Vibrational frequency response to impact loading of skull models

Area of Science:

• Biomechanics
• Mechanical Engineering
• Trauma Research

Background:

• Explosive devices cause significant injuries to soldiers, primarily through shock waves impacting the skull.
• Intracranial pressure and skull flexure are believed to be key mechanisms of injury.
• Previous analytical models of spherical shells identified high-stress areas.

Purpose of the Study:

• To extend modal analysis of spherical shells using finite element models.
• To investigate the effects of altered geometries (holes, internal fluid) on skull response to impact.
• To analyze impulse scenarios and their impact on injury mechanisms.

Main Methods:

• Finite element modeling was employed to simulate impulse scenarios on spherical shell geometries.
• Modal analyses were performed and compared with analytical solutions.
• Variations included different hole sizes, impact directions, and the presence of internal liquid.

Main Results:

• Finite element models accurately predicted modal frequencies (within 4% of analytical solutions).
• Geometric deviations from a perfect sphere resulted in the loss of discrete modal frequencies.
• Larger holes increased deformation; impacts aligned with holes amplified stress spread by 30%.
• Internal liquid significantly reduced maximum deflections by 80% by diverting load.

Conclusions:

• The study provides insights into how skull geometry and internal contents influence blast wave injury.
• Finite element analysis is a valuable tool for understanding complex biomechanical responses to impact.
• Further research should focus on developing more anatomically accurate skull models for improved injury prediction.