Fractal geometry of the fatigue fracture surface of the ZTA composites

Abstract

A fracture surface of the ceramic composite Al2O3 - ZrO2 at three-point bending during fatigue loading has been studied by scanning electron microscope. The bending strength and flexural modulus are derived under static conditions at a loading rate of 3 mm/min. The fatigue strength and fatigue limit are investigated at a frequency of 4 Hz in three stress ranges: 0.9, 0.8 and 0.7 of the average maximum static bending strengths. The surface fractal dimensions Df is determined using triangulation method. It was shown that the surface relief can be characterized by fractal relief in the local approximation. The fractal dimensionality of the studied surface changes in the relatively narrow limits Df = 2.653 - 2.742, for ceramic samples sintered at 1650 °C, and highly dependent on the number of cycles. The ceramic samples sintered at 1400 °C showed low resistance to fatigue loads with the fractal dimensionality Df = 2.710 - 2.781, which are independent of the number of cycles.