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Method for predicting fatigue life of friction stir welding joint based on grain size and microhardness

A technology for friction stir welding and microhardness, which is used in measuring devices, strength characteristics, instruments, etc., and can solve problems such as being unsuitable for predicting the fatigue life of friction stir welded joints.

Inactive Publication Date: 2020-04-17
BEIJING UNIV OF TECH
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Problems solved by technology

However, for friction stir welded joints, the microstructure and properties of different regions are different, which is equivalent to different materials. The above-mentioned model based on crack closure is not suitable for predicting the fatigue life of friction stir welded joints.

Method used

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  • Method for predicting fatigue life of friction stir welding joint based on grain size and microhardness
  • Method for predicting fatigue life of friction stir welding joint based on grain size and microhardness
  • Method for predicting fatigue life of friction stir welding joint based on grain size and microhardness

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Embodiment Construction

[0039] The sample size and shape described in step 1) are as follows figure 2 shown.

[0040] Such as figure 1 As shown, the specific implementation of a method for predicting the fatigue life of friction stir welded components based on grain size and microhardness is as follows:

[0041] Step 1): Prepare samples according to the partition characteristics of the friction stir welded joint. The middle part of the fatigue sample is arc-shaped. A total of four batches of samples are prepared, each batch of samples is more than 3, and the smallest cross-section of each batch of samples corresponds to The nugget zone (NZ), thermo-mechanical affected zone (TMAZ), heat-affected zone (HAZ) and base metal zone (BM) of fatigue samples are used to make the fracture position of each batch of samples correspond to the minimum cross section. Each batch of samples is loaded under different stress levels, and the small fatigue cracks are replicated with a film. The secant method is used to...

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Abstract

The invention discloses a method for predicting the fatigue life of a friction stir welding joint based on grain size and microhardness, and belongs to the field of fatigue diagnosis and analysis. Themethod comprises the following steps: carrying out fatigue small crack propagation replication experiments on a sample under different loading levels to obtain crack propagation data of fractures indifferent areas of the friction stir welding joint; correcting an Elber crack closing method through the microcosmic performance of each area of the friction stir welding joint, further obtaining delta Keff-da / dN crack propagation rate baselines of fractures in different areas of the joint under different stress ratio conditions, and fitting correlation coefficients C and m; determining an initialcrack size a0 and a critical crack size ac; and simulating weak areas of the friction stir welding joint under different loading levels by utilizing ABAQUS, and selecting a correction factor M and aninitial crack size a0 according to the weak areas. Through continuous cyclic calculation, when the crack size reaches the critical crack size ac, it is regarded that the crack is broken, and the fatigue life of the friction stir welding joint under different loading levels is obtained.

Description

technical field [0001] The invention relates to a fatigue life prediction method, in particular to a fatigue life prediction method suitable for friction stir welding joints based on grain size and microhardness, and belongs to the technical field of mechanical structure diagnosis and analysis. Background technique [0002] In mechanical structures, fatigue problems cannot be ignored. In engineering operation, the loads on the structure are mostly alternating loads of repeated cycles, which easily cause fatigue fracture of the structure under low stress. Fatigue strength issues are of critical importance for components subject to alternating loads. The welded part is the weakest link in the entire structure. In the failure of the welded structure, fatigue fracture accidents caused by alternating loads account for 80%-90% of the total number of failures. It is very necessary to carry out research on the microcosmic mechanism, microcosmic process and physical nature of the h...

Claims

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Application Information

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IPC IPC(8): G01N3/00G01N3/06
CPCG01N3/00G01N3/06G01N2203/0298G01N2203/0066G01N2203/0073G01N2203/0218G01N2203/0268G01N2203/0676G01N2203/0682
Inventor 孙国芹韩文彪
Owner BEIJING UNIV OF TECH
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