Assessment method of dynamic fracture containing crack-like defect structure

Abstract

The invention relates to an assessment method of a dynamic fracture containing a crack-like defect structure. The method comprises the steps of testing a relation curve of a true stress sigma true-true strain epsilon true of a structural material under different strain rates, and quasi-static yield strength sigma y; testing dynamic fracture toughness KId and quasi-static fracture toughness KIC ofthe structural material under different loading rates; fitting and building a relation between dynamic yield strength sigma yd and the strain rates, a constitutive relation among an equivalent stresssigma eq, an equivalent strain epsilon eq and an equivalent strain rate, and a relation between the dynamic fracture toughness KId and the loading rates, thus obtaining a time course change curve of astress intensity factor KI and the equivalent strain epsilon eq of a crack tip node containing the crack structure, and a time course change curve of the loading rates and the strain rates of the crack tip node; calculating fracture ratios Kr and load ratios Lr at different moments, building a dynamic failure assessment diagram, and comparing the (Lr, Kr) obtained through calculation as assessment points with a failure assessment curve. The assessment method of the dynamic fracture containing the cracklike defect structure provided by the invention has the advantages that the influence of thestrain rates and the loading rates borne on the material at the crack tip position under the dynamic load action is introduced, so that the failure assessment of the dynamic fracture containing the cracklike defect structure is realized.

Description

Technical field [0001] The invention relates to the technical field of safety engineering, in particular to a method for dynamic fracture assessment of structures containing cracks. Background technique [0002] Cracks are a very harmful defect, and equipment accidents caused by them occupy a large proportion. However, in order to ensure safety, blindly repairing or scrapping equipment containing cracks and defects will cause a huge waste of resources. For this reason, it is necessary to analyze and evaluate the crack-like defects existing on the equipment, eliminate potentially dangerous defects, and retain defects that do not threaten safety, so as to achieve the purpose of ensuring safety and reducing economic losses. [0003] 1. For the fracture failure assessment of structures with crack-like defects, the failure assessment diagram (FAD) method is generally used internationally, see British R6, my country GB / T 19624 and other standards. This method considers two failure crit...

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Problems solved by technology

However, this method also has shortcomings. For example, only the static load of the structure is considered in the assessment of fracture failure, and the influence of the strain rate and loading rate on the material at the crack tip under the action of dynamic load is not involved, so it cannot be analyzed. Reasonable and accurate assessment of fracture failure of structures containing cracks under dynamic loads

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