Numerical Simulation On Ductile Farcture Considering Micro-Plastic Damage

The application of the steel component in the production and life abroad, thebigness, high intensity, complexity of the steel structure, inclemency of thecircumstance makes the issues of safety to be focused. On the other hand, in theprocess of using the steel structure, bringing the material's potential into play furthestcan save a great deal of funds, manpower and material resources. So the researchesabout the ductile fracture have not only the value of theory, but also the underlyingmarket benefit. With the development of metallurgy and the improvement ofmetallurgic technology, the ductility of material is boosted up, so the research of thematerial's invalidation is transferred from the brittle fracture to the ductile fracture.From the middle age of 20th century, the ductile distortion and fracture have beenlucubrated broadly in many fields such as mechanics and metallurgy etc., and manysimulated models also have been put forward. Now the ductile fracture model whichis applied broadly and whose theory is consummated correspondingly is theGurson-Tvergaard Model (G-T Model) that was brought forward by Gurson in 1975and later amended by Tvergaard. This model describes the relation between theductile distortion and the extending of the voids. In the last decade of the 20th, withthe application and development of the computer technology, the G-T Model has beenput to use in more fields.Many engineering materials contain the plastic damage when they endur loading,for the safety and credibility of the materials it is valuable and important to describethe effect of the material's performance and ductile fracture process made bymicro-plastic damage. In this research X65 pipeline steel is chosen as the test material,and uniaxial tension test and COD test of X65 are made. Considering the inner microplastic damage and using the finite element method (in this research thecomputational cell model is used) to simulate the process the ductile fracture. Theparameters controlling ductile crack growth are gotten from the resistance curve ofstandard three point bending specimen, then the P-V curve of the tension test ispredicted based the cell model. Programs of solving ductile fracture parameters andprediction programs are made and proved true through experiments. Stress fields areanalyzed on the basis of finite element analyses. The results indicate that the predictedresults is in a good agreement with the experiment, and the cell model gives a gooddescription of ductile crack growth, prediction between different tests of the samematerial using the parameters is reasonable.