干涉配合疲劳强化机理的新假说

Mechanical joint, which is prone to fatigue failure, is the weakest point of aircrafts in terms of durability. As interference fitting technology is capable of extending the joint’s operating life by ten times, it’s extensively used in modem machinery especially in aviation industry. However, the current fatigue enhancing theory on interference fitting, which is called the supporting effect, is primarily based on plastic deformation and concentrated on the instant effect of pre-stress. Obviously, the fatigue enhancing mechanism of interference fitting is not thoroughly understood and the conventional enhancing theory tends to lead to contradiction with experiments. In this project, an elastic enhancing mechanism of interference fit is proposed on the grounds of the latest research. According to this hypothesis, the load transferring mechanism based on elastic deformation of interference joints contributes to regulate the structure’s mechanical parameters, which is the major cause of life extension. The elastic enhancing hypothesis, revising the interference fitting theory by taking into account the joint’s response to dynamic loading, is capable of explaining some perplexing questions in the field, and even providing an analytical method of calculating the optimum interference. In the current project, the load transferring mechanism in interference-fitted joint is to be analyzed via analytical model to validate the elastic enhancing hypothesis, and the influence of various factors on this mechanism will also be studied. Then, the analytical model is to be verified by numerical simulation and evaluated by experiments. Finally, the fatigue enhancement mechanism of interference fitting is to be discussed scientifically and exhaustively, based on which the existent perplexing problems can be resolved and the optimum interference can be deduced.

机械连接部位的疲劳失效是限制飞机综合寿命提高的瓶颈，而干涉强化技术的寿命增益可高达十倍，在现代机械尤其是航空工业中应用广泛。然而干涉配合的支撑效应理论仅基于塑性变形，且只关注预应力的静态效应。干涉强化机理的经典理论极不完善，甚至与工程实际相矛盾。基于最新的研究成果，本项目提出干涉配合弹性强化机理的假说，即基于弹性变形的传载机制对结构力学参量的调节作用，是其疲劳延寿的主要机制。该假说考虑了干涉配合结构对外载的响应，不仅从全新的角度完善了干涉强化机理理论，也可解释经典理论无法解释的疑难现象，甚至可实现最佳干涉量的理论求解。本项目拟通过理论建模分析干涉配合结构的传载机制，验证以上假说，并分析多种因素对该机制的影响；然后利用数值仿真校正该模型，再由实验评估其工程价值；最后，在理论分析的基础上给出干涉强化机理的科学、完整的论述，并对现有的疑难现象给出解释，进一步给出最佳干涉量的理论值。

机械连接部位的疲劳失效是限制飞机综合寿命提高的瓶颈，而干涉强化技术的寿命增益可高达十倍，在现代机械尤其是航空工业中应用广泛。然而干涉配合的支撑效应理论仅基于塑性变形，且只关注预应力的静态效应。干涉强化机理的经典理论极不完善，甚至与工程实际相矛盾。.基于最新的研究成果，本项目提出干涉配合弹性强化机理的假说，即基于弹性变形的传载机制对结构力学参量的调节作用，是其疲劳延寿的主要机制。首先，通过广泛调研，分析研究了干涉配合残余应力的理论求解方法；然后，基于本项目提出的干涉配合弹簧模型，分别研究了干涉配合结构对静载的响应，在此基础上进一步研究了干涉配合结构在动态载荷作用下的响应，特别是其对被连接件最小截面传载幅值的影响，提出了“幅值降低系数”用以衡量干涉配合的强化效应；结合各向同性材料的研究成果，进一步开展了复合材料干涉配合弹性强化机理的研究；通过引入弹簧模型研究了干涉配合的强化机理，分析了经典的支撑效应理论的不足之处，从弹性变形的角度对经典理论难以解释的多个问题作出了解释；最后，借助弹簧模型给出了干涉量的优化方法，并得到了最佳干涉量的解析表达式。.本项目基于弹性理论的研究表明，有效的干涉配合可使被连接件最小截面的传载幅值降低到非干涉配合结构的0.5倍以下，从而有效提高了结构的疲劳寿命。弹性强化理论考虑了干涉配合结构对外载的响应，在理论分析的基础上给出了干涉强化机理的科学、完整的论述，不仅从全新的角度完善了干涉强化机理理论，也可解释经典理论无法解释的疑难现象，甚至实现了基于弹性理论的最佳干涉量的理论解，可以为航空、国防及其他领域装备的机械连接长寿命设计提供有力的工具。