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3880 |
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Thursday, May 22, 2014, Hall H2 9:40 AM Ceramic Coatings 1 |
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Residual stress analysis on thermally sprayed coatings by means of optical and mechanical methods |
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Venancio Martínez García* / University of Stuttgart, Germany Andreas Killinger / Institut für Fertigungstechnologie keramischer Bauteile (IFKB), Universität Stuttgart, Germany Rainer Gadow/ Institut für Fertigungstechnologie keramischer Bauteile (IFKB), Universität Stuttgart, Germany Giancarlo Pedrini/ Institut für Technische Optik (ITO), Universität Stuttgart, Germany Wolfgang Osten/ Institut für Technische Optik (ITO), Universität Stuttgart, Germany |
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The residual stresses present in coatings and layer composites are strongly influenced not only by the thermal and mechanical loads during the manufacturing process, but also by the mechanical and thermophysical properties of the coating and substrate materials. Due to the mismatch of the properties between the coating and the substrate and the different thermal expansions during the different cooling stages of the process, as well as the nonuniform elastic or elastic-plastic deformations in the substrate and coating, the process should be optimized to obtain an appropriate residual stress field. The micro-hole drilling and milling method is a well known technique to measure the residual stress situation, in particular the method performed mechanically. A new system based on optical technologies is developed for the evaluation of residual stresses. In the newly developed method a laser beam is used to produce the material removal by laser ablation, leading to deformation of the surface. By means of digital holographic interferometry this deformation is measured. An experimental bending device has been designed and constructed based on the European Standard for the four-point bending test, to produce a known in-plane strain field. Measurements for different materials are carried out in order to optimize the optical and mechanical methods. Experimental results are presented. |