WB-Mech 120 Ch08 Results

8-1ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

February 23, 2009Inventory #002593

Workbench - Mechanical Introduction 12.0

Chapter 8

Results Postprocessing




Training ManualChapter Overview

• In this chapter, aspects of reviewing results will be covered:A. Viewing Results

B. Scoping Results

C. Exporting Results

D. Coordinate Systems & Directional Results

E. Solution Combinations

F. Stress Singularities

G. Error Estimation

H. Convergence

• The capabilities described in this section are applicable to all ANSYS licenses, except when noted otherwise




Training ManualA. Viewing Results

• When selecting a results branch, the Context toolbar displays ways of viewing results:

• In addition, the “Timeline” also has an animation toolbar which lets the user set animation controls

Vector Display Controls

Min/Max

Displacement Scaling Display Method Contour Settings Outline Display

Probe

Play Pause

Distribute

Markers Frame Rate Control

Export




Training Manual… Displacement Scaling

• For structural analyses (static, modal, buckling), the deformed shape can be changed:– By default, a scale factor “multiplies” actual displacements. – The user can change to true scale or undeformed displays.

True ScaleAutomatic Displacement Scaling




Training Manual

• Right Clicking on the legend in the graphics area allows the user to modify the legend controls.

• Continued . . .

Legend Controls

Edit Value

Export/Import/Switch to a saved legend setting

Horizontal/Vertical legend

Display Date/Time

Display Max/Min label on the legendSwitch to Logarithmic Scale

Switch to Scientific NotationNumber of Significant Digits

Increase/Decrease Contour Bands




Training Manual… Legend Controls

Click and drag contour dividers (or type in) to specify contour ranges.

A non-uniform distribution of contours can be used as well.

The legend bounds can be manipulated to show result distributions more clearly for contour plots.

Max/Min values are unchanged




Training Manual… Manipulating the Legend

• Independent Bands allow neutral colors to represent regions of the model above or below the specified legend limits.

Legend Contour Range




Training Manual… Display Method

• The “Geometry” button controls the contour display method. Four choices are available:

“Exterior” is the default display option and is most commonly used.

“IsoSurfaces” is useful to display regions with the same contour value.

“Capped IsoSurfaces” will remove regions of the model where the contour values are above (or below) a specified value.

“Slice Planes” allow a user to ‘cut’ through the model visually. A capped slice plane is also available, as shown on the left.

Slice Planes

IsoSurfacesExterior

Capped IsoSurfaces




Training Manual… Display Method

• Capped IsoSurfaces are manipulated by an independent controller:– Icons allow isosurface cap to be top or bottom.– The striped areas of the legend show what values will not be displayed.– The cap threshold can be controlled via the slider or by typing the value

directly

Top Capped Isosurface Bottom Capped Isosurface




Training Manual… Contour Settings

• The “Contours” button controls the way in which contours are shown on the model

Solid Fill

Contour BandsSmooth Contours

Isolines




Training Manual… Outline Display

• The “Edges” button allows the user show theundeformed geometry or mesh

No Wireframe Show Undeformed Wireframe

Show Undeformed Model Show Elements




Training ManualSection Planes

• Section Planes can be added and edited in both the preprocessor as well as the post processor.– To add a section plane select the “Draw Section Plane”

icon, then click-drag with the left mouse.– Selection planes can be turned on/off using the check

box in the details view.– Delete section planes using the delete icon.– Edit section planes by highlighting desired plane name

and using the ‘handle’ in the Graphics window.

Move a slice plane by dragging handle

Click on one side of bar to cap view

Sliced view of geometry in Preprocessor

Sliced view of model in Post Processor with results




Training ManualProbe Tool

• The Probe Tool allows you to scope a result object to a location and make that result parametric.

• The Probe Tool can be scoped to geometry, a local coordinate system or using a remote point.

• The orientation of the result item can be with respect to global or local coordinate systems.




Training Manual. . . Probe Tool

• Probe Tool example:– Local coordinate system defined as shown– Probe located at local CS– Stress results (all) requested

Local CS

Probe Location




Training ManualCharts and Tables

• Combine results data from multiple steps (static or transient) into charts and/or tables:– Select “New Chart and Table” icon.– From the details “Apply” the desired result(s).

• Use the CTRL key to select multiple results.

– Select desired display items in details.




