• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.189-195
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• 2008

The vibration isolator system(VIS) which has very low natural frequency could be designed by applying an axial compressive force to the beam-column flexure(BCF). In this paper a new shape of the BCF is suggested. It has stepwise axially varying properties by viscoelastic damping layer. So it has internal structural damping by damping layer during deformation. First the analytic solution is obtained for the BCF. And its critical load, buckling mode, stiffness and stress distributions are investigated. Also the dynamic properties of the VIS consist of the damping layered BCF are studied. Finally the optimal design procedure of damping layered BCF for the VIS is suggested. The improved performance of suggested VIS is verified by some experiments.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.361-367
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• 2014

Ultra-precision positioning plays a crucial role in emerging technologies such as electronics, bioengineering, optics, and various nanofabrication technologies. As a result, various nanopositioning methods have been presented. In particular, nanopositioning using a flexure mechanism and piezo-electric actuator is one of the most valuable methods because of its friction-free motion and subnanometer-scale motion resolution. In this study, a rotational nanoactuator based on a right-circular flexure mechanism and piezo-electric actuator was developed through a consideration of the kinematics and structural deformation. An experimental setup was constructed to verify the performance expectation. Consequently, it was demonstrated that the developed system had a maximum rotational angle of about 0.01 rad, as well as sufficient linearity with respect to the input voltage.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.213-218
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• 2004

As optical fiber communication grows, the fiber alignment become the focus of industrial attention. This greatly influence the overall production rates for the opto-electric products. We proposed multi-axis nano positioning stage for optical fiber alignment. This device has 3 DOF translation and sub nanometer resolution. This nano stage consist of 3 PZT-driven flexure stages which are stacked parallel. The displacement of it is measured with capacitance gauge and is controlled by computer-embedded main controller. The design process of flexure stage using FEM is proposed and the performance evaluation of this system is verified with experiments.

• 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 Earthquake Engineering Society of Korea
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• v.25 no.5
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• pp.191-199
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• 2021

In seismic design, hollow section concrete columns offer advantages by reducing the weight and seismic mass compared to concrete section RC bridge columns. However, the flexure-shear behavior and spirals strain of hollow section concrete columns are not well-understood. Octagonal RC bridge columns of a small-scale model were tested under cyclic lateral load with constant axial load. The volumetric ratio of the transverse spiral hoop of all specimens is 0.00206. The test results showed that the structural performance of the hollow specimen, such as the initial crack pattern, initial stiffness, and diagonal crack pattern, was comparable to that of the solid specimen. However, the lateral strength and ultimate displacement of the hollow specimen noticeably decreased after the drift ratio of 3%. The columns showed flexure-shear failure at the final stage. Analytical and experimental investigations are presented in this study to understand a correlation confinement steel ratio with neutral axis and a correlation between the strain of spirals and the shear resistance capacity of steel in hollow and solid section concrete columns. Furthermore, shear strength components (V_c, V_s·, V_p) and concrete stress were investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.361-366
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• 1999

The purpose of this study is to evaluate the structural performance of Reinforced steel fiber concrete structures using early age concrete. Reinforced concrete structures using early age concrete are result in the degradation of structural performance due to crack, overload, unexpected vibration and impact load. Specimens, designed by the over 0.75% of steel fiber incorporated, were showed the ductile behavior and failed slowly with flexure and flexure-shear. Increasing the percent of steel fiber incorporated(0.25~2.0%), the ultimate shear stress of each specimen were increased 12~40% than that of specimen SSS.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.465-472
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• 2012

This paper describes a new robust control algorithm which can be used to enhance the positioning performance of an ultra-precision positioning system. The working table is supported by flexure hinges and moved by a piezoelectric actuator, whose position is measured by an ultra-precise linear encoder. The system dynamics is very complicated because the movement of the table is governed by both the mechanical characteristics and those of the PZT actuator. So that, the dynamics of the stage was modeled roughly in this paper, and the overall system was formularized to solve the small gain problem. A series of experiments was conducted in order to verify the usefulness of the proposed algorithm. From the experimental results, the positioning performance such as the accuracy, the rise time and the hysteresis nonlinearity were greatly improved.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.823-832
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• 2004

The purpose of this research is to investigate the flexure-shear behavior of bridge columns under seismic loads. Four full scale circular reinforced concrete columns were tested under cyclic lateral load with constant axial load. The selected test variables are aspect ratio(1.825, 2.5, 4.0), transverse steel configuration, and longitudinal steel ratio. Volumetric ratio of transverse hoop of all the columns is 0.0023 in the plastic hinge region. It corresponds to $24\%$ of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. The columns showed flexural failure or flexure-shear failure depending on the test variables. Failure behavior and seismic performance are investigated and discussed in this paper.

• Journal of Advanced Navigation Technology
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• v.26 no.3
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• pp.179-184
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• 2022

The accurate wing flexure model is required to improve the transfer alignment performance of guided weapon system mounted on a wing of fighter aircraft or armed helicopter. In order to solve this problem, mechanical or stochastical modeling methods have been studying, but modeling accuracy is too low to be applied to weapon systems. The deep learning techniques that have been studying recently are suitable for nonlinear. However, operating fighter aircraft for deep-learning modeling to secure a large amount of data is practically difficult. In this paper, it was used to generate amount of flexure data samples that are similar to the actual flexure data. And it was confirmed that generated data is similar to the actual data by utilizing "measures of similarity" which measures how much alike the two data objects are.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.129-137
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• 1999

Reinforced concrete structures using early age concrete were result in the degradation of structural performance due to crack, overload, unexpected vibration and impact load. It demands urgently that reinforced concrete structure using early age concrete should be improved the serviceability and structural performance with the application of new fiber materials. Therefore specimens, designed by the test varibles, such as with or without stirrup and percent of steel fiber incorporated, were constructed and tested to evaluate and develop the structural performance of reinforced steel fiber concrete beam. Based on the test results reported in this study, the following conclusions are made. Specimens, designed by the over 0.75% of steel fiber incorporated, were showed the ductile behavior and failed slowly with flexure and flexure-shear. Comparing with the load-displacement relationship of specimen BSS, designed by the recommendations of the Ministry of Construction and Transportation, reinforced steel fiber concrete beam using early age concrete, over 0.75% of steel fiber incorporated, gets enough load carrying capacity and ductility. Increasing the percent of steel fiber incorporated(0.25~2.0%), the ultimate shear stress of each specimen were increased 12~40% than that of control specimen SSS.