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Uniaxial fatigue S-N curve-based hard metal material multi-axis high-cycle fatigue failure prediction method

A fatigue failure, hard metal technology, used in the application of stable tension/pressure to test the strength of materials, analyze materials, measuring devices, etc., can solve the problems of unclear physical meaning, lack of physical background, and complex determination of critical surfaces. To achieve the effect of easy application and simple model form

Active Publication Date: 2019-09-24
BEIHANG UNIV
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Problems solved by technology

Among them, the equivalent stress criterion is derived from the test data on the basis of the static strength theory. It has a simple form and is widely used in engineering, but lacks a reasonable physical background; the stress invariant criterion is generally based on the second invariant of the stress offset and the As a parameter, the calculation is convenient, but its effectiveness in explaining the multiaxial fatigue failure mechanism has yet to be verified; the mesoscopic integration criterion was first proposed based on the concept of stress microelements, but the physical meaning of the criterion is not yet clear; the critical surface criterion is based on the crack On the basis of initiation and growth, it is considered that under fatigue load, cracks initiate on a specific plane, and the shear stress and normal stress on this plane will affect the initiation and growth of fatigue cracks, but the determination of the critical surface is more complicated
[0004] When the existing failure criteria are used for life prediction, multiaxial fatigue tests under corresponding loading conditions are required. However, the multiaxial fatigue damage mechanism is complex, the test results are highly dispersed, and the test period is long.
Regarding the existing multiaxial high cycle fatigue failure prediction methods at home and abroad, there is no simple, economical and accurate prediction of multiaxial high cycle fatigue life.
In addition, a large number of studies have shown that under different stress amplitude ratios, the effect of phase difference changes on fatigue life is not obvious, and the fatigue life under non-proportional loading is slightly greater than that under proportional loading, that is, proportional loading is always longer than non-proportional loading. Proportional Loading Hazards

Method used

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  • Uniaxial fatigue S-N curve-based hard metal material multi-axis high-cycle fatigue failure prediction method
  • Uniaxial fatigue S-N curve-based hard metal material multi-axis high-cycle fatigue failure prediction method
  • Uniaxial fatigue S-N curve-based hard metal material multi-axis high-cycle fatigue failure prediction method

Examples

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Embodiment 1

[0047] Example 1: Prediction of High Cycle Fatigue Life of 30CrMnSiA Steel under Combined Tension-Torsion Loading

[0048] 30CrMnSiA steel tensile torsion test test piece size schematic diagram as shown figure 2 As shown, its static performance is: E=207GPa, σ s =1334MPa, G=77.2GPa, τ s =1040MPa. Through uniaxial tension-compression and pure torsion fatigue tests, the fatigue performance is obtained: the uniaxial tension-compression S-N curve is log N T =6.958-1.2294log(σ x,a -565.25), the pure torsional S-N curve is log N S =36.26-11.659logτ xy,a ; corresponds to 10 6 The condition of cycle life is that the fatigue limit of uniaxial tension and compression is σ u =565.25MPa, pure torsional fatigue limit is τ u = 393.93 MPa. The Von-Mises equivalent stress is taken as the same, and the load is applied to the test piece under different stress amplitude ratios, phase differences and average stresses, and the tensile-torsion fatigue test life of the test piece is obtain...

Embodiment 2

[0054] Example 2: Prediction of High Cycle Fatigue Life of LY12CZ Aluminum Alloy under Combined Tension-Torsion Loading

[0055] The static performance of LY12CZ aluminum alloy is: E=73GPa, σ s =545MPa, G=27.4GPa, τ s = 382MPa. The fatigue performance is: the uniaxial tension-compression S-N curve is log N T =22.72-7.37logσ x,a , the pure torsional S-N curve is log N S =24.91-8.97logτ xy,a ; The fatigue limit of uniaxial tension and compression is σ u =168.73MPa, pure torsional fatigue limit is τ u = 119.62 MPa.

[0056] 1. First, the fatigue limit ratio of the given material is equal to 0.70, which is a hard metal material. Secondly, due to the simple structure of the test piece, the stress change of the dangerous point during the tension-torsion fatigue loading process can be calculated by theoretical analysis;

[0057] 2. According to the stress change of the dangerous point obtained by calculation, it is concluded that the test piece material does not enter yield, ...

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Abstract

The invention discloses a uniaxial fatigue S-N curve-based hard metal material multi-axis high-cycle fatigue failure prediction method. According to the method, with a uniaxial tension fatigue and pure torsion fatigue S-N curve adopted as a boundary condition, and the equivalent stress amplitude and equivalent stress amplitude ratio of a material in the multi-axis fatigue loading process of the material are calculated; with the equivalent stress amplitude and equivalent stress amplitude ratio adopted as damage parameters, a fatigue S-N curve obtained from uniaxial fatigue is calculated; and a hard metal material multi-axis high-cycle fatigue failure life prediction model containing stress amplitude ratio and average stress influence is established. The method is suitable for a situation where average stress does not exist. Existing multi-axis fatigue life prediction models perform multi-axis fatigue tests under corresponding loading modes, and as a result, test cost is relatively high. Compared with the existing models in the prior art, the method disclosed by the invention is simple in form, and can obtain a uniaxial fatigue S-N curve just through a single-axis fatigue test or manual check, so as to accurately predict the fatigue life of a hard metal material under multi-axis high-cycle fatigue loading in the presence of a stress amplitude ratio and average stress.

Description

technical field [0001] The invention in this paper relates to the problem of fatigue life prediction under multi-axial loading under the action of stress amplitude ratio and average stress of hard metal materials without considering the influence of phase difference. It only needs to carry out uniaxial tension-compression and pure torsion fatigue tests or consult the manual The obtained uniaxial S-N curve can predict the multiaxial high cycle fatigue life, which is suitable for various hard metal material structures widely used in aerospace vehicles. Background technique [0002] In engineering practice, the dangerous parts of many structures are subjected to multi-axial fatigue loads, such as aircraft skins, blades and disc structures in aero-engines, etc.; in addition, gaps or other geometric changes in the structure will also cause local Stress and strain make the dangerous part in a state of multiaxial stress. In the process of multiaxial loading, there are coupling eff...

Claims

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Application Information

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IPC IPC(8): G01N3/08G01N3/26
CPCG01N3/08G01N3/26G01N2203/0026G01N2203/0252
Inventor 时新红亓新新刘天奇
Owner BEIHANG UNIV
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