Modeling of the Linear Viscoelastic Behavior of Partially Hydrogenated Polymer-Modified Asphalts

2007 ◽  
Vol 80 (2) ◽  
pp. 340-364 ◽  
Author(s):  
M. A. Vargas ◽  
R. Herrera ◽  
O. Manero
Keyword(s):  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Low Frequencies ◽  
Emulsion Model ◽  
Wide Range ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Polymer Modified Asphalt ◽  
Styrene Butadiene

Abstract The modeling of the linear viscoelastic behavior of asphalt modified with 8 wt % of partially hydrogenated poly (styrene-butadiene-styrene) triblock copolymers is analyzed. Time-temperature superposition renders master curves in a wide range of frequencies and temperatures, from which a logarithmic distribution of relaxation times is obtained using the multimode Maxwell model. In addition, the linear viscoelastic data is analyzed with an emulsion model and agreement is only found at high frequencies, where the contribution from interfacial tension is negligible. Enhanced polymer-asphalt interactions at low frequencies evidenced by a decreasing limiting slope of the storage modulus in the terminal region are not predicted by the emulsion model, and relative agreement is found considering two viscoelastic phases. The Cole-Cole representation and the fractional Maxwell model predict the viscosity of asphalt in the complex plane, but strong asymmetry in the semicircular arcs is found in the polymer-modified asphalt blends. The Havriliak-Negami model accounts for asymmetric arcs and represents the data better in specific ranges of frequency.

Linear Viscoelastic Behavior of Bentonite-Water Suspensions

2002 ◽  
Vol 12 (5) ◽  
pp. 234-240 ◽  
Author(s):  
Karim Bekkour ◽  
Nadia Kherfellah
Keyword(s):  
Low Frequency ◽  
Viscoelastic Behavior ◽  
Colloidal Dispersions ◽  
Frequency Scale ◽  
Water Suspensions ◽  
Wide Range ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Exhaustive Study ◽  
Using Data

Abstract Bentonite are extensively used materials in a wide range of applications. Creep and oscillatory shear experiments in the linear viscoelastic domain were carried out on bentonite-water suspensions at different solid fractions. It was found that bentonite dispersions exhibit important viscoelastic behavior which could be represented by the generalized Kelvin-Voigt mechanical model. It is well known that an exhaustive study of colloidal dispersions may require the determination of its viscoelastic properties over a wide frequency scale. Unfortunately, due to microstructure changes, the experiments are limited in time. In order to avoid such limitation, oscillatory data were deduced from creep curves - without actually vibrating the clay dispersions - because a periodic experiment at frequency ω is qualitatively equivalent to a creep test at time 1/ω. That is, it was possible to complete the dynamic response in the low-frequency range using data obtained from the transient response in creep.

scholarly journals Comparison of Pavement Layers Responses with Considering Different Models for Asphalt Concrete Viscoelastic Properties

2013 ◽  
Vol 21 (2) ◽  
pp. 15-20 ◽  
Author(s):  
Mehdi Koohmishi
Keyword(s):  
Asphalt Concrete ◽  
Structural Model ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Elastic Behavior ◽  
Linear Elastic ◽  
Concrete Layer ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

Abstract In this paper, a comparison between pavement responses is performed by considering two different models for the linear viscoelastic behavior of an asphalt concrete layer. Two models, the Maxwell model and the Kelvin-Voigt model, are generalized. The former is used in ABAQUS and the latter in KENLAYER. As a preliminary step, an appropriate structural model for a flexible pavement structure is developed in ABAQUS by considering linear elastic behavior for all the layers. According to this model, when the depth of a structural model is equal to 6 meters, there is a good agreement between the ABAQUS and KENLAYER results. In this model, the thickness of the pavement is equal to 30 centimeters, and the thickness of the subgrade is equal to 5.7 meters. Then, the viscoelastic behavior is considered for the asphalt concrete layer, and the results from KENLAYER and ABAQUS are compared with each other. The results indicate that the type of viscoelastic model applied to an asphalt concrete layer has a significant effect on the prediction of pavement responses and, logically, the predicted performance of a pavement.

