Study On The Influence Of Weld Morphology On Weld Strength

Q345R is a low alloy steel,which is generally used to make reactors,heat exchange and liquefied gas tanks and other pressure vessels.Once the fatigue failure of these pressure vessels occurs,it will cause great economic loss and environmental pollution.Welded joints are the most frequently damaged parts of pressure vessels.The welded fatigue strength is the key factor to restrict the fatigue life of pressure vessels.And in the actual production,welding morphology will be retained after welding,so it is urgent to study the influence of welding morphology.In view of the characteristics of fatigue failure of pressure vessels,combined with the actual demand,this paper studies the influence of weld morphology on the stress concentration of welded joints to study its influence on welding fatigue strength.By analyzing the characteristics of welding joint morphology,it can be divided into welding residual height,toe fillet,weld width and wire material.In view of the common knowledge that residual height will increase structural strength,the influence of weld morphology on stress concentration and fatigue life of welded joints is analyzed by theoretical formula.The analysis shows that the theoretical and effective stress concentration coefficients can be reduced by decreasing the residual height and increasing the radius of toe fillet,thus increasing the fatigue life of welded joints.The formula cannot reflect the influence of weld width and wire material on stress concentration and fatigue performance.The theoretical stress concentration coefficient and fatigue life of welded joints are systematically studied by establishing analysis model with finite element analysis software.The results show that reducing residual height and increasing toe fillet radius can both reduce stress concentration factor and increase fatigue life of welded structures.The change of welding width and welding wire material has little influence on the stress concentration coefficient of welded joint.Finite element analysis model for the effectiveness of the problem,in order to ensure the unity of research variables,the welding sample to stress annealing treatment,by means of several groups of typical welding fatigue specimens shall be tested,test results are almost consistent with the finite element analysis results,proved that the analysis model of the reliability,quality evaluation personnel to provide theoretical guidance for the factory.