Search

Proučili smo vlažnost in gostoto lesa ter zunanje morfološke spremembe na različno prizadetih drevesih navadne bukve (Fagus sylvatica L.) ob koncu prve vegetacijske dobe po velikem žledolomu v Sloveniji v letu 2014. Potrdili smo povezanost med deležem še aktivnega koreninskega sistema in stopnjo porjavelosti (izsušenosti) krošnje dreves ter porazdelitvijo vlažnosti lesa v deblih dreves. Pri najbolj prizadetih drevesih smo v prevodnem zunanjem delu beljave potrdili padec vlažnosti lesa pod mejo naravne biološke odpornosti (u < 60 %). Po prvi vegetacijski dobi, nismo potrdili splošnega padca gostote lesa (in z njim povezanega poslabšanja mehanskih lastnosti), ki bi bil posledica okužbe in razkroja lesa z glivami Moisture content and wood density of variously damaged uprooted European beech (Fagus sylvatica L.) trees were studied at the end of the first vegetation period after ice storm damage in Slovenian forests in 2014. The study confirmed significant correlation between the amount of active root system and necrosis of leaves and changed moisture content and its distribution in the trunks. The moisture content of wood below 60 % was confirmed in sapwood of extremely damaged trees, indicating diminished protection against wood destroying organisms. We could not confirm any reduction of wood density which would indicate deterioration of wood at the end of the first vegetation period after ice storm damage

Proučili smo fizikalne lastnosti (vlažnost in gostoto) lesa različno prizadetih izruvanih dreves navadne bukve (Fagus sylvatica L.) ob koncu prve vegetacijske dobe po velikem žledolomu v letu 2014. Raziskava je potrdila povezavo med deležem še aktivnega koreninskega sistema in stopnjo porjavelosti (izsušenosti) krošnje dreves ter vlažnostjo lesa in njenim razporedom. Pri zelo prizadetih drevesih smo v prevodnem zunanjem delu beljave potrdili zmanjšanje vlažnosti lesa pod mejo naravne biološke odpornosti (u < 60 %). Po prvi vegetacijski dobi nismo mogli potrditi zmanjšanja gostote lesa (in z njim povezanega poslabšanja mehanskih lastnosti), kar bi potrdilo okužbo in razkroj lesa z glivami. Physical properties (moisture content and density) of wood of variously damaged uprooted European beech (Fagus sylvatica L.) trees were studied at the end of the first vegetation period after the ice storm damage in Slovenian forests in 2014. The research confirmed significant correlation between the amount of active root system and necrosis of leaves and changed moisture content and its distribution in the trunks. The moisture content of wood below 60 % (indicating extinguished protection against wood destroying organisms) was found in sapwood of extremely damaged trees. At the end of the first vegetation period after damage we could not confirm any reduction of wood density (and reduced mechanical properties) which would indicate deterioration of wood.

In this study, the effect of altitude difference on the physical and mechanical properties of Scots pine (Pinus sylvestris L.) wood was investigated. For this purpose, nine Scots pine trees were selected from three altitudes: 250 m (low altitude), 700 m (intermediate altitude), and 1200 m (high altitude) located in the forestry of Sinop province (Black Sea Region in Turkey). For the physical properties of wood: air and oven dry specific gravity were determined, and for the mechanical properties of wood: compression strength parallel to the grain, static bending strength and modulus of elasticity in static bending were determined. Moreover, the variation of all wood properties was determined related to the altitude difference. The results of statistical analyses showed that the altitude difference was an important factor influencing the physical and mechanical properties of Scots pine wood. The air and oven dry density, compression strength parallel to the grain, static bending strength and modulus of elasticity in static bending were higher at intermediate altitude than at other altitudes.

