Method for accurately controlling normal-temperature sample tensile constant strain rate of universal testing machine

Abstract

The invention provides a method for accurately controlling the normal-temperature sample tensile constant strain rate of a universal testing machine. The method sequentially comprises the following steps: 1, loading at an initial elastic stage; wherein the loading termination condition ensures that the sample does not yield, each loading cycle is single-step loading, and the cross beam displacement speed meeting the target strain rate of the tensile sample is found through the relationship between the strain rate of the tensile sample and the cross beam displacement speed; 2, loading at an initial yield stage, continuing to load on the basis of the elastic stage, considering that the sample is yielded when the strain rate is suddenly increased, and carrying out two-stage loading after the sample is yielded; 3, loading in a stable strengthening stage; 4, loading in a necking stage. The method for accurately controlling the normal-temperature sample tensile constant strain rate of the universal testing machine has the beneficial effects that the strain rate in the tensile process can be accurately controlled, the total error is within 10%, and the measured physical quantity only needs loading force and displacement and time of the sample in a measurement section.

Description

technical field [0001] The invention relates to the field of dynamic testing machines, in particular to a method for precisely controlling the tensile constant strain rate of a normal-temperature sample of a universal testing machine. Background technique [0002] The dynamic testing machine carries out tensile constant strain rate control through closed-loop control method. This control method usually needs to measure multiple physical quantities, including load, beam flexibility, beam velocity, and stress rate, etc., and uses a constitutive method to iteratively calculate the strain rate control. [0003] The dynamic testing machine can control the constant strain rate of the tensile sample, but the control accuracy is low, and the iterative algorithm needs to measure a large number of physical quantities, so the calculation is difficult. Contents of the invention [0004] The invention provides a method for precise control of tensile constant strain rate of a universal...

AI Technical Summary

Problems solved by technology

[0003] The dynamic testing machine can control the constant strain rate of the tensile sample, but the control accuracy is low, and the iterative algorithm needs to measure a large number of physical quantities, and the calculation is difficult

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