Porous Rubber Research Articles

Fabrication of novel lightweight composites by a hydrogel templating technique

A non-conventional way of preparation of lightweight porous materials by templating hydrogels with a range of hydrophilic and hydrophobic scaffolding materials was explored. Sub-millimetre hydrogel slurries of polyacrylamide and gellan gum were templated with aqueous slurries of cement, gypsum and clay–cement mixtures or alternatively, dispersed in curable polydimethylsiloxane (PDMS). After the solidification of the scaffolding material, the evaporation of structured hydrogel produced porous composite material whose pores mimic the hydrogel meso-structure. We studied the density, volume contraction and the compression strength of the formed porous materials as function of the hydrogel initial volume fraction. This versatile hydrogel templating method can be applied very inexpensively to a range of scaffolding materials to yield lightweight porous materials with a great potential for use in the building industry in heat and sound insulation panels, an alternative to aerated concretes, lightweight building blocks, porous rubber substitutes and foam shock absorbers.

1317 水潤滑下での多孔性ゴムの接触状態と接触面内の流れの測定(OS01-3 + GS04 機械要素とトライボロジー + トライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

1317 水潤滑下での多孔性ゴムの接触状態と接触面内の流れの測定(OS01-3 + GS04 機械要素とトライボロジー + トライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

Pressure Dependent Properties of a Compressible Polymer

This paper deals with the investigations of a porous carbon black-filled rubber, tested with regard to its pressure and tension behaviour. In the tension range only uniaxial tests are performed while in the pressure range uniaxial as well as hydrostatic tests are performed. The uniaxial experiments are carried out in a custom-made uniaxial device and the hydrostatic tests in a pressure chamber which is specially developed for this application. The construction and use of the pressure chamber is clearly described in this paper. All experiments are related to the basic elasticity of the material. The viscoelastic behaviour is completely disregarded at this point. Not only the experiments are discussed, also the modelling of the material is looked at. The tested cellular rubber is composed of an incompressible solid phase and a compressible gas phase. For that reason a so-called structural compressibility is observed. The compressible behaviour of cellular rubber is an important property. So the main focus of the paper is on the pressure tests and the simulation of these. The existing material models for rubber like materials only deal with incompressible rubber structures. To represent the compressible behaviour, the Theory of Porous Media is used. The constitutive model is based on a polynomial approach for an incompressible material. This is complemented by a volumetric expansion term with a point of compaction to model the structural compressibility.

Theoretical Analysis on Heat Transfer Characteristics of Metal Rubber

Based on the basic components of the porous Metal Rubber (MR) materials, all kinds of heat transfer modes were analyzed. Wire helix was considered as the micro-element of Metal Rubber by analyzing the characteristics of processing components of Metal Rubber. According to the acoustoelectric analogy method, the heat transfer model of MR was established on the basis of arrangement of wire helix and Fourier Law. The formula of thermal conductivity coefficient was derived. And the LFA 427 instrument was used to obtain thermal conductivity characteristics of MR experimentally. The results showed that the model had certain application. This model was valuable for the analysis of the thermal properties and the design of Metal Rubber. It provided theoretical support for the further engineering application of Metal Rubber in the field of heat insulation.

908 多孔性ゴムと水濡れ面との摩擦における接触面挙動観察(OS9-2 機械要素とトライボロジー(2),オーガナイズドセッション:9 機械要素とトライボロジー)

908 多孔性ゴムと水濡れ面との摩擦における接触面挙動観察(OS9-2 機械要素とトライボロジー(2),オーガナイズドセッション:9 機械要素とトライボロジー)

A Study on Squeeze Film Between Rotating Porous Rubber Surface and Stationary Impermeable Rigid Surface

The theoretical and experimental study is carried out to investigate the squeeze film phenomena between a cylindrical porous block and an impermeable rigid plate. The porous rubber block is rotated and oscillated sinusoidally in the direction perpendicular to its surface, whereas the rigid plate is stationary. The deformation of the porous rubber block is evaluated with an approximate method, in which the cylindrical rubber block is simplified to be a set of concentric rings and each ring is assumed to be deformed only axially and independently from the neighboring ones. The each ring can be replaced a three-element viscoelastic model. The theoretical result agrees approximately with the experimental result and both results show that a rotational motion slightly decreases the squeeze film pressure and force due to a centrifugal force mainly acting on the film. The effects of the permeability of the porous matrix, the velocity slip at the porous surface and the surface deformation of the porous matrix on the squeeze film characteristics are made clear by comparing the results for the squeeze film between the porous rubber surface and the impermeable rigid surface with those between a pair of impermeable rigid plates.

Reproducibility experiments on measuring acoustical properties of rigid-frame porous media (round-robin tests)

This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted.

