Automotive

Material Insights by Industry Segment

Accuracy Issues in the Simulation of Quasi-Static Experiments for the Purpose of Mesh Regularization

July 22, 2015by Paul Du Bois5,676 views

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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A Simplified Approach for Strain-Rate Dependent Hyperelastic Materials with Damage

July 22, 2015by Paul Du Bois5,972 views

"Simulation of rubber-like materials is usually based on hyperelasticity. If strain-rate dependency has to be considered viscous dampers are added to the rheological model. A disadvantage of such a description is timeconsuming parameter identification associated with the damping constants. In this paper, a tabulated formulation is presented which allows fast generation of input data based on uniaxial static and dynamic tensile tests at different strain rates. Unloading, i.e. forming of a hysteresis, can also be modeled easily based on a damage formulation. We show the theoretical background and algorithmic setup of our model which has been implemented in the explicit solver LS-DYNA [1]-[3]. Apart from purely numerical examples, the validation of a soft and a hard rubber under loading and subsequent unloading at different strain rates is shown."

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Automotive High Speed Testing Hyperelastic LS-DYNA Mechanical Rate Dependency Research Papers Rubbers Yielding/Failure Analysis

A semi-analytical model for polymers subjected to high strain rates

July 22, 2015by Paul Du Bois5,770 views

"Reliable prediction of the behaviour of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behaviour properly are still not available in commercial finite element codes. First, we give an overview of material laws for thermoplastics and show how the behaviour can be characterized and approximated by using visco-elasticity and metal plasticity, respectively. Experimental work is presented to point out important phenomena like necking, strain rate dependency, unloading behaviour and damage. A constitutive model including the experimental findings is derived. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, need to be taken into account. With the present formulation, standard verification tests can be simulated successfully. Also, an elastic damage model is used to approximate the unloading behaviour of thermoplastics adequately."

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Automotive High Speed Testing LS-DYNA Mechanical Rate Dependency Research Papers Yielding/Failure Analysis

The Influence of Permanent Volumetric Deformation on the Reduction of the Load Bearing Capability of Plastic Components

July 22, 2015by Paul Du Bois5,463 views

"During the past years polymer materials have gained enormous importance in the automotive industry. Especially their application for interior parts to help in passenger safety load cases and their use for bumper fascias in pedestrian safety load cases have driven the demand for much more realistic finite element simulations. For such applications the material model 187 (i.e. MAT_SAMP-1) in LS-DYNA® has been developed. In the present paper the authors show how the parameters for the rather general model may be adjusted to allow for the simulation of crazing effects during plastic loading. Crazing is usually understood as inelastic deformation that exhibits permanent volumetric deformations. Hence a material model that is intended to be applied for polymer components that show crazing effects during the experimental study, should be capable to produce the correct volumetric strains during the respective finite element simulation. The paper discusses the real world effect of crazing, the ideas to capture these effect in a numerical model and exemplifies the theoretical ideas with a real world structural component finite element model."

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Automotive High Speed Testing LS-DYNA Mechanical Plastics Rate Dependency Research Papers

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

April 28, 2015by 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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Automotive High Speed Testing Hyperelastic LS-DYNA Mechanical Rate Dependency Research Papers Rubbers

Software for Creating and Managing Material Specifications

August 12, 2014by DatapointLabs6,941 views

Material specifications define properties for incoming materials to meet required criteria. We present software that manages creation of material specifications, input of properties and material composition; and provides a way to evaluate qualification per specification. While it is designed for OEM/Tier n environments, it is also applicable for materials suppliers.

