Določanje elastomehanskih lastnosti lesa z ultrazvokom

Bremšak, Borut (author), Straže, Aleš (mentor), Trtnik, Gregor (co-mentor)

Preverili smo uporabnost ultrazvočnega določanja elastomehanskih lastnosti smrekovega, bukovega in macesnovega lesa. Iz naključno pridobljenih večjih sortimentov smo izdelali orientirane preizkušance dimenzij 40 x 40 x 40 mm. Preizkušance smo uravnovesili pri 20 °C in 50 % relativni zračni vlažnosti. Z merilcem časa preleta PunditLab smo s strižnimi ultrazvočnimi sondami v posameznih anatomskih smereh ter ravninah določili hitrosti preleta tlačnega in strižnega valovanja. Hitrost tlačnega ultrazvočnega valovanja je bila pri vseh lesovih največja vzdolž lesnih vlaken (L), v povprečju pa 3,5x manjša v radialni (R) smeri ter 1,5x manjša v tangencialni (T) smeri lesa. Hitrosti strižnega ultrazvočnega valovanja so bile pri vseh lesovih in anatomskih ravninah manjše od hitrosti tlačnih valov. Vpliv gostote lesa na hitrost ultrazvoka ni bil potrjen. Moduli elastičnosti so bili najvišji pri bukovini, nekoliko manjši pa pri macesnovini in smrekovini. Strižni moduli so bili v L-smeri lesa v povprečju 10x manjši, v R- in T-smeri lesa pa do 5x manjši od modulov elastičnosti. Za vse testirane lesne vrste smo potrdili, da so anizotropne in da odstopajo od ortotropnosti.

• Language: Slovenian
• Keywords: les, mehanske lastnosti, anizotropija, ultrazvok
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [B. Bremšak]
• Year: 2017
• PID: 20.500.12556/RUL-95618
• UDC: 630*812.9
• COBISS.SI-ID: 2804105
• Publication date in RUL: 21.09.2017

Secondary language

• Language: English
• Title: DETERMINATION OF ELASTOMECHANICAL PROPERTIES OF WOOD BY ULTRASOUND

Abstract

The usability of ultrasonic determination of the elastomechanical properties of spruce, beech and larch wood has been verified. From randomly obtained large timber elements, we made oriented samples 40 x 40 x 40 mm. Specimens were equilibrated at 20 ° C and 50 % relative air humidity. The time of flight of compression and shear ultrasonic waves was measured by PunditLab device in the individual anatomical directions and the planes. The speed of compression ultrasonic waves was highest in all woods along the fibers (L), and on average 3.5-times smaller in radial (R) direction and 1.5-time smaller in the tangential (T) direction of the wood. The speed of the shear ultrasonic waves was less than the speed of compression waves in all woods and anatomical planes. The influence of wood density on ultrasound speed was not confirmed. The modulus of elasticity was the highest in beech, and slightly smaller in larch and spruce. The shear moduli were on average 10-times smaller along the grain, and up to 5-times smaller in R- and T-direction of wood in comparison with the modulus of elasticity. For all tested wood species we have confirmed that they are anisotropic and deviate from orthotropicity.

• Keywords: wood, mechanical properties, anisotropy, ultrasound