Simulation of springback
Simulation of springback
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DOI：
10.1016/s0020-7403(01)00083-2
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发表时间：
2002
影响因子：
7.3
通讯作者：
K. Li;W. Carden;R. Wagoner
中科院分区：
文献类型：
--
作者：
K. Li;W. Carden;R. Wagoner
回弹是成形后零件形状在弹性驱动下的变化，采用二维和三维有限元模型对回弹进行了模拟。使用固体和壳元素的模拟进行了比较，在配套文件中提出的拉伸弯曲测量。平面应力和平面应变模拟揭示了数值公差和程序对结果的巨大作用。例如，在板材厚度上需要多达51个积分点，以使精度在1%以内，而成形模拟通常需要5-9个积分点。还需要改进与工具接触的元件的数量，以及在每一步满足平衡的数值公差。在某些情况下，卸载时会发生明显的塑性变形，但弹塑性卸载方案的选择对结果影响不大。虽然2-D模拟显示出良好的一致性与实验在某些测试条件下，回弹百分之几百的差异，指出一个合金与板拉伸屈服应力附近。三维模拟提供了更好的协议，被确定为持久的反曲率的存在下，误差的主要来源。结果中的大多数剩余偏差可归因于材料模型的不准确性。特别是，包辛格效应的存在显着改变了结果，并考虑到它提供了良好的协议。当R/t大于5或6时，壳单元足以准确地预测回弹，而当曲率较大时，则需要实体单元。当R/t接近2时，用实体单元模拟的回弹趋于消失，这与论文和文献中的测量结果一致。
Springback, the elastically-driven change of shape of a part after forming, has been simulated with 2-D and 3-D finite element modeling. Simulations using solid and shell elements have been compared with draw-bend measurements presented in a companion paper. Plane-stress and plane-strain simulations revealed the dramatic role of numerical tolerances and procedures on the results. For example, up to 51 integration points through the sheet thickness were required for accuracy within 1%, compared with 5–9 typically acceptable for forming simulations. Improvements were also needed in the number of elements in contact with the tools, and in the numerical tolerance for satisfying equilibrium at each step. Significant plastic straining took place in some cases upon unloading; however the choice of elastic–plastic unloading scheme had little effect on the results. While 2-D simulations showed good agreement with experiments under some test conditions, springback discrepancies of hundreds of percent were noted for one alloy with sheet tension near the yield stress. 3-D simulations provided much better agreement, the major source of error being identified as the presence of persistent anticlastic curvature. Most of the remaining deviation in results can be attributed to inaccuracies of the material model. In particular, the presence of a Bauschinger effect changes the results markedly, and taking it into account provided good agreement. Shell elements were adequate to predict springback accurately for R/t greater than 5 or 6, while solid elements were required for higher curvatures. As R/t approaches 2, springback simulated with solid elements tends to disappear, in agreement with measurements presented in the companion paper and in the literature.