Sliding Resistance on a Constrained Rubber Layer Due to Rubber Hysteresis

2000 ◽  
Vol 73 (2) ◽  
pp. 217-224
Author(s):  
C. G. Li ◽  
P. S. Steif
Keyword(s):  
Universal Design ◽  
Rolling Resistance ◽  
Design Tool ◽  
Constitutive Law ◽  
Rubber Layer ◽  
New Class ◽  
Dependent Behavior ◽  
Theoretical Predictions ◽  
Filled Rubbers ◽  
Sliding Resistance

Abstract Sliding resistance of a rigid cylinder over a thin rubber layer due to rubber hysteresis is investigated. This problem underlies a model being developed for quantitatively accurate predictions of the performance of a new class of damping devices. As a full multiaxial constitutive law reflecting the amplitude-dependent behavior of filled rubbers is not available, this paper sets forth an approximate method of analysis which indirectly accounts for the material nonlinearity. Results of extensive finite element calculations are then reduced to compact material-independent forms which can be used as a universal design tool. Measurements of rolling resistance are also compared with theoretical predictions.

Frictional Sliding on a Constrained Rubber Layer: A Simple Model for a Class of Damping Devices

2000 ◽  
Vol 73 (2) ◽  
pp. 205-216
Author(s):  
C. G. Li ◽  
P. S. Steif
Keyword(s):  
Simple Model ◽  
Nonlinear Behavior ◽  
Constitutive Law ◽  
Dynamic Moduli ◽  
Approximate Methods ◽  
Rubber Layer ◽  
New Class ◽  
Industrial Grade ◽  
Dependent Behavior ◽  
Filled Rubbers

Abstract Resistance to the steady sliding of a cylinder over a thin rubber layer is studied theoretically. This problem underlies a model being developed for a new class of damping devices. A quantitatively accurate model requires an accounting for the amplitude-dependent dynamic moduli of industrial-grade rubbers filled with carbon black. This accounting is hindered, however, by the lack of a full multiaxial constitutive law reflecting the nonlinear, amplitude-dependent behavior of filled rubbers. Accordingly, this paper sets forth approximate methods of analysis which indirectly account for the nonlinear behavior; these ultimately lead to compact solutions which can be used in the design of new devices.

Damping and Bandgap Characteristics of a Viscoelastic Tensegrity Damper

2021 ◽  
pp. 1-47
Author(s):  
Mohamed Raafat ◽  
Amr Baz
Keyword(s):  
Mathematical Model ◽  
Material Characterization ◽  
Structural Vibrations ◽  
New Class ◽  
Structural Applications ◽  
Theoretical Predictions ◽  
Specific Frequency ◽  
The Mathematical Model ◽  
Theory And Experiments

Abstract A theoretical and experimental investigation of a new class of a tensegrity-based structural damper is presented. The damper is not only capable of attenuating undesirable structural vibrations, as all conventional dampers, but also capable of completely blocking the transmission of vibration over specific frequency bands by virtue of its periodicity. Such dual functionality distinguishes the tensegrity damper over its counterparts of existing structural dampers. Particular emphasis is placed here in presenting the concept and developing the mathematical model of the dynamics of a unit cell the damper. The model is then coupled with a Floquet-Bloch analysis in order to identify the bandgap characteristics of the damper. The predictions of the mathematical model are validated experimentally using a prototype of the damper which is built using 3D printing. A comprehensive material characterization of the damper is performed followed by a detailed extraction of the static and dynamic behavior of the damper in order to validate the theoretical predictions. Close agreement is observed between theory and experiments. The developed theoretical and experimental techniques provide invaluable means for the design of this new class of dampers particularly for critical structural applications.

Numerical analysis of history-dependent variational–hemivariational inequalities with applications to contact problems

2015 ◽  
Vol 26 (4) ◽  
pp. 427-452 ◽  
Author(s):  
MIRCEA SOFONEA ◽  
WEIMIN HAN ◽  
STANISŁAW MIGÓRSKI
Keyword(s):  
Numerical Analysis ◽  
Real World ◽  
Viscoelastic Body ◽  
Contact Problems ◽  
Uniqueness Result ◽  
Constitutive Law ◽  
Hemivariational Inequalities ◽  
New Class ◽  
Nonlinear Anal ◽  
Dependence Result

A new class of history-dependent variational–hemivariational inequalities was recently studied in Migórski et al. (2015Nonlinear Anal. Ser. B: Real World Appl.22, 604–618). There, an existence and uniqueness result was proved and used in the study of a mathematical model which describes the contact between a viscoelastic body and an obstacle. The aim of this paper is to continue the analysis of the inequalities introduced in Migórski et al. (2015Nonlinear Anal. Ser. B: Real World Appl.22, 604–618) and to provide their numerical analysis. We start with a continuous dependence result. Then we introduce numerical schemes to solve the inequalities and derive error estimates. We apply the results to a quasistatic frictional contact problem in which the material is modelled with a viscoelastic constitutive law, the contact is given in the form of normal compliance, and friction is described with a total slip-dependent version of Coulomb's law.

