• Nuclear Engineering and Technology
• /
• v.33 no.6
• /
• pp.619-625
• /
• 2001

An axial-flow-induced vibration model was proposed for a rod supported by two translational springs at both ends. For developing the model, a one-mode approximation was made based on the assumption that the first mode was dominant in vibration behavior of the single span rod. The first natural frequency and mode shape functions for the flow-induced vibration, called the FIV model were derived by using Lagrange＇s method. The vibration displacements at reactor conditions were calculated by the proposed model for the spring-supported rod and by the previous model for the simple-supported(55) rod. As a result, the vibration displacement for the spring-supported rod was larger than that of the 55 rod, and the discrepancy between both displacements became much larger as flow velocity increased. The vibration displacement for the spring-supported rod appeared to decrease with the increase of the spring constant. AS flow velocity increased, the increase rate of vibration displacement was calculated to go linearly up, and that of the rod having the short span length was larger than that of the rod having the long span length although the displacement value itself of the long span rod was larger than that of the short one.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.11
• /
• pp.1587-1592
• /
• 2010

The effects of specimen geometry and loading conditions on the stress distribution in a sandwich specimen under combined loads are investigated by elastic finite element analysis. A commercial software NASTRAN is used in plain-strain two-dimensional finite element analysis of sandwich specimens; the analysis was performed for three different specimen shape factors and four different combined displacement conditions. The results of computational analysis suggest that the effect of the combined displacement angle, which is defined as the ratio of the shear displacement to the normal displacement, on the size of the non-homogeneous stress distribution is observed only in the case of the shear stress and von Mises stress. Also as the combined displacement angle increases, the size of the nonhomogeneous stress distribution decreases in the case of the shear stress and increases in the case of the von Mises stress. In addition, as the specimen shape factor, which is defined as the ratio of the specimen length to the height, increases, the size of the non-homogeneous stress distribution under combined displacement conditions decreases significantly.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.1
• /
• pp.20-26
• /
• 2000

This paper deals with the modal analysis and the displacement of stator due to electromagnetic forces in Switched Reluctance Motor(SRM). A free-free model of the stator based on structural 3-dimensional Finite Element Method(FEM) is used for investigation the natural frequencies and the mode shapes of the stator. In addition, The displacement caused by magnetic force acting on stator pole is analyzed by the structural FEM coupled with the magnetic force. From these results, the resonance speed is obtained by the relation of the natural frequencies of the harmonic frequencies of magnetic force. And, the eccentricity with respect to rotor is predicted from the analysis result of the mechanical displacement of stator. The natural frequencies of stator are compared with experimental ones measured by modal testing.

• Journal of the Korean Society of Industry Convergence
• /
• v.13 no.3
• /
• pp.161-168
• /
• 2010

Recently, bridges have been momenttous as not only regarding function but also concerning aesthetics. However, when beauty is considered in the bridge, it is also essential that stability and economics be considered. Besides, when considering stability, an arch bridge is one of the most stable structures. The most important element is a rise ratio when regarding beauty and economics of arch bridges. The effect of dead load and DB24 load have been considered to decide proper rise ratio. Therefore, in this study, examined the value of moment, displacement and member forces, in the variation of the rise ratio of arch bridges. The most optimum shape of Nielsen arch bridges has determined by analyzing member forces, moments and displacement with parameters of rise ratio and angle of vertical members. By comparison between values, the hanger types have been also considered to derive the optimum shape of Nielsen arch bridge.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.5
• /
• pp.126-133
• /
• 2017

This report investigates the stress distribution according to the location and shape change of the circular hole for the lightweight design of the cross beam of a railway passenger car and studies the lightweight design. To design a lightweight cross beam with a circular hole, we selected the non-circular crossbeam as a basic model, examined the stress distribution and displacement by position and determined the location, shape, size and quantity of the hole for light weight. We analyzed the effects of the position and shape of the hole on the maximum equivalent stress and displacement. The influencing factors were set as the design parameters, and the stress value was examined according to the variation of each variable. By considering the stress value according to the change of each variable and selecting the design parameter with the narrowest scattering value of the stress at each position of the hollow cross beam with various hole positions and shapes, we studied a cross beam with a circle hole under identical load condition to have an equal stress distribution to that of a non-circular cross beam.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.9
• /
• pp.186-192
• /
• 2002

