研究目的
To propose a noncontact nondestructive testing (NDT) method for detecting damage in plate-like structures and identifying the location of the damage using a scanning laser source actuation technique.
研究成果
The proposed ultrasonic wave propagation imaging system and flaw imaging technique based on ND:YAG pulsed laser system and wavenumber filtering successfully detected notches in steel coupons and various types of damages in aluminum plates. Tangential damages to the incident wavefront were clearly identified, while inclined and perpendicular damages were visible but less clearly detected. Further research is needed to investigate the detectable size of flaws and to clearly detect various damages in different types of structures.
研究不足
The method's effectiveness is partially limited by the sparse scanning grid, the window for wavenumber filtering, and the filtering direction. Additionally, the detectability of various damage types (e.g., inclined and perpendicular damages to the incident wavefront) is not as clear as for tangential damages.
1：Experimental Design and Method Selection:
The study utilizes a scanning laser source actuation technique to generate guided waves and scans a specific area to detect damage. The ND:YAG pulsed laser generates Lamb waves, and a piezoelectric sensor measures the structural responses. The responses are analyzed using 3-dimensional Fourier transformation (3DFT).
2：Sample Selection and Data Sources:
Aluminum and steel plates with notches are used as samples to verify the effectiveness of the proposed method.
3：List of Experimental Equipment and Materials:
ND:YAG pulsed laser, piezoelectric sensor, Q-switched laser system, galvanometer and tilting mirror for laser-scanning path, digitizer for measuring signals.
4：Experimental Procedures and Operational Workflow:
The laser beam scans the target structure, generating ultrasonic waves. The waves are measured by a piezoelectric sensor, and the data is processed using 3DFT and wavenumber filtering to extract damage-sensitive features.
5：Data Analysis Methods:
The measured responses are analyzed using 3DFT, and damage-sensitive features are extracted by wavenumber filtering. Flaw imaging techniques are then conducted using these features.
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