人工林赤松幼龄材与成熟材力学性质的比较

根据人工林赤松Pinus densiflora木材的管胞长度、微纤丝角、管胞长宽比、基本密度、晚材率及生长轮宽度等材性指标的测试数据,采用最优分割法划分出人工林赤松的幼龄材与成熟材的界限,分析了人工林赤松幼龄材与成熟材力学性质差异的表现.结果表明:赤松的幼龄期为小于12 a,抗弯强度、抗弯弹性模量、顺纹抗拉强度、顺纹抗压强度和弦向横纹抗压强度等指标成熟材高于幼龄材,径向横纹抗压强度、弦面抗剪强度、径面抗剪强度、弦向抗劈强度和径向抗劈强度等项指标幼龄材高于成熟材.其中,抗弯强度、抗弯弹性模量、径向横纹抗压强度和弦面抗剪强度差异达0.01显著水平,顺纹抗拉强度差异达0.05显著水平.图1表6参6

Mechanical properties of juvenile and mature wood of Pinus densiflora from plantations

Based on the variation pattern of wood properties obtained from the analysis results of measurement of tracheid length,microfibril angle,ratio of tracheid length to width,basic density and late wood percentage,the boundary of juvenile and mature wood of Pinus densiflora plantation was demarcated by using optimum method of classification,and the differences of mechanical properties of juvenile wood and mature wood from Pinus densiflora plantation were analyzed,from which we can conclude that the properties of mature wood at the age of 12 years old such as modulus of rupture(MOR),modulus of elasticity(MOE),tensile strength parallel to grain,compressive strength parallel to grain and tangential strength in compression perpendicular to grain are higher than those of juvenile wood.The properties such as radical compressive strength perpendicular to grain,tangential face shearing strength,radial face shearing strength,tangential cleavage strength,radial cleavage strength of juvenile wood are higher than those of mature wood.The difference of MOR,MOE radical compressive strength perpendicular to grain,and tangential face shearing strength of juvenile and mature wood from plantation reaches 0.01 level of significance,and tensile strength parallel to grain reach 0.05 level of significance.