Analysis of elastic self-loosening of high-strength bolt under hydraulic tension tightening

Abstract During the fastening of bolts using the hydraulic tension method, elastic deformation of both the bolts and the connected components leads to a discrepancy between the set pre-tightening force and the actual force achieved after fastening. To investigate the issue of elastic self-loosening in bolts fastened by hydraulic tension, this study employs the finite element method to analyze both the elastic and elastoplastic behavior of bolts during the hydraulic tensioning process. Additionally, the paper examines the influence of various factors on springback-induced self-loosening, including the friction coefficient and preload. The findings reveal that the reduction in preload during the rebound loosening phase is not only attributed to the elastic deformation of bolts and connected parts but also to the slippage of bolts along the threaded connection interface.