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Crack Detection of Ceramics based on Laser Speckle Photometry

B. Bendjus, U. Cikalova, L. Chen

Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Maria-Reiche-Str. 2, 01109 Dresden.

received October 28, 2016, received in revised form December 20, 2016, accepted January 24, 2017

Vol. 8, No. 1, Pages 73-80   DOI: 10.4416/JCST2016-00090

Abstract

Ceramic components subjected to increasingly extreme conditions are being pushed to their performance limits. That is, the critical crack length for alumina is less than 80 µm. Therefore, to guarantee and estimate the quality of ceramics, new advanced nondestructive diagnostics methods with high resolution are required.

Laser Speckle Photometry is an innovative optical non-destructive and monitoring technique based on the detection and analysis of thermally or mechanically activated characteristic speckle dynamics in the non-stationary optical field. When an object is excited by an external thermal source, the thermal energy propagation causes a local temperature difference, which generates local thermal expansion. The local thermal expansion excites speckle movement, which can be detected by a fast digital camera. The objective of the paper is to examine the suitability of the LSP technique for the detection of micro-cracks located on the surface of ceramics. Results of measurements with different experimental parameters are presented by means of the imaging LSP method. It shows that LSP is a suitable approach for detecting cracks in ceramics. The results of successful evaluations show that the detectable resolution of the LSP technique at the current research stage is approximately 500 µm in terms of the length of cracks.

Keywords

Ceramics, speckles, micro-crack detection, non-destructive optical testing

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