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Method for measuring J integration of cracks on basis of digital-image correlation

A technology of digital image, measurement method, applied in the direction of testing material strength by applying stable tension/compression

Inactive Publication Date: 2015-04-08
DALIAN UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, there is still a lack of research on methods for measuring the J-integral using digital image correlation techniques

Method used

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  • Method for measuring J integration of cracks on basis of digital-image correlation
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  • Method for measuring J integration of cracks on basis of digital-image correlation

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Embodiment Construction

[0032] The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0033] The present invention needs to obtain material constants before calculating the J integral containing crack defects. Select 304 stainless steel to prepare standard specimens for tensile experiments, and perform uniaxial tension on the standard tensile specimens to obtain the stress-strain curves and material constants of the specimen materials, including: elastic modulus E = 195.1GPa, Poisson Ratio μ=0.267, yield stress σ 0 =279MPa, yield strain ε 0 = 0.00143.

[0034] Build an experimental system such as figure 1 As shown, the compact tensile standard specimen 1 is prepared, and a 2mm crack is prefabricated, such as figure 2 shown. Before the tensile test, it is necessary to use black and white matte paint to prepare black and white speckles on the surface of the specimen. First, spray a layer of white matte paint ...

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Abstract

The invention discloses a method for measuring the J integration of cracks on the basis of digital-image correlation, belongs to the field of fracture mechanics and engineering application and relates to the method for measuring the J integration of cracks on the basis of digital-image correlation. The method comprises the following steps: by a digital-image correlation technology, measuring and calculating a displacement field and a strain field under different loads on the surface containing crack defects, acquiring information of the displacement field and the strain field, and storing into an Excel; writing an MATLAB program, calling data information in the Excel, carrying out numerical-integration calculation and further obtaining the J integration value of the cracks. The method disclosed by the invention has the advantages that the digital-image correlation, an MATLAB technology and J-integration calculation are combined, the strain of a test piece with the cracks is acquired by the digital-image correlation technology, a calculation result of digital-image correlation is extracted by MATLAB, and numerical integration is calculated; the method has the advantages of high efficiency and strong practicability, is suitable for calculating various test pieces which contain micro-deformation cracks and have elasticity and small-range yield, and is strong in universality.

Description

technical field [0001] The invention belongs to the field of fracture mechanics and its engineering application, and relates to a crack J integral measurement method based on digital image correlation. Background technique [0002] The J-integral is an important fracture parameter that can quantitatively describe the strength of the stress-strain field at the crack tip, and is widely used in predicting the stability and propagation of cracks. At present, the methods of obtaining J integral mainly include theoretical analysis, model simplified calculation, numerical simulation and experimental measurement. Both model simplification and numerical simulation are simplified calculations of actual problems, and there are certain deviations from the actual situation. Although the theoretical analysis has strong rigor, the derivation process is cumbersome, which is not convenient for engineering practical application. The experimental measurement methods mainly include flexibilit...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08
Inventor 蒋玮黄裕龙周璇蒋险峰
Owner DALIAN UNIV OF TECH
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