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Sample records for acoustic emissions monitoring

  1. 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.

  2. 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.

  3. Acoustic-emission monitoring of steam turbines

    NASA Astrophysics Data System (ADS)

    Graham, L. J.; Randall, R. L.; Hong, C.

    1982-04-01

    A method for the on-line detection of crack growth in steam turbine rotors based on acoustic emission (AE) monitoring is discussed. A systematic study involving a number of tasks was performed to evaluate the potential for the detection and correct identification of crack growth AE signals during various turbine operating conditions. These included acoustic wave propagation and attenuation measurements, background noise characterization, laboratory rotor material tests, monitoring equipment optimization, dynamic stress analysis of the rotor under transient operation and on-line source location and signal characterization. No crack growth was detected during the monitoring periods but there was sufficient information from the combined tasks to estimate the flaw growth detectability during different operating conditions if it occurs. The experience also suggests that AE monitoring can be useful for diagnosis of other turbine problems such as blade rubbing, out-of-balance condition, bearing deterioration, lubricating oil contamination and perhaps boiler exfoliation and blade erosion.

  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. Quantitative structural health monitoring using acoustic emission

    NASA Astrophysics Data System (ADS)

    Wilcox, Paul D.; Lee, Chee Kin; Scholey, Jonathan J.; Friswell, Michael I.; Wisnom, Michael R.; Drinkwater, Bruce W.

    2006-03-01

    Acoustic emission (AE) testing is potentially a highly suitable technique for structural health monitoring (SHM) applications due to its ability to achieve high sensitivity from a sparse array of sensors. For AE to be deployed as part of an SHM system it is essential that its capability is understood. This is the motivation for developing a forward model, referred to as QAE-Forward, of the complete AE process in real structures which is described in the first part of this paper. QAE-Forward is based around a modular and expandable architecture of frequency domain transfer functions to describe various aspects of the AE process, such as AE signal generation, wave propagation and signal detection. The intention is to build additional functionality into QAE-Forward as further data becomes available, whether this is through new analytic tools, numerical models or experimental measurements. QAE-Forward currently contains functions that implement (1) the excitation of multimodal guided waves by arbitrarily orientated point sources, (2) multi-modal wave propagation through generally anisotropic multi-layered media, and (3) the detection of waves by circular transducers of finite size. Results from the current implementation of QAE-Forward are compared to experimental data obtained from Hsu-Neilson tests on aluminum plate and good agreement is obtained. The paper then describes an experimental technique and a finite element modeling technique to obtain quantitative AE data from fatigue crack growth that will feed into QAE-Forward.

  6. Using acoustic emission signals for monitoring of production processes.

    PubMed

    Tönshoff, H K; Jung, M; Männel, S; Rietz, W

    2000-07-01

    The systems for in-process quality assurance offer the possibility of estimating the workpiece quality during machining. Especially for finishing processes like grinding or turning of hardened steels, it is important to control the process continuously in order to avoid rejects and refinishing. This paper describes the use of on-line monitoring systems with process-integrated measurement of acoustic emission to evaluate hard turning and grinding processes. The correlation between acoustic emission signals and subsurface integrity is determined to analyse the progression of the processes and the workpiece quality.

  7. Acoustic emission monitoring using a multimode optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Vandenplas, Steve; Papy, Jean-Michel; Wevers, Martine; Van Huffel, Sabine

    2004-07-01

    Permanent damage in various materials and constructions often causes high-energy high-frequency acoustic waves. To detect those so called `acoustic emission (AE) events', in most cases ultrasonic transducers are embedded in the structure or attached to its surface. However, for many applications where event localization is less important, an embedded low-cost multimode optical fiber sensor configured for event counting may be a better alternative due to its corrosion resistance, immunity to electromagnetic interference and light-weight. The sensing part of this intensity-modulated sensor consists of a multimode optical fiber. The sensing principle now relies on refractive index variations, microbending and mode-mode interferences by the action of the acoustic pressure wave. A photodiode is used to monitor the intensity of the optical signal and transient signal detection techniques (filtering, frame-to-frame analysis, recursive noise estimation, power detector estimator) on the photodiode output are applied to detect the events. In this work, the acoustic emission monitoring capabilities of the multimode optical fiber sensor are demonstrated with the fiber sensor embedded in the liner of a Power Data Transmission (PDT) coil to detect damage (delamination, matrix cracking and fiber breaking) while bending the coil. With the Hankel Total Least Square (HTLS) technique, it is shown that both the acoustic emission signal and optical signal can be modeled with a sum of exponentially damped complex sinusoids with common poles.

  8. 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.

  9. Monitoring of acoustic emission activity using thin wafer piezoelectric sensors

    NASA Astrophysics Data System (ADS)

    Trujillo, Blaine; Zagrai, Andrei; Meisner, Daniel; Momeni, Sepand

    2014-03-01

    Acoustic emission (AE) is a well-known technique for monitoring onset and propagation of material damage. The technique has demonstrated utility in assessment of metallic and composite materials in applications ranging from civil structures to aerospace vehicles. While over the course of few decades AE hardware has changed dramatically with the sensors experiencing little changes. A traditional acoustic emission sensor solution utilizes a thickness resonance of the internal piezoelectric element which, coupled with internal amplification circuit, results in relatively large sensor footprint. Thin wafer piezoelectric sensors are small and unobtrusive, but they have seen limited AE applications due to low signal-to-noise ratio and other operation difficulties. In this contribution, issues and possible solutions pertaining to the utility of thin wafer piezoelectrics as AE sensors are discussed. Results of AE monitoring of fatigue damage using thin wafer piezoelectric and conventional AE sensors are presented.

  10. 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.

  11. 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

  12. 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.

  13. Fiber optic acoustic emission sensors for harsh environment health monitoring

    NASA Astrophysics Data System (ADS)

    Borinski, Jason W.; Duke, John C., Jr.; Horne, Michael R.

    2001-07-01

    Optical fiber sensors are rapidly emerging as viable alternatives to piezoelectric devices as effective means of detecting and quantifying acoustic emission (AE). Compared to traditional piezoelectric-based sensors, optical fiber sensors offer much smaller size, reduced weight, ability to operate at temperatures up to 2000 degree(s)C, immunity to electromagnetic interference, resistance to corrosive environments, inherent safety within flammable environments, and the ability to multiplex multiple sensors on a single fiber. The authors have investigated low-profile fiber optic-based AE sensors for non-destructive evaluation (NDE) systems. In particular, broadband and resonant type optical fiber sensors were developed for monitoring acoustic emission for NDE of pressurized composite vessels and commercial airframe structures. The authors developed an in-plane, broadband sensor design based on optical strain gage technology. In addition, an out-of-plane, resonant sensor was developed using micromachining techniques. The sensors have been evaluated for performance using swept frequency and impulse excitation techniques and compared to conventional piezoelectric transducers. Further, application experiments were conducted using these sensors on both aluminum lap-joints and composite fracture coupons, with collocated piezoelectric transducers. The results indicate that optical fiber AE sensors can be used as transducers sensitive to acoustic events and the indication of imminent failure of a structure, making these sensors useful in many applications where conventional piezoelectric transducers are not well suited.

  14. 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.

  15. Leak Detection by Acoustic Emission Monitoring. Phase 1. Feasibility Study

    DTIC Science & Technology

    1994-05-26

    considered the soil composition- and structure , the leak depth and rate, the acoustic array geometry on the 12 PHASE I 03 SflAIASTrNAflc C’ 111 ATON 90111...First Conference on Acoustic Emission/ Microseismic Activilty in Geologic Structures and Materials. H.R. Hardy, Jr. and F.W. Leighton, 2ditors. Trans...Recognition and Acoustical Imaging , Newport Beach, California, February 4-6. 1987. 29. M.C. Junger and D. Feit. Sounds, Structures , and Their Interaction, The

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Fatigue crack monitoring with coupled piezoelectric film acoustic emission sensors

    NASA Astrophysics Data System (ADS)

    Zhou, Changjiang

    Fatigue-induced cracking is a commonly seen problem in civil infrastructures reaching their original design life. A number of high-profile accidents have been reported in the past that involved fatigue damage in structures. Such incidences often happen without prior warnings due to lack of proper crack monitoring technique. In order to detect and monitor the fatigue crack, acoustic emission (AE) technique, has been receiving growing interests recently. AE can provide continuous and real-time monitoring data on damage progression in structures. Piezoelectric film AE sensor measures stress-wave induced strain in ultrasonic frequency range and its feasibility for AE signal monitoring has been demonstrated recently. However, extensive work in AE monitoring system development based on piezoelectric film AE sensor and sensor characterization on full-scale structures with fatigue cracks, have not been done. A lack of theoretical formulations for understanding the AE signals also hinders the use of piezoelectric film AE sensors. Additionally, crack detection and source localization with AE signals is a very important area yet to be explored for this new type of AE sensor. This dissertation presents the results of both analytical and experimental study on the signal characteristics of surface stress-wave induced AE strain signals measured by piezoelectric film AE sensors in near-field and an AE source localization method based on sensor couple theory. Based on moment tensor theory, generalized expression for AE strain signal is formulated. A special case involving the response of piezoelectric film AE sensor to surface load is also studied, which could potentially be used for sensor calibration of this type of sensor. A new concept of sensor couple theory based AE source localization technique is proposed and validated with both simulated and experimental data from fatigue test and field monitoring. Two series of fatigue tests were conducted to perform fatigue crack

  1. 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.

  2. 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.

  3. Structural health condition monitoring of rails using acoustic emission techniques

    NASA Astrophysics Data System (ADS)

    Yilmazer, Pinar

    In-service rails can develop several types of structural defects due to fatigue and wear caused by rolling stock passing over them. Most rail defects will develop gradually over time thus permitting inspection engineers to detect them in time before final failure occurs. In the UK, certain types of severe rail defects such as tache ovales, require the fitting of emergency clamps and the imposing of an Emergency Speed Restriction (ESR) until the defects are removed. Acoustic emission (AE) techniques can be applied for the detection and continuous monitoring of defect growth therefore removing the need of imposing strict ESRs. The work reported herewith aims to develop a sound methodology for the application of AE in order to detect and subsequently monitor damage evolution in rails. To validate the potential of the AE technique, tests have been carried out under laboratory conditions on three and four-point bending samples manufactured from 260 grade rail steel. Further tests, simulating the background noise conditions caused by passing rolling stock have been carried out using special experimental setups. The crack growth events have been simulated using a pencil tip break..

  4. Acoustic emission monitoring of high speed grinding of silicon nitride

    PubMed

    Hwang; Whitenton; Hsu; Blessing; Evans

    2000-03-01

    Acoustic emission (AE) monitoring of a machining process offers real-time sensory input which could provide tool condition and part quality information that is critical to effective process control. However, the choice of sensor, its placement, and how to process the data and extract useful information are challenging application-specific questions which researchers must consider. Here we report an effort to resolve these questions for the case of high speed grinding of silicon nitride using an electroplated single-layered diamond wheel. A grinding experiment was conducted at a wheel speed of 149 m s-1 and continued until the end of the useful wheel life. AE signal data were then collected for each complete pass at given grinding times throughout the useful wheel life. We found that the amplitude of the AE signal monotonically increases with wheel wear, as do grinding forces and energy. Furthermore, the signal power contained in the AE signal proportionally increases with the associated grinding power, which suggests that the AE signal could provide quantitative information of wheel wear in high-speed grinding, and could also be used to determine when the grinding wheel needs replacement.

  5. 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.

  6. The use of acoustic emission for bearing condition monitoring

    NASA Astrophysics Data System (ADS)

    Lees, A. W.; Quiney, Z.; Ganji, A.; Murray, B.

    2011-07-01

    This paper reports research currently in progress at Swansea University in collaboration with SKF Engineering & Research Centre as part of a continuing investigation into high frequency Acoustic Emission. The primary concerns are experimentally producing subsurface cracks, the type of which would occur in a service failure of a ball bearing, within a steel ball and to closely monitor the properties of this AE from crack initiation to the formation of a ball on the ball surface. It is worth noting that there is evidence that the frequency content of the AE changes during this period, although this has yet to be proved consistent or even fully explained. Conclusive evidence could lead to a system which detects such cracks in a bearing operating in real life conditions, advantageous for many reasons including safety, downtime and maintenance and associated costs. The results from two experimental procedures are presented, one of which loads a single ball held stationary in a test rig to induce subsurface cracks, which are in turn detected by a pair of broadband AE sensors and recorded via a Labview based software system. This approach not only allows detailed analysis of the AE waveforms but also approximate AE source location from the time difference between two sensors. The second experimental procedure details an adaptation of a four-ball lubricant tester in an attempt to produce naturally occurring subsurface cracks from rolling contact whilst minimising the AE arising from surface wear. This thought behind this experiment is reinforced with 3D computational modelling of the rotating system.

  7. 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.

  8. Monitoring Concrete Deterioration Due to Reinforcement Corrosion by Integrating Acoustic Emission and FBG Strain Measurements

    PubMed Central

    Li, Weijie; Xu, Changhang; Ho, Siu Chun Michael; Wang, Bo; Song, Gangbing

    2017-01-01

    Corrosion of concrete reinforcement members has been recognized as a predominant structural deterioration mechanism for steel reinforced concrete structures. Many corrosion detection techniques have been developed for reinforced concrete structures, but a dependable one is more than desired. Acoustic emission technique and fiber optic sensing have emerged as new tools in the field of structural health monitoring. In this paper, we present the results of an experimental investigation on corrosion monitoring of a steel reinforced mortar block through combined acoustic emission and fiber Bragg grating strain measurement. Constant current was applied to the mortar block in order to induce accelerated corrosion. The monitoring process has two aspects: corrosion initiation and crack propagation. Propagation of cracks can be captured through corresponding acoustic emission whereas the mortar expansion due to the generation of corrosion products will be monitored by fiber Bragg grating strain sensors. The results demonstrate that the acoustic emission sources comes from three different types, namely, evolution of hydrogen bubbles, generation of corrosion products and crack propagation. Their corresponding properties are also discussed. The results also show a good correlation between acoustic emission activity and expansive strain measured on the specimen surface. PMID:28327510

  9. Monitoring Concrete Deterioration Due to Reinforcement Corrosion by Integrating Acoustic Emission and FBG Strain Measurements.

    PubMed

    Li, Weijie; Xu, Changhang; Ho, Siu Chun Michael; Wang, Bo; Song, Gangbing

    2017-03-22

    Corrosion of concrete reinforcement members has been recognized as a predominant structural deterioration mechanism for steel reinforced concrete structures. Many corrosion detection techniques have been developed for reinforced concrete structures, but a dependable one is more than desired. Acoustic emission technique and fiber optic sensing have emerged as new tools in the field of structural health monitoring. In this paper, we present the results of an experimental investigation on corrosion monitoring of a steel reinforced mortar block through combined acoustic emission and fiber Bragg grating strain measurement. Constant current was applied to the mortar block in order to induce accelerated corrosion. The monitoring process has two aspects: corrosion initiation and crack propagation. Propagation of cracks can be captured through corresponding acoustic emission whereas the mortar expansion due to the generation of corrosion products will be monitored by fiber Bragg grating strain sensors. The results demonstrate that the acoustic emission sources comes from three different types, namely, evolution of hydrogen bubbles, generation of corrosion products and crack propagation. Their corresponding properties are also discussed. The results also show a good correlation between acoustic emission activity and expansive strain measured on the specimen surface.

  10. Monitoring the fracture behavior in ceramic matrix composites by infrared thermography and acoustic emission

    NASA Astrophysics Data System (ADS)

    Dassios, Konstantinos G.; Kordatos, Evangelos Z.; Aggelis, Dimitris G.; Exarchos, Dimitris A.; Matikas, Theodore E.

    2014-04-01

    In this work an innovative methodology was employed for monitoring the fracture behavior in silicon carbide fiberreinforced ceramic matrix composites. This new methodology was based on the combined use of IR thermography and acoustic emission. Compact tension SiC/BMAS specimens were tested with unloading/reloading loops and the thermal dissipation due to crack propagation and other damage mechanisms was monitored by IR thermography. The accuracy of this technique was benchmarked by optical measurements of crack length. In addition, using acoustic emission descriptors, such as activity during the unloading part of the cycles, provided the critical level of damage accumulation in the material. Acoustic emission allowed to closely follow the actual crack growth monitored by IR thermography, enabling quantitative measurements.

  11. Thick-film acoustic emission sensors for use in structurally integrated condition-monitoring applications.

    PubMed

    Pickwell, Andrew J; Dorey, Robert A; Mba, David

    2011-09-01

    Monitoring the condition of complex engineering structures is an important aspect of modern engineering, eliminating unnecessary work and enabling planned maintenance, preventing failure. Acoustic emissions (AE) testing is one method of implementing continuous nondestructive structural health monitoring. A novel thick-film (17.6 μm) AE sensor is presented. Lead zirconate titanate thick films were fabricated using a powder/sol composite ink deposition technique and mechanically patterned to form a discrete thick-film piezoelectric AE sensor. The thick-film sensor was benchmarked against a commercial AE device and was found to exhibit comparable responses to simulated acoustic emissions.

  12. 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.

  13. 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…

  14. Acoustic Emission Monitoring of the DC-XA Composite Liquid Hydrogen Tank During Structural Testing

    NASA Technical Reports Server (NTRS)

    Wilkerson, C.

    1996-01-01

    The results of acoustic emission (AE) monitoring of the DC-XA composite liquid hydrogen tank are presented in this report. The tank was subjected to pressurization, tensile, and compressive loads at ambient temperatures and also while full of liquid nitrogen. The tank was also pressurized with liquid hydrogen. AE was used to monitor the tank for signs of structural defects developing during the test.

  15. 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.

  16. Leak detection by acoustic emission monitoring. Phase 1. Feasibility study. Final report, August 1987-March 1988

    SciTech Connect

    Lichtenstein, B.; Winder, A.A.

    1994-05-26

    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. Acoustic, Leak detection, Underground tank, Pipeline.

  17. Acoustic Emission and Damage Monitoring During Fatigue of C-SiC Composites at Room Temperature

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Deemer, Chris; Cuneo, Jacques; Smith, Aron; Koenig, John

    2003-01-01

    Fatigue experiments were performed at room temperature for C-fiber reinforced chemical vapor infiltrated (CVI Sic) matrix and melt-infiltrated (MI) matrix composites. The goal was to associate some nondestructive parameter or acoustic emission characteristic with the processes that lead to fatigue failure. Failure only occurred at loads very close to the ultimate. However, correlations between the acoustic data and the eventual failure of the composites could be made. These will be presented with respect to health monitoring of these types of composites.

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

    DOE PAGES

    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

  19. 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.

  20. Acoustic Emission Weld Monitor System. Data Acquisition and Investigation

    DTIC Science & Technology

    1979-10-01

    TARADCOM-furnished armor plate yielded the results shown in Table 2a. Table 2b shows the nominal chemical compositions of three HY steels , namely HY80 ...AE signals, as compared with previous experience monitoring submerged arc welding of mild carbon steels , was correlated with a large number of...observed that the background AE level was at times significantly greater than that for submerged arc welding of mild steels . The relatively high number

  1. Analysis of acoustic emission signals and monitoring of machining processes

    PubMed

    Govekar; Gradisek; Grabec

    2000-03-01

    Monitoring of a machining process on the basis of sensor signals requires a selection of informative inputs in order to reliably characterize and model the process. In this article, a system for selection of informative characteristics from signals of multiple sensors is presented. For signal analysis, methods of spectral analysis and methods of nonlinear time series analysis are used. With the aim of modeling relationships between signal characteristics and the corresponding process state, an adaptive empirical modeler is applied. The application of the system is demonstrated by characterization of different parameters defining the states of a turning machining process, such as: chip form, tool wear, and onset of chatter vibration. The results show that, in spite of the complexity of the turning process, the state of the process can be well characterized by just a few proper characteristics extracted from a representative sensor signal. The process characterization can be further improved by joining characteristics from multiple sensors and by application of chaotic characteristics.

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

    PubMed

    Arvanitis, Costas D; Livingstone, Margaret S; Vykhodtseva, Natalia; McDannold, Nathan

    2012-01-01

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

  3. Controlled Ultrasound-Induced Blood-Brain Barrier Disruption Using Passive Acoustic Emissions Monitoring

    PubMed Central

    Arvanitis, Costas D.; Livingstone, Margaret S.; Vykhodtseva, Natalia; McDannold, Nathan

    2012-01-01

    The ability of ultrasonically-induced oscillations of circulating microbubbles to permeabilize vascular barriers such as the blood-brain barrier (BBB) holds great promise for noninvasive targeted drug delivery. A major issue has been a lack of control over the procedure to ensure both safe and effective treatment. Here, we evaluated the use of passively-recorded acoustic emissions as a means to achieve this control. An acoustic emissions monitoring system was constructed and integrated into a clinical transcranial MRI-guided focused ultrasound system. Recordings were analyzed using a spectroscopic method that isolates the acoustic emissions caused by the microbubbles during sonication. This analysis characterized and quantified harmonic oscillations that occur when the BBB is disrupted, and broadband emissions that occur when tissue damage occurs. After validating the system's performance in pilot studies that explored a wide range of exposure levels, the measurements were used to control the ultrasound exposure level during transcranial sonications at 104 volumes over 22 weekly sessions in four macaques. We found that increasing the exposure level until a large harmonic emissions signal was observed was an effective means to ensure BBB disruption without broadband emissions. We had a success rate of 96% in inducing BBB disruption as measured by in contrast-enhanced MRI, and we detected broadband emissions in less than 0.2% of the applied bursts. The magnitude of the harmonic emissions signals was significantly (P<0.001) larger for sonications where BBB disruption was detected, and it correlated with BBB permeabilization as indicated by the magnitude of the MRI signal enhancement after MRI contrast administration (R2 = 0.78). Overall, the results indicate that harmonic emissions can be a used to control focused ultrasound-induced BBB disruption. These results are promising for clinical translation of this technology. PMID:23029240

  4. Monitoring of Surface Grinding process using Acoustic Emission (AE) with emphasis on Cutting Fluid selection

    NASA Astrophysics Data System (ADS)

    Nisal, Tejas V.

    Correct selection of cutting fluid is an important step in all machining operations. In this study, experiments were designed and conducted on AISI 52100 steel to determine the effects of using different cutting fluids in Surface Grinding. The grinding parameters varied were wheel speed, feed, depth of cut and type of cutting fluid. The grinding responses studied here were Acoustic Emission (AE) Signals, Normal and Tangential Forces on the workpiece surface, Grinding Temperature and Surface Roughness. Potential of Acoustic Emission technique as a tool to provide efficient real-time knowledge and monitoring of the grinding process, is tested in this research. AERMS values were used to analyses the process characteristics. This paper proposes four different statistical models for predicting Grinding Temperature, Force, Acoustic Emission (AERMS) and Roughness, based on grinding parameters. This research concludes that the selection of Cutting Fluids influence the Surface finish, AE signals, Temperature and grinding Forces measured. Further, prediction of surface roughness during the grinding process using AE signal monitoring is demonstrated in this work.

  5. Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.

    PubMed

    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.

  6. Evaluating Acoustic Emission Signals as an in situ process monitoring technique for Selective Laser Melting (SLM)

    SciTech Connect

    Fisher, Karl A.; Candy, Jim V.; Guss, Gabe; Mathews, M. J.

    2016-10-14

    In situ real-time monitoring of the Selective Laser Melting (SLM) process has significant implications for the AM community. The ability to adjust the SLM process parameters during a build (in real-time) can save time, money and eliminate expensive material waste. Having a feedback loop in the process would allow the system to potentially ‘fix’ problem regions before a next powder layer is added. In this study we have investigated acoustic emission (AE) phenomena generated during the SLM process, and evaluated the results in terms of a single process parameter, of an in situ process monitoring technique.

  7. Monitoring of Acoustic Emissions Within Geothermal Areas in Iceland: A new Tool for Geothermal Exploration.

    NASA Astrophysics Data System (ADS)

    Brandsdóttir, B.; Gudmundsson, O.

    2007-12-01

    With increased emphasis on geothermal development new exploration methods are needed in order to improve general understanding of geothermal reservoirs, characterize their extent and assess the potential for sustainable power production. Monitoring of acoustic emissions within geothermal areas may provide a new tool to evaluate the spatial extent of geothermal fields and model rock-fluid interactions. Three-dimensional seismic data have been used to assess the spatial and temporal distribution of noise within several high-temperature geothermal fields in Iceland. Seismic noise in the 4-6 Hz range within the Svartsengi field can be attributed to steam hydraulics and pressure oscillations within the geothermal reservoirs. Seismic noise surveys compliment electrical resistivity soundings and TEM-surveys by providing information pertinent to the current geothermal activity and extent of steam fields within the uppermost crust of the geothermal reservoir. Information related to acoustic emissions can thus help define targets for future wells.

  8. Acoustic emission fatigue crack monitoring of a simulated aircraft fuselage structure

    NASA Astrophysics Data System (ADS)

    Lucas, Jeremy James

    The purpose of this research was to replicate the fatigue cracking that occurs in aircraft placed under loads from cyclical compression and decompression. As a fatigue crack grows, it releases energy in the form of acoustic emissions. These emissions are transmitted through the structure in waves, which can be recorded using acoustic emission (AE) transducers. This research employed a pressure vessel constructed out of aluminum and placed under cyclical loads at 1 Hz in order to simulate the loads placed on an aircraft fuselage in flight. The AE signals were recorded by four resonant AE transducers. These were placed on the pressure vessel such that it was possible to determine the location of each AE signal. These signals were then classified using a Kohonen self organizing map (SOM) neural network. By using proper data filtering before the SOM was run and using the correct classification parameters, it was shown that this is a highly accurate method of classifying AE waveforms from fatigue crack growth. This initial classification was done using AE waveform quantification parameters. The method was then validated by using both source location and then examining the waveforms in order to ensure that the waveforms classified into each category were the expected waveform types associated with each of the AE sources. Thus, acoustic emission nondestructive testing (NDT), in combination with a SOM neural network, proved to be an excellent means of fatigue crack growth monitoring in a simulated aluminum aircraft structure.

  9. 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.

  10. 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.

  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. Fiber-optic intrinsic distributed acoustic emission sensor for large structure health monitoring.

    PubMed

    Liang, Sheng; Zhang, Chunxi; Lin, Wentai; Li, Lijing; Li, Chen; Feng, Xiujuan; Lin, Bo

    2009-06-15

    A fiber-optic intrinsic distributed acoustic emission (AE) sensor is proposed. By measuring the time delay of two signals from two Mach-Zehnder interferometers, the location of AE can be deduced, and the corresponding sensor is experimentally verified to be feasible with a 206 m average location error in a 20 km sensing range, which shows that this proposed sensor is applicable for distributed AE sensing for large structure health monitoring, with the unique advantages of low cost, simple configuration, and long sensing range. The limitations of the proposed sensor are also discussed, and the future work is presented.

  13. Damage accumulation in cyclically-loaded glass-ceramic matrix composites monitored by acoustic emission.

    PubMed

    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.

  14. 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.

  15. Acoustic emission technique for monitoring the pyrolysis of composites for process control.

    PubMed

    Tittmann, B R; Yen, C E

    2008-11-01

    Carbonization is the first step in the heat and pressure treatment (pyrolysis) of composites in preparing carbon-carbon parts. These find many uses, including aircraft brakes, rocket nozzles and medical implants. This paper describes the acoustic emissions (AE) from various stages of the manufacturing process of carbon-carbon composites. This process involves carbonization at a high temperature and this results in both thermal expansion and volume change (due to pyrolysis in which a sacrificial polymer matrix is converted to carbon). Importantly the resultant matrix is porous and has a network of small intra-lamina cracks. The formation of these microcracks produces AE and this paper describes how this observation can be used to monitor (and eventually control) the manufacturing process. The aim is to speed up manufacture, which is currently time-consuming. The first section of the paper describes the design of unimodal waveguides to enable the AE to propagate to a cool environment where a transducer can be located. The second part of the paper describes various experimental observations of AE under a range of process conditions. In particular, this paper presents a technique based on detecting acoustic emissions and (1) uses wire waveguides to monitor parts within the autoclave to 800 degrees C, (2) monitors microcracking during pyrolysis, (3) uses a four-level threshold to distinguish between low- and high-amplitude cracking events, (4) recognizes the occurrence of harmful delaminations, and (5) guides the control of the heating rate for optimum efficiency of the pyrolysis process. In addition, supporting data are presented of in situ measurements of porosity, weight loss, cross-ply shrinkage, and mass spectroscopy of gases emitted. The process evolution is illustrated by the use of interrupted manufacturing cycle micrographs obtained by optical, scanning acoustic (SAM) and scanning electron (SEM) microscopy. The technique promotes in-process monitoring and

  16. Acoustic emission based monitoring of the microdamage evolution during fatigue of human cortical bone.

    PubMed

    Agcaoglu, Serife; Akkus, Ozan

    2013-08-01

    Stress fractures are frequently observed in physically active populations, and they are believed to be associated with microcrack accumulation. There are not many tools for real-time monitoring of microdamage formation during fatigue of bone, in vivo or in vitro. Acoustic emission (AE) based detection of stress waves resulting from microdamage formation is a promising method to assess the rate and energetics of microdamage formation during fatigue. The current study aims to assess the time history of the occurrence of AE events during fatigue loading of human tibial cortical bone and to determine the associations between AE variables (energy content of waves, number of AE waveforms, etc.), fatigue life, and bone ash content. Fatigue test specimens were prepared from the distal diaphysis of human tibial cortical bone (N = 32, 22 to 52 years old, male and female). The initiation of acoustic emissions was concomitant with the nonlinear increase in sample compliance and the cumulative number of AE events increased asymptotically in the prefailure period. The results demonstrated that AE method was able to predict the onset of failure by 95% of the fatigue life for the majority of the samples. The variation in the number of emissions until failure ranged from 6 to 1861 implying a large variation in crack activity between different samples. The results also revealed that microdamage evolution was a function of the level of tissue mineralization such that more mineralized bone matrix failed with fewer crack events with higher energy whereas less mineralized tissue generated more emissions with lower energy. In conclusion, acoustic emission based surveillance during fatigue of cortical bone demonstrates a large scatter, where some bones fail with substantial crack activity and a minority of samples fail without significant amount of crack formation.

  17. Strategies for rock slope failure early warning using acoustic emission monitoring

    NASA Astrophysics Data System (ADS)

    Codeglia, D.; Dixon, N.; Fowmes, G. J.; Marcato, G.

    2015-09-01

    Research over the last two decades has led to development of a system for soil slopes monitoring based on the concept of measuring Acoustic Emission (AE). A feature of the system is the use of waveguides installed within unstable soil slopes. It has been demonstrated that the AE measured through this technique are proportional to soil displacement rate. Attention has now been focused on the prospect of using the system within rock materials. The different nature of the slope material to be monitored and its setting means that different acoustic trends are measured, and development of new approaches for their interpretation are required. A total of six sensors have been installed in two pilot sites, firstly in Italy, for monitoring of a stratified limestone slope which can threaten a nationally important road, and secondly in Austria, for monitoring of a conglomerate slope that can endanger a section of the local railway. In this paper an outline of the two trial sites is given and AE data collected are compared with other physical measurements (i.e. rainfall and temperature) and traditional geotechnical instrumentation, to give an overview of recurring AE trends. These include clear AE signatures generated by stress changes linked to increased ground water levels and high energy events generated by freeze-thaw of the rock mass.

  18. Acoustic emission-based condition monitoring methods: Review and application for low speed slew bearing

    NASA Astrophysics Data System (ADS)

    Caesarendra, Wahyu; Kosasih, Buyung; Tieu, Anh Kiet; Zhu, Hongtao; Moodie, Craig A. S.; Zhu, Qiang

    2016-05-01

    This paper presents an acoustic emission-based method for the condition monitoring of low speed reversible slew bearings. Several acoustic emission (AE) hit parameters as the monitoring parameters for the detection of impending failure of slew bearings are reviewed first. The review focuses on: (1) the application of AE in typical rolling element bearings running at different speed classifications, i.e. high speed (>600 rpm), low speed (10-600 rpm) and very low speed (<10 rpm); (2) the commonly used AE hit parameters in rolling element bearings and (3) AE signal processing, feature extraction and pattern recognition methods. In the experiment, impending failure of the slew bearing was detected by the AE hit parameters after the new bearing had run continuously for approximately 15 months. The slew bearing was then dismantled and the evidence of the early defect was analysed. Based on the result, we propose a feature extraction method of the AE waveform signal using the largest Lyapunov exponent (LLE) algorithm and demonstrate that the LLE feature can detect the sign of failure earlier than the AE hit parameters with improved prediction of the progressive trend of the defect.

  19. Acoustic emissions (AE) monitoring of large-scale composite bridge components

    NASA Astrophysics Data System (ADS)

    Velazquez, E.; Klein, D. J.; Robinson, M. J.; Kosmatka, J. B.

    2008-03-01

    Acoustic Emissions (AE) has been successfully used with composite structures to both locate and give a measure of damage accumulation. The current experimental study uses AE to monitor large-scale composite modular bridge components. The components consist of a carbon/epoxy beam structure as well as a composite to metallic bonded/bolted joint. The bonded joints consist of double lap aluminum splice plates bonded and bolted to carbon/epoxy laminates representing the tension rail of a beam. The AE system is used to monitor the bridge component during failure loading to assess the failure progression and using time of arrival to give insight into the origins of the failures. Also, a feature in the AE data called Cumulative Acoustic Emission counts (CAE) is used to give an estimate of the severity and rate of damage accumulation. For the bolted/bonded joints, the AE data is used to interpret the source and location of damage that induced failure in the joint. These results are used to investigate the use of bolts in conjunction with the bonded joint. A description of each of the components (beam and joint) is given with AE results. A summary of lessons learned for AE testing of large composite structures as well as insight into failure progression and location is presented.

  20. Real-time measurement of electron beam weld penetration in uranium by acoustic emission monitoring

    SciTech Connect

    Whittaker, J.W.; Murphy, J.L.

    1991-07-01

    High quality electron beam (EB) welds are required in uranium test articles. Acoustic emission (AE) techniques are under development with the goal of measuring weld penetration in real-time. One technique, based on Average Signal Level (ASL) measurement was used to record weld AE signatures. Characteristic AE signatures were recorded for bead-on-plate (BOP) and butt joint (BJ) welds made under varied welding conditions. AE waveforms were sampled to determine what microscopic AE behavior led to the observed macroscopic signature features. Deformation twinning and weld expulsion are two of the main sources of emission. AE behavior was correlated with weld penetration as measured by standard metallographic techniques. The ASL value was found to increase approximately linearly with weld penetration in BJ welds. These results form the basis for a real-time monitoring technique for weld penetration. 5 refs.

  1. Use of Acoustic Emission to Monitor Progressive Damage Accumulation in KEVLAR® 49 Composites

    NASA Astrophysics Data System (ADS)

    Waller, J. M.; Andrade, E.; Saulsberry, R. L.

    2010-02-01

    Acoustic emission (AE) data acquired during intermittent load hold tensile testing of epoxy impregnated Kevlar® 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.

  2. Characterization of electron-beam weld processes in uranium by acoustic emission monitoring

    SciTech Connect

    Whittaker, J.W.; Murphy, J.L.

    1989-08-19

    Work was begun to characterize electron-beam (EB) welding of uranium by use of acoustic emission (AE) monitoring at the Oak Ridge Y-12 Plant. One specific objective was to determine if a correlation existed between weld penetration and an AE parameter(s). AE monitoring techniques were developed which allowed detection and recording of AE information during welding. Initial results from bead-on-plate welds of uranium imply that the AE signal varies during different processes: weld initiation, process stabilization, steady-state weld formation, weld cessation, and material cool-down. A correlation was developed between the AE ''average signal level'' (ASL) parameter and weld penetration which implies that penetration can be predicted from a given measured ASL level. 1 ref., 7 figs., 1 tab.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Acoustic emission monitoring of structural perturbations with serially multiplexed optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Liang, Yujin; Sun, Changsen; Ansari, Farhad

    2005-05-01

    Damage location and damage state identification of a hybrid Carbon-glass FRP rod was performed by means of a serially multiplexed fiber optic acoustic emission sensor. The detection and identification of acoustic emission signals along a single data stream reduces the data acquisition rigor and provides for rapid real time damage location detection in materials. Linear source location method and signature frequency spectra energy of acoustic emission signals were employed for locating the fiber breakage and distinguishing the damage state in the hybrid FRP rod, respectively.

  9. Remote monitoring and prognosis of fatigue cracking in steel bridges with acoustic emission

    NASA Astrophysics Data System (ADS)

    Yu, Jianguo Peter; Ziehl, Paul; Pollock, Adrian

    2011-04-01

    Acoustic emission (AE) monitoring is desirable to nondestructively detect fatigue damage in steel bridges. Investigations of the relationship between AE signals and crack growth behavior are of paramount importance prior to the widespread application of passive piezoelectric sensing for monitoring of fatigue crack propagation in steel bridges. Tests have been performed to detect AE from fatigue cracks in A572G50 steel. Noise induced AE signals were filtered based on friction emission tests, loading pattern, and a combined approach involving Swansong II filters and investigation of waveforms. The filtering methods based on friction emission tests and load pattern are of interest to the field evaluation using sparse datasets. The combined approach is suitable for data filtering and interpretation of actual field tests. The pattern recognition program NOESIS (Envirocoustics) was utilized for the evaluation of AE data quality. AE parameters are associated with crack length, crack growth rate, maximum stress intensity and stress intensity range. It is shown that AE hits, counts, absolute energy, and signal strength are able to provide warnings at the critical cracking level where cracking progresses from stage II (stable propagation) to stage III (unstable propagation which may result in failure). Absolute energy rate and signal strength rate may be better than count rate to assess the remaining fatigue life of inservice steel bridges.

  10. 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.

  11. 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

  12. An experimental modeling and acoustic emission monitoring of abrasive wear in a steel/diabase pair

    NASA Astrophysics Data System (ADS)

    Korchuganov, M. A.; Filippov, A. V.; Tarasov, S. Yu.; Podgornyh, O. A.; Shamarin, N. N.; Filippova, E. O.

