Residual Stress Analysis of Punched Holes in 6013 Aluminum Alloy Commercial Vehicle Side Rails

Compliance with tighter emission regulations has increased the proportion of parasitic weight in commercial vehicles. In turn, the amount of payload must be reduced to comply with transportation weight requirements. A re-design of commercial vehicle components is necessary to decrease the vehicle weight and improve payload capacity. Side rails have traditionally been manufactured from high strength steels, but significant weight reductions can be achieved by substituting steel side rails with 6013 high strength aluminum alloy side rails. Material and stress analyses are presented in this paper in order to understand the effect of manufacturing process on the material's mechanical behavior. Metallographic and tensile test experiments for the 6013-T4 alloy were performed in preparation for residual stress measurements of a punching operation. Punched holes are critical to the function of the side rail and can lead to high stress levels and cracking. Residual stresses were measured for holes positioned in the web center and near the forming edge of the side rail using x-ray diffraction methods. Comparisons are made between 6013-T4 and 6013-T6 as well as roll-formed and nonroll-formed specimens. The results have been used to identify critical areas that may be susceptible to cracking and failure.