• Journal of Welding and Joining
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• 제29권2호
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• pp.72-79
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• 2011

The scope of this investigation is to evaluate the effect of joining parameters on the microstructural features and mechanical properties of dissimilar aluminum alloys, 1mm-thickness fixing AA6K31 at the top position and fixing AA5J32 at the bottom position. The friction stir lap welds were studied under various welding conditions, rotation speed of 1000, 1250, 1500rpm and welding speed of 100, 300, 500, 700mm/min, respectively. Mechanical test has been investigated in terms of tensile shear test and hardness test. The results showed that three type nugget shapes such as onion ring, zigzag type, hooking with the void, have been observed with revolutionary pitch. All welding conditions fractured at the HAZ of top plate, A6K31 and also the strength compare with base metal of lap joints were low efficiency, 52~63%. The thickness of fractured position was decreased with the lower heat input conditions. The relationships were excellent due to linear between the effective thickness of fractured position and peak load. The fractured position was the interface between joint area and not joint area. Also the strength efficiency compared with base metal was lower than decreasing rate of thickness because the hardness was decreased at fractured position due to softened material.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.794-801
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• 2021

이 연구는 electric resistance element spot welding 프로세스를 도입하여 알루미늄 합금-강철의 이종 접합부의 기계적 강도 및 내식성을 향상시키기 위해 수행되었다. SPFC980Y 강철과 Al5052-H32가 각각 모재로써 적용되었고, S20C 강철은 리벳 element로써 음각과 양각의 형상으로 구분되며, Al5052-H32에 전기 저항 스폿 용접을 위해 리벳팅 되어 6.5 kA의 전류와 250 kgf/㎠의 가압력으로 접합되었다. 그 결과, 음각된 S20C element는 스폿 용접 공정 후 불안정한 너깃이 형성되는 반면, 양각된 S20C의 경우, 구조적으로 건전한 접합부로 건전한 내식성 및 탁월한 기계적 특성이 얻어졌다. FEM 시뮬레이션의 도입으로, 음각과 양각의 계면의 접합 특성이 수치적으로 밝혀졌으며, 시뮬레이션 결과는 미세조직 발달 양상을 수치적으로 뒷받침하였다. 이 연구는 element 스폿 용접된 H32-A5052 이종 접합부의 기계적 강도 및 부식 신뢰성에 대해 체계적으로 분석되었으며, 이 공정은 금속재료뿐만 아니라, 경량 비전도성 비철/비금속계 재료에도 적용 될 수 있기 때문에, 차세대 차체 경량화의 양산 기술로 확장 될 수 있다.

• 열처리공학회지
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• 제34권6호
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• pp.309-314
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• 2021

Due to the superior corrosion resistance and mechanical properties of TiAl alloy at high temperature, it has been utilized as a turbine wheel of a turbocharger. The dissimilar metallic bonding is usually applied to combine the TiAl turbine wheel with the SCM440 structural steel which is used as a driving shaft. In this study, the TiAl and SCM440 joint were fabricated by using a friction welding technique. During bonding process, to suppress the martensitic transformation and the formation of cracks, which might reduce a strength of the joints, Cu was used as an insert metal to relieve stress. As a result, the intermetallic compounds (IMCs) layer was observed at TiAl/Cu interface while no IMC formation was formed at SCM440/Cu interface. Since understanding of the IMCs effects on the mechanical performance of welded joint is also essential for ensuring the reliability and integrity of the turbocharger system, we estimated the nanohardness of welded joint region through nanoindentation. The relation between the microstructural feature and its mechanical property is discussed in detail.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.171-173
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• 2005

To evaluate the applicability of dissimilar metal friction stir welding in automobile manufacturing process, friction stir welding trials were carried out for typical 5000 and 6000 series aluminum alloy sheets with 2mm thickness. The sound joints of A15052 and A16061-T6 alloys were successfully formed under a wide range of welding condition. Excellent weld ability has been obtained at a condition of rotating speed 2000rpm and travel speed 100mm/min, while a radiographic test also confirmed defect free joint for this condition. Through the Erichsen cup test, the plastic formability of the FSWelded joints was found to be about 83% of base metal.

• 한국해양공학회지
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• 제27권1호
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• pp.37-42
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• 2013

The presence of a crack can increase the local stress or strain, which can cause inelastic deformation and significantly reduce the life of a component or structure. Therefore, in this study, the fatigue crack growth (FCG) behaviors of friction stir welded Al 2024-T3 and Al 7075-T6 specimens were examined, with fatigue cracks growing parallel to the dynamically recrystallized zone at variable ${\Delta}K$ values and an R ratio of 0.3. In addition, the FCG values of the base metal Al 2024-T3 and Al 7075-T6 were tested under the same conditions and parameters as comparative groups. The results showed that compared with the base metal Al 2024 specimen, which had the best fatigue property, the welded specimen had only 88% of the fatigue cycles.

