. The steam cracking experiments proved that the products obtained by PE and PEPP cracking resulted in similar or better ethylene and propylene yields than the reference samples, however the aromatic content of PEPS products reduced the ethylene and propylene yields. (author)

  8. Dual Mode Sensing with Low-Profile Piezoelectric Thin Wafer Sensors for Steel Bridge Crack Detection and Diagnosis

    Directory of Open Access Journals (Sweden)

    Lingyu Yu

    2012-01-01

    Full Text Available Monitoring of fatigue cracking in steel bridges is of high interest to many bridge owners and agencies. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In this paper, we presented a dual mode sensing methodology integrating acoustic emission and ultrasonic wave inspection based on the use of low-profile piezoelectric wafer active sensors (PWAS. After introducing the research background and piezoelectric sensing principles, PWAS crack detection in passive acoustic emission mode is first presented. Their acoustic emission detection capability has been validated through both static and compact tension fatigue tests. With the use of coaxial cable wiring, PWAS AE signal quality has been improved. The active ultrasonic inspection is conducted by the damage index and wave imaging approach. The results in the paper show that such an integration of passive acoustic emission detection with active ultrasonic sensing is a technological leap forward from the current practice of periodic and subjective visual inspection and bridge management based primarily on history of past performance.

  9. Fast electromigration crack in nanoscale aluminum film

    Science.gov (United States)

    Emelyanov, O. A.; Ivanov, I. O.

    2014-08-01

    The current-induced breakage of 20 nm thin aluminum layers deposited onto capacitor grade polypropylene (PP) films is experimentally studied. Biexponential current pulses of different amplitude (10-15 A) and duration (0.1-1 μs) were applied to the samples. Breakage occurred after fast development of electromigrating ˜200 nm-wide cracks with initial propagation velocity of ˜1 m/s under a high current density of ˜1012 A/m2. The cracks stopped when their lengths reached 250-450 μm. This behavior is explained by the balance of electromigration and stress-induced atomic fluxes.

  10. Crack Sensing Scheme in Rail Tracking System

    Directory of Open Access Journals (Sweden)

    Ch. Muneendra Rao,

    2014-01-01

    Full Text Available A major share to the Indian economy is contributed by the commercial transport railway network. So, any problems of crack detection in railway network when encountered, may be dealt with a robust and cost effective solution, else, there may be a proportionate decrease in the nations economy. This paper attempts to provide a viable solution by discussing the technical details and design aspects. The discussion continues with the explanation of different criteria involved in choosing simple components like GPS module,PC,IR-photo diode based crack detector module, modeled for effective implementation in India.

  11. Fatigue crack growth under variable amplitude loading

    Science.gov (United States)

    Sidawi, Jihad A.

    1994-01-01

    Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.

  12. Multiple Gastrointestinal Complications of Crack Cocaine Abuse

    Directory of Open Access Journals (Sweden)

    Neal Carlin

    2014-01-01

    Full Text Available Cocaine and its alkaloid free base “crack-cocaine” have long since been substances of abuse. Drug abuse of cocaine via oral, inhalation, intravenous, and intranasal intake has famously been associated with a number of medical complications. Intestinal ischemia and perforation remain the most common manifestations of cocaine associated gastrointestinal disease and have historically been associated with oral intake of cocaine. Here we find a rare case of two relatively uncommon gastrointestinal complications of hemorrhage and pancreatitis presenting within a single admission in a chronic crack cocaine abuser.

  13. Computational defect review for actinic mask inspections

    Science.gov (United States)

    Morgan, Paul; Rost, Daniel; Price, Daniel; Corcoran, Noel; Satake, Masaki; Hu, Peter; Peng, Danping; Yonenaga, Dean; Tolani, Vikram

    2013-04-01

    As optical lithography continues to extend into low-k1 regime, resolution of mask patterns continues to diminish. The limitation of 1.35 NA posed by water-based lithography has led to the application of various resolution enhancement techniques (RET), for example, use of strong phase-shifting masks, aggressive OPC and sub-resolution assist features, customized illuminators, etc. The adoption of these RET techniques combined with the requirements to detect even smaller defects on masks due to increasing MEEF, poses considerable challenges for a mask inspection engineer. Inspecting masks under their actinic-aerial image conditions would detect defects that are more likely to print under those exposure conditions. However, this also makes reviewing such defects in their low-contrast aerial images very challenging. On the other hand, inspecting masks under higher resolution inspection optics would allow for better viewing of defects post-inspection. However, such inspections generally would also detect many more defects, including printable and nuisance, thereby making it difficult to judge which are of real concern for printability on wafer. Often, an inspection engineer may choose to use Aerial and/or high resolution inspection modes depending on where in the process flow the mask is and the specific device-layer characteristics of the mask. Hence, a comprehensive approach is needed in handling defects both post-aerial and post-high resolution inspections. This analysis system is designed for the Applied Materials Aera™ mask inspection platform, all data reported was collected using the Aera.

