Symbol σ

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…then strength is a random variable and reporting a mean is an error of category. The standard treatment is the Weibull weakest-link model, in which the probability that a body of volume V survives a uniform stress $\sigma$ is $P_s = \exp\left[-V\left(\frac{\sigma}{\sigma_0}\right)^{m}\right]$. with m the Weibull modulus and $\sigma_0$ a scale parameter. A larger m means tighter scatter. A review of Weibull analysis across ceramics reports moduli of roughly 10 or below for many advanced ceramics such as alumina, hydroxyapatite and silicon carbide, below about…

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