ガスケットの粘弾塑性特性とボルト締結体の軸力緩和予測

抄録

To establish a lifetime prediction method of gasket, it is essential to grasp its visco-elastic-plastic properties and to construct a model which can predict a bolt load time variation for bolted gasketed joints due to creep and stress relaxation of gasket. In this paper, first, a strain-time equation of gasket under arbitrary multi-step unloading is established by conducting the compression and creep tests. The tests are performed for two types joint sheet gaskets, or non-asbestos and asbestos gasket. Next, the bolt load relaxations in a simple bolted joint are calculated by utilizing the established strain-time equation, and it is confirmed that the calculated results agree well with the experimental ones performed under some gasket contact stresses. In addition, the bolt load variations with time for a pipe flange connection are simulated by finite element method. As a result, it is concluded that a good agreements between numerical and experimental results are obtained by using the strain-time equation without delayed elasticity strain which occurs in a moment. Furthermore, a method which predicts a long time viscous property of gasket from short time creep test is investigated.