Three-dimensional space vector stress field strength method

Abstract

The invention provides a three-dimensional space vector stress field intensity method which comprises the following steps: (1) calculating stress distribution of an engineering structural member by applying finite element software; (2) selecting a maximum-stress point as a dangerous point; (3) by taking the dangerous point as an original point, determining N calculation directions by applying a finite element three-dimensional space vector method; (4) by taking node stress as a sample, obtaining a three-dimensional space stress field through a Pan-kriging technology; (5) calculating stress field intensity in each calculation direction based on a one-dimensional stress field intensity method; (6) determining a calculation direction of the maximum average stress gradient; (7) calculating equivalent stress by applying a three-dimensional space vector stress field intensity calculation formula. The three-dimensional space vector stress field intensity method can be successfully applied to forecasting the fatigue life when first-order bending vibration occurs in a blade. Compared with the one-dimensional stress field intensity method, the three-dimensional space vector stress field intensity method is high in calculation precision and high in stability. Compared with a conventional three-dimensional stress field intensity method, the three-dimensional space vector stress field intensity method has the advantages that a calculation radius can be determined without fatigue test data, calculation cannot be impacted by the shape of a structural space and the calculation precision is high.

Description

Technical field: [0001] The invention relates to the fatigue life prediction problem of aviation structures with stress gradients, in particular to a three-dimensional space vector stress field strength method, which is used to predict the fatigue life of aeroengine blades under first-order bending vibration. Background technique: [0002] High-cycle vibration fatigue damage caused by airflow excitation is one of the main failure modes of the blade. When the airflow excitation frequency is close to or the same as the natural frequency of the blade, it will cause the resonance of the blade. First-order bending vibration is common in resonance fatigue failure. When the blade is subject to bending vibration, there is a stress gradient in the thickness direction. If the maximum stress on the surface is selected to predict the fatigue life, there is sometimes a large error between the predicted value and the actual result. How to consider the influence of stress gradient on fatig...

AI Technical Summary

Problems solved by technology

Without fatigue test data, the traditional three-dimensional stress field strength method cannot be applied

[0005] (2) If the fatigue damage area has an irregular spatial shape, the integral area of ​​the traditional three-dimensional stress field strength method cannot be described by precise mathematical expressions

[0006] (3) If the stress distribution in the fatigue damage area changes drastically, the three-dimensional space polynomial fitting technique cannot obtain accurate results, and the amount of calculation increases significantly with the increase of the fitting order

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