Final Year Seminar
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Transcript of Final Year Seminar
NDT of fiber-reinforced composites with a new laser-ultrasound system
Guided By:Prof Arun JMechanical Eng Department
Presented By:Aaron K JohnMechanical Engineering
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
About seminar
In this new approach we utilize recent
progress in fiber laser systems andtelecommunication optics to improve thesensitivity of non-contact method
Current non contact methodMichelson Interferometer
• Combine laser beams to obtain interference pattern, to measure surface defects etc.
• Very sensitive to environmental noise
Experiment Samples
• 3.6 mm thick andcontained 19 individuallayers.
• Artificial defects ofabout 20um thick
- brass foil- tape- polymer
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
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
• When no pulsed laser present, interferometerrecords nothing• But when pulsed laser present, acoustic pulsegenerated, interferometer records the pressuredifference
Experiment with PVDF Transducer
• Polyvinylidene Fluoride (PVDF)• A type of piezoelectric transducer
Results
Signals recorded with LU (grey line) and with contactPVDF (dark line)
Result 1.
image obtained with Interferometer
Result 2.
Image obtained with contact PVDF detector
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
Conclusions
The new laser ultrasound
- is a non contact method
- does not need adjustment and stabilization
- can be mounted on any surface
- less expensive
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)
THANK YOU