• Journal of Welding and Joining
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• v.5 no.1
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• pp.42-56
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• 1987

Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.194-200
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• 1993

Grinding experiments for Al 7075 alloy were carried out to study the influence of grinding conditions and supply methods of grinding fluid on residual stress and surface roughness and grinding force. The residual stress was measured by an X-ray method. The supply method of grinding fluid with a guide nozzle has large decrease value of the tensile residual stress and of grinding force than a normal nozzle. In sparking out state of the grinding work, it is desirable to decrease the depth of cut and the workpiece feedrate for improving surface roughness and mechanical properties.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.837-842
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• 2007

This study was conducted to test the effect of residual Al on plankton community after dissolved air flotation (DAF) application. Growth rate of phytoplankton after DAF application ($0.37day^{-1}$) was about 2 times lower than that before DAF application ($0.70day^{-1}$). Under the condition of addition of nitrogen and phosphorus without light, growth rate phytoplankton in treatment without residual Al increased in difference with showing the negative growth rate in treatment with residual Al. Under the condition of light without addition of nutrient, growth rate of phytoplankton was no noticeable difference between the before and after DAF application. The relatively high settling rate (0.47 m/day) was observed in treatment after DAF application. Although the abundance of rotifer decreased, the abundance of copepod and cladoceran such as Daphnia galeata, Diaphanosoma sp. and Bosmina longirostris with relative higher grazing was no noticeable difference between the before and after DAF application. In the treatments before and after DAF application with zooplankton, growth rate of phytoplankton was $0.41{\pm}0.08day^{-1}$, $0.20{\pm}0.03day^{-1}$, respectively. This difference was in treatment after DAF application similar with those in treatments before and after DAF application without zooplankton. Those indicate that the filter-feeding effect of zooplankton on phytoplankton community may be not changed by residual Al after the DAF application. These results suggest that residual Al after DAF application be to improve water quality by inhibition of growth rate as well as increasing settling rate of phytoplankton.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.12
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• pp.47-52
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• 1996

Cl-based gas chemistry is generally used to etching for al alloy metallization. After the etching of Al alloy with Cl-based gas plasma, residual chlorine on Al alloy reacts with H$_{2}$O due to air exposure and results in Al corrosion. In this study, the corrosion phenomena of Al wer examined with XPS(X-ray photoelectron spectroscopy) and SEM (scanning electorn microscopy). It was confirmed that chlorine mainly existed at the grian boundary of Al alloy after plasma etching of Al alloy with cl-based gas chemistry and Al corrosion was largely generated at the grain boundary of Al alloy. And residual chlorine was passivated by sulfur and fluorine which were generated by SF$_{6}$ plasma. These effects of passivation reduced the Al corrosion due to air exposure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.717-722
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• 2011

The purpose of this study is to predict the residual stress in Al6061 during T6 heat treatment. In this study, the variable residual stress in case of the solid solution($530^{\circ}C$, 2h) and artificial ageing($175^{\circ}C$, 9h) of Al6061 subjected to T6 heat treatment is determined at different ageing times. A heat treatment experiment is conducted to determine the heat transfer coefficient, on the basis of which the residual stress during the T6 heat treatment is predicted. In order to take into account the relaxation of residual stress during artificial ageing, a Zener-Wert-Avrami function is used and elasto-plastic nonlinear analysis is conducted through FE-simulation. Further, the residual stress is measured by using the X-ray diffraction(XRD) method, and the result is compared with the result from the FE-simulation. It is found that the residual stress predicted form the FE-simulation is in good agreement with the residual stress measured by using the XRD method.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.73-79
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• 2011

Friction stir welding (FSW) is a solid state joining method patented in 1991 by The Welding Institute (TWI). It is widely used for joining light metals such as Al and Mg alloys. Foreign railway vehicle manufacturing companies have been applying FSW to car body welding, but domestic companies are in the beginning of feasibility study. Therefore, lots of experimental and analytical study is needed. In this study, three-dimensional finite element modeling of the friction stir welding of two Al6061-T6 plates was carried out. And temperature field and residual stresses were obtained and compared to experimental results in the literature. It is found the analytic thermal field is in a good agreement with the experimental results, but there are some differences between numerical and experimental residual stresses.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1537-1540
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• 2003

MEMS technology with micro scale is complete system utilized as the sensor. micro electro device. The metallization of MEMS is very important to transfer the power operating the sensor and signal induced from sensor part. But in the MEMS structures local stress concentration and deformation is often happened by geometrical shape and different constraint on the metallization. Therefore. this paper studies the effect of supporting type and thickness ratio about thin film thickness of the substrate thickness for the residual stress variation caused by thermal load in the multi-layer thin film. Specimens were made from materials such as Al, Au and Cu and uniform thermal load was applied, repeatedly. The residual stress was measured by FEA and nano-indentation using AFM. Generally, the specimen made of Al induced the large residual stress and the 1st layer made of Al reduced the residual stress about half percent than 2nd layer. Specimen made of Cu and Au being the lower thermal expansion coefficient induce the minimum residual stress. Similarly the lowest indentation length was measured in the Au_Cu specimen by nano-indentation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.252-255
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• 1996

Cl-based gas chemistry is generally used to etching for Al alloy metallization. After the etching of Al alloy with Cl-based gas plasma, residual chlorine on Al alloy reacts with $H_2O$ due to air exposure and results in Al corrosion. In this study, the corrosion Phenomena of Al were examined with XPS(X-ray photoelectron spectroscopy) and SEF(Scanning electron microscopy). It was confirmed that chlorine mainly existed at the grain boundary of Al alloy after plasma etching of Al alloy with Cl-based gas chemistry and Al corrosion was largely generated at the grain boundary of Al a1loy. And residual chlorine was passivated by sulfur and fluorine which were generated by SF$_{6}$ plasma. These effects of passivation reduced the Al corrosion due to air exposure.e.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.29-36
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• 1985

This study was carried out to research on the optimum condition of $MgAl_2O_4$ spinel synthesis and the chara-ceteristics of its sintered bodies. In this study the used materials-MgO $Al_2O_3$-were prepared from the extragrade chemicals $Mg(OH)_2 Al(OH)_3$ respectively. The tendency to spinel synthesis and sintering condition were discussed about additives of SEM and the characteristics of sintered bodies were measured by TMA etc, The results were as follows ; 1. The addion of $TiO_2$ promoted more effectively the sinterbility than that of $MnO_2$. 2. Residual $\alpha$-$Al_2O_3$ and MgO in theorectical composition samples were disappeared at 1$600^{\circ}C$ 3. When added MnO2 residual $\alpha$-$Al_2O_3$ and MgO were disappeared at 150$0^{\circ}C$ and 1$600^{\circ}C$ respectively. 4, . When added $TiO_2$ residual $\alpha$-$Al_2O_3$ and MgO were disappeared at 150$0^{\circ}C$ and 134$0^{\circ}C$ respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1498-1506
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• 1997

Procedures are presented for influence of shot peening on fatigue strength, fatigue life and effects of shot peening are discussed from experiments were taken between shot peened and unpeened SPS5, SM45C specimens. After the residual stress on shot peened specimens was measured by X-ray diffractometer, rotating bending fatigue tests were carried out. In addition, the compressive residual stress profile was obtained by the superposition method of three stresses which is based on Al-Obaid's equation. Predicted fatigue life considering residual stress profile which was obtained by the Al-Obaid's equation and another predicted fatigue life considering residual stress profile which was measured in test were compared. For the purpose of predicting fatigue life, Morrow's equation considering the residual stress and mean stress was used.