It has been shown both experimentally {2} and theoretically {2,3} that surface skimming SH waves propagating along symmetry axes of the texture have velocities that differ in proportion to the magnitude of any stress that lies along one of the symmetry axes. Specifically, the stress is directly proportional to the relative velocity difference through the equation -,--V ik=---V. -=ki) ( I) cr. = 2G (-V ~ ik where cr. is the stress in the direction i, G is the shear modulus and Vik is the ~elocity of an SH wave propagating in the i direction and polarized in the k direction. This rather simple relationship is particularly useful because the constant of proportionality involves only the well known shear modulus and the velocity term can be measured directly by observing the transit time shift when a transmitter-receiver pair of SH wave transducers are rotated through 90 degrees on the surface of the part. Experimentally, Equation (I) was tested on the web of railroad rails which had been loaded by a 200,000 pound mechanical testing machine {I}. The method of exciting and detecting the necessary surface skimming SH waves used electromagnetic acoustic transducers (EMATs) that operated through a magnetostrictive mechanism at high magnetic fields {4}. Wave velocities parallel and perpendicular to the axis of the rail on the web differed by the amount predicted by Equation (I) to an absolute accuracy of 30 percent in the worst case.

It has been shown both experimentally {2} and theoretically {2,3} that surface skimming SH waves propagating along symmetry axes of the texture have velocities that differ in proportion to the magnitude of any stress that lies along one of the symmetry axes. Specifically, the stress is directly proportional to the relative velocity difference through the equation -,--V ik=---V. -=ki) ( I) cr. = 2G (-V ~ ik where cr. is the stress in the direction i, G is the shear modulus and Vik is the ~elocity of an SH wave propagating in the i direction and polarized in the k direction. This rather simple relationship is particularly useful because the constant of proportionality involves only the well known shear modulus and the velocity term can be measured directly by observing the transit time shift when a transmitter-receiver pair of SH wave transducers are rotated through 90 degrees on the surface of the part. Experimentally, Equation (I) was tested on the web of railroad rails which had been loaded by a 200,000 pound mechanical testing machine {I}. The method of exciting and detecting the necessary surface skimming SH waves used electromagnetic acoustic transducers (EMATs) that operated through a magnetostrictive mechanism at high magnetic fields {4}. Wave velocities parallel and perpendicular to the axis of the rail on the web differed by the amount predicted by Equation (I) to an absolute accuracy of 30 percent in the worst case.

These Proceedings, consisting of Parts A and B, contain the edited versions of most of the papers presented at the annual Review of Progress in Quantitative Nondestructive Evaluation held at the University of California San Diego, in La Jolla, California on July 19- July 24, 1992. The Review was organized by the Center for NDE at Iowa State University and the Ames Laboratory of the USDOE in cooperation with a number of organizations including the Air Force Wright Laboratory Materials Directorate, the American Society for Nondestructive Testing, the Center for NDE at Johns Hopkins University, the Department of Energy, the Federal Aviation Administration, the National Institute of Standards and Technology, the National Science Foundation IndustrylUniversity Cooperative Research Centers, and the Working Group in Quantitative NDE. This year's Review of Progress in QNDE was attended by approximately 475 participants from the U. S. and many foreign countries who presented over 380 papers. With such a large volume of work to review, the meeting was divided into 36 sessions with as many as four sessions running concurrently. The Review covered all phases of NDE research and development from fundamental investigations to engineering applications or inspection systems, and it included all methods of inspection science from acoustics to x-rays. During the last twenty years, the participants of the Review have contributed to its steady growth. Thanks to their efforts, the Review is today one of the largest and most significant gatherings of NDE researchers and engineers anywhere in the world.