超塑性板料的成形极限

Forming Limit during Superglatic Deformation of Sheet Metals

根据超塑变形过程中的损伤演变方程和超塑性变形的特点，本文将基于粘塑性势的热粘塑性损伤势函数与Ｈｉｌｌ描述板料变形的各向异性材料屈服行为有机地结合起来，考虑了起塑变形过程中损伤与失稳的交互作用．将起塑变形全过程分为稳定变形。准稳定变形、应变路径飘移和集中性失稳发展四个阶段，用数值方法建立了超塑性板料的损伤失稳模型．然后在此基础上，以集中性失稳发生（ｄε２＝０）或临界空洞体积分数（ｆｃ）作为破坏判据，预测了板料超塑变形时的成形极限。

In the present paper, a thermo-viscoplastic damaage potential and Hill's normal anisotropy (isotropy in plane) yield criterion to be quadratic in the stresscomponents are combined to describe the interaction process of damage and instability during superplastic deformation, based on the kinetic equation for damageduring superplastic deformation and the deformation features of super plasticmaterials. The superplastic deformation process is davided into four stages,namely, stable, quasistable, strain path drift to plane strain and plane strainstages, and a damage-instability model duriug superplastic deformation of shcetmetals is developed through numerical method. On the basis of the above results and taking the occurrence of localized instability (dε2=0) or the cavity volume fraction reaching the critical value(fc)as a fracture criterion, the forming limitduring superplastic deformation of sheet metals is predicted.