A Simplified Model of Desiccant Wheel and Implementation in a Design Tool

2008 ◽  
Author(s):  
Fatemeh Esfandiari Nia ◽  
Dolf van Paassen
Keyword(s):  
Design Tool ◽  
Weather Data ◽  
Physical Parameters ◽  
Transfer Model ◽  
Desiccant Wheel ◽  
New Class ◽  
Sensitivity Studies ◽  
Optimization Routine ◽  
The Given ◽  
Air Streams

A new class of heat and mass transfer model for a desiccant wheel has been presented and implemented in a design tool. Having studied the behavior of the system in different conditions and sensitivity studies, two physical parameters have been chosen to make simplified models or correlations. Using 1500 data of model solutions, two correlations have been made by an optimization routine in Matlab. These equations correlate outlet air conditions of a desiccant wheel to inlet air conditions of air streams and also the wheel and air speeds. The correlations are limited to be used only in the given range of air conditions and wheel speed. However, the range covers the practical situation that usually happens according to the weather data. The behavior of air conditions in Mollier diagram shows that the error for simulation of a typical cooling cycle to calculate supply air conditions is reduced with a factor of almost 3 times smaller. This shows that even in those ranges with low accuracy the correlations are useful. These simplified equations will be used in the design tools as has been presented in details in this paper.

scholarly journals Micro-structured medium with large isotropic negative thermal expansion

2019 ◽  
Vol 475 (2232) ◽  
pp. 20190468 ◽  
Author(s):  
Luigi Cabras ◽  
Michele Brun ◽  
Diego Misseroni
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Simple Relation ◽  
Space Structures ◽  
New Class ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Innovative Materials ◽  
New Generation

A challenge in nano- and micro-mechanics is the realization of innovative materials exploiting auxetic behaviour to tailor thermal expansion properties. For this purpose, a new class of micro-structured media possessing an extremely wide range of tunable (positive, negative or even zero) thermal expansion is proposed and analytically and experimentally assessed. For this class of isotropic Mechanical-Auxetic Thermal-Shrinking media, the effective coefficient of thermal expansion is explicitly linked to two microstructural variables via a simple relation, allowing the design with desired values. The theoretical predictions for the negative thermal properties are fully validated by the experimental and numerical outcomes. The simplicity of the proposed structure makes the design useful for the production of a new generation of advanced media, with applications ranging from micromechanical devices to large civil and space structures.

scholarly journals Giant field-induced strains in magnetoactive elastomer composites

2013 ◽  
Vol 469 (2158) ◽  
pp. 20130385 ◽  
Author(s):  
E. Galipeau ◽  
P. Ponte Castañeda
Keyword(s):  
Exact Analytical Solution ◽  
Functional Materials ◽  
New Class ◽  
Small Strains ◽  
Magnetic Layers ◽  
Field Dependent ◽  
Theoretical Predictions ◽  
Strong Action ◽  
Elastomer Composites ◽  
Magnetoactive Elastomer

Magnetoactive elastomers (MAEs) are composite materials consisting of nearly rigid, magnetically susceptible particles embedded in a soft, magnetically insensitive elastomer matrix. These multi-functional materials exhibit field-dependent strains and changes in stiffness. However, the strains that have been achieved experimentally to date are still relatively small (of the order of 1%). The reason for these small strains can be traced back to the dipolar nature of the forces between particles. Large particle concentrations are required to generate strong forces, but large concentrations also lead to large overall stiffness for the composite material, which, in turn, tends to reduce the overall strain. In this paper, we propose a new class of MAEs with doubly layered, herringbone-type microstructures capable of generating much larger field-induced strains of up to 100%. This is accomplished by combining the strong action of magnetic torques on suitably oriented magnetic layers, which interact directly with the applied magnetic field, together with the excitation of soft modes of simple shear deformation in the elastomer layers. Theoretical predictions, based on an exact analytical solution for the macroscopic magnetoelastic response of the materials, allow for the optimization of the microstructure for enhanced magnetostriction.

Theory and validation of the master ply concept for invariant-based stiffness of composites

2017 ◽  
Vol 52 (12) ◽  
pp. 1699-1708 ◽  
Author(s):  
Sung Kyu Ha ◽  
Carlos Alberto Cimini
Keyword(s):  
Constitutive Relations ◽  
Theoretical Background ◽  
Design Tool ◽  
Material System ◽  
High Modulus ◽  
Background Theory ◽  
Material Systems ◽  
Theoretical Predictions ◽  
Epoxy Material ◽  
Normalized Parameters

The objective of this paper is to unveil the background theory behind the universal master ply assumption, based on the invariant approach, to describe ply elastic properties. It was demonstrated that using ply-based constitutive relations, trace-normalized stiffness properties can be derived for different materials. Theoretical predictions for trace-normalized parameters were plotted as functions of the unidirectional ply longitudinal modulus ( Ex), which defines the particular material system. Ply stiffness extensive empirical data were obtained from literature for four types of material systems (high modulus carbon/epoxy, standard modulus carbon/epoxy, aramid/epoxy, and glass/epoxy) and correlated quite well to theoretical predictions. Theoretical curves presented a nonlinear region for low Ex which gradually evolves to a plateau as Ex increases. It was verified that the master ply concept averaging the trace-normalized ply stiffness matrix elements can be applied for high modulus carbon/epoxy, standard modulus carbon/epoxy, and aramid/epoxy material systems. However, glass/epoxy systems can not be represented by this concept. The exposed theoretical background supports trace-based approach and enhances its effectiveness as a design tool, encompassing all the consequent advantages.