  14. Restaurant inspection frequency and food safety compliance.

    Science.gov (United States)

    Newbold, K Bruce; McKeary, Marie; Hart, Robert; Hall, Robert

    2008-11-01

    Although food premises are regularly inspected, little information is available on the effect of inspections on compliance records, particularly with respect to the impact of the frequency of inspection on compliance. The following presents the outcome of a study designed to assess the impact of increased inspection frequency on compliance measures in Hamilton, Ontario, in the absence of any other changes to food handler/safety programs or legislation. High-risk food inspection premises were randomly assigned three, four, or five inspections per year. Results indicate that no statistical difference existed in outcome measures based on frequency of inspection. When premises were grouped based on the average time between inspections, premises with greater time between inspections scored better compliance measures relative to premises that were inspected more frequently. The study was also unique for the level of consultation and collaboration sought from the public health inspectors (PHIs) assigned to the Food Safety Program. Their knowledge and experience with respect to the critical variables associated with compliance were a complementary component to the literature review conducted by the research team.

  15. Creep and Creep-Fatigue Crack Growth at Structural Discontinuities and Welds

    Energy Technology Data Exchange (ETDEWEB)

    Dr. F. W. Brust; Dr. G. M. Wilkowski; Dr. P. Krishnaswamy; Mr. Keith Wichman

    2010-01-27

    The subsection ASME NH high temperature design procedure does not admit crack-like defects into the structural components. The US NRC identified the lack of treatment of crack growth within NH as a limitation of the code and thus this effort was undertaken. This effort is broken into two parts. Part 1, summarized here, involved examining all high temperature creep-fatigue crack growth codes being used today and from these, the task objective was to choose a methodology that is appropriate for possible implementation within NH. The second part of this task, which has just started, is to develop design rules for possible implementation within NH. This second part is a challenge since all codes require step-by-step analysis procedures to be undertaken in order to assess the crack growth and life of the component. Simple rules for design do not exist in any code at present. The codes examined in this effort included R5, RCC-MR (A16), BS 7910, API 579, and ATK (and some lesser known codes). There are several reasons that the capability for assessing cracks in high temperature nuclear components is desirable. These include: (1) Some components that are part of GEN IV reactors may have geometries that have sharp corners - which are essentially cracks. Design of these components within the traditional ASME NH procedure is quite challenging. It is natural to ensure adequate life design by modeling these features as cracks within a creep-fatigue crack growth procedure. (2) Workmanship flaws in welds sometimes occur and are accepted in some ASME code sections. It can be convenient to consider these as flaws when making a design life assessment. (3) Non-destructive Evaluation (NDE) and inspection methods after fabrication are limited in the size of the crack or flaw that can be detected. It is often convenient to perform a life assessment using a flaw of a size that represents the maximum size that can elude detection. (4) Flaws that are observed using in-service detection

  16. Steam generator tube inspection in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, Shigetaka [Japan Power Engineering and Inspection Corp., Tokyo (Japan)

    1997-02-01

    Steam generator tube inspection was first carried out in 1971 at Mihama Unit-1 that is first PWR plant in Japan, when the plant was brought into the first annual inspection. At that time, inspection was made on sampling basis, and only bobbin coil probe was used. After experiencing various kinds of tube degradations, inspection method was changed from sampling to all number of tubes, and various kinds of probes were used to get higher detectability of flaw. At present, it is required that all the tubes shall be inspected in their full length at each annual inspection using standard bobbin coil probe, and some special probes for certain plants that have susceptibility of occurrence of flaw. Sleeve repaired portion is included in this inspection. As a result of analyses of eddy current testing data, all indications that have been evaluated to be 20% wall thickness or deeper shall be repaired by either plugging or sleeving, where flaw morphology is to be a wastage or wear. Other types of flaw such as IGA/SCC are not allowed to be left inservice when those indications are detected. These inspections are performed according to inspection procedures that are approved by regulatory authority. Actual inspections are witnessed by the Japan Power engineering and inspection corporation (JAPEIC)`s inspectors during data acquisition and analysis, and they issue inspection report to authority for review and approval. It is achieved high safety performance of steam generator through this method of inspections, however. some tube leakage problems were experienced in the past. To prevent recurrence of such events, government is conducting development and verification test program for new eddy current testing technology.

  17. Matrix cracking of fiber-reinforced ceramic composites in shear

    Science.gov (United States)

    Rajan, Varun P.; Zok, Frank W.

    2014-12-01

    The mechanics of cracking in fiber-reinforced ceramic matrix composites (CMCs) under general loadings remains incomplete. The present paper addresses one outstanding aspect of this problem: the development of matrix cracks in unidirectional plies under shear loading. To this end, we develop a model based on potential energy differences upstream and downstream of a fully bridged steady-state matrix crack. Through a combination of analytical solutions and finite element simulations of the constituent stresses before and after cracking, we identify the dominant stress components that drive crack growth. We show that, when the axial slip lengths are much larger than the fiber diameter and when interfacial slip precedes cracking, the shear stresses in the constituents are largely unaffected by the presence of the crack; the changes that do occur are confined to a 'core' region within a distance of about one fiber diameter from the crack plane. Instead, the driving force for crack growth derives mainly from the axial stresses-tensile in the fibers and compressive in the matrix-that arise upon cracking. These stresses are well-approximated by solutions based on shear-lag analysis. Combining these solutions with the governing equation for crack growth yields an analytical estimate of the critical shear stress for matrix cracking. An analogous approach is used in deriving the critical stresses needed for matrix cracking under arbitrary in-plane loadings. The applicability of these results to cross-ply CMC laminates is briefly discussed.

