Science.gov

Sample records for acoustic emission testing

  1. Acoustic emission from composite materials. [nondestructive tests

    NASA Technical Reports Server (NTRS)

    Visconti, I. C.; Teti, R.

    1979-01-01

    The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique particularly well suited for the study of propagating cracks. Experiments are described in which acoustic emissions were unambiguously correlated with microstructural fracture mechanisms. The advantages and limitations of the AE technique are noted.

  2. Acoustic emission testing applied to tank cars

    SciTech Connect

    Stuart, R.L. )

    1989-01-01

    A major portion of the U.S. chemical and related commodities production is transported in railroad tank cars. Performance of this equipment directly impacts the economic health of the chemical industry; therefore, it is important that tank cars be properly maintained. It is important that every effort be made to minimize the chance of product release. Metallurgical defects, such as cracks and corrosion, are examples of problems that cause downtime, add cost and limit good performance. These type defects, if undetected, have potential for threatening proper product containment. In addition, defective tank cars erode good customer relationships. This issue was studied and it was concluded that an improved nondestructive testing method applied to tank cars could lead to a safer and more efficient fleet. This paper reports on a project established to extend acoustic emission (AE) testing to tank car tanks.

  3. Magneto acoustic emission apparatus for testing materials for embrittlement

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G. (Inventor); Min, Namkung (Inventor); Yost, William T. (Inventor); Cantrell, John H. (Inventor)

    1990-01-01

    A method and apparatus for testing steel components for temper embrittlement uses magneto-acoustic emission to nondestructively evaluate the component. Acoustic emission signals occur more frequently at higher levels in embrittled components. A pair of electromagnets are used to create magnetic induction in the test component. Magneto-acoustic emission signals may be generated by applying an ac current to the electromagnets. The acoustic emission signals are analyzed to provide a comparison between a component known to be unembrittled and a test component. Magnetic remanence is determined by applying a dc current to the electromagnets, then turning the magnets off and observing the residual magnetic induction.

  4. Acoustic emission monitoring of HFIR vessel during hydrostatic testing

    SciTech Connect

    Friesel, M.A.; Dawson, J.F.

    1992-08-01

    This report discusses the results and conclusions reached from applying acoustic emission monitoring to surveillance of the High Flux Isotope Reactor vessel during pressure testing. The objective of the monitoring was to detect crack growth and/or fluid leakage should it occur during the pressure test. The report addresses the approach, acoustic emission instrumentation, installation, calibration, and test results.

  5. Development of a MEMS device for acoustic emission testing

    NASA Astrophysics Data System (ADS)

    Ozevin, Didem; Pessiki, Stephen P.; Jain, Akash; Greve, David W.; Oppenheim, Irving J.

    2003-08-01

    Acoustic emission testing is an important technology for evaluating structural materials, and especially for detecting damage in structural members. Significant new capabilities may be gained by developing MEMS transducers for acoustic emission testing, including permanent bonding or embedment for superior coupling, greater density of transducer placement, and a bundle of transducers on each device tuned to different frequencies. Additional advantages include capabilities for maintenance of signal histories and coordination between multiple transducers. We designed a MEMS device for acoustic emission testing that features two different mechanical types, a hexagonal plate design and a spring-mass design, with multiple detectors of each type at ten different frequencies in the range of 100 kHz to 1 MHz. The devices were fabricated in the multi-user polysilicon surface micromachining (MUMPs) process and we have conducted electrical characterization experiments and initial experiments on acoustic emission detection. We first report on C(V) measurements and perform a comparison between predicted (design) and measured response. We next report on admittance measurements conducted at pressures varying from vacuum to atmospheric, identifying the resonant frequencies and again providing a comparison with predicted performance. We then describe initial calibration experiments that compare the performance of the detectors to other acoustic emission transducers, and we discuss the overall performance of the device as a sensor suite, as contrasted to the single-channel performance of most commercial transducers.

  6. Could Acoustic Emission Testing Show a Pipe Failure in Advance?

    NASA Astrophysics Data System (ADS)

    Soares, S. D.; Teixeira, J. C. G.

    2004-02-01

    During the last 20 years PETROBRAS has been attempting to use Acoustic Emission (AE) as an inspection tool. In this period the AE concept has changed from a revolutionary method to a way of finding areas to make a complete inspection. PETROBRAS has a lot of pressure vessels inspected by AE and with other NDTs techniques to establish their relationship. In other hand, PETROBRAS R&D Center has conducted destructive hydrostatic tests in pipelines samples with artificial defects made by milling. Those tests were monitored by acoustic emission and manual ultrasonic until the complete failure of pipe sample. This article shows the results obtained and a brief proposal of analysis criteria for this environment of test.

  7. Acoustic emission testing of 12-nickel maraging steel pressure vessels

    NASA Technical Reports Server (NTRS)

    Dunegan, H. L.

    1973-01-01

    Acoustic emission data were obtained from three point bend fracture toughness specimens of 12-nickel maraging steel, and two pressure vessels of the same material. One of the pressure vessels contained a prefabricated flaw which was extended and sharpened by fatigue cycling. It is shown that the flawed vessel had similar characteristics to the fracture specimens, thereby allowing estimates to be made of its nearness to failure during a proof test. Both the flawed and unflawed pressure vessel survived the proof pressure and 5 cycles to the working pressure, but it was apparent from the acoustic emission response during the proof cycle and the 5 cycles to the working pressure that the flawed vessel was very near failure. The flawed vessel did not survive a second cycle to the proof pressure before failure due to flaw extension through the wall (causing a leak).

  8. Acoustic emission testing of composite vessels under sustained loading

    NASA Technical Reports Server (NTRS)

    Lark, R. F.; Moorhead, P. E.

    1978-01-01

    Acoustic emissions (AE) generated from Kevlar 49/epoxy composite pressure vessels subjected to sustained load-to-failure tests were studied. Data from two different transducer locations on the vessels were compared. It was found that AE from vessel wall-mounted transducers showed a wide variance from those for identical vessels subjected to the same pressure loading. Emissions from boss-mounted transducers did, however, yield values that were relatively consistent. It appears that the signals from the boss-mounted transducers represent an integrated average of the emissions generated by fibers fracturing during the vessel tests. The AE from boss-mounted transducers were also independent of time for vessel failure. This suggests that a similar number of fiber fractures must occur prior to initiation of vessel failure. These studies indicate a potential for developing an AE test procedure for predicting the residual service life or integrity of composite vessels.

  9. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  10. Acoustic emission monitoring of HFIR vessel during hydrostatic testing. Final report

    SciTech Connect

    Friesel, M.A.; Dawson, J.F.

    1992-08-01

    This report discusses the results and conclusions reached from applying acoustic emission monitoring to surveillance of the High Flux Isotope Reactor vessel during pressure testing. The objective of the monitoring was to detect crack growth and/or fluid leakage should it occur during the pressure test. The report addresses the approach, acoustic emission instrumentation, installation, calibration, and test results.

  11. Application of Finite Elements Method for Improvement of Acoustic Emission Testing

    NASA Astrophysics Data System (ADS)

    Gerasimov, S.; Sych, T.; Kuleshov, V.

    2016-01-01

    The paper deals with the acoustic emission sensor modeling by means of FEM system COSMOS/M. The following types of acoustic waves in the acoustic emission sensors are investigated: the longitudinal wave and transversal wave. As a material is used piezoelectric ceramics. The computed displacements are compared with physical model under consideration. The results of numerical and physical simulations of the processes of acoustic wave propagation in solebar of the freight-car truck are presented. The fields of dynamic displacements and stresses were calculated for improvement of acoustic emission testing method.

  12. FIELD TESTING OF PROTOTYPE ACOUSTIC EMISSION SEWER FLOWMETER

    EPA Science Inventory

    This investigation concerns verifying the operating principles of the acoustic emission flowmeter (U.S. Patent 3,958,458) in the natural environment of three different storm sewer field sites in Nassau County, New York. The flowmeter is a novel, passive, nonintrusive method that ...

  13. A wireless data acquisition system for acoustic emission testing

    NASA Astrophysics Data System (ADS)

    Zimmerman, A. T.; Lynch, J. P.

    2013-01-01

    As structural health monitoring (SHM) systems have seen increased demand due to lower costs and greater capabilities, wireless technologies have emerged that enable the dense distribution of transducers and the distributed processing of sensor data. In parallel, ultrasonic techniques such as acoustic emission (AE) testing have become increasingly popular in the non-destructive evaluation of materials and structures. These techniques, which involve the analysis of frequency content between 1 kHz and 1 MHz, have proven effective in detecting the onset of cracking and other early-stage failure in active structures such as airplanes in flight. However, these techniques typically involve the use of expensive and bulky monitoring equipment capable of accurately sensing AE signals at sampling rates greater than 1 million samples per second. In this paper, a wireless data acquisition system is presented that is capable of collecting, storing, and processing AE data at rates of up to 20 MHz. Processed results can then be wirelessly transmitted in real-time, creating a system that enables the use of ultrasonic techniques in large-scale SHM systems.

  14. Acoustic emission produced during burst tests of filament-wound bottles.

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.; Chiao, T. T.

    1973-01-01

    Acoustic emission was recorded during burst tests of filament-wound, composite pressure vessels. Organic and graphite fibers were tested, and two different epoxy resin systems were used: one with a low and another with a relatively high cure temperature. Acoustic emission was studied for the effects of different winding patterns, artificial flaws, winding-induced fiber fraying, different resins, and different fibers. Small effects produced in the vessels by changes in these variables were greatly magnified when they appeared as changes in acoustic emission. They would, in fact, be difficult or impossible to detect by other test means.

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

    NASA Astrophysics Data System (ADS)

    Choudhary, R. K.; Mishra, P.

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Choudhary, R. K.; Mishra, P.

    2016-06-01

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

  17. Acoustic emission analysis as a non-destructive test procedure for fiber compound structures

    NASA Technical Reports Server (NTRS)

    Block, J.

    1983-01-01

    The concept of acoustic emission analysis is explained in scientific terms. The detection of acoustic events, their localization, damage discrimination, and event summation curves are discussed. A block diagram of the concept of damage-free testing of fiber-reinforced synthetic materials is depicted. Prospects for application of the concept are assessed.

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

    SciTech Connect

    Beattie, Alan G.

    2013-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1995-04-01

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

  1. Evaluation of Acoustic Emission SHM of PRSEUS Composite Pressure Cube Tests

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2013-01-01

    A series of tests of the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) pressure cube were conducted during third quarter 2011 at NASA Langley Research Center (LaRC) in the Combined Loads Test facility (COLTS). This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. The AE signals of the later tests are consistent with the final failure progression through two of the pressure cube panels. Calibration tests and damage precursor AE indications, from preliminary checkout pressurizations, indicated areas of concern that eventually failed. Hence those tests have potential for vehicle health monitoring.

  2. Acoustic emission monitoring of a wind turbine blade during a fatigue test

    SciTech Connect

    Beattie, A.G.

    1997-01-01

    A fatigue test of a wind turbine blade was conducted at the National Renewable Energy Laboratory in the fall of 1994. Acoustic emission monitoring of the test was performed, starting with the second loading level. The acoustic emission data indicated that this load exceeded the strength of the blade. From the first cycle at the new load, an oil can type of deformation occurred in two areas of the upper skin of the blade. One of these was near the blade root and the other was about the middle of the tested portion of the blade. The emission monitoring indicated that no damage was taking place in the area near the root, but in the deforming area near the middle of the blade, damage occurred from the first cycles at the higher load. The test was stopped after approximately one day and the blade was declared destroyed, although no gross damage had occurred. Several weeks later the test was resumed, to be continued until gross damage occurred. The upper skin tore approximately one half hour after the cycling was restarted.

  3. Comments on the origin of acoustic emission in fatigue testing of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Heiple, C. R.; Carpenter, S. H.; Armentrout, D. L.

    The size of acoustic emission (AE) signals expected from inclusion fracture during fatigue testing of 7075 aluminum has been estimated on the basis of previous measurements of AE produced by the fracture of boron particles incorporated into 2219 aluminum. The AF signal size expected from deformation in the plastic zone ahead of the fatigue crack was estimated from the results of tensile tests on 7075 aluminum. The signals predicted from both processes are near or below the noise level in the fatigue experiments and are therefore far too small to account for the signals actually observed. Nearly simultaneous fracture of multiple inclusions could produce signals as large as those observed in fatigue tests of 7075 aluminum, however, fatigue tests of 7050 aluminum produced signals as large or larger than in 7075. Since 7050 has substantially fewer inclusions than 7075, the simultaneous failure of multiple inclusions is unlikely to be a major AE source in fatigue testing of either aluminum alloy. Thus, the most probable source of acoustic emission during fatigue testing of 7075 and 7050 aluminum is the crack advance itself. The measured crack advance per cycle is large enough to release sufficient elastic energy to account for the AE signals observed.

  4. Acoustic emission monitoring of hot functional testing: Watts Bar Unit 1 Nuclear Reactor

    SciTech Connect

    Hutton, P.H.; Dawson, J.F.; Friesel, M.A.; Harris, J.C.; Pappas, R.A.

    1984-06-01

    Acoustic emission (AE) monitoring of selected pressure boundary areas at TVA's Watts Bar, Unit 1 Nuclear Power Plant during hot functional preservice testing is described in this report. The report deals with background, methodology, and results. The work discussed here is a major milestone in a program supported by NRC to develop and demonstrate application of AE monitoring for continuous surveillance of reactor pressure boundaries to detect and evaluate growing flaws. The subject work demonstrated that anticipated problem areas can be overcome. Work is continuing toward AE monitoring during reactor operation.

  5. Sonification of acoustic emission data

    NASA Astrophysics Data System (ADS)

    Raith, Manuel; Große, Christian

    2014-05-01

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

  6. Acoustic emission monitoring system

    DOEpatents

    Romrell, Delwin M.

    1977-07-05

    Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

  7. Evaluation of shrinkage and cracking in concrete of ring test by acoustic emission method

    NASA Astrophysics Data System (ADS)

    Watanabe, Takeshi; Hashimoto, Chikanori

    2015-03-01

    Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.

  8. Acoustic emission analysis: A test method for metal joints bonded by adhesives

    NASA Technical Reports Server (NTRS)

    Brockmann, W.; Fischer, T.

    1978-01-01

    Acoustic emission analysis is applied to study adhesive joints which had been subjected to mechanical and climatic stresses, taking into account conditions which make results applicable to adhesive joints used in aerospace technology. Specimens consisting of the alloy AlMgSi0.5 were used together with a phenolic resin adhesive, an epoxy resin modified with a polyamide, and an epoxy resin modified with a nitrile. Results show that the acoustic emission analysis provides valuable information concerning the behavior of adhesive joints under load and climatic stresses.

  9. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  10. Acoustic Emission and Ultrasonic Characterization of Jurassic Navajo Formation Deformation During Axisymmetric Compression Testing

    NASA Astrophysics Data System (ADS)

    Rinehart, A. J.; Dewers, T. A.; Holcomb, D. J.; Broome, S. T.

    2011-12-01

    Linking continuum-scale and microscale brittle damage in rock remains a challenge impacting CO2 sequestration, secondary recovery, structural monitoring, and other geotechnical engineering applications. We examine if the mode of micromechanical failure scales directly up to continuum-scale damage-induced velocity anisotropy. Axisymmetric drained lab-dry compression experiments are performed on facies of moderately cemented finely laminated quartz arenite from the Jurassic Navajo Formation, a target reservoir rock for CO2 sequestration in Utah. The tests are 1 unconfined uniaxial compression test, 1 hydrostatic compression test, and 3 triaxial compression tests. Microscale damage is monitored using acoustic emissions (AE) and continuum scale damage is monitored with ultrasonic velocity scans. During the non-hydrostatic tests, three to five unload loops are performed pre-failure, with one unload loop performed post-failure. While stresses are increasing, AEs are monitored continuously using 1.6-mm diameter, 0.5-mm thick PZT-5A pins attached circumferentially around the cylindrical sample, and with 6-mm diameter, 2-mm thick PZT-5A discs at the ends of the sample. Before and after each unload loop, the test is paused and the AE transducers sequentially emit an ultrasonic pulse to measure wave speeds. The resulting elastic wave is detected by the other AE transducers. Post-test, the changing anisotropic velocity structure of the rock during compression and failure is compared to the locations, frequency, and relative moment tensors of the AEs measured between ultrasonic scans. Pre- and post-test visual and x-ray CT scan observations of the sample are compared to the acoustic metrics. These tiered observations of rock damage will further elucidate the scaling of microscale brittle failure to the continuum-scale This work was supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Study and Application of Acoustic Emission Testing in Fault Diagnosis of Low-Speed Heavy-Duty Gears

    PubMed Central

    Gao, Lixin; Zai, Fenlou; Su, Shanbin; Wang, Huaqing; Chen, Peng; Liu, Limei

    2011-01-01

    Most present studies on the acoustic emission signals of rotating machinery are experiment-oriented, while few of them involve on-spot applications. In this study, a method of redundant second generation wavelet transform based on the principle of interpolated subdivision was developed. With this method, subdivision was not needed during the decomposition. The lengths of approximation signals and detail signals were the same as those of original ones, so the data volume was twice that of original signals; besides, the data redundancy characteristic also guaranteed the excellent analysis effect of the method. The analysis of the acoustic emission data from the faults of on-spot low-speed heavy-duty gears validated the redundant second generation wavelet transform in the processing and denoising of acoustic emission signals. Furthermore, the analysis illustrated that the acoustic emission testing could be used in the fault diagnosis of on-spot low-speed heavy-duty gears and could be a significant supplement to vibration testing diagnosis. PMID:22346592

  13. Evaluating damage potential of cryogenic concrete using acoustic emission sensors and permeability testing

    NASA Astrophysics Data System (ADS)

    Kogbara, Reginald B.; Parsaei, Boback; Iyengar, Srinath R.; Grasley, Zachary C.; Masad, Eyad A.; Zollinger, Dan G.

    2014-04-01

    This study evaluates the damage potential of concrete of different mix designs subjected to cryogenic temperatures, using acoustic emission (AE) and permeability testing. The aim is to investigate design methodologies that might be employed to produce concrete that resists damage when cooled to cryogenic temperatures. Such concrete would be suitable for primary containment of liquefied natural gas (LNG) and could replace currently used 9% Ni steel, thereby leading to huge cost savings. In the experiments described, concrete cubes, 150 mm x 150 mm x 150 mm, were cast using four different mix designs. The four mixes employed siliceous river sand as fine aggregate. Moreover, limestone, sandstone, trap rock and lightweight aggregate were individually used as coarse aggregates in the mixes. The concrete samples were then cooled from room temperature (20°C) to cryogenic temperature (-165°C) in a temperature chamber. AE sensors were placed on the concrete cubes during the cryogenic freezing process. The damage potential was evaluated in terms of the growth of damage as determined from AE, as a function of temperature and concrete mixture design. The damage potential observed was validated with water permeability testing. Initial results demonstrate the effects of the coefficient of thermal expansion (CTE) of the aggregates on damage growth. Concrete damage (cracking) resistance generally decreased with increasing coarse aggregate CTE, and was in the order, limestone ≥ trap rock << lightweight aggregate ≥ sandstone. Work is in progress to fully understand thermal dilation and damage growth in concrete due to differential CTE of its components.

  14. Localization algorithm for acoustic emission

    NASA Astrophysics Data System (ADS)

    Salinas, V.; Vargas, Y.; Ruzzante, J.; Gaete, L.

    2010-01-01

    In this paper, an iterative algorithm for localization of acoustic emission (AE) source is presented. The main advantage of the system is that it is independent of the 'ability' in the determination of signal level to triggering the signal by the researcher. The system was tested in cylindrical samples with an AE localized in a known position; the precision in the source determination was of about 2 mm, better than the precision obtained with classic localization algorithms (˜1 cm).

  15. Evaluation of Acoustic Emission NDE of Composite Crew Module Service Module/Alternate Launch Abort System (CCM SM/ALAS) Test Article Failure Tests

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2010-01-01

    Failure tests of CCM SM/ALAS (Composite Crew Module Service Module / Alternate Launch Abort System) composite panels were conducted during July 10, 2008 and July 24, 2008 at Langley Research Center. This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests.

  16. Testing of containers made of glass-fiber reinforced plastic with the aid of acoustic emission analysis

    NASA Technical Reports Server (NTRS)

    Wolitz, K.; Brockmann, W.; Fischer, T.

    1979-01-01

    Acoustic emission analysis as a quasi-nondestructive test method makes it possible to differentiate clearly, in judging the total behavior of fiber-reinforced plastic composites, between critical failure modes (in the case of unidirectional composites fiber fractures) and non-critical failure modes (delamination processes or matrix fractures). A particular advantage is that, for varying pressure demands on the composites, the emitted acoustic pulses can be analyzed with regard to their amplitude distribution. In addition, definite indications as to how the damages occurred can be obtained from the time curves of the emitted acoustic pulses as well as from the particular frequency spectrum. Distinct analogies can be drawn between the various analytical methods with respect to whether the failure modes can be classified as critical or non-critical.

  17. Acoustic Emissions Reveal Combustion Conditions

    NASA Technical Reports Server (NTRS)

    Ramohalli, D. N. R.; Seshan, P. K.

    1983-01-01

    Turbulent-flame acoustic emissions change with air/fuel ratio variations. Acoustic emissions sensed and processed to detect inefficient operation; control system responds by adjusting fuel/air mixture for greater efficiency. Useful for diagnosis of combustion processes and fuel/air control.

  18. Study Acoustic Emissions from Composites

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Workman, Gary L.

    1997-01-01

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

  19. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H.D.; Busse, L.J.; Lemon, D.K.

    1983-10-25

    This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.

  20. Acoustic emission monitoring of polymer composite materials

    NASA Technical Reports Server (NTRS)

    Bardenheier, R.

    1981-01-01

    The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

  1. A methodology to condition distorted acoustic emission signals to identify fracture timing from human cadaver spine impact tests.

    PubMed

    Arun, Mike W J; Yoganandan, Narayan; Stemper, Brian D; Pintar, Frank A

    2014-12-01

    While studies have used acoustic sensors to determine fracture initiation time in biomechanical studies, a systematic procedure is not established to process acoustic signals. The objective of the study was to develop a methodology to condition distorted acoustic emission data using signal processing techniques to identify fracture initiation time. The methodology was developed from testing a human cadaver lumbar spine column. Acoustic sensors were glued to all vertebrae, high-rate impact loading was applied, load-time histories were recorded (load cell), and fracture was documented using CT. Compression fracture occurred to L1 while other vertebrae were intact. FFT of raw voltage-time traces were used to determine an optimum frequency range associated with high decibel levels. Signals were bandpass filtered in this range. Bursting pattern was found in the fractured vertebra while signals from other vertebrae were silent. Bursting time was associated with time of fracture initiation. Force at fracture was determined using this time and force-time data. The methodology is independent of selecting parameters a priori such as fixing a voltage level(s), bandpass frequency and/or using force-time signal, and allows determination of force based on time identified during signal processing. The methodology can be used for different body regions in cadaver experiments. PMID:25241279

  2. Study Acoustic Emissions from Composites

    NASA Technical Reports Server (NTRS)

    Walker, James; Workman,Gary

    1998-01-01

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

  3. Acoustic emission beamforming for enhanced damage detection

    NASA Astrophysics Data System (ADS)

    McLaskey, Gregory C.; Glaser, Steven D.; Grosse, Christian U.

    2008-03-01

    As civil infrastructure ages, the early detection of damage in a structure becomes increasingly important for both life safety and economic reasons. This paper describes the analysis procedures used for beamforming acoustic emission techniques as well as the promising results of preliminary experimental tests on a concrete bridge deck. The method of acoustic emission offers a tool for detecting damage, such as cracking, as it occurs on or in a structure. In order to gain meaningful information from acoustic emission analyses, the damage must be localized. Current acoustic emission systems with localization capabilities are very costly and difficult to install. Sensors must be placed throughout the structure to ensure that the damage is encompassed by the array. Beamforming offers a promising solution to these problems and permits the use of wireless sensor networks for acoustic emission analyses. Using the beamforming technique, the azmuthal direction of the location of the damage may be estimated by the stress waves impinging upon a small diameter array (e.g. 30mm) of acoustic emission sensors. Additional signal discrimination may be gained via array processing techniques such as the VESPA process. The beamforming approach requires no arrival time information and is based on very simple delay and sum beamforming algorithms which can be easily implemented on a wireless sensor or mote.

  4. Assessment of impact damage in Kevlar{reg_sign}-epoxy, filament-wound spherical test specimens by acoustic emission techniques

    SciTech Connect

    Whittaker, J.W.; Brosey, W.D.; Hamstad, M.A.

    1996-09-26

    The results of a study of the acoustic emission (AE) behavior of impact-damaged, spherical, composite test specimens subjected to thermal cycling and biaxial mechanical loading are presented. Seven Kevlar{reg_sign}-epoxy, filament-wound, spherical composite test specimens were subjected to different levels of impact damage. The seven specimens were a subset of a group of 77 specimens made with simulated fabrication-induced flaws. The specimens were subjected to two or three cycles of elevated temperature and then hydraulically pressurized to failure. The pressurization regime consisted of two cycles to different intermediate levels with a hold at each peak pressure level; a final pressurization to failure followed. The thermal and pressurization cycles were carefully designed to stimulate AE production under defined conditions. Both impacted and nonimpacted specimens produced thermo-AE (the term given to emission stimulated by thermal loading), but impacted specimens produced significantly more. Thermo-AE was produced primarily by damaged composite material. Damaged material produced emission as a function of both rising and falling temperature, but the effect was not repeatable. More seriously damaged specimens produced very large quantities of emission. Emission recorded during the static portion of the hydraulic loading cycles varied with load, time, and degree of damage. Static load AE behavior was quantified using a newly developed concept, the event-rate moment, and various correlations with residual strength were attempted. Correlations between residual strength, long-duration events, and even-rate moments were developed with varying degrees of success.

  5. Usage Autocorrelation Function in the Capacity of Indicator Shape of the Signal in Acoustic Emission Testing of Intricate Castings

    NASA Astrophysics Data System (ADS)

    Popkov, Artem

    2016-01-01

    The article contains information about acoustic emission signals analysing using autocorrelation function. Operation factors were analysed, such as shape of signal, the origins time and carrier frequency. The purpose of work is estimating the validity of correlations methods analysing signals. Acoustic emission signal consist of different types of waves, which propagate on different trajectories in object of control. Acoustic emission signal is amplitude-, phase- and frequency-modeling signal. It was described by carrier frequency at a given point of time. Period of signal make up 12.5 microseconds and carrier frequency make up 80 kHz for analysing signal. Usage autocorrelation function like indicator the origin time of acoustic emission signal raises validity localization of emitters.

  6. Spatial scanning for anomaly detection in acoustic emission testing of an aerospace structure

    NASA Astrophysics Data System (ADS)

    Hensman, James; Worden, Keith; Eaton, Mark; Pullin, Rhys; Holford, Karen; Evans, Sam

    2011-10-01

    Acoustic emission (AE) monitoring of engineering structures potentially provides a convenient, cost-effective means of performing structural health monitoring. Networks of AE sensors can be easily and unobtrusively installed upon structures, giving the ability to detect and locate damage-related strain releases ('events') in the structure. Use of the technique is not widespread due to the lack of a simple and effective method for detecting abnormal activity levels: the sensitivity of AE sensor networks is such that events unrelated to damage are prevalent in most applications. In this publication, we propose to monitor AE activity in a structure using a spatial scanning statistic, developed and used effectively in the field of epidemiology. The technique is demonstrated on an aerospace structure - an Airbus A320 main landing gear fitting - undergoing fatigue loading, and the method is compared to existing techniques. Despite its simplicity, the scanning statistic proves to be an extremely effective tool in detecting the onset of damage in the structure: it requires little to no user intervention or expertise, is inexpensive to compute and has an easily interpretable output. Furthermore, the generic nature of the method allows the technique to be used in a variety of monitoring scenarios, to detect damage in a wide range of structures.

  7. Acoustic Emission and Damage Accumulation for Various Woven C/SiC Composites Tested in Tension at Room Temperature

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Petko, Jeanne; Kiser, James D.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Modal acoustic emission (AE) has proven to be an excellent technique to monitor damage accumulation in ceramic matrix composites. In this study, AE was used to monitor tensile load-unload-reload hysteresis tests for a variety of C fiber reinforced, SiC matrix composites. C/SiC composites were reinforced with T300 and IM7 fibers, had C, multilayer, or pseudo-porous C interphases, and had chemical vapor infiltrated SiC or melt-infiltrated SiC matrices. All of the composites exhibited considerable AE during testing. The extent and nature of the AE activity will be analyzed and discussed in light of matrix cracking and the variety of composite constituents. It is hoped that understanding the nature of stress dependent damage accumulation in these materials can be of use in life modeling for these types of composites.

  8. Acoustic Emission and Damage Accumulation for Various Woven C/SiC Composites Tested in Tension at Room Temperature

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory; Petko, Jeanne; Kiser, James D.

    2002-01-01

    Modal acoustic emission (AE) has proven to be an excellent technique to monitor damage accumulation in ceramic matrix composites. In this study, AE was used to monitor tensile load-unload-reload hysteresis tests for a variety of C fiber reinforced, Sic matrix composites. C/SiC composites were reinforced with T-300 and IM7 fibers, had C, multilayer, or pseudo-porous C interphases, and had chemical vapor infiltrated Sic or melt-infiltrated SiC matrices. All of the composites exhibited considerable AE during testing. The extent and nature of the AE activity will be analyzed and discussed in light of matrix cracking and the variety of composite constituents. It is hoped that understanding the nature of stress-dependent damage accumulation in these materials can be of use in life-modeling for these types of composites.

  9. An introduction to acoustic emission

    NASA Astrophysics Data System (ADS)

    Scruby, C. B.

    1987-08-01

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

  10. Acoustic Emissions Could Indicate Weld Quality

    NASA Technical Reports Server (NTRS)

    Gustafson, P. E.; Sutch, F. S.

    1982-01-01

    Preliminary tests show quality of welds can be assessed by acoustic-emission monitor mounted on welder. Nondestructive measurement technique allows operator to determine uniformity and integrity of weld as being made, evaluate equipment performance and condition, and initiate corrective action if quality is not satisfactory.

  11. Acoustic emission data from the MFTF magnets

    SciTech Connect

    Lore, J.; Horvath, J.; Iwasa, Y.; Tamada, N.; Tsukamoto, O.

    1983-05-01

    An acoustic emission (AE) technique for monitoring mechanical disturbances in large superconducting magnets was applied during testing of the MFTF yin-yang coils. A signal processing method was developed to locate sources of AE in the magnet and distinguish the type of activity. The method was then used to provide information on conductor motion activity and structural integrity of the magnet.

  12. System for Multiplexing Acoustic Emission (AE) Instrumentation

    NASA Technical Reports Server (NTRS)

    Prosser, William H. (Inventor); Perey, Daniel F. (Inventor); Gorman, Michael R. (Inventor); Scales, Edgar F. (Inventor)

    2003-01-01

    An acoustic monitoring device has at least two acoustic sensors with a triggering mechanism and a multiplexing circuit. After the occurrence of a triggering event at a sensor, the multiplexing circuit allows a recording component to record acoustic emissions at adjacent sensors. The acoustic monitoring device is attached to a solid medium to detect the occurrence of damage.

  13. Pulse analysis of acoustic emission signals

    NASA Technical Reports Server (NTRS)

    Houghton, J. R.; Packman, P. F.

    1977-01-01

    A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis, and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train are shown to be the region in which the significant signatures of the acoustic emission event are to be found.

  14. Pulse analysis of acoustic emission signals

    NASA Technical Reports Server (NTRS)

    Houghton, J. R.; Packman, P. F.

    1977-01-01

    A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameter values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emission associated with (a) crack propagation, (b) ball dropping on a plate, (c) spark discharge, and (d) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train is shown to be the region in which the significant signatures of the acoustic emission event are to be found.

  15. Damage Characterization of Glass/Epoxy Composite Under Three-Point Bending Test Using Acoustic Emission Technique

    NASA Astrophysics Data System (ADS)

    Pashmforoush, Farzad; Fotouhi, Mohamad; Ahmadi, Mehdi

    2012-07-01

    Acoustic emission (AE) technique is an efficient non-destructive method for detection and identification of various damage mechanisms in composite materials. Discrimination of AE signals related to different damage modes is of great importance in the use of this technique. For this purpose, integration of k-means algorithm and genetic algorithm (GA) was used in this study to cluster AE events of glass/epoxy composite during three-point bending test. Performing clustering analysis, three clusters with separate frequency ranges were obtained, each one representing a distinct damage mechanism. Furthermore, time-frequency analysis of AE signals was performed based on wavelet packet transform (WPT). In order to find the dominant components associated with different damage mechanisms, the energy distribution criterion was used. The frequency ranges of the dominant components were then compared with k-means genetic algorithm (KGA) outputs. Finally, SEM observation was utilized to validate the results. The obtained results indicate good performance of the proposed methods in the damage characterization of composite materials.

  16. Acoustic emission source location

    NASA Astrophysics Data System (ADS)

    Promboon, Yajai

    The objective of the research program was development of reliable source location techniques. The study comprised two phases. First, the research focused on development of source location methods for homogeneous plates. The specimens used in the program were steel railroad tank cars. Source location methods were developed and demonstrated for empty and water filled tanks. The second phase of the research was an exploratory study of source location method for fiber reinforced composites. Theoretical analysis and experimental measurement of wave propagation were carried out. This data provided the basis for development of a method using the intersection of the group velocity curves for the first three wave propagation modes. Simplex optimization was used to calculate the location of the source. Additional source location methods have been investigated and critically examined. Emphasis has been placed on evaluating different methods for determining the time of arrival of a wave. The behavior of wave in a water filled tank was studied and source location methods suitable for use in this situation have been examined through experiment and theory. Particular attention is paid to the problem caused by leaky Lamb waves. A preliminary study into the use of neural networks for source location in fiber reinforced composites was included in the research program. A preliminary neural network model and the results from training and testing data are reported.

  17. Fatigue-crack monitoring in-flight using acoustic emission - hardware, technique, and testing

    SciTech Connect

    Hutton, P.H.; Skorpik, J.R.; Lemon, D.K.

    1981-07-01

    The three programs described represent a logical evolutionary process toward effective flaw surveillance in aircraft using AE. The Macchi tests showed that an AE system can withstand extended in-flight service and collect meaningful information relative to fatigue crack growth at a single specific location. The MIrage aircraft work seeks to extend the methods demonstrated on the Macchi into a more complex circumstance. We are now attempting to detect and locate crack growth at any of twenty fastener locations in a relatively complex geometry. The DARPA pattern recognition program seeks to develop signal identification capability that would pave the way for general monitoring of aircraft structures using AE to detect fatigue crack growth. It appears that AE technology may be capable of enhancing aircraft safety assurance while reducing inspection requirements with the associated costs.

  18. Acoustic emission monitoring of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Van Dam, Jeremy; Bond, Leonard J.

    2015-03-01

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

  19. Method and means for measuring acoustic emissions

    DOEpatents

    Renken, Jr., Claus J.

    1976-01-06

    The detection of acoustic emissions emanating from an object is achieved with a capacitive transducer coupled to the object. The capacitive transducer is charged and then allowed to discharge with the rate of discharge being monitored. Oscillations in the rate of discharge about the normally exponential discharge curve for the capacitive transducer indicate the presence of acoustic emissions.

  20. Acoustic Emission Analysis Applet (AEAA) Software

    NASA Technical Reports Server (NTRS)

    Nichols, Charles T.; Roth, Don J.

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Bekher, S.

    2016-01-01

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

  2. Acoustic emission and signal analysis

    NASA Astrophysics Data System (ADS)

    Rao, A. K.

    1990-01-01

    A review is given of the acoustic emission (AE) phenomenon and its applications in NDE and geological rock mechanics. Typical instrumentation used in AE signal detection, data acquisition, processing, and analysis is discussed. The parameters used in AE signal analysis are outlined, and current methods of AE signal analysis procedures are discussed. A literature review is presented on the pattern classification of AE signals. A discussion then follows on the application of AE in aircraft component monitoring, with an experiment described which focuses on in-flight AE monitoring during fatigue crack growth in an aero engine mount. A pattern recognition approach is detailed for the classification of the experimental data. The approach subjects each of the data files to a cluster analysis by the threshold-k-means scheme. The technique is shown to classify the data successfully.

  3. Study of Acoustic Emissions from Composites

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Workman, Gary L.

    1997-01-01

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

  4. Electronic dummy for acoustical testing

    NASA Technical Reports Server (NTRS)

    Bauer, B. B.; Di Mattia, A. L.; Rosencheck, A. J.; Stern, M.; Torick, E. L.

    1967-01-01

    Electronic Dummy /ED/ used for acoustical testing represents the average male torso from the Xiphoid process upward and includes an acoustic replica of the human head. This head simulates natural flesh, and has an artificial voice and artificial ears that measure sound pressures at the eardrum or the entrance to the ear canal.

  5. Acoustic-emission linear-pulse holography

    SciTech Connect

    Collins, H.D.; Lemon, D.K.; Busse, L.J.

    1982-06-01

    This paper describes Acoustic Emission Linear Pulse Holography which combines the advantages of linear imaging and acoustic emission into a single NDE inspection system. This unique system produces a chronological linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. Conventional linear holographic imaging uses an ultrasonic transducer to transmit energy into the volume being imaged. When the crack or defect reflects that energy, the crack acts as a new source of acoustic waves. To formulate an image of that source, a receiving transducer is scanned over the volume of interest and the phase of the received signals is measured at successive points on the scan. The innovation proposed here is the utilization of the crack generated acoustic emission as the acoustic source and generation of a line image of the crack as it grows. A thirty-two point sampling array is used to construct phase-only linear holograms of simulated acoustic emission sources on large metal plates. The phases are calculated using the pulse time-of-flight (TOF) times from the reference transducer to the array of receivers. Computer reconstruction of the image is accomplished using a one-dimensional FFT algorithm (i.e., backward wave). Experimental results are shown which graphically illustrate the unique acoustic emission images of a single point and a linear crack in a 100 mm x 1220 mm x 1220 mm aluminum plate.

  6. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

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

    NASA Technical Reports Server (NTRS)

    Christensen, W. N.

    1978-01-01

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

  8. Acoustic emission from irradiated nuclear graphite

    NASA Astrophysics Data System (ADS)

    Burchell, T. D.; Rose, A. P. G.; McEnaney, B.

    1986-08-01

    Measurements of acoustic emission (AE) from a range of four unirradiated nuclear graphites during three-point bend tests are reported. Results are in agreement with the trends found in earlier work using different AE apparatus. The technique is applied to the testing of small beam specimens cut from irradiated Civil Advanced Gas-cooled Reactor (CAGR) graphite fuel sleeves after discharge from the reactor. The AE information is explained by considering separately the known changes in graphite microstructure that occur in the reactor due to radiolytic oxidation and fast neutron irradiation. Coarsening of the material due to radiolytic oxidation increases the total number of AE events and the proportion of events of low amplitude. Fast neutron irradiation increases the fracture stress and makes the stress-strain curve more linear. As a consequence, the number of AE events is reduced along with the proportion of events of low amplitude.

  9. Field data on testing of natural gas vehicle (NGV) containers using proposed ASTM standard test method for examination of gas-filled filament-wound pressure vessels using acoustic emission (ASTM-E070403-95/1)

    SciTech Connect

    Fultineer, R.D. Jr.; Mitchell, J.R.

    1999-07-01

    There are many composite wrapped pressure vessels in service. These containers are most widely used for gas storage in natural gas vehicles (NGV). A standard has been developed for the testing of these vessels by the subcommittee ASTM E07.04.03 Acoustic Emission (AE) applications. The AE test method is supported by both field test data and laboratory destructive testing. The test method describes a global volumetric testing technique which is offered as an alternative to the current practice of visual inspection.

  10. Cyclic Crack Growth Testing of an A.O. Smith Multilayer Pressure Vessel with Modal Acoustic Emission Monitoring and Data Assessment

    NASA Technical Reports Server (NTRS)

    Ziola, Steven M.

    2014-01-01

    Digital Wave Corp. (DWC) was retained by Jacobs ATOM at NASA Ames Research Center to perform cyclic pressure crack growth sensitivity testing on a multilayer pressure vessel instrumented with DWC's Modal Acoustic Emission (MAE) system, with captured wave analysis to be performed using DWCs WaveExplorerTM software, which has been used at Ames since 2001. The objectives were to document the ability to detect and characterize a known growing crack in such a vessel using only MAE, to establish the sensitivity of the equipment vs. crack size and / or relevance in a realistic field environment, and to obtain fracture toughness materials properties in follow up testing to enable accurate crack growth analysis. This report contains the results of the testing.

  11. Solid Rocket Motor Acoustic Testing

    SciTech Connect

    Rogers, J.D.

    1999-03-31

    Acoustic data are often required for the determination of launch and powered flight loads for rocket systems and payloads. Such data are usually acquired during test firings of the solid rocket motors. In the current work, these data were obtained for two tests at a remote test facility where we were visitors. This paper describes the data acquisition and the requirements for working at a remote site, interfacing with the test hosts.

  12. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H. Dale; Busse, Lawrence J.; Lemon, Douglas K.

    1985-01-01

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  13. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. D.; Busse, L. J.; Lemon, D. K.

    1985-07-30

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  14. Damage assessed by wavelet scale bands and b-value in dynamical tests of a reinforced concrete slab monitored with acoustic emission

    NASA Astrophysics Data System (ADS)

    Zitto, Miguel E.; Piotrkowski, Rosa; Gallego, Antolino; Sagasta, Francisco; Benavent-Climent, Amadeo

    2015-08-01

    The complex Morlet Continuous Wavelet Transform (CWT) was applied to acoustic emission (AE) signals from dynamic tests conducted on a reinforced concrete slab with a shaking table. The steel reinforcement bars did not yield during the tests, but a severe loss of bond between reinforcement bars and surrounding concrete was detected. Comparison of the evolution of the scale position of maximum values of CWT coefficients and the histories of response acceleration obtained in different seismic simulations allowed us to identify the (45-64 kHz) frequency band corresponding to the fracture of concrete. The Cumulative Acoustic Emission Energy (CAE) obtained by reconstructing the AE signals in this scale (frequency) band was compared with the Cumulative Dissipated Energy (CDE) of the tested structure. The CDE is accepted as a good parameter for characterizing the mechanical damage in structures. A reasonably good agreement was found between the normalized histories of CAE and CDE. This made it possible to categorize the cracking of concrete as the main source of damage in the reinforced concrete slab. Conversely, the differences between the CAE and CDE curves observed for high levels of peak acceleration applied to the shaking table can be attributed to the deformation of the steel that formed the columns. The AE coming from the plastic deformation of the steel is not detected by CAE due to the threshold amplitude (45 dB) used in the AE monitoring, but the strain energy dissipated by the steel through plastic deformations is included in the CDE. Further, a study of the evolution of the b-value in the successive seismic simulations revealed that the b-value can capture the inception of severe cracking in the concrete, which the tests described in this study attributed mainly to the loss of bond between reinforcing steel and surrounding concrete.

  15. Does acoustic testing strand whales?

    NASA Astrophysics Data System (ADS)

    Frantzis, A.

    1998-03-01

    Mass strandings of live whales have been explained by proposing many `natural' or human-related causes. I found that a recent stranding of Cuvier's beaked whale coincided closely in time and location with military tests of an acoustic system for submarine detection being carried out by the North Atlantic Treaty Organization (NATO).

  16. Acoustic emission monitoring of reinforced and prestressed concrete structures

    NASA Astrophysics Data System (ADS)

    Fowler, Timothy J.; Yepez, Luis O.; Barnes, Charles A.

    1998-03-01

    Acoustic emission is an important global nondestructive test method widely used to evaluate the structural integrity of metals and fiber reinforced plastic structures. However, in concrete, application of the technology is still at the experimental stage. Microcracking and crack growth are the principal sources of emission in concrete. Bond failure, anchor slippage, and crack rubbing are also sources of emission. Tension zone cracking in reinforced concrete is a significant source of emission and has made application of the technique to concrete structures difficult. The paper describes acoustic emission monitoring of full-scale prestressed concrete girders and a reinforced concrete frame during loading. The tests on the prestressed concrete girders showed three sources of emission: shear-induced cracking in the web, flexural cracking at the region of maximum moment, and strand slippage at the anchorage zone. The reinforced concrete frame was monitored with and without concrete shear panels. The research was directed to early detection of the cracks, signature analysis, source location, moment tensor analysis, and development of criteria for acoustic emission inspection of concrete structures. Cracking of concrete in the tension areas of the reinforced concrete sections was an early source of emission. More severe emission was detected as damage levels in the structure increased.

  17. Acoustic emission sensor radiation damage threshold experiment

    SciTech Connect

    Beeson, K.M.; Pepper, C.E.

    1994-09-01

    Determination of the threshold for damage to acoustic emission sensors exposed to radiation is important in their application to leak detection in radioactive waste transport and storage. Proper response to system leaks is necessary to ensure the safe operation of these systems. A radiation impaired sensor could provide ``false negative or false positive`` indication of acoustic signals from leaks within the system. Research was carried out in the Radiochemical Technology Division at Oak Ridge National Laboratory to determine the beta/gamma radiation damage threshold for acoustic emission sensor systems. The individual system consisted of an acoustic sensor mounted with a two part epoxy onto a stainless steel waveguide. The systems were placed in an irradiation fixture and exposed to a Cobalt-60 source. After each irradiation, the sensors were recalibrated by Physical Acoustics Corporation. The results were compared to the initial calibrations performed prior to irradiation and a control group, not exposed to radiation, was used to validate the results. This experiment determines the radiation damage threshold of each acoustic sensor system and verifies its life expectancy, usefulness and reliability for many applications in radioactive environments.

  18. Study of acoustic emission sources and signals

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

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

  19. Considerations for acoustic emission monitoring of spherical Kevlar/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.; Patterson, R. G.

    1977-01-01

    We are continuing to research the applications of acoustic emission testing for predicting burst pressure of filament-wound Kevlar 49/epoxy pressure vessels. This study has focused on three specific areas. The first area involves development of an experimental technique and the proper instrumentation to measure the energy given off by the acoustic emission transducer per acoustic emission burst. The second area concerns the design of a test fixture in which to mount the composite vessel so that the acoustic emission transducers are held against the outer surface of the composite. Included in this study area is the calibration of the entire test setup including couplant, transducer, electronics, and the instrument measuring the energy per burst. In the third and final area of this study, we consider the number, location, and sensitivity of the acoustic emission transducers used for proof testing composite pressure vessels.

  20. Ares I Scale Model Acoustic Test Lift-Off Acoustics

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janie D.

    2011-01-01

    The lift-off acoustic (LOA) environment is an important design factor for any launch vehicle. For the Ares I vehicle, the LOA environments were derived by scaling flight data from other launch vehicles. The Ares I LOA predicted environments are compared to the Ares I Scale Model Acoustic Test (ASMAT) preliminary results.

  1. Origin of acoustic emission produced during single point machining

    SciTech Connect

    Heiple, C.R,.; Carpenter, S.H.; Armentrout, D.L.

