Nonlinear Structural Materials Module Updates

For users of the Nonlinear Structural Materials Module, COMSOL Multiphysics® version 5.5 brings plasticity, creep, viscoplasticity and viscoelasticity availability for shells, the Johnson–Cook Model for strain-rate-dependent plasticity, and enhancements for shape memory alloys. Browse these features and more below.

Plasticity, Creep, Viscoplasticity, and Viscoelasticity Extensions

The Plasticity, Creep, Viscoplasticity, and Viscoelasticity features, intended for modeling inelastic deformations in metals and alloys, are now available in the Shell interface. This is important for reducing computational time when modeling thin-walled structures. You can control the balance between accuracy and computation time by selecting the number of integration points in the through-thickness direction. You can see this new feature in the Twisting and Bending of a Metal Frame and Pressurized Orthotropic Container - Shell Version models.

A model of a metal frame with a cutout and the stress visualized in a rainbow color table. Metal frame The von Mises stress in a thin-walled frame modeled with the Shell interface after twisting and bending at a load level cause yielding.

Johnson–Cook Model for Strain-Rate-Dependent Plasticity

Metals that are deformed at a high strain rate will typically exhibit more plastic hardening than at slow speeds. The Johnson–Cook model is used for describing the influence of high strain rates on the plastic hardening. Additionally, you have the option to include the softening caused by increasing the temperature. The Johnson–Cook hardening model is available as an isotropic hardening model in the Plasticity node, and for the Chaboche and Perzyna models in the Viscoplasticity node. You can see this new feature in the Tensile Test with Strain Rate Dependent Plasticity model.

A 2D model showing plastic strain distribution and temperature increase after a tensile test at four different loading speeds. Plastic strains and temperature at different loading speeds Distribution of plastic strains (blue) and temperature increase (red) after having performed a tensile test at different loading speeds.

Enhancements for Shape Memory Alloys

In the Lagoudas material model for shape memory alloys, there are several enhancements. A stress-dependent maximum transformation strain has been introduced. This makes it possible for you to model the two-way shape memory effect (TWSME) when it is not possible to reach the maximum transformation strain due to low stress levels. A stress hardening term has been added to represent the variation in the size of the transformation hysteresis loop with the stress level. With this added term, different slopes can be observed in phase diagrams. A new Phase Transformation Direction subfeature option has been added for individual domains. In many cases, the direction of the transformation during the phase-change process is known and you can improve the convergence significantly by having the transformation direction prescribed, rather than computed. In the previous version of COMSOL Multiphysics®, there was a similar option, but it could only be applied to the structure as a whole, and not to individual domains.

Hyperelastic Material in the Layered Shell Interface

The addition of hyperelastic materials to the Layered Shell interface makes it possible to model large strains in composite shells where some of the layers are made up of rubber or other types of elastomers. Note that to access this functionality, you need the Nonlinear Structural Materials Module in addition to the Structural Mechanics Module and Composite Materials Module.

A composite panel modeled in COMSOL Multiphysics with the hyperelastic layer highlighted and the Layered Shell interface settings shown. Composite panel with a hyperelastic material A sandwich composite panel having outer linear elastic layers (composite material) and a middle hyperelastic layer (rubber material), which is highlighted.

Plasticity in Layered Shells

The addition of the Plasticity feature to the Linear Elastic Material node in the Layered Shell interface makes it possible to model plastic deformation in selected layers of a composite laminate, for example the outer metal layers in a sandwich structure. The plasticity models are the same as in the Solid Mechanics interface, with the exception that the plastic strains are assumed to be small. Note that to access this functionality, you need the Nonlinear Structural Materials Module in addition to the Structural Mechanics Module and Composite Materials Module.

A layered shell modeled in COMSOL Multiphysics with the plasticity highlighted Layered shell A layered shell in which plasticity is modeled in the top and bottom layers, which are highlighted.

New Tutorial Models

Version 5.5 brings three new tutorial models.