• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.1585-1593
• /
• 2015

3D-structured (embossed) aluminum sheets have been used in the heat insulation purpose for automative exhaust parts because of increasing their surface areas and stiffness reinforcement imposed in making the embossing pattern. However, there are many restrictions in press forming of the embossed sheet compared with the flat sheet (non-embossed one) because of its difference in the mechanical properties and the geometrical 3-dimensional shape. In this paper we investigated the deformation characteristic of embossed aluminum sheet in the incremental sheet forming process which has frequently used in the design verification and the trial manufacturing of sheet products. The single point incremental forming (SPIF) experiments for the rectangular cone forming using the CNC machine with a chemical wood-machined die and a circular tool shape showed that the formability of the embossed sheet are better than that of the flat sheet in view of the maximum angle of cone forming. This comes from the fact that the embossed sheet between the tool and the elastic die wall is plastically compressed and the flatted area contributes to increase the plastic deformation. Also the tool path along the outward movement from the center showed a better formability than that of the inward movement from the edge. However the surface quality for the tool path along the outward movement evaluated from the surface deflection is inferior than that of the tool path along the inward movement.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.09a
• /
• pp.233-241
• /
• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.09a
• /
• pp.211-219
• /
• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces stric시y related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials. In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Journal of Welding and Joining
• /
• v.26 no.6
• /
• pp.81-91
• /
• 2008

The weldability of resistance spot welding of TRIP1180 steels for automobile components investigated enhance in order to achieve understanding of weld fracture during tensile-shear strength (TSS) test. The main failure modes for spot welds of TRIP1180 steels were nugget pullout and interfacial fracture. The peak load to cause a weld interfacial failure was found to be related to fracture toughness of the weld and the weld diameter. Although interfacial fracture occurred in the spot welded samples, the load-carrying capacity of the weld was high and not significantly affected by the fracture mode. Substantial part of the weld exhibits the characteristic dimple (or elongated dimple) fractures on interfacial fractured surface also, dimple fracture areas were drawmatically increased with heat input which is propotional to the applied weld current. In spite of the high hardness values associated with the martensite microstructures due to high cooling rate. The high load-carrying ability of the weld is directly associated with the area of ductile fracture occurred in weld. Therefore, the judgment of the quality of resistance spot welds in TRIP1180 steels, the load-carrying capacity of the weld should be considered as an important factor than fracture mode.

• Applied Chemistry for Engineering
• /
• v.18 no.5
• /
• pp.454-458
• /
• 2007

The removal characteristics of ionic species, such as $Ca^{2+}$, $Mg^{2+}$, $Sr^{2+}$, $SO{_4}^{2-}$, $NO{_3}^-$, and $Cl^-$ by adsorption on the alumina were investigated. Alumina precusor powders were prepared from $Al(NO_3)_3{\cdot}9H_2O$ and $NH_4OH$. Alumina materials prepared from the heat treatment in a furnace at $450{\sim}750^{\circ}C$ for 5 h were analysed using FT-IR and the Brunauer-Emmett-Teller (BET) method. The specific surface area of the product particles decreased significantly with treatment temperature. The adsorption capacities of $SO{_4}^{2-}$and $NO{_3}^-$ on alumina were 23 mg/g and 12.4 mg/g, respectively. But, removal efficiencies of $Cl^-$ were less than 4 mg/g. In general, the removal efficiencies of the anion species were decreased with increasing treatment temperature. The best anion removal efficiency was obtained when the alumina was treated under $450^{\circ}C$. Removal efficiencies of $Ca^{2+}$, $Mg^{2+}$, and $Sr^{2+}$ were increased with increasing treatment temperature.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.2
• /
• pp.666-671
• /
• 2014

Using positive temperature coefficient (PTC) heater as supplementary heating for diesel engine vehicles with low heat source is a good method to enhance the heating performance during cold start. In this study, the PTC elements were made by using screen printing process for forming ohmic contact layer, and prototype of PTC heater was designed and made for a diesel engine vehicle. In process of designing the PTC heater, the thermal flow analysis of PTC element modules was conducted for verifying the effect of the shapes of contact surface between each of the components (cooling fin, insulator, ceramic element). We also investigated the performance characteristic (heating capacity, energy efficiency, pressure drop) of the PTC heater through the experiments. Therefore, the experimental results indicated that prototype of PTC heater had satisfactory performance. This study will be basis for improving the manufacturing process and increasing the performance of the PTC element and heater.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.2_2
• /
• pp.289-297
• /
• 2022

