February 18, 2009 | by DatapointLabs | views 4287
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.
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Plastics
Rubbers
Automotive
Building Materials
Material Supplier
Nonlinear Material Models
Structural Analysis
Abaqus
Presentations
July 27, 2015 | by Paul Du Bois | views 4284
Lightweight design is one of the major principles in automotive engineering and has made polymer materials to inherent parts of modern cars. In addition to their lightweight thermoplastics, elastomers, fabric and composites also incur important functions in passive safety. In the age of virtual prototyping, assuring these functions requires the accurate modeling of the mechanical behavior of each component. Due to their molecular structure, polymer materials often show viscoelastic characteristics such as creep, relaxation and recovery. However, considering the general state of the art in crash simulation, the viscoelastic characteristics are mainly neglected or replaced by viscoplastic or hyperelastic and strain rate dependent material models. This is either due to the available material models that are often restricted to linear viscoelasticity and thus cannot model the experimental data or due to the time consuming parameter identification. In this study, a nonlinear viscoelastic material model for foams is developed and implemented as a user material subroutine in LS-DYNA. The material response consists of an equilibrium and a non-equilibrium part. The first one is modeled with a hyperelastic formulation based on the work of Chang [8] and formerly implemented as *MAT_FU_CHANG_FOAM in LS-DYNA (*MAT_083). The second one includes the nonlinear viscoelastic behavior following the multiple integral theory by Green and Rivlin [9]. The polyurethane foam Confor CF-45 used as part of the legform impactor in pedestrian safety was chosen for its highly nonlinear viscoelastic properties to test the presented approach. The investigation shows the ability of the method to reliably simulate some important nonlinear viscoelastic phenomena such as saturation.
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Mechanical
Foams
Viscoelastic
Automotive
Nonlinear Material Models
LS-DYNA
Research Papers
September 21, 2014 | by DatapointLabs | views 4279
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.
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Plastics
High Speed Testing
Nonlinear Material Models
ANSYS
Presentations
July 27, 2015 | by Paul Du Bois | views 4274
"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"
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Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
Validation
March 10, 2013 | by DatapointLabs | views 4263
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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Plastics
Nonlinear Material Models
Structural Analysis
LS-DYNA
Composites
Research Papers
July 17, 2008 | by DatapointLabs | views 4254
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.
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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
August 24, 2015 | by Sigmasoft | views 4245
The tempering layout for injection molds is often designed departing from previous experiences. The manufacturing feasibility is the main driver when deciding where to place cooling lines. However, often the relevance of the tempering in the process profitability or in the part quality is underestimated, and due to the lack of better information sometimes the resulting tempering performs far from the optimum. As a consequence, the molding efficiency is reduced, the part quality is compromised and, once the mold is already built, sometimes expensive trial-and-error is required to bring the mold to an optimum configuration.
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Rheology
Thermal
Plastics
Automotive
Biomedical
Injection Molding
SIGMASOFT
Newsletters
September 13, 2000 | by DatapointLabs | views 4239
We discuss open issues in material models for plastics and propose better means of acquiring the right material data for Moldflow simulations using current testing technologies.
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Plastics
Material Supplier
Mold Maker/Designer
Injection Molding
Moldflow
Presentations
June 09, 2015 | by PolyXtrue | views 4234
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
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