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Advanced Material Models for Finite Element Simulations
In many finite element simulations of polymer components the most challenging step is the specification of an appropriate material model that captures the experimentally observed non-linear viscoplastic response of the material. Veryst has developed a library of user-material models that accurately captures the response of elastomers, biomaterials, thermoplastics, and thermosets. These material models can be added to commercial finite element software as an external library and enables significantly more accurate simulations and predictions of real materials than what is possible with built-in material models. The following figure shows an example of the accuracy of one of these user-material models. The figure compares the experimentally determined cyclic loading response of UHMWPE with predictions from the Three Network Model, which is specifically developed for this class of materials.
Finite Element Analysis of Reinforced Hoses High strength reinforced hoses have numerous applications in the petrochemical, marine and biomedical industries. They typically involve elastomeric base materials and multiple layers of reinforcement cords, commonly metallic or polymeric. Typical problems with high strength hoses include in-service failure due to delamination, rupture, bulging, leakage and failure of end connectors, as well as creep, and lack of torque balance. Veryst experimentally measured the stress-strain data for both reinforced and unreinforced layers at different strain rates and in different directions. The material data indicated highly anisotropic behavior with Mullins damage, damage due to delamination, and viscous flow. Standard material model available in commercial finite element codes cannot capture all these features. Instead, we selected one of our PolyUMod proprietary material models and calibrated it to closely match the experimental data. We then setup nonlinear finite element models of the reinforced hose. The appropriate models depend on the hose configuration and the failure mode under investigation. In some cases, we used 2D axisymmetric models (with twist), or 3D models when the 2D assumptions were not appropriate. In other hose modeling problems, we adopted a multi-scale approach including a macro-scale model of the hose and a micro-scale model to capture the behavior of the individual cords. For more details on our approach to reinforced hose modeling click here...
Finite Element Simulation of a Total Knee Replacement Component Many medical devices, such as artificial discs and hip implants, contain components made from UHMWPE. Like all thermoplastics, this material can undergo yielding and plastic flow, it can also be degraded due to wear and fatigue loading. These characteristics of the material response are important for the function and lifetime of the medical device. When developing a new device design it is useful to perform both experiments and a finite element study. By using an advanced material model it is possible to accurately evaluate the performance of new designs using a computer model. This approach provides a cost effective way to improve a product and reduce the time to market introduction. The following figure shows an example of a 3D simulation of a total knee replacement component using the Three-Network constitutive model.
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