Lubricants are necessary to avoid adhesion, galling, and scratching in aluminum stamping processes. In this study, various lubricants, including dry lubes and wet lubes, were evaluated using cup drawing test (CDT) for stamping of Al 5182-O aluminum sheets. The effects of surface texturing, with electro-discharge texturing (EDT) and mill finish (MF), on the friction behavior were also investigated. Furthermore, the methodology to evaluate the performance of lubricants was established based on (a) maximum applicable blank holder force (BHF) and (b) draw-in length in flange or flange perimeter of formed cups. Finite element (FE) simulations were carried out to determine the coefficient of friction (CoF) at tool–workpiece interface during deep drawing under different lubrication conditions. Flow stress data of Al 5182-O material were obtained using viscous pressure bulge (VPB) and tensile tests. In this study, it was confirmed that, in forming Al 5182-O, dry film lubricants have better lubricity than wet lubricants. A better lubrication condition was found with EDT surface texture.

Research is conducted to determine the effect of processing temperature on some of the physical and mechanical properties of a polyurethane foam called ReCrete. The polyurethane foaming process is manipulated to change the foam's density, chemistry, and mechanical properties. There is a 30-min period after ReCrete components are mixed when the materials are still undergoing significant chemical reaction. Researchers manipulate these chemical reactions by changing the environmental temperature during this process. This study investigates the effect of processing temperature on the chemistry and the resulting mechanical properties for a polyurethane foam system molded in aluminum cylinders and boxes. Processing temperature is varied from 25°C to 85°C. Researchers show that the processing temperature has a significant effect on ReCrete chemistry and density. The average density decreases by 19% over this temperature range. The chemistry, in turn, affects the static and dynamic mechanical properties. The axial compressive modulus and strength decrease by 24 and 16%, respectively. The chemistry changes that results from higher processing temperatures produce foam that is less rigid in compression, but tougher and more flexible. The dynamic flexural failure strength increases by 38% when the processing temperature is increased from 25°C to 85°C. Foam processed at 85°C has significantly greater resistance to brittle failure under impact.

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A key aspect of integrating automotive sheet into automotive production are the costs associated with joining. While the majority of sheet steel assembly is done with resistance spot welding, that has not readily translated to aluminum. Resistance spot welding of aluminum sheet is challenged by high current demand as well as reduced electrode life. In the latter case, direct current (DC) power supplied by state-of-the-art systems has exacerbated the problem. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is a first effort in examining the response of resistance spot welding on aluminum sheet to polarity-switching CD power. In this paper, the current range response between medium-frequency DC (MFDC) and polarity-switching CD was investigated. It was found that polarity-switching CD welding offered improved current ranges over MFDC. In addition, replicate mechanical testing cross-tension results were similar, but tensile shear strengths improved nominally 20–25%. Finally, some limited tests were done to assess the suitability of CD resistance spot welding in the presence of an adhesive. Current range tests with and without a prepulse were done, and both showed excellent weldability.

A major challenge for high-volume resistance spot welding of aluminum sheet is durability of the electrodes themselves. In production today, electrodes have total anticipated lives (including dressing) on the order of 1000 welds. This is largely related to the use of medium-frequency direct current (MFDC) power. The single-polarity orientation of MFDC welding results in excessive heating of one electrode (anode) and accelerated wear rates. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is the first effort in examining the response of resistance spot welding on aluminum sheet using this power source. Part 1 of this research (Ref. 1) described basic process robustness in spot welding with CD power systems. Part 2 addresses electrode life response. Duplicate electrode life tests were completed for 2000 welds without failure. These results were related to the polarity switching and short time that produced balanced and minimized wear. Additional testing was done without the use of electrode-cooling water. A limited test (500 welds) largely paralleled the ones done with cooling, suggesting that long-term spot welding with polarity-switching CD power and no water was possible.