高强度钢旋转磨损加轴向疲劳载荷下的协同疲劳行为

This project focuses on major engineering problems about multi-load fatigue life evaluation of key components under wear and fatigue loads. Put forward a concept of multi-load fatigue combined different loads, point out that co-fatigue behavior will occur under rotating wear and axial fatigue loads and interfering layers (surface wear layer and deformation layer)is the major cause. It attempts to obtain fatigue strength criterion by comparing the competitive relationship between formation rate of interfering layers and growth rate of fatigue small cracks. FEM technology is used in calculating contact stress and strain, and analysis technologies, such as ultra-micro-hardness measurements, EBSD, SEM, TEM, ultrasonic microscope and direct observation by using long distance microscope etc., are used to study the influence of interfering layers and microstructures on initiation, remove and propagation of fatigue small cracks, and the relationship between fatigue life and the factors such as wear rate, frictional load etc., so as to investigate evolution mechanism of fatigue small crack initiation and propagation. Growth rate of fatigue small cracks under wear and fatigue loads is expressed using stress intensity factor of fatigue small cracks and wear impact factor, and co-fatigue life model will finally be built to lay a theoretical foundation in component surface strength design and a new fatigue life evaluation under multi-load.

针对关键构件在磨损加疲劳服役条件下，疲劳寿命评估的重大工程问题，提出构件在不同载荷共同作用下的多载荷疲劳概念，指出磨损与疲劳共同作用下具有协同疲劳效应，干扰层（表面磨损层加形变层）是导致协同疲劳行为的主因。并通过干扰层形成速率、磨损速率与疲劳小裂纹扩展速率的竞争关系得出疲劳强度判据。采用有限元模拟技术分析干扰层的应力应变，结合超微小显微硬度仪、EBSD、SEM、TEM、超声波显微镜及长焦距显微镜等实验手段，研究干扰层及其微观组织对疲劳小裂纹萌生、消除与扩展的影响规律，磨损速率、磨损载荷与疲劳寿命的关系，获得该多载荷疲劳小裂纹萌生与扩展的演化机制。用小裂纹应力强度因子幅与磨损影响因子共同描述协同疲劳小裂纹的扩展速率，由此建立磨损-疲劳载荷下的协同疲劳寿命模型，为构件表面强度设计和协同疲劳寿命评估奠定理论基础。

许多钢铁零件服役于磨损载荷和疲劳载荷的共同作用下，即磨损—疲劳工况，如斗齿、钎具、柔轮和火车轮轨等。钢铁材料的磨损—疲劳行为与其摩擦磨损特性关系密切，摩擦磨损导致磨损—疲劳的失效行为与单一磨损失效或疲劳失效有所不同。它与摩擦磨损导致的表面材料流失、塑性变形和结构演变等都有关联，且在不同疲劳应力下的表现还有所差异。这使得零部件的磨损—疲劳寿命预测变得非常复杂。因此，如何揭示钢铁材料的摩擦磨损特性及其对磨损—疲劳行为的影响机制，建立对应的磨损—疲劳裂纹扩展模型，已成为评价钢铁材料的抗磨能力和指导钢铁材料表层结构设计，以及预测零部件磨损—疲劳寿命所面临的关键基础问题和核心技术。. 基于此，本项目重点研究了板条马氏体钢的干摩擦磨损特性，深入研究了摩擦接触表层的塑性变形行为和组织结构演变规律及其对摩擦学行为的影响机理。首次揭示了干滑动摩擦过程中的板条马氏体动态结构演变、非晶化和自润滑等科学问题的机制，并提出了相应的物理模型。结合针对应力场和裂纹扩展面的线弹性力学分析，研究了干滑动摩擦磨损特性与磨损—疲劳裂纹扩展的关联性，建立了磨损—疲劳裂纹扩展模型。首创了有别于接触疲劳（如钢轨与车轮工作环境）的大位移滑动摩擦与旋转弯曲应力共同作用下的磨损—疲劳测试方法和装置。采用上述方法和装置研究了板条马氏体钢的磨损—疲劳行为，阐明了摩擦磨损对磨损—疲劳寿命的影响规律。这一系列成果对研究钢铁材料的干摩擦磨损特性和减磨方法具有理论指导意义，也为在多载荷条件下零部件的磨损—疲劳寿命预测和表面强度设计提供了理论依据。