    2016-11-01

    The earthmoving of permafrost soil is a critical task for excavation of minerals and construction on new territories. Failure by abrasive wear is the main reason for excavation parts of earthmoving and soil cutting machines. Therefore investigation of this type of wear is a challenge for developing efficient and wear resistant working parts. This paper is focused on conducting tribological experiments with sliding the steel samples over the surface of diabase stone sample where abrasive wear conditions of soil cutting are modeled experimentally. The worn surfaces of all samples have been examined and transfer of metal and stone particles revealed. The acoustic emission (AE) signals have been recorded and related to the results of worn surface analysis. he acoustic emission (AE) signals have been recorded and related to the results of worn surface analysis. As shown the wear intensity correlates to that of acoustic emission. Both acoustic emission signal median frequency and energy are found to be sensitive to the wear mode.

  13. 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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  15. Damage evaluation for high temperature CFRP components using acoustic emission monitoring

    NASA Astrophysics Data System (ADS)

    Austin, Russell; Forsyth, David; Yu, Jianguo (Peter); ElBatanouny, Mohamed; Ziehl, Paul

    2014-02-01

    Acoustic emission (AE) monitoring can provide confidence in the reliability of a structure or component, thereby reducing unnecessary maintenance and inspection. Due to the brittle nature of carbon fiber reinforced polymer (CFRP) failure and critical applications, it is crucial to develop a real-time monitoring technique that is able to assess structural integrity of these components. Comparable assessment criteria for the evaluation of structural integrity are needed as a part of AE monitoring system. Based on Austin and Coughlin criteria, numbers of high amplitude AE hits/events, historic index, AE cumulative energy, and severity were utilized to evaluate structural damage through a numerical rating. AE signals associated with structural damage were collected through ramp-up loading and low-cycle fatigue tests. A combination of source location filtering, waveform feature analysis and pattern recognition was used to filter acquired AE signals. The effect of prescribed signal period on the Austin and Coughlin criteria was studied. Due to the fact that the number of hits does not weigh the intensity of each hit, the Austin and Coughlin criteria was modified by excluding the number-of-hit score.

  16. Acoustic emission monitoring of cement-based structures immobilising radioactive waste

    SciTech Connect

    Spasova, L.M.; Ojovan, M.I.; Hayes, M.; Godfrey, H.

    2007-07-01

    The long term performance of cementitious structures immobilising radioactive waste can be affected by physical and chemical processes within the encapsulating materials such as formation of new phases (e.g., vaterite, brucite), degradation of cement phases (e.g., CSH gel, portlandite), degradation of some waste components (e.g., organics), corrosion of metallic constituents (aluminium, magnesium), gas emission, further hydration etc. The corrosion of metals in the high pH cementitious environment is of especial concern as it can potentially cause wasteform cracking. One of the perspective non-destructive methods used to monitor and assess the mechanical properties of materials and structures is based on an acoustic emission (AE) technique. In this study an AE non-destructive technique was used to evaluate the mechanical performance of cementitious structures with encapsulated metallic waste such as aluminium. AE signals generated as a result of aluminium corrosion in a small-size blast furnace slag (BFS)/ordinary Portland cement (OPC) sample were detected, recorded and analysed. A procedure for AE data analysis including conventional parameter-based AE approach and signal-based analysis was applied and demonstrated to provide information on the aluminium corrosion process and its impact on the mechanical performance of the encapsulating cement matrix. (authors)

  17. Acoustic emission detection with fiber optical sensors for dry cask storage health monitoring

    NASA Astrophysics Data System (ADS)

    Lin, Bin; Bao, Jingjing; Yu, Lingyu; Giurgiutiu, Victor

    2016-04-01

    The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS). In the past two decades, an extensive sensor technology development has been used for structural health monitoring (SHM). Technologies for the diagnosis and prognosis of a nuclear system, such as dry cask storage system (DCSS), can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component. Fiber optical sensors have emerged as one of the major SHM technologies developed particularly for temperature and strain measurements. This paper presents the development of optical equipment that is suitable for ultrasonic guided wave detection for active SHM in the MHz range. An experimental study of using fiber Bragg grating (FBG) as acoustic emission (AE) sensors was performed on steel blocks. FBG have the advantage of being durable, lightweight, and easily embeddable into composite structures as well as being immune to electromagnetic interference and optically multiplexed. The temperature effect on the FBG sensors was also studied. A multi-channel FBG system was developed and compared with piezoelectric based AE system. The paper ends with conclusions and suggestions for further work.

  18. Acoustic emission monitoring of activation behavior of LaNi5 hydrogen storage alloy

    PubMed Central

    De Rosa, Igor Maria; Dell'Era, Alessandro; Pasquali, Mauro; Santulli, Carlo; Sarasini, Fabrizio

    2011-01-01

    The acoustic emission technique is proposed for assessing the irreversible phenomena occurring during hydrogen absorption/desorption cycling in LaNi5. In particular, we have studied, through a parametric analysis of in situ detected signals, the correlation between acoustic emission (AE) parameters and the processes occurring during the activation of an intermetallic compound. Decreases in the number and amplitude of AE signals suggest that pulverization due to hydrogen loading involves progressively smaller volumes of material as the number of cycles increases. This conclusion is confirmed by electron microscopy observations and particle size distribution measurements. PMID:27877423

  19. Acoustic emission monitoring of unstable damage growth in CFRP composites under tension

    NASA Astrophysics Data System (ADS)

    Mills-Dadson, B.; Tran, D.; Asamene, K.; Whitlow, T.; Sundaresan, M.

    2017-02-01

    Composite structural members experience extensive and complex damage that accumulate in a relatively steady pace as the structure is quasi-statically loaded. This damage progression which starts as matrix cracks, delaminations, and random fiber breaks, turns unstable when groups of adjacent fibers, ranging from four to ten fibers fail together, after about 85% of ultimate strength, as reported in the literature. Identifying this critical damage that precedes the final fracture has been difficult even in laboratory specimens. There is little consensus on successful use of AE signals to differentiate failure modes. The inability of AE patterns to identify failure modes is likely caused by the limited frequency bandwidth of available AE sensors, and the high attenuation seen in AE signals particularly in the frequency range likely to be associated with fiber fractures. As a part of this study new acoustic emission sensors capable of measuring frequencies to 2 MHz were developed. In addition, composite specimens were instrumented with sufficient number of sensors to capture high frequency signals before they are attenuated. Unidirectional, cross-ply, and quasi-isotropic carbon-epoxy composite tensile specimens were monitored while they were statically loaded to failure. Distinctly different signals corresponding to the three failure modes could be observed. High frequency acoustic emission signals with frequencies well in excess of 1MHz, mostly seen in the last 20% of the loading cycle. Signals with frequencies in the range of 300 kHz to 700 kHz and duration of the order of 50 microseconds, were observed in cross ply and quasi-isotropic specimens, and are believed to be from matrix cracks. Fewer events with frequencies below 300 kHz and duration that exceeded about 200 microseconds are believed to be from delaminations. An important observation in this study is the appearance of groups of near identical waveforms, which are believed to be from clusters of adjacent

  20. Onset of Hydraulic Fracture Initiation Monitored by Acoustic Emission and Volumetric Deformation Measurements

    NASA Astrophysics Data System (ADS)

    Stanchits, Sergey; Surdi, Aniket; Gathogo, Patrick; Edelman, Eric; Suarez-Rivera, Roberto

    2014-09-01

    In this paper, the results of laboratory studies of fracture initiation, early propagation and breakdown are reported. Three experiments were conducted on a low permeability sandstone block, loaded in a polyaxial test frame, to representative effective in situ stress conditions. The blocks were instrumented with acoustic emission (AE) and volumetric deformation sensors. In two experiments, fluids of different viscosity were injected into the wellbore, fluid injection was interrupted soon after the breakdown pressure had been reached. This allowed us to investigate hydraulic fracture initiation. In the third test, fracture initiation criteria were applied to stop hydraulic fracture propagation significantly earlier, prior to breakdown, and as it propagated a short distance from the wellbore. The analysis of AE results shows an increase in AE activity and a change in the AE spatial correlation, during the fracture initiation. This early stage of fracturing correlates strongly with the onset of rock volumetric deformation, and is confirmed by the analysis of ultrasonic transmission monitoring. The rock microstructure, after the test, was investigated by analysis of scanning electron microscope images. These indicated the development of leak-off zone near the wellbore and a dry hydraulic fracture at the farther distance from the wellbore.

  1. 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.

  2. 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

  3. 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.

  4. Cryo-induced cracking in high-alpine rock-wall, evidences from acoustic emissions monitoring

    NASA Astrophysics Data System (ADS)

    Amitrano, D.; Gruber, S.; Girard, L.

    2012-04-01

    Ice formation within rock is known to be an important driver of near-surface frost weathering as well as rock damage at the depth of several meters, which may play a crucial role for the slow preconditioning of rock fall in steep permafrost areas. This letter reports results from an experiment where acoustic emission (AE) monitoring was used to investigate rock damage in a high-alpine rock-wall induced by natural thermal cycling and freezing/thawing. The analysis of the large catalog of events obtained shows (i) robust power-law distributions in the time and energy domains, a footprint of rock micro-fracturing activity induced by stresses arising from thermal variations and associated freezing/thawing of rock; (ii) liquid water availability and rock temperature affect AE activity, suggesting the importance of freezing-induced stresses. These results suggest that the framework of further modeling studies (theoretical and numerical) should include damage, elastic interaction and poro-mechanics in order to describe freezing-related stresses.

  5. 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.

  6. Acoustic emission-based sensor analysis and damage classification for structural health monitoring of composite structures

    NASA Astrophysics Data System (ADS)

    Uprety, Bibhisha

    Within the aerospace industry the need to detect and locate impact events, even when no visible damage is present, is important both from the maintenance and design perspectives. This research focused on the use of Acoustic Emission (AE) based sensing technologies to identify impact events and characterize damage modes in composite structures for structural health monitoring. Six commercially available piezoelectric AE sensors were evaluated for use with impact location estimation algorithms under development at the University of Utah. Both active and passive testing were performed to estimate the time of arrival and plate wave mode velocities for impact location estimation. Four sensors were recommended for further comparative investigations. Furthermore, instrumented low-velocity impact experiments were conducted on quasi-isotropic carbon/epoxy composite laminates to initiate specific types of damage: matrix cracking, delamination and fiber breakage. AE signal responses were collected during impacting and the test panels were ultrasonically C-scanned after impact to identify the internal damage corresponding to the AE signals. Matrix cracking and delamination damage produced using more compliant test panels and larger diameter impactor were characterized by lower frequency signals while fiber breakage produced higher frequency responses. The results obtained suggest that selected characteristics of sensor response signals can be used both to determine whether damage is produced during impacting and to characterize the types of damage produced in an impacted composite structure.

  7. Acoustic emission monitoring of multicell reinforced concrete box girders subjected to torsion.

    PubMed

    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.

  8. 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).

  9. Monitoring of fatigue damage in metal plates by acoustic emission and thermography

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    Acoustic Emission (AE) supplies information on the fracturing behavior of different materials. In this study, AE activity was recorded during fatigue experiments in metal CT specimens with a V-shape notch which were loaded in fatigue until final failure. AE parameters exhibit a sharp increase approximately 1000 cycles before than final failure. Therefore, the use of acoustic emission parameters is discussed both in terms of characterization of the damage mechanisms, as well as a tool for the prediction of ultimate life of the material under fatigue. Additionally, an innovative nondestructive methodology based on lock-in thermography is developed to determine the crack growth rate using thermographic mapping of the material undergoing fatigue. The thermographic results on the crack growth rate of aluminium alloys were then correlated with measurements obtained by the conventional compliance method, and found to be in agreement.

  10. 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.

  11. Validation and verification of the acoustic emission technique for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Gagar, Daniel Omatsola

    The performance of the Acoustic Emission (AE) technique was investigated to establish its reliability in detecting and locating fatigue crack damage as well as distinguishing between different AE sources in potential SHM applications. Experiments were conducted to monitor the AE signals generated during fatigue crack growth in coupon 2014 T6 aluminium. The influence of stress ratio, stress range, sample geometry and whether or not the load spectrum was of constant or variable amplitude were all investigated. AE signals detected were correlated with values of applied cyclic load throughout the tests. Measurements of time difference of arrival were taken for assessment of errors in location estimates obtained using time of flight algorithms with a 1D location setup. At the onset of crack growth high AE Hit rates were observed for the first few millimetres after which they rapidly declined to minimal values for an extended period of crack growth. Another peak and then decline in AE Hit rates was observed for subsequent crack growth before yet another increase as the sample approached final failure.. AE signals were seen to occur in the lower two-thirds of the maximum load in the first few millimetres of crack growth before occurring at progressively smaller values as the crack length increased. A separate set of AE signals were observed close to the maximum cyclic stress throughout the entire crack growth process. At the failure crack length AE signals were generated across the entire loading range. Novel metrics were developed to statistically characterise variability of AE generation with crack growth and at particular crack lengths across different samples. A novel approach for fatigue crack length estimation was developed based on monitoring applied loads to the sample corresponding with generated AE signals. An acousto-ultrasonic method was used to calibrate the AE wave velocity in a representative wing-box structure which was used to successfully locate the

  12. A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock-walls

    NASA Astrophysics Data System (ADS)

    Girard, L.; Beutel, J.; Gruber, S.; Hunziker, J.; Lim, R.; Weber, S.

    2012-06-01

    We present a custom acoustic emission (AE) monitoring system designed to perform long-term measurements on high-alpine rock-walls. AE monitoring is a common technique for characterizing damage evolution in solid materials. The system is based on a two-channel AE sensor node (AE-node) integrated into a Wireless Sensor Network (WSN) customized for operation in harsh environments. This wireless architecture offers flexibility in the deployment of AE-nodes at any position of the rock-wall that needs to be monitored, within a range of a few hundred meters from a core station connected to the internet. The system achieves near real-time data delivery and allows the user to remotely control the AE detection threshold. In order to protect AE sensors and capture acoustic signals from specific depths of the rock-wall, a special casing was developed. The monitoring system is completed by two probes that measure rock temperature and liquid water content, both probes being also integrated into the WSN. We report a first deployment of the monitoring system on a rock-wall at Jungfraujoch, 3500 m a.s.l., Switzerland. While this first deployment of the monitoring system aims to support fundamental research on processes that damage rock under cold climate, the system could serve a number of other applications, including rock-fall hazard surveillance or structural monitoring of concrete structures.

  13. A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock walls

    NASA Astrophysics Data System (ADS)

    Girard, L.; Beutel, J.; Gruber, S.; Hunziker, J.; Lim, R.; Weber, S.

    2012-11-01

    We present a custom acoustic emission (AE) monitoring system designed to perform long-term measurements on high-alpine rock walls. AE monitoring is a common technique for characterizing damage evolution in solid materials. The system is based on a two-channel AE sensor node (AE-node) integrated into a wireless sensor network (WSN) customized for operation in harsh environments. This wireless architecture offers flexibility in the deployment of AE-nodes at any position of the rock wall that needs to be monitored, within a range of a few hundred meters from a core station connected to the internet. The system achieves near real-time data delivery and allows the user to remotely control the AE detection threshold. In order to protect AE sensors and capture acoustic signals from specific depths of the rock wall, a special casing was developed. The monitoring system is completed by two probes that measure rock temperature and liquid water content, both probes being also integrated into the WSN. We report a first deployment of the monitoring system on a rock wall at Jungfraujoch, 3500 m a.s.l., Switzerland. While this first deployment of the monitoring system aims to support fundamental research on processes that damage rock under cold climate, the system could serve a number of other applications, including rock fall hazard surveillance or structural monitoring of concrete structures.

  14. 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

  15. A new setup for studying thermal microcracking through acoustic emission monitoring

    NASA Astrophysics Data System (ADS)

    Griffiths, Luke; Heap, Michael; Baud, Patrick; Schmittbuhl, Jean

    2016-04-01

    Thermal stressing is common in geothermal environments and has been shown in the laboratory to induce changes in the physical and mechanical properties of rocks. These changes are generally considered to be a consequence of the generation of thermal microcracks and debilitating chemical reactions. Thermal microcracks form as a result of the build-up of internal stresses due to: (1) the thermal expansion mismatch between the different phases present in the material, (2) thermal expansion anisotropy within individual minerals, and (3) thermal gradients. The generation of cracks during thermal stressing has been monitored in previous studies using the output of acoustic emissions (AE), a common proxy for microcrack damage, and through microstructural observations. Here we present a new experimental setup which is optimised to record AE from a rock sample at high temperatures and under a servo-controlled uniaxial stress. The design is such that the AE transducer is embedded in the top of the piston, which acts as a continuous wave guide to the sample. In this way, we simplify the ray path geometry whilst minimising the number of interfaces between the microcrack and the transducer, maximising the quality of the signal. This allows for an in-depth study of waveform attributes such as energy, amplitude, counts and duration. Furthermore, the capability of this device to apply a servo-controlled load on the sample, whilst measuring strain in real time, leads to a spectrum of possible tests combining mechanical and thermal stress. It is also an essential feature to eliminate the build-up of stresses through thermal expansion of the pistons and the sample. We plan a systematic experimental study of the AE of thermally stressed rock during heating and cooling cycles. We present results from pilot tests performed on Darley Dale sandstone and Westerly granite. Understanding the effects of thermal stressing in rock is of particular interest at a geothermal site, where

  16. Acoustic Emission and Guided Ultrasonic Waves for Detection and Continuous Monitoring of Cracks in Light Water Reactor Components

    SciTech Connect

    Meyer, Ryan M.; Coble, Jamie B.; Ramuhalli, Pradeep; Watson, Bruce E.; Cumblidge, Stephen E.; Doctor, Steven R.; Bond, Leonard J.

    2012-06-28

    Acoustic emission (AE) and guided ultrasonic waves (GUW) are considered for continuous monitoring and detection of cracks in Light Water Reactor (LWR) components. In this effort, both techniques are applied to the detection and monitoring of fatigue crack growth in a full scale pipe component. AE results indicated crack initiation and rapid growth in the pipe, and significant GUW responses were observed in response to the growth of the fatigue crack. After initiation, the crack growth was detectable with AE for approximately 20,000 cycles. Signals associated with initiation and rapid growth where distinguished based on total rate of activity and differences observed in the centroid frequency of hits. An intermediate stage between initiation and rapid growth was associated with significant energy emissions, though few hits. GUW exhibit a nearly monotonic trend with crack length with an exception of measurements obtained at 41 mm and 46 mm.

  17. Assessment of the application of acoustic emission technology for monitoring the presence of sand under multiphase flow condition

    NASA Astrophysics Data System (ADS)

    El-Alej, M.; Mba, D.; Yeung, H.

    2014-04-01

    The monitoring of multiphase flow is an established process that has spanned several decades. This paper demonstrates the use of acoustic emission (AE) technology to investigate sand transport characteristic in three-phase (air-water-sand) flow in a horizontal pipe where the superficial gas velocity (VSG) had a range of between 0.2 ms-1 to 2.0 ms-1 and superficial liquid velocity (VSL) had a range of between 0.2 ms-1 to 1.0 ms-1. The experimental findings clearly show a correlation exists between AE energy levels, sand concentration, superficial gas velocity (VSG) and superficial liquid velocity (VSL).

  18. 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.

  19. Use of Modal Acoustic Emission to Monitor Damage Progression in Carbon Fiber/epoxy Composites

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    Broad-band modal acoustic emission (AE) was used to characterize micromechanical damage progression in uniaxial IM7 and T1000 carbon fiber-epoxy (C/Ep) tows, and a helical and hoop-wrapped IM7 composite overwrapped pressure vessel (COPV). To expedite analysis, tows and the COPV were subjected to an intermittent load hold tensile stress profile. Damage progression in tow specimens was followed by analyzing the Fast Fourier Transforms (FFTs) associated with AE events. FFT analysis showed that damage was usually cooperative, consisting of several failure modes occurring at once, and was dominated by fiber breakage throughout the duration of the stress profile. 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 use of FR* to predict the burst pressure of the COPV is demonstrated.

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

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Saulsberry, Regor L.; Nichols, Charles T.; Wentzel, Daniel J.

    2010-01-01

    This slide presentation reviews the use of Modal Acoustic Emission to monitor damage progression to carbon fiber/epoxy tows. There is a risk for catastrophic failure of composite overwrapped pressure vessels (COPVs) due to burst-before-leak (BBL) stress rupture (SR) failure of carbon-epoxy (C/Ep) COPVs. A lack of quantitative nondestructive evaluation (NDE) is causing problems in current and future spacecraft designs. It is therefore important to develop and demonstrate critical NDE that can be implemented during stages of the design process since the observed rupture can occur with little of no advanced warning. Therefore a program was required to develop quantitative acoustic emission (AE) procedures specific to C/Ep overwraps, but which also have utility for monitoring damage accumulation in composite structure in general, and to lay the groundwork for establishing critical thresholds for accumulated damage in composite structures, such as COPVs, so that precautionary or preemptive engineering steps can be implemented to minimize of obviate the risk of catastrophic failure. A computed Felicity Ratio (FR) coupled with fast Fourier Transform (FFT) frequency analysis shows promise as an analytical pass/fail criterion. The FR analysis and waveform and FFT analysis are reviewed

  1. Passive wireless surface acoustic wave sensors for monitoring sequestration sites CO2 emission

    SciTech Connect

    Wang, Yizhong; Chyu, Minking; Wang, Qing-Ming

    2013-02-14

    University of Pittsburgh’s Transducer lab has teamed with the U.S. Department of Energy’s National Energy Technology Laboratory (DOE NETL) to conduct a comprehensive study to develop/evaluate low-cost, efficient CO2 measuring technologies for geological sequestration sites leakage monitoring. A passive wireless CO2 sensing system based on surface acoustic wave technology and carbon nanotube nanocomposite was developed. Surface acoustic wave device was studied to determine the optimum parameters. Delay line structure was adopted as basic sensor structure. CNT polymer nanocomposite was fabricated and tested under different temperature and strain condition for natural environment impact evaluation. Nanocomposite resistance increased for 5 times under pure strain, while the temperature dependence of resistance for CNT solely was -1375ppm/°C. The overall effect of temperature on nanocomposite resistance was -1000ppm/°C. The gas response of the nanocomposite was about 10% resistance increase under pure CO2 . The sensor frequency change was around 300ppm for pure CO2 . With paralyne packaging, the sensor frequency change from relative humidity of 0% to 100% at room temperature decreased from over 1000ppm to less than 100ppm. The lowest detection limit of the sensor is 1% gas concentration, with 36ppm frequency change. Wireless module was tested and showed over one foot transmission distance at preferred parallel orientation.

  2. Real-time structural integrity monitoring using a passive quadrature demodulated, localised Michelson optical fibre interferometer capable of simultaneous strain and acoustic emission sensing

    NASA Astrophysics Data System (ADS)

    Tapanes, Edward

    1991-12-01

    A Michelson Fiber optic sensor (MFOS) is described for in-situ strain and vibration monitoring as well as acoustic emission detection in composite material structures. The phase sensitive fiber optic sensor is localized, all-fiber, and intrinsic. The MFOS was successfully embedded in Kevlar/epoxy and graphite/epoxy thermosets as well as graphite/PEEK thermoplastic in order to perform local strain and vibration measurements at the lamina level. A technique allowing acoustic emission detection in parallel with strain and vibration monitoring is illustrated.

  3. Continuous wavelet transform analysis and modal location analysis acoustic emission source location for nuclear piping crack growth monitoring

    SciTech Connect

    Mohd, Shukri; Holford, Karen M.; Pullin, Rhys

    2014-02-12

    Source location is an important feature of acoustic emission (AE) damage monitoring in nuclear piping. The ability to accurately locate sources can assist in source characterisation and early warning of failure. This paper describe the development of a novelAE source location technique termed 'Wavelet Transform analysis and Modal Location (WTML)' based on Lamb wave theory and time-frequency analysis that can be used for global monitoring of plate like steel structures. Source location was performed on a steel pipe of 1500 mm long and 220 mm outer diameter with nominal thickness of 5 mm under a planar location test setup using H-N sources. The accuracy of the new technique was compared with other AE source location methods such as the time of arrival (TOA) techniqueand DeltaTlocation. Theresults of the study show that the WTML method produces more accurate location resultscompared with TOA and triple point filtering location methods. The accuracy of the WTML approach is comparable with the deltaT location method but requires no initial acoustic calibration of the structure.

  4. Assessment of the application of acoustic emission technology for monitoring the presence of sand under multiphase flow condition

    SciTech Connect

    El-Alej, M. Mba, D. Yeung, H.

    2014-04-11

    The monitoring of multiphase flow is an established process that has spanned several decades. This paper demonstrates the use of acoustic emission (AE) technology to investigate sand transport characteristic in three-phase (air-water-sand) flow in a horizontal pipe where the superficial gas velocity (VSG) had a range of between 0.2 ms{sup −1} to 2.0 ms{sup −1} and superficial liquid velocity (VSL) had a range of between 0.2 ms{sup −1} to 1.0 ms{sup −1}. The experimental findings clearly show a correlation exists between AE energy levels, sand concentration, superficial gas velocity (VSG) and superficial liquid velocity (VSL)

  5. 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.

  6. Feasibility study of using smart aggregates as embedded acoustic emission sensors for health monitoring of concrete structures

    NASA Astrophysics Data System (ADS)

    Li, Weijie; Kong, Qingzhao; Ho, Siu Chun Michael; Lim, Ing; Mo, Y. L.; Song, Gangbing

    2016-11-01

    Acoustic emission (AE) is a nondestructive evaluation technique that is capable of monitoring the damage evolution of concrete structures in real time. Conventionally, AE sensors are surface mounted on the host structures, however, the AE signals attenuate quickly due to the high attenuation properties of concrete structures. This study conducts a feasibility study of using smart aggregates (SAs), which are a type of embedded piezoceramic transducers, as embedded AE sensors for the health monitoring of concrete structures. A plain concrete beam with two surface mounted AE sensors and two embedded SAs was fabricated in laboratory and loaded under a designed three-point-bending test. The performance of embedded SAs were compared with the traditional surface mounted AE sensors in their ability to detect and evaluate the damage to the concrete structure. The results verified the feasibility of using smart aggregates as embedded AE sensors for monitoring structural damage in concrete. Potentially, the low cost smart aggregates could function as embedded AE sensors, providing great sensitivity and high reliability in applications for the structural health monitoring of concrete structures.

  7. Integration of acoustic emission systems within Integri-TechTM analysis system for structural health monitoring of pressurised engineering plant

    NASA Astrophysics Data System (ADS)

    Ghouri, A. A.; Rafferty, Steven; Pickwell, Andy; Galbraith, Walter; Pierce, S. Gareth; Gachagan, Anthony

    2015-07-01

    The aim of this Acoustic Emission (AE) based Structural Health Monitoring project is to enable accurate location of AE sources in pressurised engineering plant and to use AE source location data to establish defect locations for use within Integri-TechTM; a finite element based analysis, monitoring and fitness for service assessment system. Integri-TechTM is a windows based system which carries out combined analysis and assessment providing fatigue life and remnant life calculations and inspection priorities presenting the results in an accessible web portal format. The software uses finite element stress models created in the companion software Model Wizard. The AE monitoring system that has been developed can be used with an array of up to four AE broad band sensor channels with associated signal processing. Using a flexible approach in MATLAB, the authors have developed algorithms which were used for analysing the received AE signals to extract information about the nature and location of the source. The ability to carry out source location and possibly perform real time monitoring (detecting cracking as it occurs) is attractive feature of the AE system developed for this project. The time of arrival (TOA) data was used by Integri-TechTM software to calculate source location using its own built-in algorithm, and this was verified independently using a MATLAB approach.

  8. Acoustic emission and guided ultrasonic waves for detection and continuous monitoring of cracks in light water reactor components

    SciTech Connect

    Meyer, R. M.; Coble, J.; Ramuhalli, P.; Watson, B.; Cumblidge, S. E.; Doctor, S. R.; Bond, L. J.

    2012-07-01

    Acoustic emission (AE) and guided ultrasonic waves (GUW) are considered for continuous monitoring and detection of cracks in Light Water Reactor (LWR) components. In this effort, both techniques are applied to the detection and monitoring of fatigue crack growth in a full scale pipe component. AE results indicated crack initiation and rapid growth in the pipe, and significant GUW responses were observed in response to the growth of the fatigue crack. After initiation, the crack growth was detectable with AE for approximately 20,000 cycles. Signals associated with initiation and rapid growth were distinguished based on total rate of activity and differences observed in the centroid frequency of hits. An intermediate stage between initiation and rapid growth was associated with significant energy emissions, though few hits. GUW exhibit a nearly monotonic trend with crack length with an exception of measurements obtained at crack lengths of 41 mm and 46 mm. Coupling variability and shadowing by the electro-discharge machining (EDM) starter notch set the lower limit of detectability. (authors)

  9. Normalization and source separation of acoustic emission signals for condition monitoring and fault detection of multi-cylinder diesel engines

    NASA Astrophysics Data System (ADS)

    Wu, Weiliang; Lin, Tian Ran; Tan, Andy C. C.

    2015-12-01

    A signal processing technique is presented in this paper to normalize and separate the source of non-linear acoustic emission (AE) signals of a multi-cylinder diesel engine for condition monitoring applications and fault detection. The normalization technique presented in the paper overcomes the long-existing non-linearity problem of AE sensors so that responses measured by different AE sensors can be quantitatively analysed and compared. A source separation algorithm is also developed in the paper to separate the mixture of the normalized AE signals produced by a multi-cylinder diesel engine by utilising the system parameters (i.e., wave attenuation constant and the arrival time delay) of AE wave propagation determined by a standard pencil lead break test on the engine cylinder head. It is shown that the source separation algorithm is able to separate the signal interference of adjacent cylinders from the monitored cylinder once the wave attenuation constant and the arrival time delay along the propagation path are known. The algorithm is particularly useful in the application of AE technique for condition monitoring of small-size diesel engines where signal interference from the neighbouring cylinders is strong.

  10. Magnetomechanical Acoustic Emission - A Review

    DTIC Science & Technology

    1986-09-01

    Nickel Alloys Ferromagnetic Materials LA Acoustic Emission Barkhausen noise O-A Residual Stress ’~20 ABSTWA 7- ontinue reverse ad. Ii nedceeory and...also called magneto-acoustic emission [13], or acoustic Barkhausen effect [1]. When a ferromagnetic sample is placed in an alternating magnetic field...transducer, which should be insensitive to a magnetic field, was attached to a sample. A flux sensing coil and a Barkhausen noise (BN) probe are also

  11. Acoustic emission signature analysis

    NASA Astrophysics Data System (ADS)

    Buck, O.; Pardee, J. W.

    1981-03-01

    Acoustic emission (AE) in plate glass and steel was studied as a function of angle. The low frequency AE in glass was studied in detail, and contributions from P, S, and Rayleigh waves identified. These results were isotropic, as expected theoretically. Limited high frequency (5 to 20 MHz) results were obtained in glass. The measurement of AE on transgranular crack growth in steel during fatigue crack growth was accomplished by use of a low noise manual hydraulic loading system and an electronic gate to reject grip noise. The concept of the wave momentum of an AE was elaborated and a measurement technique suggested. The theoretical study of this problem led to the discovery of an infinite family of elastic surface (Rayleigh-like) waves, and to further cylindrical, radially propagating plate waves.

  12. A new strategy toward Internet of Things: structural health monitoring using a combined fiber optic and acoustic emission wireless sensor platform

    NASA Astrophysics Data System (ADS)

    Nguyen, A. D.; Page, C.; Wilson, C. L.

    2016-04-01

    This paper investigates a new low-power structural health monitoring (SHM) strategy where fiber Bragg grating (FBG) rosettes can be used to continuously monitor for changes in a host structure's principal strain direction, suggesting damage and thus enabling the immediate triggering of a higher power acoustic emissions (AE) sensor to provide for better characterization of the damage. Unlike traditional "always on" AE platforms, this strategy has the potential for low power, while the wireless communication between different sensor types supports the Internet of Things (IoT) approach. A combination of fiber-optic sensor rosettes for strain monitoring and a fiber-optic sensor for acoustic emissions monitoring was attached to a sample and used to monitor crack initiation. The results suggest that passive principal strain direction monitoring could be used as a damage initiation trigger for other active sensing elements such as acoustic emissions. In future work, additional AE sensors can be added to provide for damage location; and a strategy where these sensors can be powered on periodically to further establish reliability while preserving an energy efficient scheme can be incorporated.

  13. Acoustic emission linear pulse holography

    SciTech Connect

    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.

  14. A Comparative Study of the Monitoring of a Self Aligning Spherical Journal using Surface Vibration, Airborne Sound and Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Raharjo, P.; Tesfa, B.; Gu, F.; Ball, A. D.

    2012-05-01

    A Self aligning spherical journal bearing is a plain bearing which has spherical surface contact that can be applied in high power industrial machinery. This type of bearing can accommodate a misalignment problem. The journal bearing faults degrade machine performance, decrease life time service and cause unexpected failure which are dangerous for safety issues. Non-intrusive measurements such as surface vibration (SV), airborne sound (AS) and acoustic emission (AE) measurement are appropriate monitoring methods for early stage journal bearing fault in low, medium and high frequency. This paper focuses on the performance comparison using SV, AS and AE measurements in monitoring a self aligning spherical journal bearing for normal and faulty (scratch) conditions. It examines the signals in the time domain and frequency domain and identifies the frequency ranges for each measurement in which significant changes are observed. The results of SV, AS and AE experiments indicate that the spectrum can be used to detect the differences between normal and faulty bearing. The statistic parameter shows that RMS value and peak value for faulty bearing is higher than normal bearing.

  15. Semi-real-time monitoring of cracking on couplings by neural network analysis of acoustic emission signals

    NASA Astrophysics Data System (ADS)

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

    2004-07-01

    This paper presents the results obtained during the development of a semi-real-time monitoring methodology based on Neural Network Pattern Recognition of Acoustic Emission (AE) signals for early detection of cracks in couplings used in aircraft and engine drive systems. AE signals were collected in order to establish a baseline of a gear-testing fixture background noise and its variations due to rotational speed and torque. Also, simulated cracking signals immersed in background noise were collected. EDM notches were machined in the driving gear and the load on the gearbox was increased until damaged was induced. Using these data, a Neural Network Signal Classifier (NNSC) was implemented and tested. The testing showed that the NNSC was capable of correctly identifying six different classes of AE signals corresponding to different gearbox operation conditions. Also, a semi-real-time classification software was implemented. This software includes functions that allow the user to view and classify AE data from a dynamic process as they are recorded at programmable time intervals. The software is capable of monitoring periodic statistics of AE data, which can be used as an indicator of damage presence and severity in a dynamic system. The semi-real-time classification software was successfully tested in situations where a delay of 10 seconds between data acquisition and classification was achieved with a hit rate of 50 hits/second per channel on eight active AE channels.

  16. Acoustical emission from bubbles

    NASA Astrophysics Data System (ADS)

    Longuet-Higgins, Michael S.

    1991-12-01

    The scientific objectives of this report are to investigate the dynamics of bubbles formed from a free surface (particularly the upper surface of the ocean) by breaking waves, and the resulting emission of underwater sound. The chief natural source of underwater sound in the ocean at frequencies from 0.5 to 50 kHz is known to be the acoustical emission from newly-formed bubbles and bubble clouds, particularly those created by breaking waves and rain. Attention has been drawn to the occurrence of high-speed jets directed into the bubble just after bubble closure. They have been observed both in rain-drop impacts and in the release of bubbles from an underwater nozzle. Qualitatively they are similar to the inward jets seen in the collapse of a cavitation bubble. There is also a similarity to the highly-accelerated upward jets in standing water waves (accelerations greater than 20g) or in bubbles bursting at a free surface. We have adopted a theoretical approach based on the dynamics of incompressible fluids with a free surface.

  17. Monitoring radio-frequency thermal ablation with ultrasound by low frequency acoustic emissions--in vitro and in vivo study.

    PubMed

    Winkler, Itai; Adam, Dan

    2011-05-01

    The object of this study was to evaluate the monitoring of thermal ablation therapy by measuring the nonlinear response to ultrasound insonation at the region being treated. Previous reports have shown that during tissue heating, microbubbles are formed. Under the application of ultrasound, these microbubbles may be driven into nonlinear motion that produces acoustic emissions at sub-harmonic frequencies and a general increase of emissions at low frequencies. These low frequency emissions may be used to monitor ablation surgery. In this study, a modified commercial ultrasound system was used for transmitting ultrasound pulses and for recording raw RF-lines from a scan plane in porcine (in vitro) and rabbit (in vivo) livers during radio-frequency ablation (RFA). The transmission pulse was 15 cycles in length at 4 MHz (in vitro) and 3.6 MHz (in vivo). Thermocouples were used for monitoring temperatures during the RFA treatment.In the in vitro experiments, recorded RF signals (A-lines) were segmented, and the total energy was measured at two different frequency bands: at a low frequency band (LFB) of 1-2.5 MHz and at the transmission frequency band (TFB) of 3.5-4.5 MHz. The mean energy at the LFB and at the TFB increased substantially in areas adjacent to the RF needle. These energies also changed abruptly at higher temperatures, thus, producing great variance in the received energy. Mean energies in areas distant from RF needle showed little change and variation during treatment. It was also shown that a 3 dB increase of energy at the low frequency band was typically obtained in regions in which temperature was above 53.3 ± 5° C. Thus, this may help in evaluating regions undergoing hyperthermia. In the in vivo experiments, an imaging algorithm based on measuring the LFB energy was used. The algorithm performs a moving average of the LFB energies measured at segments within the scan plane.Results show that a colored region is formed on the image and that it is

  18. A novel closure based approach for fatigue crack length estimation using the acoustic emission technique in structural health monitoring applications

    NASA Astrophysics Data System (ADS)

    Gagar, Daniel; Foote, Peter; Irving, Philip

    2014-10-01

    Use of Acoustic Emission (AE) for detecting and locating fatigue cracks in metallic structures is widely reported but studies investigating its potential for fatigue crack length estimation are scarce. Crack growth information enables prediction of the remaining useful life of a component using well established fracture mechanics principles. Hence, the prospects of AE for use in structural health monitoring applications would be significantly improved if it could be demonstrated not only as a means of detecting crack growth but also for estimation of crack lengths. A new method for deducing crack length has been developed based on correlations between AE signals generated during fatigue crack growth and corresponding cyclic loads. A model for crack length calculation was derived empirically using AE data generated during fatigue crack growth tests in 2 mm thick SEN aluminium 2014 T6 specimens subject to a tensile stress range of 52 MPa and an R ratio of 0.1. The model was validated using AE data generated independently in separate tests performed with a stress range of 27 MPa. The results showed that predictions of crack lengths over a range of 10 mm to 80 mm can be obtained with the mean of the normalised absolute errors ranging between 0.28 and 0.4. Predictions were also made using existing AE feature-based methods and the results compared to those obtained with the novel approach developed.

