• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.42-42
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• 2010

알루미늄 합금은 질량 대비 강도가 우수하고 내식성 및 저온 특성이 양호하여 구조재로서 널리 사용되고 있다. 또한 그 사용 추세가 점점 증가 하고 있으며 알루미늄 합금의 용접을 위해 현재까지 다양한 용접 공정이 적용되었다. 일반적으로 GMAW, GTAW 등의 아크 용접과 박판의 경우 저항 점용접, 그 외의 $CO_2$ laser, Nd:YAG laser와 같은 고밀도 에너지 용접 공정에 의한 연구 결과들이 많이 발표 되었다. 하지만 알루미늄 합금의 특성 상 용접부에 기공과 균열과 같은 결함들이 각 공정에서 많이 발생하며 이러한 결함을 감소시키기 위한 용접기술에 관해 많은 연구가 진행되고 있다. 본 연구에서는 GMAW, Plasma-GMAW 공정을 적용하여 알루미늄 합금의 용접특성을 비교하였다. 알루미늄 합금 Al 5052, Al 6061 4mm 두께 모재에 대해 BOP(Bead On Plate) 용접실험을 실시하였으며 생산성 측면에서 각 공정에 따라 완전 용입 시 최대 용접 속도를 측정하여 비교하였다. 용접 품질 측면에서는 비드 표면 및 단면을 검사하고 인장시험을 수행하였으며, 용접 기공과 균열을 X-ray 촬영을 통해 비교하였다. 또한 고속카메라 촬영을 통해 용접 중 플라즈마로 인한 산화막 제거 효과를 확인하고 각 공정별 용접 시작부의 아크 안정성을 평가하였다. 인장시험 결과 모든 모드에서 모재에서 파단됨을 확인 하였고, Plasma-GMAW 공정의 경우 플라즈마의 예열효과로 인하여 GMAW 보다 완전용입 기준 용접속도가 빨랐으며, 청정작용도 우수한 것으로 확인되었다.

• 한국항공우주학회지
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• 제32권1호
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• pp.44-49
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• 2004

• 소성∙가공
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• 제30권1호
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• pp.27-34
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• 2021

In this study, response surface method (RSM) was used in modeling and multi-objective optimization of the parameters of AA5052-H32 in incremental sheet forming (ISF). The goals of optimization were the maximum forming angle, minimum thickness reduction, and minimum surface roughness, with varying values in response to changes in production process parameters, such as tool diameter, tool spindle speed, step depth, and tool feed rate. A Box-Behnken experimental design (BBD) was used to develop an RSM model for modeling the variations in the forming angle, thickness reduction, and surface roughness in response to variations in process parameters. Subsequently, the RSM model was used as the fitness function for multi-objective optimization of the ISF process based on experimental design. The results showed that RSM can be effectively used to control the forming angle, thickness reduction, and surface roughness.

• 한국재료학회지
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• 제29권6호
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• pp.392-397
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• 2019

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061 three-layer clad sheet. Two AA6061 and one AA5052 sheets of 2 mm thickness, 40 mm width, and 300 mm length are stacked, with the AA5052 sheet located in the center. After surface treatment such as degreasing and wire brushing, sample is reduced to a thickness of 1.5 mm by multi-pass cold rolling. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA6061/AA5052/AA6061 complex sheet is then hardened by natural aging(T4) and artificial aging(T6) treatments. The microstructures of the as-roll bonded and age-hardened Al complex sheets are revealed by optical microscopy; the mechanical properties are investigated by tensile testing and hardness testing. After rolling, the roll-bonded AA6061/AA5052/AA6061 sheets show a typical deformation structure in which grains are elongated in the rolling direction. However, after T4 and T6 aging treatment, there is a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 sheets. The as roll-bonded specimen shows a sandwich structure in which an AA5052 sheet is inserted into two AA6061 sheets with higher hardness. However, after T4 and T6 aging treatment, there is a different sandwich structure in which the hardness of the upper and lower layers of the AA6061 sheets is higher than that of the center of the AA5052 sheet. The strength values of the T4 and T6 age-treated specimens are found to increase by 1.3 and 1.4 times, respectively, compared to that value of the starting material.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.429-431
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• 2009

Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND // <111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study, The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND // <111> texture components through asymmetric rolling in Al sheet.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.477-479
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• 2008

Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND//<111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study. The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through asymmetric rolling in Al sheet.

