Thermodynamic restrictions and wave features of a non-linear Maxwell model

2012 ◽  
Vol 47 (9) ◽  
pp. 1008-1013 ◽  
Author(s):  
A. Morro
Author(s):  
Hanen Jrad ◽  
Jean Luc Dion ◽  
Franck Renaud ◽  
Imad Tawfiq ◽  
Mohamed Haddar

Viscoelastic components are incorporated into automobile and aerospace structures system in order to damp mechanical vibrations. Viscoelastic components are a key element in designing desired dynamic behaviour of mechanical systems. Viscoelastic components dynamic characteristics are often very complex, due to the dependence of its response on several variables, such as frequency, amplitude, preload, and temperature. These dependencies can be critical in capturing the mechanical proprieties and so non linear dynamical behaviour may appear. Assuming that non linearities are due to non linear elasticity, the non linear Generalized Maxwell Model (GMM) is proposed to characterize dynamics of viscoelastic components. Parameters of GMM are identified from Dynamic Mechanical Analysis (DMA) tests for different excitation frequencies. A particular result from identification is that the non linear stiffness is dependent upon displacement amplitude and static displacement under static preload. The significance of this result is that the non linear dynamics of the viscoelastic component can be represented by a simple analytical model capable to produce accurate results. Comparison between measurements and simulations of dynamic stiffness of viscoelastic component has been carried on.


Author(s):  
Ajab Khurshid

Abstract: This report presents the work done to create a 3D model of a pavement structure, which incorporates in a most accurately way non damaging effects of asphalt layer considering the different layers that compose the pavement structure. A series of approaches have been considered from linear viscoelastic modelling using Maxwell model via UMAT subroutine to integrated viscoelastic response using Prony series available in the built in ABAQUS material library. During this work also other effects have been considered including the viscoelastic behaviour caused by creep, which is included via a separate CREEP subroutine. In order to predict also the non-linear effect of viscous elastic response the well-known Schapery's nonlinear viscoelastic constitutive model was considered. Implementing 3D Schapery’s model can be done by using again user material subroutine UMAT. It was found that the use of a nonlinear viscoelastic model substantially transformed the pavement response. A series of python scripts have been developed to create a multi-step analysis to simulate a cyclic loading application. Keywords: Viscoelasticity, Abaqus. Asphalt, Damage, Simulation, Modelling, Pavement design


2008 ◽  
Vol 575-578 ◽  
pp. 622-626
Author(s):  
Hai Hong Wu ◽  
Zhen Feng Zhao ◽  
Chang Yu Shen

The development of internal stress in injection molded parts is analyzed. Different from other researches, this study uses a new modified Maxwell model to calculate the internal stress. On the basis of the creep experiments of injection molded parts, a non-linear constitutive equation is proposed. Non-linear finite element equation to calculate the internal stress is derived. By means of this model, the internal stress of an injection molded polystyrene plate is simulated. The effects of mold wall temperature, cooling time and packing pressure on the development of internal stress are investigated. The predicting results are in good agreement with experimental data.


1967 ◽  
Vol 28 ◽  
pp. 105-176
Author(s):  
Robert F. Christy

(Ed. note: The custom in these Symposia has been to have a summary-introductory presentation which lasts about 1 to 1.5 hours, during which discussion from the floor is minor and usually directed at technical clarification. The remainder of the session is then devoted to discussion of the whole subject, oriented around the summary-introduction. The preceding session, I-A, at Nice, followed this pattern. Christy suggested that we might experiment in his presentation with a much more informal approach, allowing considerable discussion of the points raised in the summary-introduction during its presentation, with perhaps the entire morning spent in this way, reserving the afternoon session for discussion only. At Varenna, in the Fourth Symposium, several of the summaryintroductory papers presented from the astronomical viewpoint had been so full of concepts unfamiliar to a number of the aerodynamicists-physicists present, that a major part of the following discussion session had been devoted to simply clarifying concepts and then repeating a considerable amount of what had been summarized. So, always looking for alternatives which help to increase the understanding between the different disciplines by introducing clarification of concept as expeditiously as possible, we tried Christy's suggestion. Thus you will find the pattern of the following different from that in session I-A. I am much indebted to Christy for extensive collaboration in editing the resulting combined presentation and discussion. As always, however, I have taken upon myself the responsibility for the final editing, and so all shortcomings are on my head.)


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