scholarly journals RELFIT: A program for determining prony series fits to measured relaxation data

1997 ◽  
Author(s):  
R.S. Chambers
Keyword(s):  
Prony Series ◽  
Relaxation Data ◽  
Measured Relaxation

scholarly journals Analysis of Blood Flow through Viscoelastic Blood Vessel

2012 ◽  
pp. 212-215
Author(s):  
M. Unnikrishnan ◽  
Ajith. C. Menon ◽  
Deepak M. D. ◽  
John Joseph
Keyword(s):  
Blood Flow ◽  
Blood Vessel ◽  
Curve Fitting ◽  
Von Mises Stress ◽  
Prony Series ◽  
Viscoelastic Materials ◽  
Relaxation Data ◽  
Flow Through ◽  
Von Mises ◽  
Fluid Interaction

Analysis of viscoelastic material can be done through ansys multi physics software. For modelling viscoelastic materials, prony series coefficients had been generated from the stress relaxation data (shear modulus vs. time) using prony series curve fitting. Also, Ansys was used to study the fluid interaction on viscoelastic materials. First blood vessel was modelled using geometric modeller and it is exported to ansys and using prony series curve fitting, viscoelastic properties are given to the blood vessel. Blood flow was modelled in CFX. Two way coupling was established between Ansys and CFX. And the boundary conditions such as pressure pulse and mass flow rate was given to the blood flow. Then the model was solved in CFX. And the variation of pressure, von mises stress and total mesh displacement along the length of blood vessel is plotted.

Large Strain Viscoelastic Constitutive Models for Rubber, Part II: Determination of Material Constants

1995 ◽  
Vol 68 (2) ◽  
pp. 230-247 ◽  
Author(s):  
Claudia J. Quigley ◽  
Joey Mead ◽  
Arthur R. Johnson
Keyword(s):  
Finite Element ◽  
Large Strain ◽  
Strain Relaxation ◽  
Small Strain ◽  
Material Behavior ◽  
Prony Series ◽  
Relaxation Data ◽  
Material Constants ◽  
Tension And Compression ◽  
Step Strain

Abstract A method for determining material constants in large strain viscoelastic materials was demonstrated for a highly saturated nitrile rubber. Material constant selection was based on viscoelastic stress relaxation data at small and large strains, under both tension and compression, and was constrained to assure Drucker stability. Assuming that the viscoelastic strain energy function was both time and strain separable, a Prony series was constructed for the time dependent material constants. For comparison, four different Prony series were developed from collocation methods and a nonlinear regression analysis, each separately based on either large or small tensile strain relaxation data. In addition, a final Prony series was constructed from dynamic data. These Prony series were included in this comparison to judge their ability to predict both large and small strain material behavior. Finite element analyses of large and small step-strain relaxation tests and a single cycle hysteresis loop at large deformations were performed for each set of Prony series. The results were then compared to experimental behavior. The Prony series based on the constrained method accurately predicted step-strain relaxation behavior at all strain levels, for both tension and compression. The finite element results for the other Prony series show that large strain material behavior was best predicted by those Prony series based on large strain material behavior. Similar findings were found for small strain material behavior. The constrained Prony series and the two large strain based Prony series best modeled the experimental hysteresis loop.

Detection of Chemical Exchange in Methyl Groups of Macromolecules

2019 ◽  
Author(s):  
Michelle Gill ◽  
Andrew Hsu ◽  
Arthur G. Palmer, III
Keyword(s):  
Relaxation Rate ◽  
Chemical Exchange ◽  
Double Quantum ◽  
Methyl Groups ◽  
Multiple Quantum ◽  
Relaxation Data ◽  
E Coli ◽  
Methyl Trosy ◽  
Dynamics Simulations ◽  
Exchange Broadening

<div> <div> <div> <p>The zero- and double-quantum methyl TROSY Hahn-echo and the methyl <sup>1</sup>H-<sup>1</sup>H dipole- dipole cross-correlation nuclear magnetic resonance experiments enable estimation of multiple quantum chemical exchange broadening in methyl groups in proteins. The two relaxation rate constants are established to be linearly dependent using molecular dynamics simulations and empirical analysis of experimental data. This relationship allows chemical exchange broadening to be recognized as an increase in the Hahn-echo relaxation rate constant. The approach is illustrated by analyzing relaxation data collected at three temperatures for <i>E. coli </i>ribonuclease HI and by analyzing relaxation data collected for different cofactor and substrate complexes of <i>E. coli </i>AlkB. </p> </div> </div> </div>

scholarly journals Material parametrization of natural rubber based compound and characterization of crack propagation under consideration of dissipative effects

2021 ◽  
Author(s):  
Dan Pornhagen ◽  
Konrad Schneider ◽  
Markus Stommel
Keyword(s):  
Energy Dissipation ◽  
Crack Propagation ◽  
Natural Rubber ◽  
Experimental Tests ◽  
Material Behavior ◽  
Prony Series ◽  
Material Forces ◽  
Cracking Behavior ◽  
Dissipative Effects

AbstractMost concepts to characterize crack propagation were developed for elastic materials. When applying these methods to elastomers, the question is how the inherent energy dissipation of the material affects the cracking behavior. This contribution presents a numerical analysis of crack growth in natural rubber taking energy dissipation due to the visco-elastic material behavior into account. For this purpose, experimental tests were first carried out under different load conditions to parameterize a Prony series as well as a Bergström–Boyce model with the results. The parameterized Prony series was then used to perform numerical investigations with respect to the cracking behavior. Using the FE-software system ANSYS and the concept of material forces, the influence and proportion of the dissipative components were discussed.

