The Experts below are selected from a list of 2244 Experts worldwide ranked by ideXlab platform
Jennifer E Michaels - One of the best experts on this subject based on the ideXlab platform.
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multipath ultrasonic guided wave imaging in complex structures
Structural Health Monitoring-an International Journal, 2015Co-Authors: James S Hall, Jennifer E MichaelsAbstract:Ultrasonic guided wave imaging can potentially detect and localize damage over a large area with a sparse, or spatially distributed, array. However, conventional delay-and-sum imaging methods require knowledge of the propagation velocity and rely on direct-path propagation from the transmitting Transducer, to a damage location, and finally to the Receiving Transducer, limiting the applicability of these techniques to relatively simple structures. A multipath guided wave imaging algorithm is presented here that leverages the large number of echoes and reverberations present in recorded ultrasonic waveforms to successfully detect and locate damage in geometrically complex structures. Multipath guided wave imaging not only allows imaging to be performed on structures with complex features (e.g. stiffeners, lap joints, and rivets) and inhomogeneous and anisotropic materials but also significantly improves image quality with far fewer sensors compared to conventional elliptical imaging. Experimental results fr...
W. Wang - One of the best experts on this subject based on the ideXlab platform.
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double through transmission bulk wave method for ultrasonic phase velocity measurement and determination of elastic constants of composite materials
Journal of the Acoustical Society of America, 1992Co-Authors: S. I. Rokhlin, W. WangAbstract:This paper describes a modification of a nondestructive ultrasonic method for measurements of the phase velocity of bulk waves in arbitrary directions in generally anisotropic materials. In the conventional method the through‐transmission technique is used for velocity measurements at a specified angle of incidence. When this angle is changed by rotation of the sample, the transmitted beam changes position, and so the position of the Receiving Transducer must be changed. This leads to experimental difficulties and loss of precision. In the double‐transmission technique, the ultrasonic wave is reflected from reflector plates behind the sample and returns via the same path to the same position on the transmitter/receiver working in pulse‐echo mode, which eliminates the necessity of readjusting the receiver position. It is also shown that for arbitrary direction of measurement in anisotropic materials, time‐delay measurements give phase velocity regardless of the angle of deviation between phase and group ve...
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Double through‐transmission bulk wave method for ultrasonic phase velocity measurement and determination of elastic constants of composite materials
The Journal of the Acoustical Society of America, 1992Co-Authors: S. I. Rokhlin, W. WangAbstract:This paper describes a modification of a nondestructive ultrasonic method for measurements of the phase velocity of bulk waves in arbitrary directions in generally anisotropic materials. In the conventional method the through‐transmission technique is used for velocity measurements at a specified angle of incidence. When this angle is changed by rotation of the sample, the transmitted beam changes position, and so the position of the Receiving Transducer must be changed. This leads to experimental difficulties and loss of precision. In the double‐transmission technique, the ultrasonic wave is reflected from reflector plates behind the sample and returns via the same path to the same position on the transmitter/receiver working in pulse‐echo mode, which eliminates the necessity of readjusting the receiver position. It is also shown that for arbitrary direction of measurement in anisotropic materials, time‐delay measurements give phase velocity regardless of the angle of deviation between phase and group ve...
James S Hall - One of the best experts on this subject based on the ideXlab platform.
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multipath ultrasonic guided wave imaging in complex structures
Structural Health Monitoring-an International Journal, 2015Co-Authors: James S Hall, Jennifer E MichaelsAbstract:Ultrasonic guided wave imaging can potentially detect and localize damage over a large area with a sparse, or spatially distributed, array. However, conventional delay-and-sum imaging methods require knowledge of the propagation velocity and rely on direct-path propagation from the transmitting Transducer, to a damage location, and finally to the Receiving Transducer, limiting the applicability of these techniques to relatively simple structures. A multipath guided wave imaging algorithm is presented here that leverages the large number of echoes and reverberations present in recorded ultrasonic waveforms to successfully detect and locate damage in geometrically complex structures. Multipath guided wave imaging not only allows imaging to be performed on structures with complex features (e.g. stiffeners, lap joints, and rivets) and inhomogeneous and anisotropic materials but also significantly improves image quality with far fewer sensors compared to conventional elliptical imaging. Experimental results fr...
