An optimized parameter estimation method for creep data processing and its application in creep tests for nickel-based superalloy GH4049

Abstract

Some issues on parameter estimation methods are considered for the Dorn power law constitutive equation (simplified as the Dorn law). In terms of general characteristic analysis of the Dorn law, the optimized parameter estimation method is suggested and correspondingly two optimal objectives are given to obtain the material constants. The validity of the optimal method is then demonstrated by creep data processing of three typical materials. Based on the optimal method, a creep test scheme is prepared for the nickel-based superalloy GH4049 and the tensile creep behaviour is studied in detail. Through computations, the results of material constants by using the optical method show favourable agreement with those of the traditional method and multiple regression method. The optimal method has the advantages of that (a) material constants can be obtained within a relatively larger temperature and stress ranges than the traditional method and the creep test conditions are more relaxed, and (b) when the test data are quantitatively not enough or poorly dispersing, the optimal method can give a possible range of the creep activation energy, which also helps to determine if it is necessary to remedy the test data.