Quantifying the spread in crystallographic textures due to transients in strain path in shot-peening

The present work combines electron and X-Ray diffraction to delineate effects of transients in strain paths on spread in crystallographic textures produced by shot-peening and mechanical attrition. The mechanics of shot-peening was studied using finite elements and explicitly coupled with the visco-plastic self-consistent framework to simulate evolution of crystallographic textures. It was seen that peening involves highly stochastic mechanics, which results in highly diffuse crystallographic textures, this quantified as the negentropy of its orientation distribution function. Sources of this spread were found in spatially gradient mechanics of unit impacts in peening and attrition. These gradients naturally resulted from discrete, i.e. non-uniform locations of unit impacts on the treated surface. Additional sources of gradients were also found by likening the geometry of unit impacts to spherical indentations, this naturally suggesting formation of dead-metal zones close to the surface directly underneath unit impacts, followed by plastically deformed zones at larger depths. Effects of impacting media size were delineated in the context of resulting dead-metal zone dimensions. A constitutive model for predicting the spread in crystallographic textures was formulated and validated with numerically simulated simple deformation histories.