The object of this research was to provide basic information concerning the mechanical responses of the head.- The instrumentation and experimental techniques will be used in a survey of materials to be used in the construction of an artificial head.
A electromagnic shaker and a Spectral Dynamics Analyzer were used to determine the mechanical impedance of the live Macaca mulatta monkey head, live monkey head with high blood pressure, dead monkey with low blood pressure, dead monkey head with body removed, the dead monkey skull with the brain, and the dead monkey skull.
A microminiature accelerometer and pressure transducers were developed for implantation into the brain. This transducer was implanted in three of the five monkeys tested.
The acceleration on the side of the head opposite the point of application of the load for driving point impedance was recorded.
A capillary rheometer was built to determine the viscosity of human autopsy brain, monkey biopsy brain and cerebrospinal fluid. A uniaxial strain test was performed on the tissue mentioned above. The results of the mechanical impedance tests indicate that death of the brain has no effect on the imoedance although a change in blood pressure does cause a change in impedance. The head in general is non-linear with respect to acceleration. This was also found to be true for a human skull. At high frequencies there is very little motion inside the brain or on the skull, The viscosity of brain was found to be approximately 0.5 poise while the viscosity of cerebrospinal fluid was found to be approximately that of water, 0,01 poise.
Brain was found to be essentially elastic in bulk with a modulus of 300,000 psi.