Calculating strain energy density in cyclic loading of rubber-like materials
For monotonic loading, obtaining the strain energy density data is straightforward: calculating the area under the stress-strain curve.
However, obtaining the same for cyclic loading appears to be tricky. Do I have to calculate differently for the loading and unloading curves? I tried this but I get unusual curves.
Any idea on the correct method of obtaining the strain energy density data for cyclic loading? I will appreciate it. I need this data to model the Mullins effect.
Thanks in advance,
The same approach should apply for cyclic loading. The easiest way to do it numerically is to do it incrementally one data point at a time.
Note that MCalibration can plot strain energy density (and it should work for most material models ?). Here's a figure for a hyperelastic + Mullins model.
Note that the strain energy function for a Mullins model is a bit different since the damage is not "visible" until unloading.