Numerical Simulation And Analysis Of Temperature Field And Stress Field In Asymmetric Fillet Root Welding Of Medium And Thick Plates

In the fabrication of bridges,ships,heavy equipments and other load-bearing box girder structures,many T-joints with medium plates exist,involving a high number of medium plate fillet welds.The one-side V shaped groove fillet welds present asymmetry in the left and right structures,which results in high difference in thermal conduction between the two sides during root welding and affects the quality of post weld forming.Among these,the fillet root welding is the most crucial part.The corresponding welding quality directly determines the entire welded joint performance.Therefore,it is of great practical significance to study penetration forming of asymmetric fillet welds.In this paper,numerical simulation and experimental study on temperature field and stress field of asymmetric fillet root weld are carried out.The heat transfer and heat dissipation forming law of this special weld was obtained,and the stress-strain and deformation law were explored,which can provide technological reference for engineering construction.Firstly,a new equivalent heat source model,namely the equivalent double Gauss heat source model,was established.The model was based on the Gauss heat source,with consideration to the groove angle effect on the heat source.In order to verify the model accuracy,the temperature field distribution was simulated through the COMSOL multi-physics field software.The differences were compared and analyzed among the common heat source models and the equivalent heat source model for asymmetrical fillet welds.The experimental results confirmed the validity of the proposed model.The thermal cycle curves around the asymmetrical fillet welds were compared and studied.It layid a foundation for revealing the heat transfer mechanism of asymmetric fillet weld under the action of welding arc and the law of penetration forming.Then based on the established equivalent double Gauss heat source model,the welding temperature fields with different structural parameters and welding parameters were simulated.The influences of different parameters on penetration forming of fillet weld was studied quantitatively.When exploring the effect of welding angle on weld formation.Based on the equivalent double Gauss heat source model considering the influence of groove angle,the influence of welding angle on arc heat distribution is introduced.The quantitative relationship between welding angle and arc heat distribution was established,and its accuracy was verified by experiments.The results showed that the groove angle and blunt edge thickness determined the heat input required for penetrating weld,but had little effect on the weld pool profile.Welding current was very important to weld forming,which directly affected the penetration depth of the weld.Welding angle affected the distribution ratio of arc heat.Finally,the stress field model was established based on the temperature field,and the stress,strain,deformation of the weldment were analyzed.The results showed that the residual stress was mainly affected by the longitudinal stress.When the heat source moved near the point on the central line of the weld,its equivalent stress and strain would increase sharply.The side plate of the groove was warped and the maximum deformation was 1.13mm.These rules had positive guiding value for reducing welding stress and deformation of actual asymmetric fillet weld.