B G Carkhuff | PubMed Health

PubMed2005

Computational and experimental models of the human torso for non-penetrating ballistic impact.

Both computational finite element and experimental models of the human torso have been developed for ballistic impact testing. The human torso finite element model (HTFEM), including the thoracic skeletal structure and organs, was created in the finite element code LS-DYNA. The skeletal structure was assumed to be linear-elastic while all internal organs were modeled as viscoelastic. A physical human surrogate torso model (HSTM) was developed using biosimulant materials and the same anthropometry as the HTFEM. The HSTM response to impact was recorded with piezoresistive pressure sensors molded into the heart, liver and stomach and an accelerometer attached to the sternum. For experimentation, the HSTM was outfitted with National Institute of Justice (NIJ) Level I, IIa, II and IIIa soft armor vests. Twenty-six ballistic tests targeting the HSTM heart and liver were conducted with 22 caliber ammunition at a velocity of 329 m/s and 9 mm ammunition at velocities of 332, 358 and 430 m/s. The HSTM pressure response repeatability was found to vary by less than 10% for similar impact conditions. A comparison of the HSTM and HTFEM response showed similar pressure profiles and less than 35% peak pressure difference for organs near the ballistic impact point. Furthermore, the peak sternum accelerations of the HSTM and HTFEM varied by less than 10% for impacts over the sternum. These models provide comparative tools for determining the thoracic response to ballistic impact and could be used to evaluate soft body armor design and efficacy, determine thoracic injury mechanisms and assist with injury prevention.

Biomechanical Phenomena↗

PubMed1991

Multisite microprobes for neural recordings.

Multisite, passive microprobes have been developed to allow simultaneous recording of action potential activity from multiple neurons at different locations in the brain. The microprobes were fabricated using standard integrated circuit techniques. The probe is a planar structure that consists of gold electrodes sandwiched between two polyimide dielectric layers and bonded to a molybdenum structural support. Windows in the top dielectric layer expose the electrode sites and bonding pads. In two distinct versions of the probe four or six recordings sites, respectively, of approximately 25 microns 2 are arranged on a dagger-shaped structure which can penetrate the pia. The bonding pads and interconnect wires at the probe head are entirely encapsulated in a tubular fixture that is packed with silicone RTV and sealed with epoxy to protect the interconnections from contact with body fluids. The site impedances at 1 kHz are typically between 2 and 4 M omega. Probe lifetimes for continuous immersion in physiological saline solution, as measured by impedance, have exceeded 750 h. The failure mechanism is believed to be due to moisture and ion absorption in the top dielectric layer. In acute neurophysiological experiments using the four site probes, action potential activity was recorded from physiologically identified neurons in the dorsal column nuclei of anesthetized rat.

Action Potentials↗