Comparison of Physical Properties of Untreated and Heat Treated Beech and Hornbeam

Istraživanjem fizikalnih svojstava toplinski obrađene bukovine i grabovine utvrđeno je da je njihova srednja vrijednost manja i signifikantno se razlikuje od srednjih vrijednosti fizikalnih svojstava neobrađene bukovine i grabovine. Srednja vrijednost gustoće u apsolutno suhom stanju toplinski obrađene bukovine manja je za 8,5 % od neobrađene, a za grabovinu je ona manja za 7,5 %. Smanjenje srednjih vrijednosti maksimalnih utezanja toplinski obrađene bukovine i grabovine u odnosu prema neobrađenoj još je veće. Maksimalno radijalno utezanje toplinski obrađene bukovine manje je za 7 %, maksimalno tangencijalno utezanje za 23,5 %, a maksimalno volumno utezanje za 19,3 % od istih fizikalnih svojstava neobrađene bukovine. Toplinski obrađena grabovina ima srednju vrijednost maksimalnoga radijalnog utezanja za 123 %, maksimalnoga tangencijalnog utezanja za 86 % i maksimalnoga volumnog utezanja za 99,5 % manju od istih fizikalnih svojstava neobrađene grabovine. Takvim smanjenjem maksimalnih utezanja u radijalnome i tangencijalnom smjeru toplinskom obradom grabovina postaje znatno prihvatljivija za izradu proizvoda za koje je važna dimenzionalna stabilnost.The investigation of physical properties of heat treated beech wood and hornbeam wood found that their average value is lower and significantly different from average values of physical properties of untreated beech wood and hornbeam wood. The average value of density in absolutely dry condition of heat treated beech wood is smaller by 8.5% from the untreated, and the hornbeam wood is smaller by 7.5%. Reduction of average values of maximum shrinkage of heat treated beech wood and hornbeam wood is even bigger in relation to the untreated wood. Maximum radial shrinkage of heat treated beech wood is smaller by 7%, maximum tangential shrinkage by 23.5% and maximum volumetric shrinkage by 19.3% compared to the same physical properties of untreated beech wood. Heat treated hornbeam wood has an average value of maximum radial shrinkage smaller by 123%, maximum tangential shrinkage by 86% and maximum volume shrinkage by 99.5% compared to the same physical properties of untreated hornbeam wood. With such reduction in the maximum shrinkage in radial and tangential direction using heat treatment, hornbeam becomes particulary suitable for making products where dimensional stability is important

Comparison Some Physical and Mechanical Properties ofAbonos and Recent Oak (Quercus robur L.)

