• Korean Journal of Construction Engineering and Management
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• v.6 no.4 s.26
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• pp.172-180
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• 2005

The purpose of this study is to suggest a new SRC(Steel Ready mixed Concrete) lining board. The research method of this study includes problem analysis of existing lining boards a constant load test and a fatigue test. The results of this study are as follow : 1) the suggested new lining board improves the function and reduce slipperiness than existing lining boards. 2) the strength of the new SRC lining board is analyzed as superior than existing lining boards from the results of constant load test and fatigue test.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.42-52
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• 1995

An UBET(Upper Bound Elemental Techniquel) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flashless non-axisymmetric forging. To analyze the process easily, it is suggested that the deforma- tion is divided into two different parts. Those are axisymmetric part in corner and plane- strain part in lateral. The total power consumption is minimized through combination of two deformation parts by building block method, form which the upper-bound forging load, the flow pattern, the grid pattern, the velocity distribution and the effective strain are deter- mined. To show the merit of flashless forging, the results of flashless and flash-forging processes are compared through theory and experiment. Experiments have been carried out with plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agrement with the experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.319-324
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• 2004

Cross wedge rolling process is utilized to manufacture multi-stepped axis symmetrical parts. This process is generally performed under high temperature conditions in order to induce serious deformation. But cold cross wedge rolling process has been rarely studied due to the limits of deformation. Recently, the cold cross wedge rolling process has been utilized to enhance the material strength in specified parts of manufactured products. In this paper, experimental researches were carried out with various forming conditions of cold cross wedge rolling process in order to suggest the design guidance to make preform for cold cross wedge rolling. The tensile strength and the surface hardness of specified region were compared to that of initial material with the variation of the area reduction and the rotational speed of rolling die. With respect to the area reduction, the maximum tensile strength was linearly increased and the surface hardness was rapidly increased within lower percent of area reduction. The surface hardness was saturated over the rotational die speed of 0.8 RPM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.6967-6972
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• 2014

Assembly using a bolt and nut, and rivet or pin have been used widely for forming mechanical joints. The indent method is an easier process than other manufacturing techniques and the toughness of the material is excellent. On the other hand, there are many cases in which the cracks occur on the manufacturing process as the indent method. Therefore, two kinds of models, in which a pin goes into and out PCB plate in this study were developed using the CATIA program and finite element methods were performed using the ANSYS program. When a pin was passed through a PCB plate in cases 1 and 2, the maximum loads applied to the PCB plate were 79.708N and 90.277N, respectively. When the PCB plate came out of the pin in cases 1 and 2, the maximum loads were 63.783N and 33.75N, respectively. The damage prevention and durability can be improved by applying the study results to the design of real indentation.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.176-182
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• 2020

Purpose: To evaluate the effects of load direction, number of implants, and alignment of implant position on stress distribution in implant, prosthesis, and bone tissue. Materials and Methods: Four 3D models were made to simulate posterior mandible bone block: two implants and 3-unit fixed dental prosthesis (FDP) with a pontic in the center (model M1), two implants and 3-unit FDP with a cantilever pontic at one end (model M2), FDP supported by three implants with straight line placement (model M3) and FDP supported by three implants with staggered implant configuration (model M4). The applied force was 120 N axially or 120 N obliquely. Results: Peak von Mises stresses caused by oblique occlusal force were 3.4 to 5.1 times higher in the implant and 3.5 to 8.3 times higher in the alveolar bone than those stresses caused by axial occlusal force. In model M2, the connector area of the distal cantilever in the prosthesis generated the highest von Mises stresses among all models. With the design of a large number of implants, low stresses were generated. When three implants were placed, there were no significant differences in the magnitude of stress between staggered arrangement and straight arrangement. Conclusion: The effect of staggering alignment on implant stress was negligible. However, the number of implants had a significant effect on stress magnitude.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.919-925
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• 1999

