CN-116108582-B - Multiaxial high cycle fatigue life prediction method suitable for heterogeneous loading working condition

CN116108582BCN 116108582 BCN116108582 BCN 116108582BCN-116108582-B

Abstract

The invention provides a multiaxial high cycle fatigue life prediction method suitable for heterogeneous loading conditions, which mainly comprises the steps of selecting damage control parameters based on a critical surface method and performing calculation and analysis, summarizing the influence rule of a load path on the damage control parameters under heterogeneous loading conditions, redefining non-proportionality from a stress angle, simultaneously defining an additional damage coefficient by considering additional strengthening properties of a material, and establishing a multiaxial high cycle fatigue life prediction model capable of reflecting the phenomenon of fatigue life rapid reduction along with the increase of a phase difference. The model built by the invention can simultaneously consider simple loading and biaxial in-phase and out-of-phase loading, has simple form and easily-determined parameters, and is convenient for engineering application.

Inventors

PENG YAN
ZHANG WEI
LI RUJUN
GE SHITAO
LIU YANG

Assignees

燕山大学

Dates

Publication Date: 20260512
Application Date: 20230129

Claims (6)

1. A multiaxial high cycle fatigue life prediction method suitable for heterogeneous loading conditions is characterized by comprising the following steps: S1, carrying out stress state analysis on a standard thin-wall circular tube test piece to obtain any angle formed between the standard thin-wall circular tube test piece and the axial direction of the test piece Is used for the production of a high-shear-stress value, comprising the following steps: the surface of the test piece is in a plane stress state under the tension-torsion compound loading state, an axial included angle with the test piece is Normal stress on plane Shear stress The expression is as follows: Wherein, the In the event of an axial stress, , In order for the shear stress to be a high shear stress, , And The axial and tangential stress magnitudes are respectively, And The average stresses in the axial direction and the tangential direction respectively, In order to load the frequency of the signal, Is the phase angle; According to the obtained axial included angle with the test piece as Normal stress on plane Shear stress Calculating any angle with the axial direction of the test piece Is a maximum shear stress value expression of (a): Wherein, the Is the stress ratio; S2, selecting damage control parameters based on a critical plane method, and performing calculation and analysis to obtain a critical plane maximum shear stress course change curve under the heterogeneous loading path; s3, calculating an analysis result through the damage control parameters, and defining an out-of-phase loading path influence parameter g; S4, according to the out-of-phase loading path influence parameter g, considering the integral additional strengthening degree of the whole angle domain, and defining a loading path non-proportionality L; S5, comprehensively considering the additional strengthening attribute of the material and the non-proportionality L of the load path, and defining a non-proportionality additional damage coefficient ; S6, by introducing a non-proportional additional damage coefficient Establishing a multi-axis high cycle fatigue life prediction model based on a critical plane by means of a Von-Mises form and comprehensively considering the influence of the heterogeneous loading path and the additional strengthening attribute of the material, and performing multi-axis high cycle fatigue life prediction based on the multi-axis high cycle fatigue life prediction model.
2. The multi-axis high cycle fatigue life prediction method suitable for out-of-phase loading conditions according to claim 1, wherein the method is characterized in that damage control parameters are selected based on a critical plane method and calculated and analyzed to obtain a critical plane maximum shear stress course change curve under the out-of-phase loading path, and comprises the following steps: Defining a critical plane as a plane where the maximum shear stress is located, and selecting the maximum shear stress and the normal stress on the plane as damage control parameters; Analyzing the time-varying course of damage control parameters under uniaxial and biaxial in-phase loading by using Moire circle theory, and forming any angle with the axial direction of the test piece Maximum shear stress value of (2) The expression analyzes the time-varying course of the damage control parameters under the dual-axis heterogeneous loading.
3. The multi-axis high cycle fatigue life prediction method suitable for out-of-phase loading conditions according to claim 1, wherein the out-of-phase loading path influence parameter g expression formula is: Wherein, the 、 Respectively out of phase and in phase loading under the condition of having an included angle with the axial direction of A minimum of maximum shear stress on each plane of (a), 、 Maximum shear stress values on critical surfaces under out-of-phase and in-phase loading conditions, respectively, subscripts And Representing a biaxial in-phase loading and a biaxial out-of-phase loading respectively, Indicating the location of the critical plane.
4. The multi-axis high cycle fatigue life prediction method suitable for out-of-phase loading conditions according to claim 1, wherein the expression formula of the load path non-proportionality L is: Wherein, the For maximum shear stress of the critical plane, m is a proportionality coefficient, represents the additional strengthening degree of the loading path in the angle domain, For phase angle, g is the out-of-phase loading path influencing parameter.
5. The method for predicting multi-axis high cycle fatigue life applicable to out-of-phase loading conditions of claim 1, wherein the non-proportional additional damage coefficient The expression formula of (2) is: Wherein, the In order for the load path to be non-proportional, Reinforcing coefficients are added to the material.
6. The method for predicting the multiaxial high cycle fatigue life applicable to out-of-phase loading conditions according to claim 1, wherein the expression formula of the multiaxial high cycle fatigue life of out-of-phase loading conditions is: Wherein, the For the purpose of the average hydrostatic stress, For the Mises equivalent stress, the stress is, The most commonly used Basquin power function expression is chosen here for the stress-lifetime relation, The damage coefficients are appended for non-scale, Is the maximum shear stress of the critical surface.