Ispitivanje nekih fizikalnih i mehaničkih svojstava abonosa s lokacije Oštra Luka i usporedba s istim svojstvima recentne hrastovine, cilj je ovog istraživanja. Ispitana je gustoća u apsolutno suhom stanju, totalno utezanje u radijalnom i tangencijalnom smjeru te totalno volumno utezanje. Od mehaničkih svojstava ispitana je statička čvrstoća na savijanje i čvrstoća na tlak paralelno s vlakancima. Srednja vrijednost gustoće abonosa u apsolutno suhom stanju iznosi 0,704 g/cm3, srednja vrijednost totalnog utezanja u radijalnom smjeru abonosa je 10,5 %, srednja vrijednost totalnog utezanja u tangencijalnom smjeru abonosa je 18,6 %, srednja vrijednost totalnog volumnog utezanja abonosa je 27,6 %, srednja vrijednost statičke čvrstoća na savijanje abonosa je 101,3 MPa i srednja vrijednost čvrstoće na tlak paralelno s vlakancima je 52,3 MPa. Od navedenih svojstava skoro sve su srednje vrijednosti abonosa hrasta signifikantno različite, odnosno veće od srednjih vrijednosti istih svojstava recentne hrastovine, osim kod čvrstoće na tlak paralelno s vlakancima gdje ne postoji signifikantna razlika, a srednja vrijednost čvrstoće na tlak paralelno s vlakancima abonosa hrasta manja je nego recentne hrastovine.Abonos, eban and bog-wood are the terms for wood exposed to the effects of water and processes of humification in soil for a long period of time. Abonos of several tree species has been discovered so far, but the most common and also most valued is the oak abonos, often named black oak-wood, or bog-oak. Black color of bog-oak is the result of chemical interaction of tanstuff in the wood and iron in water. Water in the environment in which bog-oak is formed provides unfavorable conditions for the development of microorganisms and fungi that would otherwise decompose the wood. Deposition of minerals from the water ensures conservation and durability of wood structural elements. Aforementioned processes that form the bog-oak also change its chemical structure, and physical and mechanical properties. Time period for which the wood was under bog-oak forming conditions spans from several thousands up to several tenths of thousands of years. Uniqueness and high value of bog-oak stems from its durability, aesthetical features, black color, acoustical properties and old age. From bog-oak wood following products can be made: veneer, high-quality and high-value furniture, parts for musical instruments, high-value objects for everyday use, etc. Bog-oak wood is also very highly esteemed in artistic circles among sculptors and other artists. According to past experience, bog-oak is usually found purely by accident, most often during the construction works for the regulation of stream and river beds, ameliorative works, or because of the exploitation of gravel. Equalizing the terms bog-oak and archeological wood by some authors does not reflect the specific properties of those materials. Archeological wood is not necessarily, or very rarely is bog-oak wood, due to the usage of a number of tree species during history other than oak. On the other hand, bog-oak is archeological wood simply because of its age, even if in some cases it does not have any true archeological value. Samples for this research of technical properties of bog-oak wood were supplied by Benković Hrvoje and Franjić Darko from the area of Oštra Luka (Orašje, Bosnia and Herzegovina). Bog-oak was accidentally found on that area during the exploitation of gravel. After the discovery, it was very difficult to extract and transport parts of trees and stems of bog-oak from the depth of six meters. Divers extracted the wood from the river bed, and wood was transported to the river shore by attaching barrels to the extracted wood. Extracted parts of trees and stems were transported to the roofed warehouse and partly wrapped in plastic foil to slow down the process of drying. Wrapping in foil is necessary to prevent cracking of bog-oak wood in the case of rapid loss of water during drying. Process of slow drying has to be constantly supervised in order to prevent forming of mold. This is achieved by adjusting the surface of bog-oak under plastic foil. After the successful drying of bog-oak wood (i.e. down to the 12–18 % of water content), it is possible to saw the bog-oak wood into desired assortments. Sawed assortments are once again exposed to the process of drying to achieve water content of 12 %. Samples for this research were extracted from bog-oak assortments prepared in the way described above. Goal of this research is to determine technical, i.e. physical and mechanical properties of bog-oak wood, and to compare them with same properties of recent oak wood. Comparison is possible due to the fact that both materials originate from the same area within the distribution range of pedunculate oak (Quercus roburL.). Values of physical and mechanical properties of pedunculate oak wood were taken from the oak wood from Topolovac and Boljkovo. From the research results acquired from the testing of physical and mechanical properties of bog-oak and from its comparison with properties of recent oak several conclusions were formed. Average value of density of bog-oak in absolutely dry condition is 0.704 g/cm3, and is 15.8 % higher than that of the wood density in absolutely dry condition of recent oak. Average value of total radial shrinkage for bog-oak amounts to 10.5 % and is for 105.9 % higher than that of recent oak. Average value of total tangential shrinkage for bog-oak wood is 18.6 %, and is for 104.4 % higher than average value of total tangential shrinkage of recent oak. Average total volumetric shrinkage of bog-oak is 27.6 %, and is for 101.5 % higher than that of recent oak wood. Average value of ultimate strength in static bending for bog-oak wood was 101.3 MPa, which is for 10.8 % higher than ultimate strength in static bending of recent oak wood. Average value of ultimate stress in compression parallel to grain for bog-oak wood was 52.3 MPa and does not significantly differ from the ultimate stress in compression parallel to grain measured in the wood of recent oak, although is 1.5 % smaller

Macroscopic Characteristics and Density of Scots Pine (Pinus Sylvestris L.) from Cazin, Bosnia and Herzegowina

