Abstract
Keywords: pre-crash systems, crash actuators, side impact, DC-Neon.
The research activities presented in this paper were carried out within Sub-Project 6 of APROSYS (Advanced PROtection SYStems), an European Project to decrease the number of fatalities on European roads. SP6 deals with the development of a pre-crash system which improves structural behavior in side crash. This paper presents different studies on actuator concepts of such a system, their performance and the integration of a favorite concept.
The targeted vehicle for an actuator implementation within this study is a Daimler/Chrysler Neon (model year 1995 to 1999). For side crash structural behavior assessment, crash test results were made available as well as a numerical reference FE-model (Radioss) of the Neon, validated for Euro NCAP side impact protocol, by Cidaut, Spain, via the partnership of APROSYS.
The crash tests issued that the B-pillar was massively loaded and by this, for the actuator layout, two strategies were suggested: concepts to stiffen up locally the B-pillar (E.g. door locking to rocker and to Bpillar, continuous side impact beam from A to C pillars) and concepts which redirect crash loads away from the B-pillar to other car structures non impacted (E.g. transversal structures from struck side to the tunnel or the unstruck side). A generic FE model, previously created was used to investigate the concepts.
As outcome of this study, a crash load redirection to the unstruck side was found to be by far, most powerful. The actuator of this concept takes the crash loads directly from the incoming object at the door. The actuator activation creates a rigid connection from the struck door to stiff car regions and by this structures other than B-pillar are immediately involved in crash. From the first contact phase, much more structure is involved in the energy absorbing process.
This actuator comprises mainly a tube structure which is integrated in the seat. A bolt is pushed out and locked into the door, creating a tight connection from seat to door. The release of the bolt uses the principle of Shape Memory Alloys (SMA). The SMA wire being electrically heated in a precise temperature domain, shrinks and by this activating the mechanism for the bolt to be pushed out in a very small time span.
This system changes the crash deformation modes completely, not only the B-pillar intrusion is dramatically reduced, but as well door intrusion is reduced significantly in regions being most critical for the occupant, therefore a considerable reduction of injuries is to be expected by using such a pre-crash system.