• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.338-343
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc., In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel(SAE 9254, DIN 50CrV4) are made. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from (1) on low stress condition, the single stage shot peening is not affected by nonmetallic inclusion under metal. (2) it is possible that the two-stage shot peening increases the fatigue life and the high stress, but, that is affected by nonmetallic inclusion under metal. (3) so far, beeasily 50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.114-119
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• 2010

There are a number of studies on chemically strengthened glass. Most of them are strengthened in molten salt bath below transformation range of glass. This research is distinguished from the aforementioned studies in that single $KNO_3$ powder was used by employing screen printing technique. In this study soda-lime-silicate(SLS) glasses for bulletproof glass application with various thicknesses were used. The maximum value of the bending strength is 791MPa heat treated at $480^{\circ}C$, which is about 4.3 times higher than the parent glass, which is the highest strength of all soda-lime glasses. In this study, it is also observed that Vickers hardness increased to $657H_v$, which is about 15% higher than the parent glass($568.7H_v$) and fracture toughness was not changed. Depth profiles measured by electron probe micro analyzer(EPMA) showed a correlation between the migrations of $K^+$ ions with bending strength of ion exchanged glasses.

• Steel and Composite Structures
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• v.49 no.6
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• pp.713-728
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• 2023

This paper aims to investigate the free vibration analysis of FG plates, taking into account the effects of even and uneven porosity. The study employs the Hellinger-Reisner functional and obtains the element's bending stress and membrane stress fields from the analytical solution of the governing equations of the thick plate and plane problem, respectively. The displacement field serves as the second independent field. While few articles on free vibration analysis of circular plates exist, this paper investigates the free vibration of both rectangular and circular plates. After validating the proposed element, the paper investigates the effects of porosity distributions on the natural frequency of the FG porous plate. The study calculates the natural frequency of thin and thick bending plates with different aspect ratios and support conditions for various porosity and volume fraction index values. The study uses three types of porosity distributions, X, V, and O, for the uneven porosity distribution case. For O and V porosity distribution modes, porosity has a minor effect on the natural frequency for both circular and rectangular plates. However, in the case of even porosity distribution or X porosity distribution, the effect of porosity on the natural frequency of circular and rectangular plates increases with an increase in the volume fraction index.

• The korean journal of orthodontics
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• v.22 no.3 s.38
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• pp.647-656
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• 1992

The purpose of this study was to evaluate the elastic memory process in cold worked stainless steel wire and the effect of heat treatment on it. 0.018 inch round and $0.019\times0.025$ inch rectangular wire (ORMCO stainless wire) were used in this study. Each wire type had 4 groups: non-heat treatment group, furnace heat treatment group, electric current heat treatment group, and bending after heat treatment group. Each group was consisted of 10 specimens. With the Jig, each wire was bent into v-shape uniformly, and width of two free ends of each v-shaped wire was measured by caliper (to the point of 0.1 mm correctly) at time interval of offjig, after heat treatment, 1, 2, 3, 4 hours, 1, 2, 3, 4, 5, 6 days, 1, 2, 3, 4 weeks after. The results were as follows: 1. In non-heat treatment group and bending after heat treatment group, elastic memory process was occured $60\%$ within 1 hour, and more than $90\%$ within 1 week. 2. In furnace and electric current heat treatment group, almost all elastic memory process was occured during teat treatment, and then specimen was stabilized dimensionally. 3. Magnitude of deformation by elastic memory was greater in heat treatment group than non heat treatment group and bending after heat treatment group. 4. There was no remarkable difference in deformation pattern between 0.018 inch round wire and $0.019\times0.025$ inch rectangular wire.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.221-226
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• 2001

The basal slip (0001)1/3<1120 > dislocation velocity in sapphire ($\alpha$-$Al_2$$O_3$) single crystals was measured by four-point bending test. The bending experiment was carried out in the temperature range from 120$0^{\circ}C$ to $1400^{\circ}C$ at various engineering stresses 90MPa, 120MPa, and 150MPa. The velocity of such dislocations was estimated from the bending displacement rate of the four-point bend sample. The dependence of temperature and stress in dislocation velocity was investigated. The activation energy for dislocation velocity was determined to be about 2.2$\pm$0.4eV. In addition, the stress exponent (m) describing the stress dependence of dislocation velocities was in the range of 2.0$\pm$0.2.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.491-497
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• 2014

PURPOSE. This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION. The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.103-112
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• 1992

The ultimate bending moment of ships is one of the principle strength considered in ship design. Several methods have been proposed to predict the ultimate bending moment and its major part is, in general, predicting the ultimate compressive strength of stiffened panels. In this paper, made is the review on the methods and formulae of predicting the ultimate compressive strength and they are applied to predicting the ultimate bending moment. Safely levels of three bulk carriers have been derived evaluated for two loading conditions, stray, light ship condition and full load condition, and wave bending by Classification Society Rule(ABS, DnV and Lloyd Rule). The present reliability analysis problem is strictly non-linear and the Advanced First-Order Reliability Method has been used. From the results of parametric studies, the methods of predicting the ultimate compressive strength of stiffened panels are compared from the view point of their applicability to the reliability assessment of ships structures. The paper ends wish a brief discussion drawn from the parametric studies and the extension of the study is described.

