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Method for evaluating low-cycle fatigue performance of welded joint

A technology for low cycle fatigue and welded joints, applied in the field of low cycle fatigue performance evaluation of welded joints, can solve the problems of small joint micro-zone size, difficult to determine the fracture position, uncertain fracture position of welded joint fatigue test, etc., to achieve reliable evaluation , the effect of simple calculation

Active Publication Date: 2020-05-19
XI AN JIAOTONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The purpose of the present invention is to provide a method for evaluating the low-cycle fatigue performance of welded joints to solve the problem that the fracture position is difficult to determine during fatigue testing due to the inhomogeneity of the mechanical properties of the welded joint and the small size of the joint micro-zone. Uncertain fracture location and inaccurate strain-life curve in joint fatigue test

Method used

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  • Method for evaluating low-cycle fatigue performance of welded joint
  • Method for evaluating low-cycle fatigue performance of welded joint
  • Method for evaluating low-cycle fatigue performance of welded joint

Examples

Experimental program
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Embodiment 1

[0056] This embodiment evaluates the low-cycle fatigue performance of the plate-shaped funnel sample at the fusion line of the 4mm thick TC4 titanium alloy laser welding joint. Titanium alloy laser welding parameters are laser power 4000W, defocus distance 6mm, welding speed 1.5m / min, the macroscopic appearance of the weld cross section after welding is shown in figure 2 . The strain concentration of the funnel sample was calculated by elastic-plastic finite element method, and the local strain in the plastic zone of the funnel sample was used to evaluate the low cycle fatigue performance at the fusion line. The specific operation steps are as follows:

[0057] (1) using such as Figure 1a The funnel specimen shown was subjected to low cycle fatigue testing with the root of the funnel in the region of the fusion line. The loading waveform of the low cycle fatigue test is a triangular wave, and the strain rate is 0.004s -1 , the strain ratio is -1, and the strain amplitude ...

Embodiment 2

[0065] In this embodiment, the low cycle fatigue performance of the 4mm thick TC4 titanium alloy base material funnel sample and the traditional sample are compared. The funnel sample size of the titanium alloy base material is the same as that of the welded joint, and the fatigue sample size of the traditional sample is shown in Figure 7 . The strain concentration of the funnel sample of the base metal was obtained by elastoplastic finite element calculation, and the global strain and local strain of the funnel sample were used to evaluate the low-cycle fatigue performance of the titanium alloy base material, and the titanium alloy obtained by testing with the traditional sample The low cycle fatigue properties of the base metal were compared. The specific operation steps are as follows:

[0066] (1) Low-cycle fatigue tests were performed on the funnel sample and the traditional sample of the titanium alloy base material, and the fatigue life under different global strain ...

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Abstract

The invention relates to a method for evaluating low-cycle fatigue performance of a welded joint. Evaluation is carried out by adopting a funnel sample, and a working section of the funnel sample is composed of an arc-shaped section and a parallel section; the center of a micro area of the welded joint to be tested is placed in the middle of the arc-shaped section of the funnel sample so that thefatigue sample is broken in the micro-area to be tested, and then low-cycle fatigue performance of the micro-area of the welded joint is evaluated by adopting the local strain of the plastic area obtained through elastic-plastic finite element analysis in strain concentration. Compared with a traditional smooth test sample, the funnel test sample is adopted for testing fatigue performance of the welded micro-area, the fatigue test sample can be finally broken in the welded joint micro-area needing to be measured, and the tested fatigue performance is the fatigue performance of the welded micro-area instead of fatigue performance of the lowest-strength area in the joint. For low-cycle fatigue, the plastic zone strain is used as local strain to evaluate low-cycle fatigue performance of the funnel sample, which is more reliable than hot spot strain and dangerous section strain evaluation, and the method is simpler and more convenient than a critical distance method for calculation.

Description

technical field [0001] The invention belongs to the technical field of welding, and in particular relates to a method for evaluating low-cycle fatigue performance of welded joints. Background technique [0002] Due to the advantages of convenient processing, light weight, and ability to achieve metallurgical bonding, welded structures have been widely used in manufacturing industries such as pressure vessels, rail vehicles, aerospace, and large equipment, and are often used in occasions that withstand long-term dynamic loads. It is very important to accurately evaluate the fatigue performance of The fatigue assessment of welded joints usually uses traditional smooth specimens to evaluate the overall fatigue performance of the joints by the nominal stress-strain method or the local stress-strain method, but the traditional specimens can only test the fatigue performance of the weakest area in the welded joints, and cannot test The fatigue performance of a specific micro-area...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/32G01N3/02
CPCG01N3/32G01N3/02G01N2203/0073G01N2203/0262G01N2203/0296
Inventor 张建勋徐甄真白嘉瑜孙品品牛靖
Owner XI AN JIAOTONG UNIV
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