Linear Viscoelastic Creep Model for the Contact of Nominal Flat Surfaces Based on Fractal Geometry: Standard Linear Solid (SLS) Material

2007 ◽  
Vol 129 (3) ◽  
pp. 461-466 ◽  
Author(s):  
Osama M. Abuzeid ◽  
Peter Eberhard
Keyword(s):  
Constitutive Law ◽  
Creep Model ◽  
Viscoelastic Creep ◽  
Flat Surfaces ◽  
Proposed Model ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Creep Force ◽  
Good Agreement

The objective of this study is to construct a continuous mathematical model that describes the frictionless contact between a nominally flat (rough) viscoelastic punch and a perfectly rigid foundation. The material’s behavior is modeled by assuming a complex viscoelastic constitutive law, the standard linear solid (SLS) law. The model aims at studying the normal compliance (approach) of the punch surface, which will be assumed to be quasistatic, as a function of the applied creep load. The roughness of the punch surface is assumed to be fractal in nature. The Cantor set theory is utilized to model the roughness of the punch surface. An asymptotic power law is obtained, which associates the creep force applied and the approach of the fractal punch surface. This law is only valid if the approach is of the size of the surface roughness. The proposed model admits an analytical solution for the case when the deformation is linear viscoelastic. The modified analytical model shows a good agreement with experimental results available in the literature.

scholarly journals Using Waveguides to Model the Dynamic Stiffness of Pre-Compressed Natural Rubber Vibration Isolators

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1703
Author(s):  
Michael Coja ◽  
Leif Kari
Keyword(s):  
Natural Rubber ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Complex Problem ◽  
Wide Frequency Range ◽  
Vibration Isolators ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Frequency Magnitude ◽  
Good Agreement

A waveguide model for a pre-compressed cylindrical natural rubber vibration isolator is developed within a wide frequency range—20 to 2000 Hz—and for a wide pre-compression domain—from vanishing to the maximum in service, that is 20%. The problems of simultaneously modeling the pre-compression and frequency dependence are solved by applying a transformation of the pre-compressed isolator into a globally equivalent linearized, homogeneous, and isotropic form, thereby reducing the original, mathematically arduous, and complex problem into a vastly simpler assignment while using a straightforward waveguide approach to satisfy the boundary conditions by mode-matching. A fractional standard linear solid is applied as the visco-elastic natural rubber model while using a Mittag–Leffler function as the stress relaxation function. The dynamic stiffness is found to depend strongly on the frequency and pre-compression. The former is resulting in resonance phenomena such as peaks and troughs, while the latter exhibits a low-frequency magnitude stiffness increase in addition to peak and trough shifts with increased pre-compressions. Good agreement with nonlinear finite element results is obtained for the considered frequency and pre-compression range in contrast to the results of standard waveguide approaches.

Reloading Stress Relaxation Behavior Analysis Based on a Creep Model for High Temperature Bolting Steel

2013 ◽  
Vol 328 ◽  
pp. 950-954
Author(s):  
Wei Wei Zhang ◽  
Hong Xu ◽  
Hong Yuan Li
Keyword(s):  
High Temperature ◽  
Stress Relaxation ◽  
Steady State Creep ◽  
Relaxation Behavior ◽  
Creep Model ◽  
National Research Institute ◽  
Time Intervals ◽  
Stress Relaxation Behavior ◽  
Proposed Model ◽  
Good Agreement

An analytical method based on a creep model is being developed to investigate the effect of retightening on stress relaxation behavior for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 12Cr-1Mo-1W-1/4V stainless steel bolting material at 550°C. It was shown that the proposed model based on Altenbach-Gorash-Naumenko creep model for the primary and steady state creep could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the measured for initial stress level of 273.6MPa at 550°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

scholarly journals Influence of cheese ripening on the viscoelastic behaviour of edam cheese

2013 ◽  
Vol 19 (No. 1) ◽  
pp. 1-7 ◽  
Author(s):  
J. Buchar ◽  
I. Kubiš ◽  
S. Gajdůšek ◽  
I. Křivánek
Keyword(s):  
Viscoelastic Properties ◽  
Rheological Model ◽  
Deformation Behaviour ◽  
Viscoelastic Body ◽  
Original Method ◽  
Cheese Ripening ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Pressure Bar

The paper deals with the study of the effect of cheese ripening on parameters of a rheological model of cheese mechanical behaviour. The Edam cheese has been tested by the method of the Hopkinson Split Pressure Bar. The original method of the evaluation of viscoelastic properties has been used. The rheological model of the three element linear viscoelastic body, so called “standard linear solid” has been used. This model successfully describes the experimentally observed deformation behaviour of cheese specimens. The effect of the time of cheese ripening on the parameters of the rheological model has been demonstrated.

