• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.168-175
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• 2003

In this research, a bridge-type flexure hinge mechanism is developed and optimized to amplify the displacement of a multilayer piezostack. Developed hinge mechanism has three-dimensional structure to reduce link size, so it have high amplification ratio with respect to small size. A flexure hinge is assumed to be 6 degree-of-freedom spring elements and matrix methods are used to model a hinge mechanism. To verify derived matrix model, a displacement and frequency experiments are performed. The analysis result shows that the displacemental error between matrix model and experiments is below 10 percents and the deformation of hinge in parasitic direction should be considered In hinge modeling. Using developed matrix model, an optimal design is performed to maximize the performance of hinge mechanism.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.630-635
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• 2014

This study aims to develop a PZT-driven depth adjustment device with a flexure hinge and to investigate its static/dynamic characteristics. This device will be applied to rapidly and accurately trace a flat surface with slight waviness of up to several hundreds of micrometers in magnitude. One typical example is to cut a film coated on a steel plate. A depth control system composed of PMAC, PZT/PZT amplifier, flexure hinge/knife, and laser displacement sensor is implemented on a desktop three-axis machine and an actual cutting test is conducted on a steel workpiece with a sinusoidal-wavy surface. It is verified that the dynamic characteristics of the device limit the maximum cutting speed and depth precision.

• Structural Engineering and Mechanics
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• v.52 no.5
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• pp.857-873
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• 2014

Structural behaviors of a sustainable hybrid column with the ultra high performance cementitious composites (UHPCC) permanent form under compression and flexure were studied. Critical state and failure stage characters are analyzed for large and small eccentricity cases. A simplified theoretical model is proposed for engineering designs and unified formulas for loading capacity of the hybrid column under compression and flexure loads are derived, including axial force and moment. Non-linear numerical analysis is carried out to verify the theoretical predictions. The theoretical predictions agree well with the numerical results which are verified by the short hybrid column tests recursively. Compared with the traditional reinforced concrete (RC) column, the loading capacity of the sustainable hybrid column is improved significantly due to UHPCC confinements.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.54-59
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• 2005

Recently, the ultra-precision stage is widely used in the fields of the nano-technology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). In this paper, the ultra-precision stage which consists of flexure hinges, piezoelectric actuator, and ultra-precision linear encoder, is designed and developed. The guide mechanism which consisted of flexure hinges is analyzed by Finite Element Method. And we derived the transfer function of the system in 1st order system from step responses according to the magnitude. We performed simulation for the model to tune the control gain and applied the gains to the developed system. Experimental results found that the stage can be controlled in 5 nm resolution by PID controller.

• The Journal of Korea Robotics Society
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• v.12 no.1
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• pp.78-85
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• 2017

This paper presents the development of a 3D printer based piezo-driven vertical micro-positioning stage. The stage consists of two flexure bridge structures which amplify and transfer the horizontal motion of the piezo-element into vertical motion of the end-effector. The stage is fabricated with ABS material using a precision 3D printer. This enables a one-body design eliminating the need for assembly, and significantly increases the freedom in design while shortening fabrication time. The design of the stage was optimized using response surface analysis method. Experimental results are presented which demonstrate 100nm stepping in the vertical out-of-plane direction. The results demonstrate the future possibilities of applying 3D printers and ABS material in fabricating linear driven motion stages.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.121-129
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• 2005

Lever mechanisms are usually employed to enlarge output displacements in precision stages. In this study, theoretical analysis is done for a precision stage employing a lever and flexure hinges, including bending effect. This study presented relations between design parameters and magnification ratio. This study presents optimal values for the parameters to achieve a longer stage displacement. The analysis is verified by finite element analysis. It is found that adjusting stiffnesses can increase the travel range significantly.

• Advances in concrete construction
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• v.5 no.6
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• pp.625-638
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• 2017

The flexural behavior of Fiber reinforced polymer (FRP) sheets has gained much research interest in the flexural strengthening of reinforced concrete beams. The study on flexure includes various parameters like increase in strength of the member due to the externally bonded (EB) Fiber reinforced polymer, crack patterns, debonding of the fiber from the structure, scaling, convenience of using the fibers, cost effectiveness, etc. The present work aims to study experimentally about the reasons behind the failure due to flexure of an externally bonded FRP concrete beam. In the design of FRP-reinforced concrete structures, deflection control is as critical as much as flexural strength. A numerical model is created using Finite element (FEM) software and the results are compared with that of the experiment.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.327-336
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• 1996

This study was performed to investigate the effec% of immersion in water and thermal cycling on the mechanical peoperties of light cured restorative composite resins. Five commerically available light-cured composite resins(Photo Clearfil A : CA, Lite-Fil A . LF, Clearril Photo Posterior CP, Prisms AP.H.. PA, 2100 : ZH) were unto The specimens of 12 m in diameter and 0.7 m in thickness were made, and an immersion in $37^{\circ}C$ water for 7 days and a thermal cycling of 1000 cycles at 15 second dwell time each in $5^{\circ}C$ and $55^{\circ}C$ baths were performed. Biaxial flexure test was conducted using the ball-on-three-ball method at the crosshead speed of 0.5mm/min. In order to investigate the deterioration of composite resins during the thermal cycling test, Weibull analysis for the biaxial flexure strengths was done. Fracture surfaces and the surfaces before and after the thermal cycling test were examined by SEM. The highest Weibull modulus value of 10.09 after thermal cycling tests which means the lowest strength variation, was observed in the CP group, and the lowest value of 4.47 was obsered in the LF Group. Biaxial flexure strengths and Knoop hardness numbers significantly decreased due to the thermal cycling ($\textit{p}$< 0.01), however, they recovered when specimens were drie4 The highest biaxial flexure strength of 125.65MPa was observed in the ZH group after the thermal cycling test, and the lowest value of 64.86MPa was observed in the CA group. Biaxial flexure strengths of ZH and CP groups were higher than those of PA, CF, and CA groups after thermal cycling test($\textit{p}$< 0.05). Knoop hardness numbers of CP group after the thermal cycling test was the highest(95.47 $\pm$ 7.35kg/$mm^2$) among the samples, while that of CA group was the lowest(30.73 $\pm$ 2.58kg/$mm^2$). Knoop hardness numbers showed the significant differences between the CP group and others after the thermal cycling test(($\textit{p}$< 0.05). Fracture surfaces showed that the composite resin failure developed along the matrix resin and the filler/resin interface region, and the cracks propagated in the conical shape from the maximum tensile stress zone.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.587-588
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• 2013

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.759-763
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• 2006

Cable Stayed Bridge is mainly composed of three element. Composed element are cable. stiffening girder and Pylon. The characteristic of bridge's behavior depend on these three element's relative stiffness, shape and system of bridge. The purpose of this paper is to exame the characteristic of bridge's behavior and buckling strength of stiffening girder according to shape and flexure stiffness of pylon