Stress Relaxation Testing as an Alternative to Conventional Creep Rupture Testing

In a stress relaxation test a sample is held at a constant elongation at constant temperature and the relaxation of the stress as a function of time is recorded. From this curve the steady state creep rate can be determined. The advantages of this test compared to a conventional creep test are the short duration and the possibility to use the same sample for several tests. A testing procedure for these tests was developed and the reproducibility was checked on IN738 material. Results were compared with results from conventional creep tests. The stress relaxation testing was successfully used, among others, for remaining lifetime assessment of a turbine blade.