scholarly journals Micromechanical Modeling of Creep Behavior in Particle-Reinforced Silicone-Rubber Composites

1997 ◽  
Vol 64 (4) ◽  
pp. 781-786 ◽  
Author(s):  
Chao-Hsun Chen ◽  
Chaing-Ho Cheng
Keyword(s):  
Creep Strain ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Micromechanical Modeling ◽  
Elastic Behavior ◽  
Rubber Matrix ◽  
Secondary Creep ◽  
Rubber Composites ◽  
Creep Tests ◽  
Two Phase

A micromechanically based composite model is proposed to study the viscoelastic behavior of solid-filled rubber composites. A nonlinear So-Chen’s (1991) mechanical model which describes the viscoelastic behavior of the rubber matrix is proposed to relate volume-average deformation and stress within the two-phase composite inclusion to the remote (macroscopic) fields. The influence of the volume fractions of inclusions on the overall creep strain of a rubber-matrix composite is investigated at the level of dilute concentration. The creep rate of the rubber matrix, which depends nonlinearly on the creep strain and the primary creep and secondary creep resulting from the viscous flow of creep deformation, is also considered in addition to the usual steady-state, or secondary, creep. The method developed for the calculation of the incremental process is based upon Eshelby’s (1957) equivalence principle of an inhomogeneity-transformation problem and Mori-Tanaka’s (1973) idea of mean-field stress. In order to examine the applicability of the model as well as the nonlinear stretch parameter, a series of experiments on solid-filled silicone rubbers has been carried out, which included constant rate of tensile tests and creep tests. It is demonstrated that this simple, albeit approximate micromechanical modeling is capable of predicting the volume fraction dependence of the time dependent creep, with characteristic consistency with the known elastic behavior.

scholarly journals Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Fan Zhang ◽  
Jianjian Zhao ◽  
Dawei Hu ◽  
Qian Sheng ◽  
Jianfu Shao
Keyword(s):  
Acid Solution ◽  
Strain Rate ◽  
Creep Strain ◽  
Alkaline Solution ◽  
Confining Pressure ◽  
Creep Strain Rate ◽  
Reactive Flow ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Stage

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore.

Numerical Simulation for Mechanical Behavior of Carbon Black Filler Particle Reinforced Rubber Matrix Composites

2011 ◽  
Vol 137 ◽  
pp. 1-6
Author(s):  
Qing Li ◽  
Xiao Xiang Yang
Keyword(s):  
Carbon Black ◽  
Mechanical Behavior ◽  
Plane Stress ◽  
Volume Fraction ◽  
Filler Particle ◽  
Three Dimensional ◽  
Rubber Matrix ◽  
Two Dimensional ◽  
Rubber Composites ◽  
Dimensional Plane

In this paper, the micromechanical finite element method based on Representative Volume Element has been applied to study and analyze the macro mechanical properties of the carbon black filled rubber composites by using two-dimensional plane stress simulations and three-dimensional axisymmetric simulations under uniaxial compression respectively. The dependence of the macroscopic stress-strain behavior and the effective elastic modulus of the composites, on particle shape, particle area/volume fraction and particle stiffness has been investigated and discussed. Additionally, the simulation results of the two-dimensional plane stress model and the three-dimensional axisymmetric model are evaluated and compared with the experimental data, which shows that the two-dimensional plane stress simulations generate poor predictions on the mechanical behavior of the carbon black particle reinforced rubber composites, while the three-dimensional axisymmetric simulations appear to give a better prediction.

Microstructure and Creep Behaviors of As-Cast Mg-Zn-Er Alloys

2017 ◽  
Vol 898 ◽  
pp. 305-310
Author(s):  
Rui Jing Li ◽  
Shu Bo Li ◽  
Ke Liu ◽  
Zhao Hui Wang ◽  
Xian Du ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Creep Strain ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Optical Microscope ◽  
Quasicrystalline Phase ◽  
X Ray Diffraction ◽  
Creep Tests ◽  
Transmission Electron ◽  
Icosahedral Quasicrystalline

