A Study On The Morphological Features Of Wood Fracture And Its Model Of Fractal Mechanics Under The Effect Of Dynamic Load

In the process of producing fiber board, wood in the defiberator-refiner plate is separated into fiber under its dynamic loading. The fracture morphological features and the quantitative description of wood fracture, the fracture direction in the process and the influential factors of energy consumption have an indispensable effect on the design and research of the mechanism and the optimization of defiberator-refiner, which is one of the frontier topics in this field. By using the fractal theory and the theory of fracture mechanics, this thesis mainly studies the morphological features, the mechanical properties and the fractal features in the process of shearing the wood and impact fracture dissociation.This thesis adopts 5 representative kinds of wood as the experimental material, through the shearing fracture test, so as to obtain the image of the fracture surface and fracture of the different tree species. Then, by applying the fractal theory it will also give an analysis on the fracture orientation, fracture surface morphology and fractal characteristics of fracture surface so that we could get the relationship between fractal dimension and fractal curve. In addition, the shear strength of each tree species was calculated so as to obtain the shear direction and condition of the shear strength. This thesis discusses the correlation between shear strength and fractal dimension of fracture surface of each tree species.Through the impact fracture of the test specimen on the universal mechanical testing machine, the image of the fracture surface and the energy required for the fracture of each tree species can be obtained. By applying the fractal theory, the thesis analyzes the fracture orientation, fracture surface morphology and fractal characteristics of fracture surface, which helps to obtain the relationship between fractal dimension and fractal curve. The impact toughness of the samples of each tree species was calculated, which is obtained to the impact direction of the minimum impact toughness. By calculating the transverse impact toughness and the fractal dimension of fracture surface of each tree species it discusses the correlation between the impact toughness and the fractal dimension of the fracture surface.The experiment picks up the fiber samples from all the partition of defibrator, and finally by using the fractal theory establishes the model of double logarithm linear regression within the length, diameter and the distance to the edge of millstone of the fiber in the grinding process. It demonstrates that the change of the fiber length and diameter has the fractal feature in that process. Then, by analyzing the dimension data of the fiber length and diameter in all the partition, it reveals the features of fiber dissociation activity and the direction of its consumption when grinding the dissociation fiber.Then, the thesis also establishes the wood fracture fracture model in process of wood fracture and its fractal mechanical model under the effect of the dynamic loading by adopting the fractal theory and the theory of fracture mechanics. Through the curve analysis on both of the two models, it obtains the initial condition of fracture, the fractal effect on energy consumption and its change regularity, which provides the theoretical basis for the structure and parametric design of defibrator grinding.Through the analysis on the grinding area fiber fractal dimension, this research proposes put forward a new method to calculate the fractal dimension of fracture surface using 3D scanning As a result, it has got an authorized invention paten (ZL20130185200.4) was applied, by which it can find a new way to calculate the fractal dimension with high accuracy, non-limitation of size and repeating measurement. In spite of this, this study also deepens the research on the mechanism of dissociation fiber, which helps to save energy, improve the quality of fiber and provide the theoretical basis and the applied practice. In this sense.it has an important theoretical significance and practical application value.