On the Relationship of Surface Cold Work to Coverage in Shot Peening

Author:  J. T. Cammett (1), P. S. Prevey (2), D. J. Hornbach (2) (1) Consultant, (2) Lambda Technologies Group
Source:  The Shot Peener magazine, Vol 32, Issue 2, Spring 2018
Doc ID:  2018022
Year of Publication:  2018
Abstract:  
Introduction: Certainly, a desirable result of shot peening is creation of compressive residual stresses at the surface of a part and in near surface layers. Though often not known or seldom considered, cold work (CW) is also an inherent result of peening, and is fundamentally responsible for the creation of compressive residual stresses. Bombardment of the surface of a part by small spherical media creates plastic deformation, i.e., stretching of surface layers. Elastic resistance of underlying material, which is not plastically stretched by peening, results in compression in surface and near-surface layers. Also, not commonly known or considered is that CW can influence the stability of residual stresses from thermal exposure and mechanical applied stresses in service (Ref. 1). Discussion of this matter of residual stress stability is beyond the scope of this brief article. Readers, however, are encouraged to consult the reference supplied to determine significance to their parts and service life.