The Study of Residual Stresses for Roller Hemmed Aluminum Alloys

Many researches of automotive companies have focused on reducing weight of vehicles in order to meet the needs for high fuel efficiency. Therefore, light metals such aluminum alloys have been applied on automotive body structures. Recently, roller hemming process has been introduced for hemming of aluminum automotive closing parts such as doors, roofs, and hoods. During Roller hemming, the flange of outer panels is bent and folded along the edge of inner panel by a roller attached robot. Since the stress caused by roller hemming can affect the quality of hemmed flanges, the research has focused on the stress analysis by simulation and experiment. Residual stress has been measured in the hemmed flanges and compared to the values of finite elemental analysis.