Final Year Seminar
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Transcript of Final Year Seminar
![Page 1: Final Year Seminar](https://reader031.fdocuments.net/reader031/viewer/2022022419/58830e531a28ab31068b4e7d/html5/thumbnails/1.jpg)
NDT of fiber-reinforced composites with a new laser-ultrasound system
Guided By:Prof Arun JMechanical Eng Department
Presented By:Aaron K JohnMechanical Engineering
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Introduction
• Non contact method• Currently no non-contact NDT method approaches the
sensitivity of contact NDT method• Methods:
non-contact NDT: Michelson Interferometernew non contact NDT: LU Interferometercontact NDT: Piezoelectric Transducer
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About seminar
In this new approach we utilize recent
progress in fiber laser systems andtelecommunication optics to improve thesensitivity of non-contact method
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Current non contact methodMichelson Interferometer
• Combine laser beams to obtain interference pattern, to measure surface defects etc.
• Very sensitive to environmental noise
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Experiment Samples
• 3.6 mm thick andcontained 19 individuallayers.
• Artificial defects ofabout 20um thick
- brass foil- tape- polymer
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New laser-ultrasound method
Experiment components
1. Pulsed laser source2. Super luminescent diode (SLD)3. Polarization controller4. Receive Head5. Polarizing Beam splitters (PBS)6. Photo Detector (PD)
Interferometer
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1. laser radiation initially polarized
2.Divided into two arms with a polarization beam splitter PBS1
3.PBS2 combines the delayed beams into one fiber
4.focuses the probe radiation onto the sample surface5.Radiation back to the fiber contains 2 delayed waves, similar to incident beams
6.beams are split again to reduce noise
EXPERIMENT ARRANGMENT AND PROCEDURE
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• When no pulsed laser present, interferometerrecords nothing• But when pulsed laser present, acoustic pulsegenerated, interferometer records the pressuredifference
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Experiment with PVDF Transducer
• Polyvinylidene Fluoride (PVDF)• A type of piezoelectric transducer
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Results
Signals recorded with LU (grey line) and with contactPVDF (dark line)
Result 1.
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image obtained with Interferometer
Result 2.
Image obtained with contact PVDF detector
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Inference
1. From Result 1 we infer that the sensitivity ofthe non contact LU detector is comparable tothat of a contact piezoelectric transducer.
2. From Result 2 PVDF transducer is about oneorder of magnitude more sensitive than theSagnac detector. Hence we infer LU detectorin comparable to a piezoelectric transducer
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Conclusions
The new laser ultrasound
- is a non contact method
- does not need adjustment and stabilization
- can be mounted on any surface
- less expensive
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Reference
1. National Center for BiotechnologyInformation (USA)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3971821/
2. NDT of fiber reinforced composites with anew fiber optic pump probe laser ultrasoundsystem. (Science Direct)
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THANK YOU