mech-intro 13.0 l08 results
TRANSCRIPT
Customer Training Material
L t 8Lecture 8
Results and Postprocessing
Introduction to ANSYSIntroduction to ANSYSMechanical
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Introduction to ANSYS Mechanical
Customer Training MaterialChapter Overview• In this chapter, aspects of reviewing results will be covered:
A. Viewing ResultsB. Scoping ResultsC. Exporting ResultsD. Coordinate Systems & Directional ResultsE. Solution CombinationsF. Stress SingularitiesG. Error EstimationH. Convergence
• The capabilities described in this section are applicable to all ANSYSThe capabilities described in this section are applicable to all ANSYS licenses, except when noted otherwise
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Introduction to ANSYS Mechanical
Customer Training MaterialA. Viewing Results
• When selecting a results branch, the Context toolbar displays ways of viewing results:
Min/Max Probe
Displacement Scaling Display Method Contour Settings Outline Display
Vector Display Controls
• In addition, the “Timeline” also has an animation toolbar which lets the user set animation controls
DistributeDistribute Export
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Play Pause Markers Frame Rate Control
Introduction to ANSYS Mechanical
Customer Training Material… 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
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Introduction to ANSYS Mechanical
Customer Training MaterialLegend Controls• Right Clicking on the legend in the graphics area allows the user to
modify the 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
Increase/Decrease Contour Bands
g
Switch to Scientific NotationNumber of Significant Digits
• Continued
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Continued . . .
Introduction to ANSYS Mechanical
Customer Training Material… Legend ControlsThe legend bounds can be manipulated to show result distributions more clearly for contour plots.
Max/Min values are unchanged
Click and drag contour dividers (or type in) to specify contour ranges.
A non-uniform distribution of
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contours can be used as well.
Introduction to ANSYS Mechanical
Customer Training Material… Manipulating the Legend
• Independent Bands allow neutral colors to represent regions of the model above or below the specified legend limits.
Legend Contour Range
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Introduction to ANSYS Mechanical
Customer Training Material… Display Method• The “Geometry” button controls the contour display
method. Four choices are available:IsoSurfacesExterior
“Exterior” is the default display option and is most commonly used.
“IsoSurfaces” is useful to display regions with p y gthe same contour value.
“Capped IsoSurfaces” will remove regions of the model where the contour values are above (or below) a
Slice PlanesCapped IsoSurfaces
( )specified value.
“Slice Planes” allow a user to ‘cut’ through the model visually. A capped slice plane is also available, as shown
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also available, as shown on the left.
Introduction to ANSYS Mechanical
Customer Training Material… 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.p g p y– The cap threshold can be controlled via the slider or by typing the value
directly
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Top Capped Isosurface Bottom Capped Isosurface
Introduction to ANSYS Mechanical
Customer Training Material… Contour Settings• The “Contours” button controls the way in which
contours are shown on the model
Contour BandsSmooth Contours
Solid FillIsolines
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Introduction to ANSYS Mechanical
Customer Training Material… Outline Display• The “Edges” button allows the user show the
undeformed geometry or mesh
No Wireframe Show Undeformed Wireframe
Show Undeformed Model Show Elements
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Introduction to ANSYS Mechanical
Customer Training MaterialSection 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– 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.g p
Move a slice plane by dragging handle Sliced view of geometry in Preprocessor
Sliced view of model in Post Processor with results
Click on one side of bar to cap view
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Introduction to ANSYS Mechanical
Customer Training MaterialProbe 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.
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Introduction to ANSYS Mechanical
Customer Training Material. . . Probe Tool• Probe Tool example:– Local coordinate system defined as shown– Probe located at local CS– Stress results (all) requested
Local CS
Probe Location
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Introduction to ANSYS Mechanical
Customer Training MaterialCharts 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.
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Introduction to ANSYS Mechanical
Customer Training MaterialAnimation 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
Start/Stop/PauseControl resolution and speed
Distributed animation interpolates results while results sets animates only solution points.
Export video (avi) file
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Note: pause feature available during playback
Introduction to ANSYS Mechanical
Customer Training Material… Alerts• Alerts are simple ways of check to see if a scalar result quantity
satisfies a criterion:– 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.
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Introduction to ANSYS Mechanical
Customer Training Material… 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)
Vector Length Control Vector Density Control
Proportional Vectors Equal Length Vectors Grid AlignedElement Aligned Line Form Solid Form
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Introduction to ANSYS Mechanical
Customer Training Material… Vector Plots• Examples
Proportional LengthSolid Form, Grid Aligned p g
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Solid Form, Equal LengthEqual Length
Introduction to ANSYS Mechanical
Customer Training Material… 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
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Introduction to ANSYS Mechanical
Customer Training MaterialB. Scoping Results• Limiting results displays can be useful when postprocessing:– Scoping automatically scales the legend to results for selected regions.
• To scope contour results:p– Pre-select geometry then request the result of interest.– The non-selected geometry will be displayed as translucent.
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Introduction to ANSYS Mechanical
Customer Training Material… Scoping Surface/Part Results• Some examples of scoping results on surfaces/parts:
Scoping results on a single part
Stress results on selected surfaces
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Vector Principal Stresses on single part
Introduction to ANSYS Mechanical
Customer Training Material… Scoping Edge & Vertex Results• Results can be scoped to a single edge (or vertex):– Select edge(s) for results scoping.
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Introduction to ANSYS Mechanical
Customer Training Material. . . Construction Geometry• Construction geometry consists of either a
path or surface.• Paths are defined using coordinate systems,
model edges or existing points.• Surfaces are located and oriented using
coordinate systems.
