• Journal of Welding and Joining
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• 제14권5호
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• pp.122-133
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• 1996

In order to evaluate the cryogenic fracture characteristics of structural steels for superconducting magnets of fusion reactor, small punch (SP) testing was performed on austenitic stainless steel (JN1 base metal) and its TIG weldments at 293K, 77K and 4K. The mechanical properties with respect to the extracted location of the weld metal, on the effects of welding heat cycle about base metal near fusion line in TIG weldments were investigated. The mechanical property of the weld metal in TIG weldments depends on distance from welding root, root region of weldments having the lowest mechanical property. The base metal near fusion line showed degradation of mechanical property caused by cyclic heating during the TIG welding. Based on the test results, HAZ was found to be up to 5mm from the fusion line. It is shown that SP testing is a useful tool to evaluate the mechanical properties with respect to the microstructures changes such as HAZ as well as weld metal in TIG weldments at cryogenic temperature.

• Proceedings of the KWS Conference
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.803-808
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• 2002

A computer-aided alloy-designing technique to develop the insert metal for transient liquid phase (TLP) bonding was applied to high aluminum Ni-base superalloys. The main procedure of a mathematical programming method was to obtain the optimal chemical composition through rationally compromising the plural objective performances of insert metal by a grid-search which involved data estimation from the limited experimental data using interpolation method. The objective function Z which was introduced as an index of bonding performance of insert metal involved the melting point, hardness (strength), formability of brittle phases and void ratio (bonding defects) in bond layer as the evaluating factors. The contour maps of objective function Z were also obtained applying the interpolation method. The compositions of Ni-3.0%Cr-4.0%B-0.5%Ce (for ${\gamma}$/${\gamma}$/${\beta}$ type alloy) and Ni3.5%Cr-3.5%B-3%Ti (for ${\gamma}$/${\gamma}$ type alloy) which optimized the objective function were determined as insert metal. SEM observations revealed that the microstructure in bond layers using the newly developed insert metals indicated quite sound morphologies without forming microconstituents and voids. The creep rupture properties of both joints were much improved compared to a commercial insert metal of MBF-80 (Ni-15.5%Cr-3.7%B), and were fairly comparable to those of base metals.

• Mycobiology
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• 제35권3호
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• pp.150-153
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• 2007

New $N_2O_2$ donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and $^1H$ NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of $10{\sim}31{\mu}g/ml$.

• Proceedings of the KWS Conference
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.522-527
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• 2002

The microstructure and mechanical properties of friction stir welded OFC plates with 2mm in thickness were examined with the changing welding parameters such as welding speed, rotation speed in this study. The sounding welding conditions was acquired at the optimum welding conditions of the 41mm/min to 61mm/min of welding speed at 1250 rpm of rotation speed. The microstructure of weld zone was divided into four parts such as the base metal region (EM), thermal mechanical affected zone (TMAZ), heat affected zone (HAZ), stir zone (SZ). The grain size in the SZ and the width of weld nugget were increased with increasing welding speed. The hardness profiles of the base metal were distributed about 80HV. The HAZ is a slightly softened region of about 60~75 HV relative to the base metal. The hardness profiles of the SZ were higher than that of base metal. The tensile strength was increased with increasing welding speed. In case increasing rotation speed, tensile strength was decreased. The maximum tensile strength was about 220:MPa which was 110% of joint efficience of that of base metal at 41mm/min of welding speed, 1250rpm of rotation speed.

• Transactions of the Korean Society of Automotive Engineers
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• 제10권2호
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• pp.186-192
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• 2002

The fatigue crack propagation characteristics were investigated on dissimilar friction weld of two kind of heat-resisting steels (STR3 and STR35) commonly used in valve materials for vehicles. A small circular artificial defect was machined to induce fatigue crack at bonded line, heat affected zone and base metal of the weld on the surface of the specimens. From the results of the experiment, the fatigue limits of the materials STR3 and STR35 were obtained to be 429.0MPa and 409.4MPa respectably. The STR35 base metal and 1.0mm HAZ specimens showed 190% and 82% higher fatigue life than STR3 base metal. And the fatigue life of 1.0mm HAZ specimen was shown 99% on STR3 and 29% on STR35 higher than that of their base metal. But the fatigue life of weld interface specimen was shown 18% on STR3 and 72% on STR35 lower than that of their base metal because of the weld interface separation.

