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Quadratic elements with explicite analyses

Experimenter
Experimenter

hello everyone,

I'm running a transient dynamic analyses on Nx advanced non linear explicit, my problem is that i can't use quadratic mesh with explicit analysis.

when I run the analysis on Abaqus explicit i found out that only quadratic mesh gives result close to experimental data, so I really don't have a choice here. does anyone have a clue on this ?

Thank you.

1 REPLY

Re: Quadratic elements with explicite analyses

Legend
Legend

If you read the nx Nastran help

” Higher order elements such as the 10-node tetrahederal, 20 and 27 node brick elements are only available in implicit analysis. They are not used in explicit analysis because no suitable mass-lumping technique is available for these elements”

“The use of the central difference method is only effective when this condition is satisfied. Therefore, only lumped mass can be used in Solution 701.

 

Normally for dynamic analysis (especially high speed, explicit solvers) the linear elements are preferred to quadratic because the mass distribution is uniform .Mass at the midside nodes is greater than at the corners). That’s why you do not have the option to make the analysis with quadratic elements .

The mesh is hex or tetra? Long time ago I was Abaqus user and as  I remember they have special elements (tetra modified) .These elements, I think, had special interpolation functions. They were also very useful for convergence analysis. Because these kind of analysis may exhibit the same problems at the corners nodes as the dynamic analsyis. This may be the reason that Abaqus has this option. They developed “special” elements.