| Popis: |
Cilj istraživanja bio je utvrditi abrazijsku otpornost uzoraka recentnog i subfosilnih uzoraka hrasta lužnjaka starosti 1840 godina i 5890 godina. Subfosilni uzorci izvađeni su na području Bosanske Posavine. S obzirom na anizotropnost strukture i svojstava drva, ispitivanje je provedeno na sva tri karakteristična presjeka (poprečnom, radijalnom i tangencijalnom). Ispitivanje je provedeno na uređaju taber abrader s rotirajućim diskom, s brusnim papirima različite finoće. Intenzitet abrazijskog trošenja stavljen je u korelaciju s veličinom abrazivnih čestica, sa starošću i gustoćom uzoraka. Pokazalo se da usmjerenost strukture, prosječna veličina abrazivnog zrna, gustoća i starost imaju veliki utjecaj na abrazijsku otpornost. Najveća otpornost na abraziju dobivena je kod svih uzoraka u poprečnom, a najmanja u tangencijalnom presjeku. Povećanjem veličine abrazivnog zrna, povećava se i intenzitet trošenja uzoraka do kritične veličine abrazivnog zrna, nakon čega dolazi do smanjenja intenziteta trošenja. Najveća otpornost na abrazijsko trošenje izmjerena je kod mlađeg subfosilnog hrasta koji ima i najveću gustoću, a najmanja kod starijeg subfosilnog hrasta koji ima i najmanju gustoću. Dugogodišnji boravak hrasta lužnjaka u riječnom mulju u anaerobnim uvjetima mijenja sastav i strukturu drva. Do određene starosti navedene promjene poboljšavaju abrazijsku otpornost i povisuju gustoću, a s produljenjem vremena dolazi do smanjenja tih svojstava. The aim of the research was to investigate the abrasive wear resistance of recent and subfossil samples of thepedunculate oak that were 1840 and 5890 years old. Subfossil samples were prepared from the subfossil oak trunk found in Bosnian Posavina region. Taking into consideration the anisotropic structure and characteristics of the wood, research was undertaken in all three orthogonal planes (transverse, radial and tangential cross sections). Tests were carried out using Taber abrasion machine with a rotating disc and with sandpapers of various grit sizes. The abrasion wear intensity was correlated with the grit size, as well as with the age and the density of the samples. It was found that the direction of the structure, grit size, density and age had a considerable influence on abrasion resistance. The highest wear resistance of all samples was obtained on the transverse, while the least in the tangential cross section. By increasing the grit size, the wear intensity in the sample also increased up to the critical size of the abrasive grain, followed by a reduction in the wear intensity. The highest wear resistance was observed for younger subfossil oaks that had the highest density, while the lowest wear resistance was observed for older subfossil oaks which had the lowest density. The many years that the peduncualte oaks spent in river sludge in anaerobic conditions changed the wood's composition and structure. Up to a certain age, the aforementioned changes improved the abrasion resistance and increased the density, but over an extended period of time these properties decreased. |