scholarly journals Viscoelastic Characterization of Long-Eared Owl Flight Feather Shaft and the Damping Ability Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Jia-li Gao ◽  
Jin-kui Chu ◽  
Le Guan ◽  
Hai-xin Shang ◽  
Zhen-kun Lei
Keyword(s):  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Golden Eagle ◽  
Flight Feather ◽  
Column Material ◽  
Significant Difference ◽  
Single Column ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear

Flight feather shaft of long-eared owl is characterized by a three-parameter model for linear viscoelastic solids to reveal its damping ability. Uniaxial tensile tests of the long-eared owl, pigeon, and golden eagle flight feather shaft specimens were carried out based on Instron 3345 single column material testing system, respectively, and viscoelastic response of their stress and strain was described by the standard linear solid model. Parameter fitting result obtained from the tensile tests shows that there is no significant difference in instantaneous elastic modulus for the three birds’ feather shafts, but the owl shaft has the highest viscosity, implying more obvious viscoelastic performance. Dynamic mechanical property was characterized based on the tensile testing results. Loss factor (tanδ) of the owl flight feather shaft was calculated to be 1.609 ± 0.238, far greater than those of the pigeon (0.896 ± 0.082) and golden eagle (1.087 ± 0.074). It is concluded that the long-eared owl flight feather has more outstanding damping ability compared to the pigeon and golden eagle flight feather shaft. Consequently, the long-eared owl flight feathers can dissipate the vibration energy more effectively during the flying process based on the principle of damping mechanism, for the purpose of vibration attenuation and structure radiated noise reduction.

Modeling of Viscoelastic Solid Polymers Using a Boundary Element Formulation with Considering a Body Load

2012 ◽  
Vol 463-464 ◽  
pp. 499-504 ◽  
Author(s):  
Hosein Ashrafi ◽  
M.R. Bahadori ◽  
M. Shariyat
Keyword(s):  
Boundary Element ◽  
Body Force ◽  
Element Formulation ◽  
Viscoelastic Solid ◽  
Engineering Structures ◽  
Solid Polymers ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Body Load ◽  
Standard Linear

In this work, a boundary element formulation for 2D linear viscoelastic solid polymers subjected to body force of gravity has been presented. Structural analysis of solid polymers is one of the most important subjects in advanced engineering structures. From basic assumptions of the viscoelastic constitutive equations and the weighted residual techniques, a simple but effective boundary element formulation is implemented for standard linear solid (SLS) model. The SLS model provides an approximate representation of observed behavior of a real advanced polymer in its viscoelastic range. This approach avoids the use of relaxation functions and mathematical transformations, and it is able to solve quasistatic viscoelastic problems with any load time-dependence and boundary conditions. Problem of pressurization of thick-walled viscoelastic tanks made of PMMA polymer, which subjected to a body force, is completely analyzed.

Linear viscoelasticity

2020 ◽  
pp. 549-608
Author(s):  
Lallit Anand ◽  
Sanjay Govindjee
Keyword(s):  
Time Integration ◽  
Integral Form ◽  
Essential Elements ◽  
Kernel Functions ◽  
Three Dimensions ◽  
Storage And Loss Moduli ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear

This chapter introduces the essential elements of linear viscoelastic material behaviour and modeling in one- and three-dimensions. Both relaxation and creep phenomena are introduced and modeled using Boltzmann’s superposition integral. Various common kernel functions are introduced, as is the standard and generalized standard linear model in differential and integral form. The correspondence principle is discussed for the solution of practical problems and to connect relaxation and creep formulations. Storage and loss moduli for oscillatory loadings are discussed, as are loss tangents and dissipation. For the generalized standard linear solid its time integration via the Herrmann-Peterson recursion relation is discussed. Effects of temperature are discussed, and the concept of time-temperature equivalence is introduced.

scholarly journals Creep in oak material from the Vasa ship: verification of linear viscoelasticity and identification of stress thresholds

2020 ◽  
Vol 78 (6) ◽  
pp. 1095-1103
Author(s):  
R. Afshar ◽  
M. Cheylan ◽  
G. Almkvist ◽  
A. Ahlgren ◽  
E. K. Gamstedt
Keyword(s):  
Rheological Parameters ◽  
Stress Strain ◽  
Compressive Stresses ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Linear Viscoelastic Behaviour ◽  
Creep Deformations ◽  
High Degree ◽  
Wooden Structures

