Measurement of microslips of subsurface fatigue crack faces due to rolling loads

Abstract

The development of accurate numerical models of the growth of subsurface fatigue cracks due to rolling load needs reliable experimental data on the actual interactions between the crack faces. The distribution of microslips that occur between the crack faces and the interaction between the crack faces as a function of the magnitude and the position of the load with respect to the crack tip are of particular interest. In this study, the microslips of the faces of a subsurface fatigue crack developed in a railhead made of 900A steel were measured by the grating holographic interferometry (G H I) technique. R econstruction of each double-exposed hologram made it possible to obtain four interferograms at multiple o -axis angles. On the basis of the interferograms, two-dimensional maps of the displacement vector components were determined, making it possible to calculate the distribution over the crack length of the crack face microslips and the crack opening and closing. A speci cally designed experimental stand allowed the application of a stepwise increase in the normal load and consequently stepwise rolling of a constant load along the edge of the specimen.