• Title/Summary/Keyword: rheological processes

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Tunnel lining load with consideration of the rheological properties of rock mass and concrete

  • Lukic, Dragan C.;Zlatanovic, Elefterija M.;Jokanovic, Igor M.
    • Geomechanics and Engineering
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    • v.21 no.1
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    • pp.53-62
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    • 2020
  • Rheological processes in the rock mass for the stress-strain analysis are quite important when considering the construction of underground structures in soft rock masses, particularly in case of construction in several stages. In the analysis, it can be assumed that the reinforced concrete structure is slightly deformable in relation to the rock mass, and the rheological stress redistribution happens at the expense of the elements of rock mass. The basic elements of rheological models for certain types of rock mass and analysis of these models are presented in the first part of this paper. The second part is dedicated to the analysis of rheological processes in marl rock mass and the influence of these processes on the reinforced-concrete tunnel structure.

Physical and Rheological Properties of Thermoplasticized Crosslinked-Polyethylene Foam in Supercritical Methanol

  • Cho, Hang-Kyu;Hong, Soon-Man;Baek, Kyung-Yeol;Koo, Chong-Min;Lee, Hong-Shik;Lee, Youn-Woo
    • Macromolecular Research
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    • v.17 no.12
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    • pp.950-955
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    • 2009
  • The physical and rheological properties of thermoplasticized irradiation-crosslinked polyethylene foam using supercritical methanol treatment were investigated by GPC, FTIR, DSC, WAXS, DMTA and UDS. The polyethylene foam was selectively decrosslinked into thermoplasticized polyethylene in an appropriate supercritical methanol condition without any undesirable side reactions such as oxidation and disproportionation. The thermoplasticization was promoted with increasing reaction temperature to reach completion above $380^{\circ}C$. The supercritical reaction condition affected the crystallization behavior, and mechanical and rheological properties of the decrosslinked polyethylene foam, but not its crystallographic structure or crystallinity.

Capillary Breakup of Viscoelastic Fluid and its Extensional Rheology (점탄성유체의 Capillary Breakup 가시화 및 신장유변물성 측정)

  • Jeon, Hyun Woo;Choi, Chan Hyuck;Kim, Byung Hoon;Park, Jinsoo
    • Journal of the Korean Society of Visualization
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    • v.19 no.1
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    • pp.81-87
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    • 2021
  • Extensional flow of viscoelastic fluids is widely utilized in various industrial processes such as electrospinning, 3D printing and plastic injection molding. Extensional rheological properties, such as apparent viscosity and relaxation time, play an important role in the design and evaluation of the viscoelastic fluid-involved processes. In this work, we propose a lab-built capillary breakup extensional rheometer (CaBER) based on flow image processing to investigate the capillary breakup of polyethylene oxide (PEO) solution and its extensional rheological properties. We found that the apparent extensional viscosity and extensional relaxation time of the PEO solution are independent of the strike time. The proposed CaBER is expected to be applied to characterization of the extensional rheological properties of viscoelastic fluids at low cost with high precision.

Printing Morphology and Rheological Characteristics of Lead-Free Sn-3Ag-0.5Cu (SAC) Solder Pastes

  • Sharma, Ashutosh;Mallik, Sabuj;Ekere, Nduka N.;Jung, Jae-Pil
    • Journal of the Microelectronics and Packaging Society
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    • v.21 no.4
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    • pp.83-89
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    • 2014
  • Solder paste plays a crucial role as the widely used joining material in surface mount technology (SMT). The understanding of its behaviour and properties is essential to ensure the proper functioning of the electronic assemblies. The composition of the solder paste is known to be directly related to its rheological behaviour. This paper provides a brief overview of the solder paste behaviour of four different solder paste formulations, stencil printing processes, and techniques to characterize solder paste behaviour adequately. The solder pastes are based on the Sn-3.0Ag-0.5Cu alloy, are different in their particle size, metal content and flux system. The solder pastes are characterized in terms of solder particle size and shape as well as the rheological characterizations such as oscillatory sweep tests, viscosity, and creep recovery behaviour of pastes.

Performance Investigation of a Cylindrical Valve Featuring Electro-Rheological Fluids (전기유동유체를 이용한 실린더형 밸브의 성능 고찰)

  • Kim, K.S.;Jung, D.D.;Lee, H.J.;Choi, S.B.;Cheong, C.C.
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.4
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    • pp.148-157
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    • 1994
  • A multi-cylindrical hydraulic valve incorporating with an electro-rheological(ER) fluid is developed in this study. Field-dependent Bingham properties of the ER fluid are exploited to devise the valve system which features fast system response as well as simple mechanism. The fast response is accrued from almost instant response characteristics of the ER fluid itself, and the mechanism configuration is simplified since no nechanically moving parts are required. The material properties of the ER fluids to be utilized for modeling of the proposed valve system are firstly tested with a couette-type electroviscometer. The design and manufacturing processes are then undertaken on the basis of model parameters. The performance characteristics of the valve system are evaluated in terms of pressure variations with respect to the intensity of employed electric fields and flow rates.

