scholarly journals Developing constitutive models from EPR-based self-learning finite element analysis

Author(s):  
Ali Nassr ◽  
Akbar Javadi ◽  
Asaad Faramarzi
Aerospace ◽  
2005 ◽  
Author(s):  
Vinod P. Veedu ◽  
Davood Askari ◽  
Mehrdad N. Ghasemi-Nejhad

The objective of this paper is to develop constitutive models to predict thermoelastic properties of carbon single-walled nanotubes using analytical, asymptotic homogenization, and numerical, finite element analysis, methods. In our approach, the graphene sheet is considered as a non-homogeneous network shell layer which has zero material properties in the regions of perforation and whose effective properties are estimated from the solution of the appropriate local problems set on the unit cell of the layer. Our goal is to derive working formulas for the entire complex of the thermoelastic properties of the periodic network. The effective thermoelastic properties of carbon nanotubes were predicted using asymptotic homogenization method. Moreover, in order to verify the results of analytical predictions, a detailed finite element analysis is followed to investigate the thermoelastic response of the unit cells and the entire graphene sheet network.


1998 ◽  
Vol 51 (5) ◽  
pp. 303-320 ◽  
Author(s):  
D. W. Nicholson ◽  
N. W. Nelson ◽  
B. Lin ◽  
A. Farinella

Finite element analysis of hyperelastic components poses severe obstacles owing to features such as large deformation and near-incompressibility. In recent years, outstanding issues have, to a considerable extent, been addressed in the form of the hyperelastic element available in commercial finite element codes. The current review article, which updates and expands a 1990 article in Rubber Reviews, is intended to serve as a brief exposition and selective survey of the recent literature. Published simulations are listed. Rubber constitutive models and the measurement of their parameters are addressed. The underlying incremental variational formulation is sketched for thermomechanical response of compressible, incompressible and near-incompressible elastomers. Coupled thermomechanical effects and broad classes of boundary conditions, such as variable contact, are encompassed. Attention is given to advanced numerical techniques such as arc length methods. Remaining needs are assessed. This review article contains 142 references.


2011 ◽  
Vol 94-96 ◽  
pp. 641-646
Author(s):  
Zhao Qiang Zhang ◽  
Yong Yao

Based on the constitutive models of steel and core concrete,the failure modes and the load-displacement curves of the solid multibarrel tube-confined concrete columns(CHS inner and SHS outer) under monotonic loading are calculated by using finite element analysis (FEA) method.The analytical results reveal the rules of stress distribution in steel and core concrete.The influences of axial compression ratio, yield strength of steel tube and concrete on the load-displacement curves are discussed.Through the results,it is deeply known the working mechanism of members(CHS inner and SHS outer) subjected to the static loads.


2010 ◽  
Vol 10 (01) ◽  
pp. 151-166 ◽  
Author(s):  
YUAN LI ◽  
GLADIUS LEWIS

One feature of the literature on finite element analysis of models of cervical spine segment(s) is that an assortment of constitutive models has been used for the elastic behavior of the annulus fibrosus (AF) and the nucleus pulposus (NF). The extent to which the model assigned to each of these tissues affects the values of the biomechanical parameters of interest of the model is lacking. This issue was the subject of the present study. We used a three-dimensional solid model of the C4–C6 motion segment units (which comprised the vertebral bodies, the bony posterior elements (transverse processes, pedicles, laminae, spinous processes, and facet joints), the intervertebral discs (IVDs), the endplates, and the five major ligaments) and eight combinations of constitutive models. It was found that (1) the influence of the constitutive material models used depended on the tissue considered, with some, such as the posterior endplate of C5 and the cancellous bone of C6, showing marked sensitivity, while others, such as the cancellous bone of C4 and the cortical bone of C5, were moderately affected; and (2) the biomechanical performance of the spine model is more sensitive to the material behavior model used for the AF than it is to that used for the NF. These results suggest that experimental and computational efforts expended in obtaining the most appropriate constitutive model for the elastic behavior of the two parts of the IVD, in particular the AF, are justified.


Author(s):  
Wei Zhang ◽  
Anil Erol ◽  
Saad Ahmed ◽  
Sarah Masters ◽  
Paris von Lockette ◽  
...  

Active origami designs, which incorporate smart materials such as electroactive polymers (EAPs) and magnetoactive elastomers (MAEs) into mechanical structures, have shown good promise in engineering applications. In this study, finite element analysis (FEA) models are developed using COMSOL Multiphysics software for two configurations that incorporate a combination of active and passive material layers, namely: 1) a single-notch unimorph folding configuration actuated using only external electric field and 2) a bimorph configuration which is actuated using both electric and magnetic (i.e. multifield) stimuli. Constitutive relations are developed for both electrostrictive and magnetoactive materials to model the coupled behaviors directly. Shell elements are adopted for their capacity of modeling thin films, reduction of computational cost and ability to model the intrinsic coupled behaviors in the active materials under consideration. A microstructure-based constitutive model for electromechanical coupling is introduced to capture the nonlinearity of the EAP’s relaxor ferroelectric response; the electrostrictive coefficients are then used as input in the constitutive modeling of the coupled behavior. The magnetization of the MAE is measured by experiment and then used to calculate magnetic torque under specified external magnetic field. The objective of the study is to verify the effectiveness of the constitutive models to simulate multi-field coupled behaviors of the active origami configurations. Through quantitative comparisons, simulation results show good agreement with experimental data, which is a good validation of the shell models. By investigating the impact of material selection, location, and geometric parameters, FEA can be used in design, reducing trial-and-error iterations in experiments.


2015 ◽  
Vol 44 ◽  
pp. 171-202 ◽  
Author(s):  
Daniel J. Getter ◽  
George C. Kantrales ◽  
Gary R. Consolazio ◽  
Stephen Eudy ◽  
Sam Fallaha

2007 ◽  
Vol 7-8 ◽  
pp. 81-88
Author(s):  
Emma McCummiskey ◽  
William M. Dempster ◽  
D.H. Nash ◽  
T.R. Ashton ◽  
D.G. Stevenson

Superelastic Ni-Ti (Nitinol) is a member of the shape memory alloy (SMA) family of metals. The physical properties of Nitinol are highly dependant on a number of factors, including manufacturing method, subsequent processing, operating temperature, and strain rate. These factors complicate the prescription of material constitutive models, leading to complexities in the computational analysis of Nitinol components. The current work explores the limitations in the Nitinol material model available in existing commercial finite element (FE) software using a series of specially design experimental tests and representative FE models.


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