研究目的
To estimate crack size, shape, and orientation numerically and experimentally using Lamb waves and imaging methods.
研究成果
Both imaging methods (synthetic time reversal and Gaussian distribution) successfully quantified crack size, shape, and orientation with acceptable accuracy. Stronger scattering waves from optimal sensor configurations improve results. Methods can localize smaller holes but struggle with precise size estimation. Future work includes applying methods to fatigue cracks and acoustic emission signals.
研究不足
Scattering signals are affected by confounding factors like sensor bonding, environmental noise, and electrical connections. Size estimation for smaller damages (e.g., 1-3 mm holes) is challenging due to weaker scattering waves. The methods may underestimate or overestimate actual sizes in experiments.
1：Experimental Design and Method Selection:
A hybrid global–local approach was used for numerical simulations to predict scattering wave signals. Two imaging methods were employed: synthetic time reversal (method A) and Gaussian distribution function (method B). Experiments involved pitch-catch and pulse-echo modes with piezoelectric wafer active sensors (PWAS).
2：Sample Selection and Data Sources:
An aluminum plate specimen with a simulated crack (10 mm length) and through-thickness holes (1 to 3 mm diameter) were used. Data were collected from PWAS networks.
3：List of Experimental Equipment and Materials:
Aluminum plates (1220 mm x 1220 mm x 1.6 mm and 600 mm x 600 mm x 1.6 mm), PWAS transducers (7 mm diameter, 0.2 mm thickness), function generator, oscilloscope, damping clay.
4：6 mm and 600 mm x 600 mm x 6 mm), PWAS transducers (7 mm diameter, 2 mm thickness), function generator, oscilloscope, damping clay.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: For crack estimation, eight PWAS were used in a circular network. Three-count tone burst signals at 450 kHz were generated. Scattering waves were captured, and baseline signals were subtracted. For hole estimation, six PWAS were used, and hole size was varied. Imaging methods applied summation, multiplication, and combined algorithms.
5：Data Analysis Methods:
Scattering signals were analyzed using synthetic time reversal and Gaussian distribution. Field values of pixels were computed, and algorithms (summation, multiplication) were used for image fusion. Crack and hole sizes were estimated from imaging results.
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