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 results such as average stress, total energy, etc., in a single text file. This file can plotted later in NairnFEAMPM or in NairnFEAMPMViz or can be opened later in any spread-sheet software. The file is tab delimited with time (in alt time units) 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)>
GlobalArchive (quantity),(x),(y),<(z)>
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)'/>
<GlobalArchive type='(quantity)' pt='(x),(y),(z)'/>
<GlobalArchiveTime>1</GlobalArchiveTime>

where

• (quantity) is the global quantity to be saved in the global results file (see below)
• 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) or contactx(y,z,R,Z)) will ignore the material ID.
• The alternate form with (x),(y),(z) is used to archive results from a tracer particle. Sometimes it is useful to monitor one particle during a simulation. Although particles can be viewed after a simulation, having that information in the global file can simplify post-simulation analysis or can archive particle state more frequently. The parameters (x),(y),(z) provide initial position of the particle (z not needed in 2D simulations and (x),(y) give (R),(Z) for axisymmetric simulations). The closest particle to that position will be the tracer particle. The (quantity) can select any particle-data archive options for output. You can add any number of tracer particles to the global archiving options. Note that in script input files, a GlobalArchive command with more than two parameters implies it is providing a position.
• The optional (time) is the time interval for storing global results. In scripted file, (time) it is is in alt time units (it can be an entity that evaluates to value in time units). In XML files, it is in time units (or determined by a units attribute). 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.

Global Averaging

The output results depend on how the quantity is specified as follows:

1. If you specify (mat) the results are average for that material only and the material can be a rigid or a non-rigid material type.
2. If you do not specify a material, the results will averaged for all non-rigid materials (it normally does not make sense to average rigid and non-rigid materials together.
3. Exceptions to #2 are for contact forces on rigid particles, reaction forces on boundary conditions, and heat energy on temperture boundary conditions. These can average a single rigid
4. if you specify a tracer particles, the output will be that particle property (nothing to average) and it can be for a rigid or a non-rigid particle.

Archivable Quantities

The global archiving quantities (case insensitive), listed by category are:

