Characterization of the three-dimensional linear viscoelastic behavior of asphalt concrete mixtures

2016 ◽  
Vol 105 ◽  
pp. 356-364 ◽  
Author(s):  
Andrea Graziani ◽  
Fabrizio Cardone ◽  
Amedeo Virgili
Keyword(s):  
Asphalt Concrete ◽  
Three Dimensional ◽  
Viscoelastic Behavior ◽  
Concrete Mixtures ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

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.

A viscoelastic Timoshenko shaft finite element for dynamic analysis of rotors

2016 ◽  
Vol 24 (11) ◽  
pp. 2180-2200 ◽  
Author(s):  
Smitadhi Ganguly ◽  
A Nandi ◽  
S Neogy
Keyword(s):  
Finite Element ◽  
Elastic Strain ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Viscoelastic Behavior ◽  
Beam Shape ◽  
Unit Step ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
The Time Domain

A new shaft element is proposed for viscoelastic rotors in a spinning frame considering the shear deformation in addition to bending deformation. The Maxwell–Wiechert model is considered here to replicate linear viscoelastic behavior. This model considers additional internal damping displacement variables between elastic and viscous elements and the stress depends not only on the elastic strain and elastic strain rate, but also on additional strains and their rates corresponding to the damping variables. The present work assumes that these additional strains can be derived from continuous fictitious displacement variables, which in turn are interpolated from their nodal values using the Timoshenko beam shape functions. Therefore, in addition to the standard degrees of freedom for a three-dimensional shaft, extra degrees of freedom are defined at the nodes. The finite element matrices are assembled in state space. The time domain equations are then used for stability analysis and computation of response to a unit step load and an unbalance.

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.

Study on Rheological Characterization of Uncured Natural Rubber with Different Initial Moisture Contents Dried by Microwave

2014 ◽  
Vol 998-999 ◽  
pp. 383-386
Author(s):  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mei Chen ◽  
Mao Fang Huang ◽  
Ri Zhong Zeng
Keyword(s):  
Natural Rubber ◽  
Viscoelastic Behavior ◽  
Sweep Frequency ◽  
Rheological Characterization ◽  
Moisture Contents ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Strain Sweep ◽  
Viscous Torque

In this work, the rheological behavior of uncured natural rubber with different initial moisture contents dried by microwave was studied using RPA under frequency sweep and strain sweep modes. It can be seen from the results that the variation trend of viscous torque S`` versus sweep frequency kept with the trend of elastic torque S` versus sweep frequency. Moreover, the viscous torque S`` values were lower than those for elastic torque S`, a good linear relation curve was obtained by plotting elastic torque S` versus sweep frequency. The curve of storage shear modulus G` versus sweep strain presented a linear relationship, showed a linear viscoelastic behavior of uncured natural rubber with different initial moisture contents. This may be explained by the degradation of molecular chains of natural rubber and the van der waals forces between them.

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