Learning Forum

[tartan2020x]

Hi,nI'm trying to model the Expanded Polystyrene (EPS) Foam used for bicycle helmets. I've been using the ANSYS built in Foam, Expanded Polystyrene material provided by GRANTA Materials Data for Simulation. While this material has worked, I'm concerned that it doesn't seem to exhibit any plastic deformation. I'm hoping to introduce crushability of the foam.nI have tried incorporating EPS stress-strain data from research papers into the built-in model as uniaxial test data, but I'm still not see any plastic deformation. I believe this is because I'm not including plastic failure models and I'm wondering if there are any resources in this area? nI have tried using bilinear kinematic hardening properties, but the material fails (this may be due to incorrect values used). Specifically, I'm wondering what plasticity models should be included in the material in order to see a plastic deformation when the helmet impacts a surface?nThank youn

[ametist91]

, Has there been any development on this subject?n

[tartan2020x]

Yes, there has been some development. I continued used the built Foam, Expanded Polystyrene material. Then, based on other research papers, found that for a given density there was stress-strain data given. I entered that data into Unaxial Test Data and then added Multilinear Kinematic Hardening. For the hardening table, I entered the data from the plastic region of the stress-strain graph. This seems to be working in that there is greater crushabaility being oberved, however I'm not suire if this is the best approach? nAny other suggestions for modeling this would be appreciated.n