3 Replies Latest reply on Feb 23, 2008 11:57 PM by genexxer genexxer

    how to analize explosion in cosmos

    Designer Designer
      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
        • how to analize explosion in cosmos
          use random vibration analysis for this problem.
          its available in cosmos advanced professional
          • how to analize explosion in cosmos
            Fernando Cuenca
            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.
            • how to analize explosion in cosmos
              genexxer genexxer
              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.