• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.179-185
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• 2008

The purpose of this paper is to propose a systematic method on the weld pitch design of a vehicle sub-frame considering the fatigue life of spot welding points. The input data, which perform the fatigue analysis on the spot welding nuggets, are obtained by both the dynamic analysis of the multi-body vehicle model passing through the virtual proving ground of a typical Belgian road and the quasi-static analysis with the finite element model of the vehicle sub-frame. By utilizing the life cycle data obtained from the fatigue analysis, the welding points to perform the pitch change are determined. The sensitivity analysis on the fatigue life of the welding points is carried out by using the three-level orthogonal array design, and through the results of the sensitivity analysis, the best combination on the welding pitch is determined. This study shows that as compared with the baseline design, the sub-frame redesigned by the proposed technique improves the fatigue life about 7 percent while reducing the number of welding points about 19 percent.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1243-1248
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• 2010

Fatigue design and evaluation of welded joints are typically carried out by weld classification approach in which a family (theoretically infinite) of parallel nominal stress based S-N curves are used according to joint types and loading modes as well as extrapolation-based hot spot stress. Traditional finite element methods are not capable of consistently capturing the stress concentration effects on fatigue behavior due to their mesh-sensitivity in stress determination at welds resulted from notch stress singularity. The extrapolated hot spot stresses tend vary, depending on the element sizes, types, joint types, and loading mode. however, the equilibrium-equivalent structural stress method(E2S2) has been recently developed through several joint industry projects as a robust method to analyze welded components using finite element analysis. This method has been proven effective in correlating a large amount of published fatigue test results in the literature such as master S-N curve and has used for evaluating the fatigue life of welding components. In this study, fatigue analysis of the welding bogie frame is examined using E2S2 method with master S-N curve.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.05a
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• pp.7-16
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• 1996

Rapid increase of refrigeration & air-conditioning system( r & a system ) in modern industries brings attention to the urgency of development as a core technology in the area. And it required to the compatibility problem of r & a system to alternative refrigerant for the protection of environment. Then, it is requested to research about the lubrication characteristics of refrigerant compressor which is the core thechnology in the r & a system. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressor. Therefore, theoetical investigation of the lubrication characteristics of rotary compressor for r & a system is studied. And the Runge-Kutta method is used for the analysis of the behavior of rolling piston in the rotary compressor. The results show that the rotating speed of shaft and the discharge pressure have an important effect upon the angular velocity of the rolling piston. This results give important basic data for the further lubrication analysis and design of the rotary compressor.

• Tribology and Lubricants
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• v.27 no.1
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• pp.7-12
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• 2011

Interest in advanced machining process such as AJM(abrasive jet machining) and CMP(chemical-mechanical polishing) using micro/nano-sized abrasives has been on the increasing demand due to wide use of super alloys, composites, semiconductor and ceramics, which are difficult to or cannot be processed by traditional machining methods. In this paper, the effects of pressure, wafer moving velocity and fluid viscosity were investigated by 2-dimensional finite element analysis method considering slurry fluid flow. From the investigation, it could be found that the simulation results quite corresponded well to the Preston's equation that describes pressure/velocity dependency on material removal. The result also revealed that the stress and corresponding material removal induced by the collision of particle may decrease under relatively high wafer moving speed due to the slurry flow resistance. In addition, the increase in slurry fluid viscosity causes the reduction of material removal rate. It should be noted that the viscosity effect can vary with the shape of abrasive particle.

• Korean Journal of Logic
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• v.23 no.2
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• pp.117-159
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• 2020

In the early Wittgenstein's Tractatus, both philosophy of logic and that of mathematics belong to the most crucial subjects of it. What is the philosophical view of the early Wittgenstein in the Tractatus? Did he, for example, accept Frege and Russell's logicism or reject it? How did he stipulate the relation between logic and mathematics? How should we, for example, interpretate "Mathematics is a method of logic."(6.234) and "The Logic of the world which the proposition of logic show in the tautologies, mathematics shows in equations."(6.22)? Furthermore, How did he grasp the relation between mathematical equations and tautologies? In this paper, I will endeavor to answer these questions.

