Numerical and theoretical studies of bolted joints under harmonic shear displacement

A three-dimensional finite element model used to simulate the bolted joint is created using ABAQUS package. The stress concentration factors at the roots of the thread are first studied with a preload of 38.4 kN. Under harmonic transverse shear displacement, not only the stress variations at ten specified points of the first thread but also contact conditions between the contacting surfaces are studied. By changing the preload value, relative displacement, the coefficient of friction between the two clamped plates successively and the loading frequency, their effects on the hysteresis loops of the transverse load versus the relative displacement of the joint are then analyzed. Finally the hysteresis loops are produced by the Masing model. It is found that due to the greatest stress concentration factor, fatigue failure will occur at the root of the first thread. With the increase of preload value, the amplitude of displacement and the coefficient of friction, frictional energy dissipation of the joint increases. Very good agreement is achieved between the hysteresis loops produced from the fourth-order Masing model and the detailed ABAQUS model and therefore the fourth-order Masing model can replace the time-consuming finite element model.

本研究采用ABAQUS软件搭建了用于模拟螺栓连接副的三维有限元模型。首先以38.4 kN的预紧力为初始工况，考察了螺纹牙根处的应力集中系数。在横向简谐剪切位移激励下，本研究不仅分析了第一圈螺纹十个指定测点的应力变化，同时还探究了接触面间的接触状态。随后依次调整预紧力、相对位移、两被连接板间的摩擦系数以及加载频率，分析各参数对连接副横向载荷-相对位移迟滞回线的影响规律。最终采用Masing模型（Masing model）生成迟滞回线；研究发现，由于应力集中系数最大，第一圈螺纹的牙根处将发生疲劳失效。随着预紧力、位移幅值以及摩擦系数的增大，连接副的摩擦耗能均随之提升。四阶Masing模型（fourth-order Masing model）生成的迟滞回线与精细ABAQUS模型的计算结果吻合度极佳，因此四阶Masing模型可替代耗时较长的有限元模型。