• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.391-398
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• 2010

In this paper, we propose a sensor design by using a polysilicon strain gauge bonded to a metal diaphragm. The fabrication process of the thin polysilicon strain gauges having thicknesses of $50\;{\mu}m$ was established using conventional MEMS technologies; further, the technique of glass frit bonding of the polysilicon strain gauge to the stainless steel diaphragm was established. Performance of the polysilicon strain gauge bonded to the metal cantilever beam was evaluated. The gauge factor, temperature coefficient of resistance (TCR), nonlinearity, and hysteresis of the polysilicon strain gauge were measured. The results demonstrate that the resistance increases linearly with tensile stress, while it decreases with compressive stress. The value of the gauge factor, which represents the sensitivity of strain gauges, is 34.0; this value is about 7.15 times higher than the gauge factor of a metal-foil strain gauge. The resistance of the polysilicon strain gauge decreases linearly with an increase in the temperature, and TCR is $-328\;ppm/^{\circ}C$. Further, nonlinearity and hysteresis are 0.21 % FS and 0.17 % FS, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1591-1597
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• 2012

Adherend samples were made from unsaturated polyester and woven and mat glass fibers by the hand layup and vacuum methods. The mechanical properties of the adhesive, composite adherends, and terminal-joint and secondary-joint specimens were determined experimentally. Combinations of the experiment results and the bonding theory were used in this study. The maximum and average shear stresses were calculated based on the maximum tensile force and geometry parameters of the joint specimens. The results of the maximum and average shear stresses were compared and evaluated for six joints. The results showed that the grinding and grind/acetone joint had the highest strength among three types of terminal-joints. Similarly, the mat-mat and mat-woven joints had the highest strength among three types of secondary-joints with the same value. Conversely, no treatment and woven-woven bonding had very low strength. In each case, failure occurred always at two ends and then moved toward the middle area of the overlap length.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.47-51
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• 1995

Several intermediate glasses are investigated to bond the alumina and the hydroxyapatite (HAp). The chemical compositions of the intermediate glasses are chosen as $CaO-Al_2O_3$. The mole ratio of CaO/$Al_2O_3$ is changed from 0.5 to 3.0. The lowest melting is observed at $1355^{\circ}C$ in the specimen of CaO/$Al_2O_3$ at the mole ratio of 2. With increasing contents of $Al_2O_3$, the melting temperatures gradually increase and a number of pores are observed. The sectional microstructure shows that the good wetability is observed in higher contents of CaO specimens. This implies that the good wetability is obtained in the mole ratio range of CaO/$Al_2O_3geq2$. The phase transformations are observed after treatment but the major peaks of HAp still exist.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.126-132
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• 2013

PURPOSE. Post surface conditioning is necessary to expose the glass fibers to enable bonding between fiber post and resin cement. The purpose of the present study was to evaluate the effect of different surface conditioning on tensile bond strength (TBS) of a glass fiber reinforced post to resin cement. MATERIALS AND METHODS. In this in vitro study, 40 extracted single canal central incisors were endodontically treated and post spaces were prepared. The teeth were divided into four groups according to the methods of post surface treatment (n=10): 1) Silanization after etching with 20% $H_2O_2$, 2) Silanization after airborne-particle abrasion, 3) Silanization, and 4) No conditioning (Control). Adhesive resin cement (Panavia F 2.0) was used for cementation of the fiber posts to the root canal dentin. Three slices of 3 mm thick were obtained from each root. A universal testing machine was used with a cross-head speed of 1 mm/minute for performing the push-out tests. Two-way ANOVA and Tukey post hoc tests were used for analyzing data (${\alpha}$=0.05). RESULTS. It is revealed that different surface treatments and root dentin regions had significant effects on TBS, but the interaction between surface treatments and root canal regions had no significant effect on TBS. There was significant difference among $H_2O_2$ + Silane Group and other three groups. CONCLUSION. There were significant differences among the mean TBS values of different surface treatments. Application of hydrogen peroxide before silanization increased the bond strength between resin cements and fiber posts. The mean TBS mean values was significantly greater in the coronal region of root canal than the middle and apical thirds.

• Advances in nano research
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• v.15 no.1
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• pp.49-57
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• 2023

As composite materials are used in many applications, the modern world looks forward to significant progress. An overview of the application of composite fiber materials in sports equipment is provided in this article, focusing primarily on the advantages of these materials when applied to sports equipment, as well as an Analysis of the influence of sports equipment of fiber-reinforced composite material on social sports development. The present study investigated surface morphology and physical and mechanical properties of S-glass fiber epoxy composites containing Al₂O₃ nanofillers (for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%). A mechanical stirrer and ultrasonication combined the Al₂O₃ nanofiller with the matrix in varying amounts. A compression molding method was used to produce sheet composites. A first physical observation is well done, which confirms that nanoparticles are deposited on the fiber, and adhesive bonds are formed. Al₂O₃ nanofiller crystalline structure was investigated by X-ray diffraction, and its surface morphology was examined by scanning electron microscope (SEM). In the experimental test, nanofiller content was added at a rate of 1, 2, and 3% by weight, which caused a gradual decrease in void fraction by 2.851, 2.533, and 1.724%, respectively, an increase from 2.7%. The atomic bonding mechanism shows molecular bonding between nanoparticles and fibers. At temperatures between 60 ℃ and 380 ℃, Thermogravimetric Analysis (TGA) analysis shows that NPs deposition improves the thermal properties of the fibers and causes negligible weight reduction (percentage). Thermal stability of the composites was therefore presented up to 380 ℃. The Fourier Transform Infrared Spectrometer (FTIR) spectrum confirms that nanoparticles have been deposited successfully on the fiber.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.235-242
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• 2012