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Introduction to ANSYS Mechanical
Customer Training Material. . . Scoping to a Path or Surface• Results may be mapped onto construction geometry in the details:
Path Plot Example
Surface Plot Example
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Introduction to ANSYS Mechanical
Customer Training Material. . . Scoping to a Path• Path results may also be displayed in graphical form.• The X axis may be displayed as path location (S) or time (transient
analyses).
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Introduction to ANSYS Mechanical
Customer Training Material. . . Linearized Stress• Using the path plot feature a linearized stress calculation can be
plotted (commonly used various structural codes such as ASME).
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Introduction to ANSYS Mechanical
Customer Training MaterialC. Exporting Results
• To export Worksheet tab information:– Select the branch and click on the Worksheet tab.– Right-click the same branch and select “Export”.g p
• To export Contour Results:– Right-click on the result branch of interest and select “Export”.
• Tabular data from Mechanical can be exported to Excel:p– 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
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pExport Tables
Introduction to ANSYS Mechanical
Customer Training Material… Exporting Results• To include node locations and vector directions in results exports,
change the “Include Node Location” option to “Yes” under “Tools menu > Options… > Mechanical: Export”
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Introduction to ANSYS Mechanical
Customer Training MaterialD. 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 y p
the detail window.– Direction Deformation, Normal/Shear Stress/Strain, and Directional Heat
Flux can use coordinate systems.
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Customer Training Material… 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
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Introduction to ANSYS Mechanical
Customer Training MaterialE. 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.
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Introduction to ANSYS Mechanical
Customer Training Material. . . Solution Combinations
With the Model branch highlighted a “Solution C bi ti b h f th t tCombination can be chosen from the context menu.
A new branch is inserted where combined results b t d d t i dcan be requested and retrieved.
With the Solution Combination branch highlighted, the worksheet view allows multiple environments to be combined Note: a multiplication factor mayto be combined. Note: a multiplication factor may be included in combinations (see below).
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Solution Combination = Coef 1 * Environment 1 + Coef 2 * Environment 2 + . . .
Introduction to ANSYS Mechanical
Customer Training Material… Solution CombinationsExample: a brake caliper is simulated in both standing and rolling configurations. After the 2 environments have solved a2 environments have solved a resulting combination shows the effect of both.
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Solution Combination
Introduction to ANSYS Mechanical
Customer Training MaterialF. 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.I th d i d titi ill t th h i– 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.
ForceAreao ce
=σ As Area Zero ∞⇒σ
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Introduction to ANSYS Mechanical
Customer Training Material… Stress Singularities• In a linear static structural analysis there are several situations which
may cause artificially high stresses:
Idealized Geometry Point Constraints Point Loads
• In the above situations, refining the mesh at the artificially high stress area will keep increasing the stresses.
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∞⇒σ
Introduction to ANSYS Mechanical
Customer Training Material… 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
discontinuitiesdiscontinuities.• Apply loads and/or constraints spread over areas rather than point locations
(see below).
Example
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Point Loading Distributed Loading
Introduction to ANSYS Mechanical
Customer Training MaterialG. 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.
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Introduction to ANSYS Mechanical
Customer Training Material. . . Error Estimation
• Error plot shows region of high element energy where mesh refinement may improve the quality of the result.improve the quality of the result.
• In the thin plate example the initial solution shows higher energy levels between the 2 holes.between the 2 holes.
• The refined mesh (bottom plot) shows a reduction in local error.
• Please note, error is a relative measurecomparing individual elements to one another The actual value of the energy isanother. The actual value of the energy is generally not significant.
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Introduction to ANSYS Mechanical
Customer Training MaterialH. Convergence
• As the mesh is refined, typically the mathematical model becomes more accurate. However, there is computational cost associated with a finer mesha finer mesh.
• Obtaining an optimal mesh requires the following:– Having criteria to determine if a mesh is adequate.
I ti l t l h d d– 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
lt ith i l tiresults with previous solutions.• Mechanical has convergence controls to automate adaptive mesh
refinement to a user-specified level of accuracy.• Convergence controls cannot be used on all result items.
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Introduction to ANSYS Mechanical
Customer Training Material… Convergence
• To use this feature select a result item RMB and insert “Convergence”:– Select max/min value for convergence and allowable change.– In the Solution branch details input the max number of refinement loops.
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Introduction to ANSYS Mechanical
Customer Training Material… Convergence• After the solution is complete one can view the
results and the last mesh (symbols in the tree indicate success or failure to converge):
The mesh is refined only where needed (see below)– The mesh is refined only where needed (see below).– The Convergence branch shows the trend for each
refinement loop.
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Convergence Divergence
Introduction to ANSYS Mechanical
Customer Training Material… Convergence & Scoping • A useful technique to avoid stress singularities when using
convergence is to scope results away from them.• If the singularity 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
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Region of interest
Introduction to ANSYS Mechanical
Customer Training Material… Convergence & Scoping Example
Convergence controls added to the entire model.
Geometric discontinuity causes a stress singularity causing divergence.
Solution becomes verySolution 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.
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Accurate stresses realized in the region of interest.
Introduction to ANSYS Mechanical
Customer Training MaterialI. Workshop 8.1 – Advanced Results Processing
• Workshop 8.1 – Results Processing• Goal:
A l th h i l h b l d th f– Analyze the mechanical arm shown below and then use some of the advanced postprocessing features to review the stress and estimate the error associated with a default mesh.
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