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基于分叉理论和微分方程的特征线理论,建立了在平面应力状态下金属板料成形局部颈缩发生的判据,并根据此判据对成形过程中板料的破裂进行了预测。为了反映塑性变形局部化时塑性应变率对应力率方向的依赖性,在破裂的预测分析中采用了伊藤-吴屋的塑性应变率分量与应力率分量具有一对一关系的本构关系式。通过使用商业非线性有限元软件ABAQUS/EXPLICIT对板料成形过程进行模拟,将得出的模拟结果输入到用MATLAB编写的局部颈缩发生判据程序,实现了板料成形过程中破裂发生的预测。将提出的预测方法应用于A6022铝合金板料的刚性凸模胀形实验,预测的局部颈缩的位置和方向与实验结果大体一致。本板材成形破裂预测方法可用于汽车覆盖件成形及管材液压胀形过程中破裂的预测。
Based on the bifurcation theory and the characteristic line theory of differential equation, the criterion of local neck-in of sheet metal forming under plane stress is established. Based on this criterion, the sheet metal rupture during forming is predicted. In order to reflect the dependence of plastic strain rate on the direction of stress rate in plastic deformation localization, a constitutive equation with one-to-one relationship between the plastic strain rate component and stress component of Ito-Wu house was adopted in the prediction of fracture. Through the use of commercial nonlinear finite element software ABAQUS / EXPLICIT to simulate the sheet metal forming process, the simulation results obtained are input to the local neck shrinkage criterion program written in MATLAB to realize the prediction of the occurrence of cracking in the sheet metal forming process . The proposed prediction method is applied to the rigid convex bulging experiment of A6022 aluminum alloy sheet. The prediction of the location and direction of local neck shrinking is in good agreement with the experimental results. The method for predicting the forming failure of the sheet metal can be used for the prediction of the fracture of the automobile panel during forming and the pipe hydraulic bulging.