Computorized Reconstruction of Ultrasonic Velocity Fields for Mapping of Residual Stress
It is well known that the velocity of sound propagation through a solid is altered when a stress is applied. The velocity change is small, and dependent upon the type of wave being propagated as wall as the magnitude of the stress. Sensitivity is greatest to shear wave sound with the polarization vector parallel to the direction of stress. In this case, velocity changes as great as 0.6% have been measured. This paper describes preliminary work aimed at evaluating computerized reconstruction of velocity fields from velocity profiles to map residual stress concentrations in thick metal sections. We are currently using the Grid Technique of Sweeney and Vest for reconstructing data taken from liquid models. This method limits the number of rays and views that can be used; hence we intend to use the ART technique at a later date. We shall describe the experiment, electronic measuring system, the reconstruction method, and show reconstructions of 2% and 0.2% velocity anomalies in a liquid model and preliminary data in a steel model.
KeywordsResidual Stress Heat Affect Zone Velocity Change Ultrasonic Velocity Velocity Anomaly
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