Material characterization of liver parenchyma using specimen-specific finite element models

Area of Science:

• Biomechanics
• Materials Science
• Trauma Engineering

Background:

• The liver is frequently injured in motor vehicle crashes.
• Accurate car crash simulations require strain-rate dependent soft tissue properties for finite element (FE) models.
• Existing models lack comprehensive biomechanical data for liver parenchyma under dynamic loading.

Purpose of the Study:

• To characterize the biomechanical and failure properties of bovine liver parenchyma.
• To determine the strain-rate dependence of liver tissue mechanical behavior.
• To provide data for developing accurate FE material models for crash simulations.

Main Methods:

• Performed 30 tension tests on bovine liver parenchyma at loading rates of 0.01 s(-1), 0.1 s(-1), and 1 s(-1).
• Utilized a tensile testing setup, recording load and acceleration to calculate force time histories.
• Developed specimen-specific FE models using laser scans and applied a first-order Ogden material model.

Main Results:

• Failure Green-Lagrangian strain averaged around 50% with no significant rate dependence.
• Failure 2nd Piola-Kirchhoff stress exhibited rate dependence, ranging from 33 kPa to 94 kPa.
• FE models with simulation-based optimized parameters accurately replicated experimental load time histories.

Conclusions:

• Liver parenchyma exhibits rate-dependent failure stress, a critical factor for FE modeling.
• Specimen-specific FE models with optimized parameters provide superior accuracy compared to analytical approaches.
• The study provides essential biomechanical data for enhancing injury risk assessment in automotive collisions.