栓接结合部刚度建模与特性分析

Stiffness modelling and characteristics analysis of bolted joints

为在图纸设计阶段准确获取数控机床关键功能部件中栓接结合部的动态特性,综合考虑结合面和螺栓两部分因素,运用WM函数和功率谱函数表征表面微观形貌特征,利用统计学方法和Mindlin理论建立结合面刚度模型,最终建立栓接结合部法向与切向刚度模型,根据模态试验与有限元法对比验证所建模型的正确性。通过分析表面粗糙度、法向载荷和栓接结合部刚度之间的关系,结果表明:法向载荷的大小影响结合面微观形貌特性,载荷越大,真实接触面积越大,表面粗糙度越小;在相同法向载荷下,表面粗糙度越小,栓接结合部的刚度越大;栓接结合部的刚度随着法向载荷的增加而递增,其速率是先快后慢,且相互之间呈现明显的非线性关系,但当载荷较小时,栓接结合部的法向刚度与法向载荷呈线性关系,可采用线性化方法获取栓接结合部的动态特性。

It is important to predict the dynamical behaviors of the bolted joints in the key functional parts of the machine tool at its design stage,for which the effect of the bolts and the joint surfaces on the dynamical characteristics of the bolted joints should be considered in conjunction.For that purpose,the WM function and power spectrum function are employed to characterize the microscopic characteristics of the joint surfaces,and the stiffness model of the joint surfaces are established by statistical methods and Mindlin model.Finally,the stiffness model of the bolted joints are established,and the theoretical model are verified by comparing the modal experiment with the FEM method.The relationship among the stiffness of the bolted joints,the surface roughness of the joint surfaces and the normal load are analyzed.Theoretical calculation results show that the surface roughness value of the joint interface is subject to the normal load,i.e.as the normal loadincreases,the real contact area increases and the surface roughness value decreases.Moreover,it shows that the smaller the surface roughness value is,the larger the stiffness of the bolted joint interface is,while a constant normal load is considered.The stiffness of the bolted joints will increase very fast with the normal load starting to increase from zero,then will slow down as the normal load is large enough.The linear relation of the normal load and the stiffness of bolted joints is linearly related for small loads,thus the dynamical characteristics of the bolted joints can be obtained by the equivalent linear method.