Selective Laser Melting (SLM) is one of the revolutionary additive manufacturing (AM) technologies to produce metallic mechanical parts. To thoroughly understand the damage and fracture behavior of SLM-fabricated Ti6Al4V alloy under complex stress states, a number of tensile, compressive and torsional experiments covering various stress states were conducted with different types of the specimens. A modified GTN (Gurson-Tvergaard-Needleman) model with dual damage variables characterizing the void growth mechanism and void shear mechanism was adopted to describe and predict the ductile fracture behavior of the SLM-fabricated Ti6Al4V alloy under complex stress states. A new stress state-dependent function was introduced to extend the application of the model to negative stress triaxiality state. A finite element (FE) based inverse analysis strategy was proposed to calibrate the model parameters. The simulation results showed that the damage and fracture behavior of SLM-fabricated Ti6Al4V alloy can be well described by the modified GTN model. The morphologies of the fracture surfaces were successfully predicted by using the developed damage constitutive model, in which the variable of void fraction dominates fibrous zone failure based on the void growth mechanism, and the shear damage variable facilitates shear fracture based on the void shear mechanism.

选择性激光熔化 (SLM) 是生产金属机械零件的革命性增材制造 (AM) 技术之一。为了彻底了解 SLM 制造的 Ti6Al4V 合金在复杂应力状态下的损伤和断裂行为，对不同类型的试样进行了许多涵盖各种应力状态的拉伸、压缩和扭转实验。采用具有双损伤变量表征空隙生长机制和空隙剪切机制的改进型 GTN（Gurson-Tvergaard-Needleman）模型来描述和预测 SLM 制造的 Ti6Al4V 合金在复杂应力状态下的韧性断裂行为。引入了一个新的应力状态相关函数，以将模型的应用扩展到负应力三轴状态。提出了一种基于有限元（FE）的逆向分析策略来校准模型参数。仿真结果表明，改进的GTN模型可以很好地描述SLM制造的Ti6Al4V合金的损伤和断裂行为。利用已开发的损伤本构模型成功预测了断裂面的形貌，其中孔隙率变量基于孔隙增长机制主导纤维区破坏，剪切损伤变量促进基于孔隙剪切机制的剪切断裂。