Training ManualAnimation Controls

• The animation toolbar allows user to play, pause, and stop animations• Note: animations are accessed via the “Timeline” at the bottom of the

graphics screen

Note: pause feature available during playback

Start/Stop/Pause

Distributed animation interpolates results while results sets animates only solution points.

Export video (avi) file

Control resolution and speed




Training Manual… Alerts

• Alerts are simple ways of check to see if a scalar result quantity satisfies a criterion:– Alerts can be used on contour results (except vector results), Contact

Tool results, and Shape Finder.– Highlight the particular result branch, RMB and insert an Alert.– In the Details view, specify the criterion.

– In the Outline tree, a green checkmark indicates that the criterion is satisfied. A red exclamation mark indicates that the criterion was not satisfied.




Training Manual… Vector Plots

• Vector plots involve any result quantity with direction, such as deformation, principal stresses/strains, and heat flux– Activate vectors for appropriate quantities using the vector graphics icon

– Once the vectors are visible their appearance can be modified using the vector display controls (see next slide for examples)

Proportional Vectors Equal Length Vectors

Vector Length Control

Grid AlignedElement Aligned Line Form Solid Form

Vector Density Control




Training Manual… Vector Plots

• Examples

Solid Form, Equal Length

Proportional LengthSolid Form, Grid Aligned

Equal Length




Training Manual… Multiple Viewports

• Multiple viewports can be used to display various images at the same time (model or postprocessing data).– Useful to compare multiple results, such as results from different

environments or multiple mode shapes




Training ManualB. Scoping Results

• Limiting results displays can be useful when postprocessing:– Scoping automatically scales the legend to results for selected regions.

• To scope contour results:– Pre-select geometry then request the result of interest.– The non-selected geometry will be displayed as translucent.




Training Manual… Scoping Surface/Part Results

• Some examples of scoping results on surfaces/parts:

Scoping results on a single part

Stress results on selected surfaces

Vector Principal Stresses on single part




Training Manual… Scoping Edge & Vertex Results• Results can be scoped to a single edge (or vertex):– Select a single edge for results scoping.

– A path plot of the result mapped on the edge will be displayed.• Use the Worksheet view for a graph only path plot.




Training Manual. . . Scoping to a Path

• Results may be mapped onto a path defined by:• A coordinate system (or multiple systems). • Existing geometry (edges or points).• Existing points.





• A path is created using construction geometry.• Paths are defined using coordinate systems, model edges or existing

points.• Examples:





• Path results may be displayed in graphical form.• The X axis may be displayed as path location (S) or time (transient

analyses).




Training Manual. . . Linearized Stress

• Using the path plot feature a linearized stress calculation can be plotted (commonly used various structural codes such as ASME).




Training ManualC. Exporting Results

• To export Worksheet tab information:– Select the branch and click on the Worksheet tab.– Right-click the same branch and select “Export”.

• To export Contour Results:– Right-click on the result branch of interest and select “Export”.

• Tabular data from Simulation can be exported to Excel:– Select the cells to be exported.– Right click > Copy cell to copy all the data from the cells.– Paste into Excel.

Export Worksheet Export Results

Export Tables




Training Manual… Exporting Results

• To include node locations and vector directions in results exports, change the “Include Node Location” option to “Yes” under “Tools menu > Options… > Simulation: Export”




Training ManualD. Coordinate Systems

• Results containing directional components can be mapped to a local coordinate system:– Select from defined coordinate systems in the drop down list shown in

the detail window.– Direction Deformation, Normal/Shear Stress/Strain, and Directional Heat

Flux can use coordinate systems.




Training Manual… Coordinate Systems

• For the model shown below, displaying results in the local cylindrical system transforms stresses into that system.

Stresses in Global Y-Direction Stresses in Local Cylindrical Y-Direction




Training ManualE. Solution Combinations

• In the project schematic, duplicating an analysis cell below the Model branch (Setup, Solution or Result), allows the creation of Solution Combinations to quickly evaluate results combinations.

• Solution combinations are only valid for linear static structural analyses.

• The supports must be the same between Environments (only the loading can change).

• ANSYS Professional license and above.




Training Manual. . . Solution Combinations

With the Model branch highlighted a “Solution Combination can be chosen from the context menu.

A new branch is inserted where combined results can be requested and retrieved.

With the Solution Combination branch highlighted, the worksheet view allows multiple environments to be combined. Note: a multiplication factor may be included in combinations (see below).

Solution Combination = Coeff 1 * Environment 1 + Coef 2 * Environment 2 + . . .