• 대한기계학회논문집A
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• 제41권3호
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• pp.181-186
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• 2017

점진 판재 성형은 금형을 제작하지 않고 판재를 가공하는 방법으로써 빠른 시제품 제작과 소량 생산에 적합한 성형법이다. 이러한 점진 판재 성형의 공정 변수로 공구 직경, 매 스탭당 z-방향 깊이, 공구 이송속도, 공구 회전 속도 등은 성형품의 품질에 크게 영향을 미친다. 본 연구에서는 Al5052-O(0.8mm) 판재를 사용하여 Varying Wall Angle Conical Frustum 모델의 점진성형을 실시하였으며, 각각의 변수들의 조합에서 성형성을 판단하였다. 다구찌 기법을 사용하여 점진성형 변수들의 조합을 찾아내고, 그레이 관계형 최적화를 통하여 최적 성형 변수 값의 조합을 찾아 내였다. 최종 성형물의 품질은 성형성, 스프링 백, 두께 감소량을 측정하여 판단하였다. 본 연구의 실험 조건에서의 최적의 변수 조합은 공구직경 6 mm, 회전속도 60rpm, 매 스탭당 z-방향 깊이 0.3 mm, 이송속도 500 mm/min으로 판단되었다.

• 한국안전학회지
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• 제29권4호
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• pp.9-14
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• 2014

Self-piercing riveting(SPR) is a mechanical fastening technique which is put pressure on the rivet for joining the sheets. Unlike a spot welding, SPR joining does not make the harmful gas and $CO_2$ and needs less energy consumption. In this study, static and fatigue tests were conducted using tensile-shear specimens with Al-5052 plates for evaluation of fatigue strength of the SPR joints. During SPR joining process for the specimen, using the current sheet thickness and a rivet, the optimal applied punching force was found to be 21 kN. And, the maximum static strength of the specimen produced at the optimal punching force was 3430 N. During the fatigue tests for the specimens, interface failure mode occurred on the top substrate close to the rivet head in the most high-loading range region, but on the bottom substrate close to the rivet tail in the low -loading range region. There was a relationship between applied load amplitude $P_{amp}$ and lifetime of cycle N for the tensile-shear, $P_{amp}=3395.5{\times}N^{-0.078}$. Using the stress-strain curve of the Al-5052 from tensile test, the simulations for fatigue specimens have been carried out using the implicit finite element code ABAQUS. The relation between von-Mises equivalent stress amplitude and number of cycles was found to be ${\sigma}_{eq}=514.7{\times}N^{-0.033}$.

• 한국분말재료학회지
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• 제20권4호
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• pp.302-307
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• 2013

A5J32-T4 and A5052-H32 dissimilar aluminum alloy plates with thickness of 1.6 and 1.5 mm were welded by friction stir lap welding (FSLW). The FSLW were studied using different probe length tool and various welding conditions which is rotation speed of 1000, 1500 rpm and welding speed of 100 to 600 mm/min and material arrangement, respectively. The effects of plunge depth of tool and welding conditions on tensile properties and weld nugget formation. The results showed that three type nugget shapes such as hooking, void, sound have been observed with revolutionary pitch. This plunge depth and material arrangement were found to effect on the void and hooking formation, which in turn significantly influenced the mechanical properties. The maximum joint efficiency of the FSLWed plates was about 90% compared to base metal, A5052-H32 when the A5052-H32 was positioned upper plate and plunge depth was positioned at near interface between upper and lower plates.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.527-532
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• 2000

The armor composite material targets such as aramid FRMLs with different type and ply number of face material and different type of back-up material, were studied to determine ballistic impact resistance and dynamic failure behavior during ballistic impact. Ballistic impact resistance is determined by $\textrm{V}_{50}$ ballistic limit, a statical velocity with 50% probability for complete penetration, test method. Also dynamic failure behaviors are respectfully observed that result from $\textrm{V}_{50}$ tests. $\textrm{V}_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete penetration during high velocity impact tests. As a result, ballistic impact resistance of anodized Al 5052-H34 alloy(2 ply) is better than that of anodized Al 5052-H34 alloy(1 ply), but Titanium alloy showed the similar ballistic impact resistance. In the face material, ballistic impact resistance of titanium alloy is better than that of anodized Al 5052-H34 alloy. In the back-up material, ballistic impact resistance of T750 type aramid fiber is better than that of CT709 type aramid fiber.