• Composites Research
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• 제20권3호
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• pp.37-42
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• 2007

금속복합재료에서는 강화재와 기지재 사이의 열팽창계수 차이에 의해 복합재료 내부에 잔류응력이 남아있어 복합재료 전체의 강도저하를 가져온다. 본 연구에서는 TiNi 형상기억합금을 강화재료로써 이러한 잔류응력 문제를 해결하기 위하여 이용하였다. TiNi 형상기억합금은 형상기억효과를 이용하여 복합재료의 잔류응력문제를 해결할 뿐만 아니라 복합재료의 인장강도를 증가시키는 역할을 한다. 핫프레스 방법에 의해 제작된 형상기억복합재료의 강도증가를 위하여 냉간압연을 실시하여 실험을 실시하였다. 이와 같이 제작된 형상기억복합재료의 저온에서의 미시적 손상거동을 평가하기 위하여 음향방출기법을 이용하였다. 또한 열충격을 받은 시험편의 손상에 대한 연구도 이루어졌다.

• 전기학회논문지
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• 제63권4호
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• pp.583-588
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• 2014

In this study, there are examined to the grounding of lightning protection system and electrical continuity tests in the field. The standard for lightning protection system is different design or construction according to the characteristics of the structure. Ground is measured and compared at least four locations. According to the measured results in the field, the sampled values of the ground resistance are measured $5{\Omega}$ or less and the difference between each value is suitable as $0.2{\Omega}$ or less. The values of the electrical continuity test between ground and metal bodies are measured 3 groups such as isolated portion, the mechanical contacted portion, and the electrical continuity portion measuring $0.2{\Omega}$ or less. It is measured to be less than $0.2{\Omega}$ at all in metal bodies of underground. A metal body installed inside the structure is not isolated, but the resistance values are higher than $0.2{\Omega}$. Therefore, It must be carried out the structure having lightning protection system confirm the LPL(lightning protection level) and design the strategy.

• 유공압시스템학회논문집
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• 제7권1호
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• pp.1-5
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• 2010

This paper presents the experimental results of the radial piston type oil pump with new mechanism for a metal diaphragm hydrogen compressor. Generally, metal diaphragm type hydrogen compressor systems are operated by oil hydraulic power. In this system an oil compensating pump has been demanded to compensate for a leakage oil head chamber. The metal diaphragm type hydrogen compressor consists of an oil compensating pump, commonly used hydraulic piston pump and driven by main crank shaft. The radial piston type oil compensating pump with new rolling contacted piston mechanism is developed and experimented. The developed piston element of the radial piston pump consists of piston, steel ball, return spring, two check valves, eccentric cam and ball racer. In this study, designed 4 type pistons as and orifice hole. Operating characteristics and pressure ripple characteristics are tested under no load to 60bar loaded with every 20bar increasing step and pressure ripple and flow rate are experimentally investigated.

• 소성∙가공
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• 제24권2호
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• pp.115-120
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• 2015

Deep drawing of cylindrical cups is one of the most fundamental and important processes in sheet metal forming. Circular cups are widely used in industrial fields such as automobile and electronic appliances. Some of these cups are formed by a one-stage process, others such as battery cases and beverage cans are made by a multi-stage process. In the current study the multi-stage deep drawing of aluminum sheet metal is examined. The process consists of two deep drawing operations followed by two ironing operations. The press die, which can be used for the four-stage forming process, was manufactured allowing punch and die components to be easily changed for various experiments. The rolling direction of both the sheet and the drawn cups was always positioned toward the horizontal x-direction on the die face to minimize experimental errors during the progressive forming. The dimensional accuracy of the cylindrical cups formed at each stage and the earing defect due to the anisotropy of sheet were investigated. The influence of anisotropy on the thickness distribution was also examined. Both the thickness and the outer diameter of the cups were measured and compared for each set of experimental conditions. It was found that the dimensional accuracy of cups rapidly improves by employing the ironing process and also by increasing the amount of ironing.

• 한국생산제조학회지
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• 제9권6호
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• pp.82-88
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• 2000

The effect of the welding for the offshore structure in the TMCP steel on the fatigue crack propagation rate and crack opening-and-closure behavior was examined. The welding anisotropy of the TMCP steel and crack propagation characteristics of the excessive loading were reviewed. (1) It seemed that a heat which was generated by the welding made a compressive residual stress over the base metal, so fatigue crack propagation rate was placed lower than in case of the base metal. (20 In the base metal, an effect of the anisotropy which has an effect of fatigue crack propagation rate of the excessive load and the constant amplitude laos was not found but in the welding material case, fatigue crack propagation rate of the excessive load in the specimen of the width direction was located in the retard side as compared with a specimen rolling direction. (3) A crack opening ratio of the used TMCP stel in this study was not changed after excessive loading but a retard phenomenon of crack propagation was observed. Consequently, it was thought that all of the retard phenomenon of crack propagation did not only a cause of the crack opening-and-closure phenomenon.

