中锰TRIP钢疲劳微裂纹生长机理与寿命预测模型

中锰TRIP钢因兼具良好的强度、延性和加工硬化能力，被认为是极具发展潜力的下一代汽车轻量化材料。然而目前对中锰钢的研究还主要停留在静强度失效问题，极少涉及对其疲劳行为的研究，疲劳机理尚不明确，尤其对于疲劳微裂纹生长机理这一重要课题仍缺少系统深入的研究。本项目拟采取跨尺度原位表征手段，结合宏细观断裂力学，深入探究微观组织演化与疲劳损伤之间的相互作用机制，提出基于材料损伤微观机理的寿命评估方法。主要研究马氏体相变与应变局部化两种关键微结构效应对疲劳微裂纹生长的影响机制，提出考虑裂尖微结构演化效应的裂纹扩展驱动力参量，进而建立适用于中锰钢材料的疲劳微裂纹扩展寿命预测模型。本项目研究成果将有望对中锰钢的抗疲劳设计提供重要的理论指导，进一步提升其疲劳性能，并改进其在服役工况下疲劳寿命预测的精度。同时，本项目还将有助于深入理解微观组织小裂纹的生长机理，为金属材料多尺度疲劳模型的构建提供必要的技术支撑。

Due to its good strength, ductility and work hardening ability, medium manganese TRIP steels are considered to be next-generation automotive lightweight materials with great development potential. However, the current research on medium manganese steels mainly stays at the stage of static strength failure problem study, and rarely involves the investigation of its fatigue behaviors. The underlying fatigue mechanisms are still unclear. Especially for the important issue of fatigue microcrack growth mechanism, there is still a lack of systematic and in-depth research. This project intends to adopt the trans-scale in-situ characterization method, combined with macro-meso fracture mechanics, to deeply explore the interaction mechanism between microstructure evolution and fatigue damage, and propose a life assessment method based on the microscopic mechanism of material damage. In this project, the influence mechanisms of two key microstructure effects, martensitic transformation and strain localization, on the growth of fatigue microcracks will be studied. An appropriate parameter of crack driving force considering the evolution of crack-tip microstructure is expected to be proposed, and then the prediction model of fatigue microcrack propagation life applicable to medium manganese steels can be formulated. The research outcomes of this project will provide important theoretical guidance on the anti-fatigue design of medium manganese steels. It allows further improving its fatigue performance and enhancing the fatigue life prediction precision under service conditions. In the meanwhile, the project will also help to understand the growth mechanism of microstructurally small cracks and provide the necessary technical support for the establishment of multi-scale fatigue models for metallic materials.