MECHANICAL-BEHAVIOR OF BOLTED JOINTS UNDER STEADY HEAT-CONDUCTION

Bolted joints in heat exchangers, cylinder heads in combustion engines, and so on are subjected to heat fluxes. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. Temperature distributions of the joints are analyzed using the finite difference method. Then, methods for estimating an increment in axial bolt force and a maximum stress produced in the bolts are proposed. In the experiments, the aforementioned bolted joints are put in a furnace. Furthermore, the rectangular thick plates fastened by a bolt and nut are heated by an electric heater. Then, the temperatures on the surfaces of the clamped parts and the bolts are measured with thermocouples. The increase in axial bolt force and the maximum stress produced in the bolts under steady heat conduction or thermal changes are measured. The analytical results are in fairly good agreement with the experimental ones.