Study On Fracture Behavior In Wood And Its Character Of Acoustic Emission

The dissertation studies the fracture behavior in wood which is as biomass material. All the discussion is based on the theory of linear elastic fracture mechanics, and expounded the details by the theory and experiment:In theory, it discourses the prerequisite of linear fracture elastic mechanics when to calculate fracture toughness of wood, also points out the size requirement of sample to insure plan strain state and little scope yield; In the experiment, it contrast the traditional sample to new one, first uses the sandwich sample to test the fracture toughness. The result is close, however, the sandwich is a better maneuverability. Meanwhile, the acoustic emission technology is applied to monitor the process of fracture, and determine the fracture critical point by the ring-down count to guarantee the precise of the test. It also put forward the concept of fracture energy for the anti-fracture design.Finally, it gives an example to combine the theory study with practical applies in timber structure. In the grade of dimension lumber, it suggests to regard fracture toughness as an important parameter besides the usual MOE or MOR. Especially in key position of timber structure, considering wood is biomass material, designer should combine the allowed stress with fracture toughness for the safety of timber building.The dissertation is not only a fundamental research of wood properties, but also test the fracture parameter by new sample and new technology. What's more, it has a good combination of theory study with practical use. It will possess great significance of study on wood properties, grade of dimension lumber, and design of timber structure.