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ADINA ANSYS ANSYS FIDAP Abaqus Altair HyperXtrude Altair RADIOSS Automotive B-Sim Cadmould DIGIMAT LS-DYNA MSC.DYTRAN MSC.MARC MSC.NASTRAN Moldex3D Moldflow NX Nastran PAM-CRASH PAM-FORM POLYFLOW Blow Molding POLYFLOW Extrusion POLYFLOW Thermoforming PlanetsX PolyXtrue Polycad Presentations SIGMASOFT SOLIDWORKS Simpoe-Mold T-Sim Universal Molding VEL VISI Flow WinTXS

Comments on the Testing and Management of Plastics Material Data

May 13, 2014by DatapointLabs6,670 views

Plastics appeared as design materials of choice about 30 years ago. They brought with them huge design challenges because their multi-variable, non-linear nature was not well understood by engineers trained to work in a linear elastic world. We outline a 20 year journey accompanying our customers in their efforts to understand and simulate these remarkable materials to produce the highly reliable plastic products of today. We discuss challenges related to processes such as injection molding vs. blow-molding; coping with filled plastics; the difficulties of modeling polymers for crash applications. We include our latest findings related to volumetric yield in polymers and its relationship to failure. We describe the material database technology that was created to store this kind of multi-variable data and the analytical tools created to help the CAE engineer understand and use plastics material data.

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ANSYS Abaqus Automotive Blow Molding DIGIMAT High Speed Testing Injection Molding LS-DYNA Moldex3D Moldflow Nonlinear Material Models PAM-CRASH Plastics Presentations Structural Analysis Universal Crash Universal Molding Universal Structural

Providing an Experimental Basis in Support of FEA

April 30, 2014by DatapointLabs5,865 views

The use of CAE in design decision-making has created a need for proven simulation accuracy. The two areas where simulation touches the ground are with material data and experimental verification and validation (V&V). Precise, well designed and quantitative experiments are key to ensure that the simulation initiates with correct material behavior. Similar validation experiments are needed to verify simulation and manage the risk associated with this predictive technology.

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Abaqus Automotive Biomedical Building Materials CAE Vendor/Supplier Composites Consumer Products Electonics/Electrical Energy and Petroleum Foams Industrial Goods Material Supplier Metals Mold Maker/Designer Nonlinear Material Models Plastics Presentations Rubbers SIMULIA Structural Analysis Toys/Sporting Goods

The Use of Digital Image Correlation (DIC) and Strain Gauges to Validate Simulation

February 13, 2014by DatapointLabs5,829 views

As part of Cornell University's mechanical engineering curriculum and study of classical beam theory, an aluminium beam is deformed to a specific load. Theoretical strains are calculated at certain points along the beam using beam theory, and then verified by using strain gauges placed at these points on the beam. This experiment is then extended to simulation of the same test setup in simulation software, where strains are analyzed at the same points. Discrepancies between the simulation, theory, and strain gauge results have often plagued the test, especially when incorporating more complex beam design. Through use of digital image correlation (DIC) it is possible to pinpoint some of the problem areas in the beam analysis and provide a better understanding of the localized strains that occur at any point in the deformed beam. The use of DIC provides a full field validation of simulation data, rather than a single spot check that strain gauges can provide. This validation technique helps to eliminate error that is associated with strain gauge placement and the possibility of missing strain hot spots that can arise when analyzing complex deformations or geometries.

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ANSYS Aerospace and Defense Automotive Biomedical Building Materials CAE Vendor/Supplier Consumer Products Electonics/Electrical Industrial Goods Material Supplier Metals Mold Maker/Designer Plastics Presentations Structural Analysis Toys/Sporting Goods

Validating Simulation Using Digital Image Correlation

October 29, 2013by DatapointLabs5,843 views

There is interest in quantifying the differences between simulation and real life experimentation. This kind of work establishes a baseline for more complex simulations bringing a notion of traceability to the practice of CAE. We present the use of digital image correlation as a way to capture strain fields from component testing and compare these to simulation. Factors that are important in ensuring fidelity between simulation and experiment will be discussed.

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Abaqus Aerospace and Defense Automotive Biomedical CAE Vendor/Supplier Composites Electonics/Electrical Material Supplier Nonlinear Material Models Plastics Presentations SIMULIA Structural Analysis