Method for precisely determining hardening index of material

A strain hardening index, accurate technology, applied in the direction of applying stable tension/pressure to test the strength of materials, etc., can solve the problem that the error of the measured value cannot be guaranteed

Inactive Publication Date: 2012-07-25
XI'AN PETROLEUM UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Although there are many methods for determining the hardening index, including the maximum uniform elongation method, the maximum load method, the two-point method, the four-point method, the seven-point method, etc., the measurement error of these methods cannot be guaranteed

Method used

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  • Method for precisely determining hardening index of material
  • Method for precisely determining hardening index of material
  • Method for precisely determining hardening index of material

Examples

Experimental program
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Effect test

Embodiment 1

[0045] For a medium-carbon low-alloy steel obtained by normalizing, the structure is ferrite + pearlite, including the following steps:

[0046] First, draw the tensile curve σ-ε according to the tensile test data;

[0047] Second, determine the "starting point of strain hardening" on the tensile curve drawn in the previous step. The specific method is:

[0048] Because the material has an obvious yield point, the point at which the stress begins to rise monotonously after the material yields is taken as the "starting point of strain hardening", and the corresponding strain at this point is 0.0055;

[0049]Third, determine the "end point of strain hardening" on the tensile curve drawn in the first step,

[0050] The stress reaches the maximum value σ max The corresponding point is "the end point of strain hardening", and the corresponding strain of this point is 0.1135;

[0051] Fourth, determine two "key points" on the stretch curve,

[0052] The first "key point" should ...

Embodiment 2

[0071] For a medium-carbon low-alloy steel obtained by quenching and then tempering, the structure is ferrite + upper bainite + tempered sorbite, including the following steps:

[0072] First, draw the tensile curve σ-ε according to the tensile test data;

[0073] Second, determine the "starting point of strain hardening" on the tensile curve drawn in the previous step. The specific method is:

[0074] Because the material has an obvious yield point, the point at which the stress begins to rise monotonously after the material yields is taken as the "starting point of strain hardening", and the corresponding strain at this point is 0.01026;

[0075] Third, determine the "end point of strain hardening" on the tensile curve drawn in the first step,

[0076] The stress reaches the maximum value σ max The corresponding point is "the end point of strain hardening", and the corresponding strain of this point is 0.0722;

[0077] Fourth, determine two "key points" on the stretch cur...

Embodiment 3

[0097] For a medium-carbon low-alloy steel that is first quenched and then tempered, the structure is complete martensite, including the following steps:

[0098] First, draw the tensile curve σ-ε according to the tensile test data;

[0099] Second, determine the "starting point of strain hardening" on the tensile curve drawn in the previous step,

[0100] Because the material has an obvious yield point, the point at which the stress begins to rise monotonously after the material yields is taken as the "starting point of strain hardening", and the corresponding strain at this point is 0.01202;

[0101] Third, determine the "end point of strain hardening" on the tensile curve drawn in the first step,

[0102] The stress reaches the maximum value σ max The corresponding point is "the end point of strain hardening", and the corresponding strain of this point is 0.0643;

[0103] Fourth, determine two "key points" on the stretch curve,

[0104] The first "key point" should be: ...

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Abstract

The invention relates to a method for precisely determining a hardening index of a material. The method comprises the following steps of: 1, drawing a tensile curve Sigma-Epsilon according to tensile test data; 2, determining a starting point for generating a strain hardening action and determining a terminal point for generating the strain hardening action; 3, determining two key points (Epsilon 1, Sigma 1), (Epsilon 2, Sigma 2) on the tensile curve; and 4, dividing a strain hardening interval into three sections by using the key points, respectively determining and comparing strain hardening indexes of the three sections, dividing one section with the maximum strain hardening index into three sections, respectively determining the strain hardening indexes of the three sections, and comparing the maximum strain hardening index of the three current sections with the maximum strain hardening index of the last circulation, if the error is in a specified range, determining the maximum strain hardening index of the three current sections as the strain hardening index of the material, and if the error is beyond the specified range, circulating till the error meets the provision. The method disclosed by the invention has the characteristics of high precision, controllable precision according to the demands and freedom of influences of personal factors.

Description

technical field [0001] The invention relates to a method for accurately determining the hardening index of a material, in particular to accurately determining the hardening index of a material, and is mainly used in various structural materials. Background technique [0002] The hardening index reflects the strain hardening of the material when it continues to deform after it begins to yield. It determines the maximum stress when the material begins to shrink. If the stress exceeds this stress, the material will shrink and become thinner locally during stamping. That is, the hardening index determines the maximum uniform strain that the material can produce. This value is very important in cold forming processes such as drawing, extrusion, etc., and also determines the strength of the machine parts to withstand accidental overload, because relatively A large strain hardening index value can prevent some weak parts of the machine from continuing plastic deformation, thereby e...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08
Inventor 许天旱
Owner XI'AN PETROLEUM UNIVERSITY
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