• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2087-2095
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• 1999

One of the main causes of unwanted dimensional changes in precision metal mold casting parts is excessive and irregular residual stresses induced by temperature gradients and plastic deformation in the solidifying shell. Residual stresses can also cause stress cracking, and lower the fatigue life and fracture strength of the casting parts. In the present study, aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling units was designed and the casting specimens were produced to quantify the effects of different cooling conditions on the development of residual stresses. The layer removal method was used to measure the biaxial residual stresses in casting specimens produced from the experiments. The experimental results agreed with Tien-Richmond's theoretical model for thermal stress development for the solidifying metal plate.

• Journal of the Korean Society of Safety
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• v.26 no.6
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.623-628
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• 2015

In this paper, the shield plate was applied to the wireless power transfer (WPT) system. Then we compared transmission efficiency of WPT system between transmitter and receiver coils. The superconductor coil was applied to transmitter and receiver coils in order to increase the transmission efficiency of WPT. The superconductor coil was more effective to power transmission as its current density was higher than normal conductor coil. Efficiency of WPT between transmitter and receiver coils was changed by a quality of shielding. We used the shielding materials such as glass, iron, steels, aluminum etc. The efficiency of WPT system was depended on the shielding materials of transmitter and receiver coils. As a result, magnetic material such as aluminum, iron reduced the magnetic flux density and the efficiency of WPT. remarkably, but in non-magnetic material such as glass and plastic, the efficiency of WPT was unaffected.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.273-278
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• 2009

The experimental study is performed to investigate the optimum design of the system dissipating properly heat from the in-situ solar panel installed on site. For this purpose, six 12-Watts panels, which are set at the different conditions of the solar panels contained phase change material, changing the array of the aluminum fin and honeycomb at the back of the panel, are tested. PCM, which has $44^{\circ}C$ melting point, is chosen in this study. In order to enhance the thermal heat from the absorbed heat in PCM, finned aluminum plate is placed. Furthermore, Aluminum honeycomb is imbedded in the back container to find if it would improve the thermal conductivity of PCM. As a result, the solar panel, which is combined with honeycomb and outward fins with PCM instead of placing the fine inward, is showing the best performance in terms of controling panel temperature and efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.356-359
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• 2003

This paper deals with a flat type ultrasonic motor, which uses a longitudinal-bending multi mode vibrator of rectangular form. This ultrasonic motor was designed by combination of the first longitudinal and eighth bending mode, and the motor consisted of a straight aluminum alloy bar bonded with piezoelectric ceramic elements as a driving element. The geometrical dimensions of the rectangular aluminum vibrator were determined by Euler-Bernoulli theory In the experimental device, piezoelectric ceramics ( a piece of ceramic for the L-mode, $24\;{\times}\;8\;{\times}\;1[mm]$, and four pieces for the B-mode, $12.5\;{\times}\;8\;{\times}\;1[mm]$) were attached to one side of a aluminum plate($100\;{\times}\;8\;{\times}\;1[mm]$), and the stator was supported with a plastic case. As results, no-load rpm was 50[rev./m] when applied voltage was 150[Vrms] at the resonance frequency, and as the voltage was increased, the rpm was increased.

• Imaging Science in Dentistry
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• v.46 no.3
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• pp.203-210
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• 2016

Purpose: The purpose of this study was to investigate appropriate contrast reference values (CRVs) by comparing the contrast in phantom and clinical images. Materials and Methods: Phantom contrast was measured using two methods: (1) counting the number of visible pits of different depths in an aluminum plate, and (2) obtaining the contrast-to-noise ratio (CNR) for 5 tissue-equivalent materials (porcelain, aluminum, polytetrafluoroethylene [PTFE], polyoxymethylene [POM], and polymethylmethacrylate [PMMA]). Four panoramic radiographs of the contrast phantom, embedded in the 4 different regions of the arch-form stand, and 1 real skull phantom image were obtained, post-processed, and compared. The clinical image quality evaluation chart was used to obtain the cut-off values of the phantom CRV corresponding to the criterion of being adequate for diagnosis. Results: The CRVs were obtained using 4 aluminum pits in the incisor and premolar region, 5 aluminum pits in the molar region, and 2 aluminum pits in the temporomandibular joint (TMJ) region. The CRVs obtained based on the CNR measured in the anterior region were: porcelain, 13.95; aluminum, 9.68; PTFE, 6.71; and POM, 1.79. The corresponding values in the premolar region were: porcelain, 14.22; aluminum, 8.82; PTFE, 5.95; and POM, 2.30. In the molar region, the following values were obtained: porcelain, 7.40; aluminum, 3.68; PTFE, 1.27; and POM, - 0.18. The CRVs for the TMJ region were: porcelain, 3.60; aluminum, 2.04; PTFE, 0.48; and POM, - 0.43. Conclusion: CRVs were determined for each part of the jaw using the CNR value and the number of pits observed in phantom images.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1904-1906
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• 1999

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. It was shown that the electric voltage of a thermoelectric generator with 128 thermoelectric modules was 4.8 voltage per Kelvin, and the longitudinal stresses of an aluminum tube with a two-point constrained tube could be released more than those with a one-point constrained tube.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.71-79
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• 2010

One of methods that accomplish fuel-efficient vehicle is to reduce the overall vehicle weight by using aluminum structure typically for cross members, rails and panels in body and chassis. For aluminum structures, the use of Self Piercing Rivet(SPR) is a relatively new joining technique in automotive manufacture. To predict SPR fatigue life, fatigue behavior of SPR connections needs to be investigated experimentally and numerically. Tests and simulations on lap-shear specimen with various material combinations are performed to obtain the joining strength and the fatigue life of SPR connections. A Finite element model of the SPR specimen is developed by using a FEMFAT SPR pre-processor. The fatigue lives of SPR specimens with the curvature are predicted using a FEMFAT 4.4e based on the liner finite element analysis.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1599-1607
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• 2003

The characteristics of elastic waves emanated from crack initiation in 6061 aluminum alloy subjected to fatigue loading are investigated through experiments. The objective of the study is to determine the differences in the properties of the signals generated from fatigue test and also to examine if the sources of the waves could be identified from the temporal and spectral characteristics of the acoustic emission (AE) waveforms. The signals are recorded using nonresonant, flat, broadband transducers attached to the surface of the alloy specimens. The time dependence and power spectra of the signals recorded during the tests were examined and classified according to their special features. Six distinct types of signals were observed. The waveforms and their power spectra were found to be dependent on the crack propagation stage and the type of fracture associated with the signals. The potential application of the approach in health monitoring of structural components using a network of surface mounted broadband sensors is discussed.

• Transactions of Materials Processing
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• v.21 no.8
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• pp.467-472
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• 2012

Shaving shear-welding is a solid-state welding process, which utilizes plastic deformation of surplus material. The solid-state nature of this process contributes to high integrity and strength of the weld. The objective of this study was to investigate the effects of process variables on the material flow patterns and identify the process condition for obtaining the best weld. FEM simulations were carried out along with experimental characterizations. The results showed the importance of the cutter angles and the overlap lengths, and helped attain the optimum shaving shear-welding die and the best process condition.