Large-Strain Viscoelastic Constitutive Models for Thin Polyethylene Films

Large strain behavior of FCC polycrystals during reversed torsion are investigated through the special purpose finite element based on the classical Taylor model and the elastic-viscoplastic self-consistent (EVPSC) model with various Self-Consistent Schemes (SCSs). It is found that the response of both the fixed-end and free-end torsion is very sensitive to the constitutive models. The models are assessed through comparing their predictions to the corresponding experiments in terms of the stress and strain curves, the Swift effect and texture evolution. It is demonstrated that none of the models examined can precisely predict all the experimental results. However, more careful observation reveals that, among the models considered, the tangent model gives the worst overall performance. It is also demonstrated that the intensity of residual texture during reverse twisting is dependent on the amounts of pre-shear strain during forward twisting and the model used.

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A New Launching Method for Balloons Made of Thin Polyethylene Films

JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES ◽

10.2322/jjsass.49.187 ◽

2001 ◽

Vol 49 (569) ◽

pp. 187-193

Author(s):

Yukihiko MATSUZAKA ◽

Naoki IZUTSU ◽

Takamasa YAMAGAMI

Keyword(s):

Polyethylene Films ◽

Thin Polyethylene

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Experimental investigation and constitutive modeling of the behaviour of highly plastic Lower Rhine Clay under monotonic and cyclic loading

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0012 ◽

2020 ◽

Author(s):

Merita Tafili ◽

Torsten Wichtmann ◽

Theodoros Triantafyllidis

Keyword(s):

Cyclic Loading ◽

Large Strain ◽

Constitutive Models ◽

Rate Dependency ◽

Final Phase ◽

Inherent Anisotropy ◽

Fine Grained ◽

Cyclic Mobility ◽

Isotropic Consolidation ◽

Lower Rhine

A new experimental series on the highly plastic (I_P = 34 %) Lower Rhine Clay (LRC) is presented. The study comprises tests on normally as well as over consolidated samples under monotonic and cyclic loading. The loading velocity has been varied in order to evaluate the strain rate dependency of the LRC behaviour testifying i.a. the well-known reduction of undrained shear strength with decreasing displacement rate. Isotropic consolidation followed by a cyclic loading with constant deviatoric stress amplitude leads to a failure due to large strain amplitudes with eight-shaped effective stress paths in the final phase of the tests. The inherent anisotropy has been additionally evaluated using samples cut out in either the vertical or the horizontal direction. Furthermore, the behaviour of LRC is compared with the behaviour of low plastic Kaolin silt (I_P = 12:2 %). A new visco-hypoplastic-type constitutive model with a historiotropic yield surface has been used to simulate some of the experiments with cyclic loading. Even the eight-shaped stress loops at cyclic mobility are reproduced well with this model. The data of this paper can be also used by other researchers for the examination, calibration, improvement or development of constitutive models dedicated to fine-grained soils under monotonic and cyclic loading.

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A unified framework for computational microstructure-based snow mechanics

10.5194/egusphere-egu21-6108 ◽

2021 ◽

Author(s):

Lars Blatny ◽

Henning Löwe ◽

Stephanie Wang ◽

Johan Gaume

Keyword(s):

Mechanical Behavior ◽

Large Deformation ◽

Large Strain ◽

Constitutive Models ◽

Gaussian Random Fields ◽

Material Point ◽

Flow Rule ◽

Cohesive Elements ◽

Unified Framework ◽

Wide Range

<p>The effective mechanical behavior of snow can be deduced from microstructural homogenization through numerical simulations. Although such numerical upscaling of elasticity and strength of snow microstructures is standard (using FEM), numerical schemes to study generic features of the transition from small to large strain situations that involve yielding and failure are scarce. This prevents the development of accurate homogenized constitutive models valid for the post-failure and large deformation regimes. It has been shown that treating this transition is feasible using DEM under the assumption of particulate microstructures. However, this requires snow microstructures to be segmented into a granular collection of (usually spherical) cohesive elements. Here, we suggest generating random porous microstructures by level-cutting Gaussian random fields and using the material point method to numerically simulate them under mechanical loading. This allows investigating both small and large deformation characteristics of irregular porous media, such as snow, where a segmentation into grains and bonds can be ambiguous. We demonstrate our approach by examining elasticity and failure as a function of a wide range of solid volume fractions, from 20% (low-density snow) to 80% (high-density firn), as the most important control on the mechanical behavior. Observing that onset of failure can be well described through the second order work, we show that the failure strength follows a power law similar to that of the elastic moduli. Moreover, we propose that the failure envelope can be approximated by a porosity-dependent quadratic curve in the space of the two first stress invariants. Furthermore, we observe that plastic deformation appears to be governed by an associative plastic flow rule. Finally, these results combined with a viscoplastic Perzyna model and a sintering (hardening) model should allow us to develop a universal homogenized snow constitutive model.</p>

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A Large Strain Hyperelastic Constitutive Model for Intraluminal Thrombus From Abdominal Aortic Aneurysm

10.1115/imece1999-0456 ◽

1999 ◽

Author(s):

David H. J. Wang ◽

Michel S. Makaroun ◽

Marshall W. Webster ◽

David A. Vorp

Keyword(s):

Abdominal Aortic Aneurysm ◽

Aortic Aneurysm ◽

Constitutive Model ◽

Large Strain ◽

Constitutive Models ◽

Wall Stress ◽

Accurate Estimation ◽

Elastic Model ◽

Intraluminal Thrombus ◽

Abdominal Aortic

Abstract Rupture of abdominal aortic aneurysm (AAA) occurs when the wall stress acting on the dilated aortic wall exceeds the strength of the tissue. Therefore, accurate estimation of the wall stress distribution in AAA may be a clinically useful tool to predict their rupture. A majority of AAA contains a laminated, stationary, intraluminal thrombus (ILT) (Harter et al., 1982). Previous investigations have shown that ILT may significantly alter the wall stress acting on AAA (Inzoli et al., 1993; Mower et al., 1997; Stringfellow et al., 1987; Vorp et al., 1998; Di Martino et al., 1998). However, all of those studies used a simplified linear elastic model for ILT. This is inappropriate and can lead to inaccuracies since both AAA wall and contained ILT undergo large deformation during the cardiac cycle (Vorp et al., 1996). Therefore, to accomplish accurate stress analysis of AAA, appropriate constitutive models for both the wall and ILT are necessary. Our group has previously proposed a finite strain constitutive model for the AAA wall (Raghavan et al., in press). The purpose of this work was to derive a more suitable constitutive model and the associated mechanical properties for the ILT within AAA.

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