Nonlinear Modeling and Identification of the Dynamic Behavior of Polyurethane Foam

2001 ◽  
Author(s):  
R. Singh ◽  
P. Davies ◽  
A. K. Bajaj
Keyword(s):  
Dynamic Behavior ◽  
Polyurethane Foam ◽  
Nonlinear Modeling ◽  
Viscoelastic Model ◽  
Harmonic Excitation ◽  
Relaxation Kernel ◽  
Mass System ◽  
Response Data ◽  
State Response ◽  
Linear Viscoelastic

Abstract The analysis of the steady-state response of a polyurethane foam and mass system to harmonic excitation is given. The foam’s uni-directional dynamic behavior motion is modeled by using nonlinear stiffness, linear viscoelastic and velocity proportional damping components. The relaxation kernel for the viscoelastic model is assumed to be a sum of exponentials. Harmonic balance is used to develop one- and two-term solution approximations that are utilized for system identification. The identification process is based on least-squares minimization of a sub-optimal cost function that uses response data at various excitation frequencies and amplitudes. The effect of number, spacing and amplitudes of the harmonic input on the results of the model parameter estimation is discussed. Model-order choice and the feasibility of describing the system behavior at several input amplitudes with a single set of parameters are also addressed.

scholarly journals Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1050 ◽  
Author(s):  
Polidor Bratu ◽  
Cornelia Dobrescu
Keyword(s):  
Experimental Tests ◽  
Harmonic Excitation ◽  
Natural Soil ◽  
Response Data ◽  
High Loading Rate ◽  
Insulation Systems ◽  
Linear Viscoelastic ◽  
Vibration Parameters ◽  
Mineral Aggregates

A comprehensive investigation, including analytical modelling, numerical analysis and experimental tests, has been carried out on many linear viscoelastic systems and structures. This approach is the result of research conducted by two research institutes, ICECON and INCERC Bucharest, from Romania. Thus, analyses were performed on the dynamic behaviour of composite viscoelastic materials, anti-vibration viscoelastic systems made of discrete physical devices, road structures consisting of layers of natural soil with mineral aggregates and asphalt mixtures, and mixed mechanic insulation systems for industrial vibrations formed of elastic and viscous devices. The objectives pursued were as follows: (a) providing a mass dosage of the mixture of earth (clay, sand, mineral aggregates, water, and stabilizer) in five variants; (b) carrying out a test run with a Bomag vibratory roller with variable vibration parameters; (c) Experimental evaluation of the vibration parameters and the force transmitted to the ground, correlated with the determination of the compaction layer; (d) use of methods of analysis for physic-mechanical and geotechnical parameters; (e) rheological and numerical modeling based on Zener schematics, so the consistency and veracity of the experimental data with the numerical simulation can be determined. Finally, a study is presented for a test track, where experimental and correlated input and response data are determined to validate the rheological model with a high loading rate.

scholarly journals Vibration Equation of Fractional Order Describing Viscoelasticity and Viscous Inertia

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 850-856 ◽  
Author(s):  
Jun-Sheng Duan ◽  
Yun-Yun Xu
Keyword(s):  
Fractional Derivative ◽  
Fractional Order ◽  
Fractional Derivatives ◽  
Harmonic Excitation ◽  
Steady State Response ◽  
Vibration System ◽  
Derivative Operator ◽  
Vibration Equation ◽  
State Response ◽  
Frequency Relation

Abstract The steady state response of a fractional order vibration system subject to harmonic excitation was studied by using the fractional derivative operator ${}_{-\infty} D_t^\beta,$where the order β is a real number satisfying 0 ≤ β ≤ 2. We derived that the fractional derivative contributes to the viscoelasticity if 0 < β < 1, while it contributes to the viscous inertia if 1 < β < 2. Thus the fractional derivative can represent the “spring-pot” element and also the “inerterpot” element proposed in the present article. The viscosity contribution coefficient, elasticity contribution coefficient, inertia contribution coefficient, amplitude-frequency relation, phase-frequency relation, and influence of the order are discussed in detail. The results show that fractional derivatives are applicable for characterizing the viscoelasticity and viscous inertia of materials.

