• Title/Summary/Keyword: Plastic viscosity

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A Study of the Friction Characteristics of Plastics on Lubricated Condition (윤활상태에서 플라스틱의 마찰특성에 관한 연구)

  • 강석춘
    • Tribology and Lubricants
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    • v.8 no.1
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    • pp.48-55
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    • 1992
  • The friction characteristic of plastics (PTFE, Nylon, Acetal and phenolic) was studied on the lubricated condition with a pin on disk machine. Mineral oil without additive (base oil) and water were used as liquid lubricants at the controlled temperature. From the experimental work, it was found out that the coefficient of friction of plastics was controlled by the mechanical properities of plastic more than that of liquid for various load and temperature. Viscosity of liquid has affected on the friction only at low temperature under lighb load. Among the tested plastics, the coefficient of friction of PTFE was the lowest under light load and at low temperature while Nylon at medium load and temperature, and Acetal at heavy load and high temperature. The coefficient of friction of soft plastics like PTFE and Nylon were increased as the load and temperature were increased, while that of hard plastic (Acetal) was decreased and that of thermo setting plastic (phenolic) was mixed. Also for soft plastics, the coefficient of friction under heavy load was always higher than that under light load, while hard plastic was vice versa.

Flexural Rigidity of MMA-Modified Fiberglass Reinforced Plastic Composite Pipe (MMA 개질 강화 플라스틱 복합관의 휨강성)

  • 연규석;최종윤;백종만;권택정;정중호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.429-432
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    • 2003
  • MMA-modified fiberglass-reinforced plastic composite pipe was produced by using the binder of MMA-modified unsaturated polyester resin in which low viscosity MMA was added to unsaturated polyester resin. Sixteen specimens were made of polymer mortar and fiberglass-reinforced plastic by the centrifugal method. For these specimens the external strength tests were carried out by taking the core thickness consisting of polymer mortar and the fiberglass content per unit area as experimental variables to figure out the effect of variations of these variables influencing on flexural rigidity that is an important property for the composite pipe. Results of this study are believed to provide the basic data for more economical and practical design of MMA-modified fiberglass-reinforced plastic composite pipe.

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A Plastic Analysis of Structures under the Impact Loading (충격하중(衝擊荷重)을 받는 구조물(構造物)의 소성(塑性)모델에 따른 거동분석(擧動分析))

  • Ahn, Byoung Ki;Lee, Sang Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.2
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    • pp.21-33
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    • 1992
  • Under the intense-impulsive loading, structures are subjected to the wide range of pressures at an instantaneous time. The constitutive laws capable to describe the material behavior under the extreme pressure as well as the low pressure are necessary for the analysis of the structural behavior under the intense -impulsive loadings. In this study, two plastic models, the pressure independent Von-Mises model and the pressure dependent Drucker-Prager model, are employed for the wave propagation analysis. Governing equations of this study are conservation equations of momentum and mass in Lagrangian coordinate system which is fixed to the material. Due to the shock-front which violates the continuity assumptions inherent in the differential equations numerical artificial viscosity is used to spread the shock front over several computational zones. These equations are solved by Finite Difference Method with discretized time and space coordinates. The associate normality flow rule as a plastic theory is implemented to find the plastic strains.

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Identification of Cross-WLF Viscosity Model Parameters Using Optimization Technique (최적화기법을 이용한 Cross-WLF점도 모델 계수 추정)

  • Kim, Sun-Yong;Park, Si-Hwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.623-632
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    • 2018
  • Predicting the behavior of rheological polymers is highly shear rate- and temperature-dependent. The Cross-WLF viscosity model has become a powerful solution that describes the shear rate- and temperature-dependent characteristics. To estimate the behavior of polymers in computational simulations, the coefficients of the Cross-WLF model should be well identified. An identification technique was proposed to determine the Cross-WLF viscosity model coefficient. The assumption is that the Cross-WLF viscosity model well describes the real characteristics of polymers when the calculated viscosity with the parameters is identical to the reference data. In this study, Auto-desk Moldflow data were used as a reference. The numerical examples showed that the proposed method accurately identifies the Cross-WLF viscosity model coefficients.

Tribological Influence of Kinematic Oil Viscosity Impregnated in Nanopores of Anodic Aluminum Oxide Film (함침 오일 점도에 따른 나노동공 구조의 산화알루미늄 박막의 마찰 및 마멸 거동)

  • Kim, Dae-Hyun;Ahn, Hyo-Sok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.5
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    • pp.625-630
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    • 2013
  • The friction behavior of a 60-${\mu}m$-thick anodic aluminum oxide (AAO) film having cylindrical nanopores of 45-nm diameter was investigated as a function of impregnated oil viscosity ranging from 3.4 to 392.6 cSt. Reciprocating ball-on-flat sliding friction tests using a 1-mm-diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 to 1 N in an ambient environment. The friction coefficient significantly decreased with an increase in the oil viscosity. The boundary lubrication film remained effectively under all test conditions when high-viscosity oil was impregnated, whereas it was easily destroyed when low-viscosity oil was impregnated. Thin plastic deformed layer patches were formed on the worn surface with high-viscosity oil without evidence of tribochemical reaction and transfer of counterpart material.

