研究目的
To develop an all-optical ultrasound sensing system based on the photoacoustic principle for monitoring and investigating the initiation of early stage steel rebar corrosion in real time.
研究成果
The all-optical ultrasound sensing system effectively monitors early-stage rebar corrosion, with centroid frequency shifts correlating exponentially with mass loss. This provides a mathematical model for predicting corrosion levels, offering advantages such as immunity to electromagnetic interference and high resolution. Future work should address challenges in predicting complex corrosion processes and optimizing FBG selection for improved performance.
研究不足
Corrosion of steel rebar is a complex physicochemical process, making it hard to predict corrosion status accurately due to rust formation and expansion. External interferences like temperature changes can affect FBG performance, requiring careful selection of FBG to improve signal-to-noise ratio. The method may not fully account for all corrosion mechanisms in real-world applications.
1：Experimental Design and Method Selection:
The study uses an all-optical ultrasound sensing system based on the photoacoustic principle. Ultrasound signals are generated by gold nanocomposites coated on optical fibers and received by a fiber Bragg grating (FBG) sensor. The methodology involves generating ultrasound waves and analyzing their frequency shifts to detect corrosion.
2：Sample Selection and Data Sources:
Four No. 4 bare steel rebars are used as specimens. Accelerated corrosion tests (ACT) are conducted with different corrosion levels induced by spraying NaCl solution at varying frequencies over 2, 4, 6, and 8 days.
3：List of Experimental Equipment and Materials:
Equipment includes a nanosecond laser (Surelite-I-10, Continuum), tunable laser (NewFocus TLB-6600, Newport), photodetector (PDA10CS, THORLABS), data acquisition system (DAQ) (M2i.4032, Spectrum), multimode fiber (UM22-400, Thorlabs), FBG sensor, gold nanocomposites, and various materials like acetone, epoxy, and ultraviolet glue.
4：2i.4032, Spectrum), multimode fiber (UM22-400, Thorlabs), FBG sensor, gold nanocomposites, and various materials like acetone, epoxy, and ultraviolet glue.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The ultrasound generator is fabricated by coating gold nanocomposites on a stripped multimode fiber attached to the rebar. The FBG receiver is attached opposite the generator. Ultrasound signals are generated and detected, with data acquired and processed using short-time Fourier transform to analyze frequency shifts.
5：Data Analysis Methods:
Data is analyzed using short-time Fourier transform to obtain spectrograms. Centroid frequency shifts are calculated from the half-power level contours of the spectrograms. An exponential relationship is fitted between centroid frequency shift and mass loss of the rebar.
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