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Distribution of load has a major influence on type and severity of chest injuries. The introduction of the Hybrid III dummy into crash testing along with the requirement to measure sternum deflection for injury assessment has brought about the need to evaluate how well its thorax senses various loading conditions. Tests revealed that different load distributions, i.e. due to a diagonal shoulder belt or an airbag, did not produce the expected chest deflection patterns. This appears to be the result of both a relatively stiff sternum assembly and a nonsuitable design of the clavicle. Chest compression responses became more realistically when both, sternum and clavicle of the Hybrid II were mounted into the Hybrid Ill's thorax. As a consequence, this study suggests that the thorax of the Hybrid III dummy must be improved.

The expected improved performance of a combined restraint system where an airbag supplements the conventional safety belt was not reflected in reduced g-values on the dummy's chest. However, by the distribution of force over the wider area of the airbag and the corresponding reduction of the specific pressure exerted by the three point belt, improved occupant protection is actually produced. Therefore, measurable quantities other than acceleration should be selected to evaluate the risk of chest injury, such as belt load or chest deflection. A new method to measure the deflection of dummy ribs with strain gauges has been developed. The resulting data indicate a significantly reduced chest deflection when a combined system is used.

The risk of head or chest injuries is usually evaluated by means of acceleration measurements using a dummy. Unfortunately, this data provides no information on load distribution over the contact areas which is often related to localized fractures of the bony structure. Therefore, new methods of measuring local forces were developed. 1. Pressure indicating devices attached to a dummy's face are capable of monitoring the local pressure during impact; foil's color change is interpreted by means of digital image analysis. 2. A velocity sensitive viscous tolerance criterion was calculated from the chest compression response of a dummy instrumented with strain gauges on the ribs. The application of advanced techniques in laboratory tests clearly supports the experience of improved protection potential through the use of airbag systems.

From an acoustical point of view, the integration of seatbelt retractors in a vehicle is a real challenge that has to be met early in the vehicle development process. The buzz and rattle noise of seat belt retractors is a weak yet disturbing interior noise. Street irregularities excite the wheels and this excitation is transferred via the car body to the mounting location of the retractor. Ultimately, the inertia sensor of the locking mechanism is also excited. This excitation can be amplified by structural resonances and generate a characteristic impact noise. The objective of this paper is to describe a simulation method for an early development phase that predicts the noise-relevant low frequency local modes and consequently the contact of the retractor with the mounting panel of the car body via the finite element method.

Sensing and acting elements to guarantee the locking functions of seat belt retractors can emit noise when the retractor is subjected to externally applied vibrations. For these elements to function correctly, stiffness, inertia and friction needs to be in tune, leading to a complex motion resistance behavior, which makes it delicate to test for vibration induced noise. Requirements for a noise test are simplicity, robustness, repeatability, and independence of laboratory and test equipment. This paper reports on joint development activities for an alternative test procedure, involving three test laboratories with different equipment. In vehicle observation on parcel shelf mounted retractors, commercially available test equipment, and recent results from multi-axial component tests [1], set the frame for this work. Robustness and reliability of test results is being analyzed by means of sensitivity studies on several test parameters.

Safety considerations at Daimler-Benz are based on real-world accidents from which internal test procedures are derived. The example of the frontal collision is a clear illustration of this. In a crash against a flat, full car width barrier, a rare occurrence in real-world accidents, the impact energy is distributed over the entire width of the car. The majority of real-world frontal crashes, however, involve only partial overlap of the front. An adequately designed structure has to absorb the crash energy before it deforms the passenger compartment, i. e. by distributing the impact forces, and strategically located components must avoid the formation of blocks. In particular, the passenger compartment must be sufficiently stiff. Restraint systems and interior padding can only serve their protective purpose to their fullest if the survival space for the occupants is maintained intact.

Seatbelt retractors as important part of modern safety systems are mounted in any automotive vehicle. Their internal locking mechanism is based on mechanically sensing elements. When the vehicle is run over rough road tracks, the retractor oscillates by spatial mode shapes and its interior components are subjected to vibrations in all 6 degrees of freedoms (DOF). Functional backlash of sensing elements cause impacts with neighbouring parts and leads to weak, but persistent rattle sound, being often rated acoustically annoying in the vehicle. Current acoustic retractor bench tests use exclusively uni-directional excitations. Therefore, a silent 2 DOF test bench is developed to investigate the effect of multi-dimensional excitation on retractor acoustics, combining two slip-tables, each driven independently by a shaker. Tests on this prototype test bench show, that cross coupling between the two perpendicular directions is less than 1%, allowing to control both directions independently.

Daimler-Benz considers safety belts as the fundamental and essential restraining system. The company began offering a Supplemental Restraint System option consisting of a driver airbag system and an emergency tensioning belt retractor for the passenger in December 1980. The functional reliability of the system has proven satisfactory.