    1991-01-01

    Acoustic emission was monitored during single point, continuous machining of 4340 steel and Ti-6Al-4V as a function of heat treatment. Acoustic emission produced during tensile and compressive deformation of these alloys has been previously characterized as a function of heat treatment. Heat treatments which increase the strength of 4340 steel increase the amount of acoustic emission produced during deformation, while heat treatments which increase the strength of Ti-6Al-4V decrease the amount of acoustic emission produced during deformation. If chip deformation were the primary source of acoustic emission during single point machining, then opposite trends in the level of acoustic emission produced during machining as a function of material strength would be expected for these two alloys. Trends in rms acoustic emission level with increasing strength were similar for both alloys, demonstrating that chip deformation is not a major source of acoustic emission in single point machining. Acoustic emission has also been monitored as a function of machining parameters on 6061-T6 aluminum, 304 stainless steel, 17-4PH stainless steel, lead, and teflon. The data suggest that sliding friction between the nose and/or flank of the tool and the newly machined surface is the primary source of acoustic emission. Changes in acoustic emission with tool wear were strongly material dependent. 21 refs., 19 figs., 4 tabs.

  2. Examination of coating failure by acoustic emission

    NASA Technical Reports Server (NTRS)

    Berndt, Christopher C.

    1985-01-01

    Coatings of NiCrAlY bond coat with a zirconia - 12 wt percent yttria overlay were applied to disc-shaped specimens of U-700 alloy. A waveguide of 1 mm diameter platinum was TIG welded to the specimen and allowed it to be suspended in a tubular furnace. The specimen was thermally cycled to 1150 C, and the acoustic emission (AE) monitored. The weight gain per thermal cycle was also measured. A computer system based on the IBM-XT microcomputer was used extensively to acquire the AE data with respect to temperature. This system also controlled the temperature by using a PD software loop. Several different types of AE analyses were performed. A major feature of these tests, not addressed by previous work in this area, was that the coatings covered 100 percent of the specimen and also that the AE was amplified at two different levels. It is believed that this latter feature allows a qualitative appraisal of the relative number of cracks per AE event. The difference in AE counts between the two channels is proportional to the number of cracks per AE event, and this parameter may be thought of as the crack density. The ratio of the AE count difference to the AE count magnitude of one channel is inversely proportional to the crack growth. Both of these parameters allow the crack distribution and crack growth within each specimen to be qualitatively followed during the thermal cycling operation. Recent results which used these principles will be presented.

  3. Wavelet-based acoustic emission detection method with adaptive thresholding

    NASA Astrophysics Data System (ADS)

    Menon, Sunil; Schoess, Jeffrey N.; Hamza, Rida; Busch, Darryl

    2000-06-01

    Reductions in Navy maintenance budgets and available personnel have dictated the need to transition from time-based to 'condition-based' maintenance. Achieving this will require new enabling diagnostic technologies. One such technology, the use of acoustic emission for the early detection of helicopter rotor head dynamic component faults, has been investigated by Honeywell Technology Center for its rotor acoustic monitoring system (RAMS). This ambitious, 38-month, proof-of-concept effort, which was a part of the Naval Surface Warfare Center Air Vehicle Diagnostics System program, culminated in a successful three-week flight test of the RAMS system at Patuxent River Flight Test Center in September 1997. The flight test results demonstrated that stress-wave acoustic emission technology can detect signals equivalent to small fatigue cracks in rotor head components and can do so across the rotating articulated rotor head joints and in the presence of other background acoustic noise generated during flight operation. This paper presents the results of stress wave data analysis of the flight-test dataset using wavelet-based techniques to assess background operational noise vs. machinery failure detection results.

  4. Laboratory Hydraulic Fracture Characterization Using Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Gutierrez, M.

    2013-05-01

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

  5. Investigation of acoustic emission coupling techniques

    NASA Technical Reports Server (NTRS)

    Jolly, W. D.

    1988-01-01

    A three-phase research program was initiated by NASA in 1983 to investigate the use of acoustic monitoring techniques to detect incipient failure in turbopump bearings. Two prototype acoustic coupler probes were designed and evaluated, and four units of the final probe design were fabricated. Success in this program could lead to development of an on-board monitor which could detect bearing damage in flight and reduce or eliminate the need for disassembly after each flight. This final report reviews the accomplishments of the first two phases and presents the results of fabrication and testing completed in the final phase of the research program.

  6. Acoustic emission monitoring for assessment of steel bridge details

    SciTech Connect

    Kosnik, D. E.; Corr, D. J.; Hopwood, T.

    2011-06-23

    Acoustic emission (AE) testing was deployed on details of two large steel Interstate Highway bridges: one cantilever through-truss and one trapezoidal box girder bridge. Quantitative measurements of activity levels at known and suspected crack locations were made by monitoring AE under normal service loads (e.g., live traffic and wind). AE indications were used to direct application of radiography, resulting in identification of a previously unknown flaw, and to inform selection of a retrofit detail.

  7. Acoustic Emission of Composites Structures: Story, Success, and Challenges

    NASA Astrophysics Data System (ADS)

    Dahmene, F.; Yaacoubi, S.; Mountassir, M. EL

    This short paper is devoted to Acoustic Emission (AE) Nondestructive Testing. It's focused on the state-of-the-art of its application on composites, from the 1960's until now. The major realizations via this technique are carried out. Examples underlying the maturity of AE are debated. To continuously improve the reliability of this technique, many worldwide researchers are hardworking; some perspectives are discussed.

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

    NASA Technical Reports Server (NTRS)

    Cooper, Beth A.; Young, Judith A.

    2004-01-01

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

  9. Investigation of the nature of thermal stimulation of acoustic emission

    SciTech Connect

    Muravin, G.B.; Ship, V.V.; Lezvinskaya, L.M.

    1988-12-01

    The nature of thermal stimulation of acoustic emission was investigated. Data are given on the distribution of the density of the energy of deformation at a crack tip and the parameters of acoustic emission with different combinations of mechanical and thermal action. It was established that thermal stimulation of acoustic emission is related to advance and growth of a crack under the action of thermoelastic shear stresses. An increases in heating power causes an increase in the energy of deformation, shear stresses at the crack edges, and acoustic emission energy. The position of the minimum in the density of the energy of deformation and of the maximum in acoustic emission energy coincides with the direction of crack advance, which with the use of the method of thermally stimulated acoustic emission makes it possible to not only reveal crack-like defects but also to determine potentially dangerous directions of their development.

  10. Modeling of acoustic emission signal propagation in waveguides.

    PubMed

    Zelenyak, Andreea-Manuela; Hamstad, Marvin A; Sause, Markus G R

    2015-01-01

    Acoustic emission (AE) testing is a widely used nondestructive testing (NDT) method to investigate material failure. When environmental conditions are harmful for the operation of the sensors, waveguides are typically mounted in between the inspected structure and the sensor. Such waveguides can be built from different materials or have different designs in accordance with the experimental needs. All these variations can cause changes in the acoustic emission signals in terms of modal conversion, additional attenuation or shift in frequency content. A finite element method (FEM) was used to model acoustic emission signal propagation in an aluminum plate with an attached waveguide and was validated against experimental data. The geometry of the waveguide is systematically changed by varying the radius and height to investigate the influence on the detected signals. Different waveguide materials were implemented and change of material properties as function of temperature were taken into account. Development of the option of modeling different waveguide options replaces the time consuming and expensive trial and error alternative of experiments. Thus, the aim of this research has important implications for those who use waveguides for AE testing. PMID:26007731

  11. Modeling of Acoustic Emission Signal Propagation in Waveguides

    PubMed Central

    Zelenyak, Andreea-Manuela; Hamstad, Marvin A.; Sause, Markus G. R.

    2015-01-01

    Acoustic emission (AE) testing is a widely used nondestructive testing (NDT) method to investigate material failure. When environmental conditions are harmful for the operation of the sensors, waveguides are typically mounted in between the inspected structure and the sensor. Such waveguides can be built from different materials or have different designs in accordance with the experimental needs. All these variations can cause changes in the acoustic emission signals in terms of modal conversion, additional attenuation or shift in frequency content. A finite element method (FEM) was used to model acoustic emission signal propagation in an aluminum plate with an attached waveguide and was validated against experimental data. The geometry of the waveguide is systematically changed by varying the radius and height to investigate the influence on the detected signals. Different waveguide materials were implemented and change of material properties as function of temperature were taken into account. Development of the option of modeling different waveguide options replaces the time consuming and expensive trial and error alternative of experiments. Thus, the aim of this research has important implications for those who use waveguides for AE testing. PMID:26007731

  12. Concurrent Ultrasonic Tomography and Acoustic Emission in Solid Materials

    NASA Astrophysics Data System (ADS)

    Chow, Thomas M.

    A series of experiments were performed to detect stress induced changes in the elastic properties of various solid materials. A technique was developed where these changes were monitored concurrently by two methods, ultrasonic tomography and acoustic emission monitoring. This thesis discusses some experiments in which acoustic emission (AE) and ultrasonic tomography were performed on various samples of solid materials including rocks, concrete, metals, and fibre reinforced composites. Three separate techniques were used to induce stress in these samples. Disk shaped samples were subject to stress via diametral loading using an indirect tensile test geometry. Cylindrical samples of rocks and concrete were subject to hydraulic fracture tests, and rectangular samples of fibre reinforced composite were subject to direct tensile loading. The majority of the samples were elastically anisotropic. Full waveform acoustic emission and tomographic data were collected while these samples were under load to give information concerning changes in the structure of the material as it was undergoing stress change and/or failure. Analysis of this data indicates that AE and tomographic techniques mutually compliment each other to give a view of the stress induced elastic changes in the tested samples.

  13. Acoustic emission: The first half century

    NASA Astrophysics Data System (ADS)

    Drouillard, Thomas F.

    The technology of acoustic emission (AE) is approaching the half century mark, having had its beginning in 1950 with the work of Joseph Kaiser. During the 1950s and 1960s researchers delved into the fundamentals of acoustic emission, developed instrumentation specifically for AE, and characterized the AE behavior of many materials. AE was starting to be recognized for its unique capabilities as an NDT method for monitoring dynamic processes. In the decade of the 1970s research activities became more coordinated and directed with the formation of the working groups, and its use as an NDT method continued to increase for industrial applications. In the 1980s the computer became a basic component for both instrumentation and data analysis, and today it has sparked a resurgence of opportunities for research and development. Today we are seeing a transition to waveform-based AE analysis and a shift in AE activities with more emphasis on applications than on research. From the beginning, we have been fortunate to have had so many dedicated savants with different fields of expertise contribute in a collective way to bring AE to a mature, fully developed technology and leave a legacy of knowledge recorded in its literature. AE literature has been a key indicator of the amount of activity, the proportion of research to application, the emphasis on what was of current interest, and the direction AE has taken. The following is a brief survey of the history of acoustic emission with emphasis on development of the infrastructure over the past half century.

  14. Acoustic emission: The first half century

    SciTech Connect

    Drouillard, T.F.

    1994-08-01

    The technology of acoustic emission (AE) is approaching the half century mark, having had its beginning in 1950 with the work of Joseph Kaiser. During the 1950s and 1960s researchers delved into the fundamentals of acoustic emission, developed instrumentation specifically for AE, and characterized the AE behavior of many materials. AE was starting to be recognized for its unique capabilities as an NDT method for monitoring dynamic processes. In the decade of the 1970s research activities became more coordinated and directed with the formation of the working groups, and its use as an NDT method continued to increase for industrial applications. In the 1980s the computer became a basic component for both instrumentation and data analysis, and today it has sparked a resurgence of opportunities for research and development. Today we are seeing a transition to waveform-based AE analysis and a shift in AE activities with more emphasis on applications than on research. From the beginning, we have been fortunate to have had so many dedicated savants with different fields of expertise contribute in a collective way to bring AE to a mature, fully developed technology and leave a legacy of knowledge recorded in its literature. AE literature has been a key indicator of the amount of activity, the proportion of research to application, the emphasis on what was of current interest, and the direction AE has taken. The following is a brief survey of the history of acoustic emission with emphasis on development of the infrastructure over the past half century.

  15. Acoustic emission characterization using AE (parameter) delay

    NASA Technical Reports Server (NTRS)

    Williams, J. H., Jr.; Lee, S. S.

    1983-01-01

    The acoustic emission (AE) parameter delay concept is defined as that particular measured value of a parameter at which a specified baseline level of cumulative AE activity is reached. The parameter can be from any of a broad range of elastic, plastic, viscoelastic, and fracture mechanics parameters, as well as their combinations. Such parameters include stress, load, strain, displacement, time, temperature, loading cycle, unloading stress, stress intensity factor, strain energy release rate, and crack tip plasticity zone size, while the AE activity may be AE event counts, ringdown counts, energy, event duration, etc., as well as their combinations. Attention is given to examples for the AE parameter delay concept, together with various correlations.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  17. Pulse analysis of acoustic emission signals. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Houghton, J. R.

    1976-01-01

    A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio are examined in the frequency domain analysis, and pulse shape deconvolution is developed for use in the time domain analysis. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings.

  18. Hyperbolic source location of crack related acoustic emission in bone.

    PubMed

    O'Toole, John; Creedon, Leo; Hession, John; Muir, Gordon

    2013-01-01

    Little work has been done on the localization of microcracks in bone using acoustic emission. Microcrack localization is useful to study the fracture process in bone and to prevent fractures in patients. Locating microcracks that occur before fracture allows one to predict where fracture will occur if continued stress is applied to the bone. Two source location algorithms were developed to locate microcracks on rectangular bovine bone samples. The first algorithm uses a constant velocity approach which has some difficulty dealing with the anisotropic nature of bone. However, the second algorithm uses an iterative technique to estimate the correct velocity for the acoustic emission source location being located. In tests with simulated microcracks, the constant velocity algorithm achieves a median error of 1.78 mm (IQR 1.51 mm) and the variable velocity algorithm improves this to a median error of 0.70 mm (IQR 0.79 mm). An experiment in which the bone samples were loaded in a three point bend test until they fractured showed a good correlation between the computed location of detected microcracks and where the final fracture occurred. Microcracks can be located on bovine bone samples using acoustic emission with good accuracy and precision. PMID:23363217

  19. A potential means of using acoustic emission for crack detection under cyclic-load conditions.

    NASA Technical Reports Server (NTRS)

    Vary, A.; Klima, S. J.

    1973-01-01

    A preliminary investigation was conducted to assess the feasibility of monitoring acoustic emission signals from fatigue cracks during cyclic bend tests. Plate specimens of 6Al-4V titanium, 2219-T87 aluminum, and 18-Ni maraging steel were tested with and without crack starter notches. It was found that significant acoustic emission signals could be detected in the frequency range from 100 to 400 kHz. Cracks emanating from starter notches were monitored by the ultrasonic pulse-echo technique and periodically measured by micro-optical examination. The investigation indicated that it was possible to extract meaningful acoustic emission signals in a cyclic bend machine environment.

  20. Resonant capacitive MEMS acoustic emission transducers

    NASA Astrophysics Data System (ADS)

    Ozevin, D.; Greve, D. W.; Oppenheim, I. J.; Pessiki, S. P.

    2006-12-01

    We describe resonant capacitive MEMS transducers developed for use as acoustic emission (AE) detectors, fabricated in the commercial three-layer polysilicon surface micromachining process (MUMPs). The 1 cm square device contains six independent transducers in the frequency range between 100 and 500 kHz, and a seventh transducer at 1 MHz. Each transducer is a parallel plate capacitor with one plate free to vibrate, thereby causing a capacitance change which creates an output signal in the form of a current under a dc bias voltage. With the geometric proportions we employed, each transducer responds with two distinct resonant frequencies. In our design the etch hole spacing was chosen to limit squeeze film damping and thereby produce an underdamped vibration when operated at atmospheric pressure. Characterization experiments obtained by capacitance and admittance measurements are presented, and transducer responses to physically simulated AE source are discussed. Finally, we report our use of the device to detect acoustic emissions associated with crack initiation and growth in weld metal.

  1. Acoustic emission monitoring of composite containment systems

    NASA Astrophysics Data System (ADS)

    Maguire, John R.

    2011-07-01

    This paper considers two different types of composite containment system, and two different types of acoustic emission (AE) monitoring approach. The first system is a composite reinforced pressure vessel (CRPV) which is monitored both during construction and in-service using a broadband modal acoustic emission (MAE) technique. The second system is a membrane cargo containment system which is monitored using both a global as well as a local AE technique. For the CRPV, the damage assessment is concerned mainly with the integrity of the composite outer layer at the construction stage, and possible fatigue cracking of the inner steel liner at the in-service stage. For the membrane tank, the damage assessment is concerned with locating and quantifying any abnormal porosities that might develop in-service. By comparing and contrasting the different types of structural system and different monitoring approaches inferences are drawn as to what role AE monitoring could take in the damage assessment of other types of composite containment system. (Detailed technical data have not been included, due to client confidentiality constraints.)

  2. Reverberant Acoustic Testing and Direct Field Acoustic Testing Acoustic Standing Waves and their Impact on Structural Responses

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    The aerospace industry has been using two methods of acoustic testing to qualify flight hardware: (1) Reverberant Acoustic Test (RAT), (2) Direct Field Acoustic Test (DFAT). The acoustic field obtained by RAT is generally understood and assumed to be diffuse, expect below Schroeder cut-of frequencies. DFAT method of testing has some distinct advantages over RAT, however the acoustic field characteristics can be strongly affected by test setup such as the speaker layouts, number and location of control microphones and control schemes. In this paper the following are discussed based on DEMO tests performed at APL and JPL: (1) Acoustic wave interference patterns and acoustic standing waves, (2) The structural responses in RAT and DFAT.

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

    NASA Astrophysics Data System (ADS)

    Seniuk, Andrew G.

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

  4. In-process acoustic emission monitoring of dissimilar metal welding: Final report

    SciTech Connect

    Not Available

    1989-08-01

    A system to provide real-time, in-process acoustic emission monitoring to detect and locate flaws in bimetallic welds has been demonstrated. This system could provide reliable inspection of critical welds in cases where conventional NDE would be costly or impossible to apply. Tests were completed on four sample welds to determine the sensitivity of the system. Artificial flaws were introduced into two test samples and the acoustic emission results were verified by radiography and visual inspection techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  6. Acoustic emission technology for space applications

    SciTech Connect

    Friesel, M.A.; Lemon, D.K.; Skorpik, J.R.; Hutton, P.H.

    1989-05-01

    Clearly the structural and functional integrity of space station components is a primary requirement. The combinations of advanced materials, new designs, and an unusual environment increase the need for inservice monitoring to help assure component integrity. Continuous monitoring of the components using acoustic emission (AE) methods can provide early indication of structural or functional distress, thus allowing time to plan remedial action. The term ''AE'' refers to energy impulses propagated from a growing crack in a solid material or from a leak in a pressurized pipe or tube. In addition to detecting a crack or leak, AE methods can provide information on the location of the defect and an estimate of crack growth rate and leak rate. 8 figs.

  7. Acoustic Emission from Breaking a Bamboo Chopstick

    NASA Astrophysics Data System (ADS)

    Tsai, Sun-Ting; Wang, Li-Min; Huang, Panpan; Yang, Zhengning; Chang, Chin-De; Hong, Tzay-Ming

    2016-01-01

    The acoustic emission from breaking a bamboo chopstick or a bundle of spaghetti is found to exhibit similar behavior as the famous seismic laws of Gutenberg and Richter, Omori, and Båth. By the use of a force-sensing detector, we establish a positive correlation between the statistics of sound intensity and the magnitude of a tremor. We also manage to derive these laws analytically without invoking the concept of a phase transition, self-organized criticality, or fractal. Our model is deterministic and relies on the existence of a structured cross section, either fibrous or layered. This success at explaining the power-law behavior supports the proposal that geometry is sometimes more important than mechanics.

  8. Acoustic Emission from Breaking a Bamboo Chopstick.

    PubMed

    Tsai, Sun-Ting; Wang, Li-Min; Huang, Panpan; Yang, Zhengning; Chang, Chin-De; Hong, Tzay-Ming

    2016-01-22

    The acoustic emission from breaking a bamboo chopstick or a bundle of spaghetti is found to exhibit similar behavior as the famous seismic laws of Gutenberg and Richter, Omori, and Båth. By the use of a force-sensing detector, we establish a positive correlation between the statistics of sound intensity and the magnitude of a tremor. We also manage to derive these laws analytically without invoking the concept of a phase transition, self-organized criticality, or fractal. Our model is deterministic and relies on the existence of a structured cross section, either fibrous or layered. This success at explaining the power-law behavior supports the proposal that geometry is sometimes more important than mechanics. PMID:26849601

  9. Acoustic emission during fracture of ceramic superconducting materials

    NASA Astrophysics Data System (ADS)

    Woźny, L.; Kisiel, A.; Łysy, K.

    2016-02-01

    In the ceramic materials acoustic emission (AE) is associated with a rapid elastic energy release due to the formation and expansion of cracks, which causes generation and propagation of the elastic wave. AE pulses measurement allows monitoring of internal stresses changes and the development of macro- and micro-cracks in ceramic materials, and that in turn allows us to evaluate the time to failure of the object. In presented work the acoustic signals generated during cracking of superconducting ceramics were recorded. Results obtained were compared with other ceramic materials tested the same way. An analysis of the signals was carried out. The characteristics of the AE before destruction of the sample were determined, that allow the assessment of the condition of the material during operation and its expected lifetime.

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

    NASA Astrophysics Data System (ADS)

    Snoussi, A.

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-04-01

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

  12. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

    PubMed

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  13. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

    PubMed Central

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  14. Acoustic Emission Detection of Impact Damage on Space Shuttle Structures

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Gorman, Michael R.; Madaras, Eric I.

    2004-01-01

    The loss of the Space Shuttle Columbia as a result of impact damage from foam debris during ascent has led NASA to investigate the feasibility of on-board impact detection technologies. AE sensing has been utilized to monitor a wide variety of impact conditions on Space Shuttle components ranging from insulating foam and ablator materials, and ice at ascent velocities to simulated hypervelocity micrometeoroid and orbital debris impacts. Impact testing has been performed on both reinforced carbon composite leading edge materials as well as Shuttle tile materials on representative aluminum wing structures. Results of these impact tests will be presented with a focus on the acoustic emission sensor responses to these impact conditions. These tests have demonstrated the potential of employing an on-board Shuttle impact detection system. We will describe the present plans for implementation of an initial, very low frequency acoustic impact sensing system using pre-existing flight qualified hardware. The details of an accompanying flight measurement system to assess the Shuttle s acoustic background noise environment as a function of frequency will be described. The background noise assessment is being performed to optimize the frequency range of sensing for a planned future upgrade to the initial impact sensing system.

  15. The South Pole Acoustic Test Setup (SPATS)

    NASA Astrophysics Data System (ADS)

    Laihem, Karim; IceCube Collaboration

    2012-11-01

    New detection techniques for (GZK) neutrinos are required for instrumenting a large detector volume needed to observe the low neutrino fluxes at the EeV energy range. Studies on a larger IceCube Neutrino Observatory at the South Pole have been intensively investigated in the last decade. A larger effective volume at a reasonable cost is possible if an acoustic array is a part of a large hybrid detector which includes radio and the existing optical array. The feasibility and the physics capabilities of an acoustic array at the South Pole depend on the knowledge of the acoustic properties of the ice such as the sound speed, the attenuation length, the background noise level and the transient rate. To investigate the ice properties, the first three acoustic strings of the South Pole Acoustic Test Setup (SPATS) have been deployed in the austral summer 2006/2007, then completed with an additional string in 2007/2008. With its four strings SPATS was able to evaluate in situ the acoustic properties of the South Pole ice in the 10-100 kHz frequency range. In this paper the performance of SPATS is described, results on the acoustic ice properties are presented and a new drilling method to deploy acoustic strings in ice is introduced.

  16. Auto Emission Testing

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The photos show automobile engines being tested for nitrous oxide emissions, as required by the Environmental Protection Agency (EPA), at the Research and Engineering Division of Ford Motor Company, Dearborn. Michigan. NASA technical information helped the company develop a means of calculating emissions test results. Nitrous oxide emission readings vary with relative humidity in the test facility. EPA uses a standard humidity measurement, but the agency allows manufacturers to test under different humidity conditions, then apply a correction factor to adjust the results to the EPA standard. NASA's Dryden Flight Research Center developed analytic equations which provide a simple, computer-programmable method of correcting for humidity variations. A Ford engineer read a NASA Tech Brief describing the Dryden development and requested more detailed information in the form of a technical support package, which NASA routinely supplies to industry on request. Ford's Emissions Test Laboratory now uses the Dryden equations for humidity-adjusted emissions data reported to EPA.

  17. Acoustic emission monitoring of tensile testing of corroded and un-corroded clad aluminum 2024-T3 and characterization of effects of corrosion on AE source events and material tensile properties

    NASA Astrophysics Data System (ADS)

    Okafor, A. Chukwujekwu; Natarajan, Shridhar

    2014-02-01

    Corrosion damage affects structural integrity and deteriorates material properties of aluminum alloys in aircraft structures. Acoustic Emission (AE) is an effective nondestructive evaluation (NDE) technique for monitoring such damages and predicting failure in large structures of an aircraft. For successful interpretation of data from AE monitoring, sources of AE and factors affecting it need to be identified. This paper presents results of AE monitoring of tensile testing of corroded and un-corroded clad Aluminum 2024-T3 test specimens, and characterization of the effects of strain-rate and corrosion damage on material tensile properties and AE source events. Effect of corrosion was studied by inducing corrosion in the test specimens by accelerated corrosion testing in a Q-Fog accelerated corrosion chamber for 12 weeks. Eight (8) masked dog-bone shaped specimens were placed in the accelerated corrosion chamber at the beginning of the test. Two (2) dog-bone shaped specimens were removed from the corrosion chamber after exposure time of 3, 6, 9, and 12 weeks respectively, and subjected to tension testing till specimen failure along with AE monitoring, as well as two (2) reference samples not exposed to corrosion. Material tensile properties (yield strength, ultimate tensile strength, toughness, and elongation) obtained from tension test and AE parameters obtained from AE monitoring were analyzed and characterized. AE parameters increase with increase in exposure period of the specimens in the corrosive environment. Aluminum 2024-T3 is an acoustically silent material during tensile deformation without any damage. Acoustic emission events increase with increase of corrosion damage and with increase in strain rate above a certain value. Thus AE is suitable for structural health monitoring of corrosion damage. Ultimate tensile strength, toughness and elongation values decrease with increase of exposure period in corrosion chamber.

  18. Acoustic Emission Beamforming for Detection and Localization of Damage

    NASA Astrophysics Data System (ADS)

    Rivey, Joshua Callen

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

  19. General framework for acoustic emission during plastic deformation

    NASA Astrophysics Data System (ADS)

    Kumar, Jagadish; Sarmah, Ritupan; Ananthakrishna, G.

    2015-10-01

    Despite the long history, so far there is no general theoretical framework for calculating the acoustic emission spectrum accompanying any plastic deformation. We set up a discrete wave equation with plastic strain rate as a source term and include the Rayleigh-dissipation function to represent dissipation accompanying acoustic emission. We devise a method of bridging the widely separated time scales of plastic deformation and elastic degrees of freedom. While this equation is applicable to any type of plastic deformation, it should be supplemented by evolution equations for the dislocation microstructure for calculating the plastic strain rate. The efficacy of the framework is illustrated by considering three distinct cases of plastic deformation. The first one is the acoustic emission during a typical continuous yield exhibiting a smooth stress-strain curve. We first construct an appropriate set of evolution equations for two types of dislocation densities and then show that the shape of the model stress-strain curve and accompanying acoustic emission spectrum match very well with experimental results. The second and the third are the more complex cases of the Portevin-Le Chatelier bands and the Lüders band. These two cases are dealt with in the context of the Ananthakrishna model since the model predicts the three types of the Portevin-Le Chatelier bands and also Lüders-like bands. Our results show that for the type-C bands where the serration amplitude is large, the acoustic emission spectrum consists of well-separated bursts of acoustic emission. At higher strain rates of hopping type-B bands, the burst-type acoustic emission spectrum tends to overlap, forming a nearly continuous background with some sharp acoustic emission bursts. The latter can be identified with the nucleation of new bands. The acoustic emission spectrum associated with the continuously propagating type-A band is continuous. These predictions are consistent with experimental results. More

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  1. Estimation of crack and damage progression in concrete by quantitative acoustic emission analysis

    SciTech Connect

    Ohtsu, Masayasu

    1999-05-01

    The kinematics of cracking can be represented by the moment tensor. To distinguish moment tensor components from acoustic emission waveforms, the SiGMA (simplified Green`s functions for moment tensor analysis) procedure was developed. By applying the procedure to bending tests of notched beams, cracks in the fracture process zone of cementitious materials can be identified by kinematic means. In addition to cracks, estimation of the damage level in structural concrete is also conducted, based on acoustic emission activity of a concrete sample under compression. Depending on the damage resulting from existing microcracks, acoustic emission generated behavior is quantitatively estimated by the rate process analysis. The damage mechanics are introduced to quantify the degree of damage. Determining the current damage level using acoustic emission without information on undamaged concrete is attempted by correlating the damage value with the rate process.

  2. Tiltrotor Acoustic Flight Test: Terminal Area Operations

    NASA Technical Reports Server (NTRS)

    SantaMaria, O. L.; Wellman, J. B.; Conner, D. A.; Rutledge, C. K.

    1991-01-01

    This paper provides a comprehensive description of an acoustic flight test of the XV- 15 Tiltrotor Aircraft with Advanced Technology Blades (ATB) conducted in August and September 1991 at Crows Landing, California. The purpose of this cooperative research effort of the NASA Langley and Ames Research Centers was to obtain a preliminary, high quality database of far-field acoustics for terminal area operations of the XV-15 at a takeoff gross weight of approximately 14,000 lbs for various glide slopes, airspeeds, rotor tip speeds, and nacelle tilt angles. The test also was used to assess the suitability of the Crows Landing complex for full scale far-field acoustic testing. This was the first acoustic flight test of the XV-15 aircraft equipped with ATB involving approach and level flyover operations. The test involved coordination of numerous personnel, facilities and equipment. Considerable effort was made to minimize potential extraneous noise sources unique to the region during the test. Acoustic data from the level flyovers were analyzed, then compared with data from a previous test of the XV-15 equipped with Standard Metal Blades

  3. Fault structure, damage and acoustic emission characteristics

    NASA Astrophysics Data System (ADS)

    Dresen, G. H.; Göbel, T.; Stanchits, S.; Kwiatek, G.; Charalampidou, E. M.

    2011-12-01

    We investigate the evolution of faulting-related damage and acoustic emission activity in experiments performed on granite, quartzite and sandstone samples with 40-50 mm diameter and 100-125 mm length. Experiments were performed in a servo-controlled MTS loading frame in triaxial compression at confining pressures ranging from 20-140 MPa. We performed a series of fracture and stick-slip sliding experiments on prefractured samples. Acoustic emissions (AE) and ultrasonic velocities were monitored using up to 14 P-wave sensors glued to the cylindrical surface of the rock. Full waveforms were stored in a 16 channel transient recording system (Daxbox, PRÖKEL, Germany). Full moment tensor analysis and polarity of AE first motions were used to discriminate source types associated with tensile, shear and pore-collapse cracking. To monitor strain, two pairs of orthogonally oriented strain-gages were glued onto the specimen surface. Fracture nucleation and growth occurred from a nucleation patch mostly located at the specimen surface or at the tip of prefabricated notches inside the specimens. Irrespective of the rock type, fracture propagation is associated with formation of a damage zone surrounding the fracture surface as revealed by distribution of cracks and AE hypocenters displaying a logarithmic decay in microcrack damage with distance normal to the fault trace. The width of the damage zone varies along the fault. After fracturing, faults were locked by increasing confining pressure. Subsequent sliding was mostly induced by driving the piston at a constant displacement rate producing large single events or multiple stick-slips. With increasing sliding distance a corrugated and rough fault surface formed displaying displacement-parallel lineations. Microstructural analysis of fault surfaces and cross-sections revealed formation of multiple secondary shears progressively merging into an anastomosing 3D-network controlling damage evolution and AE activity in the fault

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Chen, Zhi

    2015-04-01

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

  6. Holographic and acoustic emission evaluation of pressure vessels

    SciTech Connect

    Boyd, D.M.

    1980-03-05

    Optical holographic interfereometry and acoustic emission monitoring were simultaneously used to evaluate two small, high pressure vessels during pressurization. The techniques provide pressure vessel designers with both quantitative information such as displacement/strain measurements and qualitative information such as flaw detection. The data from the holographic interferograms were analyzed for strain profiles. The acoustic emission signals were monitored for crack growth and vessel quality.

  7. Acoustic emission spectral analysis of fiber composite failure mechanisms

    NASA Technical Reports Server (NTRS)

    Egan, D. M.; Williams, J. H., Jr.

    1978-01-01

    The acoustic emission of graphite fiber polyimide composite failure mechanisms was investigated with emphasis on frequency spectrum analysis. Although visual examination of spectral densities could not distinguish among fracture sources, a paired-sample t statistical analysis of mean normalized spectral densities did provide quantitative discrimination among acoustic emissions from 10 deg, 90 deg, and plus or minus 45 deg, plus or minus 45 deg sub s specimens. Comparable discrimination was not obtained for 0 deg specimens.

  8. Acoustic Test Characterization of Melamine Foam for Usage in NASA's Payload Fairing Acoustic Attenuation Systems

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.; McNelis, Mark E.

    2014-01-01

    The external acoustic liftoff levels predicted for NASA's future heavy lift launch vehicles are expected to be significantly higher than the environment created by today's commercial launch vehicles. This creates a need to develop an improved acoustic attenuation system for future NASA payload fairings. NASA Glenn Research Center initiated an acoustic test series to characterize the acoustic performance of melamine foam, with and without various acoustic enhancements. This testing was denoted as NEMFAT, which stands for NESC Enhanced Melamine Foam Acoustic Test, and is the subject of this paper. Both absorption and transmission loss testing of numerous foam configurations were performed at the Riverbank Acoustical Laboratory in July 2013. The NEMFAT test data provides an initial acoustic characterization and database of melamine foam for NASA. Because of its acoustic performance and lighter mass relative to fiberglass blankets, melamine foam is being strongly considered for use in the acoustic attenuation systems of NASA's future launch vehicles.

  9. Variabilities detected by acoustic emission from filament-wound Aramid fiber/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.

    1978-01-01

    Two hundred and fifty Aramid fiber/epoxy pressure vessels were filament-wound over spherical aluminum mandrels under controlled conditions typical for advanced filament-winding. A random set of 30 vessels was proof-tested to 74% of the expected burst pressure; acoustic emission data were obtained during the proof test. A specially designed fixture was used to permit in situ calibration of the acoustic emission system for each vessel by the fracture of a 4-mm length of pencil lead (0.3 mm in diameter) which was in contact with the vessel. Acoustic emission signatures obtained during testing showed larger than expected variabilities in the mechanical damage done during the proof tests. To date, identification of the cause of these variabilities has not been determined.

  10. Characterization of corrosion damage in prestressed concrete using acoustic emission

    NASA Astrophysics Data System (ADS)

    Mangual, Jesé; ElBatanouny, Mohamed K.; Vélez, William; Ziehl, Paul; Matta, Fabio; González, Miguel

    2012-04-01

    The corrosion of reinforced concrete structures is a major issue from both a structural safety and maintenance management point of view. Early detection of the internal degradation process provides the owner with sufficient options to develop a plan of action. An accelerated corrosion test was conducted in a small scale concrete specimen reinforced with a 0.5 inch (13 mm) diameter prestressing strand to investigate the correlation between corrosion rate and acoustic emission (AE). Corrosion was accelerated in the laboratory by supplying anodic current via a rectifier while continuously monitoring acoustic emission activity. Results were correlated with traditional electrochemical techniques such as half-cell potential and linear polarization. The location of the active corrosion activity was found through a location algorithm based on time of flight of the stress waves. Intensity analysis was used to plot the relative significance of the damage states present in the specimen and a preliminary grading chart is presented. Results indicate that AE may be a useful non-intrusive technique for the detection and quantification of corrosion damage.

  11. A potential means of using acoustic emission for crack detection under cyclic-load conditions

    NASA Technical Reports Server (NTRS)

    Vary, A.; Klima, S. J.

    1973-01-01

    A preliminary investigation was conducted to assess the feasibility of monitoring acoustic emission signals from fatigue cracks during cyclic bend tests. Plate specimens of 6A1-4V titanium, 2219-T87 aluminum, and 18-Ni maraging steel were tested with and without crack starter notches. It was found that significant acoustic emission signals could be detected in the frequency range from 100 kHz to 400 kHz. Cracks emanating from starter notches were monitored by the ultrasonic pulse-echo technique and periodically measured by micro-optical examination. Methods used to reduce the effects of extraneous noises (i.e., machine noises, fretting) are described. A frequency spectrum analyzer was used to characterize the emissions and to evaluate methods used to acquire the signals (i.e., transducer location, bandwidth selection). The investigation indicated that it was possible to extract meaningful acoustic emission signals in a cyclic bend machine environment.

  12. Impact of Acoustic Standing Waves on Structural Responses: Reverberant Acoustic Testing (RAT) vs. Direct Field Acoustic Testing (DFAT)

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.

  13. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

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

    PubMed

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

    2015-01-01

    This study investigated the fracture resistance of composite resins using a three-point bending test and acoustic emission (AE) analysis. Three groups of specimens (n=15) were prepared: non-reinforced BelleGlass HP composite (NRC), unidirectional (UFRC) and multidirectional (MFRC) fiber-reinforced groups which respectively incorporated unidirectional Stick and multidirectional StickNet fibers. Specimens were loaded to failure in a universal testing machine while an AE system was used to detect audible signals. Initial fracture strengths and AE amplitudes were significantly lower than those at final fracture in all groups (p<0.05). Initial fracture strength of UFRC (170.0 MPa) was significantly higher than MFRC (124.6 MPa) and NRC (87.9 MPa). Final fracture strength of UFRC (198.1 MPa) was also significantly higher than MFRC (151.0 MPa) and NRC (109.2 MPa). Initial and final fracture strengths were significantly correlated (r=0.971). It was concluded that fiber reinforcement improved the fracture resistance of composite resin materials and the monitoring of acoustic signals revealed significant information regarding the fracture process. PMID:25904176

  15. Post Test Evaluation of HSCT Nozzle Acoustic Liner Subcomponents Subjected to a Hot Acoustic Durability Test

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Lee, Kuan

    2008-01-01

    The acoustic liner system designed for use in the High Speed Civil Transport (HSCT) was tested in a thermal-acoustic environment. Five ceramic matrix composite (CMC) acoustic tile configurations, five bulk acoustic absorbers, and one thermal protection system design were tested. The CMC acoustic tiles were subjected to two 2 3/4 hr ambient temperature acoustic exposures to measure their dynamic response. One exposure was conducted on the tiles alone and the second exposure included the tiles and the T-foam bulk absorber. The measured tile RMS strains were small. With or without the T-foam absorber, the dynamic strains were below strain levels that would cause damage during fatigue loading. After the ambient exposure, a 75-hr durability test of the entire acoustic liner system was conducted using a thermal-acoustic cycle that approximated the anticipated service cycle. Acoustic loads up to 139 dB/Hz and temperatures up to 1670 F (910 C) were employed during this 60 cycle test. During the durability test, the CMC tiles were exposed to temperatures up to 1780 F and a transient through thickness gradient up to 490 F. The TPS peak temperatures on the hot side of the panels ranged from 750 to 1000 F during the 60 cycles. The through thickness delta T ranged from 450 to 650 F, varying with TPS location and cycle number. No damage, such as cracks or chipping, was observed in the CMC tiles after completion of the testing. However, on tile warped during the durability test and was replaced after 43 or 60 cycles. No externally observed damage was found in this tile. No failure of the CMC fasteners occurred, but damage was observed. Cracks and missing material occurred, only in the fastener head region. No indication of damage was observed in the T-foam acoustic absorbers. The SiC foam acoustic absorber experienced damage after about 43 cycles. Cracking in the TPS occurred around the attachment holes and under a vent. In spite of the development of damage, the TPS maintained

  16. Nuclear Emissions During Self-Nucleated Acoustic Cavitation

    SciTech Connect

    Taleyarkhan, R.P.; Xu, Y.; West, C.D.; Lahey, R.T. Jr.; Block, R.C.; Nigmatulin, R.I.

    2006-01-27

    A unique, new stand-alone acoustic inertial confinement nuclear fusion test device was successfully tested. Experiments using four different liquid types were conducted in which bubbles were self-nucleated without the use of external neutrons. Four independent detection systems were used (i.e., a neutron track plastic detector to provide unambiguous visible records for fast neutrons, a BF{sub 3} detector, a NE-113-type liquid scintillation detector, and a NaI {gamma} ray detector). Statistically significant nuclear emissions were observed for deuterated benzene and acetone mixtures but not for heavy water. The measured neutron energy was {<=}2.45 MeV, which is indicative of deuterium-deuterium (D-D) fusion. Neutron emission rates were in the range {approx}5x10{sup 3} n/s to {approx}10{sup 4} n/s and followed the inverse law dependence with distance. Control experiments did not result in statistically significant neutron or {gamma} ray emissions.

  17. Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects

    NASA Astrophysics Data System (ADS)

    Solodov, Igor; Döring, Daniel; Busse, Gerd

    2008-06-01

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

  18. Resonant-type MEMS transducers excited by two acoustic emission simulation techniques

    NASA Astrophysics Data System (ADS)

    Ozevin, Didem; Greve, David W.; Oppenheim, Irving J.; Pessiki, Stephen

    2004-07-01

    Acoustic emission testing is a passive nondestructive testing technique used to identify the onset and characteristics of damage through the detection and analysis of transient stress waves. Successful detection and implementation of acoustic emission requires good coupling, high transducer sensitivity and ability to discriminate noise from real signals. We report here detection of simulated acoustic emission signals using a MEMS chip fabricated in the multi-user polysilicon surface micromachining (MUMPs) process. The chip includes 18 different transducers with 10 different resonant frequencies in the range of 100 kHz to 1 MHz. It was excited by two different source simulation techniques; pencil lead break and impact loading. The former simulation was accomplished by breaking 0.5 mm lead on the ceramic package. Four transducer outputs were collected simultaneously using a multi-channel oscilloscope. The impact loading was repeated for five different diameter ball bearings. Traditional acoustic emission waveform analysis methods were applied to both data sets to illustrate the identification of different source mechanisms. In addition, a sliding window Fourier transform was performed to differentiate frequencies in time-frequency-amplitude domain. The arrival and energy contents of each resonant frequency were investigated in time-magnitude plots. The advantages of the simultaneous excitation of resonant transducers on one chip are discussed and compared with broadband acoustic emission transducers.

  19. Wavelet packet transform for detection of single events in acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Bianchi, Davide; Mayrhofer, Erwin; Gröschl, Martin; Betz, Gerhard; Vernes, András

    2015-12-01

    Acoustic emission signals in tribology can be used for monitoring the state of bodies in contact and relative motion. The recorded signal includes information which can be associated with different events, such as the formation and propagation of cracks, appearance of scratches and so on. One of the major challenges in analyzing these acoustic emission signals is to identify parts of the signal which belong to such an event and discern it from noise. In this contribution, a wavelet packet decomposition within the framework of multiresolution analysis theory is considered to analyze acoustic emission signals to investigate the failure of tribological systems. By applying the wavelet packet transform a method for the extraction of single events in rail contact fatigue test is proposed. The extraction of such events at several stages of the test permits a classification and the analysis of the evolution of cracks in the rail.

  20. Acoustic emission monitoring of recycled aggregate concrete under bending

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  1. Acoustic Emissions in Borosilicate and epoxy resin composite

    NASA Astrophysics Data System (ADS)

    Gatica, N.; Guerra, S.; Vargas, Y.; Gaete, L.; Galleguillos, E.; Ruzzante, J.

    2010-01-01

    In this paper a research looking for to extend the acoustic emission (AE) technique from the evaluation of stress state of rock samples to know its composition is presented. For this purpose the rock samples were simulated by a composite made of a resin and borosilicate spheres. The epoxy resin playing the role of country rock and Borosilicate spheres represent the coarse grain. These samples were undergone to uniaxial compression test and the AE signals were recorded and studied looking for the identification of each material characteristic spectrum. The spectral analysis of these recorded signals shown that it is possible to identify the characteristic spectra of each material from the full spectra of composite.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  3. Acoustic testing of high temperature panels

    NASA Astrophysics Data System (ADS)

    Leatherwood, Jack D.; Clevenson, Sherman A.; Powell, Clemans A.; Daniels, Edward F.

    1990-10-01

    Results are presented of a series of thermal-acoustic tests conducted on the NASA Langley Research Center Thermal-Acoustic Test Apparatus to (1) investigate techniques for obtaining strain measurements on metallic and carbon-carbon materials at elevated temperature; (2) document the dynamic strain response characteristics of several superalloy honeycomb thermal protection system panels at elevated temperatures of up to 1200 F; and (3) determine the strain response and sonic fatigue behavior of four carbon-carbon panels at both ambient and elevated temperatures. A second study tested four carbon-carbon panels to document panel dynamic response characteristics at ambient and elevated temperature, determine time to failure and faliure modes, and collect continuous strain data up to panel failure. Strain data are presented from both types of panels, and problems encountered in obtaining reliable strain data on the carbon-carbon panels are described. The failure modes of the carbon-carbon panels are examined.

  4. Nonlinear acoustic nondestructive testing for concrete durability

    NASA Astrophysics Data System (ADS)

    Wu, Hwai-Chung; Warnemuende, Kraig

    2000-06-01

    Several nondestructive testing methods can be used to determine the damage in a concrete structure. Linear ultrasonic techniques, e.g. pulse-velocity and amplitude attenuation, are very common in nondestructive evaluation. Velocity of propagation is not very sensitive to the degrees of damage unless a great deal of micro-damage having evolving into localized macro-damage. This transition typically takes place around 80% of the ultimate compressive strength. Amplitude attenuation is potentially more sensitive than pulse-velocity. However, this method depends strongly on the coupling conditions between transducers and concrete, hence unreliable. A baseline test of the linear acoustics of several mortar samples was conducted. These mortar samples have been previously damaged to different levels. Several other testing methods were also performed on the same samples to form a comparison. The focus is in comparing the sensitivity of a new testing method (Non-linear Acoustic NDE) with several more traditional testing methods. Non-linearity of the material stiffness is expressed in non-linear acoustics as the effect that damage and flaws have on the modulation of a signal as it propagates through the material. Spectral (non-linear) analysis is much more sensitive to lower damage states and less dependent on the repeatability of the coupling of the transducers.

  5. Turbulence-Induced Acoustic Emission of SCUBA Breathing Apparatus

    NASA Astrophysics Data System (ADS)

    Donskoy, D.; Imas, L.; Yen, T.; Sedunov, N.; Tsionskiy, M.; Sedunov, A.

