Prediction method for multi-axial high-cycle fatigue life of plastic metal material based on critical plane approach

Abstract

The invention establishes a prediction method for the multi-axial high-cycle fatigue life of a plastic metal material based on a critical plane approach. According to the invention, a fatigue failure mode of the plastic metal material under the condition of combined loading of tension and torsion is taken into consideration, influence of a stress amplitude ratio and phase difference on the multi-axial high-cycle fatigue life under the condition of multi-axial loading is also considered, a fatigue life prediction model for prediction of the multi-axial high-cycle fatigue life is established by using linear combination of a maximum principal stress peak value and a maximum shear stress range on the basis of critical plane criteria of multi-axial fatigue and used for predicating the life of the plastic metal material bearing multi-axial high-cycle fatigue load, and the prediction method for the multi-axial high-cycle fatigue life of the plastic metal material based on the critical plane approach is eventually brought forward. The model established in the invention is based on the critical plane criteria capable of revealing damage of a physical mechanism multi-axial fatigue and takes influence of the stress amplitude ratio and phase difference on multi-axial high-cycle fatigue failure under the condition of multi-axial loading into consideration, and small dispersity and high accuracy of prediction results of the model are realized.

Description

technical field [0001] The present invention relates to the prediction of fatigue life when plastic metal materials are subjected to multiaxial fatigue loads, and specifically relates to a multiaxial high cycle fatigue failure method for metal material structures based on the critical surface method, which is applicable to various types of materials widely used in aerospace vehicles. Plastic metal material structure. Background technique [0002] In the field of aerospace, due to the complex working conditions, most load-bearing structures are subjected to multi-axis cyclic loads. For example, the skin of the fuselage of an aircraft is subjected to circumferential and The skin is subjected to bending moments and torques due to aerodynamic loads, and the gyro structure in the turbine disk of the aero-engine and the navigation system is also subjected to multi-axial loads of bending, torsion, and tension and compression. Since the initial stage of fatigue research, multiaxial...

AI Technical Summary

Problems solved by technology

[0003] In multiaxial fatigue, since there are many load characteristic parameters, such as stress (variation) amplitude, phase difference and average stress (variation), and the magnitude and direction of the principal stress (variation) change with time during the loading process, each load The influence of characteristic parameters on fatigue failure is complex, and there are still many issues that have not reached a consensus so far

Especially for multiaxial high cycle fatigue, due to insufficient theoretical analysis and experimental research, there is still no widely accepted life prediction model and failure criterion

Among the existing multiaxial high cycle fatigue failure criteria, the equivalent stress criterion and equivalent strain criterion are simple in form, but lack a reasonable physical explanation; the determination of parameters in the stress invariant criterion is more complicated; the energy in the energy criterion is a scalar quantity, which cannot Determine the crack propagation direction; the critical surface stress criterion and the critical surface strain criterion have reasonable physical explanations and have been generally accepted, but the research on the critical surface method in high cycle fatigue is still immature

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