Learning Forum

[rji229]

Hello,

 

When I use LS-Prepost to read the result files, I find that for some cases, the total internal energy will appear an extremely negative value:

Also, the total kinetic energy cannot be fully displayed (as you can see, the same part but with different time frames, it should end at 10^-6s but there is no output after 8^-6s):

However, the results are convergent for other cases (same model but with different material properties). Also, for different meshes, the results will be different as well.

 

What I want to ask is:

1. I suppose that it will be a numerical error in LS-DYNA. Are there any methods to solve it? For example, to set a smaller time step size or change some other settings in LS-Run?
2. Are there any methods in LS-Prepost to directly output the particle (nodal) internal energy? I can find the icon (internal energy in SPH Fringe Comp) but I cannot find internal energy in the history output icon, only part energy, which shows the same results as matsum. If I can get the individual results, I can manually delete the extreme particles and see the results.
3.  
4. 

Best,

Rong

[Ram Gopisetti]

Hi Rong Jin., 

I may not give you a complete solution to this issue but I can recommend using R14 as we have improved the calculation of internal energy. The contribution from artificial viscosity was underestimated before that. That being said, energy conservation can be a bit off in high deformations problems in SPH. 

For plotting the internal energy, you can use the scalar option, and since you have used the internal energy as a fringe plot you can select the node from SPH part. 

Cheers, Ram 

[rji229]

Hi Ram,

I'm still confused about how to output the strain energy of individual nodes as an XY plot in LS-Prepost.

I can only visualize and see the fringe plot, but I cannot find the icon to output data. Could you show me a more detailed method?

Best,

Rong