Reducing hour glass in blast

[thimira]

Hello everyone,
I'm trying to model a concrete member subjected to a blast load. When the model is analysed is shows very high hourglass energy, But when I try to reduce hourglass by using ELFORM 2, -1, -2 some nodes get negative volumes. How could this be resolved
Thank you

 

[Drej]

How much hourglassing energy are you getting compared to other energies in the model? Dyna manual states "confirm that the nonphysical HG energy is small relative to peak internal energy for each part (<10% as a rule-of-thumb)".

Have you tried:

1) refining your mesh around the region showing hourglassing (keep an eye on your time step though).
2) checking whether the blast is creating a point or edge load, and if so try and alleviate this.
3) using fully or selectively integrated elements (keep an eye out for shear locking) - although sounds like you might be using these already if you have an issues with negative vols.

http://www.dynasupport.com/howtos/element/hourglass

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