  18. THERMAL FRACTURE OF FUNCTIONALLY GRADED PLATE WITH PARALLEL SURFACE CRACKS

    Institute of Scientific and Technical Information of China (English)

    Yuezhong Feng; Zhihe Jin

    2009-01-01

    This work examines the fracture behavior of a functionally graded material (FGM) plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors (TSIFs) at the tips of long and short cracks are calculated using a singular integral equation technique. The critical thermal shock △T_c that causes crack initiation is calculated using a stress intensity factor criterion. Numerical examples of TSIFs and △T_c for an Al_2O_3/Si_3N_4 FGM plate are presented to illustrate the effects of thermal property gradation, crack spacing and crack length ratio on the TSIFs and △T_c. It is found that for a given crack length ratio, the TSIFs at the tips of both long and short cracks can be reduced significantly and △T_c can be enhanced by introducing appropriate material gradation. The TSIFs also decrease dramatically with a decrease in crack spacing. The TSIF at the tips of short cracks may be higher than that for the long cracks under certain crack geometry conditions. Hence, the short cracks instead of long cracks may first start to grow under the thermal shock loading.

  19. POTENTIAL FOR STRESS CORROSION CRACKING OF A537 CARBON STEEL NUCLEAR WASTE TANKS CONTAINING HIGHLY CAUSTIC SOLUTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Lam, P.; Stripling, C.; Fisher, D.; Elder, J.

    2010-04-26

    The evaporator recycle streams of nuclear waste tanks may contain waste in a chemistry and temperature regime that exceeds the current corrosion control program, which imposes temperature limits to mitigate caustic stress corrosion cracking (CSCC). A review of the recent service history found that two of these A537 carbon steel tanks were operated in highly concentrated hydroxide solution at high temperature. Visual inspections, experimental testing, and a review of the tank service history have shown that CSCC has occurred in uncooled/un-stress relieved tanks of similar construction. Therefore, it appears that the efficacy of stress relief of welding residual stress is the primary corrosion-limiting mechanism. The objective of this experimental program is to test A537 carbon steel small scale welded U-bend specimens and large welded plates (30.48 x 30.38 x 2.54 cm) in a caustic solution with upper bound chemistry (12 M hydroxide and 1 M each of nitrate, nitrite, and aluminate) and temperature (125 C). These conditions simulate worst-case situations in these nuclear waste tanks. Both as-welded and stress-relieved specimens have been tested. No evidence of stress corrosion cracking was found in the U-bend specimens after 21 days of testing. The large plate test was completed after 12 weeks of immersion in a similar solution at 125 C except that the aluminate concentration was reduced to 0.3 M. Visual inspection of the plate revealed that stress corrosion cracking had not initiated from the machined crack tips in the weld or in the heat affected zone. NDE ultrasonic testing also confirmed subsurface cracking did not occur. Based on these results, it can be concluded that the environmental condition of these tests was unable to develop stress corrosion cracking within the test periods for the small welded U-bends and for the large plates, which were welded with an identical procedure as used in the construction of the actual nuclear waste tanks in the 1960s. The

  20. Automated eddy current inspection of Space Shuttle APU turbine wheel blades

    Science.gov (United States)

    Fisher, Jay L.; Rowland, Stephen N.; Stolte, Jeffrey S.; Salkowski, Charles

    1991-01-01

    An automated inspection system based on eddy current testing (ET) techniques has been developed to inspect turbine wheel blades on the APU used in NASA's Space Transportation system. The APU is a hydrazine-powered gas turbine with a 15-cm diameter Rene 41 turbine wheel, which has 123 first-stage blades and 123 second-stage blades. The flaw detection capability of the ET system is verified through comparison with fluorescent penetrant test results. Results of the comparison indicate that ET is capable of inspecting surfaces with very restrictive geometries. The ET capability requires development of probes with extremely small coils to allow inspection within 0.4 mm of the blade root and the leading and trailing edges of the blade and within a height restriction of less than 1 mm. The color 2D presentation of the ET data provided crack-growth pattern and length information similar to those found with visual techniques. It also provided visual clues to minimize geometry effects such as generated from blade edges, a neighoring blade, and changes in the blade thickness.

  1. Coke drums inspection and evaluation using stress and strain analysis techniques

    Energy Technology Data Exchange (ETDEWEB)

    Haraguchi, Marcio Issamu [Tricom Tecnologia e Servicos de Manutencao Industrial Ltda., Piquete, SP (Brazil); Samman, Mahmod [Houston Engineering Solutions, Houston, TX (United States); Tinoco, Ediberto Bastos; Marangone, Fabio de Castro; Silva, Hezio Rosa da; Barcelos, Gustavo de Carvalho [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2012-07-01

