• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.161-168
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• 2015

This article aims to apply a friction stir spot welding for producing a lap joint of AA1100 aluminum alloy and SGACD zinc coated steel. The experiment was designed by MINITAB and then investigated the relation among the friction spot joint parameters. The experimental results are as follows. The friction spot joining could successively produce the lap joint of AA1100 aluminum alloy and SGACD zinc coated steel. Interaction between the rotate speed, the hold time and the tool insert speed affected to vary the tensile shear strength of the lap joint. The prediction of the optimized welding parameters that indicated the tensile shear strength of 1966 N was the rotated speed of 4000 rpm, the pin hold time of 6 sec, the pin insert rate of 6 mm/min with the S/N ratio of 66.56 that was higher than that of the total mean S/N ratio. The practical experiment of the predicted welding parameters indicated the tensile shear strength of 2165 N and had the S/N ratio of 66.70 that was higher than the predicted tensile shear strength.

• Journal of Advanced Marine Engineering and Technology
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• 제17권1호
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• pp.66-72
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• 1993

The brazing of Al to Al using Al-Si alloy filler metal was performed under different bonding conditions such as ratio of lap length to plate thickness, surface roughness and joint clearance of the lap joint. The adopted thickness of the base metal in this experiments were two kinds of 4mm and 7mm which were most commonly used in various field. Influence of several bonding conditions of Al/Al joint was quantitavely evaluated by bonding strength test, and microstructural analysis at the interlayer were performed by optical microscope. From above experiments, the optimum bonding conditions of the brazing bonding of Al/Al using Al-Si alloy filler metal was determined. The major results obtained are as follows. 1) The fracture occurs at brazed joint in the conditions of that the ratio of lap length to plate thickness is less than 2 in case of 7mm plate thickness. 2) The ratio of lap length to plate thickness which the fracture occurs at base metal is decreased with the decreasing of the plate thickness. 3) The joint strength is not affected by the surface roughness and joint clearance of the brazed part. 4) The heat-treatment of the brazed joint contribute to eliminate the boundary between the base metal and filler metal. However, the joint strength is not affected by the heat-treatment.

• 수산해양기술연구
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• 제28권1호
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• pp.53-60
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• 1992

In this study, cathodic protection experiment was carried out by Al-alloy sacrificial anode in marine environments which have specific resistance($\rho$) if 25~7000$\Omega$.cm and investigated protection potential, current density and loss rate of Al-alloy sacrificial anode. The main results resistance($\rho$) of 400$\Omega$.cm, the cathodic protection potential appears high about-720 mV(SCE). But below specific resistance($\rho$) of 300$\Omega$.cm, the cathodic protection potential appears low about-770 mV(SCE) and simultaneously, cathode is protected sufficiently. 2) The loss rate of Al-Alloy sacrificial anode became large with decreasing specific resistance and increasing the ratio(A sub(c)/A sub(a) of bared surface area of anode and cathode. 3) The loss rate of Al-alloy sacrificial anode(w) to the mean current density of anode(i) is as follows. w=ai+b (a, b : experimental constants)

• 한국결정성장학회지
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• 제22권5호
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• pp.218-222
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• 2012

FeNi alloy nanofibers have been prepared by an electrospinning process followed by air-calcination and H2 reduction to develop electromagnetic (EM) wave absorbers in the giga-hertz (GHz) frequency range. The thermal behavior and phase and morphology evolution in the synthetic processes were systematically investigated. Through the heat treatments of calcination and H2 reduction, as-spun PVP/FeNi precursor nanofiber has been stepwise transformed into nickel iron oxide and FeNi phases but the fibrous shape was maintained perfectly. The FeNi alloy nanofiber had the high aspect ratio and the average diameter of approximately 190 nm and primarily composed of FeNi nanocrystals with an average diameter of ~60 nm. The FeNi alloy nanofibers could be used for excellent EM wave absorbing materials in the GHz frequency range because the power loss of the FeNi nanofibers increased up to 20 GHz without a degradation and exhibited the superior EM wave absorption properties compared to commercial FeNi nanoparticles.

• 소성∙가공
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• 제14권6호
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• pp.553-558
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• 2005

A study on the microstructure, the texture and the formability of the samples after ECAPed and subsequent heat-treated AA 1050 aluminum alloy sheet have been carried out. The specimens after the ECAP showed a very fine grain size, a decrease of <100> // ND, and an increase of <111> // ND textures. The $\{111\}<112>,\;\{123\}<634>,\;\{110\}<001>,\;\{112\}<111>,\;\{110\}<111>,\;and\;\{013\}<231>$ texture components were increased in the specimens after the ECAP and subsequent heat-treatment at $400^{\circ}C$ for 1 hour. One of the most important properties in sheet metals is formability. The r-value or plastic strain ratio has was as a parameter that expressed the formability of sheet metals. The change of the plastic strain ratios after the ECAP and subsequent heat-treatment conditions were investigated and it was found that they were two times higher than those of the initial Al sheets. This could be attributed to the formation above texture components through the ECAP and subsequent heat-treatment of AA 1050 Aluminum alloy sheet.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.594-599
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• 2011

본 논문은 마그네슘합금 AZ31의 피로파손수명의 확률론적 특성과 신뢰성에 미치는 경계조건의 영향을 평가하였다. 경계조건으로 시편두께와 응력비 그리고 최대피로하중을 적용하였으며, 각 경계조건별로 세부 실험조건에 대한 피로균열전파실험을 수행하여 피로파손수명에 대한 통계 데이터를 획득하였다. 마그네슘합금의 피로파손수명의 통계적 해석을 위하여 3-모수 와이블분포를 사용하였다. 시편두께가 두꺼울수록, 응력비가 클수록, 그리고 최대피로하중이 작을수록 통계적 피로파손수명이 길게 나타났다. 반면에 시편두께가 얇을수록, 응력비가 작을수록, 그리고 최대피로하중이 클수록 신뢰성이 급격히 감소하였다.

