1. Core Research Report RCNDE IN CONFIDENCE Dept of Physics & School of Engineering University of Warwick RCNDE Meeting Stratford 2011 CORE RESEARCH PROJECT New approaches to NDE using micromachined sensors 2010-11

2. Core Research Report RCNDE IN CONFIDENCE Rapid prototyping and development of sensors. Focused on eddy current array – frequency sweep methods. Target defects specified by Rolls Royce and collaboration with Cummins on blade root inspection. Inspection needs addressed

3. Core Research Report RCNDE IN CONFIDENCE Outline of Programme Develop close packed array and verify if a static array can identify a 1mm long defect in any orientation. Experiments to sweep frequency of probe to examine resolution effects.

4. Core Research Report RCNDE IN CONFIDENCE Statement of status, progress, achievements Demonstrated close packed array resolution capability – 1mm defect detected on static array. Strong interest for some high value component surface defect inspections. Objectives for last period met.

5. Core Research Report RCNDE IN CONFIDENCE How MSL constructs a solid object (a) Desired solid object (b) Object cut up into “slices” (c) Result produced by MSL. Note vertical sides to each slice. Micro-stereolithography (MSL)

6. Core Research Report Schematic diagram of a micro-stereolithography (MSL) system – an example of a rapid prototyping system Embedded Microprocessor Digital Micro-Mirrors Resin PC UV Source Build Platform Model MSL Machine RCNDE IN CONFIDENCE Micro-stereo-lithography (MSL)

7. Core Research Report Example : Polymer ultrasonic devices Membrane fabricated separately and added to base. Bottom electrode Top electrode RCNDE IN CONFIDENCE Transducer best used as a receiver at low frequencies at a solid surface

8. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – impeller inspection – prototype 2 Prototype 2 (hard polymer) made to contain eddy current array and fit between blades as shown on left. Drawback – small changes in topography between each blade

9. Core Research Report RCNDE IN CONFIDENCE Principle of eddy-current inspection “generator” “detector” eddy current

10. Core Research Report RCNDE IN CONFIDENCE Principle of eddy-current inspection

11. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example of use of miniature coils as a flat pair ~1.4mm

12. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – sample ~1.4mm INCONEL - ~1mm micro-machined slot >1mm deep

13. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results CH2 AMP CONSTANT AC CURRENT DRIVE – 2 MHz CH1 AMP REL. AMP PHASE generator crack detector

14. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results CH2 AMPCH1 AMP REL. AMP PHASE CONSTANT AC CURRENT DRIVE – 2 MHz generator crack detector

15. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results CH2 AMPCH1 AMP REL. AMP PHASE CONSTANT AC CURRENT DRIVE – 2 MHz generator detector crack

16. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results CH1 AMP CONSTANT AC CURRENT DRIVE – 2 MHz CH1 AMP generator detector crack generator crack detector

17. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection

18. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results

19. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results

20. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results

21. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results

22. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results “parallel orientation”

23. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – flat array capabilities – results “perpendicular orientation”

24. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection “parallel orientation”

25. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection “parallel orientation”

26. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection “parallel orientation”

27. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection “perpendicular orientation”

28. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection “perpendicular orientation”

29. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – impeller inspection Laser micromachined slot ~ 1mm Thanks to Sean Winwood (Cummins) for this sample

30. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Impeller inspection – prototype MSL eddy current array for inspecting complicated shapes

31. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – impeller inspection – prototype 2 Prototype 2 (hard polymer) made to contain eddy current array and fit between blades as shown on left. Drawback – small changes in topography between each blade

32. Core Research Report RCNDE IN CONFIDENCE Polydimethylsiloxane (PDMS) is a popular material for casting flexible components from moulds. Mould is fabricated via MSL, then PDMS poured in and cured with heat. Fabricate MSL Mould Fill Mould with Liquid PDMS PDMS Cured with Heat to Give Flexible Rubber Structure MSL in Eddy Current Inspection Literally, a more ‘flexible’ approach is required

33. Core Research Report RCNDE IN CONFIDENCE MSL in Eddy Current Inspection Example – impeller inspection – prototype 3 Prototype 3 (soft deformable polymer) made to take up small differences in dimensions and shapes of blades.

34. Core Research Report The Finished Prototype The finished prototype will fit in all blade passages owing to the conformable nature of the PDMS Improvements are still required to compensate for varying stand-off as a result of the large blade to blade variation. Conformable PDMS probe body 50 coil array 40mm Thanks to Sean Winwood (Cummins) for this image

35. Core Research Report RCNDE IN CONFIDENCE Technology Transfer & Exploitation Flexible array probe undergoing further development : refine sensor delivery / lower noise multiplexing. New EngD project starting based on the MSL eddy current sensors. Sensor electronics now made available through spin-out company.

36. Core Research Report RCNDE IN CONFIDENCE Conclusions MSL is a quick and inexpensive route to optimising probe design. MSL has multifarious applications in NDE. Fairly simple and inexpensive electronics capable of high sensitivity in a number of modes (amplitude has better S:N). Flat array used to detect 1mm long target defect at MHz frequencies. Curved array shows promise - some technical challenges un- foreseen due to components being “out of specification”. Future work : refine sensor delivery lower noise multiplexing apply to different components apply MSL to ultrasonics