CHARACTERIZING THE TIME DEPENDENCE OF FILLED EPDM

2011 ◽  
Vol 84 (2) ◽  
pp. 147-165 ◽  
Author(s):  
N. Koprowski-Theiss ◽  
M. Johlitz ◽  
S. Diebels
Keyword(s):  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Nonlinear Behavior ◽  
Structural Parameter ◽  
Identification Algorithm ◽  
Rate Dependent ◽  
Tension Tests ◽  
Yeoh Model ◽  
Stochastic Identification ◽  
Basic Elasticity

Abstract The mechanical properties of a carbon black filled rubber are investigated. The main focus lays on the theoretical modeling of the basic elasticity and the viscoelastic behavior. Therefore, uniaxial tension tests at different feedrates are performed. The occurring Mullins effect can be neglected due to adequate pretreatment of the specimens. Healing effects are also verified and investigated in the examined material. The constitutive model for the basic elasticity is based on the Yeoh model, while the theory of finite viscoelasticity with an intermediate configuration is used to describe the rate dependent behavior. The healing effects are constituted with large relaxation times and not with an additional structural parameter. As the material has a strong nonlinear behavior with respect to the deformation rate, nonlinearity in the relaxation time with respect to this behavior is introduced. The material parameters of the model are estimated using a stochastic identification algorithm.

scholarly journals Experimental Investigation of Rate-Dependent Inner Hysteresis Loops in PZT

2005 ◽  
Vol 881 ◽  
Author(s):  
Alexander York ◽  
Stefan Seelecke
Keyword(s):  
Experimental Investigation ◽  
Systematic Study ◽  
Domain Switching ◽  
Piezoelectric Materials ◽  
Relaxation Times ◽  
Hysteresis Loops ◽  
Loading Rates ◽  
Rate Dependent ◽  
Realistic Modeling ◽  
Kinetics Of

AbstractThe rate-dependence of piezoelectric materials resulting from the kinetics of domain switching is an important factor that needs to be included in realistic modeling attempts. This paper provides a systematic study of the rate-dependent hysteresis behavior of a commercially available PZT stack actuator. Experiments covering full as well as minor loops are conducted at different loading rates with polarization and strain recorded. In addition, the creep behavior at different constant levels of the electric field is observed. This provides evidence of kinetics being characterized by strongly varying relaxation times that can be associated with different switching mechanisms.

Finite deformation and fractional order viscoelasticity of an auxetic foam

2022 ◽  
pp. 1045389X2110643
Author(s):  
Eugenia Stanisauskis ◽  
Paul Miles ◽  
William Oates
Keyword(s):  
Fractional Order ◽  
Finite Deformation ◽  
Viscoelastic Behavior ◽  
Integer Order ◽  
Relaxation Effects ◽  
Viscoelastic Parameters ◽  
Rate Dependent ◽  
Improve Model ◽  
Model Predictions ◽  
And Performance

Auxetic foams exhibit novel mechanical properties due to their unique microstructure for improved energy-absorption and cavity expansion applications that have fascinated the scientific community since their inception. Given the advancements in material processing and performance of polymer open cell auxetic foams, there is a strong desire to fully understand the nonlinear rate-dependent deformation of these materials. The influence of nonlinear compressibility is introduced here along with relaxation effects to improve model predictions for different stretch rates and finite deformation regimes. The viscoelastic behavior of the material is analyzed by comparing fractional order and integer order calculus models. All results are statistically validated using maximum entropy methods to obtain Bayesian posterior densities for the hyperelastic, auxetic, and viscoelastic parameters. It is shown that fractional order viscoelasticity provides [Formula: see text]–[Formula: see text] improvement in prediction over integer order viscoelastic models when the model is calibrated at higher stretch rates where viscoelasticity is more significant.

Binder/Filler Interaction and the Nonlinear Behavior of Highly-Filled Elastomers

1990 ◽  
Vol 63 (4) ◽  
pp. 488-502 ◽  
Author(s):  
R. G. Stacer ◽  
C. Hübner ◽  
D. M. Husband
Keyword(s):  
Surface Area ◽  
Strain Amplitude ◽  
Nonlinear Response ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Interaction Model ◽  
Nonlinear Behavior ◽  
Small Deformation ◽  
Amplitude Dependence ◽  
Filled Rubbers

Abstract 1. The small-deformation-viscoelastic response of elastomers containing nonreinforcing filler has been investigated. Nonlinear viscoelastic behavior was observed as a pronounced strain-amplitude dependence. The degree of this dependence was quantified using a power-law representation as a single nonlinear parameter, m. 2. The magnitude of m was a function of formulation variables. It was found that m increased with the volume fraction and particle size of filler material, as well as the volume fraction of plasticizer. Reduced values of m were observed in the presence of bonding agent and with greater degrees of apparent crosslinking. The latter was controlled in this study through imbalanced urethane cures. 3. Nonlinear behavior of elastomers containing nonreinforcing filler has been compared and contrasted with the data base for carbon-black-reinforced elastomers. The major difference is in the effect of the surface area of filler particles. Nonlinear response in black-filled rubbers increases with surface area, while the opposite is reported in this study. Additionally, the relationship between viscoelastic dissipation and the magnitude of nonlinear response, well established for black-filled rubbers, was not observed. These results indicate that the response of elastomers containing nonreinforcing filler, although nearly identical in appearance to that seen with reinforcing filler, is not driven by the same mechanism. 4. A binder/filler interaction model is proposed for materials containing nonreinforcing filler. This model is based on the ideal adhesive strength of the binder/filler interface. In this model, greater attraction between polymer and particle surfaces reduces molecular slippage during deformation, leading to a decreased dependence of the modulus on strain amplitude, or decreased nonlinearity. It is shown that the model provides reasonable predictions for the observed phenomena.

