目的 以椴木为研究对象，研究冲击载荷作用下椴木试件的断裂解离形貌特征和断裂力学特性，建立适用于木材原料断裂解离的分形断裂力学模型，并对其断裂解离力学行为进行描述。方法 对椴木试件进行冲击加载试验，分析试件断口的形貌特征和断裂力学特性，构建适用于木材原料断裂解离的分形断裂力学模型。结果 椴木试件横向冲击断裂断口裂纹形状和断口形貌特征比纵向冲击复杂，横、纵向冲击断裂断口均具有分形特征;椴木试件纵向冲击断裂韧性均值是横向冲击断裂韧性均值的1.112倍，椴木试件横、纵向冲击断口的分形维数均值分别为2.063 5和2.075 1，椴木试件横、纵向冲击韧性与其断口分形维数之间存在线性正相关关系，拟合优度分别为0.778 7和0.812 2;构建的木材原料断裂解离临界解离应力和断裂韧性的分形断裂力学模型也适用于脆性材料。结论 在木材原料冲击断裂解离时，木材原料初始裂纹长度越短，断裂解离断口越粗糙复杂，木材原料断裂解离所需要的能量越大;当裂纹沿着与冲击加载力方向垂直成大约1.055 rad方向扩展时所需的能量最小，木材原料最易沿该方向进行断裂解离。

The work aims to take basswood as the research object to study the fracture dissociation morphology and fracture mechanics characteristics of specimen under impact load and then establish a fractal fracture mechanics model suitable for fracture dissociation of wood raw material and describe its mechanical behavior in fracture dissociation. Impact load was applied to the basswood specimen, the morphology characteristics and fracture mechanics properties of the specimen were analyzed and the fractal fracture mechanics model suitable for the fracture dissociation of wood raw material was constructed. The transverse and longitudinal impact fracture of basswood specimen had fractal characteristics, but the crack shape and fracture morphology of transverse impact fracture were more complex than those of longitudinal impact fracture. The mean value for longitudinal impact fracture toughness of basswood specimen was 1.112 times that of the mean value of transverse impact fracture toughness. The mean values of transverse and longitudinal impact fracture dimensions for basswood specimen were 2.063 5 and 2.075 1, respectively. There was a linear positive correlation between the transverse and longitudinal impact toughness of basswood specimen and its fracture fractal dimension, and the goodness of fit was 0.778 7 and 0.812 2, respectively. The critical dissociation stress model of wood raw material fracture dissociation and the fractal fracture mechanics model of fracture toughness were also applicable to brittle materials. When the wood raw material dissociates under the impact load, the shorter the initial crack length of wood raw material, the rougher and more complex the fracture dissociation fracture, the greater the energy required for the fracture dissociation of wood raw material. The energy required for the crack to propagate along the direction of about 1.055 rad perpendicular to the direction of the impact load force is the smallest, and the wood raw material is most likely to be broken and dissociate along this direction.