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
– 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
• Ensure Product Integrity
• To Avoid Failures
• Better Product Design
• Lower Manufacturing Costs
• Maintain Uniform Quality Level
Methods of NDT
• Visual Testing
• Penetrant Testing
• Magnetic Particle Testing
• Infrared/Thermal Testing
• Eddy Current Testing
• Acoustic Emission Testing
• Ultrasonic Testing
Method: Eddy Currents
• 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:
– 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
• Inspiration: Hit it with a hammer, listen
• Resonance frequency
• Harmonic frequencies
• Fourier transform
Method: Acoustic Testing
• Mechanical impact on different locations
• Microphone reception
• Fourier Transform
• Correlation of multiple impact resonations
d oi:10.1006/jaer.2000.0542
Method: Acoustic Testing
Method: Acoustic Testing
Method: Acoustic Testing
• 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
– Power Supply
– Timer
– Pulser/Amplifier
– Ultrasonic Transducer
– Receiver
– Computer Display
Method: Ultrasonic Testing
Ultrasonic Transducer
• 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
• 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?