• Elastomers and Composites
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• v.56 no.1
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• pp.6-11
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• 2021

In order to develop an ultra-high-density elastomeric material for substitution of steel dynamic dampers, a new curing system and technique for high-loading of the filler were examined in this study. Mechanochemical modification of chloroprene rubber (MAH-g-CR) using an internal mixer was carried out with maleic anhydride (MAH) as a reactive monomer. The optimum amount of MAH was 10 phr and the efficient grafting of MAH on CR could be achieved at a mixing temperature of 100℃. After preparing MAH-g-CR, 50 mol% epoxidized natural rubber (ENR 50) was blended with MAH-g-CR to develop a "self-curable rubber blend system" via reaction between the functional groups of the elastomeric matrices without the curing agent and additives. The content of ENR 50 was fixed at 30 wt.% throughout evaluation of the curing behavior of the MAH-g-CR/ENR blend. Tungsten powder was added to the MAH-g-CR/ENR matrix up to 60 vol.% to obtain ultra-high-density, and the maximum density obtained was 7.57 g/㎤. Stable ts2 (scorch time) and t90 (90% cure time) could be obtained even when tungsten powder was incorporated up to 60 vol.%. In addition, the tensile strength and damping properties of MAH-g-CR/ENR containing 60 vol.% of tungsten were better than those of CR containing 60 vol.% of tungsten.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.39-48
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• 1994

An equivalent homogeneous 3-D linear composite analysis and accomponying finite element program is presented for elastomeric bearings. This study is limited to the 3-D layered system with linear, elastic, isoparametric small deformation. And we used method of multiscale to model the 3-dimensional configurations and overall response of the layered elastomeric bearings with global and local coordinates. The primary dependent variables for the theory have been selected that require only $C_o$ continuity of the finite element analysis. As a result, it is very simple and computationally economical. The presented theory can also be applied easily to the analysis of nonlinear behavior of layered systems. And those of past are not applicable to nonlinear analysis, because it uses superposition theory. Numerical examples are presented to verify the theory and to illustrate potential applications of the analysis.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.146-151
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• 2013

Carbon nanofibers (CNFs) are electrically conductive. When CNFs are used as fillers in resin, this electrical conductivity can be yielded without adversely affecting the mechanical properties of the resin. When an elastomer is adopted as the resin, a conductive elastomer can then be produced. Due to its flexibility and conductive properties, a large strain sensor based on changes in resistivity may be produced, for strain sensing in flexible structures. In this study, a patch-type large strain sensor using resistivity change in a CNF/elastomer composite was proposed. The measurement limits of the sensor were investigated experimentally, and the limit was found to be 40%, which greatly exceeded the limits of conventional metal-foiled strain gages. Also, the proposed CNF/elastomer large strain sensor can be used to measure flexible materials, while conventional strain gages cannot be used to measure such strains.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.291-295
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• 2002

O-ring seal is usual component part in various mechanical apparatus for sealing that makes efficient performance of the equipments. The sealing performance of O-ring is affected in environments of the O-rings, like that applied pressure, working temperature, pre-compressed ratio and materials. In this paper, a pressurized, compressed elastomeric bi-polymer O-ring inserted into a rectangular groove is analyzed numerically using the MARC finite element program. The calculated FEM results showed that bi-polymer O-ring that is manufactured by NBR for an inner and FFKM for an outer ring shows a low temperature distribution among various bi-polymer O-ring models. But, the normal contact stress between the flange and upper part of the O-ring is small compared to other bi-polymer model.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.139-140
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• 2006

Some of novel halogen-free, elastomeric flame retardants for nylon-6 have been developed. It is found that the S-ENP and clay have a synergistic flame retardant effect on nylon-6 resulted from the formation of two barriers on the nanocomposite residue surface at the end of combustion. A novel flame retardant ternary nanocomposite of nylon-6/ENP/nano-Magnesium hydroxide was also fabricated. The new ternary composite has better flame retardancy and thermal stability than the conventional one because nano-MH can disperse much more homogeneous in the new ternary composite than in the conventional one.

• Smart Structures and Systems
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• v.8 no.5
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• pp.471-486
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• 2011

Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite's strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.

