Finite element modeling of damage accumulation in trabecular bone under cyclic loading

Area of Science:

• Biomechanics
• Materials Science
• Computational Modeling

Background:

• Trabecular bone damage accumulation under cyclic loading is crucial for understanding bone fragility.
• Existing models often simplify the complex microstructural behavior of trabecular bone.
• Distinguishing failure mechanisms in different loading regimes is essential for accurate prediction.

Purpose of the Study:

• To develop and validate a two-dimensional finite element model for trabecular bone damage.
• To investigate damage accumulation mechanisms, specifically crack propagation and creep failure.
• To compare model predictions with experimental data for S-N curves under varying cyclic loads.

Main Methods:

• A 2D finite element model of a honeycomb-like trabecular bone structure was created.
• Trabeculae were modeled as linearly elastic beam elements with microcracks.
• Crack propagation was simulated using the Paris law, with iterative removal of fractured elements.

Main Results:

• Fracture of a small number of trabeculae significantly reduced the specimen's modulus.
• Model predictions showed good agreement with experimental S-N curves in the low-stress, high-cycle range.
• Crack propagation dominated low-stress fatigue, while creep deformation was primary in high-stress, low-cycle fatigue.

Conclusions:

• Trabecular bone fatigue failure is dependent on the stress and cycle regime.
• Microcrack growth is the primary mechanism for high-cycle, low-stress fatigue.
• Creep deformation and fracture are the primary mechanisms for low-cycle, high-stress fatigue.