Optimization Design And Experimental Research Of Double H-type Coil Of Electromagnetic Pulse Welding

With the development of modern industry,the connection between dissimilar metals is inevitable.However,the physical and chemical properties of different metals are usually very different.Traditional fusion welding and other methods are difficult to achieve reliable connection between dissimilar metals.Electromagnetic pulse welding(EMPW)technology is a new solid-state welding process,it has outstanding advantages in dissimilar metal welding,and has broad application prospects.Welding coil has important functions of conducting current and establishing magnetic field,and is a key component in electromagnetic pulse welding system.However,the multi-turn coil has problems with reinforcement,insulation,and heat dissipation,while the single-turn coil,generally has the problem of low energy utilization.The double H-type coil has simple structure and high energy utilization rate,and can be widely promoted in the industrial application of EMPW.But at present,most of the research on double H-type coil focuses on the influence of discharge voltage and sheets'gap on welding effect,and no in-depth analysis of its structure and influence has been carried out.As a result,the optimal design of double H-type coil lacks reliable theoretical basis and scientific support,limiting its wide application.Therefore,this article has launched the optimization design and experimental research of the welding coil,so as to provide a reference for the optimization design of coils.A welding effect evaluation model based on the simulation processing parameters is proposed in combination with the welding window.The main work and research achievements are as follows:(1)Theoretical analysis of the force and structural strength of the double H-type coil.A 3D finite element model of the coil and the plate,which coupling circuit-magnetic field was established,and the overall force of the coil was analysed.It is found that the force of the coil is mainly concentrated in the central area of the coil,then it is easy to bend.Therefore,a reinforcement box is used to strengthen the coil,and then the electromagnetic-structure loosely coupled 2D finite element model of the coil and the fixed box was established.The stress distribution of the coil and the fixed box with different cross-sectional widths was analysed.When the width of the coil section is greater than 2.5 mm,the welding coil can basically meet the strength requirements for welding without breaking,and the corresponding experimental verification has been obtained;the experimental results also show that when the coil section is too narrow(<7.5 mm),the coil will still bend and affect the service life of the coil.Therefore,under the experimental conditions in this article,a wider coil(>7.5 mm)should be used in electromagnetic pulse welding.(2)Combining welding window theory and simulation process parameters,a simulation evaluation model of welding effect is proposed.A finite element model of the coil and the sheets was established,which sequential coupling circuit?magnetic field and structure field,to simulate the EMPW process.V_c and?of the collision front point were obtained,and combined with the welding window theory,a simulation evaluation model of the welding effect based on the V_c/?trajectory curve based on the simulation results is first proposed.Based on the established finite element simulation model and welding effect simulation evaluation model,the process and welding effect of EMPW of copper-aluminum sheet under different discharge voltages were simulated and analysed.The corresponding experimental study of EMPW was carried out,and the macro and micro morphology and mechanical properties of the welded joint were observed.The simulation and experimental results were compared and analysed to verify the effectiveness of the evaluation model of the welding effect,and it was further corrected to make it more accurate.(3)Explore the influence of the double H-type coil structure on the welding effect,and propose an asymmetric double H-type structure coil.Based on the corrected simulation evaluation model,the simulation and experimental analysis of the welding effect of symmetrical double H-type coils with different cross-sectional widths was carried out.The results show that the cross-sectional width of the welding coil will affect the welding effect.A coil with a moderate coil width has a relatively large collision angle?and an increase rate of?,and the collision speed and the movement speed V_c of the collision front point are also large,the time interval corresponding to the V_c/?trajectory curve in the welding window is longer,and the area where the metallurgical bond is formed is wider,and the welding effect is better.Therefore,it is proposed to combine different widths to form an asymmetric double H-type coil,so as to extend the service life of the coil and improve the welding effect.After analyzing,it is found that the by using the asymmetric double H-type coil with a wider width on the side of the copper sheets has a better welding effect.