| Structural lightweighting in manufacturing increasingly requires the hybrid application of multiple materials,consequently,new challenges are being imposed on joining technology that enables connecting dissimilar materials with high reliability and convenience.Laser Shock Clinching(LSC)is a new plastic forming technique that connects similar or dissimilar sheets by using laser-induced plasma shock waves to produce plastic deformation and form interlocking structures.Based on that,novel technologies of Laser Shock Curve Clinching(LSCC)and Laser Shock Curve Adhesive-Clinching(LSCAC)are proposed in this paper,which realize the mechanical clinching and hybrid clinching-bonding of double layer foils along curves.The influences of process parameters and material flow behaviors during those processes are analyzed by experiments and numerical simulation,and the joining strength of the joints is also measured by tests.LSCC and LSCA6 would be new methods for joining large or complex structural foils.The main work and conclusions are as follows:(1)Study of Laser Shock Curve Clinching process.The LSCC process is carried out on a material combination of Al/Al/Stainless steel to obtain curved clinched joints with certain interlocking values and no surface damage,and the laser energy-pulse number process window is established.It is found that the plastic strain in the spot overlap area of the Al foil is greater than that in the non-spot overlap area,and the material flow on the inner arc side of the curve is stronger than on the outer arc side.This results in a larger interlocking value in the spot overlap area than in the non-spot overlap area,and a larger interlocking value on the inner arc side of the curve than on the outer arc side.The tensile shear tests indicate that the loading method directly affects the strength and failure mode of the joint,and both the inner arc side of the curve and the end of the joint can withstand larger loads with three clamping methods.(2)Study of the Laser Shock Curve Adhesive-Clinching Process.Experimental studies and numerical simulation of the LSCAC are conducted for Al/Adhesive/Al/Stainless steel material combinations and obtained the curved adhesive-clinching joint.The obtained joint has a larger interlocking value on the inner arc side than on the outer arc side,but tends to generate glue pockets at the undercut to impede the formation of the interlocking structure.After investigating the effects of the curing level of the adhesive,the laser energy,pulse number,the spot path and the spot step arc length,and analyzing the forming defects of a joint,the results show that the adhesive-clinching joint can achieve higher shear strength.(3)Study of the Laser Shock Line-Curve Adhesive-Clinching Process.The line-curveshaped adhesive-clinching joints with no surface damage and good joint strength are obtained by experiments,which further demonstrates the suitability of the LSCAC process for a variety of applications.Besides,the LSCAC is experimentally investigated for different hole widths B,curvature radius R,and lengths L.It was found that as B increases,the interlocking value decreases on both the inner and outer diameter sides.The Al foil is prone to damage when R is small,and it is difficult to form the interlocking structure in this case.As L increases,the Al foil deforms more uniformly,facilitating the formation of joints. |
