Comparison of Arm Up and Down in Side Impacts With BioSID and Different Armrests

BioSID dummy tests were run with the arm down at the side during loading of different armrests in simulated side impact crashes. The Hyge sled tests duplicated previous studies of BioSID with the arm up, SID, and animals. When the BioSID arm is against the side, the arm extends from the shoulder to the bottom of the third rib and has a steel shank covered by foam and vinyl. Loading through the arm transfers force to the three chest ribs and shoulder. In comparison, direct armrest loading of the chest or abdomen primarily involves a single rib and substantial rib deflection, when the armrest crush-force exceeds the strength of the rib. The Viscous response in BioSID showed the greatest difference of all criteria for the arm up or down. The response of the third rib correlated with injury risks determined from animal tests using the different armrest designs in a simulated high position. While injury data are not available for the arm at the side or for the armrest in the low position, the STIFF armrest may cause injury when the arm is not at the side and the armrest loads the liver and spleen. Rib deflection in BioSID showed the protrusion of the STIFF armrest into the abdominal region in both arm positions, because the loading was below the arm even in the down position. However, the arm extends laterally so it involves the upper ribs earlier than in the arm-up condition where more space is available. Torso deflection showed similar maxima with the arm down and a high armrest position, because the bridging action of the arm and shoulder increases the stiffness of the dummy. The armrest designs cover a range in crush characteristics for occupant protection systems based on experience with other interior safety features, knowledge of human tolerance, and results of injury in animal tests. The SOFT design was most appropriate for interior use. The STIFF design produced serious injury in companion tests with animals, and the BioSID correctly assessed injury risk by peak rib deflection or Viscous response when tested similarly. In contrast, SID and TTI(d) did not indicate injury risks or safety performance. The current study indicates that response differences can be expected with arm placement, and BioSID can assess safety implications of different armrest types and arm placement.