    2008-06-01

    Our initial study, [1], demonstrated that the primary originating source of vibration and subsequent acoustic emission from an underwater breathing apparatus is turbulent air flow pressure fluctuations occurring during the inhale phase of breathing. The process of energy release associated with the expansion of compressed air in the high pressure scuba tank, through the first stage regulator, results in a highly turbulent, unsteady, compressible air flow. The paper presents results of experimental investigation and fluid dynamic simulation of turbulence-induced acoustic emission. The simulation reveals complex supersonic flow within the regulator's valve and channel topology. The associated regulator's air turbulent pressure pulsations and underwater acoustic emission are observed in a broadband frequency range.

  6. Phonon Emission from Acoustic Black Hole

    NASA Astrophysics Data System (ADS)

    Fang, Hengzhong; Zhou, Kaihu; Song, Yuming

    2012-08-01

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

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

    SciTech Connect

    Shull, D.

    2013-03-04

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

  8. SLS Scale Model Acoustic Test Liftoff Results and Comparisons

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, Douglas; Giacomoni, Clothilde

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible design phase test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments.

  9. Acoustic emissions applications on the NASA Space Station

    SciTech Connect

    Friesel, M.A.; Dawson, J.F.; Kurtz, R.J.; Barga, R.S.; Hutton, P.H.; Lemon, D.K.

    1991-08-01

    Acoustic emission is being investigated as a way to continuously monitor the space station Freedom for damage caused by space debris impact and seal failure. Experiments run to date focused on detecting and locating simulated and real impacts and leakage. These were performed both in the laboratory on a section of material similar to a space station shell panel and also on the full-scale common module prototype at Boeing's Huntsville facility. A neural network approach supplemented standard acoustic emission detection and analysis techniques. 4 refs., 5 figs., 1 tab.

  10. Acoustic emission of coal in the postlimiting deformation state

    SciTech Connect

    Voznesenskii, A.S.; Tavostin, M.N.

    2005-08-01

    The features of acoustic emission in coal samples in the state of pre- and postlimiting deformation are considered. It is shown that in the postlimiting deformation stages and in the transient period, a contrary change is observed in a correlation coefficient of the acoustic emission activity N{Sigma} recorded in the upper and lower portions of a sample; whereas in the prelimiting deformation stages, this change is consistent. It is proposed to recognize the stages of deformation by the correlation coefficient of N{Sigma} recorded in different zones: a positive coefficient corresponds to the prelimiting stage of deformation, and a negative one corresponds to the postlimiting stage.

  11. Verification of Ares I Liftoff Acoustic Environments via the Ares I Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Counter, Douglas; Houston, Janice

    2012-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I liftoff acoustic environments and to determine the acoustic reduction gained by using an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model and Mobile Launcher with tower. Acoustic and pressure data were measured by over 200 instruments. The ASMAT results are compared to Ares I-X flight data.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  13. Locating groundwater flow in karst by acoustic emission surveys

    SciTech Connect

    Stokowski, S.J. Jr.; Clark, D.A.

    1985-01-01

    An acoustic emission survey of Newala Fm. (primarily dolomite) karst has helped to locate subsurface water flow. This survey was performed on the Rock Quarry Dome, Sevier County, Tennessee. A Dresser RS-4 recording seismograph, adjusted to provide a gain of 1000, collected acoustic emission data using Mark Products CN368 vertical geophones with 3-inch spikes. Data was collected for 5-15 second intervals. The geophones were laid out along traverses with 10, 20, or 30-ft spacing and covered with sand bags in locations of high ambient noise. Traverses were laid out: along and across lineaments known to correspond with groundwater flow in natural subsurface channels; across and along a joint-controlled sink suspected of directing groundwater flow; and across a shallow sinkhole located tangentially to the Little Pigeon River and suspected of capturing river water for the groundwater system. Acoustic emissions of channelized flowing groundwater have a characteristic erratic spiked spectral signature. These acoustic emission signatures increase in amplitude and number in the immediate vicinity of the vertical projection of channelized groundwater flow if it occurs within approximately 30 feet of the surface. If the groundwater flow occurs at greater depths the emissions may be offset from the projection of the actual flow, due to propagation of the signal along rock pinnacles or attenuation by residual soils.

  14. Subscale Acoustic Testing: Comparison of ALAT and ASMAT

    NASA Technical Reports Server (NTRS)

    Houston, Janice D.; Counter, Douglas

    2014-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option. This paper compares the acoustic measurements of two different subscale tests: the 2% Ares Liftoff Acoustic Test conducted at Stennis Space Center and the 5% Ares I Scale Model Acoustic Test conducted at Marshall Space Flight Center.

  15. Acoustic Emission Methodology to Evaluate the Fracture Toughness in Heat Treated AISI D2 Tool Steel

    NASA Astrophysics Data System (ADS)

    Mostafavi, Sajad; Fotouhi, Mohamad; Motasemi, Abed; Ahmadi, Mehdi; Sindi, Cevat Teymuri

    2012-10-01

    In this article, fracture toughness behavior of tool steel was investigated using Acoustic Emission (AE) monitoring. Fracture toughness ( K IC) values of a specific tool steel was determined by applying various approaches based on conventional AE parameters, such as Acoustic Emission Cumulative Count (AECC), Acoustic Emission Energy Rate (AEER), and the combination of mechanical characteristics and AE information called sentry function. The critical fracture toughness values during crack propagation were achieved by means of relationship between the integral of the sentry function and cumulative fracture toughness (KICUM). Specimens were selected from AISI D2 cold-work tool steel and were heat treated at four different tempering conditions (300, 450, 525, and 575 °C). The results achieved through AE approaches were then compared with a methodology proposed by compact specimen testing according to ASTM standard E399. It was concluded that AE information was an efficient method to investigate fracture characteristics.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  17. Leak detection by acoustic emission monitoring. Phase 1: Feasibility study

    NASA Astrophysics Data System (ADS)

    Lichtenstein, Bernard; Winder, A. A.

    1994-05-01

    This investigation was conducted to determine the feasibility of detecting leaks from underground storage tanks or pipelines using acoustic emissions. An extensive technical literature review established that distinguishable acoustic emission signals will be generated when a storage tank is subjected to deformation stresses. A parametric analysis was performed which indicated that leak rates less than 0.1 gallons per hour can be detected for leak sizes less than 1/32 inch with 99% probability if the transient signals were sensed with an array of accelerometers (cemented to the tank or via acoustic waveguides), each having a sensitivity greater than 250 mv/g over a frequency range of 0.1 to 4000 Hz, and processed in a multi-channel Fourier spectrum analyzer with automatic threshold detection. An acoustic transient or energy release processor could conceivably detect the onset of the leak at the moment of fracture of the tank wall. The primary limitations to realizing reliable and robust acoustic emission monitoring of underground fluid leaks are the various masking noise sources prevalent at Air Force bases, which are attributed to aircraft, motor traffic, pump station operation, and ground tremors.

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

    ERIC Educational Resources Information Center

    Mejia, Felipe

    2012-01-01

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

  19. XV-15 Tiltrotor Aircraft: 1997 Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Edwards, Bryan D.; Conner, David A.

    2003-01-01

    XV-15 acoustic test is discussed, and measured results are presented. The test was conducted by NASA Langley and Bell Helicopter Textron, Inc., during June - July 1997, at the BHTI test site near Waxahachie, Texas. This was the second in a series of three XV-15 tests to document the acoustic signature of the XV-15 tiltrotor aircraft for a variety of flight conditions and minimize the noise signature during approach. Tradeoffs between flight procedures and the measured noise are presented to illustrate the noise abatement flight procedures. The test objectives were to: (1) support operation of future tiltrotors by further developing and demonstrating low-noise flight profiles, while maintaining acceptable handling and ride qualities, and (2) refine approach profiles, selected from previous (1995) tiltrotor testing, to incorporate Instrument Flight Rules (IFR), handling qualities constraints, operations and tradeoffs with sound. Primary emphasis was given to the approach flight conditions where blade-vortex interaction (BVI) noise dominates, because this condition influences community noise impact more than any other. An understanding of this part of the noise generating process could guide the development of low noise flight operations and increase the tiltrotor's acceptance in the community.

  20. Characterizations of biobased materials using acoustic emission methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For many years, the Eastern Regional Research Center (ERRC) has demonstrated that acoustic emission (AE) is a powerful tool for characterizing the properties of biobased materials with fibrous and composite structure. AE often reveals structural information of a material that other methods cannot o...

  1. Acoustic emission during unloading of elastically stressed magnesium alloy

    NASA Technical Reports Server (NTRS)

    Lee, S. S.; Williams, J. H., Jr.

    1977-01-01

    A magnesium alloy was quasi-statically cycled elastically between zero load and tension. Both loading and unloading stress delays were found, and the unloading stress delay was further studied. An analytical expression was written for the unloading stress delay which is an elastic constitutive parameter. The potential use of these results for the acoustic emission monitoring of elastic stress states is discussed.

  2. Regularities of acoustic emission in coal samples under triaxial compression

    SciTech Connect

    Shkuratnik, V.L.; Filimonov, Y.L.; Kuchurin, S.V.

    2005-02-01

    The results are cited for the experimental study of acoustoemission processes in anthracite samples under triaxial compression by the Karman scheme at the constant rate of axial strain. From a comparison of the stress-strain and acoustoemission curves, the features of acoustic emission parameters in various deformation stages are revealed and the physicomechanical properties of coal are estimated.

  3. Mass flow rate measurement in abrasive jets using acoustic emission

    NASA Astrophysics Data System (ADS)

    Ivantsiv, V.; Spelt, J. K.; Papini, M.

    2009-09-01

    The repeatability of abrasive jet machining operations is presently limited by fluctuations in the mass flow rate due to powder compaction, stratification and humidity effects. It was found that the abrasive mass flow rate for a typical abrasive jet micromachining setup could be determined by using data from the acoustic emission of the abrasive jet impacting a flat plate. Two methods for extracting the mass flow rate from the acoustic emission were developed and compared. In the first method, the number of particle impacts per unit time was determined by a direct count of peaks in the acoustic emission signal. The second method utilizes the power spectrum density of the acoustic emission in a specific frequency range. Both measures were found to correlate strongly with the mass flow rate measured by weighing samples of blasted powder for controlled time periods. It was found that the peak count method permits measurement of the average frequency of the impacts and the mass flow rate, but can only be applied to flow rates in which the impact frequency is approximately one order of magnitude less than the frequency of the target plate ringing. The power spectrum density method of signal processing is applicable to relatively fine powders and to flow rates at which the average impact frequency is of the same order of magnitude as that of the ringing due to the impact. The acoustic emission technique can be used to monitor particle flow variations over a wide range of time periods and provides a straightforward and accurate means of process control.

  4. The applicability of acoustic emission method to modeling the endurance of metallic construction elements

    NASA Astrophysics Data System (ADS)

    Ponomarev, S. V.; Rikkonen, S.; Azin, A.; Karavatskiy, A.; Maritskiy, N.; Ponomarev, S. A.

    2015-12-01

    Acoustic emission method is the most effective nondestructive inspection technique of construction elements. This paper considers the expanded applicability of acoustic emission method to modeling the damage and the remaining operational life of building structures, including the high-ductile metals. The modeling of damage accumulation was carried out to predict endurance using acoustic emission method.

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

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  7. NASA Glenn Research Center Acoustical Testing Laboratory: Five year retrospective

    NASA Astrophysics Data System (ADS)

    Cooper, Beth A.; Akers, James C.; Passe, Paul J.

    2005-09-01

    In the five years since the NASA Glenn Research Center Acoustical Testing Laboratory (ATL) opened its doors in September, 2000, it has developed a comprehensive array of services and products that support hearing conservation goals within NASA and industry. The ATL provides acoustic emission testing and noise control engineering services for a variety of specialized customers, particularly developers of equipment and science experiments manifested for NASA's manned space missions. The ATL aggressively supports the vision of a low-noise on-orbit environment, which facilitates mission success as well as crew health, safety, and comfort. In concert with these goals, the ATL also produces and distributes free educational resources and low-noise advocacy tools for hearing conservation education and awareness. Among these are two compact discs of auditory demonstrations (of phenomena in acoustics, hearing conservation, and communication), and presentations, software packages, and other educational materials for use by engineers, audiologists, and other hearing conservation stakeholders. This presentation will highlight ATL's construction, history, technical capabilities, and current projects and will feature demonstrations of some of the unique educational resource materials that are distributed by the ATL.

  8. The Development of the Acoustic Design of NASA Glenn Research Center's New Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Mark E.; Hozman, Aron D.; McNelis, Anne M.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC's Plum Brook Station in Sandusky, Ohio, USA. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA s space exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada s acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, USA. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic design and subsequent on-going construction.

  9. The Development of the Acoustic Design of NASA Glenn Research Center's New Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Mark E.; Hozman, Aron D.; McNelis, Anne M.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC s Plum Brook Station in Sandusky, Ohio. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA s space exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada s acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic design and subsequent on-going construction.

  10. XV-15 Tiltrotor Aircraft: 1999 Acoustic Testing - Test Report

    NASA Technical Reports Server (NTRS)

    Edwards, Bryan D.; Conner, David A.

    2003-01-01

    An XV-15 acoustic test is discussed, and measured results are presented. The test was conducted by NASA Langley and Bell Helicopter Textron, Inc., during October 1999, at the BHTI test site near Waxahachie, Texas. As part of the NASA-sponsored Short Haul Civil Tiltrotor noise reduction initiative, this was the third in a series of three major XV-15 acoustic tests. Their purpose was to document the acoustic signature of the XV-15 tiltrotor aircraft for a variety of flight conditions and to minimize the noise signature during approach. Tradeoffs between flight procedures and the measured noise are presented to illustrate the noise abatement flight procedures. The test objectives were to support operation of future tiltrotors by further developing and demonstrating low-noise flight profiles, while maintaining acceptable handling and ride qualities, and refine approach profiles, selected from previous (1995 & 1997) tiltrotor testing, to incorporate Instrument Flight Rules (IFR), handling qualities constraints, operations and tradeoffs with sound. Primary emphasis was given to the approach flight conditions where blade-vortex interaction (BVI) noise dominates, because this condition influences community noise impact more than any other. An understanding of this part of the noise generating process could guide the development of low noise flight operations and increase the tiltrotor's acceptance in the community.

  11. Ares I Scale Model Acoustic Tests Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116. The test article included a 5% scale Ares I vehicle model and tower mounted on the Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments located throughout the test article. There were four primary ASMAT instrument suites: ignition overpressure (IOP), lift-off acoustics (LOA), ground acoustics (GA), and spatial correlation (SC). Each instrumentation suite incorporated different sensor models which were selected based upon measurement requirements. These requirements included the type of measurement, exposure to the environment, instrumentation check-outs and data acquisition. The sensors were attached to the test article using different mounts and brackets dependent upon the location of the sensor. This presentation addresses the observed effect of the sensors and mounts on the acoustic and pressure measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  13. Monitoring corrosion in prestressed concrete beams using acoustic emission technique

    NASA Astrophysics Data System (ADS)

    ElBatanouny, Mohamed K.; Mangual, Jesé; Vélez, William; Ziehl, Paul H.; Matta, Fabio; González, Miguel

    2012-04-01

    Early detection of corrosion can help reduce the cost of maintenance and extend the service life of structures. Acoustic emission (AE) sensing has proven to be a promising method for early detection of corrosion in reinforced concrete members. A test program is presented composed of four medium-scale prestressed concrete T-beams. Three of the beams have a length of 16 ft. 4 in. (4.98 m), and one is 9 ft. 8 in. (2.95 m). In order to corrode the specimens a 3% NaCl solution was prepared, which is representative of sea salt concentration. The beams were subjected to wet-dry cycles to accelerate the corrosion process. Two of the specimens were pre-cracked prior to conditioning in order to examine the effect of crack presence. AE data was recorded continuously while half-cell potential measurements and corrosion rate by Linear Polarization Resistance (LPR) were measured daily. Corrosion current was also being acquired constantly to monitor any change in the concrete resistivity. Results indicate that the onset of corrosion may be identified using AE features, and were corroborated with measurements obtained from electrochemical techniques. Corroded areas were located using source triangulation. The results indicate that cracked specimens showed corrosion activity prior to un-cracked specimens and experienced higher corrosion rates. The level of corrosion was determined using corrosion rate results. Intensity analysis was used to link the corrosion rate and level to AE data.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  15. CORROSION PROCESS IN REINFORCED CONCRETE IDENTIFIED BY ACOUSTIC EMISSION

    NASA Astrophysics Data System (ADS)

    Kawasaki, Yuma; Kitaura, Misuzu; Tomoda, Yuichi; Ohtsu, Masayasu

    Deterioration of Reinforced Concrete (RC) due to salt attack is known as one of serious problems. Thus, development of non-destructive evaluation (NDE) techniques is important to assess the corrosion process. Reinforcement in concrete normally does not corrode because of a passive film on the surface of reinforcement. When chloride concentration at reinfo rcement exceeds the threshold level, the passive film is destroyed. Thus maintenance is desirable at an early stage. In this study, to identify the onset of corrosion and the nucleation of corrosion-induced cracking in concrete due to expansion of corrosion products, continuous acoustic emission (AE) monitoring is applied. Accelerated corrosion and cyclic wet and dry tests are performed in a laboratory. The SiGMA (Simplified Green's functions for Moment tensor Analysis) proce dure is applied to AE waveforms to clarify source kinematics of micro-cracks locations, types and orientations. Results show that the onset of corrosion and the nu cleation of corrosion-induced cracking in concrete are successfully identified. Additionally, cross-sections inside the reinforcement are observed by a scanning electron microscope (SEM). From these results, a great promise for AE techniques to monitor salt damage at an early stage in RC structures is demonstrated.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. Acoustic emission intensity analysis of corrosion in prestressed concrete piles

    NASA Astrophysics Data System (ADS)

    Vélez, William; Matta, Fabio; Ziehl, Paul

    2014-02-01

    Corrosion of steel strands in prestressed concrete (PC) bridges may lead to substantial damage or collapse well before the end of the design life. Acoustic Emission (AE) is a suitable nondestructive technique to detect and locate corrosion in reinforced and prestressed concrete, which is key to prioritize inspection and maintenance. An effective tool to analyze damage-related AE data is intensity analysis (IA), which is based on two data trends, namely Severity (average signal strength of high amplitude hits) and Historic Index (ratio of the average signal strength of the most recent hits to the average of all hits). IA criteria for corrosion assessment in PC were recently proposed based on empirical evidence from accelerated corrosion tests. In this paper, AE data from prestressed and non-prestressed concrete pile specimens exposed to salt water wet-dry cycling for over 600 days are used to analyze the relation between Severity and Historic Index and actual corrosion. Evidence of corrosion is gained from the inspection of decommissioned specimens. The selection of suitable J and K parameters for IA is discussed, and an IA chart with updated corrosion criteria for PC piles is presented.

  18. Hydraulic Fracturing of Heterogeneous Rock Monitored by Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Stanchits, Sergey; Burghardt, Jeffrey; Surdi, Aniket

    2015-11-01

    In this paper, the results of laboratory studies of hydraulic fracture in homogeneous sandstone blocks with man-made interfaces and heterogeneous shale blocks with weak natural interfaces are reported. Tests were conducted under similar stress conditions, with fluids of different viscosity and at different injection rates. The measurements and analysis allows the identification of fracture initiation and behavior. Fracturing with high-viscosity fluids resulted in stable fracture propagation initiated before breakdown, while fracturing with low-viscosity fluids resulted in unstable fracture propagation initiated almost simultaneously with breakdown. Analysis also allows us to measure the fluid volume entering the fracture and the fracture volume. Monitoring of acoustic emission hypocenter localizations, indicates the development of created fractured area including the intersection with interfaces, fluid propagation along interfaces, crossing interfaces, and approaching the boundaries of the block. We observe strong differences in hydraulic fracture behavior, fracture geometry and fracture propagation speed, when fracturing with water and high-viscosity fluids. We also observed distinct differences between sandstone blocks and shale blocks, when a certain P-wave velocity ray path is intersected by the hydraulic fracture. The velocity increases in sandstones and decreases in shale.

  19. Fault growth and acoustic emissions in confined granite

    USGS Publications Warehouse

    Lockner, David A.; Byerlee, James D.

    1992-01-01

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

  20. Tests Of Shear-Flow Model For Acoustic Impedance

    NASA Technical Reports Server (NTRS)

    Parrot, Tony L.; Watson, Willie R.; Jones, Michael G.

    1992-01-01

    Tests described in report conducted to validate two-dimensional shear-flow analytical model for determination of acoustic impedance of acoustic liner in grazing-incidence, grazing-flow environment by use of infinite-waveguide method. Tests successful for both upstream and downstream propagations. Work has potential for utility in testing of engine ducts in commercial aircraft.

  1. Emission Enhancement of Sound Emitters using an Acoustic Metamaterial Cavity

    PubMed Central

    Song, Kyungjun; Lee, Seong-Hyun; Kim, Kiwon; Hur, Shin; Kim, Jedo

    2014-01-01

    The emission enhancement of sound without electronic components has wide applications in a variety of remote systems, especially when highly miniaturized (smaller than wavelength) structures can be used. The recent advent of acoustic metamaterials has made it possible to realize this. In this study, we propose, design, and demonstrate a new class of acoustic cavity using a double-walled metamaterial structure operating at an extremely low frequency. Periodic zigzag elements which exhibit Fabry-Perot resonant behavior below the phononic band-gap are used to yield strong sound localization within the subwavelength gap, thus providing highly effective emission enhancement. We show, both theoretically and experimentally, 10 dB sound emission enhancement near 1060 Hz that corresponds to a wavelength approximately 30 times that of the periodicity. We also provide a general guideline for the independent tuning of the quality factor and effective volume of acoustic metamaterials. This approach shows the flexibility of our design in the efficient control of the enhancement rate. PMID:24584552

  2. Acoustic emission signatures of damage modes in concrete

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    The characterization of the dominant fracture mode may assist in the prediction of the remaining life of a concrete structure due to the sequence between successive tensile and shear mechanisms. Acoustic emission sensors record the elastic responses after any fracture event converting them into electric waveforms. The characteristics of the waveforms vary according to the movement of the crack tips, enabling characterization of the original mode. In this study fracture experiments on concrete beams are conducted. The aim is to examine the typical acoustic signals emitted by different fracture modes (namely tension due to bending and shear) in a concrete matrix. This is an advancement of a recent study focusing on smaller scale mortar and marble specimens. The dominant stress field and ultimate fracture mode is controlled by modification of the four-point bending setup while acoustic emission is monitored by six sensors at fixed locations. Conclusions about how to distinguish the sources based on waveform parameters of time domain (duration, rise time) and frequency are drawn. Specifically, emissions during the shear loading exhibit lower frequencies and longer duration than tensile. Results show that, combination of AE features may help to characterize the shift between dominant fracture modes and contribute to the structural health monitoring of concrete. This offers the basis for in-situ application provided that the distortion of the signal due to heterogeneous wave path is accounted for.

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

    NASA Astrophysics Data System (ADS)

    Whitlow, Travis Laron

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

  4. Neural network/acoustic emission burst pressure prediction for impact damaged composite pressure vessels

    SciTech Connect

    Walker, J.L.; Workman, G.L.; Russell, S.S.; Hill, E.V.K.

    1997-08-01

    Acoustic emission signal analysis has been used to measure the effect impact damage has on the burst pressure of 146 mm (5.75 in.) diameter graphite/epoxy and the organic polymer, Kevlar/epoxy filament wound pressure vessels. Burst pressure prediction models were developed by correlating the differential acoustic emission amplitude distribution collected during low level hydroproof tests to known burst pressures using backpropagation artificial neural networks. Impact damage conditions ranging from barely visible to obvious fiber breakage, matrix cracking, and delamination were included in this work. A simulated (inert) propellant was also cast into a series of the vessels from each material class, before impact loading, to provide boundary conditions during impact that would simulate those found on solid rocket motors. The results of this research effort demonstrate that a quantitative assessment of the effects that impact damage has on burst pressure can be made for both organic polymer/epoxy and graphite/epoxy pressure vessels. Here, an artificial neural network analysis of the acoustic emission parametric data recorded during low pressure hydroproof testing is used to relate burst pressure to the vessel`s acoustic signature. Burst pressure predictions within 6.0% of the actual failure pressure are demonstrated for a series of vessels.

  5. TF34 Quiet Nacelle nearfield acoustic test results

    NASA Technical Reports Server (NTRS)

    Coward, W. E.; Smith, E. B.; Sowers, H. D.

    1974-01-01

    The results of the nearfield acoustic tests conducted on the TF34 Quiet Nacelle are presented. The high fan noise suppression levels being sought (26 PNdB reduction in aft noise) necessitated the use of an extensive system of special nearfield acoustic instrumentation to properly evaluate the suppression achieved. The design, operation, and test results from each of these nearfield acoustic instrumentation systems are presented.

  6. Acoustic Test Results of Melamine Foam with Application to Payload Fairing Acoustic Attenuation Systems

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.

    2014-01-01

    A spacecraft at launch is subjected to a harsh acoustic and vibration environment resulting from the passage of acoustic energy, created during the liftoff of a launch vehicle, through the vehicle's payload fairing. In order to ensure the mission success of the spacecraft it is often necessary to reduce the resulting internal acoustic sound pressure levels through the usage of acoustic attenuation systems. Melamine foam, lining the interior walls of the payload fairing, is often utilized as the main component of such a system. In order to better understand the acoustic properties of melamine foam, with the goal of developing improved acoustic attenuation systems, NASA has recently performed panel level testing on numerous configurations of melamine foam acoustic treatments at the Riverbank Acoustical Laboratory. Parameters assessed included the foam's thickness and density, as well as the effects of a top outer cover sheet material and mass barriers embedded within the foam. This testing followed the ASTM C423 standard for absorption and the ASTM E90 standard for transmission loss. The acoustic test data obtained and subsequent conclusions are the subjects of this paper.

  7. Air emissions testing

    SciTech Connect

    Johnson, L.D.

    1993-01-01

    The article presents a brief overview of air emission sampling methods and analysis procedures related to stationary sources such as incinerators, power plants, and industrial boilers. It is intended primarily for the laboratory chemist or manager who is familiar with samples and methods associated with water or waste sources, but not with those associated with air and stack gas emissions.

  8. Multiplexing Technology for Acoustic Emission Monitoring of Aerospace Vehicles

    NASA Technical Reports Server (NTRS)

    Prosser, William; Percy, Daniel

    2003-01-01

    The initiation and propagation of damage mechanisms such as cracks and delaminations generate acoustic waves, which propagate through a structure. These waves can be detected and analyzed to provide the location and severity of damage as part of a structural health monitoring (SHM) system. This methodology of damage detection is commonly known as acoustic emission (AE) monitoring, and is widely used on a variety of applications on civil structures. AE has been widely considered for SHM of aerospace vehicles. Numerous successful ground and flight test demonstrations have been performed, which show the viability of the technology for damage monitoring in aerospace structures. However, one significant current limitation for application of AE techniques on aerospace vehicles is the large size, mass, and power requirements for the necessary monitoring instrumentation. To address this issue, a prototype multiplexing approach has been developed and demonstrated in this study, which reduces the amount of AE monitoring instrumentation required. Typical time division multiplexing techniques that are commonly used to monitor strain, pressure and temperature sensors are not applicable to AE monitoring because of the asynchronous and widely varying rates of AE signal occurrence. Thus, an event based multiplexing technique was developed. In the initial prototype circuit, inputs from eight sensors in a linear array were multiplexed into two data acquisition channels. The multiplexer rapidly switches, in less than one microsecond, allowing the signals from two sensors to be acquired by a digitizer. The two acquired signals are from the sensors on either side of the trigger sensor. This enables the capture of the first arrival of the waves, which cannot be accomplished with the signal from the trigger sensor. The propagation delay to the slightly more distant neighboring sensors makes this possible. The arrival time from this first arrival provides a more accurate source location

  9. Acoustic emission monitoring of a fatigue crack

    NASA Astrophysics Data System (ADS)

    Granata, D. M.; Scott, W. R.; Davis, J.; Lee, E. U.; Boodey, J. B.; Kulowitch, P.

    AE monitoring is applied to crack detection in materials containing intermetallic compounds that have very small critical flaw sizes. The tests performed are simpler than structural monitoring since the source location is well defined and extraneous sources are limited. A correlation was found between defect propagation and AE events in the two titanium aluminide alloys studied. Because events that are apparently not crack related can occur, and because the number of events detected is threshold and gain-sensitive, the AE count alone is not an absolute measure of crack length. Parameters denoting the portion of the load cycle where events occur are valuable for identifying AE sources and cracking mechanisms. Pattern recognition algorithms can be developed on the basis of stored waveforms and load level parameters.

  10. Predicting failure: acoustic emission of berlinite under compression.

    PubMed

    Nataf, Guillaume F; Castillo-Villa, Pedro O; Sellappan, Pathikumar; Kriven, Waltraud M; Vives, Eduard; Planes, Antoni; Salje, Ekhard K H

    2014-07-01

    Acoustic emission has been measured and statistical characteristics analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress collapse occurs in a series of individual events (avalanches), and each avalanche leads to a jerk in sample compression with corresponding acoustic emission (AE) signals. The distribution of AE avalanche energies can be approximately described by a power law p(E)dE = E(-ε)dE (ε ~ 1.8) over a large stress interval. We observed several collapse mechanisms whereby less porous minerals show the superposition of independent jerks, which were not related to the major collapse at the failure stress. In highly porous berlinite (40% and 50%) an increase of energy emission occurred near the failure point. In contrast, the less porous samples did not show such an increase in energy emission. Instead, in the near vicinity of the main failure point they showed a reduction in the energy exponent to ~ 1.4, which is consistent with the value reported for compressed porous systems displaying critical behavior. This suggests that a critical avalanche regime with a lack of precursor events occurs. In this case, all preceding large events were 'false alarms' and unrelated to the main failure event. Our results identify a method to use pico-seismicity detection of foreshocks to warn of mine collapse before the main failure (the collapse) occurs, which can be applied to highly porous materials only. PMID:24919038

  11. Acoustic emission source modeling using a data-driven approach

    NASA Astrophysics Data System (ADS)

    Cuadra, J.; Vanniamparambil, P. A.; Servansky, D.; Bartoli, I.; Kontsos, A.

    2015-04-01

    The next generation of acoustics-based non-destructive evaluation for structural health monitoring applications will depend, among other reasons, on the capability to effectively characterize the transient stress wave effects related to acoustic emission (AE) generated due to activation of failure mechanisms in materials and structures. In this context, the forward problem of simulating AE is addressed herein by a combination of experimental, analytical and computational methods, which are used to form a data-driven finite element (FE) model for AE generation and associated transient elastic wave propagation. Acoustic emission is viewed for this purpose as part of the dynamic process of energy release caused by crack initiation. To this aim, full field experimental data obtained from crack initiation monitored by digital image correlation is used to construct a traction-separation law and to define damage initiation parameters. Subsequently, 3D FE simulations based on this law are performed using both a cohesive and an extended finite element modeling approach. To create a realistic computational AE source model, the transition between static and dynamic responses is evaluated. Numerically simulated AE signals from the dynamic response due to the onset of crack growth are analyzed in the context of the inverse problem of source identification and demonstrate the effects of material and geometry in crack-induced wave propagation.

  12. A New Acoustic Test Facility at Alcatel Space Test Centre

    NASA Astrophysics Data System (ADS)

    Meurat, A.; Jezequel, L.

    2004-08-01

    Due to the obsolescence of its acoustic test facility, Alcatel Space has initiated the investment of a large acoustic chamber on its test centre located in Cannes, south of France. This paper presents the main specification elaborated to design the facility, and the solution chosen : it will be located on a dedicated area of the existing test centre and will be based on technical solution already used in similar facilities over the world. The main structure consists in a chamber linked to an external envelope (concrete building) through suspension aiming at decoupling the vibration and preventing from seismic risks. The noise generation system is based on the use of Wyle modulators located on the chamber roof. Gaseous nitrogen is produced by a dedicated gas generator developed by Air-Liquide that could deliver high flow rate with accurate pressure and temperature controls. The control and acquisition system is based on existing solution implemented on the vibration facilities of the test centre. With the start of the construction in May 2004, the final acceptance tests are planned for April 2005, and the first satellites to be tested are planned for May 2005.

  13. An acoustic emission and acousto-ultrasonic analysis of impact damaged composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Workman, Gary L. (Principal Investigator); Walker, James L.

    1996-01-01

    The use of acoustic emission to characterize impact damage in composite structures is being performed on composite bottles wrapped with graphite epoxy and kevlar bottles. Further development of the acoustic emission methodology will include neural net analysis and/or other multivariate techniques to enhance the capability of the technique to identify dominant failure mechanisms during fracture. The acousto-ultrasonics technique will also continue to be investigated to determine its ability to predict regions prone to failure prior to the burst tests. Characterization of the stress wave factor before, and after impact damage will be useful for inspection purposes in manufacturing processes. The combination of the two methods will also allow for simple nondestructive tests capable of predicting the performance of a composite structure prior to its being placed in service and during service.

  14. ROANOKE WOODSTOVE EMISSION TESTS

    EPA Science Inventory

    The report discusses a project, part of the Integrated Air Cancer Project Roanoke study, that characterizes and quantifies emissions generated by burning authentic Roanoke cordwood. The burning occurred in a controlled laboratory setting using two woodstoves, each operated at two...

  15. Acoustic-emission inspection of the kinetics of fatigue cracks in turbomachinery disks

    SciTech Connect

    Banov, M.D.; Shanyavskii, A.A.; Urbakh, A.I.; Troenkin, D.A.; Konyaev, E.A.; Pykhtin, Yu.A.; Minatsevich, S.F.; Kashin, V.N.

    1988-07-01

    The kinetics of crack growth in turbomachinery disks under low-cycle fatigue conditions was investigated. The relationship between the change in acoustic emission parameters and the processes of loss of continuity of the disk material in cyclic loading was established on the basis of fratographic investigations. A comparative evaluation of the effectiveness of traditional methods of nondestructive testing applicable to the problem of early detection of cracks in disks is given.

  16. Acoustic emission signal classification for gearbox failure detection

    NASA Astrophysics Data System (ADS)

    Shishino, Jun

    The purpose of this research is to develop a methodology and technique to determine the optimal number of clusters in acoustic emission (AE) data obtained from a ground test stand of a rotating H-60 helicopter tail gearbox by using mathematical algorithms and visual inspection. Signs of fatigue crack growth were observed from the AE signals acquired from the result of the optimal number of clusters in a data set. Previous researches have determined the number of clusters by visually inspecting the AE plots from number of iterations. This research is focused on finding the optimal number of clusters in the data set by using mathematical algorithms then using visual verification to confirm it. The AE data were acquired from the ground test stand that simulates the tail end of an H-60 Seahawk at Naval Air Station in Patuxant River, Maryland. The data acquired were filtered to eliminate durations that were greater than 100,000 is and 0 energy hit data to investigate the failure mechanisms occurring on the output bevel gear. From the filtered data, different AE signal parameters were chosen to perform iterations to see which clustering algorithms and number of outputs is the best. The clustering algorithms utilized are the Kohonen Self-organizing Map (SOM), k-mean and Gaussian Mixture Model (GMM). From the clustering iterations, the three cluster criterion algorithms were performed to observe the suggested optimal number of cluster by the criterions. The three criterion algorithms utilized are the Davies-Bouldin, Silhouette and Tou Criterions. After the criterions had suggested the optimal number of cluster for each data set, visual verification by observing the AE plots and statistical analysis of each cluster were performed. By observing the AE plots and the statistical analysis, the optimal number of cluster in the data set and effective clustering algorithms were determined. Along with the optimal number of clusters and effective clustering algorithm, the mechanisms

  17. Acoustic surface waveguides for acoustic emission monitoring of fiber-reinforced plastic structures

    SciTech Connect

    Chen, H.L.R.; He, Y.; Superfesky, M. . Constructed Facilities Center)

    1994-09-01

    Acoustic surface waveguides are developed to enhance the transmission of acoustic emission (AE) signals in high attenuating fiber-reinforced plastic (FRP) structures. In this paper, the design of the surface waveguide system and the source location technique are described. Experimental results of using a surface waveguide for AE monitoring of a FRP composite pressure pipe are presented to demonstrate the effectiveness of the proposed waveguide system. A metal wire was selected as a waveguide, and pencil breaks and electronic pulses were used as artificial AE signals. The results indicate that the use of the surface waveguide can significantly increase the AE monitoring range. Also, a high transmission efficiency was experimentally determined for the epoxy joints developed to attach the surface waveguide to the FRP pipe. The proposed surface waveguide appears to be a promising technique for AE monitoring on existing FRP pressure vessels and storage tanks.

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

    NASA Astrophysics Data System (ADS)

    Chen, Ruizhu; Zhao, Junwei

    2016-05-01

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

  19. Acoustic emissions correlated with hydration of Saguaro Cactus

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Acoustic emissions correlated with hydration of Saguaro Cactus

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. Development of a MEMS acoustic emission sensor system

    NASA Astrophysics Data System (ADS)

    Greve, David W.; Oppenheim, Irving J.; Wu, Wei; Wright, Amelia P.

    2007-04-01

    An improved multi-channel MEMS chip for acoustic emission sensing has been designed and fabricated in 2006 to create a device that is smaller in size, superior in sensitivity, and more practical to manufacture than earlier designs. The device, fabricated in the MUMPS process, contains four resonant-type capacitive transducers in the frequency range between 100 kHz and 500 kHz on a chip with an area smaller than 2.5 sq. mm. The completed device, with its circuit board, electronics, housing, and connectors, possesses a square footprint measuring 25 mm x 25 mm. The small footprint is an important attribute for an acoustic emission sensor, because multiple sensors must typically be arrayed around a crack location. Superior sensitivity was achieved by a combination of four factors: the reduction of squeeze film damping, a resonant frequency approximating a rigid body mode rather than a bending mode, a ceramic package providing direct acoustic coupling to the structural medium, and high-gain amplifiers implemented on a small circuit board. Manufacture of the system is more practical because of higher yield (lower unit costs) in the MUMPS fabrication task and because of a printed circuit board matching the pin array of the MEMS chip ceramic package for easy assembly and compactness. The transducers on the MEMS chip incorporate two major mechanical improvements, one involving squeeze film damping and one involving the separation of resonance modes. For equal proportions of hole area to plate area, a triangular layout of etch holes reduces squeeze film damping as compared to the conventional square layout. The effect is modeled analytically, and is verified experimentally by characterization experiments on the new transducers. Structurally, the transducers are plates with spring supports; a rigid plate would be the most sensitive transducer, and bending decreases the sensitivity. In this chip, the structure was designed for an order-of-magnitude separation between the first

  2. Acoustic emission study of deformation behavior of nacre

    NASA Astrophysics Data System (ADS)

    Luo, Shunfei; Luo, Hongyun; Han, Zhiyuan

    2016-02-01

    A study on the acoustic emission (AE) characteristics during deformation of nacre material was performed. We found that intermittent AE events are generated during nacre deformation. These avalanches may be attributed to microfracture events of the aragonite (CaCO3) nano-asperities and bridges during tablet sliding. These events show several critical features, such as the power-law distributions of the avalanche sizes and interval. These results suggest that the underlying fracture dynamics during nacre deformation display a self-organized criticality (SOC). The results also imply that the disorder and long-range correlation between local microfracture events may play important roles in nacre deformation.

  3. Signature analysis of acoustic emission from graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Russell, S. S.; Henneke, E. G., II

    1977-01-01

    Acoustic emissions were monitored for crack extension across and parallel to the fibers in a single ply and multiply laminates of graphite epoxy composites. Spectrum analysis was performed on the transient signal to ascertain if the fracture mode can be characterized by a particular spectral pattern. The specimens were loaded to failure quasistatically in a tensile machine. Visual observations were made via either an optical microscope or a television camera. The results indicate that several types of characteristics in the time and frequency domain correspond to different types of failure.

  4. Magneto acoustical emission in nanocrystalline Mn–Zn ferrites

    SciTech Connect

    Praveena, K.; Murthty, S.R.

    2013-11-15

    Graphical abstract: Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie temperature. It is found that the magneto-acoustic emission (MAE) activity along hysteresis loop is proportional to the hysteresis losses during the same loop. This law has been verified on series of polycrystalline ferrites and found that the law is valid whatever the composition, the grain size and temperature. It is also found that the domain wall creation/or annihilation processes are the origin of the MAE. - Highlights: • The AE been measured along the hysteresis loops from 80 K to Curie temperature. • The MAE activity along hysteresis loop is proportional to P{sub h} during the same loop. • It is found that the domain wall creation/or annihilation processes are the origin of the MAE. - Abstract: Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie

  5. Modal Acoustic Emission of Damage Accumulation in Woven SiC/SiC at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Morscher, G. N.

    1998-01-01

    Ceramic matrix composites exhibit significant nonlinear stress-strain behavior that makes them attractive as potential materials for many high temperature applications. The mechanisms for this nonlinear stress-strain behavior are all associated with various types of damage in the composites, e.g. transverse matrix cracks and individual fiber failures. Modal acoustic emission has been employed to aid in discerning the damage accumulation that occurs during elevated temperature tensile stress-rupture of woven Hi-Nicalon fiber, BN interphase, SiC matrix composites. It is shown that modal acoustic emission is an effective monitor of the relative damage accumulation in the composites and locator of the damage and failure events as a function of strain (stress), time at temperature, and temperature gradients along the length of the elevated temperature test specimen.

  6. Acoustic Emission as a Tool for Damage Identification and Characterization in Glass Reinforced Cross Ply Laminates

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Loading of cross-ply laminates leads to the activation of distinct damage mechanisms, such as matrix cracking, delaminations between successive plies and fibre rupture at the final stage of loading. This study deals with the investigation of the failure of cross ply composites by acoustic emission (AE). Broadband AE sensors monitor the elastic waves originating from different sources of failure in coupons of this material during a tensile loading-unloading test. The cumulative number of AE activity, and other qualitative indices based on the waveforms shape, were well correlated to the sustained load and mechanical degradation as expressed by the gradual decrease of elastic modulus. AE parameters indicate the succession of failure mechanisms within the composite as the load increases. The proposed methodology based on Acoustic Emission for the identification of the damage stage of glass reinforced cross ply laminates is an initial step which may provide insight for the study of more complex laminations.

  7. Evaluation of Fracture in Concrete with Recycled Aggregate by Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Nishibata, Sayaka; Watanabe, Takeshi; Hashimoro, Chikanori; Kohno, Kiyoshi

    This research revealed fracture behavior of concrete in using recycled aggregates by Acoustic Emission as one of the Non-destructive Inspection. The phenomenon of acoustic emission (AE) is the propagation of elastic waves generated from a source, known as a micro-crack in an elastic material. There were taken to use low-treated recycled aggregate, crushed returned ready mixed concrete for aggregate and normal aggregate. Examination measured AE under the uniaxial compression test. The condition of load is repeated loading. As a result, fracture behavior due to low treated recycled aggregate was detected by AE. It is clarified that AE of concrete with low treated recycled aggregate appeared in low stress level. It has been understood that difference of aggregates becomes clear from Kaiser effect in repeated loading. In relation between RA value and average frequency, it has been understood the adhesion properties of the cement paste in recycled aggregate are appreciable.

  8. 21 CFR 874.1060 - Acoustic chamber for audiometric testing.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Acoustic chamber for audiometric testing. 874.1060 Section 874.1060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES EAR, NOSE, AND THROAT DEVICES Diagnostic Devices § 874.1060 Acoustic chamber...

  9. 21 CFR 874.1060 - Acoustic chamber for audiometric testing.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Acoustic chamber for audiometric testing. 874.1060 Section 874.1060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES EAR, NOSE, AND THROAT DEVICES Diagnostic Devices § 874.1060 Acoustic chamber...

  10. 21 CFR 874.1060 - Acoustic chamber for audiometric testing.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Acoustic chamber for audiometric testing. 874.1060 Section 874.1060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES EAR, NOSE, AND THROAT DEVICES Diagnostic Devices § 874.1060 Acoustic chamber...

  11. 21 CFR 874.1060 - Acoustic chamber for audiometric testing.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Acoustic chamber for audiometric testing. 874.1060 Section 874.1060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES EAR, NOSE, AND THROAT DEVICES Diagnostic Devices § 874.1060 Acoustic chamber...

  12. 21 CFR 874.1060 - Acoustic chamber for audiometric testing.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Acoustic chamber for audiometric testing. 874.1060 Section 874.1060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES EAR, NOSE, AND THROAT DEVICES Diagnostic Devices § 874.1060 Acoustic chamber...

  13. Ares I Scale Model Acoustic Test Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas

    2011-01-01

    Ares I Scale Model Acoustic Test (ASMAT) is a 5% scale model test of the Ares I vehicle, launch pad and support structures conducted at MSFC to verify acoustic and ignition environments and evaluate water suppression systems Test design considerations 5% measurements must be scaled to full scale requiring high frequency measurements Users had different frequencies of interest Acoustics: 200 - 2,000 Hz full scale equals 4,000 - 40,000 Hz model scale Ignition Transient: 0 - 100 Hz full scale equals 0 - 2,000 Hz model scale Environment exposure Weather exposure: heat, humidity, thunderstorms, rain, cold and snow Test environments: Plume impingement heat and pressure, and water deluge impingement Several types of sensors were used to measure the environments Different instrument mounts were used according to the location and exposure to the environment This presentation addresses the observed effects of the selected sensors and mount design on the acoustic and pressure measurements

  14. Online sizing of pneumatically conveyed particles by acoustic emission method

    NASA Astrophysics Data System (ADS)

    Hu, Yonghui; Qian, Xiangchen; Huang, Xiaobin; Gao, Lingjun; Yan, Yong

    2014-04-01

    Accurate determination of particle size distribution is critical to achieving optimal combustion efficiency and minimum pollutant emissions in both biomass and biomass/coal fired power plants. This paper presents an instrumentation system for online continuous measurement of particle size distribution based on acoustic emission (AE) method. Impulsive AE signals arising from impacts of particles with a metallic waveguide protruding into the flow carry information about the particle size. With detailed information about the generation, propagation and detection of impact AE signals, the particle size can be quantitatively characterized. Experimental results obtained with glass beads demonstrate the capability of the system to discriminate particles of different sizes from the recorded AE signals. The system has several appealing features such as online measurement, high sensitivity, simple structure, minimum invasiveness and low cost, which make it well suited for industrial applications.

  15. Acoustic emission monitoring of CFRP cables for cable-stayed bridges

    NASA Astrophysics Data System (ADS)

    Rizzo, Piervincenzo; Lanza di Scalea, Francesco

    2001-08-01

    The advantages of fiber-reinforced polymer (FRP) composite include excellent corrosion resistance, high specific strength and stiffness, as well as outstanding fatigue behavior. The University of California San Diego's I- 5/Gilman Advanced Technology Bridge Project will help demonstrating the use of such materials in civil infrastructures. This paper presents an acoustic emission (AE) study performed during laboratory proof tests of carbon fiber-reinforced polymer stay-cables of possible use in the I-5/Gilman bridge. Three types of cables, both braided and single strand, were tested to failure at lengths ranging from 5500 mm to 5870 mm. AE allowed to monitor damage initiation and progression in the test pieces more accurately than the conventional load versus displacement curve. All of the cables exhibited acoustic activities revealing some degree of damage well before reaching final collapse, which is expected in FRP's. It was also shown that such cables are excellent acoustic waveguides exhibiting very low acoustic attenuation, which makes them an ideal application for an AE-based health monitoring approach.