  19. Evidence of post-seismic creep type deformations derived by tilt and acoustic emission monitoring of mining induced seismic events

    NASA Astrophysics Data System (ADS)

    Milev, Alexander; Share, Pieter-Ewald; Naoi, Makoto; Durrheim, Raymond; Yabe, Yasuo; Ogasawara, Hiroshi; Nakatani, Masao

    2015-04-01

    In this study we try to understand pre- and post-failure rock behavior associated with mining induced seismic events. This involves underground installation of various high precision instruments, including geophones, acoustic emission sensors, tilt- and strain-meters at a number of sites in deep level South African gold mines. The rate of tilt, strain and the seismic ground motion were analysed in order to understand the coseismic and aseismic deformation of the rocks. A good correspondence between the coseismic and the aseismic deformations was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time, which takes place from about 19:30 until shortly before 21:00. During the blasting time and the subsequent seismic events, the coseismic tilt and strain shows a rapid increase. Much of the aseismic deformation, however, occurs independently of the seismic events and blasting. In an attempt to distinguish between the different mechanisms of tilting two types of events were recognized. The "fast" seismic events characterized with sharp increase of the tilt during the seismic rupture and "slow" seismic events characterized by creep type post seismic deformations. Tilt behaviour before and after a seismic event was also analysed. The fact that no recognizable aftertilt was observed for more of the "fast" seismic events means that there is no gradual release of stress and an associated continuous strain rate change afterwards. It can therefore be concluded that a large seismic event causes a rapid change in the state of stress rather than a gradual change in the strain rate During the monitoring period a seismic event with MW 2.2 occurred in the vicinity of the instrumented site. This event was recorded by both the CSIR integrated monitoring system and JAGUARS acoustic emission network. More than 21,000 AE aftershocks were located in the first 150 hours after the

  20. Leak detection by acoustic emissions monitoring: An experimental investigation of the acoustic properties of leaks and the attenuation characteristics of soil

    NASA Astrophysics Data System (ADS)

    Kilpatrick, James F.; March, Patrick A.

    1994-05-01

    This study experimentally explored the conditions, equipment, and methodology necessary for the acoustic detection of small leaks of jet fuel (JP4) from underground storage tank (UST) systems. The study indicates that acoustic leak detection of very small leaks is feasible. In general, significant JP4 fuel leaks which occur across a 5 PSI (pounds per square inch) or greater pressure drop are acoustically active and can be detected with proper sensors and proper placement of sensors. The primary source of leak noise is turbulent flow through the leak orifice. At lower pressures, the leak flow becomes laminar, and the leak becomes virtually silent. With direct transducer contact on the pipe or tank wall and sufficient system pressure, leaks smaller than 0.1 GPH (gallons per hour) can be detected. Larger leaks can be detected through short distances in soil. However, sand, which is the most commonly used fill material for UST systems, provides significant acoustic attenuation. Consequently, waveguides must be used when monitoring distances exceeding about 1 foot of travel through sand. Sand acts to reduce background noise levels, providing an ideal environment for acoustic leak detection using sensors mounted directly on the pipe or tank wall.

  1. 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.

  2. 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.

  3. Monitoring Fracture Propagation in a Soft Rock (Neapolitan Tuff) Using Acoustic Emissions and Digital Images

    NASA Astrophysics Data System (ADS)

    Hall, Stephen A.; Sanctis, Fiorenza De; Viggiani, Gioacchino

    2006-10-01

    Sudden and unexpected collapses of underground cavities below the city of Naples (Italy) represent a serious safety hazard. The collapses occur due to the detachment of large blocks from the cavity roofs, walls and pillars, often a long time after the original quarry excavation has been completed. It is recognised that existing discontinuities, e.g., fractures, play an important role in the failure process by inducing local stress-concentrations and reducing the overall material strength. The larger fractures, which ultimately lead to collapse occur through interaction, propagation and coalescence of these discontinuities. This paper presents recent results of experiments carried out on natural, dry specimens of Neapolitan fine-grained tuff to investigate the mechanisms involved in sample failure. A better understanding of fracture development and rock bridge behaviour is gained through a combination of AE and photographic monitoring in an experimental program considering samples with artificial pre-existing heterogeneities, which simulate the in situ discontinuities. For a range of rock bridge geometries the mechanisms and timing of different stages of the failure process are identified and characterised. The results show that, in general, a classical description of failure, for samples without artificial flaws or with only a single flaw, is followed: (1) crack closure; (2) linear stress-strain response and crack initiation with stable crack growth; (3) crack damage and unstable crack growth leading to failure. For samples with two artificial pre-existing flaws the third phase is split into two parts and failure of the sample occurs only after both the unstable propagation of external wing cracks and coalescence of the internal cracks in the bridge. In terms of the timing and duration of each phase, it is seen that phases 1 and 2 have little dependence on the flaw configuration but phase 3 seems to depend directly on this. In particular the angle in rock bridge

  4. PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

    2004-07-20

    The Portable Acoustic Monitoring Package (PAMP) has been designed to record and monitor the acoustic signal in natural gas transmission lines. In particular the three acoustic signals associated with a line leak. The system is portable ({approx}30 lbs) and is designed for line pressures up to 1000 psi. It has become apparent that cataloging of the various background acoustic signals in natural gas transmission line is very important if a system to identify leak signals is to be developed. The low-pressure (0-200 psig) laboratory test phase has been completed and a number of field trials have been conducted. Before the cataloging phase could begin, a few problems identified in field trials identified had to be corrected such as: (1) Decreased microphone sensitivity at line pressures above 250 psig. (2) The inability to deal with large data sets collected when cataloging the variety of signals in a transmission line. (3) The lack of an available online acoustic calibration system. These problems have been solved and the WVU PAMP is now fully functional over the entire pressure range found in the Natural Gas transmission lines in this region. Field portability and reliability have been greatly improved. Data collection and storage have also improved to the point were the full acoustic spectrum of acoustic signals can be accurately cataloged, recorded and described.

  5. PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)

    SciTech Connect

    John l. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-07-01

    The 1st generation acoustic monitoring package was designed to detect and analyze weak acoustic signals inside natural gas transmission lines. Besides a microphone it housed a three-inch diameter aerodynamic acoustic signal amplifier to maximize sensitivity to leak induced {Delta}p type signals. The theory and test results of this aerodynamic signal amplifier was described in the master's degree thesis of our Research Assistant Deepak Mehra who is about to graduate. To house such a large three-inch diameter sensor required the use of a steel 300-psi rated 4 inch weld neck flange, which itself weighed already 29 pounds. The completed 1st generation Acoustic Monitoring Package weighed almost 100 pounds. This was too cumbersome to mount in the field, on an access port at a pipeline shut-off valve. Therefore a 2nd generation and truly Portable Acoustic Monitor was built. It incorporated a fully self-contained {Delta}p type signal sensor, rated for line pressures up to 1000 psi with a base weight of only 6 pounds. This is the Rosemont Inc. Model 3051CD-Range 0, software driven sensor, which is believed to have industries best total performance. Its most sensitive unit was purchased with a {Delta}p range from 0 to 3 inch water. This resulted in the herein described 2nd generation: Portable Acoustic Monitoring Package (PAMP) for pipelines up to 1000 psi. Its 32-pound total weight includes an 18-volt battery. Together with a 3 pound laptop with its 4-channel data acquisition card, completes the equipment needed for field acoustic monitoring of natural gas transmission pipelines.

  6. 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.

  7. 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.

  8. Uncertainty quantification of acoustic emission filtering techniques

    NASA Astrophysics Data System (ADS)

    Zárate, Boris A.; Caicedo, Juan M.; Ziehl, Paul

    2012-04-01

    This paper compares six different filtering protocols used in Acoustic Emission (AE) monitoring of fatigue crack growth. The filtering protocols are combination of three different filtering techniques which are based on Swansong-like filters and load filters. The filters are compared deterministically and probabilistically. The deterministic comparison is based on the coefficient of determination of the resulting AE data, while the probabilistic comparison is based on the quantification of the uncertainty of the different filtering protocols. The uncertainty of the filtering protocols is quantified by calculating the entropy of the probability distribution of some AE and fracture mechanics parameters for the given filtering protocol. The methodology is useful in cases where several filtering protocols are available and there is no reason to choose one over the others. Acoustic Emission data from a compact tension specimen tested under cyclic load is used for the comparison.

  9. Non-Destructive Evaluation for Corrosion Monitoring in Concrete: A Review and Capability of Acoustic Emission Technique

    PubMed Central

    Zaki, Ahmad; Chai, Hwa Kian; Aggelis, Dimitrios G.; Alver, Ninel

    2015-01-01

    Corrosion of reinforced concrete (RC) structures has been one of the major causes of structural failure. Early detection of the corrosion process could help limit the location and the extent of necessary repairs or replacement, as well as reduce the cost associated with rehabilitation work. Non-destructive testing (NDT) methods have been found to be useful for in-situ evaluation of steel corrosion in RC, where the effect of steel corrosion and the integrity of the concrete structure can be assessed effectively. A complementary study of NDT methods for the investigation of corrosion is presented here. In this paper, acoustic emission (AE) effectively detects the corrosion of concrete structures at an early stage. The capability of the AE technique to detect corrosion occurring in real-time makes it a strong candidate for serving as an efficient NDT method, giving it an advantage over other NDT methods. PMID:26251904

  10. Non-Destructive Evaluation for Corrosion Monitoring in Concrete: A Review and Capability of Acoustic Emission Technique.

    PubMed

    Zaki, Ahmad; Chai, Hwa Kian; Aggelis, Dimitrios G; Alver, Ninel

    2015-08-05

    Corrosion of reinforced concrete (RC) structures has been one of the major causes of structural failure. Early detection of the corrosion process could help limit the location and the extent of necessary repairs or replacement, as well as reduce the cost associated with rehabilitation work. Non-destructive testing (NDT) methods have been found to be useful for in-situ evaluation of steel corrosion in RC, where the effect of steel corrosion and the integrity of the concrete structure can be assessed effectively. A complementary study of NDT methods for the investigation of corrosion is presented here. In this paper, acoustic emission (AE) effectively detects the corrosion of concrete structures at an early stage. The capability of the AE technique to detect corrosion occurring in real-time makes it a strong candidate for serving as an efficient NDT method, giving it an advantage over other NDT methods.

  11. Monitoring the integrity of the cement-metal interface of total joint components in vitro using acoustic emission and ultrasound.

    PubMed

    Davies, J P; Tse, M K; Harris, W H

    1996-08-01

    Debonding of the cement-metal interface of cemented femoral components of total hip arthroplasty has been shown from clinical and autopsy material to be a common occurrence. Experimentally, debonding has been shown to increase markedly the strains in the adjacent cement mantle. Studies of autopsy-retrieved specimens demonstrate that debonding of the cement-metal interface is a key initiating event in loosening of cemented femoral components of total hip arthroplasty. However, both the radiographic and autopsy evidence of cement-metal interfacial debonding exist after the fact, that is, after debonding has occurred. The lack of prospective data showing that debonding does indeed occur under physiologic loading and occurs prior to other forms of failure of fixation leaves uncertain the issue of debonding and its role in initiating loosening of cemented femoral components. Knowing when, where, and to what extent the cement-metal interface debonds is critical information in understanding the process of loosening of cemented femoral components. Such information would contribute to improving the durability of stems and improving cementing techniques. In this study, the two nondestructive techniques of acoustic emission and ultrasonic evaluation of the cement-metal interface of cemented femoral stems of total hip arthroplasty were combined to investigate when, where, and to what extent cement-metal debonding occurred in vitro in simulated femurs loaded physiologically in fatigue in simulated single-leg stance. Debonding of the cement-metal interface of a cemented femoral component in this model was both an initiating event and a major mechanism of compromise of the cement-metal interface. Additional acoustic emission signals arose from cracks that developed in the cement.

  12. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers.

    PubMed

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-07

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  13. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-01

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  14. Measuring acoustic emissions in an avalanche slope

    NASA Astrophysics Data System (ADS)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

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

  15. 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.

  16. Fugitive emissions monitoring trends

    SciTech Connect

    Brown, K.H.

    1997-02-01

    New Clean Air Act requirements are pushing facilities to reevaluate their monitoring programs. A description of the fugitive emission guidelines is included in this article, along with ideas about monitoring.

  17. Feasibility of detecting orthopaedic screw overtightening using acoustic emission.

    PubMed

    Pullin, Rhys; Wright, Bryan J; Kapur, Richard; McCrory, John P; Pearson, Matthew; Evans, Sam L; Crivelli, Davide

    2017-03-01

    A preliminary study of acoustic emission during orthopaedic screw fixation was performed using polyurethane foam as the bone-simulating material. Three sets of screws, a dynamic hip screw, a small fragment screw and a large fragment screw, were investigated, monitoring acoustic-emission activity during the screw tightening. In some specimens, screws were deliberately overtightened in order to investigate the feasibility of detecting the stripping torque in advance. One set of data was supported by load cell measurements to directly measure the axial load through the screw. Data showed that acoustic emission can give good indications of impending screw stripping; such indications are not available to the surgeon at the current state of the art using traditional torque measuring devices, and current practice relies on the surgeon's experience alone. The results suggest that acoustic emission may have the potential to prevent screw overtightening and bone tissue damage, eliminating one of the commonest sources of human error in such scenarios.

  18. 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.

  19. 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.

  20. Passive acoustic monitoring of bed load for fluvial applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sediment transported as bed load in streams and rivers is notoriously difficult to monitor cheaply and accurately. Passive acoustic methods are relatively simple, inexpensive, and provide spatial integration along with high temporal resolution. In 1963 work began on monitoring emissions from par...

  1. Acoustic transducer for nuclear reactor monitoring

    DOEpatents

    Ahlgren, Frederic F.; Scott, Paul F.

    1977-01-01

    A transducer to monitor a parameter and produce an acoustic signal from which the monitored parameter can be recovered. The transducer comprises a modified Galton whistle which emits a narrow band acoustic signal having a frequency dependent upon the parameter being monitored, such as the temperature of the cooling media of a nuclear reactor. Multiple locations within a reactor are monitored simultaneously by a remote acoustic receiver by providing a plurality of transducers each designed so that the acoustic signal it emits has a frequency distinct from the frequencies of signals emitted by the other transducers, whereby each signal can be unambiguously related to a particular transducer.

  2. 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.

  3. Fracture energy analysis via acoustic emission

    NASA Astrophysics Data System (ADS)

    Maslov, I. I.; Gradov, O. M.

    1986-04-01

    The results of previous studies on acoustic emission during fatigue loading are used to relate the characteristics of the acoustic signals to the fracture processes occurring at the crack tip. At stresses below the yield point of the material, discrete acoustic emissions are produced, their amplitude distribution being described by a monotonically decreasing function. At stresses near the yield point, the signals are continuous with a peak observed in the amplitude distribution function, while above the yield point the acoustic emission resumes the character it had below the yield point. It is shown that these emissions correspond to the formation of individual microfractures, to the process of macroplastic deformation and to stepwise crack propagation of the structurally disordered material, respectively.

  4. Elastic wave invariants for acoustic emission

    NASA Astrophysics Data System (ADS)

    Pardee, W. J.

    1981-07-01

    It is shown that there are four conserved properties of an elastic wave in an infinite isotropic plate: the energy, the two components of wave momentum parallel to the surface, and wave angular momentum normal to the surface. All four invariants are volume integrals of quadratic functions of the spatial (Eulerian) coordinates. The canonical energy-momentum density tensor and the orbital, spin, and total angular momentum density tensors are constructed and sufficient conditions for their conservation are demonstrated. A procedure for measuring the wave momentum of a surface wave is proposed. It is argued that these invariants are likely to be particularly useful characterizations of acoustic emission, e.g., from a growing crack. Experimental tests are proposed, and possible applications to practical monitoring problems described.

  5. 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.

  6. 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.

  7. Acoustically based fetal heart rate monitor

    NASA Technical Reports Server (NTRS)

    Baker, Donald A.; Zuckerwar, Allan J.

    1991-01-01

    The acoustically based fetal heart rate monitor permits an expectant mother to perform the fetal Non-Stress Test in her home. The potential market would include the one million U.S. pregnancies per year requiring this type of prenatal surveillance. The monitor uses polyvinylidene fluoride (PVF2) piezoelectric polymer film for the acoustic sensors, which are mounted in a seven-element array on a cummerbund. Evaluation of the sensor ouput signals utilizes a digital signal processor, which performs a linear prediction routine in real time. Clinical tests reveal that the acoustically based monitor provides Non-Stress Test records which are comparable to those obtained with a commercial ultrasonic transducer.

  8. Improve emissions monitoring

    SciTech Connect

    Vining, S.K.

    1998-01-01

    Marathon`s Texas City refinery was subject to five separate EPA regulations in addition to a state program for monitoring and repairing fugitive leaks. In this case history, the refinery sought an organizational solution that reduced monitoring costs and kept the facility fully compliant with current state and federal regulations. Equally important, the new monitoring program incorporated flexibility for future emission-reduction requirements. The paper describes the solution, regulatory background, the previous system, leak-threshold consolidation, operator ownership, and projects benefits.

  9. Acoustic Emission Health Monitoring of Fill Purge COPV's Used in Aerospace and Automotive Applications and Designed for Long Cycle Life

    NASA Technical Reports Server (NTRS)

    Waller, Jess

    2013-01-01

    Cumulative composite damage in composite pressure vessels (CPVs) currently is not monitored on-orbit. Consequently, hazards due to catastrophic burst before leak (BBL) or compromised CPV reliability cannot be ascertained or mitigated, posing a risk to crew and mission assurance. The energy associated with CPV rupture can be significant, especially with high pressure gases are under containment, and the energy releases can be severe enough to cause injury, death, loss of assets or mission. Dual-Use Rationale: CPVs similar to those used by NASA on ISS, for example, are finding increasing use in automotive and transportation industry applications. These CPVs generally have a nonload sharing liner and are repeatedly filled over their service lifetime, typically with hydrogen or compressed natural gas (CNG). The same structural health monitoring equipment and software developed by NASA WSTF for evaluating, in real-time, the health of NASA CPVs on ISS will be used to evaluate the health of automotive CPVs, the only differences being the type and design of the CPV, and the in-service lifetime pressure histories. HSF Need(s)/Performance Characteristic(s) Supported: 1) Enable on-board vehicle systems management for mission critical functions at destinations with > 3 second time delay 2) Enable autonomous nominal operations and FDIR for crewed and un-crewed systems 3) Reduce on-board crew time to sustain and manage vehicle by factor of 2x at destinations with > 6 second time delay (see Crew Autonomy sheet) 4) Reduce earth-based mission ops "back room engineering" requirements for distant mission support delay (see Mission Autonomy sheet)

  10. 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.

  11. 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.

  12. 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.

  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. Evaluation of Degradation of Ceramic Fiber Mat by Acoustic Emission

    SciTech Connect

    Ito, Kaita; Enoki, Manabu; Takahashi, Hidetomo

    2005-04-09

    Alumina-silica fiber mat is widely used as thermal insulator because of its good stability under high temperature environment. However, this material degrades gradually during long-term use under pressure and elevated temperature. In this study, cyclic compression tests of the mat were conducted and monitored acoustic emission (AE) of the mat both at room temperature and elevated temperature. The degradation of mat was evaluated by AE parameters.

  15. Evaluation of Degradation of Ceramic Fiber Mat by Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Ito, Kaita; Enoki, Manabu; Takahashi, Hidetomo

    2005-04-01

    Alumina-silica fiber mat is widely used as thermal insulator because of its good stability under high temperature environment. However, this material degrades gradually during long-term use under pressure and elevated temperature. In this study, cyclic compression tests of the mat were conducted and monitored acoustic emission (AE) of the mat both at room temperature and elevated temperature. The degradation of mat was evaluated by AE parameters.

  16. 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.

  17. Prototype acoustic resonance spectroscopy monitor

    SciTech Connect

    Sinha, D.N.; Olinger, C.T.

    1996-03-01

    This report reports on work performed for the International Atomic Energy Agency (IAEA) through the Program Office for Technical Assistance (POTAS). In this work, we investigate possible applications of nondestructive acoustics measurements to facilitate IAEA safeguards at bulk processing facilities. Two different acoustic techniques for verifying the internal structure of a processing tank were investigated. During this effort we also examined two acoustic techniques for assessing the fill level within a processing tank. The fill-level measurements could be made highly portable and have an added safeguards advantage that they can also detect stratification of fill material. This later application may be particularly useful in confirming the absence of stratification in plutonium processing tanks before accountability samples are withdrawn.

  18. Basic Information about Air Emissions Monitoring

    EPA Pesticide Factsheets

    This site is about types of air emissions monitoring and the Clean Air Act regulations, including Ambient Air Quality Monitoring, Stationary Source Emissions Monitoring, and Continuous Monitoring Systems.

  19. Surface acoustic wave dust deposition monitor

    DOEpatents

    Fasching, G.E.; Smith, N.S. Jr.

    1988-02-12

    A system is disclosed for using the attenuation of surface acoustic waves to monitor real time dust deposition rates on surfaces. The system includes a signal generator, a tone-burst generator/amplifier connected to a transmitting transducer for converting electrical signals into acoustic waves. These waves are transmitted through a path defining means adjacent to a layer of dust and then, in turn, transmitted to a receiving transducer for changing the attenuated acoustic wave to electrical signals. The signals representing the attenuated acoustic waves may be amplified and used in a means for analyzing the output signals to produce an output indicative of the dust deposition rates and/or values of dust in the layer. 8 figs.

  20. Results of acoustic emission tests on Halon fire bottles

    SciTech Connect

    Beattie, A.G.; Shurtleff, W.W.

    1996-10-01

    An acoustic emission tester for aircraft Halon bottles has been developed. The necessary load is applied by heating the bottles. Acoustic emission is monitored during the heating by six sensors held in position by a special fixture. This fixture was designed to fit spheres with diameters between 5 and 16 inches. A prototype has been undergoing testing in two commercial Halon bottle repair and test facilities. Results to date indicate that about 97 percent of the bottles tested show no indications of any flaws. The other three percent have had indications of flaws in non-critical areas of the bottles. All bottles tested to date have passed the hydrostatic test required by the Department of Transportation (DOT).

  1. 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.

  2. Air Emissions Monitoring for Permits

    EPA Pesticide Factsheets

    Operating permits document how air pollution sources will demonstrate compliance with emission limits and also how air pollution sources will monitor, either periodically or continuously, their compliance with emission limits and all other requirements.

  3. 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.

  4. Acoustic emission evaluation of reinforced concrete bridge beam with graphite composite laminate

    NASA Astrophysics Data System (ADS)

    Johnson, Dan E.; Shen, H. Warren; Finlayson, Richard D.

    2001-07-01

    A test was recently conducted on August 1, 2000 at the FHwA Non-Destructive Evaluation Validation Center, sponsored by The New York State DOT, to evaluate a graphite composite laminate as an effective form of retrofit for reinforced concrete bridge beam. One portion of this testing utilized Acoustic Emission Monitoring for Evaluation of the beam under test. Loading was applied to this beam using a two-point loading scheme at FHwA's facility. This load was applied in several incremental loadings until the failure of the graphite composite laminate took place. Each loading culminated by either visual crack location or large audible emissions from the beam. Between tests external cracks were located visually and highlighted and the graphite epoxy was checked for delamination. Acoustic Emission data was collected to locate cracking areas of the structure during the loading cycles. To collect this Acoustic Emission data, FHwA and NYSDOT utilized a Local Area Monitor, an Acoustic Emission instrument developed in a cooperative effort between FHwA and Physical Acoustics Corporation. Eight Acoustic Emission sensors were attached to the structure, with four on each side, in a symmetrical fashion. As testing progressed and culminated with beam failure, Acoustic Emission data was gathered and correlated against time and test load. This paper will discuss the analysis of this test data.

  5. 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

  6. 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.

  7. Acoustic Techniques for Structural Health Monitoring

    NASA Astrophysics Data System (ADS)

    Frankenstein, B.; Augustin, J.; Hentschel, D.; Schubert, F.; Köhler, B.; Meyendorf, N.

    2008-02-01

    Future safety and maintenance strategies for industrial components and vehicles are based on combinations of monitoring systems that are permanently attached to or embedded in the structure, and periodic inspections. The latter belongs to conventional nondestructive evaluation (NDE) and can be enhanced or partially replaced by structural health monitoring systems. However, the main benefit of this technology for the future will consist of systems that can be differently designed based on improved safety philosophies, including continuous monitoring. This approach will increase the efficiency of inspection procedures at reduced inspection times. The Fraunhofer IZFP Dresden Branch has developed network nodes, miniaturized transmitter and receiver systems for active and passive acoustical techniques and sensor systems that can be attached to or embedded into components or structures. These systems have been used to demonstrate intelligent sensor networks for the monitoring of aerospace structures, railway systems, wind energy generators, piping system and other components. Material discontinuities and flaws have been detected and monitored during full scale fatigue testing. This paper will discuss opportunities and future trends in nondestructive evaluation and health monitoring based on new sensor principles and advanced microelectronics. It will outline various application examples of monitoring systems based on acoustic techniques and will indicate further needs for research and development.

  8. 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.

  9. 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.

  10. Acoustic Emission from the Aluminium Alloy 7050.

    DTIC Science & Technology

    1979-10-01

    thick-section applications, has good stress - corrosion resistance, and is now being used in airframe construction. In this report, we present our AE...160.00 1S0.00 200.90 2SO.I9 TIMlE (sec) Fig. 8 Count-rate/time and nominal- stress /time curves for 7050 C-specimen (a) and 0-speimen lb). CO 0 CC 0T LLQ...A094 38" AERONAUTICAL RESEARCH LABS MELBOURNE (AUSTRALIA) F/6 11/6 ACOUSTIC EMISSION FROM THE ALUMINIUM ALLOY 7050 .(U) OCT 79 S M COUSLAND, C M SCALA

  11. 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.

  12. 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.

  13. Study of acoustic emission during mechanical tests of large flight weight tank structure

    NASA Technical Reports Server (NTRS)

    Mccauley, B. O.; Nakamura, Y.; Veach, C. L.

    1973-01-01

    A PPO-insulated, flight-weight, subscale, aluminum tank was monitored for acoustic emissions during a proof test and during 100 cycles of environmental test simulating space flights. The use of a combination of frequency filtering and appropriate spatial filtering to reduce background noise was found to be sufficient to detect acoustic emission signals of relatively small intensity expected from subcritical crack growth in the structure. Several emission source locations were identified, including the one where a flaw was detected by post-test x-ray inspections. For most source locations, however, post-test inspections did not detect flaws; this was partially attributed to the higher sensitivity of the acoustic emission technique than any other currently available NDT method for detecting flaws. For these non-verifiable emission sources, a problem still remains in correctly interpreting observed emission signals.

  14. Acoustic Emission Arising from Plastic Deformation and Fracture.

    DTIC Science & Technology

    1980-05-01

    Acoustic Emission Generation and deEection Li..I Acoustic Emission Theory Plastic Deformation Lm. Fracture 20. ABSTRACT (Continue orn reverse side it...deformation and fracture. Recent developments in quantitative signal detection and trans- ducer characterization are considered. Several theories of acoustic...emis- sion sources are summarized and one based on dislocation theory by M91en and Bolin is extended to provide a relation between the inelastic

  15. Acoustic Emission Based Surveillance System for Prediction of Stress Fractures

    DTIC Science & Technology

    2007-09-01

    withstand irrigation. The transducers were mounted on the specimen using cyanoacrylate glue . The acoustic emission signal from the transducers was...respectively. An acoustic emission transducer (Pico, PAC, NJ) was mounted at the mid-span of the specimens using cyanoacrylate glue . Signal from the

  16. Particle filtering based structural assessment with acoustic emission sensing

    NASA Astrophysics Data System (ADS)

    Yan, Wuzhao; Abdelrahman, Marwa; Zhang, Bin; Ziehl, Paul

    2017-02-01

    Nuclear structures are designed to withstand severe loading events under various stresses. Over time, aging of structural systems constructed with concrete and steel will occur. This deterioration may reduce service life of nuclear facilities and/or lead to unnecessary or untimely repairs. Therefore, online monitoring of structures in nuclear power plants and waste storage has drawn significant attention in recent years. Of many existing non-destructive evaluation and structural monitoring approaches, acoustic emission is promising for assessment of structural damage because it is non-intrusive and is sensitive to corrosion and crack growth in reinforced concrete elements. To provide a rapid, actionable, and graphical means for interpretation Intensity Analysis plots have been developed. This approach provides a means for classification of damage. Since the acoustic emission measurement is only an indirect indicator of structural damage, potentially corrupted by non-genuine data, it is more suitable to estimate the states of corrosion and cracking in a Bayesian estimation framework. In this paper, we will utilize the accelerated corrosion data from a specimen at the University of South Carolina to develop a particle filtering-based diagnosis and prognosis algorithm. Promising features of the proposed algorithm are described in terms of corrosion state estimation and prediction of degradation over time to a predefined threshold.

  17. Multipurpose Acoustic Sensor for Downhole Fluid Monitoring

    SciTech Connect

    Pantea, Cristian

    2012-05-04

    The projects objectives and purpose are to: (1) development a multipurpose acoustic sensor for downhole fluid monitoring in Enhanced Geothermal Systems (EGS) reservoirs over typical ranges of pressures and temperatures and demonstrate its capabilities and performance for different EGS systems; (2) determine in real-time and in a single sensor package several parameters - temperature, pressure, fluid flow and fluid properties; (3) needed in nearly every phase of an EGS project, including Testing of Injection and Production Wells, Reservoir Validation, Inter-well Connectivity, Reservoir Scale Up and Reservoir Sustainability. (4) Current sensors are limited to operating at lower temperatures, but the need is for logging at high temperatures. The present project deals with the development of a novel acoustic-based sensor that can work at temperatures up to 374 C, in inhospitable environments.

  18. 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.

  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. 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.

  2. Acoustic emissions during deformation of intact and jointed welded tuff

    NASA Astrophysics Data System (ADS)

    Holcomb, D. J.; Teufel, L. W.

    1982-07-01

    Monitoring of acoustic emissions (AE) has been widely used as a means of detecting failure in intact rock. For intact rock the technique is simple, because an increasing rate of AE is usually a sign of impending failure. However, most large rock masses contain numerous joints and the behavior of the joints controls the properties of the rock mass In particular, the failure mode often becomes stable or unstable slip (stick-slip) on a joint at stresses well below those required for failure of the intact rock. As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on intact and artificially jointed samples of Grouse Canyon tuff. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates.

  3. Correlating Inertial Acoustic Cavitation Emissions with Material Erosion Resistance

    NASA Astrophysics Data System (ADS)

    Ibanez, I.; Hodnett, M.; Zeqiri, B.; Frota, M. N.

    The standard ASTM G32-10 concerns the hydrodynamic cavitation erosion resistance of materials by subjecting them to acoustic cavitation generated by a sonotrode. The work reported extends this technique by detecting and monitoring the ultrasonic cavitation, considered responsible for the erosion process, specifically for coupons of aluminium-bronze alloy. The study uses a 65 mm diameter variant of NPL's cavitation sensor, which detects broadband acoustic emissions, and logs acoustic signals generated in the MHz frequency range, using NPL's Cavimeter. Cavitation readings were made throughout the exposure duration, which was carried out at discrete intervals (900 to 3600 s), allowing periodic mass measurements to be made to assess erosion loss under a strict protocol. Cavitation measurements and erosion were compared for different separations of the sonotrode tip from the material under test. The maximum variation associated with measurement of cavitation level was between 2.2% and 3.3% when the separation (λ) between the transducer horn and the specimen increased from 0.5 to 1.0 mm, for a transducer (sonotrode) displacement amplitude of 43.5 μm. Experiments conducted at the same transducer displacement amplitude show that the mass loss of the specimen -a measure of erosion- was 67.0 mg (λ = 0.5 mm) and 66.0 mg (λ = 1.0 mm).

  4. 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.

  5. Acoustic emission monitoring in Cooke 4 gold mine in South Africa -summary of the main findings of a 5-year SATREPS project-

    NASA Astrophysics Data System (ADS)

    Naoi, M.; Nakatani, M.; Moriya, H.; Otsuki, K.; Kgarume, T.; Philipp, J.; Murakami, O.; Masakale, T.; Ribeiro, L.; Yabe, Y.; Kawakata, H.; Ward, A.; Durrheim, R.; Ogasawara, H.

    2015-12-01

    We deployed a network targeting acoustic emissions (AEs) down to Mw~ -5 at 1-km depth in the Cooke 4 mine in South Africa as a part of a 5-year project called "Observational Studies in South African Mines to Mitigate Seismic Risks." This network of 30 sensors spans ~100 m, and collected waveform data for more than 4.5-million triggers in 5 years. We provide an overview of the main findings. 1) Naoi et al. (2015; Pageoph) reported that 90% of observed AEs aggregated along the advancing mining front. Their size distribution obeyed the Gutenberg-Richter law down to Mw -4, and their b-values were invariant with time from blasting, contradicting a previous study. 2) Moriya et al. (under review) showed that this AE aggregation consists of several tabular clusters, which were formed regularly as the mining front advanced. Although large earthquakes (Mw > 1) were not found, the clusters likely represent the preparation process of large shear fracture events because their geometry resembles large shear fractures, known by in-situ wall-rock observation, which formed concurrently with large seismic events. 3) Naoi et al. (2015; Tectonophysics) reported that the remaining 10% of AEs exhibit very sharp, planar distributions, with high b-values. They are likely events located on pre-existing geological faults loaded by mining-induced stresses. Such on-fault events are rare for intraplate faults, where microseismic events generally occur in the surrounding region. 4) Naoi et al. (2015; JGR) found planar clusters that newly emerged ahead of a mining front and gradually expanded to 20 m. They likely represent the evolution of a slow-slip patch on a pre-existing fault. The b-value of those AEs decreased drastically from 2.5 to 1.5, consistent with stress buildup by the approaching mining front. This project is supported by JST/JICA, SATREPS, JSPS KAKENHI Grant Numbers 21224012, 21246134, 26249137, 26887022, and MEXT's Earthquake and Volcano Hazards Observation and Research Program.

  6. 40 CFR 61.68 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 9 2013-07-01 2013-07-01 false Emission monitoring. 61.68 Section 61...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Vinyl Chloride § 61.68 Emission monitoring. (a) A vinyl chloride monitoring system is to be used to monitor on...

  7. 40 CFR 61.68 - Emission monitoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 8 2011-07-01 2011-07-01 false Emission monitoring. 61.68 Section 61...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Vinyl Chloride § 61.68 Emission monitoring. (a) A vinyl chloride monitoring system is to be used to monitor on...

  8. 40 CFR 61.68 - Emission monitoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 9 2014-07-01 2014-07-01 false Emission monitoring. 61.68 Section 61...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Vinyl Chloride § 61.68 Emission monitoring. (a) A vinyl chloride monitoring system is to be used to monitor on...

  9. 40 CFR 61.68 - Emission monitoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 9 2012-07-01 2012-07-01 false Emission monitoring. 61.68 Section 61...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Vinyl Chloride § 61.68 Emission monitoring. (a) A vinyl chloride monitoring system is to be used to monitor on...

  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. Sensitivity enhancement of fiber optic FBG sensor for acoustic emission

    NASA Astrophysics Data System (ADS)

    Seo, Dae-Cheol; Yoon, Dong-Jin; Kwon, Il-Bum; Lee, Seung-Suk

    2009-03-01

    A fiber optic Bragg grating based acoustic emission sensor system is developed to provide on-line monitoring of cracks or leaks in reactor vessel head penetration of nuclear power plants. Various type of fiber Bragg grating sensor including the variable length of sensing part was fabricated and prototype sensor system was tested by using PZT pulser and pencil lead break sources. In this study, we developed a cantilever type fiber sensor to enhance the sensitivity and to resonant frequency control. Two types of sensor attachment were used. First, the fiber Bragg grating sensor was fully bonded to the surface using bonding agent. Second one is that one part of fiber was partially bonded to surface and the other part of fiber will be remained freely. The resonant frequency of the fiber Bragg grating sensor will depend on the length of sensing part. Various kinds of resonant type fiber Bragg grating acoustic emission sensors were developed. Also several efforts were done to enhance the sensitivity of FBG AE sensor, which include FBG spectrum optimization and electrical and optical noise reduction. Finally, based on the self-developed acquisition system, a series of tests demonstrate the ability of the developed fiber sensor system to detect a pencil lead break event and continuous leak signal.

  12. 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.

  13. Acoustic Emission During Heating of Granitoids

    NASA Astrophysics Data System (ADS)

    Nasimov, R. M.; Diaur, N. I.; Petrov, V. A.; Poluektov, V. V.

    Studies of acoustic emission (AE) activity (A) during heating of cubic (20x20x20 mm) samples of granitoids (gneisses, adamellites, leucogranites, tonalites, monzodi- orites and quartz diorites) collected from two wells within the Nizhnekansky granitoid massif were carried out. The investigation was made in connection with the problem to design and construct an underground facility for long-term storage of radioactive waste. All samples were heated with the same rate in two consecutive cycles (heating- cooling). Maximum temperatures were 125-130 C in first cycle and 250-260 C in the second one. The observation was carried out at ultrasonic range 0.2-2 MHz. Acous- tic events threshold crossing fixed level in amplitude were accumulated in computer using special interface card and software. The acoustic events exceeded the threshold were ignored as a negligible. Maximum accumulated number in first cycle was 50-500 while in second one was until 15000. Using accumulative curve (N-T) under heating and cooling the maximum and average values of an activity (A = dN/dt, where t is time) were calculated. Analysis of obtained data indicated that determinate tempera- ture of AE activation was existed for every rock group and after that the activity had significant increase. Generally in second cycle this temperature had greater value. It was found that accumulative curve N-T had two evolution stages, they were linear and exponential growths due to temperature. The obtained N and A data were analyzed simultaneously with VP data before and after heating in the same samples in both cycles. By means of high resolution computer scanning of sample surfaces a growth of number visible fractures was observed as a result of heating. Analysis of mineral composition and texture of rock samples was made as well. Ternary diagrams (% pla- gioclase content - % potash feldspar content - number of AE events under heating) were analyzed.

