Rate-dependent crack nucleation in cartilage under microindentation.

Area of Science:

• Biomaterials Science
• Biomechanics
• Tissue Engineering

Background:

• Articular cartilage is a load-bearing tissue susceptible to damage.
• Understanding cartilage failure mechanisms is crucial for treating joint injuries.
• Previous studies have not fully elucidated the rate-dependent nature of cartilage crack nucleation.

Purpose of the Study:

• To investigate the rate-dependent crack nucleation in cartilage using microindentation.
• To explore the role of poroviscoelasticity and material behavior in cartilage failure.
• To correlate mechanical testing with microstructural observations.

Main Methods:

• Microindentation tests were performed on cartilage at varying loading rates.
• Finite element (FE) modeling within a poroviscoelastic framework was employed.
• Scanning electron microscopy (SEM) was used for microstructural analysis of crack surfaces.

Main Results:

• Cartilage exhibited rate-dependent crack nucleation, requiring more work at slower rates.
• FE analysis indicated viscoelastic relaxation and localized tensile stresses govern nucleation.
• SEM revealed significant matrix relaxation and fiber rearrangement at slower loading rates.

Conclusions:

• Viscoelastic relaxation and fiber rearrangement are key factors in rate-dependent cartilage failure.
• Tensile stresses at the indenter tip are critical for crack initiation.
• This study enhances the understanding of cartilage's mechanical failure under dynamic loading.