• 한국산업융합학회 논문집
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• 제22권2호
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• pp.191-199
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• 2019

In this paper, dissimilar friction welding were produced using 15 mm diameter solid bar in chrome molybedenum steel(SCM440) to stainless steel(STS316L) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=70 MPa, UP=140 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 8.6 mm. In addition, an acoustic emission technique was applied to evaluate the optimal friction welding condition. AE parameters including the cumulative count, amplitude and energy showed a various changes according to the friction condition. A continuous type waveforms and low frequency spectrum was presented in friction time. On the other hand, a burst type waveform and high frequency spectrum was exhibited in pressing time.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2949-2957
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• 2020

Fatigue crack growth model has been developed for dissimilar metal weld joints of a piping component under cyclic loading, where in the crack is located at the center of the weld in the circumferential direction. The fracture parameter, Stress Intensity Factor (SIF) has been computed by using principle of superposition as K_H + K_M. K_H is evaluated by assuming that, the complete specimen is made of the material containing the notch location. In second stage, the stress field ahead of the crack tip, accounting for the strength mismatch, the applied load and geometry has been characterized to evaluate SIF (K_M). For each incremental crack depth, stress field ahead of the crack tip has been quantified by using J-integral (elastic), mismatch ratio, plastic interaction factor and stress parallel to the crack surface. The associated constants for evaluation of K_M have been computed by using the quantified stress field with respect to the distance from the crack tip. Net SIF (K_H + K_M) computed, has been used for the crack growth analysis and remaining life prediction by Paris crack growth model. To validate the model, SIF and remaining life has been predicted for a pipe made up of (i) SA312 Type 304LN austenitic stainless steel and SA508 Gr. 3 Cl. 1. Low alloy carbon steel (ii) welded SA312 Type 304LN austenitic stainless-steel pipe. From the studies, it is observed that the model could predict the remaining life of DMWJ piping components with a maximum difference of 15% compared to experimental observations.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.506-519
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• 2024

To simulate the verification process using materials from a decommissioned reactor, a mock-up of the bottom-mounted instrument nozzle in the Kori 1 reactor, where the nozzle was attached to a plate by J-groove dissimilar metal welding, was fabricated. The mock-up distortion was quantified by measuring the plate surface displacement after welding. The residual stresses formed on the support plate surface and the inner surface of the nozzle were then analyzed using the hole-drilling method, contour method, and neutron diffraction. Welding simulations were performed using a 3D finite element method to validate the measured results. The measured and computed stress distributions on the support plate exhibited reasonable agreement. Conversely, the stresses on the inside of the nozzle were found to have an indisputable difference in the contour method and neutron diffraction measurements, which demonstrated strong tensile and compressive hoop stresses, respectively. The possible origins of such differences were investigated and we have provided some suggestions for a precise evaluation in the simulation. This study is expected to be useful in future research on decommissioned reactors.

• 한국생산제조학회지
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• 제25권1호
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• pp.68-74
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• 2016

The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration, and has increased the automation and flexibility of an entire industry. Laser welding of dissimilar metals has been widely used to improve the wear resistance and corrosion resistance of industrial parts. The objective of this research is to investigate the influence of process parameters on the welding of SM45C and STS304 with CW Nd:YAG lasers. Bead-on-plate welding tests were carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, strain-stress behavior, and hardness of the welded part were investigated.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.817-824
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• 2017

Residual stress is a critical element in determining the integrity of parts and the lifetime of welded structures. It is necessary to estimate the residual stress of a welding zone because residual stress is a major reason for the generation of primary water stress corrosion cracking in nuclear power plants. That is, it is necessary to estimate the distribution of the residual stress in welding of dissimilar metals under manifold welding conditions. In this study, a cascaded support vector regression (CSVR) model was presented to estimate the residual stress of a welding zone. The CSVR model was serially and consecutively structured in terms of SVR modules. Using numerical data obtained from finite element analysis by a subtractive clustering method, learning data that explained the characteristic behavior of the residual stress of a welding zone were selected to optimize the proposed model. The results suggest that the CSVR model yielded a better estimation performance when compared with a classic SVR model.