  14. Acoustic emission of retrofitted fiber-wrapped columns

    NASA Astrophysics Data System (ADS)

    El Echary, Hazem; Mirmiran, Amir

    1998-03-01

    In recent years, fiber-wrapping technique has become increasingly popular for retrofitting of existing bridge pier columns in seismic zones. By the way of confinement, the external jacket enhances strength, ductility and shear performance of the column. However, since state of the concrete core is not visible from outside of the jacket, it is of great necessity to develop proper non-destructive methods to evaluate structural integrity of the column. Extensive research on FRP-confined concrete at the University of Central Florida has shown that failure of such hybrid columns is often accompanied by considerable audible and sub-audible noise, making acoustic emission (AE) a viable NDE technique for retrofitted columns. Acoustic emission from fiber-wrapped concrete specimens were monitored. A total of 24 concrete specimens with two types of construction (bonded and unbonded) and four different number of layers (1, 3, 5 and 7) were tested under uniaxial compression. All specimens were made of S-glass fabric and polyester resin with a core diameter of 6' and a length of 12'. Some of the specimens were subjected to cycles of loading and unloading to examine the presence of the Kaiser and the Felicity effects. A 4-channel AEDSP-32/16 (Mistras-2001) machine from Physical Acoustics Corp. was used for the experiments. Results indicate that AE energy and the number of AE counts can both be good representatives for the response of confined concrete. Further, plots of AE energy versus load follows the same bilinear trend that has been observed in the stress-strain response of such specimens. Finally, Felicity effect was observed in all composite specimens.

  15. Introducing passive acoustic filter in acoustic based condition monitoring: Motor bike piston-bore fault identification

    NASA Astrophysics Data System (ADS)

    Jena, D. P.; Panigrahi, S. N.

    2016-03-01

    Requirement of designing a sophisticated digital band-pass filter in acoustic based condition monitoring has been eliminated by introducing a passive acoustic filter in the present work. So far, no one has attempted to explore the possibility of implementing passive acoustic filters in acoustic based condition monitoring as a pre-conditioner. In order to enhance the acoustic based condition monitoring, a passive acoustic band-pass filter has been designed and deployed. Towards achieving an efficient band-pass acoustic filter, a generalized design methodology has been proposed to design and optimize the desired acoustic filter using multiple filter components in series. An appropriate objective function has been identified for genetic algorithm (GA) based optimization technique with multiple design constraints. In addition, the sturdiness of the proposed method has been demonstrated in designing a band-pass filter by using an n-branch Quincke tube, a high pass filter and multiple Helmholtz resonators. The performance of the designed acoustic band-pass filter has been shown by investigating the piston-bore defect of a motor-bike using engine noise signature. On the introducing a passive acoustic filter in acoustic based condition monitoring reveals the enhancement in machine learning based fault identification practice significantly. This is also a first attempt of its own kind.

  16. Beaked Whale Group Deep Dive Behavior from Passive Acoustic Monitoring

    DTIC Science & Technology

    2015-09-30

    Acoustic Monitoring Len Thomas, Tiago Marques Centre for Research into Ecological and Environmental Modelling University of St Andrews The...is to provide novel information on beaked whale group foraging dive behavior using Passive Acoustic Monitoring (PAM) at the Atlantic Undersea Test...method capable of utilizing passive acoustic data from the hydrophone array at AUTEC to track individual clicking beaked whales within group deep

  17. The effect of contralateral acoustic stimulation on spontaneous otoacoustic emissions.

    PubMed

    Zhao, Wei; Dhar, Sumitrajit

    2010-03-01

    Evoked otoacoustic emissions are often used to study the medial olivocochlear (MOC) efferents in humans. There has been concern that the emission-evoking stimulus may itself elicit efferent activity and alter the evoked otoacoustic emission. Spontaneous otoacoustic emissions (SOAEs) are hence advantageous as no external stimulation is necessary to record the response in the test ear. Contralateral acoustic stimulation (CAS) has been shown to suppress SOAE level and elevate SOAE frequency, but the time course of these effects is largely unknown. By utilizing the Choi-Williams distribution, here we report a gradual adaptation during the presence of CAS and an overshoot following CAS offset in both SOAE magnitude and frequency from six normal-hearing female human subjects. Furthermore, we have quantified the time constants of both magnitude and frequency shifts at the onset, presence, and offset of four levels of CAS. Most studies using contralateral elicitors do not stringently control the middle-ear muscle (MEM) reflex, leaving the results difficult to interpret. In addition to clinically available measures of the MEM reflex, we have incorporated a sensitive laboratory technique to monitor the MEM reflex in our subjects, allowing us to interpret the results with greater confidence.

  18. Development of acoustic health monitoring for railroad tank cars

    NASA Astrophysics Data System (ADS)

    Gostautas, Richard; Finlayson, Richard; Godinez, Valery; Pollock, Adrian; Penya, Jose

    2005-05-01

    This paper presents the research and development of an Acoustic Health Monitoring (AHM) system that uses Guided Lamb Wave (GLW) technology to determine the thickness of railroad tank car shells for identification of wall loss due to corrosion. In recent regulatory changes, the emphasis has shifted from the traditional hydrotest to more modern methods for assuring tank car integrity. The new generation of maintenance programs will rely heavily on nondestructive testing, and will use damage tolerance concepts and risk analysis to establish inspection frequencies and items to inspect. It is the responsibility of the owners to set up experience-based maintenance programs that are suitable for the working conditions of their own particular fleets. Development of an ideal AHM system for railroad cars would be an instrument that incorporates Acoustic Emission (AE) and GLW technology. The combination of active and passive acoustic technologies integrated into a single system would be a highly efficient means of determining the structural integrity of tank cars. The integration of the GLW technology will allow identification of corrosion wall loss in a zone between two sensors, rather than at a single point (traditional ultrasonic thickness measurements). Thus, a much larger area of the structure can be inspected for approximately the same inspection cost. With a suitable integration of this new technology into the overall inspection and corrosion management program, the fleet can be more efficiently maintained and the risk of accidental release through progressive corrosion damage can be significantly reduced.

  19. Dynamic ultrasonic contact detection using acoustic emissions.

    PubMed

    Turner, S L; Rabani, A; Axinte, D A; King, C W

    2014-03-01

    For a non-contact ultrasonic material removal process, the control of the standoff position can be crucial to process performance; particularly where the requirement is for a standoff of the order of <20 μm. The standoff distance relative to the surface to be machined can be set by first contacting the ultrasonic tool tip with the surface and then withdrawing the tool to the required position. Determination of this contact point in a dynamic system at ultrasonic frequencies (>20 kHz) is achieved by force measurement or by detection of acoustic emissions (AE). However, where detection of distance from a surface must be determined without contact taking place, an alternative method must be sought. In this paper, the effect of distance from contact of an ultrasonic tool is measured by detection of AE through the workpiece. At the point of contact, the amplitude of the signal at the fundamental frequency increases significantly, but the strength of the 2nd and 3rd harmonic signals increases more markedly. Closer examination of these harmonics shows that an increase in their intensities can be observed in the 10 μm prior to contact, providing a mechanism to detect near contact (<10 μm) without the need to first contact the surface in order to set a standoff.

  20. Acoustic Emission Analysis of Prestressed Concrete Structures

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  1. 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.

  2. 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.

  3. Modern acoustic emission technique and its application in aviation industry.

    PubMed

    Geng, Rongsheng

    2006-12-22

    This paper proposes the concept of modern acoustic emission (MAE) technique and describes its application in aviation industry. Modern AE is characterized by the combination of AE parameter and waveform analysis based on the understanding of AE source mechanism, the property of sound wave propagation and the interaction between sound wave and the medium in which the sound wave is propagating. Another feature of MAE is characterized by the application of so-called fully digital AE apparatus with low noise, high speed of data transmission and accurate AE source locating capability. MAE is merely an imagination without the realization of the advanced fully digital AE instrument. The application of MAE in monitoring the conditions of aircraft structures during a fatigue test was taken as an example for showing the important role played by AE. Roles of AE in the evaluation of (environment-related) corrosion damage of aircraft were also presented.

  4. Fatigue crack localization with near-field acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Zhou, Changjiang; Zhang, Yunfeng

    2013-04-01

    This paper presents an AE source localization technique using near-field acoustic emission (AE) signals induced by crack growth and propagation. The proposed AE source localization technique is based on the phase difference in the AE signals measured by two identical AE sensing elements spaced apart at a pre-specified distance. This phase difference results in canceling-out of certain frequency contents of signals, which can be related to AE source direction. Experimental data from simulated AE source such as pencil breaks was used along with analytical results from moment tensor analysis. It is observed that the theoretical predictions, numerical simulations and the experimental test results are in good agreement. Real data from field monitoring of an existing fatigue crack on a bridge was also used to test this system. Results show that the proposed method is fairly effective in determining the AE source direction in thick plates commonly encountered in civil engineering structures.

  5. 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.

  6. Inverse problem of the acoustic emission diagnostics of materials

    NASA Astrophysics Data System (ADS)

    Abramov, O. V.; Gradov, O. M.; Iudin, M. I.

    1988-12-01

    The acoustic emission of an inclusion in an infinite medium is analyzed. For an inclusion of general form, expressions for density and transverse and longitudinal waves in the inclusion material are obtained, as are equations for the inclusion surface. Attention is given to several particular cases of inclusions of simple shape (spherical and ellipsoidal), whose parameters are determined from the spectral characteristics of the acoustic emission signal.

  7. 40 CFR 60.73 - Emission monitoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Emission monitoring. 60.73 Section 60... Emission monitoring. (a) The source owner or operator shall install, calibrate, maintain, and operate a... measuring emissions with the continuous monitoring system concurrent with measuring emissions with...

  8. 40 CFR 60.73 - Emission monitoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 7 2014-07-01 2014-07-01 false Emission monitoring. 60.73 Section 60... Emission monitoring. (a) The source owner or operator shall install, calibrate, maintain, and operate a... measuring emissions with the continuous monitoring system concurrent with measuring emissions with...

  9. 40 CFR 60.73 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Emission monitoring. 60.73 Section 60... Emission monitoring. (a) The source owner or operator shall install, calibrate, maintain, and operate a... measuring emissions with the continuous monitoring system concurrent with measuring emissions with...

  10. 40 CFR 60.73 - Emission monitoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 7 2012-07-01 2012-07-01 false Emission monitoring. 60.73 Section 60... Emission monitoring. (a) The source owner or operator shall install, calibrate, maintain, and operate a... measuring emissions with the continuous monitoring system concurrent with measuring emissions with...

  11. 40 CFR 60.73 - Emission monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Emission monitoring. 60.73 Section 60... Emission monitoring. (a) The source owner or operator shall install, calibrate, maintain, and operate a... measuring emissions with the continuous monitoring system concurrent with measuring emissions with...

  12. 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.

  13. Continuous emission monitor for incinerators

    SciTech Connect

    Demirgian, J.

    1992-01-01

    This paper describes the development of Fourier transform infrared (FTIR) spectroscopy to continuous monitoring of incinerator emissions. Fourier transform infrared spectroscopy is well suited to this application because it can identify and quantify selected target analytes in a complex mixture without first separating the components in the mixture. Currently, there is no on-stream method to determine the destruction of hazardous substances, such as benzene, or to continuously monitor for hazardous products of incomplete combustion (PICs) in incinerator exhaust emissions. This capability is especially important because of Federal regulations in the Clean Air Act of 1990, which requires the monitoring of air toxics (Title III), the Resource Conservation and Recovery Act (RCRA), and the Toxic Substances Control Act (TSCA). An on-stream continuous emission monitor (CEM) that can differentiate species in the ppm and ppb range and can calculate the destruction and removal efficiency (DRE) could be used to determine the safety and reliability of incinerators. This information can be used to address reasonable public concern about incinerator safety and aid in the permitting process.

  14. Continuous emission monitor for incinerators

    SciTech Connect

    Demirgian, J.

    1992-07-01

    This paper describes the development of Fourier transform infrared (FTIR) spectroscopy to continuous monitoring of incinerator emissions. Fourier transform infrared spectroscopy is well suited to this application because it can identify and quantify selected target analytes in a complex mixture without first separating the components in the mixture. Currently, there is no on-stream method to determine the destruction of hazardous substances, such as benzene, or to continuously monitor for hazardous products of incomplete combustion (PICs) in incinerator exhaust emissions. This capability is especially important because of Federal regulations in the Clean Air Act of 1990, which requires the monitoring of air toxics (Title III), the Resource Conservation and Recovery Act (RCRA), and the Toxic Substances Control Act (TSCA). An on-stream continuous emission monitor (CEM) that can differentiate species in the ppm and ppb range and can calculate the destruction and removal efficiency (DRE) could be used to determine the safety and reliability of incinerators. This information can be used to address reasonable public concern about incinerator safety and aid in the permitting process.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. Acoustic Monitoring of the Arctic Ice Cap

    NASA Astrophysics Data System (ADS)

    Porter, D. L.; Goemmer, S. A.; Chayes, D. N.

    2012-12-01

    Introduction The monitoring of the Arctic Ice Cap is important economically, tactically, and strategically. In the scenario of ice cap retreat, new paths of commerce open, e.g. waterways from Northern Europe to the Far East. Where ship-going commerce is conducted, the U.S. Navy and U.S. Coast Guard have always stood guard and been prepared to assist from acts of nature and of man. It is imperative that in addition to measuring the ice from satellites, e.g. Icesat, that we have an ability to measure the ice extent, its thickness, and roughness. These parameters play an important part in the modeling of the ice and the processes that control its growth or shrinking and its thickness. The proposed system consists of three subsystems. The first subsystem is an acoustic source, the second is an array of geophones and the third is a system to supply energy and transmit the results back to the analysis laboratory. The subsystems are described below. We conclude with a plan on how to tackle this project and the payoff to the ice cap modeler and hence the users, i.e. commerce and defense. System Two historically tested methods to generate a large amplitude multi-frequency sound source include explosives and air guns. A new method developed and tested by the University of Texas, ARL is a combustive Sound Source [Wilson, et al., 1995]. The combustive sound source is a submerged combustion chamber that is filled with the byproducts of the electrolysis of sea water, i.e. Hydrogen and Oxygen, an explosive mixture which is ignited via a spark. Thus, no additional compressors, gases, or explosives need to be transported to the Arctic to generate an acoustic pulse capable of the sediment and the ice. The second subsystem would be geophones capable of listening in the O(10 Hz) range and transmitting that data back to the laboratory. Thus two single arrays of geophones arranged orthogonal to each other with a range of 1000's of kilometers and a combustive sound source where the two

  20. Acoustic emission in orthopaedics: A state of the art review.

    PubMed

    Kapur, Richard A

    2016-12-08

    Acoustic emission (AE) is the phenomenon of sonic and ultrasonic wave generation by materials as they undergo deformation and fracture processes. AE monitoring is widely used throughout civil and mechanical engineering as a highly sensitive and non-destructive technique for structural health monitoring. Advances in computational power and digital data storage have generated much further interest in the possible applications of AE technology. Of particular interest has been its application within the field of Orthopaedic surgery. This paper examines the current literature surrounding the use of AE technology within Orthopaedics and provides a comprehensive overview of its current applications within Orthopaedic surgery. The use of AE technology in Orthopaedics is wide ranging and is discussed under the themes of: the study of the biomechanical properties of bone and fracture mechanics, research into failure mechanisms associated with cemented implants, prosthetic design, diagnostic value of AE and clinical application. AE technology is of great benefit as an Orthopaedic research tool where AE counts can be used to provide a surrogate marker for damage accumulation and flaws can be monitored as they develop. More recently there has been increased interest in the possible clinical applications of AE technology and an appreciation of the potential benefits for the diagnosis and treatment of Orthopaedic pathology. Despite the challenges involved when adopting AE techniques in vivo the potential of AE technology within Orthopaedics is significant. Already widely used in the research setting, clinical application has shown enormous potential and is a rapidly expanding area of contemporary research.

  1. Interferometer Detects Acoustic Emissions in Composites

    NASA Technical Reports Server (NTRS)

    Cantrell, J. H.; Clause, R. O.; Wade, J. C.; Zerwekh, P. S.

    1985-01-01

    Embedded single-mode optical fibers sample internal-stress fields directly. Statically loaded composite matrix emits pulsed ultrasonic waves which mechanically modulate embedded fiber and phase-modulate transmitted optical field. Modulation detected by optical interferometry and Fourier optical processing converted to electronic signal proportional to acoustic field amplitude integated along length of fiber embedded in specimen. Technique used for measurements of both high- and low-frequency CW acoustic fields as well as high-frequency transients.

  2. 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.

  3. 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.

  4. Electromagnetic acoustic transducers (EMATs) for erosion monitoring

    SciTech Connect

    Reimann, K.J.

    1984-05-01

    Early detection, measurement, and monitoring of erosive wear rates can alleviate problems of unpredictable shutdowns, costly downtimes, and improper process operation. The first generation of a nondestructive, noninvasive acoustic-based system was tested on pressure boundaries of fossil energy conversion plants, yielding the desired information. Multiple transducers and wave guides are needed for such a system in order to determine wear profiles in large components. The same information could, however, be obtained with a single, scanning electromagnetic transducer (EMAT). Advantages of such EMAT-based systems motivated this investigation in order to establish criteria and requirements needed for erosion monitoring at elevated (operating) temperatures. The effort concentrated on three areas: (a) development of EMAT design parameters, (b) material-EMAT interaction, and (c) signal processing. Prototype horizontal shearwave EMATs, based on design parameters selected from computer calculations of the static field, were evaluated, and their performance was compared to the performance of piezoelectric transducers. Input power requirements for a larger than 10-dB signal-to-noise (S/N) ratio were established for various structural and hardfacing materials. Effects of surface roughness and temperature were determined for different test conditions. The results indicate that accurate wall thickness measurement can be performed at elevated temperature on rough surfaces as encountered, for instance, in a cyclone. Modern data processing such as signal averaging on correlation improves the S/N ratio from 12 dB to 26 dB and enables wall thickness measurements with an accuracy of +-0.25% of total wall thickness. Additional efforts are needed to determine requirements of EMATs in scanning mode and pulsed static field operation.

  5. 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.

  6. 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.

  7. 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.

  8. 40 CFR 61.183 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic Arsenic Emissions From Arsenic Trioxide and Metallic Arsenic Production Facilities § 61.183 Emission monitoring. (a... arsenic trioxide and metallic arsenic process emission stream that exits from a control device. (b)...

  9. 40 CFR 61.183 - Emission monitoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic Arsenic Emissions From Arsenic Trioxide and Metallic Arsenic Production Facilities § 61.183 Emission monitoring. (a... arsenic trioxide and metallic arsenic process emission stream that exits from a control device. (b)...

  10. 40 CFR 61.183 - Emission monitoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic Arsenic Emissions From Arsenic Trioxide and Metallic Arsenic Production Facilities § 61.183 Emission monitoring. (a... arsenic trioxide and metallic arsenic process emission stream that exits from a control device. (b)...

  11. 40 CFR 61.183 - Emission monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic Arsenic Emissions From Arsenic Trioxide and Metallic Arsenic Production Facilities § 61.183 Emission monitoring. (a... arsenic trioxide and metallic arsenic process emission stream that exits from a control device. (b)...

  12. 40 CFR 61.183 - Emission monitoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic Arsenic Emissions From Arsenic Trioxide and Metallic Arsenic Production Facilities § 61.183 Emission monitoring. (a... arsenic trioxide and metallic arsenic process emission stream that exits from a control device. (b)...

  13. Acoustic emissions during 3.1 MHz ultrasound bulk ablation in vitro.

    PubMed

    Mast, T Douglas; Salgaonkar, Vasant A; Karunakaran, Chandrapriya; Besse, John A; Datta, Saurabh; Holland, Christy K

    2008-09-01

    Acoustic emissions associated with cavitation and other bubble activity have previously been observed during ultrasound (US) ablation experiments. Because detectable bubble activity may be related to temperature, tissue state and sonication characteristics, these acoustic emissions are potentially useful for monitoring and control of US ablation. To investigate these relationships, US ablation experiments were performed with simultaneous measurements of acoustic emissions, tissue echogenicity and tissue temperature on fresh bovine liver. Ex vivo tissue was exposed to 0.9-3.3-s bursts of unfocused, continuous-wave, 3.10-MHz US from a miniaturized 32-element array, which performed B-scan imaging with the same piezoelectric elements during brief quiescent periods. Exposures used pressure amplitudes of 0.8-1.4 MPa for exposure times of 6-20 min, sufficient to achieve significant thermal coagulation in all cases. Acoustic emissions received by a 1-MHz, unfocused passive cavitation detector, beamformed A-line signals acquired by the array, and tissue temperature detected by a needle thermocouple were sampled 0.3-1.1 times per second. Tissue echogenicity was quantified by the backscattered echo energy from a fixed region-of-interest within the treated zone. Acoustic emission levels were quantified from the spectra of signals measured by the passive cavitation detector, including subharmonic signal components at 1.55 MHz, broadband signal components within the band 0.3-1.1 MHz and low-frequency components within the band 10-30 kHz. Tissue ablation rates, defined as the thermally ablated volumes per unit time, were assessed by quantitative analysis of digitally imaged, macroscopic tissue sections. Correlation analysis was performed among the averaged and time-dependent acoustic emissions in each band considered, B-mode tissue echogenicity, tissue temperature and ablation rate. Ablation rate correlated significantly with broadband and low-frequency emissions, but was

  14. 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.

  15. 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.

  16. 40 CFR 60.264 - Emission monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Emission monitoring. 60.264 Section 60... Facilities § 60.264 Emission monitoring. (a) The owner or operator subject to the provisions of this subpart... opacity of emissions discharged into the atmosphere from the control device(s). (b) For the purpose...

  17. 40 CFR 60.264 - Emission monitoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Emission monitoring. 60.264 Section 60... Facilities § 60.264 Emission monitoring. (a) The owner or operator subject to the provisions of this subpart... opacity of emissions discharged into the atmosphere from the control device(s). (b) For the purpose...

  18. 40 CFR 60.264 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Emission monitoring. 60.264 Section 60... Facilities § 60.264 Emission monitoring. (a) The owner or operator subject to the provisions of this subpart... opacity of emissions discharged into the atmosphere from the control device(s). (b) For the purpose...

  19. 40 CFR 60.264 - Emission monitoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 7 2012-07-01 2012-07-01 false Emission monitoring. 60.264 Section 60... Facilities § 60.264 Emission monitoring. (a) The owner or operator subject to the provisions of this subpart... opacity of emissions discharged into the atmosphere from the control device(s). (b) For the purpose...

  20. 40 CFR 60.264 - Emission monitoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 7 2014-07-01 2014-07-01 false Emission monitoring. 60.264 Section 60... Facilities § 60.264 Emission monitoring. (a) The owner or operator subject to the provisions of this subpart... opacity of emissions discharged into the atmosphere from the control device(s). (b) For the purpose...

  1. Acoustic emissions during deformation of intact and jointed welded tuff

    SciTech Connect

    Holcomb, D.J.; Teufel, L.W.

    1982-07-01

    Monitoring of acoustic emissions (AE) has been widely used as a means of detecting failure in intact rock. For intact rock the technique is simple, because an increasing rate of AE is usually a sign of impending failure. However, most large rock masses contain numerous joints and the behavior of the joints controls the properties of the rock mass. In particular, the failure mode often becomes stable or unstable slip (stick-slip) on a joint at stresses well below those required for failure of the intact rock. As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on intact and artificially jointed samples of Grouse Canyon tuff. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates. Testing was done in a servo-controlled machine at axial displacement rates of 5 x 10{sup -5} cm/sec, and confining pressures ranging from 10 to 40 MPa. For the jointed samples four modes of slip were identified. First, stable sliding accompanied by a steady rate of AE. Second, stick-slip with a sharp drop in load, large displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, slow stick-slip where the load dropped and the displacements increased but the process was slow and culminated in stable sliding. Mode 4 exhibited premonitory AE and slip and after the event, a steady rate of AE during sliding. There seemed to be no way to predict which mode would occur at a given point in the test. In all cases where stable or unstable slip occurred there was a corresponding occurrence of AE. This indicates that slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip.

  2. Investigation of acoustic emission and surface treatment to improve tool materials and metal forming process

    NASA Astrophysics Data System (ADS)

    Cao, Deming

    Silicon nitride and WC-Co cermet tools are used for metal forming processes including extrusion and drawing. These materials are used to make tool dies which are exposed to deformation caused by friction and wear. Surface treatments such as ion implantation, laser blazing and coating have been found to improve surface properties, to optimize tribological behavior between the metal and die, as well as to extend service life of the tool dies. Early detection and continuous monitoring processes by non destructive testing (NDT) methods are needed in order to ensure the functionality of the wear process and extend the tool service life. Acoustic emission is one of the promising NDT methods for this application. The surface treatment chosen for this investigation was ion implantation. Three types of wear resistant materials with and without surface treatment were selected for this project; silicon nitride and two tungsten carbides (6% Cobalt and 10% Cobalt). This investigation was conducted using a pin-on-disk device for wear/friction tests of the selected materials with lubrication and/or without lubrication against both a stainless steel disk and an aluminum disk. The acoustic emissions generated during the experiments were recorded and analyzed. The results of this investigation showed that the ion implantation improved the tribological properties of the materials and reduced acoustic emission and coefficient of friction. A linear relationship between the average amplitude of the acoustic emission and the coefficient of friction of the tested materials was found. The investigation demonstrated that the acoustic emission method could be used to monitor the wear/friction processes.

  3. Wearable knee health rehabilitation assessment using acoustical emissions

    NASA Astrophysics Data System (ADS)

    Teague, Caitlin N.; Hersek, Sinan; Conant, Jordan L.; Gilliland, Scott M.; Inan, Omer T.

    2017-02-01

    We have developed a novel, wearable sensing system based on miniature piezoelectric contact microphones for measuring the acoustical emissions from the knee during movement. The system consists of two contact microphones, positioned on the medial and lateral sides of the patella, connected to custom, analog pre-amplifier circuits and a microcontroller for digitization and data storage on a secure digital card. Tn addition to the acoustical sensing, the system includes two integrated inertial measurement sensors including accelerometer and gyroscope modalities to enable joint angle calculations; these sensors, with digital outputs, are connected directly to the same microcontroller. The system provides low noise, accurate joint acoustical emission and angle measurements in a wearable form factor and has several hours of battery life.

  4. 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.

  5. Characterization of Acoustic Emission Source to Identify Fracture in Concrete

    DTIC Science & Technology

    1993-04-01

    Hardy, "An Approach to Acoustic Emission Signal Analysis," Materials Evaluation, 35, 1977 , pp. 100-106. [5] Hsu, N.N. and F.R. Breckenridge...Measurements," Journal of Applied Mechanics, 53, 1986, pp. 61-68. [17] Mindess , S., "The Fracture Process Zone in Concrete," Toughening Mechanisms in

  6. Distributed acoustic fibre optic sensors for condition monitoring of pipelines

    NASA Astrophysics Data System (ADS)

    Hussels, Maria-Teresa; Chruscicki, Sebastian; Habib, Abdelkarim; Krebber, Katerina

    2016-05-01

    Industrial piping systems are particularly relevant to public safety and the continuous availability of infrastructure. However, condition monitoring systems based on many discrete sensors are generally not well-suited for widespread piping systems due to considerable installation effort, while use of distributed fibre-optic sensors would reduce this effort to a minimum. Specifically distributed acoustic sensing (DAS) is employed for detection of third-party threats and leaks in oil and gas pipelines in recent years and can in principle also be applied to industrial plants. Further possible detection routes amenable by DAS that could identify damage prior to emission of medium are subject of a current project at BAM, which aims at qualifying distributed fibre optic methods such as DAS as a means for spatially continuous monitoring of industrial piping systems. Here, first tests on a short pipe are presented, where optical fibres were applied directly to the surface. An artificial signal was used to define suitable parameters of the measurement system and compare different ways of applying the sensor.

  7. Time-frequency Analysis for Acoustic Emission Signals of Hypervelocity Impact

    NASA Astrophysics Data System (ADS)

    Liu, W. G.; Pang, B. J.; Zhang, W.; Sun, F.; Guan, G. S.

    The risk of collision of man-made orbital debris with spacecraft in near Earth orbits continues to increase A major of the space debris between 1mm and 10mm can t be well tracked in Earth orbits Damage from these un-tracked debris impacts is a serious hazard to aircraft and spacecraft These on-orbit collisions occur at velocities exceeding 10km s and at these velocities even very small particles can create significant damage The development of in-situ impact detecting system is indispensable for protecting the spacecraft from tragedy malfunction by the debris Acoustic Emission AE detecting technique has been recognized as an important technology for non-destructive detecting due to the AE signals offering a potentially useful additional means of non-invasively gathering concerning the state of spacecrafts Also Acoustic emission health monitoring is able to detect locate and assess impact damage when the spacecrafts is impacted by hypervelocity space debris and micrometeoroids This information can help operators and designers at the ground station take effective measures to maintain the function of spacecraft In this article Acoustic emission AE is used for characterization and location for hypervelocity Impacts Two different Acoustic Emission AE sensors were used to detect the arrival time and signals of the hits Hypervelocity Impacts were generated with a two-stage light-gas gun firing small Aluminum ball projectiles 4mm 6 4mm In the impact studies the signals were recorded with Disp AEwin PAC instruments by the conventional crossing

  8. 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.

  9. Assessment of corrosion rate in prestressed concrete with acoustic emission

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    Acoustic Emission (AE) sensing was employed to assess the rate of corrosion of steel strands in small scale concrete block specimens. The corrosion process was accelerated in a laboratory environment using a potentiostat to supply a constant potential difference with a 3% NaCl solution as the electrolyte. The embedded prestressing steel strand served as the anode, and a copper plate served as the cathode. Corrosion rate, half-cell potential measurements, and AE activity were recorded continuously throughout each test and examined to assess the development of corrosion and its rate. At the end of each test the steel strands were cleaned and re-weighed to determine the mass loss and evaluate it vis-á-vis the AE data. The initiation and propagation phases of corrosion were correlated with the percentage mass loss of steel and the acquired AE signals. Results indicate that AE monitoring may be a useful aid in the detection and differentiation of the steel deterioration phases, and estimation of the locations of corroded areas.

  10. Modelling of acoustic emission generated in involute spur gear pair

    NASA Astrophysics Data System (ADS)

    Sharma, Ram Bihari; Parey, Anand; Tandon, Naresh

    2017-04-01

    Acoustic emission (AE) is an important technique for the condition monitoring and diagnostics of various mechanical system components like gear, bearing, macahine tool etc. Several researchers have found experimentally that gear operating parameters such as speed, load, specific film thickness, temperature etc. influence the energy of AE generated during meshing of the gears. But there is lack of mathematical model to comprehend the actual physical mechanism in the gear for the same. In this study, a theoretical model has been developed to establish a rapport between gear operating parameters and energy of AE on the bases of asperity contact and friction between involute surfaces of gear using Hertzian contact approach, statistical concepts, and varying sliding velocity of gear tooth mechanism. The effects of load sharing, lubrication, and dynamic load condition during the gear mesh cycle are also considered in the developed model. An experimental study has been performed for validation of developed theoretical model. A satisfactory validation has been perceived between the AE rms (root mean square) predicted by the developed theoretical model and obtained experimental results.

  11. Modal acoustic emission source determination in silicon carbide matrix composites

    NASA Astrophysics Data System (ADS)

    Morscher, G. N.

    2000-05-01

    Modal acoustic emission has been used to monitor damage accumulation in woven silicon carbide (SiC) fiber reinforced SiC matrix composites during tensile testing. There are several potential sources of damage in these systems including transverse matrix cracking, fiber/matrix interphase debonding and sliding, longitudinal cracks in between plies, and fiber breakage. In the past, it has been shown that modal AE is excellent at detecting when damage occurs and subsides, where the damage occurs along the length of the sample, and the loss in material stiffness as a consequence of damage accumulation. The next step is to determine the extent that modal AE can be used to identify specific physical sources. This study will discuss the status of this aim for this composite system. Individual events were analyzed and correlated to specific sources based on the characteristics of the received waveforms, e.g., frequency spectrum and energy, and when the event occurred during the stress-history of the tensile test. Post-test microstructural examination of the test specimens enabled some correlation between specific types of AE events and damage sources.

  12. 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.

  13. A fast source for quantitative acoustic emission and its application

    NASA Astrophysics Data System (ADS)

    Masaki, Ryuji; Takemoto, Mikio; Ono, Kanji

    1999-12-01

    We demonstrate a new artificial fracture source for quantitative acoustic emission (AE) characterization. The source utilizes the break-down of silicone oil (or other liquids) placed inside a crack (or a slit). This is a dipole source with a rise time under 0.1 μs. It is much faster than a pencil-lead-break source and allows the calibration of a sensor-structure system to 7-10 MHz. We irradiated a focused Q-switched Nd-YAG laser beam (15 to 90 mJ energy) on silicon placed in a slit on a cylindrical block. The out-of-plane displacement produced by the resultant bulk waves was monitored on the outside surface using a heterodyne-type laser interferometer. This break-down source was employed to determine the transfer functions of an AE transducer and propagation medium. Finally, we studied AE signals due to the delayed fracture of a butt-welded dual-phase stainless steel, using the break-down source for calibration. Brittle-fracture events were successfully characterized.

  14. OPERATING PROCEDURE FOR THE PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

    2004-08-29

    The Portable Acoustic Monitoring Package (PAMP) has been designed to record and monitor acoustic signals in high-pressure natural gas (NG) transmission lines. Of particular interest are the three acoustic signals associated with a pipeline fracture. The system is portable (less than 30 lbm) and can be used at all line pressures up to 1000 psig. The PAMP requires a shut-off valve equipped 1/2 inch NPT access port in the pipeline. It is fully functional over the typical pressure range found in the natural gas transmission pipelines in the West Virginia, Virginia, Pennsylvania, and Ohio areas. With the use of the PAMP, a full spectrum of acoustic signals can be recorded and defined in terms of acoustic energy in decibels. To detect natural gas pipeline infringements and leaks, the acoustic energy generated inside the line is monitored with a sensitive pressure-equalized microphone and a step function type {Delta}p transducer. The assembly is mounted on a 1000 psig pipe fitting-tree called the PAMP. The electronics required to record, store and analyze the data are described within this report in the format of an operating manual.

  15. Studies of acoustic emission from point and extended sources

    NASA Technical Reports Server (NTRS)

    Sachse, W.; Kim, K. Y.; Chen, C. P.

    1986-01-01

    The use of simulated and controlled acoustic emission signals forms the basis of a powerful tool for the detailed study of various deformation and wave interaction processes in materials. The results of experiments and signal analyses of acoustic emission resulting from point sources such as various types of indentation-produced cracks in brittle materials and the growth of fatigue cracks in 7075-T6 aluminum panels are discussed. Recent work dealing with the modeling and subsequent signal processing of an extended source of emission in a material is reviewed. Results of the forward problem and the inverse problem are presented with the example of a source distributed through the interior of a specimen.

  16. Acoustic (loudspeaker) facial EMG monitoring: II. Use of evoked EMG activity during acoustic neuroma resection.

    PubMed

    Prass, R L; Kinney, S E; Hardy, R W; Hahn, J F; Lüders, H

    1987-12-01

    Facial electromyographic (EMG) activity was continuously monitored via loudspeaker during eleven translabyrinthine and nine suboccipital consecutive unselected acoustic neuroma resections. Ipsilateral facial EMG activity was synchronously recorded on the audio channels of operative videotapes, which were retrospectively reviewed in order to allow detailed evaluation of the potential benefit of various acoustic EMG patterns in the performance of specific aspects of acoustic neuroma resection. The use of evoked facial EMG activity was classified and described. Direct local mechanical (surgical) stimulation and direct electrical stimulation were of benefit in the localization and/or delineation of the facial nerve contour. Burst and train acoustic patterns of EMG activity appeared to indicate surgical trauma to the facial nerve that would not have been appreciated otherwise. Early results of postoperative facial function of monitored patients are presented, and the possible value of burst and train acoustic EMG activity patterns in the intraoperative assessment of facial nerve function is discussed. Acoustic facial EMG monitoring appears to provide a potentially powerful surgical tool for delineation of the facial nerve contour, the ongoing use of which may lead to continued improvement in facial nerve function preservation through modification of dissection strategy.

  17. Acoustic Float for Marine Mammal Monitoring

    DTIC Science & Technology

    2009-09-30

    a matured technology, and is manufactured mainly by two companies, Webb Research (APEX) and Martec (PROVOR). Our original acoustic float, the...adding another microprocessor inside the float as originally planned, we have reprogrammed the APEX float processor board itself (apf9) by changing... echolocation clicks. The analysis revealed that by using ICI information, the ERMA detector was able to reduce the number of false positive detections to less

  18. 40 CFR 60.273 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Furnaces Constructed After October 21, 1974, and On or Before August 17, 1983 § 60.273 Emission monitoring... when the furnace is operating in the melting and refining period. All visible emissions observations... furnace static pressure monitoring device is not required on any EAF equipped with a DEC system...

  19. 40 CFR 60.273 - Emission monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Furnaces Constructed After October 21, 1974, and On or Before August 17, 1983 § 60.273 Emission monitoring... when the furnace is operating in the melting and refining period. All visible emissions observations... furnace static pressure monitoring device is not required on any EAF equipped with a DEC system...

  20. 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.

  1. 40 CFR 61.163 - Emission monitoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 9 2013-07-01 2013-07-01 false Emission monitoring. 61.163 Section 61.163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic...

  2. 40 CFR 61.163 - Emission monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Emission monitoring. 61.163 Section 61.163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic...

  3. 40 CFR 61.163 - Emission monitoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 9 2014-07-01 2014-07-01 false Emission monitoring. 61.163 Section 61.163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic...

  4. 40 CFR 61.163 - Emission monitoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 8 2011-07-01 2011-07-01 false Emission monitoring. 61.163 Section 61.163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic...

  5. 40 CFR 61.163 - Emission monitoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 9 2012-07-01 2012-07-01 false Emission monitoring. 61.163 Section 61.163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Inorganic...