A 3D Linear Viscoelastic Parametric Structural Study of Bend Stiffeners Considering Temperature

2015 ◽  
Author(s):  
Luis C. Rojas ◽  
Murilo A. Vaz
Keyword(s):  
Structural Study ◽  
Mechanical Response ◽  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Material Behavior ◽  
Linear Elastic ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Solid Finite Elements ◽  
Made In

Bend stiffener are conical structures used in flexible riser systems in order to ensure smooth stiffness transition between riser and floating units, preventing excessive curvatures and protecting from failure. Made in polyurethane, the vast majority of analysis of bend stiffener-riser systems generally assume the material behavior as linear elastic or hyperelastic; time dependence, creep or stress relaxation are not considered. This work presents a parametric structural study of bend stiffeners, considering linear elastic and linear viscoelastic behavior using fourth order Prony series considering the temperature dependence on relaxation times. Different subroutines in FORTRAN based in UMAT -ABAQUS methodology are developed in order to calculate the mechanical response of bend stiffeners (deflection and curvature), assuming homogeneity, symmetry and isotropy. Case studies using solid finite elements made for different geometrical and material models and finally were compared with other works from different authors.

scholarly journals Mapping cellular nanoscale viscoelasticity and relaxation times relevant to growth of living Arabidopsis thaliana plants using multifrequency AFM

2020 ◽  
Author(s):  
Jacob Seifert ◽  
Charlotte Kirchhelle ◽  
Ian Moore ◽  
Sonia Contera
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Walls ◽  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Fine Tuning ◽  
Simple Method ◽  
Precise Control ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

AbstractThe shapes of living organisms are formed and maintained by precise control in time and space of growth, which is achieved by dynamically fine-tuning the mechanical (viscous and elastic) properties of their hierarchically built structures from the nanometer up. Most organisms on Earth including plants grow by yield (under pressure) of cell walls (bio-polymeric matrices equivalent to extracellular matrix in animal tissues) whose underlying nanoscale viscoelastic properties remain unknown. Multifrequency atomic force microscopy (AFM) techniques exist that are able to map properties to a small subgroup of linear viscoelastic materials (those obeying the Kelvin-Voigt model), but are not applicable to growing materials, and hence are of limited interest to most biological situations. Here, we extend existing dynamic AFM methods to image linear viscoelastic behavior in general, and relaxation times of cells of multicellular organisms in vivo with nanoscale resolution, featuring a simple method to test the validity of the mechanical model used to interpret the data. We use this technique to image cells at the surface of living Arabidopsis thaliana hypocotyls to obtain topographical maps of storage E’ = 120 − 200 MPa and loss E’’= 46 − 111 MPa moduli as well as relaxation times τ = 2.2 − 2.7 µs of their cell walls. Our results demonstrate that cell walls, despite their complex molecular composition, display a striking continuity of simple, linear, viscoelastic behavior across scales–following almost perfectly the standard linear solid model–with characteristic nanometer scale patterns of relaxation times, elasticity and viscosity, whose values correlate linearly with the speed of macroscopic growth. We show that the time-scales probed by dynamic AFM experiments (milliseconds) are key to understand macroscopic scale dynamics (e.g. growth) as predicted by physics of polymer dynamics.

Combined Statistical-Mechanical Characterization of a Next Generation Textured PTFE for Extreme Environments

2018 ◽  
Author(s):  
Sannmit Shinde ◽  
Ali P. Gordon ◽  
Zachary Poust ◽  
Steve Pitolaj ◽  
Jim Drago ◽  
...  
Keyword(s):  
Extreme Environments ◽  
Viscoelastic Behavior ◽  
Ceramic Particle ◽  
Operating Conditions ◽  
Operating Environments ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Statistical Mechanical ◽  
Relaxation Responses

Pressurized vessels that transfer media from one location to another often contain a bolted connection. Gaskets are essential for these systems since they confer high levels of leak mitigation across of range of operating environments (i.e., internal pressure and temperature). The balance of both sealability and compressibility must be displayed in candidate gasket materials to be subjected to aggressive operating conditions. Historically, thin gauge gasket (i.e., 1/16” thick) confer high sealability while thick gaskets offer superior compressibility (i.e., 1/8”). Fabricated with skive cut, ceramic particle-reinforced PTFE, these materials display linear viscoelastic behavior that allow consolidation to occur. For example, GYLON® 3504 is filled with Aluminosilicate Microspheres, GYLON®3510 is filled with barium sulfate, respectively, to efficiently fill crevices along the surfaces of the flange. Novel textured PTFE gasket (3504 EPX and 3510 EPX) have been developed to simultaneously confer sealability and compressibility compared to flat products. A design of experiments (DoE) approach is applied to characterize the factors that influence load relaxation responses of the both candidate textured PTFE (dual-face honeycomb) and existing (flat) gasket styles. Using an instrumented test platform analyzed. A new parameter is presented to quantify gasket efficiency. The collection of efficiency measurement methods and approach to re-torque optimization convey a novel framework that designers can invoke to facilitate improved flange performance.

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