  16. Oscillating load-induced acoustic emission in laboratory experiment

    USGS Publications Warehouse

    Ponomarev, Alexander; Lockner, David A.; Stroganova, S.; Stanchits, S.; Smirnov, V.

    2010-01-01

    Spatial and temporal patterns of acoustic emission (AE) were studied. A pre-fractured cylinder of granite was loaded in a triaxial machine at 160 MPa confining pressure until stick-slip events occurred. The experiments were conducted at a constant strain rate of 10−7 s−1 that was modulated by small-amplitude sinusoidal oscillations with periods of 175 and 570 seconds. Amplitude of the oscillations was a few percent of the total load and was intended to simulate periodic loading observed in nature (e.g., earth tides or other sources). An ultrasonic acquisition system with 13 piezosensors recorded acoustic emissions that were generated during deformation of the sample. We observed a correlation between AE response and sinusoidal loading. The effect was more pronounced for higher frequency of the modulating force. A time-space spectral analysis for a “point” process was used to investigate details of the periodic AE components. The main result of the study was the correlation of oscillations of acoustic activity synchronized with the applied oscillating load. The intensity of the correlated AE activity was most pronounced in the “aftershock” sequences that followed large-amplitude AE events. We suggest that this is due to the higher strain-sensitivity of the failure area when the sample is in a transient, unstable mode. We also found that the synchronization of AE activity with the oscillating external load nearly disappeared in the period immediately after the stick-slip events and gradually recovered with further loading.

  17. Identifying fatigue crack geometric features from acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Bao, Jingjing; Poddar, Banibrata; Giurgiutiu, Victor

    2016-04-01

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

  18. Drive Rig Mufflers for Model Scale Engine Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Stephens, David

    2010-01-01

    Testing of air breathing propulsion systems in the 9x15 foot wind tunnel at NASA Glenn Research Center depends on compressed air turbines for power. The drive rig turbines exhaust directly to the wind tunnel test section, and have been found to produce significant unwanted noise that reduces the quality of the acoustic measurements of the model being tested. In order to mitigate this acoustic contamination, a muffler can be attached downstream of the drive rig turbine. The modern engine designs currently being tested produce much less noise than traditional engines, and consequently a lower noise floor is required of the facility. An acoustic test of a muffler designed to mitigate this extraneous noise is presented, and a noise reduction of 8 dB between 700 Hz and 20 kHz was documented, significantly improving the quality of acoustic measurements in the facility.

  19. High-temperature acoustic test facilities and methods

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome

    1994-09-01

    The Wright Laboratory is the Air Force center for air vehicles, responsible for developing advanced technology and incorporating it into new flight vehicles and for continuous technological improvement of operational air vehicles. Part of that responsibility is the problem of acoustic fatigue. With the advent of jet aircraft in the 1950's, acoustic fatigue of aircraft structure became a significant problem. In the 1960's the Wright Laboratory constructed the first large acoustic fatigue test facilities in the United States, and the laboratory has been a dominant factor in high-intensity acoustic testing since that time. This paper discusses some of the intense environments encountered by new and planned Air Force flight vehicles, and describes three new acoustic test facilities of the Wright Laboratory designed for testing structures in these dynamic environments. These new test facilities represent the state of the art in high-temperature, high-intensity acoustic testing and random fatigue testing. They will allow the laboratory scientists and engineers to test the new structures and materials required to withstand the severe environments of captive-carry missiles, augmented lift wings and flaps, exhaust structures of stealth aircraft, and hypersonic vehicle structures well into the twenty-first century.

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

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Morscher, Gregory N.

    2001-01-01

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

  1. Changes in acoustic emission peaks in precipitation strengthened alloys with heat treatment

    SciTech Connect

    Heiple, C.R.; Carpenter, S.H.

    1983-01-01

    Acoustic emission was measured during tensile deformation in a number of precipitation-strengthened alloys as a function of prior heat treatment. The alloys tested included 7075, 6061, and 2219 aluminum; a modified A-286 stainless steel (JBK-75) and an experimental beryllium-containing stainless steel; and Incoloy 903. A rms voltage peak was observed in all the alloys near the onset of plastic flow, and a second peak was usually observed in 7075, 2219, and Incoloy 903 at plastic strains greater than 1%. Some evidence of a second peak was also observed in 6061 aluminum. Changes with heat treatment in the stress and strain at which the second peak occurred were consistent with the peak arising from the fracture of inclusions. The shifts in the location of the peak were in a direction so as to make the stress on the inclusions at the second peak relatively insensitive to prior heat treatment. The amplitude distributions of acoustic emission signals were also consistent with this interpretation. The strain at which the first acoustic emission peak occurred also varied with heat treatment, but the dependence of peak location on prior aging was different for the various alloys.

  2. Issues Related to Large Flight Hardware Acoustic Qualification Testing

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Perry, Douglas C.; Kern, Dennis L.

    2011-01-01

    The characteristics of acoustical testing volumes generated by reverberant chambers or a circle of loudspeakers with and without large flight hardware within the testing volume are significantly different. The parameters attributing to these differences are normally not accounted for through analysis or acoustic tests prior to the qualification testing without the test hardware present. In most cases the control microphones are kept at least 2-ft away from hardware surfaces, chamber walls, and speaker surfaces to minimize the impact of the hardware in controlling the sound field. However, the acoustic absorption and radiation of sound by hardware surfaces may significantly alter the sound pressure field controlled within the chamber/speaker volume to a given specification. These parameters often result in an acoustic field that may provide under/over testing scenarios for flight hardware. In this paper the acoustic absorption by hardware surfaces will be discussed in some detail. A simple model is provided to account for some of the observations made from Mars Science Laboratory spacecraft that recently underwent acoustic qualification tests in a reverberant chamber.

  3. Acoustic Emission Analysis of Damage Progression in Thermal Barrier Coatings Under Thermal Cyclic Conditions

    NASA Technical Reports Server (NTRS)

    Appleby, Matthew; Zhu, Dongming; Morscher, Gregory

    2015-01-01

    Damage evolution of electron beam-physical vapor deposited (EBVD-PVD) ZrO2-7 wt.% Y2O3 thermal barrier coatings (TBCs) under thermal cyclic conditions was monitored using an acoustic emission (AE) technique. The coatings were heated using a laser heat flux technique that yields a high reproducibility in thermal loading. Along with AE, real-time thermal conductivity measurements were also taken using infrared thermography. Tests were performed on samples with induced stress concentrations, as well as calcium-magnesium-alumino-silicate (CMAS) exposure, for comparison of damage mechanisms and AE response to the baseline (as-produced) coating. Analysis of acoustic waveforms was used to investigate damage development by comparing when events occurred, AE event frequency, energy content and location. The test results have shown that AE accumulation correlates well with thermal conductivity changes and that AE waveform analysis could be a valuable tool for monitoring coating degradation and provide insight on specific damage mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. The application of acoustic emission technique to fatigue crack measurement. [in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.; Crews, J. H., Jr.

    1974-01-01

    The applicability of acoustic emission technique to measure fatigue cracks in aluminum alloy specimens was investigated. There are several variables, such as the metallurgical and the physical treatment of the specimen, that can affect the level of acoustic activity of a fatigue specimen. It is therefore recommended that the acoustic emission technique be supplemented by other nondestructive evaluation methods to obtain quantitative data on crack growth.

  6. Embedded and conventional ultrasonic sensors for monitoring acoustic emission during thermal fatigue

    NASA Astrophysics Data System (ADS)

    Trujillo, Blaine; Zagrai, Andrei

    2016-04-01

    Acoustic emission is widely used for monitoring pressure vessels, pipes, critical infrastructure, as well as land, sea and air vehicles. It is one of dominant approaches to explore material degradation under fatigue and events leading to material fracture. Addressing a recent interest in structural health monitoring of space vehicles, a need has emerged to evaluate material deterioration due to thermal fatigue during spacecraft atmospheric reentry. Thermal fatigue experiments were conducted, in which aluminum plates were subjected to localized heating and acoustic emission was monitoring by embedded and conventional acoustic emission sensors positioned at various distances from a heat source. At the same time, surface temperature of aluminum plates was monitored using an IR camera. Acoustic emission counts collected by embedded sensors were compared to counts measured with conventional acoustic emission sensors. Both types of sensors show noticeable increase of acoustic emission activity as localized heating source was applied to aluminum plates. Experimental data demonstrate correlation between temperature increase on the surface of the plates and increase in measured acoustic emission activity. It is concluded that under particular conditions, embedded piezoelectric wafer active sensors can be used for acoustic emission monitoring of thermally-induced structural degradation.

  7. Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors

    PubMed Central

    Li, Dongsheng; Cao, Hai

    2012-01-01

    The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

  8. Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

    PubMed Central

    Panjsetooni, Alireza; Bunnori, Norazura Muhamad; Vakili, Amir Hossein

    2013-01-01

    Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures. PMID:23997681

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

    PubMed

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

    2016-05-01

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

  10. Cassini/Titan-4 Acoustic Blanket Development and Testing

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.

    1996-01-01

    NASA Lewis Research Center recently led a multi-organizational effort to develop and test verify new acoustic blankets. These blankets support NASA's goal in reducing the Titan-4 payload fairing internal acoustic environment to allowable levels for the Cassini spacecraft. To accomplish this goal a two phase acoustic test program was utilized. Phase One consisted of testing numerous blanket designs in a flat panel configuration. Phase Two consisted of testing the most promising designs out of Phase One in a full scale cylindrical payload fairing. This paper will summarize this highly successful test program by providing the rationale and results for each test phase, the impacts of this testing on the Cassini mission, as well as providing some general information on blanket designs.

  11. Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

    NASA Technical Reports Server (NTRS)

    Nance, Donald; Liever, Peter; Nielsen, Tanner

    2015-01-01

    The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test, conducted at Marshall Space Flight Center. The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

  12. Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

    NASA Technical Reports Server (NTRS)

    Nance, Donald K.; Liever, Peter A.

    2015-01-01

    The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test (SMAT), conducted at Marshall Space Flight Center (MSFC). The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

  13. Maneuver Acoustic Flight Test of the Bell 430 Helicopter

    NASA Technical Reports Server (NTRS)

    Watts, Michael E.; Snider, Royce; Greenwood, Eric; Baden, Joel

    2012-01-01

    A cooperative flight test by NASA, Bell Helicopter and the U.S. Army to characterize the steady state acoustics and measure the maneuver noise of a Bell Helicopter 430 aircraft was accomplished. The test occurred during June/July, 2011 at Eglin Air Force Base, Florida. This test gathered a total of 410 data points over 10 test days and compiled an extensive data base of dynamic maneuver measurements. Three microphone configurations with up to 31 microphones in each configuration were used to acquire acoustic data. Aircraft data included DGPS, aircraft state and rotor state information. This paper provides an overview of the test.

  14. Quality Prediction of Twin Wire Arc Sprayed Coatings Using Acoustic Emission Analysis

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Wang, G.; Zielke, R.

    2013-03-01

    In this work, acoustic emission analysis is utilized in the twin wire arc spraying (TWAS) process to study the influence of the adjustable process parameters on the simultaneously obtained acoustic signals at the nozzle and at the substrate. The amplitude of recorded signals at the substrate was in general much higher than those recorded at the nozzle. At the substrate side, the amplitude of emitted acoustic signals is dependent on feedstock materials and is higher when using solid wires. The acoustic signals were recorded at the spraying gun for different gas pressures without arc ignition (as dry runs) in order to reveal the effect of the arc on the emitted acoustic signals. A correlation between controllable parameters, the acoustic signals, and the obtained in-flight particle characteristics was observed. This work contributes to the online control of TWAS processes and is one of many proposed publications in the research field of the conducted acoustic emission analysis.

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

    PubMed Central

    Aggelis, Dimitrios. G.; Strantza, Maria; Louis, Olivia; Boulpaep, Frans; Polyzos, Demosthenes; van Hemelrijck, Danny

    2015-01-01

    The study describes the acoustic emission (AE) activity during human femur tissue fracture. The specimens were fractured in a bending-torsion loading pattern with concurrent monitoring by two AE sensors. The number of recorded signals correlates well with the applied load providing the onset of micro-fracture at approximately one sixth of the maximum load. Furthermore, waveform frequency content and rise time are related to the different modes of fracture (bending of femur neck or torsion of diaphysis). The importance of the study lies mainly in two disciplines. One is that, although femurs are typically subjects of surgical repair in humans, detailed monitoring of the fracture with AE will enrich the understanding of the process in ways that cannot be achieved using only the mechanical data. Additionally, from the point of view of monitoring techniques, applying sensors used for engineering materials and interpreting the obtained data pose additional difficulties due to the uniqueness of the bone structure. PMID:25763648

  16. Monitoring damage growth in titanium matrix composites using acoustic emission

    NASA Technical Reports Server (NTRS)

    Bakuckas, J. G., Jr.; Prosser, W. H.; Johnson, W. S.

    1993-01-01

    The application of the acoustic emission (AE) technique to locate and monitor damage growth in titanium matrix composites (TMC) was investigated. Damage growth was studied using several optical techniques including a long focal length, high magnification microscope system with image acquisition capabilities. Fracture surface examinations were conducted using a scanning electron microscope (SEM). The AE technique was used to locate damage based on the arrival times of AE events between two sensors. Using model specimens exhibiting a dominant failure mechanism, correlations were established between the observed damage growth mechanisms and the AE results in terms of the events amplitude. These correlations were used to monitor the damage growth process in laminates exhibiting multiple modes of damage. Results revealed that the AE technique is a viable and effective tool to monitor damage growth in TMC.

  17. Characterisation of a laser droplet formation process by acoustic emission.

    PubMed

    Govekar, E; Klemencic, J; Kokalj, T; Jahrsdörfer, B; Muzic, P; Grabec, I

    2004-04-01

    The aim of this article is to describe an application of acoustic emission to characterise a process of laser droplet formation from a metal wire. Laser droplet formation is a crucial process in new laser droplet welding technology, where parts are joined by means of the heat content of a liquid metal droplet deposited onto the parts to be joined. A laser beam is used for heating and melting the wire tip, and for detaching the molten pendant droplet. Depending on the process parameters, three different outcomes of the process can be observed: (1) no droplet formed; (2) a droplet formed but not detached; (3) a droplet formed and detached from the wire. It is shown that AE can be used to monitor the process and to indicate the different process outcomes. PMID:15047268

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

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Verification of Ares I Liftoff Acoustic Environments via the Ares Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2012-01-01

    Launch environments, such as Liftoff Acoustic (LOA) and Ignition Overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA which are used in the development of the vibro-acoustic environments. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe to mitigate at the component level, reduction of the launch environments is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I launch environments and to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments. The ASMAT results are compared to the Ares I LOA predictions and water suppression effectiveness results are presented.

  1. Verification of Ares I Liftoff Acoustic Environments via the Ares I Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2012-01-01

    Launch environments, such as Liftoff Acoustic (LOA) and Ignition Overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA which are used in the development of the vibro-acoustic environments. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe to mitigate at the component level, reduction of the launch environments is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I launch environments and to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments. The ASMAT results are compared to the Ares I LOA predictions and water suppression effectiveness results are presented.

  2. Acoustic test and analyses of three advanced turboprop models

    NASA Technical Reports Server (NTRS)

    Brooks, B. M.; Metzger, F. B.

    1980-01-01

    Results of acoustic tests of three 62.2 cm (24.5 inch) diameter models of the prop-fan (a small diameter, highly loaded. Multi-bladed variable pitch advanced turboprop) are presented. Results show that there is little difference in the noise produced by unswept and slightly swept designs. However, the model designed for noise reduction produces substantially less noise at test conditions simulating 0.8 Mach number cruise speed or at conditions simulating takeoff and landing. In the near field at cruise conditions the acoustically designed. In the far field at takeoff and landing conditions the acoustically designed model is 5 db quieter than unswept or slightly swept designs. Correlation between noise measurement and theoretical predictions as well as comparisons between measured and predicted acoustic pressure pulses generated by the prop-fan blades are discussed. The general characteristics of the pulses are predicted. Shadowgraph measurements were obtained which showed the location of bow and trailing waves.

  3. In-flight acoustic testing techniques using the YO-3A Acoustic Research Aircraft

    NASA Technical Reports Server (NTRS)

    Cross, J. L.; Watts, M. E.

    1984-01-01

    This report discusses the flight testing techniques and equipment employed during air-to-air acoustic testing of helicopters at Ames Research Center. The in flight measurement technique used enables acoustic data to be obtained without the limitations of anechoic chambers or the multitude of variables encountered in ground based flyover testing. The air-to-air testing is made possible by the NASA YO-3A Acoustic Research Aircraft. This "Quiet Aircraft' is an acoustically instrumented version of a quiet observation aircraft manufactured for the military. To date, tests with the following aircraft have been conducted: YO-3A background noise; Hughes 500D; Hughes AH-64; Bell AH-1S; Bell AH-1G. Several system upgrades are being designed and implemented to improve the quality of data. This report will discuss not only the equipment involved and aircraft tested, but also the techniques used in these tests. In particular, formation flying position locations, and the test matrices will be discussed. Examples of data taken will also be presented.

  4. Tabulation of data from the tip aerodynamics and acoustics test

    NASA Technical Reports Server (NTRS)

    Cross, Jeffrey L.; Tu, Wilson

    1990-01-01

    In a continuing effort to understand helicopter rotor tip aerodynamics and acoustics, researchers at Ames Research Center conducted a flight test. The test was performed using the NASA White Cobra and a set of highly instrumented blades. Tabular and graphic summaries of two data subsets from the Tip Aerodynamics and Acoustics Test are given. The data presented are for airloads, blade structural loads, blade vibrations, with summary tables of the aircraft states for each test point. The tabular data consist of the first 15 harmonics only, whereas the plots contain the entire measured frequency content.

  5. Extruded Bread Classification on the Basis of Acoustic Emission Signal With Application of Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Świetlicka, Izabela; Muszyński, Siemowit; Marzec, Agata

    2015-04-01

    The presented work covers the problem of developing a method of extruded bread classification with the application of artificial neural networks. Extruded flat graham, corn, and rye breads differening in water activity were used. The breads were subjected to the compression test with simultaneous registration of acoustic signal. The amplitude-time records were analyzed both in time and frequency domains. Acoustic emission signal parameters: single energy, counts, amplitude, and duration acoustic emission were determined for the breads in four water activities: initial (0.362 for rye, 0.377 for corn, and 0.371 for graham bread), 0.432, 0.529, and 0.648. For classification and the clustering process, radial basis function, and self-organizing maps (Kohonen network) were used. Artificial neural networks were examined with respect to their ability to classify or to cluster samples according to the bread type, water activity value, and both of them. The best examination results were achieved by the radial basis function network in classification according to water activity (88%), while the self-organizing maps network yielded 81% during bread type clustering.

  6. Quantitative Analysis Of Acoustic Emission From Rock Fracture Experiments

    NASA Astrophysics Data System (ADS)

    Goodfellow, Sebastian David

    This thesis aims to advance the methods of quantitative acoustic emission (AE) analysis by calibrating sensors, characterizing sources, and applying the results to solve engi- neering problems. In the first part of this thesis, we built a calibration apparatus and successfully calibrated two commercial AE sensors. The ErgoTech sensor was found to have broadband velocity sensitivity and the Panametrics V103 was sensitive to surface normal displacement. These calibration results were applied to two AE data sets from rock fracture experiments in order to characterize the sources of AE events. The first data set was from an in situ rock fracture experiment conducted at the Underground Research Laboratory (URL). The Mine-By experiment was a large scale excavation response test where both AE (10 kHz - 1 MHz) and microseismicity (MS) (1 Hz - 10 kHz) were monitored. Using the calibration information, magnitude, stress drop, dimension and energy were successfully estimated for 21 AE events recorded in the tensile region of the tunnel wall. Magnitudes were in the range -7.5 < Mw < -6.8, which is consistent with other laboratory AE results, and stress drops were within the range commonly observed for induced seismicity in the field (0.1 - 10 MPa). The second data set was AE collected during a true-triaxial deformation experiment, where the objectives were to characterize laboratory AE sources and identify issues related to moving the analysis from ideal in situ conditions to more complex laboratory conditions in terms of the ability to conduct quantitative AE analysis. We found AE magnitudes in the range -7.8 < Mw < -6.7 and as with the in situ data, stress release was within the expected range of 0.1 - 10 MPa. We identified four major challenges to quantitative analysis in the laboratory, which in- hibited our ability to study parameter scaling (M0 ∝ fc -3 scaling). These challenges were 0c (1) limited knowledge of attenuation which we proved was continuously evolving, (2

  7. The Testing Behind the Test Facility: the Acoustic Design of the NASA Glenn Research Center's World-Class Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Mark E.; Hozman, Aron D.; McNelis, Anne M.

    2010-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC s Plum Brook Station in Sandusky, Ohio, U.S.A. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA s space exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada s acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, U.S.A. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic design and subsequent ongoing construction.

  8. The Testing Behind The Test Facility: The Acoustic Design of the NASA Glenn Research Center's World-Class Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Mark E.; McNelis, Anne M.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC?s Plum Brook Station in Sandusky, Ohio, USA. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA?s space exploration program. T he large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world?s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada?s acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, USA. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic de-sign and subsequent on-going construction.

  9. The Testing Behind The Test Facility: The Acoustic Design of the NASA Glenn Research Center's World-Class Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.; McNelis, Mark E.; McNelis, Anne M.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC's Plum Brook Station in Sandusky, Ohio, USA. Benham Companies, LLC is currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA's space exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 cu ft in volume and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world's known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada's acoustic test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, USA. The majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic design and subsequent on-going construction.

  10. Characterization of delamination and transverse cracking in graphite/epoxy laminates by acoustic emission

    NASA Technical Reports Server (NTRS)

    Garg, A.; Ishaei, O.

    1983-01-01

    Efforts to characterize and differentiate between two major failure processes in graphite/epoxy composites - transverse cracking and Mode I delamination are described. Representative laminates were tested in uniaxial tension and flexure. The failure processes were monitored and identified by acoustic emission (AE). The effect of moisture on AE was also investigated. Each damage process was found to have a distinctive AE output that is significantly affected by moisture conditions. It is concluded that AE can serve as a useful tool for detecting and identifying failure modes in composite structures in laboratory and in service environments.

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

    PubMed Central

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

    2013-01-01

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

  12. Acoustic emission from single point machining: Part 2, Signal changes with tool wear. Revised

    SciTech Connect

    Heiple, C.R.; Carpenter, S.H.; Armentrout, D.L.; McManigle, A.P.

    1989-12-31

    Changes in acoustic emission signal characteristics with tool wear were monitored during single point machining of 4340 steel and Ti-6Al-4V heat treated to several strength levels, 606l-T6 aluminum, 304 stainless steel, 17-4PH stainless steel, 410 stainless steel, lead, and teflon. No signal characteristic changed in the same way with tool wear for all materials tested. A single change in a particular AE signal characteristic with tool wear valid for all materials probably does not exist. Nevertheless, changes in various signal characteristic with wear for a given material may be sufficient to be used to monitor tool wear.

  13. Acoustic emission from single point machining: Part 2, Signal changes with tool wear

    SciTech Connect

    Heiple, C.R.; Carpenter, S.H.; Armentrout, D.L.; McManigle, A.P.

    1989-01-01

    Changes in acoustic emission signal characteristics with tool wear were monitored during single point machining of 4340 steel and Ti-6Al-4V heat treated to several strength levels, 606l-T6 aluminum, 304 stainless steel, 17-4PH stainless steel, 410 stainless steel, lead, and teflon. No signal characteristic changed in the same way with tool wear for all materials tested. A single change in a particular AE signal characteristic with tool wear valid for all materials probably does not exist. Nevertheless, changes in various signal characteristic with wear for a given material may be sufficient to be used to monitor tool wear.

  14. Comparison of Two High Intensity Acoustic Test Facilities

    NASA Astrophysics Data System (ADS)

    Launay, A.; Tadao Sakita, M.; Kim, Youngkey K.

    2004-08-01

    In two different countries, at the same period of time, the institutes in charge of the development of space activities have decided to extend their satellite integration and test center, and to implement a reverberant acoustic chamber. In Brazil the INPE laboratory (LIT : Laboratorio de Integracao e Testes) and in South Korea the KARI laboratory (SITC : Satellite Integration and Test Center) started their projects in July 2000 for the RATF (Reverberant Acoustic Test Facility) and in May 2001 for the HIAC (High Intensity Acoustic Chamber) respectively, writing the technical specifications. The kick-off meetings took place in December 2000 and in February 2002 and the opening ceremonies in December 19, 2002 in Brazil and in August 22, 2003 in Korea. This paper compares the two projects in terms of design choices, manufacturing processes, equipment installed and technical final characteristics.

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

    PubMed

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

    2014-01-01

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

  16. The Nozzle Acoustic Test Rig: an Acoustic and Aerodynamic Free-jet Facility

    NASA Technical Reports Server (NTRS)

    Castner, Raymond S.

    1994-01-01

    The nozzle acoustic test rig (NATR) was built at NASA Lewis Research Center to support the High Speed Research Program. The facility is capable of measuring the acoustic and aerodynamic performance of aircraft engine nozzle concepts. Trade-off studies are conducted to compare performance and noise during simulated low-speed flight and takeoff. Located inside an acoustically treated dome with a 62-ft radius, the NATR is a free-jet that has a 53-in. diameter and is driven by an air ejector. This ejector is operated with 125 lb/s of compressed air, at 125 psig, to achieve 375 lb/s at Mach 0.3. Acoustic and aerodynamic data are collected from test nozzles mounted in the free-jet flow. The dome serves to protect the surrounding community from high noise levels generated by the nozzles, and to provide an anechoic environment for acoustic measurements. Information presented in this report summarizes free-jet performance, fluid support systems, and data acquisition capabilities of the NATR.

  17. 40 CFR 61.67 - Emission tests.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 9 2014-07-01 2014-07-01 false Emission tests. 61.67 Section 61.67... Emission tests. (a) Unless a waiver of emission testing is obtained under § 61.13, the owner or operator of a source to which this subpart applies shall test emissions from the source, (1) Within 90 days...

  18. 40 CFR 61.67 - Emission tests.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 9 2013-07-01 2013-07-01 false Emission tests. 61.67 Section 61.67... Emission tests. (a) Unless a waiver of emission testing is obtained under § 61.13, the owner or operator of a source to which this subpart applies shall test emissions from the source, (1) Within 90 days...

  19. Constitutive acoustic-emission elastic-stress behavior of magnesium alloy

    NASA Technical Reports Server (NTRS)

    Williams, J. H., Jr.; Emerson, G. P.

    1977-01-01

    Repeated laoding and unloading of a magnesium alloy below the macroscopic yield stress result in continuous acoustic emissions which are generally repeatable for a given specimen and which are reproducible between different specimens having the same load history. An acoustic emission Bauschinger strain model is proposed to describe the unloading emission behavior. For the limited range of stress examined, loading and unloading stress delays of the order of 50 MN/sq m are observed, and they appear to be dependent upon the direction of loading, the stress rate, and the stress history. The stress delay is hypothesized to be the manifestation of an effective friction stress. The existence of acoustic emission elastic stress constitutive relations is concluded, which provides support for a previously proposed concept for the monitoring of elastic stresses by acoustic emission.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  2. Transportable Emissions Testing Laboratory for Alternative Vehicles Emissions Testing

    SciTech Connect

    Clark, Nigel

    2012-01-31

    The overall objective of this project was to perform research to quantify and improve the energy efficiency and the exhaust emissions reduction from advanced technology vehicles using clean, renewable and alternative fuels. Advanced vehicle and alternative fuel fleets were to be identified, and selected vehicles characterized for emissions and efficiency. Target vehicles were to include transit buses, school buses, vocational trucks, delivery trucks, and tractor-trailers. Gaseous species measured were to include carbon monoxide, carbon dioxide, oxides of nitrogen, hydrocarbons, and particulate matter. An objective was to characterize particulate matter more deeply than by mass. Accurate characterization of efficiency and emissions was to be accomplished using a state-of-the-art portable emissions measurement system and an accompanying chassis dynamometer available at West Virginia University. These two units, combined, are termed the Transportable Laboratory. An objective was to load the vehicles in a real-world fashion, using coast down data to establish rolling resistance and wind drag, and to apply the coast down data to the dynamometer control. Test schedules created from actual vehicle operation were to be employed, and a specific objective of the research was to assess the effect of choosing a test schedule which the subject vehicle either cannot follow or can substantially outperform. In addition the vehicle loading objective was to be met better with an improved flywheel system.

  3. Overview of the Ares I Scale Model Acoustic Test Program

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2011-01-01

    Launch environments, such as lift-off acoustic (LOA) and ignition overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. LOA environments are used directly in the development of vehicle vibro-acoustic environments and IOP is used in the loads assessment. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe for component survivability, reduction of the environment itself is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the Ares I LOA and IOP environments for the vehicle and ground systems including the Mobile Launcher (ML) and tower. An additional objective was to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. ASMAT was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116 (TS 116). The ASMAT program is described in this presentation.

  4. Acoustic Emission Monitoring of the Syracuse Athena Temple: Scale Invariance in the Timing of Ruptures

    SciTech Connect

    Niccolini, G.; Carpinteri, A.; Lacidogna, G.; Manuello, A.

    2011-03-11

    We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of magnitude scales. This evidence suggests a correlation between the aging process of the temple and the local seismic activity.

  5. Development of novel optical fiber interferometric sensors with high sensitivity for acoustic emission detection

    NASA Astrophysics Data System (ADS)

    Deng, Jiangdong

    For the purpose of developing a new highly-sensitive and reliable fiber optical acoustic sensor capable of real-time on-line detection of acoustic emissions in power transformers, this dissertation presents the comprehensive research work on the theory, modeling, design, instrumentation, noise analysis, and performance evaluation of a diaphragm-based optical fiber acoustic (DOFIA) sensor system. The optical interference theory and the diaphragm dynamic vibration analysis form the two foundation stones of the diaphragm-based optical fiber interferometric acoustic (DOFIA) sensor. Combining these two principles, the pressure sensitivity and frequency response of the acoustic sensor system is analyzed quantitatively, which provides guidance for the practical design for the DOFIA sensor probe and system. To meet all the technical requirements for partial discharge detection, semiconductor process technologies are applied, for the first time to our knowledge, in fabricating the micro-caved diaphragm (MCD) used for the DOFIA sensor probe. The novel controlled thermal bonding method was proposed, designed, and developed to fabricate high performance DOFIA sensor probes with excellent mechanical strength and temperature stability. In addition, the signal processing unit is designed and implemented with high gain, wide band response, and ultra low noise. A systematic noise analysis is also presented to provide a better understanding of the performance limitations of the DOFIA sensor system. Based on the system noise analysis results, optimization measures are proposed to improve the system performance. Extensive experiments, including the field testing in a power transformer, have also been conducted to systematically evaluate the performance of the instrumentation systems and the sensor probes. These results clearly demonstrated the feasibility of the developed DOFIA sensor for the detection of partial discharges inside electrical power transformers, with unique advantages

  6. Acoustical Testing Laboratory Developed to Support the Low-Noise Design of Microgravity Space Flight Hardware

    NASA Technical Reports Server (NTRS)

    Cooper, Beth A.

    2001-01-01

    The NASA John H. Glenn Research Center at Lewis Field has designed and constructed an Acoustical Testing Laboratory to support the low-noise design of microgravity space flight hardware. This new laboratory will provide acoustic emissions testing and noise control services for a variety of customers, particularly for microgravity space flight hardware that must meet International Space Station limits on noise emissions. These limits have been imposed by the space station to support hearing conservation, speech communication, and safety goals as well as to prevent noise-induced vibrations that could impact microgravity research data. The Acoustical Testing Laboratory consists of a 23 by 27 by 20 ft (height) convertible hemi/anechoic chamber and separate sound-attenuating test support enclosure. Absorptive 34-in. fiberglass wedges in the test chamber provide an anechoic environment down to 100 Hz. A spring-isolated floor system affords vibration isolation above 3 Hz. These criteria, along with very low design background levels, will enable the acquisition of accurate and repeatable acoustical measurements on test articles, up to a full space station rack in size, that produce very little noise. Removable floor wedges will allow the test chamber to operate in either a hemi/anechoic or anechoic configuration, depending on the size of the test article and the specific test being conducted. The test support enclosure functions as a control room during normal operations but, alternatively, may be used as a noise-control enclosure for test articles that require the operation of noise-generating test support equipment.

  7. Progressive Shear Failure in Granular Materials: Linking Force Fluctuations With Acoustic Emissions

    NASA Astrophysics Data System (ADS)

    Michlmayr, G. K.; Cohen, D. O.; Or, D.

    2011-12-01

    Natural hazards associated with rapid mass movements such as shallow landslides, rock falls or debris flows are notoriously difficult to predict even though precursor events associated with small internal failures are known to occur. In this study we focus on grain scale processes preceding the formation of a shear plane in granular materials such as frictional sliding of grain contacts, accommodation of contact networks and fracturing of grain bonds (in cohesive materials) - all of which are discrete micro-mechanical failure events that emit characteristic acoustic emissions that could be used to study internal failure and potentially provide early warning (albeit short). Experiments involving direct shear tests using glass beads and sand were combined with acoustic emission (AE) measurements using piezoelectric sensors with sensitivities to frequencies in the range of 20kHz - 200kHz and accelerometers (0.2kHz - 20kHz) buried within the sheared sample. We obtained good correlations between shear deformation and associated grain-scale mechanical behavior with key characteristics of measured AE (frequency content, signal energy). Fluctuations of shear force occurring during strain controlled deformation are assumed to represent micro-structural rearrangements of the material. We obtained exponential distributions of force fluctuation magnitudes and low frequency AE event statistics. The number of AE events increased with confining stress as well as with particle roughness and were inversely related to grain size. These results were linked with conceptual models of failure accumulation such as the fiber-bundle model. The statistics of AE event occurrence, particularly magnitude-frequency distributions may provide prediction of imminent mechanical collapse. The strong attenuation of acoustic signals within most earth materials present a major challenge to field applications requiring innovative deployment strategies such as the use of acoustic waveguides.

  8. Vibration and acoustic testing of TOPEX/Poseidon satellite

    NASA Technical Reports Server (NTRS)

    Boatman, Dave; Scharton, Terry; Hershfeld, Donald; Larkin, Paul

    1992-01-01

    The satellite was subjected to a 1.5G swept sine vibration test and a 146 dB overall level acoustic test, in accordance with Ariane launch vehicle requirements, at the NASA Goddard Space Flight Center. Extensive pretest analysis of the sine test was conducted to plan the input notching and to justify vibration testing the satellite only in the longitudinal axis. A unique measurement system was utilized to determine the six components of interface force between the shaker and the satellite in the sine vibration test. The satellite was heavily instrumented in both the sine vibration and acoustic test in order to insure that the launch loads were enveloped with appropriate margin and that satellite responses did not exceed the compatibilities of the structure and equipment. The test specification, objectives, instrumentation, and test results are described herein.

  9. Diagnostic of material defects found in pipelines made of 13 HMF steel on the basis of acoustic emission

    NASA Astrophysics Data System (ADS)

    Skubis, Jerzy; Jeziorski, Grzegorz; Ranachowski, Jerzy

    1992-07-01

    Preparatory work performed in developing a diagnostic method for testing welded joints in pressure pipelines made of 13 HMF steel by means of acoustic emission (AE) measurements is described. Within the framework of these studies the mechanical strength characteristic of the 13 HMF steel was determined in a tension test with simultaneous AE measurements. Later AE measurements were conducted on real pipeline sections with joints, during heat treatment. Acoustic emission was investigated according to the requirements of the ASME standard. Preliminary analysis of the results indicated that the AE method may be used for diagnoses of welded joints in pressure pipelines. Technical specifications of a three-channel AE analyzer manufactured by IPPT PAN (Institute of Basic Technological Problems, Polish Academy of Sciences) and used for test are sufficient for such measurements. A detailed physical interpretation of the phenomena occurring during the tests is presented.

  10. SPATIAL DISTRIBUTIONS OF ABSORPTION, LOCAL SUPPRESSION, AND EMISSIVITY REDUCTION OF SOLAR ACOUSTIC WAVES IN MAGNETIC REGIONS

    SciTech Connect

    Chou, D.-Y.; Yang, M.-H.; Zhao Hui; Liang Zhichao; Sun, M.-T.

    2009-11-20

    Observed acoustic power in magnetic regions is lower than the quiet Sun because of absorption, emissivity reduction, and local suppression of solar acoustic waves in magnetic regions. In the previous studies, we have developed a method to measure the coefficients of absorption, emissivity reduction, and local suppression of sunspots. In this study, we go one step further to measure the spatial distributions of three coefficients in two active regions, NOAA 9055 and 9057. The maps of absorption, emissivity reduction, and local suppression coefficients correlate with the magnetic map, including plage regions, except the emissivity reduction coefficient of NOAA 9055 where the emissivity reduction coefficient is too weak and lost among the noise.

  11. Granular Shear Zone Formation: Acoustic Emission Measurements and Fiber-bundle Models

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Or, Dani

    2013-04-01

    We couple the acoustic emissions method with conceptual models of granular material behavior for investigation of granular shear zone formation and to assess eminence of landslide hazard. When granular materials are mechanically loaded or sheared, they tend to produce discrete events of force network restructuring, and frictional interaction at grain contacts. Such abrupt perturbations within the granular lattice release part of the elastic energy stored in the strained material. Elastic waves generated by such events can be measured as acoustic emissions (AE) and may be used as surrogates for intermittent structural transitions associated with shear zone formation. To experimentally investigate the connection between granular shearing and acoustic signals we performed an array of strain-controlled shear-frame tests using glass beads. AE were measured with two different systems operating at two frequency ranges. High temporal resolution measurements of the shear stresses revealed the presence of small fluctuations typically associated with low-frequency (< 20 kHz) acoustic bursts. Shear stress jumps and linked acoustic signals give account of discrete events of grain network rearrangements and obey characteristic exponential frequency-size distributions. We found that statistical features of force jumps and AE events depend on mechanical boundary conditions and evolve during the straining process. Activity characteristics of high-frequency (> 30 kHz) AE events is linked to friction between grains. To interpret failure associated AE signals, we adapted a conceptual fiber-bundle model (FBM) that describes some of the salient statistical features of failure and associated energy production. Using FBMs for the abrupt mechanical response of the granular medium and an associated grain and force chain AE generation model provides us with a full description of the mechanical-acoustical granular shearing process. Highly resolved AE may serve as a diagnostic tool not only

  12. Vibro-Acoustics Modal Testing at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Pappa, Richard S.; Pritchard, Jocelyn I.; Buehrle, Ralph D.

    1999-01-01

    This paper summarizes on-going modal testing activities at the NASA Langley Research Center for two aircraft fuselage structures: a generic "aluminum testbed cylinder" (ATC) and a Beechcraft Starship fuselage (BSF). Subsequent acoustic tests will measure the interior noise field created by exterior mechanical and acoustic sources. These test results will provide validation databases for interior noise prediction codes on realistic aircraft fuselage structures. The ATC is a 12-ft-long, all-aluminum, scale model assembly. The BSF is a 40-ft-long, all-composite, complete aircraft fuselage. To date, two of seven test configurations of the ATC and all three test configurations of the BSF have been completed. The paper briefly describes the various test configurations, testing procedure, and typical results for frequencies up to 250 Hz.

  13. Acoustic emission during quench training of superconducting accelerator magnets

    NASA Astrophysics Data System (ADS)

    Marchevsky, M.; Sabbi, G.; Bajas, H.; Gourlay, S.

    2015-07-01

    Acoustic emission (AE) sensing is a viable tool for superconducting magnet diagnostics. Using in-house developed cryogenic amplified piezoelectric sensors, we conducted AE studies during quench training of the US LARP's high-field quadrupole HQ02 and the LBNL's high-field dipole HD3. For both magnets, AE bursts were observed, with spike amplitude and frequency increasing toward the quench current during current up-ramps. In the HQ02, the AE onset upon current ramping is distinct and exhibits a clear memory of the previously-reached quench current (Kaiser effect). On the other hand, in the HD3 magnet the AE amplitude begins to increase well before the previously-reached quench current (felicity effect), suggesting an ongoing progressive mechanical motion in the coils. A clear difference in the AE signature exists between the untrained and trained mechanical states in HD3. Time intervals between the AE signals detected at the opposite ends of HD3 coils were processed using a combination of narrow-band pass filtering; threshold crossing and correlation algorithms, and the spatial distributions of AE sources and the mechanical energy release were calculated. Both distributions appear to be consistent with the quench location distribution. Energy statistics of the AE spikes exhibits a power-law scaling typical for the self-organized critical state.

  14. Quantitative acoustic emission from localized sources in material fatigue processes

    NASA Astrophysics Data System (ADS)

    Shi, Zhiqiang; Jarzynski, Jacek; Jacobs, Laurence

    2000-05-01

    Fretting fatigue is the phenomenon where two contacting bodies undergoing a cyclic fatigue loading experience small amplitude oscillatory motion. Fretting fatigue is characterized by crack nucleation and the subsequent propagation of these cracks. The coupling of fatigue with fretting leads to the premature nucleation and acceleration of the early growth of fatigue cracks, resulting in a significant reduction in a structure's service life. A better understanding of the mechanics of fretting fatigue is needed to prevent and reduce the severe consequences of such damage. This research uses quantitative acoustic emission (AE) techniques to study the fretting fatigue of PH 13-8 stainless steel under different loading conditions. Specifically, this work correlates AE signals to specific fretting characteristics such as frictional force history and frictional force-displacement hysteresis loops. These results indicate a close correlation between the various stages of fretting fatigue with the frequency of AE events. For example, AE waveform characteristics (such as amplitude, energy, and frequency spectrum) enable the identification and characterization of the different stages of fatigue. As a result, it is possible to establish a relationship between AE observations and fretting crack initiation and growth.

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

    PubMed

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

    1998-08-01

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

  16. Acoustic emission of fire damaged fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    PubMed

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

    2013-01-01

    This study detected tooth-composite interfacial debonding during composite restoration by means of acoustic emission (AE) analysis and investigated the effects of composite properties and adhesives on AE characteristics. The polymerization shrinkage, peak shrinkage rate, flexural modulus, and shrinkage stress of a methacrylate-based universal hybrid, a flowable, and a silorane-based composite were measured. Class I cavities on 49 extracted premolars were restored with 1 of the 3 composites and 1 of the following adhesives: 2 etch-and-rinse adhesives, 2 self-etch adhesives, and an adhesive for the silorane-based composite. AE analysis was done for 2,000 sec during light-curing. The silorane-based composite exhibited the lowest shrinkage (rate), the longest time to peak shrinkage rate, the lowest shrinkage stress, and the fewest AE events. AE events were detected immediately after the beginning of light-curing in most composite-adhesive combinations, but not until 40 sec after light-curing began for the silorane-based composite. AE events were concentrated at the initial stage of curing in self-etch adhesives compared with etch-and-rinse adhesives. Reducing the shrinkage (rate) of composites resulted in reduced shrinkage stress and less debonding, as evidenced by fewer AE events. AE is an effective technique for monitoring, in real time, the debonding kinetics at the tooth-composite interface. PMID:23100273

  19. Temporal analysis of acoustic emission from a plunged granular bed

    NASA Astrophysics Data System (ADS)

    Tsuji, Daisuke; Katsuragi, Hiroaki

    2015-10-01

    The statistical property of acoustic emission (AE) events from a plunged granular bed is analyzed by means of actual-time and natural-time analyses. These temporal analysis methods allow us to investigate the details of AE events that follow a power-law distribution. In the actual-time analysis, the calm-time distribution, and the decay of the event-occurrence density after the largest event (i.e., the Omori-Utsu law) are measured. Although the former always shows a power-law form, the latter does not always obey a power law. Markovianity of the event-occurrence process is also verified using a scaling law by assuming that both of them exhibit power laws. We find that the effective shear strain rate is a key parameter to classify the emergence rate of power-law nature and Markovianity in granular AE events. For the natural-time analysis, the existence of self-organized critical states is revealed by calculating the variance of natural time χk, where k th natural time of N events is defined as χk=k /N . In addition, the energy difference distribution can be fitted by a q -Gaussian form, which is also consistent with the criticality of the system.

  20. Acoustic emissions (AE) during failure of granular media

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Or, Dani

    2014-05-01

    The release of shallow landslides and other geological mass movements is the result of progressive failure accumulation. Mechanical failure in disordered geologic materials occurs in intermittent breakage episodes marking the disintegration or rearrangement of load-bearing elements. Abrupt strain energy release in such breakage episodes is associated with generation of elastic waves measurable as high-frequency (kHz range) acoustic emissions (AE). The close association of AE with progressive failure events hold a promise for using such noninvasive methods to assess the mechanical state of granular Earth materials or for the development early warning methods for shallow landslides. We present numerical simulations that incorporate damage accumulation and associated stress redistribution using a fiber-bundle model. The stress released from element failure (fibers) is redistributed to the surrounding elements and eventually triggers larger failure avalanches. AE signals generated from such events and eventually hitting a virtual sensor are modeled using visco-elastic wave propagation laws. The model captures the characteristic saw-tooth shape of the observed stress-strain curves obtained from strain-controlled experiments with glass beads, including large intermittent stress release events that stem from cascading failure avalanches. The model also reproduces characteristics of AE signatures and yield a good agreement between simulation results and experimental data. Linking mechanical and AE information in the proposed modeling framework offer a solid basis for interpretation of measured field data.

  1. F-16XL and F-18 High Speed Acoustic Flight Test Databases

    NASA Technical Reports Server (NTRS)

    Kelly, J. J.; Wilson, M. R.; Rawls, J., Jr.; Norum, T. D.; Golub, R. A.

    1999-01-01

    This report presents the recorded acoustic data and the computed narrow-band and 1/3-octave band spectra produced by F-18 and F-16XL aircraft in subsonic flight over an acoustic array. Both broadband-shock noise and turbulent mixing noise are observed in the spectra. Radar and c-band tracking systems provided the aircraft position which enabled directivity and smear angles from the aircraft to each microphone to be computed. These angles are based on source emission time and thus give some idea about the directivity of the radiated sound field due to jet noise. A follow-on static test was also conducted where acoustic and engine data were obtained. The acoustic data described in the report has application to community noise analysis, noise source characterization and validation of prediction models. A detailed description of the signal processing procedures is provided. Follow-on static tests of each aircraft were also conducted for which engine data and far-field acoustic data are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  3. Modal decomposition method for acoustic impedance testing in square ducts.

