Chi-Sing Man

Department of Mathematics, University of Kentucky, Lexington, KY 40506

The presence of stress in a solid causes changes in the speeds of ultrasonic (elastic) waves propagating in it. This phenomenon is called the acoustoelastic effect, which raises the possibility of using ultrasonics as a nondestructive technique for measurement of stress. In this talk I shall first give an overview of the work of my collaborators and me on ultrasonic measurement of stress in metals, which starts from the premise that linear elasticity with initial stress should be adopted as the theoretical foundation for acoustoelasticity. I shall discuss the central problem of acoustoelasticity (namely, the separation of stress-induced and texture-induced shifts in wave velocities) and the effect of crystallographic texture on acoustoelastic coefficients. Finally I shall touch upon a current research project of mine, the objective of which is to develop an ultrasound technique for nondestructive inspection of the subsurface layer of residual stress induced by low plasticity burnishing, a surface enhancement treatment to improve the high-cycle fatigue behavior and material damage tolerance of key components such as blades and disks in gas turbine engines.