22nd ESV Conference 2011
New vehicle types are extensively tested to check almost all factors that influence ride and handling. With reference to the Association of German Car Tuners" (VDAT e.V.) valuations, approximately 10% of all cars in Germany are being modified by their owners. 28 % of those modifications" sales are divergent wheel-tire combinations, 13 % are tuning measures on the chassis suspension or wheel spacers. In almost all cases the singular modifications present a general permission for specific vehicles they have been tested in. Combined tuning measures, however, are often checked by just one inspector, following a procedure of mostly subjective assessment criteria. Today, critical attributes are only being observed, in case a vehicle is involved in an accident and the modifications are identified as crash causal factors or as a cofactor on the development of a crash. For the first time, a field study allows a survey of safety affecting chassis modifications. The test layout has to comply with some basic conditions. Different vehicle concepts with a wide margin of modifications are required to get a high transferability of the results. A total amount of more than 150 tested vehicles serves the same purpose. The tests are limited concerning the installation time of measurement techniques and the requirement that no damage, defilement or immoderate wear of the vehicles are accepted by their owners. Due to such factors as well as the driver Ìs acceptance, the vehicles are controlled by its owners instead of robots or test drivers. For keeping down the driver- influence, the lane has narrow boundaries and the driver has to drive in strictly adherence to the given instructions. After gathering all modifications, as well as static and kinematic parameters like the toe and camber angle, dynamic testing of predominantly lateral dynamics is conducted. Besides standardized tests like the ISO 3888-2 (Obstacle Avoidance) or the ISO 14512 (Braking on Surfaces with Split Coefficient of Friction), to test the influence of modified kingpin offsets caused by wheel spacers, some deviant tests are conducted. Those are required due to the demand of objective test results for road tests with vertical induced stimulation of the chassis suspension. Hence, new tests on corner braking with and without vertical stimulation have been developed. The interpretation of data includes thresholds, e.g. the maximum entrance velocity without hitting cones, on the one hand, and the analysis of characteristics of data concerning time and frequency range, "1-second values" and peak response times on the other hand. Besides the thresholds as indicators for the achievable velocities, which are mainly affected by friction coefficients, the vehicle reaction in the course of time characterizes the vehicle reaction in the threshold range and consequently the operational demands on the driver. The field study has started and promises the first long-range analysis of chassis modifications. The results offer a basis for hypothesis and resultant further test layouts for oncoming studies of the identified critical tuning measures.
Thoracic injury is one of the predominant types of severe injuries in frontal accidents. The assessment of the injury risk to the thorax in the current frontal impact test procedures is based on the uni-axial chest deflection measured in the dummy Hybrid III. Several studies have shown that criteria based on the linear chest potentiometer are not sensitive enough to distinguish between different restraint systems, and cannot indicate asymmetric chest loading, which has been shown to correlate to increased injury risk. Furthermore, the measurement is sensitive to belt position on the dummy chest. The objective of this study was to evaluate the optical multipoint chest deflection measurement system "RibEye" in frontal impact sled tests. Therefore the sensitivity of the RibEyesystem to different restraint system parameters was investigated. Furthermore, the issue of signal drop out at the 6 th rib was investigated in this study.A series of sled tests were conducted with the RibEye system in the Hybrid III 50%. The sled environment consisted of a rigid seat and a standard production three-point seat belt system. Rib deflections were recorded with the RibEye system and additionally with the standard chest potentiometer. The tests were carried out at crash pulses of two different velocities (30 km/h and 64 km/h). The tests were conducted with different belt routing to investigate the sensitivity of chest deflection measurements to belt position on the dummy chest. Furthermore, different restraint system parameters were investigated (force limiter level, with or without pretensioning) to evaluate if the RibEye measurements provide additional information to distinguish between restraint system configurations . The results showed that with the RibEye system it was possible to identify the effect of belt routing in more detail. The chest deflections measured with the standard chest potentiometer as well as the maximum deflection measured by RibEye allowed the distinction to be made between different force limiter levels. The RibEye system was also able to clearly show the asymmetric deflection of the rib cage due to belt loading. In some configurations, differences of more than 15 mm were observed between the left and side areas of the chest. Furthermore, the abdomen insert was identified as source of the problem of signal drop out at the 6th rib. Possible solutions are discussed. In conclusion, the RibEye system provided valuable additional information regarding the assessment of restraint systems. It has the potential to enable the evaluation of thoracic injury risk due to asymmetric loading. Further investigations with the RibEye should be extended to tests in a vehicle environment, which include a vehicle seat and other restraint system components such as an airbag.