scholarly journals Application of micro-computer tomography and inverse finite element analysis for characterizing the visco-hyperelastic response of bulk liver tissue using indentation

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Rajeswara R. Resapu ◽  
Roger D. Bradshaw
Keyword(s):  
Finite Element ◽  
Liver Tissue ◽  
Loading Rate ◽  
Time Dependent ◽  
Nonlinear Material ◽  
Computational Time ◽  
List Type ◽  
Prony Series ◽  
Time Dependent Behaviour ◽  
Dependent Behaviour

Abstract In-vitro mechanical indentation experimentation is performed on bulk liver tissue of lamb to characterize its nonlinear material behaviour. The material response is characterized by a visco-hyperelastic material model by the use of 2-dimensional inverse finite element (FE) analysis. The time-dependent behaviour is characterized by the viscoelastic model represented by a 4-parameter Prony series, whereas the large deformations are modelled using the hyperelastic Neo-Hookean model. The shear response described by the initial and final shear moduli and the corresponding Prony series parameters are optimized using ANSYS with the Root Mean Square (RMS) error being the objective function. Optimized material properties are validated using experimental results obtained under different loading histories. To study the efficacy of a 2D model, a three dimensional (3D) model of the specimen is developed using Micro-CT of the specimen. The initial elastic modulus of the lamb liver obtained was found to 13.5 kPa for 5% indentation depth at a loading rate of 1 mm/sec for 1-cycle. These properties are able to predict the response at 8.33% depth and a loading rate of 5 mm/sec at multiple cycles with reasonable accuracy. Article highlights The visco-hyperelastic model accurately models the large displacement as well as the time-dependent behaviour of the bulk liver tissue. Mapped meshing of the 3D FE model saves computational time and captures localized displacement in an accurate manner. The 2D axisymmetric model while predicting the force response of the bulk tissue, cannot predict the localized deformations.

scholarly journals How wide is the window opened by high-resolution relaxometry on the internal dynamics of proteins in solution?

2021 ◽  
Vol 75 (2-3) ◽  
pp. 119-131
Author(s):  
Albert A. Smith ◽  
Nicolas Bolik-Coulon ◽  
Matthias Ernst ◽  
Beat H. Meier ◽  
Fabien Ferrage
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
High Field ◽  
Rotational Diffusion ◽  
Relaxation Data ◽  
Internal Dynamics ◽  
Nmr Relaxometry ◽  
Analysis Of Dynamics

AbstractThe dynamics of molecules in solution is usually quantified by the determination of timescale-specific amplitudes of motions. High-resolution nuclear magnetic resonance (NMR) relaxometry experiments—where the sample is transferred to low fields for longitudinal (T1) relaxation, and back to high field for detection with residue-specific resolution—seeks to increase the ability to distinguish the contributions from motion on timescales slower than a few nanoseconds. However, tumbling of a molecule in solution masks some of these motions. Therefore, we investigate to what extent relaxometry improves timescale resolution, using the “detector” analysis of dynamics. Here, we demonstrate improvements in the characterization of internal dynamics of methyl-bearing side chains by carbon-13 relaxometry in the small protein ubiquitin. We show that relaxometry data leads to better information about nanosecond motions as compared to high-field relaxation data only. Our calculations show that gains from relaxometry are greater with increasing correlation time of rotational diffusion.

scholarly journals Visco-Hyperelastic Characterization of the Equine Immature Zona Pellucida

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1223
Author(s):  
Elisa Ficarella ◽  
Mohammad Minooei ◽  
Lorenzo Santoro ◽  
Elisabetta Toma ◽  
Bartolomeo Trentadue ◽  
...  
Keyword(s):  
Zona Pellucida ◽  
Soft Matter ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Nonlinear Material ◽  
Prony Series ◽  
Critical Comparison ◽  
Highly Nonlinear ◽  
Good Agreement

This article presents a very detailed study on the mechanical characterization of a highly nonlinear material, the immature equine zona pellucida (ZP) membrane. The ZP is modeled as a visco-hyperelastic soft matter. The Arruda–Boyce constitutive equation and the two-term Prony series are identified as the most suitable models for describing the hyperelastic and viscous components, respectively, of the ZP’s mechanical response. Material properties are identified via inverse analysis based on nonlinear optimization which fits nanoindentation curves recorded at different rates. The suitability of the proposed approach is fully demonstrated by the very good agreement between AFM data and numerically reconstructed force–indentation curves. A critical comparison of mechanical behavior of two immature ZP membranes (i.e., equine and porcine ZPs) is also carried out considering the information on the structure of these materials available from electron microscopy investigations documented in the literature.

Indentation load relaxation experiments with indentation depth in the submicron range

1990 ◽  
Vol 5 (10) ◽  
pp. 2100-2106 ◽  
Author(s):  
W. R. LaFontaine ◽  
B. Yost ◽  
R. D. Black ◽  
C-Y. Li
Keyword(s):  
Indentation Depth ◽  
Metal Films ◽  
Indentation Load ◽  
Hard Substrate ◽  
Flow Properties ◽  
Load Relaxation ◽  
Relaxation Data ◽  
Flow Curves ◽  
Relaxation Experiments

Indentation load relaxation (ILR) experiments with indentation depths in the submicron range are described. Under appropriate conditions, the ILR data are found to yield flow curves of the same shape as those based on conventional load relaxation data. Variations in flow properties as a function of depth in submicron metal films deposited on a hard substrate are detected by the experiments described.

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