• Title/Summary/Keyword: 4-point bending strength test

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Effect of water storage on flexural strength of silorane and methacrylate-based composite resins

  • Panahandeh, Narges;Torabzadeh, Hassan;Naderi, Hani;Sheikh-Al-Eslamian, Seyedeh Mahsa
    • Restorative Dentistry and Endodontics
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    • v.42 no.4
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    • pp.309-315
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    • 2017
  • Objectives: This study assessed the effect of water storage on the flexural strength (FS) of low shrinkage composites. Materials and Methods: A total of 165 bar-shaped specimens ($2{\times}2{\times}25mm$) were fabricated of 2 low shrinkage composites (Filtek P90 [3M ESPE], GC Kalore [GC International]) and a conventional methacrylate-based composite (Filtek Z250 [3M ESPE]). The specimens were subjected to 3-point bending test at 6 time intervals, namely: immediately after curing, at 24 hours, 1 week, 1 month, 6 months, and 1 year following storage in wet and dry conditions. The FS of the specimens were measured by applying compressive load at a crosshead speed of 1.0 mm/min. Data was analyzed using 3-way analysis of variance (ANOVA) and Tukey's test. Results: Three-way ANOVA revealed significant interactions between time, type of composite, and storage condition (p = 0.001). Tukey's multiple comparison test revealed significant reductions in FS of all composites after 6 months and 1 year of storage in distilled water compared to dry condition. Conclusions: Filtek P90 showed the highest and GC Kalore showed the lowest FS after 1 year storage in distilled water. The immediate high strength of Filtek Z250 significantly decreased at 1 year and its final value was lower than that of Filtek P90.

FLEXURE STRENGTH AND MICROSTRUCTURE OF IPS EMPRESS 2 GLASS-CERAMIC ON HEAT-PRESSING AND HEAT TREATMENTS (열가압 및 열처리에 따른 IPS Empress 2 세라믹의 굴곡강도와 미세구조)

  • Oh, Sang-Chun;Dong, Jin-Keun;Luthy, Heinz;Scharer, Peter
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.5
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    • pp.575-582
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    • 2000
  • This investigation was designed to determine whether heat-pressing and/or simulated heat treatments affected the flexure strength and the microstructure of the lithium disilicate glass-ceramic in the IPS Empress 2 system. Four groups of the specimens were prepared as follows: group 1 - as-received material, group 2 - heat-pressed material; group 3 - heat-pressed and simulated initial heat-treated material; group 4 - heat-pressed and the simulated heat-treated material with full firings for a final restoration. The three-point bending test and the scanning elec-tron microscope (SEM) analysis was conducted for the purpose of this study. The flexure strength of group 2 was significantly higher than that of group 1. However, there were no significant differences in strength among group 2, 3, and 4, and between group 1 and 4. The SEM micrographs of the lithium disilicate glass-ceramic showed the closely packed, multi-directionally interlocking microstructure of numerous lithium disilicate crystals protruding from the glass matrix. The crystals of the heat-pressed materials (group 2, 3, and 4) were a little denser and about two times bigger than those of the as-received material (group 1). This change of microstructure is more obviously exhibited particularly between group 1 and 2. However, there was no a marked difference among group 2, 3, and 4 after the heat-pressing procedure. Although there were significant increase of the strength and some changes of the microstructure after the heat-pressing operation, the combination of the heat-pressing and the simulated subsequent heat treatments did not produce the increase of strength of IPS Empress 2 glass-ceramic.

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Study on the Intermetallic Compound Growth and Interfacial Adhesion Energy of Cu Pillar Bump (Cu pillar 범프의 금속간화합물 성장과 계면접착에너지에 관한 연구)

  • Lim, Gi-Tae;Kim, Byoung-Joon;Lee, Ki-Wook;Lee, Min-Jae;Joo, Young-Chang;Park, Young-Bae
    • Journal of the Microelectronics and Packaging Society
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    • v.15 no.4
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    • pp.17-24
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    • 2008
  • Thermal annealing and electromigration test were performed at $150^{\circ}C$ and $150^{\circ}C,\;5{\times}10^4\;A/cm^2$ conditions, respectively, in order to compare the growth kinetics of intermetallic compound(IMC) in Cu pillar bump. The quantitative interfacial adhesion energy with annealing was measured by using four-point bending strength test in order to assess the effect of IMC growth on the mechanical reliability of Cu pillar bump. Only $Cu_6Sn_5$ was observed in the Cu pillar/Sn interface after reflow. However, $Cu_3Sn$ formed and grew at Cu pillar/$Cu_6Sn_5$ interface with increasing annealing and stressing time. The growth kinetics of total($Cu_6Sn_5+Cu_3Sn$) IMC changed when all Sn phases in Cu pillar bump were exhausted. The complete consumption time of Sn phase in electromigration condition was faster than that in annealing condition. The quantitative interfacial adhesion energy after 24h at $180^{\circ}C$ was $0.28J/m^2$ while it was $3.37J/m^2$ before annealing. Therefore, the growth of IMC seem to strongly affect the mechanical reliability of Cu pillar bump.