Grain boundary characteristics and corrosion behavior of Alloy 600 material were investigated using the concept of grain boundary control by thermomechanical treatment(TMT). The grain boundary character distribution (GBCD) was analyzed by electron backscattered diffraction pattern. The effects of GBeD variation on intergranular at tack(JGA) and primary water stress corrosion cracking(PWSeC) were also evaluated. Changes in the fraction of coinci dence site lattice(CSL) boundaries in each cycle of TMT process were not distinguishable, but the total eSL boundary frequencies for TMT specimens increased about 10% compared with those of the commercial Alloy 600 material. It was found from IGA tests that the resistance to IGA was improved by TMT process. However, it was found from PWSCC test that repeating of TMT cycles resulted in the gradual decrease of the time to failure and the maximum load due to change in grain boundary characteristics, while the average crack propagation rate of primary crack increased mainly due to suppression of secondary crack propagation. It is considered that these corrosion characteristics in TMT specimens is attributed to 'fine tuning of grain boundary' mechanism.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.380-388
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• 2016

Commercially pure titanium (CP Ti) has been actively used in plate heat exchangers due to its light weight, high specific strength, and excellent corrosion resistance. However, compared with automotive steels and aluminum alloys, there has not been much research on the plastic deformation characteristics and press formability of CP Ti sheet. In this study, the mechanical properties of CP Ti sheet are clarified in relation to press formability, including anisotropic properties and the stress-strain relation. The flow curve of the true stress-true strain relation is fitted well by the Kim-Tuan hardening equation rather than the Voce and Swift models. The forming limit curve (FLC) of CP Ti sheet was experimentally evaluated as a criterion for press formability by punch stretching tests. Analytical predictions were also made via Hora's modified maximum force criterion. The predicted FLC with the Kim-Tuan hardening model and an appropriate yield function shows good correlation with the experimental results of the punch stretching test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.238-244
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• 2017

A spindle with a built-in motor can be used to simplify the structure of a machine tool system, but the rotor inevitably has unbalanced mass. This paper presents an analysis of the dynamic behavior. The spindle was used in a CNC lathe and investigated using the finite element method and transfer matrices. The high-speed spindle can be very sensitive to the rotation of an unbalanced mass, which has a harmful effect on many machine tools. Thus, a balancing procedure was performed with a spindle-bearing system for the CNC lathe by numerical analysis. The balancing was performed through the influence coefficient method, and the whirl orbit radii before and after balancing were compared to evaluate the effects. The results show that the rotational speed of the spindle seriously affects the whirl responses of the spindle. The whirl responses were also affected by other factors, such as the unbalanced mass and bearing stiffness. The balancing of the assembled spindle model significantly reduced the whirl orbit magnitude.

• Journal of Sensor Science and Technology
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• v.9 no.5
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• pp.380-388
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• 2000

The finite element analysis of a micro turbine was made to investigate safety margin of its operating condition for the high aspect ratio nickel micro turbine blades fabricated by conventional LIGA-like method. From our study, we found that the fabricated turbine could not exceed its yield strength even if the pressure difference between inlet and outlet of turbine blade was about 44kPa, and the correlation of friction coefficient and the maximum stress, caused by contact friction between outer diameter of shaft and inner diameter of turbine blade, was somewhat reciprocal. The maximum stress was decreased with the increasing contact friction, when turbine blade was in its state of rotation. By the results of our study, we conclude that it is possible to fabricate metal micro turbine more easily han surface micromachining technology and to operate with no risk of metal structure's damage, which is caused by yield strength, if the operating condition with the design of micro turbine itself are optimized. It is useful to adopt other applications which have the contact problems between a moving part and the fixed one in micro structures.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.1-12
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• 2007

For the purpose of effective utilization of domestic second-grown larch as structural members, post and beam construction applying traditional construction to Japanese larch glulam members was adopted with processing by machine pre-cut method. In general, horizontal shear test by KS F 2154 is conducted to assess the horizontal shear properties of the wooden structure by post and beam construction. The frame was consisted of post and beam member with appropriate fasteners, and members have their own processed parts (notch, hole, etc.) that can be well-connected each other. The shear wall was consisted of the frame with screw-nail sheathed panel (OSB). The results of horizontal shear loading tests without vertical loads conducted on the frame and the shear wall structures, the maximum strengths were about 1.9 kN/m and about 9.7 kN/m, the shear rigidities were about 167 kN/rad, 8198 kN/rad, respectively. The strength proportion of the frame specimen was about 20% of the wall's and about 2% in initial stiffness. Nail failures are remarkable on the shear wall specimen with punching shears and shear failures. The shear load factor for the shear wall specimen by the method of Architectural Institute of Japan was 1.5, which was obtained by the bi-linear method. Loading method should be considered to obtain smooth load-deformation relationship. For the better shear performance of the structures, column base and post and beam connections and sheathed panel should be further examined as well.