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Material characterization by laser speckle photometry

: Bendjus, B.; Cikalova, U.; Schreiber, J.


Doval, A.F. ; University of Vigo, Optical Metrology Research Group; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Speckle 2012, V International Conference on Speckle Metrology. Proceedings : 10 - 12 September 2012, Vigo, Spain
Bellingham, WA: SPIE, 2012 (SPIE Proceedings 8413)
ISBN: 978-0-8194-9090-2
ISSN: 0038-7355
Paper 841315
International Conference on Speckle Metrology (Speckle) <5, 2012, Vigo>
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()

The damage and stress conditions of large industrial components have to be tested continuously. Especially welding processes in the field of coal production demand a nondestructive monitoring of internal stresses under an external load. In a first step, a new optical method, Laser Speckle Photometry was used during laboratory welding experiments under tensile and bending loads at high strength construction steels. Laser Speckle Photometry is a fast and contactless method for measuring spatial-temporal dynamics of speckle field with high temporal resolution after local heat excitation. The thermally induced change in the material structure causes changes in the speckle-field, which is formed by a probing laser. The shift of the speckle-field is analyzed by statistical methods, using correlation functions. The result of processing is the two-dimensional distribution of thermal diffusivity coefficient correlated to porosity, materials strain or hardness [1-3]. Here, the results of the welding experiments under load are presented. It is shown, that the Laser Speckle Photometry is a suitable technique for nondestructive monitoring and characterization of internal material stresses under external load.