Summary
Several factors which may affect the shrinkage of wood had been studied using loblolly pine (Pinus taeda L.). It was observed that volumetric, tangential and radial shrinkages decreased as the height increased. Longitudinal shrinkage increased with height. Only tangential shrinkage was significantly affected by the distance from the pith factor. All shrinkages were found to vary significantly according to cardinal directions. For the trees studied, lower volumetric, tangential and radial shrinkages were observed for specimens from the south side of the pith. Longitudinal shrinkage was noticeably higher in this direction.
Although shrinkage of wood for any given specific gravity was found to vary somewhat with trees, it was, in general, significantly affected by specific gravity. Volumetric, tangential and radial shrinkages increased with increasing specific gravity. The opposite was true for longitudinal shrinkage. According to regression equations derived from this study, tangential, radial and longitudinal shrinkage values were not zero but 2.79–3.45, and 0.526 percent, respectively, at zero specific gravity. Above 0.72 specific gravity, radial shrinkage of the species studied was found to be greater than tangential shrinkage.
The effect of growth rate (number of rings per inch) on shrinkage was found to be insignificant.
Zusammenfassung
Verschiedene, die Schwindung beeinflussende Faktoren wurden an Holz von Loblolly pine (Pinus taeda L.) untersucht. Es wurde festgestellt, daß die Volumenschwindung, die tangentiale und die radiale Schwindung mit zunehmender Höhenlage der Proben im Stamm abnahmen, während die Längsschwindung größer wurde. Nur die tangentiale Schwindung wurde deutlich vom Abstand der Probe von der Markröhre beeinflußt. Es zeigte sich ferner, daß alle Schwindungswerte in Abhängigkeit von den Himmelsrichtungen beträchtlich schwankten. Bei den untersuchten Bäumen waren die Volumenschwindung, die tangentiale und die radiale Schwindung von Probestücken aus dem nach Süden liegenden Stammteil geringer, wogegen die Längsschwindung in dieser Richtung merklich größer war.
Trotz gewisser Schwankungen von Stamm zu Stamm erwies sich die Schwindung deutlich von der Dichte abhängig. Die Volumenschwindung, die tangentiale und radiale Schwindung nahmen mit zunehmender Dichte ebenfalls zu, wohingegen die Längsschwindung abnahm. Die mit den erhaltenen Werten aufgestellten Regressionsgleichungen ergaben für die Tangential-, Radial- und Längsschwindung bei einer Dichte von 0 nicht ebenfalls 0, sondern 2,79%,-3,45% und 0,527%. Für Dichten über 0,72% wurde die radiale Schwindung der untersuchten Proben größer als die tangentiale.
Die Wachstumsgeschwindigkeit (Anzahl der Jahrringe pro cm) hatte keinen signifikanten Einfluß auf die Schwindung.
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Yao, J. Shrinkage properties of second-growth southern yellow pine. Wood Science and Technology 3, 25–39 (1969). https://doi.org/10.1007/BF00349982
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DOI: https://doi.org/10.1007/BF00349982