Effects of porosity and pore distribution on static strength properties of porous zirconia

Abstract

Bulk porosity, along with size and spatial distribution of pores, play key roles in strength of porous ceramics, as reported in a study on porous alumina. Hence, a fracture mechanics procedure was proposed to evaluate their strength by presuming that behavior of pore distribution is equivalent to that of crack distribution, and each pore is surrounded by virtual crack. In contrast to alumina, zirconia has distinct spherical‐shaped pores. Moreover, its strength properties vary with stabilizing additives. In this research, strength properties of yttria‐stabilized zirconia ceramics were studied to verify applicability of the procedure proposed for simulating strength of porous ceramics. The effect of pore characteristics on static strength properties was determined experimentally and confirmed by Monte‐Carlo simulations. It was revealed that simulated strength coincided with experimental results within a narrow scatter band, ie, factor of 21/2. Therefore, the proposed procedure was found to be appropriate for estimating strength of porous zirconia.

Numerical simulation on effects of pore characteristics on strength in porous ceramics

“…In previous works by the authors (Bade et al, 2019), strength properties of porous alumina and porous zirconia have been investigated experimentally, and they were also estimated by using numerical simulations based on a proposed analytical procedure. The results in previous works were shown in Fig.…”

“…The p range is set from the pore density pore and the scale parameter aS in three-parameter Weibull distribution function approximating the distribution of pore radius, which is identified based on LSM observation on the actual material surface. Other pore related parameters  and aL are set to 1.9255 and 4.4475μm from the average values in previous analyses (Bade et al, 2019), respectively. In this analysis, the additional crack length l0 is set to be l0 = 1.3 aS [μm] from the average relationship between l0 and aS used in previous analyses (Bade et al, 2019).…”

“…Other pore related parameters  and aL are set to 1.9255 and 4.4475μm from the average values in previous analyses (Bade et al, 2019), respectively. In this analysis, the additional crack length l0 is set to be l0 = 1.3 aS [μm] from the average relationship between l0 and aS used in previous analyses (Bade et al, 2019). The number of surface cracks is given by the crack density, and the type of a crack is classified into surface crack or embedded crack according to the relation between its size and its distance to the specimen surface.…”

“…properties for the respective materials can be obtained by simulation. In previous works (Bade et al, 2019), a procedure to estimate effects of pore characteristics on strength was newly developed by taking account of observed pore characteristics. In the procedure, a stress intensity factor based criterion was adopted for fracture of porous ceramics.…”

“…In this work, strength properties of porous ceramics and their relations with pore characteristics were investigated by numerical simulations based on the analytical procedure proposed in previous works (Bade et al, 2019). In the simulations, a fracture mechanics procedure was applied by taking account of the pore characteristics, especially porosity, pore density and average pore radius, and also by presuming pores to be surrounded by virtual cracks.…”