Vpliv toplotne obdelave na mehanske lastnosti jelovine : diplomski projekt

Smonkar, Gregor (author), Straže, Aleš (mentor), Fajdiga, Gorazd (comentor), Gorišek, Željko (reviewer)

Raziskali smo vpliv toplotne obdelave na mehanske lastnosti jelovine. Vizualno smo izbrali 45 jelovih žaganic, nominalnih dimenzij 4000 x 120 x 45 mm, ter jih razvrstili po gostoti v 9 razredov. Žaganice smo nato toplotno obdelali v industrijskem vakuumskem postopku v podjetju Silvaprodukt pri štirih različnih končnih temperaturah toplotne obdelave (170 °C, 190 °C, 210 °C, 230 °C), po en preizkušanec iz vsakega razreda pa smo pustili za kontrolo. Mehanske lastnosti smo proučili neporušno, z metodo frekvenčnega odziva pri prečnem in vzdolžnem vzbujanju, ter z merjenjem hitrosti ultrazvoka. Z metodo končnih elementov je bil izdelan tudi numerični model odziva preizkušancev na zunanjo mehansko motnjo. Izguba mase preizkušancev je eksponentno naraščala z višanjem temperature toplotne obdelave. Modul elastičnosti se je najbolj spremenil v vzdolžni smeri lesa; pri višanju intenzivnosti toplotne obdelave je sprva naraščal, pri najvišji temperaturi pa zopet padel. Značilnega trenda spremembe togosti v prečni smeri lesa zaradi velike variabilnosti nismo potrdili. Frekvenčni odziv pri prečnem vzbujanju preizkušancev je potrdil nižanje modula elastičnosti z višanjem nihajnega načina. Z večanjem razlik med togostjo v posameznem nihajnem načinu smo pri toplotno obdelani jelovini potrdili večjo strukturno nehomogenost. Numerični model mehanskega odziva preizkušancev je pokazal primerljive rezultate realnemu odzivu preizkušancev.

• Language: Slovenian
• Keywords: toplotna obdelava lesa, mehanske lastnosti, jelovina, modul elastičnosti
• Work type: Diploma project paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [G. Smonkar]
• Year: 2016
• Number of pages: VIII, 33 f.
• PID: 20.500.12556/RUL-117863
• UDC: 630*812.7:630*847
• COBISS.SI-ID: 2635145
• Publication date in RUL: 31.07.2020

SMONKAR, Gregor, 2016, Vpliv toplotne obdelave na mehanske lastnosti jelovine : diplomski projekt [online]. Bachelor’s thesis. Ljubljana : G. Smonkar. [Accessed 25 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=117863

Secondary language

• Language: English
• Title: Influence on heat treatment on mechanical properties of fir

Abstract

The effect of heat treatment on the mechanical properties of fir (Abies alba Mill) was researched. We selected visually 45 fir boards - samples, nominal dimensions 4000 x 120 x 45 mm, and ranked them by density in 9 classes. Samples were then heat treated in an industrial vacuum process in company Silvaprodukt, with four different end temperatures (170 °C, 190 °C, 210 °C, 230 °C), a specimen from each class was left untreated as a control. The mechanical properties were studied with non - destructive methods, with a frequency response method in transverse and longitudinal direction, and by measuring the speed of ultrasound. With finite element method we made a numerical model of the response to an external mechanical disturbance. The loss of mass of the samples was increasing exponentially with increasing thermal treatment temperature. Modulus of elasticity changed the most in longitudinal direction. With increasing temperature of heat treatment the modulus of elasticity initially grew, but then at the highest temperatures dropped again. Significant trend changes of stiffness in the transverse direction of timber, was due to the high variability not confirmed. Frequency response by transverse vibrations confirmed lowering modulus of elasticity with increasing vibration modes. With increasing difference between the stiffness in each vibration mode we confirmed major structural inhomogeneity in the heat treated fir. The numerical model of the mechanical response showed comparable results to the response of real specimens.

• Keywords: heat treatment, mechanical properties, fir (Abies alba Mill.), modul of elasticity