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Uniaxial Tensile Test of Metal Round Bar Specimen for Measurement of Stress-Strain in Large Strain Range

A technology of uniaxial tension and measurement method, which is applied in the direction of applying stable tension/pressure to test the strength of materials, etc., which can solve the problems of large error and cumbersome measurement, and achieve the goal of saving measurement time, having operability and saving measurement cost Effect

Inactive Publication Date: 2020-10-16
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Purpose of the present invention, in order to solve the radius of curvature R of the necking outer contour curve at the minimum section place in the current Bridgman method i The measurement is cumbersome and the error is large. A method for measuring the stress-strain curve of the metal round bar sample in a uniaxial tensile test with a large strain range is proposed without directly measuring the radius of curvature R of the necking outer contour curve at the minimum section. i

Method used

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  • Uniaxial Tensile Test of Metal Round Bar Specimen for Measurement of Stress-Strain in Large Strain Range
  • Uniaxial Tensile Test of Metal Round Bar Specimen for Measurement of Stress-Strain in Large Strain Range
  • Uniaxial Tensile Test of Metal Round Bar Specimen for Measurement of Stress-Strain in Large Strain Range

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Embodiment 1

[0035] (1) The present invention takes the low carbon steel round bar sample as an example, adopts figure 1 The shown round bar sample is subjected to uniaxial tensile test, the initial cross-sectional diameter of the round bar sample is 10 mm, and the gauge length section is 50 mm. Such as figure 2 As shown, the extensometer is used to measure and record the load F at each moment from the point of maximum load (neck point) to before fracture i and the instantaneous gauge length l i , formed as image 3 For the load-displacement curve shown, use the optical measurement method to record the minimum section radius a of the necking at each moment i . Where i=0~N, 0 and N correspond to the maximum load point (neck point) and the break point moment respectively;

[0036] (2) After the necking instability, the metal round bar sample always diffuses and deforms at the minimum necking point, and does not participate in the deformation outside the minimum necking point. Such as ...

Embodiment 2

[0051] The finite element analysis software ABAQUS is used to simulate the uniaxial tensile process of the round bar sample. According to the size and conditions of the uniaxial round bar sample in Example 1, the finite element model of the uniaxial tensile test process is established, and the input preset The stress-strain curve of the sample is used as a material model, and the same constraints and loading conditions are used in the simulation analysis and the test of Example 1. One end is fixed in the axial direction, and the other end is loaded with the same speed load as the axial direction of the sample, and the tensile process of the test sample is simulated. According to the method of obtaining data in the tensile test, the difference between the displacements of the two sections of the gauge length section of the simulation result is taken as the displacement value, and the resultant force of the interface of the gauge length section obtained by simulation is used to dr...

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Abstract

The invention relates to a method for measuring the large-stress range stress strain in a uniaxial tensile test of a metal round bar sample. The method comprises the following steps: building a step model for gradual expansion of unstable necking of uniaxial tension of the metal round bar sample; measuring the instant gauge length and the minimum sectional radius at a necking position of the roundbar 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; calculating the curvature radius at the minimum section of the necking position at the moment by a curvature formula; 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-stress range stress straincurve 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 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 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 instabi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/08
CPCG01N3/08
Inventor 管志平孟祥瑞李志刚马品奎宋家旺管晓芳
Owner JILIN UNIV
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