C-Scan Imaging for Bond Testing Inspection

C-Scan Imaging for Bond Testing Inspection

R. Sicard, H. Serhan

TecScan Systems Inc. www.tecscan.ca

2010 ATA NDT Forum, Sheraton Uptown Hotel/Albuquerque, NM, September 20-23, 2010

Presentation Plan

• Introduction • Background on Bond Testing

• Resonance • MIA • Pitch-and-catch

• Experimental setup • Experiments:

• Sample 1: Delaminations in carbon composite plate • Sample 2: Defects in aluminum honeycomb /carbon

composite structure • Conclusion


•Adhesive bonded components are widely used in aerospace industry •Bond testing has typically been done with

ultrasounds • Pulse-echo UT: Echo of interface • Through-transmission: Loss of echo •Guided Waves (TT): Loss/modification of echo

Introduction


Specialized instruments are commercially available

Introduction

•Objective

•Combine C-Scan and Bond testing technologies


• Add intuitive image analysis offered by C-Scan • Increase data analysis possibilities • Provide better sizing capabilities

• Specialized bond testing is typically done in three modes • Resonance • MIA (Mechanical impedance analysis) • Pitch-and-catch

Background: Bond Testing


• Principle of operation • Narrowband transducer • Ultrasonically coupled to the tested part • Excitation: monochromatic wave (typically)

Bond Testing: Resonance

Ceramic

Matching layer


• Frequency is selected to optimize conditions of standing wave • Presence of disbond modify acoustic impedance and hence

resonance frequency is affected

Bond Testing: Resonance

Disbond


Resonance frequency is damped differently by material and is monitored as amplitude and phase changes

• Principle of operation • Dual transducer with single tip contact • Excitation: Audible waves (monochromatic) • Nulling is performed on a good bond

• Driving and receiving element are in phase

Bond Testing: MIA

Driving element

Receiving element


•Disbond: Change of Material Stiffness • Affects loading of the receiving element

• Receiving element no longer in phase with driving element

Bond Testing: MIA

Decrease in stiffness

Disbond


Difference in amplitude and phase between driving and receiving elements reveals the presence of disbonds

• Principle of operation • Separate emitter and receiver • No couplant required • Three modes of operation

• RF • Impulse (tone burst) • Frequency sweep

Bond Testing: Pitch-and-Catch

Emitter element Receiving element


•Waves travel from transmitter to receiver •Disbond or delamination: thin plate section

• Guided (Lamb) waves


Disbond


• Predominance of flexural waves A0 mode •Amplitude and phase shifts are function of

changes of thickness, i.e. presence of disbond



Experimental Setup

• BondMaster 1000e+

• 14 bit waveform digitizer

• ARMANDA: Portable XY Scanner

• TecView™ BT software


• Sample 1: Carbon/Epoxy composite with Teflon® inserts • 8 plies, 0°/90°, thickness = 1.9 mm

• Reference: 10 MHz C-Scan inspection (PE)

Depth: ~1 mm

(0.039’’)

Depth: ~1.25 mm

(0.049’’)

Experiments: Sample 1


• Resonance probe (250 kHz) • Scanning Resolution: 1 mm x 1 mm (0.025’’ x 0.025’’) • Scanning velocity: 50 mm/s (2 ’’/s)

UT (10 MHz)

BT - C-Scan of Amplitude



• Phase: Variations indicate different depths • Display similar to time-of-flight or thickness C-Scan

BT - C-Scan of Phase

UT (10 MHz) - TOF



• Alarms: • C-Scans based on alarm detection can provide

information about defects

BT - C-Scan of Phase

UT (10 MHz) - TOF



• Sizing comparisons (-6 dB drop):

• Sizing of BT @ 250 kHz is comparable to UT @ 10 MHz

Insert 1 X

Insert 1 Y

Insert 2 X

Insert 2 Y

UT – 10 MHz 13 ± 1 mm 12 ± 1 mm 6 ± 1 mm 7 ± 1 mm

BT – 250 kHz 11 ± 1 mm 11 ± 1 mm 6 ± 1 mm 6 ± 1 mm

Insert 1

Insert 2



• Sample 2: Aerospace standard for bond defects • Honeycomb cores (Aluminum)

• 0.187’’ and 0.250’’ • Composite plates (carbon/epoxy) • Typical defects

• Delaminations • Core unbonds • Excessive adhesive • Crushed cores



• Resonance probe (110 kHz): • Amplitude C-Scan



• Resonance probe (110 kHz) • Phase C-Scan



• Null can be adjusted in post-processing • Null performed prior to inspection



• Null can be adjusted in post-processing • Point Null performed in post-processing



• Null can be adjusted in post-processing • Line Null performed in post-processing



Conclusion

• Specialized Bond Testing benefits from C-Scan imaging • Image provides intuitive display of results • Alarm based results still apply • Sizing capabilities are improved and comparable to

conventional UT • Commercial units possess the analog outputs for

impedance-type display (Resonance & MIA) • Trigger options would be required for RF and Swept

frequency techniques (Pitch-and-Catch)


TecScan Systems Inc.

75, De Mortagne Blvd., Suite 122 Boucherville (Québec)

Canada, J4B 6Y4

www.tecscan.ca

C-Scan Imaging for Bond Testing Inspection

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