Assessment of potential forearm fracture due to deployment of driver air bags is examined through a series of static air bag deployments with a specially instrumented Hybrid III dummy. The objective of the study was to determine the feasibility of measuring accelerations and bending moments on the Hybrid III dummy forearm as a potential injury index for arm fracture.
Study of the National Accident Sampling System data has shown that in isolated circumstances, deployment of an air bag while the driver is making a turn can lead to fractures of the lower arm. To examine this phenomenon, the Hybrid III dummy was instrumented with accelerometers and strain gages to allow measurement of the accelerations and moments on the right arm. The arm was oriented over the steering wheel towards the eleven o'clock position during deployment of the air bag. Accelerations were measured on the arm at the wrist, elbow, and shoulder. Moments in two axes were measured at two locations below the elbow. A series of tests were conducted with air bag equipped steering wheels in two different clock orientations. The steering wheel air bag assemblies were from more than one manufacturer representing different inflator rates and module cover designs.
The testing indicated that measurement of meaningful accelerations and bending moments was feasible using the specially instrumented Hybrid III dummy arm. Wide differences in peak accelerations and bending moments were associated with air bag inflator rates, covers, and steering wheel clock orientation. Comparison of the response measurements on the dummy's arm with relevant biomechanical data are presented. The results indicate that under the conditions tested, certain air bag modules produced levels of bending moments in the dummy's arm which would exceed the published skeletal fracture reference values, whereas other modules resulted in responses at or below those thresholds.