• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.93-99
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• 2013

Parts and structures such as piston rod and knuckle joint for the use of hydraulic cylinder are often welded together in some fashion, usually due to cost and process effectiveness. Welding strongly affects the material by the process of heating and subsequent cooling as well as by the fusion process with additional filler material. Furthermore, a weld is usually far from being perfect, containing inclusions, pores, cavities, undercuts etc. As a consequence, fatigue failures appear in welded structures mostly at the welds rather than in the base metal, even if the latter contains notches. For this reason, fatigue analyses are of high practical interest for all welded structures under the action of cyclic loads. This paper describes the influence of welding parameters, material combinations and heat treatment on the fatigue behavior of welded cylinder rod. In addition, statistical characterization of stress-life response in weldment of hydraulic cylinder rod are presented.

• Fibers and Polymers
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• v.2 no.1
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• pp.140-143
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• 2001

To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

• Journal of Korea Foundry Society
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• v.32 no.1
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• pp.16-23
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• 2012

In this study, we develop the lower pressure die casting with rheo-forming process of A356 aluminum alloy and vacuum system which can control the crystal size and obtain the high strengthened-light material. Using this process, we fabricate the thin plate for bipolar plate through the low pressure die casting with electromagnetic stirring and vacuum-evacuation which can control the crystal grain by electromagnetic stirring. Thin plate ($110mm{\times}130mm{\times}1mm$) is fabricated by this process. The average Vickers hardness of thin plate is about 77 HV.

• Tribology and Lubricants
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• v.25 no.3
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• pp.182-186
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• 2009

Extruders can be basically divided into bisk and screw type of extruders. Though plastic extruders are often used for its simplicity for water and oil transportation pumps, these days screw extruders are mostly used. Screws are used in many extrusion processes to manufacture complex and complicated shaped parts made of plastics, medicine materials, food, polymer composites, iron and ceramic powders, etc. Also, material correction of deformities is caused by flow and physicochemical reaction phenomenonand material extrusion is processed according to heat transfer. various material comes to hopper because extruder has function by blender and mixing of materials can go well before come out through dice. These change process is so complicated that process condition is decided by trial and error that process condition is underground mainly at extrusion molding process.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.611-618
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• 2011

Flow forming is an incremental forming process in which rollers are used to form cylindrical parts with repeated turning of both roller and starting material. Both sheet and tube can be used as the starting material. The process is highly useful for producing hollow shaped parts from a tube, with the benefit of the average strain in the final shape being significantly lower than that from a sheet material. In the present study, the flow forming process was studied and optimized for producing a hollow shaped part from seamless steel tube by both experiment and numerical analysis. Upon considering the difficulty of forming seamless steel sheet, the thickness reduction was distributed over several tool paths. In the end, an optimum process condition was attained, and the experiment verified the simulation results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.287-290
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• 2002

Stainless steel used widely in various fields of industry have the characteristics of difficulty-to-cut. This difficulty comes from its peculiarity, for example work hardening, vibration, etc. And these peculiarity on the cutting process have an effect on tool wear or life shortness of tools. To solve these problems several method have been developed. Hot-machining is one way of these method. when a material is heated, organization of material is soften. So cutting process becomes easy. When such a hot-machining method applies on drilling process and then heated material is processed, cutting force is less than usual drilling process cutting force. In this paper, cutting force is compared heated SUS 304 with usual SUS 304. And shape of chips is also compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.178-181
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• 2002

We studied the characteristics of polishing pad, which can apply W CMP process for global planarization of multilevel interconnection structure. Also we investigated the effects of different sets of polishing pad. The purpose of this experiment is the cost reduction by the increase of pad life time and decrease of cycle time and slurry usage with new pad. Especially we studied the effect of polishing pad for CMP process by this experiment of polishing pad that is consumables material during CMP process. We expecting the increase of process throughput and improvement of device manufacturing yield because we can choose optimum polishing pad through this result.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1292-1293
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• 2006

A non-equilibrium powder metallurgy processing such as an MA/SPS (Mechanical Alloying / Spark Plasma Sintering) process is examined in a Ti-48moll%Al. TiAl intermetallic compound is a potential light-weight/high-temperature structural material. One of the major problems, however, limiting the practical use of the material is its poor workability. From this point, the powder metallurgy (PM) processing route has been attractive alternative of the conventional processing for such material The MA/SPS process is able to apply to a LIGA process. Optimization of the pseudo-superplasticity enables to fabricate micro-parts made of fine grained ceramics composites of TiAl by the LIGA process.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.77-82
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• 2008

Rubbing-roller is used for manufacturing liquid crystal display, and static displacement of the rubbing-roller becomes bigger as length of the rubbing roller made of aluminum is getting longer. Therefore, material of the rubbing-roller is changed from aluminum to CFRP(Carbon Fiber Reinforced plastic). Recently thermal spraying is applied to manufacturing process of long rubbing-roller. The thermal spraying has disadvantages such as increment of manufacturing time and fraction defective caused by density of stainless steel particle. In this study, fitting process by drawing was suggested and FEM analysis with Tsai-Wu failure theory and fitting experiments are carried out to find adequate shrink allowance. The suggested shrink allowance gives proper adhesive force, and CFRP failure is not occurred. Furthermore, the fitting process is applied to long rubbing-roller and availability of the fitting process is studied by measurement of roundness, straightness and shear strength.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.35-40
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• 2008

In OLED vacuum evaporation process, the essential requirements include good uniformity of the film thickness over a glass substrate. And, it is commercially significant to improve the consuming efficiency of material of the evaporant which is deposited on the substrate because of high price of organic materials. In this paper, to achieve the better thickness uniformity and the better organic material consuming rate, a process optimization algorithm was developed by understanding vacuum evaporation process parameters that affect the material consuming efficiency and the uniformity of film thickness. Based on the method developed in this study, the vacuum evaporation process of OLED was successfully controlled. The developed method allowed the manufacture of high quality OLED displays with cheaper fabrication cost.