Influence of surface roughness on the scatter in hardness measurements - a numerical study

The quasi-static indentation of a fractal surface is numerically simulated to characterize the scatter resulting from surface roughness in terms of surface roughness parameters. Results show that the surface irregularities or roughness which are characterized by fractal dimension, and rms height of asperity, play a role in the scatter in hardness measurements. The scatter due to rough surface decreases at higher loads of indentation. For a given rough surface, the load required to keep the scatter due to surface roughness within the required limit is higher for harder rocks than softer ones. The scatter due to surface roughness follows the power law, and it can be quantified.