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 t he 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 rect angular 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 ar e analyzed using the finite difference method. Then, methods for estim ating an increment in axial bolt force and a maximum stress produced i n the bolts are proposed. In the experiments, the aforementioned bolte d joints are put in a furnace. Furthermore, the rectangular thick plat es 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 ar e measured with thermocouples. The increase in axial bolt force and th e maximum stress produced in the bolts under steady heat conduction or thermal changes are measured. The analytical results are in fairly go od agreement with the experimental ones.