In this study, the effect of altitude difference on the physical and mechanical properties of Scots pine (Pinus sylvestris L.) wood was investigated. For this purpose, nine Scots pine trees were selected from three altitudes: 250 m (low altitude), 700 m (intermediate altitude), and 1200 m (high altitude) located in the forestry of Sinop province (Black Sea Region in Turkey). For the physical properties of wood: air and oven dry specific gravity were determined, and for the mechanical properties of wood: compression strength parallel to the grain, static bending strength and modulus of elasticity in static bending were determined. Moreover, the variation of all wood properties was determined related to the altitude difference. The results of statistical analyses showed that the altitude difference was an important factor influencing the physical and mechanical properties of Scots pine wood. The air and oven dry density, compression strength parallel to the grain, static bending strength and modulus of elasticity in static bending were higher at intermediate altitude than at other altitudes., U radu su prikazani rezultati istraživanja utjecaja nadmorske visine staništa na fizikalno-mehanička svojstva drva običnog bora (Pinus sylvestris L.). Za istraživanje je odabrano devet stabala običnog bora u šamama pokrajine Sinop (u crnomorskoj regiji Turske) s lokacija različite nadmorske visine: 250 m (mala nadmorska visina), 700 m (srednja nadmorska visina) i 1200 m (velika nadmorska visina). Od fizikalnih svojstava u istraživanju je određena gustoća drva u zrakosuhom i apsolutno suhom stanju, a od mehaničkih svojstava određene su tlačna čvrstoća paralelno s vlakancima, statička čvrstoća na savijanje i modul elastičnosti pri statičkom savijanju. Varijacije svih spomenutih svojstava drva određene su s obzirom na visinske razlike lokacija s kojih su uzorci uzeti. Rezultati statističke analize pokazali su da je nadmorska visina staništa važan čimbenik koji utječe na fizikalnomehanička svojstva drva običnog bora. Vrijednosti gustoće drva u prosušenom i apsolutno suhom stanju, tlačne čvrstoće paralelno s vlakancima, statičke čvrstoće na savijanje i modul elastičnosti u statičkom savijanju bili su najveći za uzorke uzete s lokacije na srednjoj nadmorskoj visini.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Thermomechanical treatments seek to increase the wood density, throught of the temperature and pressure combination, which results in a material with improved physical and mechanical properties. Thus, the study aimed to evaluate the influence of thermomechanical treatments in Pinus elliottii Engelm and Eucalyptus grandis W. Hill ex Maiden wood. So, were prepared from five trees of each species, wood pieces that have been submitted to six different thermomechanical treatments. For this purpose, we used a laboratory oil bath to perform preheating of wood and a hydraulic press with the temperatures of the dishes ranging from 150 to 190°C. Compression time used was between 30 and 60 min. After, physical (compression rate, weight loss, equilibrium moisture content, density, dimensional stability and hygroscopicity), mechanical (static bending, dynamic bending and Janka hardness), surface (colorimetry and roughness) and infrared spectroscopy (ATR-IR) tests were performed. For statistical analysis, we used qualitative factorial 3 x 2, with three temperature levels and two compression time and Tukey test. Furthermore, it was performed to compare the treatments with the control. The main results for the technological properties showed that the degree of compression and mass loss increased with the temperature increase. The equilibrium moisture content decreased and the density obtained increases. For the dimensional stability was observed that there was a reduction of the effect of the return densified wood, and hygroscopicity was increased in both wood species. The mechanical properties showed increases with the densification, except for the Janka hardness and dynamic flexion in E. grandis wood treated with high temperatures. Infrared spectroscopy showed degradation of the amorphous cellulose and hemicellulose, providing a proportional increase of crystalline cellulose and lignin. The color of the densified wood was changed presenting surface browning, measured by decrease in brightness L* parameter. Roughness was reduced, making the surface softer wood. Before the alterations, it is indicated using thermomechanical treatment with temperature of 150°C and the compression time of 60 min. In this respect, it is recommended the use of densified wood floors and coatings, even for softwoods (conifers). Os tratamentos termomecânicos visam aumentar a densidade da madeira, por meio da combinação entre temperatura e pressão, o que resulta em um material com as propriedades físico-mecânicas melhoradas. Nesse sentido, o presente estudo teve como objetivo avaliar a influência dos tratamentos termomecânicos na madeira. Para tanto, foram confeccionadas peças de madeira, a partir de cinco árvores de Pinus elliottii Engelm e Eucalyptus grandis W. Hill ex Maiden que foram submetidas a seis tratamentos termomecânicos. Para tal, foi utilizado um banho de óleo laboratorial para realizar o pré-aquecimento da madeira e uma prensa hidráulica com a temperatura dos pratos variando de 150 a 190°C e o tempo de compressão entre 30 e 60 min. Na sequência, foram realizados os ensaios físicos (grau de compressão, perda de massa, teor de umidade de equilíbrio, densidade, estabilidade dimensional e higroscopicidade), mecânicos (flexão estática, flexão dinâmica e dureza Janka), de superfície (colorimetria e rugosidade) e espectroscopia no infravermelho (ATR-IR). Para a análise estatística foi utilizado o arranjo fatorial qualitativo 3 x 2, com três níveis de temperatura (150, 170 e 190°C) e dois de tempo de compressão (30 e 60 min) e comparados pelo teste de Tukey. Além disso, foi realizado a comparação dos tratamentos com o controle pelo teste de Dunnett. Os principais resultados encontrados para as propriedades tecnológicas mostraram que o grau de compressão, a perda de massa e a densidade aumentaram com o acréscimo da temperatura, já o teor de umidade de equilíbrio apresentou decréscimo com a elevação da temperatura. Para a estabilidade dimensional foi observado que houve redução pelo efeito do retorno da madeira densificada e a higroscopicidade foi aumentada na madeira de ambas as espécies. As propriedades mecânicas apresentaram acréscimo com a densificação, com exceção para a dureza Janka e flexão dinâmica da madeira de E. grandis tratada com altas temperaturas. Por meio da espectrometria no infravermelho foi verificado a partir da razão de pico que houve degradação de hemiceluloses e celulose amorfa, proporcionando aumento proporcional de celulose cristalina e lignina. A coloração da madeira densificada foi alterada apresentando escurecimento superficial, quantificado pelo decréscimo do parâmetro de claridade L*. Já a rugosidade foi reduzida, tornando a superfície da madeira mais suave. Diante das alterações ocorridas é indicado utilizar tratamento termomecânico com a temperatura de 150°C e o tempo de compressão de 60 min. Nesse aspecto, é recomendado a utilização da madeira densificada como assoalhos e revestimentos, mesmo para as madeiras macias (coníferas).

