Modeling of grain pull-out forces in polycrystalline alumina

A first generation, two-dimensional finite element (FE) model of grain pull-out in an alumina post fracture tension (PFT) specimen was constructed using the photomicrographs of the specimen surface. Frictional resistance to grain pull-out was generated by the intergranular compressive stresses due to randomly distributed, anisotropic thermal contractions during cool down in the fabrication process. The FE model consisted of an assembly of 11 sheets, each with an idealized microstructure of uniform grain size. The observed intragranular fracture sites and remnants of elastic grain bridging, both of which were generated prior to the PFT test, were accounted for by reducing the number of bridging sites. Elastic loading and unloading of the FE model emulated the cyclic load/unload PFT data.