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
• 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
“Test object, material or system without impairing its future usefulness”
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
doi: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
• Sound Waves• 100 KHz to 50 MHz for NDT• Short Wavelength
– Reflections Off Small Defects• Requires Elastic Medium
What is Ultrasound?
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
• Electrical Energy Mechanical Energy• Piezoelectric Effect• Alternating Voltage Applied To Crystal• Crystal Expands and Contracts
– Creates High Frequency Alternating Charge on Crystal
Ultrasonic Transducer
Method: Ultrasonic Testing
• High Frequency/Short Wavelength– Minimal Propagation in Air Medium
• Types of Couplants– Oil– Glycerine– Water
• Another Option– Direct Contact Transducer
Couplants
Method: Ultrasonic Testing
• Fast Response• Accuracy• High Sensitivity• Flexibility• Penetrating Power
Advantages of Ultrasonic Testing
Method: Ultrasonic Testing
• Sensitivity• Resolution• Noise Discrimination
Limitations of Ultrasound
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?