Mechanical APDL Basic Analysis Guide

7.2.5.3. Interpolating Data Along the Path

The following commands are available for this purpose:
Command(s):PDEF
GUI: Main Menu> General Postproc> Path Operations> path operation
Command(s):PVECT
GUI: Main Menu> General Postproc> Path Operations> Unit Vector

These commands require that the path be defined first.

Using the PDEF command, you can interpolate virtually any results data along the path in the active
results coordinate system: primary data (nodal DOF solution), derived data (stresses, fluxes, gradients,
etc.), element table data, and so on.The rest of this discussion (and in other documentation) refers to
an interpolated item as a path item. For example, to interpolate the thermal flux in the X direction along
a path, the command would be as follows:

PDEF,XFLUX,TF,X

The XFLUX value is an arbitrary user-defined name assigned to the path item.TF and X together
identify the item as the thermal flux in the X direction.

Note

You can make the results coordinate system match the active coordinate system (used to

define the path) by issuing the following pair of commands:

*GET,ACTSYS,ACTIVE,,CSYS

RSYS,ACTSYS

The first command creates a user-defined parameter (ACTSYS) that holds the value defining the currently
active coordinate system. The second command sets the results coordinate system to the coordinate
system specified by ACTSYS.

7.2.5.4. Mapping Path Data

POST1 uses {nDiv(nPts-1) + 1} interpolation points to map data onto the path (where nPts is the number
of points on the path and nDiv is the number of path divisions between points (PATH)). When you
create the first path item, the program automatically interpolates the following additional geometry
items: XG, YG, ZG, and S.The first three are the global Cartesian coordinates of the interpolation points
and S is the path length from the starting node. These items are useful when performing mathematical
operations with path items (for instance, S is required to calculate line integrals). To accurat ely map
data across material discontinuities, use the DISCON = MAT option on the PMAP command (Main
Menu> General Postproc> Path Operations> Define Path> Path Options).

To clear path items from the path (except XG, YG, ZG, and S), issue PDEF,CLEAR. To form additional
labeled path items by operating on existing path items, use the PCALC command (Main Menu> Gen-
eral Postproc> Path Operations>operation).

The PVECT command defines the normal, tangent, or position vectors along the path. A Cartesian co-
ordinate system must be active for this command. For example, the command shown below defines a
unit vector tangent to the path at each interpolation point.

PVECT,TANG,TTX,TTY,TTZ

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The General Postprocessor (POST1)