Fatigue life calibration method based on nominal stress method

Abstract

The invention discloses a fatigue life calibration method based on a nominal stress method and belongs to the technical field of aircraft strength design. The method comprises the steps that first, for test pieces of the same material with different surface quality, values of parameters alpha and A of an S-N curve are basically identical, and a theoretical fatigue limit C is determined as a uniquesensitive parameter needing optimization; second, according to a load stress spectrum designated in advance, mid-value life t<50> corresponding to the load stress spectrum is determined as an objective for optimization, an initial value is set, the value of the theoretical fatigue limit C is continuously adjusted, the nominal stress method is repeatedly utilized to calculate the mid-value life till the calculated life is equal to a set target mid-value t<50>, and the corresponding C value at the moment is a corrected C value in a three-parameter expression of the S-N curve; and third, the determined nominal stress method and the corresponding theoretical fatigue limit C are verified, the parameters obtained through optimization and the nominal stress method are adopted through verification to perform life prediction under other load spectra, and therefore life calculation results under other load spectra have high precision.

Description

technical field [0001] The invention belongs to the technical field of aircraft strength design, and in particular relates to a fatigue life calibration method based on a nominal stress method. Background technique [0002] At present, when the life analysis under the random spectrum is performed on the key parts of aircraft fatigue, due to the complex load interaction in the random spectrum, there is no generally applicable high-precision damage accumulation model that can predict its fatigue life well. [0003] However, it is found through research that serialized aircraft often have great inheritance in structure and load spectrum, so the fatigue test results of existing models can be used to predict the fatigue life of subsequent models. Contents of the invention [0004] Purpose of the present invention: In order to solve the above-mentioned problems, the present invention proposes a life calibration method based on nominal stress legislation, which can still ensure t...

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Problems solved by technology

[0002] At present, when the life analysis under the random spectrum is performed on the key parts of aircraft fatigue, due to the complex load interaction in the random spectrum, there is no generally applicable high-precision damage accumulation model that can better predict its fatigue life

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