• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.364-368
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• 1992

The conventional loading process of workpieces for a CNC lathe is performaed either by human or by a general robot. It is not suitable for a general robot to load workpieces because of high price and inefficiency. Starting from the description of the environment around CNC lathes and the analysis ofloading process, we have developed the task-oriented loading manipulator. The characteristics of a loading manipulator are the following: to load/unload heavy workpieces, to decrease the whole porcess time. The air-chuck to load heavy workpiece has high clamping force and light weight. A loading manipulator has accomplished both the integration of independent automation techniques and cost-down effect of product. A loading manupulator developed in this project has been designed for general loading process. The loading manipulator is capable of carrying heavy payload with respect to weight of robot in short cycle time.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.539-556
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• 2004

In this paper, the design, fabrication and characterization of a piezoelectric friction damper are presented. It was sized with the proposed practical procedure to minimize the story drift and floor acceleration of an existing 1/4-scale, three-story frame structure under both near-fault and far-field earthquakes. The design operation friction force in kip was numerically determined to range from 2.2 to 3.3 times the value of the peak ground acceleration in g (gravitational acceleration). Experimental results indicated that the load-displacement loop of the damper is nearly rectangular in shape and independent of the excitation frequency. The coefficient of friction of the damper is approximately 0.85 when the clamping force on the damper is above 400 lbs. It was found that the friction force variation of the damper generated by piezoelectric actuators with 1000 Volts is approximately 90% of the expected value. The properties of the damper are insensitive to its ambient temperature and remain almost the same after being tested for more than 12,000 cycles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.642-650
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• 2008

In this paper, structural behavior of Gasket and GDL of a PEMFC stack is studied to improve the performance and to secure the safety. In the Gasket analysis Mooney-Rivlin strain energy function is used to consider hyperelasticity of load and displacement. The material properties is determined by testing specimens of the gasket at uni-axial and equi-biaxial mode and compared with finite element analysis results. By measuring a thickness change, the material property of GDL is determined. The pressure drop of a unit cell is measured along the channel for the clamping force. A cross sectional change of channel base on the experimental data is obtained experimentally and compare with FEM analysis results.

• Journal of the Korean Solar Energy Society
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• v.36 no.3
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• pp.25-31
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• 2016

Gaskets are usually used for the sealing of flange joints. The joint is usually composed of two flanges, a ring gasket and clamping bolts. The metal ring gasket is suitable for pipe flanges, pumps and valve joints in high temperature and high pressure environments. A very high surface stress is developed between a ring type joint gasket and the flange groove when the ring type joint is bolted up in a flange. The dimensions of flanges and ring joint gaskets for the pipe sizes that are in common use are specified in the ANSI codes. However, sometimes it is necessary to make a new design for the flange joint which is not specified in the codes, as the equipment is getting larger and larger in size. This paper presents the contact behavior of Class 600 ring joint gaskets with oval and octagonal cross sections. Five different sizes of gaskets are employed in the analysis, and one of them is newly designed on the basis of analysis results obtained from existing models. Three load steps are used to find the stress, stain and contact pressure etc., and to compare the contact characteristics among the models due to the bolt clamping force and the working surface pressure. ANSYS Workbench version15 is used to conduct the finite element analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.815-820
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• 2005

ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was $1100^{\circ}C$. The average grain sizes were showed increased from $8.6{\mu}m\;to\;10{\mu}m$, and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient $\alpha$, of all were with increasing the amount of glass-frit more than 70, in case of added on $0.03wt\%$ glass-frit was 83. And leakage current were less than $1{\mu}A$ with applied at $82\%$ of varistor voltage. The clamping voltage ratio of the specimens added $0.03wt\%$ glass-frit was 1.41 at applied 25A $[8/20\;{\mu}s]$. In the specimen added $0.03wt\%$ glass-frit, endurance of surge current and deviation of varistor voltage were $6200A/cm^2,\;\Delta-1.67\%$, respectively and clamping voltage ratio was 2.33. In the Specimen added $0.03wt\%$ glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at $85^{\circ}C$, and deviation of the varistor voltage were $\Delta-1.29\%$.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.3
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• pp.147-154
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• 2003

