The forming limits and failure properties of three distinct advanced high-strength steels (AHSS) have been investigated under various stress states in tensile tests with optimized specimen geometries. In addition to the commonly observed failure patterns governed by localized necking and ductile fracture for two of the AHSS, after substantial plastic deformation at room temperature, cleavage fracture occurs for a large range of stress states in a laboratory quenching and partitioning steel with superior tensile properties. The competition between failure patterns, encompassing ductile and cleavage fractures with and without necking, is governed by the mechanical properties of materials and the stress states, as a transition of failure mechanisms occurs with increasing triaxiality. The forming limit framework is, therefore, further extended to seamlessly integrate cleavage fracture in this study, where the competition between various failure mechanisms is demonstrated using three AHSS in the space of critical strain and principal stress. These findings shed light on the importance of considering cleavage fracture strength as a parameter besides the strength-ductility synergy in advanced high-strength metallic materials, and the proposed framework also gives a more comprehensive guide in designing and conducting the sheet metal forming processes.

中文翻译：

---

考虑各种失效机制的成形极限框架：局部化、延性断裂和解理断裂

使用优化的样本几何形状，在拉伸试验中的各种应力状态下研究了三种不同的先进高强度钢 (AHSS) 的成形极限和失效特性。除了两种 AHSS 常见的由局部颈缩和延性断裂控制的失效模式外，在室温下发生大量塑性变形后，在具有优异拉伸性能的实验室淬火和分配钢中，在大范围的应力状态下会发生解理断裂。 。失效模式之间的竞争，包括带颈缩和不带颈缩的延性断裂和解理断裂，由材料的机械性能和应力状态决定，因为随着三轴度的增加，失效机制会发生转变。因此，在本研究中，成形极限框架进一步扩展为无缝集成解理断裂，其中使用临界应变和主应力空间中的三种 AHSS 证明了各种失效机制之间的竞争。这些发现揭示了除了先进高强度金属材料的强度-延展性协同作用之外，考虑解理断裂强度作为参数的重要性，并且所提出的框架还为设计和进行金属板材成形工艺提供了更全面的指导。