• 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.

• International Journal of Reliability and Applications
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• 제8권2호
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• pp.153-173
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• 2007

Wood-plastic composites (WPC) are gaining market share in the building industry because of durability/maintenance advantages of WPC over traditional wood products and because of the removal of chromated copper arsenate (CCA) pressure-treated wood from the market. In order to ensure continued market share growth, WPC manufacturers need greater focus on reliability, quality, and cost. The reliability methods outlined in this paper can be used to improve the quality of WPC and lower manufacturing costs by reducing raw material inputs and minimizing WPC waste. Statistical methods are described for analyzing stiffness (tangent modulus of elasticity: MOE) and flexural strength (modulus of rupture: MOR) test results on sampled WPC panels. Descriptive statistics, graphs, and reliability plots from these test data are presented and interpreted. Sources of variability in the MOE and MOR of WPC are suggested. The methods outlined may directly benefit WPC manufacturers through a better understanding of strength and stiffness measures, which can lead to process improvements and, ultimately, a superior WPC product with improved reliability, thereby creating greater customer satisfaction.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.12-19
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• 2006

It is positively necessary to study on the stiffness of a 13degree-type impact tester in order to improve the fracture prediction of impact testing in wheels using FE(finite-element) analysis. The 13degree-type impact tester consists of an impact striker, a wheel fixer, a steel plate, and four cylindrical rubbers. Important parts of the tester are the steel plate and four cylindrical rubbers which play a role of absorbing impact energy during impact testing. Because of these buffers, the RF(reaction force) variation of the lower part in the 13degree-type impact tester showed the tendency like a damped harmony oscillation during impact testing. In order to investigate the stiffness of a 13degree-type impact tester, this work measured each stiffness of a steel plate and cylindrical rubbers. The stiffness of a cylindrical rubber was measured using a compressive tester. On the other hand, the stiffness of a steel plate was predicted by simulating experimental method using FE analysis.

• Smart Structures and Systems
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• 제21권5호
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• pp.653-668
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• 2018

This work proposes and investigates re-centering negative stiffness dampers (NSDs) for vibration suppression in high-speed trains. The merit of the negative stiffness feature is demonstrated by active controllers on a high-speed train. This merit inspires the replacement of active controllers with re-centering NSDs, which are more reliable and robust than active controllers. The proposed damper design consists of a passive magnetic negative stiffness spring and a semi-active positioning shaft for re-centering function. The former produces negative stiffness control forces, and the latter prevents the amplification of quasi-static spring deflection. Numerical investigations verify that the proposed re-centering NSD can improve ride comfort significantly without amplifying spring deflection.

• 한국안전학회지
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• 제33권4호
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• pp.46-53
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• 2018

This study examined the maximum resistant moment and nonlinear rotational stiffness of wedge joint between the vertical and horizontal members of system supports. To examine the maximum resistant moment and propose the nonlinear rotation stiffness of wedge joint, 6 specimens were tested and additional 3 specimens, where the horizontal member was welded to the vertical member, were tested to compare the moment capacity of wedge joints. The average maximum moment in the tested wedge joint was 1.183 kNm which represented about 70 % of the maximum moment developed in the welded specimens. And, as simulating nonlinear rotational stiffness of the wedge joint, a tri-linear model was suggested. The rotational stiffness was estimated as 23.095 kNm/rad in first stage, 7.945 kNm/rad in second stage, and 3.073 kNm/rad in third stage. For the failure mode, the specimen with the wedge joint showed the failure of joint between vertical and horizontal members. However, the specimen with welded joint represented the yielding of horizontal members.

• 제어로봇시스템학회논문지
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• 제13권9호
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• pp.910-914
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• 2007

In this paper, an experimental study is performed to adjust position of compliance center of Elastomer Shear Pad Remote Center Compliance (ESP RCC) device, which is used on precise peg in hole process. In the study, variation of the lateral/axial stiffness of the ESP is proposed as a control parameter to adjust the position of compliance center of the ESP RCC. The variation of the stiffness of the ESP is achieved by controlling the shear stress of the ESP. To control the shear stress of the ESP, position of top side of the ESP is changed while remaining bottom side of the ESP is fixed on the RCC plate. To evaluate effect of the proposed idea, stiffness variations of the ESP on various shear stresses are measured, and variation of the compliance center is measured with the ESP RCC that can control the position of compliance center by using the shear stress. The measured data shows unique characteristics that have not been shown in other types of ESP VRCCs.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.94-99
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• 2004

The global stiffnesses and vibration characteristics of vehicle structures are mainly influenced by local stiffnesses of the joint structures consisted of complicated thin-walled panels. In this paper, the parametric study for the stiffnesses of the center pillar-roof rail joint of vehicle structure is performed through the linear static analysis. The analysis result shows that the reinforcement panel much affects the joint stiffness of out-plane direction (i.e., z-direction). And also, the flange radius and width of the joint structure much affect the Joint stiffness of out-plane direction. The study shows that vehicle joint stiffnesses can be effectively determined in designing vehicle structure through the parametric study.

• 대한기계학회논문집A
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• 제24권1호
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• pp.110-117
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• 2000

Vibration modes obtained from a modal analysis can be better explained from a screw theoretical standpoint. A vibration mode can be geometrically interpreted as a pure rotation about the vibration center in a plane and as the twisting motion on a screw in a three dimensional space. This paper, presents the method to diagonalize a spatial stiffness matrix by use of a parallel axis congruence transformation. It also describes that the stiffness matrix diagonalized by a congruence transformation, can have the planes of symmetry depending on the location of the center of elasticity. For a plane of symmetry, any vibration mode can be expressed by the axis of vibration. Analytical solutions for the axis of vibration has been derived.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1608-1614
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• 2002

This Paper presents a novel piston friction force measurement system that has characteristics of relieving the Pressure force acting on the upper surface of the liner; the system uses general rubber O-rings for combustion chamber sealing, and does not need special changes to the piston top land. The lower supporter of the floating liner increases stiffness in liner axial direction, and results in the increase of natural frequency. The upper supporter has multi-layer structure designed fer low axial stiffness and high radial stiffness. With the use of the present system, the effects of variation in clearance and piston ring tension were studied.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.231-240
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• 2014

In the present research, fatigue behavior of chopped strand mat/epoxy composites has been studied with two different techniques. First, the normalized stiffness degradation approach as a well-known model for unidirectional and laminated composites was utilized to predict the fatigue behavior of chopped strand mat/epoxy composites. Then, the capability of the fatigue damage accumulation model for chopped strand mat/epoxy composites was investigated. A series of tests has been performed at different stress levels to evaluate both models with the obtained results. The results of evaluation indicate a better correlation of the normalized stiffness degradation technique with experimental results in comparison with the fatigue damage accumulation model.