木材断口分形的初步研究

木材是一种天然的多孔性生物高分子材料,结构复杂且变异性大,所以木材断裂表面定量分析的难度很高,对于木材内部裂纹产生、发展的研究一直没有大的突破.在木材断裂力学的研究中,国内外科学家运用传统的断裂试验方法研究居多,但普遍结论是规律不明显或找不到规律(费本华,1999).木材研究者们一直在寻找一种定量描述木材断裂表面形态的新指标,并希望在此基础上预测木材强度和了解木材断裂机制(Schmitt et al.,1996;Qin et al.,1999).

An Approach to Study the Fractal Character of Wood Fracture

It is very difficult to characterize the fracture surface of wood with traditional way because of its irregularity and complexity. This paper, inspired from slit island method (SIM) and mass fractal method, proposes a new method, by which the change of sectional area with spatial location in wood fractures can be determined, to quantify the character of fracture surfaces. The experiment is done by continuously microtoming a fractured sample embedded with paraffin at intervals of hundreds micron along the longitudinal axis from tip to end of fracture. The results indicate there exists a linear correlation between the area and the corresponding location in a double logarithm coordinate. The slope, here termed as section variation dimension (D-L), is located between 2.23 to 2.75 with the D-L of pressed zone being smaller than that of tensile zone for a wood fractured by static bending, and D-L can be used to describe quantitatively the complexity of fracture surface of wood.