Heterogeneous material crack stress intensity factor calculation method applying DIC technology

Abstract

The invention discloses a heterogeneous material crack stress intensity factor calculation method applying a DIC technology. The heterogeneous material crack stress intensity factor calculation methodcomprises the steps of: preparing a standard compression or tensile test piece of a heterogeneous material, carrying out unidirectional compression or stretching on the standard compression or tensile test piece to obtain an elastic modulus and a Poisson's ratio; preparing a heterogeneous material standard fracture test piece with cracks, and preparing speckles for carrying out a DIC test on thesurface of peripheral regions of the cracks; implementing a fracture experiment on the test piece to obtain a displacement field and a crack size of the region near a crack tip under different loads;selecting different integral paths, dividing subunits in an integral region, and calculating J-integral values of the subunits; performing filtering processing on the J-integral values, then performing superposition to obtain J-integral values on the integral paths, and converting the J-integral values into stress intensity factors K; repeating the above steps, calculating J-integral values underdifferent loads / displacements, and acquiring the stress intensity factor K at each loading moment. The heterogeneous material crack stress intensity factor calculation method has the advantages of high efficiency, high precision, high universality and the like.

Description

technical field [0001] The invention relates to the field of fracture mechanics and engineering technology, in particular to a method for calculating stress intensity factors of cracks in heterogeneous materials using DIC technology. Background technique [0002] The stress intensity factor K of crack problems in complex structures is difficult to calculate with theoretical expressions, but if the displacement field or stress field near the crack tip in complex structures is obtained by other methods, the stress intensity factor K of cracks can be calculated. In recent years, the digital image correlation (DIC) method has been widely used in the displacement field measurement of materials and components. This method has the advantages of high precision, simple use, non-contact, and post-processing of displacement data. By using the DIC method to measure the displacement field on the surface of the component, the stress intensity factor of the crack in the complex structure ...

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Problems solved by technology

However, if this method is applied to the J-integral calculation of the crack problem in heterogeneous materials, there are still the following problems: ①Because the existing DIC method cannot accurately measure the displacement field of the free boundary of the object, resulting in the subunits near the crack The J-integral value cannot be calculated accurately; ②Because there are often microcracks and micropores on the surface of heterogeneous materials, and the roughness is high, the stress field around the microcracks and micropores often has strong oscillations, In turn, it affects the calculation accuracy of the J-integral and the stress intensity factor K of the crack problem in heterogeneous materials, and even singular values ​​appear, so that it cannot be applied to engineering calculations

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