Development of Strength Confirmation Testing Method of Ceramics by Reliability Engineering

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The aim of this research is to develop the method of strength confirmation testing of ceramics by the reliability engineering. The principal results of the research are summarized as follows.1.The mean reliability was applied to the determination of design-allowable stress S_a for the case where the material strength follows a two-parameter Weibull distribution. It was found that for the case when the shape parameter alpha is known and only the scale parameter beta is unknown, the design-allowable stress S_a was obtained analytically and for the case when both alpha and beta are unknown, S_a was obtained numerically.2.The mean reliability was applied to the estimation of the size of reliability for the case when a design-allowable stress is determined by reliability R and confidence level C.It was found that for the case when the strength follows a normal distribution and Weibull distribution, the mean reliability was obtained analytically or numerically and for the case when the distr … More ibution of strength is unknown, the lower limit of the mean reliability was obtained by the product reliability R by confidence level C regardless of the distribution of strength.3.The ring crack initiation load was studied for a ceramic ball from a statistical point of view experimentally. The ring crack initiation load P_R was much larger than the static load rating given by the ISO method for steel bearings. The former is about ten times of the latter.4.Which of the inter-ball variability and the intra-ball variability is responsible for the scatter of the ring crack initiation load P_R of ceramic bearing balls was studied experimentally. It was found that scatter of P_R evaluated by measuring P_R at per single position per ball is mainly due to intra-ball variability or spatial variation of P_R within one ball.5.The mechanism of crushing fracture of ceramic bearing balls was studied experimentally. It wa found that a radial crack led to final fracture.6.The rolling fatigue of ceramic bearing balls was studied experimentally. It was found that the rolling fatigue life followed approximately a two-parameter Weibull distribution. Less