Effect of ATD Certification Specification Variance on Full-scale Sled Testing Performance
Principal Investigator: Matthew Maltese, PhD, The Children’s Hospital of Philadelphia
The anthropomorphic test device (ATD), or crash test dummy, is widely used to develop crash safety systems and designed to be biofidelic (humanlike) for a prescribed collision condition. To ensure biofidelic reliability, an ATD is required to pass certification tests for biomechanical response within a specific allowable range. To date, it is unknown how this allowable range influences the ATD’s kinematic/kinetic response in full-scale crash or sled testing. For example, the chest certification procedure for the Hybrid III ATD has an upper range and lower range of allowable chest deflection, but it is unknown how an ATD’s full-scale sled test response at the upper end of the certification range compares to one at the lower end. This study was conducted to answer that question by determining the effects of variance in chest certification test performance on injury metrics and kinematics in simulated frontal sled tests.
Investigators used a finite element model (FEM) of the Hybrid III 6-year-old ATD to simulate the pendulum impact chest certification test procedure. To produce simulations with deflection responses at the extreme ends of the certification corridor, the rib damping material (RDM) thickness and material properties within regulatory drawing package limits were parametrically varied. Two FEMs were then created – one at the higher and one at the lower chest certification window boundaries. To determine the effect of chest certification variance on injury metrics in frontal impacts, the two models were restrained within a harness child restraint system on the FMVSS 213 test bench and varying severities of frontal crash acceleration pulses were simulated.
Results show a higher chest deflection response for the Low RDM model as compared to the High RDM model in all frontal crash simulations, leading to a difference in head acceleration of as much as 40 percent. The High RDM model also recorded a greater Head Injury Criterion (HIC) value than the Low RDM model at speeds of 33.5 mph and 43.5 mph; however, at 38.5 mph the Low model recorded a higher HIC value.
Results showed that the Hybrid III 6-year-old model was insensitive to changes in deflection when fine-tuning RDM material properties but was sensitive when the RDM thickness is varied within the specifications of the ATD drawing packages. These findings indicate that variance in chest certification test response could significantly affect the kinematics and injury severity of a 6-year-old occupant involved in a frontal crash.
Future research might aim to develop models that calibrate at the extreme ends of the certification corridor for three body regions (head, chest, and knee) to study how this affects injury kinematics in a frontal crash at various sled pulses.
Chest deflection differences in models with high (red) and low (blue) rib damping material thicknesses.
Project Team Members: Kristy Arbogast, PhD, The Children’s Hospital of Philadelphia; Aditya Belwadi, PhD, The Children’s Hospital of Philadelphia
Student: Sriram Moparthy, The Children's Hospital of Philadelphia
IAB Mentors: Keith Nagelski, Britax Child Safety, Inc.; Matthew Goehle, Calspan Corporation; Mike Kulig, Calspan Corporation; Eric Dahle, Evenflo Company Inc.; Tara Cozier, Graco Children’s Products Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Ron Burton, Transportation Research Center Inc.