• Korean Journal of Computational Design and Engineering
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• v.12 no.4
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• pp.308-320
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• 2007

A multi-agent and web based engineering framework concerning the automation of fatigue durability analysis for welded bogie frame of railway vehicles is presented. Mostly, this kind of design or analysis includes complex workflow, huge amounts of information processing, and problem solving. Macro programs of I-DEAS, APDL of ANSYS, and in-house fatigue code are utilized for parametric geometry representation, automatic mesh generation, static stress analysis, fatigue durability analysis, post-processing, and data sorting. The engineering framework is implemented on the JADE. Since every task requires a fairly complex process and specialized knowledge, the multi-agent based framework is very useful to keep the independency among several disciplines or tasks and to use distributed hardware and software resources. All engineering programs are integrated by XML wrapper. Related database of the engineering framework and web based user interfaces are also developed. A parametric study is carried out to take into account the effect of geometrical change of transom support bracket on its cumulative fatigue damage. The developed engineering framework reduced remarkably the time and costs required in designing and solving engineering problems.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.618-623
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• 2001

In a practical vibration isolation system, vibration is transmitted from the source to the receiver through several paths such as more than one inter-connected point and multi-degree of freedom at each connection point. Therefore, the major path investigation for vibration transmission among them is often required in a point of view of isolation. For the path analysis of multi-dimensional vibration isolation system, it is useful to employ the concept of vibration power in high frequency range where radiation of noise from the receiver structure is concerned. The idea is simple to understand and formulate but rather complicated to apply in practice. For an accurate estimation of power flow especially over a high frequency range, it is well known in theory that rotational motions should be taken into consideration together with translational motions at inter-connected points. In reality, however, power transmissions related to rotational terms are often neglected mainly due to difficulties in the instrumentation. In this paper, necessary formula and measurable mechanical quantities for vibration power analysis will be reviewed and experimental results with rotational terms included for compressor system in a commercial air conditioner will be shown.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.98-108
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• 1998

Hull design data is currently prepared by a 2D CAD system and re-input to 3D CAD systems specialized for detail design or to a structural analysis system. In this paper, sharing design data among different CAD systems has been studied. Based on STEP methodology, a neutral model is generated from 2D AutoCAD drawings. To handle a geometric data of this model, the non-manifold model of ACIS is used because it can support various CAD data representation such as 2D graphic entities, 3D wireframe, 3D surface model, and solid B-Rep/CSG model. It is observed that a mon-manifold model can easily be transformed to a 3-D wireframe model for the hull detail design system AutoDef or a FE model for the structural analysis system Nastran.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.2
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• pp.189-196
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• 2014

Automated design program using commercial process integration and optimization program was developed for conceptual design of fighter-class aircraft. Wind tunnel test data and performance analysis results were compared for the verification of analysis tool of this program, and the usefulness of the tool was found. After integration with radar cross section analysis tool, the correlation with configuration design variables of wing, tail and performance parameters was identified by design of experiment, and the optimized configuration for weight and RCS was derived from optimization of empty weight and average frontal RCS value. After parameter definition of fuselage, the program can be implemented for full aircraft configuration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.194-200
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• 2000

Researches on the FRF-based substructuring method have been mainly focused on vibratory response analysis. Present study is concerned about the application of the method to the dynamic stress analysis of a compressor mounting bracket in a passenger car. This is performed by using reaction forces that can be obtained by the FRF-based substructuring method. The air-conditioner system, composed of a compressor, a bracket and a test jig, is analyzed by using the FRF-based substructuring method. The experimental and numerical FRFs are combined to calculate the system responses and reaction forces at the connection point. The dynamic reaction forces plugged into the bracket FE model to compute the compute the stresses of the bracket. Dynamic stresses by the present method are compared with those from FE model. The comparison shows possibility of practical usage of the method for the real problem.