• Title/Summary/Keyword: Fracture Performance

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A 2-year clinical evaluation of Sculpture crowns

  • Ku, Chul-Whoi;Yang, Hong-So
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.6
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    • pp.806-813
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    • 2000
  • Statement of problems. There are only a few studies available that deal with the clinical behavior of ceromer systems as potential substitutes for metal-ceramic crowns. Purpose. This prospective study was initiated to evaluate the clinical performance of 35 Sculpture crowns after 2 years in service. Material and methods. Thirty five Sculpture crowns were placed for 20 patients (7 men and 13 women). All patients were treated by the same dentist, and all restorations were fabricated by the same dental laboratory. Crown placement involved both the anterior and posterior regions of the dental arches. Patients were evaluated by two examiner at baseline, 12, and 24 months using the CDA quality assessment system in addition to periodontal criteria. Results. Of 34 crowns remaining in the study after 2 years, only one crown had experienced a marginal fracture. The crown was replaced as a result of recurrent caries. All remaining crowns were ranked as either excellent or acceptable for surface and color, anatomic form, and marginal integrity. Conclusion. The 2-year clinical observations and ranking with the CDA quality assessment criteria supported the conclusion that Sculpture crowns may be used in substitutes for metal-ceramic crowns.

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Properties of Electrical Performance on Stator Coil of Traction Motor by Accelerated lest using Transient Surge (과도서지를 이용한 가속열화 시험법에 따른 견인전동기 고정자 코일의 전기적 특성 변화)

  • 박현준;장동욱;이길헌;최종선;김저우
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.9
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    • pp.783-789
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    • 2003
  • The winding problems of traction motor are the major determinant of motor's life. The root cause of winding failure is gradual deterioration of the insulation due to thermal, electrical, mechanical and environmental stresses. The aging of the insulation reduces the electrical and mechanical strength of the insulation. At same point, a voltage surge or mechanical shock from a traction motor start will fracture or break down the insulation. To achieve the expected life usually requires extensive laboratory evaluation of the insulation systems and the use of accelerated aging tests. There are several nondestructive test available for checking, the condition of motor insulation, the probable extent of aging, and the rate of which aging is taking place. So the insulation characteristics of stator coil were each analyzed by measurement of dielectric loss(tan$\sigma$), capacitance and partial discharge. The method of diagnosis is able to analyze the insulation condition and evaluate the life of the traction motor.

Modeling mesoscale uncertainty for concrete in tension

  • Tregger, Nathan;Corr, David;Graham-Brady, Lori;Shah, Surendra
    • Computers and Concrete
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    • v.4 no.5
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    • pp.347-362
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    • 2007
  • Due to heterogeneities at all scales, concrete exhibits significant variability in mechanical behavior from sample to sample. An understanding of the fundamental mechanical performance of concrete must therefore be embedded in a stochastic framework. The current work attempts to address the connection between a two-dimensional concrete mesostructure and the random local material properties associated within that mesostructure. This work builds on previous work that has focused on the random configuration of concrete mesostructures. This was accomplished by developing an understanding of the effects of variations in the mortar strength and the mortar-aggregate interfacial strength in given deterministic mesostructural configurations. The results are assessed through direct tension tests that are validated by comparing experimental results of two different, pre-arranged mesostructures, with the intent of isolating the effect of local variations in strength. Agreement is shown both in mechanical property values as well as the qualitative nature of crack initiation and propagation.

Structural coupling mechanism of high strength steel and mild steel under multiaxial cyclic loading

  • Javidan, Fatemeh;Heidarpour, Amin;Zhao, Xiao-Ling;Al-Mahaidi, Riadh
    • Steel and Composite Structures
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    • v.27 no.2
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    • pp.229-242
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    • 2018
  • High strength steel is widely used in industrial applications to improve the load-bearing capacity and reduce the overall weight and cost. To take advantage of the benefits of this type of steel in construction, an innovative hybrid fabricated member consisting of high strength steel tubes welded to mild steel plates has recently been developed. Component-scale uniaxial and multiaxial cyclic experiments have been conducted with simultaneous constant or varying axial compression loads using a multi-axial substructure testing facility. The structural interaction of high strength steel tubes with mild steel plates is investigated in terms of member capacity, strength and stiffness deterioration and the development of plastic hinges. The deterioration parameters of hybrid specimens are calibrated and compared against those of conventional steel specimens. Effect of varying axial force and loading direction on the hysteretic deterioration model, failure modes and axial shortening is also studied. Plate and tube elements in hybrid members interact such that the high strength steel is kept within its ultimate strain range to prevent sudden fracture due to its low ultimate to yield strain ratio while the ductile performance of plate governs the global failure mechanism. High strength material also significantly reduces the axial shortening in columns which prevents undesirable frame deformations.

Estimation of Heat Transfer Characteristics for a Solar Chemical Reactor (고온 태양열 화학반응기 열전달 성능 평가)

  • Kang, Kyung-Mun;Lee, Ju-Han;Cho, Hyun-Suk;Seo, Tae-Beom
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2221-2226
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    • 2008
  • The objective of this paper is to describe the experimental and numerical investigation of the analysis of the heat transfer in a solar chemical reactor. These are compared about methane steam reforming process in the solar chemical reactor which was a volumetric absorber consisting of honeycomb and a multilayered catalyst supports. With this high operating temperature, convective heat loss, thermal fracture are important features for designing SCR. In order to estimate the system performance and to design the actual solar reactor with various conditions, CFD analysis was used in this study. The nickel oxide porous metal is inserted inside the solar chemical reactor to increase the conversion rate of the reforming reaction. Simulation has been carried out based on the experimental data. According to the simulation results, the optimum methane-steam mole ratio and thickness and numbers of catalyst supports were obtained.

