Nonlinear Structural Materials Module Updates

For users of the Nonlinear Structural Materials Module, COMSOL Multiphysics® version 5.3a brings shape memory alloys, modeled with the Lagoudas or Souza-Auricchio models, and improvements to the porous plasticity feature. Learn about these features below.

Shape Memory Alloys

Shape memory alloys are becoming increasingly popular, particularly for medical applications. The mechanical description of shape memory alloys is complex, since the intriguing behavior of these materials is caused by phase transformations, which can be triggered both by mechanical stresses and changes in temperature. The two most common mathematical models for describing shape memory alloys have been added: Lagoudas and Souza-Auricchio. When using either model, you have the ability to define the Austenite and Martensite material properties, as well as phase transformation properties, such as start and finish temperatures. Associated with this is a new interface for heat transfer in shape memory alloys, available in the Heat Transfer Module.

Heat Transfer in Shape Memory Alloys

The behavior of shape memory alloys (SMA) is tightly related to temperature, and any structural changes (Austenite ↔ Martensite) will release or absorb energy, changing the thermal properties of the alloys. The Shape Memory Alloy feature in the heat transfer interfaces accounts for the Martensite and Austenite volume fraction. Effective thermal properties are then defined from the thermal properties of each phase. This Shape Memory Alloy feature is designed to be combined with the new Shape Memory Alloy feature included with the Nonlinear Structural Materials Module. To include it in your model, select the Heat transfer in alloys check box in the main Heat Transfer interface node, and the Shape Memory Alloy feature will be available as a Domain boundary condition.

Enhancements to Porous Plasticity

The porous plasticity material models have been augmented with plastic hardening and options for taking void nucleation into account.

Improved Default Plots

The default plots in the structural mechanics physics interfaces have been updated to produce more informative visualizations. The Application Library tutorials have been updated accordingly. Some of the more prominent changes that you will see are as follows:

  • The color table for von Mises stress plots is RainbowLight
  • The color table for mode shape plots, for eigenfrequency and linear buckling studies, is AuroraBorealis
  • Mode shape plots have the legend switched off to emphasize that the amplitude of a mode does not have a physical meaning
  • The color table for section force plots in the Beam and Truss interfaces is Wave, with a symmetric color range
    • This makes it possible to immediately distinguish between tension and compression, for example
  • In contact analysis, a plot of the contact pressure is added, as either a line plot (2D) or contour plot (3D)
  • The default plot for Stress Linearization now has a legend for the graphs
  • The default Undeformed geometry plot, produced by the Shell interface, has new colors
  • When a material model like plasticity or creep is used, a contour plot of a relevant strain quantity, like the effective plastic strain, overlays the stress plot
    • Applicable for the Nonlinear Structural Materials Module and the Geomechanics Module
  • In the Fatigue interface, the Traffic color table is used for predicted cycles to failure and for usage factors
    • Applicable for the Fatigue Module
A visual comparison of the improved default plot in COMSOL Multiphysics version 5.3a and an older software version.

In this example, you can see brighter colors in the stress plot (RainbowLight color table), and plastic strain contours and contact pressure contours have been added by default. For comparison, a plot from the default plot in COMSOL Multiphysics® version 5.3 of the same model is shown.

In this example, you can see brighter colors in the stress plot (RainbowLight color table), and plastic strain contours and contact pressure contours have been added by default. For comparison, a plot from the default plot in COMSOL Multiphysics® version 5.3 of the same model is shown.

New Tutorial Model: Uniaxial Loading of Shape Memory Alloy

In this tutorial model, three different loading scenarios are used in order to highlight different behaviors of a shape memory alloy:

  1. A loading-unloading cycle at different temperatures, displaying the superelasticity property at higher temperatures
  2. A scheme with partial loading-unloading at constant temperature, showing the strong hysteresis effect
  3. A loading cycle that produces a residual strain, followed by a temperature increase, which resets the strain to zero, thus showing the shape memory effect
A 1D plot from the Uniaxial Loading of Shape Memory Alloy tutorial model.

Stress vs. strain for a loading-unloading cycle at different temperatures.

Stress vs. strain for a loading-unloading cycle at different temperatures.

Application Library path:
Nonlinear_Structural_Materials_Module/Shape_Memory_Alloys/uniaxial_loading_of_shape_memory_alloy