• Smart Structures and Systems
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• v.21 no.3
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• pp.349-358
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• 2018

This paper investigates the free vibration analysis of double-beam system coupled by a two-degree-of-freedom mass-spring system. In order to generalize the model, the main beams are assumed to be elastically restrained against translation and rotation at one end and free at the other. Furthermore, the mass-spring system is elastically connected to the beams at adjustable positions by means of four translational and rotational springs. The governing differential equations of the beams and the mass-spring system are derived and analytically solved by using the Fourier transform method. Moreover, as a second way, a finite element solution is derived. The frequency parameters and mode shapes of some diverse cases are obtained using both methods. Comparison of obtained results by two methods shows the accuracy of both solutions. The influence of system parameters on the free vibration response of the studied mechanical system is examined.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.319-322
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• 2003

For the analysis of leveling process by the 3-dimensional elastic-plastic finite element method, a finite element analysis program modeling large deformation of shell has been developed. This program fur analyzing large deformation of sheet during leveling includes spring-back analysis as well as efficient contact treatment between sheet and rolls of leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. Besides the leveling examples, problems within the category of large strain and rotation, such as 3-dimensional roll-up and gutter occurrence at continuous bending-unbending process are also tested for verification of the program. The residual curvatures of strip predicted by finite element analysis are within 20% error range of the experiment. The formation and direction of anticlastic curvature or gutter during bending-unbending under tension is predicted and this agrees with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.199-207
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• 2003

The Timoshenko beam model has been known as the most accurate model for representing beam structures. However, the Timoshenko beam model may give rise to a significant error when it is applied to multi-stepped beam structures. This paper is intended to demonstrate the modeling error of Timoshenko beam based finite element model for multi-stepped beam structures and to suggest a new modeling method to improve the accuracy. A tentative bending spring is introduced into the stepped section to represent the softening effect due to the presence of step. This paper also proposes a finite element modeling method in the light with the tentative bending spring model for the step softening effect. The proposed method rigorously adapts computation results from a commercial finite element code. The validity of the proposed method is demonstrated through a series of simulation and experiment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.77-83
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• 2013

This paper presents the feasibility on the application of composite coil spring, which has great interest in the automobile industry. In order to obtain much lighter weight of the composite spring, it will be necessary to optimize the design variables such as fiber angles and diameter of coil, etc. First of all, mechanical properties were measured to consider the effects of FVR and ply angles for carbon fiber composite material. And the shear modulus with respect to ply angles were derived based on twisting angles calculated by torsional beam model. Next we determined the design parameters of composite coil spring, which has equivalent spring rate to the steel coil spring. In order to assess the proposed method, finite element model of the composite spring was developed and analysed to obtain the spring constant. The results showed that static spring rate of the composite spring was in a good agreement with that of steel spring.

• International Journal of Railway
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• v.1 no.3
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• pp.122-127
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• 2008

Rubber components are widely used in many application such as vibration isolators, damping, ride quality. Rubber spring is used in primary suspension system for railway vehicle. Characteristics and useful life prediction of rubber spring was very important in design procedure to assure the safety and reliability. Non-linear properties of rubber material which are described as strain energy function are important parameter to design and evaluate of rubber spring. These are determined by physical tests which are uniaxial tension, equi-biaxial tension and pure shear test. The computer simulation was executed to predict and evaluate the load capacity and stiffness for rubber spring. In order to investigate the useful life, the acceleration test were carried out. Acceleration test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the acceleration test, several useful life prediction for rubber spring were proposed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.1
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• pp.9-15
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• 2003

This Paper deals with the design of Moving Magnet type Linear Oscillatory Actuator(MM-LOA) using spring damper based on the design procedure and the characteristic analysis. MM-LOA is applied to variable load such as vaccum pump and compressor, The structure of piston type is selected to reduce a noise. MM-LOA has over-displacement in starting state because of the low inertia of mover To improve the starting characteristic, spring damper is used. The optimum spring constant of spring damper is detected and in consideration of spring damper, MM-LOA redesigned. The parameter is calculated by Finite Element Method(FEM). For the dynamic characteristic analysis, time differential method composed of voltage and kinetic equation is used. The propriety of the improved model is verified through the experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.1-6
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• 1998

A leaf spring plays an important role in a passenger bus. Since characteristic of a leaf spring has a hysteresis behaviour, modeling technique for a leaf spring is an important issue for passenger bus analysis. In this paper, modeling technique for a leaf spring is presented. First, non-linear FEM model of a leaf spring is constructed then it is used to make an approximated model to be used in dynamic analysis. The modeling procedure is ex-plained in step by step approach. Then, this model is applied to dynamic analysis of a mini-bus with flexible body and non-linear dynamic force element. The results are compared with test data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.33-41
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• 2011

This study presents modeling technologies applicable to an unbonded post-tension system using a finite element software package. In this study, both direct modeling method and multiple spring method were used. The direct modeling method adopts tube-to-tube contact elements to represent the physical feature of a post-tension system. The multiple spring method uses virtual tendons attached to the real tendons using a number of rigid axial springs that freely rotate at the ends. Both modeling technologies provide accurate predictions. However, only the multiple spring method provides numerically stable and reliable responses with a consideration of concrete tension stiffening effects. Therefore, the multiple spring method turned out to be a generally applicable modeling technology for the unbonded post-tension system. Comparisons were made for the analytical and experimental results for the verification of the selected method, and parameter studies were carried out to confirm the appropriateness of the modeling assumptions and parameters adopted in the analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.59-66
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• 2017

In this paper, to protect the piping in nuclear power plants and various plant facilities, we have developed a damper using the friction method and carried out a study to analyze the performance. Friction typed damper means a device for attenuating vibration by generating a frictional force to the bearing and the shaft by applying a compressive force to the MER-Spring. In order to analyze the performance of the damper, the properties of MER-Spring and friction materials were analyzed, a study on the effects of friction was carried out, and the behavior of this equation was established. And, to determine whether deformation of the material and to examine the reliability of the behavior equation established, prototypes was produced and, through a performance test and finite element analysis of a damper made of specimens, they were analyzed. As a result, it is noted that the reliability of the material was confirmed, the coefficient of friction have to be adjusted according to the velocity, cyclic loading test and finite element analysis results show exhibits excellent results. In addition, a review of the dynamic loads in the future shall be performed for the usage in more broad fields.

• Steel and Composite Structures
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• v.25 no.1
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• pp.117-126
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• 2017

The component method is an analytical approach for investigating the moment-rotation relationship of steel connections. In this study, the component method was improved from two aspects: (i) load analysis of mechanical model; and (ii) combination of spring elements. An optimized component method with more reasonable component models, spring arrangement position, and boundary conditions was developed using finite element analysis. An experimental testing program in two major-axis and two minor-axis connections under symmetrically loading was carried out to verify this method. The initial rotational stiffness obtained from the optimized component method was consistent with the experimental results. It can be concluded that (i) The coupling stiffness between column and beam flanges significantly affects the effective height of the tensile-column web. (ii) The mechanical properties of the bending components were obtained using an equivalent t-stub model considering the bending capacity of bolts. (iii) Using the optimized mechanical components, the initial rotational stiffness was accurately calculated using the spring system. (iv) The characteristics of moment-rotation relationship for beam to column connections were effectively expressed by the SPRING element analysis model using ABAQUS. The calculations are simpler, and the results are accurate.