Inertia effects on characterization of dynamic response of brain tissue

Area of Science:

• Biomechanics
• Materials Science
• Neuroscience

Background:

• Traumatic brain injury (TBI) modeling requires understanding soft tissue mechanical responses at high loading rates.
• Current testing methods for biological tissues, like the annular specimen technique, may introduce artifacts.
• Radial inertia effects can complicate the interpretation of dynamic mechanical tests on soft materials.

Purpose of the Study:

• To characterize the dynamic mechanical response of fresh bovine brain tissue.
• To evaluate the validity of the annular specimen geometry for high-rate testing.
• To develop and validate a novel torsion technique for pure shear testing of soft tissues.

Main Methods:

• Modified Kolsky bar techniques were employed to test annular specimens of bovine brain tissue.
• High-speed imaging was used to capture radial deformation at a strain rate of 2000s⁻¹.
• A novel torsion technique was developed to achieve pure shear conditions under dynamic loading.

Main Results:

• High-speed images showed inhomogeneous deformation in annular specimens, attributed to radial inertia.
• The annular specimen geometry, intended to minimize inertia, still exhibited significant radial stress components.
• The novel torsion technique provided pure shear stress-strain data, distinct from the uniaxial compression results.

Conclusions:

• The annular specimen geometry may not fully eliminate radial inertia effects in dynamic testing of soft tissues.
• Radial inertia significantly influences the deformation behavior and stress state in brain tissue under high-rate compression.
• A torsion-based method offers a more accurate approach for determining the constitutive behavior of soft biological tissues under dynamic shear loading.