Hertzian Contact Damage in Porous Alumina Ceramics

A study has been made of Hertzian contact damage in compressive shear stress field beneath the contact area. The observed microcrack density increases with grain size, porous and dense liquid-phase-sintered aluminas. Indentation stress–strain curves show increasing nonlinearity as the implying a threshold microstructural scale for crack initiation. In contrast, the micromechanisms controlling failure in materials become more porous, illustrating an increasing component of “quasi-plasticity” in the contact damage. porous ceramics under contact loading are not well understood. This is despite many studies on analogous processes in porous Observations of the surface and subsurface damage patterns using a bonded-interface sectioning technique reveal a rocks. The mechanical behavior of porous ceramics is of considerable practical importance in applications that require a transition in the Hertzian damage process, from classical tension-driven cone cracks in the high-density material, to high degree of porosity, e.g. filters, thermal barrier coatings, sensors, and preforms for subsequent infiltration. Accordingly, distributed shearand compression-driven subsurface damage and deformation in the porous materials. Strength tests studies are being conducted to investigate low-cost processing on specimens subjected to cyclic indentations reveal a subroutes for aluminas with different degrees of porosity, using stantially higher susceptibility to fatigue in the most porous readily available mineral additives. structure. The specific purpose of the present study is twofold: (i) to determine experimentally the influence of porosity in liquidphase-sintered (LPS) alumina ceramics under contact damage