    Coke drums deform due to a complex combination of mechanical and thermal cyclic stresses. Bulges have progressive behavior and represent the main maintenance problem related to these drums. Bulge failure typically result in through-wall cracks, leaks, and sometimes fires. Such failures generally do not represent a great risk to personnel. Repairs needed to maintain reliability of these vessels might require extensive interruption to operation which in turn considerably impacts the profitability of the unit. Therefore the condition, progression and severity of these bulges should be closely monitored. Coke drums can be inspected during turnaround with 3D Laser Scanning and Remote Visual Inspection (RVI) tools, resulting in a detailed dimensional and visual evaluation of the internal surface. A typical project has some goals: inspect the equipment to generate maintenance or inspection recommendations, comparison with previous results and baseline data. Until recently, coke drum structural analysis has been traditionally performed analyzing Stress Concentration Factors (SCF) thought Finite Element Analysis methods; however this technique has some serious technical and practical limitations. To avoid these shortcomings, the new strain analysis technique PSI (Plastic Strain Index) was developed. This method which is based on API 579/ ASME FFS standard failure limit represents the state of the art of coke drum bulging severity assessment has an excellent correlation with failure history. (author)

  2. Development and field validation of advanced array probes for steam generator inspection

    Energy Technology Data Exchange (ETDEWEB)

    Dodd, C.V.; Pate, J.R. [Oak Ridge National Lab., TN (United States)

    1995-04-01

    The aging of the steam generators at the nation`s nuclear power plants has led to the appearance of new forms of degradation in steam generator tubes and an increase in the frequency of forced outages due to major tube leak events. The eddy-current techniques currently being used for the inspection of steam generator tubing are no longer adequate to ensure that flaws will be detected before they lead to a shutdown of the plant. To meet the need for a fast and reliable method of inspection, ORNL has designed a 16-coil eddy-current array probe which combines an inspection speed similar to that of the bobbin coil with a sensitivity to cracks of any orientation similar to the rotating pancake coil. In addition, neural network and least square methods have been developed for the automatic analysis of the data acquired with the new probes. The probes and analysis software have been tested at two working steam generators where we have found an increase in the signal-to-noise ratio of a factor of five an increase in the inspection speed of a factor of 75 over the rotating pancake coil which maintaining similar detection and characterization capabilities.

  3. A study on in-pipe inspection mobile robots, 3; Basic strategy of inspection path planning for inspection mobile robots

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Toshio (Nagoya Univ. (Japan). Faculty of Engineering); Hosokai, Hidemi; Uemura, Masahiro

    1990-01-01

    This paper deals with inspection path planning for in-pipe inspection mobile robots which have the capability of moving through complicated pipeline networks. It is imperative that the robot systems have an inspection path planning system for such networks for their reasonable and rational operation, controlled by themselves or by the operators. The planning mainly requires two projects: the selection of the place to put the robot in or out, and the generation of the paths in the networks. This system provides the for complicated problems with plural inspection points using a basic strategy of systematically producing patterns and dividing partial problems of simple searches based on rules. (author).

  4. STIP-V Inspection Report

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, Tarik A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Quintana, Matthew Estevan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Romero, Tobias J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-25

    The Los Alamos National Laboratory samples from the STIP-­V irradiation arrived at LANL on December 24th, 2014, after some delays en-­route from the Paul Scherrer Institute (PSI). The samples were transferred to the Wing 9 hot cells in early January and unpacked and inspected in cell with the Hirox Digital Optical microscope. The complete sample matrix of LANL specimens can be seen in table one. Due to space and budgetary issues, no TEM samples were sent back to LANL. Additionally the HT9-­WO, HT9-­Shot and T91-Shot samples are actually bend bars, rather than the tensile samples listed.

  5. Quality Inspection of Printed Texts

    DEFF Research Database (Denmark)

    Pedersen, Jesper Ballisager; Nasrollahi, Kamal; Moeslund, Thomas B.

    2016-01-01

    Inspecting the quality of printed texts has its own importance in many industrial applications. To do so, this paper proposes a grading system which evaluates the performance of the printing task using some quality measures for each character and symbols. The purpose of these grading system is two......-folded: for costumers of the printing and verification system, the overall grade used to verify if the text is of sufficient quality, while for printer's manufacturer, the detailed character/symbols grades and quality measurements are used for the improvement and optimization of the printing task. The proposed system...

  6. Instant Adobe Edge Inspect starter

    CERN Document Server

    Khan, Joseph

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This easy-to-understand Starter guide will get you up to speed with Adobe Edge Inspect quickly and with little effort.This book is for frontend web developers and designers who are developing and testing web applications targeted for mobile browsers. It's assumed that you have a basic understanding of creating web applications using HTML, CSS, and JavaScript, as well as being familiar with running web pages from local HTTP servers. Readers are a

  7. Technical justification for ASME code section xi crack detection by visual examination

    Energy Technology Data Exchange (ETDEWEB)

    Nickell, R.E. [Applied Science and Technology, Poway, CA (United States); Rashid, Y.R. [ANATECH Corp., San Diego (United States)

    2001-07-01

    A critical technical element of nuclear power plant license renewal in the United States is the demonstration that the effects of aging do not compromise the intended safety function(s) of a system, structure, or component during the extended term of operation. The demonstration may take either of two forms. First, it can be shown that the design basis for the system, structure, or component is sufficiently robust that the aging effects have been insignificant through the current license term, and will continue to be insignificant through the extended term. Alternatively, it can be shown that, while the aging effects may be potentially significant, those effects can be managed and functionality maintained by defined programmatic activities during the extended term of operation. The first of the two approaches is generally provided by the construction basis, such as construction in accordance with the ASME Code Section III and other consensus codes and standards. The second of the two approaches is often provided by periodic inservice inspection and testing, in accordance with the ASME Code Section XI. The purpose of the ASME Section XI inspections and tests is to assure that systems, components, and structures are fit for continued service until the next scheduled inspection or test. The purpose of this paper is to document the effectiveness of the current ASME Code Section XI visual examination procedures in detecting the effects of aging for systems, structures, and components that are tolerant of mature cracks. (author)

  8. Crack Growth along Interfaces in Porous Ceramic Layers

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Horsewell, Andy

    2001-01-01

    Crack growth along porous ceramic layers was studied experimentally. Double cantilever beam sandwich specimens were loaded with pure bending moments to obtain stable crack growth. The experiments were conducted in an environmental scanning electron microscope enabling in situ observations...

