Stress reduction experiments during constant-strain-rate tests in Cu and Ge

Abstract

Abstract The technique of rapid reductions in applied stress (dip test) is occasionally performed in creep testing. In the work reported here, the technique was applied during a constant-strain-rate test. Both variants, the stress dip test and the strain dip test, give equivalent results. The specimen strain has to be measured in both cases; however, the strain dip technique is preferred since anelastic effects do not interfere. It is shown that the response of Cu and Ge single crystals to fast stress reductions, on the level of the internal stress and below it, is strongly material dependent, reflecting differences in microstructural processes involved in the plastic deformation. These processes are discussed. Acknowledgements It was a pleasure to discuss with Dr Milička, Professor Blum and Professor Nix our difficulties while defining the experimental procedure and interpreting the first results. The fond National Suisse supplied the financial support for this study. The transmission electron microscopy facilities at the Centre Interdépartemental de Microscopie Electronique (Ecole Polytechnique Fédérale de Lausanne) were used.