DEVELOPMENT OF A NOVEL FINITE ELEMENT MODEL AND MATERIAL DEGRADATION MODEL FOR SPRUCE TIMBER SPECIMENS

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Absztrakt (kivonat)

An important prerequisite for the optimal use of wood as a structural building material is the determination of the strength properties of wood components using a method, that is as economical as possible. In recent years, numerical methods, such as the finite element method, have become increasingly popular as computing power has increased dramatically. Nowadays, numerous finite element models have been developed to describe wood materials. Therefore, wood as a material has been studied in a wide range of anatomical scales, trying to represent it with abstractions as accurate and realistic as possible. Based on the current literature, my research examines Norway spruce (picea abies) at the meso scale by approximating the annual ring pattern of specimens to obtain conclusions about their load-bearing capacity and deformation shape. The failure mechanism and the fracture of the specimens are also investigated. The goal of my research is to develop a finite element modeling technique that can be used to investigate test specimens individually. The modeling process includes a variety of exact and abstract methods. To develop an appropriate methodology, my research includes a thorough review of the recent literature. A further goal of my research is the development and parameterization of a finite element fracture mechanics model for Norway spruce specimens, as well as the comparison of its results with measurement data. For modeling individual specimens using finite element methods, a photoanalytical processing tool was developed that recognizes the specimen in the photo and the pattern of annual rings within it. This tool is required to create a finite element model of the individual specimens. Thus, the product of my research is a finite element modeling technique that allows to determine the load carrying capacity of a given specimen with a good approximation before measurements are performed, and a finite element damage model that allows to calculate the crack propagation in the specimen during overloading in case of brittle fracture by numerical simulation.

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