火力楠心材与边材颜色和物理力学性质

研究火力楠心材与边材的颜色和物理力学性质，为该树种木材的合理开发和利用提供参考。采用CIE Lab颜色系统表征木材的颜色参数（明度指数L^*、红绿轴色品指数a^*、黄蓝轴色品指数b^*）；按照国家标准测量木材的物理性质（密度、干缩性、湿胀性）和力学性质（顺纹抗压强度、横纹抗压强度、抗弯强度、抗弯弹性模量、顺纹抗剪强度、硬度、冲击韧性、顺纹抗拉强度、抗劈力、握钉力）。结果表明，火力楠心材的L^*、a^*和b^*均小于边材，表明心材的颜色偏向黑色的程度更大，而偏向红色和黄色的程度更小，整体颜色更加暗深；火力楠心材与边材的总色差属人视觉感觉差异“可察觉”。火力楠心材的密度小于边材，二者密度均属中等；心材的差异干缩大于边材，二者气干干缩的不均匀性均属小；心材的体积干缩系数小于边材，二者干缩性均属很小。火力楠边材的吸水增重率大于心材，表明边材的渗透性优于心材。火力楠边材的硬度、冲击韧性、抗劈力和握钉力大于心材，而其余力学指标小于心材。火力楠心材和边材的顺纹抗压强度、抗弯强度、顺纹抗剪强度、端面硬度和冲击韧性，均属木材各项力学指标品质分级的中等及以上水平。火力楠心材的综合强度和综合品质系数均大于边材，二者均分别属高强度和强重比很高。

Variations of Color,Physical and Mechanical Properties in Heartwood and Sapwood of Michelia macclurei

The variations of color,physical and mechanical properties in heartwood and sapwood of Michelia macclurei were studied,to provide scientific reference for the reasonable processing and utilization of this wood.The CIELab color system was used to measure the color parameters of the wood (lightness L^*,green-red axis value a^*,blue-yellow axis value b^*).The physical properties (density,shrinkage,swelling) and mechanical properties (compression strength parallel to grain,compression strength perpendicular to grain,modulus of rupture,modulus of elasticity,shearing strength parallel to grain,hardness,impact toughness,tensile strength parallel to grain,cleavage strength,nail holding power) of the wood were determined according to the Chinese national standards.The results showed that the values of L^*,a^* and b^* of the heartwood were lower than those of the sapwood,indicating that the color of heartwood was blacker,less red and yellow.The color difference between the heartwood and sapwood belonged to the “perceivable” of human visual perception difference.Compared to sapwood,the heartwood had lower density,lower volumetric shrinkage coefficient,and higher ratio of tangential shrinkage to radial shrinkage.The heartwood and sapwood both belonged to the medium density grade,the very small shrinkage grade,and the small uneven air-dry shrinkage grade.The water absorption rate of sapwood was higher than that of heartwood,indicating that sapwood had better permeability.The hardness,impact toughness,cleavage strength,and nail holding power of the sapwood were higher than those of the heartwood,while the other mechanical indexes were opposite.The compression strength parallel to grain,modulus of rupture,shearing strength parallel to grain,cross hardness and impact toughness of the heartwood and the sapwood belonged to the medium or above level of the mechanical index classification of wood.The comprehensive strength and the comprehensive quality coefficient of the heartwood were higher than those of the sapwood.The heartwood and sapwood both belonged to the high strength grade,and the very high ratio of strength to weight grade.