Crack Propagation Analysis Using Interface Element (Report I) : Theoretical Formulation and Potential Fields of Application(Mechanics, Strength & Structure Design)
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Fiber reinforced composite materials and the composites with a thin film coating are applied in various fields as structural materials because of their high specific strength and stiffness which contribute to weight savings. The conventional materials, such as metals and ceramics, are also used under severe conditions due to the recent improvement of their performances. From the point of view of safe design of the structures, it is very important to estimate the fracture strength of materials with a reasonable accuracy. Many methods to evaluate the failure strength of materials have been proposed. There are basically two approaches. One is the macroscopic approach in which the concepts of stress intensity factor, energy release rate and J-integral are employed. The other is the microscopic approach such as the simulation of crack propagation using molecular dynamics. To evaluate the strength of a structural component, both the macroscopic and the microscopic nature of the phenomena must be taken into account. It is also noted that problems, such as ductile crack growth in metals and brittle fracture of ceramics and composite materials, are highly nonlinear and time dependent. Thus, extremely heavy computation is required. In addition, the mechanisms of crack extension or interface stripping have not been thoroughly clarified. In this study, a new and simple method is developed in order to simulate the fracture phenomena that can be considered as the formation of new surface as a result of crack propagation. Based on the fact that surface energy must be supplied for the formation of new surface, a potential function representing the surface energy density is introduced in the finite element method. The proposed method is applied to the mode-I and II crack propagation problems and its capability for static and dynamic analyses is demonstrated.
- Transactions of JWRI
Transactions of JWRI 27(2), 67-72, 1998-12