Restarting an LS-DYNA Analysis

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 dnodump 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 NR1
• 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 CPUs

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 rd3dump01

5
Small Restart

• Only certain changes are permitted. The keywords
  in the RESTART section of the Users 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 irestart_in.k rd3dump01
• 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 Qremap on the
  execution line)
• DELETE commands should not be used in a full
  restart.
• To eliminate elements, dont include their
  definition in the full restart deck
• Do not use INITIAL_VELOCITY for nodes carried
  over from previous run. Use CHANGE_VELOCITY_ltopt
  iongt 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 nd3fullXX on execution line, not rd3dumpXX

9
Exercise 3a and 3b