Assessment of fatigue load spectrum from fracture surface topography

The possibility of deducing load spectrum parameters from fatigue failure surfaces is explored by applying innovative, three-dimensional topographic characterization and analysis techniques to failure surfaces in aluminum sheet. Precise, high-resolution elevation maps of fracture surfaces were obtained using confocal optics scanning laser microscopy. Elevation power spectral density curves resulting from a fast Fourier transform of the elevation data appear sensitive to stress intensity range and environment. A conjugate fracture surface matching procedure, FRASTA, can detect and may provide a way to quantify overloads.