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Fracture resistance of CAD-CAM all-ceramic surveyed crowns with different occlusal rest seat designs

  • Chaturvedi, Saurabh;Alqahtani, Turki;Alsolami, Saleh;Alqahtani, Abdulbari;Das, Gotam;Alsubaiy, Ebrahim
    • The Journal of Advanced Prosthodontics
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    • v.13 no.1
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    • pp.36-45
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    • 2021
  • Purpose. To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Materials and Methods. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3rd of buccolingual width of an unprepared tooth) or narrow (1/3rd of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used. Results. The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs (P<.001). Conclusion. The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

Comparative Analysis of Substrate Wet Surface Adhesion and Substrate Movement Response Performance Testing Methods for Injection Type Repair Materials Used in Leakage Cracks of Concrete Structure in Underground Environment (지하 습윤 환경에서 콘크리트 구조물 균열 누수에 사용되는 주입형 보수재료의 부착 성능과 거동 대응 성능 평가의 상관성 분석 연구)

  • Kim, Soo-Yeon;Oh, Kyu Hwan;Oh, Snag-Keun
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.34 no.9
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    • pp.19-26
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    • 2018
  • The focus of this study was centered around 15 common injection type water leakage repair materials (3 different types for each; synthetic polymer, cementitious, acrylic, epoxy, urethane) used in concrete structures of Korea and analyzing their wet surface adhesion performance in accordance to the ISO TS 16774 Test Method for Repair Materials for Water-leakage Cracks in Underground Concrete Structures, Part 4: Test Method for Adhesion on Wet Concrete Surface, and the results of this study was taken to be place under a comparative analysis with the results of the preceeding study on response to substrate movement performance study. The results of this comparative study showed that other than 1 specimen of 1 type of the acrylic and 3 specimens of 1 type of the synthetic polymer type materials, all of the 93% of the specimens used in this study showed stable adhesion on wet substrate surface, and we were able to determine that materials that have proper response properties against substrate movement are highly flexible and have high adhesion properties, but their adhesion properties on wet substrate would change based on their viscosity.

Development of a process to apply uniform pressure to bond CFRP patches to the inner surface of undercut-shaped sheet metal parts (언더컷 형상의 판재 성형품에 보강용 CFRP 패치의 접합을 위한 공정기술 개발)

  • Lee, Hwan-Ju;Jeon, Yong-Jun;Cho, Hoon;Kim, Dong-Earn
    • Design & Manufacturing
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    • v.14 no.4
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    • pp.65-70
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    • 2020
  • Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

Process Design and Economic Evaluation of Condensate Recycling Process for Steam Consumption Reduction (스팀 사용 저감을 위한 응축수 재활용 공정설계 및 경제성 평가)

  • Kim, Jinuk;Choi, Yeongryeol;Cho, Hyungtae;Kim, Junghwan
    • Applied Chemistry for Engineering
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    • v.31 no.6
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    • pp.660-667
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    • 2020
  • This study focused on the epoxy resin production process, which uses the steam of 155 ℃ or higher as a heat source, and discards all condensate generated. A part of the process is operated at low temperatures of 70 ℃ or below, thus there are opportunities to reduce the steam consumption by recycling wasted condensate as a heat source for the low temperature section of process. In this study, we developed process models that can reduce steam by recovering waste heat through recycling condensate and conducted a case study to find an optimal condensate recycling system. Three different process designs were proposed and economic evaluations were performed by comparing annual capital costs and steam savings in each case. Finally, an annual steam consumption of the low-temperature section could be reduced by up to 67.6%, which could also bring an additional economic benefit of 522.1 million won/yr.

Comparison of Mechanical Properties on Helical/Hoop Hybrid Wound HNT Reinforced CFRP Pipe with Water Absorption Behavior (CFRP 파이프의 와인딩 적층 패턴 설계 및 HNT 나노입자 보강에 따른 수 환경에서의 기계적 물성 평가)

  • Choi, Ji-Su;Park, Soo-Jeong;Kim, Yun-Hae
    • Composites Research
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    • v.34 no.3
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    • pp.174-179
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    • 2021
  • Currently, fluid transfer steel pipes take a lot of time and expense to maintain all facilities due to new construction and painting or corrosion and aging. Therefore, this study was conducted for designing a CFRP pipe structure with high corrosion resistance and chemical resistance as a substitute for steel pipes. The helical/hoop pattern was cross-laminated to improve durability, and HNT was added to suppress the moisture absorption phenomenon of the epoxy. The HNT/CFRP pipe was manufactured by a filament winding process, and performed a mechanical property test, and a moisture absorption test in distilled water at 70℃. As a result, the highest bending strength was obtained when the hoop pattern was laminated with a thickness equivalent to 0.6% of the pipe. The 0.5 wt% HNT specimen had the highest moisture absorption resistance. Also, the delamination phenomenon at the interlayer interface was delayed, resulting in the lowest strength reduction rate.

