A comparison between steady state creep and stress relaxation in copper

Experimental data from creep and stress relaxation tests on copper specimens were compared on the basis of strain rate–stress curves in the temperature range 150–630 °C. Results from the two loading methods are often assumed to be complementary such that results from one can be used to calculate behaviour in the other. This was found not to be the case for this material. At a particular temperature, curves generated from steady state creep intersected sets of curves from relaxation tests, although as the temperature increased, the correspondence between results became better until they were fairly similar at the highest temperature. Several reasons for the non-correspondence are discussed including the possibility that the material is in different structural states induced by deformation which precedes the onset of either steady state creep or stress relaxation.