Preparation and calculation method of brazed joint fracture toughness sample

Abstract

The invention provides a preparation and calculation method of a brazed joint fracture toughness sample. A sample is prepared by smearing a brazing flux in the brazing process, and the tip of an initial crack is located in the range of a brazed joint micro-area. In the aspect of calculating the fracture toughness, the nanoindentation size effect is comprehensively considered, and the elastic modulus, the yield strength and the hardening index of a diffusion affected zone (on a fracture path) of the brazed joint are calculated. A loading linear displacement control mode is adopted, and a J-[delta]a resistance curve is obtained according to an unloading flexibility method through multiple times of loading / unloading. The fracture resistance J0.2 BL is determined based on a passivation line equation of the power hardening elastic-plastic constitutive structure. The method solves the problems that in a conventional fracture toughness experiment, the initial crack size of a current machining mode is far larger than that of a brazed joint, a crack tip is difficult to form at the brazed joint, and reliable performance parameters for resisting crack propagation are difficult to obtain. According to the invention, the problems of experiment and analysis methods for measuring the fracture toughness of the brazed joint are solved, and the method is crucial to further research on the fracture mechanism of the brazed joint.

Description

technical field [0001] The invention relates to the technical field of fracture toughness testing, in particular to a sample preparation and calculation method for the fracture toughness of brazed joints. Background technique [0002] Brazing technology has the advantages of small welding deformation, high dimensional accuracy, and smooth welding structure. Therefore, it is widely used in the welding process of compact components. A large number of experimental studies have shown that components are prone to failure at brazed joints under extreme service conditions such as high temperature and high pressure. The brazing joint is the weakest part of the whole component, which determines the safety and reliability of the long-term operation of the component. During the brazing process, the limitations of the solder wetting properties and the brazing process, as well as the Kirkendall phenomenon will produce defects such as microcracks and holes, which are the main inducing f...

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Problems solved by technology

[0004] The problem to be solved in the present invention is to propose a sample preparation and calculation method for the fracture toughness of brazed joints in view of the deficiencies in the prior art, which is used to solve the problem of crack propagation in the brazed joint until the component breaks in the brazed structure and difficult It is difficult to obtain the mechanical properties of the micro-zone at room temperature, it is difficult to form a crack tip at the brazed joint, and it is even more difficult to obtain a reliable performance parameter that resists crack growth.

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