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Evaluation of Flexural Strength Capacity of Large Scale RC Slabs Strengthened with Prestressed CFRP Plate (긴장된 CFRP판으로 보강된 대규모 RC 슬래브의 휨성능 평가)

  • Hong, Ki-Nam;Han, Sang-Hoon;Lee, Byong-Ro;Gwon, Yong-Gil;Woo, Sang-Kyun
    • Journal of the Korean Society of Safety
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    • v.25 no.3
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    • pp.71-77
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    • 2010
  • This paper presents the results of a study on flexural capacity of large size RC slabs strengthened with carbon fiber reinforced polymer(CFRP) plates. A total of 5 specimens of 6.0m length were tested in four point bending after strengthening them with externally bonded CFRP plates. The CFRP plates were bonded without prestress and with two prestress levels, 0.4% and 0.6% of CFRP plate strain. Test variables included the type of strengthening, prestressing level, and the effects according to each test variables are analysed. The experimental results show that proposed methods can increase significantly the flexural capacity such as strength, stiffness of the beam and the increase ranged between 36.2% and 63.2% of the load-carrying capacity of the control beams. The non-prestressed specimen failed by separation of the plate from the beam due to premature debonding while most of the prestressed specimens failed by CFRP plate fracture. And the cracking loads and maximum loads were increased proportionally to the prestress level.

Current Status of $SiC_{f}/SiC$ Composites Material in Fusion Reactor

  • Yoon, Han-Ki;Lee, Sang-Pill
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.166-171
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    • 2007
  • The characterization of monolithic SiC and SiCf/SiC composite materials fabricated by NITE and RS processes was investigated in conjunction with the detailed analysis of their microstructure and density. The NITE-SiC based materials were fabricated, using a SiC powder with average size of 30 nm. RS- SiCf/SiC composites were fabricated with a complex slurry of C and SiC powder. In the RS process, the average size of starting SiC particle and the blending ratio of C/SiC powder were $0.4\;{\mu}m$ and 0.4, respectively. The reinforcing materials for /SiC composites were BN-SiC coated Hi-Nicalon SiC fiber, unidirectional or plain woven Tyranno SA SiC fiber. The characterization of all materials was examined by the means of SEM, EDS and three point bending test. The density of NITE-SiCf/SiC composite increased with increasing the pressure holding time. RS-SiCf/SiC composites represented a great decrease of flexural strength at the temperature of $1000\;^{\circ}C.$

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Influence of CuO Dopants on the Sintering Ability and Phase Stability of Yttria-Stabilized Tetragonal Zirconia Polycrystals (Y-TZP의 燒結性 및 相 安定性에 대한 CuO添加의 影響)

  • Pee, Jae-Hwan;Kim, Yun-Hae;Motozo Hayakawa
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2 s.32
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    • pp.35-40
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    • 1999
  • Effects of CuO addition on the sintering ability and the phase stability of Y-TZP. (Yttria doped Tetragonal Zirconia Polycrystals) were studied. The CuO dopants were found to be quite effective in reducing the sintering temperature to obtain full density and refining the grain size. The maximum allowable concentration of the dopants was limited to 0.3%mol% for CuO to maintain fully tetragonal phase. With the addition of these dopants, the flexual strength decreased by 20% in comparison with the undoped specimen but the fracture toughness increased by 15%.

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Flexural Strength of Reinforced Concrete Beams Containing Recycled Coarse Aggregate (순환굵은골재를 사용한 철근콘크리트 보의 휨강도)

  • Yang, In-Hwan;An, Seul-Ki;Hwang, Chul-Sung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.1
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    • pp.30-39
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    • 2017
  • This paper concerns flexural strength of reinforced concrete beams containing recycled coarse aggregate (RCA) with compressive strength ranging from 31 to 38 MPa. The experimental parameters were replacement ratio of RCA and rebar ratio. Replacement ratio of RCA was 0, 30, 50 and 100%, and rebar ratio was 0.50, 0.79 and 1.14%. The RCA concrete beams were tested by using four-point bending test, and experimental results were discussed regarding crack and failure patterns, load-deflection relationship. Crack pattern of concrete beams with RCA was similar to that of concrete beams with natural coarse aggregate (NCA) but overall crack spacing of concrete beams with RCA was smaller than that of concrete beams with NCA. The crack width of RCA and NCA concrete beams was similar to each other. In addition, the test results of flexural strength were compared to the design code predictions. The design code predictions for flexural strength underestimated the experimental results. Therefore, the design code predictions for flexural strength of RCA concrete beams would offer conservative design.

