• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.83-88
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• 2011

Magnesium alloys have been focussed for the applications for lightweight of vehicle and electronics due to their high strength, low specific density and good damping capacity. This paper deals with the creep strength of Mg-Nd-Zr-Zn alloy. For the alloy, pure magnesium(99.9%) was melt with atmosphere of $0.3%SF_6$ and $25%CO_2$. After melting, 0.3% of zinc was inserted to stir for 10min at elevated temperature of $770^{\circ}C$. Master alloys of Mg-15%Nd and Mg-15%Zr were stirred in furnace. The creep tests were performed to obtain creep rate and rupture in the temperature range of 200 to $220^{\circ}C$ and 280 to $310^{\circ}C$ at an applied stress of 156 to 172MPa and 78 to 94MPa, respectively. The deformation mechanism was predicted dislocation climb from measured apparent activation energy and stress exponent. Also the increaser the temperature and stress the lower the stress exponent and activation energy. Finally, LMP parameter gives good information for the predicted creep rupture life.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.133-138
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• 2017

Recently, CFRP composites are widely used as lightweight materials have with excellent mechanical properties and can beare widely used in various fields. In general, thermosetting resins are used for CFRP. However, in recent years, studies have been carried out using thermoplastic resins have been actively carried out to overcome the disadvantages of thermosetting resins. The LFT-D system is a molding method in which a fiber is directly cut to a the desired length while being impregnated with a thermoplastic resin to produce a compound and that is then press-molding molded to form the product. In this paper, before the production of the trailing arm, the compression molding analysis was carried out in order to grasp the problems that may occur during production. Through cCompression molding analysis was applied to calculate of the minimum press pressure and to compare and analysis analyze the molding conditions characteristic required to formfor forming the trailing arm.

• 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 for Precision Engineering
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• v.25 no.1
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• pp.99-107
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• 2008

There are being a lot of studies for achievement of high speed Dehydration, high-strength and Lightweight of washing machine in the latest washing machine business. It is essential that strength of mechanical press-Joining (MPJ) for spin drum is improved to attain that target. MPJ of spin drum is composed of seaming and caulking process. Because Seaming process of MPJ has various design factors such as thickness, bending radius, seaming width, caulking press width and the dynamic factor such as multistage plastic working, elastic recovery, residual stress, the optimum conditions can't be easily determined. Using a design of experiment (DOE) based on the FEM (Finite Element Method), which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor during drum MPJ and proposed optimum condition using center composition method among response surface derived from regression equation of simulation-based DOE.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.196-197
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• 2013

This study is the experiment for manufacturing the Lightweight non-cement matrix based on the Blast furnace slag. And, the matrix was manufactured matrix by generating the bubble just by the reaction of KOH that is the alkali accelerator and paper ash, instead of the general foaming agent, that is the waste managed of incineration the pulp sludge generated in the process of manufacturing the paper. Consequently, the density according to the addition rate of KOH represented the tendency to increase. And it showed up that density of the matrix adding KOH 22.5% was the lowest. As to the strength test result, strength following addition rate of KOH increased. Since the bubble is generated in the reaction of KOH and paper ash, this shows the very low intensity but it is determined to be the result that the amount of vacant space is decreased because the bubble generated in the mixture process comes up as the specific gravity difference.

• Design & Manufacturing
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• v.11 no.2
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• pp.15-19
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• 2017

Carbon fiber reinforced plastic (CFRP) is applied as structural material. CFRP is excellent in plane strength / stiffness and don't haves rust. Lightweight, rigid and robust at the same time as transportation material. Aluminum alloy and reinforcement material The application is increasing rapidly. In this study, the prototype of a semi - Monocoque structure frame, Longeron, Stringer, Skin of the aircraft, restraining the rigidity Clips of the aircraft was designated as the target product and the experiment was conducted. ln the experiment, (1) For CFRTP 3 points, data on heating, transfer, and cooling were measured using Thermo Couple, and optimum temperature required for flexible state was obtained. Heating was performed at a temperature 15% higher than the provided temperature. (2) By using a pneumatic press during molding, by dividing LH, center and RH according to the cooling time, thickness parameter of the target product due to the load is measured, and thickness control and time-deviations were analyzed and cross sections were observed with a low magnification microscope.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.60-67
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• 2019

Recently, lightweight materials such as Ti alloys have been used increasingly in the aerospace and high-tech industries for weight loss and fuel efficiency. Because of built-up edges and workpiece deflection due to low stiffness, the Ti alloys have poor machinability. In our study, systematic experiments were conducted to investigate the milling characteristics of the Ti alloy (Ti-6A1-4V) with endmills. The independent variables in the experiment were spindle speed, feed per tooth, and axial depth. Cutting force, acceleration RMS, and surface roughness were measured. Using the response surface method, the optimal cutting conditions were analyzed to improve machining quality and productivity.

• Tribology and Lubricants
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• v.35 no.1
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• pp.24-29
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• 2019

In this work we investigated the friction and wear characteristics of a magnesium alloy, which has been receiving much attention as a light metal in industrial applications such as automobiles and aerospace. Magnesium is one of the lightest structural material that has high specific strength, lightweight, low density and good formability. However, current issue of using magnesium alloy is that magnesium has weakness against temperature. As the temperature increases, magnesium undergoes poor creep resistance and ease of softening, and therefore, its mechanical strength decreases sharply. To solve this issue, a new type of magnesium alloy that retains high strength at high temperature has been proposed. The tribological behavior of this alloy was investigated using a tribotester with reciprocating motion and heating plate. A stainless steel ball was used as a counter surface. Results showed that extrusion process has similar wear behavior to the commonly used casting process but retains good mechanical strength and durability. The presence of an alloying element enhanced the wear properties especially in high temperature. This study is expected to be utilized as fundamental data for the replacement of high density materials currently used in mechanical industries to a much lighter and durable heat-resistant materials.

• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.1-6
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• 2018

Recently, bicycle has means of effective healthy transportation, and riding the bicycles is considered as popular recreational and sporting activities. Also, the saddle, steering system, driving device and braking device are researched briskly because of consumer's need for driving performance and comfort. Especially, the importance of a cassette responsible for transmission function by transmitting power to the drive shaft through the chain is very focused. The writer conducted structural analysis for the sprocket of each level using the ANSYS widely used for the analysis. Speed shifting performance was enhanced by minimization / simplification of shifting point through a sort of tooth profile of the cassette. By partitioning a clear value type and other shifting point, it has been modified to enable smooth speed-shifting. In addition, as titanium precision forming process, this study studied the molding technique by blanking and dies forging for mass production of the cassette. so it could be expected that the entire drive train would utilize that in the future. The stamping process capability for thin materials for the mass production of the sprockets is applicable to producing automobile parts, so lightweight component production is likely to be possible through that, for the safety of driving.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.8
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• pp.86-92
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• 2021

As interest and demand for high value-added industries, including the global automobile and aerospace industries, have increased recently, demand for line centers with excellent performance that can respond to the production system for producing high value-added products is also rapidly increasing. A line center improves productivity based on the installed area using a multi-spindle compared to a conventional machining center. However, as the number of spindles increases, the weight increases and results in structural problems owing to the heat and vibration generated by each spindle. Therefore, it is necessary to improve machining precision through the structural improvement of the line center. This study presents research on the stabilization design of the line center through structural stability analysis through structural analysis to develop a compact multi-axis line center. An optimization model of the line center has been proposed to improve the processing precision and increase the rigidity by performing weight reduction based on the structural analysis results.