This article investigates the quality of the machining surface of the five most common invasive tree species in Slovenia, i.e., black locust (Robinia pseudoacacia L.), boxelder maple (Acer negundo L.), horse chestnut (Aesculus hippocastanum), honey locust (Gleditsia triacanthos) and tree of heaven (Ailanthus altissima). The machining tests were made according to the American Society for Testing and Materials (ASTM) D1666-17 standard, where the quality of the surfaces after planing, routing and turning were evaluated with visual assessment, and the area and profile roughness parameters were also determined on selected specimens. The results showed that boxelder maple, horse chestnut and honey locust can be machined very well in all the studied operations, with the best results in routing and a little less good by turning, whereas the tree of heaven had the best quality in planing, and the worst by turning. Among all studied tree species, the black locust had the worst quality in planing, but the quality at routing was very similar to other tested species. The research also showed that there is little or no significant relationship between the qualities of the various types of machining for tested tree species.

med predelavo, se zaradi visoke kurilnosti bukovine običajno namenjajo pridobivanju toplotne energije, torej v energetske namene. Na tržišču se pojavljajo v obliki drv, peletov in briketov, ki kot energenti ne dosegajo visoke dodane vrednosti. Iz surovine višje kakovosti je mogoče izdelati številne polizdelke in izdelke z visoko dodano vrednostjo, kar pa terja predvsem učinkovito delovanje gozdno-lesne verige in je podrobneje predstavljeno v prispevkih Kropivšek in Čufar (2015) ter Čufar et al. (2017) in je bilo temeljiteje preučevano v sklopu CRP projekta Racionalna raba lesa listavcev s poudarkom na bukovini. Poleg mehanskih in ostalih (tudi obdelovalnih) lastnosti pa lahko s pridom izkoriščamo tudi kemijsko strukturo bukovine za pridobivanje niza tržno zanimivih spojin (Zule, 2015). S tem se odpira široko področje inovativnih rab bukovine s poudarkom na celovitejši izrabi surovine slabše kakovosti in lesnih ostankov, ob hkratnem zagotavljanju načel krožnega gospodarstva (European Commission, 2017).

This research was conducted to determine the impact bending strength and dynamic bending strength of Norway spruce wood from Slovenia. An accelerometer was added to the impact pendulum in order to capture the material's response to an instantaneous load. Impact bending strength of specimens were determined by standard method measuring the height of pendulum before and after the break. While measuring the impact pendulum decelerations during the fracture of the specimen, the impact bending strength and dynamic bending strength was calculated. Correlations between the measured properties were determined, for which the R 2 was in the range 0.88 to 0.51 between the standard and accelerometer method and between the impact bending strength and dynamic bending strength, respectively. The results confirmed that the methods used to determine the impact bending strength were comparable and that it was possible to determine dynamic bending strength on the basis of impact pendulum deceleration measurement.

