Mass spring lattice modeling of the scanning laser source technique

Area of Science:

• Non-destructive testing
• Ultrasonic NDT
• Laser ultrasonics

Background:

• Surface-breaking defects pose significant challenges in material integrity assessment.
• Conventional NDT methods may struggle with detecting small or sub-surface flaws.
• Laser ultrasonics offers a contactless approach for material inspection.

Purpose of the Study:

• To numerically simulate the Scanning Laser Source (SLS) technique for detecting surface-breaking defects.
• To validate the simulation model against experimental observations of SLS.
• To explore the capability of SLS for sizing sub-wavelength surface cracks.

Main Methods:

• Numerical simulation using the mass spring lattice model.
• Modeling thermoelastic laser generation of ultrasound with shear dipole distribution.
• Utilizing spatial and temporal energy profiles of pulsed laser sources.
• Scanning the laser source over an aluminum block with a surface-breaking crack.

Main Results:

• Observed variations in amplitude and spectral content of laser-generated ultrasound over defective areas.
• The numerical model accurately captured experimentally observed SLS amplitude and spectral signatures.
• Demonstrated the potential of SLS to detect and characterize surface-breaking cracks.

Conclusions:

• The mass spring lattice model provides a reliable simulation for the SLS technique.
• SLS is a promising tool for detecting small surface-breaking defects.
• Further exploration into SLS for crack sizing, especially sub-wavelength defects, is warranted.