• Journal of Ship and Ocean Technology
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• 제8권3호
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• pp.50-60
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• 2004

In this paper, a continuum-based design sensitivity analysis (DSA) method is developed for the weakly coupled thermo-elasticity problems. The temperature and displacement fields are described in a common domain. Boundary value problems such as an equilibrium equation and a heat conduction equation in steady state are considered. The direct differentiation method of continuum-based DSA is employed to enhance the efficiency and accuracy of sensitivity computation. We derive design sensitivity expressions with respect to thermal conductivity in heat conduction problem and Young's modulus in equilibrium equation. The sensitivities are evaluated using the finite element method. The obtained analytical sensitivities are compared with the finite differencing to yield very accurate results. Extensive developments of this method are useful and applicable for the optimal design problems incorporating welding and thermal deformation problems.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.385-389
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• 2003

To make high speed spindle system work properly, sensors with outstanding resolution and dynamic characteristics are essential. An optical fiber displacement sensor is based on simple principles. Electrical signal responds to the optical flux change due to the displacement change between a target and a sensor probe. In this paper, the performance of optical fiber displacement sensor has been investigated according to properties of optical fiber Firstly, optical loss has been measured before and after polishing optical fiber endface. Secondly, allowance of optical fiber bending has been tested. thirdly sensitivity and linear range of the sensor has been found out according to the shape of cross section of optical fiber.

• 대한기계학회논문집A
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• 제26권1호
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• 한국공작기계학회논문집
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• 제13권5호
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• pp.55-61
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• 2004

Chatter monitoring is also important for realizing an unmanned machining system. while many researches were done on this area, it is still a difficult job to detect very small amplitude amount of chattering. A monitoring system using a capacitive spindle displacement sensor was developed to monitor cutting vibration in turning in this research. The variance of the measured spindle displacement signals using the developed sensor was calculated and utilized to quantify the small vibration in machining. The results were compared with variance obtained using a tool dynamometer. The result showed that the developed system could be utilized in monitoring the subtle changes of cutting vibrations with high sensitivity confidence.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.516-522
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• 2003

Monitoring chattering is also important for realizing an unmanned machining system While many researches were done on this area, it is still a difficult job to detect very small amplitude amount of chattering. A monitoring system using a capacitive spindle displacement sensor was developed to monitor cutting vibration in turning in this research. The variance of the measured spindle displacement signals using the developed sensor was calculated and utilized to quantity the small vibration in machining. The results were compared with variance obtained using a tool dynamometer. The result showed that the developed system could be utilized in monitoring the subtle changes of cutting vibrations with high sensitivity confidence.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.123-129
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• 2003

Drift design using resizing techniques can be a very practical method in drift design of high-rise buildings since it cannot require sensitivity analysis and structural re-analysis. Resizing techniques has used the cross sectional areas as design variable and supposed that displacement participation factors are inversely proportional to structural weights. Efficiency of resizing techniques based on displacement participation factors may depend on proper selection of sectional properties as design variables. In this study, two different drift design methods with the different sectional properties as design variables are presented and applied to a 20-story structure.

• 전산구조공학
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• 제7권1호
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• pp.91-98
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• 1994

선박, 자동차, 항공기등 수송체 구조해석에 유한요소법이 사용됨에 따라 초기 설계 후 대형 복합구조물의 해석이 ANSYS, NASTRA등의 범용 유한요소 코드에 의해 수행되고 있다. 설계변경을 시도할 때 설계자의 경험과 인지만으로 대형 구조물의 성능변경을 예측하기는 어렵다. 비록 대형 컴퓨터의 사용으로 구조 재해석이 용이하나 정량적 및 이론적 설계수정방향 없이는 인력과 계산시간 소모를 초래하고 때로는 시간 제약으로 충분한 재해석을 못할 수가 있다. 이때 긴요하게 사용될 수 있는 정보는 민감도로서 설계변수 변화에 대한 구조응답 변화를 수치적으로 나타내므로 설계변경에 도움을 줄 수 있다. 본 논문에서 계산된 정확한 민감도는 선체데크구조와 수송체구조물 프레임 강성도를 설계 변수로 하였으며 구조물 진동저감 설계에 사용될 수 있다. 즉 유한요소법에 의한 구조 재해석에 의하지 않고 민감도 값으로 구조 진동변위 증감을 예측할 수 있음이 예제로 보여지고 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.708-710
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• 2003

This paper presents design sensitivity analysis for the electromagnetic force and torque obtained from Coulomb's virtual work method using the adjoint variable method. And virtual displacement field is calculated from a static structural analysis. Derived equations are verified by comparison with finite different method. And topology optimization for a c-core is given as a verification example.

• Journal of Mechanical Science and Technology
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• 제14권2호
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• pp.197-206
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• 2000

A boundary integral equation method in the shape design sensitivity analysis is developed for the elasticity problems with axisymmetric non-homogeneous bodies. Functionals involving displacements and tractions at the zonal interface are considered. Sensitivity formula in terms of the interface shape variation is then derived by taking derivative of the boundary integral identity. Adjoint problem is defined such that displacement and traction discontinuity is imposed at the interface. Analytic example for a compound cylinder is taken to show the validity of the derived sensitivity formula. In the numerical implementation, solutions at the interface for the primal and adjoint system are used for the sensitivity. While the BEM is a natural tool for the solution, more generalization should be made since it should handle the jump conditions at the interface. Accuracy of the sensitivity is evaluated numerically by the same compound cylinder problem. The endosseous implant-bone interface problem is considered next as a practical application, in which the stress value is of great importance for successful osseointegration at the interface. As a preliminary step, a simple model with tapered cylinder is considered in this paper. Numerical accuracy is shown to be excellent which promises that the method can be used as an efficient and reliable tool in the optimization procedure for the implant design. Though only the axisymmetric problem is considered here, the method can be applied to general elasticity problems having interface.

• 대한전기학회논문지
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• 제38권11호
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• pp.941-949
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• 1989

This two-part paper presents a control method that allows for stable interaction of a robot manipulator with environment. In part 1, we focus on the input output relationships (unstructured modeling) of the robot and environment dynamics. This analysis leads to a general condition for stability of the robot and environment taken as a whole. This stability condition, for stable maneuver, prescribes a finite sensitivity for robot and environment where sensitivity of the robot (or the environment) is defined as a mapping forces into displacement. According to this stability condition, smaller sensitivity either in robot or in environment leads to narrower stability range. In the limit, when both systems have zero sensitivity, stability cannot be guaranteed. These models do not have any particular structure, yet they can model a wide variety of industrial and research robot manipulators and environment dynamic behavior. Although this approach of modeling may not lead to and design procedure, it will allow us to understand the fundamental issues in stability when a robot interacts with an environment.