Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Radially sawn timber : The influence of annual ring orientation on crack formation and deformation in water soaked pine (Pinus silvstris L) and spruce (Picea abies Karst) timber10.1007/s001070050224
This work describes deformation and crack formation in sawn timber of pine and spruce after first drying and subsequent cycles of resoaking in water and drying. The influence of annual ring orientation and the occurrence of juvenile wood was determined. In addition, the influence of compression wood, annual ring orientation at the edges of the cross section, the position of the board surface in relation to the pith, and the condition of the board surface i.e. whether wet or dry during resoaking were studied. When timber is exposed to repeated cycles of wetting and drying, warp, viz spring, bow, twist and cup, increases and is greater after the first cycle. The influence of annual ring orientation on spring, bow and twist depends on the type of deformation and on the kind of wood. Generally, the results indicated that timber with vertical and semi (half) vertical annual rings show less deformation (mean values) than plain sawn timber and timber containing pith. Cup is mainly caused by transverse anisotropy and is strongly influenced by the radius of the annual ring. Therefore, timber with vertical annual rings do not show any cup. Spring, twist and, especially bow are strongly influenced by compression wood. Large amount of compression wood in sawn timber increases such deformation. The distance between sawn timber in the log and the pith with surrounding juvenile wood is of vital significance for cracking. During moisture cycling, the amount of boards that develop cracks increased irrespective of their prior location in the cross section of the stem. Timber sawn from near the pith or distinctly containing pith has a higher relative crack length compared to timber sawn away from and lacking pith. In timber exposed to repeated cycles of wetting and drying the crack length increases irrespective of its prior location in the stem.
Radially sawn timber : The influence of annual ring orientation on crack formation and deformation in water soaked pine (Pinus silvstris L) and spruce (Picea abies Karst) timber10.1007/s001070050224
This work describes deformation and crack formation in sawn timber of pine and spruce after first drying and subsequent cycles of resoaking in water and drying. The influence of annual ring orientation and the occurrence of juvenile wood was determined. In addition, the influence of compression wood, annual ring orientation at the edges of the cross section, the position of the board surface in relation to the pith, and the condition of the board surface i.e. whether wet or dry during resoaking were studied. When timber is exposed to repeated cycles of wetting and drying, warp, viz spring, bow, twist and cup, increases and is greater after the first cycle. The influence of annual ring orientation on spring, bow and twist depends on the type of deformation and on the kind of wood. Generally, the results indicated that timber with vertical and semi (half) vertical annual rings show less deformation (mean values) than plain sawn timber and timber containing pith. Cup is mainly caused by transverse anisotropy and is strongly influenced by the radius of the annual ring. Therefore, timber with vertical annual rings do not show any cup. Spring, twist and, especially bow are strongly influenced by compression wood. Large amount of compression wood in sawn timber increases such deformation. The distance between sawn timber in the log and the pith with surrounding juvenile wood is of vital significance for cracking. During moisture cycling, the amount of boards that develop cracks increased irrespective of their prior location in the cross section of the stem. Timber sawn from near the pith or distinctly containing pith has a higher relative crack length compared to timber sawn away from and lacking pith. In timber exposed to repeated cycles of wetting and drying the crack length increases irrespective of its prior location in the stem.
Radially sawn timber : The influence of annual ring orientation on crack formation and deformation in water soaked pine (Pinus silvstris L) and spruce (Picea abies Karst) timber10.1007/s001070050224
Sandberg, Dick (Autor:in)
01.01.1997
doi:10.1007/BF02990541
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
cracking , star-sawing , distortion , spruce , wood quality , mechano-sorption , wood , cup , quarter sawing , Wood Science , Trävetenskap , pine
DDC:
690
Modeling the longitudinal variation of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)
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