Fatigue Analysis and Defect Size Evaluation of Filled NBR including Temperature Influence.

Area of Science:

• Materials Science
• Polymer Science
• Mechanical Engineering

Background:

• Filled non-crystallizing elastomers exhibit complex fatigue behavior.
• Understanding fatigue mechanisms is crucial for material design and performance prediction.

Purpose of the Study:

• To investigate the fatigue behavior of filled non-crystallizing elastomers.
• To analyze fatigue crack initiation and growth regimes.
• To establish a fracture mechanics approach for predicting fatigue life.

Main Methods:

• Axisymmetric dumbbell specimens were subjected to fatigue testing.
• Wöhler curves were plotted to determine power law behavior.
• Hysteresis curves, moduli, energies, and forces were analyzed to distinguish fatigue regimes.
• Fracture mechanics and X-ray microcomputed tomography (μ-CT) were employed.
• J-integral evaluation was performed for notched and unnotched specimens.

Main Results:

• A power law relationship was observed in the fatigue behavior.
• Heat buildup due to cyclic loading was monitored.
• Fracture surface analysis revealed distinct regions of initiation, fatigue striation, and catastrophic failure.
• Notched samples showed a significant reduction in fatigue life.
• A critical defect size for fatigue was calculated at approximately 9 μm.
• A geometry-independent correlation between J-integral and fatigue life was established.

Conclusions:

• Fatigue behavior in these elastomers can be described by a power law.
• Fracture mechanics provides valuable insights into fatigue failure mechanisms.
• The critical defect size is influenced by material properties and testing conditions.
• The J-integral offers a robust parameter for correlating fatigue life across different geometries.