The microstructure and creep behaviors of cast Mg-xZn-yEr (x=3,6,9 wt.%, x/y=6) alloys were investigated by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). XRD results indicated that the main phase compositions of as-cast Mg-xZn-yEr alloys were the icosahedral quasicrystalline phase (I-phase) and α-Mg solid solution. The I-phase mainly distributed in the dendritic and staccato strips. The creep tests were conducted under the condition of 448 K, 70 MPa for 100 h. As the addition of Er increased from 0.5 wt.% to 1.5 wt.%, the total creep strain decreased from 0.962% to 0.512%, and the steady state creep rate decreased from 1.411×10-8s-1 to 4.917×10-9s-1. The I-phase had a tendency to be bulky and continuous, as the volume fraction of Er element increased. Ascribed to the I-phase, the creep strain happened and effectively blocked the movement of dislocations, resulting in the strengthened as-cast Mg-Zn-Er alloys and improved creep resistance. Based on the investigation of creep behaviors, the creep mechanism of the as-cast alloy was mainly grain boundary slipping.

Fused Silica Filled Silicone Rubber Composites for Flexible Electronic Applications

2015 ◽  
Vol 830-831 ◽  
pp. 537-540 ◽  
Author(s):  
L.K. Namitha ◽  
M.T. Sebastian
Keyword(s):  
Silicone Rubber ◽  
Moisture Absorption ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Filler Loading ◽  
Fused Silica ◽  
Rubber Matrix ◽  
Rubber Composites ◽  
Filling Fraction ◽  
Filler Volume Fraction

Silicone rubber composites filled with fused silica were prepared through sigma mixing followed by hot pressing. Filling fraction of fused silica in the silicone rubber matrix was varied from 0-0.51 volume fraction (Vf) and its effects on dielectric properties at different frequencies, thermal properties and moisture absorption were investigated. The results indicate that with the increase of filler volume fraction the relative permittivity increases and dielectric loss decreases. The coefficient of thermal expansion decreased and the moisture absorption increased marginallyas the filler loading increased.

Shape of creep curves in frozen soils and polycrystalline ice

1987 ◽  
Vol 24 (4) ◽  
pp. 623-629 ◽  
Author(s):  
Anatoly M. Fish
Keyword(s):  
Constitutive Equation ◽  
Creep Strain ◽  
Failure Time ◽  
Frozen Soil ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Creep Tests ◽  
Creep Curves ◽  
Polycrystalline Ice

A new method was developed for determining creep parameters, particularly the time to failure, from a single linear plot in which an individual creep curve forms a straight line for primary and tertiary creep. Secondary creep is considered to be a principal point on this line that predetermines the onset of failure. The times to failure can be predicted even when creep tests are not complete by extrapolating information obtained for primary creep. Based upon T. H. Jacka's test data, prediction of creep strain was evaluated using the constitutive equation of A. M. Fish for entire creep and compared with the modified Sinha equation of M. F. Ashby and P. Duval for attenuating creep as well as with models for primary and secondary creep. It is shown that the shape of the creep curves, and thus the creep parameters, varies with stress, temperature, and other factors. Hence, a family of creep curves cannot be described by a constitutive equation with a single set of creep parameters that do not take into account these variations without loss in the accuracy of the creep strain calculations. Key words: frozen soil, polycrystalline, ice, creep, failure, time to failure, attenuation, constitutive modelling.

Percolation Phenomenon in Thermal Conductivity of Carbon Black Filled Rubber and Morphology

2010 ◽  
Vol 146-147 ◽  
pp. 575-580
Author(s):  
Jun Ping Song
Keyword(s):  
Thermal Conductivity ◽  
Carbon Black ◽  
Natural Rubber ◽  
Percolation Threshold ◽  
Volume Fraction ◽  
Graphitized Carbon Black ◽  
Rubber Matrix ◽  
Rubber Composites ◽  
Percolation Behavior ◽  
Percolation Phenomenon

