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William H. Prosser

Bio: William H. Prosser is an academic researcher from Langley Research Center. The author has contributed to research in topics: Acoustic emission & Acoustic wave. The author has an hindex of 18, co-authored 54 publications receiving 1137 citations.


Papers
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01 Jan 2003
TL;DR: A prototype multiplexing approach has been developed and demonstrated in this study, which reduces the amount of AE monitoring instrumentation required and the reduction in the expense of data acquisition hardware.
Abstract: 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 determination The multiplexer also identifies which channels are acquired by encoding TTL logic pulses onto the latter portion of the signals This prototype system was demonstrated using pencil lead break (Hsu-Neilsen) sources on an aluminum plate It performed as designed providing rapid low noise trigger based switching with encoded channel identification this multiplexing approach is not limited to linear arrays, but can be easily extended to monitor sensors in planar ot three dimensional arrays A 32 channel multiplexing system is under development that will allow arbitrary sensor placement Another benefit of this multiplexing system is the reduction in the expense of data acquisition hardware In addition, the reduced weight and power requirements are of extreme importance for proposed AE systems on aerospace vehicles

5 citations

Book ChapterDOI
01 Jan 1991
TL;DR: The existing techniques for measurements of the nonlinearity can be divided into two main categories: strain dependence of the ultrasonic velocity (induced by stress, temperature, etc.) and harmonic generation in the solids as discussed by the authors.
Abstract: A consideration of nonlinearity is essential for describing many important physical phenomena and processes in solids. The determination of nonlinearity is of importance for the characterization of materials, especially the newly developed ones. The existing techniques for measurements of the nonlinearity can be divided into two main categories. One is the measurements of strain dependence of the ultrasonic velocity (induced by stress, temperature, etc.). The other is the measurements of the harmonic generation in the solids.

5 citations

Proceedings ArticleDOI
TL;DR: In a response to the Columbia Accident Investigation Board's recommendations following the loss of the Space Shuttle Columbia in 2003, NASA developed methods to monitor the orbiters while in flight so that on-orbit repairs could be made before reentry if required.
Abstract: In a response to the Columbia Accident Investigation Board’s recommendations following the loss of the Space Shuttle Columbia in 2003, NASA developed methods to monitor the orbiters while in flight so that on‐orbit repairs could be made before reentry if required. One method that NASA investigated was an acoustic based impact detection system. A large array of ground tests successfully demonstrated the capability to detect and localize impact events on the Shuttle’s wing structure. Subsequently, a first generation impact sensing system was developed and deployed on the Shuttle Discovery, the first Shuttle scheduled for return to flight.

4 citations

Patent
22 Nov 1991
TL;DR: In this paper, an ultrasonic wave is applied to an anisotropic sample material in an initial direction and an angle of flux deviation of the wave front is measured from this initial direction, induced by the unknown applied load.
Abstract: An ultrasonic wave is applied to an anisotropic sample material in an initial direction and an angle of flux deviation of the ultrasonic wave front is measured from this initial direction. This flux deviation angle is induced by the unknown applied load. The flux shift is determined between this flux deviation angle and a previously determined angle of flux deviation of an ultrasonic wave applied to a similar anisotropic reference material under an initial known load condition. This determined flux shift is then compared to a plurality of flux shifts of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift.

4 citations

Proceedings ArticleDOI
19 Apr 2004
TL;DR: In this paper, a piezoelectric acoustic sensor made from piezoceramic ribbons is presented, which is capable of sensing high frequency acoustic emissions and impact in a composite/metallic plate.
Abstract: This paper looks at developing novel piezoelectric acoustic sensors, which are capable of sensing high frequency acoustic emissions and impact in a composite/metallic plate. The fabrication of the piezoelectric acoustic sensors made from piezoceramic ribbons would be described in details. An attempt was made to build directionality into the sensing system itself. Continuous sensors placed at right angles on a plate are being discussed as a new approach to measure and locate the source of acoustic waves. Novel signal processing algorithms based on bio - inspired neural systems for spatial filtering of large numbers of embedded sensor arrays in laminated composite media is presented. It is expected that this present work would help in development of sensing techniques for highly efficient health monitoring of integrated aerospace vehicles and structures.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: A comprehensive review on the state of the art of Lamb wave-based damage identification approaches for composite structures, addressing the advances and achievements in these techniques in the past decades, is provided in this paper.

1,350 citations

Journal ArticleDOI
TL;DR: In this paper, the capability of embedded piezoelectric wafer active sensors (PWAS) to excite and detect tuned Lamb waves for structural health monitoring is explored.
Abstract: The capability of embedded piezoelectric wafer active sensors (PWAS) to excite and detect tuned Lamb waves for structural health monitoring is explored. First, a brief review of Lamb waves theory is presented. Second, the PWAS operating principles and their structural coupling through a thin adhesive layer are analyzed. Then, a model of the Lamb waves tuning mechanism with PWAS transducers is described. The model uses the space domain Fourier transform. The analysis is performed in the wavenumber space. The inverse Fourier transform is used to return into the physical space. The integrals are evaluated with the residues theorem. A general solution is obtained for a generic expression of the interface shear stress distribution. The general solution is reduced to a closed-form expression for the case of ideal bonding which admits a closed-form Fourier transform of the interfacial shear stress. It is shown that the strain wave response varies like sin a, whereas the displacement response varies like sinc a. ...

890 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented an experimental and analytical survey of candidate methods for in situ damage detection of composite materials, including delamination, transverse ply cracks and through-holes.
Abstract: Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents part of an experimental and analytical survey of candidate methods for in situ damage detection of composite materials. Experimental results are presented for the application of Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage modes, including delamination, transverse ply cracks and through-holes. Linear wave scans were performed on narrow laminated specimens and sandwich beams with various cores by monitoring the transmitted waves with piezoceramic sensors. Optimal actuator and sensor configurations were devised through experimentation, and various types of driving signal were explored. These experiments provided a procedure capable of easily and accurately determining the time of flight of a Lamb wave pulse between an actuator and sensor. Lamb wave techniques provide more information about damage presence and severity than previously tested methods (frequency response techniques), and provide the possibility of determining damage location due to their local response nature. These methods may prove suitable for structural health monitoring applications since they travel long distances and can be applied with conformable piezoelectric actuators and sensors that require little power.

752 citations

Journal ArticleDOI
TL;DR: The structural health monitoring (SHM) system is of primary importance because it is the structure that provides the integrity of the system, and the related non-destructive test and evaluation methods are discussed in this review.
Abstract: Renewable energy sources have gained much attention due to the recent energy crisis and the urge to get clean energy. Among the main options being studied, wind energy is a strong contender because of its reliability due to the maturity of the technology, good infrastructure and relative cost competitiveness. In order to harvest wind energy more efficiently, the size of wind turbines has become physically larger, making maintenance and repair works difficult. In order to improve safety considerations, to minimize down time, to lower the frequency of sudden breakdowns and associated huge maintenance and logistic costs and to provide reliable power generation, the wind turbines must be monitored from time to time to ensure that they are in good condition. Among all the monitoring systems, the structural health monitoring (SHM) system is of primary importance because it is the structure that provides the integrity of the system. SHM systems and the related non-destructive test and evaluation methods are discussed in this review. As many of the methods function on local damage, the types of damage that occur commonly in relation to wind turbines, as well as the damage hot spots, are also included in this review.

721 citations

Journal ArticleDOI
TL;DR: In this article, the second-order acousto-elastic coefficient (SOC) was measured in a variety of materials including plastics, metals, composites and adhesives.

430 citations