Black alder dynamic and static modulus of elasticity comparison on different moisture levels

Käesolevas bakalaureusetöös antakse ülevaade sanglepa dünaamilise ja staatilise elastsusmooduli võrdlemisest erinevatel niiskustasemetel. Töö eesmärgiks oli uurida kuidas sõltub puidu dünaamiline ja staatiline elastsusmoodul niiskustasemest ning prognoosida puidu dünaamilise elastsusmooduli ja tiheduse kaudu paindetugevust. Katseid tehti 30-katsekehaga, mis jagati kuueks ja neid kuivatati 6-le erinevale niiskustasemele. Iga niiskustaseme juures tehti 5 katsekehaga ultraheli levimise kiiruse ja lineaarmõõtmete mõõtmised ning elastsusmooduli mõõtmist puidukatsemasinaga Instron. Lõpuks mõõdeti kõigi katsekehade paindetugevust. Üldised võrdlused staatilise ja dünaamilise elastsusmooduli vahel tehti niiskustasemetel alla ja üle 30%. Tulemustest selgus, et ultraheli levimise kiiruse ja niiskussisalduse vaheline lineaarne seos on kõige tugevam üle 30% niiskustasemel radiaalsuunas, R= 0,728. Alla 30% niiskussisalduse on ultraheli levimise kiiruse ja niiskussisalduse vaheline seos kõige tugevam pikisuunas, R= -0,469. Paindetugevuse prognoosimine tiheduse kaudu osutus usaldusväärseks üle ja alla 30% niiskustaseme.This bachelor thesis gives an overview of the comparison of Black alder dynamic and static modulus of elasticity in different moisture levels. The main purpose of the study was to investigate how different moisture levels of wood influence the dynamic and static modulus of elasticity and predict the dynamic modulus of elasticity and density of the wood through the bending strength. Experiments were performed with 30 test pieces, which were divided into six, and they were dried to a 6 different humidity levels. In every different levels of humidity there were made linear and ultrasound measurements by 5 test-pieces and there were made modulus of elasticity measurments by testing machine Instron. Test ended with the measurement of wood bending strength. General comparisons were made with static and dynamic modulus of elasticity, between moisture level lower and higher than 30%. The results showed that the relationship between spread of the ultrasonic velocity and the moisture content was the greatest at the moisture level more than 30% in radial direction , R = 0.728 . The biggest relationship between spread of the ultrasonic velocity and the moisture content in the longitudinal direction was at the moisture level less than 30 %, R = -0.469 . Bending strength prediction of the density proved to be a reliable at the moisture level of less or more than 30%