A combined DEM-FEM method for simulating the actual peen forming process to estimate forming effectiveness

Peen forming processing is widely applied for shaping complex thin-walled components in the aerospace industry. The aim of this research is to accurately predict the random peen forming effectiveness using a novel strategy which is combined with the DEM-FEM method. First, based on a modified "spherical expansion," an analytical expression for calculating the impact model is presented and used in the simulations. Second, a particle generator is set up and the PD3D discrete element is adopted to generate thousands of shots in random order. And a coupled DEM-FEM model is developed to calculate the compressive stresses introduced on the surface of the components. Third, the induced stress field, which is separately fitted with a segmented function, is introduced to the finite element model to obtain the resultant shape of the plate. Considering the interaction of shots, it is proved by the random model that the shot density has an influence on the impact velocity. Comparison analysis indicates that neglecting collisions leads to overestimating the magnitude of induced stress and the maximum stress depth. Moreover, the quantitative relationship between the peening strength, coverage and the average induced stress is revealed. Besides, narrow strip experiments are conducted, which demonstrate that the simulated shapes are consistent with the scanned three-dimensional experimental shapes with the same forming parameters.