Finite Element Analysis of the Thermal and Mechanical Behaviors of Bolted Joint.

Abstract

A bolted joint is frequently used under thermal load in practical applications, such as internal combustion engines, steam and gas turbines, pressure vessels, etc. In order to accurately evaluate the thermal stresses thus produced, the effects 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. An empirical equation, which can compute the thermal contact coefficient at the interface for various contact conditions, has been presented in the previous paper. In this study, a simple equation for evaluating apparent thermal contact coefficient is proposed, which can calculate the amounts of heat flow through small gaps. By incorporating the effects of such contact resistances, i.e., in case of two planes being in contact or with small gaps, into the finite element formulation, a numerical approach is proposed, which can elucidate how the bolt stress is varied with time under thermal load. It is shown that among various factors, coefficient of linear expansion has dominant effects on the variations of bolt stress.