• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.504-509
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• 2003

In this paper, a multi-step optimization using a G.A.(Genetic Algorithm) with variable penalty function is introduced to the structural design optimization of a high speed machining center. The design problem, in this case, is to find out the best cross-section shapes and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously. The first step is the cross-section shape optimization, in which only the section members are selected to survive whose cross-section area have above a critical value. The second step is a static design optimization, in which the static compliance and the weight of the machine structure are minimized under some dimensional constraints and deflection limits. The third step is a dynamic design optimization, where the dynamic compliance and the structure weight are minimized under the same constraints as those of the second step. The proposed design optimization method was successful applied to the machining center structural design optimization. As a result, static and dynamic compliances were reduced to 16% and 53% respectively from the initial design, while the weight of the structure are also reduced slightly.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.63-66
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• 2001

Recently, as the demand for high efficiency, multi function machine tools is increasing, domestic machine tool industries are investing in research and development for precision machine tools with high speed. This trend is closely correlated with the design technique which is necessary to make new type machine tool compatible with new production system. To achieve high precision, high speed machine tools with reduced chatter, it is needed to develop dynamically rigid structure. In this paper, dynamic optimization of machine structure is presented. At this procedure of dynamic design, dynamic compliance is minimized using Simple Genetic Algorithm(SGA)

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.108-113
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• 2002

This paper presents a multi-step structural design optimization method fur machine tool structures using a genetic algorithm with dynamic penalty. The first step is a sectional topology optimization, which is to determine the best sectional construction that minimize the structural weight and the compliance responses subjected to some constraints. The second step is a static design optimization, in which the weight and the static compliance response are minimized under some dimensional and safety constraints. The third step is a dynamic design optimization, where the weight static compliance, and dynamic compliance of the structure are minimized under the same constraints. The proposed design method was examined on the 10-bar truss problem of topology and sizing optimization. And the results showed that our solution is better than or just about the same as the best one of the previous researches. Furthermore, we applied this method to the topology and sizing optimization of a crossbeam slider for a high-speed machining center. The topology optimization result gives the best desirable cross-section shape whose weight was reduced by 38.8% than the original configuration. The subsequent static and dynamic design optimization reduced the weight, static and dynamic compliances by 5.7 %, 2.1% and 19.1% respectively from the topology-optimized model. The examples demonstrated the feasibility of the suggested design optimization method.

• 한국지반공학회논문집
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• 제19권4호
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• pp.191-200
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• 2003

본 연구는 말뚝 부마찰력 저감용으로 사용하는 역청재료의 유변학적 특성을 분석한 결과이다. 역청재료는 효과적으로 부마찰력을 저감시키고 경제적인 장점으로 인하여 말뚝의 부마찰력 저감 공법으로 사용하여 왔다. 본 연구에서는 세 종류의 말뚝용 역청재료를 선택하여 비교 시험을 실시하였다. 물리적 특성시험으로는 침입도 시험, 연화점 시험 및 침입도 지수를 실시하였으며 유변학적 시험으로는 동적전단 유동기를 사용하여 위상각, 복합계수, 크리프시험 및 흐름시험을 시험온도 15, 30, 45 및 6$0^{\circ}C$에서 수행하였다. 시험 결과는 역청재료의 유변학적 특성을 나타내는 위상각, G$^*$/sin $\delta$, 크리프 컴플라이언스 및 전단점도로 분석하여 상호 비교하였다. 시험 결과 온도와 위상각은 비례관계를 나타냈으며 G$^*$/sin $\delta$는 반비례 관계를 보였다. 또한, 크리프 컴플라이언스는 하중시간이 증가함에 따라 증가하여 역청재료가 시간의 변화에 따라 점성유체로 작용하는 것으로 나타났다. 크리프시험으로 인한 시간 및 온도의 변화는 크리프 컴플라이언스 값을 크게 변화 시켰으나 전단점도의 변화는 그다지 심하게 나타나지 않아서 말뚝 역청재료의 평가에는 크리프 컴플라이언스를 측정 할 수 있는 크리프시험이 적절한 것으로 평가되었다. 본 연구에서 유변학적 시험을 실시한 결과 물리적 시험으로부터 분석할 수 없는 온도와 시간의 변화에 따른 역청재료의 특성변화를 상세하게 분석할 수 있었는데 이러한 시험 결과는 말뚝용 역청재료의 선정에 큰 영향을 미칠 것으로 판단된다.

