Finite Element Simulation Of Zirconia Ceramics Three-dimensional Crack-growth And Indentation Testing

Zirconia ceramics is a kind of inorganic non-metallic materials,which has excellent mechanical properties and biocompatibility,as raw materials of whole porcelain tooth widely used in the field of dental restorations,namely the medical zirconia ceramics. As oral repair material, with high toughness and high strength, good biocompatibility, performance and aesthetic effect,whole porcelain tooth can be produced very closely to the real teeth. The zirconia ceramics fracture toughness enhancement is closely related to the phase transformation toughening effect of the material. So this article emphatically discusses the phase transformation toughening effect of zirconia ceramics on the crack initiation and propagation.A continuum based constitutive law for materials subjected to phase transformations has been suitably implemented into a commercial finite element code. Zero thickness cohesive elements have been used to simulate materials' crack initiation and propagation process. At first, a three-dimensional cohesion finite element model of uniaxial tensile of zirconia ceramic plate is established to simulate crack initiation and propagation process, studying the effect of zirconia ceramics material's shear phase transformation factor, the hardening parameter, cohesive element strength of interface, crack radius on the crack propagation rate, the phase transformation distribution near the crack. Flake crack of finite element simulation results show that shear phase transformation component has significant effects on fracture toughness of material; the greater phase transformation hardening parameter, the more difficult for phase transformation to happen; also find that cohesive element strength of interface has significant influence on phase transformation distribution near the crack.Then, three-dimensional finite element model of the spherical indentation and vickers indentation have been established to study the phase transformation distribution near the indentation and effect of phase transformation toughening on indentation crack. Indentation finite element simulation results show that the crack near Indentation appears to present a gradual reduce trend from the surface to the inside. The indentation crack,Vickers finite element simulation results show that zirconia ceramics' crack produced mainly in the unloading process because of the residual stress. Phase transformation can inhibit the zirconia ceramic crack initiation and propagation by producing the phase transformation toughening effect, promote the crack initiation and propagation by producing the residual stress,which shows phase transformation is not only the factor of inhibiting the propagation of the crack, and the factor of promoting crack propagation.