• Journal of the Korean Wood Science and Technology
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• 제45권1호
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• pp.53-61
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• 2017

본 연구에서는 고강성, 고인성의 경량화된 목질접합부를 제작하기 위하여 슬릿 가공된 기둥부재 중앙에 강판 대용인 목질접합물을 삽입하고 기둥부재와 목질접합물만 결합된 시험편들을 제작하였다. 시험편들은 강판을 사용한 대조군 시험편과 모멘트 저항성능을 비교분석하였다. GFRP보강목질적층판과 핀으로 제작된 시험편들은 강판삽입형 시험편 보다 평균 24% 저하된 최대모멘트가 측정되었으나 양호한 인성이 관찰되었다. 파괴형상은 기둥부재의 연단부분에서 연륜을 따라 파괴되었다. 집성재와 목질적층판을 접착제로 일체화한 강절형 시험편은 대조군 시험편보다 초기강성이 2.8배 향상되었고, 최대모멘트도 평균 40% 향상된 경향을 보였다. 강절형 시험편들은 접착층 주위에서 파단되었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.167-172
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• 1998

An algorithm of Thermal-elastohydrodynamic lubrication analysis for the piston ring is developed. This algorithm contains cavitation boundary condition so it automatically satisfies conservation of mass. 1-D Reynolds equation and 2-D energy equation are solved simultaneously by using Gauss-Jordan method and Newton-Raphson method. Minimum film thickness and friction force are calculated for 1 cycle. There is little difference between the results caculated by isothermal rigid and EHL analysis in entire cycle. In the results of THL, shear heating effect and temperature boundary condition affect the minimum film thickness and friction force prediction. The minimum film thickness and the friction force calculated by THL are lower than those caculated using isothermal assumption.

• 한국정밀공학회지
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• 제13권2호
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• pp.102-109
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• 1996

Effects of frictional laws on finite element solutions in metal forming were investigated in this paper. A rigid-viscoplastic finite element formulation was given with emphasis on the frictional laws. The Coulomb friction and the constant shear friction laws were compared through finite element analyses of compression of rings and cylinders with different aspect ratios, ring-gear forging, multi-stage cold extrusion and hot strip rolling under the isothermal condition. It has been shown that two laws may yield quite different results when the aspect ratio of a process and the fractional contact region are large.

• 한국정밀공학회지
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• 제12권1호
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• pp.29-37
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• 1995

In many metal forming processes, it is common to use stress rings for reducing elastic deformation and failures of forming dies. But, shrink fit of dies inner diameter of die insert, machining is reuqired after shrink fit processes. The reduction of inner diameter can be predicted by the analysis of elastic-plastic finite element method. The dimension of dies before shrink fit can be determined to minimize or remove machining after shrink fit processes by deformation analysis of die. The computation of contacting stresses along die surface was analyzied by rigid plasitic finite element method, and data were interpolated by the contact search algorithm. In this paper, we propose the analysis method of forging dies after shrink fit and forming to improve dimensional accuracy of final products.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1286-1291
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• 2000

A new electro-rheological squeeze film damper (ER SFD) has been sealed with slotted piston rings which have electrodes at the inside of the constant gap. The slotted ER SFD can prevent the problem of electric discharge which might be occurred in the previous configuration of an ER SFD. The current paper presents the extraction of linearized dynamic coefficients within small orbit where these coefficients are controlled by the application of electric strength. Test rig has been modified to isolate the damper section for dynamic coefficient extraction. The results show that rotordynamic coefficients, damping and inertia terms, increase with increasing supply voltages, while stiffness coefficients decrease with increasing supply voltages. Rotating speed of rigid Shaft does not affect these coefficients.

