• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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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.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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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.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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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.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.45-52
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• 2002

It has been known that tensile residual stresses occurring by the thermal expansion coefficient mismatch between fiber and matrix is a cause of the weak strength of metal matrix composites(MMCs). In order to solve this problem, TiNi alloy fiber was used as a reinforced material in TiNi/A16001 shape memory alloy composite in this study. TiNi alloy fiber improves the tensile strength of the composite by causing compressive residual stress in matrix on the basis of its shape memory effect. Pre-strain was imposed to generate the compressive residual stresses inside the TiNi/A16001 shape memory alloy composites. AE technique was used to quantify the microscopic damage behavior of the composite at high temperature. The effect of applied pre-strains on the AE behavior was also evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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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.

• Clean Technology
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• v.9 no.2
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• pp.57-61
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• 2003

A novel nitric acid-free desmut solution has been developed to remove smut, which is produced from a NaOH etching, on the surface of aluminum alloy metal in metal surface treatment processes. Comparing with the performance of 5% $HNO_3$ desmut solution, the mixed acid solution containing 2% $H_2O_2$, 0.5% HF, and 10% $H_2SO_4$ shows the same effect of smut removal for aluminum alloy samples of A16061 and A15052. To examine the surface alterations of the aluminum samples, in addition, the surface analysis is carried out with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA).

• Transactions of Materials Processing
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• v.14 no.5 s.77
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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.

• Proceedings of the KSME Conference
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• 2001.11a
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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.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.233-239
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• 2004

Smart material is used in various applications such as for glass frame, for medical instruments and for a part of sensors. Smart composite materials ran be applied to a part of aircraft and to the on-line monitoring system for industrial structures, using the shape memory effect. However, it is very difficult to simulate and analyze the shape memory effect in smart composites. In this paper, a two dimensional axisymmetric model was proposed to analyze the smart composite of one fiber and matrix using the finite element method(FEM). The finite element analysis was carried out in two renditions of the room temperature(293K) and a higher temperature (363K). The results we.e compared with the experimental results to confirm the validity of the analysis. In addition, the acoustic emission(AE) technique was used to study the microscopic damage behavior and the effect of pre-strains on TiNi/A16061 shape memory alloy composite.