Analysis of self-loosening behavior of high strength bolts based on accurate thread modeling

Abstract

The self-loosening of high strength bolt caused by vibration has been widely studied. However, the short-term self-loosening behavior of the high strength bolt when it is not subject to an external load has not received attention. This behavior will also lead the bolt preload to attenuate. Since the theoretical analysis of self-loosening behavior is difficult, this paper uses the finite element method to construct an accurate three-dimensions model with thread lift angle for numerical analysis. A new method is proposed to analyze the self-loosening behavior. The self-loosening behavior caused by the elasticity and plasticity of the bolted joint at different deformation periods is compared and analyzed. Besides, the evolution of the self-loosening behavior under different conditions is explored. The analysis results show that the torsional deformation of the thread leads to the relative slip of the internal and external threads. This results in the self-loosening of the thread in the elastic condition. In the elastic–plastic deformation condition, the self-loosening behavior is caused by the relative slip of the internal and external threads and plastic deformation. The weight of plastic deformation is greater. In addition, this behavior has the characteristics of increasing with increased tightening torque and decreasing with increased friction coefficient.