• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.69-75
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• 2009

This study is analyzed by impact simulation according to material property at terminal case of hand phone. Maximum equivalent stress or strain at plastic is 40 times as great as that at magnesium alloy. And the next greatest stress or strain is shown at aluminium alloy. The value of maximum equivalent stress is shown as 6.5 Mpa in case of plastic, magnesium alloy and aluminium alloy. Maximum shear strain at plastic is 40 times as great as that at magnesium alloy. And the next greatest strain is shown at aluminium alloy. The value of deformation or strain at magnesium alloy and aluminium alloy is not different.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.1
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• pp.137-163
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• 1990

The properties of a investment material can be described by the consistency at the slurry state, the setting time, the compressive strength and the thermal expansion during the casting. In this study the effect of the production parameters which are included the ratio of quartz and cristobalite, the content of binder, the water powder ratio and the content and concentration of additives on the Properties of the gypsum-bonded investments has been investigated with help of the consistency test, the vicat needle test, the compressive strength test, the thermal expansion test, x-ray diffraction and DTA thermal differential test. The experimental results showed that the constitution of a investment with W/P ratio of 0.34, 30% of gypsum, 0.8% aluminium sulfate, 2% magnesium sulfate, 0.6% sodium phosphate was adapted for the properties of the KDA Spec. No. 13 type I investment. The important experimental results are summarized as follows. 1. The consistency of the investment decreased with increasing amount of aluminium sulfate and decreasing amount of sodium phosphate. An addition of magnesium sulfate up to 2% an increase of the consistency was shown. But 3% magnesium sulfate in investment showed a decrease of the consistency. The consistency did not vary significantly with a variation of the content of gypsum and cristobalite and the W/P ratio. 2. Aluminium sulfate and the magnesium sulfate promoted the hardening and the aluminium phosphate delayed the hardening. The setting time increased with amount of gypsum. The effect of the matrix on the setting time was insignificant. With the W/P ratio of 0.34 the setting time was 14 min. 3. The compressive strength decreased with the amount of aluminium sulfate up to 0.25% and increased with the amount of aluminium sulfate greater than 3%. The compressive strength decreased as decreasing the amount of magnesium sulfate and gypsum and as increasing the W/P ratio. The effect of the refractory on the compressive strength was also not significant. With the W/P ratio of 0.34 the compressive strength was $34Kg/mm^2$. 4. The 1st thermal expansion was found at the temperature near and the steady state or the contraction stage was found at the temperature between $250^{\circ}C$ and $500^{\circ}C$. After this stage the 2nd thermal expansion took place at the temperature near $500^{\circ}C$. The amount of thermal expansion increased with decreasing the content of magnesium sulfate, aluminium sulfate and gypsum and the W/P ratio. And the amount of thermal expansion increased as the content of sodium phosphate and cristobalite. With the W/P ratio of 0.34 the amount of total expansion was 1.2%.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.139-165
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• 1991

The properties of a investment material can be described by the consistency at the slurry state, the setting time, the compressive strength and the thermal expansion during the casting. In this study the effect of the production parameters which are included the ratio of quartz and cristobalite, the content of binder, the water powder ratio and the content and concentration of additives on the properties of the gypsum-bonded investments has been investigated with help of the consistency test, the vicat needle test, the compressive strength test, the thermal expansion test, x-ray diffraction and DTA thermal differential test. The experimental results showed that the constitution of a investment with W/P ratio of 0.34, 30% of gypsum, 0.8% aluminium sulfate, 2% magnesium sulfate, 0.6% sodium phosphate was adapted for the properties of the KDA Spec. No. 13 type I investment. The important experimental results are summarized as follows. 1. The consistency of the investment decreased with increasing amount of aluminium sulfate and decreasing amount of sodium phosphate. An addition of magnesium sulfate up to 2% an increase of the consistency was shown. But 3% magnesium sulfate in investment showed a decrease of consistency. The consistency did not vary significantly with a variation of the content of gypsum and cristobalite and the W/P ratio. 2. Aluminium sulfata and the magnesium sulfate promoted the hardening and the aluminium phoshpate delayed the hardening. The setting time increased with amount of gypsum. The effect of the matrix on the setting time was insignificant. With the W/P ratio of 0.34 the setting time was 14 min. 3. The compressive strength decreased with the amount of aluminium sulfate up to 0.25% and increased with the amount of aluminium sulfate greater than 3%. The compressive strength decreased as decreasing the amount of magnesium sulfate and gypsum and as increasing the W/P ratio. The effect fo the refractory on the compressive strength was also not significant. With the W/P ratio of 0.34 the compressive strength was $34Kg/mm^2$. 4. The 1st thermal expansion was found at the temperature near $250^{\circ}C$ and the steady state or the contraction stage was found at the temperature between $250^{\circ}C$ and $500^{\circ}C$. After this stage the 2nd thermal expansion took place at the temperature near $500^{\circ}C$. The amount of thermal expansion increased with decreasing the content of magnesium sulfate, aluminium sulfate and gypsum and the W/P ratio. And the amount of thermal expansion increased as the content of sodium phosphate ad cristobalite. With the W/P ratio of 0.34 the amount of total expansion was 1.2%.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.231-236
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• 2011

