ABAQUS/Explicit: Guideline on Hourglass control energy limit? 1

[ShadowWarrior]

What is the guideline on Hourglass control energy limit?

Somewhere its suggested to keep it less than 1-2% of the Internal energy; somewhere else its less than 5% of Strain energy and somewhere else its said to be less than 10% of Total energy.

We need a definite guideline on this, a fixed parameter and a fixed value.

 

[Dave442]

You are trying to get your C3D8R results to match your C3D8I results. But you don't know if your C3D8I results are accurate.

As I stated before, your mesh looks coarse. Although your assembly has 380,000 elements, your 0.075 mm mesh has ~4 elements through the strut diameter and ~8 elements around the strut perimenter (not sure how much better this is for the 0.06 mm mesh). This level of refinement may not be adequate. Particularly if the struts are subjected to bending. Additionally, the performance of C3D8I elements deteriorates considerably if the elements are not rectangular. When the elements are trapezoidal, for example, their performance is not much better than regular displacement elements. Looking at the elements through your strut cross-section, they appear to be trapezoidal.

You can find this info in the theory manual: "Section 3.2.5 Continuum elements with incompatible modes"

You need to establish what the actual force-displacement curve looks like and use that to determine an appropriate discretisation scheme.

 

[ShadowWarrior]

Thanks Dave442, but my hands are tied with computational power, so additional mesh refinement is not possible.

For future reference -
1. The only parameter should be checked is (ALLAE/ALLIE)*100% (w.r.t Internal energy, not Strain energy or Total energy).
2. LS-DYNA website mentions 10% is okay, ABAQUS documentation says 1-2%. But practically it depends on the discretion of the analysts, as long as it is less than 10% of the Internal energy.

 

[IceBreakerSours]

You also want that ratio to be small in the duration of the analysis that you care most about (e.g., the end of a static analysis).

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