Experimental verification of constitutive equations for creep and the interaction of creep and plasticity under biaxial loading conditions

More than 80 creep experiments have been carried out on the austenitic steel WN 1.4948 (18 Cr-11 Ni steel similar to AISI 304 SS). These experiments were intended to arrive at sufficiently accurate and experimentally verified constitutive equations for creep deformations arising from arbitrary loading conditions. The test programme did consist of constant load and programme loading creep tests on solid specimens, including relaxation and recovery parts as well as stepwise increasing and decreasing loads. Furthermore tubular specimens were submitted to loading programmes that were combinations of an axial load, torsional load and internal pressure, thus covering the complete range of principal stress ratios. The constitutive equations were based on the so-called fraction model. (orig./HP)