Stress and friction evolution in the bolt during and after assembly

The stress distribution within threaded connections exhibits significant complexity attributable to the intricate interfacial friction between mating surfaces, which critically influences the coupled relationship among tightening torque, rotational angle, and axial preload. This study establishes a comprehensive assembly analytical framework incorporating three critical factors: thread contact deformation, screw body distortion, and frictional distribution evolution during and after assembly processes. Through this model, three distinct deformation patterns and corresponding stress distribution characteristics in bolted joints have been systematically identified. Subsequent numerical simulations quantitatively reveal the generation mechanisms of these stress patterns under varying operational conditions. Particularly, parametric analysis demonstrates that reduced stiffness of clamped components amplifies both rotational displacement and axial deformation of fasteners. The proposed methodology further elucidates the mechanism underlying post-assembly preload relaxation phenomena. Experimental validation through quasi-static testing confirms measurement consistency across torque-preload-angle parameters, with theoretical predictions showing excellent consistency with experimental data. This analytical advancement enhances fundamental understanding of bolted joint mechanics while providing theoretical guidance for engineering applications in precision assembly and structural safety assessment.