VTKArchive Custom Task

A MPM Calculations#Custom Tasks to archive grid results to a "VTK Legacy" file format.

Introduction

A VTKArchive custom task allows exporting of data extrapolated to the grid during the calculation. The standard archiving is based on particle data. This task's alternative to get grid data is most useful for visualization of results from 3D calculations. The files can be read by third-party visualization applications. A good option is the free, multi-platform ParaView application. The exported files have been written to work well with ParaView. If you export multiple archives in a single run, ParaView can load them as a block and animate the results. There are books and web sites on the use of ParaView.

Task Scheduling

In scripted files, a VTKArchive custom tasks is scheduled using

CustomTasks VTKArchive
Parameter archiveTime,(timeInterval)
Parameter firstArchiveTime,(firstTime)
Parameter (quantity)
   . . .

In XML files, this tasks is scheduled using a Schedule element, which must be within the single <CustomTasks> block:

<Schedule name='VTKArchive'>
   <Parameter name='archiveTime'>(timeInterval)</Parameter>
   <Parameter name='firstArchiveTime'>(firstTime)</Parameter>
   <Parameter name='(quantity)'/>
        . . .
</Schedule>

where the first two parameters, both of which are optional, are

• (timeInterval) - Enter the time interval (in ms) between saving of VTK archives. If this parameter is omitted, the VTK archive files are written on the same steps as the [[MPM Archiving Options}particle archives]]. The one exception is that no VTK archive is written before the first step.
• (firstTime) - Enter the time to save the first results (in ms). After this time is reached, subsequent archives will be spaced by the entered (timeInterval) This parameter is ignored unless the (timeInterval) parameter is set as well. To get a VTK archive after the first step, enter (firstTime) of zero.

Archivable Quantities

All remaining parameters define a calculation value (by name in (quantity)) to be archived. You can specify any number of quantities to include as manuy results as you want in the output VTK files. The (quantity) options are:

• mass - Archive nodal mass (in g). This option is useful for creating contours that visualize the boundaries of the object. The surface can then be colored in any other archived result.
• material - The material number to visualize different materials in a composite (it is extrapolated to the grid, which will blur material edges compared to particle plots).
• displacement - Archive displacement vector (in mm).
• velocity - Archive velocity vector (in mm/sec). For problems with cracks, it is the center of mass velocity.
• stress - Archive stress tensor (in MPa).
• pressure - Archive pressure (in MPa).
• equivstress - Archive equivalent stress (also know as von Mises stress) (in MPa).
• strain - Archive strain tensor, which is elastic strain for materials that partition elastic and plastic strain, but total strain for all others (absolute).
• deltav - Archive relative volume change (V-V0)/V0 (absolute).
• equivstrain - Archive equivalent strain from above strain (absolute).
• plasticstrain - Archive plastic strain tensor (absolute). Some materials have plastic strain, but hyperelastic materials have left Cauchy Green strain in the particle's plastic strain.
• totalstrain - Archive total strain tensor (absolute, elastic+plastic strain for materials that separate them).
• temperature - Archive temperature (in K). Mostly useful when conduction calculations are activated.
• concentration - Archive concentration (in wt %). Only useful when diffusion calculations are activated.
• strainenergy - Archive strain energy in J.
• heatenergy - Archive heat energy in J.
• plasticenergy - Archive plastic energy (in J).
• contactforce - Nodal force on the grid for MultiMaterialMode simulations when they include rigid contact materials. It is force of the rigid material on the object in Newtons.

Output Style

Archived vectors will include all components of the vector and applications like ParaView can view the magnitude or any single component for constructing graphics. Archived tensors will include all components of the tensor. In ParaView, the magnitude and components 0 through 8 of tensors will be listed. The numbers correspond to the following tensor components:

( xx   xy   xz )   ( 0  1  2 )
| yx   yy   yz | = | 3  4  5 |
( zx   zy   zz ) = ( 6  7  8 )