Arc backstepping measuring method of uniaxial stretch-strain of metal round bar test specimen

Abstract

The invention relates to an arc backstepping measuring method of uniaxial stretch-strain of a metal round bar test specimen, and belongs to the technical field of metal material mechanical property testing. The arc backstepping measuring method is based on an arc rotating body model with step-by-step expansive uniaxial stretching instability necking of the metal round bar test specimen, scale distance elongation in the stretching process of the round bar test specimen is only needed to be measured, coordination information of the outer contour of the test bar after breaking is extracted, and arc radius of necking and minimum cross section radius of necking at each moment are calculated through backstepping and directly substituted into a Bridgman algorithm to calculate real stress and realstrain at the moment. According to the arc backstepping measuring method, the test and measuring link of the minimum cross section radius of necking and the curvature radius of the outer contour in an existing method are eliminated, measuring precision of a stress-strain curve of a large strain range is improved, and the arc backstepping measuring method has significance for metal material mechanical property testing.

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] Purpose of the present invention, in order to solve the difficult problem that the measurement of radius of curvature 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 Bridgman method at present, propose a kind of uniaxial tensile test of metal round bar sample Large 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 by extracting the necking outer contour curve of the broken test rod

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