DirectedAcousticShearography<br />-or-What youcan not seeCAN hurt you<br />Russell Kurtz, PHDChief Scientist, RANscitechAp...
During the past decade, a large percentage of the aircraft accidents reported were caused by corrosion or other buried dam...
When these defects occur in modern materials made up of several layers, detection can be difficult and expensive.<br />Dis...
Aloha Airlines Flight 243, April 28, 1988<br />It is , therefore, critical to develop a Nondestructive Evaluation (NDE) Te...
Existing NDE Technologies<br />HolographyEddy CurrentThermography<br />Better at finding surface cracks than buried cracks...
Directed Acoustic Shearography<br />FAST<br />Shearography using an acoustic stress source is the basis of Directed Acoust...
THEORY<br />RAN Science and Technology LLC<br />
Differential Surface Metrology<br />Presentation to SPIEApril 2010Orlando, Florida<br />by<br />Russell Kurtz, PHDChief Sc...
Shearography Stress Methods<br />0.3-in. auto part<br />Apply Heat<br />Acoustic Signal<br />Takes between 3 and 60 second...
Directed Acoustic Shearography<br />An acoustic signal could be a good source of stressIFit could be focused.<br />This ca...
The PA<br />A 2D array of transducers whose relative phase and intensity can be controlled<br />Able to focus the signal d...
Advantages of DAS<br />0.3-in. auto part<br />Spherical Wave Acoustic Signal<br />Acoustic Intensity:0.274 W/cm²<br />Coll...
DAS Also Improves Resolution<br />For accurate determination of defect depth, a minimum of four scans must be performed at...
MODELING & EXPERIMENT<br />RAN Science and Technology LLC<br />
Test Coupons<br />0.1-in. thick aluminum, 2x4 inches, drilled on 1-inch centers. One side (a) polished, the other (b) roug...
Finite Element Modeling<br />We found that a 0.1-in. diameter collimated beam,with an acoustic power of 125mW, would induc...
Experiment<br /><ul><li> Run at low frequency (20 kHz) due to limitations of the equipment (ideal closer to 500 kHz)
 Tested at two voltages (0-9 V and 0-30 V) corresponding  to 450mW and 1.5 W acoustic power
 Acoustic intensities equivalent to 590 mW/cm² at lower voltage and 2.0 W/cm² at higher </li></ul>RAN Science and Technolo...
Results<br />Net deflection increase 2.9 µm with 9 V<br />Net deflection increase 10 µm with 30 V<br />0.4<br />0.2<br />0...
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Directed Acoustic Shearography Or What You Cant See Can Hurt You

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Superior scientific technology to find buried defects in metal

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Directed Acoustic Shearography Or What You Cant See Can Hurt You

