ULTRASONIC CHARACTERIZATION OF NEAR-SURFACE MATERIAL PROPERTIES IN SHOT PEENED WASPALOY

摘要

When a stream of shot impinges a metal surface, a near-surface layer undergoes an intensive cold working resulting in material property changes. One of the effects induced by shot peening, a near-surface compressivc stress, helps to slow down initiation and propagation of surface breaking cracks resulting in an extended fatigue life of a component. The capability to non-dcstructively evaluate near-surface residual stress would greatly aid the assurance of proper fatigue life in these components. This paper presents results from an ultrasonic characterization study of shot peened Waspaloy surfaces. Rayleigh wave velocity measurements by a V(z)-curve method were made on smooth and shot peened samples using line-focus ultrasonic transducers. Several factors are believed to influence measured surface wave velocity including surface roughness, near-surface grain reorientation (texture), and residual stress. In this study we estimate quantitatively the effect of these factors and discuss how these effects can be separated and accounted for in residual stress measurements.