According to GIDAS, frontal collisions remain the most frequently accident type (51 %). Since the primary seatbelt restraint systems were used up to 88 % of the time in accidents, the belt could be used for additional reversible PRE-PULSE tensioning in the longer lasting PRE-Phase. With sophisticated adaptions in the MADYMO input deck and a procedure, introduced as a "PATCHWORK VALIDATION", it is possible to simulate the low-g phase up to 1500 ms before impact and the high-g phase during the impact without interruption. With this approach, it is possible to obtain results for the injury criteria with Hill Hybrid Dummies for load cases, e.g. US-NCAP. According to the results of this investigation, conducted with dummies and volunteers in tests and simulations, the effect of additional reversible PRE-PULSE retraction in the longer PRE-CRASH phase has been confirmed. With the derived optimal theoretical operation point of PRE-PULSE determined, it is possible to reduce the loads on the occupant significantly. The optimal theoretical operation point means that the maximum speed of the occupant torso rearwards must simultaneously coincide with the point of impact (t = 0). In non-braking situations at about t = -140 ms and in braking situations up to t = -200 ms before the impact, a belt tensioning followed by maintenance of the retraction force is able to accelerate the occupant torso rearwards. With torso speed of 0.5 -1 m/s in the braking situation and a neck movement back to the seat rest of up to 100 mm, it is possible to improve the Ride- Down for the occupant. Via additional PRE-PULSE activation at the optimal theoretical operation point, e.g. in braking situations, injury criteria for the US-NCAP load case can be reduced 10-20 %, depending on the criteria considered. Variations around the operation point for the PRE-PULSE activation have shown that still higher forces intensify the effect and approach the impact. An attempt to amplify the PREPULSE effect, through changing the trigger point of the conventional pyrotechnical pretensioner, did not bring any additional benefit. Standard pyrotechnical retraction is too short for decisive amplification of the beneficial effect. Further improvement may be reached through specific adjustments and adaptations to the conventional airbags and belt restraint systems. Due to torso movement rearwards and the larger distance to the instrument panel, longer lasting and guided energy absorption is possible. In a next step, further simulations with human active models in MADYMO and LSDDYNA with THUMS will allow comparison of the previous results as well as the human test results. Finally, sled tests with the additional PRE-PULSE activation in the operation points, e.g. in braking situations, can further confirm the best application for future car integration. Given these activities, the next step in the course of an integrated safety approach to an unavoidable accident is set.


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    Title :

    Movement in the PRE-crash situation - A simulation research with a reversible PRE-SAFE pulse system


    Contributors:


    Publication date :

    2010


    Size :

    26 Seiten, 18 Bilder, 12 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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