Learning Forum

[euklidespl]

Hello. I performed two simulations of the tension of a metal sample in the LS-Dyna program using a material model called mat018 "Power Law" and noticed that the stress-strain graph in simulation "B" is not rounded (smooth) as in simulation "A". The lack of smoothness (rounding) occurs at the yield point, i.e. where the material changes from an elastic state to a plastic state. I also noticed that changing the density of the material to a lower one improves the rounding of the stress-strain curve (both effective values). Are there any settings (apart from density) that improve the smoothness of the function at the yield point?

[Armin]

Hello,

Assuming that you're using the explicit solver of LS-DYNA, changing the density will alter the critical time step size in your model and that may explain why you have smoother curve when the density is lowered (time step size is lower, please refer to the link below). If you're employing mass-scaling for your simulation, try using the *CONTROL_TIMESTEP card where you can control the time step size using the DT2MS variable.

Time Step in Explicit Dynamics - Lesson 2