An Accelerated Method for Creep Prediction From Short Term Stress Relaxation Tests

Abstract

With the development of ultrasupercritical power generation technology, creep strength of hightemperature materials should be considered for safety evaluation and engineering design. However, longtime creep testing should be conducted by traditional creep assessment methods. This paper established a highefficient prediction method for steady creep strain rate and creep strength based on shortterm relaxation tests. Equivalent stress relaxation time and equivalent stress relaxation rate were defined according to stress relaxation characteristics and the Maxwell equation. An accelerated creep prediction approach from shortterm stress relaxation tests was proposed by defining the equivalent relaxation rate as the creep rate during the steady stage. Stress relaxation and creep tests using hightemperature material 1Cr10NiMoW2VNbN steel were performed to validate the proposed model. Results showed that the experimental data are in good agreement with those predicted solutions. This indicates that shortterm stress relaxation tests can be used to predict longterm creep behavior conveniently and reliably, and the proposed method is suitable for creep strength design and creep life prediction of 9–12%Cr steel used in ultrasupercritical unit at 600 آ°C.