Observation of Rubber Fatigue Testing Specimens Using Two Types of X-Ray CT Systems

Importance of the Topic

Rubber products are widely used in automotive, industrial, and medical sectors. Fatigue and aging can lead to functional failures, making nondestructive evaluation of internal defects essential for ensuring reliability and extending service life.

Study Objectives and Overview

This study demonstrates the use of two complementary X-ray computed tomography (CT) techniques to observe and quantify micro-defect progression in rubber fatigue specimens cycled at different counts.

Methodology

• Fatigue testing of vulcanized acrylonitrile rubber with carbon black at 250, 500, and 1000 cycles.
• Specimens were imaged nondestructively to capture defect development before macroscopic failure.

Instrumentation Used

• Microfocus absorption CT (inspeXio SMX-225CT FPD HR Plus) with sample stretching and serial sectioning for high-magnification volumetric analysis.
• Phase-contrast CT (Xctal 5000) employing dark-field imaging and fluoroscopy to detect microcracks without sample deformation or magnification.

Key Results and Discussion

• Absorption CT revealed that both the number and total volume of internal defects increased with cycle count, and the largest defect size grew as fatigue progressed.
• Phase-contrast fluoroscopy highlighted microcracks smaller than the imaging resolution; dark-field images clearly distinguished cracks from dense inclusions.
• Phase-contrast CT cross-sections provided simultaneous absorption and dark-field views, enabling assessment of crack orientation, depth, and approximate size.

Benefits and Practical Applications

Nondestructive CT imaging allows precise quantification of defect evolution and efficient detection of early-stage cracks. This capability supports material development, quality assurance, and predictive maintenance in rubber component manufacturing.

Future Trends and Potential Applications

• Integration of absorption and phase-contrast modalities for real-time fatigue monitoring.
• Implementation of automated defect classification using machine learning.
• Extension to diverse elastomers and complex geometries, including in-field inspection systems.

Conclusion

Combining high-resolution microfocus CT with sensitive phase-contrast imaging offers a comprehensive toolkit for nondestructive analysis of fatigue-induced defects in rubber, enhancing understanding of damage progression and supporting improved durability assessments.