ホットプレス窒化珪素の曲げ強度(<小特集>セラミック材料小特集)

概要

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The three point bending tests were carried out on hot-pressed Si_3N_4 containing Y_2O_3 and Al_2O_3 to grasp the characteristics of mechanical strength of ceramics, and the probability density distribution of failure stress for 415 specimens was obtained. Then, the fracture origins were observed by a scanning electron microscope: The relation between the type of fracture origin and the bending strength was investigated. The results are as follows : (1) The experimental probability density for the most fitted well the theoretical Weibull distribution, but for several percents of low strength, the experimental failure probability did not fit and was higher than the theoretical one. (2) There were four main types of fracture origins, and the same three types of fracture origins appeared in the low strength specimens. Therefore, the difference in the failure probability for the low strength region could not be explained by the difference in the type of fracture origin. (3) As the results of investigating all fracture surfaces, the surface fracture was 18% of all bars. and the internal fracture was 79%. The mean strength and the Weibull modulus of each group were almost equal, respectively. Therefore, the true stress at the internal fracture origin equalled the average of about 90% of that at the surface fracture origin.
社団法人日本材料学会の論文
1981-10-15