Modeling capability for realizing engineered residual stress due to mechanical surface treatment

Laser Peening (LP) and Low Plasticity Burnishing (LPB) are two recently emerging surface treatment technologies capable of introducing deep, near-surface residual stress. While judicious use of these treatments is often of significant benefit to structural component fatigue lives, no prediction model currently exists to help reduce the significant empirical burden generally associated with their implementation. This proposal outlines a methodology for developing a computational design tool for the implementation of LP and LPB. The introduction of residual stress is based on eigenstrain, embodied in a finite element context. Through superposition, the residual stress field and the reactionary stress field due to applied loading can be combined, offering valuable insight into the resultant stress field. Most importantly, the resultant stress field can be evaluated for detrimental tensile stress regions sometimes generated inadvertently in these deep surface treatments. Although the methodology is of a general nature, turbine engine blades are selected for a component-specific design in this study proposal. LP is applied to the leading edge of these blades to suppress crack growth due to Foreign Object Damage (FOD). The effect of LP on FOD-nucleated crack growth and the fatigue life of compensatory tensile stress regions are to be assessed and verified.