Purpose: The purpose of this study was to compare the fracture behavior of Zironia, glass infiltrated Alumina and PFM full crown system. Materials and methods: Fifteen crowns for each of 3 experimental groups (Zironia, glass infiltrated Alumina and PFM full crown) were made by the conventional method. The crowns mounted on the testing jig were inclined in 30 degrees to the long axis of the tooth and the universal testing machine was used to measure the fracture strength. Results: 1. The mean fracture strengths were $588.3{\pm}49.6MPa$ for zirconia system, $569.1{\pm}61.8MPa$ for PFM system and $551.0{\pm}76.5MPa$ for glass-infiltrated alumina system (P>.05). 2. The mean shear bond strengths were $25.5{\pm}5.6MPa$ for zirconia system, $38.9{\pm}5.0MPa$ for Ni-Cr alloy system and $39.4{\pm}5.1MPa$ for glass-infiltrated alumina system. 3. The chemical bonding was observed at interfaces between PFM or glass-infiltrated alumina and veneering porcelain, however, no chemical bonding was observed at interface between zirconia and veneering porcelain. Conclusion: With the study, the fracture strengths of PFM crown system had a higher fracture strength than conventional zirconia system crown and glass-infiltrated alumina crowns. and than the shear bond strengths glass-infiltrated alumina system had a higher shear bond strength than conventional PFM system and zirconia system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.206-210
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• 2018

Two kinds of bioactive glass were coated on the Ti6Al4V alloy by the enameling technique. In order to reduce the thermal stress due to the difference in expansion coefficient with the alloy with the secondary coating forming hydroxyapatite, the difference in expansion coefficient between the alloy and the two glasses was adjusted at $2{\times}10^{-6}/^{\circ}C$ intervals. FE-SEM and EDS analysis showed that good adhesion was formed between the Ti6Al4V alloy and the primary coating by diffusion bonding. After immersion in SBF solution, it was confirmed from FT-IR that hydroxycarbonate apatite formed in the secondary coating was not different from bulk bioactive glass.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.1-6
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• 2002

Micro engine that includes Micro scale combustor is fabricated. Design target was focused on the observation of combustion driven actuation in MEMS scale. Combustor design parameters are somewhat less than the size recommended by feasibility test. The engine structure is fabricated by isotropic etching of the photosensitive glass wafers. Electrode is formed by electroplating of the Nickel. Photosensitive glass can be etched isotropically with almost vertical angle. Bonding and assembly of structured photosensitive glass wafer from the engine. Combustor size was determined to be 1mn scale. Piston in cylinder moves by fuel injection and reaction. In firing test, adequate engine operation including ignition, flame propagation and piston motion was observed. Present study warrants further application research on MEMS scale internal combustion power units.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.533-538
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• 2014

Today, silicon and epoxy resin are used as materials of conversion lenses for white LEDs on the basis of their good bonding and transparency in LED packages. But these materials give rise to long-term performance problems such as reaction with water, yellowing transition, and shrinkage by heat. These problems are major factors underlying performance deterioration of LEDs. In this study, in order to address these problems, we fabricated a conversion lenses using glass, which has good chemical durability and is stable to heat. The fabricated conversion lenses were applied to a remote phosphor type. In this experiment, the conversion lens for white LED was coated on a glass substrate by a screen printing method using paste. The thickness of the coated conversion lens was controlled during 2 or 3 iterations of coating. The conversion lens fabricated under high heat treatment temperature and with a thin coating showed higher luminance efficiency and CCT closer to white light than fabricated lenses under low heat treatment temperature or a thick coating. The conversion lens with $32{\mu}m$ coating thickness showed the best optical properties: the measured values of the CCT, CRI, and luminance efficiency were 4468 K, 68, and 142.22 lm/w in 20 wt% glass frit, 80 wt% phosphor with sintering at $800^{\circ}C$.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.149-153
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• 2000

Substituting composite structures for conventional metallic structures has many advantages because of higher specific stiffness and specific strength of composite materials. In this work, one-piece propeller shafts composed of carbonfepoxy and glass/epoxy composites were designed and manufactured for a rear wheel drive automobile satisfying three design specifications, such as static torque transmission capability, torsional buckling and the fundamental natural bending frequency. Single lap adhesively bonded joint was employed to join the composite shaft and the aluminum yoke. For the optimal adhesive joining of the composite propeller shaft to the aluminum yoke, the torque transmission capability of the adhesively bonded composite shaft was calculated with respect to bonding length and yoke thickness by finite element method and compared with the experimental result. Then an optimal design method was proposed based on the failure model which incorporated the nonlinear mechanical behavior of aluminum yoke and epoxy adhesive. From the experiments and FEM analyses, it was found that the static torque transmission capability of composite propeller shaft was maximum at the critical yoke thickness, and it saturated beyond the critical length. Also, it was found that the one-piece composite propeller shaft had 40% weight saving effect compared with a two-piece steel propeller shaft.