• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.765-766
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• 2012

• Journal of the Korean Society for Precision Engineering
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• v.34 no.4
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• pp.243-246
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• 2017

In this study, flexible fixtures and end effectors are conceptually designed for the holding of thin-walled carbon-fiber reinforced-plastic (CFRP) workpieces in machining processes. Firstly, the fixture scenarios and system requirements for the conceptual designs of flexible-fixture and core units are proposed, including the propounding of the workpiece-holding mechanism and the core-unit requirements. A ball-joint pneumatic system is determined as a locking mechanism of the flexible-fixture system for the machining of thin-walled components. Secondly, conceptual designs of the core units are suggested with the driven requirements from the fixture scenarios. A self-tilting mechanism and an end-effector return mechanism are also proposed. Finally, the prototypes of the core units are manufactured, and the workpiece-holding capacity of each prototype is measured.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3109-3117
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• 1994

To operate a flexible mechanism in high speed its weight must be reduced as far as the structural strength does not decrease too much, but a light-weighted mechanism causes undesirable elastodynamic responses deteriorating the system performance. Besides, clearance within the connections of mechanisms causes rapid wear, increased noise and vibration. Even if the problems described above must be considered in the initial design stage, there has been no effective design process which takes account of the correlation between dynamic characteristics of flexible mechanism and the clearance effect at the joint. In this study, the generalized elastodynamic governing equations which include dynamic characteristics and boundary conditions of flexible mechanism are derived by variational calculus and solved by using FFM theory. To take the clearance effect at joint into account a new dynamic model is presented and also the method of modified stiffness/damping matrix is proposed to activate the dynamic clearance model, which cooperates with the developed governing equation very easily. As the results of this study, the proposed method(modified stiffness/damping matrix) to calculate clearance effect was proved to be superior to the existing one(force reaction method) in solution convergency and calculation performance. Besides this method can be easily adopted to the complex shape joint without calculation of reaction force direction.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.59-63
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• 2013

A bendable electronic module has been developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In flexible embedded electronic module, a thin silicon chip was embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. To confirm reliability and durability of prototype bendable module, the following tests were conducted: Moisture sensitivity level, thermal shock test, high temperature & high humidity storage test, and pressure cooker tester. Those experiments to induce failure of the module due to temperature variations and moisture are the experiment to verify the reliability. Failure criterion was 20% increase in bump resistance from the initial value. The mechanism of the increase of the bump resistance was analyzed by using non-destructive X-ray analysis and scanning acoustic microscopy. During the pressure cooker test (PCT), delamination occurred at the various interfaces of the bendable embedded modules. To investigate the failure mechanism, moisture diffusion analysis was conducted to the pressure cooker's test. The hygroscopic characteristics of the encapsulating polymeric materials were experimentally determined. Analysis results have shown moisture saturation process of flexible module under high temperature/high humidity and high atmosphere conditions. Based on these results, stress factor and failure mechanism/mode of bendable embedded electronic module were obtained.

• The Journal of Korea Robotics Society
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• v.3 no.4
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• pp.323-330
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• 2008

This work deals with a 4-DOF flexible continuum robot that employs a spring as its backbone. The mechanism consists of two modules and each module has 2 DOF. The special features of the proposed mechanism are the flexibility and the backdrivability of the whole body by using a spring backbone. Thus, even in the case of collision with human body, this device can ensure safety. The design and the kinematics for this continuum mechanism are introduced. The performance of this continuum mechanism was shown through simulation and experiment.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.143-151
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• 2001

In the paper, a robust control mechanism is presented to maneuver a flexible spacecraft with the deflection reduction during large slewing operation at the same time. For deflection reduction and maneuvering of the flexible spacecraft, a control mechanism is developed with the application of stochastic optimal sliding-mode control, a linear tracking model and input shaping technique. A start-coast-stop maneuver is employed as a slewing strategy. It is shown that the control mechanism with he strategic maneuver results in better performance and is more efficient than rigid-body-like maneuver, by applying to the Spacecraft Control Laboratory Experiment (SCOLE) system in a space environment.