  9. A MOVING CRACK IN A NONHOMOGENEOUS MATERIAL STRIP

    Institute of Scientific and Technical Information of China (English)

    Wang Baolin; Han Jiecai

    2006-01-01

    This paper considers an anti-plane moving crack in a nonhomogencous material strip of finite thickness. The shear modulus and the mass density of the strip are considered for a class of functional forms for which the equilibrium equation has analytical solutions. The problem is solved by means of the singular integral equation technique. The stress field near the crack tip is obtained. The results are plotted to show the effect of the material non-homogeneity and crack moving velocity on the crack tip field. Crack bifurcation behaviour is also discussed. The paper points out that use of an appropriate fracture criterion is essential for studying the stability of a moving crack in nonhomogeneous materials. The prediction whether the unstable crack growth will be enhanced or retarded is strongly dependent on the type of the fracture criterion used. is a suitable failure criterion for moving cracks in nonhomogeneous materials.

  10. Partial discharge-induced crack growth in dielectric materials

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Partial discharge(PD) of an air-filled semi-permeable crack in a dielectric material is studied based on the streamer-type discharge mechanism to explore the effects of applied mechanical-electric fields on crack growth.Within the frame of two-dimensional deformation,the electric field inside the crack is first derived by taking the crack deformation into account.Then,the effects of electric field before PD are discussed through considering the contribution of the induced electric field inside the deformed crack space to the total energy release rate.Finally,PD and its effects on crack growth are investigated.It is found that:(1) before PD,the applied electric field always retards crack growth;(2) during PD,the applied electric field can induce crack growth in dielectric materials.

  11. Cracking the Genetic Code | NIH MedlinePlus the Magazine

    Science.gov (United States)

    ... this page please turn Javascript on. Cracking the Genetic Code, From NIH Director Dr. Francis S. Collins Past Issues / ... moment in science in 2000: Cracking of the genetic code raised the prospect of pinpointing the root causes ...

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

    Science.gov (United States)

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

    2016-04-01

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

  13. Fatigue crack shape prediction based on vertex singularity

    Directory of Open Access Journals (Sweden)

    Hutař P.

    2008-11-01

    Full Text Available Due to the existence of vertex singularity at the point where the crack intersects the free surface, stress distribution around the crack tip and the type of the singularity is changed. In the interior of the specimen the classical singular behaviour of the crack is dominant and can be described using analytic equations. Contrary to this, at the free surface or in the boundary layer close to free surface the vertex singularity is significant. The influence of vertex singularity on crack behaviour and a crack shape for a three-dimensional structure is described in this paper. The results presented make it possible to estimate fatigue crack growth rate and crack shape using the concept of the generalized stress intensity factor. The estimated fatigue crack shape can help to provide a more reliable estimation of the fatigue life of the structures considered.

  14. Pharmacy inspections: constitutional without a warrant?

    Science.gov (United States)

    Simonsmeier, L M

    1979-01-01

    The implications of the 1978 U.S. Supreme Court decision in Marshall vs. Barlow's, Inc., regarding warrantless inspections of pharmacies are discussed. Reviewed are the Fourth Amendment to the U.S. Constitution, related U.S. Supreme Court decisions (Camera vs. Municipal Court and See vs. City of Seattle), new "probable cause" standards, and exceptions to the requirement of warrants for inspections. The effect of the Barlow's case with specific reference to FDA, DEA and state board of pharmacy inspections is discussed. Although the Barlow's case has provided further case law in the area of administrative inspections, each case still requires individual resolution. DEA inspections are well delineated by statute and regulation. Under the "licensing exceptions," warrantless pharmacy inspections by the FDA and by boards of pharmacy are probably permissible.

  15. Backlit Keyboard Inspection Using Machine Vision

    Institute of Scientific and Technical Information of China (English)

    Der-Baau Perng; Hsiao-Wei Liu; Po-An Chen

    2015-01-01

    Abstract⎯A robust system for backlit keyboard inspection is revealed. The backlit keyboard not only has changeable diverse colors but also has the laser marking keys. The keys on the keyboard can be divided into regions of function keys, normal keys, and number keys. However, there might have some types of defects: incorrect illuminating area, non-uniform illumination of specified inspection region (IR), and incorrect luminance and intensity of individual key. Since the illumination features of backlit keyboard are too complex to inspect for human inspector in the production line, an auto-mated inspection system for the backlit keyboard is proposed in this paper. The system was designed into the operation module and inspection module. A set of image processing methods were developed for these defects inspection. Some experimental results demonstrate the robustness and effectiveness of the proposed system.

