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| Preliminary results from the validation phase of the UltraLight Steel Auto Closures (ULSAC) study, confirm that innovative design combined with currently available steel technologies can reduce weight significantly with no cost increase while meeting state-of-the-art structural performance for vehicle safety. These findings have been confirmed by the actual manufacture of a ‘window frameless’ door that is 33% lighter than the benchmarked average for all door types in the concept phase and 42% lighter than the benchmarked average for frameless doors in the validation. The ULSAC study has been commissioned by an international consortium of 30 sheet steel producers to assist their automotive customers with viable lightweighting solutions. The consortium has contracted Porsche Engineering Services to provide engineering management for the programme. To create a lightweight mass-efficient closure, while exceeding the crash safety requirements for lateral stiffness and side intrusion, the ULSAC study has completely reappraised the typical car door. This new approach has enabled the Porsche engineering team to reduce weight in key areas, while strengthening important strategic locations such as hinges and latches. The high strength required for the basic structure has been achieved by replacing the normal steel inner panel with four steel tubes. Two hydroformed tubes in 280MPa high-strength steel form the latch and hinge uprights, while two straight tubes in 800MPa ultra-high-strength steel form the adjoining upper and lower longitudinal members. A stamped laser-welded tailored blank of 1.2mm and 1mm gauge 140MPa mild steel provides an additional reinforcing inner front member, which incorporates the mirror flag. The resulting mass of the basic steel structure, at 10.5kg, is almost 2kg lighter than the target mass of 12.3kg. Independent studies by Massachusetts Institute of Technology show the closures can be manufactured in high volume (+250,000) with no cost penalty. The manufacturing cost for a pair of ULSAC door structures built to the target mass is £91 (133 Euros). The investment in innovative processes like hydroforming and laser welding are compensated through huge savings in material costs. Commenting on the success of the ULSAC design, Simon Kragtwijk of Corus Light Strip Products, said: "The preliminary results of the study, showing that significant mass reduction with steel closure structures can be achieved with high structural performance and no cost penalty, are indeed remarkable." For further information about the preliminary results from the validation phase of the UltraLight Steel Auto Closures (ULSAC) study, please download the PDF file. | |
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