• Journal of Korea Foundry Society
• /
• v.28 no.3
• /
• pp.136-140
• /
• 2008

A new concept of salt core, a melting temperature of which is lower than the solidus temperature of cast alloy, was introduced to produced an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The main goal of this study is to develop a new integrated net-shape forming technology using fusible core of lower melting temperature than that of a casting alloy. This integrated net-shape forming technology would be very successful and cost-effective for producing the integrated products having a complicated inner shape or requiring under-cut. The technology for measuring and evaluating a various property of fusible core such as a thermal conductivity and thermal expansion coefficient, melting temperature was established. Also, the work space can be cleaned without a pollution inducing products.

• Journal of Korea Foundry Society
• /
• v.19 no.5
• /
• pp.403-409
• /
• 1999

Mg-Zn-Zr ternary alloys containing 6wt% Zn and (0, 0.4, 0.6)wt% Zr, which is added for grain refinement, can be cast into complex shape by squeeze casting. The influence of Zn and Zr as additional elements on microstructure and mechanical characteristics is investigated by OM, SEM, WDX, XRD and microvickers hardness measurement. The microstructure of Mg-Zn-Zr alloys consists of primary ${\alpha}-Mg$ and MgZn eutectic compound between dendrites. The grain size is decreased from $136{\mu}m$ to $97\;{\mu}m$ by Zr addition, resulting in that the hardness is increased from 42Hv to 59Hv. Furthermore, the grain size is changed to $83{\beta}$ and the hardness is increased to 65Hv by additional infiltration pressure. These results indicate that the Zr addition and additional infiltration pressure are effective for grain refinement acting as an important factor to increase the hardness. The increment in hardness by the Zr addition is slightly larger than that by the additional infiltration pressure.

• Journal of Korea Foundry Society
• /
• v.17 no.3
• /
• pp.267-275
• /
• 1997

Fabrication of high strength Mg-Li-Al alloys by squeeze casting was established by the stabilization of melt and mold temperatures, applied pressure and the refining method. The entrapment of inclusions during pouring was prevented using 30 ppi alumina foam filter. The as-cast microstructure consists of a mixture of ${\alpha}$ and ${\beta}$ phases including AILi and $MgLi_2$, Al particles, which are distributed in the ${\beta}$ matrix. The grain sizes of gravity and squeeze casting alloys were 288 ${\mu}m$ and 207 ${\mu}m$ respectively. The addition of Al in Mg-Li alloys promoted the formation of second phase particles, which were adjusted to optimize the properties of Mg-Li-Al alloys. The Mg-10wt%Li-5wt%Al alloy after heat treatment at $350^{\circ}C$ for 1 hour showed the maximum hardness value. This is due to the facts that the amounts of ${\alpha}$ and ${\beta}$ phases and their distributions are dependent upon the solution treatment temperature, and that the amounts of AILi and $MgLi_2Al$ particles are dependent upon the Al content.

• Tribology and Lubricants
• /
• v.40 no.1
• /
• pp.28-37
• /
• 2024

This paper presents the development of a squeeze film damper (SFD) test rig and experimental identification of the effects of clearance, damper length, journal eccentricity ratio, excitation amplitude, oil supply pressure, and oil flow rate on the damping coefficients of a test SFD with open ends and a central groove. Test data are compared with predictions from a simple model developed for short SFDs with open ends and a central groove. The test results show a significant decrease in the damping coefficient with increasing clearance and a dramatic increase with damper length, which are in good agreement with the simple model predictions. According to the simple model, the damping coefficient is inversely proportional to the cube of the clearance and directly proportional to the cube of the length. An increase in the journal eccentricity ratio results in a dramatic increase in the damping coefficient by as much as 15 times that of the concentric case, particularly at low excitation frequencies. By contrast, the measured damping coefficient remains almost constant with changes in the excitation amplitude and supply pressure, which are not major factors in the damper design. In general, the test data agree well with the simple model predictions, excluding cases that show increases in the SFD length and journal eccentricity, which indicate significant dependency on the excitation frequency.