  16. User interface inspection methods a user-centered design method

    CERN Document Server

    Wilson, Chauncey

    2014-01-01

    User Interface Inspection Methods succinctly covers five inspection methods: heuristic evaluation, perspective-based user interface inspection, cognitive walkthrough, pluralistic walkthrough, and formal usability inspections. Heuristic evaluation is perhaps the best-known inspection method, requiring a group of evaluators to review a product against a set of general principles. The perspective-based user interface inspection is based on the principle that different perspectives will find different problems in a user interface. In the related persona-based inspection, colleagues assume the

  17. A study on detection of micro-cracks in the dissimilar metal weld through ultrasound infrared thermography

    Science.gov (United States)

    Park, Heesang; Choi, Manyong; Park, Jeounghak; Kim, Wontae

    2014-01-01

    This study was conducted to investigate a possibility of detecting stress corrosion crack defects in a pipe welded with dissimilar metals (STS304 and SA106 Gr. b) through infrared ultrasound thermography and lock-in phase method. The ultrasound generator was set as 250 W in output and 19.8 kHz in frequency. With experiment results, this study could detect, cracks located inside the dissimilar metal weld pipe through lock-in infrared thermography and compare thermography images obtained from both the inside and the outside when the ultrasound vibration was applied to the outer part of the pipe. Besides, after cutting off the pipe in the axial direction, this study conducted PT inspection. As a result, it was found there existed more than a single crack in a certain range inside the pipe, which made hot spots appear in a wide range on the thermography image. Moreover, through ultrasound infrared thermography and lock-in phase method this study verified the possibility of detecting micro-sized shattered cracks through ultrasound thermography, which were not easy to detect with the existing techniques.

  18. Crack Detection for Aerospace Quality Spur Gears

    Science.gov (United States)

    Decker, Harry J.

    2002-01-01

    Health and Usage Monitoring System research and development involves analysis of the vibration signals produced by a gearbox throughout its life. There are two major advantages of knowing the actual lifetime of a gearbox component: safety and cost. In this report, a technique is proposed to help extract the critical data and present it in a manner that can be easy to understand. The key feature of the technique is to make it independent of speed, torque and prior history for localized, single tooth damage such as gear cracks. This extraction technique is demonstrated on two sets of digitized vibration data from cracked spur gears. Standard vibration diagnostic parameters are calculated and presented for comparison. Several new detection algorithms are also presented. The results of this study indicate that crack detection methods examined are not robust or repeatable. The proposed techniques provide a limited improvement to existing diagnostic parameters. Current techniques show that the cracks progressed at a much faster rate than anticipated which reduced available time for detection.

  19. Fatigue crack growth in Aluminium Alloys

    NARCIS (Netherlands)

    Van Kranenburg, C.

    2010-01-01

    Fatigue is a gradual process of local strength reduction. It is a phenomenon of damage accumulation at stress concentrations caused by fluctuating stresses and/or strains. In metals this results in microscopic cracks. These will start to grow under continued cyclic loading until final failure occurs

  20. Crack Propagation in Compressor Rotor Blade

    Science.gov (United States)

    2012-08-01

    by local Public Affairs Office) 13. SUPPLEMENTARY NOTES 14. ABSTRACT Turbomachine blading crack propagation and initiations are one of...the most important problems. Design, operation and modernization of the contemporary turbomachines are impossible without a detailed numerical and...Rao, J. S., Turbine Blade Life Estimation, Narosa Publishing House, (2000). Rao, J. S., Narayan, R. and Ranjith, M. C., Lifing of Turbomachine

  1. Environmentally assisted cracking in light water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Chung, H.M.; Gruber, E.E. [and others

    1996-07-01

    This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from April 1995 to December 1995. Topics that have been investigated include fatigue of carbon and low-alloy steel used in reactor piping and pressure vessels, EAC of Alloy 600 and 690, and irradiation-assisted stress corrosion cracking (IASCC) of Type 304 SS. Fatigue tests were conducted on ferritic steels in water that contained various concentrations of dissolved oxygen (DO) to determine whether a slow strain rate applied during different portions of a tensile-loading cycle are equally effective in decreasing fatigue life. Crack-growth-rate tests were conducted on compact-tension specimens from several heats of Alloys 600 and 690 in simulated LWR environments. Effects of fluoride-ion contamination on susceptibility to intergranular cracking of high- and commercial- purity Type 304 SS specimens from control-tensile tests at 288 degrees Centigrade. Microchemical changes in the specimens were studied by Auger electron spectroscopy and scanning electron microscopy to determine whether trace impurity elements may contribute to IASCC of these materials.

  2. Stress Corrosion Cracking of Pipeline Steels

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper provides a review of the differences between high pH and near-neutral pH stress corrosion cracking ofpipeline steels, influencing factors, and mechanisms. The characteristics and historical information on both forms ofSCC are discussed. The prospect for research in the future is also presented.

