Thermally induced variation of bolt load considering thermal contact resistance

Bolted joints is widely used in mechanical Engineering. The interface formed by two members in contact represents thermal contact resistance to flow of heat from one member to another. As a result, temperature difference occurs at the contact interfaces of the joints while the bolts still have a continuous thermal distribution through the joints. The consistent thermal distribution between bolts and the connectors may cause mismatch of thermal expansion and thus lead to variation of bolt load. This paper is mainly focused on the bolt fastened multiple discs which is one common structure of gas turbine rotors. The temperature distribution of connecting discs is presented under axial thermal gradient considering thermal contact resistance and variation of bolt load induced by thermal mismatch is presented in both a pair of discs and multiple discs in contact. Also studied is the effect of initial contact pressure, surface roughness, initial temperature and thickness of components. Results show that axial thermal gradient changes the bolt load to an extent depending on the thickness arrangement of discs. And axial thermal gradient increase the bolt load at a lower initial contact pressure, higher thickness increment of discs, larger surface roughness. Moreover, higher axial thermal gradient leads to larger bolt load. The result is of significance to structural design and preload of bolt joints serving in thermal environments.