Method for Measuring Stress and Strain in Large Strain Range in Uniaxial Tensile Test of Metal Plate Specimens

Abstract

The invention relates to a method for measuring the large-stress range stress strain in a uniaxial tensile test of a metal plate sample. The method comprises the following steps: building a step modelfor gradual expansion of unstable necking of uniaxial tension of the metal plate sample; measuring the instant gauge length and the minimum sectional width at a necking position of the plate sample after extension instability; building an interpolation curve expression of the necking profile on the basis of necking step coordinates of the necking step model at each moment; solving the parametersof the necking step model according to the mechanical relationship of necking in the width direction and the thickness direction and the principle of volume conservation; finally calculating the actual stress and actual strain at the moment through a Bridgman method. By adopting the method, the test measuring link for the necking outer profile curvature radius in the existing method is omitted, and the measuring accuracy of a large-strain range stress-strain curve is improved, so that the method has important significance to the mechanical performance test of metal materials.

Description

technical field [0001] The invention relates to the test of mechanical properties of metal materials and the constitutive relationship of materials, in particular to a method for measuring stress-strain curves in large strain ranges in uniaxial tensile tests of metal plate samples. Background technique [0002] The uniaxial tensile test is a basic method for testing the mechanical properties of metal materials. Usually, the load instantaneous gauge length curve of the material is obtained by the uniaxial tensile test, and then the load-instantaneous gauge length curve is assumed to be uniformly deformed within the gauge range of the sample. The distance-length curve is converted into a stress-strain curve. However, the sample begins to shrink after the maximum load point, and the sample deforms unevenly within the gauge length range. Therefore, it is inaccurate to directly convert the load-instantaneous gauge length curve to the stress-strain curve after tensile instability...

AI Technical Summary

Problems solved by technology

The measurement of the radius of curvature at the minimum section of the stretched necking profile of the sheet is cumbersome, and the measurement accuracy cannot be guaranteed. This is the reason why the Bridgman method has not been applied to the stretched sheet.

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