On the Determination of a Viscoelastic Model for Stress Analysis of Plastics

1956 ◽  
Vol 23 (3) ◽  
pp. 416-420
Author(s):  
D. R. Bland ◽  
E. H. Lee
Keyword(s):  
Stress Analysis ◽  
Viscous Flow ◽  
Viscoelastic Material ◽  
Graphical Method ◽  
Viscoelastic Model ◽  
Element Model ◽  
Viscoelastic Response ◽  
Frequency Range ◽  
Complex Compliance

Abstract A method of assessing whether or not the measured variation of complex compliance with frequency for a viscoelastic material is consistent with a four-element model is presented. The four-element model was chosen since it is relatively simple to analyze, and exhibits the three main types of viscoelastic response; namely, instantaneous elasticity, viscous flow, and delayed elasticity. If the compliance measurements are found to conform with the behavior of a four-element model over the whole or part of the frequency range studied, a graphical method of determining the model constants is presented. The significance of the application of such a model to stress analysis under transient loading is discussed.

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.

Stiffened Panels Modal and Stress Analysis Based on ANSYS

2014 ◽  
Vol 644-650 ◽  
pp. 4701-4704
Author(s):  
Tian Bing Ma ◽  
Jian Jun Zhang ◽  
Fei Du
Keyword(s):  
Stress Analysis ◽  
Structural Strength ◽  
Dynamic Strength ◽  
Element Model ◽  
Stiffened Panel ◽  
Response Analysis ◽  
Maximum Point ◽  
Frequency Response Analysis ◽  
Frequency Range ◽  
Stiffened Panels

Reinforced panel is prone to serious damage and its life becomes shorter under the influence of vibration and noise. It is necessary to test its dynamic strength. In this paper, firstly, using ANSYS to set finite element model of stiffened panels and make a modal analysis to extract the natural modal frequency and vibration type, then conducting frequency response analysis according to the experiment with the boundary conditions and the set frequency range, finally through ANSYS stress analysis, pointing out the maximum point of structural stress response. The research provides a reference for checking the dynamic strength experiments conducted to improve the design and structural strength of stiffened panel.

Damping Control in a Sandwich Structure With SMP Core

2015 ◽  
Author(s):  
Pauline Butaud ◽  
Morvan Ouisse ◽  
Emmanuel Foltête
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Sandwich Structure ◽  
Damping Ratio ◽  
Shape Memory Polymer ◽  
Viscoelastic Model ◽  
Element Model ◽  
Numerical Approach ◽  
Wide Frequency Range ◽  
Frequency Range

A shape memory polymer (SMP), the tBA/PEGDMA, is elaborated and characterized. The dynamic mechanical characterization of this SMP highlights promising damping properties. The frequency and temperature dependency of the SMP is represented by a viscoelastic model allowing the introduction of the material in the design process of complex structures. A composite sandwich is developed by coupling the SMP with aluminum skins. A finite element model is developed for modeling the behavior of the SMP when integrated in a sandwich structure. The damping performances obtained by the numerical approach are validated experimentally using modal analysis. The experimental results are found to be in good agreement with the predictions of the finite element model. Furthermore, it is found that the controlled heating of the SMP core allows damping the structure over a wide frequency range. The SMP core temperature is tuned from the time-temperature superposition through a calibration curve to correspond to optimal values of damping ratio in the frequency range of interest; a vibration attenuation of about 20dB is observed.

Rhesus Monkey Intervertebral Disk Viscoelastic Response to Shear Stress

1983 ◽  
Vol 105 (1) ◽  
pp. 51-54 ◽  
Author(s):  
B. S. Kelley ◽  
J. F. Lafferty ◽  
D. A. Bowman ◽  
P. A. Clark
Keyword(s):  
Shear Stress ◽  
Rhesus Monkey ◽  
Material Properties ◽  
Mechanical Model ◽  
Viscoelastic Model ◽  
Intervertebral Disk ◽  
Viscoelastic Response ◽  
Relaxation Functions ◽  
Experimental Strain

A viscoelastic model of the shear response of the Rhesus monkey intervertebral disk, represented by a series chain of four Kelvin units is presented. Two types of investigations are carried out to assess the validity of the model: 1) determination of material properties by comparison with experimental strain creep behavior of the disk; and 2) validation of this viscoelastic model by accurately predicting the experimental results of stress relaxation tests. The use of the series Kelvin units approach provides the first analytical mechanical model capable of predicting the creep and relaxation functions for the intervertebral disk in shear.

A Graphical Method for Storage Coefficient Determination from Quasi-Steady State Flow Data

1996 ◽  
Vol 27 (4) ◽  
pp. 247-254 ◽  
Author(s):  
Zekâi Şen
Keyword(s):  
Steady State ◽  
Graphical Method ◽  
Pumping Test ◽  
Quasi Steady State ◽  
Flow Data ◽  
Steady State Flow ◽  
Storage Coefficient ◽  
State Flow ◽  
Aquifer Test

A simple, approximate but practical graphical method is proposed for estimating the storage coefficient independently from the transmissivity value, provided that quasi-steady state flow data are available from a pumping test. In the past, quasi-steady state flow distance-drawdown data have been used for the determination of transmissivity only. The method is applicable to confined and leaky aquifers. The application of the method has been performed for various aquifer test data available in the groundwater literature. The results are within the practical limits of approximation compared with the unsteady state flow solutions.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

scholarly journals A computationally efficient hybrid 2D–3D subwoofer model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ahmad H. Bokhari ◽  
Martin Berggren ◽  
Daniel Noreland ◽  
Eddie Wadbro
Keyword(s):  
Hybrid Model ◽  
3D Model ◽  
Element Model ◽  
Acoustic Properties ◽  
Computational Time ◽  
Average Response ◽  
Frequency Range ◽  
Computationally Efficient ◽  
Lumped Element ◽  
Lumped Element Model

AbstractA subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

scholarly journals The determination of binding parameters when the total and free substrate concentrations are not approximately equal

1979 ◽  
Vol 179 (3) ◽  
pp. 697-700 ◽  
Author(s):  
N Gains
Keyword(s):  
Substrate Concentration ◽  
Graphical Method ◽  
Enzyme Concentration ◽  
Binding Parameters ◽  
Free Concentration ◽  
Equilibrium Binding ◽  
Substrate Concentrations

By using a standard graphical method values of Km and V may be found that are independent of the conditions and assumptions that the total substrate concentration approximates to its free concentration and that Km is much larger than the enzyme concentration. The procedure is also applicable to the determination of equilibrium binding parameters of a ligand to a macromolecule.

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