Material Property/State Characterization by Laser Speckle Photometry
Ulana CIKALOVA; Beatrice BENDJUS; Juergen SCHREIBER
Proceedings: 18th World Conference on Nondestructive Testingw (18th WCNDT)(2012)
abstract:Variations of material conditions have to be tested continuously. For this goal, an optical method to determine a parameter that correlates to the coefficient of temperature diffusivity, called Laser Speckle Photometry (LSP), was developed. Thermal diffusivity is a property of conductive materials that can by be used for the characterization of micro-structural material properties, such as hardness, porosity, and/or the fatigued state. Laser Speckle Photometry is based on the detection and analysis of thermally activated characteristic speckle dynamics with high temporal resolution. The parameter of the thermal diffusivity, called speckle diffusivity, is determined using a correlation function from the pixel intensity of the speckle image variations during the thermal heating or cooling process. A direct correlation between the speckle diffusivity and material properties/state was found. The results of several investigations of porous metallic and ceramic materials are presented. In addition, results of successful evaluations of the damage state of construction steel are also presented. It is shown that the laser speckle photometry is a suitable approach for nondestructive characterization and monitoring of materials properties.
keywords:Speckle, Thermal Diffusivity, Nondestructive Testing, Condition Monitoring, Porosity, Hardness, Stress, Fatigue, Fractal Dimension
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