Learning Forum

[valerio.incocciati]

Good evening,

I'm trying to characterize a polymeric material (POM) with 187 SAMP-1 material model. At the moment, Force-Displacement values from FEM are different from experimental ones. This because the simulations starts necking, and force values go down quicky.
At the moment, I can not understand what makes the material necking and how can calibrate this phenomena (in exp. values, force goes down slowly).
Can someone help me regarding how to handle with this issue? Thank you in advance.

[Ram Gopisetti]

Hi, 

Please refer to the link https://lsdyna.ansys.com/wp-content/uploads/2025/02/validation-of-a-samp-1-material-card-for-polypropylene-based-materials.pdf to learn about the framework for calibrating MAT_SAMP-1. 

Once the ultimate tensile strength is identified, it marks the onset of necking. The corresponding strain at this point can be considered the plastic strain at failure. Beyond this stage, the stress-strain curves typically decline and may no longer align with the experimental test data.

Additionally, both the TNM/TNV and Bergström-Boyce models are capable of capturing the onset of necking behavior. These models are also supported in LS-DYNA, providing robust tools for simulating post-necking material response.

Cheers, Ram