螺栓联接界面表面分形及接触研究

Study on Fractal Behavior and Contact of Bolt Connected Surfaces

针对由螺栓联接的两个粗糙表面微观特征和实际接触情况进行了研究。采用分形函数模拟生成了粗糙面轮廓曲线,发现分形参数对传统粗糙度参数有影响;探讨了分形维数D与机械加工面传统粗糙度参数Ra的关系;利用表面分形模拟数据和实验测量数据建立了有限元接触模型。运用Abaqus软件对模型计算表明:随着接触载荷(螺栓预紧力)的增加,接触面积也相应增加;在相同接触载荷(螺栓预紧力)下,表面越光滑,接触面积越大;当接触面积增加到某一值后,改变不明显,且接触面积小于名义接触面积。这一结论可以很好的解释超声波能量在螺栓联接界面的传递机理,即预紧力-真实接触面积-能量三者的关系,为超声波能量法在螺栓松动监测中的应用提供理论基础。

In order to study roughness characterization and real contact area of the two bolt connected surfaces,the fractal theory is applied to surface morphology. Profile curves were generated by using two-dimensional fractal function,and it was found that the fractal parameters were to have an effect on the traditional parameter（Ra）. The relationship between the fractal dimension D and the surface roughness Ra of the machined surfaces was discussed. Abaqus software was then used to simulate contact behavior. The visualization shows that real contact area is increased with the increase of contact load（bolt fastening force）,larger if surfaces more smooth under the same contact load（bolt fastening force）,will change little when contact area is increased to a certain value,and less than nominal contact area. This conclusion can explain the ultrasonic energy transferring through bolt connected surfaces,namely the relationship between bolt fastening force,real contact area and energy,which will supply a theoretical basis for detection of bolt loosing based on ultrasonic energy.