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Restarting an LS-DYNA Analysis PowerPoint Presentation
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Restarting an LS-DYNA Analysis

Restarting an LS-DYNA Analysis

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Restarting an LS-DYNA Analysis

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  1. Restarting an LS-DYNA Analysis • Introduction • Simple Restart • Small Restart • Full Restart

  2. Restarts • All 3 classes of restarts require a binary dump file which contains a complete record of the model (stress, strain, deformation, etc) at a particular point in time. • Binary dump files are written during an analysis at intervals according to *DATABASE_BINARY_D3DUMP and/or *DATABASE_BINARY_RUNRSF. • In addition, a binary d3dump file is automatically written at the normal termination of a run unless “d=nodump” on the execution line. • In v. 971, the number of runrsf files retained is controlled by the parameter NR in *database_binary_runrsf. • Default is NR=1 • If NR is greater than 1, the runrsf files are written in cyclical fashion.

  3. Restarts • When doing a restart: • Use the same executable • Use same numbers of CPU’s

  4. Simple Restart • Restart made from any dump file written prior to termination time. • No changes are made (not even termination time) and thus no input file is needed. • Sample execution line: ls971 r=d3dump01

  5. Small Restart • Only certain changes are permitted. The keywords in the *RESTART section of the User’s Manual (excepting *STRESS_INITIALIZATION) pertain to small restarts. Some of the changes allowed in a small restart… • change termination time • change output intervals • change timestep controls • modify load curves • add nodal boundary conditions • delete contacts, parts, elements • Rigid/Deformable switching of parts • Need a binary dump file and a small restart input deck, the latter of which might be as simple as … *KEYWORD *CONTROL_TERMINATION 15e-03 *END Sample execution line: ls971 i=restart_in.k r=d3dump01 where restart_in.k is the small restart input deck.

  6. Full Restart • Changes of a general nature can be made including addition of parts, loads, and contacts. • A full restart requires a binary dump file and a full restart input deck. In the full restart input deck a full description of the model is given. • Input for retained parts, materials, contacts, loads, etc. is copied directly from the original input deck • That input which is copied from the original input deck can be modified as desired • Input for new parts, materials, contacts, loads, etc. is added • The command *STRESS_INITIALIZATION must be specified in the full restart input deck for parts to be initialized. • Initializes stress, strain, displacement, etc. for all parts which are carried over or, optionally, for only a subset of those parts

  7. Full Restart • One cannot change the mesh topology of preexisting parts when doing a full restart • Except for solid elements (use Q=remap on the execution line) • *DELETE commands should not be used in a full restart. • To eliminate elements, don’t include their definition in the full restart deck • Do not use *INITIAL_VELOCITY for nodes carried over from previous run. Use *CHANGE_VELOCITY_<option> to modify velocities of such nodes. • Preexisting contacts that are to be initialized should include the _ID option so that the contact ID numbers in the original input deck match those in the full restart input deck.

  8. Full Restart • BEWARE! Output from full restart will overwrite existing output in version 970 • Submit full restart from a new directory • Output from original run and output from full restart cannot be combined and must be postprocessed separately • Version 971 will append output from full restart to exisiting output. • The binary dump file necessary to submit a full restart when running MPP-DYNA is named d3fullXX (not d3dumpXX) • Use n=d3fullXX on execution line, not r=d3dumpXX

  9. Exercise 3a and 3b