Stress relaxation test of Hastelloy C-276 alloy and its creep constitutive equation

The stress relaxation tests of Hastelloy C-276 alloy were conducted at different temperatures(750,800,850 and 900 ℃) and corresponding initial stress levels(250,250,250 and 200 MPa),respectively.Based on the experimental stress relaxation curves,the relationship between creep strain rate and stress was derived.Then,a set of creep constitutive equations were built for Hastelloy C-276 alloy and the material constants of these equations were determined by fitting the creep strain rate-stress curves.The creep constitutive equations were used to simulate the stress relaxation process of Hastelloy C-276 alloy by integrating these equations into finite element software MSC.Marc.The simulated stress relaxation curves agree well with the experimental ones,which verify the reliability of the creep constitutive equations.