A Creep-Fatigue Life Prediction Method for Materials

Abstract

The invention provides a creep-fatigue life prediction method of a material, which includes respectively performing a creep test, a fatigue test and a creep-fatigue interaction test of the material at the same test temperature; The relationship between the failure strain energy density wf of the material and the dissipation rate of the inelastic strain energy density; according to the fatigue test, the fatigue damage df of the material per cycle is obtained; according to the creep-fatigue interaction test, the half-life cycle is obtained Hysteresis loop, and establish the functional relationship of the stress σ(t) under the half-life cycle of the material within the maximum tensile strain holding time as a function of time t; according to the relationship between wf and wf, the fatigue damage df, and the stress σ( t) the relationship with time t, and combined with the hysteresis loop, calculate the creep damage dc under the half-life cycle; use the linear cumulative damage rule to predict the creep-fatigue of the material under the creep-fatigue interaction Lifetime The present invention enables accurate prediction of material life under creep-fatigue interactions.

Description

technical field [0001] The invention relates to the field of life prediction, in particular to a material creep-fatigue life prediction method. Background technique [0002] In the fields of energy power, petrochemical industry, and aerospace, many structural components are controlled by strain waveforms under high temperature conditions for a long time, and the number of cycle failure cycles is often less than 10. 5 Second, that is, under high temperature and low cycle fatigue loads, its life is often constrained by multiple mechanisms such as creep, fatigue and creep-fatigue interaction. The life prediction of materials under the condition of creep-fatigue interaction is one of the most important links in the structural integrity of materials, so the research on creep-fatigue life prediction is very meaningful. [0003] Since the 1950s, domestic and foreign scholars have done a lot of research work on the damage behavior of materials under creep-fatigue interaction, and h...

AI Technical Summary

Problems solved by technology

Among them, the frequency correction model is an extension of the classic Manson-Coffin equation with respect to the holding time, but this model only roughly considers the influence of frequency and plastic strain range on life, and does not explain the effect of creep on creep-fatigue life from a mechanistic perspective. influence; although the strain range distinction method has formed a relatively mature theoretical system, and derived models such as the strain energy range method, it is still based on a purely phenomenological method, lacking physical meaning and its parameter fitting The steps are relatively complicated; the time-fraction model and the ductility depletion model are also based on linear cumulative damage. This type of method has physical meaning and can be better applied to structural components through the damage interaction diagram, but the life prediction results of the time-fraction model are often too large. Non-conservative and ductile exhaustion models are too conservative

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