Utjecaj usmjerenosti strukture na savojnu čvrstoću drva

master's thesis

• Title (english): Effect of anisotropy on bending strength of wood
• Author: Antun Balaton
• Mentor: Vera Rede (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-12-08, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Drvo je prirodni polimer, lako obradiv, dostupan i ekološki prihvatljiv materijal. Zbog anizotropne strukture, usmjerena su i mehanička svojstva. U ovom radu istražen je utjecaj usmjerenosti strukture na savojnu čvrstoću i savojni modul elastičnosti subfosilnog drva brijesta.Subfosilno drvo je konzervirano drvo koje je više stotina godina bilo u vodi tekućici, u vrlo specifičnim uvjetima. Brijest se vrlo rijetko nađe kao subfosilno drvo, a zbog holandske bolesti je gotovo nestao iz prirodnih šuma jugoistočne Europe. Uzorci za ispitivanje izrezani su iz približno 670 godina starog debla, izvađenog iz korita rijeke Save između Grebnica i Domaljevca u Bosanskoj posavini. Mikroskopskom analizom triju karakterističnih presjeka (poprečnog, radijalnog i tangencijalnog) utvrđeno je da se radi o drvu iz roda Ulmus(brijest). Savojna čvrstoća i savojni modul elastičnosti određeni su metodom savijanja u tri točke. Ispitane su tri serije uzoraka – LT, L45° i LR. Smjer savojne sile bio je okomit na vlakanca kod svih ispitanih uzoraka, a variran je smjer sile u odnosu na tijek godova: 0° (LT), 45° (L45°) i 90° (LT). Za oba ispitana svojstva najviše vrijednosti izmjerene su u seriji L45°. Vrijednosti u LT seriji su neznatno više od vrijednosti u LR seriji. Rezultati su statistički obrađeni Weibullovom razdiobom. Koeficijent determinacije Weibullove funkcije je vrlo visok (blizu 1), za sve tri serije, za oba svojstva. Utvrđeno je da vrijednosti savojne čvrstoće i savojnog modula elastičnosti subfosilnog drva brijesta u odnosu na recentni brijest nisu niže, unatoč 700-godišnjem boravku u vrlo specifičnim uvjetima.

Abstract (english)

Wood is a natural polymer, easily workable, affordable and environmentally friendly material. Because of anisotropic structure, mechanical properties are directed. In this thesis, the influence of orientation structure was studied on bending strength and bending modulus of elasticity on subfossil elm wood. Subfossil wood is preserved trunk that is hundreds of years have been in the water streams, in very specific condition. Elm is very rarely found as subfossil wood, because of the Dutch disease has almost disappeared from the natural forests of Southeast Europe. The test samples were cut from about 670 years old trunk extracted from the river Sava, between Grebnice and Domaljevac in Bosanska posavina. The microscopic analysis of three typical sections (cross, radial and tangential) hasshown that trunk is a tree of the genus Ulmus (elm). Bending strength and bending modulus of elasticity were determined by the three point bending test. Three different series of samples - LT, L45 ° and LR were examined. Direction of flexural force was vertical to the fibers in all tested samples, and the direction of force is changed in relation to the course of the growth rings: 0 ° (LT), 45 ° (L45 °) and 90 ° (LT). For both tested properties the values are the largest in the series L45 °. The values in the LT series are slightly higher than the values of the LR series. The results were statistically analyzed by Weibull distribution. The coefficient of determination of Weibull function is very high (close to 1) for all series and for both properties. It was found that the value of bending strength and bending modulus of elasticity of the subfossil elm wood are not lower in order to the recent elm, despite the 700-years staying in very specific conditions.

• Keywords: savojna čvrstoća; savojni modul elastičnosti; subfosilno drvo; Weibullova distribucija
• Keywords (english): bending strengh; bending modulus of elasticity; subfossil wood; Weibull distribution
• Language: croatian
• URN:NBN: urn:nbn:hr:235:248024
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-24 12:47:55