Hydrophobic Organic/Inorganic Composite Films with 3D Hierarchical Nanostructured Surfaces (3D 계층적 나노구조화된 표면을 갖는 소수성 유/무기 복합 필름)

  • Seo, Huijin;Ahn, Jinseong;Park, Junyong
    • Composites Research
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    • v.34 no.4
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    • pp.264-268
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    • 2021
  • In this study, we propose a method for fabricating hydrophobic coatings/films with three-dimensional (3D) hierarchical nanostructured organic/inorganic composite surfaces. An epoxy-based, large-area 3D ordered nanoporous template is first prepared through an advanced photolithography technique called Proximity-field nanoPatterning (PnP). Then, a hierarchically structured surface is generated by densely impregnating the template with silica nanoparticles with an average diameter of 22 nm through dip coating. Due to the coexisting micro- and nano-scale roughness on the surface, the fabricated composite film exhibits a higher contact angle (>137 degrees) for water droplets compared to the reference samples. Therefore, it is expected that the materials and processes developed through this study can be used in various ways in the traditional coating/film field.

Effect of Hydrothermal Reaction Conditions on Piezoelectric Output Performance of One Dimensional BaTiO3 Nanotube Arrays (1차원 BaTiO3 나노튜브 어레이의 압전발전성능에 수열합성 반응조건이 미치는 영향)

  • Lee, Jae Hoon;Hyeon, Dong Yeol;Heo, Dong Hun;Park, Kwi-Il
    • Journal of Powder Materials
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    • v.28 no.2
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    • pp.127-133
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    • 2021
  • One-dimensional (1D) piezoelectric nanostructures are attractive candidates for energy generation because of their excellent piezoelectric properties attributed to their high aspect ratios and large surface areas. Vertically grown BaTiO3 nanotube (NT) arrays on conducting substrates are intensively studied because they can be easily synthesized with excellent uniformity and anisotropic orientation. In this study, we demonstrate the synthesis of 1D BaTiO3 NT arrays on a conductive Ti substrate by electrochemical anodization and sequential hydrothermal reactions. Subsequently, we explore the effect of hydrothermal reaction conditions on the piezoelectric energy conversion efficiency of the BaTiO3 NT arrays. Vertically aligned TiO2 NT arrays, which act as the initial template, are converted into BaTiO3 NT arrays using hydrothermal reaction with various concentrations of the Ba source and reaction times. To validate the electrical output performance of the BaTiO3 NT arrays, we measure the electricity generated from each NT array packaged with a conductive metal foil and epoxy under mechanical pushings. The generated output voltage signals from the BaTiO3 NT arrays increase with increasing concentration of the Ba source and reaction time. These results provide a new strategy for fabricating advanced 1D piezoelectric nanostructures by demonstrating the correlation between hydrothermal reaction conditions and piezoelectric output performance.

Electrode Fabrication of MWCNT-PDMS Strain Sensors by Wet-etching (습식 식각을 이용한 MWCNT-PMDS 변형율 센서 전극 생성에 관한 연구)

  • Jung, La-Hee;Hwang, Hui-Yun
    • Composites Research
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    • v.34 no.6
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    • pp.387-393
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    • 2021
  • This paper investigated the electrical properties of multiwall carbon nanotube reinforced polydimethylsiloxane (CNT-PDMS) strain sensors with copper electrodes on the wet-etched surface. MWCNT-PDMS strain sensors were fabricated according to the wt% of MWCNT. Surfaces on the electrode area were wet-etched with various etching duration and silver epoxy adhesives were spread on the wet-etched surface. Finally, we attached the copper electrodes to the MWCNT-PMDS strain sensors. We checked the electric conductivities by the two-probe method and sensing characteristics under the cyclic loading. We observed the electric conductivity of MWCNT-PDMS strain sensors increased sharply and the scattering of the measured data decreased when the surface of the electrode area was wet-etched. Initial resistances of MWCNT-PDMS strain sensors were inversely proportion to wt% of MWCNT and the etching duration. However, the resistance changing rates under 30% strain increased as wt% of MWCNT and the etching duration increased. Decreasing rate of the electric resistance change after 100 repetitions was smaller when wt% of MWCNT was larger and the etching duration was short. This was due to the low initial resistance of the MWCNT-PMDS strain sensors by the wet-etching.

Study on Improvement of Thermal Stability of Dendrite-shape Copper Particles by Electroless Silver Plating (Dendrite 형상 구리 입자의 무전해 은 도금에 의한 열적 안정성 향상에 관한 연구)

  • Hwang, In-Seong;Nam, Kwang Hyun;Chung, Dae-won
    • Applied Chemistry for Engineering
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    • v.33 no.6
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    • pp.574-580
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    • 2022
  • While in the process of electroless plating of dendrite-shape copper with silver, various silver-coated copper (Ag@Cu) particles were prepared by using both displacement plating and reducing electroless plating. The physicochemical properties of Ag@Cu particles were analyzed by scanning electron microscope- energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller analysis (BET), and it was confirmed that the silver coated by the reducing electroless plating was formed as nano-particles on the copper surface. Ag@Cu particles were compounded with an epoxy resin to prepare a conductive film, and its thermal stability was evaluated. We investigated the effect of the difference between the displacement plating and reducing electroless plating on the initial resistance and thermal stability of conductive films.

An experimental and numerical investigation on fatigue of composite and metal aircraft structures

  • Pitta, Siddharth;Rojas, Jose I.;Roure, Francesc;Crespo, Daniel;Wahab, Magd Abdel
    • Steel and Composite Structures
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    • v.43 no.1
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    • pp.19-30
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    • 2022
  • The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.