Papers by Author: T. Kato

Abstract: To simplify the recycling of automobiles, aluminium alloy sheets were joined by means of a self-piercing rivet. Although steel rivets used in conventional self-pierce riveting are removed from the aluminium alloy sheets in recycling, the removal is not required for aluminium alloy rivets. The joined sheets with the rivets are directly melted due to the same material, aluminium. For the joining of aluminium alloy sheet by the aluminium rivets, the joinability was improved by the designed shape of the rivet and die. To pierce the upper sheet, the diameter and edge angle of the rivet are modified. The diameter of the depth and the cavity of the die were also designed from trial and error using finite element simulation. The effectiveness of the designed rivet and die were evaluated from an experiment on riveting. The aluminium alloy sheets were joined by the optimised aluminium alloy self-piercing rivet and their effectiveness measured.

Abstract: The aluminium alloy and mild steel sheets were joined with mechanical clinching. Deforming behaviour of the two sheets during the clinching was observed from finite element simulation and an experiment to avoid defects. The fracture of the upper sheet, necking and separation are caused by the small upper sheet thickness in the thick total thickness, the small lower sheet thickness in the thick total thickness and the small lower sheet thickness, respectively. The joining range for the combination of the upper aluminium alloy sheet of and the lower steel sheet of is larger than that of the reverse combination. The effect of the difference between the flow stresses of the two sheets on the deformation behaviour was examined.

Abstract: The joinability of three aluminium alloy sheets using a self-piercing rivet was evaluated from a finite element simulation and experiment. The self-piercing riveting is hopeful as replacement of spot resistance welding generally used for steel sheets, because it is not easy to apply the resistance welding to joining of three aluminium alloy sheets due to the high thermal conductivity. Defects in the riveting are categorized into the penetration through the lower sheet, the necking of the lower sheet and the short overlap of sheets to obtain optimum joining conditions. The penetration and the necking are caused by small total thickness. The short overlap tends to occur as the ratio of lower sheet and total thickness is small. In addition, the cross-tension test was simulated by the finite element method to evaluate the joint strength.