Lightweight, package and performance improvements of a shock tower by using steel–aluminium hybrid-casting technique

Abstract

In this work, a shock tower of a mid-size vehicle using steel (St)–aluminium (Al) hybrid-casting technology was developed with current shock towers as a benchmark. The use of this hybrid-casting technology, which features a ductile material connection between steel and cast aluminium, makes it possible to combine the design advantages of cast aluminium with the mechanical properties of high-strength steels. Based on this combination, a new shock tower concept was developed that offers advantages over the state of the art in terms of package, weight, stiffness and crash performance. To develop the new shock tower, connection points and package spaces in the periphery of the Honda Accord MY 2011 were analysed and defined. Based on quasi-static misuse load cases and topology optimization, it was possible to develop a load-compliant rib structure for the hybrid-cast shock tower reinforced by steel in the dome area. A so-called tension band for the IIHS small overlap crashworthiness evaluation test (SOL) was also integrated into the new shock tower to ensure homogeneous load distribution. The new shock tower was tested virtually in comparison with the reference steel shock tower and an Al-cast shock tower in quasi-static and dynamic crash load cases. In the quasi-static test, the hybrid-cast shock tower showed significantly increased stiffness. In the dynamic load cases, a significant overall homogenization of force distribution on the existing load paths in die front body structure was achieved. In addition, 5 mm package space for spring and damper could be gained for better driving behaviours of the car.