A COMPARATIVE STUDY OF THE PHYSICOCHEMICAL PROPER TIES AND BOND STRENGTH TO METAL BETWEEN THE REGULAR OPAQUE POWDER AND CORE POWDER (도재소부전장금관용 Opaque 분말과 도재전장관용 core 분말의 물리화학적 성질 및 금속과의 결합력에 대한 비교연구)

  • Lim, Jang-Seop;Chung, Chang-Mo;Jeon, Young-Chan
    • The Journal of Korean Academy of Prosthodontics
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    • v.35 no.1
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    • pp.144-164
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    • 1997
  • The purpose of this study were to investigate the chemical composition, mean particle size, linear thermal expansion coefficient and metal-bonding strength of the regular opaque powder and core powder. In this study, 4 types of ceramic powders, namely Duceram Jacket Opaque powder, Duceram Opaque powder, Vita Hi-Ceram powder, Vita VMK Paint On-88 powder were used. Chemical composition was evaluated by EDS(Energy Dispersive X-ray Spectrophotometer, Oxford QX-2000, England), particle size was measured by MALVERN Instruments(MALVERN Instruments SB. OC., U.S.A.. ad linear thermal expansion coefficient was measured by dilatometer(Motoyama, Japan). Bond strength was measured by the Universal tsting machine(Istron Co., Ltd., U.S.A.). The Results were as follows : 1. Through recognition of the relative difference in chemical composition between the core powder and the regular opaque powder, the difference in the proportion of $Al_2O_3$ in each type of material is demonstrated ; Duceram Jaket Opaque powder : 30.16%, Duceram Opaque powder : 16.60%, Vita Hi-Ceram : 63.64%, Vita VMK Paint-On 88 : 16.16%. 2. There was no significant difference in the proportion of metal-bonding materials between the core powder and the regular opaque powder. 3. In the regular opaque powder, alkaline materials were incoporated in order to increase the coefficient of thermal expansion. 4. In the particle size analysis, there was no significant difference in mean particle size or in the particle size distribution between the core powder and the regular opaque powder. 5. In the thermal expansion test for temperature range of $25-600^{\circ}C$, the regular opaque powder had higher coefficient of thermal expansion than that of core powder. 6. In the 4 point flexural bending test, there was no statistically significant difference in the mean bond strength between the core powder and the opaque powder among the Duceram products.

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Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering

  • Bae, Eun-Jeong;Kim, Ji-Hwan;Kim, Woong-Chul;Kim, Hae-Young
    • The Journal of Advanced Prosthodontics
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    • v.6 no.4
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    • pp.266-271
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    • 2014
  • PURPOSE. The purpose of this study was to compare the fracture strength of the metal and the bond strength in metal-ceramic restorations produced by selective laser sintering (SLS) and by conventional casting (CAST). MATERIALS AND METHODS. Non-precious alloy (StarLoy C, DeguDent, Hanau, Germany) was used in CAST group and metal powder (SP2, EOS GmbH, Munich, Germany) in SLS group. Metal specimens in the form of sheets ($25.0{\times}3.0{\times}0.5mm$) were produced in accordance with ISO 9693:1999 standards (n=30). To measure the bond strength, ceramic was fired on a metal specimen and then three-point bending test was performed. In addition, the metal fracture strength was measured by continuing the application of the load. The values were statistically analyzed by performing independent t-tests (${\alpha}=.05$). RESULTS. The mean bond strength of the SLS group (50.60 MPa) was higher than that of the CAST group (46.29 MPa), but there was no statistically significant difference. The metal fracture strength of the SLS group (1087.2 MPa) was lower than that of the CAST group (2399.1 MPa), and this difference was statistically significant. CONCLUSION. In conclusion the balling phenomenon and the gap formation of the SLS process may increase the metal-ceramic bond strength.

An Effect of TIG Dressing on Fatigue Characteristics of Non Load-Carrying Fillet Welded Joints (TIG처리에 따른 하중비전달형 필렛용접부의 피로특성)

  • Jung, Young Hwa;Kyung, Kab Soo;Hong, Sung Wook;Kim, Ik Gyeom;Nam, Wang Hyone
    • Journal of Korean Society of Steel Construction
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    • v.12 no.5 s.48
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    • pp.617-628
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    • 2000
  • In this study, the 4-point bending test has been performed in order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strength of as-welded specimens has been satisfied the grade of fatigue strength prescribed in specifications of domestics and AASHTO & JSSC, and fatigue strength at $2{\times}106cycles$ of TIG-dressing specimens has been increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks have been occurred at several points, where the radius of curvature and flank angle in the weld bead toes are low, and grown as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has been closely related to the flank angel and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has been largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

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