超塑自由胀形中空穴发展过程的有限元模拟

On Cavity Development in Superplastic Bulging

将Ｈｉｌｌ的正变异性屈服方程与修正的Ｇｕｒｓｏｎ多孔韧性材料的粘塑性势有机地结合起来，建立了超塑成形中材料内部空穴体积分数的累积增大模型，按此模型采用刚粘塑性有限元法模拟了超塑自由胀形中空穴的发展过程，并对模拟结果进行了实验验证。

In the process of forming aerospace components with superplastic bulging technology,cavitation frequently occurs, causing deterioration of mechanical properties. We deem that the prevention of such cavitation requires a suitable model, which we have f&iled to find in the open literature. We now present such a model.Our model is mathematically expressed with eqs. (15) and (16). Briefly speaking, this model is established by combining adroitly Hill's quadratic yield criterion with the modified Gurson 's viscoplastic potential for porous ductile materials. Our model is called by us the internal cavity volume fraction accumulational model. For our experiments we take Chinese aluminum alloy LY12CZ (corresponding to US 2024) and Chinese brass H62. We cut specimens from the same 2mm thick sheets. Figs. 3(LY 12CZ) and 4(H62) show the variation of f, the volume fraction of cavity, with ε, the average strain. Solid curves represent results calculated according to our model. Both Figs. 3 and 4 show fairly good agreement between calculated curves and test data.