[Retraction]Characterization of carbon black nanoparticles using asymmetrical flow field-flow fractionation (AsFlFFF)

  • Kim, Kihyun;Lee, Seungho;Kim, Woonjung
    • Analytical Science and Technology
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    • v.32 no.3
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    • pp.77-87
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    • 2019
  • High viscosity carbon black dispersions are used in various industrial fields such as color cosmetics, rubber, tire, plastic and color filter ink. However, carbon black particles are unstable to heat due to inherent characteristics, and it is very difficult to keep the quality of the product constant due to agglomeration of particles. In general, particle size analysis is performed by dynamic light scattering (DLS) during the dispersion process in order to select the optimum dispersant in the carbon black dispersion process. However, the existing low viscosity analysis provides reproducible particle distribution analysis results, but it is difficult to select the optimum dispersant because it is difficult to analyze the reproducible particle distribution at high viscosity. In this study, dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) analysis methods were compared for reproducible particle size analysis of high viscosity carbon black. First, the stability of carbon black dispersion was investigated by particle size analysis by DLS and AsFlFFF according to milling time, and the validity of analytical method for the selection of the optimum dispersant useful for carbon black dispersion was confirmed. The correlation between color and particle size of particles in high viscosity carbon black dispersion was investigated by using colorimeter. The particle size distribution from AsFlFFF was consistent with the colorimetric results. As a result, the correlation between AsFlFFF and colorimetric results confirmed the possibility of a strong analytical method for determining the appropriate dispersant and milling time in high viscosity carbon black dispersions. In addition, for nanoparticles with relatively broad particle size distributions such as carbon black, AsFlFFF has been found to provide a more accurate particle size distribution than DLS. This is because AsFlFFF, unlike DLS, can analyze each fraction by separating particles by size.

A Study on Viscosity Reducing of Cement-Based Materials by Replacing Byproducts and Adding Low-Viscosity Type HRWR (산업부산물 치환 및 저점도형 고성능 감수제를 사용한 시멘트 계열 재료의 점도저하 방안 연구)

  • Son, Bae-Geun;Han, Dongyeop
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.4
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    • pp.353-358
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    • 2017
  • The aim of this research is providing a fundamental idea on reducing viscosity of high performance cementitous materials. In rheological aspect, to determine the fluidity of the cementitious materials, both yield stress and viscosity should be controlled. For the high performance cementitious materials with low water-to-binder ratio and high volume fraction, it was difficult to reduce the viscosity with superplasticizer while reducing yield stress was relatively easy. Hence, in this research, with the goal of reducing viscosity of the cementitious materials, both ways of reducing viscosity were suggested: achieving proper combination of powder conditions, and adding low-viscosity typed water reducer. First, by replacing various byproduct powders, specifically, raw coal ash and wasted limestone powder showed favorable results on reducing viscosity of the cement paste. Regarding the low viscosity typed superplasticizer, it showed a good performance on reducing viscosity comparing with generic superplasticizer. Therefore, based on the results of this research, it is expected to provide a fundamental idea on reducing viscosity of cementitious materials by various methods.

Rheological Studies on the Aqueous Suspension of Korean Bentonite (국산벤토나이트 현탁액의 유동학적 성질)

  • Kim, Eun-Hee;Rhee, Gye-Ju
    • YAKHAK HOEJI
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    • v.34 no.5
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    • pp.302-310
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    • 1990
  • A study has been made of the Korean bentonite aqueous suspension contrast with American bentonite by means of XRD IR swelling, gel formation and rheogram at various conditions such as concentration, temperature and pH. The Korean bentonite was identified as montmorillonite clay containig a small proprotion of crystoballite and mordenite, and its swelling power were acceptable for requirements of Korean pharmacopeia regulations though its values were not satisfied. Korean bentonite swelled to 10 times and American one did to 15 times compared to its bulkiness of powder. The rheogram of Korean bentonite suspension reveals bulged pseudoplatic flow with yield value at higher concentration and pseudoplastic flow without yield value at lower concentration. The higher the concentration, the greater were the apparent viscosity and hysteresis loop. Korean bentonite suspension showed insignificant temperature dependence on both apparent viscosity and hysteresis loop and it was more temperature dependent on viscosity but less on hysteresis loop than those of American sample. The pH dependence was so high on viscosity that apparent minimum value was near pH 7 and maximum value at pH 3 or 7. The hysteresis loop appeared minimum over the pH range 5-7 and maximum near pH 3 or 11. The Korean bentonite was inferior to the American bentonite in swelling volume, gel formation, thioxotropy, however, it would be possible to improve the quality of Korean bentonite by developing the method of purification for bentonite clay.

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Dynamic Simulation of Solid Particle Considering Change by Viscosity in Rheology Material (반응고 재료에서 점성을 고려한 고상입자의 거동예측을 위한 수치모사 해석)

  • Kwon, K.Y.;Kang, C.G.
    • Transactions of Materials Processing
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    • v.18 no.1
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    • pp.26-38
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    • 2009
  • It was reported that the semi-solid forming process has many advantages over the conventional forming process, such as a long die life, good mechanical properties and energy savings. It is very important, however, to control liquid segregation to gain mechanical property improvement of materials. During forming process, rheology material has complex characteristics, thixotropic behavior. Also, difference of velocity between solid and liquid in the semi-solid state material makes a liquid segregation and specific stress variation. Therefore, it is difficult for a numerical simulation of the rheology process to be performed. General plastic or fluid dynamic analysis is not suitable for the behavior of rheology material. The behavior and stress of solid particle in the rheology material during forging process is affected by viscosity, temperature and solid fraction. In this study, compression experiments of aluminum alloy were performed under each other tool shape which is rectangle shape(square array), rectangle shape(hexagonal array), and free shape tool. In addition, the dynamics behavior compare with Okano equation to power law model which is viscosity equation.