Non Destructive Testing:
Finding Defects in Metal Objects
Design Team 4:
•Chad Church
•Ron Fox
•John Vogel
•Geoff Brigham
•Matt Hamm
Agenda
• The Need For Non-Destructive Testing
• Methods of NDT
– Eddy Currents
– Acoustic
– Ultrasonic Testing
• Summary
Non-Destructive Testing
“Test object, material or system without impairing its future usefulness”
• Industrial Application
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Crack Detection
Wall Thinning
Porosity
Thickness of Material
• Medical Application
– Ultrasound
– X-Ray
http://zone.ni.com/cms/images/devzone/tut/a/7e46be30706.gif
Benefits of NDT
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Ensure Product Integrity
To Avoid Failures
Better Product Design
Lower Manufacturing Costs
Maintain Uniform Quality Level
Methods of NDT
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Visual Testing
Penetrant Testing
Magnetic Particle Testing
Infrared/Thermal Testing
Eddy Current Testing
Acoustic Emission Testing
Ultrasonic Testing
Method: Eddy Currents
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Eddy current probe is a coil of wire
Induces a magnetic field
Induces a current in the part
Induces a magnetic field
Induces a current in the probe
Measure the Current
VICTORY!
Method: Eddy Currents
• Detect:
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Conductivity
Magnetic Permeability
Distance
Presence of a flaw
• Depth of penetration
• “Skin effect”
• Exponential drop-off
Method: Eddy Currents
• Limitations
• Aluminum parts
• Iron parts
Method: Acoustic Testing
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Inspiration: Hit it with a hammer, listen
Resonance frequency
Harmonic frequencies
Fourier transform
Method: Acoustic Testing
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Mechanical impact on different locations
Microphone reception
Fourier Transform
Correlation of multiple impact resonations
oi:10.1006/jaer.2000.0542
Method: Acoustic Testing
Method: Acoustic Testing
Method: Acoustic Testing
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Variety of material and composition
Environmental deterioration
Damping
Access to many points
Method: Ultrasonic Testing
What is Ultrasound?
• Sound Waves
• 100 KHz to 50 MHz for NDT
• Short Wavelength
– Reflections Off Small Defects
• Requires Elastic Medium
http://www.olympus-ims.com/data/File/panametrics/UT-technotes.en.pdf
Method: Ultrasonic Testing
• Components of an Ultrasonic Flaw Detector
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Power Supply
Timer
Pulser/Amplifier
Ultrasonic Transducer
Receiver
Computer Display
Method: Ultrasonic Testing
Ultrasonic Transducer
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Electrical Energy
Mechanical Energy
Piezoelectric Effect
Alternating Voltage Applied To Crystal
Crystal Expands and Contracts
– Creates High Frequency Alternating Charge on Crystal
Method: Ultrasonic Testing
Couplants
• High Frequency/Short Wavelength
– Minimal Propagation in Air Medium
• Types of Couplants
– Oil
– Glycerine
– Water
• Another Option
– Direct Contact Transducer
Method: Ultrasonic Testing
Advantages of Ultrasonic Testing
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Fast Response
Accuracy
High Sensitivity
Flexibility
Penetrating Power
Method: Ultrasonic Testing
Limitations of Ultrasound
• Sensitivity
• Resolution
• Noise Discrimination
Summary
• Necessary to use a Non Destructive Testing
• Eddy Currents
– Abilities
– Problems
• Acoustic
– Abilities
– Problems
• Ultrasound
– Abilities
– Problems
• Team Designed Method
(http://www.youtube.com/watch?v=IE6wk1Z-bLc&NR=1)
Questions?