Experimental Research And Numerical Simulation Of Laser Shock Welding Of Ni And Dissimilar Metal Foil

In view of the great difference in melting point,thermal expansion coefficient and thermal conductivity between Ni and other materials,it is difficult to realize welding.In this paper,a new method of laser shock welding(LSW)is proposed to realize welding.This dissertation proposes a new method of LSW to achieve welding to achieve welding.The interface morphology,jet phenomenon and mechanical properties of welded joints of Ti/Ni sheet welded by LSW under different process parameters were studied.The element diffusion phenomenon near the bonding interface of LSW Al/Ni samples was studied by molecular dynamics simulation and verified by experiments.Finally,the welding process and welding mechanism are studied by SPH simulation,and it is verified that the experimental results are basically consistent with the numerical results.The main research contents and results of thisarticle are as follows:First,the welded between Ti and Ni was achieved using a LSW process.The experimental results show that the springback phenomenon occurs in the center of the solder joint,which is mainly due to the difficult discharge of the jet and gas near the welding area and the transmission and reflection of the shock wave.It is found that the waveform of the welding interface changes from flat to small microwave and further to obvious with the increase of laser energy.With the flight distance increases,the wavelength and amplitude of the Ti/Ni bonding interface first increase and then decrease,and the springback degree of the Ti/Ni bonding interface decreases gradually.With the thickness increase of Ti,the wavelength and amplitude and the springback degree of the central area will gradually decrease.With the increase of the substrate thickness,the welding interface waveform increases and the springback degree of the central area decreases obviously.The tensile shear test and nano-indentation tester measurement experiments revealed the mechanical properties of the welded specimens.Secondly,the LSW method is used to realize the welding of Al and Ni.The mechanism of atomic diffusion welding of Al and Ni in the LSW process is revealed.The results of molecular dynamics simulation and EDS line scanning analysis show that there is a certain element diffusion between Al and Ni in LSW.The mechanism is that the instantaneous environment of high temperature and pressure will be produced in the process of high speed collision,which promotes the diffusion of atoms.Simulation shows that the diffusion rate of Al atom is higher than that of Ni atom,while Ni atom diffuses more easily and diffuses deeply into Al atom.The diffusion difference decreases with the increase of loading speed.Experimental comparison found that Ti/Ni welding effect is better than Al/Ni under the same process parameters.Finally,the smooth fluid dynamics(SPH)method was used to simulate LSW.The SPH method was used to research the process of LSW,springback,cracking phenomena,and the spray phenomenon that was not observed in the experiment.The results show that the Ti/Ni bonding interface will change from straight to wavy with welding propagates from the center to the edge,which may be the result of the joint action of Kelvin-Helmholtz flow instability mechanism and composite plate indentation mechanism.The wavelength and amplitude of the Ti/Ni bonding interface waveform increase with the initial impact velocity of the composite plate increases.With the thickness increase of Ti,the wavelength and amplitude of the Ti/Ni will continue to decrease.As the flight distance increases,the wavelength and amplitude will increase and then decrease.The welding characteristics of Ti/Ni bonding interface are studied and analyzed.The results show that the effective plastic strain,high temperature and internal energy of the welding interface are mainly distributed in the wave of the interface,the area near interface has shear stress in the opposite direction,and the pressure near the collision point is as high as GPaThis dissertation systematically studies LSW Ni and dissimilar metal foils,which provides theoretical and experimental guidance for its industrial application.