Experimental creep study of metals under multiaxial stress conditions

Theoretical and experimental methods of creep analysis of metals subjected to multiaxial stress are presented. A concept of the surface, on which energy is dissipated at a constant rate, has been applied to the secondary creep behaviour discussion. It is shown that such a concept can be successfully applied when describing evolution of the material creep properties due to different types of plastic predeformation. A determination procedure of experimental isochronous creep rupture surfaces basing on creep tests on pure copper is reported. The curves of the same time to rupture determined on the basis of experimental programme are compared with theoretical predictions resulted from application of the most often used creep rupture criteria. It is shown that the Sdobyrev creep rupture criterion gives the most accurate description of the experimental results.