Homogenization-based constitutive models for porous elastomers and implications for macroscopic instabilities: I—Analysis

The purpose of this paper is to provide homogenization-based constitutive models for the overall, finite-deformation response of isotropic porous rubbers with random microstructures. The proposed model is generated by means of the “second-order” homogenization method, which makes use of suitably designed variational principles utilizing the idea of a “linear comparison composite.” The constitutive model takes into account the evolution of the size, shape, orientation, and distribution of the underlying pores in the material, resulting from the finite changes in geometry that are induced by the applied loading. This point is key, as the evolution of the microstructure provides geometric softening/stiffening mechanisms that can have a very significant effect on the overall behavior and stability of porous rubbers. In this work, explicit results are generated for porous elastomers with isotropic, (in)compressible, strongly elliptic matrix phases. In spite of the strong ellipticity of the matrix phases, the derived constitutive model may lose strong ellipticity, indicating the possible development of shear/compaction band-type instabilities. The general model developed in this paper will be applied in Part II of this work to a special, but representative, class of isotropic porous elastomers with the objective of exploring the complex interplay between geometric and constitutive softening/stiffening in these materials.

1005 回転する多孔質ゴム円板と剛体面間に形成されたスクイズフィルムの潤滑特性に関する実験的研究(OS10-1 潤滑,オーガナイズドセッション:10 機械要素とトライボロジー)

1005 回転する多孔質ゴム円板と剛体面間に形成されたスクイズフィルムの潤滑特性に関する実験的研究(OS10-1 潤滑,オーガナイズドセッション:10 機械要素とトライボロジー)

A Methodology to Construct Approximate Constitutive Equations for Porous Rubber Elastic Materials

The present paper makes use of methods from theory of ductile fracture, which was developed to prevent catastrophic failures of steel vessels, for example gas pipelines. A number of structures are made of porous materials, with elastic, isochoric matrix, or of such materials which may become porous when they are subjected to excessive mechanical loads. Predicting the behavior of such structures requires a continuous model which accounts well for porous materials. In the oil and gas industry context, fluid tightness sheaths or gaskets enter this category. Indeed, these constituents are often made of polymers and may become porous in case of rapid pressure drop. Forecast of their behavior in such circumstances, in particular global tightness forecast, calls for a continuous model accounting for porous materials behavior with sufficient accuracy. The aim of the present paper is to adapt a methodology from ductile fracture theory to construct such a model, through the analysis of a hollow sphere considered as a material Representative Volume Element (RVE). The mechanical problem is written under a variational form, within the framework of material elastic behavior. In the vicinity of the central void, large strains are encountered. The well-known Gurson theory [Gurson, A.L. (1977) J. Eng. Mater. - T. ASME, 99, 2-15] which was developed in the above mentioned context of steel ductile failure is adapted to provide an approximation of the macroscopic (RVE scale) stress tensor. This approximation constitutes the announced model. Computations are performed for one classical rubber elastic behavior (Neo-Hookean model), which is the simplest model combining elasticity and large strain. Finite Element Method computations show that the approximation is sufficiently tight.

Analysis on infiltrative characteristics of deformable porous matal rubber material and paramaters identification

The effect of deformation of porous material on infiltrative performance is investigated.Based on Darcy theory and Boit principle, the Reynolds equation and mathematical expression of deformable metal rubber (MR) material under laminar flow are obtained according to the change of porosity of metal rubber. It is shown that the throttle of MR material is dependent on its porosity and diameter of metal wires. It will be of great value for the application of MR in throttle field.

A Study on Squeeze Films Between Porous Rubber Surface and Rigid Surface: Analysis Based on the Viscoelastic Continuum Model

The squeeze-film effect between a porous rubber surface and a rigid surface has been investigated as a problem of viscoelastic hydrodynamic lubrication (VEHL). An axisymmetric continuum model is introduced to estimate the surface deformation of a cylindrical porous rubber block based on a three-element viscoelastic model. The coefficients in the viscoelastic constitutive equation are experimentally determined and then the deformation of the porous rubber block is calculated by the FEM technique. The approximate solutions for the fluid pressures in the squeeze film are obtained from the equation of motion, which includes both local and convective inertia terms, and the continuity equation, using the perturbation method. Experimental data on the squeeze-film pressures and forces are also obtained under the sinusoidal squeezing motion of a rigid plate facing a cylindrical porous rubber block. It is found that the difference between the VEHL solutions and the EHL (elastohydrodynamic lubrication) solutions becomes more marked for a higher frequency of squeeze oscillation due to the effect of viscoelasticity of the porous rubber. The VEHL solutions hence correspond better to the measured results and yield a smaller surface deformation of the porous rubber block than the EHL solutions as the frequency of squeeze oscillation increases. The results also show that the fluid inertia effect due to the flow in the squeeze film becomes noticeable for a higher frequency of the squeezing motion as the effect of viscoelasticity of the porous rubber.