  6. Acoustic Emission Signatures During Failure of Vertebra and Long Bone.

    PubMed

    Goodwin, Brian D; Pintar, Frank A; Yoganandan, Narayan

    2017-03-14

    Clinical classification of an injury has traditionally involved medical imaging, patient history, and physical examination. The pathogenesis or process of injury has been viewed as a crucial component to estimating fracture stability and direct treatment. However, injury classification systems generally exclude pathogenesis and injury mechanisms because these components are often difficult to elucidate. Furthermore, the development of bone damage relative to the mechanical response is difficult to quantify, which limits the ability to define injury and develop injury criteria. Past advents of new knowledge about the mechanisms and progression of fracture have refined safety standards and engineering design for limiting injury. Post-hoc methodologies for identifying and classifying injuries for post-mortem human surrogate (PMHS) research are well established. Though bone fractures can be classified post hoc, questions remain. Surface acoustic sensing (SAS) is an effective approach to augment PMHS experimentation. The objective was to develop and validate an acoustic-emission-based method to characterize bone fractures during injurious loading conditions using acoustic emissions (AEs) in two bone types: vertebral body (VB) and long bone (LB). The newly developed method incorporated the Stockwell transform to estimate the relative energy release rate (RERR) from bone fracture using acoustic signal processing. Fractures were characterized through AE burst durations and frequency content. Results indicated that VB fractures from compression are prolonged processes compared to LB fracture, which was staccato in nature. Significant (p < 0.01) differences between burst duration and frequency content were identified between the two bone types.

  7. Structural tests using a MEMS acoustic emission sensor

    NASA Astrophysics Data System (ADS)

    Oppenheim, Irving J.; Greve, David W.; Ozevin, Didem; Hay, D. Robert; Hay, Thomas R.; Pessiki, Stephen P.; Tyson, Nathan L.

    2006-03-01

    In a collaborative project at Lehigh and Carnegie Mellon, a MEMS acoustic emission sensor was designed and fabricated as a suite of six resonant-type capacitive transducers in the frequency range between 100 and 500 kHz. Characterization studies showed good comparisons between predicted and experimental electro-mechanical behavior. Acoustic emission events, simulated experimentally in steel ball impact and in pencil lead break tests, were detected and source localization was demonstrated. In this paper we describe the application of the MEMS device in structural testing, both in laboratory and in field applications. We discuss our findings regarding housing and mounting (acoustic coupling) of the MEMS device with its supporting electronics, and we then report the results of structural testing. In all tests, the MEMS transducers were used in parallel with commercial acoustic emission sensors, which thereby serve as a benchmark and permit a direct observation of MEMS device functionality. All tests involved steel structures, with particular interest in propagation of existing cracks or flaws. A series of four laboratory tests were performed on beam specimens fabricated from two segments (Grade 50 steel) with a full penetration weld (E70T-4 electrode material) at midspan. That weld region was notched, an initial fatigue crack was induced, and the specimens were then instrumented with one commercial transducer and with one MEMS device; data was recorded from five individual transducers on the MEMS device. Under a four-point bending test, the beam displayed both inelastic behavior and crack propagation, including load drops associated with crack instability. The MEMS transducers detected all instability events as well as many or most of the acoustic emissions occurring during plasticity and stable crack growth. The MEMS transducers were less sensitive than the commercial transducer, and did not detect as many events, but the normalized cumulative burst count obtained

  8. 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).

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Acoustic Emission Sensing for Maritime Diesel Engine Performance and Health

    DTIC Science & Technology

    2016-05-01

    increases in big end bearing clearance were not definitely identified from the acoustic emission signals. DST Group recommends that for any subsequent...and excessive big end bearing clearance. The diesel engine, with considerably lower background AE, showed distinct patterns of AE generation in...The detection of excess big end bearing clearance up to 0.25 mm was elusive and requires more investigation as the AE systems failed to detect any

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

    PubMed

    Sreekala, S; Ananthakrishna, G

    2003-04-04

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

  15. Emission enhancement of sound emitters using an acoustic metamaterial cavity.

    PubMed

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

    2014-03-03

    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.

  16. 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

  17. 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.

  18. Development of a portable passive-acoustic bedload monitoring system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A hydrophone-based passive acoustic bedload-monitoring system was designed, tested and deployed by researchers at the University of Mississippi and the National Sedimentation Laboratory in Oxford, MS. The hydrophone system was designed to be easily deployed and operated by non-experts. In addition, ...

  19. The DMON2: A Commercially Available Broadband Acoustic Monitoring Instrument

    DTIC Science & Technology

    2015-09-30

    Monitoring Instrument Mark Baumgartner, Tom Hurst, Jim Partan, & Lee Freitag Woods Hole Oceanographic Institution Biology and AOPE Departments...MS #33 266 Woods Hole Road Woods Hole, MA 02543 phone: (508) 289-2678 fax: (508) 457-2134 email: mbaumgartner@whoi.edu Award Number...snow, or high winds). To meet this urgent need, engineers at the Woods Hole Oceanographic Institution developed the digital acoustic monitoring (DMON

  20. Advanced Technologies for Acoustic Monitoring of Bird Populations

    DTIC Science & Technology

    2009-04-01

    Dr. Kenneth Rosenberg (Cornell Lab of Ornithology ) titled ―Migratory Bird Monitoring Using Automated Acoustic and Internet Technologies‖ (Legacy... Ornithology . At the time that SI-1461 was awarded to Cornell University (April 2005), Fristrup was named as Principal Investigator. In November 2005...1986; Wilson and Watts 2006). Standard protocols for monitoring whip-poor-will populations call for an observer to listen for a six-minute sample period

  1. Acoustic emissions during deformation of jointed rock

    SciTech Connect

    Holcomb, D.J.; Teufel, L.W.

    1984-12-31

    As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on samples of Grouse Canyon tuff containing sawcut joints. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates. Testing was done in a servocontrolled machine at displacement rates of 2 x 10{sup -5} in/sec, and confining pressures ranging from 1500 to 6000 psi. Four modes of slip on joints were identified. First, stable sliding accompanied by a steady rate of AE. Second, stick-slip with a sharp drop in load, large displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, stable stick-slip where the load dropped and the displacements increased but the process was slow and culminated in stable sliding. Mode 4 exhibited premonitory AE and slip and after the event, a steady rate of AE during sliding. In all cases where premonitory slip or stable sliding occurred there was a corresponding occurrence of AE, indicating slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip and the extent of slip in modes 1, 3, and 4. Increasing slip rate leads to increasing AE rate. However, mode 2 stick-slip appears to be undetectable by this method.

  2. Investigation of fatigue crack growth in acrylic bone cement using the acoustic emission technique.

    PubMed

    Roques, A; Browne, M; Thompson, J; Rowland, C; Taylor, A

    2004-02-01

    Failure of the bone cement mantle has been implicated in the loosening process of cemented hip stems. Current methods of investigating degradation of the cement mantle in vitro often require sectioning of the sample to confirm failure paths. The present research investigates acoustic emission as a passive experimental method for the assessment of bone cement failure. Damage in bone cement was monitored during four point bending fatigue tests through an analysis of the peak amplitude, duration, rise time (RT) and energy of the events emitted from the damage sections. A difference in AE trends was observed during failure for specimens aged and tested in (i) air and (ii) Ringer's solution at 37 degrees C. It was noted that the acoustic behaviour varied according to applied load level; events of higher duration and RT were emitted during fatigue at lower stresses. A good correlation was observed between crack location and source of acoustic emission, and the nature of the acoustic parameters that were most suited to bone cement failure characterisation was identified. The methodology employed in this study could potentially be used as a pre-clinical assessment tool for the integrity of cemented load bearing implants.

  3. Waveform Based Acoustic Emission Detection and Location of Matrix Cracking in Composites

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.

    1995-01-01

    The operation of damage mechanisms in a material or structure under load produces transient acoustic waves. These acoustic waves are known as acoustic emission (AE). In composites they can be caused by a variety of sources including matrix cracking, fiber breakage, and delamination. AE signals can be detected and analyzed to determine the location of the acoustic source by triangulation. Attempts are also made to analyze the signals to determine the type and severity of the damage mechanism. AE monitoring has been widely used for both laboratory studies of materials, and for testing the integrity of structures in the field. In this work, an advanced, waveform based AE system was used in a study of transverse matrix cracking in cross-ply graphite/epoxy laminates. This AE system featured broad band, high fidelity sensors, and high capture rate digital acquisition and storage of acoustic signals. In addition, analysis techniques based on plate wave propagation models were employed. These features provided superior source location and noise rejection capabilities.

  4. 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

    2014-07-09

    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.

  5. 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.

  6. Wideband flat frequency response of thermo-acoustic emission

    NASA Astrophysics Data System (ADS)

    Hu, Hanping; Wang, Yandong; Wang, Zedong

    2012-08-01

    Many advantages of thermo-acoustic (TA) ultrasound over the conventional electro-acoustic ultrasound are mainly attributed to its unique nature—constant (flat) amplitude-frequency response over a wide frequency range. However, realization of the TA flat frequency response itself has so far remained unclear due to the lack of theoretical investigation. In this work, using analysis of thermal-mechanical coupling and thermal wave penetration depth for TA emission in gas, the mechanism and regularities of flat frequency response are clarified. The limits of both frequency and space for the existence of flat frequency response of TA ultrasound are revealed. In addition, the performance evaluation and selection techniques for both TA material and its backing are presented. Therefore, the most important feature of TA ultrasound from a technical standpoint is studied more completely.

  7. A Volcano Monitoring Seismo-Acoustic Network in the CNMI

    NASA Astrophysics Data System (ADS)

    Howard, J. E.; Crippen, S. E.; Hayward, C.; Quick, J. E.

    2011-12-01

    In late spring and early summer of 2011, a seismo-acoustic network was installed in the Commonwealth of the Northern Mariana Islands (CNMI) for volcano monitoring. The network consists of a seismo-acoustic array on Saipan, an acoustic array on Sarigan with one seismometer, and a seismic network on Anatahan. On Saipan the array consists of a central site and 3 embedded triangular arrays with apertures of 100 m, 300 m and 1000 m. Four 50-foot porous hoses in a clover-leaf arrangement are used for spatial filtering at each acoustic site. Broadband seismometers were installed at the central site and the 1000 m sites. The Sarigan Array consists of a central acoustic site with 5 surrounding sites evenly spaced at 50 m radius, and one broadband seismic station. Two hoses were used for each site on Sarigan. Four broadband seismic stations were also installed on Anatahan which last erupted in 2005. Data from each array is sent by radio telemetry to the Emergency Management Office on Saipan, where it is routed to the USGS and SMU. Data will be used for volcano monitoring which will allow the CNMI to resume economic activity in the uninhabited northern islands. Initial data streams show high seismic noise levels as expected for an island installation. The Sarigan acoustic sites are also noisy as a result of being more exposed to wind than the Saipan sites. Many small events have already been observed in the infrasound data. This network was installed through the collaborative efforts of CNMI, USGS and SMU.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Samuel, Stanley

    2007-12-01

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

  10. Signal processing methodologies for an acoustic fetal heart rate monitor

    NASA Technical Reports Server (NTRS)

    Pretlow, Robert A., III; Stoughton, John W.

    1992-01-01

    Research and development is presented of real time signal processing methodologies for the detection of fetal heart tones within a noise-contaminated signal from a passive acoustic sensor. A linear predictor algorithm is utilized for detection of the heart tone event and additional processing derives heart rate. The linear predictor is adaptively 'trained' in a least mean square error sense on generic fetal heart tones recorded from patients. A real time monitor system is described which outputs to a strip chart recorder for plotting the time history of the fetal heart rate. The system is validated in the context of the fetal nonstress test. Comparisons are made with ultrasonic nonstress tests on a series of patients. Comparative data provides favorable indications of the feasibility of the acoustic monitor for clinical use.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. The acoustic emissions of cavitation bubbles in stretched vortices.

    PubMed

    Chang, Natasha A; Ceccio, Steven L

    2011-11-01

    Pairs of unequal strength, counter-rotating vortices were produced in order to examine the inception, dynamics, and acoustic emission of cavitation bubbles in rapidly stretching vortices. The acoustic signatures of these cavitation bubbles were characterized during their inception, growth, and collapse. Growing and collapsing bubbles often produced a sharp, broadband, pop sound. The spectrum of these bubbles, and the peak resonant frequency can generally be related to quiescent flow bubble dynamics and corresponding resonant frequencies. However, some elongated cavitation bubbles produced a short tonal burst, or chirp, with frequencies on the order of a few kilohertz. Theses frequencies are too low to be related to resonant frequencies of a bubble in a quiescent flow. Instead, the frequency content of the acoustic signal during bubble inception and growth is related to the volumetric oscillations of the bubble while it interacted with vortical flow that surrounds the bubble (i.e., the resonant frequency of the vortex-bubble system). A relationship was determined between the observed peak frequency of the oscillations, the highly stretched vortex properties, and the water nuclei content. It was found that different cavitation spectra could relate to different flow and fluid properties and therefore would not scale in the same manner.

  17. Acoustic emissions in granular structures under gravitational destabilization

    NASA Astrophysics Data System (ADS)

    Thirot, J.-L.; Le Gonidec, Y.; Kergosien, B.

    2012-05-01

    In this work, we perform experiments in an acoustic tank to record acoustic emissions (AEs) occurring when a granular medium is submitted to a gravitational destabilization. The granular medium is composed of monodisperse glass beads filling a box which can be inclined from α=0° up to the avalanche threshold angle α0=28°. To respect quasi-static conditions, the angle increases by steps less than 3°/mn. An omnidirectional hydrophone records the continuous acoustic field in the bead structure until the avalanche occurs. We compare the results for different experimental configurations, in particular for dry and water saturated granular media, but also for different bead diameters (d=8, 3 and 0.3 mm) in order to span the viscosity range of the granular structure. We show that the AE signatures strongly depend on the viscosity parameter, which can be related to the Stokes number and the fluid/solid density ratio. The transition from a viscous to an inertial dynamic of the granular structure is discussed, based on these experimental results.

  18. Burst prediction by acoustic emission in filament-wound pressure vessels

    NASA Technical Reports Server (NTRS)

    Gorman, Michael R.

    1990-01-01

    Acoustic emission in 51-cm diameter graphite/epoxy pressure vessels was monitored during pressurization (hydrotesting). Several vessels were subjected to impact by a blunt impactor, but only after the vessels had been proofed; that is, pressurized to 80 percent of nominal burst pressure as determined from control (unimpacted) vessels. AE activity was then monitored throughout a series of successively higher pressure cycles ranging from 10 to 60 percent of ultimate. Each cycle included a ramp up to pressure followed by a 4-min hold period and then pressure unload. The event rate was high, and especially modified AE analyzers had to be used to acquire the data. This paper presents the AE event count versus pressure history of these tests and demonstrates the ability of the AE technique to monitor the growth of damage and to estimate the effect on ultimate strength. The number of events that occurred during pressure holds proved to be a reasonable estimator of vessel performance.

  19. 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.

  20. Compensating for ear-canal acoustics when measuring otoacoustic emissions.

    PubMed

    Charaziak, Karolina K; Shera, Christopher A

    2017-01-01

    Otoacoustic emissions (OAEs) provide an acoustic fingerprint of the inner ear, and changes in this fingerprint may indicate changes in cochlear function arising from efferent modulation, aging, noise trauma, and/or exposure to harmful agents. However, the reproducibility and diagnostic power of OAE measurements is compromised by the variable acoustics of the ear canal, in particular, by multiple reflections and the emergence of standing waves at relevant frequencies. Even when stimulus levels are controlled using methods that circumvent standing-wave problems (e.g., forward-pressure-level calibration), distortion-product otoacoustic emission (DPOAE) levels vary with probe location by 10-15 dB near half-wave resonant frequencies. The method presented here estimates the initial outgoing OAE pressure wave at the eardrum from measurements of the conventional OAE, allowing one to separate the emitted OAE from the many reflections trapped in the ear canal. The emitted pressure level (EPL) represents the OAE level that would be recorded were the ear canal replaced by an infinite tube with no reflections. When DPOAEs are expressed using EPL, their variation with probe location decreases to the test-retest repeatability of measurements obtained at similar probe positions. EPL provides a powerful way to reduce the variability of OAE measurements and improve their ability to detect cochlear changes.

  1. Acoustic emission as a screening tool for ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Ojard, Greg; Goberman, Dan; Holowczak, John

    2017-02-01

    Ceramic matrix composites are composite materials with ceramic fibers in a high temperature matrix of ceramic or glass-ceramic. This emerging class of materials is viewed as enabling for efficiency improvements in many energy conversion systems. The key controlling property of ceramic matrix composites is a relatively weak interface between the matrix and the fiber that aids crack deflection and fiber pullout resulting in greatly increased toughness over monolithic ceramics. United Technologies Research Center has been investigating glass-ceramic composite systems as a tool to understand processing effects on material performance related to the performance of the weak interface. Changes in the interface have been shown to affect the mechanical performance observed in flexural testing and subsequent microstructural investigations have confirmed the performance (or lack thereof) of the interface coating. Recently, the addition of acoustic emission testing during flexural testing has aided the understanding of the characteristics of the interface and its performance. The acoustic emission onset stress changes with strength and toughness and this could be a quality tool in screening the material before further development and use. The results of testing and analysis will be shown and additional material from other ceramic matrix composite systems may be included to show trends.

  2. Acoustic emissions verification testing of International Space Station experiment racks at the NASA Glenn Research Center Acoustical Testing Laboratory

    NASA Astrophysics Data System (ADS)

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

    2005-09-01

    The Acoustical Testing Laboratory (ATL) at the NASA John H. Glenn Research Center (GRC) in Cleveland, OH, 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's primary customer has been the Fluids and Combustion Facility (FCF), a multirack microgravity research facility being developed at GRC for the USA Laboratory Module of the International Space Station (ISS). Since opening in September 2000, ATL has conducted acoustic emission testing of components, subassemblies, and partially populated FCF engineering model racks. The culmination of this effort has been the acoustic emission verification tests on the FCF Combustion Integrated Rack (CIR) and Fluids Integrated Rack (FIR), employing a procedure that incorporates ISO 11201 (``Acoustics-Noise emitted by machinery and equipment-Measurement of emission sound pressure levels at a work station and at other specified positions-Engineering method in an essentially free field over a reflecting plane''). This paper will provide an overview of the test methodology, software, and hardware developed to perform the acoustic emission verification tests on the CIR and FIR flight racks and lessons learned from these tests.

  3. Acoustic methods to monitor sliver linear density and yarn strength

    DOEpatents

    Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, Apostolos C.

    1997-01-01

    Methods and apparatus are provided for monitoring sliver and yarn characteristics. Transverse waves are generated relative to the sliver or yarn. At least one acoustic sensor is in contact with the sliver or yarn for detecting waves coupled to the sliver or yarn and for generating a signal. The generated signal is processed to identify the predefined characteristics including sliver or yarn linear density. The transverse waves can be generated with a high-powered acoustic transmitter spaced relative to the sliver or yarn with large amplitude pulses having a central frequency in a range between 20 KHz and 40 KHz applied to the transmitter. The transverse waves can be generated by mechanically agitating the sliver or yarn with a tapping member.

  4. 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.

  5. Evaluation of acoustic emission technique for crack growth measurement in aeronautical structures

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.

    1974-01-01

    An investigation has been conducted concerning the possibility to use the acoustic emission technique for the measurement of fatigue crack growth in aluminum alloy specimens. Two types of aluminum alloys were tested in the investigation. It was found that the acoustic emission technique provides a reliable indication of changes in the crack dimensions over relatively short periods of time. The level of acoustic activity serves as an indicator of the size of the cracks.

  6. The Identification of the Deformation Stage of a Metal Specimen Based on Acoustic Emission Data Analysis.

    PubMed

    Zou, Shenao; Yan, Fengying; Yang, Guoan; Sun, Wei

    2017-04-07

    The acoustic emission (AE) signals of metal materials have been widely used to identify the deformation stage of a pressure vessel. In this work, Q235 steel samples with different propagation distances and geometrical structures are stretched to get the corresponding acoustic emission signals. Then the obtained acoustic emission signals are de-noised by empirical mode decomposition (EMD), and then decomposed into two different frequency ranges, i.e., one mainly corresponding to metal deformation and the other mainly corresponding to friction signals. The ratio of signal energy between two frequency ranges is defined as a new acoustic emission characteristic parameter. Differences can be observed at different deformation stages in both magnitude and data distribution range. Compared with other acoustic emission parameters, the proposed parameter is valid in different setups of the propagation medium and the coupled stiffness.

  7. Ductile Deformation of Dehydrating Serpentinite Evidenced by Acoustic Signal Monitoring

    NASA Astrophysics Data System (ADS)

    Gasc, J.; Hilairet, N.; Wang, Y.; Schubnel, A. J.

    2012-12-01

    Serpentinite dehydration is believed to be responsible for triggering earthquakes at intermediate depths (i.e., 60-300 km) in subduction zones. Based on experimental results, some authors have proposed mechanisms that explain how brittle deformation can occur despite high pressure and temperature conditions [1]. However, reproducing microseismicity in the laboratory associated with the deformation of dehydrating serpentinite remains challenging. A recent study showed that, even for fast dehydration kinetics, ductile deformation could take place rather than brittle faulting in the sample [2]. This latter study was conducted in a multi-anvil apparatus without the ability to control differential stress during dehydration. We have since conducted controlled deformation experiments in the deformation-DIA (D-DIA) on natural serpentinite samples at sector 13 (GSECARS) of the APS. Monochromatic radiation was used with both a 2D MAR-CCD detector and a CCD camera to determine the stress and the strain of the sample during the deformation process [3]. In addition, an Acoustic Emission (AE) recording setup was used to monitor the microseismicity from the sample, using piezo-ceramic transducers glued on the basal truncation of the anvils. The use of six independent transducers allows locating the AEs and calculating the corresponding focal mechanisms. The samples were deformed at strain rates of 10-5-10-4 s-1 under confining pressures of 3-5 GPa. Dehydration was triggered during the deformation by heating the samples at rates ranging from 5 to 60 K/min. Before the onset of the dehydration, X-ray diffraction data showed that the serpentinite sustained ~1 GPa of stress which plummeted when dehydration occurred. Although AEs were recorded during the compression and decompression stages, no AEs ever accompanied this stress drop, suggesting ductile deformation of the samples. Hence, unlike many previous studies, no evidence for fluid embrittlement and anticrack generation was found

  8. An acoustic emission study of cutting bauxite refractory ceramics by abrasive water jets

    NASA Astrophysics Data System (ADS)

    Momber, A. W.; Mohan, R. S.; Kovacevic, R.

    1999-08-01

    This article discusses the material removal process in bauxite refractory ceramics cut by abrasive water jets. Several parameters of the process were changed during the experiments. The experiments were monitored online by the acoustic emission (AE) technique. It was found that AE signals are able to sense the material removal process as well as the machining performances very reliably. Unsteady material removal mode consisting of matrix removal and intergranular fracture was very well represented in the AE signals by an unsteady time dependent signal type characterized by burst emissions and a frequency domain signal associated with a twin-peak shape. The particular characteristics of the signal depend on the energy involved in the process.

  9. 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.

  10. Acoustic Emission Analysis of Shuttle Thermal Protection System

    NASA Technical Reports Server (NTRS)

    Lane, John; Hooker, Jeffery; Immer, Christopher; Walker, James

    2004-01-01

    Acoustic emission (AE) signals generated from projectile impacts on reinforced and advanced carbon/carbon (RCC and ACC) panels, fired from a compressed-gas gun, identify the type and severity of damage sustained by the target. This type of testing is vital in providing the required "return to flight" (RTF) data needed to ensure continued and safe operation of NASA's Space Shuttle fleet. The gas gun at Kennedy Space Center is capable of propelling 12-inch by 3-inch cylinders of external tank (ET) foam at exit velocities exceeding 1,000 feet per second. Conventional AE analysis techniques require time domain processing of impulse data, along with amplitude distribution analysis. It is well known that identical source excitations can produce a wide range of AE signals amplitudes. In order to satisfy RTF goals, it is necessary to identify impact energy levels above and below damage thresholds. Spectral analysis techniques involving joint time frequency analysis (JTFA) are used to reinforce time domain AE analysis. JTFA analysis of the AE signals consists of short-time Fourier transforms (STFT) and the Huang-Hilbert transform (HHT). The HHT provides a very good measure of the instantaneous frequency of impulse events dominated by a single component. Identifying failure modes and cracking of fibers from flexural and/or extensional mode acoustic signals will help support in-flight as well as postflight impact analysis.

  11. 76 FR 18415 - Continuous Emission Monitoring

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-04

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 75 Continuous Emission Monitoring CFR Correction In Title 40 of the Code of Federal... units. The owner or operator of an affected unit that combusts wood, refuse, or other material...

  12. 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.

  13. Laser method of acoustical emission control from vibrating surfaces

    NASA Astrophysics Data System (ADS)

    Motyka, Zbigniew

    2013-01-01

    For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

  14. Near-field beamforming analysis for acoustic emission source localization.

    PubMed

    He, Tian; Pan, Qiang; Liu, Yaoguang; Liu, Xiandong; Hu, Dayong

    2012-07-01

    This paper attempts to introduce a near-field acoustic emission (AE) beamforming method to estimate the AE source locations by using a small array of sensors closely placed in a local region. The propagation characteristics of AE signals are investigated based on guided wave theory to discuss the feasibility of using beamforming techniques in AE signal processing. To validate the effectiveness of the AE beamforming method, a series of pencil lead break tests at various regions of a thin steel plate are conducted. The potential of this method for engineering applications are explored through rotor-stator rubbing tests. The experimental results demonstrate that the proposed method can effectively determine the region where rubbing occurs. It is expected that the work of this paper may provide a helpful analysis tool for near-field AE source localization.

  15. A wireless acoustic emission sensor remotely powered by light

    NASA Astrophysics Data System (ADS)

    Zahedi, F.; Huang, H.

    2014-03-01

    In this paper, wireless sensing of acoustic emission (AE) signals using a battery-free sensor node remotely powered by light is presented. The wireless sensor consists of a piezoelectric wafer active sensor (PWAS) for AE signal acquisition and a wireless transponder that performs signal conditioning, frequency conversion, and wireless transmission. For signal conditioning, a voltage follower that consumes less than 2 mW was introduced to buffer the high impedance of the PWAS from the low impedance of the wireless transponder. A photocell-based energy harvester with a stable voltage output was developed to power the voltage follower so that the wireless AE sensor can operate without an external power source. The principle of operation of the battery-free wireless AE sensor node and the sensor interrogation system is described, followed by a detailed description of the hardware implementation. The voltage follower and the wireless channel were characterized by ultrasound pitch-catch and pencil lead break experiments.

  16. 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

  17. 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.

  18. 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.

  19. Knee acoustic emission: a potential biomarker for quantitative assessment of joint ageing and degeneration.

    PubMed

    Shark, L K; Chen, H; Goodacre, J

    2011-06-01

    Based on a single time-point study of 34 healthy and 19 osteoarthritic knees in three different age groups (early, middle and late adulthood), this paper reports the potential of knee acoustic emission as a biomarker to monitor joint ageing and degeneration. Measurements were made of short transient high frequency acoustic emission signals generated by knee joints under stress during repeated sit-stand-sit movements along with joint angle. A statistically significant feature profile was established using a four-phase model of sit-stand-sit movements and two waveform features. The four-phase movement model is derived from joint angle measurement during repeated sit-stand-sit movements, and it consists of the ascending-acceleration and ascending-deceleration phases in the sit-to-stand movement, followed by the descending-acceleration and descending-deceleration phases in the stand-to-sit movement. The two statistically significant waveform features are extracted from AE measurement during repeated sit-stand-sit movements, and they consist of the peak magnitude value and average signal level of each AE burst. In addition to the use of bilateral plots, statistical distributions and 2D colour histograms to visualise the differences and similarities among participants, use of principal component analysis showed not only distinct data clusters corresponding to participating groups, but also an age- and disease-related trajectory progressing from the early adulthood healthy group to the late adulthood healthy group followed by the middle adulthood osteoarthritic group to the late adulthood osteoarthritic group. Furthermore, this trajectory shows increasing areas for each data cluster, with a highly compact cluster for the early adulthood healthy group at one end and a widely spread cluster for the late adulthood osteoarthritic group at the other end. From these results, a strong basis is formed for further development of knee acoustic emission as a convenient and non

  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. 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

  2. Acoustic monitoring of laboratory faults: locating the origin of unstable slip events

    NASA Astrophysics Data System (ADS)

    Korkolis, Evangelos; Niemeijer, André; Spiers, Christopher

    2015-04-01

    Over the past several decades, much work has been done on studying the frictional properties of fault gouges at earthquake nucleation velocities. In addition, post-experiment microstructural analyses have been performed in an attempt to link microphysical mechanisms to the observed mechanical data. However, all observations are necessarily post-mortem and it is thus difficult to directly link transients to microstructural characteristics. We are developing an acoustic monitoring system to be used in sliding experiments using a ring shear apparatus. The goal is to locate acoustic emission sources in sheared granular assemblages and link them to processes that act on microstructures responsible for the frictional stability of the simulated fault gouge. The results will be used to develop and constrain microphysical models that explain the relation of these processes to empirical friction laws, such as rate- and state-dependent friction. The acoustic monitoring setup is comprised of an array of 16 piezo-electric sensors installed on the top and bottom sides of an annular sample, at 45 degree intervals. Acoustic emissions associated with slip events can be recorded at sampling rates of up to 50 MHz, in triggered mode. Initial experiments on 0.1 to 0.2 mm and 0.4 to 0.5 mm diameter glass beads, at 1 to 5 MPa normal stress and 1 to 30 um/s load point velocity, have been conducted to estimate the sensitivity of the sensor array. Preliminary results reveal that the intensity of the audible signal is not necessarily proportional to the magnitude of the associated stress drop for constant loading conditions, and that acoustic emissions precede slip events by a small amount of time, in the order of a few milliseconds. Currently, our efforts are focused on developing a suitable source location algorithm with the aim to identify differences in the mode of (unstable) sliding for different types of materials. This will help to identify the micromechanical mechanisms operating

  3. Nondestructive monitoring damage in composites using scanning laser acoustic microscopy

    NASA Technical Reports Server (NTRS)

    Wey, A. C.; Kessler, L. W.; Dos Reis, H. L. M.

    1992-01-01

    Several Nicalon fiber reinforced LAS (lithium alumino-silicate) glass matrix composites were tested to study the relation between the residual strength and the different amounts of damage. The samples were fatigued by four-point cyclic loading at a 5 Hz rate at 500 C for a different number of cycles. 10 MHz scanning laser acoustic microscope (SLAM) images were taken to monitor damage on the samples. Our SLAM results indicate that there were defects already existing throughout the sample before fatigue, and the resultant damage pattern from fatigue could be related to the initial defect distribution in the sample. Finally, the fatigued samples were fractured and the residual strength data could not be explained by the cyclic fatigue alone. Rather, the damage patterns evident in the SLAM images were needed to explain the scatter in the data. The results show that SLAM is useful in nondestructively monitoring damage and estimating residual strength of fatigued ceramic composites.

  4. Evaluation of the sensitivity of electro-acoustic measurements for process monitoring and control of an atmospheric pressure plasma jet system

    NASA Astrophysics Data System (ADS)

    Law, V. J.; O'Neill, F. T.; Dowling, D. P.

    2011-06-01

    The development of non-invasive process diagnostic techniques for the control of atmospheric plasmas is a critical issue for the wider adoption of this technology. This paper evaluates the use of a frequency-domain deconvolution of an electro-acoustic emission as a means to monitor and control the plasma formed using an atmospheric pressure plasma jet (APPJ) system. The air plasma system investigated was formed using a PlasmaTreat™ OpenAir applicator. Change was observed in the electro-acoustic signal with changes in substrate type (ceramic, steel, polymer). APPJ nozzle to substrate distance and substrate feature size were monitored. The decoding of the electro-acoustic emission yields three subdatasets that are described by three separate emission mechanisms. The three emissions are associated with the power supply fundamental drive frequency and its harmonics, the APPJ nozzle longitudinal mode acoustic emission and its odd overtones, and the acoustic surface reflection that is produced by the impedance mismatch between the discharge and the surface. Incorporating this knowledge into a LabVIEW program facilitated the continuous deconvolution of the electro-acoustic data. This enabled the use of specific frequency band test limits to control the APPJ treatment process which is sensitive to both plasma processing conditions and substrate type and features.

  5. Tools for automated acoustic monitoring within the R package monitoR

    USGS Publications Warehouse

    Katz, Jonathan; Hafner, Sasha D.; Donovan, Therese

    2016-01-01

    The R package monitoR contains tools for managing an acoustic-monitoring program including survey metadata, template creation and manipulation, automated detection and results management. These tools are scalable for use with small projects as well as larger long-term projects and those with expansive spatial extents. Here, we describe typical workflow when using the tools in monitoR. Typical workflow utilizes a generic sequence of functions, with the option for either binary point matching or spectrogram cross-correlation detectors.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  7. Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

    NASA Astrophysics Data System (ADS)

    Cohen, D.; Hooyer, T. S.; Iverson, N. R.; Thomason, J. F.; Jackson, M.

    2006-09-01

    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.

  8. Visualization of stress wave propagation via air-coupled acoustic emission sensors

    NASA Astrophysics Data System (ADS)

    Rivey, Joshua C.; Lee, Gil-Yong; Yang, Jinkyu; Kim, Youngkey; Kim, Sungchan

    2017-02-01

    We experimentally demonstrate the feasibility of visualizing stress waves propagating in plates using air-coupled acoustic emission sensors. Specifically, we employ a device that embeds arrays of microphones around an optical lens in a helical pattern. By implementing a beamforming technique, this remote sensing system allows us to record wave propagation events in situ via a single-shot and full-field measurement. This is a significant improvement over the conventional wave propagation tracking approaches based on laser doppler vibrometry or digital image correlation techniques. In this paper, we focus on demonstrating the feasibility and efficacy of this air-coupled acoustic emission technique by using large metallic plates exposed to external impacts. The visualization results of stress wave propagation will be shown under various impact scenarios. The proposed technique can be used to characterize and localize damage by detecting the attenuation, reflection, and scattering of stress waves that occurs at damage locations. This can ultimately lead to the development of new structural health monitoring and nondestructive evaluation methods for identifying hidden cracks or delaminations in metallic or composite plate structures, simultaneously negating the need for mounted contact sensors.

  9. 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.

  10. Spatiotemporal patterns of acoustic emission (AE) activity in salt mine

    NASA Astrophysics Data System (ADS)

    Maghsoudi, S.; Cesca, S.; Hainzl, S.; Kaiser, D.; Dahm, T.

    2012-04-01

    Assessing the magnitude of completeness (Mc) is essential for the correct interpretation of earthquake catalogs. Knowledge on the spatiotemporal variation of Mc allows the mapping of other seismicity parameters, such as b-values. Spatial and temporal variations of b-values can indicate structural heterogeneities, stress perturbations and time-dependent fracturing processes. In order to precisely estimate Mc in strongly heterogeneous media, we propose a 3D development of the probabilistic magnitude of completeness (PMC) method, which relies on the analysis of network detection capabilities, to study spatial distribution of the Mc and b-value estimations for mining networks. We used a large dataset including more than 1 million acoustic emissions (AE), recorded at the Morsleben salt mine, Germany. Our study shows that the PMC estimations strongly depend on the source-receiver direction, and cannot be correctly accounted using a standard approach. The comparison between Mc using the 3D PMC method and Gutenberg-Richter methods show agreements for two reference depth ranges. Following our approach, we estimate Mc ranging between 1.25 (AE ,relative acoustic magnitude), at the center of the network, and 3.5, at further distances outside the network. Our method provides small-scale details about the capability of sensors to detect an AE event, and spatial distributions of Mc and b-value, which can be linked to the presence of structural heterogeneities or cavities in specific directions. Effects of heterogeneities on detection analysis are confirmed by synthetic tests using waveform modeling in heterogeneous media. This work has been funded by the German BMBF "Geotechnologien" project MINE (BMBF03G0737A).

  11. 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).

  12. 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

  13. Correlation between solar acoustic emission and phase of the solar cycle

    NASA Astrophysics Data System (ADS)

    Chen, R.; Zhao, J.

    2015-12-01

    The solar acoustic emission is closely related to solar convection and magnetic field. Understanding the relation between the acoustic emission and the phase of a solar cycle is important to understand the dynamics of solar cycles and excitation of acoustic waves. In this work we use 4 years of SDO/HMI data from 05/2010 to 04/2014, covering the growing phase of the solar cycle 24, to study the acoustic emissions of the whole sun and of only the quiet sun regions respectively, at multiple frequency bands. We also analyze the correlations between the acoustic emissions and solar activity level indexed by daily sunspot number and magnetic flux. The results show that the correlation between the whole-sun acoustic emission and solar activity level is negative for low frequencies at 2.5-4.5 mHz, with a peak value around -0.9, and is positive for high frequencies at 4.5-6.0 mHz, with a peak value around 0.9. For high frequencies, the acoustic emission excess in sunspot halos overwhelms the emission deficiency in sunspot umbrae and penumbrae. The correlation between the quiet-sun acoustic emission and solar activity level is negative for 2.5-4.0 mHz and positive for 4.0-5.5 mHz, with peak values over ±0.8. This shows that the solar background acoustic power, with active regions excluded, is indeed varying during a solar cycle, implying the excitation frequencies or depths are highly related to the solar magnetic field.

  14. Using Acoustic Tomography to Monitor Deep Ocean Currents in the Eastern Gulf of Mexico

    DTIC Science & Technology

    2010-06-01

    Toward the improved prediction and monitoring of deep-water currents and eddies in the Gulf of Mexico , the Gulf Eddy Monitoring System group (GEMS...proposes that a network of acoustic transmitter receiver pairs be deployed in the northeastern Gulf of Mexico . Acoustic travel times are inverted to

  15. Experimental facility for the study of acoustic emission registered in the primary circuit components of WWER power units

    NASA Astrophysics Data System (ADS)

    Petrosyan, V. G.; Hovakimyan, T. H.; Yeghoyan, E. A.; Hovhannisyan, H. T.; Mayilyan, D. G.; Petrosyan, A. P.

    2017-01-01

    This paper is dedicated to the creation of a facility for the experimental study of a phenomenon of background acoustic emission (AE), which is detected in the main circulation loop (MCL) of WWER power units. The analysis of the operating principle and the design of a primary feed-and-blow down system (FB) deaerator of NPP as the most likely source of continuous acoustic emission is carried out. The experimental facility for the systematic study of a phenomenon of continuous AE is developed. A physical model of a thermal deaerator is designed and constructed. A thermal monitoring system is introduced. An automatic system providing acoustic signal registration in a low frequency (0.03-30 kHz) and high frequency (30-300 kHz) bands and study of its spectral characteristics is designed. Special software for recording and processing of digitized electrical sensor signals is developed. A separate and independent principle of study of the most probable processes responsible for the generation of acoustic emission signals in the deaerator is applied. Trial series of experiments and prechecks of acoustic signals in different modes of the deaerator model are conducted. Compliance of basic technological parameters with operating range of the real deaerator was provided. It is shown that the acoustic signal time-intensity curve has several typical regions. The pilot research showed an impact of various processes that come about during the operation of the deaerator physical model on the intensity of the AE signal. The experimental results suggest that the main sources of generation of the AE signals are the processes of steam condensation, turbulent flow of gas-vapor medium, and water boiling.

