Photothermal inspection of material changes in ceramic surfaces induced by mechanical load or laser treatment

Bernhard Schmitz; Jurgen Geerkens; Gert Goch

doi:10.1117/12.250735

18 September 1996 Photothermal inspection of material changes in ceramic surfaces induced by mechanical load or laser treatment

Bernhard Schmitz, Jurgen Geerkens, Gert Goch

Author Affiliations +

Proceedings Volume 2782, Optical Inspection and Micromeasurements; (1996) https://doi.org/10.1117/12.250735
Event: Lasers, Optics, and Vision for Productivity in Manufacturing I, 1996, Besancon, France

Abstract

Mechanical or structural changes on surfaces and in near- surface layers become detectable by photothermal measurement techniques, when they correlate with alterations of thermal properties. We apply this approach on the detection of variations in ceramic surfaces (silicon nitride, WIDIANIT or alumina) wherein a mechanical impact load or a thermal surface treatment have been induced. Vickers indentations model the mechanical load during grinding and a thermal surface treatment was performed by pulsed laser illumination. Afterwards, the treated areas are either scanned stepwise resulting in a lateral resolution comparable to microscopic images (thermal microscopy) or examined at different modulation frequencies. The photothermal images show remarkable changes near the marked areas depending on the different loading strengths. Proceeding from the photothermal signals' amplitude and phase the depths and profiles of thermal conductivity variations can be reconstructed. Certainly, mechanical changes on surfaces and in near-surface layers, cracks and plastic deformations as well as alterations of the microcrystalline structures are responsible for these effects. Finally, we intend improving the surface finishing by the applied laser and thermal treatments.

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Bernhard Schmitz, Jurgen Geerkens, and Gert Goch "Photothermal inspection of material changes in ceramic surfaces induced by mechanical load or laser treatment", Proc. SPIE 2782, Optical Inspection and Micromeasurements, (18 September 1996); https://doi.org/10.1117/12.250735

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