A combination of hyperelastic & viscoelastic material models have been used successfully for many years in elastomer sealing applications to calculate the time dependence of the seal performance.  The typical time frame of interest is minutes, hours and days. The sealing performance in that application mimics the rubber behavior seen in a stress relaxation test. The hyperelastic and viscoelastic material model coefficients can be readily determined using calibration tools in Abaqus/CAE.   

In recent years there has been a desire to model the time dependence of elastomers in other applications, such as the strain rate dependence of the material exhibited during the impact of a dummy model during a vehicle crash.  The typical time frame of interest in these events is a fraction of a second.  The attached paper documents the use of stress relaxation testing, taken at short times, to calibrate a Prony series viscoelastic material model for elastomers.  The paper reaches the following conclusions:

• Stress relaxation testing, performed over short time periods, can be used effectively to calibrate a Prony series viscoelastic material model for elastomers.  The standard tools in Abaqus/CAE can be used for this calibration from the stress relaxation data.
• The resulting hyperelastic-viscoelastic material model represents the strain rate dependence of the material quite well during the loading phase of impact or dynamic events.  This is shown by comparing to a family of constant strain-rate test data (figure 14 in the attached paper). Thus, the combined usage of the hyperelastic and linear viscoelastic material models can be used for the transient dynamic event analysis, especially when interested in peak load conditions.
• The Prony series viscoelastic material model, when calibrated from stress relaxation test data, does a poor job of replicating the hysteresis loop seen in a load / unload cycle of deformation. This material model will not accurately capture the energy dissipated in load / unload transient dynamic events.  The hysteresis loops generated by the hyperelastic-viscoelastic material model are quite narrow when compared to the real material behavior.

We have also added a new Example Problem Manual article 5.1.7 Coupled thermomechanical analysis of viscoelastic dampers.  This article can be found in the Abaqus2106 docs.  This article demonstrates that you can calibrate a hyperelastic+Prony series viscoelastic model from hysteresis test data and it will match the test data hysteresis loops, but the material model will do a poor job of matching the stress relaxation type of behavior.  This article is also very interesting because it presents a fully thermomechanical material model that generates heat due to mechanical cycling.

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