• 소성∙가공
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• 제15권8호
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• pp.574-580
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• 2006

Anisotropy has an important effect on the strain distribution in aluminum alloy sheet forming, and it is closely related to the thinning and formability of sheet metals. Thus, the anisotropy of the material should be properly considered for the realistic analyses of aluminum sheet forming processes. For this, anisotropy can be approached in two different scales: phenomenological and microstructural (polycrystal) models. Recent anisotropic models (Yld2000-2d; Barlat et al.[1] 2003, Cuitino et al.[2] 1992) were employed in this work. For the simulation using shell element, the method which can impose plane stress condition in the polycrystal model is developed. Lankford values and yield stress ratios are calculated along various directions. As planar anisotropic behavior, a circular cup deep drawing simulation was carried out to compare the phenomenological and microstructure models in terms of earing profile.

• Journal of Welding and Joining
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• 제34권3호
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• pp.23-30
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• 2016

This paper discusses the optimization of friction stir spot welding (FSSW) process parameters for joining Aluminum alloy (AA6061-T6) with Magnesium alloy (AZ31B) sheets. Prior to optimization an empirical relationship was developed to predict the Tensile Shear Fracture Load (TSFL) incorporating the four most important FSSW parameters, i.e., tool rotational speed, plunge rate, dwell time and tool diameter ratio, using response surface methodology (RSM). The experiments were conducted based on four factor, five levels central composite rotatable design (CCD) matrix. The maximum TSFL obtained was 3.61kN, with the tool rotation of 1000 rpm, plunge rate of 16 mm/min, dwell time of 5 sec and tool diameter ratio of 2.5.

• Journal of Welding and Joining
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• 제22권4호
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• pp.43-49
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• 2004

Conventional method for electrode force application in resistance spot welding(RSW) processes is to use pneumatic cylinder. However, due to its inherent problems in pneumatic power system such as compressibility of air and poor transient response characteristics, new electrode force system with servo control are recently introduced in RSW machine. This machine is called “servogun”. The purpose of this study is to evaluate performance of servogun in case of spot welding of aluminum alloy. Aluminum alloy(A5052) sheets are spot welded using pneumatic gun and servogun. Both results are compared by means of macro cross-section etching test and tensile shear strength test. Numerous previous research have reported nugget with many voids and cracks are not uncommon defects in spot welds with aluminum alloy. The experimental results show similar defects in case of pneumatic gun. In contrast, use of servogun considerably reduced generation of voids and cracks. In case of step-wise increased forging force at the end of welding cycle with servogun, crack-free and void-free nuggets have been observed. The performance of servogun has been also verified by series of tensile shear test. Higher strength values have been achieved with servogun in comparison to that of pneumatic gun.

• Journal of Welding and Joining
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• 제33권2호
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• pp.78-84
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• 2015

Self-piercing rivet(SPR) is mechanical joining methods and which can be joining dissimilar materials. Unlike conventional riveting, SPR also needs no pre-drilled holes. During plastically deformation, SPR pierces upper sheet and joins it to under sheet. SPR has been mainly applied to the joining the automobile body and some materials, such as glass fiber reinforced polymer and aluminum alloy, which represent the sheet-formed materials for lightweight automobile. Glass fiber reinforced plastic(GFRP) has been considered as a partial application of the automobile body which is lighter than steels and stronger than aluminium alloys. It is needed SPR to join Al alloy sheets and GFRP ones. In this paper, in order to design the rivet and anvil, which are suitable for GFRP, the joinability was examined through simulations of SPR joining between GFRP and Al alloy sheets. For this study, AutoCAD was used for the modeling and the simulated using commercial FEM code DEFORM-2D. The simulated results for SPR process joining between GFRP and Al alloys were confirmed by the same conditions as experimental trials.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.105-108
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• 2003

Sheets of aluminum alloy 1100 were asymmetrically cold rolled in a rolling mill with different roll speeds. In order to promote the shear deformation during asymmetrical rolling, cold rolling without lubrication was performed. The evolution of texture components during asymmetrical rolling was investigated by the calculation of the orientation distribution function (ODF) using the monoclinic sample symmetry. The strain state during asymmetrical rolling was tackled by means of FEM calculations. Asymmetrical rolling gave rise to the development of pronounced strain gradients throughout the thickness layers which resulted in the formation of strong texture gradients in the aluminum sheet.

