Characteristics of Bolted Flanged Joints with a Flat Cover by Tap Bolts in a Pressure Vessel Subjected to Heat Conduction

When a bolted joint is under thermal change, where the material of clamped parts is different from that of the bolts, a variation in axial bolt force is produced due to the difference in thermal properties between the bolts and the clamped parts. In this paper, a variation of axial bolt force in a bolted joint under thermal change, in which a hollow cylinder manufactured from aluminum alloy is fastened to a body (hollow cylinder) with a tap bolt manufactured from steel, is examined both theoretically and experimentally. In addition, mechanical behaviors of a bolted flanged joint with a flat cover in which the cover, the gasket and the flange are manufactured from aluminum alloy and tap bolts of steel are examined when the inner circumference of the joint is subjected to heat conduction. With the use of the finite difference method, the temperature distribution in the connection is analyzed. A variation of axial bolt force and a maximum stress produced in the tap bolts are analyzed. In the experiments, temperature distribution was measured by thermocouples, the variation in axial bolt force and the maximum stress produced in the tap bolts by strain gauges when the inner circumference of vessel was heated (cooled). The numerical results are in fairly good agreement with the experimental results.