engleski

Annual ring orientation effect on bending strength of subfossil elm wood

ABSTRACT The effect of annual rings’ orientation on bending strength was examined on subfossil elm wood. Elm is extremely rarely found as subfossil wood, and during the last 50-60 years it has almost disappeared from natural forest stands of south-eastern Europe, due to the Elm Dutch disease. The samples were cut from approximately 670 years old subfossil elm trunk retrieved from the bed of the river Sava in the area between the villages Grebnice and Domaljevac in north Bosnia. The wood was identified to the genus level based on optical microscopy analysis of three wood sections - transverse, tangential and radial. Bending strength was determined by the three- point bending test. The load was applied to the longitudinal-tangential surface (LT) and to the longitudinal-radial surface (LR). The bending strength values of subfossil elm do not differ from the values of recent elm, despite the 700- year resting in anoxic river conditions. Bending strength in LT direction was slightly higher than bending strength in LR direction. The coefficient of variation and the standard deviation of the arithmetical mean were higher for LT direction. It was found that the measured bending strength for both directions follow Weibull distribution. Coefficient of determination of Weibull functions were close to 1 for both directions. The Weibull shape parameter was higher for LR direction.

subfossil elm wood ; bending strength ; annual ring orientation ; Weibull distribution

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