• 한국정밀공학회지
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• 제14권6호
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• pp.44-51
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• 1997

Crinding of stainless steel, aluminium alloy, copper alloy, and titanium alloy are difficult to obtain high quality finish, because they have the mechanical properties such as low hardness, high toughness. The low hardness and the high toughness result in the loading of wheel and the poor surface finish. In order to perform the grinding operations for these sorts of materials easily, the discontinuous grinding wheel wiht multi-porous grooves has been newly developed. The multi-porous grooves inthe discontinuous grinding wheel were formed during grinding wheel manufacturing process. In this paper, discontinuous grinding wheels having intermittent ratio 0.66, 0.81 and number of grooves 18,32 have been manufactured and grinding surface characteristics of these grinding wheels for SUS304 have been analyzed. Discontinuous grinding temperature according to intermittent ratiohas been also estimated by simulation. The discontinuous grinding wheels increase the grinding performance considerably. It is desirable to use the discontinuous grinding wheel in grinding the materials with high efficiency and accuracy.

• 소성∙가공
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• 제33권3호
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• pp.178-184
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• 2024

In this study, we investigated the effects of extrusion ratio and extrusion temperature on the microstructure and tensile properties of extruded Mg-6Al-0.3Mn-0.3Ca-0.2Y (SEN6) alloy. As the extrusion ratio and temperature increase, dynamic recrystallization during extrusion is promoted, leading to the formation of a fully recrystallized microstructure with increased grain size. Additionally, the increases in extrusion ratio and temperature lead to texture strengthening, exhibiting a higher maximum texture intensity. The extruded materials contain three types of secondary phases, i.e., Al₈Mn₄Y, Al₂Y, and Al₂Ca, with irregular or polygonal shapes. The quantity, size, distribution, and area fraction of the second-phase particles are nearly identical between the two materials. Despite its larger grain size, the tensile yield strength of the material extruded at 450 ℃ and an extrusion ratio of 25 (450-25) is higher than that of the material extruded at 325 ℃ and an extrusion ratio of 10 (325-10), which is mainly attributed to the stronger texture hardening effect of the former. The ultimate tensile strength is similar in the two materials, owing to the higher work hardening rate in the 325-10 extrudate. Despite differences in grain size and recrystallization fraction, numerous twins are formed throughout the specimen during tensile deformation in both materials; consequently, the two materials exhibit nearly the same tensile elongation.

• 한국해양공학회지
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• 제7권1호
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• pp.124-132
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• 1993

In order to examine the effect of anisotropy and stress ratio on fatigue crack propagation rate and opening-closing behavior and also arrest behavior by single tension peak overload, the fatigue tests of constant amplitude atress and single tension peak overload adding to cycle of constant amplitude were carried out in stress ratio of -0.4, -0.2, and 0.4 with materials of T-L and L-T directions in 2024-T3 aluminum alloy plate. Crack opening-closing begavior were measured by the compliance method using COD gage and strain gage. In case of the crack opening-closing behavior was measured by strain gage, the effect of stress ratio is unchangeable. But in the case of COD gage, that is remarkably decreased. Fictitious effective stress intensity factor(U sub(f)) and effective stress intensity factor ratio(U) in L-T direction was higher than those in T-L direction and also threshold arrest overload ratio incrased as stress ratio decreased and that of T-L direction was higher than that in L-T direction.

• 한국수소및신에너지학회논문집
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• 제3권2호
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• pp.9-15
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• 1992

Electroless copper plating method using an alkaline bath have been employed in copper coating of the (LM)Ni4.5Co0.1MnO.2A10.2 hydrogen storage alloy powders for electrode preparation. The plating were conducted without any pretreatment of alloy powders. For the preparation of the electrodes, about 0.12g of the copper coated alloy powder (copper to alloy ratio 1/3 by weight) was compacted with pressure of 6 tons/cm2 at room temperature. The disk-type compacts had a diameter of 10mm and thickness of about 0.24mm. The electrode characteristics were examined through SEM observations and electrochemical measurements in a half cell. The electrochemical measurement showed that the maximum discharge capacity of the electrodes prepared by using alkaline bath were 245mAh per gram of coated alloy (327mAh per gram of alloy) and appeared a considerable degradation with increasing number of cycles. The decrease of the discharge capacity after 100 cycles was about 30% It can be suggested that, with a slight of improvement, this electroless copper plating method could be applied to the preparation of the rare earth-nickel based alloy electrode.