time step calculation

beytut

Hello 

 

I have two geometry rectangular and hexagonal.  I used same material and same mesh size for both.   

why  their time step is different.

 

 

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Simon Križnik

Hi,

 

the difference is because the characteristic element length is computed differently for shell and hexahedral elements:

-Quad Shell: The square root of the shell area

The critical length can vary with: • Shell formulation • Hourglass control parameters • Numerical damping • Membrane damping

-8-node Hexahedral: Volume / largest face area

 

I think the characteristic element length should be the same if element shape is close to ideal (square and cube), but could be different for distorted shapes.