Simulation of cold expansion strengthening of TC21 alloy

Mandrel cold expansion and split-sleeve expansion of TC21 titanium alloy lugs were simulated by elastic-plastic finite element method. Based on the simulation results, the residual stress distributions around the hole were analyzed. Combining the fatigue experiments of lugs after mandrel cold expansion and split-sleeve expansion, the strengthening effects of the two processes were evaluated. Results show that the residual stress distributions along the direction of radial, circumferential and thickness have some changes. The distribution of the residual stress after mandrel cold expansion is more uniform than that after split-sleeve expansion. Both the two kinds of processes can strengthen the holes, while the effect of mandrel cold expansion is much better.