Creep behaviour of nimonic and R.R. 59 alloys

The Ramberg-Osgood relation which adequately describes the stress-strain curve of a strain-hardening material is extended to formulate the constitutive laws for creep. The constitutive laws which describe primary creep adequately are extended to secondary creep. The results are verified for the case of R.R. 59 at 200°C, Nimonic 80A and Nimonic 90 alloys at 750°C.