Passive skeletal muscle response to impact loading: experimental testing and inverse modelling

Area of Science:

• Biomechanics
• Materials Science
• Computational Modeling

Background:

• Accurate mechanical models of passive muscle tissue are essential for human body impact simulations.
• Previous models may not fully capture the complex, rate-dependent behavior of muscle under impact conditions.

Purpose of the Study:

• To experimentally investigate the mechanical response of porcine muscle tissue under high strain rate compression.
• To develop and validate a constitutive model for passive muscle tissue suitable for impact modeling.

Main Methods:

• Performed compressive loading tests on porcine muscle using a drop-tower rig at strain rates from 11,600%/s to 37,800%/s.
• Utilized inverse analysis to fit experimental data to a 1st order Ogden hyperelastic material law with a quasilinear viscoelastic (QVL) expansion.
• Optimized material parameters to minimize prediction errors for load and deformation.

Main Results:

• Observed nonlinear stress-stretch relationships and significant rate dependency in muscle tissue.
• Experimental data showed engineering stresses ranging from 5.95 kPa to 43.66 kPa across different directions and strain rates.
• The developed Ogden-QVL model accurately predicted tissue response with less than 3% error in boundary condition force.

Conclusions:

• The 1st order Ogden hyperelastic model with a three-term QVL expansion effectively captures the mechanical response of passive muscle tissue at high strain rates.
• This validated model shows promise for application in whole-body impact simulations.
• Experimental challenges like fluid exudation and strain variation were noted, highlighting the complexity of muscle tissue testing.