Fatigue life calculation method based on a frequency domain under variable temperature vibration

Abstract

The invention discloses a fatigue life calculation method based on a frequency domain under variable temperature vibration. The method comprises the following steps: acquiring vibration stress-time load process and temperature time load process of a key position of the heat bearing structure to separate and decompose into two signals; and generating a power spectrum density spectrum of the load spectrum through fast Fourier transform; carrying out statistical parameter induction, and determining autocorrelation functions respectively; calculating to obtain a rain flow amplitude probability density function of the vibration load by adopting a Dirlik method; temperature intervals are weighted according to the time intervals of the divided intervals; respectively calculating the fatigue damage under the combination of the S-N curve parameters at different temperatures and the rain current amplitude probability density function of the vibration load, multiplying the fatigue damage under each temperature interval by the corresponding weight, and finally accumulating to obtain the total fatigue damage of the vibration fatigue under the continuous variable temperature. Through the comparison with a traditional time domain method, the method can well predict the damage of the key heat bearing structure of the aircraft.

Description

technical field [0001] The invention relates to a frequency domain-based fatigue life calculation method under variable temperature vibration, and its application field belongs to the field of mechanical parts. Background technique [0002] During the flight of a hypersonic vehicle, the key structure of the airframe is subject to the coupling effect of engine noise, random vibration loads of the outer shock wave, and constantly changing high-temperature loads on the surface, and the service environment is extremely harsh. Fatigue damage is caused under the environment, which seriously affects the service life of hypersonic aircraft. The main failure mode of the key structure of a hypersonic vehicle is the vibration fatigue damage at high temperature, and the continuous variable temperature vibration fatigue strength design of the key heat-bearing structure is an important content of the strength design. [0003] At present, the vibration fatigue life prediction at high temp...

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Problems solved by technology

[0003] At present, the vibration fatigue life prediction at high temperature mainly considers the isothermal fatigue life prediction at a constant temperature, ignoring the damage caused by temperature changes to the heat-bearing structure of the aircraft, which has large errors and uncertainties.

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