Abstract
To increase the usage of high-strength steel and aluminium alloy sheets for lightweight automobile body panels, the joinability of sheet combinations including a 780-MPa high-strength steel and an aluminium alloy A5052 sheets by mechanical clinching and self-pierce riveting was investigated for different tool shapes in an experiment. All the sheet combinations except for the two steel sheets by self-pierce riveting, i.e., the two steel sheets, the two aluminium alloy sheets, and the steel-aluminium alloy sheets, were successfully joined by both the joining methods without the gaps among the rivet and the sheets. Then, to show the durability of the joined sheets, the corrosion behaviour and the joint strength of the aged sheets by a salt spray test were measured. The corrosion and the load reduction of the clinched and the riveted two aluminium alloy sheets were little. The corrosion of the clinched two steel sheets without the galvanized layer progressed, and then the load after 1176 h decreased by 85%. In the clinched two galvanized steel sheets, the corrosion progress slowed down by 24%. In the clinched steel and aluminium alloy sheets, the thickness reduction occurred near the minimum thickness of the upper sheet and in the upper surface on the edge of the lower aluminium alloy sheet, whereas the top surface of the upper sheet and the upper surface of the lower sheet were mainly corroded in the riveted joint. The load reduction was caused by the two thickness reductions, i.e., the reduction in the minimum thickness of the upper sheet and the reduction in the flange of the aluminium alloy sheet. Although the load of the clinched steel without the galvanized coating layer and aluminium alloy sheets decreased by about 20%, the use of the galvanized steel sheet brought the decrease by about 11%. It was found that the use of the galvanized steel sheets is effective for the decrease of strength reduction due to corrosion.
Highlights
To reduce the weight of automobiles, the application of highspecific-strength sheets to body parts is increasing
Because the progress of the corrosion does not reach the joint even T = 1176 h in this sheet combinations and in the two aluminium alloy sheets in Fig. 13, the corrosion in the joint was prevented by joining without the gaps in the joined cross-section; the load reduction was mainly caused by the thickness reduction
The 780-MPa high-strength steel and aluminium alloy A5052 sheets were joined by mechanical clinching and self-pierce riveting, and the salt spray test was performed to measure the corrosion behaviour and strength reduction, and the following results were obtained: (1) Except for the two steel sheets by self-pierce riveting, all sheet combinations including the two steel sheets, the two aluminium alloy sheets, and the steel-aluminium alloy sheets were successfully joined by mechanical clinching and self-pierce riveting without the gaps among the rivet and sheets
Summary
To reduce the weight of automobiles, the application of highspecific-strength sheets to body parts is increasing. Joinabilities of self-pierce riveting are investigated to join aluminium alloy sheets [13], aluminium alloy and mild steel sheets [14], aluminium alloy and high-strength steel sheets [15], aluminium alloy and coated steel sheet [16], and metal sheet-polymer [17], i.e., many sheet combinations for joining automobile parts are possible to join by self-pierce riveting and mechanical clinching. It is desirable to evaluate durability on a same corrosion test with a same sheet combination including the high-strength steel and aluminium alloy sheets of joined by clinching and riveting. Mechanical clinching and self-pierce riveting were performed on the sheet combinations including 780MPa high-strength steel and aluminium alloy A5052 sheets, and the optimum conditions to have the maximized interlock were obtained. To show the durability of joints, and to compare with the self-pierce riveted joints, the corrosion behaviour and joint strength of the aged joints by the salt spray test were measured
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