• Stresses
  1. sxx, syy, szz, sxy, sxz, or syz - average element of the stress tensor in pressure units
  2. sRR, sZZ, sTT, or sRZ - average element of the axisymmetric stress tensor in pressure units (synonyms for sxx, syy, szz, and sxy)
• Strains and Deformation
  1. exx, eyy, ezz, exy, exz, or eyz - average element of the total Biot strain tensor in alt strain units.
  2. eRR, eZZ, eTT, or eRZ - average element of the axisymmetric total Biot strain tensor in alt strain units (synonyms for exx, eyy, ezz, and exy)
  3. exxe, eyye, ezze, exye, exze, or eyze - average element of the elastic Biot strain tensor in alt strain units, which is tptal Biot strain minus plastic Biot strain for plasticity materials.
  4. eRRe, eZZe, eTTe, or eRZe - average element of the axisymmetric elastic Biot strain tensor alt strain units (synonyms for exxe, eyye, ezze, and exye)
  5. exxp, eyyp, ezzp, exyp, exzp, or eyzp - average element of the plastic Biot strain tensor in alt strain units
  6. eRRp, eZZp, eTTp, or eRZp - average element of the axisymmetric plastic Biot strain tensor in alt strain units (synonyms for exxe, eyye, ezze, and exye)
  7. Fij (where i and j are x, y, or z) - any component of the total deformation gradient (absolute)
  8. Fij (where i and j are R or Z) - any component of the total axisymmetric deformation gradient (absolute, synonyms for the x or y versions).
  9. velx, vely, or velz - average component of velocity in velocity units
  10. velR or velZ - average component of axisymmetric velocity in velocity units (synonyms for velx or vely)
  11. dispx, dispy, or dispz - average component of displacement in length units
  12. dispR or dispZ - average component of axisymmetric displacement in length units (synonyms for dispx or dispy)
• Momenta
  1. px, py, or pz - average component of momentum (in force-time units)
  2. pR or pR - average component of axisymmetric momentum (in force-time units) (synonyms for px or py)
  3. Lx, Ly, or Lz - average component of angular momentum (in energy-time units) (note that only Lz is non-zero in 2D or axisymmetric calculations).
  4. Lpx, Lpy, or Lpz - average component of particle spin angular momentum (in energy-time units) (note that only Lpz is non-zero in 2D or axisymmetric calculations and the simulation must be tracking particle spin for any compononent to be non zero).
  5. wpx, wpy, or wpz - average component of particle spin velocity (in 1/time units) (note that only wpz is non-zero in 2D or axisymmetric calculations and the simulation must be tracking particle spin for any compononent to be non zero).
• Contact and Reaction Forces
  1. 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 force units.
  2. contactR or contactZ - component of the total contact force per radian on the axisymmetric grid in force units (synonyms for contactx or contacty)
  3. reactionx, reactiony, or reactionz - component of the reaction force at nodes with velocity boundary conditions in force units. 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. When the ExtrapolateRigid mode is used, set (material) to -40 to get reaction force for all rigid materials (and in this mode it is not possible to get separate forces on different rigid materials).
  4. reactionR or reactionZ - component of the reaction force per radian at axisymmetric nodes with velocity boundary conditions in force units (synonyms for reactionx or reactiony and see those options for meaning of the (material) option)
• Temperature and Heat
  1. temp - average temperature (when doing thermal calculations)
  2. Heat Energy - total heat energy in energy units
  3. Friction Work - total friction work converted into heat in energy units.
  4. heatWatts - the reaction heating rate at nodes with temperature boundary conditions in energy/time units. If option (material) specifies a material, the heating rate will be for all temperature conditions created by that rigid material; if (material) is omitted the force will sum all temperature boundary conditions (specified or created by rigid particles); if (material) < 0, the heating rate will be only for temperature boundary conditions with that boundary condition ID.
• Thermodynamics Functions
  1. Work Energy - total work energy in energy units, which is cumulative σ.dε
  2. Strain Energy - total strain energy in energy units, which is cumulative σ.(dε-dε_res)
  3. Kinetic Energy - total kinetic energy in energy units on the particles
  4. Grid Kinetic Energy - total kinetic energy in energy units on the grid
  5. Heat Energy - total heat energy in energy units
  6. Entropy - total entropy in energy units/K
  7. Internal Energy - sum of work and heat energy (U = w + q) in energy units
  8. Helmholz Energy - total Helmholz free energy (A = U - TS) in energy units
  9. Interface Energy - total energy associated with cracks having imperfect interfaces in energy units.
  10. Plastic Energy - total dissipated energy in energy units
• Damping Terms
  1. alpha - the total grid damping coefficient, α_g(t), which is a combination of constant and feedback grid damping terms (in 1/time units)
  2. palpha - the total particle damping coefficient, α_p(t), which is a combination of constant and feedback particle damping terms (in 1/time units) (OSParticulas only).
• Damage Mechanics
  1. Decohesion - This quantity will result in a second global archive file (with extension .decohn) that will have a tab-delimited list of information about particle decohesions when using softening materials. Without this option, decohesion information is written to the main output file. With this option, all that output is diverted to a file and it includes some additional information. It is most useful in 3D simulations with lots of decohesion.
• Other Properties
  1. crack length # - the length of crack number # specified in the quantity name.
  2. debonded crack length # - the debonded length of crack number # specified in the quantity name.
  3. concentration or porepressure - weight fraction concentration (when doing diffusion calculations) or pore pressure (pressure units) (when doing poroelasticity calculations)
  4. CPU time - total CPU time for the current calculation (in time units)
  5. Step number - the current MPM step number
  6. Elapsed time - elapsed clock time for the current calculation (in time units)

Notes

1. When global archiving of strains, they are calculated as a Biot strain in the current configuration. The Biot strain is defined is V-I where V is the left-stretch tensor. This strain is also the Seth-Hill strain with m=1/2 in current configuration. For small strain problems it is equivalent to the small strain tensor.
2. 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.
3. The global archive text will be be stored at the path given in the archiving options with extension .global.
4. Note that all terms involving heat ("Heat Energy", "Entropy", "Internal Energy", and "Helmholz Energy") will only be physically correct if all materials have specified their heat capacity.