• 한국공작기계학회논문집
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• 제17권4호
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• pp.22-28
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• 2008

Friction stir welding(FSW) is an relatively new solid state joining process. A1606l-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process(FSP) uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile playa major role in deciding FSP zone formation in A16061-T6 aluminium alloy. Tow different tool pin profiles have been used to fabricate the joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• 한국정밀공학회지
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• 제19권2호
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• pp.72-78
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• 2002

Thermomechanical behavior and mechanical properties of A16061 matrix composite with shape memory alloy(SMA) fiber are studied by using fnite element analysis(FEA). The smartness of the SMA is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when healed after being prestrained. In this paper, an analytical model is assumed two dimentional axisymetric model of one fiber and around the matrix. To evaluate the strength of composite usig FEM, the concept of smart composite was simulated on computer. The Shape memory effect(SME) simulation is very difficult using FEM because of the nonlinear analysis and the elastic plastic analysis. Thus, in this paper, the FEA was carried out at two critical temperature conditions; room temperature and high temperature(363K). The analysis is compare the finite element analysis result with the test result for the analysis validity.

• 한국정밀공학회지
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• 제20권1호
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• pp.196-204
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A16061-T6, and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.135-138
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• 2007

A semi-solid forming processing has been developed for manufacturing near net-shape components. The semi-solid forming has two methods. One is thixo-forming with reheating prepared billet, the other is rheo- forming with cooled melt until semi-solid state. In indirect forging processing, this experiment used aluminum rheology materials by electromagnetic stirring system. Rheology material is made by A16061. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. Forged samples are found microstructures and mechanical properties. Forged samples are accomplished heat treatment T6 for high mechanical properties.

• 비파괴검사학회지
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• 제22권1호
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• pp.45-52
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• 2002

금속복합재료 (MMC) 내부에서의 강화재와 기지재사이의 열팽창계수의 차이에 의해 발생하는 인장잔류응력은 복합재료의 인장강도를 저하시키는 심각한 문제중의 하나이다. 따라서 본 연구에서는 TiNi/A16061 형상기억복합재료내부의 인장잔류응력의 문제를 해결하기 위하여 강화재로써 TiNi 합금을 사용하였다. TiNi 합금은 형상기억효과를 이용하여 복합재료내부에 압축잔류응력을 발생시킴으로써 인장강도를 증가시키는 역할을 한다. 복합재료내부에 압축잔류응력을 발생시키기 위하여 예변형(pre-strain)을 가하였다. 본 연구에서는 예변형의 변화에 따른 압축잔류응력의 영향을 평가하였으며 AE 기법을 이용하여 고온에서의 복합재료의 미시적 손상거동과 예변형의 영향을 평가하였다.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1897-1906
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• 2003

A finite element analysis for near-net-shape forming of A16061 powder was performed under warm rubber isostatic pressing and warm die pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain a part with better density distributions. The shape of rubber mold was designed by determining a cavity shape that provides a desired shape of the final powder compact. To simulate densification and deformed shape of a powder compact during pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program(ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy Potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for Al6061 powder compacts under warm die pressing and warm isostatic pressing.

• 청정기술
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• 제9권2호
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• pp.57-61
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• 2003

금속가공 공정에서 알루미늄 합금소재의 알칼리 에칭 후 표면에 발생한 스머트(Smut) 를 제거하기 위해 무질산 디스머트(Nitric acid-free desmut) 용액을 개발하였다. 과산화수소(2%), 불산(0.5%) 및 황산(10%)을 혼합한 산용액이 NaOH 수용액에 처리한 A16061 및 A15052 규격의 알루미늄 합금 소재에 대한 스머트 제거효과가 5% 질산수용액의 사용할 경우와 유사하게 관찰되었다. 스머트 제거를 위한 혼합 산용액 처리 전 후 소재 표면을 SEM-EPMA 분석을 통해 확인하였다.

• 소성∙가공
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• 제14권5호
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• pp.460-465
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• 2005

The temperature difference between die and workpiece has been frequently caused to various surface defects. The distribution and change for the temperature of forged part should be analyzed to prevent the generation of various defects related with the temperature. The surface temperature changes were affected with the interface heat transfer coefficient. Therefore, the coefficient is necessary to predict the temperature changes of die and workpiece. In this study, the experimental and FE analysis were performed to evaluate the coefficient with a function of pressure, temperature, material, and etc. The closed die upsetting was used to measure the coefficient on pressure over the flow stress. AISI1045, A16061, and Cu-OFHC were used to analyze the effect of material. The coefficient was increased with step-up of pressure between die and workpiece. And, A16061 was larger than that of the AISI1045 and Cu-OFHC up to the five times.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.186-191
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• 2001

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 shape memory alloy(SMA) composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation and volume fraction of TiNi alloy. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 SMA composite. In addition, two dimensional AE source location technique was applied to inspect the crack initiation and propagation in composite.

• 비파괴검사학회지
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• 제24권3호
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• pp.233-239
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• 2004

지능재료는 안경테, 치아 교정과 같은 의료용 재료, 각종 센서 및 밸브 등의 광범위한 분야에서 적용되고 있다. 이와 같은 지적재료의 형상기억효과를 이용한 지적복합재료는 항공기의 부품, 산업구조물 및 항공산업에서도 그들 시스템의 모니터링을 위하여 사용되어 질 수 있다. 그러나 지능복합재료의 형상기억효과에 대한 분석과 시뮬레이션은 대단히 어렵다. 본 연구에서는 유한요소법을 이용하여 기지재와 하나의 강화섬유에 대한 2차원의 축 대칭 모델에 대하여 분석하였다. 상온(293K)과 고온(363K)에서 각각 해석되었으며 해석결과와 실험결과와의 강도 값을 비교 검토하였다. 더불어 음향방출 기법을 이용하여 지능복합재료(TiNi/A16061)의 예변형률과 고온에서의 미시적 손상거동을 평가하였다.