• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1359-1365
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• 2014

In this study, 1-way fluid structure interaction analysis(FSI) for the shutter, component of side jet thruster was performed to evaluate the safety. Driving torque to open nozzle, thermal and high pressure load of hot gas was applied to shutter. Thus, the shutter must be designed to endure this load during combustion. We carried out computational fluid dynamics analysis to obtain the pressure, temperature, and heat transfer coefficient of hot gas of side jet thruster. We then used the data as the load condition for a thermal structural analysis using a mapping method. The locations with the maximum stress and temperature distributions were found. We compared the maximum stress with the tensile stress of shutter material according to temperature to evaluate the safety. We also analyzed the radial deformation of the shutter to set the proper interface gap with the side jet thruster parts.

• Transactions of Materials Processing
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• v.22 no.8
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• pp.463-469
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• 2013

In the previous work, a new forging process design, which included incremental upsetting, diffusion bonding and cogging, was suggested as a method to manufacture 1.9wt%C ultrahigh carbon workrolls. The previous study showed that incremental upsetting and diffusion bonding are effective in closing voids and healing of the closed void. In addition, compression tests of the 1.9wt%C ultrahigh carbon steel revealed that new microvoids form within the blocky cementite at temperatures of less than $900^{\circ}C$ and that local melting can occur at temperatures over $1120^{\circ}C$. Thus, the forging temperature should be controlled between 900 and $1120^{\circ}C$. Based on these results, incremental upsetting and diffusion bonding were used to check whether they are effective in closing and healing voids in a 1.9wt%C ultrahigh carbon steel. The incremental upsetting and diffusion bonding were performed using sub-sized specimens of 1.9wt%C ultrahigh carbon steel. The specimen was deformed only in the radial direction during the incremental upsetting until the reduction ratio reached about 45~50%. After deformation the specimens were kept at $1100^{\circ}C$ for the 1 hour in order to obtain a high bonding strength for the closed void. Finally, microstructural observations and tensile tests were conducted to investigate void closure behavior and bonding strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1549-1556
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• 2011

Tensile and creep tests were performed at various temperatures to investigate the mechanical properties of plastics used in automotive instrument panels. Mechanical properties such as Young's modulus and Poisson's ratios changed markedly with the test temperature. Three-point bending creep tests were performed for three kinds of plastics under four loading conditions. Coefficients in the time-hardening power law creep equation were obtained from the experiment, and the creep behavior was represented by a simple expression. The results of finite element creep analysis showed good agreement with the experimental results, while the difference between the numerical and experimental results increased with the load.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.241-249
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• 1994

We studied on the effects of hot-worm rolling on recrystalized structures and tensile strength in over-aged 7075 A1 alloy, to develop the process for improving properties. It showed more clear effect of the grain refinement with over-aging before plastic deformation. That means, the coarse precipitates from over-aging play a roll as nucleation sites in the course of recrystallization. And on this study, the relations between yield strength and grain size was not satisfied with Hall-Petch equation because of the elongated structure, but the yield strength is proportional to aspect ratio of grains. In TMT process for improving strength and toughness, the worm working is available for increase of those properties than cold working.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.295-304
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• 2011

The first step in improving our understanding of uncertainties suclt as rock mass strength parameters and deformation modulus in rock masses around high-level radioactive waste disposal repositories, for improved safety, is to study the process of crack development in intact rock. Therefore, in this study, the fracture process and crack development were examined in samples of KURT granite taken from the KAERI Underground Research Tunnel (KURT), based on acoustic emission (AE) and moment tensor analysis. The results show that crack initiation, coalescence, and unstable crack occurred at rock uniaxial compressive strengths of 0.45, 0.73, and 0.84, respectively. In addition, moment tensor analysis indicated that during the early stage of loading, tensile cracks were predominant. With increasing applied stress, the number of shear cracks gradually increased. When the applied stress exceeded the stress level required for crack damage, unstable shear cracks which directly result in failure of the rock were generated along the failure plane.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.6
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• pp.281-287
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• 2014

Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for engine mount bracket prepared by gravity casting (as-cast) and die-casting (as-diecast) process have been investigated. For the microstructural characterization, the inductively coupled plasma mass spectrometry (ICP-MS), optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA) analyses are conducted. For the intermetallic phases, the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are also conducted with quantitative and qualitative analysis. Micro Vickers hardness and static tensile test are achieved in order to measure mechanical properties of alloys. Secondary dendrite arm spacing (SDAS) of as-cast and as-diecast show 37um and 18um, respectively. A large amount of coarsen eutectic Si, $Al_2Cu$ intermetallic phase and Fe-rich phases are identified in the Al-6Si-2Cu alloy. Mechanical properties of gravity casting alloy are much higher than those of die-casting alloy. Especially, yield strength and elongation of gravity casting alloy show 2 times higher than die-casting alloy. After shot peening, shot peening refined the surface grains and Si particles of the alloys by plastic deformation. The surface hardness value shows that shot peening alloy has higher value than unpeening alloy.