URL: http://sutod.selcuk.edu.tr/sutod/article/view/245, Bu yazıda, emprenye işlemine tabi tutulacak olan ahşabın anatomik yapısına bağlı olarak bünyesinde özümseyebileceği koruyucu sıvı içerilme düzeyine etkisi bulunan ağaç malzeme fiziksel özelliklerinin deneysel bir sıra çerçevesinde belirlenmesi (ahşap koruma alanında çalışan araştırmacılara kolaylık sağlaması) amacıyla örnek bir kılavuz olarak geliştirilmiş olan Şematik Rehber kullanımı örneklenmiştir., A guide and flow chart have been designed to give an ideal experimental sequence for wood scientists to determine wood physical properties for preservation permeability studies. A novel guide give many advantages to the wood scientists due to its easy to use for data assembly and the experimental processing, i.e. wood anatomy, wood density, shrinkage and swelling, moisture content, fibre saturation point, kiln and oven drying, liquid permeability and subsequent data handling.

Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling and experiments. The results also illustrate the strong decrease of TSt with increasing temperature at a constant MC level.

In this paper, the following values of the physical and mechanical properties of thermally modified wood in organic oils of: water absorption, deliquescence, the maximum shrinkage, the MOR in static bending, compression and shear parallel to grain, the MOE in static bending. Raising the temperature and time of thermal modification leads to a deterioration of the mechanical and physical properties of the wood better. It is concluded that the operation of a suitable timber under low mechanical stress, or in their absence, as well as in conditions of high humidity.

Se estudió la densidad, contracción, higroscopicidad y punto de saturación de la pared celular en la madera de ejemplares jóvenes de tres especies importantes en la producción maderera española: Pinus pinaster, Pinus sylvestris y Pinus radiata. Se muestrearon 29 pinos procedentes de raleos efectuados en diferentes masas forestales de Galicia (noroeste de España). El material de ensayo fueron probetas de pequeñas dimensiones sin defectos. La madera de Pinus pinaster resultó semipesada y más inestable en dimensiones ante los cambios de humedad que las de Pinus radiata y Pinus sylvestris, que resultaron ligeras y relativamente estables, especialmente Pinus radiata. La densidad en Pinus pinaster fue similar a la obtenida en estudios anteriores sobre pies adultos. Pinus radiata y Pinus sylvestris presentaron madera más ligera que la de pies adultos. Las propiedades relativas a la estabilidad dimensional fueron similares en la madera joven analizada y en la madera de pies adultos, a excepción de la madera de Pinus radiata, que resultó más estable en la muestra que en la madera adulta. La variación entre zonas del fuste y entre individuos fue notable para las variables densidad y peso específico, aun en el caso de árboles muestreados en un mismo rodal y estación. Wood density, shrinkage, hygroscopicity and fibre saturation point were studied in young trees corresponding to three important species in the spanish timber production (Pinus pinaster, Pinus sylvestris and Pinus radiata). Twenty-nine thinned pines from different stands of Galicia (northwestern Spain) were sampled. The test material was small size defect-free specimens. The wood of Pinus pinaster exhibited intermediate density and more instability in dimensions, due to environmental moisture changes, than wood of Pinus radiata and Pinus sylvestris. These woods were light and relatively stable, especially Pinus radiata. The density in Pinus pinaster was similar to that obtained in previous studies on adult trees. Pinus radiata and Pinus sylvestris showed lower density than adult trees. The shrinkage properties were similar in the analyzed young wood and in the wood of adult trees, excepting the wood sampled for Pinus radiata, more stable than adult wood. Even with a sample of trees from the same stand in a specific site, there were significant differences in wood density among positions in each tree and among trees. SI

El presente artículo muestra los resultados obtenidos de las propiedades físicas como: gravedad especifica anhidra, seca al aire y en estado verde; densidad verde, seca al aire, anhidra y básica; y contracciones radial, tangencial y volumétrica. Propiedades mecánicas tales como: flexión estática en estado verde y seca al aire, compresión paralela al grano en estado verde y seca al aire. Además ensayos de trabajabilidad de cepillado, moldurado, taladrado y torneado de la Acacia melanoxylon. Se usaron metodologías establecidas por ASTM, ICONTEC y COPANT. Estos ensayos se realizaron en los laboratorios del Instituto de Ensayos e Investigación (IEI) de la facultad de Ingenleria, Universidad Nacional de Bogotá.