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Axial Impact Characteristics of Dummy and Cadaver Lower Limbs
Published May 31, 1998 by National Highway Traffic Safety Administration in United States
Axial impact tests conducted at the Medical College of Wisconsin on isolated cadaver lower limbs and the original version of the 50th percentile Hybrid III dummy lower limb were examined to characterize their dynamic response. Unlike the more recent version of the Hybrid III dummy lower limb, the original Hybrid III dummy lower limb allows only 30 degrees of foot rotation in dorsiflexion and lacks biofidelic heel pad compression characteristics. This original version of the Hybrid III dummy lower limb will henceforth be referred to a HIII-o dummy lower limb. Results of the tests suggested that the axial force measured in the HIII-o lower limb was higher than that measured in the cadaver lower limb for similar impacts applied to the plantar surface of the foot.
The dynamic properties of the cadaver and HIII-o dummy lower limb were characterized by representing the lower limb in the axial impact tests as a single-degree-of-freedom system with a Kelvin element having liner stiffness and damping properties. The stiffness and damping coefficients of the cadaver and HIII-o dummy lower limbs were obtained from linear regression using the measured accelerations on the pendulum and the leg as input and output of the system, respectively. The average stiffness and damping coefficients were estimated to be 963 kN/m and 0.21 for the cadaver and 3256 kN/m and 0.26 for the HIII-o dummy lower limbs, respectively.
The axial force response ratio between the HIII-o dummy and cadaver lower limbs under similar impact conditions was obtained using Runge-Kutta simulations of the equation of motion for the single-degree-of-freedom system. The axial force response ratio was represented as a function of the rise time of the axial force (the time to maximum force) in the HIII-o dummy lower limb. The axial force ratio between HIII-o dummy and cadaver is greater than one for HIII-o dummy axial force rise times below 55 msec (short duration tibia force pulse). The axial force in the HIII- o dummy and cadaver are approximately the same for long-duration HIII-o dummy axial force pulse.
- Shashi M. Kuppa - Conrad Technologies Inc.
- N. Yoganandan - Medical College of Wisconsin
- F. A. Pintar - Medical College of Wisconsin
- Rolf H. Eppinger - National Highway Traffic Safety Administration
- Emily Sun - National Highway Traffic Safety Administration
- Nopporn Khaewpong - National Highway Traffic Safety Administration
- Michael Kleinberger - National Highway Traffic Safety Administration
- Gregg S. Klopp - University of Virginia
- Jeff R. Crandall - University of Virginia
- Greg Hall - University of Virginia