• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.5-10
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• 2001

Due to the development of high-strength fibers and adhesives, it is now possible to repair cracked metallic plates by bonding reinforced patches to the plate over the crack. In this study, pre-cracked aluminum 6061-T6 alloy plates repaired with bonded carbon/epoxy composite patch are applied to investigate the effect of various patch shapes on the tensile strength and the fatigue behavior of the structure. A non-patch-boned cased and 2 type-50$\times$50, 40$\times$20 mm-composite patch-bonded cases were tested to obtain fracture loads and fatigue crack growth rate. The results showed that the patch-bonded repair improves the static strength by 17% and the fatigue life by 200% compared to non-repaired case. It means that patch-boned repair is more effective in the fatigue life. It was also revealed that the patching method along crack growth direction is more efficient in cost and weight reduction. By observing the fractography, patch-bonded repair specimens demonstrated zigzag fracture patterns compared with the non-patched specimens, which shows a typical ductile fracture.

• Korean Journal of Materials Research
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• v.32 no.3
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• pp.161-167
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• 2022

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061/AA5052 layered sheet. Two AA6061 and one AA5052 sheets of 2mm thickness, 40mm width and 300mm length are alternately stacked, then reduced to a thickness of 2.0 mm by multi-pass cold rolling after surface treatment such as degreasing and wire brushing. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at a rolling speed of 6.0 m/sec. The roll-bonded AA6061/AA5052/AA6061/AA5052 layered sheet is then hardened by natural aging (T4) and artificial aging (T6) treatments. The microstructure of the as-roll bonded and the age-hardened Al sheets was revealed by SEM observation; the mechanical properties were investigated by tensile testing and hardness testing. After T4 and T6 aging treatment, the specimens had a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 regions. The as-roll-bonded specimen showed a clad structure in which the hardness of AA5052 regions was higher than that of AA6061 regions. However, after T4 and T6 aging treatment, specimens exhibited different structures, with hardness of AA6061 regions higher than that of AA5052 regions. Strengths of T6 and T4 age-treated specimens were found to increase by 1.55 and 1.36 times, respectively, compared to the value of the starting material.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.625-634
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• 1986

The strain distribution on a welded aluminum alloy transition joint produced by a static tensile load has been measured using a moire method combined with photoelastic coating method. The test specimens were made of aluminum alloy 6061-T6 and 2014-T6 butt welded with ER-4043 filler metal, and were post welded heat treated (solid solution heat treatment 502.deg. C 70min.) and precipitated (artificial aging 171.deg. C 600min.) to cause an abrupt change of mechanical properties between the base metals and weld metal. The photoelastic epoxy rubber was cemented on the specimen grating which had been reproduced on the specimen surface by using an electropolishing. The measurements were compared with strains computed by Finite Element Analysis. The following results were abtained. (1) The maximum strain were distributed along the center line in the transverse directiion of the weld metal. (2) The strain gradient along the fusion line increased approaching the V-groove tip and the maximum value was observed at a quarter of width from the V-groove tip. (3) The moire method combined with photoelastic coating was proved very useful for real time strain measurement in the welded aluminum alloy transition joint.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.663-668
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• 2016

Increasing fuel economy and reducing air pollution have been unavoidable issues in the development of new cars, and one of the important methods is decreasing vehicle weight. Weight can be reduced by using lightweight materials such as aluminum alloy. Dynamic stiffness analysis was performed and compared for different materials for the knuckle for a car. The dynamic stiffness of 6061 aluminum alloy was about 30% higher than that of FCD600 cast iron. Usually, materials that have high dynamic stiffness show excellent vibration resistance because the dynamic stiffness can affect the vibration characteristics. In order to design a lighter and more reliable chassis component using 6061 aluminum alloy (AA6061-T6), a new knuckle shape is suggested by adding section ribs to an existing knuckle model. The effect of each design change on the reliability and component weight was investigated using computer aided engineering (CAE).

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.115-118
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• 2000

The development of high-strength fibers such as boron/epoxy and carbon/epoxy and adhesives has made it possible to repair cracked metallic plates by bonding reinforcing patches to the plate over the crack. In this study, aluminum 6061-T6 alloy plates with the high strength are applied to specimens with a cracked bolt hole to study the effect of diverse patch materials on the fatigue behavior of this structure. Additionally, the observation of the effort of different patch sizes on the specimen was performed. The results shows that the patch repair can improve the static strength by about 17% and the fatigue life by 200% compared with non-repaired case. And it was also revealed that the patching method along to crack growth direction is mort efficient in cost and weight reduction.

• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.26-32
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• 2013

A digital image correlation(DIC) method is a whole-field measurement technique that acquires surface displacements and strains from images information which characterized a random speckle as intensity grey levels. Recently years, this DIC method is being developed and used increasingly in various research. In this study, we tried to apply to aluminum alloy(Al 6061-T6) using DIC method and strain gauge. DIC results demonstrated the usefulness and ability to determine a strain. The test specimen used in this study was an aluminum alloy(Al 6061-T6, thickness 1 mm). For a strain measurement, a strain gauge was attached at the center of a specimen. A specimen was lightly sprayed with a white paint and a black dot pattern was sprayed on its fully dried white surface to obtain a random speckle. The experimental apparatus used to perform the tensile test consisted of universal dynamic tester(5 kN; T.O. Co.) under displacement speed of 0.5, 1.0 and 3.0 mm/min. A Model 5100 B Scanner(V. Co.) used to obtain a strain. A CCD camera connected to a PC uses to record the images of the specimen surface. After acquisition, the images were transferred to PC where the DIC software was implemented. An acquired image was evaluated by the DIC program. DIC method for displacement and strain was suggests and it results show a good consistent remarkably. DIC results demonstrated the usefulness and ability to determine surface strain was better than by using classical measurements. The strain field measurement using a DIC is so useful that it can be applied to map strain distributions at a full area. DIC method can evaluate a strain change so it can predict a location of fracture. The findings of the investigation suggest that the DIC method is an efficient and reliable tool for full-field monitoring and detailed damage characterization of materials.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.49-54
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• 2020

The purpose of this study is to investigate the effects of the change in the spindle speed and the feed rate on the diameter change of a hole using a boring cutter for the internal boring process of AL6061-T4 alloys. The experimental results are quantitatively analyzed by applying the factor analysis and the response surface analysis of the experimental design method. The tendency of the diameter change according to the change in the spindle speed and feed level is also evaluated. During the internal boring process of AL6061-T4 alloys, the main factor affecting the diameter change is the spindle speed in which the diameter decreases as the number of revolutions increases. In addition, the diameter tends to increase as the feed is increased; however, as the number of spindle revolutions increases, the influence of the feed decreases.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.421-429
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• 2018

In this study, various electrochemical experiments were carried out to compare the corrosion characteristics of AA5052-O, AA5083-H321 and AA6061-T6 in seawater. The electrochemical impedance and potentiostatic polarization measurements showed that the corrosion resistance is decreased in the order of AA5052-O, AA5083-H321 and AA6061-T6, with AA5052-O being the highest resistant. This is closely associated with the property of passive film formed on three tested Al alloys. Based on the slope of Mott-Schottky plots of an n-type semiconductor, the density of oxygen vacancies in the passive film formed on the alloys was determined. This revealed that the defect density is increased in the order of AA5052-O, AA5083-H321 and AA6061-T6. Considering these facts, it is implied that the addition of Mg, Si, and Cu to the Al alloys can degrade the passivity, which is characterized by a passive film structure containing more defect sites, contributing to the decrease in corrosion resistance in seawater.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.693-699
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• 2009

This paper shows mechanical properties and behaviors of macro- and micro-structures on friction stir welded specimen with 6061-T6 aluminum alloy plate. It apparently results in defect-free weld zone jointed at welding conditions like the traverse speed of 267mm/min, tool rotation speed of 2500rpm, pin inserted depth of 4.5mm and tilting angle of $2^{\circ}$ with tool dimensions such as tool pin diameter of 5mm, shoulder diameter of 15mm and pin length of 4.5mm. The tensile stress ${\sigma}_T=228MPa$ and the yield point ${\sigma}Y=141MPa$ are obtained at the condition of traverse speed of 267mm/min and tool rotation speed of 2500rpm. With the constant rotation speed, the higher traverse speed become, the higher tensile stress and yielding point become. Vickers hardness for welding zone profile were also presented.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.63-69
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• 2006

This study deals with the friction welding of A2024- T6 to A6061- T6; The friction time was variable conditions under the conditions of spindle revolution of 2000rpm, friction pressure of 50MPa, upset pressure of 100MPa, and upset time of 5.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied, of friction weld, and so the results were as follows. 1. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 292MPa, which is $94.2\%$ of the base material's tensile strength(310MPa). At the same condition, the maximum shear strength was 2l2MPa, which is equivalent to $103\%$ of the base material's shear strength (205MPa). 2. At the same condition, the maximum vickers hardness was Hv 146 at A2024- T6 nearby weld interface, which is higher Hv3 than condition of the friction time 0.5seconds, and the maximum vickers hardness was Hvl20 from weld interface of A6061-T6, which is higher Hv28 then base material's. 3. The results of microstructure analysis show that the structures of two base materials have fractionized and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.