• Advances in materials Research
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• 제9권2호
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• pp.99-107
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• 2020

Reinforced aluminum alloy base composites have become increasingly popular for engineering applications, since they usually possess several desirable properties. Recently, Warm Accumulative Roll Bonding (WARB) process has been used as a new novel process to fabricate particle reinforced metal matrix composites. In the present study, TiO₂ particles are used as reinforcement in aluminum metal matrix composites fabricated through warm accumulative roll bonding process. Firstly, the raw aluminum alloy 1060 strips with TiO₂ as reinforcement particle were roll bonded to four accumulative rolling cycles by preheating for 5 min at 300℃before each cycle. The mechanical and bonding properties of composites have been studied versus different volume contents of TiO₂ particles by tensile test, peeling test and vickers micro-hardness test. Moreover, the fracture surface and peeling surface of samples after the tensile test and peeling test have been studied versus different amount of TiO₂ volume contents by scanning electron microscopy. The results indicated that the strength and the average vickers micro-hardness of composites improved by increasing the volume content of TiO₂ particles and the amount of their elongation and bonding strength decreased significantly.

• 한국주조공학회지
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• 제38권3호
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• pp.55-59
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• 2018

To optimize the conductivity and to reduce the weight by as much as possible, Al-Cu composites were prepared through a suction-casting procedure. Pure copper metal foam was infiltrated by melted aluminum with the use of the vacuum, after which warm rolling was conducted to remove several remaining pores at the interface between the Cu foam and the aluminum matrix. Despite the short casting time, significant dissolution of Cu into the melt was observed. Moreover, it was found that various Al-Cu intermetallic compounds arose at the interface during the isothermal heating process after the casting and rolling steps. The average thickness of the Al-Cu intermetallic compound tended to increase in proportion to the heating time. The electrical and thermal conductivity levels of the cast composites were found to be comparatively low, mainly due to the dissolution of the Cu foam and the formation of intermetallics at the interface.

• Progress in Superconductivity
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• 제13권3호
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• pp.184-188
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• 2012

$MgB_2$ superconducting sheets have been fabricated by powder rolling method using mixture of Mg and B powders. Sheet-type $MgB_2$ bulk samples of ~10 mm width and 50-100 mm long were squeezed out after compacted by two rotating rolls of 130 mm diameter with gap distance of 0.5 mm and speed of ~40 cm/min (~1 rpm). The nominal composition of Mg, which is ductile metal, was added up to 30% to facilitate forming the $MgB_2$ sheets. The annealed samples at $900^{\circ}C$ and 3 hrs showed superconducting transition temperature of ~32 K and critical current densities at zero fields were ${\sim}10^5A/cm^2$ at 5 K and ${\sim}5{\times}10^4A/cm^2$ at 20 K.

• Journal of Magnetics
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• 제16권2호
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• pp.177-180
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• 2011

0.30 mm thick and 90 mm wide thin foils made of Fe-6.5wt.%Si alloy were successfully fabricated by traditional rolling. The as-rolled sheets had good shapes and shining metal luster. The effects of annealing temperature on the magnetic properties of the sheets were investigated. Excellent Dc properties ($H_c$: 11.55 A/m, ${\mu}_m$: 23710, and $B_s$: 1.439 T) were obtained at an annealing temperature of 1453 K for 1.5 h. At low frequencies ($\leq$ 1 kHz), heat treatment temperature has little effect on iron loss which remained at the level of 9.8 W/kg. Annealing at 1273 K for 1.5 h is optimum for frequencies above 5 kHz.

• Journal of Welding and Joining
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• 제12권1호
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• pp.73-79
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• 1994

Low cycle fatigue test was performed by companion specimens method to compare the properties of cyclic strain for the weldments of controlled rolling steel CR60 and welding structural steel SM58Q. And the result does not showed any difference of low cycle fatigue life between weldments. Especially, the values of coefficient of cyclic plastic strain $C_{p}$ and exponent of cyclic plastic strain $K_{p}$ of heat affected zones of CR60 steel and SM58Q steel were same. And $C_{p}$ and $K_{p}$ of CR60 steel were equal to the values of weld it means a good combination between the base metal, the heat affected zone and the weld of CR60 steel.eel.eel.