COMSOL: How to Calibrate the Extended Tube Model


The Extended Tube model is a hyperelastic material model for isotropic rubber-like materials that was developed by Kaliske and Heinrich [Rubber Chem. Tech, 72, 4, 1999]. What makes the Extended Tube model so interesting is that can be shown (see for example my Polymer Mechanics book) to match the experimentally observed equilibrium response of rubbers very well. The model is based on two energy function that when combined are able to capture the response in different loading modes. My article on the Extended Tube model in  Ansys contains more information about the model theory.

In this article I will demonstrate how to use MCalibration to quickly and easily calibrate and used Extended Tube model in a COMSOL Multiphysics simulation.

Step 1: Read in the Experimental Data in MCalibration

Read in the experimental data by drag-and-drop experimental data files, or by loading them one by one. The following image shows one example with experimental data from three different loading modes: uniaxial tension, plane strain tension, and biaxial tension.

Step 2: Select the COMSOL Multiphysics Extended Tube Model

Select the COMSOL Extended Tube model from the list of available material models.

Step 3: Calibrate the Material Model

If you like, add a Poisson’s Ratio load case to search for the bulk modulus, then click Run Calibration.

Step 4: Import the Material Model Into COMSOL Multiphysics

Export the calibrated material model as a COMSOL txt-file. Open a COMSOL Multiphysics window and enter the material parameters for the Extended Tube model. That is it! You can now use that material model in any COMSOL simulation.

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