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

by DatapointLabs6,059 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

From Manufacturing to Design Validation

by Altair Engineering6,044 views

[We] introduced the topic of injection molding process simulation and the influence of the manufacturing process on structural analysis. The strength and stiffness of a part can be inaccurately represented if the manufacturing process conditions are not properly considered. This results in a different calculation of system natural frequencies or improper estimation of the energy absorbing characteristics. We continue on this topic, extending the scope to advanced technologies available in the Altair Partner Alliance (APA) to help solve the problem of proper design validation with fiber reinforced plastics.

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Aerospace and DefenseAltair RADIOSSAutomotiveDIGIMATInjection MoldingMechanicalMoldex3DNewslettersPapersStructural AnalysisValidation

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

by Paul Du Bois6,027 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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AutomotiveHigh Speed TestingLS-DYNAMechanicalRate DependencyResearch PapersYielding/Failure Analysis

Development of Material Input Data for Solid Elements under Crash Loads

by Paul Du Bois6,017 views

"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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AutomotiveHigh Speed TestingLS-DYNAMechanicalMetalsRate DependencyResearch PapersValidationYielding/Failure Analysis

Mold Tempering: Conformal Cooling - yes or no?

by Sigmasoft5,988 views

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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AutomotiveBiomedicalInjection MoldingNewslettersPlasticsRheologySIGMASOFTThermal

Simulating Plastics in Drop and Crash Tests 

by DatapointLabs5,964 views

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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ANSYSAbaqusAerospace and DefenseAltair RADIOSSAutomotiveBiomedicalConsumer ProductsHigh Speed TestingIndustrial GoodsLS-DYNAMSC.DYTRANMaterial SupplierNonlinear Material ModelsPAM-CRASHPackagingPlasticsResearch PapersStructural AnalysisToys/Sporting Goods

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

by Paul Du Bois5,946 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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Aerospace and DefenseAutomotiveExtrusionLS-DYNAMechanicalMetalsNonlinear Material ModelsResearch PapersYielding/Failure Analysis