考虑螺纹柔性的螺栓连接临界松动载荷计算方法

Computing Method of Bolted Joint Critical Loosening Load with Flexible Thread

螺栓连接松动是螺栓失效的一种重要形式。工程中,螺栓连接节点常常会受到交替变化的横向动态载荷作用,由于螺栓轴线与受力方向垂直,螺栓容易因预紧力降低而发生松动,从而改变螺栓连接节点乃至整个结构的固有力学特性。为研究横向载荷作用下螺栓连接的临界松动载荷,通过建立螺栓连接的力学模型对螺纹的受力情况进行分析,并在此基础上考虑螺纹柔性提出一种螺栓连接临界松动载荷的计算方法。设计并加工了螺栓连接横向振动试验装置,对螺栓连接的临界松动载荷进行了试验研究,通过对比理论计算结果和试验结果,验证了计算方法的准确性。基于提出的理论计算方法,给出了横向载荷作用下螺纹应力的分布规律,对比了刚性螺纹模型和柔性螺纹模型的应力分布特点,结果发现柔性螺纹模型可以很好地反映螺纹应力的整体变化情况。

Bolted joint loosening is one of the important modes of bolted joint failure. In the project, the bolted joints are often subjected to alternating lateral dynamic loads, and the bolts tend to loosening very easily as the bolt axis is perpendicular to the direction of the pretension forces. The reductions of the preload will change the inherent mechanical properties of the bolted joints and even cause the failure of entire structure. In order to study the critical loosening load of the bolted joint under the lateral load, the mechanical model of the bolted joint is established, and the forces of thread are analyzed. A new computing method of the bolted critical loosening load with flexible thread is derived. A set of experimental device for lateral vibration is designed and assembled, which is used to test the mechanical behavior of bolted joint under lateral vibration. The presented calculation method of bolted critical loosening load is verified by comparing the theoretical calculation and experimental results. The distribution law of thread stress under lateral load is given based on the new theoretical calculation method, and the stress distribution characteristics of rigid thread model and flexible thread model are compared. The results show that the thread stress given by flexible thread model can reflect the overall variation of thread stress.