Work-Hardening During Peening

Author:  Prof. Dr. David Kirk, Coventry University, U.K.
Source:  The Shot Peener magazine, Vol 31, Issue 3, Summer 2017
Doc ID:  2017024
Year of Publication:  2017
Abstract:  
INTRODUCTION Shot peening is normally applied in order to improve the fatigue properties of components. This improvement is due to two factors: (1) Work-hardening of the surface layer and (2) Compressive residual stress in the surface layer. This article is about work-hardening and fatigue improvement and is aimed at shot peeners rather than scientists. The key to understanding work-hardening is a crystal defect called a “dislocation.” In the early 1900s, scientists were baffled as to why metals started to plastically deform at much smaller stresses than their predicted theoretical strength. About 1934,various scientists proposed that the puzzle could be explained if the metals contained "dislocations”. Many metallurgists remained skeptical of this dislocation theory until the development of the transmission electron microscope in the late 1950s. With further research, based on transmission electron microscopy, we can now understand how work-hardening progresses during plastic deformation.