Black poplar (Populus nigra L.) was thermally modified in superheated steam at 160 °C, 190 °C, and 220 °C for 2 h. The research identified correlations between the chemical composition and selected mechanical properties of thermally modified wood. The higher treatment temperatures significantly lowered the modulus of rupture (MOR) and the Brinell hardness (BH). These correlations were particularly apparent at higher temperatures (190 °C and 220 °C) when thermally modified wood experienced stronger hemicelluloses degradation, which was indicated by an increase in the content of non-structural substances. The wood properties including compressive strength parallel to the grain (CS), modulus of elasticity during bending (MOE), and compressing (MCS) were affected less by the chemical changes caused by the thermal processing of wood. Moreover, the level of wood moisture content also affected these changes.
Correlation between the share of latewood and the density of sawn timber from the Silesian Forestry Region. The paper describes the results of density measurements and the share of latewood in pine wood samples (Pinus sylvestris L.) from the Silesian Forestry Region in Poland. The samples were obtained from sawn timber from different kinds of log: butt, middle and top. The place from which the timber was obtained (three different log kinds) was taken into account when assessing the correlation between wood density and the share of latewood.
Comparison results of visual and machine strength grading of Scots pine sawn timber from the
Silesian Forestry Region in Poland. The paper presents an analysis of the strength grading results performed by
two methods – visual (appearance) and machine, carried out for sawn timber obtained from the Silesian Forestry
Region in Poland. Visual strength grading was performed in accordance with PN-D-94021:2013, while the
machine strength grading with the use of MTG device from Brookhuis Electronics BV. As a result of the tests, it
was confirmed that the machine grading results in a very small share of sawn timber classified as rejects. At the
same time, during machine strength grading there were some sawn timber pieces that were not classified for any
class or a reject. Based on its visual appearance, such timber elements should be graded as rejects.
Annual growth ring width was considered relative to the mechanical properties of timber from the Silesian Forestry Region in Poland. The timber was acquired from raw wood aged approximately 120 years old, with log quality A, B, and C. The study was conducted on 210 pieces of timber; 70 of them were from each part of the log: butt, middle, and top. The tested parameters, modulus of elasticity (MOE) and modulus of rupture (MOR), were measured on fully dimensional timber (40 × 138 × 3500 mm3) that had been dried and planed in industrial conditions. The density of wood (stereometric method) and annual rings width were calculated after MOR and MOE determination on samples including the entire cross-section cut near the failure zone. The tests revealed that the correlation between the width of growth rings and MOE or MOR depended on the log area: it was the highest for timber from butt logs and the lowest for timber from top logs. Moreover, the correlation between growth ring width and MOE or MOR depended also on the quality class of the logs from which the samples were obtained: it was the highest for timber from class A, and the lowest for class C.
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