MPM Global Archiving Options

Global archiving is an option to save selected calculated results in a single file. This section explains how to use this feature.

Introduction

In MPM calculations, the solution is stored in a series of archive files. You can optionally create a global results file which will store selected calculated result such as average stress, total energy, etc., in a single text file. This file can plotted latter in NairnFEAMPM or in NairnFEAMPMViz or can be opened later any spread-sheet software. The file is tab delimited with time (in msec) in the first column and all requested results in subsequent columns.

Input Commands

In script input files, global archiving is set up with the following commands:

GlobalArchive (quantity),<(mat)>
GlobalArchiveTIme (time)

In XML input files, global archive is set up with the following commands, which must be within the <MPMHeader> element:

<GlobalArchive type='(quantity)' mat='(mat)'/>
<GlobalArchiveTime units='ms'>1</GlobalArchiveTime>

where

• (quantity) is the global quantity to be save in the global results file. The case-sensitive options are:
  1. sxx, syy, szz, sxy, sxz, or syz - average element of the stress tensor in MPa
  2. sRR, sZZ, sTT, or sRZ - average element of the axisymmetric stress tensor in MPa (synonyms for sxx, syy, szz, and sxy)
  3. exx, eyy, ezz, exy, exz, or eyz - average element of the total strain tensor in %, which is sum of elastic and plastic strain for plasticity materials
  4. eRR, eZZ, eTT, or eRZ - average element of the axisymmetric total strain tensor % (synonyms for exx, eyy, ezz, and exy)
  5. exxe, eyye, ezze, exye, exze, or eyze - average element of the strain tensor in %, which is elastic strain only for plasticity materials
  6. eRRe, eZZe, eTTe, or eRZe - average element of the axisymmetric elastic strain tensor % (synonyms for exxe, eyye, ezze, and exye)
  7. exxp, eyyp, ezzp, exyp, exzp, or eyzp - average element of the plastic strain tensor in %
  8. eRRp, eZZp, eTTp, or eRZp - average element of the axisymmetric plastic strain tensor % (synonyms for exxe, eyye, ezze, and exye)
  9. velx, vely, or velz - average component of velocity in mm/sec
  10. velR or velZ - average component of axisymmetric velocity in mm/sec (synonyms for velx or vely)
  11. dispx, dispy, or dispz - average component of displacement in mm
  12. dispR or dispZ - average component of axisymmetric displacement in mm (synonyms for dispx or dispy)
  13. contactx, contacty, or contactz - component of the total contact force on the grid for multimaterial mode simulations when they include rigid materials that have SetDirection=8. It is a sum of all contact forces for the rigid material on the object in Newtons.
  14. contactR or contactZ - component of the total contact force per radian on the axisymmetric grid in N (synonyms for contactx or contacty)
  15. reactionx, reactiony, or reactionz - component of the reaction force at nodes with velocity boundary conditions in N. If option (material> specifies a material, the force will be for all velocity conditions created by that rigid material; if (material) is omitted the force will sum all velocity boundary conditions (specified or created by rigid particles); if (material) < 0, the force will be only for velocity boundary conditions with that boundary condition ID.
  16. reactionR or reactionZ - component of the reaction force per radian at axisymmetric nodes with velocity boundary conditions in N (synonyms for reactionx or reactiony and see them for meaning of (material))
  17. temp - average temperature (when doing thermal calculations)
  18. concentration - weight fraction concentration (when doing diffusion calculations)
  19. Work Energy - total work energy in J
  20. Kinetic Energy - total kinetic energy in J on the particles
  21. Grid Kinetic Energy - total kinetic energy in J on the grid
  22. External Work - total external work in J
  23. Heat Energy - total heat energy in J
  24. Entropy - total entropy in J
  25. Internal Energy - sum of work and heat energy (U = w +q) in J
  26. Helmholz Energy - total Helmholz free energy (A = U - TS) in J
  27. Interface Energy - total energy associated with cracks having imperfect interfaces in J.
  28. Plastic Energy - total plastic energy in J
  29. Thermal Energy - approximate total thermal energy (ρ C_p ΔT²/(2 T₀) where T₀ is the stress free temperature) - only meaningful when doing conduction calculations and only accurate when temperature changes are small.
  30. alpha - the evolving global damping coefficient, α, when using feedback damping (in 1/sec)
  31. Step number - the current MPM step number
  32. Elapsed time - elapsed clock time for the current calculation (in secs)
  33. CPU time - total CPU time for the current calculation (in secs)
• The optional (mat) is the material ID for a previously defined material. Most of the global quantities are averaged over particles. You can specify this optional second parameter with a material ID and the average will be only for particles of that material type. Omit this parameter (or attribute) to indicate an average over all particles. Most quantites on the grid (e.g., Grid Kinetic Energy but not reactionx(y,z,R,Z)) will ignore the material ID.
• The optional (time) is the time interval for storing global results. In scripted file, (time) is in milliseconds (it can be an entity). In XML files, a units attribute determines the time units. If the time interval is not specified, it will be set to the archiving interval specified in the archiving options. Specifying another time lets these two archiving times be different if desired.

When running isothermal calculations with an isolated system with all particles at the stress free temperature, the usual mechanics energies are found from:

• Strain Energy = Work Energy + Interface Energy
• Total Energy = Strain Energy + Kinetic Energy
• Potential Energy = Strain Energy - External Work

For non-isothermal calculations or problems that induce residual stress with temperatures that differ from stress free temperature, the usual thermoelastic energies are currently not available without additional tracking.

Notes

1. You can store as many quantities as you want in the global results file by having any number of GlobalArchive commands, but only one option can be in each command. Each quantity will be in a labeled column in the global archive text file.
2. The global archive text will be be stored at the path given in the archiving options with extension .global.
3. Note that all terms involving heat ("Heat Energy", "Entropy", "Internal Energy", and "Helmholz Energy") will only the physically correct if all material have specified their heat capacity.