Hertzian Contact Damage in Porous Alumina Ceramics

Abstract
A study has been made of Hertzian contact damage in porous and dense liquid‐phase‐sintered aluminas. Indentation stressstrain curves show increasing nonlinearity as the materials become more porous, illustrating an increasing component of “quasi‐plasticity” in the contact damage. Observations of the surface and subsurface damage patterns using a bonded‐interface sectioning technique reveal a transition in the Hertzian damage process, from classical tension‐driven cone cracks in the high‐density material, to distributed shear‐ and compression‐driven subsurface damage and deformation in the porous materials. Strength tests on specimens subjected to cyclic indentations reveal a substantially higher susceptibility to fatigue in the most porous structure.

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