Abstract
Micro-mechanical testing machine was designed for thin films. In this system, a laser speckle correlation measurement technique is applied for measuring strain for thin film specimen. A laser beam (He-Ne laser, Wavelength: 632.8nm, Power: 5mW) is irradiated on the thin film specimen, and the resultant laser speckle pattern was observed by a CCD camera (768pixel×512pixel). The change of laser speckle patterns during loading were recorded and analyzed. Fe-3mass%Si thin films with thickness of 25μm were used for confirming the validity of measurement systems. Tensile tests were carried out successfully for the thin films and the stress-displacement curves were obtained. Laser speckle patterns were able to observe and these patterns were changed progressively during loading of thin film specimen. Cross correlation technique was applied to obtain the displacement of each speckle. When the specimen were moved to one direction without loading, the displacement values were obtained with accuracy of 3.9μm, and this indicates that this technique is very useful for measuring microscopic displacement of thin films, however, the surface displacement was not able to measure properly. This is due to the slight change of surface roughness during loading of film specimen.
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