構造部材を意識したスギ12品種の木材性質 : スギ材材質評価法確立を目指して

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スギ品種ごとに木材性質の特徴を明らかにして，構造部材としての材質評価の方向づけを明確にすることを目指している．そこで，12品種の樹幹内胸高部位の成熟材を用いて，晩材率，容積密度数，晩材仮道管長を測定するとともに，無欠点縦圧縮試験片で気乾材の強さ試験を行った．木材基本性質（Intrinsic Wood Properties）である容積密度数と晩材仮道管長，さらに縦圧縮強さと縦圧縮ヤング率は，品種間に差異が認められた．山方，晩材率と縦圧縮強さ，気乾比重と縦圧縮強さ，晩材仮道管長と比縦圧縮ヤング率との間に相関関係が認められた．すなわち，スギ無欠点材では品種名がわからなくても，圧縮強さは晩材率や比重（あるいは容積密度数）を指標にして，圧縮ヤング率は比重（あるいは容積密度数）と仮道管長を指標に採ることで，推定できるであろう．この研究に用いた指標では，相互間に密接な関係が存在し，とくに容積密度数と晩材仮道管長との間には負の相関関係が認められ，晩材仮道管長から容積密度数を推定できることが示唆された．なお，圧縮強さと圧縮ヤング率との間に，それぞれの品種内で相関関係が認められる．しかし，12品種を一括して示すとき，圧縮強さと圧縮ヤング率の間に相関関係を認めることができない．There are numerous cultivars of sugi (Cryptomeria japonica) in Japan and sugi cultivars in kyushu, in where vegetative reproduction based on rooted cuttings is very common, consist mainly of clones. Although intrinsic wood properties have been recognized to be closely related to the inherent nature of tree, very little information on the influence of hereditary effect of the clone on variation of wood properties among cultivars is available. It is accordingly the purpose of this experimental study to seek the wood quality indices which are meaningful to lead vigorous timber utilization as structural members. The experimental results obtained were summarized as follows : 1) The mean values of basic density obtained from green volume and ovendry weight, of latewood-tracheid length, and of compressive mechanical properties parallel to the grain, as shown in Tables 1 and 2, depend on the cultivar. Consequently, the difference of cultivars on wood properties can not be ignored. 2) It is difficult to keep on ensuring the cultivar's name at the stage of end-use of sawn timber, and the following results are useful to establish the wood quality system. The specific gravity at air-dry condition and the percentage of latewood are valid as the indices to estimate the compressive strength as shown in Figs. 1 and 4. The latewood-tracheid length is a valid wood quality index to estimate the specific Young's modulus as shown in Fig. 2, 3) There are significant relationships among the latewood percentage, the basic density, and the latewood-tracheid length as shown in Figs. 3 and 5. 4) No correlation between the compressive strength and the Young's modulus is found for twelve cultivars as shown in Fig. 7, though the compressive strength was correlated to the Young's modulus within cultivars (Fig. 6). It would be questionable to introduce a stress grading machine into the sawn timber grading of a mixture of cultivars.
九州大学の論文

構造部材を意識したスギ12品種の木材性質 : スギ材材質評価法確立を目指して

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