Study On Process And Connection Mechanism Of Magnetic Pulse Crimping-welding Of 5A02 Aluminum Alloy And CFRP Tube

Lightweight was particularly important for the future development of automobiles.The use of lightweight materials was a way to achieve lightweight.Carbon fiber reinforced plastics with its high strength,small proportion and other advantages were gradually applied to the automotive industry,which resulted in some connection problems between carbon fiber reinforced plastics and metal materials.Magnetic pulse connection technology could efficiently realize the connection of heterogeneous materials and solve the problem of the connection between carbon fiber composites and metals.In this paper,a new method was proposed to realize the crimping-welding connection between carbon fiber pipes and aluminum tubes by using magnetic pulse technology.Numerical simulation,process test,mechanical properties analysis,microstructure analysis,connection mechanism analysis were carried out in view of the structure of the magnetic pulse crimping-welding connection.Firstly,LS-DYNA commercial software was used to establish a numerical model.The model could be coupled with electromagnetic field and structural field.The magnetic pulse crimping-welding process was simulated by boundary element and finite element method.The distribution of electromagnetic force,inductive current and deformation process of outer tube were analyzed.The results showed that the electromagnetic force points to the central direction of the outer tube.The inductive current on the outer tube was distributed along the loop and was concentrated in the position corresponding to the field shaper.The current and force was concentrated on the outer surface of the tube.The deformation of outer tube was approximately in agreement with the test.When the energy increased,the electromagnetic force of the outer tube increased,the collision velocity with the liner became larger,and the acceleration time was shorter.Secondly,the magnetic pulse crimping-welding process test was carried out under the condition of different discharge energy,according to the results of numerical simulation and pre-test.The acceleration process of the outer tube was obtained by using the Photon Doppler velocity Measurement System(PDV).The influence of the discharge energy on the microstructure and mechanical properties of the crimping-welding structure was investigated.The collision velocity between the tube and the liner was obtained by the PDV test.The error between the collision velocity obtained by the PDV test and the result obtained by the numerical simulation was within 10%.The results of mechanical properties test show ed that high quality connections with tensile strength and torsional strength exceeding the strength of the base material could be obtained under suitable discharge parameters.The microstructure test found that the waveform interface appeared in the welding zone under three kinds of energy.With the increase of discharge energy,the wavelength and amplitude of the waveform increased correspondingly.No obvious delamination defects were found on the surface of carbon fiber circular holes.The surface became smoother than before discharge.The hardness value of the deformation zone increased.The more intense the grain deformation,the greater the corresponding hardness value increased.Finally,the connection mechanism of magnetic pulse crimping-welding structure was revealed.When revealing the distribution of welding area,the realization condition of magnetic pulse welding was analyzed firstly.The suitable collision angle and collision speeding was the necessary conditions for the magnetic pulse welding.Then the distribution of welding area was observed by stripping test.It is found that there are two elliptical welds parallel to the working area of field shaper,rather than annular welding zone.According to the theory of magnetic pulse welding,the reasons for the distribution of the welding region were explained.In the radial cross section,the range of zero-degree collision angle was too large,the remaining space was not enough to meet the deformation of the outer tube.No effective welding zone could be formed in this section,which was in agreement with the test results.In the axial cross section,the range of zero-degree collision angle was small.Then the collision angle increased gradually.There was a suitable collision angle to achieve the welding.When the selected section was parallel to the axial section,the deformation of the outer tube is similar to the deformation of the axial section.With the accumulation of multiple sections,two elliptical welding zone parallel to the field shaper were formed.