Wavelet analysis of fretting experimental data

Wavelet analysis is being used to rationalize information at various scales in several branches of science, including particle physics, biology, electrical engineering, fluid mechanics, and medicine. However, this powerful technique has not been applied to characterizing structures of materials, fretting damage for the present case, even though many critical questions could be addressed. In particular, the following unsolved problems are considered in this paper: (a) The first problem deals with the quantitative characterization of fretted surfaces in a Ti-6Al-4V alloy. This is investigated by analyzing profilometric digital images of fretted surfaces obtained at a range of magnifications. Wavelet analysis of the data is able to identify, by examining the wavelet coefficients, dominant length scales as those regions in the scale-space where the energy of the wavelet transform and/or peaks of local concentration dominate. For the range of magnifications examined, i.e., from 1.25x to 100x, the similar to 20x magnification is identified as the one with the most useful information. (b) An alternative procedure is employed for the second use of wavelets which deals with the non-uniformity of the contact regions. Recent theoretical work has shown that during contact with partial slip, the morphology of the partially slipping regions does not change. Wavelet analysis is employed to identify those regions, which result in the "pattern" of the fretted surface morphology.