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 this 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. Also see the following article on: (1) how to use the model in  Ansys; and (2) 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.

Extended Tube Model predictions

Step 2: Select the COMSOL Multiphysics Extended Tube Model

Select the COMSOL implementation of the model from the list of available material models.

Step 3: Calibrate the Extended Tube Model

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

Extended Tube Model predictions

Step 4: Import the Calibrated 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 model. That is it! You can now use that material model in any COMSOL simulation.

Extended tube model in the COMSOL GUI

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