Forecasting method for creep-fatigue life of material

Abstract

The invention provides a forecasting method for creep-fatigue life of a material. The method comprises the following steps: respectively performing a creep test, a fatigue test and a creep-fatigue interaction test for the material at a same test temperature; establishing a relation between the failure strain energy density wf and a non-elastic strain energy density dissipation rate of the material under a log-log coordinate according to the creep test; acquiring the fatigue damage df of the material per period according to the fatigue test; acquiring a hysteresis loop under a half-life period according to the creep-fatigue interaction test and establishing a function relation of the change of the stress Sigma (t) of the material under the half-life period within the maximum tensile strain maintaining time along with the change of time t; calculating the creep damage dc under the half-life period by combining with the hysteresis loop and based on the relation between wf and the function as shown in the specification and the relation of change of the fatigue damage df and the stress Sigma (t) along with the change of time t; and utilizing a linear accumulating damage rule to forecast the creep-fatigue life of the material under a creep-fatigue interaction. According to the method provided by the invention, the life of the material under the creep-fatigue interaction can be accurately forecasted.

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...

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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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