The creep and relaxation behaviour of high temperature pipe flanges was inv
estigated. Constitutive laws to describe the relaxation and creep behaviour
have been developed based on uniaxial creep and relaxation tests. They hav
e been implemented in Finite element program code in order to calculate bot
h the time dependent inelastic deformations as well as the stress strain si
tuation in flanges. Different types of flanges have been investigated. For
verification model flanges have been tested. Experimental results and numer
ical analysis have been compared.