| Abstract [eng] |
In this master's thesis the research on pine (Pinus sylvestris) and spruce (Picea abies) grown in Lithuania was conducted. The aim of the research is to determine the variations among density, natural frequency of wood, dynamic and static stiffness, sizes of knots and flutes as well as the strength of the wood; moreover, to compare the efficiency all of these non-destructive tests while determining the strength of wood. The research was needed to estimate interrelations between physical and mechanical wood properties and to evaluate the correlations between the stiffness-strength of wood grown in Lithuania and Northern Europe. The tests were carried out in the laboratory of Kaunas University of Technology and UAB “Stora Enso Lithuania”; the test program contained 120 samples of spruce and 120 samples of pine. The tests were carried out according to relevant EN standards in order to determine the stiffness-strength of wood. Three non-destructive tests were carried out: Timber Grader MTG, Metriguard, 4-point test according to EN408 and the destructive bending test. Other measurements such as wood moisture, the area of knots in the zone of a failure, flutes and their influence on the strength of wood were calculated as well. The wood was divided into classes according to LST EN 338 standard for the strength of timber. After conducting the tests, the results showed that pine and spruce growing in Lithuania match the strength of Northern European wood and even exceed it. The most accurate methods to determine the strength of wood were also estimated according to the results of the stiffness. It has been noticed that the samples of bigger square profile withstand higher loads while being bent, however, after recalculating to the strength, the strength of such samples appeared to become weaker due to more faults in the cross-section. |
