Element Results

Element results such as stresses and heat fluxes are in the element coordinate systems when KCN = SOLU. Nodal requests for element results (for example, PRNSOL,S,COMP) average the element values at the common node; that is, the orientation of the node is not a factor in the output of element quantities.

For nearly all solid elements, the default element coordinate systems are parallel to the global Cartesian coordinate system.

For shell elements and the remaining solid elements, the default element coordinate system can differ from element to element.

For layered shell and layered solid elements, Mechanical APDL initially selects the element coordinate system when KCN = SOLU. You can then select the layer coordinate system via the LAYER command.

Nodal Results

Nodal results such as degrees of freedom and reactions can be properly rotated only if the resulting component set is consistent with the degree-of-freedom set at the node. The degree-of-freedom set at a node is determined by the elements attached to the node.

Results at nodes with a 2D degree-of-freedom set (UX and UY, for example) should not be rotated out of the 2D plane.

Existing Local Coordinate Systems (KCN > 10)

When KCN > 10, and the specified system is subsequently redefined, reissue the RSYS command for results to be rotated into the redefined system.

Solution Coordinate Systems (KCN = SOLU)

For element quantities, solution coordinate systems are the element coordinate system for each element. For nodal quantities, they are the nodal coordinate systems.

If an element or nodal coordinate system is not defined, Mechanical APDL uses the global Cartesian coordinate system.

If you issue a LAYER,N command (where N refers to a layer number), the results appear in the layer coordinate system. (SOLU is the default for spectrum analyses.)

The default coordinate system for certain elements, notably shells, is not global Cartesian and is frequently not aligned at adjacent elements. Avoid setting KCN = SOLU with such elements, as it can make nodal averaging of component element results (such as SX, SY, SZ, SXY, SYZ, and SXZ) invalid.

When post-processing expanded nodal results in a cyclic symmetry analysis (/CYCEXPAND), use of RSYS,SOLU is recommended so that the appropriate cyclic nodal coordinate system is used (see CYCLIC command). For any other coordinate system (for example, RSYS,1), cyclic rotation is not carried out, and nodal results at all sectors are expressed in the specified coordinate system (KCN). See Result Coordinate System in the Cyclic Symmetry Analysis Guide for more details.

Layered Coordinate System (KCN = LSYS)

For layered shell and solid elements, the results appear in their respective layer coordinate systems. For a specific layer of interest, issue a LAYER,N command (where N refers to a layer number).

If a model has both nonlayered and layered elements, you can use RSYS,SOLU and RSYS,LSYS simultaneously (with RSYS,SOLU applicable to nonlayered elements and RSYS,LSYS applicable to layered elements).

To reverse effects of the LSYS option, issue an RSYS,0 command.

LSYS is the default for spectrum analysis.

PowerGraphics (/GRAPHICS,POWER)

Mechanical APDL plots PLVECT vector arrow displays (such temperature, velocity, and force) in the global Cartesian coordinate system (RSYS = 0). Subsequent operations revert to your original coordinate system.

When using solution coordinate systems for results output (RSYS,SOLU), the deformed or displaced shape in a POST1 contour display can be unexpected (although the contours are displayed in the expected colors). The program does not rotate displacement values (Ux,Uy,Uz) to global; instead, the displacements (stored locally) are added directly to the global coordinates (X,Y,Z). For example, if in PREP7 the nodes are rotated 90 degrees about the z axis and the global Uy displacements are relatively large, the Ux values will be large, causing the model to display a large deformation in the global X direction.

Large Deflection

If large deflection is active (NLGEOM,ON), Mechanical APDL rotates the element component result directions by the amount of rigid body rotation.

Mechanical APDL displays the element component results in the initial global coordinate system for the following elements: SHELL181, SHELL281, ELBOW290, PLANE182, PLANE183, SOLID185, SOLID186, SOLID187, SOLID272, SOLID273, SOLID285, SOLSH190, SHELL208, SHELL209, CPT212, CPT213, CPT215, CPT216, CPT217, PLANE222, PLANE223, SOLID225, SOLID226, and SOLID227.

All other element result transformations, therefore, are also relative to the initial global system.

Nodal degree-of-freedom results are based on the initial geometry.

For all other element types, component results displayed in the co-rotated coordinate system include the element rigid body rotation from the initial global coordinate system, and all other element result transformations are relative to the rotated global system.