    PubMed

    Schultz, Todd; Cattafesta, Louis N; Sheplak, Mark

    2006-12-01

    Accurate duct acoustic propagation models are required to predict and reduce aircraft engine noise. These models ultimately rely on measurements of the acoustic impedance to characterize candidate engine nacelle liners. This research effort increases the frequency range of normal-incidence acoustic impedance testing in square ducts by extending the standard two-microphone method (TMM), which is limited to plane wave propagation, to include higher-order modes. The modal decomposition method (MDM) presented includes four normal modes in the model of the sound field, thus increasing the bandwidth from 6.7 to 13.5 kHz for a 25.4 mm square waveguide. The MDM characterizes the test specimen for normal- and oblique-incident acoustic impedance and mode scattering coefficients. The MDM is first formulated and then applied to the measurement of the reflection coefficient matrix for a ceramic tubular specimen. The experimental results are consistent with results from the TMM for the same specimen to within the 95% confidence intervals for the TMM. The MDM results show a series of resonances for the ceramic tubular material exhibiting a monotonic decrease in the resonant peaks of the acoustic resistance with increasing frequency, resembling a rigidly-terminated viscous tube, and also evidence of mode scattering is visible at the higher frequencies. PMID:17225402

  4. Acoustic emission feedback control for control of boiling in a microwave oven

    DOEpatents

    White, Terry L.

    1991-01-01

    An acoustic emission based feedback system for controlling the boiling level of a liquid medium in a microwave oven is provided. The acoustic emissions from the medium correlated with surface boiling is used to generate a feedback control signal proportional to the level of boiling of the medium. This signal is applied to a power controller to automatically and continuoulsly vary the power applied to the oven to control the boiling at a selected level.

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

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

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

  6. Estimation of the Tool Condition by Applying the Wavelet Transform to Acoustic Emission Signals

    SciTech Connect

    Gomez, M. P.; Piotrkowski, R.; Ruzzante, J. E.; D'Attellis, C. E.

    2007-03-21

    This work follows the search of parameters to evaluate the tool condition in machining processes. The selected sensing technique is acoustic emission and it is applied to a turning process of steel samples. The obtained signals are studied using the wavelet transformation. The tool wear level is quantified as a percentage of the final wear specified by the Standard ISO 3685. The amplitude and relevant scale obtained of acoustic emission signals could be related with the wear level.

  7. Barkhausen Effect and Acoustic Emission in a Metallic Glass - Preliminary Results

    SciTech Connect

    Lopez Sanchez, R.; Piotrkowski, R.; Ruzzante, J.E.

    2004-02-26

    Magneto Acoustic Emission, which is Barkhausen Noise (BN) and Acoustic Emission (AE), depends on microstructure and existing residual stresses in magnetic materials. Preliminary results obtained by magnetization along two perpendicular directions on a metal glass foil are presented. Signals were analyzed with Statistic, Fast Fourier and Wavelet methods. Results are part of a Joint Research Project of the Faculty of Science, Cantabria University, Spain, and the Elastic Waves Group of the National Atomic Energy Commission, Argentina.

  8. Acoustic emission monitoring from a lab scale high shear granulator--a novel approach.

    PubMed

    Watson, N J; Povey, M J W; Reynolds, G K; Xu, B H; Ding, Y

    2014-04-25

    A new approach to the monitoring of granulation processes using passive acoustics together with precise control over the granulation process has highlighted the importance of particle-particle and particle-bowl collisions in acoustic emission. The results have shown that repeatable acoustic results could be obtained but only when a spray nozzle water addition system was used. Acoustic emissions were recorded from a transducer attached to the bowl and an airborne transducer. It was found that the airborne transducer detected very little from the granulation and only experienced small changes throughout the process. The results from the bowl transducer showed that during granulation the frequency content of the acoustic emission shifted towards the lower frequencies. Results from the discrete element model indicate that when larger particles are used the number of collisions the particles experience reduces. This is a result of the volume conservation methodology used in this study, therefore larger particles results in less particles. These simulation results coupled with previous theoretical work on the frequency content of an impacting sphere explain why the frequency content of the acoustic emissions reduces during granule growth. The acoustic system used was also clearly able to identify when large over-wetted granules were present in the system, highlighting its benefit for detecting undesirable operational conditions. High-speed photography was used to study if visual changes in the granule properties could be linked with the changing acoustic emissions. The high speed photography was only possible towards the latter stages of the granulation process and it was found that larger granules produced a higher magnitude of acoustic emission across a broader frequency range. PMID:24491527

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  10. Monitoring Thermal Fatigue Damage In Nuclear Power Plant Materials Using Acoustic Emission

    SciTech Connect

    Meyer, Ryan M.; Ramuhalli, Pradeep; Watson, Bruce E.; Pitman, Stan G.; Roosendaal, Timothy J.; Bond, Leonard J.

    2012-04-26

    Proactive aging management of nuclear power plant passive components requires technologies to enable monitoring and accurate quantification of material condition at early stages of degradation (i.e., pre-macrocrack). Acoustic emission (AE) is well-suited to continuous monitoring of component degradation and is proposed as a method to monitor degradation during accelerated thermal fatigue tests. A key consideration is the ability to separate degradation responses from external sources such as water spray induced during thermal fatigue testing. Water spray provides a significant background of acoustic signals, which can overwhelm AE signals caused by degradation. Analysis of AE signal frequency and energy is proposed in this work as a means for separating degradation signals from background sources. Encouraging results were obtained by applying both frequency and energy filters to preliminary data. The analysis of signals filtered using frequency and energy provides signatures exhibiting several characteristics that are consistent with degradation accumulation in materials. Future work is planned to enable verification of the efficacy of AE for thermal fatigue crack initiation detection. While the emphasis has been placed on the use of AE for crack initiation detection during accelerated aging tests, this work also has implications with respect to the use of AE as a primary tool for early degradation monitoring in nuclear power plant materials. The development of NDE tools for characterization of aging in materials can also benefit from the use of a technology such as AE which can continuously monitor and detect crack initiation during accelerated aging tests.

  11. C-Coupon Studies of SiC/SiC Composites. Part 1; Acoustic Emission Monitoring

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Hurwitz, Frances I.; Calomino, Anthony M.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Modal acoustic emission (AE) was used to monitor the acoustic activity during room temperature and elevated temperature c-coupon tests for a variety of SiC/SiC systems including composites containing Sylramic (trademark), ZMI (trademark), or Hi-Nicalon (trademark) fibers with melt-infiltrated or polymer-infiltrated SiC matrices. Modal AE proved excellent at monitoring matrix cracking in the curved portion of the C-coupon specimen with increasing load. This included the load at which the first AE event occurred and the location of AE events during the test that were, presumably, caused by the formation and growth of interlaminar cracks and, at higher loads, transverse cracks. Graphical techniques were employed to estimate the load for first AE. It was determined that for this test with these material systems, the first AE could be estimated within the load range bounded by the load at which initial deviation from linearity of the load-displacement curve occurs and the load where the 98% offset of the linear regression fit intercepted the load-displacement curve. The calculation of interlaminar tensile (ILT) stress from the load for first AE was determined for all the systems. Ultimate ILT strength usually corresponded to ILT stress determined from the ultimate load to failure of the C-coupon test, which was considerably higher than the first cracking stress.

  12. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Article's Absorption During Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    The exposure of a customer's aerospace test-article to a simulated acoustic launch environment is typically performed in a reverberant acoustic test chamber. The acoustic pre-test runs that will ensure that the sound pressure levels of this environment can indeed be met by a test facility are normally performed without a test-article dynamic simulator of representative acoustic absorption and size. If an acoustic test facility's available acoustic power capability becomes maximized with the test-article installed during the actual test then the customer's environment requirement may become compromised. In order to understand the risk of not achieving the customer's in-tolerance spectrum requirement with the test-article installed, an acoustic power margin evaluation as a function of frequency may be performed by the test facility. The method for this evaluation of acoustic power will be discussed in this paper. This method was recently applied at the NASA Glenn Research Center Plum Brook Station's Reverberant Acoustic Test Facility for the SpaceX Falcon 9 Payload Fairing acoustic test program.

  13. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Article's Absorption during Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    The exposure of a customers aerospace test-article to a simulated acoustic launch environment is typically performed in a reverberant acoustic test chamber. The acoustic pre-test runs that will ensure that the sound pressure levels of this environment can indeed be met by a test facility are normally performed without a test-article dynamic simulator of representative acoustic absorption and size. If an acoustic test facilitys available acoustic power capability becomes maximized with the test-article installed during the actual test then the customers environment requirement may become compromised. In order to understand the risk of not achieving the customers in-tolerance spectrum requirement with the test-article installed, an acoustic power margin evaluation as a function of frequency may be performed by the test facility. The method for this evaluation of acoustic power will be discussed in this paper. This method was recently applied at the NASA Glenn Research Center Plum Brook Stations Reverberant Acoustic Test Facility for the SpaceX Falcon 9 Payload Fairing acoustic test program.

  14. Sensoring fusion data from the optic and acoustic emissions of electric arcs in the GMAW-S process for welding quality assessment.

    PubMed

    Alfaro, Sadek Crisóstomo Absi; Cayo, Eber Huanca

    2012-01-01

    The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms. PMID:22969330

  15. Sensoring Fusion Data from the Optic and Acoustic Emissions of Electric Arcs in the GMAW-S Process for Welding Quality Assessment

    PubMed Central

    Alfaro, Sadek Crisóstomo Absi; Cayo, Eber Huanca

    2012-01-01

    The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms. PMID:22969330

  16. Nonlinear ball chain waveguides for acoustic emission and ultrasound sensing of ablation

    NASA Astrophysics Data System (ADS)

    Pearson, Stephen H.

    Harsh environment acoustic emission and ultrasonic wave sensing applications often benefit from placing the sensor in a remote and more benign physical location by using waveguides to transmit elastic waves between the structural location under test and the transducer. Waveguides are normally designed to have high fidelity over broad frequency ranges to minimize distortion -- often difficult to achieve in practice. This thesis reports on an examination of using nonlinear ball chain waveguides for the transmission of acoustic emission and ultrasonic waves for the monitoring of thermal protection systems undergoing severe heat loading, leading to ablation and similar processes. Experiments test the nonlinear propagation of solitary, harmonic and mixed harmonic elastic waves through a copper tube filled with steel and elastomer balls and various other waveguides. Triangulation of pencil lead breaks occurs on a steel plate. Data are collected concerning the usage of linear waveguides and a water-cooled linear waveguide. Data are collected from a second water-cooled waveguide monitoring Atmospheric Reentry Materials in UVM's Inductively-Coupled Plasma Torch Facility. The motion of the particles in the dimer waveguides is linearly modeled with a three ball and spring chain model and the results are compared per particle. A theoretical nonlinear model is presented which is capable of exactly modeling the motion of the dimer chains. The shape of the waveform propagating through the dimer chain is modeled in a sonic vacuum. Mechanical pulses of varying time widths and amplitudes are launched into one end of the ball chain waveguide and observed at the other end in both time and frequency domains. Similarly, harmonic and mixed harmonic mechanical loads are applied to one end of the waveguide. Balls of different materials are analyzed and discriminated into categories. A copper tube packed with six steel particles, nine steel or marble particles and a longer copper tube

  17. Active control of the acoustic boundary conditions of combustion test rigs

    NASA Astrophysics Data System (ADS)

    Bothien, Mirko R.; Moeck, Jonas P.; Oliver Paschereit, Christian

    2008-12-01

    In the design process of burners for gas turbines, new burner generations are generally tested in single or multi burner combustion test rigs. With these experiments, computational fluid dynamics, and finite element calculations, the burners' performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behaviour and the emission characteristics is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match, or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavourable dynamics at the same conditions in the engine. In this work, a method is proposed which uses an active control scheme to manipulate the acoustic boundary conditions of the test rig. Using this method, the boundary conditions can be continuously modified, ranging from anechoic to fully reflecting in a broad frequency range. The concept is applied to an atmospheric combustion test rig with a swirl-stabilized burner. It is shown that the test rig's properties can be tuned to correspond to those of the full-scale engine. For example, the test rig length can be virtually extended, thereby introducing different resonance frequencies, without having to implement any hardware changes. Furthermore, the acoustic boundary condition can be changed to that of a choked flow without actually needing the flow to be choked.

  18. 40 CFR 61.67 - Emission tests.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Emission tests. 61.67 Section 61.67 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Vinyl Chloride § 61.67 Emission tests. (a) Unless a waiver of...

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

    PubMed Central

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

    2012-01-01

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

  20. Acoustic emission during pitting and transgranular crack initiation in type 304 stainless steel

    SciTech Connect

    Jones, R.H.; Friesel, M.A. )

    1992-09-01

    This paper reports that the acoustic emission (AE) response of a low-carbon type 304 stainless steel (SS) (UNS S30400) during pitting and transgranular stress corrosion cracking (TGSCC) has been measured. Tests were conducted in 0.01 and 1 M NaCl with the pH adjusted to 1 with HCl at potentials of -380 mV and 0 mV (SCE) for no applied stress and with a stress equal to 75% of the yield strength of the material. Acoustic emission signals were detected using piezoelectric sensors attached to each end of cylindrical samples. The two detectors allowed the discrimination between signals generated within the sample gauge section from those generated elsewhere. The AE activity during pitting corrosion was significant; it was concluded that the AE signals did not emanate from cracking or dislocation activity. Applied stress exhibited an inconsistent effect on the AE rate, but it did shorten the transition time from low to high AE rates. The AE rate increased slightly with increasing sample current in 0.01 M NaCl and with increasing corrosion rate, resulting form an increase in salt concentration from 0.01 to 1 M NaCl. Hydrogen and oxygen gas bubble formation was not observed on the samples, and the electrochemical conditions were not consistent with their formation; therefore, AE form bubble formation was ruled out.

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

    PubMed

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

    2012-01-01

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

  2. Finite Element and Plate Theory Modeling of Acoustic Emission Waveforms

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Hamstad, M. A.; Gary, J.; OGallagher, A.

    1998-01-01

    A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the response of the flexural plate mode to a point source, step-function load, applied on the plate surface. The second approach used a dynamic finite element method to model the problem using equations of motion based on exact linear elasticity. Calculations were made using properties for both isotropic (aluminum) and anisotropic (unidirectional graphite/epoxy composite) materials. For simulations of anisotropic plates, propagation along multiple directions was evaluated. In general, agreement between the two theoretical approaches was good. Discrepancies in the waveforms at longer times were caused by differences in reflections from the lateral plate boundaries. These differences resulted from the fact that the two methods used different boundary conditions. At shorter times in the signals, before reflections, the slight discrepancies in the waveforms were attributed to limitations of Mindlin plate theory, which is an approximate plate theory. The advantages of the finite element method are that it used the exact linear elasticity solutions, and that it can be used to model real source conditions and complicated, finite specimen geometries as well as thick plates. These advantages come at a cost of increased computational difficulty, requiring lengthy calculations on workstations or supercomputers. The Mindlin plate theory solutions, meanwhile, can be quickly generated on personal computers. Specimens with finite geometry can also be modeled. However, only limited simple geometries such as circular or rectangular plates can easily be accommodated with the normal mode solution technique. Likewise, very limited source configurations can be modeled and plate theory is applicable only to thin plates.

  3. Acoustic Emission Signals in Thin Plates Produced by Impact Damage

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Gorman, Michael R.; Humes, Donald H.

    1999-01-01

    Acoustic emission (AE) signals created by impact sources in thin aluminum and graphite/epoxy composite plates were analyzed. Two different impact velocity regimes were studied. Low-velocity (less than 0.21 km/s) impacts were created with an airgun firing spherical steel projectiles (4.5 mm diameter). High-velocity (1.8 to 7 km/s) impacts were generated with a two-stage light-gas gun firing small cylindrical nylon projectiles (1.5 mm diameter). Both the impact velocity and impact angle were varied. The impacts did not penetrate the aluminum plates at either low or high velocities. For high-velocity impacts in composites, there were both impacts that fully penetrated the plate as well as impacts that did not. All impacts generated very large amplitude AE signals (1-5 V at the sensor), which propagated as plate (extensional and/or flexural) modes. In the low-velocity impact studies, the signal was dominated by a large flexural mode with only a small extensional mode component detected. As the impact velocity was increased within the low velocity regime, the overall amplitudes of both the extensional and flexural modes increased. In addition, a relative increase in the amplitude of high-frequency components of the flexural mode was also observed. Signals caused by high-velocity impacts that did not penetrate the plate contained both a large extensional and flexural mode component of comparable amplitudes. The signals also contained components of much higher frequency and were easily differentiated from those caused by low-velocity impacts. An interesting phenomenon was observed in that the large flexural mode component, seen in every other case, was absent from the signal when the impact particle fully penetrated through the composite plates.

  4. Acoustic and Aerothermal Performance Test of the Axisymmetric Coannular Ejector Nozzle. Volume 2; Acoustic Performance

    NASA Technical Reports Server (NTRS)

    Herkes, William

    2000-01-01

    Acoustic and propulsion performance testing of a model-scale Axisymmetric Coannular Ejector nozzle was conducted in the Boeing Low-speed Aeroacoustic Facility. This nozzle is a plug nozzle with an ejector design to provide aspiration of about 20% of the engine flow. A variety of mixing enhancers were designed to promote mixing of the engine and the aspirated flows. These included delta tabs, tone-injection rods, and wheeler ramps. This report addresses the acoustic aspects of the testing. The spectral characteristics of the various configurations of the nozzle are examined on a model-scale basis. This includes indentifying particular noise sources contributing to the spectra and the data are projected to full-scale flyover conditions to evaluate the effectiveness of the nozzle, and of the various mixing enhancers, on reducing the Effective Perceived Noise Levels.

  5. Acoustic results of the Boeing model 360 whirl tower test

    NASA Technical Reports Server (NTRS)

    Watts, Michael E.; Jordan, David

    1990-01-01

    An evaluation is presented for whirl tower test results of the Model 360 helicopter's advanced, high-performance four-bladed composite rotor system intended to facilitate over-200-knot flight. During these performance measurements, acoustic data were acquired by seven microphones. A comparison of whirl-tower tests with theory indicate that theoretical prediction accuracies vary with both microphone position and the inclusion of ground reflection. Prediction errors varied from 0 to 40 percent of the measured signal-to-peak amplitude.

  6. Acoustic results of the Boeing model 360 whirl tower test

    NASA Astrophysics Data System (ADS)

    Watts, Michael E.; Jordan, David

    1990-09-01

    An evaluation is presented for whirl tower test results of the Model 360 helicopter's advanced, high-performance four-bladed composite rotor system intended to facilitate over-200-knot flight. During these performance measurements, acoustic data were acquired by seven microphones. A comparison of whirl-tower tests with theory indicate that theoretical prediction accuracies vary with both microphone position and the inclusion of ground reflection. Prediction errors varied from 0 to 40 percent of the measured signal-to-peak amplitude.

  7. Tip aerodynamics and acoustics test: A report and data survey

    NASA Technical Reports Server (NTRS)

    Cross, Jeffrey L.; Watts, Michael E.

    1988-01-01

    In a continuing effort to understand helicopter rotor tip aerodynamics and acoustics, a flight test was conducted by NASA Ames Research Center. The test was performed using the NASA White Cobra and a set of highly instrumented blades. All aspects of the flight test instrumentation and test procedures are explained. Additionally, complete data sets for selected test points are presented and analyzed. Because of the high volume of data acquired, only selected data points are presented. However, access to the entire data set is available to the researcher on request.

  8. The correlation dimension: A robust chaotic feature for classifying acoustic emission signals generated in construction materials

    NASA Astrophysics Data System (ADS)

    Kacimi, S.; Laurens, S.

    2009-07-01

    In the field of acoustic emission (AE) source recognition, this paper presents a classification feature based on the paradigm of nonlinear dynamical systems, often referred to as chaos theory. The approach considers signals as time series expressing an underlying dynamical phenomenon and enclosing all the information regarding the dynamics. The scientific knowledge on nonlinear dynamical systems has considerably improved for the past 40 years. The dynamical behavior is analyzed in the phase space, which is the space generated by the state variables of the system. The time evolution of a system is expressed in the phase space by trajectories, and the asymptotic behavior of trajectories defines a space area which is referred to as a system attractor. Dynamical systems may be characterized by the topological properties of attractors, such as the correlation dimension, which is a fractal dimension. According to Takens theorem, even if the system is not clearly defined, it is possible to infer topological information about the attractor from experimental observations. Such a method, which is called phase space reconstruction, was successfully applied for the classification of acoustic emission waveforms propagating in more or less complex materials such as granite and concrete. Laboratory tests were carried out in order to collect numerous AE waveforms from various controlled acoustic sources. Then, each signal was processed to extract a reconstructed attractor from which the correlation dimension was computed. The first results of this research show that the correlation dimension assessed after phase space reconstruction is very relevant and robust for classifying AE signals. These promising results may be explained by the fact that the totality of the signal is used to achieve classifying information. Moreover, due to the self-similar nature of attractors, the correlation dimension, and thus a correlation dimension-based classification approach, is theoretically

  9. Linking acoustic emission signatures with grain-scale mechanical interactions during granular shearing

    NASA Astrophysics Data System (ADS)

    Michlmayr, G.; Cohen, D.; Or, D.

    2012-04-01

    Acoustic Emissions (AE) are high frequency (kHz range) elastic body waves, generated in deforming granular material during particle collisions, frictional slip, or other types of abrupt grain-scale mechanical interactions. The direct link with particle micro-mechanics makes AE a useful tool for gaining insights into mechanical aspects of progressive shear failure in granular material and slow granular flows. The formation of shear plane in granular matter involves numerous internal restructuring and failure events with distinct dynamics resembling features of critical phase transition. Following establishment of a shear plane, subsequent deformation involves episodic slip events interrupted by arrested flow (stick-slip behavior). We developed a model for interpreting measured AE signatures in terms of micro-failures during progressive granular shear a considering AE generation mechanisms and propagation of acoustic signals within granular material. Results from shear frame experiments include information on strains, stresses and acoustic emissions during deformation controlled tests on glass beads and sand. The number of failure associated AE event rates peaks with maximum shear resistance of the granular material. Intermittent slip events during stick-slip deformation are found to be closely related to low frequency AE events (~1kHz). Statistics of AE events and their temporal development are reproduced using a simple fiber-bundle model. A conceptual AE generation and propagation model accounts for conversion of mechanical events into elastic waves. In addition to gaining insights concerning grain-scale mechanical interactions, the AE method offers a useful tool for monitoring hazardous geologic mass movements, such as landslides, rock avalanches or debris flows.

  10. 40 CFR 89.119 - Emission tests.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 21 2013-07-01 2013-07-01 false Emission tests. 89.119 Section 89.119... Provisions § 89.119 Emission tests. (a) Manufacturer testing. (1) Upon completion of service accumulation, the manufacturer must test each test engine using the specified test procedures, except as provided...

  11. Study of acoustic emission signals during fracture shear deformation

    NASA Astrophysics Data System (ADS)

    Ostapchuk, A. A.; Pavlov, D. V.; Markov, V. K.; Krasheninnikov, A. V.

    2016-07-01

    We study acoustic manifestations of different regimes of shear deformation of a fracture filled with a thin layer of granular material. It is established that the observed acoustic portrait is determined by the structure of the fracture at the mesolevel. Joint analysis of the activity of acoustic pulses and their spectral characteristics makes it possible to construct the pattern of internal evolutionary processes occurring in the thin layer of the interblock contact and consider the fracture deformation process as the evolution of a self-organizing system.

  12. Estimation of durability of GFRP laminates under stress-corrosive environments using acoustic emission

    SciTech Connect

    Fujii, Yoshimichi; Ramakrishna, S.; Hamada, Hiroyuki

    1996-12-31

    The objective of this investigation was to estimate the creep life of glass fiber reinforced plastic (GFRP) materials subjected to stress-corrosive environments using acoustic emission (AE). The laminates were fabricated using combinations of rigid bisphenolic polyester resin (LP-1), flexible vinylester resin (R806), random fiber mat and woven cloth. The creep tests were conducted in 5% nitric acid environment. The rigid matrix composites displayed higher AE count rate than the flexible matrix composites. For given creep testing conditions, the woven cloth reinforced specimens displayed higher number of AE counts than the random mat reinforced specimens. The creep life decreased with increasing creep stress, whereas the AE count rate increased with increasing creep stress. A linear relationship was found between the creep life and the AE count rate.

  13. Acoustic emission characteristics of subsoil subjected to vertical pile loading in sand

    NASA Astrophysics Data System (ADS)

    Mao, Wuwei; Aoyama, Shogo; Goto, Shigeru; Towhata, Ikuo

    2015-08-01

    The response of the subsoil subjected to pile loading is crucial to clarify the bearing mechanism of pile foundations. This study presents a novel acoustic emission (AE) method to monitor the subsoil behavior in a model pile testing system. The AE testing aims to capture the "micro-noises" released from sand grain dislocation and crushing around the pile shaft during penetration. The correlations between the pile settlement and the AE characteristics including count, amplitude and energy are revealed and discussed, highlighting that the ground density and the shear zone formed during pile penetration mainly affect the AE behavior. The results also suggest that the yielding of ground can be determined based on the development of the AE activity. The technique shows promise as an in-situ methodology for monitoring of subsoil behavior during the process of pile loading.

  14. Acoustic emission characteristics of copper alloys under low-cycle fatigue conditions

    NASA Technical Reports Server (NTRS)

    Krampfner, Y.; Kawamoto, A.; Ono, K.; Green, A.

    1975-01-01

    The acoustic emission (AE) characteristics of pure copper, zirconium-copper, and several copper alloys were determined to develop nondestructive evaluation schemes of thrust chambers through AE techniques. The AE counts rms voltages, frequency spectrum, and amplitude distribution analysis evaluated AE behavior under fatigue loading conditions. The results were interpreted with the evaluation of wave forms, crack propagation characteristics, as well as scanning electron fractographs of fatigue-tested samples. AE signals at the beginning of a fatigue test were produced by a sample of annealed alloys. A sample of zirconium-containing alloys annealed repeatedly after each fatigue loading cycle showed numerous surface cracks during the subsequent fatigue cycle, emitting strong-burst AE signals. Amplitude distribution analysis exhibits responses that are characteristic of certain types of AE signals.

  15. On acoustic emission for failure investigation in CFRP: Pattern recognition and peak frequency analyses

    NASA Astrophysics Data System (ADS)

    Gutkin, R.; Green, C. J.; Vangrattanachai, S.; Pinho, S. T.; Robinson, P.; Curtis, P. T.

    2011-05-01

    This paper investigates failure in Carbon Fibre Reinforced Plastics CFRP using Acoustic Emission (AE). Signals have been collected and post-processed for various test configurations: tension, Compact Tension (CT), Compact Compression (CC), Double Cantilever Beam (DCB) and four-point bend End Notched Flexure (4-ENF). The signals are analysed with three different pattern recognition algorithms: k-means, Self Organising Map (SOM) combined with k-means and Competitive Neural Network (CNN). The SOM combined with k-means appears as the most effective of the three algorithms. The results from the clustering analysis follow patterns found in the peak frequencies distribution. A detailed study of the frequency content of each test is then performed and the classification of several failure modes is achieved.

  16. Acoustic Emission Weld Monitoring in the 2195 Aluminum-Lithium Alloy

    NASA Technical Reports Server (NTRS)

    Walker, James L.

    2005-01-01

    Due to its low density, the 2195 aluminum-lithium alloy was developed as a replacement for alloy 2219 in the Space Shuttle External Tank (ET). The external tank is the single largest component of the space shuttle system. It is 154 feet long and 27.6 feet in diameter, and serves as the structural backbone for the shuttle during launch, absorbing most of the 7 million plus pounds of thrust produced. The almost 4% decrease in density between the two materials provides an extra 7500 pounds of payload capacity necessary to put the International Space Station components into orbit. The ET is an all-welded structure; hence, the requirement is for up to five rewelds without hot cracking. Unfortunately, hot cracking during re-welding or repair operations was occurring and had to be dealt with before the new super lightweight tank could be used. Weld metal porosity formation was also of concern because it leads to hot cracking during weld repairs. Accordingly, acoustic emission (AE) nondestructive testing was employed to monitor the formation of porosity and hot cracks in order to select the best filler metal and optimize the weld schedule. The purpose of this work is to determine the feasibility of detecting hot cracking in welded aluminum-lithium (Al-Li) structures through the analysis of acoustic emission data. By acoustically characterizing the effects of reheating during a repair operation, the potential for hidden flaws coalescing and becoming "unstable" as the panel is repaired could be reduced. Identification of regions where microcrack growth is likely to occur and the location of active flaw growth in the repair weld will provide the welder with direct feedback as to the current weld quality enabling adjustments to the repair process be made in the field. An acoustic emission analysis of the source mechanisms present during welding has been conducted with the goals of locating regions in the weld line that are susceptible to damage from a repair operation

  17. Detection of Delamination in Composite Beams Using Broadband Acoustic Emission Signatures

    NASA Technical Reports Server (NTRS)

    Okafor, A. C.; Chandrashekhara, K.; Jiang, Y. P.

    1996-01-01

    Delamination in composite structure may be caused by imperfections introduced during the manufacturing process or by impact loads by foreign objects during the operational life. There are some nondestructive evaluation methods to detect delamination in composite structures such as x-radiography, ultrasonic testing, and thermal/infrared inspection. These methods are expensive and hard to use for on line detection. Acoustic emission testing can monitor the material under test even under the presence of noise generated under load. It has been used extensively in proof-testing of fiberglass pressure vessels and beams. In the present work, experimental studies are conducted to investigate the use of broadband acoustic emission signatures to detect delaminations in composite beams. Glass/epoxy beam specimens with full width, prescribed delamination sizes of 2 inches and 4 inches are investigated. The prescribed delamination is produced by inserting Teflon film between laminae during the fabrication of composite laminate. The objectives of this research is to develop a method for predicting delamination size and location in laminated composite beams by combining smart materials concept and broadband AE analysis techniques. More specifically, a piezoceramic (PZT) patch is bonded on the surface of composite beams and used as a pulser. The piezoceramic patch simulates the AE wave source as a 3 cycles, 50KHz, burst sine wave. One broadband AE sensor is fixed near the PZT patch to measure the AE wave near the AE source. A second broadband AE sensor, which is used as a receiver, is scanned along the composite beams at 0.25 inch step to measure propagation of AE wave along the composite beams. The acquired AE waveform is digitized and processed. Signal strength, signal energy, cross-correlation of AE waveforms, and tracking of specific cycle of AE waveforms are used to detect delamination size and location.

  18. Ares I Scale Model Acoustic Test Above Deck Water Sound Suppression Results

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) program test matrix was designed to determine the acoustic reduction for the Liftoff acoustics (LOA) environment with an above deck water sound suppression system. The scale model test can be used to quantify the effectiveness of the water suppression system as well as optimize the systems necessary for the LOA noise reduction. Several water flow rates were tested to determine which rate provides the greatest acoustic reductions. Preliminary results are presented.

  19. Regularities of acoustic emission and thermoemission memory effect in coal specimens under varying thermal conditions

    SciTech Connect

    Shkuratnik, V.L.; Kuchurin, S.V.; Vinnikov, V.A.

    2007-07-15

    The experimental data on acoustic emission regularities are presented for specimens of different genetic coal types exposed to a wide range of cyclic heating modes. Peculiarities of formation and manifestation of thermal-emission memory effect depending on amplitude and duration of the thermal-field action are revealed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  1. Field tests of acoustic telemetry for a portable coastal observatory

    USGS Publications Warehouse

    Martini, M.; Butman, B.; Ware, J.; Frye, D.

    2006-01-01

    Long-term field tests of a low-cost acoustic telemetry system were carried out at two sites in Massachusetts Bay. At each site, an acoustic Doppler current profiler mounted on a bottom tripod was fitted with an acoustic modem to transmit data to a surface buoy; electronics mounted on the buoy relayed these data to shore via radio modem. The mooring at one site (24 m water depth) was custom-designed for the telemetry application, with a custom designed small buoy, a flexible electro-mechanical buoy to mooring joint using a molded chain connection to the buoy, quick-release electro-mechanical couplings, and dual hydrophones suspended 7 m above the bottom. The surface buoy at the second site (33 m water depth) was a U.S. Coast Guard (USCG) channel buoy fitted with telemetry electronics and clamps to hold the hydrophones. The telemetry was tested in several configurations for a period of about four years. The custom-designed buoy and mooring provided nearly error-free data transmission through the acoustic link under a variety of oceanographic conditions for 261 days at the 24 m site. The electro mechanical joint, cables and couplings required minimal servicing and were very reliable, lasting 862 days deployed before needing repairs. The acoustic communication results from the USCG buoy were poor, apparently due to the hard cobble bottom, noise from the all-steel buoy, and failure of the hydrophone assembly. Access to the USCG buoy at sea required ideal weather. ??2006 IEEE.

  2. Design and manufacturing of scanning probe acoustic microscope test phantom

    NASA Astrophysics Data System (ADS)

    Chen, Xiaohui; Fang, Xiaoyue; Song, Jitao; Ding, Mingyue

    2015-03-01

    Acquiring nondestructive internal structures acoustic image as well as the morphology images using scanning probe acoustic microscope (SPAM) is a challenge and no known metrology tools to identify the ultrasonic internal resolution and detectable depth of SPAM in a nondestructive way. Monitoring these defects necessitates the identification of their technical parameters of SPAM. In this paper, the specific materials (test phantoms) were designed and processed so that the ultrasound internal resolution of SPAM in nondestructive imaging of the embedded or buried substructures as well as the morphology images were measured. Experimental results demonstrated the successful identification of embedded or buried defects under the test phantom with the resolution of 50nm for SPAM as well as the detectable depth of more than 100μm.

  3. Detecting Acoustic Emissions With/Without Dehydration of Serpentine Outside P-T Field of Conventional Brittle Failure

    NASA Astrophysics Data System (ADS)

    Jung, H.; Fei, Y.; Silver, P. G.; Green, H. W.

    2005-12-01

    It is currently thought that earthquakes cannot be triggered at depths greater than ~60 km by unassisted brittle failure or frictional sliding, but could be triggered by dehydration embrittlement of hydrous minerals (Raleigh and Paterson, 1965; Green and Houston, 1995; Kirby, 1995; Jung et al., 2004). Using a new multianvil-based system for detecting acoustic emissions with four channels at high pressure and high temperature that was recently developed (Jung et al., 2005), we tested this hypothesis by deforming samples of serpentine. We found that acoustic emissions were detected not only during/after the dehydration of serpentine, but even in the absence of dehydration. These emissions occurred at high pressure and high temperature, and thus outside pressure-temperature field of conventional brittle failure. Backscattered-electron images of microstructures of the post-run specimen revealed fault slip at elevated pressure, with offsets of up to ~500 μm, even without dehydration. Analysis of P-wave travel times from the four sensors confirmed that the acoustic emissions originated from within the specimen during fault slip. These observations suggest that earthquakes can be triggered by slip along a fault containing serpentine at significantly higher pressure and temperature conditions than that previously thought, even without dehydration. They are thus consistent with faulting mechanisms that appeal to dehydration embrittlement, as well as those that rely solely on the rheology of non-dehydrated serpentine.

  4. 40 CFR 61.123 - Emission testing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... or nodulizing kiln. If emissions from a calciner or nodulizing kiln are discharged through more than... calciner or kiln shall be the sum of the emission rates from each of the stacks. (d) Each emission test... nodulizing kiln shall be determined by multiplying the measured polonium-210 emission rate in curies per...

  5. 40 CFR 61.123 - Emission testing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... or nodulizing kiln. If emissions from a calciner or nodulizing kiln are discharged through more than... calciner or kiln shall be the sum of the emission rates from each of the stacks. (d) Each emission test... nodulizing kiln shall be determined by multiplying the measured polonium-210 emission rate in curies per...

  6. 40 CFR 61.123 - Emission testing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... or nodulizing kiln. If emissions from a calciner or nodulizing kiln are discharged through more than... calciner or kiln shall be the sum of the emission rates from each of the stacks. (d) Each emission test... nodulizing kiln shall be determined by multiplying the measured polonium-210 emission rate in curies per...

  7. 40 CFR 61.123 - Emission testing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... or nodulizing kiln. If emissions from a calciner or nodulizing kiln are discharged through more than... calciner or kiln shall be the sum of the emission rates from each of the stacks. (d) Each emission test... nodulizing kiln shall be determined by multiplying the measured polonium-210 emission rate in curies per...

  8. 40 CFR 61.123 - Emission testing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... or nodulizing kiln. If emissions from a calciner or nodulizing kiln are discharged through more than... calciner or kiln shall be the sum of the emission rates from each of the stacks. (d) Each emission test... nodulizing kiln shall be determined by multiplying the measured polonium-210 emission rate in curies per...

  9. NASA Engineering and Safety Center (NESC) Enhanced Melamine (ML) Foam Acoustic Test (NEMFAT)

    NASA Technical Reports Server (NTRS)

    McNelis, Anne M.; Hughes, William O.; McNelis, Mark E.

    2014-01-01

    The NASA Engineering and Safety Center (NESC) funded a proposal to achieve initial basic acoustic characterization of ML (melamine) foam, which could serve as a starting point for a future, more comprehensive acoustic test program for ML foam. A project plan was developed and implemented to obtain acoustic test data for both normal and enhanced ML foam. This project became known as the NESC Enhanced Melamine Foam Acoustic Test (NEMFAT). This document contains the outcome of the NEMFAT project.

  10. Hybrid Wing Body Aircraft Acoustic Test Preparations and Facility Upgrades

    NASA Technical Reports Server (NTRS)

    Heath, Stephanie L.; Brooks, Thomas F.; Hutcheson, Florence V.; Doty, Michael J.; Haskin, Henry H.; Spalt, Taylor B.; Bahr, Christopher J.; Burley, Casey L.; Bartram, Scott M.; Humphreys, William M.; Lunsford, Charles B.; Popenack, Thomas G.; Colbert, Scott E.; Hoad, Danny; Becker, Lawrence; Stead, Dan; Kuchta, Dennis; Yeh, Les

    2013-01-01

    NASA is investigating the potential of acoustic shielding as a means to reduce the noise footprint at airport communities. A subsonic transport aircraft and Langley's 14- by 22-foot Subsonic Wind Tunnel were chosen to test the proposed "low noise" technology. The present experiment studies the basic components of propulsion-airframe shielding in a representative flow regime. To this end, a 5.8-percent scale hybrid wing body model was built with dual state-of-the-art engine noise simulators. The results will provide benchmark shielding data and key hybrid wing body aircraft noise data. The test matrix for the experiment contains both aerodynamic and acoustic test configurations, broadband turbomachinery and hot jet engine noise simulators, and various airframe configurations which include landing gear, cruise and drooped wing leading edges, trailing edge elevons and vertical tail options. To aid in this study, two major facility upgrades have occurred. First, a propane delivery system has been installed to provide the acoustic characteristics with realistic temperature conditions for a hot gas engine; and second, a traversing microphone array and side towers have been added to gain full spectral and directivity noise characteristics.

  11. Multivariate data-driven modelling and pattern recognition for damage detection and identification for acoustic emission and acousto-ultrasonics

    NASA Astrophysics Data System (ADS)

    Torres-Arredondo, M.-A.; Tibaduiza, D.-A.; McGugan, M.; Toftegaard, H.; Borum, K.-K.; Mujica, L. E.; Rodellar, J.; Fritzen, C.-P.

    2013-10-01

    Different methods are commonly used for non-destructive testing in structures; among others, acoustic emission and ultrasonic inspections are widely used to assess structures. The research presented in this paper is motivated by the need to improve the inspection capabilities and reliability of structural health monitoring (SHM) systems based on ultrasonic guided waves with focus on the acoustic emission and acousto-ultrasonics techniques. The use of a guided wave based approach is driven by the fact that these waves are able to propagate over relatively long distances, and interact sensitively and uniquely with different types of defect. Special attention is paid here to the development of efficient SHM methodologies. This requires robust signal processing techniques for the correct interpretation of the complex ultrasonic waves. Therefore, a variety of existing algorithms for signal processing and pattern recognition are evaluated and integrated into the different proposed methodologies. As a contribution to solve the problem, this paper presents results in damage detection and classification using a methodology based on hierarchical nonlinear principal component analysis, square prediction measurements and self-organizing maps, which are applied to data from acoustic emission tests and acousto-ultrasonic inspections. At the end, the efficiency of these methodologies is experimentally evaluated in diverse anisotropic composite structures.

  12. Emissions reduction and pyrolysis gas destruction in an acoustically driven dump combustor

    SciTech Connect

    Pont, G.; Cadou, C.P.; Karagozian, A.R.; Smith, O.I.

    1998-04-01

    The research described here focuses on the enhancement of hazardous waste and pyrolysis gas surrogate destruction and the reduction in nitric oxide and unburned hydrocarbon emissions in an acoustically resonant dump combustor. While several prior studies have focused on flowfield interrogation and hazardous waste surrogate destruction under conditions of natural acoustic excitation, the present study focuses on the device`s behavior under externally forced acoustic excitation. The effect of external forcing on hazardous waste surrogate destruction in the device was recently found to be significant, yielding destruction rates for the surrogate SF{sub 6} that increased by as much as four orders of magnitude with acoustic forcing at specific resonant modes. The present study also indicates a significant improvement in performance with external forcing at the same acoustic modes as those explored earlier. Emissions of NO are seen to decrease by nearly 60%, unburned hydrocarbons are seen to drop by over two orders of magnitude, and waste and pyrolysis gas surrogate destruction is seen to increase by nearly three orders of magnitude, all with external forcing at a specific acoustic mode of the device. The present observations further support the idea that acoustically resonant conditions can render the dump combustor device extremely efficient as well as highly controllable as a small-scale thermal treatment system.

  13. Implementation of an acoustic emission proximity detector for use in generating glass optics

    SciTech Connect

    Blaedel, K.L.; Piscotty, M.A.; Taylor, J.S.

    1996-11-11

    We are using the approach acoustic emission (AE) signal during a grinding operation to detect the proximity of the grinding wheel relative to a brittle material workpiece and are using this detection as a feed- back control signal in our CNC. The repeatability of the AE signal during the wheel approach is the key that allows AE to be used as a proximity detector and is demonstrated at LLNL to be about mm. We noted significant changes of the AE signal as process parameters are modified, but conclude that with a quick CNC calibration routine and holding the parameters constant during a given operation, the AE system can be successfully used to sense pre- contact wheel- to- workpiece separation. Additionally, the AE sensing system allows real- time monitoring during grinding to provide in- process information. The first prototype of an AE system on a commercially available generator is currently be tested at the Center for Optics Manufacturing.

  14. Acoustic emission detection of rail defect based on wavelet transform and Shannon entropy

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Feng, Naizhang; Wang, Yan; Shen, Yi

    2015-03-01

    In order to detect cracks in railroad tracks, various experiments have been examined by Acoustic Emission (AE) method. However, little work has been done on studying rail defect detection at high speed. This paper presents a study on AE detection of rail defect at high speed based on rail-wheel test rig. Meanwhile, Wavelet Transform and Shannon entropy are employed to detect defects. Signals with and without defects are acquired, and characteristic frequencies from them at different speeds are analyzed. Based on appropriate decomposition level and Energy-to-Shannon entropy ratio, the optimal wavelet is selected. In order to suppress noise effects and ensure appropriate time resolution, the length of time window is investigated. Further, the characteristic frequency of time window is employed to detect defect. The results clearly illustrate that the proposed method can detect rail defect at high speed effectively.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  16. Classification of acoustic emission signals using wavelets and Random Forests : Application to localized corrosion

    NASA Astrophysics Data System (ADS)

    Morizet, N.; Godin, N.; Tang, J.; Maillet, E.; Fregonese, M.; Normand, B.

    2016-03-01

    This paper aims to propose a novel approach to classify acoustic emission (AE) signals deriving from corrosion experiments, even if embedded into a noisy environment. To validate this new methodology, synthetic data are first used throughout an in-depth analysis, comparing Random Forests (RF) to the k-Nearest Neighbor (k-NN) algorithm. Moreover, a new evaluation tool called the alter-class matrix (ACM) is introduced to simulate different degrees of uncertainty on labeled data for supervised classification. Then, tests on real cases involving noise and crevice corrosion are conducted, by preprocessing the waveforms including wavelet denoising and extracting a rich set of features as input of the RF algorithm. To this end, a software called RF-CAM has been developed. Results show that this approach is very efficient on ground truth data and is also very promising on real data, especially for its reliability, performance and speed, which are serious criteria for the chemical industry.

  17. Delamination fracture and acoustic emission in carbon, aramid and glass-epoxy composites

    SciTech Connect

    Dharan, C.K.H.

    1987-02-01

    Results of an investigation into the opening mode (Mode I) delamination fracture behavior of carbon, aramid and glass-epoxy composites are described. The effect of loading rate and reinforcement geometry (unidirectional vs woven) on fracture toughness was determined, and observation of the fracture surface was used to derive possible microfailure modes. The results show that the crack energy release rate for a woven composite was greater than that of unidirectionally reinforced composites. Acoustic emission was employed to detect crack initiation in an attempt to obtain correlation with the delamination fracture toughness. The earliest signal appeared to correlate well with the delamination fracture toughness, indicating that the processes involved in fracture initiation determines the magnitude of the steady state fracture toughness. Results show that the three materials tested behave in different ways (i.e., have different failure modes) during delamination, suggesting that a single theory cannot be expected to explain delamination in all composite materials.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  19. A proposed standard for evaluating structural integrity of reinforced concrete beams by acoustic emission

    SciTech Connect

    Yuyama, Shigenori; Okamoto, Takahisa; Shigeishi, Mitsuhiro; Ohtsu, Masayasu; Kishi, Teruo

    1999-07-01

    A series of studies has been performed to evaluate the structural integrity of reinforced concrete (RC) beams by acoustic emission (AE). Cyclic loadings were applied to RC beams with a single reinforcing bar, large repaired beams, beams deteriorated due to corrosion of reinforcement, and two beams with different damage levels in an aging dock. The test results demonstrated that the Kaiser effect starts to break down when shear cracking starts to play a primary role. It has been also shown that high AE activity is observed during unloadings after serious damage (slips between the concrete and the reinforcement or those between the original concrete and the repaired part) has occurred. A standard for evaluating structural integrity of RC beams by AE is proposed, based on these results.

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

    PubMed

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

    1981-11-01

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

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

    NASA Technical Reports Server (NTRS)

    Hinton, Yolanda L.

    1999-01-01

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

  2. Fatigue damage monitoring for basalt fiber reinforced polymer composites using acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Wang, Wentao; Li, Hui; Qu, Zhi

    2012-04-01

    Basalt fiber reinforced polymer (BFRP) is a structural material with superior mechanical properties. In this study, unidirectional BFRP laminates with 14 layers are made with the hand lay-up method. Then, the acoustic emission technique (AE) combined with the scanning electronic microscope (SEM) technique is employed to monitor the fatigue damage evolution of the BFRP plates in the fatigue loading tests. Time-frequency analysis using the wavelet transform technique is proposed to analyze the received AE signal instead of the peak frequency method. A comparison between AE signals and SEM images indicates that the multi-frequency peaks picked from the time-frequency curves of AE signals reflect the accumulated fatigue damage evolution and fatigue damage patterns. Furthermore, seven damage patterns, that is, matrix cracking, delamination, fiber fracture and their combinations, are identified from the time-frequency curves of the AE signals.

