Surface roughness effects have a remarkable influence on photothermal measurements from steel samples and seriously distort hardness depth profiling. The thermal response of rough surfaces is described by an effective layer whose properties are defined by global roughness numbers like root- mean square roughness and peak-to-valley-roughness. Calculations of roughness effects as well as measurements from rough steel samples were performed and compared to each other. A good correspondence between the model and experiment was found which demonstrates the suitability of the effective layer model for a description of roughness. (C) 2001 American Institute of Physics. References: 6
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