Strain control method of cantilever bending and loading low-circle fatigue test

Abstract

The invention introduces a strain control method of a cantilever bending and loading low-circle fatigue test. The strain control method is characterized in that a COD gauge integral holding knife edge is designed on an original test sample, the one-to-one correspondence between strain at the position of the COD gauge holding knife edge and strain measured by a resistance strain gauge at a surface crack front is established through pre-calibration. According to the correspondence, the strain at the position of the COD gauge holding knife edge is used to replace strain at a test sample surface crack front measured by the resistance strain gauge, and corresponding strain at the position of the COD gauge holding knife edge is inputted into a computer, thereby realizing strain control of the cantilever bending and loading low-circle fatigue test. The method is capable of improving test measuring accuracy, increasing data reliability, saving cost, lowering labor intensity, and solving the technical problem that test samples are scrapped as a testing machine is led to lose stability suddenly when the resistance strain gauge is easily fatigue and damaged in strain sticking method of the resistance strain gauge.

Description

technical field [0001] The invention relates to a test technology, in particular to a strain control method of a cantilever bending load low cycle fatigue test. Background technique [0002] Low cycle fatigue, which refers to higher cyclic stress (generally exceeding the yield strength of the test material) and shorter number of cycles (generally less than 10 5 ) fatigue, also known as plastic fatigue or strain fatigue. The low-cycle fatigue test is a kind of cyclic loading test under the control of the strain mode, using a certain strain ratio and a low test frequency (generally 0.1Hz~1.0Hz), and simulating the working conditions of the testing machine to achieve The purpose of testing low-cycle fatigue performance parameters of materials is to provide test basis for engineering design. In essence, the plastic deformation of low-cycle fatigue is much higher than the elastic deformation. Therefore, in order to meet the reality and ensure the accuracy of control, strain is ...

AI Technical Summary

Problems solved by technology

[0005] The technical problem to be solved by the present invention is to provide a strain control method for cantilever bending loading low-cycle fatigue test, which overcomes the low accuracy of approximately constant strain at the leading edge of low-cycle fatigue surface cracks by continuously adjusting the load or the displacement of the actuator of the testing machine and solve the problem that directly using the resistance strain gauge to control the strain at the front edge of the surface crack can easily make the testing machine out of control and cause the sample to be scrapped

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