Deep drawing simulations using the finite element method embedding a multi-level crystal plasticity constitutive law: Experimental verification and sensitivity analysis
Deep drawing simulations using the finite element method embedding a multi-level crystal plasticity constitutive law: Experimental verification and sensitivity analysis
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DOI：
10.1016/j.cma.2019.05.035
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发表时间：
2019-09
影响因子：
7.2
通讯作者：
T. Barrett;M. Knezevic
中科院分区：
文献类型：
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作者：
T. Barrett;M. Knezevic
本文提出了一个多层次的模拟框架，旨在板料成形分析的实验验证。具体而言，从合金AA 6022-T4片材的圆柱形杯模拟的深冲压使用嵌入在隐式有限元中的基于物理的弹塑性自洽（EPSC）多晶均匀化模型进行，并通过实验验证。EPSC模型考虑了微观结构的演变和在单晶水平上作用的变形机制的方向性，以预测材料的行为。它是校准和验证作为一个独立的模型，使用流动应力和R比数据，以及通过单轴和平面应变拉伸实验沿沿着几个方向测量的等剪切等高线。此外，有关的循环响应，包括非线性卸载和Bauschinger效应的特殊性也通过大应变拉压数据校准。与实验测量结果一致，有限元中的工艺模拟预测了杯的方向相关变薄，特别是在冲头半径周围和杯边缘周围的杯高度变化，称为制耳。通过比较实验和预测，R比的作用被揭示为杯高度的准确预测的关键。进一步的敏感性分析表明，初始织构有很强的影响R比，而引入硬化的影响较小。对有限元类型选择的精度和效率进行了分析，结果表明：三维八节点单元（C3 D8 R）和连续壳三维八节点单元（SC 8 R）上级平面壳三维四节点单元（S4 R），前者精度最高，后者计算效率高。事实证明，本文提出的模拟框架可用于预测与材料行为相关的现象以及由此产生的几何变化，这对于金属板材成形工艺的优化至关重要。
This paper presents experimental verification of a multi-level simulation framework aimed at sheet metal forming analysis. Specifically, deep drawing of a cylindrical cup simulations from alloy AA6022-T4 sheets are carried out using a physically based elasto-plastic self-consistent (EPSC) polycrystalline homogenization model embedded in implicit finite elements and verified experimentally. The EPSC model takes into account the evolution of microstructure and directionality of deformation mechanisms acting at the single-crystal level in predicting material behavior. It is calibrated and validated as a standalone model using flow stress and R-ratio data as well as iso-shear contours measured along several directions of the sheet through uniaxial and plane strain tension experiments. Furthermore, the particularities pertaining to cyclic response including non-linear unloading and the Bauschinger effect are also calibrated through large strain tension–compression data. Consistent with experimental measurements, the process simulations in finite elements predict directionally dependent thinning of the cup, especially around the punch radius and variation in the cup height around the rim of the cup, referred to as earing. By comparing experiments and predictions, role of the R-ratio is revealed as critical for the accurate prediction of the cup height. Further sensitivity analysis shows that initial texture has a strong influence on the R-ratio, while introducing a minor effect on hardening. The analysis into the choice of finite element types in terms of their accuracy and efficiency shows that the 3D 8 nodal elements (C3D8R) and continuum shell 3D 8 nodal elements (SC8R) are superior over the planar shell 3D 4 nodal elements (S4R) with the former being the most accurate and the latter being computationally efficient. It is demonstrated that the simulation framework presented in this paper can be used to predict phenomena pertaining to material behavior and resulting geometrical changes important for optimization of the sheet metal forming processes.