  16. Acoustic monitoring method and system in laser-induced optical breakdown (LIOB)

    DOEpatents

    O'Donnell, Matthew; Ye, Jing Yong; Norris, Theodore B.; Baker, Jr., James R.; Balogh, Lajos P.; Milas, Susanne M.; Emelianov, Stanislav Y.; Hollman, Kyle W.

    2008-05-06

    An acoustic monitoring method and system in laser-induced optical breakdown (LIOB) provides information which characterize material which is broken down, microbubbles in the material, and/or the microenvironment of the microbubbles. In one embodiment of the invention, femtosecond laser pulses are focused just inside the surface of a volume of aqueous solution which may include dendrimer nanocomposite (DNC) particles. A tightly focused, high frequency, single-element ultrasonic transducer is positioned such that its focus coincides axially and laterally with this laser focus. When optical breakdown occurs, a microbubble forms and a shock or pressure wave is emitted (i.e., acoustic emission). In addition to this acoustic signal, the microbubble may be actively probed with pulse-echo measurements from the same transducer. After the microbubble forms, received pulse-echo signals have an extra pulse, describing the microbubble location and providing a measure of axial microbubble size. Wavefield plots of successive recordings illustrate the generation, growth, and collapse of microbubbles due to optical breakdown. These same plots can also be used to quantify LIOB thresholds.

  17. A multi-channel acoustics monitor for perioperative respiratory monitoring: preliminary data.

    PubMed

    Jafarian, Kamal; Amineslami, Majid; Hassani, Kamran; Navidbakhsh, Mahdi; Lahiji, Mohammad Niakan; Doyle, D John

    2016-02-01

    This study pertains to a six-channel acoustic monitoring system for use in patient monitoring during or after surgery. The base hardware consists of a USB data acquisition system, a custom-built six-channel amplification system, and a series of microphones of various designs. The software is based on the MATLAB platform with data acquisition drivers installed. The displayed information includes: time domain signals, frequency domain signals, and tools to aid in the detection of endobronchial intubation. We hypothesize that the above mentioned arrangement may be helpful to the anesthesiologist in recognizing clinical conditions like wheezing, bronchospasm, endobronchial intubation, and apnea. The study also evaluated various types of microphone designs used to transduce breath sounds. The system also features selectable band-pass filtering using MATLAB algorithms as well as a collection of recordings obtained with the system to establish what respiratory acoustic signals look like under various conditions.

  18. 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.

  19. Characterization of Longitudinal Splitting and Fiber Breakage in Gr/Ep using Acoustic Emission Data

    NASA Technical Reports Server (NTRS)

    Ely, Thomas M.; Hill, Eric K.

    1993-01-01

    A composite tensile test specimen was designed such that fiber breakage and longitudinal splitting occurred at a known position in the specimen. By studying the acoustic signature of each failure mechanism distinct characteristics in the data were identified that uniquely related the acoustic emission parameters with either fiber breakage or longitudinal splitting.

  20. Guided wave acoustic monitoring of corrosion in recovery boiler tubing

    SciTech Connect

    Quarry, M J; Chinn, D J

    2004-02-19

    Corrosion of tubing used in black-liquor recovery boilers is a major concern in all pulp and paper mills. Extensive corrosion in recovery boiler tubes can result in a significant safety and environmental hazard. Considerable plant resources are expended to inspect recovery boiler tubing. Currently, visual and ultrasonic inspections are primarily used during the annual maintenance shutdown to monitor corrosion rates and cracking of tubing. This Department of Energy, Office of Industrial Technologies project is developing guided acoustic waves for use on recovery boiler tubing. The feature of this acoustic technique is its cost-effectiveness in inspecting long lengths of tubes from a single inspection point. A piezoelectric or electromagnetic transducer induces guided waves into the tubes. The transducer detects fireside defects from the coldside or fireside of the tube. Cracking and thinning on recovery boiler tubes have been detected with this technique in both laboratory and field applications. This technique appears very promising for recovery boiler tube application, potentially expediting annual inspection of tube integrity.

  1. Operational Performance Analysis of Passive Acoustic Monitoring for Killer Whales

    SciTech Connect

    Matzner, Shari; Fu, Tao; Ren, Huiying; Deng, Zhiqun; Sun, Yannan; Carlson, Thomas J.

    2011-09-30

    For the planned tidal turbine site in Puget Sound, WA, the main concern is to protect Southern Resident Killer Whales (SRKW) due to their Endangered Species Act status. A passive acoustic monitoring system is proposed because the whales emit vocalizations that can be detected by a passive system. The algorithm for detection is implemented in two stages. The first stage is an energy detector designed to detect candidate signals. The second stage is a spectral classifier that is designed to reduce false alarms. The evaluation presented here of the detection algorithm incorporates behavioral models of the species of interest, environmental models of noise levels and potential false alarm sources to provide a realistic characterization of expected operational performance.

  2. Damage depth estimation on a fatigue loaded composite structure using thermography and acoustic emission

    NASA Astrophysics Data System (ADS)

    Zalameda, Joseph N.; Winfree, William P.; Horne, Michael R.

    2017-02-01

    Passive thermography and acoustic emission data were obtained on a three stringer panel during periodic fatigue loading. The acoustic emission data were 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. Furthermore, sudden changes in thermally measured damage growth related to a previously measured higher energy acoustic emission event are studied to determine damage depth. A thermal model with a periodic flux heat source is presented to determine the relationship between the damage depth and thermal response. The model results are compared to the measured data. Lastly, the practical application and limitations of this technique are discussed.

  3. Surface Acoustic Wave (SAW) Resonators for Monitoring Conditioning Film Formation.

    PubMed

    Hohmann, Siegfried; Kögel, Svea; Brunner, Yvonne; Schmieg, Barbara; Ewald, Christina; Kirschhöfer, Frank; Brenner-Weiß, Gerald; Länge, Kerstin

    2015-05-21

    We propose surface acoustic wave (SAW) resonators as a complementary tool for conditioning film monitoring. Conditioning films are formed by adsorption of inorganic and organic substances on a substrate the moment this substrate comes into contact with a liquid phase. In the case of implant insertion, for instance, initial protein adsorption is required to start wound healing, but it will also trigger immune reactions leading to inflammatory responses. The control of the initial protein adsorption would allow to promote the healing process and to suppress adverse immune reactions. Methods to investigate these adsorption processes are available, but it remains difficult to translate measurement results into actual protein binding events. Biosensor transducers allow user-friendly investigation of protein adsorption on different surfaces. The combination of several transduction principles leads to complementary results, allowing a more comprehensive characterization of the adsorbing layer. We introduce SAW resonators as a novel complementary tool for time-resolved conditioning film monitoring. SAW resonators were coated with polymers. The adsorption of the plasma proteins human serum albumin (HSA) and fibrinogen onto the polymer-coated surfaces were monitored. Frequency results were compared with quartz crystal microbalance (QCM) sensor measurements, which confirmed the suitability of the SAW resonators for this application.

  4. Surface Acoustic Wave (SAW) Resonators for Monitoring Conditioning Film Formation

    PubMed Central

    Hohmann, Siegfried; Kögel, Svea; Brunner, Yvonne; Schmieg, Barbara; Ewald, Christina; Kirschhöfer, Frank; Brenner-Weiß, Gerald; Länge, Kerstin

    2015-01-01

    We propose surface acoustic wave (SAW) resonators as a complementary tool for conditioning film monitoring. Conditioning films are formed by adsorption of inorganic and organic substances on a substrate the moment this substrate comes into contact with a liquid phase. In the case of implant insertion, for instance, initial protein adsorption is required to start wound healing, but it will also trigger immune reactions leading to inflammatory responses. The control of the initial protein adsorption would allow to promote the healing process and to suppress adverse immune reactions. Methods to investigate these adsorption processes are available, but it remains difficult to translate measurement results into actual protein binding events. Biosensor transducers allow user-friendly investigation of protein adsorption on different surfaces. The combination of several transduction principles leads to complementary results, allowing a more comprehensive characterization of the adsorbing layer. We introduce SAW resonators as a novel complementary tool for time-resolved conditioning film monitoring. SAW resonators were coated with polymers. The adsorption of the plasma proteins human serum albumin (HSA) and fibrinogen onto the polymer-coated surfaces were monitored. Frequency results were compared with quartz crystal microbalance (QCM) sensor measurements, which confirmed the suitability of the SAW resonators for this application. PMID:26007735

  5. Acoustic emission spectra and sonochemical activity in a 36 kHz sonoreactor.

    PubMed

    Son, Younggyu; Lim, Myunghee; Khim, Jeehyeong; Ashokkumar, Muthupandian

    2012-01-01

    During ultrasound-induced cavitation in liquids, acoustic emissions at fundamental and harmonic frequencies can be detected. The effect of acoustic emissions at harmonic frequencies on the sonochemical and sonophysical activities has not been explored, especially in large-scale sonoreactors. In this study, the acoustic emissions in the range, 0-250 kHz in a 36 kHz sonoreactor with varying liquid heights were studied and compared with the sonochemical activities. The acoustic pressures at both fundamental and harmonics decreased drastically as the liquid height was increased due to the attenuation of sound energy. It was observed that the increase in input power resulted in only an increase in the acoustic emissions at derivative frequencies such as, harmonics and subharmonics. The sonochemical activity, evaluated in terms of sonochemiluminescence and H2O2 yield, was not significantly enhanced at higher input power levels. This suggests that at higher power levels, the "extra" acoustic energy is not effectively used to generate primary cavitation activity; rather it is converted to generate acoustic emissions at harmonic and subharmonic frequencies. This is an important observation for the design of energy efficiency large-scale sonochemical reactors.

  6. MEMS acoustic emission transducers designed with high aspect ratio geometry

    NASA Astrophysics Data System (ADS)

    Saboonchi, H.; Ozevin, D.

    2013-09-01

    In this paper, micro-electro-mechanic systems (MEMS) acoustic emission (AE) transducers are manufactured using an electroplating technique. The transducers use a capacitance change as their transduction principle, and are tuned to the range 50-200 kHz. Through the electroplating technique, a thick metal layer (20 μm nickel + 0.5 μm gold) is used to form a freely moving microstructure layer. The presence of the gold layer reduces the potential corrosion of the nickel layer. A dielectric layer is deposited between the two electrodes, thus preventing the stiction phenomenon. The transducers have a measured quality factor in the range 15-30 at atmospheric pressure and are functional without vacuum packaging. The transducers are characterized using electrical and mechanical tests to identify the capacitance, resonance frequency and damping. Ultrasonic wave generation using a Q-switched laser shows the directivity of the transducer sensitivity. The comparison of the MEMS transducers with similar frequency piezoelectric transducers shows that the MEMS AE transducers have better response characteristics and sensitivity at the resonance frequency and well-defined waveform signatures (rise time and decay time) due to pure resonance behavior in the out-of-plane direction. The transducers are sensitive to a unique wave direction, which can be utilized to increase the accuracy of source localization by selecting the correct wave velocity at the structures.

  7. 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.

  8. 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).

  9. Stimulated emission of phonons in an acoustic cavity

    NASA Astrophysics Data System (ADS)

    Tilstra, Lieuwe Gijsbert

    2001-10-01

    This thesis will present experiments on stimulated emission of phonons in dilute ruby following complete population inversion of the Zeeman-split E(2E) Kramers doublet by selective pulsed optical pumping into its upper component. The resulting phonon avalanches are detected by use of the R1 luminescence emanating from the inverted zone, located near the end face where the laser beam enters the crystal. The phonons appear to team up into a highly directional phonon beam. The phonon frequency is tunable from, say, 10-100 GHz via the magnetic field splitting of the doublet. Remarkably, the population of the lower doublet component, which is a measure of the number of phonons generated, evolves with a sequence of distinct steps. The time interval in between these steps equals 2L/v, corresponding to the time the phonons need to return to the inverted zone by reflection at the opposite end face at a distance L. The end faces of the ruby crystal thus form an acoustic cavity. The phonon beam passes the inverted zone repeatedly to be amplified further, in a manner similar to light in an optical laser. In other words, the basic ingredients for a phonon laser have been established.

  10. 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.

  11. Adaptation of PWAS transducers to acoustic emission sensors

    NASA Astrophysics Data System (ADS)

    Yu, Lingyu; Momeni, Sepandarmaz; Godinez, Valery; Giurgiutiu, Victor

    2011-04-01

    Piezoelectric wafer active sensors (PWAS) are non-intrusive transducers that can convert mechanical energy into electrical energy, and vice versa. They are well known for their dual use as either actuators or sensors. Though PWAS has shown great potential for active sensing, its capability for acoustic emission (AE) detection has not yet been exploited. In the reported work, we have explored the implementation of PWAS transducers for both passive (AE sensors) and active (in-situ ultrasonic transducers) sensing using a single PWAS network. The objective of the work presented in this paper is to adapt PWAS as AE sensors and compare it to the commercially available AE transducers such as PAC R15. An experiment has been designed to show how PWAS can be used for AE detection and the results were compared to a standard AE sensor, PAC R15I. Tests on compact tension specimens have also been conducted to show PWAS capability to pick up AE events during fatigue loading. PWAS field installation technology has been tested with packaging similar to that used for traditional strain gauges. The performance of packaged PWAS has been compared with that of conventional AE transducers R15I. We have found that PWAS not only can detect the presence of AE events but also can provide a wide frequency bandwidth. At this stage, PWAS underperforms the commercial AE sensors. To make PWAS ready for field test, signal to noise ratio needs to be significantly improved.

  12. 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.

  13. 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.

  14. 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.

  15. Acoustic Emission Parameters of Three Gorges Sandstone during Shear Failure

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Liu, Yixin; Peng, Shoujian

    2016-12-01

    In this paper, an experimental investigation of sandstone samples from the Three Gorges during shear failure was conducted using acoustic emission (AE) and direct shear tests. The AE count rate, cumulative AE count, AE energy, and amplitude of the sandstone samples were determined. Then, the relationships among the AE signals and shearing behaviors of the samples were analyzed in order to detect micro-crack initiation and propagation and reflect shear failure. The results indicated that both the shear strength and displacement exhibited a logarithmic relationship with the displacement rate at peak levels of stress. In addition, the various characteristics of the AE signals were apparent in various situations. The AE signals corresponded with the shear stress under different displacement rates. As the displacement rate increased, the amount of accumulative damage to each specimen decreased, while the AE energy peaked earlier and more significantly. The cumulative AE count primarily increased during the post-peak period. Furthermore, the AE count rate and amplitude exhibited two peaks during the peak shear stress period due to crack coalescence and rock bridge breakage. These isolated cracks later formed larger fractures and eventually caused ruptures.

  16. Accurate Simulation of Acoustic Emission Sources in Composite Plates

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Gorman, M. R.

    1994-01-01

    Acoustic emission (AE) signals propagate as the extensional and flexural plate modes in thin composite plates and plate-like geometries such as shells, pipes, and tubes. The relative amplitude of the two modes depends on the directionality of the source motion. For source motions with large out-of-plane components such as delaminations or particle impact, the flexural or bending plate mode dominates the AE signal with only a small extensional mode detected. A signal from such a source is well simulated with the standard pencil lead break (Hsu-Neilsen source) on the surface of the plate. For other sources such as matrix cracking or fiber breakage in which the source motion is primarily in-plane, the resulting AE signal has a large extensional mode component with little or no flexural mode observed. Signals from these type sources can also be simulated with pencil lead breaks. However, the lead must be fractured on the edge of the plate to generate an in-plane source motion rather than on the surface of the plate. In many applications such as testing of pressure vessels and piping or aircraft structures, a free edge is either not available or not in a desired location for simulation of in-plane type sources. In this research, a method was developed which allows the simulation of AE signals with a predominant extensional mode component in composite plates requiring access to only the surface of the plate.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  18. 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.

  19. Analysis of Acoustic Emission Signals During Laser Spot Welding of SS304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Lee, Seounghwan; Ahn, Suneung; Park, Changsoon

    2014-03-01

    In this article, an in-process monitoring scheme for a pulsed Nd:YAG laser spot welding (LSW) is presented. Acoustic emission (AE) was selected for the feedback signal, and the AE data during LSW were sampled and analyzed for varying process conditions such as laser power and pulse duration. In the analysis, possible AE generation sources such as melting and solidification mechanism during welding were investigated using both the time- and frequency-domain signal processings. The results, which show close relationships between LSW and AE signals, were adopted in the feature (input) selection of a back-propagation artificial neural network, to predict the weldability of stainless steel sheets. Processed outputs agree well with LSW experimental data, which confirms the usefulness of the proposed scheme.

  20. Neural network prediction of aluminum-lithium weld strengths from acoustic emission amplitude data

    SciTech Connect

    Hill, E.V.K. . Aerospace Engineering Dept.); Israel, P.L. . Computer Science Dept.); Knotts, G.L. )

    1993-09-01

    Acoustic emission (AE) flaw growth activity was monitored in aluminum-lithium weld specimens from the onset of tensile loading to failure. Data on actual ultimate strengths together with AE data from the beginning of loading up to 25 percent of the expected ultimate strength were used to train a backpropagation neural network to predict ultimate strengths. Architecturally, the fully interconnected network consisted of an input layer for the AE amplitude data, a hidden layer to accommodate failure mechanism mapping, and an output layer for ultimate strength prediction. The trained network was then applied to the prediction of ultimate strengths in the remaining six specimens. The worst case prediction error was found to be +2.6 percent.

  1. Size Differentiation Of A Continuous Stream Of Particles Using Acoustic Emissions

    NASA Astrophysics Data System (ADS)

    Nsugbe, E.; Starr, A.; Foote, P.; Ruiz-Carcel, C.; Jennions, I.

    2016-11-01

    Procter and Gamble (P&G) require an online system that can monitor the particle size distribution of their washing powder mixing process. This would enable the process to take a closed loop form which would enable process optimisation to take place in real time. Acoustic Emission (AE) was selected as the sensing method due to its non-invasive nature and primary sensitivity to frequencies which particle events emanate. This work details the results of the first experiment carried out in this research project. This experiment involved the use of AE to distinguish between the sizes of sieved polyethylene particle (53-250microns) and glass beads (150-600microns) which were dispensed on a target plate using a funnel. By conducting a threshold analysis of the impact peaks in the signal, the sizes of the particles could be distinguished and a signal feature was found which could be directly linked to the sizes of the particles.

  2. Intensity-demodulated fiber-ring laser sensor system for acoustic emission detection.

    PubMed

    Han, Ming; Liu, Tongqing; Hu, Lingling; Zhang, Qi

    2013-12-02

    We theoretically and experimentally demonstrate a fiber-optic ultrasonic sensor system based on a fiber-ring laser whose cavity consisting of a regular fiber Bragg grating (FBG) and a tunable optical band-pass filter (TOBPF). The FBG is the sensing element and the TOBPF is used to set the lasing wavelength at a point on the spectral slope of the FBG. The ultrasonic signal is detected by the variations of the laser output intensity in response to the cold-cavity loss modulations from the ultrasonically-induced FBG spectral shift. The system demonstrated here has a simple structure and low cost, making it attractive for acoustic emission detection in structure health monitoring.

  3. Neural Network Prediction of Aluminum-Lithium Weld Strengths from Acoustic Emission Amplitude Data

    NASA Technical Reports Server (NTRS)

    Hill, Eric v. K.; Israel, Peggy L.; Knotts, Gregory L.

    1993-01-01

    Acoustic Emission (AE) flaw growth activity was monitored in aluminum-lithium weld specimens from the onset tensile loading to failure. Data on actual ultimate strengths together with AE data from the beginning of loading up to 25 percent of the expected ultimate strength were used to train a backpropagation neural network to predict ultimate strengths. Architecturally, the fully interconnected network consisted of an input layer for the AE amplitude data, a hidden layer to accommodate failure mechanism mapping, and an output layer for ultimate strength prediction. The trained network was the applied to the prediction of ultimate strengths in the remaining six specimens. The worst case prediction error was found to be +2.6 percent.

  4. Non-stationary drying of ceramic-like materials controlled through acoustic emission method

    NASA Astrophysics Data System (ADS)

    Kowalski, Stefan Jan; Szadzińska, Justyna

    2012-12-01

    This paper presents results of convective drying of ceramic-like materials in non-stationary conditions. The effect of periodically changing drying parameters at different frequencies and amplitudes on material quality has been investigated. During drying tests the destruction of the material was controlled trough the acoustic emission method and monitored with a digital camera. The experiments were carried out on cylindrically shaped samples made of KOC kaolin clay. The non-stationary drying consisted in periodical changes of the drying medium temperature and humidity. It has been found that a properly arranged methodology of non-stationary drying positively affects the product quality, mainly when drying is carried on with periodical changes of air humidity and to lesser extent with periodical changes of air temperature.

  5. Detection and Identification of Concrete Cracking in Reinforced Concrete by Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Ohtsu, Masayasu

    2003-03-01

    Cracking in concrete due to corrosion of rebars in reinforced concrete is one of critical problems in concrete structures. To clarify cracking process, acoustic emission (AE) measurement is applied. In an accelerated corrosion test, AE events are detected and monitored continuously. Comparing with permeation of chloride ions, it is found that onset of corrosion and nucleation of cracking can be qualified from AE activity. Applying SiGMA procedure, nucleation mechanisms of cracks due to expansion of corrosive product are identified. During extension of the surface crack, tensile cracks are nucleated dominantly. For the spalling crack, both the tensile and the shear cracks are generated, as the former dominates the latter approaching to a stress-free surface. In contrast, it is found that the internal crack is nucleated mainly due to shear-crack motion.

  6. Acoustic emission during fatigue crack propagation in SiC particle reinforced Al matrix composites

    SciTech Connect

    Niklas, A.; Froyen, L.; Wevers, M.; Delaey, L.

    1995-12-01

    The acoustic emission (AE) behavior during fatigue propagation in aluminum 6061 and aluminum 6061 matrix composites containing 5, 10, and 20 wt pct SiC particle reinforcement was investigated under tension-tension fatigue loading. The purpose of this investigation was to monitor fatigue crack propagation by the AE technique and to identify the source(s) of AE. Most of the AEs detected were observed at the top of the load cycles. The cumulative number of AE events was found to correspond closely to the fatigue crack growth and to increase with increasing SiC content. Fractographic studies revealed an increasing number of fractured particles and to a lesser extent decohered particles on the fatigue fracture surface as the crack propagation rate (e.g., {Delta}K) or the SiC content was increased.

  7. Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys. Volume 1

    DTIC Science & Technology

    1983-05-01

    behavior during the deforma- S. tion and fracture of a series of rather microstruc - turally complex Naval alloy steels. ’. a a a...investigation the acoustic emission behavior of thre Naval alloy steels (HY 80, HY 100 and HY 130) was characterized during tensile elongation and bend type...and fracture modes despite a slight dif- ference in microstructures. They also exhibited identical "-’=, acoustic emission behavior within statistical

  8. 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.

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

    SciTech Connect

    White, T.L.

    1991-02-26

    This patent describes an acoustic emission based feedback system for controlling the boiling level of a liquid medium in a microwave oven. 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 continuously vary the power applied to the oven to control the boiling at a selected level.

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

    SciTech Connect

    White, T.L.

    1990-05-02

    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 continuously vary the power applied to the oven to control the boiling at a selected level. 2 figs.

  11. 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.

  12. 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.

  13. 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

  14. Cavitation controlled acoustic probe for fabric spot cleaning and moisture monitoring

    DOEpatents

    Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, Apostolos C.

    1997-01-01

    A method and apparatus are provided for monitoring a fabric. An acoustic probe generates acoustic waves relative to the fabric. An acoustic sensor, such as an accelerometer is coupled to the acoustic probe for generating a signal representative of cavitation activity in the fabric. The generated cavitation activity representative signal is processed to indicate moisture content of the fabric. A feature of the invention is a feedback control signal is generated responsive to the generated cavitation activity representative signal. The feedback control signal can be used to control the energy level of the generated acoustic waves and to control the application of a cleaning solution to the fabric.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

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

  17. Monitoring polymer properties using shear horizontal surface acoustic waves.

    PubMed

    Gallimore, Dana Y; Millard, Paul J; Pereira da Cunha, Mauricio

    2009-10-01

    Real-time, nondestructive methods for monitoring polymer film properties are increasingly important in the development and fabrication of modern polymer-containing products. Online testing of industrial polymer films during preparation and conditioning is required to minimize material and energy consumption, improve the product quality, increase the production rate, and reduce the number of product rejects. It is well-known that shear horizontal surface acoustic wave (SH-SAW) propagation is sensitive to mass changes as well as to the mechanical properties of attached materials. In this work, the SH-SAW was used to monitor polymer property changes primarily dictated by variations in the viscoelasticity. The viscoelastic properties of a negative photoresist film were monitored throughout the ultraviolet (UV) light-induced polymer cross-linking process using SH-SAW delay line devices. Changes in the polymer film mass and viscoelasticity caused by UV exposure produced variations in the phase velocity and attenuation of the SH-SAW propagating in the structure. Based on measured polymer-coated delay line scattering transmission responses (S(21)) and the measured polymer layer thickness and density, the viscoelastic constants c(44) and eta(44) were extracted. The polymer thickness was found to decrease 0.6% during UV curing, while variations in the polymer density were determined to be insignificant. Changes of 6% in c(44) and 22% in eta(44) during the cross-linking process were observed, showing the sensitivity of the SH-SAW phase velocity and attenuation to changes in the polymer film viscoelasticity. These results indicate the potential for SH-SAW devices as online monitoring sensors for polymer film processing.

  18. Passive acoustic monitoring of human physiology during activity indicates health and performance of soldiers and firefighters

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael V.

    2003-04-01

    The Army Research Laboratory has developed a unique gel-coupled acoustic physiological monitoring sensor that has acoustic impedance properties similar to the skin. This facilitates the transmission of body sounds into the sensor pad, yet significantly repels ambient airborne noises due to an impedance mismatch. The sensor's sensitivity and bandwidth produce excellent signatures for detection and spectral analysis of diverse physiological events. Acoustic signal processing detects heartbeats, breaths, wheezes, coughs, blood pressure, activity, motion, and voice for communication and automatic speech recognition. The health and performance of soldiers, firefighters, and other first responders in strenuous and hazardous environments can be continuously and remotely monitored with body-worn acoustic sensors. Comfortable acoustic sensors can be in a helmet or in a strap around the neck, chest, and wrist. Noise-canceling sensor arrays help remove out-of-phase motion noise and enhance covariant physiology by using two acoustic sensors on the front sides of the neck and two additional acoustic sensors on each wrist. Pulse wave transit time between neck and wrist acoustic sensors will indicate systolic blood pressure. Larger torso-sized arrays can be used to acoustically inspect the lungs and heart, or built into beds for sleep monitoring. Acoustics is an excellent input for sensor fusion.

  19. Real-time temperature estimation and monitoring of HIFU ablation through a combined modeling and passive acoustic mapping approach.

    PubMed

    Jensen, C R; Cleveland, R O; Coussios, C C

    2013-09-07

    Passive acoustic mapping (PAM) has been recently demonstrated as a method of monitoring focused ultrasound therapy by reconstructing the emissions created by inertially cavitating bubbles (Jensen et al 2012 Radiology 262 252-61). The published method sums energy emitted by cavitation from the focal region within the tissue and uses a threshold to determine when sufficient energy has been delivered for ablation. The present work builds on this approach to provide a high-intensity focused ultrasound (HIFU) treatment monitoring software that displays both real-time temperature maps and a prediction of the ablated tissue region. This is achieved by determining heat deposition from two sources: (i) acoustic absorption of the primary HIFU beam which is calculated via a nonlinear model, and (ii) absorption of energy from bubble acoustic emissions which is estimated from measurements. The two sources of heat are used as inputs to the bioheat equation that gives an estimate of the temperature of the tissue as well as estimates of tissue ablation. The method has been applied to ex vivo ox liver samples and the estimated temperature is compared to the measured temperature and shows good agreement, capturing the effect of cavitation-enhanced heating on temperature evolution. In conclusion, it is demonstrated that by using PAM and predictions of heating it is possible to produce an evolving estimate of cell death during exposure in order to guide treatment for monitoring ablative HIFU therapy.

  20. A Fiber-Optic Sensor for Acoustic Emission Detection in a High Voltage Cable System.

    PubMed

    Zhang, Tongzhi; Pang, Fufei; Liu, Huanhuan; Cheng, Jiajing; Lv, Longbao; Zhang, Xiaobei; Chen, Na; Wang, Tingyun

    2016-11-30

    We have proposed and demonstrated a Michelson interferometer-based fiber sensor for detecting acoustic emission generated from the partial discharge (PD) of the accessories of a high-voltage cable system. The developed sensor head is integrated with a compact and relatively high sensitivity cylindrical elastomer. Such a sensor has a broadband frequency response and a relatively high sensitivity in a harsh environment under a high-voltage electric field. The design and fabrication of the sensor head integrated with the cylindrical elastomer is described, and a series of experiments was conducted to evaluate the sensing performance. The experimental results demonstrate that the sensitivity of our developed sensor for acoustic detection of partial discharges is 1.7 rad / ( m ⋅ Pa ) . A high frequency response up to 150 kHz is achieved. Moreover, the relatively high sensitivity for the detection of PD is verified in both the laboratory environment and gas insulated switchgear. The obtained results show the great potential application of a Michelson interferometer-based fiber sensor integrated with a cylindrical elastomer for in-situ monitoring high-voltage cable accessories for safety work.

  1. A Fiber-Optic Sensor for Acoustic Emission Detection in a High Voltage Cable System

    PubMed Central

    Zhang, Tongzhi; Pang, Fufei; Liu, Huanhuan; Cheng, Jiajing; Lv, Longbao; Zhang, Xiaobei; Chen, Na; Wang, Tingyun

    2016-01-01

    We have proposed and demonstrated a Michelson interferometer-based fiber sensor for detecting acoustic emission generated from the partial discharge (PD) of the accessories of a high-voltage cable system. The developed sensor head is integrated with a compact and relatively high sensitivity cylindrical elastomer. Such a sensor has a broadband frequency response and a relatively high sensitivity in a harsh environment under a high-voltage electric field. The design and fabrication of the sensor head integrated with the cylindrical elastomer is described, and a series of experiments was conducted to evaluate the sensing performance. The experimental results demonstrate that the sensitivity of our developed sensor for acoustic detection of partial discharges is 1.7 rad/(m⋅Pa). A high frequency response up to 150 kHz is achieved. Moreover, the relatively high sensitivity for the detection of PD is verified in both the laboratory environment and gas insulated switchgear. The obtained results show the great potential application of a Michelson interferometer-based fiber sensor integrated with a cylindrical elastomer for in-situ monitoring high-voltage cable accessories for safety work. PMID:27916900

  2. Detection of acoustic emission from cavitation in tissue during clinical extracorporeal lithotripsy.

    PubMed

    Coleman, A J; Choi, M J; Saunders, J E

    1996-01-01

    A 1-MHz focused hydrophone has been used to search for acoustic emission expected to arise from cavitation occurring in tissue during clinical extracorporeal shock-wave lithotripsy (ESWL). The hydrophone is acoustically coupled to the patient's skin and the focus directed at depth in tissue under ultrasound guidance. The measured amplitude-time variation of the acoustic emission from tissue near the shock-wave focus of the Storz Modulith SL20 lithotripter has been examined in four patients. There is evidence of increased amplitude acoustic emission at 1 MHz from regions within tissue that also appear hyperechoic in simultaneously acquired ultrasound images. The acoustic emission from these regions decays from an initial peak to the noise level in about 500 microseconds following each shock-wave pulse. Within this period, a second peak, often of higher amplitude than the first, is typically observed about 100 microseconds after the shockwave. The time between the initial and second peaks is found to increase with increasing shock-wave amplitude. The results are similar to those previously observed from cavitation induced by shock-wave exposure in water and indicate that the 1-MHz acoustic emission arises from inertial cavitation in tissue during clinical ESWL.

  3. 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.

  4. 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.

  5. Identification of the Onset of Cracking in Gear Teeth Using Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Pullin, R.; Clarke, A.; Eaton, M. J.; Pearson, M. R.; Holford, K. M.

    2012-08-01

    The development of diagnostic methods for gear tooth faults in aerospace power transmission systems is an active research area being driven largely by the interests of military organisations or large aerospace organisations. In aerospace applications, the potential results of gear failure are serious, ranging from increased asset downtime to, at worst, catastrophic failure with life-threatening consequences. New monitoring techniques which can identify the onset of failure at earlier stages are in demand. Acoustic Emission (AE) is the most sensitive condition monitoring tool and is a passive technique that detects the stress wave emitted by a structure as cracks propagate. In this study a gear test rig that allows the fatigue loading of an individual gear tooth was utilised. The rig allows a full AE analysis of damage signatures in gear teeth without the presence of constant background noise due to rotational and frictional sources. Furthermore this approach allows validation of AE results using crack gauges or strain gauges. Utilising a new approach to AE monitoring a sensor was mounted on the gear and used to continuously capture AE data for a complete fatigue load cycle of data, rather than the traditional approach where discrete signals are captured on a threshold basis. Data was captured every 10th load cycle for the duration of the test. A developed fast fourier transform analysis technique was compared with traditional analytical methods. In this investigation the developed techniques were validated against visual inspection and were shown to be far superior to the traditional approach.

  6. Comparison of alternatives to amplitude thresholding for onset detection of acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Bai, F.; Gagar, D.; Foote, P.; Zhao, Y.

    2017-02-01

    Acoustic Emission (AE) monitoring can be used to detect the presence of damage as well as determine its location in Structural Health Monitoring (SHM) applications. Information on the time difference of the signal generated by the damage event arriving at different sensors in an array is essential in performing localisation. Currently, this is determined using a fixed threshold which is particularly prone to errors when not set to optimal values. This paper presents three new methods for determining the onset of AE signals without the need for a predetermined threshold. The performance of the techniques is evaluated using AE signals generated during fatigue crack growth and compared to the established Akaike Information Criterion (AIC) and fixed threshold methods. It was found that the 1D location accuracy of the new methods was within the range of < 1 - 7.1 % of the monitored region compared to 2.7% for the AIC method and a range of 1.8-9.4% for the conventional Fixed Threshold method at different threshold levels.

  7. 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.

  8. Tropospheric emissions: monitoring of pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Chance, Kelly; Liu, Xiong; Suleiman, Raid M.; Flittner, David E.; Al-Saadi, Jassim; Janz, Scott J.

    2013-09-01

    TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch circa 2018. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian tar sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (~2 km N/S×4.5 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring together with European Sentinel-4 and Korean GEMS.

  9. Monitoring hydraulic fracturing with seismic emission volume

    NASA Astrophysics Data System (ADS)

    Niu, F.; Tang, Y.; Chen, H.; TAO, K.; Levander, A.

    2014-12-01

    Recent developments in horizontal drilling and hydraulic fracturing have made it possible to access the reservoirs that are not available for massive production in the past. Hydraulic fracturing is designed to enhance rock permeability and reservoir drainage through the creation of fracture networks. Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. Based on data acquisition, seismic monitoring techniques have been divided into two categories: downhole and surface monitoring. Surface monitoring is challenging because of the extremely low signal-to-noise ratio of the raw data. We applied the techniques used in earthquake seismology and developed an integrated monitoring system for mapping hydraulic fractures. The system consists of 20 to 30 state-of-the-art broadband seismographs, which are generally about hundreds times more sensible than regular geophones. We have conducted two experiments in two basins with very different geology and formation mechanism in China. In each case, we observed clear microseismic events, which may correspond to the induced seismicity directly associated with fracturing and the triggered ones at pre-existing faults. However, the magnitude of these events is generally larger than magnitude -1, approximately one to two magnitudes larger than those detected by downhole instruments. Spectrum-frequency analysis of the continuous surface recordings indicated high seismic energy associated with injection stages. The seismic energy can be back-projected to a volume that surrounds each injection stage. Imaging seismic emission volume (SEV) appears to be an effective way to map the stimulated reservior volume, as well as natural fractures.

  10. 40 CFR 61.55 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for Mercury § 61.55 Monitoring of emissions and operations. (a) Wastewater treatment plant sludge incineration and drying plants. All the sources for which mercury emissions exceed 1.6 kg (3.5 lb) per 24-hour....54, shall monitor mercury emissions at intervals of at least once per year by use of Method 105...

  11. 40 CFR 61.55 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for Mercury § 61.55 Monitoring of emissions and operations. (a) Wastewater treatment plant sludge incineration and drying plants. All the sources for which mercury emissions exceed 1.6 kg (3.5 lb) per 24-hour....54, shall monitor mercury emissions at intervals of at least once per year by use of Method 105...

  12. 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.

  13. Can acoustic emission detect the initiation of fatigue cracks: Application to high-strength light alloys used in aeronautics

    NASA Technical Reports Server (NTRS)

    Bathias, C.; Brinet, B.; Sertour, G.

    1978-01-01

    Acoustic emission was used for the detection of fatigue cracking in a number of high-strength light alloys used in aeronautical structures. Among the features studied were: the influence of emission frequency, the effect of surface oxidation, and the influence of grains. It was concluded that acoustic emission is an effective nondestructive technique for evaluating the initiation of fatigue cracking in such materials.

  14. 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.

  15. Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys. Volume 2

    DTIC Science & Technology

    1983-05-01

    Emission Laser Beam Interferometer HY80 , 100, 130 Steels Mechanical Deformation Nondestructive Evaluation 2. ABSTRACT (Conetnue an rovere eli if necoo y...publication, J. Applied Phys.). 43. A. Peterlin, B.B. Djordjvic, J.C. Murphy, R.E. Green, "Acoustic Emission During Craze Forma- tion in Polymers

  16. 40 CFR 60.703 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... recovery device in the recovery system: (i) A condenser exit (product side) temperature monitoring device... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Monitoring of emissions and operations... Processes § 60.703 Monitoring of emissions and operations. (a) The owner or operator of an affected...

  17. Acoustic monitoring system to quantify ingestive behavior of free-grazing cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methods to estimate intake in grazing livestock include using markers, visual observation, mechanical sensors that respond to jaw movement and acoustic recording. In most of the acoustic monitoring studies, the microphone is inverted on the forehead of the grazing livestock and the skull is utilize...

  18. 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.

  19. 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.