• 한국안전학회지
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• 제30권4호
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• pp.1-7
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• 2015

Self-piercing riveting (SPR) process is gaining popularity due to its many advantages. The SPR does not require a pre-drilled hole and has capability to join a wide range of similar or dissimilar materials and combinations of materials. This study investigated the fatigue strength of self-piercing rivet joint with aluminum alloy (Al-5052) and steel (SPCC) sheets. Static and fatigue tests on tensile-shear specimens were conducted. From the static strength aspect, the optimal punching force for the specimen with upper SPCC (U.S) sheet and lower aluminum alloy(L.A) sheets was 34 kN. During static test the specimens fractured in pull-out fracture mode due to influence of plastic deformation of joining area. There was a relationship between applied load amplitude $P_{amp}$ and number of cycles N ; $P_{amp}=19588N_f^{-0.211}$ and $P_{amp}=4885N_f^{-0.083}$ for U.S-L.A and U.A-L.S specimens, respectively. U.A-L.S fatigue specimens failed due to fretting crack initiation around the rivet neck between upper and lower sheets.

• 대한기계학회논문집A
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• 제34권8호
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• pp.997-1006
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• 2010

차체 경량화를 위해 알루미늄과 같은 경량금속의 사용은 이종소재 사용은 새로운 접합기술을 요구한다. 클린칭 접합은 이종소재 접합기술 중의 하나로 접합소재의 강도차이에 의해 접합특성이 달라진다. 본 연구에서는 Al5052 합금소재에 대한 고장력강판(SPFC440, 590, 780)에 대한 클린칭 접합특성을 평가하였다. 유한요소해석과 인장전단시험을 통해 클린칭 접합특성인 클린칭 접합의 기학적 구속량과 접합강도를 평가하였다. 상부소재가 고장력강판인 경우, SPFC780 은 상부소재의 네킹으로 클린칭 접합이 불가능하였다. 또한 상부소재의 강도가 증가함에 따라 접합강도가 증가하는 특성을 나타내었다. 하부소재가 고장력강판인 경우, 기하학적 구속량인 목두께 및 언더컷과 접합강도는 하부소재의 강도가 증가함에 따라 감소하는 경향을 나타내었다.

• Corrosion Science and Technology
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• 제22권5호
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• pp.322-329
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• 2023

There are a variety of heat exchangers used in automobiles, such as shell and tube heat exchangers, double tube heat exchangers, and plate heat exchangers. Most of them are water-cooled to prevent engine overheating. There have been reports of corrosion damage to these heat exchangers due to continuous wetting caused by external temperature differences, road pollutants, and snow removal. In addition, galvanic corrosion, which occurs when two dissimilar materials come into contact, has been identified as a major cause. In this study, corrosion characteristics and galvanic corrosion behavior of Al alloy (AA3003, AA4045 and AA7072) used in automobile heat exchangers were analyzed. Effective clad materials for heat exchanger tubes and fins were also evaluated. It was found that AA7072 should be applied as the cladding material for fin AA3003 and that AA4045 was suitable as a cladding material for tube AA3003 because this clad materials application was the most effective clad design to delay the occurrence of pinhole in the tube. Main factors influencing galvanic corrosion dissolution were found to be galvanic corrosion potential difference and galvanic corrosion current density.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.153-160
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• 2015

This article is aimed to study the effects of resistance spot welding (RSW) on the lap joint properties between AA1100 aluminum alloy and SGACD zinc coated steel and its properties. The summarized experimental results are as follows. The summarized experimental results are as follows. The optimum welding parameters that produced maximum tensile shear strength of 2200 N was a welding current of 95 kA, a holding time of 10 cycles, and a welding pressure of 0.10 MPa. Increasing of welding current, increased the tensile shear strength of the joint and also increased the amount of aluminum dispersion at the joint interface. The lap joint of steel over the aluminum (Type I) showed the higher joint tensile shear strength than a lap joint of aluminum over the steel (Type II). The indentation depth and the ratio of the indentation depth to the plate thickness decreased when the welding current was increased in the type I lap joint and also decreased when the welding current was decreased in the type II lap joint. The interface structure showed the formation of the brittle $FeAl_3$ intermetallic compound that deteriorated the joint strength.