• The Journal of the Korean dental association
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• v.53 no.9
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• pp.644-655
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• 2015

Purpose: This study was conducted to evaluate the effect of the fixture abutment connection type and diameter on the screw joint stability in external butt joint for 2nd surgery and internal cone connected type implant system for 1st and 2nd surgery using ultimate fracture strength. Materials and Methods: USII system, SSII system and GSII system of Osstem Implant were used. Each system used the fixture with two different diameters and cement-retained abutments, and tungsten carbide / carbon coated abutment screws were used. Disc shaped stainless steel metal tube was attached using resin-based temporary cement. The experimental group was divided into seven subgroups, including the platform switching shaped specimen that uses a regular abutment in the fixture with a wide diameter in USII system. A static load was increased to the metal tube at 5mm deviated point from the implant central axis until it reached the compression bending strength at a rate of 1mm/min. Then the deformations and patterns of fracture in threaded connection were compared. Results and Conclusion: 1. In the comparison between the Regular diameter, compression bending strength of SSII system was higher than USII system and GSII system. There was no significant difference between USII system and GSII system. 2. In the comparison between wide diameter, compression bending strength was increased in the order of GSII system, USII system, and SSII system. 3. In comparison between the implant diameter, compression bending strength of the wide diameter was greater than the regular diameter in any system(P<0.05). 4. There was no significant difference between the platform switching (III group) and the regular diameter (I group) in USII system. 5. In USII system, fracture of abutment screw and deformation of both fixture and abutment were observed in I, II and III subgroups. 6. Failure pattern of SSII system, which was the fracture of abutment screw and deformation of the abutment and fixture, was observed in both IV and V subgroups. Fracture of some fixtures was observed in subgroup V. 7. Failure pattern of GSII system, which was the fracture of the abutment screw and deformation of the fixture and the abutment, was observed in both VI and VII subgroups. Apart from other subgroups, subgroup VII demonstrated no bending neither the fracture at the top of the fixture. The compressive deformation of internal slope in the fixture was the only thing observed in subgroup VII.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.77-77
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• 2017

Titanium and its alloys offer attractive properties in a variety of applications. These are widely used for the field of biomedical implants because of its good biocompatibility and high corrosion resistance. Titanium anodizing is often used in the metal finishing of products, especially those can be used in the medical devices with dense oxide surface. Based on SAE/AMS (Society of Automotive Engineers/Aerospace Material Specification) 2488D, it has the specification for industrial titanium anodizing that have three different types of titanium anodization as following: Type I is used as a coating for elevated temperature forming; Type II is used as an anti-galling coating without additional lubrication or as a pre-treatment for improving adherence of film lubricants; Type III is used as a treatment to produce a spectrum of surface colours on titanium. In this study, we have focused on Type II anodization for the medical (dental and orthopedic) application, the anodized surface was modified with gray color under alkaline electrolyte. The surface characteristics were analyzed with Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM), surface roughness, Vickers hardness, three point bending test, biocompatibility, and corrosion (potentiodynamic) test. The Ti-6Al-4V alloy was used for specimen, the anodizing procedure was conducted in alkaline solution (NaOH based, pH>13). Applied voltage was range between 20 V to 40 V until the ampere to be zero. As results, the surface characteristics of anodic oxide layer were analyzed with SEM, the dissecting layer was fabricated with FIB method prior to analyze surface. The surface roughness was measured by arithmetic mean deviation of the roughness profile (Ra). The Vickers hardness was obtained with Vickers hardness tester, indentation was repeated for 5 times on each sample, and the three point bending property was verified by yield load values. In order to determine the corrosion resistance for the corrosion rate, the potentiodynamic test was performed for each specimen. The biological safety assessment was analyzed by cytotoxic and pyrogen test. Through FIB feature of anodic surfaces, the thickness of oxide layer was 1.1 um. The surface roughness, Vickers hardness, bending yield, and corrosion resistance of the anodized specimen were shown higher value than those of non-treated specimen. Also we could verify that there was no significant issues from cytotoxicity and pyrogen test.

• Computers and Concrete
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• v.11 no.1
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• pp.63-73
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• 2013

In this study, the effect of reducing cement by proportional addition of waste powder rubber on the performance of concrete under impact three-point bending loading were investigated experimentally and numerically. Concrete specimens were prepared by adding 5%, 10% and 20 % of rubber powder as filler to the mix and decreasing the same percentage of cement. For each case, three beams of $50mm{\times}100mm{\times}500mm$ were loaded to failure in a drop-weight impact machine by subjecting them to 20 N weight from 300mm height, while another three similar beams were tested under static load. The bending load-displacement behavior was analyzed for the plain and rubberized specimens, under static and impact loads. A three dimensional finite-element method simulation was also performed by using LUSAS V.14 in order to study the impact load-displacement behavior, and the predictions were validated with the experimental results. It was observed that, despite decreasing the cement content, the proportional addition of powder rubber until 10% could yield enhancements in impact tup, inertial load and bending load.