PSI - Issue 28

L.R. Botvina et al. / Procedia Structural Integrity 28 (2020) 1686–1693 L.R. Botvina et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 2. Cumulative distributions of microhardness values in inverse coordinates, described as eq. 3.

2.2. Correlation of γ -parameter with ultrasonic attenuation coefficient and grain aspect ratio It was established, that γ-parameter is related to non-destructive testing parameters – it is highly correlated with attenuation coefficient of ultrasonic waves α and grain aspect ratio ξ, which supports the idea of γ being representative parameter (fig.3 a, b). Change in the slope of cumulative distributions reflects full state of material, including its physical properties and deformation level. This important fact can lead to future development of research on the relationship of statistical estimation methods and non-destructive testing methods, that will possibly allow to lower number of experiments to determine statistical fracture material state data.

Fig. 3. (a) Correlation between acoustic parameter α and γ-parameter; (b) correlation between grain aspect ratio ξ and γ-parameter.

3. Statistical analysis of fatigue failure 3.1. Fatigue fracture of ceramics

For testing of proposed statistical method of inverse coordinates in fatigue failure data from the literature was used (Sakai and Fujitani, 1989). The authors used 20 alumina ceramic specimens for fatigue testing per each stress amplitude and standard three-parameter Weibull distributions for analysis:



     /







( ) 1 exp     x F x

(4),