• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.310-313
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• 2005

In recent years, as the robot technology is developed, the researches on the artificial muscle actuator that enable robot to move dexterously like biological organ become active. The widely used materials for artificial muscle are the shape memory alloy and the electro-active polymer. These actuators have the higher energy density than the electro-mechanical actuator such as motor. However, there are some drawbacks for actuator. SMA has the hysterical dynamic characteristics. In this paper, the simulation of anthropomophic robotic hand is performed using ADAMS and the segmented binary control for reducing the hysteresis of SMA is proposed. SMA is controlled by thermo-electric module. The relations between the force and the hysteresis are developed to verify the validity of the suggested method.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.361-364
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• 2018

Binary Ti-Al alloys below 51.0 mass%Al content exhibit a breakaway, transferring from parabolic to linear rate law. The second $Al_2O_3$ layer might have some protectiveness before breakaway. Ti-63.1 mass%Al oxidized at 1173 K under parabolic law. Breakaway oxidation is observed in every alloy, except for Ti-63.1 mass%Al. After breakaway, oxidation rates of the binary TiAl alloys below 34.5 mass%Al obey almost linear kinetics. The corrosion rate of Ti-63.1 mass%Al appears to be almost parabolic. As content greater than 63.0 mass% is found to be necessary to form a protective alumina film. Addition of Mo improves the oxidation resistance dramatically. No breakaway is observed at 1123 K, and breakaway is delayed by Mo addition at 1173 K. At 1123 K, no breakaway, but a parabolic increase in mass gain, are observed in the Mo-added TiAl alloys. The binary Ti-34.5 mass%Al exhibits a transfer from parabolic to linear kinetics. At 1173 K, the binary alloys show vary fast linear oxidation and even the Mo-added alloys exhibit breakaway oxidation. The 2.0 mass%Mo-added TiAl exhibits a slope between linear and parabolic. At values of 4.0 and 6.0 mass% added TiAl alloys, slightly larger rates are observed than those for the parabolic rate law, even after breakaway. On those alloys, the second $Al_2O_3$ layer appears to be persistently continuous. Oxidation resistance is considerably degraded by the addition of Mn. Mn appears to have the effect of breaking the continuity of the second $Al_2O_3$ layer.

• 연구논문집
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• s.29
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• pp.163-171
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• 1999

A new titanium alloy system. Ti-xFe-ySi (x,y=0-4 wt%). was designed and characterized with the point at low cost and high strength for casting applications. Fe improved room and elevated temperature mechanical properties owing to solid solution hardening and beta phase stabilization. Si yielded titanium silicides and Si addition over 1 wt% resulted in poor ductility due to coarse silicide chains at prior beta boundaries. The optimum composition was found to be Ti-4Fe-(0.5-1)Si in the viewpoint of tensile strength and ductility which are comparable to the Ti-6Al-4V. The metal-mould reaction was also examined for Ti-xFe and Ti-xSi binary alloy system. The thickness of surface reaction layer w as not affected significantly with Fe content, while it was decreased with Si content. In the Ti-4Si alloy, no reaction layer was found. The depth of surface hardening layer was about $200\mum$ regardless of the mould materials.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.05a
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• pp.95-96
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• 2013

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1437-1446
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• 2000

A numerical analysis on the freeze coating process of a non-isothermal finite dimensional plate with a binary alloy is performed to investigate the growth and decay behavior of the solid and the mushy layer of the freeze coat and a complete procedure to calculate the process is obtained in this study. The continuously varying solid and mushy layers are immobilized by a coordinate transform and the resulting governing differential equations are solved by a finite difference technique. To account for the latent heat release and property change during solidification, proper phase change models are adopted. And the convection in the liquid melt is modeled as an appropriate heat transfer boundary condition at the liquid/mushy interface. The present results are compared with analytic solutions derived for the freeze coating of infinite dimensional plates and the discrepancy is found to be less than 0.5 percent in relative magnitude for all simulation cases. In addition the conservation of thermal energy is checked. The results show that the freeze coat grows proportional to the 1.2 square of axial position as predicted by analytic solutions ar first. But after the short period of initial growth, the growth rate of the freeze coat gradually decreases and finally the freeze coat starts to decay. The effects of various non-dimensional processing parameters on the behavior of freeze coat are also investigated.

