A Hyperbolic Backward Measurement Method for Uniaxial Tensile Stress-Strain of Metal Round Bar Specimens

Abstract

The invention discloses a hyperbolic inversion measurement method for the uniaxial tensile stress and strain of a metal round bar sample, which belongs to the technical field of testing the mechanical properties of metal materials. The extended hyperbolic rotating body model only needs to measure the elongation of the gauge length during the stretching process of the round bar sample, and extract the coordinate information of the outer contour curve of the broken test bar, and calculate the necking hyperbolic equation and necking at each moment by back-calculating The minimum section radius, that is, the radius of curvature at the minimum section at the constriction at this moment can be obtained through the curvature radius formula, and finally the true stress and true strain at this moment can be calculated by the Chen Chi method. The invention omits the test and measurement link of the minimum section radius of the necking and the curvature radius of the outer contour in the existing method, and improves the measurement accuracy of the stress-strain curve in a large strain range, which is of great significance for the mechanical performance test of metal materials.

Description

technical field [0001] The invention belongs to the technical field of mechanical property testing of metal materials, and in particular relates to a method for measuring stress-strain curves in large strain ranges in uniaxial tensile tests of metal round bar samples. Background technique [0002] The uniaxial tensile test is a basic method for testing the mechanical properties of metal materials. Usually, the load-gauge length elongation curve of the material is obtained by the uniaxial tensile test, and then the load- The gauge elongation curve is converted to 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, and the specimen gradually changes from the uniaxial stress state to the triaxial stress state after necking. Since the c...

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Problems solved by technology

[0003] The purpose of the present invention, in order to solve the difficult problem that the radius of curvature measurement of minimum section radius of necking and necking outer contour curve at the minimum section place is loaded down with trivial details and error is big in Chen Chi method at present, propose a kind of metal round bar sample uniaxial tensile test large The strain range stress-strain curve measurement method does not need to directly measure the radius of curvature of the minimum section radius of the necking and the necking outer contour curve at the smallest section, but reverses it by extracting the necking outer contour curve of the broken test rod

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