Method for obtaining J resistance curve of ductile material by I type crack elastoplasticity theoretical equation

Abstract

The invention discloses a method for obtaining the J resistance curve of a ductile material by an I type crack elastoplasticity theoretical equation. The method comprises the following steps: performing tensile or bending test on an I type through crack sample to obtain the P-h curve of the sample, substituting the P-h curve into the elastoplasticity theoretical equation to obtain the real-time crack length and J integral of the sample corresponding to any loading point, and performing crack propagation correction on the J integral result by an incremental technology to obtain the J resistancecurve of the material. The method avoids an error caused by the approximate solution of the plastic factor eta p during the calculation of the J integral by using traditional test methods, and is convenient to carry out the fracture toughness test of the ductile material at a high temperature, under irradiation or in other special environments.

Description

technical field [0001] The invention relates to the theory and method of fracture toughness testing of ductile materials, and is especially convenient for testing the fracture toughness of materials in special environments such as high temperature, and specifically relates to a method for obtaining the J resistance curve of ductile materials with the elastic-plastic theoretical formula of type I cracks. Background technique [0002] In nuclear power, petrochemical, aerospace and other fields, there are a large number of components that serve under high temperature, high pressure, radiation and other conditions. As time goes by, the materials will inevitably undergo corrosion, oxidation and other phenomena, resulting in material degradation and damage. Carrying out the fracture toughness test of service materials is of great significance to the reliability and safety assessment of structures. [0003] After years of development, there are many classic fracture toughness testi...

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Problems solved by technology

[0003] After years of development, there are many classic fracture toughness testing methods such as unloading flexibility method, load separation method and potential method. However, the existing methods have certain difficulties in measuring the real-time crack length of the sample.

For example, the unloading flexibility in the unloading flexibility method is sensitive to the crack length, and the crack length prediction deviation is often too large in the application; the load separation method needs to use an empirical deformation function when predicting the real-time crack length of the sample, and needs to test Crack length at the initial and unloading time; the relationship between potential and crack length is an empirical formula with a narrow scope of application when measuring the real-time crack length of the sample by the potentiometric method, and the test and crack length estimation are easily affected by environmental factors

In addition, the above methods all need the plastic factor η when calculating the J integral p The solution of , however, the exact solution of η p It is more difficult, and the results of finite element approximate regression are often used

In 1981, Kumar et al compiled the Handbook of Elastic-Plastic Fracture Mechanics (EPRI Handbook), and proposed a method for estimating the J-resistance curve of ductile materials by combining finite elements and experiments. The implicit equation of the finite element results requires interpolation of a large number of discrete table data, and then the J resistance curve of the material can be obtained by drawing the crack thrust diagram. The process is cumbersome and the influence of crack growth on the J resistance curve cannot be considered.

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