一种结合部法向刚度的预估方法

A Method of Estimating Normal Stiffness of Joint

提出一种结合部法向刚度的预估方法。通过表面形貌测量仪获取粗糙表面的轮廓数据,拟合生成粗糙表面轮廓曲线,在此基础上建立考虑摩擦的二维粗糙表面的有限元弹塑性接触模型,用罚函数法计算压力在0～0.8 MPa的加载过程中接触层的应力、位移和接触面积。计算结果表明,粗糙表面真实的接触面积在低载荷下快速增大,高载荷下的增大速度很缓慢,在载荷为0.8 MPa时的接触面积与名义面积的比为0.3%,真实的接触面积远低于宏观的接触面积;载荷为0.8 MPa时两个表面最高的法向接触应力为924 MPa,最高的Mises应力为434 MPa,接触点附近的材料处于塑性状态,接触点上的应力远高于基体内部应力;分析模型的法向接触刚度取决于少数接触点的接触刚度,接触点的接触刚度则取决于接触点的形貌。采用不同几何尺寸的试样试验,获得的结合部法向刚度数据与计算结果能比较好地吻合,表明该方法是可行的。

A method of estimating normal stiffness of joint is presented.By profilometer,profile data of coarse surface are obtained and then planar joint model of finite element is established,which is based on elastic-plastic contact analysis including friction between coarse surfaces.By penalty function method,stress,displacement and contact area in contact layer are calculated when load pressure is 0～0.8 MPa.Results of numerical analysis indicate that real contact area of coarse suface rapidly increases under lower pressure and slowly increases under high pressure.When pressure is 0.8 MPa,ratio of real contact area to nominal contact area is only 0.3%,real area of contact is far less than nominal area of contact.At the same time,maximum of normal contact stress is 924 MPa and maximum of Mises stress is 434 MPa,material nearby the contact spot is in plastic state and stress is much higher than substrate.Normal contact stiffness of analysis model depends on contact stiffness of a few contact spots,which depend on profile of contact spots.In experimental results of contact specimens with different dimension,normal stiffness of joint accords with normal stiffness from numerical analysis,which indicates the method is valid.