Numerical Research on the Effect of Boundary Constraint in Shot Peen Forming

Shot peen forming is widely used in aerospace industry to form the thin components with complex contour by introducing compressive stresses. The compressive stresses are hypothetically introduced into a perfectly constrained target in conventional researches. However, the desired curvatures are obtained incrementally in actual forming process. In this paper, a stepping numerical model is proposed to study the effect of boundary constraints on the peening stresses and resulting curvatures. First, axisymmetric simulations are carried out to determine optimal mesh sizes. Then, simulations with a three-dimensional target subjected to 65 shot impacts step by step are carried out with applying different intermittently released boundary constraints. It is found that the boundary constraints can significantly influence the evolutions of peening stress and curvature. Finally, comparison of numerical and experimental results shows that actually obtained peen forming curvatures lie between the numerical results with perfectly constraints and that with relatively loose constrains.