Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2012 ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam, which is used in many engineering applications, exhibits nonlinear and viscoelastic behavior. To date, several models have been proposed to characterize the complex behavior of foams from the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. A nonlinear viscoelastic model, which is an extension of previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is assumed in the model that total stress is decomposed into the sum of a nonlinear elastic component, which is modeled by a higher order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures are developed to estimate the model parameters using uniaxial compression data from experiments conducted at different rates. The performance of this model is compared to that of other nonlinear viscoelastic models.

Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam is used in many engineering applications. It exhibits nonlinear and viscoelastic behavior which makes it difficult to model. To date, several models have been developed to characterize the complex behavior of foams. These attempts include the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. In this research, a nonlinear viscoelastic model, which is an extension to previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is hypothesized that total stress can be decomposed into the sum of a nonlinear elastic component, modeled by a higher-order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures were developed to estimate the model parameters using uniaxial cyclic compression data from experiments conducted at six different rates. The estimated model parameters for individual tests were used to develop a model with parameters that are a function of strain rates. The parameter estimation technique was modified to also develop a comprehensive model which captures the uniaxial behavior of all six tests. The performance of this model was compared to that of other nonlinear viscoelastic models.

A Nonlinear Viscoelastic Model for the Relaxation Behavior of Tendon

2012 ◽  
Author(s):  
Frances M. Davis ◽  
Raffaella De Vita
Keyword(s):  
Stress Relaxation ◽  
Relaxation Function ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Relaxation Behavior ◽  
Successful Model ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Linear Viscoelastic ◽  
Nonlinear Viscoelastic Model

Tendons are viscoelastic materials which undergo stress relaxation when held at a constant strain. The most successful model used to describe the viscoelastic behavior of tendons is the quasi-linear viscoelastic (QLV) model [1]. In the QLV model, the relaxation function is assumed to be a separable function of time and strain. Recently, this assumption has been shown to be invalid for tendons [2] thus suggesting the need for new nonlinear viscoelastic models.

A nonlinear viscoelastic model of lung tissue mechanics

1991 ◽  
Vol 71 (3) ◽  
pp. 826-833 ◽  
Author(s):  
B. Suki ◽  
J. H. Bates
Keyword(s):  
Lung Tissue ◽  
Linear Models ◽  
Viscoelastic Model ◽  
Low Frequency ◽  
Simulated Data ◽  
Tissue Mechanics ◽  
Model Parameters ◽  
Volume Dependence ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Viscoelastic Model

There have been a number of attempts recently to use linear models to describe the low-frequency (0–2 Hz) dependence of lung tissue resistance (Rti) and elastance (Eti). Only a few attempts, however, have been made to account for the volume dependence of these quantities, all of which require the tissues to be plastoelastic. In this paper we specifically avoid invoking plastoelasticity and develop a nonlinear viscoelastic model that is also capable of accounting for the nonlinear and frequency-dependent features of lung tissue mechanics. The model parameters were identified by fitting the model to data obtained in a previous study from dogs during sinusoidal ventilation. The model was then used to simulate pressure and flow data by use of various types of ventilation patterns similar to those that have been employed experimentally. Rti and Eti were estimated from the simulated data by use of four different estimation techniques commonly applied in respiratory mechanics studies. We found that the estimated volume dependence of Rti and Eti is sensitive to both the ventilation pattern and the estimation technique, being in error by as much as 217 and 22%, respectively.

Comparison Between a Quasilinear and a Nonlinear Viscoelastic Model for Brain Tissue

2000 ◽  
Author(s):  
Kurosh K. Darvish ◽  
Jeff R. Crandall
Keyword(s):  
Brain Tissue ◽  
Viscoelastic Model ◽  
Constitutive Models ◽  
Viscoelastic Behavior ◽  
Bovine Brain ◽  
Integral Model ◽  
Nonlinear Viscoelastic ◽  
Hereditary Integral ◽  
Nonlinear Constitutive Models ◽  
Nonlinear Viscoelastic Model

Abstract The nonlinearity of the viscoelastic behavior of brain tissue was studied. Two nonlinear constitutive models were developed using the experimental results of forced vibrations on bovine brain samples, namely a quasilinear viscoelastic model and a multiple hereditary integral model. The latter was found to be superior especially at higher frequencies (above 27 Hz).

Numerical Techniques to Model Fractional-Order Nonlinear Viscoelasticity in Soft Elastomers

2018 ◽  
Author(s):  
Paul Miles ◽  
Graham Pash ◽  
William Oates ◽  
Ralph C. Smith
Keyword(s):  
Fractional Order ◽  
Fractional Derivatives ◽  
Nonlinear Viscoelasticity ◽  
Nonlinear Modeling ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Accurate Approximation ◽  
Modeling Framework ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Viscoelastic Model

Dielectric elastomers are employed on a wide variety of adaptive structures. Many of these soft elastomers exhibit significant rate-dependencies in their response. Accurately quantifying this viscoelastic behavior is non-trivial and in many instances a nonlinear modeling framework is required. Fractional-order operators have been applied to modeling viscoelastic behavior for many years, and recent research has shown fractional-order methods to be effective for nonlinear frameworks. This implementation can become computationally expensive to achieve an accurate approximation of the fractional-order derivative. In this paper, we demonstrate the effectiveness of using quadrature techniques in approximating the Riemann-Liouville definition for fractional derivatives in the context of developing a nonlinear viscoelastic model.