Application of a Viscoelastic Model for Polyester Mooring

2010 ◽  
Author(s):  
J. W. Kim ◽  
J. H. Kyoung ◽  
A. Sablok
Keyword(s):  
Material Properties ◽  
Viscoelastic Model ◽  
Practical Method ◽  
Time Dependent ◽  
Mooring Line ◽  
New Model ◽  
Global Performance ◽  
Excitation Period ◽  
Linear Viscoelastic ◽  
Floating Platforms

A new practical method to simulate time-dependent material properties of polyester mooring line is proposed. The time-dependent material properties of polyester rope are modeled with a standard linear solid (SLS) model, which is one of the simplest forms of a linear viscoelastic model. The viscoelastic model simulates most of the mechanical properties of polyester rope such as creep, strain-stress hysteresis and excitation period-dependent stiffness. The strain rate-stress relation of the SLS model has been re-formulated to a stretch-tension relation, which is more suitable for implementation into global performance and mooring analyses tools for floating platforms. The new model has been implemented to a time-domain global performance analysis software and applied to simulate motion of a spar platform with chain-polyester-chain mooring system. The new model provides accurate platform offset without any approximation on the mean environmental load and can simulate the transient effect due to the loss of a mooring line during storm conditions, which has not been possible to simulate using existing dual-stiffness models.

A non-linear viscoelastic model with structure-dependent relaxation times

1976 ◽  
Vol 1 (2) ◽  
pp. 147-157 ◽  
Author(s):  
D. Acierno ◽  
F.P. La Mantia ◽  
G. Marrucci ◽  
G. Rizzo ◽  
G. Titomanlio
Keyword(s):  
Relaxation Times ◽  
Viscoelastic Model ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Model

STRESS RELAXATION OF MAGNETORHEOLOGICAL FLUIDS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2655-2661
Author(s):  
W. H. LI ◽  
G. CHEN ◽  
S. H. YEO ◽  
H. DU
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Model ◽  
Relaxation Modulus ◽  
Damping Function ◽  
Mr Fluids ◽  
Large Step ◽  
Linear Viscoelastic ◽  
Predicted Values ◽  
Two Parameters ◽  
Step Strain

In this paper, the experimental and modeling study and analysis of the stress relaxation characteristics of magnetorheological (MR) fluids under step shear are presented. The experiments are carried out using a rheometer with parallel-plate geometry. The applied strain varies from 0.01% to 100%, covering both the pre-yield and post-yield regimes. The effects of step strain, field strength, and temperature on the stress modulus are addressed. For small step strain ranges, the stress relaxation modulus G(t,γ) is independent of step strain, where MR fluids behave as linear viscoelastic solids. For large step strain ranges, the stress relaxation modulus decreases gradually with increasing step strain. Morever, the stress relaxation modulus G(t,γ) was found to obey time-strain factorability. That is, G(t,γ) can be represented as the product of a linear stress relaxation G(t) and a strain-dependent damping function h(γ). The linear stress relaxation modulus is represented as a three-parameter solid viscoelastic model, and the damping function h(γ) has a sigmoidal form with two parameters. The comparison between the experimental results and the model-predicted values indicates that this model can accurately describe the relaxation behavior of MR fluids under step strains.

Identification of Structural Parameters in Mistuned Bladed Disks

1997 ◽  
Vol 119 (3) ◽  
pp. 428-438 ◽  
Author(s):  
Marc P. Mignolet ◽  
Chung-Chih Lin
Keyword(s):  
Maximum Likelihood ◽  
Least Squares ◽  
Structural Model ◽  
Structural Parameters ◽  
Model Parameters ◽  
Disk Model ◽  
Response Data ◽  
State Response ◽  
Bladed Disk ◽  
True Model

The present investigation focused on the estimation of the parameters of a structural model to represent “at best” a set of measurements of the steady state response of a mistuned bladed disk. The applicability of the least squares and maximum likelihood approaches to the identification of the bladed disk model from this data is first investigated. The advantages and drawbacks of these techniques motivate the introduction of a new mixed least squares-maximum likelihood formulation which is shown to recover well the true model parameters from noisy simulated response data.

A non-linear viscoelastic model for sediments flocculated in the presence of seawater salts

2015 ◽  
Vol 482 ◽  
pp. 500-506 ◽  
Author(s):  
Christian Goñi ◽  
Ricardo I. Jeldres ◽  
Pedro G. Toledo ◽  
Anthony D. Stickland ◽  
Peter J. Scales
Keyword(s):  
Viscoelastic Model ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Model
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