Numerical Prediction Method for Elasto-Viscoplastic Behavior of Glass Fiber Reinforced Polyurethane Foam Under Various Compressive Loads and Cryogenic Temperatures

2015 ◽  
Author(s):  
Chi-Seung Lee ◽  
Myung-Sung Kim ◽  
Kwang-Ho Choi ◽  
Myung-Hyun Kim ◽  
Jae-Myung Lee
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Glass Fiber ◽  
Polyurethane Foam ◽  
Prediction Method ◽  
Nonlinear Behavior ◽  
Cryogenic Temperatures ◽  
Fiber Reinforced ◽  
Rate Dependent ◽  
Glass Fiber Reinforced

In the present study, the material characteristics of a glass fiber-reinforced polyurethane foam (RPUF) which is widely adopted to a liquefied natural gas (LNG) insulation system was investigated by a series of compressive tests under room and cryogenic temperatures. In addition, a temperature- and strain rate-dependent constitutive model was proposed to describe the material nonlinear behavior such as increase of yield stress and plateau according to temperature and strain rate variations. The elasto-viscoplastic model was transformed to an implicit form, and was implemented into the ABAQUS user-defined subroutine, namely, UMAT. Through a number of simulation using the developed subroutine, the various stress-strain relationships of RPUF were numerically predicted, and the material parameters associated with the constitutive model were identified. In order to validate the proposed method, the computational results were compared to a series of test of RPUF.

scholarly journals Viscoelastic Rheological Behaviors of Polypropylene and LMPP Blends

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3485
Author(s):  
Feichao Zhu ◽  
Sohail Yasin ◽  
Munir Hussain
Keyword(s):  
Large Amplitude ◽  
Viscoelastic Behavior ◽  
Nonlinear Behavior ◽  
Oscillatory Shear ◽  
Large Amplitude Oscillatory Shear ◽  
Mechanical Responses ◽  
Nonlinear Viscoelastic ◽  
Linear Viscoelastic ◽  
Viscoelastic Behaviors ◽  
Linear And Nonlinear

Dynamic oscillatory shear testing is used to investigate polymeric viscoelastic behaviors. Small and large amplitude oscillatory shear tests are the canonical method for characterizing the linear and nonlinear viscoelastic behaviors of any polymeric material. With prominent and abundant work on linear viscoelastic studies, the nonlinear behavior is evasive in terms of generating infinite higher harmonics in the nonlinear regime. For this reason, intrinsic nonlinearities from large amplitude oscillatory shear (LAOS) studies have recently been used for insights on microstructural behaviors. This study is carried out for linear and nonlinear viscoelastic behavior with a main focus on LAOS of isostatic polypropylene (iPP) and relatively new low molecular weight and low modulus polypropylene-based polyolefin (LMPP) blends. The morphological results showed reduced spherulitic crystal nucleus size and increased distribution in blends with increasing LMPP. The blends showed subtle linear viscoelastic responses with strong nonlinear mechanical responses to variant strain and stress compared to pure iPP. The intracycle strain thickening and intracycle strain stiffening of high-content LMPP blends were comparatively dominant at medium strain amplitudes.

A Second Generation of Numerical Implementation of Nonlinear Piezoelectric Models in Commercially Available Tools

2008 ◽  
Author(s):  
M. A. Siddiq Qidwai ◽  
V. G. DeGiorgi
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Domain Switching ◽  
Piezoelectric Materials ◽  
Nonlinear Behavior ◽  
Material Behavior ◽  
Device Performance ◽  
Performance Improvements ◽  
Rate Dependent ◽  
Theoretical Developments

Domain switching based nonlinear behavior is characteristic of relaxor-type piezoelectric material such as PMN-PT single crystals. These materials offer significant device performance improvements over traditional polycrystalline piezoelectric materials such as PZT-5A. The promise of increased performance of these materials has led to work in development of constitutive characterizations so that material behavior under load and material failure mechanisms can be understood and predicted. However, there is a gap between development of such theoretical developments and in workable manifestations available as part of commercial finite element codes for use in device design. In the current work, the authors extend previously documented implementation of a macro-mechanical constitutive model which addresses domain switching, into a commercially available finite element code. A rate dependent version of the constitutive model has been successfully realized and used to reproduce a variety of piezoelectric constitutive behaviors.

Modeling of Polymeric Liquid Material Properties Effect on Pressure Transients in the Elastic Pipe

2020 ◽  
Vol 990 ◽  
pp. 272-276
Author(s):  
Semyon Levitsky ◽  
Rudolf Bergman
Keyword(s):  
Material Properties ◽  
Pulse Propagation ◽  
Pressure Pulse ◽  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Polymer Processing ◽  
Elastic Tube ◽  
Polymeric Liquid ◽  
Dimensional Approximation

Material properties of polymeric liquids are of great importance for different technological processes. Particularly, such liquids demonstrate viscoelastic behavior in non-stationary transportation regimes, widely used in polymer processing, which influence the operation of the equipment. The paper is devoted to the modeling of pressure transient in a long thin-walled elastic tube with polymeric liquid. As distinct to previous results of the authors, material properties of the liquid are described by generalized Maxwell rheological equation accounting for a spectrum of relaxation times. It is supposed that the pressure pulse is generated at the tube end and propagates along the waveguide with the speed influenced by the tube geometry and wall elasticity, and the liquid compressibility and viscoelasticity. The problem is formulated in a quasi-one-dimensional approximation and solved by the operational method. The resulting relation for the pressure in the wave is inverted numerically. Effect of liquid relaxation time distribution on the pressure pulse propagation is studied. The results are relevant for the dynamic operation of equipment for polymer processing; they can be useful also for material characterization of high-molecular liquids.

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