  1. 1. DirectedAcousticShearography<br />-or-What youcan not seeCAN hurt you<br />Russell Kurtz, PHDChief Scientist, RANscitechApril 2010<br />
  2. 2. During the past decade, a large percentage of the aircraft accidents reported were caused by corrosion or other buried damage<br />
  3. 3. When these defects occur in modern materials made up of several layers, detection can be difficult and expensive.<br />Disassembly itself causes damage and some composites can’t be disassembled at all.<br />Defect<br />LAYERS OF METAL<br />
  4. 4. Aloha Airlines Flight 243, April 28, 1988<br />It is , therefore, critical to develop a Nondestructive Evaluation (NDE) Technology that can find these buried defects, corrosion, or damage spots rapidly, accurately, and efficiently.<br />
  5. 5. Existing NDE Technologies<br />HolographyEddy CurrentThermography<br />Better at finding surface cracks than buried cracks<br />X-Ray ImagingTHz TransmissionComputed Tomography<br />Require access to both sides of a piece<br />Capable of detecting buried defects (with thermal source), but very slow<br />Shearography<br />
  6. 6. Directed Acoustic Shearography<br />FAST<br />Shearography using an acoustic stress source is the basis of Directed Acoustic Shearography<br />
  7. 7. THEORY<br />RAN Science and Technology LLC<br />
  8. 8. Differential Surface Metrology<br />Presentation to SPIEApril 2010Orlando, Florida<br />by<br />Russell Kurtz, PHDChief ScientistRAN Science & Technology<br />Reference scan<br />Stress scan<br />Shear scan<br />Applied stress interacts with any voids, cracks, or defects<br />Stress scan subtracted from reference scan<br />RAN Science and Technology LLC<br />
  9. 9. Shearography Stress Methods<br />0.3-in. auto part<br />Apply Heat<br />Acoustic Signal<br />Takes between 3 and 60 seconds for thermal equilibrium to be reached<br />Stress propagates through depth virtually instantly<br />However, a typical spherical wave is not a good choice as its intensity decreases as fast as the depth squared<br />RAN Science and Technology LLC<br />
  10. 10. Directed Acoustic Shearography<br />An acoustic signal could be a good source of stressIFit could be focused.<br />This can be accomplished with a Phased Array Acoustic Transducer (PA)<br />RAN Science and Technology LLC<br />
  11. 11. The PA<br />A 2D array of transducers whose relative phase and intensity can be controlled<br />Able to focus the signal down to a narrow spot, or create a collimated beam of acoustic intensity<br />RAN Science and Technology LLC<br />
  12. 12. Advantages of DAS<br />0.3-in. auto part<br />Spherical Wave Acoustic Signal<br />Acoustic Intensity:0.274 W/cm²<br />Collimated Acoustic Beam(diameter 0.1 in)<br />Acoustic Intensity:19.7 W/cm²<br />RAN Science and Technology LLC<br />
  13. 13. DAS Also Improves Resolution<br />For accurate determination of defect depth, a minimum of four scans must be performed at different angles. The exact number depends on the thickness of the material.<br />RAN Science and Technology LLC<br />
  14. 14. MODELING & EXPERIMENT<br />RAN Science and Technology LLC<br />
  15. 15. Test Coupons<br />0.1-in. thick aluminum, 2x4 inches, drilled on 1-inch centers. One side (a) polished, the other (b) rough. Rough side with small defect made by a 1/32-inch drill.<br />(a)<br />(b)<br />RAN Science and Technology LLC<br />
  16. 16. Finite Element Modeling<br />We found that a 0.1-in. diameter collimated beam,with an acoustic power of 125mW, would induce a surface deflectionof >7.5 µm if it encountered the 1/32-in. defect.<br />RAN Science and Technology LLC<br />
  17. 17. Experiment<br /><ul><li> Run at low frequency (20 kHz) due to limitations of the equipment (ideal closer to 500 kHz)
  18. 18. Tested at two voltages (0-9 V and 0-30 V) corresponding to 450mW and 1.5 W acoustic power
  19. 19. Acoustic intensities equivalent to 590 mW/cm² at lower voltage and 2.0 W/cm² at higher </li></ul>RAN Science and Technology LLC<br />
  20. 20. Results<br />Net deflection increase 2.9 µm with 9 V<br />Net deflection increase 10 µm with 30 V<br />0.4<br />0.2<br />0.0<br />-0.2<br />-0.4<br />0.4<br />0.2<br />0.0<br />-0.2<br />-0.4<br />2.0<br />1.5<br />1.0<br />0.5<br />0.0<br />–0.5<br />6<br />4<br />2<br />0<br />-2<br />y-Position (in.)<br />Difference (μm)<br />y-Position (in.)<br />Difference (μm)<br />-0.4 -0.2 0.0 0.2 0.4<br />x-Position (in.)<br />-0.4 -0.2 0.0 0.2 0.4<br />x-Position (in.)<br />RAN Science and Technology LLC<br />
  21. 21. Summary<br />The concept of Directed Acoustic Shearography has been proven<br />We found it!<br />RAN Science and Technology LLC<br />
  22. 22. Conclusion<br />Still keep your eye out for alligators<br />

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