• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.158-166
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• 2002

A mathematical model and dynamic characteristics ova continuously variable damper for semi-active suspen- sion systems are investigated. After analyzing the geometry of a typical continuously variable damper, mathematical models fur individual components including piston, orifices, spring, and valves are first derived and then the flow equations for extension and compression strokes are investigated. To verify the developed mathematical model, the dynamic response of the model are simulated using MATLAB/SIMULINK and are compared with experimental results. The proposed model can be used not only for mechanical components design but also for control system design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1166-1172
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• 2006

This paper describes an alignment method of the ion column which is used for a focused-ion-beam machining system. The alignment parameters for mechanical and electrical components are introduced, and also sample images are used for evaluating the experiments. The experimental results show that geometrical positions of mechanical components have an influence on the quality of emitted ion beam. In addition, we can successfully align the traveling axis of ions by using mechanical and electrical methods.

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.8-14
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• 2000

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And tensile test, $k_{IC}$ test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.286-291
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• 2000

The finite element analyses of mechanical rubber components are executed to predict the behavior of deformation and stress distribution in destgn step. The non-linear properties of rubber which are described as strain energy functions are important parameters to design and evaluate rubber components. These are determined by material tests which are tension, compression and shear test. The behaviors of loads-displacements of rubber components such as a roll tubber spring and resilient ring and additional spring for railway suspension system are evaluated by using commercial FEA code. It is shown that the results by FEA simulations are in close agreement with the test results.

• International Journal of Aerospace System Engineering
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• v.5 no.2
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• pp.8-15
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• 2018

For small earth observation satellites, alignment between the optical components is important for precise observation. However, satellite cameras are structurally subject to misalignment in the launch environment where vibration excitations and impacts apply, and in space environments where zero gravity, vacuum, radiant heat and degassing occur. All of these variables can cause misalignment among the optical components. The misalignment among optical components results in degradation of image quality, and a re-alignment process is needed to compensate for the misalignment. This process of re-alignment between optical components is referred to as a refocusing process. In this paper, we proposed a 3 - axis focusing mechanism to perform the refocusing process. This mechanism is attached to the back of the secondary mirror and consists of three piezoelectric inertia-friction actuators to compensate the x-axis, y-axis tilt, and de-space through three-axis motion. The fabricated focus mechanism demonstrated excellent servo performance by experimenting with PD servo control.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.663-669
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• 2004

A nuclear power plant is composed of a number of primary components. Maintaining the integrity of these components is one of the most critical issues in nuclear industry. In order to maintain the integrity of these primary components, a complicated procedure is required including regular in-service inspection, failure assessment, fracture mechanics analysis, etc. Also, experts in different fields have to co-operate to resolve the integrity issues on the basis of inspection results. This integrity evaluation process usually takes long, and thus, is detrimental for the plant productivity. Therefore, an effective safety evaluation system is essential to manage the integrity issues on a nuclear power plant. In this paper, a web-based fatigue life evaluation system for primary components in nuclear power plant is proposed. This system provides engineering knowledge-based information and concurrent and collaborative working environment through internet, and thus, is expected to raise the efficiency of integrity evaluation procedures on primary components of a nuclear power plant.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• Journal of Biosystems Engineering
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• v.26 no.1
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• pp.11-20
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• 2001

Experiments under the stationary and harvesting condition, were performed in order to investigate the vibration characteristics of a head-feeding combine. 6 degrees of freedom components of acceleration at the location of the center of the gravity, and 3 degrees of freedom components of acceleration at the location of the operator seat were measured independently. The vibration characteristics of the combine were estimated with the power spectral density of the time series data of accelerations. From this research, the following results were obtained. 1. Vibration of a head-feeding combine under the stationary condition(engine, thresher and cutter are driven without harvesting) is mainly influenced by the engine. Further, 1/3, 1/2 (sub-harmonic) frequency components of the engine are observed besides engine driving frequency component(45Hz). 2. Vibration of a head-feeding combine under the harvesting condition is influenced by the engine, threshing unit and driving unit. Namely, some kinds of vibration frequency components in harvesting are observed compared with stationary condition. Further, sub-harmonic frequency components of the engine are observed besides engine driving frequency component as same as stationary condition. From these results, it may be concluded that vibration of a head-feeding combine is characteristics of semi-periodic and nonlinear vibration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1821-1828
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• 2010

Laser shock peening(LSP) is an innovative surface treatment technique, and it has been successfully used to improve the fatigue performance of metallic components. It is widely known, that cracks caused by metal fatigue occur only at the location where the metal is subject to tension, and not at the location where the metal is subjected to compression. Therefore, LSP can be employed to improve fatigue life because it generates a high-magnitude compressive residual stress on the surface and interior of metallic components. In this study, we analyzed the applicability of the LSP method in improving fatigue performance and evaluated the various parameters that influence the compressive residual stress. Further, we analyzed the change in the mechanical properties such as surface dynamic stress and the compressive residual stress on the surface and interior of metallic components.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1045-1050
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• 2010

Fatigue analysis and lifetime evaluation are very important in design procedure for assuring the safety and reliability of rubber components for mechanical systems. Till recently, the technology for the design, analysis, and evaluation of rubber products was required to manufacture rubber products with high quality, fidelity, and reliability. However, in the rubber-manufacturing companies in Korea, the processes of compound mixing, manufacturing of rubber products, and improvement of rubber properties are based on the trial-and-error method and experience. The objectives of this study are to establish methods for testing rubber materials, to develop a database of the properties of rubber materials, to evaluate the performance of rubber components, and to develop a system for predicting fatigue life. A method to predict fatigue-life of rubber components was proposed; in this method, the finite-element analysis and fatigue damage parameter as determined from a fatigue test are incorporated.