重型机床大型结构件高强栓接松弛机理及优化设计方法研究

The high-strength bolted structures are the main form of fixed connections for the large-sized structures of heavy-duty machine tools. The relaxation properties of high-strength bolted joints are important foundation problem for the accuracy and relibility of heavy-duty machine tools, which is affected by the micro and macro-scale factors. First of all, this project studies the three-dimensional multi-scale morphology and surface characterization of the high-strength bolted joints surface, and analyzes the multi-scale contact characteristics. The mechanical relationship of micro-scale contact condition, surface morphology, deformation characteristic function and contact stiffness, damping can be established. The multi-scale contact mechanical model can be obtained. Secondly, the surface micro-slipping model of the high-strength bolted joints surface can be obtained based on energy dissipation theory. The mechanism of micro-slipping wear and local contact fatigue can be proposed based on the micro-slipping model. And one can obtained the law of effect of the surface contact state about the high strength bolt fatigue relaxation mechanism and structure residual stress distribution. Thirdly, the coordination condition and the coupling mechanism between factors are studied, and the mechanical constitutive equations and macro mechanics characterization methods of relaxation characteristics for the high-strength bolted structure can be established. Then, we bulid the complete relaxation mechanism of high strength bolted structure. Finally, the influence of relaxation characteristics of high strength bolted structure on the precision of the machine tool is studied. The matching method of high strength bolted structure is proposed for the whole machine tool. The basic experiments and field tests are provided to validate the proposed method. The research results are helpful for the improving the stability of precision and reliability of heavy-duty machine tools, which have important theoretical and practical significance for meeting the great strategic demand of related industries.

高强栓接是重型机床大型结构件固定连接的主要形式，其松弛特性受宏微观多因素耦合作用影响，是重型机床精度保持性和可靠性的重要基础问题。项目从栓接表面三维多尺度形貌与表征出发，分析多尺度下粗糙表面微宏观接触特性，构造微观接触状态、表面形貌及变形表征函数与接触刚度、阻尼之间的力学关系，建立栓接表面多尺度接触力学模型；通过基于能量耗散的表面微动滑移，提出微动磨损与局部接触疲劳行为的损伤机理，并建立螺栓疲劳松弛与结构残余应力重分布对表面接触状态的影响规律；研究各因素间的协调作用及耦合机理，建立高强栓接结构松弛特性力学本构关系模型和宏观力学表征方法，形成完整的高强栓接结构松弛机理研究体系；分析高强栓接结构松弛对机床精度的影响规律，提出面向整机的栓接结构优配方法，并通过基础实验和现场测试对研究结果进行验证。研究成果对提高重型机床的精度保持性与可靠性，满足相关行业重大战略需求具有重要理论与实际意义。

本项目在深入企业调研的基础上，总结归纳出了影响螺栓松弛机理的主要影响因素。项目从栓接表面三维形貌出发，根据多尺度下粗糙表面微宏观接触特性，构建了高强栓接表面的微观接触状态、表面形貌及变形表征函数与接触刚度、阻尼之间的力学本构关系模型；建立了真实再现高强栓接表面粗糙度、形状误差、波纹度等信号成分的多尺度重构模型；通过基于能量耗散的表面微动滑移，提出了复合载荷作用下接触表面滑移区、混合区与粘着区判据，揭示了高强栓接表面微动磨损与局部接触疲劳行为的损伤机理；研究了高强栓接表面接触刚度、阻尼与微动疲劳与磨损之间的非线性关系，通过预估接触表面刚度、阻尼特性，建立了考虑疲劳与磨损因素影响的高强栓接结构宏观动力学表征模型；综合考虑宏微观因素的耦合作用，建立了多因素耦合作用下的高强栓接结构松弛模型，真实表征了高强栓接结构松弛特性的宏观动力学行为，全面揭示了高强栓接结构的松弛机理。