Theoretical and Experimental Studies of Micro-Surface Crack Detections Based on BOTDA

Area of Science:

• Structural Health Monitoring
• Optical Sensing Technologies
• Materials Science

Background:

• Micro-surface crack detection is crucial for assessing the integrity of civil infrastructure.
• Brillouin scattering in optical fibers offers a promising method for non-destructive crack detection.
• A gap exists in comparing theoretical models with experimental data for Brillouin-scattering-based optical sensors.

Purpose of the Study:

• To present and demonstrate a distributed optical fiber sensor for monitoring micro-surface cracks.
• To compare theoretical simulations with experimental results for enhanced accuracy and validation.
• To investigate the relationship between crack characteristics and Brillouin scattering signals.

Main Methods:

• Utilized finite element methods to construct a 3D beam model for Brillouin optical time domain analysis (BOTDA) simulation.
• Numerically investigated the impact of crack opening displacement (COD) on Brillouin frequency shifts (distributed strain).
• Designed and conducted experiments on a 15m beam to validate simulation findings for crack detection.

Main Results:

• Simulation indicated a significant increase in Brillouin peak amplitude (27 με to 140 με) with enlarged COD (0.002 mm to 0.009 mm).
• Experimental results confirmed the capability to detect COD within the 0.002-0.009 mm range.
• Experimental data showed strong consistency with simulation predictions, validating the sensor's performance.

Conclusions:

• The developed distributed optical fiber sensor effectively monitors micro-surface cracks in civil structures.
• The study successfully bridged the gap between theoretical prediction and experimental validation for Brillouin scattering sensors.
• Future research directions include refining the sensing method and exploring broader applications in structural health monitoring.