Test method for J-R resistance curve of high-toughness material

Abstract

The invention relates to a test method for a J-R resistance curve of a high-toughness material. The method comprises the steps of sample processing, three point bending test, determination of crack length, calculation of J-integration at every load, establishment of a difference function, recursive calculation of crack length and p-V data pairs and construction of the J-R resistance curve. According to the invention, an extensometer is not employed for testing opening displacement and unloading flexibility of a crack mouth; instead, a testing machine is used for direct acquisition of deformation of a three point bending sample and a load-displacement curve in the whole process of fracture; then, the J-R resistance curve of the material is obtained through a series of calculation; therefore, the problem of restriction of testing apparatuses caused by large deformation of a sample in the testing of high-toughness materials is overcome, a J-R resistance curve in the situation of expandedlong size crack is measured, and the test method is applicable to measuring of J-R resistance curves of samples at different temperature and with different dimension.

Description

technical field [0001] The invention relates to a material mechanical performance testing technology, in particular to a testing method for a J-R resistance curve of a high-toughness material. Background technique [0002] In the safety and reliability design and evaluation of pressure vessels and pipelines, the current research and development trend at home and abroad is to design and evaluate according to the criterion of leak before break (LBB: leak before break). The purpose of the LBB analysis evaluation is to confirm that the fluid leakage through the crack can be detected before the crack reaches the limit length of rapid destabilizing growth. Therefore, in the LBB analysis and evaluation, the elastic-plastic fracture mechanics method is mainly used to calculate the stability of the crack growth. For this reason, it is necessary to accurately measure the resistance curve of the material when the crack is extended in a long ductility, that is, the J-R resistance curve....

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Problems solved by technology

[0004] However, with the continuous improvement of engineering structural materials and the improvement of their toughness, when the J-R resistance curve is tested by the elastic unloading flexibility method, it is found that due to the high toughness and high ductility of this type of material, the crack tip is severely passivated and will Ductile crack initiation occurs after extensive yielding

At this time, due to the large macroscopic deformation of the sample, due to the limitation of the extensometer range of the testing machine and the calculation and control software, the complete unloading compliance load-displacement curve during the crack growth process cannot be measured, and only about 1mm can be obtained by test calculation The J-R curve of a small amount of crack growth, which cannot meet the requirements of LBB analysis and evaluation

In addition, because materials such as nuclear power components usually work at higher temperatures, due to the limitation of testing instruments, it is generally difficult to measure the J-R resistance curve of materials at high temperatures using the unloading flexibility method

Moreover, in the integrity evaluation of engineering structures considering seismic dynamic loads, it is necessary to test and evaluate the J-R resistance curve of materials under dynamic loads, so it is difficult to use the unloading compliance method suitable for quasi-static loading

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