• KSTLE International Journal
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• v.2 no.1
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• pp.40-45
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• 2001

The paper deals with a non-linear finite element analysis of the thermomechanical distortions of an elastomeric O-ring seal including a temperature gradient. Axial compression of O-ring seals, as well as the influence of the temperature gradients and various O-ring seal models, are investigated based on the axisymmetric analysis. The highest temperature occurs near the interface of the O-ring between the dovetail groove bottom and the O-ring seal. The calculated FEM results indicate that the composite O-ring with the diametral ratio, 0.8 shows very stable and recommendable compared with other seal models far elevated temperatures and corrosive environments.

• Tribology and Lubricants
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• v.15 no.4
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• pp.297-303
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• 1999

O-rings in automotive engines are important components such as a coolant pipe, engine oil circulating lines and fuel injector for sealing that makes efficient performance of the engine. Life cycle of O-rings is effected in environments of the O-ring seal, like that applied pressure, working temperature, precompressed ratio and materials. It is related in extrusion, expansion and fatigue failure of O-rings. In this paper, an pressurized, compressed elastomeric O-ring inserted into a rectangular groove is analysed numerically using the nonlinear finite element method. The calculated FEM results showed that extrusion ratio and contact stress are strongly related to the gap clearance and edge radius of the groove.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.2
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• pp.146-156
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• 2001

The purpose of this study was twofold. One was to evaluate the wettability of 4 elastomeric impression materials on tooth and different kinds of filling materials. The other was to identify the effect of topical surfactants sprayed on the surface of each impression. The elastomeric impression mate rials used in this experimental study were one polyether(Impregum F) and three polyvinyl siloxanes(Provil novo, Zerosil, Imprint). The abutments were prepared for 3/4 crown or onlay on the extracted human first molar. The filling materials used in this study for the duplication of prepared abutment were composite resin, amalgam, and casting metal. Impression was taken by manufacturer's recommendations and the number of voids on the impression surface was counted. The topical surfactants were Spannex $II^{(R)}$ and $Cohere^{(R)}$. The wettability was evaluated by comparing the number of voids between non-treated group and treated groups. The results were as follows : 1. $Zerosil^{(R)}$ showed the least number of voids on the impression surface. The number of voids increased in order of Provil $novo^{(R)}$, Impregum $F^{(R)}$, and $Imprint^{(R)}$. 2. Impregum $F^{(R)}$ and $Zerosil^{(R)}$ showed the least number of voids on the surface of dental stone master cast. The number is inclosed in order of Provil $novo^{(R)}$ and Imprint 3. When abutment material is tooth, the number of voids on the surface of master cast was smallest compared with that of other abutment materials. The number of voids increased in order of casting metal, amalgam and composite resin 4. The number of voids on the surface of the dental stone master cast was smallest when Spannex $II^{(R)}$ was used, followed by $Cohere^{(R)}$ treated group and non-treated group. These results suggest that the difference in wettability caused by the types of rubber base impression materials as well as abutment materials can affect the number of voids. And the use of topical surfactant for rubber base impression materials can improve the wettability of the materials and enhance the accurate master cast which has fewer surface voids.

• Earthquakes and Structures
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• v.15 no.5
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• pp.513-528
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• 2018

A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems could have different impacts. These kinds of earthquakes can damage the tanks readily. Hence, the seismic behaviour and vibration of cylindrical liquid storage tanks, subjected to earthquakes, is of paramount importance, and it is investigated in this paper. The Finite Element Method is used to evaluate seismic response in addition to the reduction of excessive liquid sloshing in the tank when subjected to the long-period ground motion. The non-linear stress-strain behaviour pertaining to polymers and rubbers is implemented while non-linear contact elements are employed to describe the 3-D surface-to-surface contact. Therefore, Nonlinear Procedures are used to investigate the fluid-structure interactions (FSI) between liquid and the tank wall while there is incompressible liquid. Part I, examines the effect of the flexibility of the isolation system and the tank aspect ratio (height to radius) on the tank wall radial displacements of the tank wall and the liquid sloshing heights. Maximum stress and base shear force for various aspect ratios and different base-isolators, which are subjected to three seismic conditions, will be discussed in Part II. It is shown that the composite-base isolator is much more effective than other isolators due to its high flexibility and strength combined. Moreover, the base isolators may decrease the maximum level pertaining to radial displacement.