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Three-dimensional finite element simulation and application of high-strength bolts

  • Long, Liji;Yan, Yongsong;Gao, Xinlin;Kang, Haigui
    • Steel and Composite Structures
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    • v.20 no.3
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    • pp.501-512
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    • 2016
  • High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

Lifetime Performance of EB-PVD Thermal Barrier Coatings with Coating Thickness in Cyclic Thermal Exposure

  • Lu, Zhe;Lee, Seoung Soo;Lee, Je-Hyun;Jung, Yeon-Gil
    • Korean Journal of Materials Research
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    • v.25 no.10
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    • pp.571-576
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    • 2015
  • The effects of coating thickness on the delamination and fracture behavior of thermal barrier coating (TBC) systems were investigated with cyclic flame thermal fatigue (FTF) and thermal shock (TS) tests. The top and bond coats of the TBCs were prepared by electron beam-physical vapor deposition and low pressure plasma spray methods, respectively, with a thickness ratio of 2:1 in the top and bond coats. The thicknesses of the top coat were 200 and $500{\mu}m$, and those of the bond coat were 100 and $250{\mu}m$. FTF tests were performed until 1140 cycles at a surface temperature of $1100^{\circ}C$ for a dwell time of 5 min. TS tests were also done until more than 50 % delamination or 1140 cycles with a dwell time of 60 min. After the FTF for 1140 cycles, the interface microstructures of each TBC exhibited a sound condition without cracking or delamination. In the TS, the TBCs of 200 and $500{\mu}m$ were fully delaminated (> 50 %) within 171 and 440 cycles, respectively. These results enabled us to control the thickness of TBC systems and to propose an efficient coating in protecting the substrate in cyclic thermal exposure environments.

Bonding performance and fracture strength of resin-infiltrated zirconia blocks for CAD/CAM systems (캐드캠 시스템에서 사용되는 레진침투 지르코니아 블록의 접착양상과 파절강도)

  • Kim, Sa-Hak;Kim, Chong-Kyen;Kim, Wook-Tae;Kim, Jae-Hong
    • Journal of Technologic Dentistry
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    • v.38 no.4
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    • pp.273-280
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    • 2016
  • 연구목적: 본 연구의 목적은 통상적으로 사용되는 글라스 세라믹과 고분자를 침투시킨 지르코니아 소재로 제작된 코어와 레진 시멘트의 굴곡강도 및 결합강도를 비교하여 하이브리드 기술이 치과 재료의 물리적인 성질에 미치는 영향을 조사하기 위함이다. 연구방법: 본 두 가지의 통상적으로 사용되는 세라믹소재[Vita PM9(GC) and I-JAM(ZC)] 와 다른 두 가지 하이브리드 세라믹 소재 [CELTRA Duo(ZRC) and Vita Enamic(RIZ)] 를 평가하였다. 각 그룹의 소재를 선택하여 결합강도와 굴곡강도, 그리고 scanning electron microscopy(SEM)을 이용하여 표면분석을 시행하였다. 도출된 결과 데이터는 일원분산분석(One-way ANOVA)을 통해 분석되었으며, 제1종 오류의 수준은 0.05로 하였다. 연구결과: RIZ 그룹에서 가장 높은 결합강도를 보였으며(p<0.05), ZC 그룹이 가장 낮은 결과를 보였다. 상대적으로 굴곡강도는 ZC 그룹이 가장 높은 수치를 나타내었으며, RIZ 그룹이 가장 취약했다. 연구결론: 하이브리드 기술로 제작된 소재(RIZ 그룹)는 우수한 레진 시멘트와의 결합강도를 보였지만, 그에 비해 굴곡강도는 상대적으로 통상적인 지르코니아 소재보다 비교적 취약한 결과를 보였다.

Interference Effects on the Thickness of a Pulse Pressure Sensor Array Coated with Silicone (맥 센서 어레이(array)의 실리콘(silicone) 코팅 두께에 따른 센서 간 간섭효과)

  • Jun, Min-Ho;Jeon, Young Ju;Kim, Young-Min
    • Journal of Sensor Science and Technology
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    • v.25 no.1
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    • pp.35-40
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    • 2016
  • Pulse diagnosis is one of the representative diagnostic methods in Oriental medicine. In this study, a pulse pressure sensor array coated with silicone, which includes 6 piezo-resistive sensors and 1 thermistor, is fabricated for pulse measurement. It is necessary to coat the pulse sensor array with silicone to avoid the fracture or damage of pressure sensors when the sensor is in contact with the skin and a constant pressure is applied. However, the silicone coating on the pulse sensor array can cause signal interference among the sensors in the pulse sensor array. The interference number (IN), a calculation for expressing the degree of interference among channels, is changed according to the silicone thickness on the pulse sensor array. The IN is increased by a thick silicone coating, but the fabrication error, an important index for the mass production of the sensor array, is reduced by the thickness of the silicone coating. We propose that the thickness of the silicone on the pulse sensor array is an important consideration for the performance of the fabricated sensor and manufacturing repeatability.

The Shape Optimization of washing Machine Shaft for High-Speed Rotation through Analysis of Static and Dynamic Characteristics (정특성 및 동특성 해석을 통한 고속세탁기 주축의 형상 최적화)

  • Kim, Eui-Soo;Lee, Jung-Min;Kim, Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.5
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    • pp.132-139
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    • 2008
  • To meet demand of big capacity and high speed rotation for washing machine, more stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. Also, Vibration occurs due to the frequency of the rotating parts. But, shaft has various design factors such as diameter and distance between bearings according to configuration of shaft, the optimal values can't be easily determined. Using a design of experiment (DOE) based on the FEM (Finite Element Method), which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor under bending, twist and vibration and proposed optimum design using center composition method among response surface derived from regression equation of simulation-based DOE.