| As is known to all,reducing the residual stress and deformation,and improving the microstructure properties of the joints are served as the best way to be put forward recently,which can improve the welding quality and thereby reduce the accident rate.During the experiment,the real-time ultrasonic impact is exerted on the back of the weld,which produces the positive tensile plastic deformation so as to reduce the welding deformation and residual stress.Meanwhile,the vibration caused by the ultrasonic shock also plays an important role in improving the microstructure and properties of the weld.Because most of the welds in our industrial production are not exactly the single position welding seams,but the combination of two or more position welding.So study on the influence which the ultrasonic impact has on the welding deformation,residual stress and the organization and performance of the joints becomes the focus of this topic in different welding positions.In view of this,the research mainly studies on the regularities of the effect which the ultrasonic shock has on the deformation and stress and so on,when it is separately applied at a distance of 10mm(D0=10mm),30mm(D0=10mm)and 50mm(D0=10mm)away from the axis of the welding arc,respectively in horizontal fillet position welding(PB),horizontal position welding(PC),vertical up welding(PF).The study plan include three parts: experiment in the laboratory,experiment in the production environment of shipyard and numerical simulation.From the analysis of the experiment results in laboratory,we can conclude that during PC-position welding process,when the ultrasonic shock is carried on the position where the D0 is respectively equal to 50 mm which makes significant effect,real-time ultrasonic impact treatment can reduce the transverse and longitudinal deformation,transverse and longitudinal residual stress by 68.08%,27.38% and 21.41%?64.38% respectively,when compared to that without ultrasonic impact.During PB-position welding process,when the ultrasonic shock is carried on the position where the D0 is respectively equal to 10 mm,30mm and 50 mm,the angular distortion is reduced by 25%,10% and 25% when compared to that without ultrasonic shock.And during the PF-position welding process,the transverse and longitudinal deformation,transverse and longitudinal residual stress with the ultrasonic impact is respectively reduced by 60.42%,38.26% and 11.22%,22.81%.Moreover,the real-time ultrasonic impact treatment will result in the decrease of weld width and increase of the reinforcement.When the distance D0 is equal to 10 mm,the real-time ultrasonic impact treatment is contributed to refining the columnar crystals.When the distance D0 is equal to 50 mm,the hardness of the whole joint tends to homogenize.Comparing the experiment results from shipyard and laboratory,we can conclude that during PC-position welding process,when the ultrasonic shock is carried on the position where the D0 is respectively equal to 50 mm which makes significant effect.Real-time ultrasonic impact treatment can reduce transverse deformation better than longitudinal.During the PF-position welding process,D0 is respectively equal to 10 mm and 30 mm,the reduce effort is significant.Real-time ultrasonic impact treatment can reduce transverse deformation better than longitudinal.The trend from shipyard result and laboratory result is the same.For the numerical simulation part,to simulate the complex process of a combination between heat-transfer and mechanics for welding,the temperature distribution was got from Fourier equation by Finite Element Method(FEM)firstly.Then the results are applied as temperature load to welding line with nonlinear mechanical properties.For obtaining the final stress and displacement after the whole welding process,birth-death element method was utilized to assist simulation of horizontal position welding and vertical position welding.Except for analysis corresponding to experimental results,more situations with different load distance and load scale were studied with the application of numerical simulation.From the analysis of the numerical simulation results,we can conclude that during PC-position welding process,when imposed loads is 100N(40% load rate)the ultrasonic shock is carried on the position where the D0 is respectively equal to 30 mm makes significant effect.During PF-position welding process,when imposed loads is 50N(20% load rate)the ultrasonic shock is carried on the position where the D0 is respectively equal to 30 mm makes significant effect.Comparing the numerical simulation results and experiment results from laboratory,we can conclude that during PC-position welding process,when the ultrasonic shock is carried on the position where the D0 is respectively equal to 50 mm which makes significant effect.Real-time ultrasonic impact treatment can reduce transverse deformation better than longitudinal.During the PF-position welding process,the reduce effort is significant.Real-time ultrasonic impact treatment can reduce transverse deformation better than longitudinal.The trend from numerical simulation results and laboratory result is the same. |
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