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Effect of Magnetic Force on Rheological and Compressive Properties of Magneto-Rheological Rubber Composites with Iron Particle and Carbon Nanotubes (자기력이 철 분말 및 탄소나노튜브 강화 자기유동 고무 복합재료의 유동 및 압축 특성에 미치는 영향)

  • Ryu, Sang Ryeoul;Lee, Dong Joo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.2
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    • pp.153-160
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    • 2013
  • An orthotropic magneto-rheological rubber composite (MRRC) based on a general-purpose rubber can be manufactured by using an electromagnetic device during the curing processes of rubber mixtures. The magnetic transmissivity of MRRCs increases with the iron particle (IP) content, and that of aligned MRRCs with a 2-T magnetic field is 1.8 to 2 times higher as compared to that of randomly dispersed MRRCs. The effect of a 2-T magnetic field on carbon nanotube (CNT) reinforced MRRC has been identified clearly, and the magnetic transmissivity is found to be 3.7%. The compressive stress of MRRC (IP 90 + CNT 5, 2 T alignment) under a magnetic field of 0.49 T is 2.1 times higher as compared to that of the matrix. The MR effect of MRRC increases with the IP content, and that of aligned MRRC with the IP 90 and 2 T magnetic field is 20.4%. It is confirmed that the magnetic field when making the specimen and when performing the compression test greatly impacts the compression characteristics.

Changes in Physicochemical and Rheological Properties of Fish Meat Paste during Repeated Freezing and Thawing Process (냉동고기풀의 동결-해동 반복에 의한 물리$\cdot$화학적 성질 및 물성변화)

  • CHOI Hyeon-Mee;KIM Mu-Nam;CHUN Soon-Sil;LEE Keun-Tai
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.22 no.3
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    • pp.115-120
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    • 1989
  • Physicochemical changes were investigated during repeated freezing and thawing processes using fish meat paste of alaska pollack (Theragra chalcogramma). During repeated thawing process, the solubility of myofibrillar protein, $Ca^{++}-ATPase$ activity, water holding capacity (WHC), electrophoretic patterns and rheological properties were evaluated at various thawing temperatures. Solubility of myofibrillar protein and $Ca^{++}-ATPase$ activity were decreased with increasing thawing temperatures. Thawing temperatures and the frequency of freezing and thawing processes did not affect WHC significantly. Upon repeated freezing and thawing cycles, electrophoretic patterns showed that only the amount of myosin heavy chain was decreased, whereas the amount of actin remained constant. Young's modulus for viscoelasticity of fish meat pastes increased with increasing thawing temperatures and the value showed maximum at third cycle and decreased thereafter.

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"Cohesiveness of Hyaluronic Acid Fillers": Evaluation Using Multiple Cohesion Tests

  • Kyun Tae Kim;Won Lee;Eun-Jung Yang
    • Archives of Plastic Surgery
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    • v.51 no.1
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    • pp.14-19
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    • 2024
  • Background Hyaluronic acid fillers can be manufactured using various processes. They have multiple properties, including their concentration, degree of modification, and rheological data. Cohesion is one such property to evaluate gel integrity; however, there is no standardized method for calculating this parameter. This study aimed to evaluate different tests for calculating hyaluronic acid cohesion and discuss the importance of hyaluronic acid cohesion as a consideration when selecting fillers. Methods The cohesion levels of five different hyaluronic acid fillers with different rheological properties were evaluated and compared using the drop weight, compression, tack, and dispersion time tests. Results The cohesion tests yielded different results in the samples. Samples 2 and 4 showed approximately two times the number of droplets when compared with Sample 5 in drop weight test. Samples 1, 2, 3, and 4 were superior to Sample 5 in tack test. Samples 1, 2, and 3 showed cohesive appearances at 95 seconds in most cases in dispersion test. Rheological test results did not reflect the measures of cohesion. Conclusion Although there are no definite standardized tests to evaluate the cohesion of hyaluronic acid fillers, our proposed tests showed similar results for different hyaluronic acid filler products. Further studies are needed to evaluate the cohesion of hyaluronic acid fillers and determine the clinical use of this distinguishing characteristic for clinicians selecting the product of choice. Level of evidence statement: These data are Level IV evidence.

Prediction of the Film Thickness Variation through Film Insert Thermoforming (필름 인서트 열성형 시 필름 두께분포 예측)

  • Kim, G.Y.;Lee, K.O.;Kang, S.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.281-284
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    • 2008
  • Film insert melding is one of the surface processes that enhances functional or aesthetic qualities of an existing product's surface. In general, film insert molding consists of three processes including thermoforming, trimming and injection molding. Thermoforming, which is the first process of film insert molding, is the most important process because the variation of film thickness has an effect on the mold design and process conditions for the subsequent processes, that are, trimming and injection molding. This study is focused on predicting the film thickness distribution through film insert thermoforming process using commercial FEM code. In order to describe rheological behavior of thermoplastic film (ABS), G'Sell's viscoelastic constitutive law was adopted. The numerical model of film insert thermoforming was established, and the simulation to predict film thickness distribution was performed. Comparison between the results of simulation and experiment was made to validate the proposed finite element analysis.

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