Computer simulation of high temperature creep recovery and work hardening rate measurement techniques

Abstract

A computer program has been developed to simulate the high temperature creep recovery–work hardening rate measurement techniques. The algorithm of the procedure is based on the commonly used mathematical relations between internal stress σi, creep rate <mml:math><mml:mrow><mml:mover><mml:mi>ɛ</mml:mi><mml:mi>˙</mml:mi></mml:mover></mml:mrow></mml:math>, applied stress σ, and recovery–work hardening behaviour of metals. The program has subsequently been used to simulate such experiments on a hypothetical model material with known recovery–work hardening behaviour. The analysis of the results reveals significant discrepancies between the measured and the actual recovery as well as work hardening rates particularly when the steady state internal stress/applied stress ratio is low. This has been attributed partly to the use of applied stress in the expressions for the measured recovery r′–work hardening h′ rates and partly to the fact that the measured recovery time ∆t m and the measured instantaneous plastic strain ∆ɛm are functions of the internal stress/applied stress ratio. A method for correcting the estimated values of r′ and h′ has also been suggested. Measurement of internal stress and recovery and work hardening rate were carried out on two metals, namely Al and Ag, at two different temperatures and over a wide range of stresses, to evaluate the material constants which have been used later to simulate mathematically the experiments mentioned above on these metals. A direct comparison between the experimental and the simulated strain–time plots has been made to justify the analytical procedure adopted in this work.