• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.883-888
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• 2008

Various effluents generated in cooking processes contribute a great deal to indoor air pollution among many other indoor pollutants such as dusts from outdoor and carbon dioxide from human body. Kitchen exhaust hoods are not believed to exhaust indoor contaminants properly in many cases, while generating too much noise. Instead of focusing on individual products of kitchen hoods, we should address the problem by attacking the ventilation system as a whole including vertical shafts and building air-tightness. In this study, it is intended to investigate the pressure distribution along the vertical shaft depending on various system parameters, such as shaft size, concurrent hood usage rate, roof fan, inlet pressure loss, and outdoor temperature. The maximum static pressure in the vertical shaft has been obtained using the method of design of experiments and analyzed by the analysis of variance. The results can be used for the design of kitchen exhaust systems by analyzing the pressure distributions in vertical shafts.

• Transactions of Materials Processing
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• v.20 no.5
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• pp.362-368
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• 2011

For the purpose of improving crashworthiness qualities and maximizing weight saving efficiency, TWB's(tailor welded blanks) of quench-hardenable boron steel sheet formed by hot stamping processes has been used for automotive BIW (body in white) applications. In this work, the flow behaviors of TWB of quench-hardenable boron steel sheet were investigated in uniaxial tension tests at elevated temperature. TWB's having a uniform thickness of 1.4mm were fabricated by laser welding. Specimens with two weld line directions were used to test the mechanical property and reliability of the weld zone. After heating at $950^{\circ}C$ for 5min, the specimens were subjected to tension test at 650, 700 and $800^{\circ}C$ with a strain rate of 0.01 /s and at $700^{\circ}C$ with strain rates of 0.01, 0.1 and 1/s. The ultimate strength of the weld zones was higher than that of the base materials at 650 and $700^{\circ}C$, but was similar to the base metal at $800^{\circ}C$. Fracture occurred at the base material at 650 and $700^{\circ}C$, but at the weld zone at $800^{\circ}C$.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.72-81
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• 2011

In the present day, the needs of new steel for lightweight car-body have been increased in the automotive industry. however, the resistance spot welding is difficult to apply to the new steel because of the narrow weld current range and defects. As the solutions to these problems, adhesive bonding process is proposed. Adhesive bonding which reduce noise and vibration can be applied to joining the new steel. In this study, crash tests of b-pillar applied the resistance spot welding, structural adhesive bonding, the mixture of the structural adhesives and resistance spot welding were performed. And FEM crash model for b-pillar applied the structural adhesive bonding was developed. The results of experiment and analysis on b-pillar crash test were compared to verify the validity.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.598-603
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• 2009

Resistance spot welding has been investigated to apply for manufacturing car bodies because of its high productivity. So quality of resistance spot weld is one of the major concerns for both automobile and aerospace industry. Current design trends in automotive manufacture have shifted emphasis to alternative lightweight materials in order to aid in producing vehicles with higher fuel efficiency and lower down the vehicle emission level for environmental control. There is increasing emphasis to provide lighter cars. Therefore there is an effort to use high strength steels such as HSLA, dual phase, in car body. However there is used in restricted because of difficulty in producing consistently high quality resistance spot welds. In this study, resistance spot welding schedules were developed to achieve acceptable welds with improved static mechanical properties. Improved resistance spot welding schedules were developed using post heating current to reduce the cooling rate, or in-process tempering to reduce the hardness of the weld produced. The effects of resistance spot welding process parameter on hardening fracture mode and static mechanical properties of the joints were determined.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.477-482
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• 2009

This study analyzes the result with dynamic simulation about deformation according to time when a car impacts bollard. These results are shown as followings. The maximum deformation is shown at the lower part of front grass in case of the impact of front or passenger seat but this deformation is shown at the lower part of rear bumper in case of double impact. The maximum equivalent stress is shown at the upper part by the side grass of driver seat at the elapsed time of 0.00075 second after impact in case of the impact of front or passenger seat but this deformation is shown at the front bonnet at the elapsed time of 0.004 second after the additional impact in case of double impact. The maximum total deformation or equivalent stress is shown nearly same in case of the impact of front or passenger seat. But the value of this deformation or equivalent stress in case of the impact of front or passenger seat is shown with 2 times or more than 17% respectively as this value in case of double impact.