Plantažni uzgoj bijelog bora (Pinus sylvestris L.), u svijetu se primjenjuje duže vrijeme. Istraživanje makroskopskih karakteristika i gustoće plantažno uzgojenog bijelog bora (Pinus sylvestris L.) s područja Cazina u Bosni i Hercegovini, provedeno je radi stjecanja spoznaja o makroskopskim karakteristikama i gustoći tako uzgojenog bijelog bora (Pinus sylvestrisL.) Od makroskopskih karakteristika mjerena je širina goda, širina zone kasnog drva i izračunavano učešće zone kasnog drva. Određivana je gustoća u apsolutno suhom stanju i nominalna gustoća. Raspon širine goda kod istraživane borovi ne je velik, a srednjom vrijednosti za sva tri debljinska razreda zajedno od 3,6 mm. Srednje vrijednosti širine goda za svaki debljinski razred međusobno se signifikantno razlikuju. Srednja vrijednost učešća zone kasnog drva je 38,6 % za sva tri debljinska razreda zajedno. Srednje vrijednosti učešća zona kasnog drva za svaki pojedini debljinski razred se signifikantno međusobno razlikuju. Srednja vrijednost gustoće u apsolutno suhom stanju je 0,469 g/cm3 za sva tri debljinska razreda. Srednja vrijednost gustoće u apsolutno suhom stanju kod sva tri debljinska razreda se međusobno signifikantno razlikuje. Srednja vrijednost nominalne gustoće je 0,419 g/cm3, za sva tri debljinska razreda zajedno. Srednje vrijednosti nominalnih gustoća kod sva tri debljinska razreda se međusobno signifikantno razlikuju.Plantation cultivation of Scots pine (Pinus sylvestrisL.) in the world applies a longer period of time. The study of macroscopic properties and density of plantation grown Scots pine from the area of Cazin in Bosnia and Herzegovina was carried out in order to acquire knowledge about the macroscopic characteristics and density so grown pine. Plantation growth (Buckman, 1985) is primarily carried out for species of wood which, in short rotation, accomplish the greatest financial and general useful functions in a given area. Under the provisions of ISO 3129 from year 1975, 76 test trees for studying were selected. From department 30 of unit Gata 40 test trees were taken, and from department 26 of unit Gata 36 test trees were taken. All relevant parameters were collected on selected test trees: geographical position, diameter at breast height, ground plan projection of tree top, tree orientation toward cardinal points, total tree height, height to first living branch and stump height (Kličić, 2006). Test trees were classified into three diameter classes: (1) 11 to 20 cm of diameter at breast height, (2) 21 to 30 cm of diameter at breast height and (3) 31 to 40 cm of diameter at breast height. From each test tree test sample of about 70 cm length was made, beginning at breast height. Following macroscopic properties were measured: ring width, latewood width and latewood percentage was calculated. Density was measured in oven dry condition and also basic density. The range of ring width of studied Scots pine is large and ranges from 0.3 mm to 16.6 mm, with mean value for all three diameter classes of 3.6 mm. The range of ring width can be also seen through the variance of 4.28. Mean values of ring width for each diameter class mutually differ significantly. Distribution trend of ring width in radial direction is downward, with no major signs of achieving more constant values for all diameter classes. Latewood percentage ranges from 1.7 % to 90 % with mean value of 38.6 % for all three diameter classes together. Distribution trend of latewood percentage in radial direction is growing. Density in oven dry condition ranges from 0.308g/cm3to 0.690 g/cm3, with mean value of 0.469 g/cm3for all three diameter classes. Wood in trees of diameter at breast height from 11 to 20 cm has mean value of density in oven dry condition of 0.482 g/cm3, in trees of diameter at breast height from 21 to 30 cm mean value of density in oven dry condition is 0.481 g/cm3, and in trees of diameter at breast height from 31 to 40 cm is 0.453g/cm3. Mean value of density in oven dry condition for all three diameter classes is significantly different. Distribution trend of density in oven dry condition is growing for all three diameter classes, without any indication of achieving more constant values. Basic density ranges from 0.283 g/cm3to 0.644 g/cm3, with mean value of 0.419g/cm3 for all three diameter classes together. Mean values of basic density for all three diameter classes mutually differ significantly

Welding of thermally modified hornbeam

Tehnika rotacijskog zavarivanja primjenjuje se pri zavarivanju moždanika (klina) u podlogu. Tijekom zavarivanja zbiva se kemijsko fizički proces koji nastaje kao posljedica trenja zbog rotacije moždanika i utiskivanja u statičnu podlogu, uz određeni zador. U radu su prikazani rezultati zavarivanja moždanika u podlogu od termički modificirane (grabovine obrađene na temperaturi od 200 °C u trajanju 48 h) i nemodificirane grabovine. U nemodificiranoj je grabovini izvlačna sila (moždanika iz podloge) veća (prosječno 84 %) nego u modificiranoj. To je posljedica manje krtosti i cjepivosti nemodificiranog drva te kraćeg trajanja procesa zavarivanja (utiskivanja moždanika).Welding of dowels in the base is carried out by technology of rotation welding. During welding, a physical-chemical process takes place as a result of mechanical friction because of dowel rotation and impression into the static base with the set tightness. This article shows the results of dowel welding in thermally modified (treated at the temperature of 200°C for 48 h) and non-modified hornbeam base. Embedded force (dowel out of base) is grater with non-modified hornbeam (on average 84 %) than with modified hornbeam. This is the effect of less brashness and cleaving of non-modified wood and shorter time of welding (dowel impression)

Some Physical and Mechanical Properties of Recent and Heat Treated Ash– Fraxinus Excelsior L.

