Method for controlling whole-course displacement in program-controlled metal material stretching test

Abstract

The invention provides a method for controlling whole-course displacement in a program-controlled metal material stretching test. The control method is arranged is a test application program of an electro-hydraulic servo or electronic universal testing machine; the control method comprises the following steps of: displacement control in the first stage, displacement control in the second stage, displacement control in the third stage and the displacement control in the fourth stage. The method has the effects that the control method provides a mathematic model which automatically computes theflexibility of the system in the testing process, and the model is simple and reliable and aims at the system flexibility computation on each testing sample. The whole test is carried out automatically, great convenience is brought to the testing personnel, and the working efficiency and accuracy of the yield strength test are improved obviously. The method is applicable to the requirements on thestretching rates at different stages of various metal material samples; furthermore, rate conversion is smoothly transitional before the yield stage is finished; and the discontinuity is not introduced on the stress-strain curve. The method is applicable to the production, research and technical reconstruction on a stretching testing machine.

Description

technical field [0001] The invention relates to a test method in the material science test technology, in particular to a method for controlling the whole process displacement of a metal material tensile test under program control. Background technique [0002] The tensile test rate has a significant effect on the yield strength test of metallic materials. Although many national and international standards for tensile tests around the world have stipulated the tensile rate, even if different laboratories use the same tensile rate, for example, enter the yield with a constant 2mm / min beam separation rate before yielding stage, the measured yield strength will have greater dispersion. This is because most laboratories do not consider the effect of system compliance on the actual deformation rate on the specimen. [0003] If the strain rate control method based on the feedback of the extensometer is used to eliminate the influence of the flexibility of the tensile testing mac...

AI Technical Summary

Problems solved by technology

The variation of the tensile rate of the high-flexibility test system may even reach hundreds of times, which will inevitably affect the accuracy of the test results

[0005] Because it is generally believed that the system flexibility testing process is complicated, few people consider the influence of system flexibility at present, so that the test results made by different testing machines are not comparable

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