• 소성∙가공
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• 제12권3호
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• pp.244-250
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• 2003

Sheets of aluminum alloy 1100 were asymmetrically cold rolled in a rolling mill with different roll speeds. In order to promote the shear deformation during asymmetrical rolling, cold rolling without lubrication was performed with a roll speed ratio of 1.5/l.0. The evolution of texture components during asymmetrical rolling was investigated by the calculation of the orientation distribution function (ODF) using the monoclinic sample symmetry. The strain state during asymmetrical rolling was tackled by means of FEM calculations. Asymmetrical rolling gave rise to the development of pronounced strain gradients throughout the thickness layers which resulted in the formation of strong texture gradients in the aluminum sheet.

• 한국자동차공학회논문집
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• 제24권5호
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• pp.566-574
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• 2016

Fiber metal laminates, which are hybrid materials consisting of metal sheets and composite layers, have contributed to aerospace and automotive industries due to their reduced weight and improved damage tolerance characteristics. In this study, the impact performance of the laminates, which are comprised of a self-reinforced polypropylene and two aluminum sheets, and the pure aluminum alloy sheet material were investigated experimentally via numerical simulation. In order to compare the impact performance, the laminates and aluminum alloy were examined by assessing the impact force, energy time histories, and specific energy absorption. ABAQUS is a commercial software that is used to simulate the actual drop-weight tests. Based on this study, it is noted that the impact performance of the laminates was superior to that of the aluminum alloy. In addition, a good agreement between the experimental and numerical results can be achieved when the impact force and energy time histories from the experiments and the numerical simulations are compared.

• 대한기계학회논문집A
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• 제38권7호
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• pp.735-742
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• 2014

Self-piercing rivet(SPR)은 이종재료 접합을 위해 사용되는 결합용 기계요소로써, 대표적으로는 알루미늄 합금과 강판 등 용융점이 서로 다른 재료의 접합에 사용된다. SPR 접합은 일반 리벳접합과 달리 스스로 홀을 가공하며 삽입되기 때문에 사전의 홀 가공이 필요 없다.(1) 상부판재를 천공하고 하부판재와 함께 소성 변형되어 결합된다. 자동차의 차체 경량화를 위해서는 알루미늄 합금과 같은 경량소재가 사용되며, 부분적으로 스틸과 알루미늄 합금의 이종재료 접합이 요구된다. 그러나 알루미늄 합금과 강판은 용융점이 다르므로 기존의 차체 결합방법으로 이용되고 있는 저항 용접이 불가능하다. 이에 따라, 기계적 결합방법의 하나인 SPR 접합이 요구된다.(2) 따라서 본 연구에서는 강소성 유한요소해석 프로그램을 이용하여 리벳과 판재의 접합 성형성을 검토하고, 고장력 강판을 접합할 수 있는 새로운 형상의 SPR을 설계하였다. 또한 해석결과와 실험의 비교를 통하여 해석의 신뢰성을 검증하였다.

• 한국표면공학회지
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• 제27권4호
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• pp.207-214
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• 1994

In consideration of global environmental protection and fuel saving, aluminum alloy sheets for auto body panels such as hood, fender etc., are expected one of the most promising materials for weight saving of cars. The chemical conversion coating is required to prevent the filiform corrosion occurring on painted aluminum. However the conventional process for the composited material mixed with aluminum and steel is complexs; aluminum part is chromated and assembled to the body, and then the steel body undergoes Zn phosphating. In order to overcome the low productivity due to the complex process and the environmental problem with a conventional process, a simultaneous zinc phosphating process for alsuminum and steel in an assembled condition is demanded. Newly developed phosphate solution has been investigated to characterize the phosphating behavior under various conditions. The optimum conditions of the phosphating solution for the application of the paint treatment derived as follows : about 0.3 for the ratio of Zn to $PO_4$, , 200~500 ppm for the concentration of fluoride ion, and 2.5~4.0 for pH. The concentration of dissolved aluminum ion must be kept below 2--ppm and suitable accelerator is found to be a mixture of 1g/$\ell$ $NO_2\;^-$, and 6g/$\ell$ $NO_3\;^-$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.58-61
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• 1998

Anisotropy is closely related to the formability of sheet metal and should be considered carefully for more realistic analysis of actual sheet metal forming operations. In order to better describe anisotropic plastic properties of aluminum alloy sheets, a planar anisotropic yield function which accounts for the anisotropy of uniaxial yield stresses and strain rate ratios simultaneously was proposed recently[1]. This yield function was used in the finite element simulations of cup drawing tests for an aluminum alloy 2008-T4. Isotropic hardening with a fixed initial back stress based on experimental tensile and compressive test results was assumed in the simulation. The computation results were in very good agreement with the experimental results. It was shown that the initial back stress as well as the yield surface shape have a large influence on the prediction of the cup height profile.