Review of Ultrasonic Velocity Methods of Determining Residual Stress

摘要

Residual stress is the stress remaining in a body when all external forces have been removed. Residual stresses can occur as a result of fabrication, assembly, load history, heat treatment or welding. They may be compressive or tensile, and often contribute to the occurrence of component failure. The contribution of these stresses to premature structural failure has long been recognized. However their measurement has usually been difficult and in many cases not possible. Recognition of the benefits of knowing the value of residual stresses has led to recent efforts to improve the capability of known methods of measuring them and to the development of new techniques. The residual stresses in a body can be divided into two classes depending on the extent of the stress. In typical engineering materials, residual microstresses extend over a few grains, whereas residual macrostresses which are most amenable to the practical measurement methods discussed in this paper. It notes that while velocity methods have not been refined to the stage of practical use, they show considerable promise. The theoretical basis, and the experimental techniques of the ultrasonic methods are reviewed with emphasis on the separation of the competing effects of texture and stress on ultrasonic velocity.