Deformation of cell wall in wood (Department of Forestry)

スギ材が繊維軸方向に圧縮荷重を受けたとき, 早・晩材や放射組織が切線断面のSlip planeにおよぼす影響を検討した。圧縮破壊した材は早材部, 移行材部, 晩材部の全ての材部にほぼ同数のSlip planeを生じるが, 放射組織に接する仮道管壁には集中的にSlip planeを生じる。放射組織の高さ方向のSlip plane分布状態はRay marginに最も高密度であり, 晩材部は中央部に向かって指数関数的に減少するが, 全材部が必ずしも指数関数的に減少しない。Slip plane数はひずみ量と共に増加するが, Ray margin付近には特に多数発生する。ひずみ量が小さい場合に, 放射組織に接する仮道管壁のSlip planeは他の仮道管壁よりも多いが, ひずみが破壊ひずみ以上に著しく大きくなると, 放射断面では放射組織に接しない仮道管壁のSlip planeが多くなる。放射断面と切線断面とでは, Slip planeを生じる仮道管の位置が異なり, ひずみ吸収の機構に差異が認められた。Influence of early and late wood and ray on the slip planes in radial tracheid walls of SUGI-wood (Cryptomeria japonica), which was subjected to longitudinal compression, was studied by polarizing microscope. The number of slip planes were much the same number in wood within one growth increment of failed wood. But slip planes were more numerous in tracheid walls contact with ray than other tracheid walls. Slip planes of the tracheid walls in contact with ray developed preferentially at the tracheid walls in contact with ray margin and decreased exponentially from ray margin to center cell of the ray in late wood, But in early and transition wood, they did not decrease exponentially. Relation between strain and slip planes in radial and tangential wall of tracheid was summarized as follows. In the limits of 120% strain to the strain at maximum stress, slip planes in tangential walls of tracheid developed more at the walls in contact with ray than walls out of contact with ray. At the higher strain, slip planes developed more at walls out of contact with ray than walls in contact with ray. In radial walls of tracheid, slip planes developed preferntially at walls in contact with ray. Development of slip planes in tracheid walls were diffrent between radial and tangential wall of tracheid. And the mechnism of strain development in a tracheid was considered to be different at the tangential and radial wall of a tracheid