This paper presents a high-frequency boost type ZVS-PWM chopper-fed DC-DC power converter with a single active auxiliary edge-resonant snubber at the load stage which can be designed for power conditioners such as solar photovoltaic generation, fuel cell generation, battery and super capacitor energy storages. Its principle operation in steady-state is described in addition to a prototype setup. The experimental results of boost type ZVS-PWM chopper proposed here, are evaluated and verified with a practical design model in terms of its switching voltage and current waveforms, the switching v-i trajectory and the temperature performance of IGBT module, the actual power conversion efficiency, and the EMI of radiated and conducted emissions, and then discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, and can be reduced the EMI conducted emission.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.1
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• pp.5-14
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• 2007

It is necessary for development of drawing product with press to have suitable material selection & all process design and the problem during press process has been cleared from judgement of experience & trial and error. Recently we can estimate press process result from computer aided design & FEM. But we can get more reliable result when we can put more precise process variants during FEM. In case of using a drawbead that is used for the material inflow, it is considered for us to put material property, other analysis condition & friction figure when material is passing through the drawbead for better FEM. From our study, we have drawn an analogy bead connection depth, friction figure & drawing and restraining load according to kinds of lubrication from experiment & FEM for the drawbead. We applied above result to the drawing experiment & FEM and confirmed the validity. We could notice the relation between friction figure & drawing load and the friction figure variation according to kinds of lubrication. It is expected to draw more precise analogy that can be used for real process due to more precise process variants application to FEM.

• Journal of Technologic Dentistry
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• v.37 no.3
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• pp.115-120
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• 2015

Purpose: The purpose of this study is a finite element analysis of supporting bone according to custom abutment angle. Methods: Implant fixture was selected with a diameter of 4 mm and the length of 13 mm. The fixture and abutment was designed by a combination of the abutment screw clamping force to produce a custom abutment model of $0^{\circ}$, $15^{\circ}$, $25^{\circ}$ and $35^{\circ}$. The loading condition of 176 N was applied to the lingual surface of the crown, near to the incisor edge, and horizontal load. An oblique load of $90^{\circ}$ was applied long axis of the implant fixture analyze the stress of supporting bone. Results: The result of mechanical analysis was observed that the supporting bone stress analysis of the horizontal load, the von Mises stress values (MPa) are given in the order of TH00 (432.6) > TH25 (418.0) > TH15 (417.4) > TH35 (415.8), the oblique load, the von Mises stress values are given in the order of TO00 (459.3) > TO15 (399.6) > TO25 (374.8) > TO35 (343.4) Conclusion: The $35^{\circ}$ abutment over the current clinical tolerance limits will be available for clinical application.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.136-143
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• 2011

The oversized and slotted holes are frequently required for the built-up in construction sites. The foreign provisions specify the reduction of the slip load subjected to the size of bolt holes and the direction of load. There are no domestic building codes and researches on the bolt holes. Therefore, it is necessary to evaluate a change of joint strength quantitatively according to the bolt-hole size and surface condition by means of experiment. This study was conducted to evaluate the slip load subjected to the size of bolt holes, and measured on a change of clamping force of high strength bolts during 168 and 800 hours to analyze the trend of relaxation after fastening bolts. Torque shear bolts defined on KS B 2819 was used for the specimen. Test results exhibit that the variation on the slip load of the others was below 10% by contrast with the standard hole and the highest rate of relaxation was 2.66% of the initial clamping force at the case of the long-slotted hole of 2.5D.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.486-491
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• 2004

A comparative study on the implant screw loosening under the initial clamping force and cyclic loads was conducted. The experiments were performed to evaluate the screw loosening behavior of the internal and external implant systems. It was found that the screw loosening torques of implant systems were significantly affected by the way how the abutment and fixture were connected due to the difference in the load transfer mechanism between abutment and fixture.