Low-temperature fatigue property characterization and life estimation method

Abstract

The invention discloses a low-temperature fatigue property characterization and life estimation method. The method comprises three major steps of step 1, through considering the influence of a stress ratio, deriving an S-N-R curved surface characterizing the fatigue property by adopting a Goodman equilife curve based on a three-parameter power function expression, and performing data processing by virtue of a linear regression theory; step 2, through considering an interaction effect of loads under spectrum loading, proposing a corrected spectrum loading fatigue life estimation model based on a Willenborg/Chang model and a crack tip plastic zone theory, and giving out a fatigue damage increment representation method; and step 3, calculating the low-temperature spectrum loading fatigue life of a material by adopting an accumulative damage theory. The method is simple and practical; and a low-temperature fatigue property characterization model can be constructed only by a constant-load fatigue property curved surface and an actually measured flight load spectrum of the material in a low-temperature environment, and the spectrum loading fatigue life is estimated, so that the method has important academic meanings and engineering application values.

Description

technical field [0001] The invention provides a method for low-temperature fatigue performance characterization and life estimation, belonging to the technical field of metal structure fatigue reliability. Background technique [0002] In practical engineering, materials are often damaged by alternating loads, resulting in fatigue cracks; and fracture failure occurs after a certain cyclic stress, thus posing a threat to the safety of the structure. Low temperature is an unavoidable environmental factor in the use of materials. For example, due to the influence of flight altitude and climate, the working temperature of aircraft in some areas reaches -60 °C; the working temperature of liquid nitrogen storage equipment and low-temperature superconducting materials is even lower. At -250℃; in the low temperature environment, the material often undergoes fatigue-ductile-brittle transition and cyclic hardening, and its macroscopic properties usually change, and the fatigue behavio...

AI Technical Summary

Problems solved by technology

At present, there is still a lack of more accurate and practical low-temperature fatigue performance characterization models and life estimation methods. Therefore, a simple and practical low-temperature fatigue performance characterization and life estimation method is invented. The low-temperature fatigue performance characterization model can be constructed by using the fatigue performance surface and the measured flight load spectrum, and the spectral fatigue life of the material can be estimated. This invention has important academic significance and engineering application value

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