Self-Sensing Nonlinear Ultrasonic Fatigue Crack Detection under Temperature Variation ^†

Area of Science:

• Materials Science
• Non-Destructive Testing
• Mechanical Engineering

Background:

• Fatigue cracks pose significant risks in structural integrity.
• Temperature variations complicate traditional ultrasonic crack detection.
• Nonlinear ultrasonic methods show promise for enhanced defect characterization.

Purpose of the Study:

• To propose and validate a self-sensing nonlinear ultrasonic technique for fatigue crack detection under varying temperatures.
• To minimize data acquisition system nonlinearity for improved crack identification.
• To prevent temperature-induced false alarms in fatigue crack monitoring.

Main Methods:

• Utilizing a self-sensing piezoelectric transducer (PZT) to record linear (α) and nonlinear (β) ultrasonic parameters.
• Employing finite element method (FEM) simulations for numerical pre-validation.
• Conducting experimental validation on an aluminum plate with an induced fatigue crack.

Main Results:

• The self-sensing PZT scheme effectively minimizes system nonlinearity.
• Distinct behaviors of α and β parameters differentiate fatigue cracks from temperature effects.
• Successful experimental detection of fatigue cracks under unpredictable temperature conditions was achieved.
• A low positive false alarm rate of 0.12% was recorded.

Conclusions:

• The proposed self-sensing nonlinear ultrasonic technique reliably detects fatigue cracks in the presence of temperature variations.
• This method offers a robust solution for structural health monitoring in dynamic environments.
• The technique enhances the accuracy and reliability of non-destructive testing for fatigue damage.