• Journal of Industrial Technology
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• v.19
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• pp.15-23
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• 1999

Active damping system is generally used for the vibration suppression and precise motion control for the flexible structure. This application can be easily found on the space structure and driving mechanism of optical storage devices. Although a control system using the flexible structure has many advantages over using rigid mechanism in driving energy saving, system weights, and etc., more complex and precise control strategies are required. A position control system using flexible structure and the concept of active damper is designed and manufactured, which is driven by slide DC motor and moving coil motor located at the tip of the flexible beam. Dynamic characteristics of this system are investigated by analytic and experimental ways. By the comparison of those two results, a nominal reference model for this system is proposed.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.69-70
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• 1997

Polyimides and related polymers, when synthesized from aromatic monomers, have generally rigid chain structures resulting in a low gas permeability. The rigidity of polymer chains reduces the segmental motion of chains and works as a good barrier against gas transport. To overcome the limit of use as materials of gas separation membranes due to low gas permeability, block copolymers with the incorporation of flexible segments like siloxane linkage and ether linkage have been studied. These block copolymers have microphase-separated structures composed of microdomains of flexible poly(dimethylsiloxane) or polyether segments and of rigid polyimides segments. In case of rigid-flexible block copolymers, the characteristics of both phases for gas permeation are of great difference. The permeation of gas molecules occurs favorably through microdomains of flexible segments, whereas those of rigid segments hinder the permeation of gas molecules. Accordingly the increase of content of flexible segments in a rigid polymer matrix will increase the gas permeability of the membrane linearly. However, this prediction does not satisfy enough many experimental results and in particular the drastic increase of the permeability is observed in a certain volume fraction. It was proposed that the gas transport mechanism is dominated by diffusion rather than gas solubility in a certain content of flexible phase if solution-diffusion mechanism is adopted. However, the transition from solubility-dependent to diffusion-dependent cannot be explained by the understanding of mechanism itself. Therefore, we consider an effective chemical path which permeable phase can form in a microheterogenous medium, and percolation concept is introduced to describe the permeability transition at near threshold where for the first time a percolation path occurs. The volume fraction of both phases is defined as V$_{\alpha}$ and V$_{\beta}$ in block copolymers, and the volume of $\beta$ phase in the threshold forming geometrically a traversing channel is defined as V$_{\betac}$. The formation mechanism of shortest chemical channel is schematically depicted in Fig. 1.

• Journal of the Korean Operations Research and Management Science Society
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• v.33 no.1
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• pp.19-33
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• 2008

In the previous double auction research for the market optimization, two basic assumptions are usually applied - (1) each trader has a linear or quasi-linear utility function of price and quantity, and (2) buyers as well as sellers have identical utility functions. However, in practice, each buyer and seller in a double auction market may have diverse utility functions for trading goods. Therefore, a flexible and integrated double auction mechanism that can integrate all traders' diverse utility functions is necessary. In particular, the flexible mechanism is more useful in a synchronous double auction because traders can properly change utilities in each round. Therefore, in this paper, we propose a flexible synchronous double auction mechanism in which traders can express diverse utility functions for the price and quantity of the goods, and optimal total market utility is guaranteed. In order to optimize the total market utility which consists of multiple complex utility functions of traders. We show the viability of the proposed mechanism through a several simulation experiments.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.51-66
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• 2022

The article presents the results of finite element analyses carried out on skirted footings. The bearing capacity increases with the provision of the flexible and rigid skirt, but the effectiveness varies with various other factors. The skirts are more efficient in the case of cohesionless soils than cohesive and c-ϕ soils. Efficiency reduces with an increase in the soil strength and footing depth. The rigid skirt is relatively more efficient compared to the flexible skirt. In contrast, to the flexible skirt, the efficiency of the rigid skirt increases continuously with skirt length. The difference in the effectiveness of both skirts becomes more noticeable with an increase in the strength parameters, skirt length, and footing depth. The failure mechanism also changes significantly with the inclusion of a rigid skirt. The rigid skirt behaves as a solid embedded footing, and the failure mechanism becomes confined with an increase in the skirt length. Few small-scale laboratory tests were carried out to study the flexible and rigid skirt and verify the numerical study results. The numerical analysis results are further used to develop nonlinear equations to predict the enhancement in bearing capacity with the provision of the rigid and flexible skirts.