Deterioration in durability of structures due to the steel corrosion is difficult to determine whether or not corrosion is initiated and how much propagated, and moreover, repair and maintenance are not easy to deal with. Therefore, preventive treatments can be the best option to avoid the deterioration. Various methods for preventing corrosion of steel, such as electrochemical treatments, anti-corrosion agents and steel surface coatings, are being developed, but economic and environmental aspects make it difficult to apply them to in-situ field. Thus, the purpose of this study was to improve corrosion resistance by using CA-based clinker that are relatively simple and expected to be economically profitable Existing CA-based clinkers had problems such as flash setting and low strength development during the initial hydration process, but in order to solve this problem, CA clinker with low initial reactivity were used as binder in this study. The cement paste used in the experiments was replaced with CA₂ clinker for 0%, 10%, 20%, and 30% in OPC. And the mixture used in the chloride binding test for the extraction of water-soluble chloride was intermixed with Cl- 0.5%, 1%, 2%, and 3% by weight of binder content. To evaluate characteristic of hydration heat evolution, calorimetry analysis was performed and simultaneously chloride binding capacity and acid neutralization capacity were carried out. The identification of hydration products with curing ages was verified by X-ray diffraction analysis. The free chloride extraction test showed that the chlorine ion holding ability improved in order OC 10 > OC 30 > OC 20 > OC 0 and the pH drop resistance test showed that the resistance capability in pH 12 was OC 0 > OA 10 > OA 20 > OA 30. The XRD analyses showed that AFm phase, which can affect the ability to hold chlorine ions, tended to increase when CA₂ was mixed, and that in pH12 the content of calcium hydroxide (Ca(OH)₂), which indicates pH-low resistance, decreased as CA₂ was mixed

• Journal of the Society of Disaster Information
• /
• v.8 no.1
• /
• pp.18-26
• /
• 2012

Accordingly architectural structure is getting high-rise and bigger, a use of high strength and high performance concrete has been increasing. High performance concrete has cons of explosion in a fire. This Explosion in the fire can cause the loss of the sheath on a concrete surface, therefore it effects that increasing a rate of heat transmission between the steel bar and inner concrete. Preventing this explosion of high performance concrete in the fire, many kinds of researches are now in progressing. Typically, researches with using Polypropylene-fiber and Steel-fiber can prove controling the explosion, but the reduction of mobility was posed as a problem of workability. Consequently, to solve the problem as mentioned above, concrete cans secure fire resisting capacity through the using of coating liquid, including Ester-lubricant and non-ionic characteristic surfactant. This research has been drawn a ideal condition in compressive strength areas of concrete by an experiment. When applying 13mm of polyamide-fiber, proper fiber mixing volume by compressive strength areas of concrete is $0.8kg/m^3$ in 60MPa, $1.0kg/m^3$ in 80MPa, $1.5kg/m^3$ in $100MPa/m^3$. These amount of a compound can control the explosion.

• Composites Research
• /
• v.30 no.2
• /
• pp.116-125
• /
• 2017

The purpose of this study is to develop silicon carbide fiber showing an excellent mechanical properties under highly oxidative conditions at high temperature. Polycarbosilane(PCS) as a preceramic precursor was used for making the SiC fiber. PCS fiber was taken by melt spinning method followed by melting the PCS at $300{\sim}350^{\circ}C$ in N2 gas. The Curing of PCS fiber was carried out in air oxygen chamber, prior to high temperature pyrolysis. Degree of cure was calculated by characteristic peak's ratio of Si-H to $Si-CH_3$ in FT-IR spectra before and after curing of PCS fiber. The properties of SiC fiber was affected greatly by the degree of cure. The SiC fiber produced by controlling fiber tension during heat treatment showed good properties. The SiC fiber exposed to $1000^{\circ}C$ at air from 1 min. up to maximum 50 hrs showed around 60% reduction in tensile strength. We found that large amount of carbon content on the fiber surface after long-term exposure has resulted in lower tensile strength.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.6
• /
• pp.3389-3395
• /
• 2014

Conventional methods, such as the clock time control method and temperature difference control method, for defrost control often encounter mal-defrost and a waste of energy. Therefore, a more efficient method is needed to control defrosting precisely. A photoelectric sensor unit consisting of an emitter and a collector was installed in the front of outdoor heat exchanger. Accurate defrost control was performed by monitoring and using the change in output voltage according to the presence of frost. In this study, experiments were performed to determine if the performance and characteristic curves obtained using the clock time control method can be reproduced using a photoelectric sensor under the heating and defrosting capacity test condition described at KS C 9306. The output voltage of the phototransistor (receiver) and heating capacity, power consumption, and surface temperature of the outdoor heat exchanger, were compared. The results showed that photoelectric sensors can be used as a defrost control method. On-off control timing of the clock time defrosting method was in good agreement with those predicted by the output voltage of the photoelectric sensor.