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Mindlin 판의 강성 및 질량행렬 계산법의 수정을 통한 유한 요소의 성능향상
김용우,민옥기,박춘수 연세대학교 산업기술연구소 1990 논문집 Vol.22 No.2
An improved scheme for calculating stiffness and mass matrices of Mindlin plate is suggested through the eigen analysis of rectangular plates. The significant error due to locking phenomenon can be alleviated by employing the modified shape function in calculating stiffness matrix without reduced integration. Further, the application of Gauss-Lobatto quadrature to mass matrix improves the behavior of numerical results in cooperation with the stiffness matrix calculated by the modified shape function. To illustrate these facts, 9-noded rectangular plate element is used, which is widely used in practice. Results for rectangular plate with all edges simply-supported and all edges built-in are presented, which demonstrated the effects of the modified shape function and the validity of Gauss-Lobatto quadrature for mass matrix.
崔鎔湜,金福起,石昌星 成均館大學校 科學技術硏究所 1992 論文集 Vol.43 No.1
Under large scale yielding conditions crack propagation is found to be governed by parameters based on the J-integral or on the crack opening displacement. But, initiation of crack propagation of ductile material seems to be controlled by just one parameter that is the strain, This paper describes a relation between the critical value of J-integral (J_IC) and the failure strain(ε_C) in uniaxial tensile test in the region of maximum reduction in area.
김기용,윤준오,이수호,신헌규 울산대학교 의과대학 1992 울산의대학술지 Vol.1 No.1
The ankle joint is a modified complex hinge joint which plays an important role in weight bearing, walking and standing. So, the goals of treatment of ankle fracture are anatomical positioning of the talus in the mortise and regaining a smooth articular surface. The Lauge-Hansen classification of ankle fracture is useful because it characterized the mechanism and sequence of injury and in particular, emphasizes the associated ligamentous injuries. But, it is more complex and all fractures do not conform exactly to one of the described pattern. The Danis-Weber classification of ankle fracture is simpler, emphasized the importance of the lateral side of the ankle, and is usuful in planning surgical treatment. Initially this system did not distinguish the extent of involvement and was too inclusive. The problem has been addressed in the AO classification. The system proposed by Tile is easy to remember and emphasized the importance of assessing and relating stability to the structures that are injured. We analyzed 124 cases of ankle fracture, most of which were treated surgically by AO methods, in the Orthopedic Department, University of Ulsan Medical College, Asan Medical Center from July 1989 to March 1992. The results obtained from this study were as follows : 1. The most common victim was 3rd-5th decade's man. 2. The most common type of Danis-Weber classification was type C(36.3%) and most common type of AO classification was type C1(15.3%), C2(15.3%). According to the classification of Lauge-Hansen, the most common type was pronation-external rotation (42.7%). 3. In Danis-Weber type B and C, satisfactory results were obtained by operative treatment. 4. Danis-Weber's classification and A-O classification were very practical criteria for treatment of the ankle fracture.
김기용,조우신,빈성일,백승일 울산대학교 의과대학 1992 울산의대학술지 Vol.1 No.1
The knee joint is the largest weight bearing joint. As the fractures of Knee joint in volve the articular surface and the surrounding soft tissues, permanent disabilities such as deformities, joint stiffness, instability and post-traumatic arthritis may ensue following treatment. Many authors have recommended various methods of treatment for these fractures. Recently, however, a trend toward internal fixation has become evident and good results have been reported by several authors. This study is to present 40 cases of knee joint fractures which were treated at Asan Medical Center from May 1989 to April 19992. The results were as follows ; 1. The causes of injury were traffic accident(60%), fall down(12.5%), slip down(12.5%) and sports injury(10%). 2. There were 23cases in 22 males and 17 females in series and average was 46.8 years ranging from 19 years to 82 years. 3. In femoral condylar fractures, the most frequent type was C2(8 cases ; 42.2%) and in tibial condylar fractures, B1(7 vases ; 35.5%) by the A.O. classification. 4. 7 Cases were treated by conservative method 32 cases by operative method and 1 cases by amputation. 5. Satisfactory results were obtained 73.3% in femoral condylar fractures and 88.2% in tibial condylar fractures by operative treatment. We concluded that satisfactory results were obtained from operative treatment with procedures of anatomical reduction, rigid fixation and early joint motion.
彈塑性破壞靭性値 J_IC의 決定法과 問題點에 대한 考察
崔鎔湜,金福起,石昌星 成均館大學校 科學技術硏究所 1992 論文集 Vol.42 No.2
Elastic-plastic fracture toughness J_IC can be used as an effective design criterion in elastic-plastic fracture mechanics. But there exist many problems in the test methods. Generally, the determintion of J_IC was performed according to ASTM E 813, the Standard of J_IC Test Methed but the J_IC value can be affected by many factors. In the J_IC test methods approved by ASTM and JSME, there are discrepancies such as the definition of J_IC, the slope of the blunting line, curve fitting method and the measurement of crack extension and so on. In this study, two major issues were discussed. Test method of J_IC : problems encountered with test method and improvements in techniques. The discrepancy of test methods : effect of specimen size, error caused by first data point of valid data, apparent negative crack growth phenomenon and the test method for high and low temperature.
김세윤,민옥기,김용우 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2
This paper deals with the minimum weight optimization of Mindlin plate under stress, displacement, eigen value, and design variable constraints. Modified shape functions and a full integration are employed in finite element analysis to remove errors due to spurious constraints and spurious modes. The weight of Mindlin plate, modeled by 9-noded rectangular Mindlin plate element, is minimized by choosing the thickness of element as a design variable and by using gradient projection method with analysis of design sensitivity for constraints. The numerical example is selected to compare the result of the present formulation with that of published one. This comparison shows that the procedure presented in this paper can be applicable to weight minimization of plate in practice.