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Considerations of the Initial Crack Damage Effect on the Advanced Idealized Plate Unit
백점기,서흥원,Paik, Jeom-K.,Suh, Heung-W. The Society of Naval Architects of Korea 1994 大韓造船學會 論文集 Vol.31 No.2
This paper attempts to incorporate the initial crack damage effect into the existing idealized plate unit. For this purpose, a new concept which indicates the equivalent, reduced material properties due to initial cracks at the structural unit level, not at he microscopic aspect, is suggested, and a simplified mechanical plate model for the initially cracked plate in axial tension is formulated as a function of initial crack length, based on the finite-element solutions obtained by crack propagation analysis.
白点基,徐興源 부산대학교 공과대학 1992 工大論文集 Vol.43 No.-
The aim of the present paper is to develop a computer program predicting the ultimate fracture strength of initially cracked structures under monotonically increasing external loads. For this purpose, two kinds of 3-D isoparametric solid elements, one 6-node wedge element and another 8-node brick element are formulated along the small deformation theory. Plasticity in the element is checked using von Mises' yield criterion. Elasto-plastic stiffness matrix of the element is calculated taking account of strain hardening effect. If the principal strain at crack tip exceeds the critical fracture strain depending on the material property, the crack tip is supposed to be opened and the crack tip node which was previously constrained in the direction perpendicular to the crack line is becomes free. After that, the crack may be propagated to the adjacent node. Once a crack tip node is fractured, the energy of the newly fractured node should be released which is to be absorbed by the remaining part. The accumulated reaction force which was carried by the newly fractured node so far is then applied in the opposite direction. During the action of crack tip relief force, since unloading may occur in the yielded element, the unloading check should be made. If the yielded element unloads, the elastic stress-strain equation is used in the calculation of the stiffness matrix of the element, while for the loading elements, the elastoplastic stress-strain equation is continuously used. Verification of the computer program is made comparing with the experimental results for center cracked panel subjected to tensil and bending load. Also some factors affecting ultimate fracture strength of initially cracked plates are investigated. It is concluded that the computer program developed here gives an accurate solution and may be useful tool for predicting the ultimate fracture load of initially cracked structural systems under monotonically increasing external loads.