![]() The complete stress-strain relation, on the other hand, corresponds with a top-level material node, such as the Cam-Clay material model, and is used to define a material model from the ground up. It allows for the implementation of materials similar to the built-in material models available as subnodes under the Linear Elastic Material node for example, plasticity and creep. ![]() Using only an inelastic strain contribution is quite powerful in itself. The external library can either completely define the stress-strain relation, or only return an inelastic strain contribution to the available material models. This makes it possible to program your own material models and distribute such models as add-ons. By writing a wrapper function in C code, you can also use material functions written in another programming language. You can now access external material functions, written in C code, which have been compiled into a shared library. It has been added to the set of shift functions in the Viscoelasticity node.A new way to specify user-defined material models is included in COMSOL Multiphysics version 5.2. The Tool–Narayanaswamy–Moynihan shift function is commonly used to describe the glass transition temperature in glasses and polymers. For time-domain analyses using the Generalized Maxwell and Standard Linear Solid viscoelastic models, performance has been improved by up to one order of magnitude. Using a fractional time derivative representation makes it easier to fit material data to experiments for some materials. Conceptually, it consists of a set of Kelvin elements (spring and dashpot elements in parallel) connected in series.įor frequency-domain analyses, all of the viscoelasticity models ( Generalized Maxwell, Generalized Kelvin-Voigt, Maxwell, Kelvin-Voigt, Standard Linear Solid, and Burgers) have been augmented by a fractional derivative representation. The Generalized Kelvin-Voigt model has a Prony series representation with several time constants. The Maxwell material can be considered as a type of liquid, since its long-term deformation under a constant stress is unbounded. Two new viscoelasticity models have been added: Maxwell and Generalized Kelvin-Voigt. View screenshot Viscoelasticity Improvements You can view this functionality in the new Mechanical Multiport System: Elastic Wave Propagation in a Small Aluminum Plate tutorial model. To compute and identify the propagating modes, the Boundary Mode Analysis study is available in combination with the port conditions. The power of reflected and transmitted waves is available in postprocessing. ![]() The port condition supports S-parameter (scattering parameter) calculation, but it can also be used as a source to just excite a system. The combined setup with several Port conditions provides a superior nonreflecting condition for waveguides to a perfectly matched layer (PML) configuration or the Low-Reflecting Boundary feature, for example. Combining several Port conditions on the same boundary allows a consistent treatment of a mixture of propagating waves, for example, longitudinal, torsional, and transverse modes. A given Port condition supports one specific propagating mode. The new Port boundary condition, available with the Solid Mechanics interface, is designed to excite and absorb elastic waves that enter or leave solid waveguide structures. View screenshot Port Boundary Condition for Elastic Wave Propagation
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