FE simulation of edge fracture considering pre-damage from blanking process
FE simulation of edge fracture considering pre-damage from blanking process
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DOI：
10.1016/j.ijsolstr.2015.06.023
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发表时间：
2015-10
影响因子：
3.6
通讯作者：
Kai Wang;L. Greve;T. Wierzbicki
中科院分区：
文献类型：
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作者：
Kai Wang;L. Greve;T. Wierzbicki
边缘断裂一直是先进高强度钢 (AHSS) 成形过程中的一个众所周知的挑战。问题的难点主要在于面外剪切和面内拉伸的复杂加载路径。现有的有限元模型无法高精度地预测边缘断裂。在当前的研究中，采用了两种方法来解决 DP780 钢板的问题。第一种方法是一次有限元模拟方法，在关键区域使用尺寸为 0.01 毫米的非常精细的实体单元。在模拟冲孔过程后，使用相同的有限元模型继续进行后续的扩孔模拟。换句话说，在执行扩孔模拟时，所有材料参数均继承自板材冲裁工艺。在一笔模拟的鼓励下，提出了一种两步唯象预损伤映射模型（PDMM），并将其用于边缘断裂预测。该模型在步骤 I 中使用 2D 轴对称模型执行孔冲裁模拟。步骤 I 中使用的网格尺寸在关键区域中约为 0.01 毫米。然后，将步骤 I 中在孔边缘附近获得的模型映射/规定的预损伤和等效塑性应变 (PEEQ) 信息映射到步骤 II 中具有 0.1 mm 量级的规则网格尺寸的实体单元或壳单元模型。结果表明，两种方法都能准确预测 HER 方面的边缘断裂。由于 3D 实体单元网格非常精细，一笔模拟需要巨大的计算能力，但它可以准确预测裂纹的细节分布和方向。更简化的 PDMM 模型可以更快地预测边缘断裂，并且可用于实体单元和壳单元模型，但丢失了一笔模拟捕获的一些细节。
Edge fracture has been a well-known challenge in the forming processes of Advanced High Strength Steels (AHSS). The difficulty of the problem mainly lies in the complex loading path of out-of-plane shearing followed by in-plane stretching. Existing Finite Element models can not predict edge fracture with good accuracy. In the current study, two methods were implemented to tackle the problem for the DP780 steel sheet. The first method was a one-stroke FE simulation methodology making use of very fine solid elements of size of 0.01 mm in the critical region. After simulating the hole blanking process, a subsequent hole expansion simulation was continued with the same FE model. In other words, all material parameters were inherited from the sheet blanking process when performing the hole expansion simulation. Encouraged by the one-stroke simulation, a two-step phenomenological Pre-Damage Mapping Model (PDMM), was proposed and used in edge fracture prediction. This model performed the hole blanking simulation using a 2D axisymmetric model in step I. The mesh size used in step I was of order of 0.01 mm in the critical region. Then the model mapped/prescribed pre-damage and equivalent plastic strain (PEEQ) information obtained in step I in the vicinity of the hole edge to a solid element or shell element model with regular mesh size of order of 0.1 mm in step II. The results showed that both methods accurately predict edge fracture in terms of HER. The one-stroke simulation requires enormous computational power due to the very fine 3D solid element mesh, but it provides an accurate prediction of the detail distribution and orientation of cracks. The more simplified PDMM model gives a much quicker prediction of edge fracture and can be used in both solid element and shell element models, but loses some details captured by one-stroke simulation.