A kind of graphitized carbon black 40B2 was incorporated in natural rubber matrix and vulcanizates were prepared. The content of carbon black varied from 4 to 100phr for 100phr of natural rubber. Thermal conductivity of the CB/rubber composites was studied as a function of CB loadings and temperature. TEM and SEM were employed to explore the morphology of the carbon black and the composites. It was found that percolation phenomenon existed in thermal conductivity of CB/rubber composites at different filler loadings, which was much similar with percolation behavior in electrical conductivity properties of many composites, and the percolation threshold was about 13.63%. The influence of temperature on thermal conductivity was more obviously within the region from the percolation threshold to the volume fraction of 26.2%.However, no great effect could be found on the percolation behavior of the composites in thermal conductivity. The result of TEM indicated that the mean size of CB particles was about 25nm, the maximum size of CB aggregates was about 125nm, and the CB aggregates were multichain in shape. The results of SEM showed that the distribution of CB differed at different filler loadings. Before the percolation threshold, the CB aggregates existed isolatedly, nevertheless at the percolation threshold, some long chains made up of CB aggregates ran through the rubber matrix, which resulted in the rapid increase in thermal conductivity value, and then with the addition of CB loadings, the number of chains increased. When the volume fraction was up to 26.2%, some three dimensional networks formed.

Effect of α2 Precipitation on Creep and Tensile Properties of Ga-Added Near-α Titanium Alloys

2018 ◽  
Vol 941 ◽  
pp. 747-752 ◽  
Author(s):  
Tomonori Kitashima ◽  
Masuo Hagiwara ◽  
Tsutomu Ito ◽  
Masao Hayakawa ◽  
Satoshi Iwasaki
Keyword(s):  
Tensile Properties ◽  
Creep Strain ◽  
Room Temperature ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
Lamellar Microstructure ◽  
Tensile Tests ◽  
Strain Rates ◽  
Bimodal Microstructure ◽  
Creep Tests

The effect of α2precipitation on the creep and tensile properties was investigated for bimodal and lamellar microstructures in two Ga-added near-α Ti alloys with Al equivalences of 10.6 and 11.5. Fine α2phase formed in the α phase of both alloys. The volume fraction of the α2phase for the Al equivalences of 10.6 and 11.5 is equivalent to 57.6 % and 73.3 %, respectively, in the binary Ti-Al system at 600 °C. Creep tests were carried out under a constant stress of 310 MPa at 600 °C and tensile tests were performed at room temperature. Lamellar microstructure showed lower minimum creep strain rates than bimodal microstructure for both alloys. The increase in Al equivalence increased creep life by a factor of 1.6 and decreased the minimum creep strain rate from 6.51 × 10-8s-1to 3.99 × 10-8s-1in bimodal microstructure. In addition, the increase in Al equivalence decreased room temperature tensile elongation although both alloys contained a similar volume fraction of equiaxed α in a bimodal microstructure.

scholarly journals Common Origin of Filler Network Related Contributions to Reinforcement and Dissipation in Rubber Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2534
Author(s):  
Sriharish Malebennur Nagaraja ◽  
Sven Henning ◽  
Sybill Ilisch ◽  
Mario Beiner
Keyword(s):  
Network Topology ◽  
Filler Content ◽  
Matrix Composition ◽  
Rubber Matrix ◽  
Butadiene Rubber ◽  
Rubber Composites ◽  
Different Temperatures ◽  
Filler Network ◽  
General Perspective ◽  
Rubber Filler

A comparative study focusing on the visco–elastic properties of two series of carbon black filled composites with natural rubber (NR) and its blends with butadiene rubber (NR-BR) as matrices is reported. Strain sweeps at different temperatures are performed. Filler network-related contributions to reinforcement (ΔG′) are quantified by the classical Kraus equation while a modified Kraus equation is used to quantify different contributions to dissipation (ΔGD″, ΔGF″). Results indicate that the filler network is visco-elastic in nature and that it is causing a major part of the composite dissipation at small and intermediate strain amplitudes. The temperature dependence of filler network-related reinforcement and dissipation contributions is found to depend significantly on the rubber matrix composition. We propose that this is due to differences in the chemical composition of the glassy rubber bridges connecting filler particles since the filler network topology is seemingly not significantly influenced by the rubber matrix for a given filler content. The underlying physical picture explains effects in both dissipation and reinforcement. It predicts that these glassy rubber bridges will soften sequentially at temperatures much higher than the bulk Tg of the corresponding rubber. This is hypothetically due to rubber–filler interactions at interfaces resulting in an increased packing density in the glassy rubber related to the reduction of free volume. From a general perspective, this study provides deeper insights towards the molecular origin of reinforcement and dissipation in rubber composites.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

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