• Journal of Powder Materials
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• v.5 no.2
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• pp.98-110
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• 1998

$Ti_{52}Al_{48}$ and $(Ti_{52}Al_{48})_{100-x}B_x(x=0.5, 2, 5)$ alloys have been Produced by mechanical milling in an attritor mill using prealloyed powders. Microstructure of binary $Ti_{52}Al_{48}$ powders consists of grains of hexagonal phase whose structure is very close to $Ti_2Al$. $(Ti_{52}Al_{48})_{95}B_5$ powders contains TiB2 in addition to matrix grains of hexagonal phase. The grain sizes in the as-milled powders of both alloys are nanocrystalline. The mechanically alloyed powders were consolidated by vacuum hot pressing (VHP) at 100$0^{\circ}C$ for 2 hours, resulting in a material which is fully dense. Microstructure of consolidated binary alloy consists of $\gamma$-TiAl phase with dispersions of $Ti_2AlN$ and $A1_2O_3$ phases located along the grain boundaries. Binary alloy shows a significant coarsening in grain and dispersoid sizes. On the other hand, microstructure of B containing alloy consists of $\gamma$-TiAl grains with fine dispersions of $TiB_2$ within the grains and shows the minimal coarsening during annealing. The vacuum hot pressed billets were subjected to various heat treatments, and the mechanical properties were measured by compression testing at room temperature. Mechanically alloyed materials show much better combinations of strength and fracture strain compared with the ingot-cast TiAl, indicating the effectiveness of mechanical alloying in improving the mechanical properties.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.123-126
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• 2007

In this work, the dispersion behavior of $Y_2O_3$ particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and ${\theta}$ phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of $Y_2O_3$ particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of $Y_2O_3$ particles is probably due to the difference in the val- ues of specific gravity between $Y_2O_3$ particles and primary phases. At eutectic composition, $Y_2O_3$ particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that $Y_2O_3$ particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.15-23
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• 1991

The damping capacities of the nonthermoelastic bcc type lath martensite and of the nonthermoelastic hcp type thin plate martensite in Fe-Mn alloys were studied. Fe-17%Mn alloy showing the hcp type thin plate martensite was superior to Fe-4%Mn alloy having the bcc type lath martensite in damping capacity. The damping capacity of the Fe-17%Mn alloy became greater with increasing the hcp martensite volume fraction. The damping mechanism of the Fe-4%Mn alloy was well explained by the dislocation model. However, the damping mechanism of the Fe-17%Mn alloy was explained on the basis of austenite/martensite interface moving model. The two alloys showed almost same levels of tensile strength. However, the elongation was greater in the Fe-17%Mn alloy than in the Fe-4%Mn alloy, showing lower yield strength in the former than in the latter. This result was considered to be attributed to formation of stress-induced martensite during tension test.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1043-1044
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• 2006

Compositional dependence of corrosion behavior of rapidly solidified Mg-rich Mg-Zn-Y alloys in NaCl aqueous solution has been investigated. Mg-Zn-Y ternary alloys containing small amounts of Zn exhibited low corrosion rate, although the $Mg_{98}Y_2$ (at. %) binary alloy showed severe corrosion with violet evolution of hydrogen. The alloy with highest corrosion-resistance was $Mg_{97.25}Zn_{0.75_Y_2$, its corrosion rate was about 1 mm year-1 in 0.17 M (1.0 wt. %) NaCl solution. $Mg_{97.25}Zn_{0.75}Y_2$ alloy exhibited passive region in anodic polarization curves when immersed in NaCl solution. Rapidly solidification and small amount of Zn addition may bring about an increase in electrochemical homogeneity of Mg-Zn-Y alloys, resulting in enhancement of corrosion resistance.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.113-119
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• 1995

We have reported that an Fe-17wt%Mn alloy exhibits the highest damping capacity in the Fe-Mn binary system. In the present work, the effects of copper content on the damping capacity, atmospheric corrosion and mechanical properties were studied. The damping capacities were measured at room temperature for the air cooled Fe-17wt%Mn alloy having copper content from 0.1wt% to 1.1wt%. The damping capacity of the Fe-17wt %Mn alloy was decreased with increasing copper content. However, the addition of Copper was found to improve mechanical properties and atmospheric corrosion resistance. These mechanical properties were attributed to the formation of stress-induced martensite during tensile test.