J. Korean Ceram. Soc. > Volume 52(6); 2015 > Article
 Journal of the Korean Ceramic Society 2015;52(6): 417. doi: https://doi.org/10.4191/kcers.2015.52.6.417
 Effect of Porous Substrate on the Strength of Asymmetric Structure Chul Kim, Sang Hyun Park, Taewoo Kim, Kee Sung Lee School of Mechanical Systems Engineering, Kookmin University ABSTRACT In this study, we investigate the effect of porous $Al_2O_3$ substrate on the strengths of asymmetric structures after we prepare such a structure consisting of a dense $Li_2ZrO_3$ top layer and porous $Al_2O_3$ substrate layer. The porosity and elastic modulus of the substrate layer are controlled by sintering temperature, which has three values of 1150, 1250 and $1350^{circ}C$. The porosity is controlled in the range of ~ 30-50 vol%, elastic modulus is ~80-120 GPa and elastic mismatch $E_s/E_c$ is ~ 0.6-1.0. Indentation stress-strain curves are obtained and analyzed to evaluate the yield stress of the asymmetric structure by concentrated local loading of WC balls. Conventional flexural strengths are also obtained to evaluate the strength of the asymmetric structure. The results indicate that the local yield strength of the asymmetric structure has mid-values between the top and the substrate layer; however, the flexural strength of the asymmetric structure are mainly influenced by elastic modulus and strength of the substrate. Key words: Coatings, Porous materials, Strength, Elastic constants, Indentation
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