A CAD Tool for Virtual Laser Shock Peening of Rotorcraft Components

The objective of this project is to develop a test-validated CAD tool for performing virtual laser shock peening(LSP) simulations of rotorcraft components. Virtual LSP peening can be used, in conjunction with virtual fatigue testing, to conduct simulations to assess the effects of variations in process parameters, i.e., laser beam power density and size, number of layers, and the overlay pattern, on the durability and damage tolerance of components such as gears and shafts. The foundation for the virtual LSP is a hybrid empirical/analytical process model of laser peening which allows the residual stress and plastic strain distributions throughout a member to be predicted from the process parameters and from the beam overlay pattern. The hybrid empirical/analytical process model combines parametric test data, along with the elastic strain solution for a half-space subjected to blast pressure loading, to synthesize, via the method of strain invariance, an approximate elastoplastic solution to the equations governing the propagation into the material of a shock wave formed by the laser pulse. The process model is computationally efficient, and allows estimates of the residual stress distribution, the part distortion due to the plastic strains, and the crack nucleation and crack growth lives to be obtained by straightforward CAD modeling operations. The CAD tool will also have, in addition to the virtual LSP simulation capability, a virtual shot peening capability, so that hybrid peening schemes involving LSP peening followed by a final layer of LSP peening can be evaluated. The feasibility of using such a tool to shorten the manufacturing process development time for a laser peened gear will be demonstrated and validated via testing in Phase II.