Experimental cavitation studies in a model head-neck system

Abstract

The response of two different fluid-filled head-neck models to impact was studied experimentally to provide information concerning the validity of the widely prevalent cavitation hypothesis of brain damage. The structures consisted of an acrylic spherical shell with an outside diameter of about 188 mm and a human calvarium with a clear polyester resin occiput, representing the head, each coupled to an articulated artificial viscoelastic neck. Transient phenomena were initiated by the impact of either cylindrical projectiles fired from a pneumatic gun or by the pendulum drop of an aluminum spherical shell onto a small truncated aluminum cone attached to the head models. A short strain-gaged aluminum cylinder served to measure the input force history, while the pressure in the brain-simulating fluid was ascertained by means of Z-cut tourmaline crystals located along the impact axis at the coup, center and contrecoup positions. The occipital regions of the models were photographed at framing rates of 4000–8000 s −1 to visually examine the cavitation phenomena. Coup, contrecoup and resonating cavitation were detected and found to coincide temporally with negative pressure transients in both head-neck models. These results lend some support to the cavitation theory as a possible mechanism for brain damage.