  20. Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

    DTIC Science & Technology

    2013-09-30

    sperm whales , beaked whales , minke whales , and humpback whales . Most methods developed will be generalizable to other species. Report Documentation Page...and uncertain ocean environments. J. Acoust. Soc. Am. 101, 3539–3545. Nosal E‐M, LN Frazer (2007). Sperm whale three‐dimensional track, swim...A (2005). Three-dimensional passive acoustic tracking of sperm whales (Physeter macrocephalus) in ray-refracting environments. J. Acoust. Soc. Am

  1. Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

    DTIC Science & Technology

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Improvements to Passive Acoustic Tracking Methods for...www.soest.hawaii.edu/ore/faculty/nosal LONG-TERM GOALS The long-term goal of this project is to improve model-based passive acoustic methods for...and applicability of model-based passive acoustic tracking methods for marine mammals: 1) Invert for sound speed profiles, hydrophone position and

  2. Tropospheric emissions: Monitoring of pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Zoogman, P.; Liu, X.; Suleiman, R. M.; Pennington, W. F.; Flittner, D. E.; Al-Saadi, J. A.; Hilton, B. B.; Nicks, D. K.; Newchurch, M. J.; Carr, J. L.; Janz, S. J.; Andraschko, M. R.; Arola, A.; Baker, B. D.; Canova, B. P.; Chan Miller, C.; Cohen, R. C.; Davis, J. E.; Dussault, M. E.; Edwards, D. P.; Fishman, J.; Ghulam, A.; González Abad, G.; Grutter, M.; Herman, J. R.; Houck, J.; Jacob, D. J.; Joiner, J.; Kerridge, B. J.; Kim, J.; Krotkov, N. A.; Lamsal, L.; Li, C.; Lindfors, A.; Martin, R. V.; McElroy, C. T.; McLinden, C.; Natraj, V.; Neil, D. O.; Nowlan, C. R.; O`Sullivan, E. J.; Palmer, P. I.; Pierce, R. B.; Pippin, M. R.; Saiz-Lopez, A.; Spurr, R. J. D.; Szykman, J. J.; Torres, O.; Veefkind, J. P.; Veihelmann, B.; Wang, H.; Wang, J.; Chance, K.

    2017-01-01

    TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution ( 2.1 km N/S×4.4 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide), water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring

  3. Field performance of an acoustic scour-depth monitoring system

    USGS Publications Warehouse

    Mason, Jr., Robert R.; Sheppard, D. Max

    1994-01-01

    The Herbert C. Bonner Bridge over Oregon Inlet serves as the only land link between Bodie and Hatteras Islands, part of the Outer Banks of North Carolina. Periodic soundings over the past 30 years have documented channel migration, local scour, and deposition at several pilings that support the bridge. In September 1992, a data-collection system was installed to permit the off-site monitoring of scour at 16 bridge pilings. The system records channel-bed elevations at 15-minute intervals and transmits the data to a satellite receiver. A cellular phone connection also permits downloading and reviewing of the data as they are being collected. A digitally recording, acoustic fathometer is the main component of the system. In November 1993, current velocity, water-surface elevation, wave characteristics, and water temperature measuring instruments were also deployed at the site. Several performance problems relating to the equipment and to the harsh marine environment have not been resolved, but the system has collected and transmitted reliable scour-depth and water-level data.

  4. Passive acoustic monitoring of Cook Inlet beluga whales (Delphinapterus leucas).

    PubMed

    Lammers, Marc O; Castellote, Manuel; Small, Robert J; Atkinson, Shannon; Jenniges, Justin; Rosinski, Anne; Oswald, Julie N; Garner, Chris

    2013-09-01

    The endangered beluga whale (Delphinapterus leucas) population in Cook Inlet, AK faces threats from a variety of anthropogenic factors, including coastal development, oil and gas exploration, vessel traffic, and military activities. To address existing gaps in understanding about the occurrence of belugas in Cook Inlet, a project was developed to use passive acoustic monitoring to document the year-round distribution of belugas, as well as killer whales (Orcinus orca), which prey on belugas. Beginning in June 2009, ten moorings were deployed throughout the Inlet and refurbished every two to eight months. Despite challenging conditions consisting of strong tidal currents carrying debris and seasonal ice cover, 83% of mooring deployments were successfully recovered. Noise from water flow, vessel traffic, and/or industrial activities was present at several sites, potentially masking some signals. However, belugas were successfully detected at multiple locations. Detections were relatively common in the upper inlet and less common or absent at middle and lower inlet locations. Killer whale signals were also recorded. Some seasonal variability in the occurrence of both belugas and killer whales was evident.

  5. Acoustical method of whole-body hydration status monitoring

    NASA Astrophysics Data System (ADS)

    Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

    2016-07-01

    An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

  6. Clean Air Markets - Part 75 Emissions Monitoring Policy Manual

    EPA Pesticide Factsheets

    Learn about monitoring mass sulfur dioxide and mass carbon dioxide emissions, nitrogen oxide emission rate, and heat input by units affected by the Acid Rain Program and the Clean Air Interstate Rule.

  7. 40 CFR Part 75 Emissions Monitoring Policy Manual

    EPA Pesticide Factsheets

    Provides guidance on the requirements of 40 CFR Part 75 through a series of questions and answers that can be used by units to monitor mass sulfur dioxide emissions, mass carbon dioxide emissions, nitrogen oxide rate and heat input.

  8. Size Distribution of Sperm Whales Acoustically Identified during Long Term Deep-Sea Monitoring in the Ionian Sea.

    PubMed

    Caruso, Francesco; Sciacca, Virginia; Bellia, Giorgio; De Domenico, Emilio; Larosa, Giuseppina; Papale, Elena; Pellegrino, Carmelo; Pulvirenti, Sara; Riccobene, Giorgio; Simeone, Francesco; Speziale, Fabrizio; Viola, Salvatore; Pavan, Gianni

    2015-01-01

    The sperm whale (Physeter macrocephalus) emits a typical short acoustic signal, defined as a "click", almost continuously while diving. It is produced in different time patterns to acoustically explore the environment and communicate with conspecifics. Each emitted click has a multi-pulse structure, resulting from the production of the sound within the sperm whale's head. A Stable Inter Pulse Interval (Stable IPI) can be identified among the pulses that compose a single click. Applying specific algorithms, the measurement of this interval provides useful information to assess the total length of the animal recorded. In January 2005, a cabled hydrophone array was deployed at a depth of 2,100 m in the Central Mediterranean Sea, 25 km offshore Catania (Ionian Sea). The acoustic antenna, named OνDE (Ocean noise Detection Experiment), was in operation until November 2006. OνDE provided real time acoustic data used to perform Passive Acoustic Monitoring (PAM) of cetacean sound emissions. In this work, an innovative approach was applied to automatically measure the Stable IPI of the clicks, performing a cepstrum analysis to the energy (square amplitude) of the signals. About 2,100 five-minute recordings were processed to study the size distribution of the sperm whales detected during the OνDE long term deep-sea acoustic monitoring. Stable IPIs were measured in the range between 2.1 ms and 6.4 ms. The equations of Gordon (1991) and of Growcott (2011) were used to convert the IPIs into measures of size. The results revealed that the sperm whales recorded were distributed in length from about 7.5 m to 14 m. The size category most represented was from 9 m to 12 m (adult females or juvenile males) and specimens longer than 14 m (old males) seemed to be absent.

  9. Size Distribution of Sperm Whales Acoustically Identified during Long Term Deep-Sea Monitoring in the Ionian Sea

    PubMed Central

    Caruso, Francesco; Sciacca, Virginia; Bellia, Giorgio; De Domenico, Emilio; Larosa, Giuseppina; Papale, Elena; Pellegrino, Carmelo; Pulvirenti, Sara; Riccobene, Giorgio; Simeone, Francesco; Speziale, Fabrizio; Viola, Salvatore; Pavan, Gianni

    2015-01-01

    The sperm whale (Physeter macrocephalus) emits a typical short acoustic signal, defined as a “click”, almost continuously while diving. It is produced in different time patterns to acoustically explore the environment and communicate with conspecifics. Each emitted click has a multi-pulse structure, resulting from the production of the sound within the sperm whale’s head. A Stable Inter Pulse Interval (Stable IPI) can be identified among the pulses that compose a single click. Applying specific algorithms, the measurement of this interval provides useful information to assess the total length of the animal recorded. In January 2005, a cabled hydrophone array was deployed at a depth of 2,100 m in the Central Mediterranean Sea, 25 km offshore Catania (Ionian Sea). The acoustic antenna, named OνDE (Ocean noise Detection Experiment), was in operation until November 2006. OνDE provided real time acoustic data used to perform Passive Acoustic Monitoring (PAM) of cetacean sound emissions. In this work, an innovative approach was applied to automatically measure the Stable IPI of the clicks, performing a cepstrum analysis to the energy (square amplitude) of the signals. About 2,100 five-minute recordings were processed to study the size distribution of the sperm whales detected during the OνDE long term deep-sea acoustic monitoring. Stable IPIs were measured in the range between 2.1 ms and 6.4 ms. The equations of Gordon (1991) and of Growcott (2011) were used to convert the IPIs into measures of size. The results revealed that the sperm whales recorded were distributed in length from about 7.5 m to 14 m. The size category most represented was from 9 m to 12 m (adult females or juvenile males) and specimens longer than 14 m (old males) seemed to be absent. PMID:26675588

  10. 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

  11. 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.

  12. Stress-Induced Fracturing of Reservoir Rocks: Acoustic Monitoring and μCT Image Analysis

    NASA Astrophysics Data System (ADS)

    Pradhan, Srutarshi; Stroisz, Anna M.; Fjær, Erling; Stenebråten, Jørn F.; Lund, Hans K.; Sønstebø, Eyvind F.

    2015-11-01

    Stress-induced fracturing in reservoir rocks is an important issue for the petroleum industry. While productivity can be enhanced by a controlled fracturing operation, it can trigger borehole instability problems by reactivating existing fractures/faults in a reservoir. However, safe fracturing can improve the quality of operations during CO2 storage, geothermal installation and gas production at and from the reservoir rocks. Therefore, understanding the fracturing behavior of different types of reservoir rocks is a basic need for planning field operations toward these activities. In our study, stress-induced fracturing of rock samples has been monitored by acoustic emission (AE) and post-experiment computer tomography (CT) scans. We have used hollow cylinder cores of sandstones and chalks, which are representatives of reservoir rocks. The fracture-triggering stress has been measured for different rocks and compared with theoretical estimates. The population of AE events shows the location of main fracture arms which is in a good agreement with post-test CT image analysis, and the fracture patterns inside the samples are visualized through 3D image reconstructions. The amplitudes and energies of acoustic events clearly indicate initiation and propagation of the main fractures. Time evolution of the radial strain measured in the fracturing tests will later be compared to model predictions of fracture size.

  13. 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.

  14. Mesoscale analysis of failure in quasi-brittle materials: comparison between lattice model and acoustic emission data.

    PubMed

    Grégoire, David; Verdon, Laura; Lefort, Vincent; Grassl, Peter; Saliba, Jacqueline; Regoin, Jean-Pierre; Loukili, Ahmed; Pijaudier-Cabot, Gilles

    2015-10-25

    The purpose of this paper is to analyse the development and the evolution of the fracture process zone during fracture and damage in quasi-brittle materials. A model taking into account the material details at the mesoscale is used to describe the failure process at the scale of the heterogeneities. This model is used to compute histograms of the relative distances between damaged points. These numerical results are compared with experimental data, where the damage evolution is monitored using acoustic emissions. Histograms of the relative distances between damage events in the numerical calculations and acoustic events in the experiments exhibit good agreement. It is shown that the mesoscale model provides relevant information from the point of view of both global responses and the local failure process. © 2015 The Authors. International Journal for Numerical and Analytical Methods in Geomechanics published by John Wiley & Sons Ltd.

  15. Seismic and Acoustic Array Monitoring of Signal from Tungurahua Volcano, Ecuador

    NASA Astrophysics Data System (ADS)

    Terbush, B. R.; Anthony, R. E.; Johnson, J. B.; Ruiz, M. C.

    2012-12-01

    Tungurahua Volcano is an active stratovolcano located in Ecuador's eastern Cordillera. Since its most recent cycle of eruptive activity, beginning in 1999, it has produced both strombolian-to-vulcanian eruptions, and regular vapor emissions. Tungurahua is located above the city of Baños, so volcanic activity is well-monitored by Ecuador's Instituto Geofisico Nacional with a seismic and infrasound network, and other surveillance tools. Toward better understanding of the complex seismic and acoustic signals associated with low-level Tungurahua activity, and which are often low in signal-to-noise, we deployed temporary seismo-acoustic arrays between June 9th and 20th in 2012. This deployment was part of a Field Volcano Geophysics class, a collaboration between New Mexico Institute of Mining and Technology and the Escuela Politecnica Nacional's Instituto Geofísico in Ecuador. Two six-element arrays were deployed on the flank of the volcano. A seismo-acoustic array, which consisted of combined broadband seismic and infrasound sensors, possessed 100-meter spacing, and was deployed five kilometers north of the vent in an open field at 2700 m. The second array had only acoustic sensors with 30-meter spacing, and was deployed approximately six kilometers northwest of the vent, on an old pyroclastic flow deposit. The arrays picked up signals from four distinct explosion events, a number of diverse tremor signals, local volcano tectonic and long period earthquakes, and a regional tectonic event of magnitude 4.9. Coherency of both seismic and acoustic array data was quantified using Fisher Statistics, which was effective for identifying myriad signals. For most signals Fisher Statistics were particularly high in low frequency bands, between 0.5 and 2 Hz. Array analyses helped to filter out noise induced by cultural sources and livestock signals, which were particularly pronounced in the deployment site. Volcan Tungurahua sources were considered plane wave signals and could

  16. Improving the Navy’s Passive Underwater Acoustic Monitoring of Marine Mammal Populations

    DTIC Science & Technology

    2013-09-30

    number of “High-frequency Acoustic Recording Package” ( HARP ) monitoring sites off the California coast (Fig. 1). The low-frequency content of these...in certain situations where efficient long range propagation can occur (e.g., at Hoke Seamount). Humpback calls will be detected in the HARP data...environments. Figure 1. Upper row of plots show the bathymety at three HARP passive acoustic monitoring sites: (left to right) Santa

  17. 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

  18. The acoustic emission of a distributed mode loudspeaker near a porous layer.

    PubMed

    Prokofieva, E Yu; Horoshenkov, Kirill V; Harris, N

    2002-06-01

    Experimental and theoretical modeling of the vibro-acoustic performance of a distributed mode loudspeaker (DML) suggest that their acoustic emission can be significantly affected by the presence of a porous layer. The amplitude of the surface velocity of the panel and the acoustic pressure on the porous surface are reduced largely in the vicinity of structural resonances due to the additional radiation damping and visco-thermal absorption phenomenon in the porous layer. The experimental results suggest that a porous layer between a rigid base and a DML panel can considerably alter its acoustic emission in the near field and in the far field. This is illustrated by a reduction in the level of fluctuations in the emitted acoustic pressure spectra. These fluctuations are normally associated with the interference between the sound emitted by the front surface of the speaker and that emitted from the back. Another contribution comes from the pronounced structural resonances in the surface velocity spectrum. The results of this work suggest that the acoustic boundary conditions near a DML can be modified by the porous layer so that a desired acoustic output can be attained.

  19. Tropospheric Emissions: Monitoring of Pollution Overview

    NASA Technical Reports Server (NTRS)

    Chance, Kelly; Liu, Xiong; Suleiman, Raid M.; Flittner, David; Al-Saadi, Jay; Janz, Scott

    2015-01-01

    TEMPO is now well into its implementation phase, having passed both its Key Decision Point C and the Critical Design Review (CDR) for the instrument. The CDR for the ground systems will occur in March 2016 and the CDR for the Mission component at a later date, after the host spacecraft has been selected. TEMPO is on schedule to measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions by 50 percent. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO provides much of the atmospheric measurement capability recommended for GEO-CAPE in the 2007 National Research Council Decadal Survey, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond. Instruments from Europe (Sentinel 4) and Asia (GEMS) will

  20. Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Chance, Kelly; Liu, Xiong; Suleiman, Raid M.; Flittner, David E.; Al-Saadi, Jassim; Janz, Scott J.

    2014-06-01

    TEMPO, selected by NASA as the first Earth Venture Instrument, will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest-cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, reducing uncertainty in air quality predictions by 50 %. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO makes the first tropospheric trace gas measurements from GEO, by building on the heritage of five spectrometers flown in low-earth-orbit (LEO). These LEO instruments measure the needed spectra, although at coarse spatial and temporal resolutions, to the precisions required for TEMPO and use retrieval algorithms developed for them by TEMPO Science Team members and currently running in operational environments. This makes TEMPO an innovative use of a well-proven technique, able to produce a revolutionary data set. TEMPO provides much of the atmospheric measurement

  1. Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Chance, K.; Liu, X.; Suleiman, R. M.; Flittner, D. E.; Al-Saadi, J. A.; Janz, S. J.; Tempo Science Team

    2013-05-01

    TEMPO has been selected by NASA as the first Earth Venture Instrument. It will measure atmospheric pollution for greater North America from space using ultraviolet/visible spectroscopy. TEMPO measures from Mexico City to the Canadian tar/oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (Mexico City is measured at 1.6 km N/S by 4.5 km E/W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, reducing uncertainty in air quality predictions by 50%. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO makes the first tropospheric trace gas measurements from GEO, by building on the heritage of five spectrometers flown in low-earth-orbit (LEO). These LEO instruments measure the needed spectra, although at coarse spatial and temporal resolutions, to the precisions required for TEMPO and use retrieval algorithms developed for them by TEMPO Science Team members and currently running in operational environments. This makes TEMPO an innovative use of a well proven technique, able to produce a revolutionary

  2. Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Chance, K.; Liu, X.; Suleiman, R. M.; Flittner, D. E.; Janz, S. J.

    2012-12-01

    TEMPO is a proposed concept to measure pollution for greater North America using ultraviolet/visible spectroscopy. TEMPO measures from Mexico City to the Canadian tar/oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (9 km2). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, reducing uncertainty in air quality predictions by 50%. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO makes the first tropospheric trace gas measurements from GEO, by building on the heritage of five spectrometers flown in low-earth-orbit (LEO). These LEO instruments measure the needed spectra, although at coarse spatial and temporal resolutions, to the precisions required for TEMPO and use retrieval algorithms developed for them by TEMPO Science Team members and currently running in operational environments. This makes TEMPO an innovative use of a well proven technique, able to produce a revolutionary data set. TEMPO provides much of the atmospheric measurement capability recommended for GEO-CAPE in the 2007

  3. Real-Time Debonding Monitoring of Composite Repaired Materials via Electrical, Acoustic, and Thermographic Methods

    NASA Astrophysics Data System (ADS)

    Grammatikos, S. A.; Kordatos, E. Z.; Matikas, T. E.; Paipetis, A. S.

    2014-01-01

    The electrical properties of composite materials have been thoroughly investigated recently for the detection and monitoring of damage in carbon fiber-reinforced polymers (CFRPs) under mechanical loading. Carbon nanotubes are incorporated in the polymer matrix of CFRPs for the enhancement of their electrical properties. The electrical properties have shown to be sensitive to the damage state of the material and hence their monitoring provides the profile of their structural deterioration. The aim of the paper is the cross-validation and benchmarking of an electrical potential change monitoring (EPCM) technique against acoustic emission (AE) and lock-in thermography (LT). All techniques successfully identified damage and its propagation. Thermography was more efficient in quantifying damage and describing dynamically the debond topology, as it provided full 2D imaging of the debond in real time. EPCM was successful in providing quantitative information on debond propagation and its directionality. AE provided consistent information on damage propagation. All techniques identified three stages in the fatigue life of the interrogated coupons. The representation of the fatigue behavior as a function of life fraction, the correlation of AE data with EPCM and LT data, and most importantly the consistent behavior of all tested coupons allowed for both the direct and indirect cross-correlation of all employed methodologies, which consistently identified all aforementioned fatigue life stages.

  4. Fatigue features study on the crankshaft material of 42CrMo steel using acoustic emission

    NASA Astrophysics Data System (ADS)

    Shi, Yue; Dong, Lihong; Wang, Haidou; Li, Guolu; Liu, Shenshui

    2016-09-01

    Crankshaft is regarded as an important component of engines, and it is an important application of remanufacturing because of its high added value. However, the fatigue failure research of remanufactured crankshaft is still in its primary stage. Thus, monitoring and investigating the fatigue failure of the remanufacturing crankshaft is crucial. In this paper, acoustic emission (AE) technology and machine vision are used to monitor the four-point bending fatigue of 42CrMo, which is the material of crankshaft. The specimens are divided into two categories, namely, pre-existing crack and non-preexisting crack, which simulate the crankshaft and crankshaft blank, respectively. The analysis methods of parameter-based AE techniques, wavelet transform (WT) and SEM analysis are combined to identify the stage of fatigue failure. The stage of fatigue failure is the basis of using AE technology in the field of remanufacturing crankshafts. The experiment results show that the fatigue crack propagation style is a transgranular fracture and the fracture is a brittle fracture. The difference mainly depends on the form of crack initiation. Various AE signals are detected by parameter analysis method. Wavelet threshold denoising and WT are combined to extract the spectral features of AE signals at different fatigue failure stages.

  5. Acoustic Emission Detection and Prediction of Fatigue Crack Propagation in Composite Patch Repairs Using Neural Networks

    SciTech Connect

    Okafor, A. Chukwujekwu; Singh, Navdeep; Singh, Navrag

    2007-03-21

    An aircraft is subjected to severe structural and aerodynamic loads during its service life. These loads can cause damage or weakening of the structure especially for aging military and civilian aircraft, thereby affecting its load carrying capabilities. Hence composite patch repairs are increasingly used to repair damaged aircraft metallic structures to restore its structural efficiency. This paper presents the results of Acoustic Emission (AE) monitoring of crack propagation in 2024-T3 Clad aluminum panels repaired with adhesively bonded octagonal, single sided boron/epoxy composite patch under tension-tension fatigue loading. Crack propagation gages were used to monitor crack initiation. The identified AE sensor features were used to train neural networks for predicting crack length. The results show that AE events are correlated with crack propagation. AE system was able to detect crack propagation even at high noise condition of 10 Hz loading; that crack propagation signals can be differentiated from matrix cracking signals that take place due to fiber breakage in the composite patch. Three back-propagation cascade feed forward networks were trained to predict crack length based on the number of fatigue cycles, AE event number, and both the Fatigue Cycles and AE events, as inputs respectively. Network using both fatigue cycles and AE event number as inputs to predict crack length gave the best results, followed by Network with fatigue cycles as input, while network with just AE events as input had a greater error.

  6. Diamond wheel wear sensing with acoustic emission --wheel wear mechanisms and the effects of process variables

    SciTech Connect

    Tang, Jianshe; Dornfeld, D.; Syoji, Katsuo

    1996-12-31

    The wear of diamond wheels has significant influence on the surface finish of ground ceramics and the resulting subsurface fracture damage. For optimization and control of the grinding process it is necessary to monitor the wear states of the grinding wheels. A project on diamond wheel wear sensing with acoustic emission was started recently in the Laboratory of Manufacturing Automation at the University of California at Berkeley. The main aims of the project are: (a) to identify the possible wheel wear patterns at different combinations of bond materials, grits, and grinding conditions; (b) to develop suitable AE signal processing methods to extract the AE features to represent the wheel wear characteristics, and establish a strategy for using AE for in-process monitoring of diamond wheel wear in grinding of ceramics. This paper presents the results of part of the project. It mainly focuses on the diamond wheel wear mechanisms, the effects of process variables including basic wheel elements and grinding parameters, and the relationship with AErms and AE frequency content.

  7. 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.

  8. Design considerations for the acoustic emission testing of large composite specimens

    NASA Astrophysics Data System (ADS)

    Scholey, Jonathan J.; Wilcox, Paul D.; Wisnom, Michael R.; Friswell, Mike I.

    2009-03-01

    Acoustic emission (AE) testing is a sensitive technique capable of detecting many types of defect with a sparse sensor array making it an attractive structural health monitoring technology. The widespread application of the technology is limited by a lack of predictive modelling and in part, the lack of quantitative source characteristics. The vast majority of current laboratory AE testing is conducted on small coupons which cannot be used to generate quantitative source characteristics since reflected wave energy from the specimen edges influences the received waveforms. An alternative approach is to test on large specimens where the modal properties of propagating waves can be examined with no influence from reflected wave energy. However, the design and testing of large specimens is not trivial. The work in this paper discusses the design of large fibre reinforced composite (FRC) specimens which are suitable for making quantitative source measurements. The design considerations include the minimum plate dimensions and placement of sensors. A novel technique, referred to as the location-time plot technique, is described which links propagation characteristics, specimen dimensions and sensor locations to map the dispersion of elastic waves in plates. The technique is demonstrated in the design of a simple AE experiment on a highly anisotropic plate. The technique is then used in the design of a practical AE testing arrangement for monitoring delamination from artificial defects in a large FRC plate. Experimental waveforms, recorded using this AE testing arrangement, are presented and are shown to be in agreement with the location-time plot technique.

  9. Acoustic Emission of Large PRSEUS Structures (Pultruded Rod Stitched Efficient Unitized Structure)

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Juarez, Peter D.

    2016-01-01

    In the role of structural health monitoring (SHM), Acoustic Emission (AE) analysis is being investigated as an effective method for tracking damage development in large composite structures under load. Structures made using Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) for damage tolerant, light, and economical airframe construction are being pursued by The Boeing Company and NASA under the Environmentally Responsible Aircraft initiative (ERA). The failure tests of two PRSEUS substructures based on the Boeing Hybrid Wing Body fuselage concept were conducted during third quarter 2011 and second quarter 2015. One fundamental concern of these tests was determining the effectiveness of the stitched integral stiffeners to inhibit damage progression. By design, severe degradation of load carrying capability should not occur prior to Design Ultimate Load (DUL). While minor damage prior to DUL was anticipated, the integral stitching should not fail since this would allow a stiffener-skin delamination to progress rapidly and alter the transfer of load into the stiffeners. In addition, the stiffeners should not fracture because they are fundamental to structural integrity. Getting the best information from each AE sensor is a primary consideration because a sparse network of sensors is implemented. Sensitivity to stiffener-contiguous degradation is supported by sensors near the stiffeners, which increases the coverage per sensor via AE waveguide actions. Some sensors are located near potentially critical areas or "critical zones" as identified by numerical analyses. The approach is compared with the damage progression monitored by other techniques (e.g. ultrasonic C-scan).

  10. 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.

  11. Acoustic Emission Detection and Prediction of Fatigue Crack Propagation in Composite Patch Repairs Using Neural Networks

    NASA Astrophysics Data System (ADS)

    Okafor, A. Chukwujekwu; Singh, Navdeep; Singh, Navrag

    2007-03-01

    An aircraft is subjected to severe structural and aerodynamic loads during its service life. These loads can cause damage or weakening of the structure especially for aging military and civilian aircraft, thereby affecting its load carrying capabilities. Hence composite patch repairs are increasingly used to repair damaged aircraft metallic structures to restore its structural efficiency. This paper presents the results of Acoustic Emission (AE) monitoring of crack propagation in 2024-T3 Clad aluminum panels repaired with adhesively bonded octagonal, single sided boron/epoxy composite patch under tension-tension fatigue loading. Crack propagation gages were used to monitor crack initiation. The identified AE sensor features were used to train neural networks for predicting crack length. The results show that AE events are correlated with crack propagation. AE system was able to detect crack propagation even at high noise condition of 10 Hz loading; that crack propagation signals can be differentiated from matrix cracking signals that take place due to fiber breakage in the composite patch. Three back-propagation cascade feed forward networks were trained to predict crack length based on the number of fatigue cycles, AE event number, and both the Fatigue Cycles and AE events, as inputs respectively. Network using both fatigue cycles and AE event number as inputs to predict crack length gave the best results, followed by Network with fatigue cycles as input, while network with just AE events as input had a greater error.

  12. Towards identifying the dynamics of sliding by acoustic emission and vibration

    NASA Astrophysics Data System (ADS)

    Korchuganov, M. A.; Filippov, A. V.; Tarasov, S. Yu.; Podgornyh, O. A.; Shamarin, N. N.; Filippova, E. O.

    2016-11-01

    The results of experiments with high load and sliding speed sliding conditions on tribologically mated pairs such as steel 1045/steel 1045 (test 1), steel 1045/basalt (test 2) and Hadfield steel/basalt (test 3) have been carried out in order to identify their response in terms of the acoustic emission and vibration signals. The steel to rock and rock to steel transfer has been revealed by examining the worn surfaces of both steel and rock samples with the use of laser scanning microscopy. The AE signal characteristics have been determined for the tribological pairs studied. The dynamics of sliding has been evaluated by measuring the vibration accelerations. Relationship between wear mode and either acoustic emission signal or vibration signal has been established. The minimal vibration oscillations amplitude and acoustic emission signal energy have been found out in sliding Hadfield steel/basalt pair.

  13. 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.

  14. Surface Acoustic Wave Monitor for Deposition and Analysis of Ultra-Thin Films

    NASA Technical Reports Server (NTRS)

    Hines, Jacqueline H. (Inventor)

    2015-01-01

    A surface acoustic wave (SAW) based thin film deposition monitor device and system for monitoring the deposition of ultra-thin films and nanomaterials and the analysis thereof is characterized by acoustic wave device embodiments that include differential delay line device designs, and which can optionally have integral reference devices fabricated on the same substrate as the sensing device, or on a separate device in thermal contact with the film monitoring/analysis device, in order to provide inherently temperature compensated measurements. These deposition monitor and analysis devices can include inherent temperature compensation, higher sensitivity to surface interactions than quartz crystal microbalance (QCM) devices, and the ability to operate at extreme temperatures.

  15. 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

    2015-10-21

    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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys. Phase I.

    DTIC Science & Technology

    1981-07-01

    boundaries; formation and growth of twins, crazes , microcracks, I t i4 2 Fig. 1. Typical acoustic emission waveforms as detected with piezoelectric transducers...captured on the Nicolet. Materials presently available for testing are 6Ak 4V and 6AZ 2Cb lTa lMo titanium alloys; HY80 , HY100 and HY 130 steel; 2024...Djordjevic, J. C. Murphy, and R. E. Green, Jr., "Acoustic Emission During Craze Formation in Polymers (submitted for publication in J. AppI. Phys.). 32. W

  1. USE OF ACOUSTIC EMISSION TO DIAGNOSE BREAKDOWN IN ACCELERATOR RF STRUCTURES

    SciTech Connect

    Nelson, Janice L.

    2003-05-12

    Accelerator structures of a wide variety have been damaged by RF breakdowns. Very little is known about the mechanisms that cause the breakdown and the damage although there has been theoretical work [1,2]. Using an array of ultrasonic acoustic emission sensors we have been able to locate and classify breakdown events more accurately than possible using microwave techniques. Data from the technique has led to improvements in the design of the NLC X-band RF structure. We report results of acoustic emission studies at the DESY TESLA Test Facility and the SLAC NLC Test Accelerator.

  2. Detection of rolling contact sub-surface fatigue cracks using acoustic emission technique

    SciTech Connect

    Yoshioka, T. )

    1993-04-01

    A method of locating the position of acoustic emission sources has been developed to analyze the mechanism of rolling contact fatigue. Using this method, sub-surface fatigue cracks were found at positions corresponding to the actual source positions of acoustic emissions. When fatigue tests were run under maximum stresses of 5.75 GPa and lubricant film parameters of 0.19, the cracks propagated parallel to the surface, had a maximum length of approximately 200 microns in the rolling direction of balls, and were distributed between 50 microns and 200 microns below the surface. Although the lubricant film parameter was small, no cracks from the surface were found. 12 refs.

  3. Continuous emission monitoring and accounting automated systems at an HPP

    NASA Astrophysics Data System (ADS)

    Roslyakov, P. V.; Ionkin, I. L.; Kondrateva, O. E.; Borovkova, A. M.; Seregin, V. A.; Morozov, I. V.

    2015-03-01

    Environmental and industrial emission monitoring at HPP's is a very urgent task today. Industrial monitoring assumes monitoring of emissions of harmful pollutants and optimization of fuel combustion technological processes at HPP's. Environmental monitoring is a system to assess ambient air quality with respect to a number of separate sources of harmful substances in pollution of atmospheric air of the area. Works on creating an industrial monitoring system are carried out at the National Research University Moscow Power Engineering Institute (MPEI) on the basis of the MPEI combined heat and power plant, and environmental monitoring stations are installed in Lefortovo raion, where the CHPP is located.

  4. Unique gel-coupled acoustic sensor array monitors human voice and physiology

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael

    2002-11-01

    The health and performance of soldiers, firefighters, and other first responders in strenuous and hazardous environments can be continuously and remotely monitored with body-worn acoustic sensors. The Army Research Laboratory's gel-coupled acoustic physiological monitoring sensor has acoustic impedance properties similar to the skin that facilitate the transmission of body sounds into the sensor pad, yet significantly repel ambient airborne noises due to an impedance mismatch. Acoustic signal processing detects physiological events such as heartbeats, breaths, wheezes, coughs, blood pressure, activity, motion, and voice for communication and automatic speech recognition. Acoustic sensors can be in a helmet or in a strap around the neck, chest, and wrist. Although the physiological sounds have high SNR, the acoustic sensor also responds to motion-induced artifacts that sometimes obscure meaningful physiology. A noise-canceling sensor array configuration helps remove motion noise by using two acoustic sensors on the front sides of the neck and 2 additional acoustic sensors on each wrist. The motion noise detected on all 4 sensors will be dissimilar and out of phase, yet the physiology on all 4 sensors is covariant. Pulse wave transit time between neck and wrist will indicate systolic blood pressure. Data from a firefighter experiment will be presented.

  5. Remote acoustic monitoring of North Atlantic right whales (Eubalaena glacialis) reveals seasonal and diel variations in acoustic behavior.

    PubMed

    Matthews, Leanna P; McCordic, Jessica A; Parks, Susan E

    2014-01-01

    Remote acoustic monitoring is a non-invasive tool that can be used to study the distribution, behavior, and habitat use of sound-producing species. The North Atlantic right whale (Eubalaena glacialis) is an endangered baleen whale species that produces a variety of stereotyped acoustic signals. One of these signals, the "gunshot" sound, has only been recorded from adult male North Atlantic right whales and is thought to function for reproduction, either as reproductive advertisement for females or as an agonistic signal toward other males. This study uses remote acoustic monitoring to analyze the presence of gunshots over a two-year period at two sites on the Scotian Shelf to determine if there is evidence that North Atlantic right whales may use these locations for breeding activities. Seasonal analyses at both locations indicate that gunshot sound production is highly seasonal, with an increase in the autumn. One site, Roseway West, had significantly more gunshot sounds overall and exhibited a clear diel trend in production of these signals at night. The other site, Emerald South, also showed a seasonal increase in gunshot production during the autumn, but did not show any significant diel trend. This difference in gunshot signal production at the two sites indicates variation either in the number or the behavior of whales at each location. The timing of the observed seasonal increase in gunshot sound production is consistent with the current understanding of the right whale breeding season, and our results demonstrate that detection of gunshots with remote acoustic monitoring can be a reliable way to track shifts in distribution and changes in acoustic behavior including possible mating activities.

  6. Effluent emissions monitoring at the DOE Hanford Site

    SciTech Connect

    Vance, L.W.

    1993-05-01

    There are numerous regulatory requirements controlling the effluent emissions monitoring at a U.S. Department of Energy site. This paper defines how these regulatory effluent emissions monitoring requirements and the Quality Assurance oversight of these requirements were implemented by Westinghouse Hanford Company, the operations contractor, at the DOE Hanford Site.

  7. Assessment of error rates in acoustic monitoring with the R package monitoR

    USGS Publications Warehouse

    Katz, Jonathan; Hafner, Sasha D.; Donovan, Therese

    2016-01-01

    Detecting population-scale reactions to climate change and land-use change may require monitoring many sites for many years, a process that is suited for an automated system. We developed and tested monitoR, an R package for long-term, multi-taxa acoustic monitoring programs. We tested monitoR with two northeastern songbird species: black-throated green warbler (Setophaga virens) and ovenbird (Seiurus aurocapilla). We compared detection results from monitoR in 52 10-minute surveys recorded at 10 sites in Vermont and New York, USA to a subset of songs identified by a human that were of a single song type and had visually identifiable spectrograms (e.g. a signal:noise ratio of at least 10 dB: 166 out of 439 total songs for black-throated green warbler, 502 out of 990 total songs for ovenbird). monitoR’s automated detection process uses a ‘score cutoff’, which is the minimum match needed for an unknown event to be considered a detection and results in a true positive, true negative, false positive or false negative detection. At the chosen score cut-offs, monitoR correctly identified presence for black-throated green warbler and ovenbird in 64% and 72% of the 52 surveys using binary point matching, respectively, and 73% and 72% of the 52 surveys using spectrogram cross-correlation, respectively. Of individual songs, 72% of black-throated green warbler songs and 62% of ovenbird songs were identified by binary point matching. Spectrogram cross-correlation identified 83% of black-throated green warbler songs and 66% of ovenbird songs. False positive rates were  for song event detection.

  8. Acoustic Monitoring of Ebullitive Flux from a Mire Ecosystem in Subarctic Sweden

    NASA Astrophysics Data System (ADS)

    Burke, S. A.; Varner, R. K.; Palace, M. W.; Wik, M.; Crill, P. M.; McCalley, C. K.; Amante, J.

    2012-12-01

    Methane (CH4) is a potent green house gas with wetlands being the largest natural source to the atmosphere. Studies in the Stordalen Mire, a dynamic peatland complex 11km east of the Abisko Scientific Research Station (ANS) in northern Sweden, that focused on CH4 transport to the atmosphere from peatlands have shown increased emissions over the past decades. Ebullitive flux (bubbling) is a potentially significant pathway of CH4 from mire/lake ecosystems. Ebullitive fluxes were successfully monitored acoustically in peat and lakes in 2011. This work expands those measurements with installation of sensors in ponds and permafrost thaw margins in 2012. Eighteen acoustic sensors were installed in peat (6), pond (6), and lake (6) sites at Stordalen Mire. Recorders collected acoustic data continuously from each sensor and gas samples were collected from the traps at least once per week beginning 7 July. The CH4 concentration in the gas was measured using gas chromatography and selected samples were also analyzed for 13C-CH4 using a Quantum Cascade Laser (QCL). The acoustic data were evaluated using a MATLAB program for determine the timing and volume of each ebullition event. The CH4 ebullitive flux from the peat was greater in July 2011 than during the same period in 2012. In comparison, the ponds and thaw margins released CH4 at a faster rate in 2012 than was observed in the peat and lake sensors in 2011. Inter-annual differences in ebullitive rates suggest that weather scale differences between years may control CH4 ebullitive flux. 13C-CH4 measured in the pore waters of pond sediment suggests that not all ponds are dominated by the same production processes. However, 13C-CH4 measured in bubbles and sediments are not different, implying little or no oxidation of CH4 during transport to the water surface. Our data suggests that changes in atmospheric pressure and water table height correlated with the ebullitive release in all three sub-ecosystems.

