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™. The 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.

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

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.

Summary of experimental data. The experimental data was obtained from PolymerFEM.com

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.

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.