• 한국정밀공학회지
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• 제16권6호
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• pp.114-122
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• 1999

By using the FEM, a method for the stress analysis of the presented dies has been proposed. In this method, FEM and Lame equation are used for the analysis of the die insert and the stress ring, respectively. The proposed method includes the calculation of the contact pressure between the die insert and the stress ring. To show the validity, the proposed method has been applied to the simple test problem. The results of the stress analysis have been compared with the results of ANSYS, a commercial FE-code. Cold extrusion has been simulated by using the rigid-plastic FEM and the results of the deformation analysis have been used as the input of the die structure analysis. The stress states of the prestressed extrusion die have been obtained. The stress analysis of the die insert with stress rings has also been performed during extrusion.

• 소음진동
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• 제10권6호
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• pp.1029-1034
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• 2000

A new electro-rheological squeeze film damper (ER-SFD) has been sealed with slotted piston rings which have electrodes at the inside of the constant gap. The slotted ER-SFD can prevent the problem of electric discharge which might be occurred in the previous configuration of an ER-SFD. The current paper presents the extraction of linearized dynamic coefficients within small orbit where these coefficients are controlled by the application of electric strength. Test rig has been modified to isolate the damper section for dynamic coefficient extraction. The results show that rotordynamic coefficients, damping and inertia terms, increase with increasing supply voltages, while stiffness coefficients decrease with increasing supply voltages. notating speed of rigid shaft does not affect these coefficients.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.649-664
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• 2015

In this study, the authors present an analytical approach to find the axisymmetric buckling load of two joined isotropic conical shells under axial compression. The problem of two joined conical shells may be considered as the generalized form of joined cylindrical and conical shells with constant or stepped thicknesses. Thickness of each cone is constant; however it may be different from the thickness of the other cone. The boundary conditions are assumed to be simply supported with rigid rings. The governing equations for the conical shells are obtained and solved with an analytical approach. A simple closed-form expression is obtained for the buckling load of two joined truncated conical shells. Results are compared and validated with the numerical results of finite element method. The variation of buckling load with changes in the thickness and semi-vertex angles of the two cones is studied. Finally, application of the results in practical design and range of engineering validity are investigated.

• Structural Engineering and Mechanics
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• 제40권2호
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• pp.279-295
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• 2011

A solution of space curved bars with generalized Winkler soil found by means of Transfer Matrix Method is presented. Distributed, concentrated loads and imposed strains are applied to the beam as well as rigid or elastic boundaries are considered at the ends. The proposed approach gives the analytical and numerical exact solution for circular beams and rings, loaded in the plane or perpendicular to it. A well-approximated solution can be found for general space curved bars with complex geometry. Elastic foundation is characterized by six parameters of stiffness in different directions: three for rectilinear springs and three for rotational springs. The beam has axial, shear, bending and torsional stiffness. Numerical examples are given in order to solve practical cases of straight and curved foundations. The presented method can be applied to a wide range of problems, including the study of tanks, shells and complex foundation systems. The particular case of box girder distortion can also be studied through the beam on elastic foundation (BEF) analogy.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.667-694
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• 2015

The suspended dome system is a new structural form that has become popular in the construction of long-span roof structures. Suspended dome is a kind of new pre-stressed space grid structure that has complex mechanical characteristics. In this paper, an optimum topology design algorithm is performed using the enhanced colliding bodies optimization (ECBO) method. The length of the strut, the cable initial strain, the cross-sectional area of the cables and the cross-sectional size of steel elements are adopted as design variables and the minimum volume of each dome is taken as the objective function. The topology optimization on lamella dome is performed by considering the type of the joint connections to determine the optimum number of rings, the optimum number of joints in each ring, the optimum height of crown and tubular sections of these domes. A simple procedure is provided to determine the configuration of the dome. This procedure includes calculating the joint coordinates and steel elements and cables constructions. The design constraints are implemented according to the provision of LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Constitution). This paper explores the efficiency of lamella dome with pin-joint and rigid-joint connections and compares them to investigate the performance of these domes under wind (according to the ASCE 7-05), dead and snow loading conditions. Then, a suspended dome with pin-joint single-layer reticulated shell and a suspended dome with rigid-joint single-layer reticulated shell are discussed. Optimization is performed via ECBO algorithm to demonstrate the effectiveness and robustness of the ECBO in creating optimal design for suspended domes.