Effects Of Several Factors On Plastic Zone At The Cracking Tip Of Welded Joint With FEM

The technique of numerical simulation has become a new direction in the research field of welding for the future. Based on summarizing the results of the former researchers and dissecting the theory of FEM (finite element method), the paper raises its research contents. Attached to the existence of HAZ (heat affected-zone), it is analyzed with the elastic-plastic FEM that the material parameters, the cracking shapes and thegeometry factors have effects on the plastic zone at the cracking tip of welded joint.The results indicate that these factors affect the size and spread of plastic zone to a different extent. Considered the existence of HAZ or not, the simulated results have a obvious distinction; the increase of the elastic modulus value in the weld metal has a different effect on the change of the plastic zones of the under-matched and over-matched welded joint. The plastic zones evidently diminish from the sharp cracking to the blunt cracking, but the plastic zones slightly increase when the cracking is blunter. On the same conditions, the plastic zone of the three-dimensional model is less than that of the two-dimensional model. The decrease of the plastic zone at the cracking tip reduces the value of the crack growth driving force at the cracking tip, which affects the fracture-resistant capability of welded joint. This provides a certain theory and criterion for us to further research the fracture-resistant capability of welded joint.