板料超塑性拉伸失稳研究

ON THE INSTABILITY OF SHEET METALS DURING SUPERPLASTIC TENSION

基于板料超塑性变形的特点，本文将超塑性变形全过程分为稳定变形、准稳定变形、应变路径漂移和集中性失稳发展四个阶段，依据增量理论，用数值方法建立了一普遍适用的失稳模型。然后在此基础上，依板料发生集中性失稳（ｄε＿２＝０）为许用变形程度的极限，预测了板料超塑变形时的成形极限曲线。对铝合金ＬＹ１２ＣＺ和半硬态黄铜Ｈ６２的超塑性实验研究表明：用本文提出的失稳模型预测的超塑性板料的成形极限与实验结果具有较好的一致性。

In the present paper, the thorough superplastic deformation process is divided into four stages, namely, stable, quasistable, strain path drift to plane strain and plane strain stages. According to the incremental theory, a damage -instability model is developed by means of numerical methods. Then on the basis of the above results and by the consideration of the occurrence of localized instability (d = 0) as a limit criterion, theforming limit is predicted during superplastic deformation of sheets. Good agreement is found between the experimental results and the superplastic forming limit predicted by the model in this paper through the experimental investigation of LY12CZ aluminium alloy and H62 Brass sheets.