Pipkorn 1 EFFECTS OF ACTIVE STRUCTURES ON INJURIES IN MEDIUM SEVERITY FRONTAL IMPACTS Bengt Pipkorn Autoliv Research Sweden Anders Kullgren Folksam Research and Department for Public Health Sciences, Karolinska Institutet, Sweden Paper Number 09-0380 ABSTRACT An evaluation of the influence of crash pulse shape on the risk to sustain injuries in medium severity frontal collisions was carried out by reconstructing a number of real world accidents using mathematical simulations. Ten crashes with restrained occupants, recorded crash pulses and known injury outcomes were selected for reconstruction. The crashes were selected from the Folksam accident database. Delta-V and mean acceleration were derived from the recorded crash pulses. The injury outcome was collected from hospital records and questionnaires and coded according to the 2005 version of AIS. Only restrained occupants were included. Computer simulations using a mathematical model of the 50%-ile Hybrid III dummy were used to evaluate the influence of the crash pulse on the loading of the occupants. The restraint system was a state of the art system with a driver side airbag and a belt system equipped with a pretensioner and a load limiter. Simulations were carried out in which the crash pulse shape was varied according to what can be achieved with the frontal longitudinal beam in which the crush force can be varied. Injury reducing benefits for the occupants were achieved by varying the crash pulse shape in medium severity impacts. The principal technical solution to vary the crash pulse is to pressurize the frontal longitudinal beams in the frontal structure prior to impact. In low and medium-speed impacts, the beams are not pressurized to use the available crush distance of the vehicle front. In high-speed impacts, the beams are pressurized to increase the force level of the beam and use the available crush distance of the vehicle front efficiently. INTRODUCTION An evaluation of the CCIS (Co-operative Crash Injury Study) database of front seated occupant injuries in small family cars involved in frontal crashes with an equivalent test speed (ETS) of 20-40 km/h was performed. Thorax injuries (AIS 2+) were found to be more numerous than any other type of injury. The vast majority of chest injuries were skeletal. The sample sizes were limited but there were fewer serious chest injuries to front seat passengers in newer cars (registered 2000 or later) than in old cars (registered 1983 to 1997). There was no such reduction of chest injuries evident for drivers but injuries to other body parts decreased in newer cars. As a matter of fact serious chest injuries to older drivers in newer cars increased sharply. Also there was no decrease of serious chest injuries for young female drivers of newer cars. The manufacturers of cars are faced with the problem of a continuing down sizing and mass reduction trend to reach low fuel consumption levels and to minimize environmental impact. One limiting factor is the need to provide a sufficiently long deformation zone in the frontal part of the car body. Conventional test methods to perform crash tests into deformable or non-deformable barriers at speeds between 40-64 km/h (25 to 40 mph) have resulted in cars with specific crash pulses and restraint systems tuned to give a low occupant loading. It can be reasoned that in real life, given the many different crash types that occur in real life, the importance of tailored crash pulses do not have such a significant effect. However, it can be stated that the longer the crush depth the lower the loading on the occupants will be, given that the crash pulse is not too heavily skewed with a high deceleration level at the end of the crash. The concept of crash pulse tuning to reduce occupant loads in barrier testing has been discussed and evaluated previously [1,2]. Recent advances provide the opportunity for crash pulse variation in real time through variable beam buckling force technology. Such technology will have at least a three fold