• Journal of Welding and Joining
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• 제23권5호
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• pp.61-68
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• 2005

Dissimilar joining of Al 6013-T4 alloys and austenite stainless steel was carried out using friction stir welding technique. Microstructures near the weld zone and mechanical properties of the joint have been investigated. Microstructures in the stainless steel side were composed of the heat affected zone and the plastically deformed zone, while those in the Al alloy side were composed of the recrystallized zone including stainless steel particles, the thermo-mechanically affected zone and the heat affected zone. TEM micrographs revealed that the interface region was composed of the mixed layers of elongated stainless steel and ultra-fine grained Al alloy with lamella structure and intermetallic compound layer. Thickness of the intermetallic layer was approximately 300nm and was identified as the A14Fe with hexagonal close packed structure. Mechanical properties, such as tensile and fatigue strengths were lower than those of 6013 Al alloy base metal, because tool inserting location was deviated to Al alloy from the butt line, which resulted in the lack of the stirring.

• Journal of Welding and Joining
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• 제19권6호
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• pp.608-613
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• 2001

In this study, the rotary bending fatigue test was carried out with two kinds of base metal, martensite stainless steel STR3 and austenite stainless steel STR35 and the dissimilar friction welded material with them. To compare the fatigue fifes according to the notch positions, the small circular defect was worked on the bonded line, 1.0mm and 0.5mm distance form the bonded line. The fatigue limits of the STR3 and STR35 base metal were 429.0MPa and 409.4MPa respectably. In comparison with fatigue life at the same notch positions, the STR35 specimens showed about 190% for base metal, 82% for 1.0mm distance notched specimens higher than that of the STR3. But the fatigue life of the 0.5mm distance notched STR35 specimen showed about 35% lower than that of the STR3 specimen. And the bonded line notched specimen was much lower fatigue life than the other specimens because of separation of the bonded line.

• 대한기계학회논문집A
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• 제24권2호
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• pp.438-448
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• 2000

Mechanical press joining technique has been used in sheet metal joining processes because of its simple process and possibility of joining dissimiliar metals, such as steel and aluminum. The static and cyclic behavior of single overlap AI-alloy and steel(SPCC) joints has been investigate. Relationships were developed to estimate the strength of the joint taking into consideration base metal strength properties and the geometry of the joint. Fatigue test results have shown that fatigue resistance of the SPCC mechanical press joints is almost equal to that of the spot weld at the life of $10^6$ cycles. Also, the dissimilar material jointed specimen with upper SPCC plate and button diameter corresponding to the nugget diameter of the spot welded specimen has almost same strength as the same material jointed specimen and as the spot welded specimen.

• 대한기계학회논문집A
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• 제41권3호
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• pp.219-224
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• 2017

본 연구는 수송기계 축 등에 이용되는 캠 형상 부분만을 기존의 단조품인 SF45와 축 부분은 일반기계구조용 탄소강재인 SM45C를 직경 20 mm를 이용하여 이종 마찰용접을 수행하였다. 최적조건을 규명하기 위해 인장시험 등 용접품질과의 상관관계를 고찰하였고, 또한 최적조건에서 마찰용접 후 열처리를 시행하여 용접재(As-welded)와 후열처리재(PWHT)에 대한 회전굽힘 피로시험을 시행하였다. 결과적으로 두 이종재가 강한 혼합으로 계면에서도 개재물 및 산화막이 플래시로 토출되어 양호한 접합상태임을 확인하였다. 더욱이 모재(SF45)와 후열처리재의 피로한도 각각 180 MPa, 250 MPa로 나타났다. 이는 후열처리재가 SF45 모재에 비해 약 40 %의 피로수명이 향상되었음을 확인하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.41-41
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• 2009

To evaluate the applicability of dissimilar joining between Mg and Al alloys in automobile manufacturing process, solid state joining processes such as magnetic pulse welding(MPW), friction stir welding(FSW) and friction spot joining(FSJ) were attempted successfully. MPW process has been concentrated mainly on round section tube to tube and tube to bar welds. AZ31 Mg alloy has been successfully welded to pure Al A1070 as well as to Al alloy A3003. While, for friction stir welding of dissimilar sheet joints, AZ31B/A6061 with the thickness of 2mm were used and a square butt joint with a good quality was obtained at the conditions of 0.8mm/sec of travel speed and tool rotation speed of 850rpm. The maximum tensile strength of 179 MPa, which was about 80 % of the Mg base metal tensile strength, has been obtained. Finally, friction spot joining was attempted to make a dissimilar lap joint between AZ31(0.8mm) and A6061(1mm), while the joint exhibited the same level of tensile shear strength as that of similar Mg joint.