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A Dynamic Fracture Evaluation Method for Structures Containing Crack-like Defects

A defect structure and dynamic technology, applied in the direction of applying stable tension/pressure to test the strength of materials, can solve problems such as failure evaluation of failure to fracture, and achieve a wide range of applications and clear physical meaning.

Active Publication Date: 2019-08-30
HEFEI GENERAL MACHINERY RES INST +1
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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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  • A Dynamic Fracture Evaluation Method for Structures Containing Crack-like Defects
  • A Dynamic Fracture Evaluation Method for Structures Containing Crack-like Defects
  • A Dynamic Fracture Evaluation Method for Structures Containing Crack-like Defects

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specific Embodiment

[0033] The present invention is described in further detail below in conjunction with embodiment. It should be understood that the following examples are for illustrative purposes only, but do not limit the scope of the present invention. Specific examples are as follows:

[0034] For a steel impeller, the diameters of the inner and outer holes are 150mm and 400mm respectively, the impeller has 15 blade channels, and the rotational speed is 10000r / min. There are radial cracks 1 on the edge of impeller disc 2 and wheel cover 3, and the depth of crack 1 is 15mm. Assuming that the edge position of crack 1, i.e. the rubbing position 4, has a dynamic rubbing load in the reverse rotation direction, the relationship between the load F and the action time t is F=F max cos(πt / T-π / 2)), where T=1×10 -4 s, F max =1×10 3 N. In order to assess whether the impeller will break and fail under the specific dynamic rubbing load, the method provided by the present invention is now used for ...

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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 dynamic fracture evaluation method for a structure containing crack defects. Background technique [0002] Crack is a kind of extremely harmful defect, and the equipment accidents caused by it account for a large proportion. However, in order to ensure safety, blindly repairing or scrapping equipment with cracks will cause a huge waste of resources. For this reason, it is necessary to analyze and evaluate the crack defects existing on the equipment, eliminate potential dangerous defects, and retain safety-threatening defects, so as to achieve the purpose of ensuring safety and reducing economic losses. [0003] For fracture failure assessment of structures containing cracks, the failure assessment diagram (FAD) method is widely used in the world at present, refer to British R6, my country's GB / T 19624 and other standards. This method considers the two failure crite...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/08
Inventor 吴乔国陈学东范志超聂德福
Owner HEFEI GENERAL MACHINERY RES INST
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