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