马尾松木材早晚材急变,致使径、弦向性能差异显著.研究了径、弦向弯曲荷载作用下马尾松木材抗弯强度、抗弯弹性模量及破坏形态的差异,使用扫描电子显微镜观察了径、弦向受力时破坏面的区别.结果表明:马尾松木材的抗弯强度、抗弯弹性模量均是弦向大于径向,且差异显著.径、弦向拉伸断裂面均比较粗糙;剪切破坏通常发生在管胞间,裂纹会沿着纹孔的边缘扩展,纹孔常呈现出完整形态.弦向受力时,拉伸断裂面表层管胞扭转现象明显,管胞壁产生裂隙,剪切破坏发生在径切面的木射线细胞处.径向受力时,拉伸断裂面表层管胞无明显扭转现象,剪切破坏发生在早晚材边界处.%Transition of masson pine from the earlywood to the latewood is abrupt that causes the significant differences between wood properties on radial and tangential directions.Differences of MOR,MOE and breaking modes of masson pine were analyzed,and different breaking surfaces were observed by scanning electron microscope (SEM) under radial and tangential bending load.The results show that MOR and MOE on tangential directions are greater than that on radial directions.Tensile fracture surfaces show relative roughness,shear breaking occurs between tracheids,and cracks extend around the tracheid pits while pits are not damaged on both directions.Obvious tracheid twist can be found on tensile fracture surfaces that causes cracks on tracheid walls and shear breaking occurrs in wood ray cells of radial sections under tangential bending load.However,there is no obvious tracheid twist on the tensile fracture surfaces and shear breaking occurrs in the earlywood and the latewood boundary under tangential bending load.
展开▼
