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Elongational Viscosity of LDPEs and Polystyrenes using Entrance Loss Data

by PolyXtrue5,524 views

For two low-density polyethylenes and two polystyrenes, axisymmetric and planar elongational viscosities are estimated using entrance loss data from capillary and slit rheometers, respectively. The elongational viscosity is estimated by optimizing the values of various parameters in the Sarkar–Gupta elongational viscosity model such that the entrance loss predicted by a finite element simulation agrees with the corresponding experimental data. The predicted entrance loss is in good agreement with the experimental data at high flow rates. The difference in the experimental and predicted entrance loss at lower flow rates might have been caused by large error in the experimental data in this range.

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ExtrusionPlasticsPolyXtrueResearch PapersRheology

Estimation of Elongational Viscosity of Polymers From Entrance Loss data Using Individual parameter Optimization

by PolyXtrue5,362 views

The elongational viscosity model proposed by Sarkar and Gupta (Journal of Reinforced Plastics and Composites 2001, 20, 1473), along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the elongational viscosity model. To improve the computational efficiency, various elongational viscosity parameters are optimized individually. Estimated elongational viscosity for a Low Density Polyethylene (DOW 132i) is reported for two different temperatures.

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ExtrusionPlasticsPolyXtrueResearch PapersRheology

Estimation of Elongational Viscosity of Polymers for Accurate Prediction of Juncture Losses in Injection Molding

by PolyXtrue5,245 views

A new elongational viscosity model along with the Carreau-Yasuda model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the new elongational viscosity model.

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ExtrusionInjection MoldingPlasticsPolyXtrueResearch PapersRheology

Estimation of Elongational Viscosity Using Entrance Flow Simulation

by PolyXtrue5,529 views

A new elongational viscosity model along with the Carreau-Yasuda model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer die. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the new elongational viscosity model. For two different polymers, the predicted elongational viscosity is compared with the corresponding predictions from Cogswell’s analysis and K-BKZ model.

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ExtrusionPlasticsPolyXtrueResearch PapersRheology

Comparison of Crash Models for Ductile Plastics

by DatapointLabs6,503 views

There is interest in quantifying the accuracy of different material models being used in LS-DYNA today for the modeling of plastics. In our study, we characterize two ductile, yet different materials, ABS and polypropylene for rate dependent tensile properties and use the data to develop material parameters for the material models commonly used for plastics: MAT_024 and its variants, MAT_089 and MAT_187. We then perform a falling dart impact test which produces a complex multi-axial stress state and simulate this experiment using LS-DYNA. For each material model we are able to compare simulation to actual experiment thereby obtaining a measure of fidelity of the simulation to reality. In this way, we can assess the benefits of using a particular material model for plastics simulation.

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LS-DYNAMechanicalPlasticsRate DependencyResearch PapersValidation

A Simplified Approach to the Simulation of Rubber-like Materials under Dynamic Loading

by Paul Du Bois5,554 views

"The simulation of rubber materials is becoming increasingly important in automotive crashworthiness simulations. Although highly sophisticated material laws are available in LS-DYNA to model rubber parts, the determination of material properties can be non-trivial and time consuming. In many applications, the rubber component is mainly loaded uniaxially at rather high strain rates. In this paper a simplified material model for rubber is presented allowing for a fast generation of input data based on uniaxial static and dynamic test data."

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AutomotiveHigh Speed TestingHyperelasticLS-DYNAMechanicalRate DependencyResearch PapersRubbers

Use of Digital Image Correlation to Obtain Material Model Parameters for Composites 

by DatapointLabs5,636 views

The development of material parameters for FEA is heavily reliant on precision material data that captures the stress-strain relationship with fidelity. While conventional methods involving UTMs and extensometers are quite adequate for obtaining such data on a number of materials, there are important cases where they have been known to be inadequate. The testing of composites to obtain directional properties remains a complex task because of the difficulty related to measuring these properties in different orientations. Digital Image Correlation (DIC) methods are able to capture the stress-strain relationship all the way to failure. In this paper, we combine DIC and conventional methods to measure directional properties of composites. We exploit the unique capability of DIC to retroactively place virtual strain gauges in areas of critical interest in the test specimen. Utilising an Iosipescu fixture, we measure shear properties of structured composites in a variety of orientations to compute the parameters of an orthotropic linear elastic material model. Model consistency is checked by validation using Abaqus.

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AbaqusAerospace and DefenseCompositesNonlinear Material ModelsResearch PapersSIMULIAStructural Analysis

Applying Digital Image Correlation Methods to SAMP-1 Characterization 

by DatapointLabs5,565 views

SAMP-1 is a complex material model designed to capture non-Mises yield and localization behavior in plastics. To perform well, it is highly dependent on accurate post-yield material data. A number of assumptions and approximations are currently used to translate measured stress-strain data into the material parameters related to these inputs. In this paper, we look at the use of direct localized strain measurements using digital image correlation (DIC) as a way to more directly extract the required data needed for SAMP-1.

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CompositesLS-DYNANonlinear Material ModelsPlasticsResearch PapersStructural Analysis

The Need for Simulation-Quality Material Data

by DatapointLabs5,260 views

Material testing for simulation is about understanding how to best describe a material’s behavior as input for the CAE code. Such testing requires expertise and experience beyond testing performed in a typical test laboratory; while the test instruments may be the same, the knowledge of CAE and experience with diverse materials is increasingly important. FEA software such as ANSYS is being increasingly used for non-linear simulations. We discuss how DatapointLabs' uncommon material expertise helps you avoid problems when the data is being generated these applications.

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Research Papers

Characterization of Damage in Hyperelastic Materials Using Standard Test Methods and Abaqus

by DatapointLabs5,771 views

Over the past couple of decades, standard test methods and material models have existed for rubber-like materials. These materials were classified under the category of Hyperelastic materials. Well established physical test methods and computational procedures exist for the characterization of the material behavior in tension, compression, shear volumetric response, tear strength etc. However, effective modeling of the fracture behavior of hyperelastic materials using finite element techniques is very challenging. In this paper, we make an attempt to demonstrate the use of such standard test methods and the applicability of such test data for performing finite element analyses of complex nonlinear problems using Abaqus. Our goal is to demonstrate the effective use of standard physical test data to model multi-axial loading situations and fracture of hyperelastic materials through tear tests and indentation test simulations.

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AbaqusIndustrial GoodsMaterial SupplierNonlinear Material ModelsResearch PapersRubbersStructural Analysis