The influence of force limiter to the injury severity by using a 3-point belt and driver air bag in frontal collisions

Kallieris, Dimitrios; Rizzetti, Andreas; Wirên, Bernd v.; Mattern, Rainer

The number of the new registered passenger cars –with combined 3-point belt / driver side air bag restraint systems– is steadily increasing. The air bag offers an additional protection of the head, neck and torso. However, the thorax responses and kinematics by crash simulations show that a time adjustment of the shoulder belt and the air bag effectiveness is needed; furthermore correlations of the response and injury severity are required. For these aims 3() mph frontal collisions were performed with 14 human cadavers. The subjects' thorax was instrumented with the 12-acce1erometer array and two chest bands and restrained with 3-point belt, driver air bag or 3-point belt-driver air bag combination.

The results show, that by using a combined 3-point standard belt (6% elongation)driver side air bag, the thoracic injury pattern is located under the shoulder belt. The same observation was found by using belts with 16% elongation in combination with the driver side air bag. The chest contours show, that the 3-point belt causes high local compression of the chest along the shoulder belt path, which suggests there would be a high risk for thoracic injuries. On the other hand, the air bag, used by itself as a passive restraint system, distributes forces uniformly over the front of the chest,

This study asks if it is possible to obtain both the thoracic injury mitigating benefits of an air bag only restraint and the all-impact-direction benefits of the belt from a restraint system combination by adding a force limiter to the shoulder belt. For this reason, tests with force limiters were performed. The force limiter with the level of 4 kN showed, through examination of the chest band contours, a more bag like uniform compression of the chest and reduces therefore the injury risk. Non or AIS 1 injuries were found in the cervical spine and AIS 0 to AIS 1 was observed in the thorax, even in the age range 60 to 65 years. The chest compression amounts 4 to S cm, and the resultant vertebral accelerations were in the average 30 t0 40 g's; at these levels the thorax of the most cadavers remained uninjured 0r an injury severity of AIS 2 was observed.

It is concluded, that when a driver side air bag is combined with a 3-point belt system that limits the torso belt loop load to 4 kN, additional injury mitigation benefits for both the cervical spine and the thorax are obtained in frontal Collisions.

Year

Entry

1975

Schmidt G, Kallieris D, Barz J, Mattern R, Klaiber J. Neck and thorax tolerance levels of belt-protected occupants in head-on collisions. In: Proceedings of the 19th Stapp Car Crash Conference. November 17-19, 1975; San Diego, CA. Warrendale, PA: Society of Automotive Engineers:225-257. SAE 751149.

1995

Mertz HJ, Williamson JE, Vander Lugt DA. The effect of limiting shoulder belt load with air bag restraint. In: Proceedings of the SAE International Congress & Exposition. February 27–March 2, 1995; Detroit, MI. Warrendale, PA: Society of Automotive Engineers. SAE 950886.

1982

Kallieris D, Mattern R, Schmidt G, Klaus G. Comparison of three-point belt and air bag-knee bolster systems: injury criteria and injury severity at simulated frontal collisions. In: Proceedings of the 1982 International IRCOBI Conference on the Biomechanics of Impact. September 8-10, 1982; Cologne, Germany.166-183.

1989

Eppinger RH. On the development of a deformation measurement system and its application toward developing mechanically based injury indices. In: Proceedings of the 33rd Stapp Car Crash Conference. October 4-6, 1989; Washington, DC. Warrendale, PA: Society of Automotive Engineers:21-28. SAE 892426.

1994

Huelke DF, Moore JL, Compton TW, Samuels J, Levine RS. Upper extremity injuries related to air bag deployments. In: Advances in Occupant Restraint Technologies: Joint AAAM-IRCOBI Special Session. September 22, 1994; Lyon, France.55-78.