• Journal of Korea Foundry Society
• /
• v.20 no.3
• /
• pp.167-172
• /
• 2000

Squeeze casting was performed to fabricate the SiC whisker reinforced magnesium matrix composites, and the suitability of the squeeze casting for the production of the sound composites was determined by micro/macro-structures observations and tensile test. The two-directional infiltration of the melt and the removal of air during infiltration using the devised mold were necessary to produce the composites. The pressure of 100 MPa was effective for the production of composites with the SiC whisker volume fraction of 30%, but the pressure should be lower than 50 MPa in case of below 20% in the volume fraction. The SiC whiskers in the squeeze cast composites were randomly and densely aligned, and the SiC whiskers/magnesium interfaces were continuously well-bonded. The elastic modulus, 0.2% proof stress and tensile strength in the composite were about 2.5times, l0times and 4times as large as those of magnesium, respectively, indicating that the squeeze casting sufficiently provides the high strength magnesium composites reinforced with SiC whiskers.

• Journal of Welding and Joining
• /
• v.31 no.5
• /
• pp.77-81
• /
• 2013

We have investigated thermal stability of the mechanical and thermal conductive properties of Cu/STS/Cu 3 layered clad metal lead frame material for a LED device package at different temperatures ranging from RT to $200^{\circ}C$. The fabricated Cu/STS/Cu clad metal has a good thermal stability for the mechanical tensile strength and thermal conductivity of the over 50 $Kg/mm^2$ to the $150^{\circ}C$ and 270 $W/m{\cdot}K$ to the $200^{\circ}C$, respectively. This clad metal lead frame material at a high temperature of $150^{\circ}C$ shows a reinforced mechanical tensile strength by 1.5 times to conventional pure copper lead frame materials and also a comparable thermal conductivity to typical copper alloy lead frame materials.

• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.17-25
• /
• 2002

Recently, many studies have been carried out to process on the purpose of lightness in a transport parts because of the saving energy, the environmental problem. The cast-forging process can be expected to lower costs without decreasing the mechanical properties. So, the finest microstructure is needed to get for applying the cast-forging process with Al-Si alloy because the microstructure affects to the cast-forging process. For refinement treatment of eutectic Si and Al solid-solution phase, Sr and TiB were added in Al-Si alloys. The finest microstructure could be observed when 0.075 wt.%Sr and 0.1 wt.%TiB were added respectively. In this case, tensile strength and elongation much more increased than as casting. After high temperature deformation simulation test with grain refinement specimens was carried out, about 70N per unit $area(mm^2)$ of specimen was confirmed. After hot forging, tensile strength and elongation were increased. It was considered because casting defect was removed by compressive working.

• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.26-34
• /
• 2002

For application of cast-forging process with Al-Si alloys, casting experiments are carried out by adding Sr and TiB to Al-Si alloys for grain refinement treatment. We experimented on the mechanical properties according to microstructural changes, forging ability test and also investigated the mechanical properties after forging. The finest microstructure could be observed respectively when 0.05 wt.%Sr and 0.1 wt.%TiB were added. In this case, tensile strength and elongation increased much more than as casting. After high temperature deformation simulation test with grain refinement specimens was carried out, about 60N per unit $area(mm^2)$ of specimen was confirmed. After hot forging, tensile strength and elongation were increased. It was considered that casting defect was removed by compressive working.

• Journal of Korea Foundry Society
• /
• v.32 no.6
• /
• pp.289-295
• /
• 2012

Mg-Al-Sn-Si system alloy, as a promising cheap heat-resistant Mg alloy for automobile engine part, has been investigated. Refinement of microstructure and precipitation of thermally stable secondary phases are important goal for the design of heat-resistant Mg alloy. In this study, the effect of Ce on the microstructure and room temperature mechanical properties of Mg-Al-Sn-Si alloy was investigated. High thermally stable $Mg_2Si$ phases in Mg-Al-Sn-Si alloy is very useful intermetallic compound. However, the $Mg_2Si$ phases often result in poor mechanical properties due to the coarse chinese type $Mg_2Si$ phases. The experimental specimens were fabricated by fluxless melting under $CO_2+SF_6$ atmosphere and poured into the permanent pre-heated at $200^{\circ}C$. It was told that Ce addition can modify $Mg_2Si$ phases and refine microstructure and improve the tensile strength, yield strength and elongation.

