• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.538-541
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• 2004

In turbomachinery rotor, there are small differences in the structural and/or geometrical properties of individual blades, which are referred to as blade mistuning. Mistuning effects of the forced response of bladed disks can be extremely large as often reported in many studies. In this paper, the pattern optimization of intentional mistuning for bladed disks considering with damping and coupling effect is the focus of the present investigation. More specifically, the class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say) and Genetic Algorithm is used to optimize the arrangement of these blades around the disk to reduce the forced response of blade with different damping and coupling stiffness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.141-142
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• 2010

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1049-1052
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• 2008

내력벽시스템에 사용되는 연결보는 횡변위 조절을 위하여 효과적으로 사용되는 요소이나, 단면의 폭과 춤이 시스템에 의하여 제한되므로 연성능력을 향상시키기 위한 철근의 상세처리가 어럽다. 이러한 이유로 지진에 의하여 횡력이 발생할 경우 가장 먼저 연결보에 손상이 발생하게 될 것이므로, 본 연구에서는 연결보가 있는 내력벽 시스템의 성능을 평가하고자 하였다. 이러한 성능평가는 FEMA 400의 수정된 등가 선형의 절차에 의하여 수행되었다. 평가를 위한 모델은 15층이고 연결보의 강성은 변동이 없으며 질량을 변화하여 구조물의 주기를 변화하였다. 요구 스펙트럼 산정은 KBC 2005의 계수를 곱하지 않은 스펙트럼을 사용하였다. 성능 평가 결과로서, 토질 SD에 대하여 대부분의 모델에서 인명안전 수준에서 검토된 연결보의 제한 변위가 성능점 보다 작게 나타났다. 전반적으로 시스템의 주기가 짧아질수록 연결보의 손상도에 의하여 성능점이 감소되는 현상을 나타내었다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.160-167
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• 2004

A two degree-of-freedom mathematical model is presented to investigate the friction mechanism of a disc brake system. A contact parameter is introduced to describe the coupling between the in-plane and the out-of-plane motions. The model with the contact parameter is considered under the assumption that the out-of-plane motion depends on the friction force along the in-plane motion. In order to describe the relationship between the friction force and the out-of plane motion, the dynamic friction coefficient is considered as a function of both relative velocity and normal farce. Using this friction law, a contact stiffness matrix along the normal direction can be obtained. The out-of-plane motion is then investigated by both the stability analysis and the numerical analysis for various parametric conditions. The results show that the stiffness parameters of the pad and the disc must be controlled at the same time. Also, the numerical analysis shows the existence of limit cycle caused by the effect of intermittent contact stiffness.

• Steel and Composite Structures
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• 제31권6호
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• pp.591-600
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• 2019

Based on the energy-variational principle, a coupling vibration analysis model of high-speed railway simply supported beam bridge-track structure system (HSRBTS) was established by considering the effect of shear deformation. The vibration differential equation and natural boundary conditions of HSRBTS were derived by considering the interlayer slip effect. Then, an analytic calculation method for the natural vibration frequency of this system was obtained. By taking two simply supported beam bridges of high-speed railway of 24 m and 32 m in span as examples, ANSYS and MIDAS finite-element numerical calculation methods were compared with the analytic method established in this paper. The calculation results show that two of them agree well with each other, validating the analytic method reported in this paper. The analytic method established in this study was used to evaluate the natural vibration characteristics of HSRBTS under different interlayer stiffness and length of rails at different subgrade sections. The results show that the vertical interlayer compressive stiffness had a great influence on the high-order natural vibration frequency of HSRBTS, and the effect of longitudinal interlayer slip stiffness on the natural vibration frequency of HSRBTS could be ignored. Under different vertical interlayer stiffness conditions, the subgrade section of HSRBTS has a critical rail length, and the critical length of rail at subgrade section decreases with the increase in vertical interlayer compressive stiffness.

• 제어로봇시스템학회논문지
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• 제7권1호
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• pp.1171-1177
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• 2001

This paper provides a guideline for specifying the operational compliance characteristics considering the location of compliance center and the grasp points in assembly tasks using robot hands. Through various assembly tasks, we analyze the conditions of the achievable operational stiffness matrix with respect to the location of compliance center and the grasp points. Also, we show that some of coupling stiffness elements in the operational space cannot be planned arbitrarily. As a result it is concluded that the location of compliance center on the grasped object and the grasp points play important roles for successful assembly tasks and also the operational stiffness matrix should be carefully specified by considering those conditions.

• 한국정밀공학회지
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• 제26권5호
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• pp.128-134
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• 2009

This paper aims to design a variable-stiffness type economical safety joint for service robots. The safety joint was designed to have a passive shock absorbing mechanism for protecting human from a catastrophic collision under service condition of robots. A simple mechanism composed of two action disks for switching the load transfer, a spring and a screw for pre-load was proposed. In order to evaluate the performance of the safety joint a testing platform which can carry out the static and impact tests was also designed and fabricated. From the test results, the designed safety joint was proved to have a variable load-carrying capacity and about 42% impact absorption capacity with simple manipulation of the control screw.

• 소음진동
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• 제10권4호
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• pp.648-654
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• 2000

A procedure to determine the realizable optimal positions of rigid supports is suggested to get a maximum fundamental natural frequency. a measured frequency response function based substructure-coupling technique is used to model the supported structure. The optimization procedure carries out the eigenvalue sensitivity analysis with respect to the stiffness of supports. As a result of such stiffness optimization, the optimal rigid-support positions are shown to be determined by choosing the position of the largest stiffness. The optimally determined support conditions are verified to satisfy the eigenvalue limit theorem. To demonstrate the effectiveness of the proposed method, the optimal support positions of a plate model are investigated. Experimental results indicate that the proposed method can effectively find out the optimal support conditions of the structure just based on the measured frequency response functions without any use of numerical model of the structure.

• Structural Engineering and Mechanics
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• 제57권3호
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• pp.389-402
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• 2016

Based on the traditional mechanical model of thin-walled straight beam, the paper makes analysis and research on the pre-twisted thin-walled beam finite element numerical model. Firstly, based on the geometric deformation differential relationship, the Saint-Venant warping strain of pre-twisted thin-walled beam is deduced. According to the traditional thin-walled straight beam finite element mechanical model, the finite element stiffness matrix considering the Saint-Venant warping deformations is established. At the same time, the paper establishes the element stiffness matrix of the pre-twisted thin-walled beam based on the classic Vlasov Theory. Finally, by calculating the pre-twisted beam with elliptical section and I cross section and contrasting three-dimensional solid finite element using ANSYS, the comparison analysis results show that pre-twisted thin-walled beam element stiffness matrix has good accuracy.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.78-78
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• 2000

This paper provides a guideline for specifying the operational compliance characteristics considering the location of compliance center and the grasp points in assembly tasks using robot hands, To be specific, some of coupling stiffness elements cannot be planned arbitrary. Through T-type assembly task, we analyze the conditions of the achievable operational stiffness matrix with respect to the location of compliance center and the grasp points. It is concluded that the location of compliance center on the grasped object and the grasp points play important roles for successful assembly tasks and also the operational stiffness matrix should be carefully specified by considering those conditions.