Experiments and Simulations of Double Side Shot Peened Aluminum

Author:  Siavash Ghanbari, Daniel J. Chadwick, Michael D. Sangid,b David F. Bahr
Source:  ICSP-13
Doc ID:  2017093
Year of Publication:  2017
Introduction: Shot peening is a well-established and cost effective method to induce compressive residual stresses in metallic components using a localized cold working process. Shot peening increases fatigue life in many applications via cold working a surface using a stochastic delivery of high-velocity relatively spherical media (shot), which leads to plastic deformation in the near surface region of the part. The important parameters in the shot peening process include properties of the shot itself (i.e. the shot mass, hardness and size);processing parameters such as the velocity of the shot and the angle at which the shot impacts the surface; and finally, the properties of the material being processed, such as the sample hardness (or yield strength), strain hardening behavior, and the friction between the shot and sample [1]. Many researchers have carried out numerical and experimental studies for predicting or measuring residual stresses distribution as well as the effect of the shot peening processing parameters on the resulting stress distribution [2]. Nanoindentation, also referred to as instrumented indentation since it measures load and indentation penetration depth during the indentation, can be used to measure the mechanical properties of bulk materials in small scales. The metal substrate after shot peening is affected by the residual stresses which will change yielding and plastic straining [3]. Nanoindentation parameters such as hardness [4], loading and unloading behavior and pile-up area, can be affected by residual stresses. Some researchers showed residual stresses does not always influence the hardness [5]. A method developed by Suresh et al analyzed the entire instrumented loading curve in order to estimate the residual stresses by nanoindentation method. In this method, suitable for obtaining equi-biaxial residual stresses, both stress-free and stressed samples need to be compared with each other. Lee et al suggested a new method to obtain the equi-biaxial residual stresses by using stress relaxation with the shear plastic deformation [6].

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