20.500.12556/RUL-161199 Določanje kakovosti hlodovine iglavcev z nedestruktivnimi metodami Determination of quality of softwood logs by non-destructive methods Smrekovi hlodovini (Picea abies) z žagarskega obrata (n = 15), in z domače dražbe vrednejših sortimentov lesa (n = 17) smo kakovost določali vizualno, skladno z veljavnimi standardi. Hlodovini smo z metodo frekvenčnega odziva pri vzdolžnem nihanju določili hitrost preleta zvoka in dušenja v prvih treh nihajnih načinih. Licitirana hlodovina je bila večjih premerov, med 51 in 79 cm, in je spadala v A – kakovostni razred. Hlodi z žagarskega obrata so bili manjših premerov (27 – 59 cm), in smo jih uvrstili v B (47 %) in C kakovostni razred (53 %). Hitrost zvoka pri hlodovini C kakovosti je bila v 2. in 3. nihajnem načinu značilno nižja (v < 4000 m/s) od hitrosti zvoka pri hlodovini iz A in B kakovostnih razredov. Rezultat sovpada z večjo pojavnostjo notranjih strukturnih anomalij, zlasti grč in naraščanja njihove velikosti, ki smo jih največ evidentirali v hlodovini najslabše kakovosti (C). Dušenje zvoka ni bilo značilno povezano s kakovostjo smrekove hlodovine. Ugotovili smo, da čelne razpoke na hlodih značilno povečajo dušenje zvoka v 2. in 3. vzdolžnem nihajnem načinu. Spruce logs (Picea abies) from the sawmill (n = 15) and from the domestic auction of more valuable timber (n = 17) were visually assessed for quality according to the applicable standards. The sound velocity and damping in the first three vibration modes of the logs were determined in parallel using the longitudinal vibration resonance method. The auctioned logs had a larger diameter (between 51 and 79 cm) and belonged to quality class A. The logs from the sawmill had a smaller diameter (27-59 cm) and were classified in quality classes B (47 %) and C (53 %). The speed of sound was significantly lower (v < 4000 m/s) in the grade C logs than in the grade A and B logs, and only in the second and third vibration modes. This result is consistent with the greater occurrence of internal structural anomalies, particularly knots and their increasing size, observed mainly in the worst grade (C) logs. Vibration damping was not significantly related to the quality of the spruce logs. Cracks at the ends of the logs were found to significantly increase vibration damping in the second and third vibration modes. les smreka hlodovina kvaliteta lesa akustične lastnosti nedestruktivno merjenje wood spruce logs wood quality acoustic properties nondestructive testing true false false [L. Krančič] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2024-09-08 07:17:52 2024-09-08 07:17:55 2025-08-08 13:41:32 0000-00-00 00:00:00 2024 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 630*832.181:812.12 243857 206730243 DIP_Krancic_Laura_2024.pdf DIP_Krancic_Laura_2024.pdf 1 1B9C4B2D6D715508DCE15D2A68837A25 bc2142ea824a9fd35eb135aa2ef07381fa372ade7a7cc1c5cb9870fd80c7b115 abcaac19-6da1-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=190084 Biotehniška fakulteta 0 0 0