On Implementation of a Finite Element Visco-Hyperelastic Material Model for Spinal Ligaments in Explicit Time...

Area of Science:

• Biomechanics
• Computational Mechanics
• Materials Science

Background:

• Human spinal ligaments exhibit complex visco-hyperelastic behavior.
• Accurate modeling is essential for understanding spinal injuries and designing treatments.
• Existing models may lack stability under high strain rate conditions.

Purpose of the Study:

• To develop and validate a transversely isotropic, visco-hyperelastic constitutive model for human spinal ligaments.
• To implement the model using the Finite Element Method (FEM) in Ansys LS-Dyna.
• To enhance simulation stability and computational efficiency, particularly for high strain rate scenarios.

Main Methods:

• Developed a constitutive model combining Neo-Hookean and polynomial functions with viscous elements.
• Integrated Infinite Impulse Response (IIR) filtering for numerical stability.
• Acquired material parameters via nonlinear least squares fitting to experimental data.
• Validated the model against analytical solutions across multiple strain rates (0.5-300 s⁻¹).

Main Results:

• The FEM model accurately described the visco-hyperelastic behavior of spinal ligaments under high strain rates.
• IIR filtering successfully mitigated numerical instabilities in explicit time integration schemes.
• Model validation showed excellent agreement with analytical solutions across statistical metrics.
• The model demonstrated robustness across a wide range of strain rates.

Conclusions:

• The developed constitutive model provides a reliable tool for simulating spinal ligament biomechanics.
• The novel IIR filtering technique improves the computational performance and stability of FEM simulations.
• This model has potential applications for other soft tissues with visco-hyperelastic properties.
• The validated model can be applied to analyze various ligamentous structures in biomechanical studies.