S. I. Rokhlin - One of the best experts on this subject based on the ideXlab platform.
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double through transmission bulk wave method for ultrasonic phase velocity measurement and determination of elastic constants of composite materials
Journal of the Acoustical Society of America, 1992Co-Authors: S. I. Rokhlin, W. WangAbstract:This paper describes a modification of a nondestructive ultrasonic method for measurements of the phase velocity of bulk waves in arbitrary directions in generally anisotropic materials. In the conventional method the through‐transmission technique is used for velocity measurements at a specified angle of incidence. When this angle is changed by rotation of the sample, the transmitted beam changes position, and so the position of the Receiving Transducer must be changed. This leads to experimental difficulties and loss of precision. In the double‐transmission technique, the ultrasonic wave is reflected from reflector plates behind the sample and returns via the same path to the same position on the transmitter/receiver working in pulse‐echo mode, which eliminates the necessity of readjusting the receiver position. It is also shown that for arbitrary direction of measurement in anisotropic materials, time‐delay measurements give phase velocity regardless of the angle of deviation between phase and group ve...
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Double through‐transmission bulk wave method for ultrasonic phase velocity measurement and determination of elastic constants of composite materials
The Journal of the Acoustical Society of America, 1992Co-Authors: S. I. Rokhlin, W. WangAbstract:This paper describes a modification of a nondestructive ultrasonic method for measurements of the phase velocity of bulk waves in arbitrary directions in generally anisotropic materials. In the conventional method the through‐transmission technique is used for velocity measurements at a specified angle of incidence. When this angle is changed by rotation of the sample, the transmitted beam changes position, and so the position of the Receiving Transducer must be changed. This leads to experimental difficulties and loss of precision. In the double‐transmission technique, the ultrasonic wave is reflected from reflector plates behind the sample and returns via the same path to the same position on the transmitter/receiver working in pulse‐echo mode, which eliminates the necessity of readjusting the receiver position. It is also shown that for arbitrary direction of measurement in anisotropic materials, time‐delay measurements give phase velocity regardless of the angle of deviation between phase and group ve...
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High‐frequency ultrasonic wave propagation in polycrystalline materials
The Journal of the Acoustical Society of America, 1992Co-Authors: S. I. Rokhlin, T. K. Bolland, Laszlo AdlerAbstract:Ultrasonic propagation through a multigrained anisotropic medium is studied in the high‐frequency (geometric) region via supercomputer simulation. The grains and their boundaries are considered randomly oriented. Material texture is also included in the model. A ray‐tracing approach is used with an exact solution for reflection and transmission of ultrasonic waves at grain boundaries. Transmission losses are studied for both phase‐sensitive and phase‐insensitive Receiving Transducers. Dependence of transmission loss and wave phase distribution on grain size and anisotropy is considered. It is shown that at high anisotropies the transmission loss for a fixed distance between transmitter and phase‐sensitive receiver passes through a minimum as a function of the grain size. The wave‐front orientation angles and the beam deviations at the Receiving Transducer are also found.
John Ditri - One of the best experts on this subject based on the ideXlab platform.
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FINITE SIZE AND SPECIMEN THICKNESS INFLUENCE IN ACOUSTO-ULTRASONIC NDE
2016Co-Authors: Brian Pavlakovic, Joseph L. Rose, John DitriAbstract:Acousto-ultrasonics (AU) uses a pair of Transducers to charactel1ze distributed damage in composite plates. A Transducer placed nOl1nal to the surface creates resonances which propagate as plate waves. Once the Receiving Transducer picks up the signal, simple analysis techniques, such as the zeroth or first moment of the power spectrum, are applie
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Finite Size and Specimen Thickness Influence in Acousto-Ultrasonic NDE
Review of Progress in Quantitative Nondestructive Evaluation, 1995Co-Authors: Brian Pavlakovic, Joseph L. Rose, John DitriAbstract:Acousto-ultrasonics (AU) uses a pair of Transducers to characterize distributed damage in composite plates. A Transducer placed normal to the surface creates resonances which propagate as plate waves. Once the Receiving Transducer picks up the signal, simple analysis techniques, such as the zeroth or first moment of the power spectrum, are applied to create a Stress Wave Factor (SWF). The SWF is then used to quantify the damage state of the composite once the system has been properly trained.