Second-Order Estimates for the Macroscopic Response and Loss of Ellipticity in Porous Rubbers at Large Deformations

This work presents the application of a recently proposed “second-order” homogenization method (Ponte Castaneda, 2002) to generate estimates for effective behavior and loss of ellipticity in hyperelastic porous materials with random microstructures that are subjected to finite deformations. The main concept behind the method is the introduction of an optimally selected “linear thermoelastic comparison composite”, which can then be used to convert available linear homogenization estimates into new estimates for the nonlinear hyperelastic composite. In this paper, explicit results are provided for the case where the matrix is taken to be isotropic and strongly elliptic. In spite of the strong ellipticity of the matrix phase, the homogenized “second-order” estimates for the overall behavior are found to lose ellipticity at sufficiently large compressive deformations corresponding to the possible development of shear band-type instabilities (Abeyaratne and Triantafyllidis, 1984). The reasons for this result have been linked to the evolution of the microstructure, which, under appropriate loading conditions, can induce geometric softening leading to overall loss of ellipticity. Furthermore, the “second-order” homogenization method has the merit that it recovers the exact evolution of the porosity under a finite-deformation history in the limit of incompressible behavior for the matrix.

Development of Systems for Ball Cleaning of Condensers and Experience of Their Operation

The development of a method for cleaning steam turbine condenser tubes with the help of porous rubber balls (Taprogge Company, Germany) by Russian specialists is presented. The filter for extra cleaning of the cooling water suggested by the VTI forms an autonomous system of water cleaning, which eliminates contamination of the water chambers and tube boards of the condenser.

A Study on Squeeze Films between Porous Rubber Surface and Rigid Surface. 2nd Report. Effects of Permeability of Porous Matrix and Fluid Inertia Force in Squeeze Film.

A theoretical study is carried out to investigate the squeeze film phenomena between a cylindrical porous rubber block and a rigid plate. The porous rubber block is stationary, while the rigid plate is oscillated sinusoidally in the direction perpendicular to its surface or dropped on the porous rubber surface, subjected to its own weight and the squeeze film force. The deformation of the porous rubber block is evaluated with an axisymmetric continuum model based on a three element visco elastic model. The approximate solutions for the film pressure including the fluid inertia effect are obtained using the perturbation method. for each type of rigid plate motion, the numerical results show various effects of the permeability of porous rubber block and the fluid inertia force on squeeze film characteristics such as the film pressure, force, thickness and the leakage flow from the squeeze film.

A Study on Squeeze Films between Porous Rubber Surface and Rigid Surface. 1st Report, Analysis with Visco-Elastic Continuum Model.

A Study on Squeeze Films between Porous Rubber Surface and Rigid Surface. 1st Report, Analysis with Visco-Elastic Continuum Model.

513 多孔質ゴムを用いた周期スクイズフィルム軸受の潤滑特性(O.S.5-3 軸受の高性能化)(オーガナイズドセッション5 : トライボロジーと機械要素およびその応用技術)

513 多孔質ゴムを用いた周期スクイズフィルム軸受の潤滑特性(O.S.5-3 軸受の高性能化)(オーガナイズドセッション5 : トライボロジーと機械要素およびその応用技術)

Eco-Materials in Railway-Recycling and Chemical Analysis.

In this paper, organic materials are studied for environmental purposes. First, recycled materials, such as anti-vibration blocks made of SBR track pads are used for reducing vibration of railway as a means to develop. It is found that low density and porous rubber blocks have suitable properties for reducing vibration and exhibit good performance. Second, an elemental analysis is carried out to evaluate environmental consciousness and development of desirable material in the future. Based on this result, desirable concepts of future materials, such as making simple components and reducing heavy metals, are proposed.

The Effective Elastic Constants of Solids Containing Spherical Exclusions

This paper considers the effective elastic properties of solids containing random arrangements of spherical exclusions. The fully three-dimensional response of an elastic material containing voids undergoing a uniaxial tensile test is simulated using the boundary element method (BEM). The effective Young's modulus and the effective Poisson's ratio are calculated as a function of the void volume fraction by comparing numerical solutions of matrix materials with and without voids. Because these effective properties depend on the microstructure, scatter about a mean value is observed for an ensemble of random configurations of voids at a given volume fraction. The effect of the number of voids on the scatter is studied. To validate the numerical results, comparisons are made with analytic solutions and experimental results. Since the authors could fine no experimental results for the effective Poisson's ratio, experiments were conducted on porous rubber samples to confirm the numerical results.

Effect of Porosity on Dynamic Mechanical Properties of Rubber in Compression

Abstract Cylindrical samples of different levels of porosity were prepared from a model carbon black filled rubber and tested in compression. Dynamic properties were determined with dynamic loads and dynamic displacements superimposed on static loads. Nonlinear stress-strain curves of porous rubber blocks produced a dependence of dynamic properties on the mode of testing. Both storage and loss moduli as well as tan γ were found to depend on the levels of porosity. The loss modulus was found to increase with higher strain levels in porous samples, while the storage modulus changed because of reduced sample stiffness. The dynamic data was in agreement with the results of Goodrich flexometer tests on porous and solid samples. The results suggest that the introduction of porosity reduces service life of rubber parts by providing stress raisers for crack initiation, rather than through changing the dynamic properties.