| 1. |
- Nilsson, Börje, et al.
(författare)
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A method for under bark detection of the wood grain angle radial dependence
- 2007
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Ingår i: Wood Material Science and Engineering. - : Taylor & Francis. - 1748-0272. ; 2:3,4, s. 118-129
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Tidskriftsartikel (refereegranskat)abstract
- Twist in wood, being closely related to spiral grain, may cause serious problems in building structures, furniture, and joinery. It is therefore of great interest to sort out, at an early stage in the manufacturing process, trees, logs and boards that have an access of spiral grain. The spiral grain pattern is described by a helical deviation of the fibre direction in relation to the longitudinal direction of a living tree or a log and seems to be an indicator for other defects such as compression wood. Remote microwave sensing of spiral grain has received a large interest during the latest two decades. Its development has been impeded by the large variation with moisture content of the microwave properties of wood and by the complexity in modelling the electromagnetic field in a log with spiral grain. A review is presented of a direct method with no requirement of information on moisture content for boards. This procedure has recently been generalized to cylindrical logs and trees having a constant slope of the grain. A further generalization is presented here to allow for the normal spiral grain pattern with radially changing slope of grain in wood under bark. Based on this theory, a measurement procedure is proposed for the detection of wood grain angle with radial dependence, requiring no information on moisture content in the sapwood, also applicable for completely or partially frozen wood. A suitable application would be an instrument to use in the forest for measurements on living trees or logs.
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| 2. |
- Säll, Harald, et al.
(författare)
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Bending strength and stiffness of aspen sawn timber
- 2007
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Ingår i: Quality Control for Wood and Wood Products. - : COST, Warsaw. ; , s. 6-
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Konferensbidrag (refereegranskat)abstract
- In order to investigate the possibility of using sawn timber of European aspen (Populus tremula L.) as a structural material, 150 pieces of the dimension 45 x 120 mm2 were selected from a sawmill in the south of Sweden. The material was visually strength graded using the Nordic standard INSTA 142 and the British standard BS 4978-1996, respectively. The timber pieces were also subjected to flat-wise bending in a Cook-Bolinder Ò strength grading machine. Finally all specimens were tested in edge-wise bending according to the European testing standard EN 408. Global and local moduli of elasticity as well as bending strength were determined. The results indicate that the visual grading rules, intended for use on Norway spruce and Scots pine, seem to work fairly well on European aspen. However, grading in a flat-wise bending machine like the Cook-Bolinder seems to give a lower correlation between stiffness and strength for aspen timber than generally found for coniferous. Further, the correlation between density and bending strength was found to be very low for the aspen timber tested. It was also noticed that the aspen timber has a slightly higher bending strength and modulus of elasticity than is the case for normal qualities of Norway spruce. The study indicates that sawn timber of European aspen grown in southern Sweden can be visually graded and used as structural material.
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| 3. |
- Säll, Harald, et al.
(författare)
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Bending strength and stiffness of aspen sawn timber
- 2007
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Ingår i: COST Action E53 The First Conference: Quality Control for Wood and Wood Products.. - : Warsaw University of Life Sciences.
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Konferensbidrag (refereegranskat)
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| 4. |
- Säll, Harald, et al.
(författare)
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Masurbjörk
- 2008
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Bok (populärvet., debatt m.m.)abstract
- Detta häfte är en introduktion till dig som är intresserad av att ekonomiskt utveckla ditt skogsbruk genom odling och användning av masurbjörk, Skandinaviens värdefullaste trädslag. Vi vill här kort ge dig grundfakta så att du kan förstå den ekonomiska möjlighet som odling av klonade masurbjörk för med sig, också i ditt skogsbruk.
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