The ductile fracture behavior of a high strength steel is investigated using a micromechanics-based approach with the objective to build a predictive framework for the fracture strain and crack propagation under different loading conditions. Part I of this study describes the experimental results and the determination of the elastoplastic behavior and damage nucleation under different stress triaxiality and Lode parameter values. The damage mechanism starts early void nucleation from elongated inclusions, either by particle cracking under loading oriented along the major axis, or by matrix decohesion when the main loading is transverse. Void nucleation is followed by plastic growth and coalescence. The long inclusion axis is preferentially aligned in one direction leading to significant failure anisotropy with the fracture strain in the transverse direction being almost 50% lower compared to the longitudinal one, even though the plastic behavior is isotropic. The experimental data are first used to calibrate the elastoplastic model. An enhanced anisotropic nucleation model is then developed and integrated into the Gurson–Tvergaard–Needleman scheme. The parameters identification of the anisotropic nucleation model is finally performed and validated towards the experimental results. All these elements are subsequently used in Part II to simulate the full failure behavior of all testing specimens in the entire spectrum of stress states, from nucleation to final failure.

使用基于微力学的方法研究了高强度钢的延性断裂行为，目的是为不同载荷条件下的断裂应变和裂纹扩展建立预测框架。本研究的第一部分描述了实验结果以及在不同应力三轴性和Lode参数值下的弹塑性行为和损伤成核的确定。破坏机理是从细长的夹杂物开始的早期空核形核，这是通过沿主轴定向的载荷作用下的颗粒开裂，或当主载荷为横向载荷时通过基体脱粘来实现的。空隙成核之后是塑性生长和聚结。长的夹杂物轴优先沿一个方向排列，从而导致明显的各向异性，即使塑性行为是各向同性的，横向断裂应变也比纵向断裂应变低近50％。首先将实验数据用于校准弹塑性模型。然后，开发了增强的各向异性成核模型，并将其集成到Gurson-Tvergaard-Needleman方案中。最后进行各向异性成核模型的参数辨识，并针对实验结果进行验证。随后在第二部分中使用所有这些元素来模拟从成核到最终破坏的整个应力状态谱中所有测试样本的完全破坏行为。即使塑性行为是各向同性的。首先将实验数据用于校准弹塑性模型。然后，开发了增强的各向异性成核模型，并将其集成到Gurson-Tvergaard-Needleman方案中。最后进行各向异性成核模型的参数辨识，并针对实验结果进行验证。随后在第二部分中使用所有这些元素来模拟从成核到最终破坏的整个应力状态谱中所有测试样本的完全破坏行为。即使塑性行为是各向同性的。首先将实验数据用于校准弹塑性模型。然后，开发了增强的各向异性成核模型，并将其集成到Gurson-Tvergaard-Needleman方案中。最后进行各向异性成核模型的参数辨识，并针对实验结果进行验证。随后在第二部分中使用所有这些元素来模拟从成核到最终破坏的整个应力状态谱中所有测试样本的完全破坏行为。最后进行各向异性成核模型的参数辨识，并针对实验结果进行验证。随后在第二部分中使用所有这些元素来模拟从成核到最终破坏的整个应力状态谱中所有测试样本的完全破坏行为。最后进行各向异性成核模型的参数辨识，并针对实验结果进行验证。随后在第二部分中使用所有这些元素来模拟从成核到最终破坏的整个应力状态谱中所有测试样本的完全破坏行为。