Method for predicting fatigue life of brazed welding joint based on finite volume strain energy
A technology for fatigue life prediction and welded joints, applied in the direction of applying stable tension/pressure to test the strength of materials, measuring devices, instruments, etc., can solve the unclear physical meaning, the lack of a unified prediction method for mixed crack behavior, and brazed joints Effectiveness has not been verified and other problems, to achieve the effect of overcoming single usage, realizing scientific prediction, and realizing fatigue life
Active Publication Date: 2021-11-19
NANJING UNIV OF TECH
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[0002] Although the traditional fatigue crack growth rate prediction method based on stress intensity, that is, the method based on the Paris equation and its modified equation can effectively predict the crack growth rate to a certain extent, there are still the following problems: 1. The physical meaning is still unclear. 2. . There is no uniform prediction method for mixed crack behavior, and it needs to be corrected for different situations. 3. The effectiveness of brazed joints has not been verified
For crack growth, the J-integral method can be used to describe the energy release rate at the front of the crack, but the calculation of the J-integral is based on the assumption of monotonic loading. For the fatigue crack growth under alternating loads, especially under tension and compression loads, the monotonic Loading assumptions cannot be established
Therefore, the J-integral-based energy method cannot effectively predict the fatigue crack growth rate of brazed welded joints.
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[0027] In order to explain in detail the technical content, structural features, achieved goals and effects of the technical solution, the following will be described in detail in conjunction with specific embodiments and accompanying drawings.
[0028] Please also refer to 1 to Figure 7 , as shown in the figure, this embodiment provides a method for predicting the fatigue life of brazed welded joints based on finite volumetric strain energy. The predicted object is S30408 brazed welded joints, the base material is S30408 austenitic stainless steel, and the brazing material is nickel Base solder, the thickness of the solder after brazing is 50 μm, the test steps include: brazing weld joint critical pure tensile, shear cohesion energy (G IC and G IIC ) value determination, weld residual stress σ of brazed welded joints r Measurement, evaluation of fracture toughness of welded joints, measurement of crack growth rate da / dt of brazed welded joints and prediction of fatigue...
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Abstract
The invention discloses a method for predicting the fatigue life of a brazed welding joint based on finite volume strain energy. The method comprises the following steps: measuring critical pure stretching and shear cohesion energy values of the brazed welding joint; measuring the residual stress [sigma]r of a welding seam of the brazing welding joint; evaluating the fracture toughness of the welding joint; measuring the crack growth rate da / dt of the brazed welding joint; and achieving predicting of the fatigue life of the brazed welding joint by using finite volume strain energy. According to the scheme, through a series of tests, the relation between the crack front end control volume strain energy density and the fatigue crack growth rate of the brazed welding joint is established, the defects that a traditional prediction method is single in use condition and low in precision are overcome, and evaluation of the crack propagation rate of the brazed welding joint in a complex loading mode is achieved, and thus the scientific prediction of the fatigue life of the brazed welding joint is achieved.
Description
technical field [0001] The invention relates to the technical field of fatigue life evaluation of special equipment, in particular to a method for predicting the fatigue life of brazed welded joints based on finite volume strain energy. Background technique [0002] Although the traditional fatigue crack growth rate prediction method based on stress intensity, that is, the method based on the Paris equation and its modified equation can effectively predict the crack growth rate to a certain extent, there are still the following problems: 1. The physical meaning is still unclear. 2. 1. There is no unified prediction method for mixed crack behavior, and it needs to be corrected for different situations. 3. The effectiveness of brazed joints has not been verified. Based on Griffith's fracture theory, the crack growth process is essentially a process of energy release, and the energy method is also widely used in the fields of ductile fracture and creep life prediction. For cra...
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IPC IPC(8): G01N3/08
CPCG01N3/08G01N2203/0003G01N2203/0017G01N2203/0066G01N2203/0073G01N2203/0075G01N2203/0676
Inventor 李庆生杨新俊杨思晟凌祥
Owner NANJING UNIV OF TECH