Strengthening Steels by Inducing Residual Stresses Via Mechanical Attrition

Abstract

Making stronger and tougher structural steels has long been a desire for scientists and engineers. In particular, nano-crystallization techniques have been recently been developed as one of the most effective ways to optimize surface structure and therefore develop the local and global mechanical behavior in such a way as to increase strength without compromising ductility. In this paper, we present a computational analysis on a popular surface nano-crystallization technology that involves the use of hundreds of small hard balls which are vibrated using high-power ultrasound so that they impact onto the surface of a material at high speed. We focus specifically on the generation of beneficial residual stress in improving the damage-tolerant properties of an austenitic stainless steel as the target material. Different multiple impact models are investigated to develop a more realistic model for the strengtening process.