• Journal of Fashion Business
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• v.20 no.2
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• pp.124-133
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• 2016

Currently the fashion industry is developing to create a novel culture due to the very sensitive and knowledge-oriented advancement of the IT industry. With fast turnover of information, consumers have come to have a more diverse desire for purchasing. Cubical expression techniques, which empathizes formativeness, can be a creative expression method adjusting into the trend of this era. Along with functional aspects of consumers, even in a textile manufacturing sector, new materials are required to meet sensitive and emotional aspects. Consumers' desire for new and creative designs and the development and adoption of new materials are essential to meet their emotions. The IT industry and fashion industry are forced to combine and a 3D apparel CAD system has been developed, enabling virtual clothing to be represented within a computer virtual space. All processes such as design, pattern creation, sewing and simulation are possible in 3D level. Digital clothing can shorten the production process time and is very effective in that it can reduce clothing waste generated during the sample production. This paper reviewed the works of Dutch designer, Iris van Herpen, who has developed formative designs. She tries to build, construct, and sculpt employing diversified materials other than soft textile materials, as shown in her series of fashion shows. The materials include films, 3D printed polymers, stiff and sheer organza, and artificial leather textiles. A few characteristics of her works have been selected in order to prepare patterns exhibiting the traits. The paper further focused on the physical features of the textile materials used to express similar techniques and its various forms were reviewed.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.6-10
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• 2012

The main objective of this work was studying the influence of paraffin oil(PO) on the adhesion properties at low temperature in styrene-butadiene-styrene(SBS) copolymer and crumb rubber(CR) modified asphalt. The temperature susceptibility of SBS/CR asphalt and PO/SBS/CR/asphalt blends were measured by penetration and softening point. Adhesion properties at low temperature and dispersion of modifiers in PO/SBS/CR/asphalt blends were evaluated by universal test machine and florescence microscopy, respectively. The adhesion properties of PO/SBS/CR/asphalt blends at low temperature increased in the proportion of SBS contents with both 5 and 10 wt % of paraffin oil. Results showed that the maximum tensile adhesion strength and toughness energy at $-20^{\circ}C$ were obtained when PO and SBS contents were 10 wt % and 6 wt %, respectively. The addition of PO is effective for enhancing the flexibility of SBS/CR/asphalt blends and leads to the increase of toughness at low temperature.

• Journal of Technologic Dentistry
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• v.40 no.1
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• pp.41-47
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• 2018

Purpose: The purpose of this study was to analyze the biomechanical properties of the dental implants on the supporting bone using three-dimensional finite element method when three different abutment materials were applied to the implant system. Methods: Three different dental implant models were fabricated by applying Ti, PEEK, and CRE-PEEK (60% carbon-reinforced PEEK) to abutment material. The abutment and connecting screw from the fixture was applied with a tightening torque of 20 Ncm. And then, total loads of 150 N were applied in an $30^{\circ}oblique$ direction (to the vertical). The structural stability of dental implants on the supporting bone was analyzed using Von Mises stress and principal stress values. Results: The maximum tensile stress of the cortical bone was highest at 12.6 MPa in the PEEK abutment (Model-B). Ti abutment (Model-A) and CRE-PEEK abutment (Model-C) showed similar stress distributions (10.6 and 10.3 MPa, respectively). And the maximum compressive principal stress was similar in all models. The Von Mises stress value delivered to the bone around the implant was highest at 16.5 MPa in Model-B. On the other hand, Model-A and C showed similar stress distributions (14.0 and 13.8 MPa, respectively). In addition, the maximum equivalent stress applied to the abutment was highest at 629.8 MPa in Model-A. The stress distribution in Model-C was 573.9 MPa. Whereas, Model-B showed the lowest value at 165.6 MPa. Conclusion : The dental implant supporting bone system using PEEK material seems to have the possibility of supporting bone fracture. It was found that the CRE-PEEK abutment can reduce the elastic deformation and reduce the stress value of the interfacial bone.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.23-31
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• 2002

The purpose of this study is to investigate the size effect on inelastic behavior of reinforced concrete bridge piers. A computer program, named RCAHEST(reinforced concrete analysis in higher evaluation system technology), for the analysis for reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel. To determine the size effect on bridge pier inelastic behavior, a 1/4-scale replicate model was also loaded for comparison with the full-scale bridge pier behavior.