The effects of magnesium and calcium ions on phosphorus removal by aluminium coagulation were investigated with various jar tests using settled raw sewage. Maximum TP (total phosphate) removal occurred at pH around 5~6 with aluminium coagulation, and it decreased above pH 6. TP and $H_nPO_4^{n-3}$ removal efficiencies, however, were kept above 95% at pH above 6 by adding the divalent metallic ions like magnesium or calcium ions on aluminium coagulation process. At molar ratio of Al/P ($Al^{3+}/H_nPO_4^{n-3}$) above 3, TP removal efficiency was as high as 80%, and residual TP less than 0.2 mg/L occurred at Al/P ratio above 6. TP removal efficiency was improved by adding magnesium or calcium ions and the optimum $Al^{3+}/Mg^{2+}$ and $Al^{3+}/Ca^{2+}$ ratios were about 2. The required dose of aluminium coagulant was reduced for equivalent amount of TP removal by adding magnesium or calcium ions, as a result sludge generation was also reduced.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.83-89
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• 2016

As the world's industrial development quickens, the highways and regional expressways have been expanding to serve the logistics and transportation needs of people. The burgeoning road construction has led to a growing interest in roadside installations. These must have reliable performance over long periods, reduced maintenance and high durability. Steel roadside barriers are prone to corrosion and other compromises to their functionality. Therefore, using high anti-corrosion steel material is now seen as a viable solution to this problem. Thus, the objective of this paper is to expand the scope of applications for high anti-corrosion steel material for roadside barriers. This paper assesses the impact safety such as structural performance, occupant protection performance and post-impact vehicular response performance by a simulation review on roadside barriers built with high strength anti-corrosion steel materials named as hot-dip zinc-aluminium-magnesium alloy-coated steel. The simulation test results for the roadside barriers built with high strength anti-corrosion steels with reduced sectional thickness meet the safety evaluation criteria, hence the proposed roadside barrier made by high strength and high anti-corrosion hot-dip zinc-aluminium-magnesium alloy-coated steel will be a good solution to serve safe impact performance as well as save maintenance cost.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.12-19
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• 2022

The propellants used in the gas generator of the ducted rocket are fuel-rich propellants, which contain an excessive amount of metal fuel and a small amount of oxidizing agent compared to general solid rocket propellants. In this paper, boron powder and MgAl(Magnesium-Aluminium alloy) were applied to produce fuel-rich propellants. The optimum formulation was determined by characterizing these metal fuel-rich propellants. Analysis of combustion products in the gas generators confirmed that the fuel-rich propellants containing fine boron powder itself instead of boron-bead could be useful in gas generators.

• Advances in materials Research
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• v.1 no.2
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• pp.147-160
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• 2012

In the present study, diffusion bonding was carried out between AZ31B magnesium and AA2024 aluminium in the temperature range of $405^{\circ}C$ to $475^{\circ}C$ for 15 min to 85 min and 5MPa to 20 MPa uniaxial loads was applied. Interface quality of the joints was assessed by microhardness and shear testing. Also, the bonding interfaces were analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive spectrometer and XRD. The maximum bonding and shear strength was obtained at $440^{\circ}C$, 12 MPa and 70 min. The maximum hardness values were obtained from the area next to the interface in magnesium side of the joint. The hardness values were found to decrease with increasing distance from the interface in magnesium side while it remained constant in aluminium side. It was seen that the diffusion transition zone near the interface consists of various phases of $MgAl_2O_4$, $Mg_2SiO_4$ and $Al_2SiO_5$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.128-131
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• 2004

Magnesium alloys are being extensively used in weight-saving applications and as a potential replacement for plastics in electronic and computer applications. Magnesium alloy has some good characteristics, EMI shielding property and high specific strength. Nevertheless their high brittleness make it uneasy to process the magnesium. Magnesium alloys are extruded like aluminium alloys. The present work was done to find a characteristic of magnesium alloy(AZ31) changing the extrusion ratio 8.5, 19.1, 49 respectly and changing the die half angle $30^{\circ},\;45^{\circ},\;60^{\circ}$. Here this present done by the hydrostatic extrusion in the hot condition, $310^{\circ}$. The higher the extrusion ratio goes, the higher the extrusion force goes.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.573-579
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• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.30-35
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• 2003

In this study, sand cast AZ91E and zirconium grain refined MEZ are representative of two typical groups of magnesium alloys: those containing aluminium and those containing no aluminium but with zirconium as a grain refiner. The corrosion performance of these two alloys was evaluated and compared in 5%wt NaCI solution through measurements of weight loss and polarisation curves and examination of microstructure. Corrosion damage of AZ91E was deeper and more localised than that of MEZ, while MEZ had a lower rate of cathodic hydrogen evolution and a higher rate of anodic dissolution than AZ91E. These differences in behaviour can be related to the differences in microstructure and chemical composition between the two alloys.