• Korea lubricating oil industries association bulletin
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• no.12
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• pp.12-19
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• 1985

• Journal of Drive and Control
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• v.17 no.1
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• pp.21-26
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• 2020

The load characteristics of a piston pump holder due to the squeeze effect are influenced by the surface shape and gap thickness of the holder (cradle). Therefore, the pressure distribution and the load capacity of the piston pump holder due to the squeeze effect are studied by using the CFD software and the surface shape and gap thickness of the piston pump holder are considered. In order to verify the accuracy of numerical results, the load capacities of a circular plate holder are numerically studied, and the accuracy of numerical results is verified by comparing with the theoretical results. Also, the pressure distribution and load capacity of the rectangular plate holder of a piston pump are obtained by using the CFD software. The results show that the load capacity of the square plate holder with grooves is slightly higher at a low gap thickness, but the effects of the number and arrangement of grooves on the load capacity of the holder are weak. We conclude that the load capacity and the maximum pressure are slightly affected due to the existence of grooves on the holder surface, and the fluid storing effect of the holder surface grooves during the operation is likely to prevent the dry-sticking phenomenon.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1398-1401
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• 2005

The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy were investigated using nano/micro-indentation and mechanical scratching, combined wit optical microscopy and atomic force microscope(AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at $150^{\circ}C$ for different times(0, 2, 4, 8, 10, 16, 24, 36 and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness ($H_V$) and indentation ($H_{IT}$) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3474-3490
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• 1996

A metal matrix composites(MMCs) for A16061 reinforced with silicon carbide particles is fabricated by melt-stirring method. The primary products of MMCs billets are prepared by volume fractions 5 vol% to 20 vol% and particle size $13\mu m$ to $22\mu m$.This paper will be made to examine the microstructure and mechanical properties of fabricated $SiC_p$/Al 6061 composite by melt-stirring and squeeze casting method. The MMC billets is extruded at $500^{\circ}C$ under the constant extrusion velocity $V_e$=2mm/min using curved shape die. Extrusion force, particle rearrangement, micro structure and mechanical properties of extruded composites will be investigated. The mechanical properties of primary billets manufactured by melt-stirring and squeeze casting method will be compared with extrusion specimen. The effect of volume fraction and size of the reinforcements will be studied. The increase in uniformity of particle dispersion is the major reason for an improvement in reliability due to hot extrusion with optimal shape die. Experimental Young's modulus and 0.2% offset yield strength for the extruded MMCs will be compared with theretical values calculated by the Eshelby method. A method will be proposed for the prediction of Young's modulus and yield strength in $SiC_p$ reinforced MMCs.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.8 no.2
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• pp.7-12
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• 2010

Purpose : The purpose of this study was to determine the effects of hip adduction using a ball on the activation of the vastus medialis oblique (VMO) and the vastus lateralis (VL) during dynamic semisquat exercises. Methods : Twenty seven participants performed three repetitions of a double-leg semisquat and squeeze semisquat (semisquat with hip adduction using a ball) at $60^{\circ}$ knee flexion. The activation of the VMO and the VL was recorded at dominant leg during both semisquat exercises using surface electromyography (MP 100). EMG data were normalized to the maximal voluntary isometric contraction (MVIC) of the quadriceps produced during seated, isometric knee extension. Results : Results of paired t-test analyses revealed that there were no differences between activity of the VMO and the VL in both double-leg semisquat and squeeze semisquat. The activity of the VMO was significantly increased in squeeze semisquat whereas there was no difference in activity of the VL between double-leg semisquat and squeeze semisquat. Conclusion : Combining hip adduction using a ball with semisquat at $60^{\circ}$ knee flexion preferentially increases the activity of the VMO. We can conclude that semisquat at $60^{\circ}$ knee flexion with hip adduction using a ball selectively recruits the VMO. Rehabilitation for quadricep imbalance should consider these findings when selecting exercises which could preferentially activate the VMO.

