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Analýza tahové-tlakové asymetrie u koeficientů příčné deformace pomocí metody korelace digitálního obrazu
Zadina, Jan
This thesis deals with the analysis of tensile-compressive asymmetry in the coefficients of transverse deformation (Poisson's ratios) of spruce wood (Picea abies L. Karst) in all three principal directions of growth, i.e. for the complete set of 6 Poisson's ratios. Tensile and compressive stress within one direction was applied to the same test specimen, and the digital image correlation (DIC) method was used to analyze surface deformations. For this purpose, the surface of the test specimens in two adjacent planes was recorded by cameras during mechanical loading, and the deformations were fully evaluated from the digital images, from which the Poisson's ratios were subsequently calculated. The evaluation of Poisson's ratios was performed using statistical tests. Statistical t-tests were performed to test the equality of means to compare the tensile and compressive Poisson's ratios, which showed differences between the compressive and tensile Poisson's ratios only in some cases. A one-way ANOVA and Scheffé's test were also performed to compare the different directions with each other, which showed a distribution of large and small Poisson's ratios mainly in tension. A regression analysis was also performed to determine the degree of correlation between the tensile and compressive Poisson's ratios, and correlation was demonstrated in the radial and tangential directions. Regression analysis was also performed to examine the relationship with wood density, which showed a slight correlation with some of the Poisson's ratios.

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