Eigenstrain Generated by Shot Peening in Udimet 720LI Inferred By Means of Finite Element and Analytical Models

Author:  M. Satraki, A. Evans, A. King, G. Bruno, P. Wither
Source:  Conf Proc: ICSP-9 (pg 442-447)
Doc ID:  2005122
Year of Publication:  2005
Abstract:  
ABSTRACT The residual stress in shot peened Udimet 720Li was determined by laboratory X-ray diffraction measurements. Depth profiles were obtained by electrochemical layer removal and a tensile peak was observed sub surface. A correction for layer removal was applied and the corrected data has been used to calculate the profile of the eigenstrain necessary to generate such a residual stress profile. Calculations were made applying two methods: 1) A Finite Element Model (FEM) using a thermally driven expansion to simulate the eigenstrain, 2) A simple analytical model. The latter took into account strain hardening, as measured in fatigue tests, and stress balance. Using the eigenstrain profile, the geometrically necessary cold work stored in the component was calculated. Results show a very good agreement between the two different models. The analytical method predicts a compressive misfit, while this was explicitly discarded in the FEM model. The calculated cold work is essentially the same for both models, but shows different behaviour from the peak integral width.