Comparison of X-ray line profile and dip test measurements of internal stresses during high temperature creep of copper

Internal stresses resulting in polycrystalline copper from creep deformation at temperatures of 773 and 873 K were investigated by two different methods. The first one was the analysis of asymmetric X-ray line profiles. The second one was the dip test technique, which consisted in observation of strain rate after stress changes. The values of internal stresses obtained by these two methods turn out to be not identical, but a close analysis in terms of the composite model shows that the difference in data arises from differences in the definitions of internal stresses. A relation between the internal stresses based on the composite model has been derived which reveals that the data received by the two methods are fully compatible when a reasonable value of dislocation interaction coefficient is chosen.