Review the Results

Results from a static analysis are written to the structural results file, Jobname.RST. They consist of the following data:

• Primary data:

– Nodal displacements (UX, UY, UZ, ROTX, ROTY, ROTZ)

• Derived data:

– Nodal and element stresses – Nodal and element strains – Element forces

– Nodal reaction forces – and so on

2.3.6.1. Postprocessors

You can review these results using POST1, the general postprocessor, and POST26, the time-history processor.

• POST1 is used to review results over the entire model at specific substeps (time-points). Some typical POST1 operations are explained below.

• POST26 is used in nonlinear static analyses to track specific result items over the applied load history. See Chapter 8, “Nonlinear Structural Analysis” for the use of POST26 in a nonlinear static analysis. For a complete description of all postprocessing functions, see Chapter 4, “An Overview of Postprocessing” in the ANSYS Basic Analysis Guide.

2.3.6.2. Points to Remember

• To review results in POST1 or POST26, the database must contain the same model for which the solution was calculated.

• The results file (Jobname.RST) must be available.

2.3.6.3. Reviewing Results Data

1. Read in the database from the database file.

Command(s): RESUME

GUI: Utility Menu> File> Resume from

2. Read in the desired set of results. Identify the data set by load step and substep numbers or by time. (If you specify a time value for which no results are available, the ANSYS program will perform linear inter-polation on all the data to calculate the results at that time.)

Command(s): SET

GUI: Main Menu> General Postproc> Read Results> By Load Step

3. Perform the necessary POST1 operations. Typical static analysis POST1 operations are explained below.

2.3.6.4. Typical Postprocessing Operations

Option: Display Deformed Shape

Use the PLDISP command to display a deformed shape (Main Menu> General Postproc> Plot Results> De-formed Shape). The KUND field on PLDISP gives you the option of overlaying the undeformed shape on the display.

Option: List Reaction Forces and Moments

The PRRSOL command lists reaction forces and moments at the constrained nodes (Main Menu> General Postproc> List Results> Reaction Solu).

To display reaction forces, issue /PBC,RFOR,,1 and then request a node or element display [NPLOT or EPLOT].

(Use RMOM instead of RFOR for reaction moments.) Option: List Nodal Forces and Moments

Section 2.3: Performing a Static Analysis

Use the PRESOL,F (or M) command to list nodal forces and moments (Main Menu> General Postproc> List Results> Element Solution).

You can list the sum of all nodal forces and moments for a selected set of nodes. Select a set of nodes and use this feature to find out the total force acting on those nodes:

Command(s): FSUM

GUI: Main Menu> General Postproc> Nodal Calcs> Total Force Sum

You can also check the total force and total moment at each selected node. For a body in equilibrium, the total load is zero at all nodes except where an applied load or reaction load exists:

Command(s): NFORCE

GUI: Main Menu> General Postproc> Nodal Calcs> Sum @ Each Node

The FORCE command (Main Menu> General Postproc> Options for Outp) dictates which component of the forces is being reviewed:

• Total (default)

• Static component

• Damping component

• Inertia component

For a body in equilibrium, the total load (using all FORCE components) is zero at all nodes except where an applied load or reaction load exists.

Option: Line Element Results

For line elements, such as beams, spars, and pipes, use ETABLE to gain access to derived data (stresses, strains, and so on) (Main Menu> General Postproc> Element Table> Define Table). Results data are identified by a combination of a label and a sequence number or component name on the ETABLE command. See the ETABLE discussion in The General Postprocessor (POST1) in the ANSYS Basic Analysis Guide for details.

Option: Error Estimation

For linear static analyses using solid or shell elements, use the PRERR command to list the estimated solution error due to mesh discretization (Main Menu> General Postproc> List Results> Percent Error). This command calculates and lists the percent error in structural energy norm (SEPC), which represents the error relative to a particular mesh discretization.

Option: Structural Energy Error Estimation

Use PLESOL,SERR to contour the element-by-element structural energy error (SERR) (Main Menu> General Postproc> Plot Results> Contour Plot> Element Solu). Regions of high SERR on the contour display are good candidates for mesh refinement. (You can activate automatic mesh refinement by means of the ADAPT command - see the ANSYS Modeling and Meshing Guide for more information.) See Section 5.3.6: Estimating Solution Error in the ANSYS Basic Analysis Guide for more details about error estimation.

Option: Contour Displays

Use PLNSOL and PLESOL to contour almost any result item, such as stresses (SX, SY, SZ...), strains (EPELX, EPELY, EPELZ...), and displacements (UX, UY, UZ...) (Main Menu> General Postproc> Plot Results> Contour Plot>

Nodal Solu or Element Solu).

The ^KUND field on PLNSOL and PLESOL gives you the option of overlaying the undeformed shape on the display.

Use PLETAB and PLLS to contour element table data and line element data (Main Menu> General Postproc>

Element Table> Plot Element Table and Main Menu> General Postproc> Plot Results> Contour Plot> Line Elem Res).

Caution: Derived data, such as stresses and strains, are averaged at the nodes by the PLNSOL command.

This averaging results in "smeared" values at nodes where elements of different materials, different shell thicknesses, or other discontinuities meet. To avoid the smearing effect, use selecting (described in Chapter 7, “Selecting and Components” in the ANSYS Basic Analysis Guide) to select elements of the same material, same shell thickness, and so on before issuing PLNSOL. Alternatively, use PowerGraphics with the AVRES command (Main Menu> General Postproc> Options for Outp) to not average results across different materials and/or different shell thicknesses.

Option: Vector Displays

Use PLVECT to view vector displays (Main Menu> General Postproc> Plot Results> Vector Plot> Predefined) and PRVECT to view vector listings (Main Menu> General Postproc> List Results> Vector Data).

Vector displays (not to be confused with vector mode) are an effective way of viewing vector quantities, such as displacement (DISP), rotation (ROT), and principal stresses (S1, S2, S3).

Option: Tabular Listings

Use these commands to produce tabular listings:

Command(s): PRNSOL (nodal results), PRESOL (element-by-element results) PRRSOL (reaction data), and so on

GUI: Main Menu> General Postproc> List Results> solution option

Use the NSORT and ESORT commands to sort the data before listing them (Main Menu> General Postproc>

List Results> Sorted Listing> Sort Nodes or Sort Elems).

Other Postprocessing Capabilities

Many other postprocessing functions - mapping results onto a path, load case combinations, and so on - are available in POST1. See Chapter 4, “An Overview of Postprocessing” in the ANSYS Basic Analysis Guide for details.