• Title/Summary/Keyword: Three-point Bending

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Comparison between fiber-reinforced polymers and stainless steel orthodontic retainers

  • Lucchese, Alessandra;Manuelli, Maurizio;Ciuffreda, Claudio;Albertini, Paolo;Gherlone, Enrico;Perillo, Letizia
    • The korean journal of orthodontics
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    • v.48 no.2
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    • pp.107-112
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    • 2018
  • Objective: The aim of this study was to examine the properties of fiber-reinforced composite and stainless steel twisted retainers for orthodontic retention. Methods: Three different span lengths (5.0, 8.0, and 14.0 mm) of fiber-reinforced composite were investigated. The three fiber-reinforced composite retainer groups were subdivided according to the storage condition (dry and wet), resulting in a total of six groups. Each stainless steel and fiber-reinforced composite group was comprised of six specimens. The three-point bending flexural test was conducted using a universal testing machine. ANOVA was used to assess differences in the maximum load and maximum stress according to the span length, material, and storage condition. Post-hoc comparisons were performed if necessary. Results: The maximum stress and maximum load were significantly (p < 0.001) associated with the span length, material, and storage condition. The significant interaction between the material and span length (p < 0.001) indicated the differential effects of the material for each span length on the maximum stress and maximum load, with the difference between materials being the highest for the maximum span length. Conclusions: Our findings suggest that fiber-reinforced composite retainers may be an effective alternative for orthodontic retention in patients with esthetic concerns or allergy to conventional stainless steel wires.

Effect of biofilm formation, and biocorrosion on denture base fractures

  • Sahin, Cem;Ergin, Alper;Ayyildiz, Simel;Cosgun, Erdal;Uzun, Gulay
    • The Journal of Advanced Prosthodontics
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    • v.5 no.2
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    • pp.140-146
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    • 2013
  • PURPOSE. The aim of this study was to investigate the destructive effects of biofilm formation and/or biocorrosive activity of 6 different oral microorganisms. MATERIALS AND METHODS. Three different heat polymerized acrylic resins (Ivocap Plus, Lucitone 550, QC 20) were used to prepare three different types of samples. Type "A" samples with "V" type notch was used to measure the fracture strength, "B" type to evaluate the surfaces with scanning electron microscopy and "C" type for quantitative biofilm assay. Development and calculation of biofilm covered surfaces on denture base materials were accomplished by SEM and quantitative biofilm assay. According to normality assumptions ANOVA or Kruskal-Wallis was selected for statistical analysis (${\alpha}$=0.05). RESULTS. Significant differences were obtained among the adhesion potential of 6 different microorganisms and there were significant differences among their adhesion onto 3 different denture base materials. Compared to the control groups after contamination with the microorganisms, the three point bending test values of denture base materials decreased significantly (P<.05); microorganisms diffused at least 52% of the denture base surface. The highest median quantitative biofilm value within all the denture base materials was obtained with P. aeruginosa on Lucitone 550. The type of denture base material did not alter the diffusion potential of the microorganisms significantly (P>.05). CONCLUSION. All the tested microorganisms had destructive effect over the structure and composition of the denture base materials.

Microstructure and Strength Property of Reaction Sintered SiC Materials (반응소결 SiC 재료의 미세조직 및 강도 특성)

  • LEE SANG-PILL;SHIN YUN-SEOK;LEE JIN-KYUNG
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.05a
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    • pp.380-385
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    • 2004
  • The efficiency of complex slurry preparation route for developing the high performance SiC matrix of RS-SiCf/SiC composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of nw/ten silicon were prepared with various C/SiC complex matrix slurries, which associated with both different sizes of starting SiC particles and blending ratios of starting SiC and carbon particles. The characterization of RS-SiC materials was examined by means of SEM, TEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, process optimization methodology is also discussed. The flexural strength of RS-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

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Remaining life prediction of concrete structural components accounting for tension softening and size effects under fatigue loading

  • Murthy, A. Rama Chandra;Palani, G.S.;Iyer, Nagesh R.
    • Structural Engineering and Mechanics
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    • v.32 no.3
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    • pp.459-475
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    • 2009
  • This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

Analysis for Defect Evaluation of Pipes in Nuclear Power Plant (원전 배관의 결함 평가를 위한 해석)

  • Lee, Joon-Seong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.7
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    • pp.3121-3126
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    • 2013
  • The integrity evaluation of pipes in nuclear power plant are essential for the safety of reactor vessel, and integrity must be assured when flaws are found. Accurate stress intensity analyses and crack growth rate data of surface-cracked components are needed for reliable prediction of their fatigue life and fracture strengths. Fatigue design and life assessment are the essential technologies to design the structures such as pipe, industrial plant equipment and so on. The effect of crack spacing on stress intensity factor K values was studied using three-dimensional finite element method (FEM). For the case of cylinder under internal pressure, a significant increase in K values observed at the deepest point of the surface crack. Also, this paper describes the fatigue analysis for cracked structures submitted to bending loads.