  3. Spectral Characteristics of Continuous Acoustic Emission (AE) Data from Laboratory Rock Deformation Experiments

    NASA Astrophysics Data System (ADS)

    Flynn, J. William; Goodfellow, Sebastian; Reyes-Montes, Juan; Nasseri, Farzine; Young, R. Paul

    2016-04-01

    Continuous acoustic emission (AE) data recorded during rock deformation tests facilitates the monitoring of fracture initiation and propagation due to applied stress changes. Changes in the frequency and energy content of AE waveforms have been previously observed and were associated with microcrack coalescence and the induction or mobilisation of large fractures which are naturally associated with larger amplitude AE events and lower-frequency components. The shift from high to low dominant frequency components during the late stages of the deformation experiment, as the rate of AE events increases and the sample approaches failure, indicates a transition from the micro-cracking to macro-cracking regime, where large cracks generated result in material failure. The objective of this study is to extract information on the fracturing process from the acoustic records around sample failure, where the fast occurrence of AE events does not allow for identification of individual AE events and phase arrivals. Standard AE event processing techniques are not suitable for extracting this information at these stages. Instead the observed changes in the frequency content of the continuous record can be used to characterise and investigate the fracture process at the stage of microcrack coalescence and sample failure. To analyse and characterise these changes, a detailed non-linear and non-stationary time-frequency analysis of the continuous waveform data is required. Empirical Mode Decomposition (EMD) and Hilbert Spectral Analysis (HSA) are two of the techniques used in this paper to analyse the acoustic records which provide a high-resolution temporal frequency distribution of the data. In this paper we present the results from our analysis of continuous AE data recorded during a laboratory triaxial deformation experiment using the combined EMD and HSA method.

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

    PubMed Central

    de Agustina, Beatriz; Marín, Marta María; Teti, Roberto; Rubio, Eva María

    2014-01-01

    The polishing process is the most common technology used in applications where a high level of surface quality is demanded. The automation of polishing processes is especially difficult due to the high level of skill and dexterity that is required. Much of this difficulty arises because of the lack of reliable data on the effect of the polishing parameters on the resulting surface roughness. An experimental study was developed to evaluate the surface roughness obtained during Robot Assisted Polishing processes by the analysis of acoustic emission signals in the frequency domain. The aim is to find out a trend of a feature or features calculated from the acoustic emission signals detected along the process. Such an evaluation was made with the objective of collecting valuable information for the establishment of the end point detection of polishing process. As a main conclusion, it can be affirmed that acoustic emission (AE) signals can be considered useful to monitor the polishing process state. PMID:25405509

  5. THE THERMOELASTIC PHASE TRANSITION IN Au-Cd ALLOYS STUDIES BY ACOUSTIC EMISSION

    SciTech Connect

    Baram, I.; Rosen, M.

    1980-03-01

    The acoustic emission generated during the thermoelastic phase transitions in polycrystalline Au-47.5 at.% Cd and in Au-49 at.% Cd alloys was recorded and analyzed. The emission detected is a manifestation of the frictional energy dissipated by the moving interfaces during the nucleation and growth stages of the reversible phase transitions. It was found that the amount of energy dissipated depends upon the direction of the transformation, the heating or cooling rates, and the specific crystallographic features of the martensitic phases. Premartensitic acoustic activity was detected in both alloys at temperatures of about 25 {degrees}C before the M{sub s} point. The dynamics and kinetics of martensitic thermoelastic phase transformations are discussed in terms of the accompanying generation of acoustic emission.

  6. Adaptation to Room Acoustics Using the Modified Rhyme Test

    PubMed Central

    Brandewie, Eugene; Zahorik, Pavel

    2012-01-01

    The negative effect of reverberant sound energy on speech intelligibility is well documented. Recently, however, prior exposure to room acoustics has been shown to increase intelligibility for a number of listeners in simulated room environments. This room adaptation effect, a possible extension of dynamic echo suppression, has been shown to be specific to reverberant rooms and requires binaural input. Because this effect has been demonstrated only using the Coordinated Response Measure (CRM) corpus it is important to determine whether the increase in intelligibility scores reported previously was due to the specific nature of the CRM task. Here we demonstrate a comparable room-acoustic effect using the Modified Rhyme Test (MRT) corpus in multiple room environments. The results are consistent with the idea that the room adaptation effect may be a natural phenomenon of listening in reverberant environments. PMID:23437415

  7. The pattern of acoustic emission under fluid initiation of failure: Laboratory modeling

    NASA Astrophysics Data System (ADS)

    Potanina, M. G.; Smirnov, V. B.; Ponomarev, A. V.; Bernard, P.; Lyubushin, A. A.; Shoziyoev, Sh. P.

    2015-03-01

    The results of the laboratory experiment on the initiation of acoustic emission in a loaded specimen by wetting a part of its surface without a material increase in the pore pressure are analyzed. The experiment was conducted on the lever press at the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences (Sobolev and Ponomarev, 2011). Infusion of water into the surface of the specimen initiated the swarm acoustic emission, which, after having migrated to the area with higher stresses, culminated in the formation of a macrofracture. The analysis revealed the regularities in the excitation and relaxation of the acoustic activity in response to different types of initiation: the forced excitation by stepwise increasing the load at the initial stage of the experiment; excitation resulting from fluid diffusion, which can be associated with the reduction in the material strength due to wetting; excitation that reflects the preparation for the emergence of a macrofracture in the area with the highest Coulomb stresses; and spontaneous excitation of swarm activity at the stage of relaxation of the acoustic emission after the formation of a macrofracture. The features revealed in the acoustic time series at the stages of excitation and decay of the emission are qualitatively similar to the trends identified in the variations of seismic parameters during the natural swarms, preparation of the sources of the strong earthquakes, and relaxation of the aftershocks. In particular, the obtained results support the hypothesis of fluid initiation of nonvolcanic seismic swarms.

  8. Engine exhaust characteristics evaluation in support of aircraft acoustic testing

    NASA Astrophysics Data System (ADS)

    Ennix, Kimberly A.

    1994-02-01

    NASA Dryden Flight Research Facility and NASA Langley Research Center completed a joint acoustic flight test program. Test objectives were (1) to quantify and evaluate subsonic climb-to-cruise noise and (2) to obtain a quality noise database for use in validating the Aircraft Noise Prediction Program. These tests were conducted using aircraft with engines that represent the high nozzle pressure ratio of future transport designs. Test flights were completed at subsonic speeds that exceeded Mach 0.3 using F-18 and F-16XL aircraft. This paper describes the efforts of NASA Dryden Flight Research Facility in this flight test program. Topics discussed include the test aircraft, setup, and matrix. In addition, the engine modeling codes and nozzle exhaust characteristics are described.

  9. Engine exhaust characteristics evaluation in support of aircraft acoustic testing

    NASA Technical Reports Server (NTRS)

    Ennix, Kimberly A.

    1993-01-01

    NASA Dryden Flight Research Facility and NASA Langley Research Center completed a joint acoustic flight test program. Test objectives were (1) to quantify and evaluate subsonic climb-to-cruise noise and (2) to obtain a quality noise database for use in validating the Aircraft Noise Prediction Program. These tests were conducted using aircraft with engines that represent the high nozzle pressure ratio of future transport designs. Test flights were completed at subsonic speeds that exceeded Mach 0.3 using F-18 and F-16XL aircraft. This paper describes the efforts of NASA Dryden Flight Research Facility in this flight test program. Topics discussed include the test aircraft, setup, and matrix. In addition, the engine modeling codes and nozzle exhaust characteristics are described.

  10. Engine exhaust characteristics evaluation in support of aircraft acoustic testing

    NASA Technical Reports Server (NTRS)

    Ennix, Kimberly A.

    1994-01-01

    NASA Dryden Flight Research Facility and NASA Langley Research Center completed a joint acoustic flight test program. Test objectives were (1) to quantify and evaluate subsonic climb-to-cruise noise and (2) to obtain a quality noise database for use in validating the Aircraft Noise Prediction Program. These tests were conducted using aircraft with engines that represent the high nozzle pressure ratio of future transport designs. Test flights were completed at subsonic speeds that exceeded Mach 0.3 using F-18 and F-16XL aircraft. This paper describes the efforts of NASA Dryden Flight Research Facility in this flight test program. Topics discussed include the test aircraft, setup, and matrix. In addition, the engine modeling codes and nozzle exhaust characteristics are described.

  11. Additional evidence of nuclear emissions during acoustic cavitation.

    PubMed

    Taleyarkhan, R P; Cho, J S; West, C D; Lahey, R T; Nigmatulin, R I; Block, R C

    2004-03-01

    Time spectra of neutron and sonoluminescence emissions were measured in cavitation experiments with chilled deuterated acetone. Statistically significant neutron and gamma ray emissions were measured with a calibrated liquid-scintillation detector, and sonoluminescence emissions were measured with a photomultiplier tube. The neutron and sonoluminescence emissions were found to be time correlated over the time of significant bubble cluster dynamics. The neutron emission energy was less than 2.5 MeV and the neutron emission rate was up to approximately 4 x 10(5) n/s. Measurements of tritium production were also performed and these data implied a neutron emission rate due to D-D fusion which agreed with what was measured. In contrast, control experiments using normal acetone did not result in statistically significant tritium activity, or neutron or gamma ray emissions. PMID:15089363

  12. Vibration and Acoustic Test Facility (VATF): User Test Planning Guide

    NASA Technical Reports Server (NTRS)

    Fantasia, Peter M.

    2011-01-01

    Test process, milestones and inputs are unknowns to first-time users of the VATF. The User Test Planning Guide aids in establishing expectations for both NASA and non-NASA facility customers. The potential audience for this guide includes both internal and commercial spaceflight hardware/software developers. It is intended to assist their test engineering personnel in test planning and execution. Material covered includes a roadmap of the test process, roles and responsibilities of facility and user, major milestones, facility capabilities, and inputs required by the facility. Samples of deliverables, test article interfaces, and inputs necessary to define test scope, cost, and schedule are included as an appendix to the guide.

  13. Characterization of acoustic emissions resulting from particle collision with a stationary bubble.

    PubMed

    Zhang, Wen; Spencer, Steven J; Coghill, Peter

    2013-05-01

    The present work characterizes the acoustic emissions resulting from the collision of a particle driven under gravity with a captive bubble. Conventional methods to investigate the bubble particle collision interaction model measure a descriptive parameter known as the collision time. During such a collision, particle impact may cause a strong deformation and a following oscillation of the bubble-particle interface generates detectable passive acoustic emissions (AE). Experiments and models presented show that the AE frequency monotonically decreases with the particle radius and is independent of the impact velocity, whereas the AE amplitude has a more complicated relationship with impact parameters. PMID:23654360

  14. A signal processing approach for enhanced Acoustic Emission data analysis in high activity systems: Application to organic matrix composites

    NASA Astrophysics Data System (ADS)

    Kharrat, M.; Ramasso, E.; Placet, V.; Boubakar, M. L.

    2016-03-01

    Structural elements made of Organic Matrix Composites (OMC) under complex loading may suffer from high Acoustic Emission (AE) activity caused by the emergence of different emission sources at high rates with high noise level, which finally engender continuous emissions. The detection of hits in this situation becomes a challenge particularly during fatigue tests. This work suggests an approach based on the Discrete Wavelet Transform (DWT) denoising applied on signal segments. A particular attention is paid to the adjustment of the denoising parameters based on pencil lead breaks and their influence on the quality of the denoised AE signals. The validation of the proposed approach is performed on a ring-shaped Carbon Fiber Reinforced Plastics (CFRP) under in-service-like conditions involving continuous emissions with superimposed damage-related transients. It is demonstrated that errors in hit detection are greatly reduced leading to a better identification of the natural damage scenario based on AE signals.

  15. Design, characterization, and experimental use of the second generation MEMS acoustic emission device

    NASA Astrophysics Data System (ADS)

    Ozevin, Didem; Greve, David W.; Oppenheim, Irving J.; Pessiki, Stephen

    2005-05-01

    We describe the design, fabrication, testing and application (in structural experiments) of our 2004 (second generation) MEMS device, designed for acoustic emission sensing based upon experiments with our 2002 (first generation) device. Both devices feature a suite of resonant-type transducers in the frequency range between 100 kHz and 1 MHz. The 2002 device was designed to operate in an evacuated housing because of high squeeze film damping, as confirmed in our earlier experiments. In additional studies involving the 2002 device, experimental simulation of acoustic emissions in a steel plate, using pencil lead break or ball impact loading, showed that the transducers in the frequency range of 100 kHz-500 kHz presented clearer output signals than the transducers with frequencies higher than 500 kHz. Using the knowledge gained from the 2002 device, we designed and fabricated our second generation device in 2004 using the multi-user polysilicon surface micromachining (MUMPs) process. The 2004 device has 7 independent capacitive type transducers, compared to 18 independent transducers in the 2002 device, including 6 piston type transducers in the frequency range of 100 kHz to 500 kHz and 1 piston type transducer at 1 MHz to capture high frequency information. Piston type transducers developed in our research have two uncoupled modes so that twofold information can be acquired from a single transducer. In addition, the piston shape helps to reduce residual stress effect of surface micromachining process. The center to center distance between etch holes in the vibrating plate was reduced from 30 μm to 13 μm, in order to reduce squeeze film damping. As a result, the Q factor under atmospheric pressure for the 100 kHz transducer was increased to 2.37 from 0.18, and therefore the vacuum housing has been eliminated from the 2004 device. Sensitivities of transducers were also increased, by enlarging transducer area, in order to capture significant small amplitude acoustic

  16. Acoustic tests of duct-burning turbofan jet noise simulation

    NASA Technical Reports Server (NTRS)

    Knott, P. R.; Stringas, E. J.; Brausch, J. F.; Staid, P. S.; Heck, P. H.; Latham, D.

    1978-01-01

    The results of a static acoustic and aerodynamic performance, model-scale test program on coannular unsuppressed and multielement fan suppressed nozzle configurations are summarized. The results of the static acoustic tests show a very beneficial interaction effect. When the measured noise levels were compared with the predicted noise levels of two independent but equivalent conical nozzle flow streams, noise reductions for the unsuppressed coannular nozzles were of the order of 10 PNdB; high levels of suppression (8 PNdB) were still maintained even when only a small amount of core stream flow was used. The multielement fan suppressed coannular nozzle tests showed 15 PNdB noise reductions and up to 18 PNdB noise reductions when a treated ejector was added. The static aerodynamic performance tests showed that the unsuppressed coannular plug nozzles obtained gross thrust coefficients of 0.972, with 1.2 to 1.7 percent lower levels for the multielement fan-suppressed coannular flow nozzles. For the first time anywhere, laser velocimeter velocity profile measurements were made on these types of nozzle configurations and with supersonic heated flow conditions. Measurements showed that a very rapid decay in the mean velocity occurs for the nozzle tested.

  17. Acoustic-Structure Interaction in Rocket Engines: Validation Testing

    NASA Technical Reports Server (NTRS)

    Davis, R. Benjamin; Joji, Scott S.; Parks, Russel A.; Brown, Andrew M.

    2009-01-01

    While analyzing a rocket engine component, it is often necessary to account for any effects that adjacent fluids (e.g., liquid fuels or oxidizers) might have on the structural dynamics of the component. To better characterize the fully coupled fluid-structure system responses, an analytical approach that models the system as a coupled expansion of rigid wall acoustic modes and in vacuo structural modes has been proposed. The present work seeks to experimentally validate this approach. To experimentally observe well-coupled system modes, the test article and fluid cavities are designed such that the uncoupled structural frequencies are comparable to the uncoupled acoustic frequencies. The test measures the natural frequencies, mode shapes, and forced response of cylindrical test articles in contact with fluid-filled cylindrical and/or annular cavities. The test article is excited with a stinger and the fluid-loaded response is acquired using a laser-doppler vibrometer. The experimentally determined fluid-loaded natural frequencies are compared directly to the results of the analytical model. Due to the geometric configuration of the test article, the analytical model is found to be valid for natural modes with circumferential wave numbers greater than four. In the case of these modes, the natural frequencies predicted by the analytical model demonstrate excellent agreement with the experimentally determined natural frequencies.

  18. Use of Modal Acoustic Emission to Monitor Damage Progression in Carbon Fiber/Epoxy and Implications for Composite Structures

    NASA Technical Reports Server (NTRS)

    Waller, J. M.; Nichols, C. T.; Wentzel, D. J.; Saulsberry R. L.

    2010-01-01

    Broad-band modal acoustic emission (AE) data was used to characterize micromechanical damage progression in uniaxial IM7 and T1000 carbon fiber-epoxy tows and an IM7 composite overwrapped pressure vessel (COPV) subjected to an intermittent load hold tensile stress profile known to activate the Felicity ratio (FR). Damage progression was followed by inspecting the Fast Fourier Transforms (FFTs) associated with acoustic emission events. FFT analysis revealed the occurrence of cooperative micromechanical damage events in a frequency range between 100 kHz and 1 MHz. Evidence was found for the existence of a universal damage parameter, referred to here as the critical Felicity ratio, or Felicity ratio at rupture (FR*), which had a value close to 0.96 for the tows and the COPV tested. The implications of using FR* to predict failure in carbon/epoxy composite materials and related composite components such as COPVs are discussed. Trends in the FFT data are also discussed; namely, the difference between the low and high energy events, the difference between early and late-life events, comparison of IM7 and T1000 damage progression, and lastly, the similarity of events occurring at the onset of significant acoustic emission used to calculate the FR.

  19. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Articles Absorption During Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    It is important to realize that some test-articles may have significant sound absorption that may challenge the acoustic power capabilities of a test facility. Therefore, to mitigate this risk of not being able to meet the customers target spectrum, it is prudent to demonstrate early-on an increased acoustic power capability which compensates for this test-article absorption. This paper describes a concise method to reduce this risk when testing aerospace test-articles which have significant absorption. This method was successfully applied during the SpaceX Falcon 9 Payload Fairing acoustic test program at the NASA Glenn Research Center Plum Brook Stations RATF.

  20. Design and performance of the South Pole Acoustic Test Setup

    NASA Astrophysics Data System (ADS)

    Abdou, Y.; Becker, K.-H.; Berdermann, J.; Bissok, M.; Bohm, C.; Böser, S.; Bothe, M.; Carson, M.; Descamps, F.; Fischer-Wolfarth, J.-H.; Gustafsson, L.; Hallgren, A.; Heinen, D.; Helbing, K.; Heller, R.; Hundertmark, S.; Karg, T.; Krieger, K.; Laihem, K.; Meures, T.; Nahnhauer, R.; Naumann, U.; Oberson, F.; Paul, L.; Pohl, M.; Price, B.; Ribordy, M.; Ryckbosch, D.; Schunck, M.; Semburg, B.; Stegmaier, J.; Sulanke, K.-H.; Tosi, D.; Vandenbroucke, J.; Wiebusch, C.

    2012-08-01

    The South Pole Acoustic Test Setup (SPATS) was built to evaluate the acoustic characteristics of the South Pole ice in the 10-100 kHz frequency range, for the purpose of assessing the feasibility of an acoustic neutrino detection array at the South Pole. The SPATS hardware consists of four vertical strings deployed in the upper 500 m of the South Pole ice cap. The strings form a trapezoidal array with a maximum baseline of 543 m. Each string has seven stages equipped with one transmitter and one sensor module (glaciophone). Sound is detected or generated by piezoelectric ceramic elements inside the modules. Analogue signals are sent to the surface on electric cables where they are digitized by a PC-based data acquisition system. The data from all strings are collected on a central computer in the IceCube Laboratory from where they are sent to a central data storage facility via a satellite link or stored locally on tape. A technical overview of SPATS and its performance is presented.

  1. Acoustic emission detection of macro-cracks on engraving tool steel inserts during the injection molding cycle using PZT sensors.

    PubMed

    Svečko, Rajko; Kusić, Dragan; Kek, Tomaž; Sarjaš, Andrej; Hančič, Aleš; Grum, Janez

    2013-01-01

    This paper presents an improved monitoring system for the failure detection of engraving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signals' peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process. PMID:23673677

  2. Acoustic Emission Detection of Macro-Cracks on Engraving Tool Steel Inserts during the Injection Molding Cycle Using PZT Sensors

    PubMed Central

    Svečko, Rajko; Kusić, Dragan; Kek, Tomaž; Sarjaš, Andrej; Hančič, Aleš; Grum, Janez

    2013-01-01

    This paper presents an improved monitoring system for the failure detection of engraving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signals' peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process. PMID:23673677

  3. Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

    USGS Publications Warehouse

    Cohen, D.; Hooyer, T.S.; Iverson, N.R.; Thomason, J.F.; Jackson, M.

    2006-01-01

    Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice slid over it. Vertical stresses, water pressure, and cavity height in the lee of the step were also measured. Water was pumped to the lee of the step several times over 8 days. Pumping initially caused opening of a leeward cavity, which then closed after pumping was stopped and water pressure decreased. During cavity closure, acoustic emissions emanating mostly from the vicinity of the base of the crack in the step increased dramatically. With repeated pump tests this crack grew with time until the step's lee surface was quarried. Our experiments indicate that fluctuating water pressure caused stress thresholds required for crack growth to be exceeded. Natural basal water pressure fluctuations should also concentrate stresses on rock steps, increasing rates of crack growth. Stress changes on the bed due to water pressure fluctuations will increase in magnitude and duration with cavity size, which may help explain the effect of sliding speed on erosion rates. Copyright 2006 by the American Geophysical Union.

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Vigeesh, G.; Hasan, S. S.

    2013-06-01

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

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

    SciTech Connect

    Jones, Kevin C.; Solberg, Timothy D.; Avery, Stephen; Vander Stappen, François; Janssens, Guillaume; Prieels, Damien; Bawiec, Christopher R.; Lewin, Peter A.; Sehgal, Chandra M.

    2015-12-15

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

  7. Acoustic Testing of Flight Hardware Using Loudspeakers: How Much do We Know About This Method of Testing?

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Kern, Dennis L

    2011-01-01

    Loudspeakers have been used for acoustic qualification of spacecrafts, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Even though a lot of hardware has been acoustic tested using this method, the nature of the acoustic field generated by controlling an ensemble of speakers with and without the hardware in the test volume has not been thoroughly investigated. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. Unlike the reverberant chamber acoustic test, for which the acoustic field in most chambers is known to be diffuse except below several tens of Hz where acoustic standing waves and large spatial variations exist, the characteristics of the acoustic field within the speaker test volume has not been quantified. It has only been recently that a detailed acoustic field characterization of speaker testing has been made at Jet Propulsion Laboratory (JPL) with involvement of various organizations. To address the impact of non-uniform acoustic field on structures, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The analysis of the data from this exercise reveals that there are significant differences both in the acoustic field and in the structural responses. In this paper the differences between the two methods are reviewed in some detail and the over- or under-testing of articles that could pose un-anticipated structural and flight qualification issues are discussed. A framework for discussing the validity of the speaker acoustic testing method with the current control system and a path forward for improving it will be provided.

  8. Effects of specimen resonances on acoustic-ultrasonic testing

    NASA Technical Reports Server (NTRS)

    Williams, J. H., Jr.; Kahn, E. B.; Lee, S. S.

    1983-01-01

    The effects of specimen resonances on acoustic ultrasonic (AU) nondestructive testing were investigated. Selected resonant frequencies and the corresponding normal mode nodal patterns of the aluminum block are measured up to 75.64 kHz. Prominent peaks in the pencil lead fracture and sphere impact spectra from the two transducer locations corresponded exactly to resonant frequencies of the block. It is established that the resonant frequencies of the block dominated the spectral content of the output signal. The spectral content of the output signals is further influenced by the transducer location relative to the resonant frequency nodal lines. Implications of the results are discussed in relation to AU parameters and measurements.

  9. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    SciTech Connect

    Paul, S.C.; Pirskawetz, S.; Zijl, G.P.A.G. van; Schmidt, W.

    2015-03-15

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage.

  10. Property evaluation of thermal sprayed metallic coating by acoustic emission analysis

    SciTech Connect

    Ishida, Asako; Mizutani, Yoshihiro; Takemoto, Mikio; Ono, Kanji

    2000-03-01

    The authors analyzed acoustic emission signals from plasma sprayed sheets by first obtaining the Young's modulus, Poisson's ratio, and density. The sheets of a high Cr-Ni alloy (55Cr-41Ni-Mo, Si, B) were made by low pressure plasma spraying (LPPS) and heat treated. Utilizing laser induced surface acoustic waves (SAWs), the group velocity dispersion data of Rayleigh waves was obtained and matched to that computed by Adler's matrix transfer method. They monitored the acoustic emissions (Lamb waves) produced by microfractures in free standing as sprayed coating subjected to bending. Fast cleavage type microfracture with source rise time of around 2 {micro}s occurred as precursors to the final brittle fracture. The velocity and time-frequency amplitude spectrograms (wavelet contour maps) of the Lamb waves were utilized for the source location and fracture kinetic analyses.

  11. Xylem cavitation resistance can be estimated based on time-dependent rate of acoustic emissions.

    PubMed

    Nolf, Markus; Beikircher, Barbara; Rosner, Sabine; Nolf, Anton; Mayr, Stefan

    2015-10-01

    Acoustic emission (AE) analysis allows nondestructive monitoring of embolism formation in plant xylem, but signal interpretation and agreement of acoustically measured hydraulic vulnerability with reference hydraulic techniques remain under debate. We compared the hydraulic vulnerability of 16 species and three crop tree cultivars using hydraulic flow measurements and acoustic emission monitoring, proposing the use of time-dependent AE rates as a novel parameter for AE analysis. There was a linear correlation between the water potential (Ψ) at 50% loss of hydraulic conductivity (P50 ) and the Ψ at maximum AE activity (Pmaxrate ), where species with lower P50 also had lower Pmaxrate (P < 0.001, R(2)  = 0.76). Using AE rates instead of cumulative counts for AE analysis allows more efficient estimation of P50 , while excluding problematic AE at late stages of dehydration. PMID:26010417

  12. Acoustic Testing of the Cassini Spacecraft and Titan 4 Payload Fairing. Part 1; Introduction and Test Configuration

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.

    1997-01-01

    NASA Lewis Research Center recently led a multi-organizational acoustic test program. This testing consisted of acoustically exciting a Cassini spacecraft simulator in a full scale 60 foot high Titan 4 payload fairing with various acoustic blanket designs and configurations in a large reverberant acoustic chamber. The primary purpose of this test program was to measure the fairing's internal acoustics and spacecraft vibration, especially the Radioisotope Thermoelectric Generators (RTG) vibration, and to quantify the mitigation efforts in reducing these levels. Key to this reduction effort was the utilization of new acoustic blanket designs. This paper will provide the background and rationale for performing this test program, state the test program's primary and secondary objectives and describe the test matrix, hardware and instrumentation. A second part companion paper will provide the test results and data analysis.

  13. Crack propagation analysis using acoustic emission sensors for structural health monitoring systems.

    PubMed

    Kral, Zachary; 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

  14. Acoustic emission-microstructural relationships in ferritic steels. Part 1: The effect of cooling rate

    NASA Astrophysics Data System (ADS)

    Wadley, H. N. G.; Scruby, C. B.

    1985-06-01

    Acoustic emission is controlled during deformation and fracture by the dynamics of dislocation motion and crack advance. The nature of the relationship between defect dynamics and acoustic emission in tensile samples of specially prepared low alloy steels containing 3.25 wt.% Ni, 1 wt.% Mn and a variable carbon content from 0.06 to 0.49 wt.% is studied. The most energetic signals are from microstructures with an initially low dislocation density and a ferrite dimension of approx. 10 microns, indicating the propagation of high velocity dislocations in ferrite to be the origin of acoustic emission during deformation. This is consistent with a model in which the product of glide distance and velocity (which are both controlled by microstructure) determines the amplitude of the acoustic emission. During subcritical micro-fracture, intergranular and alternating shear modes of microcracking in high strength conditions generate detectable signals. Both involve the rapid growth of cracks over distances of 10 to 100 micron. The ductile dimple mode of fracture is found to generate no detectable signals despite wide variations in dimple spacing and fracture stress. This is consistent with the recognized view that such fracture occurs under essentially static conditions.

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

    DOE PAGESBeta

    Kral, Zachary; 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).more » 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.« less

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

    PubMed Central

    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

  17. Acoustic emission during tensile deformation of M250 grade maraging steel

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Chandan Kumar; Rajkumar, Kesavan Vadivelu; Chandra Rao, Bhaghi Purna; Jayakumar, Tamanna

    2012-05-01

    Acoustic emission (AE) generated during room temperature tensile deformation of varyingly heat treated (solution annealed and thermally aged) M250 grade maraging steel specimens have been studied. Deformation of microstructure corresponding to different heat treated conditions in this steel could be distinctly characterized using the AE parameters such as RMS voltage, counts and peak amplitude of AE hits (events).

  18. Data quality enhancement and knowledge discovery from relevant signals in acoustic emission

    NASA Astrophysics Data System (ADS)

    Mejia, Felipe; Shyu, Mei-Ling; Nanni, Antonio

    2015-10-01

    The increasing popularity of structural health monitoring has brought with it a growing need for automated data management and data analysis tools. Of great importance are filters that can systematically detect unwanted signals in acoustic emission datasets. This study presents a semi-supervised data mining scheme that detects data belonging to unfamiliar distributions. This type of outlier detection scheme is useful detecting the presence of new acoustic emission sources, given a training dataset of unwanted signals. In addition to classifying new observations (herein referred to as "outliers") within a dataset, the scheme generates a decision tree that classifies sub-clusters within the outlier context set. The obtained tree can be interpreted as a series of characterization rules for newly-observed data, and they can potentially describe the basic structure of different modes within the outlier distribution. The data mining scheme is first validated on a synthetic dataset, and an attempt is made to confirm the algorithms' ability to discriminate outlier acoustic emission sources from a controlled pencil-lead-break experiment. Finally, the scheme is applied to data from two fatigue crack-growth steel specimens, where it is shown that extracted rules can adequately describe crack-growth related acoustic emission sources while filtering out background "noise." Results show promising performance in filter generation, thereby allowing analysts to extract, characterize, and focus only on meaningful signals.

  19. ORGANIC EMISSION MEASUREMENTS VIA SMALL CHAMBER TESTING

    EPA Science Inventory

    The paper discusses the measurement of organic emissions from a variety of indoor materials, using small (166 liter) environmental test chambers. The following materials were tested: adhesives, caulks, pressed wood products, floor waxes, paints, solid insecticides. For each mater...

  20. 40 CFR 89.119 - Emission tests.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... emission standards. (c) Use of carryover test data. In lieu of testing to certify an engine family for a... used to certify that engine family in previous years. This “carryover” data is only allowable if...

  1. 40 CFR 89.119 - Emission tests.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... emission standards. (c) Use of carryover test data. In lieu of testing to certify an engine family for a... used to certify that engine family in previous years. This “carryover” data is only allowable if...

  2. 40 CFR 89.119 - Emission tests.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... emission standards. (c) Use of carryover test data. In lieu of testing to certify an engine family for a... used to certify that engine family in previous years. This “carryover” data is only allowable if...

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  4. Gearbox Tooth Cut Fault Diagnostics Using Acoustic Emission and Vibration Sensors — A Comparative Study

    PubMed Central

    Qu, Yongzhi; He, David; Yoon, Jae; Van Hecke, Brandon; Bechhoefer, Eric; Zhu, Junda

    2014-01-01

    In recent years, acoustic emission (AE) sensors and AE-based techniques have been developed and tested for gearbox fault diagnosis. In general, AE-based techniques require much higher sampling rates than vibration analysis-based techniques for gearbox fault diagnosis. Therefore, it is questionable whether an AE-based technique would give a better or at least the same performance as the vibration analysis-based techniques using the same sampling rate. To answer the question, this paper presents a comparative study for gearbox tooth damage level diagnostics using AE and vibration measurements, the first known attempt to compare the gearbox fault diagnostic performance of AE- and vibration analysis-based approaches using the same sampling rate. Partial tooth cut faults are seeded in a gearbox test rig and experimentally tested in a laboratory. Results have shown that the AE-based approach has the potential to differentiate gear tooth damage levels in comparison with the vibration-based approach. While vibration signals are easily affected by mechanical resonance, the AE signals show more stable performance. PMID:24424467

  5. Gearbox tooth cut fault diagnostics using acoustic emission and vibration sensors--a comparative study.

    PubMed

    Qu, Yongzhi; He, David; Yoon, Jae; Van Hecke, Brandon; Bechhoefer, Eric; Zhu, Junda

    2014-01-01

    In recent years, acoustic emission (AE) sensors and AE-based techniques have been developed and tested for gearbox fault diagnosis. In general, AE-based techniques require much higher sampling rates than vibration analysis-based techniques for gearbox fault diagnosis. Therefore, it is questionable whether an AE-based technique would give a better or at least the same performance as the vibration analysis-based techniques using the same sampling rate. To answer the question, this paper presents a comparative study for gearbox tooth damage level diagnostics using AE and vibration measurements, the first known attempt to compare the gearbox fault diagnostic performance of AE- and vibration analysis-based approaches using the same sampling rate. Partial tooth cut faults are seeded in a gearbox test rig and experimentally tested in a laboratory. Results have shown that the AE-based approach has the potential to differentiate gear tooth damage levels in comparison with the vibration-based approach. While vibration signals are easily affected by mechanical resonance, the AE signals show more stable performance. PMID:24424467

  6. Investigation of Hydraulic Fracture Propagation Using a Post-Peak Control System Coupled with Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Chen, Li-Hsien; Chen, Wei-Chih; Chen, Yao-Chung; Benyamin, Leo; Li, An-Jui

    2015-05-01

    This study investigates the fracture mechanism of fluid coupled with a solid resulting from hydraulic fracture. A new loading machine was designed to improve upon conventional laboratory hydraulic fracture testing and to provide a means of better understanding fracture behavior of solid media. Test specimens were made of cement mortar. An extensometer and acoustic emission (AE) monitoring system recorded the circumferential deformation and crack growth location/number during the test. To control the crack growth at the post-peak stage the input fluid rate can be adjusted automatically according to feedback from the extensometer. The complete stress-deformation curve, including pre- and post-peak stages, was therefore obtained. The crack extension/growth developed intensively after the applied stress reached the breakdown pressure. The number of cracks recorded by the AE monitoring system was in good agreement with the amount of deformation (expansion) recorded by the extensometer. The results obtained in this paper provide a better understanding of the hydraulic fracture mechanism which is useful for underground injection projects.

  7. Determination of Initial Crack Strength of Silicon Die Using Acoustic Emission Technique

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Chi; Su, Yen-Fu; Yang, Shin-Yueh; Liang, Steven Y.; Chiang, Kuo-Ning

    2015-07-01

    The current market demand for high-efficiency, high-performance, small-sized electronic products has focused attention on the use of three-dimensional (3D) integrated circuits (IC) in the design of electronic packaging. Silicon wafers can be ground and polished to reduce their thickness and increase the chip stacking density. However, microcracks can result from the thinning and stacking process or during use of an electronic device over time; therefore, estimation of the cracking strength is an important issue in 3D IC packaging. This research combined the ball breaker test (BBT) with an acoustic emission (AE) system to measure the allowable force on a silicon die. To estimate the initial crack strength of a silicon die, the BBT was combined with finite-element (FE) analysis. The AE system can detect the initial crack and the subsequent bulk failure of the silicon die individually, thus avoiding overestimation of the die strength. In addition, the results of the modified ball breaker test showed that edge chipping did not affect the silicon die strength. However, the failure force and silicon die strength were reduced as the surface roughness of the test specimen increased. Thus, surface roughness must be controlled in the BBT to prevent underestimation of the silicon die strength.

  8. Acoustic emission monitoring of concrete columns and beams strengthened with fiber reinforced polymer sheets

    NASA Astrophysics Data System (ADS)

    Ma, Gao; Li, Hui; Zhou, Wensong; Xian, Guijun

    2012-04-01

    Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering. During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of concrete crack patterns during the loading process was revealed.

  9. Detection of stress corrosion cracking of high-strength steel used in prestressed concrete structures by acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Ramadan, S.; Gaillet, L.; Tessier, C.; Idrissi, H.

    2008-02-01

    The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures.

  10. Fractal characteristics and acoustic emission of coal containing methane in triaxial compression failure

    NASA Astrophysics Data System (ADS)

    Kong, Xiangguo; Wang, Enyuan; Hu, Shaobin; Shen, Rongxi; Li, Xuelong; Zhan, Tangqi

    2016-01-01

    Aimed at exploring the influence of methane to coal and studying fractal characteristics and acoustic emission (AE) features in the damage evolution, the triaxial compression experiments of coal containing methane were conducted, and acoustic emission response was collected simultaneously in the loading process. Based on the method for calculating the correlation dimension, the fractal dimension was calculated with regard to time series of acoustic emission. Our experimental results indicate that AE response and fractal dimension can reflect the evolution and propagation of cracks in the loading process. Corresponding to the load-time, acoustic emission experiences active, linearly increasing, rapidly augmenting and decreasing stage. However, the fractal dimension of AE develops from chaos to orderly state. Late loading, a continued slowdown in fractal dimension, can be used as a precursory signal of coal sample destruction. In addition, the amount of gas in the coal sample will influence the evolution of pore and fracture, which causes a variation in the acoustic emission signals and fractal dimension. The maximum bearing load reduces 18.85% and 49.18% within pore pressure of 0.75 and 1.5 MPa, compared with it (24.4 kN) of the coal sample (without gas). What's more, the increase of pore pressure will cause the growth of AE count and energy, but the correlation dimension of AE parameters drops. This study is helpful for us to understand the effects of methane to coal and the evolution mechanism of cracks, and it can be applied to the research on occurrence mechanism and early warning of coal and gas outburst.

  11. Validation and Simulation of Ares I Scale Model Acoustic Test - 2 - Simulations at 5 Foot Elevation for Evaluation of Launch Mount Effects

    NASA Technical Reports Server (NTRS)

    Strutzenberg, Louise L.; Putman, Gabriel C.

    2011-01-01

    The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. Expanding from initial simulations of the ASMAT setup in a held down configuration, simulations have been performed using the Loci/CHEM computational fluid dynamics software for ASMAT tests of the vehicle at 5 ft. elevation (100 ft. real vehicle elevation) with worst case drift in the direction of the launch tower. These tests have been performed without water suppression and have compared the acoustic emissions for launch structures with and without launch mounts. In addition, simulation results have also been compared to acoustic and imagery data collected from similar live-fire tests to assess the accuracy of the simulations. Simulations have shown a marked change in the pattern of emissions after removal of the launch mount with a reduction in the overall acoustic environment experienced by the vehicle and the formation of highly directed acoustic waves moving across the platform deck. Comparisons of simulation results to live-fire test data showed good amplitude and temporal correlation and imagery comparisons over the visible and infrared wavelengths showed qualitative capture of all plume and pressure wave evolution features.

  12. Hydraulic Fracture Propagation through Preexisting Discontinuity Monitored by Acoustic Emission and Ultrasonic Transmission

    NASA Astrophysics Data System (ADS)

    Stanchits, S.; Lund, J.; Surdi, A.; Edelman, E.; Whitney, N.; Eldredge, R.; Suarez-Rivera, R.

    2011-12-01

    Hydraulic fracturing is critical to enhance hydrocarbon production from ultra-low permeability unconventional reservoirs, and is the common completion methodology for tight formations around the world. Unfortunately, these reservoirs are often highly heterogeneous and their heterogeneity imparts a degree of geometrical complexity in hydraulic fractures that is poorly understood. Fracture complexity (e.g. branching) results in higher surface area and could be beneficial to production provided it remains conductive. Understanding the sources and consequences of fracture complexity is thus of high importance to completion and production operations. In this study we postulate that textural complexity in tight heterogeneous formations induces fracture complexity, and that the main sources of textural complexity are associated with veins, bed boundaries, lithologic contacts, and geologic interfaces. We thus study the effect of interfaces on hydraulic fracture propagation under laboratory conditions by Acoustic Emission (AE) and Ultrasonic Transmission (UT) monitoring techniques. The experiments were conducted on low permeability sandstone blocks of 279 x 279 x 381 mm length with saw cut discontinuities oriented orthogonally to the expected direction of fracture propagation. The rock is loaded in a poly-axial test frame to representative effective in-situ stress conditions of normal and deviatoric stress. Hydraulic fracturing was initiated by injection of silicon oil into a borehole drilled off center from the block. Acoustic emission (AE) events were continuously monitored during testing using nineteen P-wave sensors. Additional sensors were installed to periodically monitor ultrasonic transmission (UT) along various directions oblique and perpendicular to the fracture and the interface. The AE and UT data were recorded using a Vallen AMSY-6 system, with 16-bit amplitude resolution and 5 MHz sampling rate. Detailed analysis of AE localizations allowed us to identify

  13. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  15. An echolocation model for the restoration of an acoustic image from a single-emission echo

    NASA Astrophysics Data System (ADS)

    Matsuo, Ikuo; Yano, Masafumi

    2004-12-01

    Bats can form a fine acoustic image of an object using frequency-modulated echolocation sound. The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. It is therefore necessary to restore the acoustic image from limited information. The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and location. Here, by introducing some reasonable constraints, a method is proposed for restoring an acoustic image from the echo. The configuration is extrapolated from the amplitude spectrum of the restricted frequency range by using the continuity condition of the amplitude spectrum at the minimum frequency of the emission and the minimum phase condition. The determination of the location requires extracting the amplitude spectra, which vary with its location. For this purpose, the Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The location is estimated from the temporal changes of the amplitude spectra. .

  16. Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

    NASA Technical Reports Server (NTRS)

    Wood, Jessica J.; Foster, Lee W.

    2013-01-01

    A Multilayer Insulation (MLI) and Broad Area Cooling (BAC) shield thermal control system shows promise for long-duration storage of cryogenic propellant. The NASA Cryogenic Propellant Storage and Transfer (CPST) project is investigating the thermal and structural performance of this tank-applied integrated system. The MLI/BAC Shield Acoustic and Thermal Test was performed to evaluate the MLI/BAC shield's structural performance by subjecting it to worst-case launch acoustic loads. Identical thermal tests using Liquid Nitrogen (LN2) were performed before and after the acoustic test. The data from these tests was compared to determine if any degradation occurred in the thermal performance of the system as a result of exposure to the acoustic loads. The thermal test series consisted of two primary components: a passive boil-off test to evaluate the MLI performance and an active cooling test to evaluate the integrated MLI/BAC shield system with chilled vapor circulating through the BAC shield tubes. The acoustic test used loads closely matching the worst-case envelope of all launch vehicles currently under consideration for CPST. Acoustic test results yielded reasonable responses for the given load. The thermal test matrix was completed prior to the acoustic test and successfully repeated after the acoustic test. Data was compared and yielded near identical results, indicating that the MLI/BAC shield configuration tested in this series is an option for structurally implementing this thermal control system concept.

  17. 40 CFR 61.13 - Emission tests and waiver of emission tests.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... waiver of emission testing is obtained under this section, the owner or operator shall test emissions... under paragraph (b) of this section, but the notification must occur before the performance test... to conduct the performance test. The performance test shall be conducted as soon as practicable...

  18. Frequency Characteristics of Acoustic Emission Signals from Cementitious Waste-forms with Encapsulated Al

    SciTech Connect

    Spasova, Lyubka M.; Ojovan, Michael I.

    2007-07-01

    Acoustic emission (AE) signals were continuously recorded and their intrinsic frequency characteristics examined in order to evaluate the mechanical performance of cementitious wasteform samples with encapsulated Al waste. The primary frequency in the power spectrum and its range of intensity for the detected acoustic waves were potentially related with appearance of different micro-mechanical events caused by Al corrosion within the encapsulating cement system. In addition the process of cement matrix hardening has been shown as a source of AE signals characterized with essentially higher primary frequency (above 2 MHz) compared with those due to Al corrosion development (below 40 kHz) and cement cracking (above 100 kHz). (authors)

  19. Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals

    NASA Astrophysics Data System (ADS)

    Kubakaddi, S. S.

    2016-05-01

    Cerenkov acoustic phonon emission is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) when it is driven by a dc electric field E. Numerical calculations are made for Cd3As2 in which mobility and electron concentration are large. We find that Cerenkov emission of acoustic phonons takes place when the electron drift velocity vd is greater than the sound velocity vs. This occurs at small E (˜few V/cm) due to large mobility. Frequency (ωq) and angular (θ) distribution of phonon emission spectrum P(ωq, θ) are studied for different electron drift velocities vd (i.e., different E) and electron concentrations ne. The frequency dependence of P(ωq, θ) shows a maximum Pm(ωq, θ) at about ωm ≈ 1 THz and is found to increase with the increasing vd and ne. The value of ωm shifts to higher region for larger ne. It is found that ωm/ne1/3 and Pm(ωq, θ)/ne2/3 are nearly constants. The latter is in contrast with the Pm(ωq, θ)ne1/2 = constant in conventional bulk semiconductor. Each maximum is followed by a vanishing spectrum at nearly "2kf cutoff," where kf is the Fermi wave vector. Angular dependence of P(ωq, θ) and the intensity P(θ) of the phonon emission shows a maximum at an emission angle 45° and is found to increase with increasing vd. P(θ) is found to increase linearly with ne giving the ratio P(θ)/(nevd) nearly a constant. We suggest that it is possible to have the controlled Cerenkov emission and generation of acoustic phonons with the proper choice of E, θ, and ne. 3DDS with large ne and mobility can be a good source of acoustic phonon generation in ˜THz regime.

  20. Measurement of transmission loss characteristics using acoustic intensity techniques at the KU-FRL Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1983-01-01

    The transmission loss characteristics of panels using the acoustic intensity technique is presented. The theoretical formulation, installation of hardware, modifications to the test facility, and development of computer programs and test procedures are described. A listing of all the programs is also provided. The initial test results indicate that the acoustic intensity technique is easily adapted to measure transmission loss characteristics of panels. Use of this method will give average transmission loss values. The fixtures developed to position the microphones along the grid points are very useful in plotting the intensity maps of vibrating panels.

  1. Classification of alkali-silica reaction and corrosion distress using acoustic emission

    NASA Astrophysics Data System (ADS)

    Abdelrahman, Marwa; ElBatanouny, Mohamed; Serrato, Michael; Dixon, Kenneth; Larosche, Carl; Ziehl, Paul

    2016-02-01

    The Nuclear Regulatory Commission regulates approximately 100 commercial nuclear power reactor facilities that contribute about 20% of the total electric energy produced in the United States. Half of these reactor facilities are over 30 years old and are approaching their original design service life. Due to economic and durability considerations, significant portions of many of the facilities were constructed with reinforced concrete, including the containment facilities, cooling towers, and foundations. While most of these concrete facilities have performed exceptionally well throughout their initial expected service life, some are beginning to exhibit different forms of concrete deterioration. In this study, acoustic emission (AE) is used to monitor two main concrete deterioration mechanisms; alkali-silica reaction (ASR) distress and corrosion of reinforcing steel. An accelerated ASR test was conducted where specimens were continuously monitored with AE. The results show that AE can detect and classify damage due to ASR distress in the specimens. AE was also used to remotely monitor active corrosion regions in a reactor facility. AE monitoring of accelerated corrosion testing was also conducted on a concrete block specimen cut from a similar reactor building. Electrochemical measurements were conducted to correlate AE activity to quantifiable corrosion measurements and to enhance capabilities for service life prediction.

