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A Nonlinear Estimation Method of High Cycle Fatigue Crack Initiation Life of Metal Structures

A non-linear estimation and high-cycle fatigue technology, applied in calculation, computer-aided design, geometric CAD, etc., can solve the problem of low calculation accuracy of spectral fatigue life

Active Publication Date: 2021-09-21
NORTHWESTERN POLYTECHNICAL UNIV
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Problems solved by technology

[0005] Aiming at the low calculation accuracy of complex load spectrum fatigue life calculation in engineering, the invention proposes a nonlinear estimation method of high cycle fatigue crack initiation life of metal structure details, which is practical for engineering and can significantly improve the fatigue life estimation of structural dangerous points precision

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  • A Nonlinear Estimation Method of High Cycle Fatigue Crack Initiation Life of Metal Structures
  • A Nonlinear Estimation Method of High Cycle Fatigue Crack Initiation Life of Metal Structures
  • A Nonlinear Estimation Method of High Cycle Fatigue Crack Initiation Life of Metal Structures

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Embodiment

[0105] The effectiveness of the method of the present invention is illustrated by selecting two types of structural parts of aluminum alloy 2024-T3 materials commonly used in aerospace structures as examples. designed as figure 2 The constant-amplitude spectrum fatigue test of the smooth round bar shown, such as image 3 The shown perforated plate is used as a typical detail structure for fatigue tests under multilevel block spectrum and random spectrum.

[0106] Step 1: The stress ratio R is obtained by fitting the constant-amplitude cyclic fatigue test data 0 =-1 parameter under cyclic loading. The material constants E and ν are obtained through the static tensile test of the material or the relevant manual directly. For the aluminum alloy 2024-T3, the elastic modulus E=72000MPa, Poisson's ratio v=0.33; the parameters of the nonlinear hardening model are obtained by fitting: Mesoscopic initial yield stress σ 0 is 20MPa, Q ∞ is 70MPa, b is 200, M is 0.45, Figure 4 Sho...

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Abstract

A nonlinear estimation method for high cycle fatigue crack initiation life of metal structures, identifying the parameter values ​​of the nonlinear hardening model; establishing a finite element model; calculating the mesoscopic weak inclusion mesoscopic elastic-plastic cyclic stress-strain response; correcting the cumulative plastic strain increment ; Add pressure damage correction coefficient h; Repeatedly sequence the fatigue random load spectrum for any structural dangerous point, repeatedly carry out the mesocosmic weak inclusion stress-strain calculation one by one, provide the corrected damage evolution model according to the present invention, and repeat the calculation according to the random load sequence Calculate the damage increment of this repetition, and accumulate it to the fatigue damage caused by the previous load history, until the total fatigue damage under the calculated load spectrum of the structural dangerous point is obtained. The invention has important engineering application value and significance for high-precision calculation of the fatigue crack initiation life of complex structures with complex load spectrums.

Description

technical field [0001] The invention relates to the field of fatigue life analysis of metal structure details, in particular to a nonlinear estimation method of metal high-cycle fatigue crack initiation life. Background technique [0002] The aircraft shell structure is a finite life structure, usually with a life cycle of 25 to 30 years. It is not uncommon for fatigue cracks to occur due to various alternating loads in flight use, and the reduction of structural fatigue performance seriously affects its safety in use. Usually, the load spectrum suffered by the structure during service is mostly in the form of random load sequence or multi-level load block. At present, the fatigue crack initiation life estimation of engineering structures still widely adopts the linear accumulation method or simple nonlinear method based on the S-N curve. The fatigue life estimation of details often has several times of deviation, which makes it difficult to effectively grasp the long-term...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F30/23G06F30/15
CPCG06F30/15G06F30/23G06F2119/04G06F2119/14
Inventor 李晓虹孙秦刘潇然
Owner NORTHWESTERN POLYTECHNICAL UNIV
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