Effect Of Shot-peening On Surface Crack Propagation In Plane-bending Fatigue

Author:  Misum, Ohhashi, Ohkubo
Source:  Proc.of 4th Conf.of Irish Durability & Frac. Comm.
Doc ID:  1986046
Year of Publication:  1986
Abstract:  
In most cases, fatigue failure of structures starts from the surface of materials and propagates into the inside. Therefore, various surface treatment processes accompanied with compressive residual stress are adopted to improve the mechanical characteristics of the surface layer. Understanding fatigue surface crack propagation is essential to investigate the fatigue characteristics of surface strengthened materials. Concerning the effect of residual stresses on the through-thickness crack propagation, it can be shown that there is a decrease of growth rate by compressive residual stresses and an increase due to tensile residual stresses in welding, induction hardening, quenching and tempering, shot-peening and cold working. It is also recognized that the crack growth rate in specimens with residual stresses can be correlated with that in ones without residual stress in terms of the effective stress intensity based on the crack closure. Meanwhile in the case of semi-elliptical surface crack propagation, Kawashara suggested that the direct application of the Paris formula using numerical solutions of stress intensity factor had not much advantage in precision nor in simplification of anlyses. This report presents the effect of compressive residual stresses after shot-peening on the surface crack growth and on the crack opening behavior along a semi-elliptical crack front which is estimated under the assumption that the data for the crack growth rate at local crack front should obey the Paris law. Descriptors: Carbon steels-- Mechanical properties; Bending fatigue; Crack propagation-- Stress effects; Residual stress; Shot peening