ABAQUS/Explicit: maximum initial strain-rate where Smooth step (Amplitude) is applicable?

[ShadowWarrior]

Smooth step (Amplitude) is helpful in avoiding excessive distortion at the beginning of the analysis, but I was wondering what is the maximum initial strain-rate we can use it? Say for example, in quasi-static the strain rate is 10^-4 s^-1 and Smooth step gives a better result than Ramp loading. So what is the upward limit of strain-rate that we can use the Smooth step, 1 s^-1? 10 s^-1? or 100 s^-1??

 

[Mustaine3]

There is no general answer - that's model dependent.

 

[ShadowWarrior]

Should not the loading be instantaneous for impact loading? I just want to make sure up to which strain-rate I can use Smooth step.

 

[IceBreakerSours]

How much artificially induced inertia can you live with?

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[ShadowWarrior]

@IceBreakerSours, is there any way to measure artificially induced inertia? And is there any suggested guideline/limit?

 

[Dave442]

check the energy history for your analysis.

for a quasi-static explicit analysis, kinetic energy should be a small percentage of internal energy.

these slides might be helpful:

http://imechanica.org/files/l5-quasi-static.pdf

 

[IceBreakerSours]

Unless I am missing something, aren't you simply going from F1=m*a_original to F2=m*a_artificial? You just monitor inertial energies or plot the second derivative of a nodal x/y/z displacement or something like that.

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[ShadowWarrior]

@Dave442, Thanks for the tip, I always follow this rule while doing quasi-static analysis in ABAQUS/Explicit.

In the experiment I am applying loading as "linear ramp", but in the simulation I am defining loading as "Smooth step". While in quasi-static strain-rate (10^-4 s^-1) this is not something important, my concern is that at high strain-rates (strain rate >1 s^-1) the difference becomes something problematic?