NDT with shearography og TV-holography - theory and applications Eiolf Vikhagen, PhD Optonor AS Trondheim
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NDT withshearography og TV-holography
- theory and applications
Eiolf Vikhagen, PhDOptonor ASTrondheim
Optonor part of the”Trondheim Group”
which has been working withspeckle interferometry for several decades
Environment with many publicationsconsiderable research activities
Customers:
Rolls-Royce, Honeywell, Panasonic, Nokia, Toyota, Suzuki, Volvo Aero, HIH, Nissan, Honda, Suzuki, US Air Force, Ocè, Huges Aircraft, Siemens, Fiat Avio, Hitachi, Vibro-Meter, Saab, Royal Norwegian Air Force, Bang&Olufsen and many other companies, research groups and Universities in Europe, USA and Asia.
TV-holography – how it works
Shearography - how it works
Comparison TV-holography to shearography
• Shearography more stable in noisy environments and in-field measurements
• Shearography can be used on larges surfaces• Shearography can tolerate more loading of the obect
because shearography acquires less total displacementinformation
• TV-holography has better signal-to-noise ratio• TV-holography defines the shape and boarders of the
defects better than shearography• TV-holography should be used in quiet or in vibration
isolated environments
How to detect defects
• Excite or load the object gently with pressure vacuum, mechanicalforces, heating, single frequency vibrations, white noise excitation
• Measure surface deformations/vibrations with high sensitivity• Look for deviations in deformation pattern or vibration patterns or
modes
TV-holography: Thermal loading of material with delamination
Phase map 3D plot
Line plot Spatial derivative
Shearografi: Termisk pålastning av materiale med delaminering
Phase map 3D plot
Line plot Spatial derivative
Shearography: Detection of core failure by mechanical pressure
Vibration testing in traditional holographic mode (shear)
Panel with debonds, excited at two different frequencies
New technology from TV-holography modal analysis systems
Panel with debond, 4770 Hz
Vibration testing TV-holography
Panel with two defects
Vibration testing TV-holografi
Panel with surface crack
Vibration testing shearography
Panel with core failure and debond
Vibration testing shearography
Panel with core failure and debond – amplitude map
Vibration testing shearography
Panel with defect
Vibration testing TV-holography
Panel with unknown defect
Shearography: Testing of large structures with nano waves
Sandwich ship structure
Shearography: Testing of large structures with nano waves
Principle with rayleigh waves
Shearography: Testing of large structures with nano waves
Ship structure
Shearography: Testing of large structures with nano waves
Traditional shearography does not indicate defect
Shearography: Testing of large structures with nano waves
High sensitivity system show defect
Shearography: Testing of large structures with nano waves
The new shearography system candetect nano waves in normal workhop environments because of:
• Gradient functionality• New lock-in type recording
Shearography: Testing of large structures with nano waves
Comparison of coin-tapping (left) to shearography (right)
NEW SHEAROGRAPHY PRINCIPLE
- Nanowave testing
Sandwich panel withdamaged area marked in red
Concluding remarks
• New innovations make shearography and TV-holography more useful in NDT applications
• Many different types of defects can be detected
• The methods have several modes of operationfor both static and dynamic excitation
• New shearography technology gives increasedpotential for testing of large structures
• Important to find optimal excitation methodfor each NDT application
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