• Proceedings of the KWS Conference
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.263-265
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• 2006

• Journal of Technologic Dentistry
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• 제14권1호
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• pp.133-138
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• 1992

The base of a metal base denture that is made of acrylic resin base and metal in lined by soft liner named silicon rubber and its merits are as follows. 1. It has a good retention and fastness. 2. It has a good comfort and stability. 3. It is easy to mix various kinds of base materials. 4. It is easy to repair. 5. The pressure of bone and mucosal tissue is decreased and bite force is dispersed.

• Corrosion Science and Technology
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• 제14권2호
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• pp.54-58
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• 2015

A heavy oil of low quality has been mainly used in the diesel engine of the merchant ship as the oil price has been significantly jumped for several years. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, 1.25Cr-0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion resistance of the heat affected and weld metal zones was also increased than that of the base metal zone. Furthermore, it appeared that the corrosive products with red color and local corrosion like as a pitting corrosion were more frequently observed on the surface of the base metal zone compared to the heat affected and weld metal zones. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the 1.25Cr-0.5Mo electrode.

• The Journal of Korean Academy of Prosthodontics
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• 제34권2호
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• pp.363-372
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• 1996

A common site of fracture in maxillary complete denture is on the anteroposterior midline that coincides with the notch for relief of the labial frenum. Various approaches to reduce the incidence of this type of fracture have been suggested. The most widely used technique is the reinforcement of acrylic resin denture base with several solid metal forms. But few comparative studies on the efficacy of metal reinforcements have been reported. This study was conducted to compare reinforcing effects of commonly available metal reinforcements, which include wire, metal mesh embedded in the denture base and metal plate affixed to the impression surface of denture base by silicoating technique. This was load on the posterior. The strain gauges were oriented perpendicular to the anteroposterior midline of maxillary polished denture surface at one labial and the four palatal sites Non-renforced denture was used as control. The results were as follows : 1. In the non-reinforced denture group, only tensile strains on the palatal polished surface were observed. The tensile strains decreased in the order of incisive papilla, posterior denture border area, mid palatal area and rugae area. Compressive strain was observed on the labial polished surface. 2. As compared with the non-reinforced denture group, the metal plate or the metal mesh reinforced denture groups showed reduced palatal tensile strains,and the metal mesh reinforcement had a better reinforcing effect than the metal plate. But both reinforced denture groups showed no difference in the amount of compressive strain on the labial polished surface when compared to the non-reinforced denture group. 3. The metal wire positioned just above the labial notch decreased the compressive strain on the labial polished surface. But the presence of metal wires in the palatal polished surface caused increase in tensile strains in the area.

• Journal of Technologic Dentistry
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• 제22권1호
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• pp.79-88
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• 2000

The objective of this finite element method study was to analyze the stress distribution induced in a maxillary central incisor Ni-Cr base metal coping ceramic crowns with various margin design. Margin designs of crown in this experiment were knife-edge metal margin on chamfer finishing line of tooth preparation(M1), butt metal margin on shoulder finishing line(M2), reinforced butt metal margin on shoulder finishing line(M3), beveled metal margin on bevelde shoulder finishing line(M4). Two- dimensional finite element models of crown designs were subjected to a simulated biting force of 100N which was forced over porcelain near the lingual incisal edge. Base on plane stress analysis, the maxium von Miss stresses(Mpa) in porcelain venner was 0.432, in metal coping was 0.579, in dentin abutment was 0.324 for M1 model, and M2 model revealed in porcelain was 0.556, in metal coping was 0.511, in dentin was 0.339, and M3 model revealed in porcelain was 0.556, in metal coping was 0.794, in dentin was 0.383 for M4 model. All values of each material in metal-ceramic crown were much below the critical failure values.