Analytical Fatigue Life Prediction of Shot Peened Inconel 718

Author:  Thierry Klotz, Dorian Delbergue, Hong Yan Miao, Philippe Bocher, Martin Lévesque, Myriam Brochu
Source:  ICSP-13
Doc ID:  2017075
Year of Publication:  2017
Abstract:  
Introduction: Shot peening is commonly used on mechanical parts submitted to cyclic loads. During the process,compressive residual stresses and work hardening are introduced at the shot peened surface [1]. These two factors delay crack initiation and propagation and thus increase fatigue life. It is also reported that shot peening can modify the crack initiation mechanisms and relocate the crack initiation sites from the surface to the subsurface [2,3]. However, shot peening increases the surface roughness [4] which results in stress concentrations that can alter the fatigue life if the shot peening parameters are not carefully chosen [5,6]. In the aerospace industry, shot peening is usually not accounted for in the design stage but is rather considered as a safety margin. Understanding and modeling shot peening effects on crack initiation and propagation mechanisms would provide the essential grounds to account for the process beneficial effects at the design stage. This would lead to considerably lighter parts and would reduce the trials and errors required to define optimal peening parameters. This study aims at modeling crack initiation and propagation in shot peened Inconel 718 for different shot peening conditions and applied stress levels.