Investigation of Cavitation Using a Modified Hopkinson Apparatus

Abstract

Head injury, specifically mild Traumatic Brain Injury, has been identified as an increasingly common injury resulting from blast exposure. Advanced modeling has demonstrated the possibility of relatively high negative pressure at the posterior of the skull for frontal blast exposure, attributed to reflection and focusing of the stress waves due to curvature of the skull. It has been hypothesized that high negative pressures could lead to injury, possibly by cavitation of the cerebrospinal fluid (CSF). However, the cavitation pressure for CSF has not been measured directly in the literature, and thresholds are required for detailed numerical head models. Furthermore, the values for cavitation pressure of fluids in the literature vary widely, postulated to be due to varying levels of impurities and dissolved gases. In this study, a Split Hopkinson Pressure Bar apparatus was modified for tensile loading with a sealed confinement chamber and was used to investigate the cavitation properties of water. The modified apparatus was able to generate a tensile wave on the order of 3.4 MPa resulting in cavitation in the water sample. Future work will utilize this technique to investigate the cavitation pressure of CSF directly.