Topographical characterization of electron beam sculpted surfaces by pulse phase thermography

Ang, K.C., Wood, R.J.K., Wang, L., Dulieu-Barton, J.M., Dance, B.G.I. and Buxton, A.L. (2007) Topographical characterization of electron beam sculpted surfaces by pulse phase thermography. Advanced Infrared Technology and Applications 9, Leon, Mexico. 07 - 11 Oct 2007. 1 pp .

Abstract

Pulse Phase Thermography (PPT) utilises an infrared detector to record variations in surface temperature when heated by a thermal source. PPT has been used to examine defects and detect damage in metal and composite structures. In recent work, PPT has been proposed as a means of making measurements of rough surfaces. 2 - 4 This paper investigates the use of PPT in measuring features in grossly sculpted metallic surfaces produced by a direct writing technique known as Surfi-Sculpt®. 5 - 6 Such features include protrusions and pits, which are formed within seconds by material displacement produced by subjecting the surface to a high energy focused electron beams. The dimensions of the features can vary between 0.1?m and 10mm high or deep and a quality assessment procedure for assessing the dimensional accuracy of the features has yet to be developed. PPT provides a possible option for a quality assessment procedure. This technique can monitor the reflections from the sculpted surface of the photons from a pulsed energy source. The temperature decay rate can then be mapped and related to the geometrical feature by accounting for the thermal diffusivity of the sample.
This paper develops a novel experimental setup to measure sculpted protrusions of titanium alloy Ti6Al4V with dimensions 5mm x 2.5mm (width to height). The experimental setup consists of a 17 Watt-hour flash light pulsed at 0.6ms duration and a FPA infrared detector with 320 x 256 pixel array resolution at 269 Hz maximum frame rate. The transmitted heat pulse is captured in video mode in the time domain by the detector and FFT is used to produce amplitude and phase data in the frequency domain. The contrast in the phase data is used to establish the frequency at which the feature becomes visible in the IR data and is the basis for determining the geometry of the feature.

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Contributors

Author: R.J.K. Wood

Author: L. Wang

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