  9. 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

  10. 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

  11. 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.

  12. Monitoring rock freezing and thawing by novel geoelectrical and acoustic techniques

    NASA Astrophysics Data System (ADS)

    Murton, Julian B.; Kuras, Oliver; Krautblatter, Michael; Cane, Tim; Tschofen, Dominique; Uhlemann, Sebastian; Schober, Sandra; Watson, Phil

    2016-12-01

    Automated monitoring of freeze-thaw cycles and fracture propagation in mountain rockwalls is needed to provide early warning about rockfall hazards. Conventional geoelectrical methods such as electrical resistivity tomography (ERT) are limited by large and variable ohmic contact resistances, requiring galvanic coupling with metal electrodes inserted into holes drilled into rock, and which can be loosened by rock weathering. We report a novel experimental methodology that combined capacitive resistivity imaging (CRI), ERT, and microseismic event recording to monitor freeze-thaw of six blocks of hard and soft limestones under conditions simulating an active layer above permafrost and seasonally frozen rock in a nonpermafrost environment. Our results demonstrate that the CRI method is highly sensitive to freeze-thaw processes; it yields property information equivalent to that obtained with conventional ERT and offers a viable route for nongalvanic long-term geoelectrical monitoring, extending the benefits of the methodology to soft/hard rock environments. Contact impedances achieved with CRI are less affected by seasonal temperature changes, the aggregate state of the pore water (liquid or frozen), and the presence of low-porosity rock with high matrix resistivities than those achieved with ERT. Microseismic monitoring has the advantage over acoustic emissions that events were recorded in relevant field distances of meters to decameters from cracking events. For the first time we recorded about 1000 microcracking events and clustered them in four groups according to frequency and waveform. Compared to previous studies, mainly on ice-cracking in glaciers, the groups are attributed to single- or multiple-stage cracking events such as crack coalescence.

  13. 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).

  14. Navy vehicles: acoustic emission related to nondestructive testing. Final report, 1980-1987

    SciTech Connect

    Ono, K.

    1988-04-12

    This investigation was aimed at studying acoustic emission for applications to residual stress measurements and for the evaluation of structural integrity of engineering structures. Effects of microstructure, composition and prior cold working on magnetomechanical acoustic emission(MAE) have been studied. Magnetization behavior, magnetostriction and Barkhausen noise are affected by stress as well as other parameters. These responses have been measured simultaneously in order to identify the stress level uniquely. Combinations of advanced signal analysis methods and MAE measurements have been studied to identify the optimum parameters for applications. This work has established mechanisms of MAE signal generation, effects of various parameters that influence the MAE behavior of materials and signal processing techniques that allow materials characterization via MAE. Included are neutron-irradiated reactor-vessel steels, large-size steel plates as well as single crystals of various ferromagnetic metals and alloys. In the second part of this study, acoustic emission from materials undergoing plastic deformation and fracture were examined in an attempt to improve detection capability of the impending structural failure. Acoustic emission characteristics of reactor-vessel steels, advanced aluminum alloys and metal and ceramic-matrix composite materials have been evaluated in detail.

  15. Based on optical fiber Michelson interferometer for acoustic emission detection experimental research

    NASA Astrophysics Data System (ADS)

    Liang, Yijun; Qu, Dandan; Deng, Hu

    2013-08-01

    A type of Michelson interferometer with two optical fiber loop reflectors acoustic emission sensor is proposed in the article to detect the vibrations produced by ultrasonic waves propagating in a solid body. Two optical fiber loop reflectors are equivalent to the sensing arm and the reference arm instead of traditional Michelson interferometer end reflecter Theoretical analyses indicate that the sensitivity of the system has been remarkably increased because of the decrease of the losses of light energy. The best operating point of optical fiber sensor is fixed by theoretical derivation and simulation of computer, and the signal frequency which is detected by the sensor is the frequency of input signal. PZT (Piezoelectric Ceramic) is powered by signal generator as known ultrasonic source, The Polarization controller is used to make the reflected light interference,The fiber length is changed by adjusting the DC voltage on the PZT with the fiber loop to make the sensor system response that ΔΦ is closed to π/2. the signal basis frequency detected by the sensor is the frequency of the input signal. Then impacts the surface of the marble slab with home-made mechanical acoustic emission source. And detect it. and then the frequency characteristic of acoustic emission signal is obtained by Fourier technique. The experimental results indicate that the system can identify the frequency characteristic of acoustic emission signal, and it can be also used to detect the surface feeble vibration which is generated by ultrasonic waves propagating in material structure.

  16. Acoustic emission localization in plates with dispersion and reverberations using sparse PZT sensors in passive mode

    NASA Astrophysics Data System (ADS)

    Perelli, Alessandro; De Marchi, Luca; Marzani, Alessandro; Speciale, Nicolò

    2012-02-01

    A strategy for the localization of acoustic emissions (AE) in plates with dispersion and reverberation is proposed. The procedure exploits signals received in passive mode by sparse conventional piezoelectric transducers and a three-step processing framework. The first step consists in a signal dispersion compensation procedure, which is achieved by means of the warped frequency transform. The second step concerns the estimation of the differences in arrival time (TDOA) of the acoustic emission at the sensors. Complexities related to reflections and plate resonances are overcome via a wavelet decomposition of cross-correlating signals where the mother function is designed by a synthetic warped cross-signal. The magnitude of the wavelet coefficients in the warped distance-frequency domain, in fact, precisely reveals the TDOA of an acoustic emission at two sensors. Finally, in the last step the TDOA data are exploited to locate the acoustic emission source through hyperbolic positioning. The proposed procedure is tested with a passive network of three/four piezo-sensors located symmetrically and asymmetrically with respect to the plate edges. The experimentally estimated AE locations are close to those theoretically predicted by the Cramèr-Rao lower bound.

  17. ENVIRONMENTAL TECHNOLOGY VERIFICATION (ETV) TEST OF DIOXIN EMISSION MONITORS

    EPA Science Inventory

    The performance of four dioxin emission monitors including two long-term sampling devices, the DMS (DioxinMonitoringSystem) and AMESA (Adsorption Method for Sampling Dioxins and Furans), and two semi-real-time continuous monitors, RIMMPA-TOFMS (Resonance Ionization with Multi-Mir...

  18. WORKSHOP ON SOURCE EMISSION AND AMBIENT AIR MONITORING OF MERCURY

    EPA Science Inventory

    AN EPA/ORD Workshop on Source Emission and Ambient Air Monitoring of Mercury was held on 9/13-14/99, Bloomington, Minnesota. The purpose of the workshop was to discuss the state-of-the-science in source and ambient air mercury monitoring as well as mercury monitoring research and...

  19. Acoustic vector sensor beamforming reduces masking from underwater industrial noise during passive monitoring.

    PubMed

    Thode, Aaron M; Kim, Katherine H; Norman, Robert G; Blackwell, Susanna B; Greene, Charles R

    2016-04-01

    Masking from industrial noise can hamper the ability to detect marine mammal sounds near industrial operations, whenever conventional (pressure sensor) hydrophones are used for passive acoustic monitoring. Using data collected from an autonomous recorder with directional capabilities (Directional Autonomous Seafloor Acoustic Recorder), deployed 4.1 km from an arctic drilling site in 2012, the authors demonstrate how conventional beamforming on an acoustic vector sensor can be used to suppress noise arriving from a narrow sector of geographic azimuths. Improvements in signal-to-noise ratio of up to 15 dB are demonstrated on bowhead whale calls, which were otherwise undetectable using conventional hydrophones.

  20. Real-time monitoring of acoustic linear and nonlinear behavior of titanium alloys during cyclic loading

    SciTech Connect

    Frouin, J.; Maurer, J.; Sathish, S.; Eylon, D.; Na, J.K.; Matikas, T.E.

    2000-07-01

    Variation in acoustic nonlinearity has been monitored in real time during fatigue, on four dog-bone specimens of Ti-6Al-4V, under low cycle fatigue conditions, from the virgin state all the way to fracture. The results of these experiments show that the acoustic nonlinearity undergoes large changes during the fatigue and follows a similar trend for the material under given fatigue test conditions. Transmission electron microscopic (TEM) examination of the samples with similar composition fatigues to different stages indicates a gradual change in the microstructure and dislocation density, which correlates with the changes in acoustic nonlinearity.

  1. Application of acoustic emission on the characterization of fracture in textile reinforced cement laminates.

    PubMed

    Blom, J; Wastiels, J; Aggelis, D G

    2014-01-01

    This work studies the acoustic emission (AE) behavior of textile reinforced cementitious (TRC) composites under flexural loading. The main objective is to link specific AE parameters to the fracture mechanisms that are successively dominating the failure of this laminated material. At relatively low load, fracture is initiated by matrix cracking while, at the moment of peak load and thereafter, the fiber pull-out stage is reached. Stress modeling of the material under bending reveals that initiation of shear phenomena can also be activated depending on the shape (curvature) of the plate specimens. Preliminary results show that AE waveform parameters like frequency and energy are changing during loading, following the shift of fracturing mechanisms. Additionally, the AE behavior of specimens with different curvature is very indicative of the stress mode confirming the results of modeling. Moreover, AE source location shows the extent of the fracture process zone and its development in relation to the load. It is seen that AE monitoring yields valuable real time information on the fracture of the material and at the same time supplies valuable feedback to the stress modeling.

  2. Toward a probabilistic acoustic emission source location algorithm: A Bayesian approach

    NASA Astrophysics Data System (ADS)

    Schumacher, Thomas; Straub, Daniel; Higgins, Christopher

    2012-09-01

    Acoustic emissions (AE) are stress waves initiated by sudden strain releases within a solid body. These can be caused by internal mechanisms such as crack opening or propagation, crushing, or rubbing of crack surfaces. One application for the AE technique in the field of Structural Engineering is Structural Health Monitoring (SHM). With piezo-electric sensors mounted to the surface of the structure, stress waves can be detected, recorded, and stored for later analysis. An important step in quantitative AE analysis is the estimation of the stress wave source locations. Commonly, source location results are presented in a rather deterministic manner as spatial and temporal points, excluding information about uncertainties and errors. Due to variability in the material properties and uncertainty in the mathematical model, measures of uncertainty are needed beyond best-fit point solutions for source locations. This paper introduces a novel holistic framework for the development of a probabilistic source location algorithm. Bayesian analysis methods with Markov Chain Monte Carlo (MCMC) simulation are employed where all source location parameters are described with posterior probability density functions (PDFs). The proposed methodology is applied to an example employing data collected from a realistic section of a reinforced concrete bridge column. The selected approach is general and has the advantage that it can be extended and refined efficiently. Results are discussed and future steps to improve the algorithm are suggested.

  3. A practical approach for quantifying acoustic emission signals using diffuse field measurements

    NASA Astrophysics Data System (ADS)

    Scholey, Jonathan J.; Wilcox, Paul D.

    2009-03-01

    Acoustic Emission (AE) testing is capable of detecting a wide range of defects using a relatively sparse sensor array and as a result is a candidate structural health monitoring technology. The widespread application of the technology is restricted by a lack of predictive modelling capability and quantitative source characteristic information. Most AE tests are conducted on small coupons where source characteristics are estimated using the early arriving part of the AE signal. The early arriving part of an AE signal, and therefore the source characteristics, are dependent on the source location, source orientation and specimen geometry making them unsuitable for use in predictive models. The work in this paper is concerned with making source characterisation measurements based on the diffuse field of an AE signal. A practical approach for calibrating the diffuse field amplitude is proposed and is demonstrated on AE signals from electrochemically accelerated corrosion of a 316L stainless steel plate. The diffuse field amplitude of several AE events is calculated and reported as an equivalent absolute force. The low signal to noise ratio and high attenuation of elastic wave energy are found to reduce the accuracy of the results.

  4. 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.

  5. Acoustic emission detection of early stages of cracks in rotating gearbox components

    NASA Astrophysics Data System (ADS)

    Xiang, Dan

    2017-02-01

    Many critical, highly loaded rotating gearbox components have fast crack propagation rates. Early detection of cracks in gearbox is critical to mitigating the risk of catastrophic failure. Acoustic Emission (AE) techniques have proven to be capable of continuously monitoring the crack initiation and propagation. Due to the long distance of AE signal propagation from the AE sources to the sensors installed in the housing, the AE signal suffers from severe attenuation and noises. Accurate AE signal classification technology that is capable of extracting the true AE signal out of background noises generated by the surrounding environment of a gearbox is desired. In this paper, an innovative feature extraction and analysis based AE signal classification technology is developed to address this issue. Potential AE signals are first pulled out of the noisy background in real-time through a set of automated AE detection algorithms. Then features including count, energy, duration, amplitude, rise time, amplitude rise time ratio, etc. are extracted and analyzed. Through the comparison and correlation of features extracted from signals recorded by multiple AE sensors, respective feature thresholds are determined to distinguish noises from real AE signal. The classification results are experimentally validated through fatigue tests.

  6. The evaluation of moisture damage for CFRC pipes in conjunction with acoustic emission

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Su, Yu-Min; Liu, Yanjun; Tia, Mang

    2014-03-01

    The objective of this study was to evaluate the in-situ serviceability of cellulose fiber reinforced concrete (CFRC) pipes using Acoustic Emission (AE). Three-edge-bearing test was conducted on CFRC pipes in the laboratory in accordance with ASTM C497-05. Pipes were saturated in water for various periods of time to simulate the practical field situations of CFRC pipes with different service life exposed to moisture effects. AE sensors and LVDT were installed on pipes detect the damage phases during loading. Both monotonic and cyclic loading modes were conducted on the CFRC pipes. Results showed that the CFRC pipes generally exhibited the nonlinear load-displacement behavior before failure, yet the level of ductility was reduced with longer exposure to moisture condition. AE data were evaluated through two feature signals, that is, intensity analysis and calm ratio analysis. Results showed that AE can detect the onset of damage and the ultimate failure of CFRC pipes. Additionally, the analysis on CFRC pipes subjected to various moisture effects showed different features of AE results. It is found that intensity analysis can distinguish different periods of exposure to moisture and levels of ductility, which make it feasible to monitor the health of CFRC pipes under moisture effects.

  7. Application of Acoustic Emission on the Characterization of Fracture in Textile Reinforced Cement Laminates

    PubMed Central

    Blom, J.; Wastiels, J.; Aggelis, D. G.

    2014-01-01

    This work studies the acoustic emission (AE) behavior of textile reinforced cementitious (TRC) composites under flexural loading. The main objective is to link specific AE parameters to the fracture mechanisms that are successively dominating the failure of this laminated material. At relatively low load, fracture is initiated by matrix cracking while, at the moment of peak load and thereafter, the fiber pull-out stage is reached. Stress modeling of the material under bending reveals that initiation of shear phenomena can also be activated depending on the shape (curvature) of the plate specimens. Preliminary results show that AE waveform parameters like frequency and energy are changing during loading, following the shift of fracturing mechanisms. Additionally, the AE behavior of specimens with different curvature is very indicative of the stress mode confirming the results of modeling. Moreover, AE source location shows the extent of the fracture process zone and its development in relation to the load. It is seen that AE monitoring yields valuable real time information on the fracture of the material and at the same time supplies valuable feedback to the stress modeling. PMID:24605050

  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. 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.

  10. Acoustic Emission Investigation of Rolling/Sliding Contact Fatigue Failure of NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Guolu, Li; Zhonglin, Xu; Tianshun, Dong; Haidou, Wang; Jinhai, Liu; Jiajie, Kang

    2016-10-01

    NiCr-Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.

  11. Acoustic-wave sensor for ambient monitoring of a photoresist-stripping agent

    DOEpatents

    Pfeifer, K.B.; Hoyt, A.E.; Frye, G.C.

    1998-08-18

    The acoustic-wave sensor is disclosed. The acoustic-wave sensor is designed for ambient or vapor-phase monitoring of a photoresist-stripping agent such as N-methylpyrrolidinone (NMP), ethoxyethylpropionate (EEP) or the like. The acoustic-wave sensor comprises an acoustic-wave device such as a surface-acoustic-wave (SAW) device, a flexural-plate-wave (FPW) device, an acoustic-plate-mode (APM) device, or a thickness-shear-mode (TSM) device (also termed a quartz crystal microbalance or QCM) having a sensing region on a surface thereof. The sensing region includes a sensing film for sorbing a quantity of the photoresist-stripping agent, thereby altering or shifting a frequency of oscillation of an acoustic wave propagating through the sensing region for indicating an ambient concentration of the agent. According to preferred embodiments of the invention, the acoustic-wave device is a SAW device; and the sensing film comprises poly(vinylacetate), poly(N-vinylpyrrolidinone), or poly(vinylphenol). 3 figs.

  12. Acoustic-wave sensor for ambient monitoring of a photoresist-stripping agent

    DOEpatents

    Pfeifer, Kent B.; Hoyt, Andrea E.; Frye, Gregory C.

    1998-01-01

    The acoustic-wave sensor. The acoustic-wave sensor is designed for ambient or vapor-phase monitoring of a photoresist-stripping agent such as N-methylpyrrolidinone (NMP), ethoxyethylpropionate (EEP) or the like. The acoustic-wave sensor comprises an acoustic-wave device such as a surface-acoustic-wave (SAW) device, a flexural-plate-wave (FPW) device, an acoustic-plate-mode (APM) device, or a thickness-shear-mode (TSM) device (also termed a quartz crystal microbalance or QCM) having a sensing region on a surface thereof. The sensing region includes a sensing film for sorbing a quantity of the photoresist-stripping agent, thereby altering or shifting a frequency of oscillation of an acoustic wave propagating through the sensing region for indicating an ambient concentration of the agent. According to preferred embodiments of the invention, the acoustic-wave device is a SAW device; and the sensing film comprises poly(vinylacetate), poly(N-vinylpyrrolidinone), or poly(vinylphenol).

  13. Acoustic emission applied to detect workpiece burn during grinding

    SciTech Connect

    Aguiar, P.R. de; Willett, P.; Webster, J.

    1999-07-01

    Overly-aggressive or otherwise inappropriate grinding of metals can produce an undesirable change in metallurgical properties of the material being processed; usually this is referred to as workpiece burn. In this experimental paper the acoustic signature of grinding is collected, and compared to the processed workpiece condition, for thirteen data sets including both relatively hard (Inconel) and soft (52100 bearing steel) metals. This work is distinguished by its use of a high sampling rate (2.56 MHz) in data acquisition and in its processing of the raw, rather than RMS/filtered, data samples. Signs of burn are seen in the frequency domain, and in the correlation between wheel rotations.

  14. 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.

  15. 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.

  16. Monitoring the progress of emission inventories

    SciTech Connect

    Levy, J.A. Jr.; Solomon, D.; Husk, M.; Irving, B.; Kruger, D.; Levin. L.

    2006-12-15

    This issue of EM contains three articles which focus on the latest improvements on the emissions inventory process. The first, 'Building the national emissions inventory: challenges and plans for improvements' by Doug Solomon and Martin Husk (pages 8-11), looks at the US national emissions inventory. The next, 'Greenhouse gas inventories - a historical perspective and assessment of improvements since 1990' by Bill Irving and Dina Kruger (pages 12-19) assesses improvements in national and international greenhouse gas emissions inventories over the last 15 years. The third article, 'The global mercury emissions inventory' by Leonard Levin (pages 20-25) gives an overview of the challenges associated with conducting a worldwide inventory of mercury emissions.

  17. Information theory filters for wavelet packet coefficient selection with application to corrosion type identification from acoustic emission signals.

    PubMed

    Van Dijck, Gert; Van Hulle, Marc M

    2011-01-01

    The damage caused by corrosion in chemical process installations can lead to unexpected plant shutdowns and the leakage of potentially toxic chemicals into the environment. When subjected to corrosion, structural changes in the material occur, leading to energy releases as acoustic waves. This acoustic activity can in turn be used for corrosion monitoring, and even for predicting the type of corrosion. Here we apply wavelet packet decomposition to extract features from acoustic emission signals. We then use the extracted wavelet packet coefficients for distinguishing between the most important types of corrosion processes in the chemical process industry: uniform corrosion, pitting and stress corrosion cracking. The local discriminant basis selection algorithm can be considered as a standard for the selection of the most discriminative wavelet coefficients. However, it does not take the statistical dependencies between wavelet coefficients into account. We show that, when these dependencies are ignored, a lower accuracy is obtained in predicting the corrosion type. We compare several mutual information filters to take these dependencies into account in order to arrive at a more accurate prediction.

  18. Information Theory Filters for Wavelet Packet Coefficient Selection with Application to Corrosion Type Identification from Acoustic Emission Signals

    PubMed Central

    Van Dijck, Gert; Van Hulle, Marc M.

    2011-01-01

    The damage caused by corrosion in chemical process installations can lead to unexpected plant shutdowns and the leakage of potentially toxic chemicals into the environment. When subjected to corrosion, structural changes in the material occur, leading to energy releases as acoustic waves. This acoustic activity can in turn be used for corrosion monitoring, and even for predicting the type of corrosion. Here we apply wavelet packet decomposition to extract features from acoustic emission signals. We then use the extracted wavelet packet coefficients for distinguishing between the most important types of corrosion processes in the chemical process industry: uniform corrosion, pitting and stress corrosion cracking. The local discriminant basis selection algorithm can be considered as a standard for the selection of the most discriminative wavelet coefficients. However, it does not take the statistical dependencies between wavelet coefficients into account. We show that, when these dependencies are ignored, a lower accuracy is obtained in predicting the corrosion type. We compare several mutual information filters to take these dependencies into account in order to arrive at a more accurate prediction. PMID:22163921

  19. Complex monitoring and alert network for electromagnetic, infrasound, acoustic seismotectonic phenomena

    NASA Astrophysics Data System (ADS)

    -Emilian Toader, Victorin; Moldovan, Iren-Adelina; Constantin, Ionescu

    2014-05-01

    The Romanian seismicity recorded in 2013 three important events: the largest seismic "silence", the shortest sequence of two earthquakes greater than 4.8R in less than 14 days after the "Romanian National Institute for Earth Physics" (NIEP) developed a digital network, and a very high crustal activity in Galati area. We analyze the variations of the telluric currents and local magnetic field, variations of the atmospheric electrostatic field, infrasound, temperature, humidity, wind speed and direction, atmospheric pressure, variations in the earth crust with inclinometers and animal behavior. The general effect is the first high seismic energy discontinuity that could be a precursor factor. Since 1977 Romania did not register any important earthquake that would generate a sense of fear among the population. In parallel with the seismic network NIEP developed a magneto-telluric, bioseismic, VLF and acoustic network. A large frequency spectrum is covered for mechanical vibration, magnetic and electric field with ground and air sensors. Special software was designed for acquisition, analysis and real time alert using internet direct connection, web page, email and SMS. Many examples show the sensitivity of telluric current, infrasound, acoustic records (from air-ground), and the effect of tectonic stress on the magnetic field or ground deformation. The next update of the multidisciplinary monitoring network will include measurement of ionization, radon emission, sky color, solar radiation and extension of infrasound and VL/LF equipment. NOAA Space Weather satellites transmit solar activity magnetic field data, X ray flux, electron, and proton flux information useful for complex analysis.

  20. Passive acoustic monitoring of bed load discharge in a large gravel bed river

    NASA Astrophysics Data System (ADS)

    Geay, T.; Belleudy, P.; Gervaise, C.; Habersack, H.; Aigner, J.; Kreisler, A.; Seitz, H.; Laronne, J. B.

    2017-02-01

    Surrogate technologies to monitor bed load discharge have been developed to supplement and ultimately take over traditional direct methods. Our research deals with passive acoustic monitoring of bed load flux using a hydrophone continuously deployed near a river bed. This passive acoustic technology senses any acoustic waves propagated in the river environment and particularly the sound due to interparticle collisions emitted during bed load movement. A data set has been acquired in the large Alpine gravel-bedded Drau River. Analysis of the short-term frequency response of acoustic signals allows us to determine the origin of recorded noises and to consider their frequency variations. Results are compared with ancillary field data of water depth and bed load transport inferred from the signals of a geophone array. Hydrophone and geophone signals are well correlated. Thanks to the large network of deployed geophones, analysis of the spatial resolution of hydrophone measurements shows that the sensor is sensitive to bed load motion not only locally but over distances of 5-10 m (10-20% of river width). Our results are promising in terms of the potential use of hydrophones for monitoring bed load transport in large gravel bed rivers: acoustic signals represent a large river bed area, rather than being local; hydrophones can be installed in large floods; they can be deployed at a low cost and provide continuous monitoring at high temporal resolution.

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

    SciTech Connect

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

    1996-12-31

    The use acoustic emission (AE) sensing as a method to monitor proximity between a grinding wheel and a brittle material workpiece is being developed at Lawrence Livermore National Laboratory (LLNL) and the Center for Optics Manufacturing (COM) in Rochester, NY. Significantly reducing the amount of expensive {open_quote}air-grinding{close_quote} is one of the primary motivations behind this effort, along with lessening the chances of a crash which could damage the wheel, part and machine tool. AE sensing is well developed and routinely used in the metal working industry for {open_quote}initial contact{close_quote} sensing or tool breakage, for example, and in monitoring diamond turning and grinding processes. However, using AE sensing to switch from a rapid to a final in-feed rate at the detection of initial-contact between the grinding wheel and a brittle material workpiece, such as an optical glass, is often unacceptable during fine grinding (less than 10 {mu}m grit wheels) which produce surfaces with roughness values of 100 {Angstrom} rms or less. In the approach taken here, the authors are sensing the AE prior to contact between the workpiece and the tool. The coolant between the workpiece and the grinding wheel is used as an AE medium to transfer AE signals generated by the relative motions of the coolant, workpiece and wheel. Capitalizing on the repeatability of the AE approach signal, the authors have developed a system to detect the proximity of the grinding wheel relative to the workpiece prior to initial contact.

  2. Crustal stress, seismicity, acoustic emission (AE), and tectonics: the Kefallinì;a (Greece) case study

    NASA Astrophysics Data System (ADS)

    Gregori, G. P.; Poscolieri, M.; Paparo, G.; Ventrice, G.; de Simone, S.; Rafanelli, C.

    2009-04-01

    New inferences - confirming previous results (see references)- are presented dealing with a few years Acoustic Emission (AE) records collected at Kefallinìa (Ionian Islands, Greece). A physical distinction between HF (high frequency) vs. LF (low frequency) AE is required. Step-wise changes of the AE underground conductivity are evidenced, and can be suitably handled. "Smooth" results concern (i) the annual variation, (ii) some long-lasting stress "solitons" crossing through the area, and (iii) tidal effects. In particular, every AE station can be operated like a monitoring station both for Earth's tides and for the free oscillations of the Earth. In addition, Kefallinìa exhibits a much peculiar groundwater circulation, in which conduit flow is dominant, that originates a specific (and unique) AE effect. By means of AE time-series analysis, "extreme" or "catastrophic" events can be also monitored and possibly related to relevant tectonic occurrences (either earthquakes, or maybe other occasional phenomena). They can be investigated, and have a regional - rather than local - character. Therefore, every interpretation based on a single station record - being biased by some arbitrariness - can only result indicative. A standardized procedure and software is proposed for routine AE data handling and analysis. References.: Lagios et al., 2004. In Proc. SCI 2004 (The 8th World Multi-Conference on Systemics, Cybernetics and Informatic), Orlando, Florida, July 1004, 6 pp. Poscolieri et al., 2006. In. G. Cello and B. D. Malamud, (eds), 2006. Geol. Soc. London, Special Publ., 261, 63-78. Poscolieri et al., 2006a. Nat. Hazards Earth Syst. Sci., 6, 961-971.

  3. Acoustic emission and fatigue damage induced in plasma-sprayed hydroxyapatite coating layers.

    PubMed

    Laonapakul, Teerawat; Otsuka, Yuichi; Nimkerdphol, Achariya Rakngarm; Mutoh, Yoshiharu

    2012-04-01

    In order to improve the adhesive strength of hydroxyapatite (HAp) coatings, grit blasting with Al(2)O(3) powder and then wet blasting with HAp/Ti mixed powders was carried out on a commercially pure Ti (cp-Ti) substrate. Subsequently, an HAp/Ti bond coat layer and HAp top coat layer were deposited by plasma spraying. Fatigue tests of the HAp-coated specimens were carried out under four-point bending. Acoustic emission (AE) signals during the entire fatigue test were monitored to investigate the fatigue cracking behavior of the HAp-coated specimens. The HAp-coated specimens could survive up to 10(7) cycles without spallation of the HAp coating layers at the stress amplitude of 120 MPa. The HAp-coated specimens without HAp/Ti bond coat layer showed shorter fatigue life and easy crack nucleation compared to the HAp-coated specimens with HAp/Ti bond coat layer. The delamination and spallation of the HAp top coat with HAp/Ti bond coat on cp-Ti was not observed until the crack propagated into the cp-Ti during the final fracture stage of the fatigue cycle. Therefore, the HAp/Ti bond coat layer was found to greatly improve the fatigue damage resistance of the HAp coating layer. Three stages of the fatigue failure behavior of the HAp top coat with HAp/Ti bond coat on a cp-Ti substrate can be clearly estimated by the AE monitoring technique. These stages are cracks nucleating and propagating in the coating layer, cracks propagating in the substrate, and cracks propagating unstably to final fracture.

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

    NASA Astrophysics Data System (ADS)

    White, Michael Shane

    2005-09-01

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

  5. Electrochemical NOx Sensor for Monitoring Diesel Emissions

    SciTech Connect

    Woo, L Y; Glass, R S

    2008-11-14

    Increasingly stringent emissions regulations will require the development of advanced gas sensors for a variety of applications. For example, compact, inexpensive sensors are needed for detection of regulated pollutants, including hydrocarbons (HCs), CO, and NO{sub x}, in automotive exhaust. Of particular importance will be a sensor for NO{sub x} to ensure the proper operation of the catalyst system in the next generation of diesel (CIDI) automobiles. Because many emerging applications, particularly monitoring of automotive exhaust, involve operation in harsh, high-temperature environments, robust ceramic-oxide-based electrochemical sensors are a promising technology. Sensors using yttria-stabilized zirconia (YSZ) as an oxygen-ion-conducting electrolyte have been widely reported for both amperometric and potentiometric modes of operation. These include the well-known exhaust gas oxygen (EGO) sensor. More recently, ac impedance-based (i.e., impedance-metric) sensing techniques using YSZ have been reported for sensing water vapor, hydrocarbons, CO, and NO{sub x}. Typically small-amplitude alternating signal is applied, and the sensor response is measured at a specified frequency. Most impedance-metric techniques have used the modulus (or magnitude) at low frequencies (< 1 Hz) as the sensing signal and attribute the measured response to interfacial phenomena. Work by our group has also investigated using phase angle as the sensing signal at somewhat higher frequencies (10 Hz). The higher frequency measurements would potentially allow for reduced sampling times during sensor operation. Another potential advantage of impedance-metric NO{sub x} sensing is the similarity in response to NO and NO{sub 2} (i.e., total-NO{sub x} sensing). Potentiometric NO{sub x} sensors typically show higher sensitivity to NO2 than NO, and responses that are opposite in sign. However, NO is more stable than NO{sub 2} at temperatures > 600 C, and thermodynamic calculations predict {approx}90

  6. Locomotive emissions monitoring program annual report, 1995

    SciTech Connect

    1997-12-31

    The report is to include data on the traffic moved and the fuel consumed, estimates of the consequent emissions of certain exhaust gases, and information on any improvements in equipment or operating practices that will lead to reduced emissions. This is the first such annual report.

  7. [Acoustic respiratory rate monitoring in a patient with a tracheostomy: a case report].

    PubMed

    Toda, Yuichiro; Morimatsu, Hiroshi; Hayashi, Masao; Shimizu, Kazuyoshi; Morita, Kiyoshi

    2014-02-01

    Acoustic respiratory rate (RRa) monitoring has been validated for patients after general anesthesia and has been shown to be a useful technique. However, its feasibility in patients with a tracheostomy has not been assessed yet. Successful monitoring of RRa in a patient with a tracheostomy is described in this case report. A 56-year-old male patient was scheduled for cranioplasty after severe subarachnoidal hemorrhage under general anesthesia. A tracheostomy tube had been placed in the patient because of airway obstruction and altered spontaneous breathing. The acoustic sensor was placed at the usual position and RRa was successfully monitored by Rad 87 (Masimo Corp., Irvine). Statistical analysis was made for comparison of respiratory rate determined by RRa monitoring with respiratory rate visually counted by intensive care nurses. There was no statistically significant difference between the two respiratory rates (P = 0.82). RRa monitoring is useful even in patients with a tracheostomy.

  8. 40 CFR 60.373 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-Acid Battery Manufacturing Plants § 60.373 Monitoring of emissions and operations. The owner or operator of any lead-acid battery manufacturing facility subject to the provisions of this subpart...

  9. 40 CFR 60.373 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-Acid Battery Manufacturing Plants § 60.373 Monitoring of emissions and operations. The owner or operator of any lead-acid battery manufacturing facility subject to the provisions of this subpart...

  10. 40 CFR 60.314 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Surface Coating of Metal Furniture § 60.314 Monitoring of emissions and operations. (a) The owner or... measurement device shall be installed in the gas stream immediately before and after the catalyst bed....

  11. 40 CFR 60.663 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Distillation Operations § 60.663 Monitoring of emissions and operations. (a) The owner or operator of an... distillation unit within an affected facility at a point closest to the inlet of each boiler or process...

  12. 40 CFR 60.663 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) Distillation Operations § 60.663 Monitoring of emissions and operations. (a) The owner or operator of an... distillation unit within an affected facility at a point closest to the inlet of each boiler or process...

  13. 40 CFR 60.663 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) Distillation Operations § 60.663 Monitoring of emissions and operations. (a) The owner or operator of an... distillation unit within an affected facility at a point closest to the inlet of each boiler or process...

  14. 40 CFR 60.663 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) Distillation Operations § 60.663 Monitoring of emissions and operations. (a) The owner or operator of an... distillation unit within an affected facility at a point closest to the inlet of each boiler or process...

  15. 40 CFR 60.663 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) Distillation Operations § 60.663 Monitoring of emissions and operations. (a) The owner or operator of an... distillation unit within an affected facility at a point closest to the inlet of each boiler or process...

  16. A CAVITY RINGDOWN SPECTROSCOPY MERCURY CONTINUOUS EMISSION MONITOR

    SciTech Connect

    Christopher C. Carter, Ph.D.

    2002-01-01

    The first quarter of this project to develop a Cavity Ringdown Spectroscopy mercury continuous emission monitor involved acquisition and verification of the laser system to be used, initial cavity design, and initial software development for signal processing and data acquisition.

  17. 40 CFR 60.613 - Monitoring of emissions and operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) Air Oxidation Unit Processes § 60.613 Monitoring of emissions and operations. (a) The owner or... from each air oxidation reactor within an affected facility at a point closest to the inlet of...

  18. Common humpback whale (Megaptera novaeangliae) sound types for passive acoustic monitoring.

    PubMed

    Stimpert, Alison K; Au, Whitlow W L; Parks, Susan E; Hurst, Thomas; Wiley, David N

    2011-01-01

    Humpback whales (Megaptera novaeangliae) are one of several baleen whale species in the Northwest Atlantic that coexist with vessel traffic and anthropogenic noise. Passive acoustic monitoring strategies can be used in conservation management, but the first step toward understanding the acoustic behavior of a species is a good description of its acoustic repertoire. Digital acoustic tags (DTAGs) were placed on humpback whales in the Stellwagen Bank National Marine Sanctuary to record and describe the non-song sounds being produced in conjunction with foraging activities. Peak frequencies of sounds were generally less than 1 kHz, but ranged as high as 6 kHz, and sounds were generally less than 1 s in duration. Cluster analysis distilled the dataset into eight groups of sounds with similar acoustic properties. The two most stereotyped and distinctive types ("wops" and "grunts") were also identified aurally as candidates for use in passive acoustic monitoring. This identification of two of the most common sound types will be useful for moving forward conservation efforts on this Northwest Atlantic feeding ground.

  19. Acoustic method respiratory rate monitoring is useful in patients under intravenous anesthesia.

    PubMed

    Ouchi, Kentaro; Fujiwara, Shigeki; Sugiyama, Kazuna

    2017-02-01

    Respiratory depression can occur during intravenous general anesthesia without tracheal intubation. A new acoustic method for respiratory rate monitoring, RRa(®) (Masimo Corp., Tokyo, Japan), has been reported to show good reliability in post-anesthesia care and emergency units. The purpose of this study was to investigate the reliability of the acoustic method for measurement of respiratory rate during intravenous general anesthesia, as compared with capnography. Patients with dental anxiety undergoing dental treatment under intravenous anesthesia without tracheal intubation were enrolled in this study. Respiratory rate was recorded every 30 s using the acoustic method and capnography, and detectability of respiratory rate was investigated for both methods. This study used a cohort study design. In 1953 recorded respiratory rate data points, the number of detected points by the acoustic method (1884, 96.5 %) was significantly higher than that by capnography (1682, 86.1 %) (P < 0.0001). In the intraoperative period, there was a significant difference in the LOA (95 % limits of agreement of correlation between difference and average of the two methods)/ULLOA (under the lower limit of agreement) in terms of use or non-use of a dental air turbine (P < 0.0001). In comparison between capnography, the acoustic method is useful for continuous monitoring of respiratory rate in spontaneously breathing subjects undergoing dental procedures under intravenous general anesthesia. However, the acoustic method might not accurately detect in cases in with dental air turbine.

  20. Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

    DTIC Science & Technology

    2015-09-30

    the “unknown” of interest is sound speed (hence temperature and salinity) while in this project it is source location. 7 REFERENCES...and applicability of model-based passive acoustic tracking methods for marine mammals: 1) Invert for sound speed profiles, hydrophone position and...animal position(s). Arrival time predictions are made using a sound propagation model, which in turn uses information about the environment