Abstract

Continuum damage mechanics (CDM) studies the deterioration of mechanical properties in materials that leads to material failure. The Lemaitre’s ductile damage model is known as a suitable criterion for damage growth in ductile materials. The standard Lemaitre’s model cannot accurately predict the damage growth in most of bulk metal forming processes with a combination of tension and compression loadings. In this paper, first, an explicit step-by-step algorithm of the Lemaitre’s ductile damage model conjugated with the crack closure effect in compressive loadings is provided and directly presented for the computational implementations. Then, employing the proposed algorithm, a user-defined material subroutine is developed and implemented. In the following, a few bulk metal forming processes under compressive loadings are numerically simulated. Finally, the numerical simulation results are compared with the prediction results of the standard model and also experimental tests. The comparison confirms the high precision of the modified model vs. the standard model. Hence, it is concluded that the modified Lemaitre’s model can truly predict the damage behavior of ductile materials in bulk metal forming processes with combined tensile and compressive loadings.

摘要

连续损伤力学 (CDM) 研究导致材料失效的材料机械性能恶化。Lemaitre 的延性损伤模型被认为是延性材料损伤增长的合适标准。标准勒梅特模型无法准确预测大多数具有拉伸和压缩载荷组合的块体金属成形过程中的损伤增长。在本文中，首先，提供了与压缩载荷中裂纹闭合效应共轭的勒梅特延性损伤模型的明确分步算法，并直接用于计算实现。然后，采用所提出的算法，开发并实现了用户定义的材料子程序。下面，对压缩载荷下的一些块体金属成形过程进行了数值模拟。最后，将数值模拟结果与标准模型的预测结果以及实验测试进行了比较。比较证实了修改模型与标准模型相比具有较高的精度。因此，得出的结论是，修改后的勒梅特模型可以真实地预测延性材料在具有拉伸和压缩载荷组合的块体金属成形过程中的损伤行为。