Experimental Study on the Crash Performance of Aluminum and Steel Rails

Increasing government mandated CAFE´ standards are forcing the OEMs to aggressively reduce vehicle weight. Aluminum, with a density of about a third of that of steel, has been established as a viable alternative to steel for the construction of the automotive body structure. However, for aluminum sheet metals, there are still lingering concerns about the reliability and robustness of the available joining techniques such as spot-welding, riveting etc. The investigation reported in this paper was aimed at evaluating the relative performance of self-pierced riveted aluminum rails as compared to spot-welded mild steel and high strength steel rails. A series of straight and curved (S-shaped) rails made of aluminum, mild steel, and high strength steel have been tested. Other design parameters considered in this study include sheet metal thickness, rivet/weld location, rivet/weld spacing, adhesives, temperature, and impact speed. As were observed from the tests, axial crush mode dominated the deformation of all straight rails while bending dominated the deformation of the curved rails. Statistical analysis was performed to find the relative importance and effects of each variable on the average crush load, maximum load and energy absorption. For aluminum rails, the thickness of the sheet metal was found to be the primary controlling factor for both straight and S-rails. Other factors i.e. rivet spacing/location, adhesives, temperature and impact speed, had no significant affect on the performance of the rails. For the steel rails, the sheet metal thickness, impact speed, temperature and material properties, were all found to be significant for the crash behavior. It was also found that the aluminum rails have higher specific energy absorption than the steel rails confirming that aluminum as a material is more efficient in absorbing crush energy than steel.