July 22, 2015 | by Paul Du Bois | views 4368
Generating a LS-DYNA material model from cupon-level quasi-static experimental data, developing appropriate failure characteristics, and scaling these characteristics to mesh sizes appropriate for a variety of simulation models requires a regularization procedure. During an Investigation of an anisotropic material model for extruded aluminum, numerical accuracy issues led to unrealistic mesh regularization curves and non-physical simulation behavior. Sensitivity problems due to constitutive material behavior, small mesh sizes, single precision simulations, and simulated test velocity all contributed to these accuracy issues. Detailed analysis into the sources of innaccuracy led to the conclusion that in certain cases, double precision simulations are necesscary for accurate material characterization and mesh regularization.
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Mechanical
Metals
Yielding/Failure Analysis
Aerospace and Defense
Automotive
Extrusion
Nonlinear Material Models
LS-DYNA
Research Papers
June 09, 2015 | by PolyXtrue | views 4182
Bi-layer flow in a profile coextrusion die was
simulated. Prediction of post-die changes in extrudate
profile was included in the simulation. Mesh partitioning
technique was used to allow the coextrusion simulation
without modifying the finite element mesh in the profile
die. Effect of polymer viscosities on the change in profile
shape after the polymers leave the die is analyzed. It is
found that a difference in the viscosities of the coextruded
polymers can lead to a highly non-uniform velocity
distribution at die exit. Accordingly, post-die changes in
extrudate shape were found to be widely different when
the polymers in the two coextruded layers were changed.
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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4191
Flow in a flat die with coat hanger type of manifold is
simulated allowing slip on die walls. Flow in the same die
was also simulated by enforcing the no-slip condition on
the walls. With slip on the die walls, the pressure drop,
shear rate, stress, as well as temperature increase in the
die, all were smaller than the corresponding values with
no-slip condition on the walls. For the case with slip on
die walls, since the shear rate is smaller, the elongation
rate in the die is found to be the dominant fraction of the
total strain rate. Due to its high computational efficiency,
the software employed in this work can be effectively
used to design extrusion dies for fluids exhibiting slip on
die walls.
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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4103
The flow in a coat-hanger die is simulated using the axisymmetric and planar elongational viscosities of a low-density polyethylene (LDPE) resin. Elongational viscosity is found to affect the velocity distribution at the die exit. Also, the predicted pressure drop in the die changed significantly when the effect of elongational viscosity was included in the simulation. However, elongational viscosity had only a minor effect on the temperature distribution in the die. Predicted pressure drop is compared with the corresponding experimental data.
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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4241
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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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4054
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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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 3996
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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Rheology
Plastics
Extrusion
Injection Molding
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4272
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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Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
March 12, 2015 | by DatapointLabs | views 5653
Finite-element analysis and injection-molding simulation are two technologies that are seeing widespread use today in the design of plastic components. Limitations exist in our ability to mathematically describe the complexity of polymer behavior to these software packages. Material models commonly used in finite-element analysis were not designed for plastics, making it difficult to correctly describe non-linear behavior and plasticity of these complex materials. Time-based viscoelastic phenomena further complicate analysis. Dealing with fiber fillers brings yet another layer of complexity. It is vital to the plastics engineer to comprehend these gaps in order to make good design decisions. Approaches to understanding and dealing with these challenges, including practical strategies for everyday use, will be discussed.
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Mechanical
Plastics
Blow Molding
Extrusion
Injection Molding
Nonlinear Material Models
Structural Analysis
Thermoforming
LS-DYNA
Abaqus
DIGIMAT
Presentations
January 19, 2011 | by DatapointLabs | views 4044
We present a methodology for DIGIMAT users to perform the DIGIMAT MX reverse engineering process to obtain material parameter inputs for crash, elasto-plastic, creep and visco-elasticity. The injection-molding process used involves a standardized plaque geometry with fully developed flow, with test specimens taken from a specific plaque location. A standardized testing procedure is applied and the resulting DIGIMAT MX inputs are handled in a streamlined data stream, which saves time and improves the reliability of the reverse engineering process. The DIGIMAT MX reverse engineering itself can be performed as a service in collaboration with e-Xstream. This gives the user a speedy and tightly controlled process for performing complex finite element analysis with filled plastics
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Blow Molding
Extrusion
High Speed Testing
Injection Molding
Nonlinear Material Models
Structural Analysis
DIGIMAT
Presentations
August 03, 2010 | by DatapointLabs | views 4559
Ultra-high molecular weight polyethylene (UHMWPE) is used extensively in orthopedic applications within the human body. Components made from these materials are subject to complex loading over extended periods of time. Modeling of components used in such applications depends heavily on having material data under in-vivo conditions. We present mechanical and visco-elastic properties measured in saline at 37C. Comparisons to conventionally measured properties at room temperature are made.
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Plastics
Biomedical
Blow Molding
Extrusion
Injection Molding
Nonlinear Material Models
Structural Analysis
Moldflow
Abaqus
ANSYS
SIGMASOFT
Papers
POLYFLOW Blow Molding
POLYFLOW Extrusion
POLYFLOW Thermoforming
May 16, 2008 | by DatapointLabs | views 4708
We present a perspective on material modeling as applied to mold analysis requirements. Melt-solid transitions and the case for a unified material model are discussed, along with prediction of post-filling material behavior and shrinkage, and the impact of viscous heating on flow behavior and material degradation.
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Plastics
Rubbers
Foams
Metals
Aerospace and Defense
Automotive
Biomedical
Consumer Products
Energy and Petroleum
Electonics/Electrical
Industrial Goods
CAE Vendor/Supplier
Packaging
Home Appliances
Blow Molding
Extrusion
Injection Molding
Nonlinear Material Models
Moldflow
Composites
Presentations
Gels
Oils/Lubricants
Waxes
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Paul Du Bois
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