Cavitation damage measurement by 3D laser profilometry

A 3D laser profilometry technique was proposed to measure material damage due to cavitating flows. A software for automatic analysis of the sample surfaces pitted by cavitation was developed and used to treat several experimental results. The special software provides the radius, depth and volume for every single indentation (pit). It evaluates also the volume damage rate Vd and the pit number rate Nd for every analyzed sample surface. The method used to determine the geometric characteristics of each indentation, as well as the applied approach to treat the overlapping pits problem are explained. This technique of cavitation damage measurement was applied to analyze the sample surfaces (copper, stainless steel and aluminum) damaged in the EDF Modulab test loop under different flow conditions. The influence of the test duration and the analysis cut-off parameters (related to the measurement resolution threshold) on the evaluation of the volume damage rates Vd and of the pit number rates Nd was analyzed. Nd values appeared to be strongly related to the treatment and analysis parameters while the evaluation of Vd seemed to be more reliable to characterize cavitation aggressiveness. Whatever the applied technique is, the quality of the obtained results (Vd, Nd, …) is directly related to the well control of test duration and cut-off parameters.