• Carbon letters
• /
• v.3 no.3
• /
• pp.127-132
• /
• 2002

Unidirectional polymer composites were prepared using high-strength carbon fibers as reinforcement and phenolic resin as matrix precursor with keeping fiber volume fraction at 30, 40, 50 and 60% respectively. These composites were carbonized at $1000^{\circ}C$ and graphitised at $2600^{\circ}C$ in the inert atmosphere. The carbonized and graphitised composites were characterized for mechanical properties as well as microstructure. Microscopic studies were carried out of the polished surface of carbonized and graphitised composites after etching by chromic acid, to understand the effect of fiber volume fraction on oxidation at fiber-matrix interface. It is found that the flexural strength in polymer composites increases with fiber volume fraction and so does for the carbonised composites. However, the trend was found to be reversed in graphitised composites. In all the carbonized composites anisotropic region has been observed at fiber-matrix interface which transforms into columnar type microstructure upon graphitisation. The extension of strong and weak columnar type microstructure is function of fiber volume fraction. SEM microscopy of the etched surface of the sample reveal that composites containing 40% fiber volume has minimum oxidation at the interface, revealing a strong interfacial bonding.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.135-142
• /
• 2004

The apparent advantages of FRP (fiber reinforced plastics) composites over the conventional structural materials may be attributed to their high specific strength and stiffness. Other affordable properties of FRPs including an excellent durability make them particularly attractive for the structures in severe service conditions. Therefore, the material and sectional properties of a FRP structural component should be designed to meet its specific requirements and service conditions. This paper is performed the material property optimization under optimum design of pultruded FRP bridge deck section. In the problem formulation, an objective function is selected to minimize the maximum R(strength ratio). The thickness of layers, volumes of fibers and matrix fiber orientation, and stacking sequence of FRPs are used as the design variables. Strength ratio in the design code, material failure criteria and pultruded manufacture thickness are selected as the design constraints to enhance the material performance of FRP decks. From the results of the numerical investigation, we obtained the optimum deck section profile for conventional using object.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.43 no.5
• /
• pp.34-42
• /
• 2011

A fiber processing method, which might be an alternative for conventional refining process, was introduced. The method consists of repetitive, gentle, mechanical impacts on fibers, followed by fiber uncurling process. This method was very effective for OCC and BCTMP for increasing WRVs (water retention value) while keeping fiber lengths from shortening. For OCC and BCTMP, gentle mechanical impacts on fibers using Hobart mixer increased breaking lengths and tear strengths simultaneously at fast drainage level, and straightening fibers using kady mill increased those strength properties further. For SwBKP and HwBKP, only mechanical impacts using the Hobart mixer were effective on increasing tensile and tear strength at fast drainage, but there were no further increase by kady mill treatment. The strength increases of BCTMP by this alternative fiber processing method were exceptionally high. An extensive engineering development should be followed to actualize this fiber processing mechanism in an energy-effect way.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.4
• /
• pp.490-494
• /
• 2011

In this paper, using by rapid heating and cooling systems for injection molding and temperatures to changes. In the process of molding temperature and pressure inside the mold was found. In addition, the tensile strength of test specimens were molded, mechanical properties of injection molded parts were identified on mold temperature. Copper could withstand more tensile force than NAK. Therefore, it can be concluded that materials with high heat conductivity must be used in thin walled products.

• Advances in materials Research
• /
• v.4 no.3
• /
• pp.179-192
• /
• 2015

The study presents a preliminary investigation on the applicability of Shirasu (a pyroclastic flow deposit characterized by high percentage of volcanic glass) in geopolymer. Comparative study on compressive strength and internal pore structure has been done between geopolymers with alkali activated Shirasu and fly ash as aluminosilicates. Mortar mix proportions are selected based on variations in ratio of alkaline activators to aluminosilicate and also on silica to alkali hydroxide ratio. From the experimental study, Shirasu geopolymer exhibited fairly good compressive strength. Mix proportion based on silica to alkali hydroxide ratio is observed to have profound effect on strength development.