  2. Accurate Damage Location in Complex Composite Structures and Industrial Environments using Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Eaton, M.; Pearson, M.; Lee, W.; Pullin, R.

    2015-07-01

    The ability to accurately locate damage in any given structure is a highly desirable attribute for an effective structural health monitoring system and could help to reduce operating costs and improve safety. This becomes a far greater challenge in complex geometries and materials, such as modern composite airframes. The poor translation of promising laboratory based SHM demonstrators to industrial environments forms a barrier to commercial up take of technology. The acoustic emission (AE) technique is a passive NDT method that detects elastic stress waves released by the growth of damage. It offers very sensitive damage detection, using a sparse array of sensors to detect and globally locate damage within a structure. However its application to complex structures commonly yields poor accuracy due to anisotropic wave propagation and the interruption of wave propagation by structural features such as holes and thickness changes. This work adopts an empirical mapping technique for AE location, known as Delta T Mapping, which uses experimental training data to account for such structural complexities. The technique is applied to a complex geometry composite aerospace structure undergoing certification testing. The component consists of a carbon fibre composite tube with varying wall thickness and multiple holes, that was loaded under bending. The damage location was validated using X-ray CT scanning and the Delta T Mapping technique was shown to improve location accuracy when compared with commercial algorithms. The onset and progression of damage were monitored throughout the test and used to inform future design iterations.

  3. Monitoring acoustic emission (AE) energy in slurry impingement using a new model for particle impact

    NASA Astrophysics Data System (ADS)

    Droubi, M. G.; Reuben, R. L.; White, G.

    2015-10-01

    A series of systematic impact tests have been carried out to investigate the influence of particle size, free stream velocity, particle impact angle, and nominal particle concentration on the amount of energy dissipated in a carbon steel target using a slurry impingement erosion test rig, as indicated by the acoustic emission (AE) recorded by a sensor mounted on the back of the target. Silica sand particles of mean particle size 152.5, 231, and 362.5 μm were used for impingement on the target at angles varying between 30° and 90° while the free stream velocity was changed between 4.2 and 12.7 m/s. In previous work by the authors, it was demonstrated that the AE time series associated with particle-laden air striking a carbon steel target could be described as the cumulation of individual particle arrival events each drawn from a statistical distribution model. The high arrival rate involved in a slurry jet poses challenges in resolving individual particle impact signatures in the AE record, and so the model has been extended in this paper to account for different particle carrier-fluids and to situations where arrivals cannot necessarily be resolved.

  4. Development of Methodology to Assess the Failure Behaviour of Bamboo Single Fibre by Acoustic Emission Technique

    NASA Astrophysics Data System (ADS)

    Alam, Md. Saiful; Gulshan, Fahmida; Ahsan, Qumrul; Wevers, Martine; Pfeiffer, Helge; van Vuure, Aart-Willem; Osorio, Lina; Verpoest, Ignaas

    2016-06-01

    Acoustic emission (AE) was used as a tool for detecting, evaluating and for better understanding of the damage mechanism and failure behavior in composites during mechanical loading. Methodology was developed for tensile test of natural fibres (bamboo single fibre). A series of experiments were performed and load drops (one or two) were observed in the load versus time graphs. From the observed AE parameters such as amplitude, energy, duration etc. significant information corresponding to the load drops were found. These AE signals from the load drop occurred from such failure as debonding between two elementary fibre or from join of elementary fibre at edge. The various sources of load at first load drop was not consistent for the different samples (for a particular sample the value is 8 N, stress: 517.51 MPa). Final breaking of fibre corresponded to saturated level AE amplitude of preamplifier (99.9 dB) for all samples. Therefore, it was not possible to determine the exact AE energy value for final breaking. Same methodology was used for tensile test of three single fibres, which gave clear indication of load drop before the final breaking of first and second fibre.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  6. Contralateral acoustic stimulation alters the magnitude and phase of distortion product otoacoustic emissions

    PubMed Central

    Deeter, Ryan; Abel, Rebekah; Calandruccio, Lauren; Dhar, Sumitrajit

    2009-01-01

    Activation of medial olivocochlear efferents through contralateral acoustic stimulation (CAS) has been shown to modulate distortion product otoacoustic emission (DPOAE) level in various ways (enhancement, reduction, or no change). The goal of this study was to investigate the effect of a range of CAS levels on DPOAE fine structure. The 2f1-f2 DPOAE was recorded (f2∕f1=1.22, L1=55 dB, and L2=40 dB) from eight normal-hearing subjects, using both a frequency-sweep paradigm and a fixed frequency paradigm. Contamination due to the middle ear muscle reflex was avoided by monitoring the magnitude and phase of a probe in the test ear and by monitoring DPOAE stimulus levels throughout testing. Results show modulations in both level and frequency of DPOAE fine structure patterns. Frequency shifts observed at DPOAE level minima could explain reports of enhancement in DPOAE level due to efferent activation. CAS affected the magnitude and phase of the DPOAE component from the characteristic frequency region to a greater extent than the component from the overlap region between the stimulus tones. This differential effect explains the occasional enhancement observed in DPOAE level as well as the frequency shift in fine structure patterns. PMID:19894823

  7. Acoustic emission characterization of the onset of corrosion in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Di Benedetti, M.; De Cais, E.; Karim, Z.; Loreto, G.; Presuel, F.; Nanni, A.

    2012-04-01

    The development of techniques capable of evaluating deterioration of reinforced concrete (RC) is instrumental to the advancement of the structural health monitoring (SHM) and service life estimate for constructed facilities. One of the main causes leading to degradation of RC is the corrosion of the steel reinforcement. This process can be modeled phenomenologically, while laboratory tests aimed at studying durability responses are typically accelerated in order to provide useful results within a realistic period of time. Among nondestructive methods, acoustic emission (AE) is emerging as a tool to detect the onset and progression of deterioration mechanisms. In this paper, the development of accelerated corrosion and continuous AE monitoring test set-up for RC specimens are presented. Relevant information are provided with regard to the characteristics of the corrosion circuit, continuous measurement and acquisition of corrosion potential, selection of AE sensors and AE parameter setting. Results from small-scale pre-notched RC specimens aim to isolate the frequency spectrum where the corrosion first takes place. Waveform analysis critical in the definition of a prognosis model will extend the AE dataset for the onset of corrosion.

  8. Acoustic emission monitoring of low velocity impact damage in graphite/epoxy laminates during tensile loading

    NASA Technical Reports Server (NTRS)

    Parker, Bradford H.

    1992-01-01

    An acoustic emission (AE) system was set up in a linear location data acquisition mode to monitor the tensile loading of eight-ply quasi-isotropic graphite/epoxy specimens containing low velocity impact damage. The impact damage was induced using an instrumented drop weight tower. During impact, specimens were supported by either an aluminum plate or a membrane configuration. Cross-sectional examinations revealed that the aluminum plate configuration resulted in primarily matrix cracking and back surface fiber failure. The membrane support resulted in only matrix cracking and delamination damage. Penetrant enhanced radiography and immersion ultrasonics were used in order to assess the amount of impact damage in each tensile specimen. During tensile loading, AE reliably detected and located the damage sites which included fiber failure. All specimens with areas of fiber breakage ultimately failed at the impact site. AE did not reliably locate damage which consisted of only delaminations and matrix cracking. Specimens with this type of damage did not ultimately fail at the impact site. In summary, AE demonstrated the ability to increase the reliability of structural proof tests; however, the successful use of this technique requires extensive baseline testing.

  9. Acoustic emissions generated in aged dental composites using a laser thermoacoustic technique.

    PubMed

    Lee, S Y; Lin, C T; Dong, D R; Huang, H M; Shih, Y H

    2000-09-01

    The heating up of dental composites by laser will produce acoustic emissions (AEs) that may be related to fracture mechanisms in the composites. It has been proved that the mechanical properties of dental composites are affected by storage in food simulating liquids, i.e. 75% ethanol, which has a solubility parameter approximating to that of bisphenol glycidyl dimethacrylate (BisGMA) resin. A new method was innovated to evaluate the laser-induced AEs in dental composites aged by 75% ethanol solution. Model systems (50/50 BisGMA/TEGDMA resin filled with 0% and 75 wt.% 5-10 microm silanized BaSiO6) as well as three commercial composites (Marathon One, Z100 and Herculite XRV) were used in this study. Nine samples acting as the control group were tested to establish the correlation of AEs to laser power. The effect of ageing by immersion in 75% ethanol on AEs and diametral tensile strength (DTS) was then evaluated. A quasi-continuous wave CO2 laser was used to heat up the composites. AEs of frequency 100-200 kHz were collected, filtered, recorded and processed using a 4610 Smart Acoustic Monitor. Burst patterns, which formally were assumed to be correlated to fracture mechanisms, were also identified from the data obtained at laser power > or = 5 W for commercial composites and > or = 4 W for model systems. Higher laser powers cause the AE to increase for all composites except unfilled model resin. AEs as a function of power for all aged systems were flat (< 100 events) below 4 W. Emissions then rose sharply to > 1000 events at 7.1 W. Statistically significant differences were found between the AEs obtained at 5 W (commercial composites) and those at 4.3 W (model systems) for material systems and storage times. Marathon One was less affected by the laser and an abrupt change in AE was found between days 0 and 7 of storage for all commercial composites. The AE value from the unfilled model resin was found to be significantly different from that of the model composites

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  11. NASA Rat Acoustic Tolerance Test 1994-1995

    NASA Technical Reports Server (NTRS)

    Holley, Daniel C.; Mele, Gary D.; Naidu, Sujata

    1996-01-01

    The major objective of this Cooperative Agreement was to develop a noise level specification for laboratory rats in the Centrifuge Facility Specimen Chambers (Space Station Biological Research Project), and to validate the specification for 3 noise octave bands: center frequencies 8 kHz, 16, kHz, and 32 kHz. This has been accomplished. Objective measures were used to verify that the chronic noise exposure was not harmful to the animals from physiological and behavioral perspectives. These measures were defined in the Stress Assessment Battery Validation for the Rat Acoustic Tolerance Test. In addition, the effects of the chronic noise exposure on rat hearing was assessed by the Brainstem Auditory Evoked Potential Method (BAER).

  12. Testing of metal-ceramic joint using scanning acoustic microscopy.

    PubMed

    Könönen, M; Kivilahti, J

    1991-07-01

    The objective of the investigation was to compare the results obtained from examination of titanium-porcelain joints by means of both scanning acoustic microscopy (C-SAM) and scanning electron microscopy (SEM). A dental porcelain (Ducera, Dental GmbH) mechanically compatible with titanium was fired to sand-blasted or electrolytically polished commercially pure titanium (grade 1) specimens. The firing was carried out in an ordinary dental furnace according to manufacturer's instructions. There was a good correlation between the C-SAM and SEM methods regarding the ability to detect air-filled defects in the porcelain/titanium interface. The results show that the C-SAM method, being non-destructive as well as time-and-money-saving, can be useful in the testing of metal-ceramic joints. PMID:1813346

  13. Ares I Scale Model Acoustic Test Overpressure Results

    NASA Technical Reports Server (NTRS)

    Casiano, M. J.; Alvord, D. A.; McDaniels, D. M.

    2011-01-01

    A summary of the overpressure environment from the 5% Ares I Scale Model Acoustic Test (ASMAT) and the implications to the full-scale Ares I are presented in this Technical Memorandum. These include the scaled environment that would be used for assessing the full-scale Ares I configuration, observations, and team recommendations. The ignition transient is first characterized and described, the overpressure suppression system configuration is then examined, and the final environment characteristics are detailed. The recommendation for Ares I is to keep the space shuttle heritage ignition overpressure (IOP) suppression system (below-deck IOP water in the launch mount and mobile launcher and also the crest water on the main flame deflector) and the water bags.

  14. Direct-field acoustic testing of a flight system : logistics, challenges, and results.

    SciTech Connect

    Stasiunas, Eric Carl; Gurule, David Joseph; Babuska, Vit; Skousen, Troy J.

    2010-10-01

    Before a spacecraft can be considered for launch, it must first survive environmental testing that simulates the launch environment. Typically, these simulations include vibration testing performed using an electro-dynamic shaker. For some spacecraft however, acoustic excitation may provide a more severe loading environment than base shaker excitation. Because this was the case for a Sandia Flight System, it was necessary to perform an acoustic test prior to launch in order to verify survival due to an acoustic environment. Typically, acoustic tests are performed in acoustic chambers, but because of scheduling, transportation, and cleanliness concerns, this was not possible. Instead, the test was performed as a direct field acoustic test (DFAT). This type of test consists of surrounding a test article with a wall of speakers and controlling the acoustic input using control microphones placed around the test item, with a closed-loop control system. Obtaining the desired acoustic input environment - proto-flight random noise input with an overall sound pressure level (OASPL) of 146.7 dB-with this technique presented a challenge due to several factors. An acoustic profile with this high OASPL had not knowingly been obtained using the DFAT technique prior to this test. In addition, the test was performed in a high-bay, where floor space and existing equipment constrained the speaker circle diameter. And finally, the Flight System had to be tested without contamination of the unit, which required a contamination bag enclosure of the test unit. This paper describes in detail the logistics, challenges, and results encountered while performing a high-OASPL, direct-field acoustic test on a contamination-sensitive Flight System in a high-bay environment.

  15. Acoustic Emissions, Velocities And Permeability Evolution During Formation Of Compaction Bands In Sandstone.

    NASA Astrophysics Data System (ADS)

    Fortin, J.; Stanchits, S.; Dresen, G.; Schubnel, A.; Gueguen, Y.

    2004-12-01

    Compaction bands are zones of localized deformation observed in high porosity rock (Mollema et al. [1996], Klein et al. [2001], Fortin et al. [2003]). These planar bands form perpendicular to the direction of maximum compression. Compaction bands display significantly reduced porosity and are potentially important permeability barriers in reservoir rocks and aquifers. To investigate localized compaction and changes in physical properties of porous sandstone, we performed triaxial tests on Bleurswiller sandstone, (50% quartz 30% feldspars and 20% clay, 25% porosity), on Fontainebleau sandstone (100% quartz, 25% porosity) and on Flechtingen sandstone (65-75% quartz, calcite and illite 15%, porosity 5.5-7%). Experiments were performed under wet conditions at a pore pressure of 10 MPa. Thirteen experiments were performed at the Laboratoire de Geologie (Ecole Normal Superieur Paris) and at GeoForschungsZentrum Potsdam. Evolution of volumetric strain, elastic wave velocities and permeability were recorded at confining pressures of 12 and 180 MPa. Acoustic Emission (AE) characteristics during deformation were studied at GeoForschungsZentrum Potsdam. To monitor velocity change and microcracking of sandstone, 10 P-wave sensors and 8 polarized S-wave piezoelectric sensors were glued to the cylindrical surface of the samples. To monitor fracture-induced anisotropy, two additional P sensors were installed in axial direction. Fully digitized waveforms were recorded by 10 MHz/16bit Data Acquisition System with an accuracy of AE hypocenters determination of about 2.5 mm. Location of acoustic emission events reveal the evolution of localized compaction bands in sandstone subjected to axial compression. The formation of the bands depends on rock type and effective pressure. Our experiments show a reduction of permeability across compaction bands by about one to two orders of magnitude (Vajdova et al. [2004]; Holcomb et al., [2003]) suggesting that the bands may act as barriers to

  16. Acoustic Performance of Drive Rig Mufflers for Model Scale Engine Testing

    NASA Technical Reports Server (NTRS)

    Stephens, David, B.

    2013-01-01

    Aircraft engine component testing at the NASA Glenn Research Center (GRC) includes acoustic testing of scale model fans and propellers in the 9- by15-Foot Low Speed Wind Tunnel (LSWT). This testing utilizes air driven turbines to deliver power to the article being studied. These air turbines exhaust directly downstream of the model in the wind tunnel test section and have been found to produce significant unwanted noise that reduces the quality of the acoustic measurements of the engine model being tested. This report describes an acoustic test of a muffler designed to mitigate the extraneous turbine noise. The muffler was found to provide acoustic attenuation of at least 8 dB between 700 Hz and 20 kHz which significantly improves the quality of acoustic measurements in the facility.

  17. Detection of bond failure in the anchorage zone of reinforced concrete beams via acoustic emission monitoring

    NASA Astrophysics Data System (ADS)

    Abouhussien, Ahmed A.; Hassan, Assem A. A.

    2016-07-01

    In this study, acoustic emission (AE) monitoring was utilised to identify the onset of bond failure in reinforced concrete beams. Beam anchorage specimens were designed and tested to fail in bond in the anchorage zone. The specimens included four 250 × 250 × 1500 mm beams with four variable bonded lengths (100, 200, 300, and 400 mm). Meanwhile, an additional 250 × 250 × 2440 mm beam, with 200 mm bonded length, was tested to investigate the influence of sensor location on the identification of bond damage. All beams were tested under four-point loading setup and continuously monitored using three distributed AE sensors. These attached sensors were exploited to record AE signals resulting from both cracking and bond deterioration until failure. The variations in the number of AE hits and cumulative signal strength (CSS) versus test time were evaluated to achieve early detection of crack growth and bar slippage. In addition, AE intensity analysis was performed on signal strength of collected AE signals to develop two additional parameters: historic index (H (t)) and severity (S r). The analysis of these AE parameters enabled an early detection of both first cracks (at almost the mid-span of the beam) and bar slip in either of the anchorage zones at the beams’ end before their visual observation, regardless of sensor location. The results also demonstrated a clear correlation between the damage level in terms of crack development/measured free end bar slip and AE parameters (number of hits, CSS, H(t), and S r).

  18. Avco Lycoming emission and flight test results

    NASA Technical Reports Server (NTRS)

    Duke, L. C.

    1976-01-01

    The Avco Lycoming flight test program for reduced emissions was conducted to determine and document the lean fuel schedule limits for current production aircraft based on flight safety. Based on analysis of the emissions profile, Avco Lycoming proposed to evaluate the effect of leaner schedules in the idle/taxi, climb, and approach modes. These modes were selected as areas where it was felt that possible improvements could be made with the greatest improvement in cyclic emissions reduction. The fuel systems to produce these leaner stepped fuel schedules were tailored specifically for the flight test.

  19. Codetection of acoustic emissions during failure of heterogeneous media: New perspectives for natural hazard early warning

    NASA Astrophysics Data System (ADS)

    Faillettaz, Jerome; Or, Dani; Reiweger, Ingrid

    2016-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. Influence of geometry on the fracturing behavior of textile reinforced cement monitored by acoustic emission

    NASA Astrophysics Data System (ADS)

    Aggelis, D. G.; Blom, J.; El Kadi, M.; Wastiels, J.

    2014-03-01

    In this work the flexural behavior of textile reinforced cement (TRC) laminate is examined using acoustic emission (AE). The TRC composite is a combination of inorganic phosphate cement (IPC) with randomly distributed glass fibres. IPC has been developed at the "Vrije Universiteit Brussel" and shows a neutral pH meaning that glass fibers are hardly attacked. During bending, stresses lead to the activation of damage mechanisms like matrix cracking, delaminations and fiber pull-out being in succession or overlapping in time. AE records the responses of the damage propagation events and allows the monitoring of the fracture behavior from the onset to the final stage. The effect of the span in three-point bending tests, which is varied to create different stress fields, is targeted. Parameters like duration and frequency reveal information about the mode of the damage sources in relation to the span. Results show that as the span decreases, the dominant damage mode shifts away from bending and acquires more shear characteristics by increasing the interlaminar shearing events.

  3. Acoustic Emission Source Location Using a Distributed Feedback Fiber Laser Rosette

    PubMed Central

    Huang, Wenzhu; Zhang, Wentao; Li, Fang

    2013-01-01

    This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage in structures such as those found in civil applications. The directional sensitivity of DFB fiber laser is investigated by calculating location coefficient using a method of digital signal analysis. In this, autocorrelation is used to extract the location coefficient from the periodic AE signal and wavelet packet energy is calculated to get the location coefficient of a burst AE source. Normalization is processed to eliminate the influence of distance and intensity of AE source. Then a new location algorithm based on the location coefficient is presented and tested to determine the location of AE source using a Delta (Δ) DFB fiber laser rosette configuration. The advantage of the proposed algorithm over the traditional methods based on fiber Bragg Grating (FBG) include the capability of: having higher strain resolution for AE detection and taking into account two different types of AE source for location. PMID:24141266

  4. A novel technique for acoustic emission monitoring in civil structures with global fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Verstrynge, E.; Pfeiffer, H.; Wevers, M.

    2014-06-01

    The application of acoustic emission (AE)-based damage detection is gaining interest in the field of civil structural health monitoring. Damage progress can be detected and located in real time and the recorded AEs hold information on the fracture process which produced them. One of the drawbacks for on-site application in large-scale concrete and masonry structures is the relatively high attenuation of the ultrasonic signal, which limits the detection range of the AE sensors. Consequently, a large number of point sensors are required to cover a certain area. To tackle this issue, a global damage detection system, based on AE detection with a polarization-modulated, single mode fiber optic sensor (FOS), has been developed. The sensing principle, data acquisition and analysis in time and frequency domain are presented. During experimental investigations, this AE-FOS is applied for the first time as a global sensor for the detection of crack-induced AEs in a full-scale concrete beam. Damage progress is monitored during a cyclic four-point bending test and the AE activity, detected with the FOS, is related to the subsequent stages of damage progress in the concrete element. The results obtained with the AE-FOS are successfully linked to the mechanical behavior of the concrete beam and a qualitative correspondence is found with AE data obtained by a commercial system.

  5. Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion

    PubMed Central

    Bagherifaez, Marya; Behnia, Arash; Majeed, Abeer Aqeel; Hwa Kian, Chai

    2014-01-01

    Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis. PMID:25180203

  6. Impact of hygrometry changes on creep behaviour of a porous rock and associated acoustic emission.

    NASA Astrophysics Data System (ADS)

    Grgic, D.; Amitrano, D.

    2009-04-01

    Static fatigue of a polycrystalline porous rock (iron ore) was studied by performing multi step uniaxial creep tests under partially saturated conditions, and the impact of water saturation was analyzed. The samples were, in a first step set to a partial water saturation of 90%. In a second step, the samples were saturated completely in order to simulate the impact of flooding corresponding to the conditions of abandoned iron mines. We recorded axial and transversal strain and acoustic emission (EA). The experimental results show that the water saturation induces a strong increase in AE activity and dilatant inelastic volumetric strain. This is associated with a notable decrease in Young's modulus and in the b-value of the Gutenberg-Richter law (i.e., the relative number of large-amplitude events increases) as the rock approaches failure, indicating that microfracturing plays an important role in the creep process. Water saturation accelerates static fatigue through hydro-mechanical coupling and subcritical stress corrosion cracking. The chemical reactions involved in the corrosion of iron ore and leading to a decrease in its intrinsic mechanical properties are described. These reactions play a major role in the static fatigue of iron ore, which on a large scale is probably the main mechanism explaining certain collapses in underground iron mines. It is also shown that creep straining of iron ore is partially reversible after stress removal, indicating that it results also from time-dependent viscoplastic mechanism (i.e., dislocation creep).

  7. Acoustic emission from single point machining: Source mechanisms and signal changes with tool wear

    SciTech Connect

    Heiple, C.R.; Carpenter, S.H.; Armentrout, D.L.; McManigle, A.P.

    1994-05-01

    Acoustic emission (AE) was monitored during single point, continuous machining of 4340 steel and Ti-6Al-4V as a function of heat treatment. Heat treatments that increase the strength of 4340 steel substantially increase the amount of AE produced during deformation, while heat treatments that increase the strength of Ti-6Al-4V dramatically decrease the amount of AE produced during deformation. There was little change in root-mean-square (rms) AE level during machining for either alloy as a function of prior heat treatment, demonstrating that chip deformation is not a major source of AE in single point machining. Additional data from a variety of materials suggest that sliding friction between the nose and/or flank of the tool and the newly machined surface is the primary source of AE. Changes in AE signal characteristics with tool wear were also monitored during single point machining. No signal characteristic changed in the same way with tool wear for all materials tested. A single change in a particular AE signal characteristic with tool wear valid for all materials probably does not exist. Nevertheless, changes in various signal characteristics with wear for a given material may be sufficient to be used to monitor tool wear.

  8. Analytical modelling of acoustic emission from buried or surface-breaking cracks under stress

    NASA Astrophysics Data System (ADS)

    Ben Khalifa, W.; Jezzine, K.; Hello, G.; Grondel, S.

    2012-03-01

    Acoustic emission (AE) is a non-destructive testing method used in various industries (aerospace, petrochemical and pressure-vessel industries in general, power generation, civil engineering, mechanical engineering, etc...) for the examination of large structures subjected to various stresses (e.g. mechanical loading).The energy released by a defect under stress (the AE phenomenon) can propagate as guided waves in thin structures or as surface Rayleigh waves in thick ones. Sensors (possibly permanently) are positioned at various locations on the structure under examination and are assumed to be sensitive to these waves. Then, post-processing tools typically based on signal processing and triangulation algorithms can be used to inverse these data, allowing one to estimate the position of the defect from which emanates the waves measured. The French Atomic Energy Commission is engaged in the development of tools for simulating AE examinations. These tools are based on specific models for the AE sources, for the propagation of guided or Rayleigh waves and for the behaviour of AE sensors. Here, the coupling of a fracture mechanics based model for AE source and surface/guided wave propagation models is achieved through an integral formulation relying on the elastodynamic reciprocity principle. As a first approximation, a simple piston-like model is used to predict the sensitivity of AE sensors. Predictions computed by our simulation tool are compared to results from the literature for validation purpose.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  10. Implementing wavelet packet transform for valve failure detection using vibration and acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Sim, H. Y.; Ramli, R.; Abdullah, M. A. K.

    2012-05-01

    The efficiency of reciprocating compressors relies heavily on the health condition of its moving components, most importantly its valves. Previous studies showed good correlation between the dynamic response and the physical condition of the valves. These can be achieved by employing vibration technique which is capable of monitoring the response of the valve, and acoustic emission technique which is capable of detecting the valves' material deformation. However, the relationship/comparison between the two techniques is rarely investigated. In this paper, the two techniques were examined using time-frequency analysis. Wavelet packet transform (WPT) was chosen as the multi-resolution analysis technique over continuous wavelet transform (CWT), and discrete wavelet transform (DWT). This is because WPT could overcome the high computational time and high redundancy problem in CWT and could provide detailed analysis of the high frequency components compared to DWT. The features of both signals can be extracted by evaluating the normalised WPT coefficients for different time window under different valve conditions. By comparing the normalised coefficients over a certain time frame and frequency range, the feature vectors revealing the condition of valves can be constructed. One way analysis of variance was employed on these feature vectors to test the significance of data under different valve conditions. It is believed that AE signals can give a better representation of the valve condition as it can detect both the fluid motion and material deformation of valves as compared to the vibration signals.

  11. The design and calibration of particular geometry piezoelectric acoustic emission transducer for leak detection and localization

    NASA Astrophysics Data System (ADS)

    Yalcinkaya, Hazim; Ozevin, Didem

    2013-09-01

    Pipeline leak detection using an acoustic emission (AE) method requires highly sensitive transducers responding to less attenuative and dispersive wave motion in order to place the discrete transducer spacing in an acceptable approach. In this paper, a new piezoelectric transducer geometry made of PZT-5A is introduced to increase the transducer sensitivity to the tangential direction. The finite element analysis of the transducer geometry is modeled in the frequency domain to identify the resonant frequency, targeting 60 kHz, and the loss factor. The numerical results are compared with the electromechanical characterization tests. The transducer response to wave motion generated in different directions is studied using a multiphysics model that couples mechanical and electrical responses of structural and piezoelectric properties. The directional dependence and the sensitivity of the transducer response are identified using the laser-induced load function. The transducer response is compared with a conventional thickness mode AE transducer under simulations and leak localization in a laboratory scale steel pipe.

  12. Distortion product otoacoustic emission suppression tuning and acoustic admittance in human infants: Birth through 6 months

    PubMed Central

    Abdala, Carolina; Keefe, Douglas H.; Oba, Sandra I.

    2009-01-01

    Previous work has reported non-adultlike distortion product otoacoustic emission (DPOAE) suppression in human newborns at f2 =6000 Hz, indicating an immaturity in peripheral auditory function. In this study, DPOAE suppression tuning curves (STCs) were recorded as a measure of cochlear function and acoustic admittance/reflectance (YR) in the ear canal recorded as a measure of middle-ear function, in the same 20 infants at birth and through 6 months of age. DPOAE STCs changed little from birth through 6 months, showing excessively narrow and sharp tuning throughout the test period. In contrast, several middle-ear indices at corresponding frequencies shifted systematically with increasing age, although they also remained non-adultlike at 6 months. Linear correlations were conducted between YR and DPOAE suppression features. Only two correlations out of 76 were significant, and all but three YR variables accounted for <10% of the variance in DPOAE suppression tuning. The strongest correlation was noted between admittance phase at 5700 Hz and STC tip-to-tail (R=0.49). The association between middle-ear variables and DPOAE suppression may be stronger during other developmental time periods. Study of older infants and children is needed to fully define postnatal immaturity of human peripheral auditory function. PMID:17552713

  13. Acoustic emission source location on large plate-like structures using a local triangular sensor array

    NASA Astrophysics Data System (ADS)

    Aljets, Dirk; Chong, Alex; Wilcox, Steve; Holford, Karen

    2012-07-01

    A new acoustic emission (AE) source location method was developed for large plate-like structures, which evaluates the location of the source using a combined time of flight and modal source location algorithm. Three sensors are installed in a triangular array with a sensor to sensor distance of just a few centimeters. The direction from the sensor array to the AE source can be established by analysing the arrival times of the A0 component of the signal to the three sensors whilst the distance can be evaluated using the separation of S0 and A0 mode at each sensor respectively. The close positioning of the sensors allows the array to be installed in a single housing. This simplifies mounting, wiring and calibration procedures for non-destructive testing (NDT) and structural health monitoring (SHM) applications. Furthermore, this array could reduce the number of sensors needed to monitor large structures compared to other methods. An automatic wave mode identification method is also presented.

  14. Nonlinear Kalman Filtering for acoustic emission source localization in anisotropic panels.

    PubMed

    Dehghan Niri, E; Farhidzadeh, A; Salamone, S

    2014-02-01

    Nonlinear Kalman Filtering is an established field in applied probability and control systems, which plays an important role in many practical applications from target tracking to weather and climate prediction. However, its application for acoustic emission (AE) source localization has been very limited. In this paper, two well-known nonlinear Kalman Filtering algorithms are presented to estimate the location of AE sources in anisotropic panels: the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). These algorithms are applied to two cases: velocity profile known (CASE I) and velocity profile unknown (CASE II). The algorithms are compared with a more traditional nonlinear least squares method. Experimental tests are carried out on a carbon-fiber reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers to validate the proposed approaches. AE sources are simulated using an instrumented miniature impulse hammer. In order to evaluate the performance of the algorithms, two metrics are used: (1) accuracy of the AE source localization and (2) computational cost. Furthermore, it is shown that both EKF and UKF can provide a confidence interval of the estimated AE source location and can account for uncertainty in time of flight measurements. PMID:23972569

  15. Acoustic emission studies for leather using dual sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Since leather is sold by the square foot, destructive tests lessen the square footage of the material and infringe on the leather manufacturer’s total profit. Therefore there is a need for developing an instrument to perform nondestructive testing of the physical properties of leather. In this inv...

  16. Measurement resolution of noise directivity patterns from acoustic flight tests

    NASA Technical Reports Server (NTRS)

    Conner, David A.

    1989-01-01

    The measurement resolution of noise directivity patterns from acoustic flight tests was investigated. Directivity angle resolution is affected by the data reduction parameters, the aircraft velocity and flyover altitude, and by deviations of the aircraft from the desired flight path. Equations are developed which determine bounds for the lateral and longitudinal directivity angle resolution as a function of the nominal directivity angle. The equations are applied to a flight test data base and the effects of several flight conditions and data reduction parameters on the directivity angle resolution are presented. The maximum directivity angle resolution typically occurs when the aircraft is at or near the overhead position. In general, directivity angle resolution improves with decreasing velocity, increasing altitude, increasing sampling rate, decreasing block size, and decreasing block averages. Deviations from the desired ideal flight path will increase the resolution. For the flight experiment considered in this study, an average of two flyovers were required at each test condition to obtain an acceptable flight path. The ability of the pilot to maintain the flight track improved with decreasing altitude, decreasing velocity, and practice. Due to the prevailing wind conditions, yaw angles of as much as 20 deg were required to maintain the desired flight path.

  17. Numerical simulation of the tip aerodynamics and acoustics test

    NASA Astrophysics Data System (ADS)

    Tejero E, F.; Doerffer, P.; Szulc, O.; Cross, J. L.

    2016-04-01

    The application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, our invention of Rod Vortex Generators (RVGs) has been analyzed for helicopter rotor blades in hover with success. As a step forward, the study has been extended to forward flight conditions. For this reason, a validation of the numerical modelling for a reference helicopter rotor (without flow control) is needed. The article presents a study of the flow-field of the AH-1G helicopter rotor in low-, medium- and high-speed forward flight. The CFD code FLOWer from DLR has proven to be a suitable tool for the aerodynamic analysis of the two-bladed rotor without any artificial wake modelling. It solves the URANS equations with LEA (Linear Explicit Algebraic stress) k-ω model using the chimera overlapping grids technique. Validation of the numerical model uses comparison with the detailed flight test data gathered by Cross J. L. and Watts M. E. during the Tip Aerodynamics and Acoustics Test (TAAT) conducted at NASA in 1981. Satisfactory agreements for all speed regimes and a presence of significant flow separation in high-speed forward flight suggest a possible benefit from the future implementation of RVGs. The numerical results based on the URANS approach are presented not only for a popular, low-speed case commonly used in rotorcraft community for CFD codes validation but preferably for medium- and high-speed test conditions that have not been published to date.

  18. Results of acoustic tests of a Prop-Fan model

    NASA Astrophysics Data System (ADS)

    Metzger, F. B.; Brown, P. C.

    1987-06-01

    Results of acoustic tests in a low speed open jet anechoic wind tunnel are presented for a counter rotation Prop-Fan model. The model tested had 5 front and 5 rear rotor blades with swept planform. Noise spectra are presented showing the influence of operating and configuration variables such as: (1) power absorption, (2) tip speed, (3) rotor-rotor spacing, (4) power split between the front and rear blade rows, (5) variation of the RPM ratio between front and rear blade rows, (6) tractor versus pusher (pylon effects), and (7) angle of attack. In addition to model scale results, calculated levels derived from test are presented showing the influence of the above variables on Effective Perceived Noise Level of a 13.1 ft diameter Prop-Fan at a flyover distance of 1500 ft. It was found that the strongest effects are caused by tip speed and power absorption. A significant finding was that there is an optimum operating tip speed for minimum noise for a given power absorption. Effects of other parametric variations are generally small but measurable. In order to minimize noise to meet airplane certification limits, operation at moderate tip speeds and power absorption is shown to be desirable. Accuracy of predicted Effective Perceived Noise Level is shown to be good with the best accuracy in the 590 to 670 ft/sec tip speed range.

  19. Results of acoustic tests of a Prop-Fan model

    NASA Technical Reports Server (NTRS)

    Metzger, F.B.; Brown, P. C.

    1987-01-01

    Results of acoustic tests in a low speed open jet anechoic wind tunnel are presented for a counter rotation Prop-Fan model. The model tested had 5 front and 5 rear rotor blades with swept planform. Noise spectra are presented showing the influence of operating and configuration variables such as: (1) power absorption, (2) tip speed, (3) rotor-rotor spacing, (4) power split between the front and rear blade rows, (5) variation of the RPM ratio between front and rear blade rows, (6) tractor versus pusher (pylon effects), and (7) angle of attack. In addition to model scale results, calculated levels derived from test are presented showing the influence of the above variables on Effective Perceived Noise Level of a 13.1 ft diameter Prop-Fan at a flyover distance of 1500 ft. It was found that the strongest effects are caused by tip speed and power absorption. A significant finding was that there is an optimum operating tip speed for minimum noise for a given power absorption. Effects of other parametric variations are generally small but measurable. In order to minimize noise to meet airplane certification limits, operation at moderate tip speeds and power absorption is shown to be desirable. Accuracy of predicted Effective Perceived Noise Level is shown to be good with the best accuracy in the 590 to 670 ft/sec tip speed range.

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  1. Passive Acoustic Tomography Tested for Measuring Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Kleppe, John

    2004-01-01

    The requirements of higher performance, better fuel economy, and lower emissions place an increasing premium on knowing the internal operating parameters of jet engines. One of the most important is the gas temperature in the post combustor section of the engine. Typically the gas temperature is measured with a thermocouple probe or by some optical technique such as Rayleigh scattering. Probes, while providing valuable information, have several limitations. The probe signal must be corrected for radiation and conduction losses, probes provide only a point measurement, and probes must be constructed of materials whose melting points are lower than the temperature of the environment into which they are inserted. Some of the disadvantages of probes are overcome by various optical techniques. Nothing needs to be inserted into the flow, and the temperature can be directly related to the signal by known physical laws. However, optical techniques require optical access (i.e., a window) and a light source (such as a laser), and they are very sensitive to the presence of particles in the flow. To overcome these problems, researchers from the NASA Glenn Research Center and The University of Nevada are developing a technique that uses sound instead of light to measure gas temperature. Like optical techniques, it is nonintrusive--no probe need be exposed to the combustion environment--and the temperature is directly related to a measured quantity--the speed of sound, which is proportional to the square root of the absolute temperature. The temperature profile inside the engine is constructed from the differences in arrival time between correlated signals from an array of microphones placed around the circumference of the engine. In much the same way as a complete picture of the inside of your body can be constructed from an array of x-ray photographs taken at different angles, the temperature profile in the engine is constructed from the angular array of microphones. It is

  2. Acoustic Emission Source Location in Unidirectional Carbon-Fibre-Reinforced Plastic Plates Using Virtually Trained Artificial Neural Networks

    SciTech Connect

    Caprino, G.; Lopresto, V.; Leone, C.; Papa, I.

    2010-06-02

    Acoustic emission source location in a unidirectional carbon-fibre-reinforced plastic plate was attempted employing Artificial Neural Network (ANN) technology. The acoustic emission events were produced by a lead break, and the response wave received by piezoelectric sensors, type VS150-M resonant at 150 kHz. The waves were detected by a Vallen AMSY4 eight-channel instrumentation. The time of arrival, determined through the conventional threshold crossing technique, was used to measure the dependence of wave velocity on fibre orientation. A simple empirical formula, relying on classical lamination and suggested by wave propagation theory, was able to accurately model the experimental trend. Based on the formula, virtual training and testing data sets were generated for the case of a plate monitored by three transducers, and adopted to select two potentially effective ANN architectures. For final validation, experimental tests were carried out, positioning the source at predetermined points evenly distributed within the plate area. A very satisfactory correlation was found between the actual source locations and the ANN predictions.

  3. Acoustic Emission and Guided Wave Monitoring of Fatigue Crack Growth on a Full Pipe Specimen

    SciTech Connect

    Meyer, Ryan M.; Cumblidge, Stephen E.; Ramuhalli, Pradeep; Watson, Bruce E.; Doctor, Steven R.; Bond, Leonard J.

    2011-05-06

    Continuous on-line monitoring of active and passive systems, structures and components in nuclear power plants will be critical to extending the lifetimes of nuclear power plants in the US beyond 60 years. Acoustic emission and guided ultrasonic waves are two tools for continuously monitoring passive systems, structures and components within nuclear power plants and are the focus of this study. These tools are used to monitor fatigue damage induced in a SA 312 TP304 stainless steel pipe specimen. The results of acoustic emission monitoring indicate that crack propagation signals were not directly detected. However, acoustic emission monitoring exposed crack formation prior to visual confirmation through the detection of signals caused by crack closure friction. The results of guided ultrasonic wave monitoring indicate that this technology is sensitive to the presence and size of cracks. The sensitivity and complexity of GUW signals is observed to vary with respect to signal frequency and path traveled by the guided ultrasonic wave relative to the crack orientation.

  4. Online acoustic emission monitoring of combustion turbines for compressor stator vane crack detection

    NASA Astrophysics Data System (ADS)

    Momeni, Sepandarmaz; Koduru, Jaya P.; Gonzalez, Miguel; Zarate, Boris; Godinez, Valery

    2013-03-01

    Combustion turbine components operate under extreme environmental conditions and are susceptible to failure. Turbine blades are the most susceptible components and need to be regularly inspected to assure their integrity. Undetected cracks on these blades may grow quickly due to the high fatigue loading to which they are subjected and eventually fail causing extensive damage to the turbine. Cracks in turbine blades can originate from manufacturing errors, impact damages or the due to corrosion from the aggressive environment in which they operate. The component most susceptible to failure in a combustion turbine is the mid-compressor blades. In this region, the blades experience the highest gradients in temperature and pressure. Cracks in the rotator blades can be detected by vibration monitoring; while, the stator vanes or blades cracking can only be monitored by Acoustic Emission (AE) method. The stator vanes are in contact with the external casing of the turbine and therefore, any acoustic emission activity from the blades can be captured non-intrusively by placing sensors on the turbine casing. The acoustic emission activity from cracks that are under fatigue loading is significantly higher than the background noise and hence can be captured and located accurately by a group of AE sensors. Using a total of twelve AE sensors per turbine, the crack generation and propagation in the stator vanes of the mid-compressor section is monitored continuously. The cracks appearing in the stator vanes is clearly identified and located by the AE sensors.

  5. MEASUREMENTS OF ABSORPTION, EMISSIVITY REDUCTION, AND LOCAL SUPPRESSION OF SOLAR ACOUSTIC WAVES IN SUNSPOTS

    SciTech Connect

    Chou, D.-Y.; Liang, Z.-C.; Yang, M.-H.; Zhao Hui; Sun, M.-T.

    2009-05-01

    The power of solar acoustic waves in magnetic regions is lower relative to the quiet Sun. Absorption, emissivity reduction, and local suppression of acoustic waves contribute to the observed power reduction in magnetic regions. We propose a model for the energy budget of acoustic waves propagating through a sunspot in terms of the coefficients of absorption, emissivity reduction, and local suppression of the sunspot. Using the property that the waves emitted along the wave path between two points have no correlation with the signal at the starting point, we can separate the effects of these three mechanisms. Applying this method to helioseismic data filtered with direction and phase-velocity filters, we measure the fraction of the contribution of each mechanism to the power deficit in the umbra of the leading sunspot of NOAA 9057. The contribution from absorption is 23.3 {+-} 1.3%, emissivity reduction 8.2 {+-} 1.4%, and local suppression 68.5 {+-} 1.5%, for a wave packet corresponding to a phase velocity of 6.98 x 10{sup -5} rad s{sup -1}.

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

    PubMed

    Kurz, Jochen H

    2015-12-01

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

  7. [study of acoustic trauma in hunters using otoacoustic emission recording].

    PubMed

    Santaolalla Montoya, F; Martínez Ibargüen, A; Sánchez del Rey, A

    1998-03-01

    Transitory otoacoustic emissions (TOAE) were analyzed in 48 ears of male hunters (age range: 30-45 years: mean age: 37 years) and in a population with normal hearing. All the ears had TOAE. The incidence of TOAE for the 1, 2, 3, 4, 5 and 6 KHz frequential bands was significantly lower in hunters than in the normal subjects (p < 0.001). The mean amplitude of TOAE was significantly lower in hunters (9.2 dB SPL) than in the control group (16 dB SPL; p < 0.001). The amplitude of the TOAE for the frequencies 1, 2, 3, 4, 5 and 6 KHz was significantly lower in hunters than in controls (p < 0.001). PMID:9650309

  8. Differential responses to acoustic damage and furosemide in auditory brainstem and otoacoustic emission measures

    NASA Astrophysics Data System (ADS)

    Mills, David M.

    2003-02-01

    Characteristics of distortion product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs) were measured in Mongolian gerbil before and after the introduction of two different auditory dysfunctions: (1) acoustic damage with a high-intensity tone, or (2) furosemide intoxication. The goal was to find emission parameters and measures that best differentiated between the two dysfunctions, e.g., at a given ABR threshold elevation. Emission input-output or ``growth'' functions were used (frequencies f1 and f2, f2/f1=1.21) with equal levels, L1=L2, and unequal levels, with L1=L2+20 dB. The best parametric choice was found to be unequal stimulus levels, and the best measure was found to be the change in the emission threshold level, Δx. The emission threshold was defined as the stimulus level required to reach a criterion emission amplitude, in this case -10 dB SPL. (The next best measure was the change in emission amplitude at high stimulus levels, specifically that measured at L1×L2=90×70 dB SPL.) For an ABR threshold shift of 20 dB or more, there was essentially no overlap in the emission threshold measures for the two conditions, sound damage or furosemide. The dividing line between the two distributions increased slowly with the change in ABR threshold, ΔABR, and was given by Δxt=0.6 ΔABR+8 dB. For a given ΔABR, if the shift in emission threshold was more than the calculated dividing line value, Δxt, the auditory dysfunction was due to acoustic damage, if less, it was due to furosemide.

  9. Feasibility study of acoustic emission monitoring of pinch welding tritium reservoir fill stems at the Savannah River Site

    SciTech Connect

    Clark, E.A.

    1990-01-01

    A study was conducted to determine whether acoustic emission monitoring would be feasible in monitoring the solid-state resistance pinch weld used to seal tritium reservoirs at the Savannah River Site. Experiments were performed using a commercially available acoustic emission detection system, with a transducer mounted on a flat milled onto one of the pinch weld electrodes. Welds were made using a wide range of weld power, from very cold, with no metallurgical bond, to hot, with local fusion and excessive material injection into the tube bore. The tubes were drawn type 316L stainless steel. The welds were confined (anvils prevented material flow outward from the sides of the tube not being forced inward by the electrodes) and all were made using the same electrode force. The total number of ringdown counts for each weld was more correlated with weld power and bond length than total energy counts or total number of hits. The onset of large acoustic emission at higher weld power coincides with the injection of material into the tube bore, termed extrusion if arising from a solid state weld or spitting if arising from a weld with local fusion. Since large extrusions and spits, identified by radiography, cause rejection of production welds, a useful function of acoustic emission monitoring of pinch welding might be to detect the onset of extrusion or spitting. The low level of acoustic emission at production weld power levels (and below), the variability of acoustic emission at power levels causing extrusion and spitting, and the inability of acoustic emission to distinguish welds made with oxidized stems indicates that acoustic emission monitoring would not be a useful nondestructive evaluation of reservoir pinch welding at the Savannah River Site. 3 refs., 3 figs.

