Analysis of Heat Flow Around Bolted Joints and Variations of Axial Bolt Force

A bolted joint is widely used for the structures and machines subjected to thermal load, such as pressure vessels, internal combustion engines, brake disks, etc. In order to accurately evaluate the thermal stresses thus produced, the effect of thermal contact resistance at the interface and the heat flow through small gaps, which exist around the objective bolted joint, must be taken into account. In this paper, a numerical approach is proposed to solve the mechanical and thermal behaviors of bolted joints with high accuracy and computation efficiency, where empirical equations for thermal contact coefficient and apparent thermal contact coefficient are incorporated into commercial engineering software. By conducting systematic three-dimensional finite element analyses, it has been quantitatively elucidated how the supplied heat flows through each part of a bolted joint and how the axial bolt stress and bolt bending stress vary with time. It is concluded that bolted joints made of the materials with low thermal conductivity show specific heat flow patterns around the bolted joint and generate a large amount of variations in both axial bolt stress and bolt bending stress.