Papers by Author: Y. Abe

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: A multi-stage stamping process of one-piece automobile steel wheels from tubes was developed to decrease the loss of material for the blanking. In this process, the tube is nosed into a cup with a central hole, and then the taper bottom and side wall of the cup are formed into disk and rim portions of the wheel, respectively. The tube is produced by bending a rectangular sheet into a tube and by welding both edges of the bent sheet to prevent the loss of material for the blanking. The stamping sequence of the one-piece wheels was designed by finite element simulation. The central hole of the cup was decreased to a desired diameter of the hub hole without buckling and wrinkling by a 5-stages nosing operation. The taper bottom of the cup was reversely drawn, and then was flared without folding by 2 stages. The wall thickness of the formed wheel was thick and thin in the disk and rim portions, receptively, and thus the requirement of strength of wheels is satisfied. A one-piece wheel having a hub hole was successfully formed by the designed sequence in a miniature experiment.

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.

Abstract: A forming sequence of one-piece automobile steel wheels without welding was designed. In this forming process, the one-piece wheel was formed from a circular blank only by multi-stage stamping operations, and a deeply drawn cup was formed into the wheel. Two humps of the rim flange for fixing the tire were formed in the flaring and flanging stages. The humps of the rim in the opening and outer side were formed by buckling the inner flange of the rim, and by swelling the outer flange with an upper die having a short land, respectively. In addition, the number of stages was considerably reduced from 16 stages to only 9 stages by combining the deep drawing and ironing stages and by adding a holding die in the flaring stages. The forming sequence of the one-piece wheels was evaluated by both finite element simulation and miniature experiment.

Abstract: The wall thickness around an inner corner in 3-stages formed cups with a flange was increased by means of conical punches in the 1st and 2nd stages. Since the strength of the formed cups is greatly improved by the increase in wall thickness, the weight of the formed products is reduced by an optimum distribution obtained from the increase in wall thickness. The increase in thickness around the inner corner is obtained by compressing the side wall and conical bottom of the cup in the 3rd stage. As the punch angle increases, the increase in thickness at the inner corner becomes large. The amount of compression is expressed by a drawn volume after the 2nd stage. A maximum 9% increase in wall thickness around the inner corner was successfully obtained for the punch angle of 25º.