Fastening reliability analysis of bolted joint anti-self-loosening

In the absence of external forces, the preload of the bolted joint will decrease due to self-loosening after the tightening process is completed. Self-loosening of a bolted joint will result in unstable contact between connected components, affecting the overall performance of mechanical equipment. This paper proposes a method for fastening reliability analysis of bolted joints considering the uncertainty of preload, friction coefficients, and material properties. The finite element method (FEM) is used to study the self-loosening behavior of a bolted joint under elastic conditions. The metamodel is constructed based on the proposed finite element model to improve computational efficiency. In addition, the fastening reliability of the bolted joint is calculated using the Monte Carlo simulation (MCS) method. Finally, the practical application of calculating the fastening reliability and a detailed analysis is presented to evaluate the proposed method's efficiency. The results show that the recovery of accumulated elastic deformation of a bolted joint generates self-loosening. In contrast, the torsional elastic deformation of the bolt rod causes relative rotation between the bolt and the nut. When the characteristic parameters obey the normal distribution, the probability distribution of preload reduction ratio approximately obeys the normal distribution. According to the proposed reliability calculation method, the reliability of bolted joint self-loosening is 99.7725% when the preload reduction ratio exceeding 0.026 is considered as self-loosening failure.