• Tribology and Lubricants
• /
• v.40 no.2
• /
• pp.54-60
• /
• 2024

This study experimentally identifies the effects of end shape, clearance, total damper length, journal eccentricity ratio, oil supply pressure, and oil flow rate on the damping coefficient of a squeeze film damper (SFD) with piston ring seal ends and a central groove. The SFD is composed of a lubricating fluid flowing between the outer race of a rolling element bearing and cartridge, along with an anti-rotation pin to prevent the rotation of the outer race. The device provides additional viscous damping to a rotating system. Additionally, piston ring seals attached at both ends of the damper increase the damping coefficient of the rotating system by reducing oil leakage. Because these different design conditions affect the damping coefficient of an SFD, we perform experiments including different conditions. Tests show that the damping coefficient increases significantly in the SFD with piston ring seal ends compared with the SFD with open ends. The damping coefficient also increases with increasing total damper length and journal eccentricity ratio, and decreases with increasing clearance. Additionally, in contrast to the trend observed for the SFD with open ends, the damping coefficient for the SFD with piston ring seal ends increases with increasing supply pressure and flow rate as the frequency decreases but shows consistent results as the frequency increases.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.208.2-208.2
• /
• 2005

• Journal of Korea Foundry Society
• /
• v.14 no.3
• /
• pp.258-266
• /
• 1994

AC4A $Al/Al_2O_3+SiC_p$ hybrid composites were fabricated by the squeeze infiltration technique. Effect of applied pressure, volume fraction of reinforcement($Al_2O_3$ and SiC) and SiC particle size($4.5{\mu}m$, $6.5{\mu}m$ and $9.3{\mu}m$) on the solidification microstructure of the hybrid composites were examined. Mechanical properties were estimated preliminarly by fractographic observation, hardness measurement and wear test. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements and refined matrix. Some aggregation of SiC particle caused by particle pushing was observed especially in the hybrid composites containg in fine particle($4.5{\mu}m$). Refined matrix was attributed to applied pressure and increased nucleation sites with addition of reinforcements. Fractured facet also revealed finer for the hybrid composites possibly due to refined matrix. Hardness and wear resistance increased with volume fraction of reinforcements. For hybrid composites with $9.3{\mu}m$ SiC, hardness was somewhat lower and wear resistance higher than other composites.

• Journal of Korea Foundry Society
• /
• v.18 no.3
• /
• pp.275-282
• /
• 1998

The squeeze casting of a Mg-5wt%Al-0.6wt%Zr alloy was carried out to investigate the conditions for the formation and the prevention of macrodefects, such as macrosegregation and shrinkage defects. The effects of the process parameters, the applied pressure, the die temperature, and the pouring temperature on the formation of macrodefcts were investigated in correlation with the evolution of macrostructure. Three types of macrodefects were found; macrosegregation only, shrinkage defects only, both macrosegregation and shrinkage defects. It was found that the pouring temperature, the die temperature, and the applied pressure are closely related to the formation of macrodefects. Sound castings without macrosegregation and shrinkage defects can be obtained under the conditions of 80 MPa$730^{\circ}C$$760^{\circ}C$, and $180^{\circ}C$<$T_D$<$250^{\circ}C$.

• Journal of the Korean Society of Safety
• /
• v.22 no.6
• /
• pp.27-34
• /
• 2007

Static or dynamic elastomeric O-ring seals are installed between joining parts, and play key roles of high pressure-tightening. Sealing performance and structural safety of the O-ring are dependent on groove design, plain diameter, squeeze and applications such as pressure and temperature. In this study, to solve O-ring problem squeezed and highly pressurized under laterally one-sided constrained condition, hyperelastic FE analyses are performed, and FE results are compared with measured ones by computer-aided tomography, deformed shape and extrusion depth of the O-ring. Through the comparisons, FE analysis technique was verified. In order to evaluate design sensitivity, Taguchi method was used to select FE analysis cases. Adjustment parameters are clearance gap, groove comer radius, plain diameter and squeeze. By means of verified FE analysis technique, it has been analysed how the parameters have effects on contact stress fields, internal stress fields, and extrusion depths. Sealing performance has been evaluated based on contact stress fields and contact widths, and structural safety on internal stress and strain, extrusion lengths.

• Journal of the Korean Society of Safety
• /
• v.18 no.3
• /
• pp.8-13
• /
• 2003

Equivalent Reynolds equation of truncated cone type SFD bearing using nonnewtonian EV fluid is derived. The 3 nondimensional oil film pressures and its forces are obtained with axial and circumferential pressure gradient of bearing respectively, and dynamic characteristics for the stability of rotor-bearing system are obtaind through the governing equation for an elastic rotational shaft. It is shown that EV fluid is less sensitive to the changes of oil-film than newtonian fluids for dynamic characteristics. Therefore, results show that it is better to use an EV fluid with truncated cone type SFD bearing for the vibration control of rotational machines.