Description

Multiaxial high cycle fatigue life prediction method suitable for heterogeneous loading working condition Technical Field The invention relates to the field of service safety assessment of mechanical components, in particular to a multi-axis heterogeneous load working condition high cycle fatigue life prediction method research, and especially relates to a multi-axis high cycle fatigue life prediction method suitable for heterogeneous load working conditions. Background Fatigue is a development process in which a mechanical component undergoes a localized permanent structural change after it is subjected to a sufficient cyclic disturbance load. Fatigue failure is the most common form of failure in the modern industry. The service loaded environment of the mechanical component in real life is quite complex, the research aiming at multi-axis fatigue life prediction becomes a hot spot, and particularly, the multi-axis high-cycle fatigue research under heterogeneous loading can more pertinently meet the current requirements on the complex service environment, high quality and long service life of the mechanical component. The existing multiaxial high cycle fatigue failure criteria can not fully cover all possible situations, but for some specific situations, some criteria prediction effects are more accurate, wherein the criteria include an equivalent stress criterion, a stress invariant criterion, a critical surface stress criterion and the like. The critical surface method is proposed based on crack initiation and propagation mechanism, focuses on a fatigue failure surface, has definite physical meaning, has higher accuracy of calculation results, and is widely accepted at present. The Matake criterion takes the maximum surface of the shearing stress amplitude as a critical surface, and the fatigue damage control parameter is constructed by linear combination with the maximum normal stress on the critical surface, which is a more classical criterion in the critical surface method, and Ohka-Wa and Vu and the like find that under the multiaxial loading condition, crack expansion is divided into a first stage of expansion along the maximum shearing stress plane and a second stage of expansion along the axial stress when crack initiation and expansion behaviors of S45C steel and C35 steel are researched by using a crack replication technology, and the transition length of the second stage is influenced by the stress amplitude ratio and the phase difference of the loading. Verreman and the like are subjected to multi-axis high-cycle fatigue tests, analysis shows that stress amplitude is greatly affected by the extension and expansion shapes of cracks along the depth direction, liu Jia and the like select strain as damage control parameters based on a critical surface principle, and fatigue life prediction is performed on 4 materials such as 1045HR steel and the like, so that a prediction result is ideal. Jiang Chao, and the like, by analyzing critical plane strain parameters, a new multi-axis low-cycle fatigue life prediction model is established by considering plastic strain, the method is simple and the prediction effect is good, but the application condition of multi-axis high-cycle fatigue is not further considered based on the stress angle. The above methods are mostly applicable to low cycle fatigue and fail to adequately account for the additional strengthening behavior caused by the out-of-phase loading path. Disclosure of Invention The existing fatigue prediction method is mainly suitable for low-cycle fatigue, and the technical problem of additional strengthening behavior caused by the out-of-phase loading path cannot be fully considered, so that the multi-axis high-cycle fatigue life prediction method suitable for the out-of-phase loading working condition is provided. The invention has simple principle, is convenient for engineering application, and can simultaneously consider the working conditions of simple loading and multi-axis in-phase and out-phase loading. The invention adopts the following technical means: A multiaxial high cycle fatigue life prediction method suitable for heterogeneous loading conditions comprises the following steps: s1, carrying out stress state analysis on a standard thin-wall circular tube test piece to obtain a maximum shear stress value forming an arbitrary angle theta with the axial direction of the test piece; S2, selecting damage control parameters based on a critical plane method, and performing calculation and analysis to obtain a critical plane maximum shear stress course change curve under the heterogeneous loading path; s3, calculating an analysis result through the damage control parameters, and defining an out-of-phase loading path influence parameter g; S4, according to the out-of-phase loading path influence parameter g, considering the integral additional strengthening degree of the whole angle domain, and defining a non-proportionality L; S5, comprehensivel