针叶材在超细粉碎过程中细胞壁断裂的理论计算

摘要

将针叶材的超微结构破坏分为细胞壁间分离和细胞壁断裂两种形式.在制备其超细木粉过程中,涉及到针叶材细胞的破壁力计算时,提出以细胞壁中存在大量的原生细观缺陷作为已存在的裂纹,将单一细胞壁看作是带有裂纹体受拉应力的平板,利用弹塑性断裂力学中J积分与积分路径无关这一常数的性质,避开裂纹尖端的弹塑性区域进行理论计算,应用J积分与应力强度因子在平面应力下的关系,计算出针叶材细胞壁断裂韧性的大小,并将不同针叶树种的木材细胞断裂韧性数值与其相应的细胞壁抗拉强度实验结果相比较,得出以此理论计算木材细胞断裂韧性值较为合理,表明利用J积分计算木材细胞壁断裂韧性这一方法是可行的.%The ultrastructure damage of coniferous timber could be divided into two forms namely separation and fracture of cell wall.Refer to the cell wall rupture calculation during the course of preparing superfine wood powder,it is proposed that taking the existing microscopic defects in cell wall as the cracks,and viewing a single cell wall as the flat-panel with cracks body tensile stress,making use of the nature that elastic-plastic fracture mechanics J-integral and integral path-independent,to avoid the crack tip plastic region in theoretical calculation,applying the relationship of J-integral and stress intensity factor in plane stress,the cell wall fracture toughness could be calculated.Comparing the calculation results of cell wall fracture toughness of different coniferous tree species with the experimental results of tensile strength,it is concluded that the results of this calculation method was reasonable,which implied that it was feasible to calculate timber cell wall fracture toughness of coniferous timber using J-integral.