Training Manual… Solution Combinations

In the trivial example here, 2 environments contain equal and opposite loads. The resulting combination is as expected (essentially zero).

Combination




Training ManualF. Stress Singularities

• In most finite-element analyses as the mesh is refined one expects to get mathematically more precise results.– Quantities directly solved for (degrees of freedom) such as

displacements and temperatures typically converge with little difficulty.– Derived quantities, such as stresses, strains, and heat flux, should also

converge as the mesh is refined but typically not as smoothly as DOF.– In some cases these derived quantities will not converge as the mesh is

refined and may even diverge.– These cases are sometimes the result of some form of stress singularity.

Area

Force As Area Zero




Training Manual… Stress Singularities

• In a linear static structural analysis there are several situations which may cause artificially high stresses:

• In the above situations, refining the mesh at the artificially high stress area will keep increasing the stresses.

Idealized Geometry Point Constraints Point Loads




Training Manual… Stress Singularities

• The Remedy:– If the singularity is not in an area of interest one can usually scope results to

regions of interest.– If the singularity is in the area of interest there are several ways to obtain more

accurate stress results:• Model geometry with fillets or other details which do not cause geometric discontinuities.• Apply loads and/or constraints spread over areas rather than point locations (see below).

Point Loading Distributed Loading

Example




Training ManualG. Error Estimation

• You can insert an Error result based on stresses (structural), or heat flux (thermal) to help identify regions of high error (see example next page).

• These regions show where the model could benefit from a more refined mesh in order to get a more accurate answer.

• Regions of high error also indicate where refinement will take place if convergence is used.




Training Manual

• Error plot shows region of high element energy where mesh refinement may improve the quality of the result.

• In the thin plate example the initial solution shows higher energy levels between the 2 holes.

• The refined mesh (bottom plot) shows a reduction in local error.

• Please note, error is a relative measure comparing individual elements to one another. The actual value of the energy is generally not significant.

. . . Error Estimation




Training ManualH. Convergence

• As the mesh is refined, typically the mathematical model becomes more accurate. However, there is computational cost associated with a finer mesh.

• Obtaining an optimal mesh requires the following:– Having criteria to determine if a mesh is adequate.– Investing more elements only where needed.

• Performing these tasks manually is cumbersome and inexact:– The user would have to manually refine the mesh, resolve, and compare

results with previous solutions.

• Simulation has convergence controls to automate adaptive mesh refinement to a user-specified level of accuracy.

• Convergence controls cannot be used on all result items.




Training Manual… Convergence

• To use this feature select a result item RMB and insert “Convergence”:– Select max/min value for convergence and allowable change (20% default).– In the Solution branch details input the max number of refinement loops.

• Input a reasonable value, such as 1 to 4, so that Simulation will not try to refine the mesh indefinitely.





• Simulation will automatically refine the mesh and resolve:– At least two iterations are required (initial solution and

first refinement loop).– The “Max Refinement Loops” value controls the number

of allowable iterations (2 to 4 max loops is usually sufficient).

– The mesh will automatically be refined in areas deemed necessary based on error approximation techniques.

– The convergence status is displayed by the “Convergence” branch:

• Not converged: a red exclamation mark will appear• Converged: a green checkmark will be shown

– The result branches will display only the last solution.





• After the solution is complete, one can view the results and the last mesh:– Note that the mesh is refined only in high energy regions, as shown in

the example below.– The Convergence branch shows the trend for each refinement loop.

Convergence Divergence




Training Manual… Convergence & Scoping

• In addition to adding details to remove stress singularities, one can also converge on scoped results.

• If the artificially high stress region is not of interest, one can scope results on selected part(s) or surface(s) and add convergence controls to those results only:– Provides control on where to perform mesh refinement.– Ignores areas of artificially high stresses which are not of interest.

– Example:

Possible stress singularity

Region of interest




Training Manual… Convergence & Scoping Example

Convergence controls added to the entire model.

Geometric discontinuity causes a stress singularity causing divergence.

Solution becomes very costly by including the stress singularity.

Convergence controls on scoped results allows adaptive refinement only in user-specified locations.

Provides more control over the mesh and the adaptive solution.

Accurate stresses realized in the region of interest.




Training Manual

• Workshop 8 – Advanced Results Processing• Goal:– Analyze the high pressure vent assembly shown below and then

use some of the advanced postprocessing features to review the stress and deflection results.

I. Workshop 8 – Advanced Results Processing

Documents

WB-Mech 120 Ch08 Results