• 대한금속재료학회지
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• 제49권11호
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• pp.893-899
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• 2011

Fabrication of a complex aluminum alloy by the ARB process using dissimilar aluminum alloys has been carried out. Two-layer stack ARB was performed for up to six cycles at ambient temperature without a lubricant according to the conventional procedure. Dissimilar aluminum sheets of AA1050 and AA5052 with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled to 50% reduction such that the thickness became 1 mm again. The sheet was then cut into two pieces of identical length and the same procedure was repeated for up to six cycles. A sound complex aluminum alloy sheet was successfully fabricated by the ARB process. The tensile strength increased as the number of ARB cycles was increased, reaching 298 MPa after 5 cycles, which is about 2.2 times that of the initial material. The average grain size was $24{\mu}m$ after 1 cycle, and became $1.8{\mu}m$ after 6 cycles.

• 한국분말재료학회지
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• 제31권1호
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• pp.37-42
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• 2024

Friction stir spot welding (FSSW) is a solid-state joining process and a rapidly growing dissimilar material welding technology for joining metallic alloys in the automotive industry. Welding tool shape and process conditions must be appropriately controlled to obtain high bonding characteristics. In this study, FSSW is performed on dissimilar materials AA5052-H32 aluminum alloy sheet and SPRC440 steel sheet, and the influence of the shape of joining tool and tool insertion depth during joining is investigated. A new intermetallic compound is produced at the aluminum and steel sheets joint. When the insertion depth of the tool is insufficient, the intermetallic compound between the two sheets did not form uniformly. As the insertion depth increased, the intermetallic compound layer become uniform and continuous. The joint specimen shows higher values of tensile shear load as the diameter and insertion depth of the tool increase. This shows that the uniform formation of the intermetallic compound strengthens the bonding force between the joining specimens and increases the tensile shear load.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1968-1973
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• 2004

Structural degradations are often experienced on the components of nuclear power plants in reactor pressure vessels (RPV) and steam generators (SG) when these components are exposed to high temperature and high pressure for a long period of time. Such conditions result in the change of microstructures and of mechanical properties of materials, which requires an evaluation of the safeguards related to structural integrity. In a primary reactor cooling system (RCS), a dissimilar weld zone exists between cast stainless steel (CF8M) in a pipe and low-alloy steel (SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time under the operating temperature between 290 and 33$0^{\circ}C$. Under the same conditions, it is well known that degradation is not observed in low alloy steel. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for various times at 43$0^{\circ}C$, respectively. Then, The various mechanical test for the dissimilar welds are performed.

• 한국기계가공학회지
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• 제19권9호
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• pp.33-39
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• 2020

Self-piercing rivets are often used in the automotive industry, among other industries, as mechanical components to join multiple materials such as aluminum alloys. Self-piercing rivets have a strong sealing property, although there is considerable scope for their performance improvement. In this study, to enhance the performance of self-piercing rivets, the hybrid self-piercing riveting (SPR) technique, using the existing SPR and structural adhesive, was proposed. Moreover, heterogeneous material specimens subjected to the hybrid SPR technique were manufactured and tested. The joint strength of the test pieces of different materials was evaluated through finite element analyses.

• Journal of Welding and Joining
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• 제15권2호
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• pp.43-53
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• 1997

The complete joining method for dissimilar press punch materials and its real-time evaluation method is not available at present. Brazing method has been used for joining them, but it is known that the welded joint by the brazing has the lower bonding efficiency and reliability than the diffusion welding. The friction welding with a diffusion mechanism in bonding was applied in this study. This work was carried out to determine the proper friction welding conditions and to analyze mechanical properties of friction welded joints of sintered carbide tool materials (SKNM50 for the blade part of press punch) to alloy steel (SCM440 for the shank part of press punch) using aluminum (A6061 for the interlayer material) as an insert material between the sintered carbide tool materials and the alloy steel. In addition, acoustic emission test was carried out during friction welding to evaluate the weld quality.

• Journal of Welding and Joining
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• 제34권5호
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• pp.19-25
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• 2016

Global warming is hot issue to keep the earth everlastingly. Despite the increase of the world population and the energy demand, the world oil supply and the oil price are hold the steady state. If we are not decrease the world population and the energy consumption, unforeseeable energy crisis will come in the immediate future. AMT acronym of Advanced Materials for Transportation is a non-profitable IEA-affiliated organization to mitigate the oil consumption and the environment contamination for the transportation. In recent, Annex X Multi-materials Joining was added to enhance the car body weight reduction cause the high fuel efficiency and the low emission of exhaust gas. Multi-materials are the advanced materials application technology to optimize the weight, the performance and the cost with the combination of different materials such as Al-alloy, Mg- alloy, AHSS and CFRP. In this study, the trends of AMT strategy and Al-alloy based multi-materials joining technology were review. Also several technologies for Al-alloy dissimilar joining were investigated.

• 한국안전학회지
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• 제9권1호
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• pp.9-18
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• 1994

In this study, we conducted experimental tests to evaluate fracture behaviors of fresh-butt welded metal by Acoustic Emission technique. We selected similar welding and dissimilar welding process, the one welded for SM45C, SS41 and SUS304 of each material, the other for SM45C and SS41, SM45C and SUS304 and SS41 and SUS304. The fracturing processes of weld metal were estimatied through the fracture toughness test with compact tension specimens and fractography analysis. In ASTM test method E-399, type I curves for materials of this study were obtained by load-cod diagram of fracture toughness test. and 5% offset load( $P_{5}$) was estimated as the estimated crack initial load( $P_{Q}$), The estimated crack initial load( $P_{Q}$) of similar welding materials generally lower than base matal, and then SM45C appeared greatly in decreasing rate of PB, SS41 and SUS304 appeared in order. $P_{Q}$ of dissimilar welding materials were lower than the similar welding materials. $P_{Q}$ of welding of SM45C and SS41 appeared in small, SUS304 and SS41 appeared greatly in dissimilar welding materials. In fracture toughness test, AE counts increased before the inflection point of the slope, decreased after that. It was found that increasing of AE counts were due to the microcrack formation at the crack tip near the $P_{5}$ point through AE data. For welding materials in this study, both low and high AE amplitude appeared simulataneously. It was confirmed that the low AE amplotude was due to formation of micro void, micro crack or micro dimple, the high AE amplitude was caused by microvoid coalescence and quasi-cleavage fracture through analyses of fractograpy.apy.apy.apy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.769-772
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• 1997

In this study, By employing two dimensional(2-D) Boundary Element Method(BEM) stress analysis was carried to investigate stress distributions on the brazing joint of a Hardmetal and a HSS. Two model was proposed to analyze stress singularity in brazed interface. The stress results from the BEM were considered influence of the kind of materials , thickness of filled metal and length of vertical brazing adhesive. From those obtained results , the peak point of stress was founded in the lower part of two interface was made by brazing. As the thickness and length changed, the maximum stress tended to change in the peak point.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.33-38
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• 2002

Nowdays, related with vehicle weight reduction, many automotive maker are trying to develop spaceframe. If aluminum member and steel member are applied together in constructing spaceframe, there will be many advantages in aspect of inclosing strength and saving weight of automotive. In this case, joining method of aluminum and steel members has to be proposed. For this method, electomagnetic joining has many advantages compared to welding. In this paper, joining of aluminum tube and steel tube using eletomagnetic pressure was studied and strength of joint was evaluated through commission test.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1991년도 특별강연 및 추계학술발표 개요집
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• pp.35-37
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• 1991