• Korean Journal of Materials Research
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• v.31 no.12
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• pp.690-696
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• 2021

The purpose of this study is to develop a zirconium-based alloy with low modulus and magnetic susceptibility to prevent the stress-shielding effect and the generation of artifacts. Zr-7Cu-xSn (x = 1, 5, 10, 15 mass%) alloys are prepared by an arc melting process. Microstructure characterization is performed by microscopy and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness and compression test. The magnetic susceptibility is evaluated using a SQUID-VSM. The average magnetic susceptibility value of the Zr-7Cu-xSn alloy is 1.176 × 10^-8 cm³g^-1. Corrosion tests of zirconium-based alloys are conducted through polarization test. The average Icorr value of the Zr-7Cu-xSn alloy is 0.1912 ㎂/cm². The elastic modulus value of 14 ~ 18 GPa of the zirconium-based alloy is very similar to the elastic modulus value of 15 ~ 30 GPa of the human bone. Consequently, the Sn added zirconium alloy, Zr-7Cu-xSn, is very interesting and attractive as a biomaterial that reduces the stress-shielding effect caused by differences of elastic modulus between human bone and metallic implants. In addition, this material has the potential to be used in metallic dental implants to effectively eliminate artifacts in MRI images due to low magnetic susceptibility.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.1
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• pp.8-19
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• 2022

The metallic implant materials are widely used in biomedical industries due to their specific mechanical strenth, corrosion registance, and superior biocompatability. These metallic materials, however, suffer from the stress-shielding effect and the generation of artifacts in the magnetic resonance imaging exam. In the present study, we develope a Zr-based alloys for the biomedical implant materials with low elastic modulus and low magnetic susceptibility. The Zr-7Si-xSn alloys were fabricated by an arc melting process. The elastic modulus was 24~31 GPa of the zirconium-based alloy. The average magnetic susceptibility value of the Zr-7Si-xSn alloy was 1.25 × 10^-8cm³g^-1. The average I_corr value of the Zr-7Si-xSn alloy was 0.2 ㎂/cm². The Sn added zirconium alloy, Zr-7Si-xSn, is very interested and attractive as a biomaterial that reduces the stress-shielding effect caused by the difference of elastic modulus between human bone and metallic implant.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3459-3469
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• 2022

Matrix composites of n-WO₃/n-Bi₂O₃/PVA with different loadings of n-WO₃/n-Bi₂O₃ mixtures (0-15 wt%) and starch (0 and 3 wt%) were fabricated by using melt-mixing method. The X-ray attenuation capability were evaluated based on mass attenuation coefficient (μ/⍴) using a general diagnostic X-ray machine at 40-100 kVp. The effect of starch addition on the dispersion of the fillers in the PVA matrix were observed by using FESEM through morphological analysis. The fabricated samples have shrunken and caused their thickness to be decreased (0.35 mm-0.55 mm) after the drying process even though fixed thickness (2.0 mm) was set initially. The density and HVL values of the samples with 3 wt% starch was seen lower than samples without starch (0 wt%), however the former have provided improvement in filler dispersion and better X-ray attenuation capability compared to the latter. As conclusion, the matrix composite of n-WO₃/n-Bi₂O₃/PVA with 15 wt% of n-Bi₂O₃, 8 wt% of n-WO₃ and 3 wt% starch can be selected as the best promising candidate for X-ray shielding materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.608-611
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• 2002

In GMAW(Gas Metal Arc Welding) process, bead geometry (penetration, bead width and height) is a criterion to estimate welding quality. Bead geometry is affected by welding current, arc voltage and travel speed, shielding gas, CTWB (contact- tip to workpiece distance) and so on. In this paper, welding process variables were selected as welding current, arc voltage and travel speed. And bead geometry was reasoned from the chosen welding process variables using negro-fuzzy algorithm. Neural networks was applied to design FL(fuzzy logic). The parameters of input membership functions and those of consequence functions in FL were tuned through the method of learning by backpropagation algorithm. Bead geometry could be reasoned from welding current, arc voltage, travel speed on FL using the results learned by neural networks.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.107-110
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• 2003

The electromagnetic intereference(EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanoube(MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-filled glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivities of MWNT/epoxy composites with process variables and MWNT concentrations in X-band(8.2GHz- 12.4GHz). Process variables changed the degree of dispersion, which influenced permittivities and permittivities increased rapidly from 0.5wt% to 1.0wt%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.383-388
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• 1995

The ARC light has been measured using photo-detect system under different TIG welding condition. Light detect system consists of photo diode, ND Filter, OP Amp. A/D convertor and PC. The purpose of this experiment is to show the relationship between ARC light and process variables such as welding current, torch travel speed, etc. The results can be applied to estimate the condition of welding process and the quality of welding products. The signal of ARC light has periodic patterns in good TIG welding condition whereas in abnormal condition the signal has different pattern. Amount of Ar shielding gas and distance from electrode to specimen affect the signal pattern significantly.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.53-56
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• 2007

Magnesium sheet used in electrical device due to mobility and EMF shielding characteristics. Magnesium case by press forming was advantageous compare with conventional die casting process, because of its thin gauge of wall and surface quality. But it need to makes the boss to fix inner part or assemble the case. CD stud welding was effective way for joining the boss to the thin gauge case of the electrical devices. In this study, we investigated the performances of the magnesium boss welder To measure the process parameters such as the force and the weld current, we design the monitoring system for CD stud welding. We test the characteristics of CD stud welding for AZ31 sheets at some variables. Finally we select the optimum welding range of magnesium sheets in CD stud welding process.

• Journal of Aerospace System Engineering
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• v.7 no.2
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• pp.47-54
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• 2013

This paper describes and analyzes the HIRF protection standards of the helicopter category focused on external RF environments. In addition, this paper presents an ideal process of airplane design to accomplish the successful certification. Furthermore, this paper proposes practical recommendations to reduce RF energy on aircraft using specific EMI/EMC techniques such as shielding, grounding and filtering methods. Most of the proposed methods in this paper were key issues during the certification process of KC-100 small airplane which is Korea's first trial aircraft for civil airplane certification.

• Journal of Welding and Joining
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• v.10 no.2
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• pp.32-42
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• 1992

A method of optimization of process parameters in Arc Welding has been discussed in this paper. The method of investigation is based on the numerical calculation of weld bead by a finite element method and non-linear optimization technique is applied to estimated the optimization process parameters from the numerical calculation. The common package program(ANSYS 4.4A) was used to obtain the process parameters for a thin plate arc welding (TIG, CO$_{2}$). The results on some test are satisfactory and the used method of this paper is a useful guide to the optimum welding condition.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.602-606
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• 2006

The electrostatic is well known phenomena. The fires and explosions caused by electrostatic occur often in the coating mechanical system. This paper presents various cases of electrostatic hazards, reasons why electrostatic hazards are happened, and methods for preventing electrostatic hazards. Generally the electrostatic can be lead to corona discharging, streaming electrification, and impinging electrification in the coating process. Corona discharging happens at electrostatic spray gun with 70 kV. Streaming electrification occurs at mixing process between paint and thinner, and transportation process with thinner. Impinging electrification is shown when the thinner are sprayed to drums. For the purpose of preventing the electrostatic discharge and damage, conductors should be ground, surface electric potential of should be decreased in using electrostatic shielding and ground, and flow of thinner should be controlled acceptable velocity.