• Tribology and Lubricants
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• v.16 no.5
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• pp.365-372
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• 2000

Tribological behavior of novolac resin-based friction materials with three different relative amounts of graphite and zirconium silicate was investigated by using a pad-on-disk type friction tester. The goal of this paper is to examine the effects of the relative amount of a lubricant and an abrasive in the automotive friction material on friction and wear characteristics at elevated temperature. Friction and wear of friction materials were affected by the existence of transfer film(3$\^$rd/ body layer) at friction interface and the composition of friction material, especially lubricant amount. The friction material with higher content of graphite indicated homogenized and durable transfer film, and resulted in stable friction coefficient regardless of the increase in friction heat. The experimental result also showed that the higher concentration of ZrSiO$_4$ in friction material aggravated friction stability and wear resistance due to the higher friction heat generated at fiction interface during high temperature friction test.

• Journal of Welding and Joining
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• v.23 no.5
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• pp.25-29
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• 2005

Steel has been mainly used in the automotive industry, because of good mechanical properties, weldability and so on. However, there has been increase in using aluminum to reduce the weight of vehicle. This leads to improve fuel efficiency and to reduce air pollution. A steel-aluminum hybrid body structure is recently used not only to reduce the weight of vehicle but also to increase safety. In this paper, the laser beam joining method is suggested to join steel and aluminum. To avoid making brittle intermetallic compounds(IMC) that reduce mechanical properties of the joint area, only aluminum is melted by laser irradiation and wetted on the steel surface. The brittle IMC layer is formed with small thickness at the interface between steel and aluminum. By controlling the process parameters, brittle IMC layer thickness is suppressed under 10 micrometers which is a criterion to maintain good mechanical properties.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.113-120
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• 2005

Because of the turbulent markets and the increasing demand on product quality, the application of new technology to practice is increasingly important. In case of automotive industries, they take interest in laser welding to solve these problems because laser welding has many advantages such as good accessibility, welding quality, fast welding speed and so on. To apply this technology to welding of car body, the data of laser welding are collected through lots of the experiment according to the material, geometry and layer number of welding points. Based on the experiment results and the information of product, i.e. the car side panel, the clustering of stitches for laser welding was carried out and the optimal equipments are selected through the comparison between the requirements of welding and the potential of equipments. Using these results, laser welding cell for the car side panel are configured with the concept of the digital manufacturing, which ensures maximum planning security with visualization and simulation. Finally, the optimal laser welding cell is chosen by the evaluation of alternative cells with assessment criteria.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.48-54
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• 2016

The use of Zn coated steel has increased in the automotive industry due to its excellent corrosion resistance. Conventionally the BIW(body-in-white) structure and the hang-on parts have been made of Zn coated steel and more recently Zn coated steel began to be applied in the chassis parts. During gas metal arc (GMA) welding of the chassis part, lap fillet joint used to be adopted but spatter generation and porosities are most important concerns. In the industrial applications, an intentional joint gap was made to avoid the weld defects but it is not easy to control the size of joint gap. In this research, gas tungsten arc (GTA) is combined with GMA welding where GTA precedes GMA. As pulsed arc was adopted as GMA, GTA was oscillated along the longitudinal direction by pulsing GMA, but the arc oscillation did not disturb the molten droplet transfer of GMA welding. By increasing the distance between GTA and GMA, the length of weld pool increased and porosity could be reduced. Moreover porosity in the welds was fully removed when the distance between two arcs was 15 mm.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.99-105
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• 2010

Inverter DC resistance spot welding process has been very widely used for joining such as automotive body sheet metal. Because the lobe area of DC welding is larger than AC welding and DC welding has low electrode wear. So the use of Inverter DC resistance spot welding process has been further increased. And the application of high tensile steel is growing for light weight vehicle. To improve the weldability of high strength steel, the development of Inverter DC resistance spot welding system is more conducted. However, Inverter DC resistance spot welding system has a few problems. Current waveform is unstable and the expulsion has been occurred by characteristics of steel. In this study, inverter DC resistance spot welding system was made. And Fuzzy control algorithm was applied for constant current. The genetic algorithm was applied to optimize the fuzzy scaling factors, in order to optimize the fuzzy control.