how to analize explosion in cosmos

Discussion created by Designer Designer on Jan 17, 2008
Latest reply on Feb 23, 2008 by genexxer genexxer

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hi there...

any body have experience on how to analize explosion in cosmos ?
i think the difficult thing is how to represent the pressure.

thanks

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3 Replies

1-6IQYAK Feb 11, 2008 2:23 AM
use random vibration analysis for this problem.
its available in cosmos advanced professional
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Fernando Cuenca Feb 21, 2008 1:34 PM
You can set up a dynamic analysis in which the explosion is simulated by a pulse force with very short acting time. The issue is calculating the value of the explosion force and the location.
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genexxer genexxer Feb 23, 2008 11:57 PM
This can be hugely tricky business, particularly if you're going
generally non-linear. There are a number of convergence parameters
you'll need to juggle just to get the arithmetic to work out. You
can't make a rigid assumption because that implies an infinite force
acting over zero time. Consequently to make the problem solve you
need to choose time intervals and contact stiffnesses properly. There
are rules of thumb for it and probably some built-in defaults, but it
usually takes some playing around. There's the issue of energy
dissipation. In real impacts a fair amount of energy is dissipated in
stress waves, but this mechanism is usually impractical to model. You
can use damping to dissipate energy, but Rayleigh damping (the only
thing you've got in time-domain analysis) doesn't work very well and
has to be tailored to each run. If you neglect the energy dissipation
the results are hugely conservative. In particular you end up with
all sorts of unrealistic rebounding. You also need to set the
integration time step and the mesh size to balance modeling
practicalities against the reality of an impact.

You might want to give some thought to simulating the collision
loading with a shock spectrum and do the problem with a response
spectrum analysis.
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how to analize explosion in cosmos

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