Working with any material model requires defining appropriate material parameters from experimental data. This can be challenging when the advanced material model is non-linear. To facilitate parameter extraction, Veryst Engineering has developed MCalibration™. This software enables semi-automatic extraction of pertinent material parameters from experimental data. This application is provided with the PolyUMod user-material libraries, but is also commercially available through a stand-alone license. Contact Dr. Jorgen Bergstrom if you would like a quotation for the software.

The following are some of the key features of MCalibration:

• Is available for both Windows and Linux computers.
• Can extract material parameters for the all material models in the PolyUMod library. The PolyUMod library is available for Abaqus, ANSYS, and LS-DYNA.
• Can extract the material parameters for many common hyperelastic and metal plasticity models.
• Can extract the material parameters for all built-in material models in Abaqus.
• The optimal set of material parameters can be exported into text files that can be directly read by Abaqus, ANSYS, and LS-DYNA.
• The parameter extraction is more powerful than the built-in features of Abaqus and ANSYS in that it allows for multiple experimental test with different weight functions.
• Can calibrate viscoelastic, viscoplastic, and anistropic material models.
• Can quickly check the stability of any supported material model.
• Can perform virtual experiments in different loading modes, and different stress or strain histories.
• The calibration can be performed on a subset of the material parameters, and parameters can have upper and lower bounds.
• Most material models can be calibrated without any call to Abaqus or ANSYS. MCalibration do not require that a FE program is installed on the computer.

The following examples illustrate the use of the MCalibration parameter extraction tool.

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Example 1: Calibration of the Bergstrom-Boyce Model to Experimental Data for an Elastomer

Consider a chloroprene rubber tested in uniaxial compression at two different strain rates, at room temperature. The following figure shows the experimental data.


The Bergstrom-Boyce material model with Mullins effect in this case can be calibrated to the experimental data using the MCalibration™ input file shown in the following figure.

Screenshot of the MCalibration™ program after the calibration is performed. The R² value of the calibrated model predictions is 0.990.

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Example 2: Calibration of the Three Network Model to Experimental Data for Polyethylene (PE)

This example shows how to calibrate the Three Network Model (TNM) to experimental data for UHMWPE. The experimental data consists of uniaxial tension at a strain rate of 0.005/s and cyclic data at a strain rate of 0.01/s.

The experimental data sets are shown graphically in the following figure.


The TNM is an advanced material model for glassy thermoplastic materials and is a good choice for modeling the behavior of UHMWPE.

The Three Network Model can be calibrated to the experimental data using the input file shown in the following figure.


Screenshot of the MCalibration™ program after the calibration is performed. The R² value of the calibrated model predictions is 0.996.

The material parameters obtained from the calibration program are automatically saved in a number of different formats that can be directly read by the finite element pre-processor, such as Abaqus/CAE. The MCalibration™ program can be used to calibrate all material models in the PolyUMod libraries and a selection of other material models that are commonly available in FE programs.