Nanostructured Hydroxyapatite for Biomedical Applications: From Powder to Bioceramic

  • Eslami, Hossein;Tahriri, Mohammadreza;Moztarzadeh, Fathollah;Bader, Rizwan;Tayebi, Lobat
    • Journal of the Korean Ceramic Society
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    • v.55 no.6
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    • pp.597-607
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    • 2018
  • In this study, a wet chemical method was used to synthesize nanostructured hydroxyapatite for biomedical applications. Diammonium hydrogen phosphate and calcium nitrate 4-hydrate were used as starting materials with a sodium hydroxide solution as an agent for pH adjustment. Scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, differential thermal analysis, thermal gravimetric analysis, atomic absorption spectroscopy, and ethylenediaminetetraacetic acid (EDTA) titration analysis were used to characterize the synthesized powders. Having been uniaxially pressed, the powders formed a disk-like shape. The sinterability and electrical properties of the samples were examined, and the three-point bending test allowed for the measurement of their mechanical properties. Sedimentation analysis was used to analyze the slurry ability of hydroxyapatite. As in-vitro biological properties of the samples, biocompatibility and cytotoxicity were assessed using osteoblast-like cells and the L929 cell line, respectively. Solubility was assessed by employing a simulated body fluid.

A Study on Fatigue Crack Propagation Behavior in Random Short-Fiber SMC Composites (비규칙 단섬유강화 SMC 복합재료의 피로균열 전파거동에 관한 연구)

  • Kim, Jae-Dong;Koh, Sung-Wi
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.2
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    • pp.204-212
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    • 1990
  • The SMC composite, now being considered in certain structural applications, is anticipated to experience repeated loading during service. Thus, understanding of the fatigue behavior is essential in proper use of the composite material. In this paper, using the SMC composite composed of E-glass chopped strand and unsaturated polyester resin three point bending fatigue tests are carried out to investigate the fatigue crack propagating behavior under various cyclic stresses and fatigue damage of various microcrack forms. The following results are obtained from this study; 1) Most of the total fatigue life of the SMC composite is consumed at the initial extension or the growth of the macroscopic crack. 2) A Paris' type power-law relationship between the crack propagation rate and stress intensity factor range is obtained, and the value of material constant m is much higher (m=9~11)than that of other metals. 3) In case of high cyclic stress the fatigue damage show high microcrack density and short crack length, but in case of low cyclic stress does it vice versa. 4) Fatigue damage is characterized by microcrack density, crack length and distribution of crack orientation.

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Improvement of Mechanical Interfacial Properties of Epoxy/Clay Nanocomposites Using Silane Intercalant (실란유기화제를 이용한 에폭시/클레이 나노복합재료의 기계적 계면 물성 향상)

  • Park, Soo-Jin;Seo, Dong-Il;Lee, Jae-Rock
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2001.10a
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    • pp.125-128
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    • 2001
  • In this wort, the $Na^+-MMT$ has organically modified with silane intercalant to prepare the polymer/clay nanocomposites. The pH. X-ray diffraction (XRD), and contact angles were used to analyze the surface properties of clay and the exfoliation phenomenon of clay interlayer, The mechanical interfacial properties of epoxy/clay nanocomposites were investigated by three-point bending test. From the experimental results. the surface modification made by silane intercalant on clay surface leads to an increase of distance of silicate layers, surface acid value. and electron acceptor parameter of organoclay. The treatments are also necessary and useful for epoxy to intercalate into the interlayer by interacting of electron donor-accepter between basic epoxy and clay surface. The mechanical interfacial properties of the nanocomposites was improved by the presence of dispersed clay nanolayer containing low content of organoclay in comparison with the conventional, which increase the interfacial adhesion between dispersed clay and epoxy resins.

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FEM Analysis of Smart Skin Structure Specimen (스마트 스킨 구조물 시편의 유한요소 해석)

  • 전지훈;황운봉
    • Composites Research
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    • v.16 no.4
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    • pp.59-65
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    • 2003
  • FEM analysis of the smart skin structure, and application of the sandwich structures investigated. The honeycomb manufactures only provide stillness of thickness direction and transverse shear modulus. Although these are dominant mechanical properties. the other mechanical properties are needed in FEM analysis. Hence, this work shows procedures of obtaining those mechanical properties. Honeycomb material was assumed to be ar, isotropic material and properties are estimated by its dominant honeycomb properties. The other honeycomb properties are then obtained by mechanical properties of Nomex. Buckling test and three point bending test were simulated by ABAQUS. Both the shell and solid element models were used. The results were compared with experimental results and analytical approaches. They showed good agreements. This study shows a guideline of FEM analysis of smart skin structure using commercial a FEM package.

High Temeprature Strength Property of Continuous SiC Fiber Reinforced SiC Matrix Composites (SiC 장섬유 강화 SiC 기지 복합재료의 고온강도 특성)

  • Shin, Yun-Seok;Lee, Sang-Pil;Lee, Jin-Kyung;Lee, Joon-Hyun
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.102-105
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    • 2005
  • The mechanical properties of $SiC_f/SiC$ composites reinforced with continuous SiC fiber have been investigated in conjunction with the detailed analysis of their microstructures. Especially, the effect of test temperature on the characterization of $SiC_f/SiC$ composites was examined. In this composite system, a braiding Hi-Nicalon SiC fibric was selected as a reinforcement. $SiC_f/SiC$ composites have been fabricated by the reaction sintering process, using the complex matrix slurry with a constant composition ratio of SiC and C particles. The characterization of $RS-SiC_f/SiC$ composites was investigated by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the high temperature applicability of $RS-SiC_f/SiC$ composites was discussed.

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