Effects of curved geometry on residual stress in laser peening

Abstract

Prevention of failure in materials has been extensively researched for centuries by people all over the world. Sustained or cyclic loading is a major cause of failure in many situations. There can be other contributing factors, such as manufacturing defects and the presence of unfavorable residual stresses. But residual stresses can also play a positive role and can enhance the life of the component, if applied properly. Laser peening (LP) is a surface enhancement technique that can impede crack initiation and propagation by inducing favorable compressive residual stresses in the peened components. Laser peening can generate deeper compressive stresses compared with other surface enhancement techniques, such as shot peening, and it has been used to improve the fatigue life of components in aerospace, automotive and medical applications. In this work, the effects of laser peening are studied by using two dimensional finite element simulation models created with ABAQUS©. Crack initiation often occurs along the curved regions or fillets of structural components because of the presence of high stress concentrations. These critical regions are modeled as a curved geometry to capture the curvature effects using simulation models. Concave and convex simulation models are created and compared with flat geometry to investigate the effects of curvature in a laser peening problem. A mechanism of residual stress generation in curved models is used to explain the residual stress results obtained from finite element models. The results predict that increasing the radius of curvature in a concave model decreases the compressive residual stress generated in the component while increasing the radius of curvature of a convex model increases the compressive residual stress induced in the material when compared with a flat component.