Stable and unstable fatigue prediction for A572 structural steel using acoustic emission

The association of acoustic emission (AE) signals with crack growth behavior in the material of interest is the basis for monitoring the fatigue damage of in-service steel structures with the AE method. A model including the absolute energy rate of AE, stress intensity, fracture toughness and load ratio is presented to predict crack extension and remaining fatigue life for stable and unstable crack stages. The model is based on the Forman equation, and the balance between AE signal energy and the energy released due to crack growth. Results from AE-monitored fatigue tests with load ratios of 0.02, 0.1 and 0.7 are utilized to validate the presented model. To separate AE signals associated with crack growth from noise, a combined approach involving pattern recognition and analysis of waveform features was employed. Prediction procedures are demonstrated based on the presented model and experimental data. Reasonable agreement exists between the observed and predicted test results. The presented model conservatively estimates fatigue damage and remaining fatigue life.

► A fatigue prognosis methodology based on acoustic emission (AE) energy is presented.
► The methodology applies to stable and unstable cracking in structural steel.
► Agreement between predicted results and experimental results is demonstrated.
► AE-based fatigue life prediction is extended to unstable cracking stage.
► Critical cracking level can be estimated with the presented models.