Rolling resistance of articular cartilage due to interstitial fluid flow

1997 ◽  
Vol 211 (5) ◽  
pp. 419-424 ◽  
Author(s):  
G A Ateshian ◽  
H Wang
Keyword(s):  
Fluid Flow ◽  
Articular Cartilage ◽  
Friction Coefficient ◽  
Interstitial Fluid ◽  
Frictional Coefficient ◽  
Rolling Resistance ◽  
Rolling Contact ◽  
Interstitial Fluid Flow ◽  
Tissue Properties ◽  
Theoretical Predictions

A mechanism which may contribute to the frictional coefficient of diarthrodial joints is the rolling resistance due to hysteretic energy loss of viscoelastic cartilage resulting from interstitial fluid flow. The hypothesis of this study is that rolling resistance contributes significantly to the measured friction coefficient of articular cartilage. Due to the difficulty of testing this hypothesis experimentally, theoretical predictions of the rolling resistance are obtained using the solution for rolling contact of biphasic cylindrical cartilage layers [Ateshian and Wang (1)]. Over a range of rolling velocities, tissue properties and dimensions, it is found that the coefficient of rolling resistance μR varies in magnitude from 10−6 to 10−2; thus, it is generally negligible in comparison with experimental measurements of the cartilage friction coefficient (10−3-10−1) except, possibly, when the tissue is arthritic. Hence, the hypothesis of this study is rejected on the basis of these results.

Swelling of Constrained Rubber Layers: Effect on Free Energy of Detachment

2001 ◽  
Vol 74 (1) ◽  
pp. 89-99
Author(s):  
A. N. Gent ◽  
W. J. Hung ◽  
M. F. Tse
Keyword(s):  
Bond Rupture ◽  
Stored Energy ◽  
Rigid Substrate ◽  
Representative Case ◽  
Rubber Layer ◽  
Available Energy ◽  
Degree Of Swelling ◽  
Theoretical Predictions ◽  
Released Energy ◽  
Intrinsic Strength

Abstract The degree of swelling of a rubber layer by a compatible liquid has been calculated for cases when the layer is constrained, for example when it is bonded to a rigid substrate. The stored energy residing in swollen layers is also computed. From these results the amount of energy is determined that becomes available if a bonded layer separates from a substrate and then becomes free to swell further. The released energy is shown to be quite high, of the order of 10 MJ/m3 in a representative case. Attention is drawn to the importance of the layer thickness when this energy is applied to bond rupture. For layers having a thickness of the order of 1 mm or greater, the available energy is greater than the intrinsic strength of the bond or of the swollen elastomer itself. In accord with this conclusion, soft rubber layers, sandwiched between and bonded to flexible but inextensible backings, are observed to separate spontaneously and then tear away from the backing when swollen by a compatible liquid. And layers that are still attached to the backing become sharply curved before tearing loose, in rough agreement with the theoretical predictions.

Development of Time Dependent Stress-Strain Simulation of Clay

2009 ◽  
Vol 25 (1) ◽  
pp. 27-40 ◽  
Author(s):  
C.-Y. Ou ◽  
C.-C. Liu ◽  
C.-K. Chin
Keyword(s):  
Constitutive Law ◽  
Time Dependent ◽  
Soil Behavior ◽  
Creep Tests ◽  
Clay Model ◽  
Model Sets ◽  
Dependent Behavior ◽  
Modified Cam Clay ◽  
Parametric Studies ◽  
Cam Clay

AbstractThe objective of this study is to derive a time dependent effective based constitutive law on the basis of framework of the Modified Cam-Clay model. This model takes into account the anisotropic characteristics and creep behavior, based on the theory of viscoplasticity. The model sets the initial yield surface symmetric to the Ko line for modeling the initial Ko condition. A method is then developed to compute the gyration and expansion of the loading surface to simulate the anisotropic behavior due to the principal stress gyration after shear. The creep or time dependent behavior is considered in the model by adopting Kutter and Sathialingam's model, which was derived from Taylor's secondary consolidation theory and Bjerrum's delayed compression model. Compared with the Modified Cam-Clay model, the model requires five additional parameters to describe the soil behavior. All of the additional parameters can be obtained through conventional soil tests or parametric studies. The model is evaluated through a series of simulation of undrained shear tests and undrained creep tests.

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