  3. Pregnant crack addicts in a psychiatric unit

    Directory of Open Access Journals (Sweden)

    Gabriela de Moraes Costa

    2012-01-01

    Full Text Available OBJECTIVE: In this study we aim to characterize a sample of 85 pregnant crack addicts admitted for detoxification in a psychiatric inpatient unit. METHOD: Cross-sectional study. Sociodemographic, clinical, obstetric and lifestyle information were evaluated. RESULTS: Age of onset for crack use varied from 11 to 35 years (median = 21. Approximately 25% of the patients smoked more than 20 crack rocks in a typical day of use (median = 10; min-max = 1-100. Tobacco (89.4%, alcohol (63.5% and marijuana (51.8% were the drugs other than crack most currently used. Robbery was reported by 32 patients (41.2%, imprisonment experience by 21 (24.7%, trade of sex for money/drugs by 38 (44.7%, home desertion by 33 (38.8%; 15.3% were positive for HIV, 5.9% for HCV, 1.2% for HBV and 8.2% for syphilis. After discharge from the psychiatric unit, only 25% of the sample followed the proposed treatment in the chemical dependency outpatient service. CONCLUSION: Greater risky behaviors for STD, as well as high rates of maternal HIV and Syphilis were found. Moreover, the high rates of concurrent use of other drugs and involvement in illegal activities contribute to show their chaotic lifestyles. Prevention and intervention programs need to be developed to address the multifactorial nature of this problem.

  4. SURFACING ELECTRODE WITH CRACKING RESISTANCE AND WEARABILITY

    Institute of Scientific and Technical Information of China (English)

    Yang Shanglei; Lu Xueqin; Lou Songnian; Zou Zengda

    2005-01-01

    A new surfacing electrode is developed with cracking resistance and wearability based on high microhardness of TiC and VC, carbides of Ti and V are formed in deposited metal by means of high temperature arc metallurgic reaction. The results show the hardness of surfacing metal increases with the increase of ferrotitanium (Fe-Ti), ferrovanadium (Fe-V) and graphite in the coat. However,when graphite reaches the volume fraction of 11%, the hardness reaches its peak value, and when beyond 11%, the hardness falls off. As Fe-Ti, Fe-V and graphite increase, the cracking resistance of deposited metal and usability of electrode declines. Carbides are dispersedly distributed in the matrix structure. The matrix microstructure of deposited metal is lath martensite. Carbides present irregular block. When using the researched surfacing electrode to continue weld with non-preheated, no seeable crack or only a few micro-cracks can be observed in the surface of deposited metal. The hardness is above 60 HRC. The wear resistance is better than that of EDZCr-C-15.

  5. The Lead Crack Fatigue Lifting Framework

    Science.gov (United States)

    2010-04-01

    fracture properties of high strength aluminium and titanium alloys. ____________________ ________________________________________________ Russel...and the fatigue crack growth properties of high strength aluminium and titanium alloys. Russell and Simon have also collaborated on a chapter on...forms of machining damage (scratches, grooves, burrs, small tears and nicks); etch pits from surface treatments ( pickling , anodising); porosity

  6. 3D characterisation of RCF crack networks

    Directory of Open Access Journals (Sweden)

    Ahlström Johan

    2014-06-01

    Full Text Available Rolling contact fatigue (RCF damage is becoming more frequent with increased traffic and loading conditions in the railway industry. Defects which are characterized by a two-lobe darkened surface and a V-shaped surface-breaking crack are often so-called squats. The origination and propagation of squats in railway rails is the topic of many recent studies; the associated crack networks develop with complicated geometry near the surface of rails that is difficult to characterise using most non-destructive methods. The cracks can be examined with repeated metallographic sectioning, but the process is time-consuming and destructive. In order to reduce time, as well as information and material loss, high-resolution and high-energy X-ray imaging of railway rails was done in the current study. Combining the exposures from a range of angles using image analysis, a 3D representation of the complex crack network is achieved. The latter was complemented with metallographic sectioning to determine the accuracy of prediction of the geometrical reconstruction.

  7. Repairing Hidden Cracks in Coolant Tubes

    Science.gov (United States)

    Mills, R. C., Sr.; Duesberg, J.

    1984-01-01

    Repair technique closes leaks in tubes or conduits where access limited to wall opposite crack. Technique applicable to any tubular assembly where tubes bundled together or bonded to supporting shell, such as in heat exchangers. Procedure provides structural support to area failed and uninterrupted flow without significantly altering heat-transfer profile.

  8. Instantaneous crack detection using dual PZT transducers

    Science.gov (United States)

    Kim, Seung Bum; Sohn, Hoon

    2008-03-01

    A new guided wave based nondestructive testing (NDT) technique is developed to detect crack damage in metallic plates commonly used in aircraft without using prior baseline data or a predetermined decision boundary. In conventional guided wave based techniques, damage is often identified by comparing the "current" data obtained from a potentially damaged condition of a structure with the "past" baseline data collected at the pristine condition of the structure. However, it has been reported that this type of pattern comparison with the baseline data can lead to increased false alarms due to its susceptibility to varying operational and environmental conditions of the structure. In order to tackle this issue, a reference-free damage detection technique is previously developed using two pairs of collocated lead zirconate titanate transducers (PZTs) placed on both sides of a plate. In this study, this reference-free technique is further advanced so that the PZT transducers can be placed only on one side of the specimen. Crack formation creates Lamb wave mode conversion due to a sudden change in the thickness of the structure. Then, the proposed technique instantly detects the appearance of the crack by extracting this mode conversion from the measured Lamb waves. This study suggests a reference-free statistical approach that enables damage classification using only the current data set. Numerical and experimental results are presented to demonstrate the applicability of the proposed technique to instantaneous crack detection.