• Korean Journal of Metals and Materials
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• v.46 no.7
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• pp.412-419
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• 2008

Creep behavior of the squeeze infiltrated AS52 Mg matrix composites reinforced with 15 vol% of aluminum borate whiskers($Al_{18}B_4O_{33}w$) fabricated squeeze infiltration method was investigated. Microstructure of the composites was observed as uniformly distributed reinforcement in the matrix without any particular defects of casting pores etc.. Creep test was carried out at the temperature of 150 and $200^{\circ}C$ under the applied stress range of 60~120 MPa. The creep resistance of the composite was significantly improved comparing with the unreinforced AS52 Mg alloy. The creep behavior of composites might be interpreted with the substructure invariant model successfully for the composite. Threshold stress of the composite exist for the creep deformation of the composite. The analysis of the creep behavior of the composite with threshold stress indicated that creep deformation was controlled by the lattice diffusion process of AS52 Mg matrix at given effective stresses and temperatures. Activation energy was also calculated to check lattice diffusion controlled creep behavior of the composite.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.248-257
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• 1994

Research in heat transfer and solidification commonly involves experimentation and mathematical modeling with associated numerical analysis and computation. Inverse problems in heat transfer are part of this paradigm. During the solidification of metal casting, an interfacial heat transfer resistance exists at the boundary between the casting and the mold, and this heat transfer resistance usually varies with time. In the case of the squeeze casting the contact heat transfer resistance is decreased by pressure and ideal contact is almost accomplished. In the present work, heat transfer coefficient, which is inverse value of the heat transfer resistance, was used for convenience. A numerical technique, Non-Linear Estimation has been adopted for calculation of the casting/mold interfacial heat transfer coefficient during the squeeze casting process. In this method, the measured temperature data from experiment were used. The computational results were applied to the analysis of heat transfer and solidification.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1051-1057
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• 2003

This study is about controlled impurities, which make metal alloys, especially AC4CH alloy that is made by restraining 0.2％ Fe and Aluminum to make a matrix material. A metal matrix composite is produced using the squeeze casting method. The first step in the squeeze casting method is to add some organic binder including aluminum borate whisker into the matrix. After the fabrication of a metal matrix composite, each is individually appended to an inanimate binder such as SiO$_2$, Al$_2$O$_3$, and TiO$_2$. Through experiments the mechanical property changes were investigated between the metal matrix composite and AC4CH alloy. This study proves the superiority of the mechanical property of a metal matrix composites over AC4CH according to the previous tests and results that were mentioned above. One excellent property of matrix material composites is the infiltrated TiO$_2$ reinforcement. This material is a good substitute for the existing materials that are used in the development of industries today.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.319-324
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• 2001

A finite element model for the process of squeeze casting for metal matrix composites (MMCs) in cylindrical mold is developed. The fluid flow and the heat transfer are the fundamental phenomena in the squeeze casing process. To describe heat transfer with solidification of molten aluminum, the energy equation in terms of temperature and enthalpy are applied to two dimensional axisymmetric model which is similar to the experimental system. And one dimensional flow model is employed to simulate the transient metal flow. The direct iteration technique was used to solve the resulting nonlinear algebraic equations. A computer program is developed to calculate the enthalpy, temperature and fluid velocity. Cooling curves and temperature distribution during infiltration and solidification are calculated for pure aluminum. The temperature is measured and recorded experimentally. At two points of the perform inside and one point of the mold outside, thermocouple wire are installed. The time-temperature data are compared with the calculated cooling curves. The experimental results show that the finite element model can estimate the solidification time and predict the cooling process.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.67-70
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• 2000

Mechanical properties of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of (15%$AI_20_3{\cdot}SiO_2$)/Al composites. Intermetallic compound formed by reaction between molten aluminum and reinforcing powder was uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3$NI using EDS and X-ray diffraction analysis. Microhardness and flexural strength of hybrid composites were higher than that of (15%$AI_20_3{\cdot}SiO_2$)/Al Composite. In-Situ fracture tests were Conducted on (15%$AI_20_3{\cdot}SiO_2$)/Al Composites and (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites to identify the microfracture process. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al composites, microcracks were initiated mainly at the short fiber / matrix interfaces. As the loading was continued, the crack propagated mainly along the separated interfacial regions and the well developed shear bands. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites, microcracks were initiated mainly by the short fiber/matrix interfacial debonding. The crack proceeded mainly through the intermetallic compound clusters