SIGNIFICANCE OF IMAGINARY INITIAL STRAIN- RATE AND STRAIN-RATE ACCELERATION FACTOR IN A CONSTANT-LOAD CREEP

It has been recognized that the logarithm of creep rate varies linearl y with true strain in a constant load creep. This empirical law is val id over a wide range of strain and is expressed by a following equatio n; In epsilon = ln epsilon(0) + S epsilon, where, epsilon(0) is the st rain rate, epsilon(0) is the imaginary initial strain rate, S is the s train rate acceleration factor and epsilon is the true strain. This eq uation has a potential as a powerful tool for creep life and remaining life assessment technology. In the present paper, the physical signif icance oi the two parameters, i. e., epsilon(0) and S, and their stres s and temperature dependences were examined by a simple thought experi ment and dislocation models. It was made clear that the imaginary init ial creep rate is identical principally with a steady-state creep rate and the stress dependence of S is determined mainly by the work-harde ning during creep.