July 27, 2015 | by Paul Du Bois | views 4486
"Heavy trucks have large masses and only small deformation zones. Because of this, they are loaded
relatively severe in case of a crash. Under those conditions structural response is characterised not
only by plastic deformation but also by failure in terms of cracks or fracture. Hence, failure prediction is
essential for designing such parts.
The following article describes the procedure of generating material models for failure prognosis of
solid parts in the Commercial Vehicles Division at Daimler.
Sheet metal parts are mostly discretised by shell elements. In this case the state of stress is
characterized by hydrostatic pressure over von-Mises effective stress, the so-called triaxiality. For
many real-life load cases which can be modeled by thin shells this ratio is between –2/3 and –2/3.
Within this range the Gurson material model with the Tvergaard Needlemann addition leads to
sufficiently accurate results. Furthermore, the Gurson material model allows considering the effect of
element size, which amongst others is important for ductile materials.
Most often however, in the case of solid parts the state of stress is more complex, which results in a
triaxiality smaller than –1 or larger than 2/3. Gurson material models are usually validated based on
shell meshes and tensile tests with flat bar specimen. If applied to solid parts, these models tend to
underpredict failure . Thus, for solid parts the GURSON_JC material model is used.
The Johnson Cook parameters are derived from an existing Gurson material model. Afterwards the
material model is adapted to test results by modifying the load curve giving failure strain against
triaxiality. This requires tensile tests"
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
Validation
July 30, 2015 | by Helmut Gese | views 4486
"The Crash Simulation of Magnesium Structures with Finite Element Methods demands
the use of suitable material and failure models. An associated plasticity model
describing the complex asymmetric yield behaviour in tension and compression of
Mg extrusions has been developed during the InMaK-project (Innovative Magnesium
Compound Structures for Automobile Frames) supported by the German Federal
Ministry for Education and Research (BMBF). Differences to the material model 124
in LS-DYNA are exposed. In order to describe the failure behaviour of Mg extrusions
under multiaxial loading in FEM crash simulation this constitutive model has been
combined with a fracture model for ductile and shear fracture. The fracture model
has been added to the user defined constitutive magnesium model in LS-DYNA. The
experimental investigations carried out on model components are compared with
numerical derived results. Experimental methods for fracture parameter evaluation
are shown and general aspects of metal failure due to fracture as well as different
modelling techniques are discussed."
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 14, 1998 | by DatapointLabs | views 4472
We discuss material properties in injection molding simulations, including the definition of property requirements, identification of evaluation parameters, and the role of material properties at each stage of the injection molding process, from mold filling through cooling, post-filling and shrinkage/warpage considerations.
...read full post
Plastics
Material Supplier
Mold Maker/Designer
Packaging
Injection Molding
Moldflow
Moldex3D
Cadmould
C-MOLD
Presentations
September 21, 2014 | by DatapointLabs | views 4467
Plastics exhibit non-linear viscoelastic behavior followed by a combination of deviatoric and volumetric plastic deformation until failure. Capturing these phenomena correctly in simulation presents a challenge because of the inadequacy of currently used material models. We follow an approach where we outline the general behavioral phenomena, then prescribe material models for handling different phases of plastics deformation. Edge cases will then be covered to complete the picture. Topics to be addressed include: Using elasto-plasticity; When to use hyperelasticity; Brittle polymers – filled plastics; Failure modes to consider; Criteria for survival; Choosing materials; Spatial non-isotropy from injection molding; Importance of residual stress; Visco-elastic and creep effects; Strain-rate effects for drop test and crash simulations; Fitting material data to FEA material models.
...read full post
Plastics
High Speed Testing
Nonlinear Material Models
ANSYS
Presentations
April 07, 2013 | by DatapointLabs | views 4464
Today, CAE is integrated with modern automotive product development. This creates new challenges for departments that support new product development. In the materials arena, the testing is elevated to much higher levels of sophistication and precision to accommodate the complex material models used in CAE. It is no longer simple matter to convert raw data into material model parameters. We present an end-to-end strategy that gives automakers a well managed pathway to transforming to simulation-based design. We operate a quick-turnaround expert material testing lab to support high-end CAE and product development. We provide a data management software designed specifically to capture and display material data of any complexity. The software can transform raw material data into material parameter files for most commonly used simulations. The CAE Modeler software is of adequate sophistication to fit equations to data, visualize material models along with raw data, and output material cards. Examples for high strain-rate crash material modeling will be presented.
...read full post
Automotive
CAE Vendor/Supplier
Nonlinear Material Models
Structural Analysis
Presentations
July 17, 2008 | by DatapointLabs | views 4448
If you want a crash simulation involving plastics to yield useful results, it is important to model the material behavior appropriately. The high strain rates have a significant effect on the properties, and failure can be ductile or brittle in nature, depending on a number of factors.
...read full post
Plastics
Aerospace and Defense
Automotive
Biomedical
Consumer Products
Material Supplier
Toys/Sporting Goods
Industrial Goods
Packaging
High Speed Testing
Nonlinear Material Models
Structural Analysis
LS-DYNA
Abaqus
ANSYS
MSC.DYTRAN
PAM-CRASH
Altair RADIOSS
Research Papers
February 18, 2009 | by DatapointLabs | views 4447
Abaqus’ Non-linear NVH capability permits the capture of material behavior of rubber seals and bushings, plastic parts and foam inserts which have a significant influence on the simulation. In this presentation, we discuss material calibration procedures for this application.
...read full post
Plastics
Rubbers
Automotive
Building Materials
Material Supplier
Nonlinear Material Models
Structural Analysis
Abaqus
Presentations
March 10, 2013 | by DatapointLabs | views 4445
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.
...read full post
Plastics
Nonlinear Material Models
Structural Analysis
LS-DYNA
Composites
Research Papers
June 09, 2015 | by PolyXtrue | views 4441
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.
...read full post
Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
June 09, 2015 | by PolyXtrue | views 4414
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.
...read full post
Rheology
Plastics
Extrusion
PolyXtrue
Research Papers
tweet
share
share