Study On Fracture Performance And Engineering Safety Evaluation Method Of Welded Joints Containing Crack On Fusion Line

As it is the very complex welded structure with mechanical heterogeneity and geometrical uncontinuity,and welding is thermal physicochemistrical process,it makes welded joints heterogeneous in mechanical properties and organization,so welding on the structure of production,processing and practical application have caused great problems.Fracture analysis and integrity assessment of welded joints is a focus issue in research of the current defects assessment method.By using the finite element method,equivalent stress-strain field on the crack tip which was on the fusion line of welded joints containing the mixed modeⅠ+Ⅱcrack on the fusion line had been carefully calculated and analysed.Based on this,considering crack tip displacement filed, characterization features and mode of COD and displacement-component were discussed,while compound angleφabout displacement-component D_Ⅰand D_Ⅱwas also discussed considering the numerical results of equivalent stress-strain field.The results show that,load levels, material matching and material geometric parameter have influence on the crack tip equivalent stress-strain field,the fracture parameter COD,its displacement-component and compound angleφ,displacement-component D_Ⅰis domination for the fracture parameter COD,and plastic zone of welded joints depends on compound angleφ.As a result,the above factors must be considered during fracture analysis and integrity assessment of welded joints containing crack on the fusion line.Based on above numerical results,considering the defects assessment method of uniform materials,engineering estimation formula of COD and compound angleφof the welded joints containing crack on fusion line were obtained when coefficient of engineering estimation formula was modified and data was processed in different load levels,material matching and material geometric parameter.It can be seen that the results of engineering estimation is in good according to that of finite element analysis.So an engineering integrity assessment way,which is rather complete and easy in use for the practical engineering for welded structures is obtained.