Investigation of spruce (Picea abies) and pine (Pinus sylvestris) structural timber with different strength grading methods

Käesolevas magistritöös käsitletakse erinevaid tugevussorteerimise meetodeid. Töö eesmärgiks oli võrrelda visuaalse tugevussorteerimise tulemusi masintugevussorteerimiste tulemustega ning kontrollida neid purustaval meetodil saadud paindekatse tulemustega kuuse- ja männipuidust elementide näitel. Puidu füüsikalis-mehaanilised omadused määrati vastavalt standardile laboratoorselt. Visuaalne tugevussorteerimise viidi läbi standardi NS-INSTA 142:2009 alusel. Masinsorteerimisel kasutati seadmeid Timber Grader MTG ja Fakopp Microsecond Timer. Viimasega teostati puitelementide mõõtmised otsesel ja kaudsel meetodil. Tulemused sõltusid valitud meetodist, masintugevussorteerimise puhul katseseadmest ning puuliigist. Kõige tugevamad seosed saadi purustaval paindekatsel mõõdetud staatilise elastsusmooduli ja Timber Grader seadmega mõõdetud staatilise elastsusmooduli vahel; korrelatsioon männipuidust katsekehadel r=0,96 ja kuusepuidust katsekehadel r=0,90. Tugevaid seoseid andis Fakopp seade otseste mõõtmiste korral männipuidust katsekehadel (r=0,70...0,85). Kuusepuidust katsekehade puhul saadi otsestel mõõtmistel keskmised seosed (r=0,68...0,69). Visuaalsel tugevussorteerimisel ilmnes suur valedesse tugevusklassidesse sorteeritud katsekehade arv. Kokkuvõtvalt võib uurimustöö põhjal öelda, et tugevussorteerimise korral on vajalik katsekehadele tulemusi vaadata puuliigipõhiselt. Kindlasti on selles valdkonnas vaja jätkata lisauuringute tegemisega.The present master thesis takes under observation the investigation of wood strength grading methods. The purpose of this work is to compare visual strength grading with machine strength grading and verification of these results by destructive tests with spruce and pine wood elements as an example. The physical-mechanical properties of wood were determined in laboratory conditions according to the standard. Visual visual strength grading were determined according to the standard NS-INSTA 142:2009. In machine strength grading were carried out using devices like Timber Grader MTG and Fakopp Microsecond Timer. The measurements were performed from the elements using direct and indirect methods. Results were dependent by the method chosen, machine strength grading by the test device and by the wood species. The strongest links were obtained to the destructively measured static bending modulus of elasticity and the Timber Grader static modulus of elasticity measured between the device; correlation in pine test species was r=0,96 and r=0,90 in test species of spruce. Strong correlation was between the device Fakopp direct measurements of the pine test species (r=0,70...0,85). Spruce wood test species were obtained by direct measurements of the medium correlation (r=0,68...0,69). Huge amount wrong strength classes were created in visual strength grading. In conclusion, that the strength of the sort depends on the type of wood. The weakest results revealed in visual strenght grading and the strongest results were in machine strenght grading