Linking acoustic emission signatures to the initiation and growth of small fatigue cracks in CrMoV steel

Establishing a link between acoustic emission (AE) signatures and the initiation and growth of small fatigue cracks is crucial for monitoring damage evolution in pressure-bearing components. An investigation was conducted using in-situ AE monitoring and optical microscopy to study small fatigue crack growth (SFCG) behavior in CrMoV steel. Results show that the small crack growth rate exhibits a V-shaped fluctuation pattern that gradually attenuates with increasing crack length. AE parameters, including amplitude and entropy, effectively differentiate the stages of microstructural small crack growth, physical small crack growth, and final fracture. Furthermore, strong correlations are identified among crack path morphology, fracture surface features, and trends in both crack growth rate and cumulative AE activity. The study elucidates the intrinsic link between small crack growth and AE responses, providing a basis for enhanced fatigue damage monitoring and assessment in metallic materials.