Computer simulation of tire rolling resistance using finite element method: Effect of linear and nonlinear viscoelastic models

2018 ◽  
Vol 233 (11) ◽  
pp. 2746-2760 ◽  
Author(s):  
Mehdi Rafei ◽  
Mir Hamid Reza Ghoreishy ◽  
Ghasem Naderi
Keyword(s):  
Research Work ◽  
Viscoelastic Model ◽  
Rolling Resistance ◽  
Experimental Tests ◽  
Material Model ◽  
Resistance Force ◽  
Model Parameters ◽  
Inflation Pressure ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic

This research work is devoted to the study of the effect of model parameters and material properties on tire rolling resistance. The main goal of this research is to investigate and clarify the effect of the adopted hyper-viscoelastic material model on tire rolling resistance simulation results. For this purpose, some new approaches were used and current shortcomings were introduced. Computer simulations were carried out using Abaqus standard command line. Linear and parallel rheological framework viscoelastic models were implemented and rolling resistance of a passenger car tire was determined. Different parametric simulations were carried out and the results were compared with rolling resistance data obtained from experimental tests. The results revealed that the calculated rolling resistance force depends on the implemented viscoelastic model. The linear viscoelastic model could not accurately predict the trend of rolling resistance with variation of tire inflation pressure and applied load. On the contrary, parallel rheological framework could cope with this trend. The parallel rheological framework model is more sensitive to inflation pressure. However, the sensitivity of both models to applied vertical load is nearly the same. Although cornering simulation is independent of the adopted viscoelastic model, the type of viscoelastic model could affect the footprint contact pressure contour.

scholarly journals Mechanical Behavior of Liquid Nitrile Rubber-Modified Epoxy Resin under Static and Dynamic Loadings: Experimental and Constitutive Analysis

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1565 ◽  
Author(s):  
Xiao Xu ◽  
Shiqiao Gao ◽  
Zhuocheng Ou ◽  
Haifu Ye
Keyword(s):  
Epoxy Resin ◽  
Dynamic Compression ◽  
Viscoelastic Model ◽  
Nitrile Rubber ◽  
Elastic Behavior ◽  
Model Parameters ◽  
Strain Rates ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Nonlinear Viscoelastic Model

Quasi-static and dynamic compression experiments were performed to study the influence of liquid nitrile rubber (LNBR) on the mechanical properties of epoxy resin. The quasi-static experiments were conducted by an electronic universal machine under strain rates of 0.0001/s and 0.001/s, while a Split Hopkinson Pressure Bar (SHPB) system was adopted to perform the dynamic tests for strain rates up to 5600/s. The standard Zhu-Wang-Tang (ZWT) nonlinear viscoelastic model was chosen to predict the elastic behavior of LNBR/epoxy composites under a wide range of strain rates. After some necessary derivation and data fitting, a set of model parameters for the tested materials were finally obtained. Meanwhile, the incremented form of the ZWT nonlinear viscoelastic model were deduced and implemented into the user material program of LS-DYNA. A simulation-test contrast had been performed to verify the validity and feasibility of the algorithm. The results showed that the viscoelastic behavior of epoxy resin can be effectively simulated.

Free volume based nonlinear viscoelastic model for polyurea over a wide range of strain rates and temperatures

2021 ◽  
Vol 152 ◽  
pp. 103650
Author(s):  
Chencheng Gong ◽  
Yan Chen ◽  
Ting Li ◽  
Zhanli Liu ◽  
Zhuo Zhuang ◽  
...  
Keyword(s):  
Free Volume ◽  
Viscoelastic Model ◽  
Strain Rates ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Nonlinear Viscoelastic Model

On the Nonlinear Viscoelastic Behaviour of the PVC-Coated Fabric

2010 ◽  
Vol 160-162 ◽  
pp. 1476-1481 ◽  
Author(s):  
Wu Lian Zhang ◽  
Xin Ding ◽  
Xu Dong Yang
Keyword(s):  
Viscoelastic Model ◽  
Constitutive Relationship ◽  
Viscoelastic Behaviour ◽  
Viscoelastic Response ◽  
Nonlinear Parameters ◽  
Creep And Recovery ◽  
Nonlinear Viscoelastic ◽  
Coated Fabric ◽  
Nonlinear Viscoelastic Model

The nonlinear viscoelastic response of a PVC-Coated Fabric has been studied. For the needs of the present study, creep and recovery tests in tension of both the warp and the weft directions at the different stress levels were executed while measurements were made of the creep and recovery strain response of the system. For the description of the viscoelastic behaviour of the material, Schapery’s nonlinear viscoelastic model was used. For the description of the nonlinear viscoelastic response and the determination of the nonlinear parameters, a method by using a combination of analytical formulations and numerical procedures based on a modified version of Schapery’s constitutive relationship where an instantaneous plastic and a transient plastic terms were added, has been developed. The method has been successfully applied to the current tests.

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