EFFECT OF GROWTH RING ON HARDNESS AND BENDING STRENGTH IN BEECH ( FAGUS SYLVATICA L)

The beech wood (Fagus sylvatica L) is the most widespread deciduous wood in our forests. It is one of the most widely spread materials not only in the Wood processing Industry but also in construction, chemistry and paper industry. This study focuses on the effect of the growth rings on the mechanical properties of beech and more specifically on the static bending and Janka hardness . The tests were carried out in the Wood study laboratory in the Faculty of Forest Sciences. 240 samples in sizes 2x2x32 were prepared, following the UNI ISO standard 31-33 prerequisites, which were classified according to the number of rings in the transversal section and according to the angle formed by the force direction with the annual growth ring in the transversal section for the static bending and 138 samples in size.5 x 5 x 5 cm After carrying out the tests in the static bending, it resulted that the maximum tension value was 144N/mm2.It is notised that acording to the number of the annual rings in the transversal section the maximum tension is present in the samples that have a small number of rings in the transversal section (4-5 rings) a value which is 3% higher than the group of samples that have 6-7 rings in the transversal section and 10% higher than the group of samples which have 8- 11 rings in the transversal section .For the hardness test resulted that the mean value was 538 kG in radial section, 640 kG in transversal section and 546 kG in tangential section, the highest hardness was in transversal section and in samples with 8-10 growth rings.