  10. Acoustic and microwave tests in a cylindrical cavity for acoustic gas thermometry at high temperature.

    PubMed

    Zhang, K; Feng, X J; Gillis, K; Moldover, M; Zhang, J T; Lin, H; Qu, J F; Duan, Y N

    2016-03-28

    Relative primary acoustic gas thermometry (AGT) determines the ratios of thermodynamic temperatures from measured ratios of acoustic and microwave resonance frequencies in a gas-filled metal cavity on isotherms of interest. When measured in a cavity with known dimensions, the frequencies of acoustic resonances in a gas determine the speed of sound, which is a known function of the thermodynamic temperature T. Changes in the dimensions of the cavity are measured using the frequencies of the cavity's microwave resonances. We explored techniques and materials for AGT at high temperatures using a cylindrical cavity with remote acoustic transducers. We used gas-filled ducts as acoustic waveguides to transmit sound between the cavity at high temperatures and the acoustic transducers at room temperature. We measured non-degenerate acoustic modes in a cylindrical cavity in the range 295 Kacoustic frequencies increased from 2×10(-6) at 295 K to 5×10(-6) at 797 K. In addition, we measured the frequencies of several transverse magnetic (TM) microwave resonances up to 1000 K in order to track changes in the cavity's length L and radius R. The fractional standard deviation of the values of L deduced from three TM modes increased from 3×10(-6) for T<600 K to 57 × 10(-6) at 1000 K. We observed similar inconsistencies in a previous study. PMID:26903106

  11. Application of fiber grating-based acoustic sensor in progressive failure testing of e-glass/vinylester curve composites

    NASA Astrophysics Data System (ADS)

    Azmi, Asrul Izam; Raju, Raju; Peng, Gang-Ding

    2012-02-01

    This paper reports an application of phase shifted fiber Bragg grating (PS-FBG) intensity-type acoustic sensor in a continuous and in-situ failure testing of an E-glass/vinylester top hat stiffener (THS). The narrow transmission channel of the PS-FBG is highly sensitive to small perturbation, hence suitable to be used in an effective acoustic emission (AE) assessment technique. The progressive failure of THS was tested under transverse loading to experimentally simulate the actual loading in practice. Our experimental tests have demonstrated, in good agreement with the commercial piezoelectric sensors, that the important failures information of the THS was successfully recorded by the simple intensity-type PS-FBG sensor.

  12. Acoustic Quality of the 40- by 80- Foot Wind Tunnel Test Section After Installation of a Deep Acoustic Lining

    NASA Technical Reports Server (NTRS)

    Soderman, Paul T.; Jaeger, Stephen M.; Hayes, Julie A.; Allen, Christopher S.

    2002-01-01

    A recessed, 42-inch deep acoustic lining has been designed and installed in the 40- by 80- Foot Wind Tunnel (40x80) test section to greatly improve the acoustic quality of the facility. This report describes the test section acoustic performance as determined by a detailed static calibration-all data were acquired without wind. Global measurements of sound decay from steady noise sources showed that the facility is suitable for acoustic studies of jet noise or similar randomly generated sound. The wall sound absorption, size of the facility, and averaging effects of wide band random noise all tend to minimize interference effects from wall reflections. The decay of white noise with distance was close to free field above 250 Hz. However, tonal sound data from propellers and fans, for example, will have an error band to be described that is caused by the sensitivity of tones to even weak interference. That error band could be minimized by use of directional instruments such as phased microphone arrays. Above 10 kHz, air absorption began to dominate the sound field in the large test section, reflections became weaker, and the test section tended toward an anechoic environment as frequency increased.

  13. A comparative evaluation of piezoelectric sensors for acoustic emission-based impact location estimation and damage classification in composite structures

    NASA Astrophysics Data System (ADS)

    Uprety, Bibhisha; Kim, Sungwon; Mathews, V. John; Adams, Daniel O.

    2015-03-01

    Acoustic Emission (AE) based Structural Health Monitoring (SHM) is of great interest for detecting impact damage in composite structures. Within the aerospace industry the need to detect and locate these events, even when no visible damage is present, is important both from the maintenance and design perspectives. In this investigation, four commercially available piezoelectric sensors were evaluated for usage in an AE-based SHM system. Of particular interest was comparing the acoustic response of the candidate piezoelectric sensors for impact location estimations as well as damage classification resulting from the impact in fiber-reinforced composite structures. Sensor assessment was performed based on response signal characterization and performance for active testing at 300 kHz and steel-ball drop testing using both aluminum and carbon/epoxy composite plates. Wave mode velocities calculated from the measured arrival times were found to be in good agreement with predictions obtained using both the Disperse code and finite element analysis. Differences in the relative strength of the received wave modes, the overall signal strengths and signal-to-noise ratios were observed through the use of both active testing as well as passive steel-ball drop testing. Further comparative is focusing on assessing AE sensor performance for use in impact location estimation algorithms as well as detecting and classifying damage produced in composite structures due to impact events.

  14. An Ex Vivo Study of the Correlation between Acoustic Emission and Microvascular Damage

    PubMed Central

    Samuel, Stanley; Cooper, Michol A.; Bull, Joseph L.; Fowlkes, J. Brian; Miller, Douglas L.

    2009-01-01

    The objective of this study was to conduct an ex vivo examination of correlation between acoustic emission and tissue damage. Intravital microscopy was employed in conjunction with ultrasound exposure in cremaster muscle of male Wistar rats. Definity® microbubbles were administered intravenously through the tail vein (80 μL.kg-1.min-1infusion rate) with the aid of a syringe pump. For the pulse repetition frequency (PRF) study, exposures were performed at four locations of the cremaster at a PRF of 1000, 500, 100 and 10 Hz (one location per PRF per rat). The 100-pulse exposures were implemented at a peak rarefactional pressure (Pr) of 2 MPa, frequency of 2.25 MHz with 46 cycle pulses. For the pressure amplitude threshold study, 100-pulse exposures (46 cycle pulses) were conducted at various peak rarefactional pressures from 0.5 MPa to 2 MPa at a frequency of 2.25 MHz and PRF of 100 Hz. Photomicrographs were captured before and 2-minutes post exposure. On a pulse-to-pulse basis, the 10 Hz acoustic emission was considerably higher and more sustained than those at other PRFs (1000, 500, and 100 Hz) (p < 0.05). Damage, measured as area of extravasation of red blood cells (RBC's), was also significantly higher at 10 Hz PRF than at 1000, 500, and 100 Hz (p < 0.01). The correlation of acoustic emission to tissue damage showed a trend of increasing damage with increasing cumulative function of the relative integrated power spectrum (CRIPS; R2 = 0.75). No visible damage was present at Pr ≤ 0.85 MPa. Damage, however, was observed at Pr ≥ 1.0 MPa, and it increased with increasing acoustic pressure. PMID:19560856

  15. Low frequency acoustic emissions from large horizontal axis wind turbines

    NASA Technical Reports Server (NTRS)

    Hubbard, Harvey H.; Shepherd, Kevin P.

    1989-01-01

    Available test data and theoretical predictions of LF noise from large wind turbines of the type to be used for energy generation are briefly summarized. The main LF noise sources are identified as tower-wake/blade interactions and rotor-plane inflow gradients. Sound-pressure time histories, measured and calculated narrow-band and rotational noise spectra, and noise radiation patterns for the WTS-4 and WWG-0600 wind turbines are presented graphically.

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

    NASA Astrophysics Data System (ADS)

    Bulanov, Alexey V.; Nagorny, Ivan G.

    2015-10-01

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

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

    SciTech Connect

    Bulanov, Alexey V.; Nagorny, Ivan G.

    2015-10-28

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

  18. Payload bay atmospheric vent airflow testing at the Vibration and Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Johnston, James D., Jr.

    1988-01-01

    Several concerns related to venting the Space Shuttle Orbiter payload bay during launch led to laboratory experiments with a flight-type vent box installed in the wall of a subsonic wind tunnel. This report describes the test setups and procedures used to acquire data for characterization of airflow through the vent box and acoustic tones radiated from the vent-box cavity. A flexible boundary-layer spoiler which reduced the vent-tone amplitude is described.

  19. NASA LeRC's Acoustic Fill Effect Test Program and Results

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; Mcnelis, Mark E.; Manning, Jerome E.

    1994-01-01

    NASA Lewis Research Center, in conjunction with General Dynamics Space Systems Division, has performed a test program to investigate the acoustic fill effect for an unblanketed payload fairing for a variety of payload simulators. This paper will discuss this test program and fill factor test data, and make comparisons with theoretical predictions. This paper will also address the NASA acoustic fill effect standard which was verified from the test data analysis.

  20. Test of an Acoustic Mechanism for Atmospheric Heating in Dynamo-Deficient F Stars

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1996-01-01

    In a qualitative sense, the heating of chromospheres and coronae has long been ascribed to either acoustic or magnetic heating. However, quantitative discussions of the energy balance with detailed comparison to the fluxes of chromospheric emission lines have begun to appear only recently. The aim of this work is to observe F stars where magnetic effects might be expected to be rather small, thereby allowing us hopefully to access acoustically heated atmospheres.

  1. Acoustic emission source location in complex structures using full automatic delta T mapping technique

    NASA Astrophysics Data System (ADS)

    Al-Jumaili, Safaa Kh.; Pearson, Matthew R.; Holford, Karen M.; Eaton, Mark J.; Pullin, Rhys

    2016-05-01

    An easy to use, fast to apply, cost-effective, and very accurate non-destructive testing (NDT) technique for damage localisation in complex structures is key for the uptake of structural health monitoring systems (SHM). Acoustic emission (AE) is a viable technique that can be used for SHM and one of the most attractive features is the ability to locate AE sources. The time of arrival (TOA) technique is traditionally used to locate AE sources, and relies on the assumption of constant wave speed within the material and uninterrupted propagation path between the source and the sensor. In complex structural geometries and complex materials such as composites, this assumption is no longer valid. Delta T mapping was developed in Cardiff in order to overcome these limitations; this technique uses artificial sources on an area of interest to create training maps. These are used to locate subsequent AE sources. However operator expertise is required to select the best data from the training maps and to choose the correct parameter to locate the sources, which can be a time consuming process. This paper presents a new and improved fully automatic delta T mapping technique where a clustering algorithm is used to automatically identify and select the highly correlated events at each grid point whilst the "Minimum Difference" approach is used to determine the source location. This removes the requirement for operator expertise, saving time and preventing human errors. A thorough assessment is conducted to evaluate the performance and the robustness of the new technique. In the initial test, the results showed excellent reduction in running time as well as improved accuracy of locating AE sources, as a result of the automatic selection of the training data. Furthermore, because the process is performed automatically, this is now a very simple and reliable technique due to the prevention of the potential source of error related to manual manipulation.

  2. Monitoring Rock Failure Processes Using the Hilbert-Huang Transform of Acoustic Emission Signals

    NASA Astrophysics Data System (ADS)

    Zhang, Ji; Peng, Weihong; Liu, Fengyu; Zhang, Haixiang; Li, Zhijian

    2016-02-01

    Rock fracturing generates acoustic emission (AE) signals that have statistical parameters referred to as AE signal parameters (AESP). Identification of rock fracturing or the failure process stage using such data raises several challenges. This study proposes a Hilbert-Huang transform-based AE processing approach to capture the time-frequency characteristics of both AE signals and AESP during rock failure processes. The damage occurring in tested rock specimens can be illustrated through analysis using this method. In this study, the specimens were 25 × 60 × 150 mm3 in size and were compressed at a displacement rate of 0.05 mm/min until failure. The recorded data included force and displacement, AE signals, and AESP. The AESP in the last third of the strain range period and 14 typical moments of strong AE signals were selected for further investigation. These results show that AE signals and AESP can be jointly used for identification of deformation stages. The transition between linear and nonlinear deformation stages was found to last for a short period in this process. The instantaneous frequency of the AE effective energy rate increased linearly from 0.5 to 1.5 Hz. Attenuation of elastic waves spreading in rock samples developed with deformation, as illustrated in the Hilbert spectra of AE signals. This attenuation is frequency dependent. Furthermore, AE signals in the softening process showed a complex frequency distribution attributed to the mechanical properties of the tested specimen. The results indicate that rock failure is predictable. The novel technology applied in this study is feasible for analysis of the entire deformation process, including softening and failure processes.

  3. Titanium honeycomb acoustic lining structural and thermal test report. [for acoustic tailpipe for JT8D engine

    NASA Technical Reports Server (NTRS)

    Joynes, D.; Balut, J. P.

    1974-01-01

    The results are presented of static, fatigue and thermal testing of titanium honeycomb acoustic panels representing the acoustic tailpipe for the Pratt and Whitney Aircraft JT8D Refan engine which is being studied for use on the Boeing 727-200 airplane. Test specimens represented the engine and tailpipe flange joints, the rail to which the thrust reverser is attached and shear specimens of the tailpipe honeycomb. Specimens were made in four different batches with variations in configuration, materials and processes in each. Static strength of all test specimens exceeded the design ultimate load requirements. Fatigue test results confirmed that aluminum brazed titanium, as used in the Refan tailpipe design, meets the fatigue durability objectives. Quality of welding was found to be critical to life, with substandard welding failing prematurely, whereas welding within the process specification exceeded the panel skin life. Initial fatigue testing used short grip length bolts which failed prematurely. These were replaced with longer bolts and subsequent testing demonstrated the required life. Thermal tests indicate that perforated skin acoustic honeycomb has approximately twice the heat transfer of solid skin honeycomb.

  4. Acoustic emission and sorptive deformation induced in coals of various rank by the sorption-desorption of gas

    NASA Astrophysics Data System (ADS)

    Majewska, Zofia; Ziętek, Jerzy

    2007-09-01

    Simultaneous measurements of acoustic emission (AE) and expansion/contraction of coal samples subjected to gas sorption-desorption processes were conducted on high-and medium-rank coal. The aim of this study was to examine the influence of the coal rank and type of sorbate on measured AE and strain characteristics. The experimental equipment employed in this study consisted of a pressure vessel and associated pressurisation and monitoring units. The arrangement of pressure-vacuum valves permitted the coal sample to be pressurised and depressurised. Carbon-dioxide and methane were used as sorbats. Acoustic emission and strains were recorded continuously for a period of 50 hours during sorption and for at least 12 hours during the desorption process. Tests were conducted on cylindrical coal samples at 298 K. The experimental data were presented as plots of AE basic parameters versus time and in strain diagrams. These studies lead to the following conclusions: 1. There are significant differences in AE and strain characteristics for the two systems (coal-CO2 and coal-CH4); 2. There is a direct influence of rank and type of coal on its behaviour during the sorption-desorption of gas. An attempt has been made to interpret the results obtained on the grounds of the copolymer model of coal structure. More research is needed into this topic in order to get a quantitative description of the observed facts.

  5. Detecting the activation of a self-healing mechanism in concrete by acoustic emission and digital image correlation.

    PubMed

    Tsangouri, E; Aggelis, D G; Van Tittelboom, K; De Belie, N; Van Hemelrijck, D

    2013-01-01

    Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process. PMID:24381518

  6. Traceability of Acoustic Emission measurements for a proposed calibration method - Classification of characteristics and identification using signal analysis

    NASA Astrophysics Data System (ADS)

    Griffin, James

    2015-01-01

    When using Acoustic Emission (AE) technologies, tensile, compressive and shear stress/strain tests can provide a detector for material deformation and dislocations. In this paper improvements are made to standardise calibration techniques for AE against known metrics such as force. AE signatures were evaluated from various calibration energy sources based on the energy from the first harmonic (dominant energy band) [1,2]. The effects of AE against its calibration identity are investigated: where signals are correlated to the average energy and distance of the detected phenomena. In addition, extra tests are investigated in terms of the tensile tests and single grit tests characterising different materials. Necessary translations to the time-frequency domain were necessary when segregating salient features between different material properties. Continuing this work the obtained AE is summarised and evaluated by a Neural Network (NN) regression classification technique which identifies how far the malformation has progressed (in terms of energy/force) during material transformation. Both genetic-fuzzy clustering and tree rule based classifier techniques were used as the second and third classification techniques respectively to verify the NN output giving a weighted three classifier system. The work discussed in this paper looks at both distance and force relationships for various prolonged Acoustic Emission stresses. Later such analysis was realised with different classifier models and finally implemented into the Simulink simulations. Further investigations were made into classifier models for different material interactions in terms of force and distance which add further dimension to this work with different materials based simulation realisations. Within the statistical analysis section there are two varying prolonged stress tests which together offer the mechanical calibration system (automated solenoid and pencil break calibration system). Taking such a

  7. Oscillating bubble concentration and its size distribution using acoustic emission spectra.

    PubMed

    Avvaru, Balasubrahmanyam; Pandit, Aniruddha B

    2009-01-01

    New method has been proposed for the estimation of size and number density distribution of oscillating bubbles in a sonochemical reactor using acoustic emission spectra measurements. Bubble size distribution has been determined using Minnaert's equation [M. Minnaert, On musical air bubbles and sound of running water, Philanthr. Mag. 16 (1933) 235], i.e., size of oscillating bubble is inversely related to the frequency of its volume oscillations. Decomposition of the pressure signal measured by the hydrophone in frequency domain of FFT spectrum and then inverse FFT reconstruction of the signal at each frequency level has been carried out to get the information about each of the bubble/cavity oscillation event. The number mean radius of the bubble size is calculated to be in the range of 50-80 microm and it was not found to vary much with the spatial distribution of acoustic field strength of the ultrasound processor used in the work. However, the number density of the oscillating bubbles and the nature of the distribution were found to vary in different horizontal planes away from the driving transducer surface in the ultrasonic bath. A separate set of experiments on erosion assessment studies were carried out using a thin aluminium foil, revealing a phenomena of active region of oscillating bubbles at antinodal points of the stationary waves, identical to the information provided by the acoustic emission spectra at the same location in the ultrasonic bath. PMID:18752981

  8. Development of an Acoustic Impedance Tube Testbed for Material Sample Testing

    NASA Technical Reports Server (NTRS)

    Doty, Benjamin J.; Kolaini, Ali R.

    2012-01-01

    Acoustic impedance tube method: uses Traveling wave amplitudes are measured on either side of a sample in a tube. Many acoustic properties of the sample can be calculated. It is Simple and inexpensive to set up, ideal for high volume optimization tests

  9. Acoustic resonance in tube bundles -- Comparison of full scale and laboratory test results

    SciTech Connect

    Eisinger, F.L.

    1995-12-01

    Full scale operational data from steam generator tube bundles exposed to hot gases in crossflow are compared with small scale laboratory test results with cold air. Vibration thresholds based on input energy, acoustic particle velocity and effective damping are evaluated and compared. It is shown that these parameters play an important role in the development, or suppression of acoustic resonance.

  10. Validation and Simulation of ARES I Scale Model Acoustic Test -1- Pathfinder Development

    NASA Technical Reports Server (NTRS)

    Putnam, G. C.

    2011-01-01

    The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. To take advantage of this data, a digital representation of the ASMAT test setup has been constructed and test firings of the motor have been simulated using the Loci/CHEM computational fluid dynamics software. Within this first of a series of papers, results from ASMAT simulations with the rocket in a held down configuration and without water suppression have then been compared to acoustic data collected from similar live-fire tests to assess the accuracy of the simulations. Detailed evaluations of the mesh features, mesh length scales relative to acoustic signals, Courant-Friedrichs-Lewy numbers, and spatial residual sources have been performed to support this assessment. Results of acoustic comparisons have shown good correlation with the amplitude and temporal shape of pressure features and reasonable spectral accuracy up to approximately 1000 Hz. Major plume and acoustic features have been well captured including the plume shock structure, the igniter pulse transient, and the ignition overpressure. Finally, acoustic propagation patterns illustrated a previously unconsidered issue of tower placement inline with the high intensity overpressure propagation path.

  11. Novel Cell Design for Combined In Situ Acoustic Emission and X-ray Diffraction of Cycling Lithium Ion Batteries

    SciTech Connect

    Rhodes, Kevin J; Kirkham, Melanie J; Meisner, Roberta Ann; Parish, Chad M; Dudney, Nancy J; Daniel, Claus

    2011-01-01

    An in situ acoustic emission (AE) and X-ray diffraction (XRD) cell for use in the study of battery electrode materials has been devised and tested. This cell uses commercially available coin cell hardware retrofitted with a metalized polyethylene terephthalate (PET) disk which acts as both an X-ray window and a current collector. In this manner the use of beryllium and its associated cost and hazard is avoided. An AE sensor may be affixed to the cell face opposite the PET window in order to monitor degradation effects, such as particle fracture, during cell cycling. Silicon particles which were previously studied by the AE technique were tested in this cell as a model material. The performance of these cells compared well with unmodified coin cells while providing information about structural changes in the active material as the cell is repeatedly charged and discharged.

  12. Novel cell design for combined in situ acoustic emission and x-ray diffraction study during electrochemical cycling of batteries

    SciTech Connect

    Rhodes, Kevin; Meisner, Roberta; Daniel, Claus; Kirkham, Melanie; Parish, Chad M.; Dudney, Nancy

    2011-07-15

    An in situ acoustic emission (AE) and x-ray diffraction cell for use in the study of battery electrode materials has been designed and tested. This cell uses commercially available coin cell hardware retrofitted with a metalized polyethylene terephthalate (PET) disk, which acts as both an x-ray window and a current collector. In this manner, the use of beryllium and its associated cost and hazards is avoided. An AE sensor may be affixed to the cell face opposite the PET window in order to monitor degradation effects, such as particle fracture, during cell cycling. Silicon particles, which were previously studied by the AE technique, were tested in this cell as a model material. The performance of these cells compared well with unmodified coin cells, while providing information about structural changes in the active material as the cell is repeatedly charged and discharged.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  14. Acoustic emission detection of microcrack formation and development in cementitious wasteforms with immobilised Al.

    PubMed

    Spasova, L M; Ojovan, M I

    2006-12-01

    An acoustic emission (AE) technique was applied for early detection, characterisation and time progress description of cracking phenomenon caused by the corrosion of Al encapsulated in cement matrix. The study was conducted on an ordinary Portland cement (OPC) system encapsulating high purity Al bar. Acoustic signals were generated and released during immersing of the sample in deionised water. A computer controlled PCI-2 based AE system processed the signals detected by piezoelectric transducers. A subsequent comparative study of the AE data collected with those obtained from a reference OPC sample has been applied. Recorded AE activity confirmed that the process of initiation and development of Al corrosion causes significant mechanical stresses within the cement matrix. Our analysis demonstrated possibility to differentiate AE signals based on their characteristics, and potentially correlate detected AE with the fracture processes in the cement system encapsulating Al. PMID:16828968

  15. Remote Diagnosis of Dug-in Areas and Bottom Pipe by Main Acoustic Emission Method Using a Self-organizing Wireless Network

    NASA Astrophysics Data System (ADS)

    Kravtsova, Ye; Shram, V.; Lysyannikova, N.; Bezborodov, Yu; Selsky, A.; Lysyannikov, A.

    2016-06-01

    This paper discusses methods of nondestructive testing, the main method is method of acoustic flue gas emission. It was found that the use of this method in the diagnosis of bottom pipe and dug-in areas allows to reduce time, does not require surface dressing to a certain value, provides almost instant information about the defect at a great distance to the nearest gas-pumping station and is not inferior to the reliability of the control other existing methods.

  16. Preliminary Results of Field Emission Cathode Tests

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Kovaleski, Scott D.

    2001-01-01

    Preliminary screening tests of field emission cathodes such as chemical vapor deposited (CVD) diamond, textured pyrolytic graphite, and textured copper were conducted at background pressures typical of electric thruster test facilities to assess cathode performance and stability. Very low power electric thrusters which provide tens to hundreds micronewtons of thrust may need field emission neutralizers that have a capability of tens to hundreds of microamperes. From current voltage characteristics, it was found that the CVD diamond and textured metals cathodes clearly satisfied the Fowler-Nordheim emission relation. The CVD diamond and a textured copper cathode had average current densities of 270 and 380 mA/sq cm, respectively, at the beginning-of-life. After a few hours of operation the cathode emission currents degraded by 40 to 75% at background pressures in the 10(exp -5) Pa to 10(exp -4) Pa range. The textured pyrolytic graphite had a modest current density at beginning-of-life of 84 mA/sq cm, but this cathode was the most stable of all. Extended testing of the most promising cathodes is warranted to determine if current degradation is a burn-in effect or whether it is a long-term degradation process. Preliminary experiments with ferroelectric emission cathodes, which are ceramics with spontaneous electric polarization, were conducted. Peak current densities of 30 to 120 mA/sq cm were obtained for pulse durations of about 500 ns in the 10(exp -4) Pa pressure range.

  17. Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles

    NASA Astrophysics Data System (ADS)

    Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent

    2014-09-01

    Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en- route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0-200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.

  18. Wind Turbine Generator System Acoustic Noise Test Report for the ARE 442 Wind Turbine

    SciTech Connect

    Huskey, A.; van Dam, J.

    2010-11-01

    This test was conducted on the ARE 442 as part of the U.S. Department of Energy's (DOE's) Independent Testing project. This project was established to help reduce the barriers of wind energy expansion by providing independent testing results for small turbines. In total, five turbines are being tested at the National Wind Technology Center (NWTC) as a part of this project. Acoustic noise testing is one of up to five tests that may be performed on the turbines, including duration, safety and function, power performance, and power quality tests. The acoustic noise test was conducted to the IEC 61400-11 Edition 2.1.

  19. Evaluation of SHM System Produced by Additive Manufacturing via Acoustic Emission and Other NDT Methods

    PubMed Central

    Strantza, Maria; Aggelis, Dimitrios G.; de Baere, Dieter; Guillaume, Patrick; van Hemelrijck, Danny

    2015-01-01

    During the last decades, structural health monitoring (SHM) systems are used in order to detect damage in structures. We have developed a novel structural health monitoring approach, the so-called “effective structural health monitoring” (eSHM) system. The current SHM system is incorporated into a metallic structure by means of additive manufacturing (AM) and has the possibility to advance life safety and reduce direct operative costs. It operates based on a network of capillaries that are integrated into an AM structure. The internal pressure of the capillaries is continuously monitored by a pressure sensor. When a crack nucleates and reaches the capillary, the internal pressure changes signifying the existence of the flaw. The main objective of this paper is to evaluate the crack detection capacity of the eSHM system and crack location accuracy by means of various non-destructive testing (NDT) techniques. During this study, detailed acoustic emission (AE) analysis was applied in AM materials for the first time in order to investigate if phenomena like the Kaiser effect and waveform parameters used in conventional metals can offer valuable insight into the damage accumulation of the AM structure as well. Liquid penetrant inspection, eddy current and radiography were also used in order to confirm the fatigue damage and indicate the damage location on un-notched four-point bending AM metallic specimens with an integrated eSHM system. It is shown that the eSHM system in combination with NDT can provide correct information on the damage condition of additive manufactured metals. PMID:26506349

  20. Acoustic emission, microstructure, and damage model of dry and wet sandstone stressed to failure

    NASA Astrophysics Data System (ADS)

    Zang, Arno; Wagner, Christian F.; Dresen, Georg

    1996-08-01

    Twenty-three uniaxial compression tests were performed on dry and wet Flechtingen sandstone from Germany. Compressive strength of wet core is 60% of the strength of dry core. Before fracture, the transverse P wave speed drops by 13% and the pulse amplitude by 22% for wet and 37% for dry cores. Accumulated strain energy doubles for dry core. Acoustic emissions (AE) are detected with 10 sensors for 19 cores. AE activity starts at 84% of the fracture strength of wet cores (55 MPa) and at 91% of the strength of dry cores (87 MPa). The ratio of located to recorded AE is 0.37 for dry and 0.13 for fully wet cores. AE hypocenter patterns document the development of two opposite fracture cones. The negative slope of cumulative AE-amplitude frequency distribution drops by 50% before failure in dry cores. The slope of the wet core drops and recovers. Energy discrimination of AE detected by a broadband sensor resolves different stages of damage and captures the onset of the dilatant throughgoing macrofracture. Using the analogy to visible light microfracturing events are separated into high-energy short pulses (blue AE) and low-energy pulses with long duration times (red AE). Blue AE are explained by intragranular grain breakage, red AE by multiple stick slip on crack planes or grain boundaries. Deformed cores show highly fractured calcite cement and mostly intact quartz grains. The stochastic damage model for brittle composites developed highlights that microfracturing of the sandstone is controlled by the amount and distribution of the weak mineral (calcite).

  1. Wear detection by means of wavelet-based acoustic emission analysis

    NASA Astrophysics Data System (ADS)

    Baccar, D.; Söffker, D.

    2015-08-01

    Wear detection and monitoring during operation are complex and difficult tasks especially for materials under sliding conditions. Due to the permanent contact and repetitive motion, the material surface remains during tests non-accessible for optical inspection so that attrition of the contact partners cannot be easily detected. This paper introduces the relevant scientific components of reliable and efficient condition monitoring system for online detection and automated classification of wear phenomena by means of acoustic emission (AE) and advanced signal processing approaches. The related experiments were performed using a tribological system consisting of two martensitic plates, sliding against each other. High sensitive piezoelectric transducer was used to provide the continuous measurement of AE signals. The recorded AE signals were analyzed mainly by time-frequency analysis. A feature extraction module using a novel combination of Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) were used for the first time. A detailed correlation analysis between complex signal characteristics and the surface damage resulting from contact fatigue was investigated. Three wear process stages were detected and could be distinguished. To obtain quantitative and detailed information about different wear phases, the AE energy was calculated using STFT and decomposed into a suitable number of frequency levels. The individual energy distribution and the cumulative AE energy of each frequency components were analyzed using CWT. Results show that the behavior of individual frequency component changes when the wear state changes. Here, specific frequency ranges are attributed to the different wear states. The study reveals that the application of the STFT-/CWT-based AE analysis is an appropriate approach to distinguish and to interpret the different damage states occurred during sliding contact. Based on this results a new generation of condition monitoring

  2. Damage characterization on human femur bone by means of ultrasonics and acoustic emission

    NASA Astrophysics Data System (ADS)

    Strantza, M.; Polyzos, D.; Louis, O.; Boulpaep, F.; Van Hemelrijck, D.; Aggelis, D. G.

    2015-07-01

    Human bone tissue is characterized as a material with high brittleness. Due to this nature, visible signs of cracking are not easy to be detected before final failure. The main objective of this work is to investigate if the acoustic emission (AE) technique can offer valuable insight to the fracture process of human femur specimens as in other engineering materials characterization. This study describes the AE activity during fracture of whole femur bones under flexural load. Before fracture, broadband AE sensors were used in order to measure parameters like wave velocity dispersion and attenuation. Waveform parameters like the duration, rise time and average frequency, were also examined relatively to the propagation distance as a preparation for the AE monitoring during fracture. After the ultrasonic study, the samples were partly cast in concrete and fixed as cantilevers. A point load was applied on the femur head, which due to the test geometry resulted in a combination of two different patterns of fracture, bending and torsion. Two AE broadband sensors were placed in different points of the sample, one near the fixing end and the other near the femur head. Preliminary analysis shows that parameters like the number of acquired AE signals and their amplitude are well correlated with the load history. Furthermore, the parameters of rise time and frequency can differentiate the two fracture patterns. Additionally, AE allows the detection of the load at the onset of fracture from the micro-cracking events that occur at the early loading stages, allowing monitoring of the whole fracture process. Parameters that have been used extensively for monitoring and characterization of fracture modes of engineering materials seem to poses characterization power in the case of bone tissue monitoring as well.

  3. Evaluation of SHM system produced by additive manufacturing via acoustic emission and other NDT methods.

    PubMed

    Strantza, Maria; Aggelis, Dimitrios G; de Baere, Dieter; Guillaume, Patrick; van Hemelrijck, Danny

    2015-01-01

    During the last decades, structural health monitoring (SHM) systems are used in order to detect damage in structures. We have developed a novel structural health monitoring approach, the so-called "effective structural health monitoring" (eSHM) system. The current SHM system is incorporated into a metallic structure by means of additive manufacturing (AM) and has the possibility to advance life safety and reduce direct operative costs. It operates based on a network of capillaries that are integrated into an AM structure. The internal pressure of the capillaries is continuously monitored by a pressure sensor. When a crack nucleates and reaches the capillary, the internal pressure changes signifying the existence of the flaw. The main objective of this paper is to evaluate the crack detection capacity of the eSHM system and crack location accuracy by means of various non-destructive testing (NDT) techniques. During this study, detailed acoustic emission (AE) analysis was applied in AM materials for the first time in order to investigate if phenomena like the Kaiser effect and waveform parameters used in conventional metals can offer valuable insight into the damage accumulation of the AM structure as well. Liquid penetrant inspection, eddy current and radiography were also used in order to confirm the fatigue damage and indicate the damage location on un-notched four-point bending AM metallic specimens with an integrated eSHM system. It is shown that the eSHM system in combination with NDT can provide correct information on the damage condition of additive manufactured metals. PMID:26506349

  4. COKE QUENCH TOWER EMISSION TESTING PROGRAM

    EPA Science Inventory

    The report gives results of a field study to further define quench tower organic emissions, the character and magnitude of which are virtually unknown. (Limited testing in 1976 indicated that a large quantity of organic material was emitted from quench towers, but these data were...

  5. Acoustic emission detection in carbon composite materials using Fiber Bragg Grating optical sensors

    NASA Astrophysics Data System (ADS)

    Mabry, Nehemiah J.

    In light of ongoing efforts to reduce weight but maintain durability, designers have examined the use of carbon fiber reinforced polymer (CFRP) composite materials for a number of aerospace and civil structures. Along with this research has been the study of determining reliable sensing and monitoring capabilities to avoid catastrophic failure. Fiber Bragg Grating (FBG) sensors are known to carry several advantages in this area, one of which is their proven ability to detect acoustic emission (AE) Lamb waves in composite structures. AE is produced in these materials by failure mechanisms such as resin cracking, fiber debonding, fiber pullout and fiber breakage. In this study FBG sensors were attached to CFRP laminates to detect acoustic emission events. Also Felicity Ratio (FR) measurements were made as they accumulated damage. FR is obtained directly from the ratio of the stress level at the onset of significant emission versus the maximum prior stress at the same AE level. The main objective of this paper is to describe the results of acousto-optic experiments using FBG sensors and present it as a way of determining accumulated damage in a carbon composite structure.

  6. Stress Corrosion Cracking—Crevice Interaction in Austenitic Stainless Steels Characterized By Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Leinonen, H.; Schildt, T.; Hänninen, H.

    2011-02-01

    Stress corrosion cracking (SCC) susceptibility of austenitic EN1.4301 (AISI 304) and EN1.4404 (AISI 316L) stainless steels was studied using the constant load method and polymer (PTFE) crevice former in order to study the effects of crevice on SCC susceptibility. The uniaxial active loading tests were performed in 50 pct CaCl2 at 373 K (100 °C) and in 0.1 M NaCl at 353 K (80 °C) under open-circuit corrosion potential (OCP) and electrochemical polarization. Pitting, crevice, and SCC corrosion were characterized and identified by acoustic emission (AE) analysis using ∆ t filtering and the linear locationing technique. The correlation of AE parameters including amplitude, duration, rise time, counts, and energy were used to identify the different types of corrosion. The stages of crevice corrosion and SCC induced by constant active load/crevice former were monitored by AE. In the early phase of the tests, some low amplitude AE activity was detected. In the steady-state phase, the AE activity was low, and toward the end of the test, it increased with the increasing amplitude of the impulses. AE allowed a good correlation between AE signals and corrosion damage. Although crevice corrosion and SCC induced AE signals overlapped slightly, a good correlation between them and microscopical characterization and stress-strain data was found. Especially, the activity of AE signals increased in the early and final stages of the SCC experiment under constant active load conditions corresponding to the changes in the measured steady-state creep strain rate of the specimen. The results of the constant active load/crevice former test indicate that a crevice can initiate SCC even in the mild chloride solution at low temperatures. Based on the mechanistic model of SCC, the rate determining step in SCC is thought to be the generation of vacancies by selective dissolution, which is supported by the low activity phase of AE during the steady-state creep strain rate region.

  7. Laboratory test and acoustic analysis of cabin treatment for propfan test assessment aircraft

    NASA Technical Reports Server (NTRS)

    Kuntz, H. L.; Gatineau, R. J.

    1991-01-01

    An aircraft cabin acoustic enclosure, built in support of the Propfan Test Assessment (PTA) program, is described. Helmholtz resonators were attached to the cabin trim panels to increase the sidewall transmission loss (TL). Resonators (448) were located between the trim panels and fuselage shell. In addition, 152 resonators were placed between the enclosure and aircraft floors. The 600 resonators were each tuned to a 235 Hz resonance frequency. After flight testing on the PTA aircraft, the enclosure was tested in the Kelly Johnson R and D Center Acoustics Lab. Laboratory noise reduction (NR) test results are discussed. The enclosure was placed in a Gulfstream 2 fuselage section. Broadband (138 dB overall SPL) and tonal (149 dB overall SPL) excitations were used in the lab. Tonal excitation simulated the propfan flight test excitation. The fundamental tone was stepped in 2 Hz intervals from 225 through 245 Hz. The resonators increase the NR of the cabin walls around the resonance frequency of the resonator array. The effects of flanking, sidewall absorption, cabin adsorption, resonator loading of trim panels, and panel vibrations are presented. Increases in NR of up to 11 dB were measured.

  8. Mapping acoustic emissions from hydraulic fracture treatments using coherent array processing: Concept

    SciTech Connect

    Harris, D.B.; Sherwood, R.J.; Jarpe, S.P.; Harben, P.E.

    1991-09-01

    Hydraulic fracturing is a widely-used well completion technique for enhancing the recovery of gas and oil in low-permeability formations. Hydraulic fracturing consists of pumping fluids into a well under high pressure (1000--5000 psi) to wedge-open and extend a fracture into the producing formation. The fracture acts as a conduit for gas and oil to flow back to the well, significantly increasing communication with larger volumes of the producing formation. A considerable amount of research has been conducted on the use of acoustic (microseismic) emission to delineate fracture growth. The use of transient signals to map the location of discrete sites of emission along fractures has been the focus of most research on methods for delineating fractures. These methods depend upon timing the arrival of compressional (P) or shear (S) waves from discrete fracturing events at one or more clamped geophones in the treatment well or in adjacent monitoring wells. Using a propagation model, the arrival times are used to estimate the distance from each sensor to the fracturing event. Coherent processing methods appear to have sufficient resolution in the 75 to 200 Hz band to delineate the extent of fractures induced by hydraulic fracturing. The medium velocity structure must be known with a 10% accuracy or better and no major discontinuities should be undetected. For best results, the receiving array must be positioned directly opposite the perforations (same depths) at a horizontal range of 200 to 400 feet from the region to be imaged. Sources of acoustic emission may be detectable down to a single-sensor SNR of 0.25 or somewhat less. These conclusions are limited by the assumptions of this study: good coupling to the formation, acoustic propagation, and accurate knowledge of the velocity structure.

  9. Detection of acoustic emission from composite laminates using PVF2 transducers

    NASA Technical Reports Server (NTRS)

    Stiffler, R.; Henneke, E. G., II; Herakovich, C. T.

    1983-01-01

    Polyvinylidene fluoride (PVF2), a semicrystalline polymer exhibiting piezoelectricity, is presently used as a sensing transducer in acoustic emission (AE) monitoring of several different composite laminate materials in order to obtain both quasi-static and fatigue loading results. AE signals obtained from PVF2 transducers are compared with those obtained by standard AE sensors. It is noted that PVF2 transducers may, through the application of spectral signal analysis, be able to distinguish between two distinct failure modes which have been observed in two composite laminates of the same material, but employing different lamina stacking sequences.

  10. Acoustic emission: Standards and technology update. ASTM special technical publication 1353

    SciTech Connect

    Vahaviolos, S.J.

    1999-07-01

    The purpose of this symposium was to discuss the evolution of technology of acoustic emission (AE) over the years in instrumentation, applications, standards and codes and its overall worldwide acceptance. The papers in this conference are divided into the following sections: (1) AE Sources: Characterization; (2) Concrete Applications; (3) Integrity and Leak Detection/Location Methods; (4) AE Sensors, Standards, and Quantitative AE; (5) Diverse Industrial Applications; (6) AE Sources: Research Topics; (7) Transportation Applications, Standards, and Methodology; and (8) Compressed Gas Applications and Standards. Separate abstracts were prepared for some of the papers in this volume.

  11. Study of fracture mechanisms of short fiber reinforced AS composite by acoustic emission technique

    SciTech Connect

    Kida, Sotoaki; Suzuki, Megumu

    1995-11-01

    The fracture mechanisms of short fiber reinforced AS composites are studied by acoustic emission technique for examining the effects of fiber contents. The loads P{sub b} and P{sub c} which the damage mechanisms change are obtained at the inflection points of the total AE energy curve the energy gradient method. The damages are generated by fiber breaking at the load point of P{sub b} and P{sub c} in B material, and by the fiber breaking and the debonding between resin and fiber at the load points of P{sub b} and P{sub c} in C material.

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

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Wu, Chunxian

    2016-01-01

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

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

    PubMed

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

    2016-02-01

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

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

    SciTech Connect

    Li, Xibing; Dong, Longjun

    2014-02-15

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

  15. Acoustic Emission as a Tool for Exploring Deformation Mechanisms in Magnesium and Its Alloys In Situ

    NASA Astrophysics Data System (ADS)

    Vinogradov, Alexei; Máthis, Kristian

    2016-06-01

    Structural performance of magnesium alloys depends strongly on specific deformation mechanisms operating during mechanical loading. Therefore, in situ monitoring of the acting mechanisms is a key to performance tailoring. We review the capacity of the advanced acoustic emission (AE) technique to understand the interplay between two primary deformation mechanisms—dislocation slip and twinning—in real time scale. Details of relative contributions of dislocation slip and deformation twinning to the mechanical response of pure Mg and Mg-Al alloy are discussed in view of AE results obtained with the aid of recently proposed spectral and signal categorization algorithms in conjunction with with neutron diffraction data.

  16. Amplification and directional emission of surface acoustic waves by a two-dimensional electron gas

    SciTech Connect

    Shao, Lei; Pipe, Kevin P.

    2015-01-12

    Amplification of surface acoustic waves (SAWs) by electron drift in a two-dimensional electron gas (2DEG) is analyzed analytically and confirmed experimentally. Calculations suggest that peak power gain per SAW radian occurs at a more practical carrier density for a 2DEG than for a bulk material. It is also shown that SAW emission with tunable directionality can be achieved by modulating a 2DEG's carrier density (to effect SAW generation) in the presence of an applied DC field that amplifies SAWs propagating in a particular direction while attenuating those propagating in the opposite direction.

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

    NASA Astrophysics Data System (ADS)

    Weiß, M.; Kapfinger, S.; Reichert, T.; Finley, J. J.; Wixforth, A.; Kaniber, M.; Krenner, H. J.

    2016-07-01

    A coupled quantum dot-nanocavity system in the weak coupling regime of cavity-quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a fSAW ≃ 800 MHz surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function, g(2). All relevant frequencies of our experiment are faithfully identified in the Fourier transform of g(2), demonstrating high fidelity regulation of the stream of single photons emitted by the system.

  18. Integrated acoustic emission/vibration sensor for detecting damage in aircraft drive train components

    NASA Astrophysics Data System (ADS)

    Godínez-Azcuaga, Valery F.; Ozevin, Didem; Finlayson, Richard D.; Anastasopoulos, Athanasios; Tsimogiannis, Apostolos

    2007-04-01

    Diaphragm-type couplings are high misalignment torque and speed transfer components used in aircrafts. Crack development in such couplings, or in the drive train in general, can lead to component failure that can bring down an aircraft. Real time detection of crack formation and growth is important to prevent such catastrophic failures. However, there is no single Nondestructive Monitoring method available that is capable of assessing the early stages of crack growth in such components. While vibration based damage identification techniques are used, they cannot detect cracks until they reach a considerable size, which makes detection of the onset of cracking extremely difficult. Acoustic Emission (AE) can detect and monitor early stage crack growth, however excessive background noise can mask acoustic emissions produced by crack initiation. Fusion of the two mentioned techniques can increase the accuracy of measurement and minimize false alarms. However, a monitoring system combining both techniques could prove too large and heavy for the already restricted space available in aircrafts. In the present work, we will present a newly developed integrated Acoustic Emission/Vibration (AE/VIB) combined sensor which can operate in the temperature range of -55°F to 257°F and in high EMI environment. This robust AE/VIB sensor has a frequency range of 5 Hz-2 kHz for the vibration component and a range of 200-400 kHz for the acoustic emission component. The sensor weight is comparable to accelerometers currently used in flying aircraft. Traditional signal processing approaches are not effective due to high signal attenuation and strong background noise conditions, commonly found in aircraft drive train systems. As an alternative, we will introduce a new Supervised Pattern Recognition (SPR) methodology that allows for simultaneous processing of the signals detected by the AE/VIB sensor and their classification in near-real time, even in these adverse conditions. Finally, we

  19. A Correlated Study of the Response of a Satellite to Acoustic Radiation Using Statistical Energy Analysis and Acoustic Test Data

    SciTech Connect

    CAP,JEROME S.; TRACEY,BRIAN

    1999-11-15

    Aerospace payloads, such as satellites, are subjected to vibroacoustic excitation during launch. Sandia's MTI satellite has recently been certified to this environment using a combination of base input random vibration and reverberant acoustic noise. The initial choices for the acoustic and random vibration test specifications were obtained from the launch vehicle Interface Control Document (ICD). In order to tailor the random vibration levels for the laboratory certification testing, it was necessary to determine whether vibration energy was flowing across the launch vehicle interface from the satellite to the launch vehicle or the other direction. For frequencies below 120 Hz this issue was addressed using response limiting techniques based on results from the Coupled Loads Analysis (CLA). However, since the CLA Finite Element Analysis FEA model was only correlated for frequencies below 120 Hz, Statistical Energy Analysis (SEA) was considered to be a better choice for predicting the direction of the energy flow for frequencies above 120 Hz. The existing SEA model of the launch vehicle had been developed using the VibroAcoustic Payload Environment Prediction System (VAPEPS) computer code [1]. Therefore, the satellite would have to be modeled using VAPEPS as well. As is the case for any computational model, the confidence in its predictive capability increases if one can correlate a sample prediction against experimental data. Fortunately, Sandia had the ideal data set for correlating an SEA model of the MTI satellite--the measured response of a realistic assembly to a reverberant acoustic test that was performed during MTI's qualification test series. The first part of this paper will briefly describe the VAPEPS modeling effort and present the results of the correlation study for the VAPEPS model. The second part of this paper will present the results from a study that used a commercial SEA software package [2] to study the effects of in-plane modes and to

  20. NASA/GE quiet engine C acoustic test results

    NASA Technical Reports Server (NTRS)

    Kazin, S. B.; Pass, J. E.

    1974-01-01

    The acoustic investigation and evaluation of the C propulsion turbofan engine are discussed. The engine was built as a part of the Quiet Engine Program. The objectives of the program are as follows: (1) to determine the noise levels produced turbofan bypass engines, (2) to demonstrate the technology and innovations which will reduce the production and radiation of noise in turbofan engines, and (3) to acquire experimental acoustic and aerodynamic data for high bypass turbofan engines to provide a better understanding of noise production mechanisms. The goals of the program called for a turbofan engine 15 to 20 PNdB quieter than currently available engines in the same thrust class.