IZVLEČEKV raziskavi smo preučevali količinsko-kakovostni izkoristek bukovine od stoječega drevesa do žaganega lesa. Zanimala nas je ocena kakovosti posameznih dreves in njen vpliv na kakovostne razrede proizvodov iz tega lesa. Pri razvrščanju stoječih dreves smo upoštevali aktualno 5-stopenjsko lestvico ocenjevanja kakovosti Zavoda za gozdove Slovenije (ZGS). Pri ocenjevanju gozdnih sortimentov smo uporabljali standard SIST EN 1316-1:2013, pri ocenjevanju žaganega lesa pa pravila Evropskega združenja žagarske industrije (EOS). Na vzorcu ocenjenih in nato posekanih dreves smo ugotavljali povezave med kakovostjo dreves, iz njih izdelanih sortimentov okroglega lesa in kakovostjo končnih žagarskih izdelkov. V vzorec so bila enakovredno zajeta drevesa vseh petih kakovostnih stopenj. Pri izdelavi gozdnih sortimentov smo dobili največ hlodov B-kakovosti (51 %) in največ žaganega lesa EOS-C-kakovosti (52 %). Iz bukovih dreves odlične kakovosti smo dobili 35 % najkakovostnejših sortimentov in iz teh sortimentov 8 % najkakovostnejšega žaganega lesa. Odločilni kriterij razvrščanja po kakovosti so pri sortimentih okroglega lesa slepice in pri žaganem lesu mrtve in trhle grče.Ključne besede: listavci, bukev, kakovost, napake lesa, žagan les ABSTRACTThe research addresses beech wood, from a standing tree to sawn wood. It focuses on the quality evaluation of individual trees and its impact on the later products made of the respective wood. For the needs of observing the quality of standing trees, the current 5-class scale for quality evaluation of the Slovenia Forest Service (SFS) was used. To evaluate the wood assortment, the SIST EN 1316-1:2013 standard was applied, while the evaluation of sawn wood was performed as per the rules of the European Organisation of the Sawmill Industry (EOS). On the basis of the sample of evaluated and eventually harvested trees, the correlations between the quality of trees, roundwood products made of them and the quality of final sawn products were established. The sample equally included trees of all five quality classes. The production of wood assortment provided the most logs of B quality (51%) and the highest quantity of sawn wood of EOS-C quality (52%). Beech trees of excellent quality provided 35% of the wood assortment of highest quality and these provided 8% of the sawn wood of the highest quality. The key criteria for the classification by quality were covered knots for forest products and dead and unsound knots for sawn wood.Key words: broadleaves, beech, standards, quality, defects in wood, sawn wood (Lipoglavšek, 1994, 1996, Rebula, 2002, Kadunc, 2006, Prka, 2003, Stankić in sod., 2014. Tako se obravnave zgolj gozdarske problematike praviloma končajo na kamionski cesti, kjer se proizvodni proces v gozdu zaključuje. Na istem mestu praviloma opravimo tudi izmero količin, ocenimo kakovost in oddamo sortimente v celoti. Po drugi strani pa se raziskave o kakovosti hlodovine ter količinah in kakovosti proizvodov, izdelanih iz teh hlodov, praviloma začnejo na žagarskem obratu (Šoškić in ...

V raziskavi smo preučevali fizikalne in mehanske lastnosti lesa v deblih navadnih bukev (Fagus sylvatica L.), izruvanih med žledolomom. Lastnosti smo preučevali na vzporednih preizkušancih sveže in osušene bukovine, ki smo jih sistematično vzorčili po radialni in vertikalni smeri dreves. Določili smo gostoto, togost, upogibno trdnost, strižno trdnost v smeri lesnih vlaken ter tlačno trdnost lesa v vseh anatomskih smereh. Togost smo primerjalno vrednotili med statično 4-točkovnim upogibom in nedestruktivno z merjenjem hitrosti ultrazvoka ter z določanjem frekvenčnega odziva. V drevesih, ki so izruvana obležala v gozdu od februarja do konca vegetacijske dobe 2014 in so imela delno ohranjen koreninski sistem, aktivno krošnjo in zadosten kapilarni tok, nismo zaznali sprememb gostote in mehanskih lastnosti, ki bi bile posledica razkroja lesa. Tako v svežem kot osušenem stanju smo ugotovili značilni vzorec porazdelitve gostote in trdnosti. Gostota lesa je po višini dreves naraščala, v radialni smeri od stržena proti periferiji debla pa smo zaznali rahel trend zmanjševanja. Mehanske lastnosti z izjemo prečne tlačne trdnosti se povečujejo tako po višini debla kot tudi od stržena proti kambiju in so bile vedno boljše pri osušenem kot pri svežem lesu. Zanesljivost nedestruktivnih metod za določanje togosti je večja pri ocenjevanju osušenega lesa. Za oceno upogibne trdnosti z nedestruktivnimi metodami še vedno priporočamo vzporedno vizualno opredelitev značilnosti lesa.