Abstract Creep deformation is a general problem for large wooden structures, and in particular for shipwrecks in museums. In this study, experimental creep data on the wooden cubic samples from the Vasa ship have been analysed to confirm the linearity of the viscoelastic response in the directions where creep was detectable (T and R directions). Isochronous stress–strain curves were derived for relevant uniaxial compressive stresses within reasonable time spans. These curves and the associated creep compliance values justify that it is reasonable to assume a linear viscoelastic behaviour within the tested ranges, given the high degree of general variability. Furthermore, the creep curves were fitted with a one-dimensional standard linear solid model, and although the rheological parameters show a fair amount of scatter, they are candidates as input parameters in a numerical model to predict creep deformations. The isochronous stress–strain relationships were used to define a creep threshold stress below which only negligible creep is expected. These thresholds ranges were 0.3–0.5 MPa in the R direction and 0.05–0.2 MPa in the T direction.

Isothermal and Nonisothermal Creep of Lightly Crosslinked cis-1,4-Polybutadiene

1977 ◽  
Vol 50 (5) ◽  
pp. 884-894
Author(s):  
J. M. Caruthers ◽  
R. E. Cohen
Keyword(s):  
Activation Energy ◽  
Large Deformations ◽  
Creep Data ◽  
Creep Experiment ◽  
Viscoelastic Creep ◽  
Temperature Superposition ◽  
Linear Viscoelastic ◽  
Nonisothermal Method ◽  
Nonisothermal Creep ◽  
Good Agreement

Abstract A nonisothermal creep experiment has been analyzed to ascertain its suitability for determining the temperature dependence of low-activation-energy viscoelastic processes in elastomers far above Tg. The nonisothermal method was employed to determine the activation energy for creep near 35°C in a lightly crosslinkedcis-1,4-polybutadiene elastomer at small strains within the linear viscoelastic region and at various large deformations up to rupture. The observed activation energy was essentially independent of the level of strain, and the value of ΔHa (∼ 11 kcal/mol) determined via the nonisothermal creep method was in good agreement with the result (∼12 kcal/mol) obtained via time-temperature superposition of isothermal linear viscoelastic creep data. The nonisothermal data allowed for an estimate of the volume of the “flow unit” associated with the controlling viscoelastic creep mechanism, attributed here to slippage of entanglements within lightly crosslinked network.

Approximate Analysis of Creep Strains and Stresses at Notches

2003 ◽  
Author(s):  
J. E. Nun˜ez ◽  
G. Glinka
Keyword(s):  
Elastic Stress ◽  
Notch Root ◽  
Constitutive Law ◽  
Time Dependent ◽  
Creep Model ◽  
Linear Elastic ◽  
Material Creep ◽  
Dependent Strain ◽  
Neuber's Rule ◽  
Good Agreement

A method for the estimation of creep induced strains and stresses at notches has been developed. The purpose of the method is to generate a solution for the time-dependent strain and stress at the notch root based on the linear-elastic stress state, the constitutive law, and the material creep model. The proposed solution is an extension of Neuber’s rule used for the case of time-independent plasticity. The method was derived for both localized and non-localized creep in a notched body. Predictions were compared with finite element data and good agreement was obtained for various geometrical and material configurations in plane stress conditions.

scholarly journals Dynamic force microscopy simulator (dForce): A tool for planning and understanding tapping and bimodal AFM experiments

2015 ◽  
Vol 6 ◽  
pp. 369-379 ◽  
Author(s):  
Horacio V Guzman ◽  
Pablo D Garcia ◽  
Ricardo Garcia
Keyword(s):  
Viscoelastic Model ◽  
Surface Force ◽  
Dissipated Energy ◽  
Dynamic Force ◽  
Force Microscopy ◽  
Linear Viscoelastic ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Optimal Accuracy ◽  
The One

We present a simulation environment, dForce, which can be used for a better understanding of dynamic force microscopy experiments. The simulator presents the cantilever–tip dynamics for two dynamic AFM methods, tapping mode AFM and bimodal AFM. It can be applied for a wide variety of experimental situations in air or liquid. The code provides all the variables and parameters relevant in those modes, for example, the instantaneous deflection and tip–surface force, velocity, virial, dissipated energy, sample deformation and peak force as a function of time or distance. The simulator includes a variety of interactions and contact mechanics models to describe AFM experiments including: van der Waals, Hertz, DMT, JKR, bottom effect cone correction, linear viscoelastic forces or the standard linear solid viscoelastic model. We have compared two numerical integration methods to select the one that offers optimal accuracy and speed. The graphical user interface has been designed to facilitate the navigation of non-experts in simulations. Finally, the accuracy of dForce has been tested against numerical simulations performed during the last 18 years.

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