• 대한기계학회논문집
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• 제19권3호
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• pp.688-696
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• 1995

Cemented carbides, best known for their superior mechanical properties such as high strength, high hardness and high wear resistance, have a wide range of industrial applications including metal working tools, mining tools, and wear resistance components. The cobalt has been used as a binder in the WC-based hard composites due to its outstanding wetting and adhesion characteristics even though its expensiveness. Therefore many studies attempted to find a better substitute for cobalt as binder to decrease production costs. This investigation is a pre-step to study dynamic fracture characteristic evaluation of a WC-Co hardmetal were evaluated by using the instrumented Charpy impact testing procedures. It was found that the dynamic characteristics of used strain amplifier were very important experimental factors to extract valid dynamic fracturing data in WC-Co specimens. It was suggested by showing some experimental examples that when we wished to evaluate dynamic fracture toughness for cemented carbide composites by using the instrumented Charpy impact testing procedure, a careful attention must be given to obtain valid results.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.162-169
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• 2009

This paper describes a study on dynamic characteristics analysis and dynamic compliance evaluation of a 5-axis multi-tasking machine tool of ram-head type. Structural dynamics analysis and evaluation are necessary to machine tool design and development to secure good machine tool performance against tough and harsh machining conditions. In this study, natural frequencies and corresponding vibration modes of the machine tool structure were analyzed by using both F.E.M. modal analysis and impulse hammer test. Furthermore, dynamic compliance of the machine tool was analyzed by using F.E.M. and also measured by using a hydraulic exciter test. Both the theoretical analysis and experimental test results showed good agreement with each other.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.81-85
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• 2005

In this paper, the structural design optimization of a wafer grinding machine using a multi-step optimization with genetic algorithm is presented. The design problem, in this study, is to find out the optimum configuration and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously under several design constraints. The first design step is shape optimization, in which the best structural configuration is found by getting rid of structural members that have no contributions to the design objectives from the given initial design configuration. The second and third steps are sizing optimization. The second design step gives a set of good design solutions having higher fitness for lightweight and minimum static compliance. Finally the best solution, which has minimum dynamic compliance and weight, is extracted among those good solution set. The proposed design optimization method was successfully applied to the structural design optimization of a high precision wafer grinding machine. After optimization, both static and dynamic compliances are reduced more than $92\%\;and\;93\%$ compared with the initial design, which was designed empirically by experienced engineers. Moreover the weight of the optimized structure are also slightly reduced than before.

• 한국생산제조학회지
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• 제7권1호
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• pp.89-94
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• 1998

With increasing demands on automatic and high-capability manufacturing, the dynamic performance of machine tools becomes more and more important. In this paper, the correlation between dynamic compliance of the cutting system and the commencing point of chatter vibration in turning is checked by impulse excitation method and cutting tests for some cutting system. The correlation between chucking conditions of workpiece and the commencing point of chatter vibration is clarified, and it is proven that there is a mutual relations between them. Chatter vibration commenced at certain level of dynamic compliance of the cutting system regardless of the kind of the system. It shows the possibility of dynamic performance test of a lathe by means of impulse excitation method.

• 한국소음진동공학회논문집
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• 제20권8호
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• pp.727-733
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• 2010

Optical tables provide a platform for the establishment and test of measurement systems which use Laser. Therefore, not only static characteristics such as surface flatness, static stiffness and etc. but dynamic response characteristics is very important design parameter. The dynamic stiffness is generally estimated through the modal test, and compliance is used as a representative performance standard. Recently there is an example of defining the dynamic deflection coefficient and using it as a new performance standard of the dynamic stiffness, but it is not generalized yet in industry. In this study, we verify the validity of existing DDC calculus by making an experiment on granite. And for improvement in damping performance of optical tables, we are going to evaluate the effect of fillers on the compliance, then develop an epoxy adhesive based on the result of this experiment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1561-1564
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• 2003

In the dynamic analysis model of full vehicles, the ball joint is usually modeled as an ideal joint. Searching a ball joint, the engineering plastic covers metal and the plastic has little compliance. It is expected that the compliance will physically have an influence on load transfer. This thesis presents a dynamic model considering the compliance of a ball joint, and studies an influence related to load transfer. It models the compliance of a ball joint to 3 directional spring. Likewise, it researches the load of a ball joint via a four-post simulation of a full vehicle, comparing with a model considered compliant and the model of an ideal joint. As a result, the difference between the compliance and the ideal joint model was determined. For this reasons, to conduct precision load prediction for durability analysis, dynamic analysis considering the compliance of bali joint should be required.