多载荷历程作用下螺栓结合部特性实验及分析

Experimental and Analysis of Characteristics of Bolt Joint Under Multiple Load History

以往对结合部刚度特性的研究多着重于不同粗糙度结合部的横向对比,较少或忽视了同一结合部在载荷作用下多次循环历程加载时加载前后刚度特性的纵向对比,以及忽视多次循环历程加载时加载前后表面部分微凸体高度变化的纵向对比。实际上,不论刚度特性还是界面部分微凸体,在多次载荷历程作用下都会变化,这就使预测设备的动静态性能复杂化。针对这一问题,本文基于实验研究了粗糙表面单元螺栓结合部刚度特性在循环载荷历程作用下的变化规律,为量化研究和更好的应用这一规律,对本文各载荷历程曲线进行了数值拟合。纵向比较研究发现:单元结合部刚度特性随载荷作用历程循环次数的变化而变化,即:随着载荷历程作用次数的增加,单元螺栓结合部变形减小,结合部刚度增加。为进一步了解刚度特性变化的机理,还对结合部接触表面进行了载荷作用后的显微镜观察,发现结合部螺栓孔附近的表面部分微凸体高度在螺栓多次循环预紧力作用下有不同程度的塑性变形。

In the past,most of the studies on the joint stiffness characteristics focused on the transverse comparison of the joint with different roughness,less or ignored the longitudinal comparison of the stiffness characteristics of the same joint before and after loading with multiple cyclic loading,and the longitudinal comparison of the change of height of some micro convex bodies change before and after loading with multiple cyclic loading.In fact,both stiffness and height of some micro convex bodies will change under multiple load cycles,which makes it more complex to predict the dynamic and static performance of the equipment.In order to solve this problem,the variation law of the stiffness characteristics of the bolt joint of rough surface element under the cyclic load history based on experiments is studied.In order to quantitatively study and better apply this law,the load history curves are fitted.The longitudinal comparative study shows that the stiffness characteristics of the element joint change with the change of the load cycle times,that is,with the increasing of load history,the deformation of the element bolt joint decreases,and the joint stiffness increases.In order to further understand the mechanism of the change in stiffness characteristics,the microscopic observation of the contact surface of the joint before and after the load is also carried out.It is found that the height of the micro convex body of the surface near the bolt hole of the joint has the different degrees of plastic deformation under the repeated cyclic preload of the bolt.