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

Author:  Misumi, M.-Obhashi, T.-Ohkubo, M.
Source:  Adv. in Surf. Treat.Tech.Vol. 3,55-62 (Pergamon)
Doc ID:  1986092
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 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 the case of semi-elliptical surface crack propagation, Kawahara suggested that the direct application of Paris formula using numerical solutions of stress intensity factor had not much advantages in precision nor in simplification of analyses. This report presents the effect of compressive residual stresses after shot-peening on the surface crack growth and on the crack opening behavior along semi-elliptical crack which is estimated under the assumption that the data for the crack growth rate at local crack front should obey Paris law. Descriptors: Carbon steels-- Mechanical properties; Bending fatigue; Crack propagation-- Stress effects; Residual stress; Shot peening