  9. Durability of cracked fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Nielsen, Laila

    1997-01-01

    (capillary water uptake) is used, involving an in-situ method and a laboratory method. Three different concrete qualities as well as steel fibres (ZP) and polypropylene fibres (PP) are used. Results of the durability tests on cracked FRC-beams are compared to results for uncracked FRC-beams and beams without...

  10. 46 CFR 59.10-5 - Cracks.

    Science.gov (United States)

    2010-10-01

    ... does not exceed 12 inches in length and after completion the weld is stress-relieved. Cracks in... the root of the weld shall be chipped or ground out to insure a clean surface of the originally... CFR 59.01-2). For thicknesses exceeding three-fourths inch, suitable U grooves should be employed....

  11. Fluid catalytic cracking : feedstocks and reaction mechanism

    NARCIS (Netherlands)

    Dupain, X.

    2006-01-01

    The Fluid Catalytic Cracking (FCC) process is one of the key units in a modern refinery. Traditionally, its design is primarily aimed for the production of gasoline from heavy oil fractions, but as co-products also diesel blends and valuable gasses (e.g. propene and butenes) are formed in

  12. Arc termination cracks in Inconel 718 and Incoloy 903

    Science.gov (United States)

    Bayless, E.; Mccaig, J.; Poorman, R.

    1978-01-01

    The welding of the nickel base, heat resistant alloys that are used extensively for welded Shuttle engine components revealed solidification cracking characteristics at weld termination points. If not detected and removed, these crater cracks may cause costly component failure. To better understand this characteristic, welding termination techniques were studied and methods developed to eliminate crater cracks. It was determined that weld termination solidification cracking can be eliminated by controlled decrease of welding current, welding voltage, wire feed, and travel speed.

  13. Analysis of Multiple Cracks in an Infinite Functionally Graded Plate

    Science.gov (United States)

    Shbeeb, N. I.; Binienda, W. K.; Kreider, K. L.

    1999-01-01

    A general methodology was constructed to develop the fundamental solution for a crack embedded in an infinite non-homogeneous material in which the shear modulus varies exponentially with the y coordinate. The fundamental solution was used to generate a solution to fully interactive multiple crack problems for stress intensity factors and strain energy release rates. Parametric studies were conducted for two crack configurations. The model displayed sensitivity to crack distance, relative angular orientation, and to the coefficient of nonhomogeneity.

  14. Onset of Propagation of Planar Cracks in Heterogeneous Media

    OpenAIRE

    Ramanathan, Sharad; Fisher, Daniel S.

    1997-01-01

    The dynamics of planar crack fronts in hetergeneous media near the critical load for onset of crack motion are investigated both analytically and by numerical simulations. Elasticity of the solid leads to long range stress transfer along the crack front which is non-monotonic in time due to the elastic waves in the medium. In the quasistatic limit with instantaneous stress transfer, the crack front exhibits dynamic critical phenomenon, with a second order like transition from a pinned to a mo...

  15. Recommendations of the MRP-139: Inspection of Welds dissimilar in Nozzles PWR reactor vessel in Spain; Recomendaciones del MRP-139: Inspeccion de soldaduras disimilares en Vasijas de Reactor en Espana

    Energy Technology Data Exchange (ETDEWEB)

    Gadea, J. R.; Willke, A.; Regidor, J. J.; Tecnatom, S. A.

    2010-07-01

    The guide EPRI MRP-139, which provides the way forward for the inspection and evaluation of dissimilar butt welds, the primary system of PWR reactors, indicating the type of nondestructive testing to be done in these areas, based on discovered several cases of default in lnconel alloys 600 and 182 in American and European plants. The phenomenon of cracking.

  16. CRACK2. Modelling calcium carbonate deposition from bicarbonate solutions in cracks in concrete

    DEFF Research Database (Denmark)

    Brodersen, Knud Erik

    2003-01-01

    The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description ofthe model. Hydroxyl ions are transported...... by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. Thecementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide...... dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migratingions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack...

  17. Computer vision technology in log volume inspection

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Log volume inspection is very important in forestry research and paper making engineering. This paper proposed a novel approach based on computer vision technology to cope with log volume inspection. The needed hardware system was analyzed and the details of the inspection algorithms were given. A fuzzy entropy based on image enhancement algorithm was presented for enhancing the image of the cross-section of log. In many practical applications the cross-section is often partially invisible, and this is the major obstacle for correct inspection. To solve this problem, a robust Hausdorff distance method was proposed to recover the whole cross-section. Experiment results showed that this method was efficient.

  18. 33 CFR 127.403 - Inspections.

    Science.gov (United States)

    2010-07-01

    ...) WATERFRONT FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied Natural Gas Maintenance § 127.403 Inspections. The operator...

  19. Non-Destructive Inspection Lab (NDI)

    Data.gov (United States)

    Federal Laboratory Consortium — The NDI specializes in applied research, development and performance of nondestructive inspection procedures (flourescent penetrant, magnetic particle, ultrasonics,...

  20. 14 CFR 91.409 - Inspections.

    Science.gov (United States)

    2010-01-01

    ... procedures manual available and readily understandable to pilot and maintenance personnel containing, in... the name and address of the person responsible for scheduling the inspections required by the...