Obrada jasena (Fraxinus excelsiorL.) na temperaturi od 200 oC uzrokovala je značajne promjene tehničkih svojstava odnosno fizikalnih i mehaničkih svojstava, tako obrađenog drva. Gustoća jasenovine u apsolutno suhom stanju signifikantno je manja od gustoće recentne. Ista je pojava uočena i kod utezanja u radijalnom i tangencijalnom smjeru i također volumnog utezanja. Istraživana mehanička svojstava: čvrstoće na tlak u longitudinalnom smjeru, statič ke čvrstoće na savijanje, tvrdoće u longitudinalnom, radijalnom i tangencijalnom smjeru toplinski obrađene jasenovine, također su signifikantno manja od recentne. Obrada jasenovine na visokoj temperaturi polučila je drvo veće dimenzionalne stabilnosti, odnosno manjih veličina linearnih i volumnog utezanja, ali manjih mehaničkih svojstava jasenovine.The aim of this paper is to study differences in some physical and mechanical properties of heat treated and recent wood. Wood used in this research was ash (Fraxinus excelsiorL.) from the area of Otok, region of Slavonia in Croatia. The felled tree was 85 years old with the diameter at breast height of 53 centimetres. A heart board was made from the tree trunk in the north-south direction, 4 metre long and 6 centimetres thick. The heart board was dried naturally with an average water content of 12 %. The heart board was sawn in four equal parts so that four heart boards were obtained – each 1 metre long. Looking from stump to top of the tree, the first and third heart boards were not heat treated and they were used for establishing the properties of recent ash. From the above four heart boards, samples were made for determining macroscopic, physical and mechanical properties of recent and heat treated ash. Treatment of ash (Fraxinus excelsiorL.) at the temperature of 200 oC caused significant changes of technical properties relatively physical and mechanical properties of the treated wood. Maximum possible number of samples was made for each physical and mechanical property in radial direction, i.e. from heart to bark. Maximum shrinkage was determined in radial and tangential direction, as well as maximum volume shrinkage, density in absolutely dry condition, nominal density and water content after a fortnight of soaking in water of physical properties. Determination was also made of compression strength parallel to the grain, static bending strength, hardness in longitudinal, radial and tangential direction. The investigation of some physical and mechanical properties of recent ash (Fraxinus excelsiorL.) and heat treated ash at 200 oC show diametrically different values of investigated properties. The investigation of mechanical properties of recent ash was carried out on samples with water content of 12 %, while the water content of the heat treated ash samples was 4 %. In order to be able to compare the results of mechanical properties, their values were converted to the water content of 4 % for recent ash and 12 % for heat treated ash. For increasing or decreasing mechanical properties of wood, correction factor was used in accordance with Forest Product Laboratory, Madison. The comparison of mean values of physical and mechanical properties of recent and heat treated ash was carried out in accordance with Mann-Whitney test with the help of statistical software Statistica. Density distribution in absolutely dry condition in radial direction of heat treated ash deviates from the distribution common for recent ash. The loss of mass with a relatively constant sample volume is evident in radial direction, and especially in the heart section. Mean value of density in absolutely dry condition of recent ash is higher by 8.4 % than density of heat treated ash. Shrinkage in radial and tangential direction and volume shrinkage of recent ash are higher that shrinkage in heat treated ash. Shrinkage in radial direction is higher by 70 %, in tangential direction by 62.2 % and volume shrinkage by 63.7 %. All above said physical properties of recent ash are significantly different from physical properties of heat treated ash. The investigated mechanical properties of recent ash are also significantly higher than mechanical properties of heat treated ash. Compression strength in longitudinal direction of recent ash is higher by 36.8 %, static bending strength is higher by 48 %, hardness in longitudinal direction (cross-cut) is higher by 31.3 %, hardness in radial direction (tangential cut) is higher by 22.8 % and hardness in tangential direction (radial cut) is higher by 25.9 % than the stated mechanical properties of heat treated ash at 200 oC. All investigated mechanical properties of recent ash differ significantly from these properties of heat treated ash. Dimensional stability of ash under such regime of heat treatment resulted in increased dimensional stability, and however the investigated mechanical properties are significantly lower. The above said percentages of higher values of mechanical properties of recent ash than of heat treated ash with water content of 12 % and 4 % indicate that they are similar at 12 % and 4 %. The similarity of these percentages indicates that the correction coefficients for calculating mechanical properties at different water contents is also satisfactory for heat treated ash

Dimensional Stability of Olive (Olea europaea L.) and Teak (Tectona grandis L.)

Olive, as a wood species, can be compared by its dimensional stability with teak wood, which is mainly used for products exposed to external conditions. Mean density in absolutely dry condition of researched olive wood is 0.810 g/cm3 while the average value of teak wood is 0.610 g/cm3. Regardless of higher density, the mean value of total tangential shrinkage for olive wood is only by 3.6 % higher than the one for teak wood, so the value for olive wood is 5.6 % and for teak wood 5.4 %. Based on this research of density in absolutely dry condition and total shrinkage, olive wood can be considered as a possible alternative indigenous species for use in products that are daily exposed to external conditions