Abstract
By considering the tightening process, a three-dimensional elastic finite element analysis is conducted to explore the mechanism of bolt self-loosening under transverse cyclic loading. According to the geometrical features of the thread, a hexahedral meshing is implemented by modifying the node coordinates based on cylinder meshes and an ABAQUS plug-in is made for parametric modeling. The accuracy of the finite element model is verified and validated by comparison with the analytical and experimental results on torque-tension relationship. And, then, the fastening states acquired by different means are compared. The results show that the tightening process cannot be replaced by a simplified method because its fastening state is different from the real process. With combining the tightening and self-loosening processes, this paper utilizes the relative rotation angles and velocities to investigate the slip states on contact surfaces instead of the Coulomb friction coefficient method, which is used in most previous researches. By contrast, this method can describe the slip states in greater detail. In addition, the simulation result reveals that there exists a creep slip phenomenon at contact surface, which causes the bolt self-loosening to occur even when some contact facets are stuck.
Highlights
The bolt joint, as a very common component in engineering, is widely used in a variety of industrial machines because of its simple configuration, convenient operation, and low cost [1]
Due to the complex working environment, bolt joints often experience self-loosening with increasing service time, which can cause a decrease in the structure stiffness and in some cases may even lead to fatal consequences if it remains undetected [2]
Pai and Hess [4, 5] introduced the concept of localized slip and classified the self-loosening process into four different types: (1) localized head slip with localized thread slip; (2) localized head slip with complete thread slip; (3) complete head slip with localized thread slip; (4) complete head slip with complete thread slip
Summary
The bolt joint, as a very common component in engineering, is widely used in a variety of industrial machines because of its simple configuration, convenient operation, and low cost [1]. The results by Yokoyama et al [10] revealed that loosening occurs only when the rotation angle around bolt axis which is applied to clamped component reaches a critical value, and the thread surface undergoes a complete slip. Nassar et al [15,16,17] proposed a more accurate mathematical model to predict the variation of the preload during the self-loosening process by investigating the relationship between the bearing friction torque, the thread friction torque, and the pitch torque components. There are two main approaches: one is to model the bolt body and the thread separately and connect them using a tie constraint [19, 20] In this way, the two parts can be modeled with hexahedral meshes. The mechanism of bolt self-loosening is analyzed using the relative motion of nodes and a creep slip phenomenon is illustrated
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