More negative jacobian problems, non-initial ones this time

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  • hkrynauw
    Junior Member
    • Feb 2010
    • 18

    More negative jacobian problems, non-initial ones this time

    So after a bit of coding I managed to get my node numbering consistent. Currently preview reports no negative element volumes and my model runs, as long as I do not touch any of the elements in one of the entities. I have removed the other parts as they are behaving properly and left only the culprits. The moment I apply a force to any of the node, apply fixed displacement to them or get them near a contact interface, the wheels come off.

    I realise there are some unused nodes - they are part of the geometry which I removed.

    Any help will be very much appreciated!
    Hugo
  • ateshian
    Developer
    • Dec 2007
    • 1824

    #2
    Hi Hugo,

    Your mesh is insufficiently constrained. You need more boundary conditions to prevent infinite motion upon the application of a load.

    Also, you use a multi-step analysis (from t=0 to t=1, then from t=1 to t=2) but you apply a load boundary condition in the second step, which increases from 0 to 1 when t increases from 0 to 1. This means that, at the start of the second step (t=1), the applied load suddenly jumps to 1. This may cause convergence problems, even after you provide sufficient constraints.

    Best,

    Gerard

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