Numerical modelling of small disc creep test

Abstract

The small disc creep test is described. The disc creep curves observed need to be related to the creep properties of the material obtained by conventional testing. This relationship should include a means of assessing the creep damage which is initially present in the material and therefore to an estimate of remanent life. There are difficulties with such correlations and these are shown to be related to an imperfect understanding of the complex nature of the small punch test. This understanding can be improved by suitable physical modelling of the deformation occurring. The present paper describes a suitable finite element model and verifies the model against experimental observations of disc creep tests. The model uses a realistic creep deformation law which includes strain hardening, thermal softening and damage accumulation for 0·5Cr0·5Mo0·25V steel. It is shown that the results obtained from the test are sensitive not only to the initial condition of the specimen but also to the conditions of the test (e.g. the values of frictional forces at the punch/specimen interface). The paper makes suggestions of how the model may be used to optimise the disc creep test.