As industry is developed, the faster transportation of freight train is demanded. The optimum design of a structure requires the determination of economical member size and shape of a structure which will satisfy the design conditions and the functions. In this study, it is attempted to minimize the dead weight of bogie frame. From the numerical results in the shape and size optimization of the bogie frame, it is known that the weight can be reduced up to 17.45% with the displacement, stress, first natural frequency and critical buckling-load constraints. The first natural frequency and the critical buckling load of the optimized model is larger than that of the lowest design value. Stress and displacement conditions are also satisfied within the design conditions. From the results, the optimal model is stable and useful for the improvement of railway carriages.

• Smart Structures and Systems
• /
• v.31 no.5
• /
• pp.531-543
• /
• 2023

Base isolation is one of the most widely implemented and well-known technique to reduce structural vibration and damages during an earthquake. However, while the base-isolated structure reduces storey drift significantly, it also increases the base drifts causing many practical problems. This study proposes the use of Shape Memory Alloys (SMA) wires for the reduction in base drift while controlling the overall structure vibrations. A multi-degree-of-freedom (MDOF) structure along with base isolators and Shape-Memory-Alloys (SMA) wires in diagonal is tested experimentally and analytically. The isolation bearing considered in this study consists of laminates of steel and silicon rubber. The performance of the proposed structure is evaluated and studied under different loadings including harmonic loading and seismic excitation. To assess the seismic performance of the proposed structure, shake table tests are conducted on base-isolated MDOF frame structure incorporating SMA wires, which is subjected to incremental harmonic and historic seismic loadings. Root mean square acceleration, displacement and drift are analyzed and discussed in detail for each story. To better understand the structure response, the percentage reduction of displacement is also determined for each story. The result shows that the reduction in the response of the proposed structure is much better than conventional base-isolated structure.

• Structural Engineering and Mechanics
• /
• v.88 no.1
• /
• pp.83-94
• /
• 2023

An accurate and highly efficient inverse element labelled iPCB is developed based on the inverse finite element method (iFEM) for real-time shape estimation of plane-curved structures (such as arch bridges) utilizing onboard strain data. This inverse problem, named shape sensing, is vital for the design of smart structures and structural health monitoring (SHM) procedures. The iPCB formulation is defined based on a least-squares variational principle that employs curved Timoshenko beam theory as its baseline. The accurate strain-displacement relationship considering tension-bending coupling is used to establish theoretical and measured section strains. The displacement fields of the isoparametric element iPCB are interpolated utilizing nonuniform rational B-spline (NURBS) basis functions, enabling exact geometric modelling even with a very coarse mesh density. The present formulation is completely free from membrane and shear locking. Numerical validation examples for different curved structures subjected to different loading conditions have been performed and have demonstrated the excellent prediction capability of iPCBs. The present formulation has also been shown to be practical and robust since relatively accurate predictions can be obtained even omitting the shear deformation contributions and considering polluted strain measures. The current element offers a promising tool for real-time shape estimation of plane-curved structures.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.6
• /
• pp.511-521
• /
• 2010

This paper presents a simplified analysis method of determining the initial shape of suspension bridges, including the horizontal tension force of the main cable and the locations of each hanging point, considering the force equilibrium condition of each hanging point. This method is effective because it requires less effort than the methods used in other studies, for which complicated non-linear analysis was used, to comparatively determine the exact initial shape. The accuracy and validity of the present method are demonstrated by comparing the results of this study with those of previous researchers' numerical examples, including 2D and 3D models.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.723-726
• /
• 2002

In the recent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. The dynamic characteristic analysis of SMA is necessary for actuator application and many common researches report the material characteristics of SMA sufficiently. However, the research of dynamic characteristics is very deficient. In this paper, the helical spring is fabricated with NiTi SMA wire of high resistivity The farce, response speed, temperature, and displacement are measured by digital force gauge, infrared thermometer, and laser displacement sensor so that the dynamic characteristics of this SMA actuator is analyzed.