Buckling Example

882019 Buckling Example

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Course in ANSYS

Example0500

Computational Mechanics AAU EsbjergANSYS



Example ndash Column beam

E = 210000Nmm2

n = 03

L = 1000mm

a = 10mm

b = 10mmF =

ObjectiveCompute the critical buckling load and displaythe mode shape

TasksCreate a table and compare results with resultsobtained from buckling theoryDisplay the deflection figure

Example0500 2Computational Mechanics AAU EsbjergANSYS



Modelling considerationsbull As you begin your model generation you will (consciously or

unconsciously) make a number of decisions that determine how youwill mathematically simulate the physical system ndash What are the objectives of your analysis ndash Will you model all or just a portion of the physical system ndash How much detail will you include in your model ndash What kinds of elements will you use How dense should your finite

element mesh bebull In general you will attempt to balance computational expense (CPU

time etc) against precision of results as you answer thesequestions

bull The decisions you make in the planning stage of your analysis willlargely govern the success or failure of your analysis efforts




Modelling considerationsbull Linear or Higher Order Elementsbull Take Advantage of Symmetry

ndash The axis of symmetry must coincide with the global Cartesian Y-axis ndash Negative nodal X-coordinates are not permitted ndash The global Cartesian Y-direction represents the axial direction the

global Cartesian X-direction represents the radial direction and theglobal Cartesian Z-direction corresponds to the circumferential direction

ndash Your model should be assembled using appropriate element typesbull For axisymmetric models use applicable 2-D solids with KEYOPT(3) = 1

andor axisymmetric shells In addition various link contact combinationand surface elements can be included in a model that also containsaxisymmetric solids or shells (The program will not realize that these otherelements are axisymmetric unless axisymmetric solids or shells are present)

bull How Much Detail to Includebull Appropriate Mesh Density




Example - titleUtility Menu gt File gt Change Jobname

jobname Example0500 Command line entryGUI

Enter Example0500

Utility Menu gt File gt Change Title title Column beam

Enter Column beam




Example - KeypointsPreprocessor gt Modeling gt Create gt Keypoints gt In Active CS

PREP7K

K1000

General format

KXYZ

Keypoint numberX Keypoint x-coordinate

Y Keypoint y-coordinateZ Keypoint z-coordinate

Note An empty result in automaticnumbering

Enter 000 and

Press ApplyEnter 010000 andPress Apply


Note An empty boxresult in a zero It isallowed to enter 00in each box



Example - NumberingSwitch on Keypoint numbersUtility Menu gt PlotCtrls gt Numbering


Press OK



Example - LinesPreprocessor gt Modeling gt Create gt Lines gt Lines gt Straight LineCreate a line between Keypoint 1 and Keypoint 2L12


HINT By clicking with the right-hand mouse button you shiftbetween the PickUnpickfunction This is indicated bythe direction of the cursorarrow

Pick upward arrow

Unpick downward arrow

Press OK or Cancelto finish selection



Example ndash Element TypePreprocessor gt Element Type gt AddEditDelete

Press Add




Example - Element TypePreprocessor gt Element Type gt AddEditDelete

Press Options


Press Help to learn more about theelement



Example ndash Real ConstantsPreprocessor gt Real Constants gt Add

Place the cursor

on the relevantelement andpress OK




Example - Real ConstantsPreprocessor gt Real Constants gt Add

Press OK

Press Closeto finish

Enter cross-sectional data




Example - Material PropertiesPreprocessor gt Material Props gt Material Models

Double Clickto step in thematerial tree





EnterModulus of elasticity

EnterPoissonrsquos ratio

Click hereto Close




Example - MeshingPreprocessor gt Meshing gt Size Cntrls gt ManualSize gt Lines gt Picked Lines


SelectPickLines tospecifymesh sizefor

Press OK when finish with selection Enter 3



Example - MeshingPreprocessor gt Meshing gt Mesh gt Lines

Select individual lines to be meshed

Select all lines defined to be meshed




Example ndash Analysis TypeSolution gt Analysis Type gt New Analysis




Example ndash Analysis Type

Solution gt Analysis Type gt New Analysis

File gt Write DB log fileEnter ldquoexample0500lgwrdquo






Example ndash Define LoadsSolution gt Define Loads gt Apply gt Structural gt Displacement gt On Keypoints

Select keypoint 1

Select All DOF to fixclamp the beam

Press OKExample0500 20






Example - Save

Display of Analysis model

Save the model




Example - SolveSolution gt Solve gt Current LS

Press OK




Example - Finish


Press Finish to end the static solution





Eigen Buckling ndash Analysis OptionsMain Menugt Solutiongt Analysis Typegt Analysis Options


Enter 3





Example ndash Subspace OptionsSubspace working sizeDefaults to NMODE + 4(where NMODE is input on

the MODOPT or BUCOPTcommand) Minimum is 8Maximum is NMODE

+NPAD The larger thevalue the smaller thenumber of iterations (butmore time per iteration)

Number of extra vectors

used in the iterationsDefaults to 4 The totalnumber of vectors used isNMODE +NPAD




Example ndash Subspace OptionsNumber of modes permemory block If 0 (or blank)perform data managementin-memory for all modes (no

disk IO) If greater than zerouse some disk IO (slower fordecreasing NPERBK valuesbut may be needed for large

problems) The minimumnonzero value is the numberof degrees of freedom pernode for the model




Example ndash Subspace OptionsMaximum number ofsubspace iterations(defaults to 100) Feweriterations will be done ifconvergence occurs beforethe 100th iterationConvergence occurswhenever the normalizedchange in the eigenvaluecalculations betweensuccessive iterations for thefirst NMODE eigenvalues is

less than 10E-5Minimum number of subspace iterationscompleted before a shift is performed Thedefault is 5 and the minimum is 2 UseFREQB on the MODOPT command orSHIFT on the BUCOPT command to define

the initial shift pointExample0500 30




Example ndash Subspace OptionsSturm sequence checkkeyALL --

Perform check at allshift points as well asat the end point(default)

PART --Perform check onlyat all shift points

NONE --

Do not performSturm sequencecheck

Number of Jacobi iterations used per subspaceiteration (used only with the JCG and PCG options onthe EQSLV command) Defaults to the number ofdegrees of freedom divided by the maximum wave

front for the model The minimum is 5Example0500 31




Eigen Buckling ndash Expanding Modes


Enter 3

Shift to Yes to Calculateelement results

Main Menugt Solutiongt Load Step Opts gt ExpansionPass gtSingle Expand gt Expand Modes





Example ndash Output Window




Example - Finish


Press Finish to end the eigen buckling solution



Example ndash Results Summary




Example ndash Read Results


General Postproc gt Plot Results gt Deformed Shape

Select ldquoDef+undeformedrdquo

and Press OK



Example - PostProcessing








and Press OK











and Press OK





l h



Example - Finish





Example ndash Column beam

E = 210000Nmm2

n = 03

L = 1000mm

a = 10mm

b = 10mmF =

ObjectiveCompute the critical buckling load and displaythe mode shape

TasksCreate a table and compare results with resultsobtained from buckling theoryDisplay the deflection figure























Enter Example0500


Enter Column beam





PREP7K

K1000

General format

KXYZ




Enter 000 and








Press OK






Pick upward arrow






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish
























Enter Example0500


Enter Column beam





PREP7K

K1000

General format

KXYZ




Enter 000 and








Press OK






Pick upward arrow






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






PREP7K

K1000

General format

KXYZ




Enter 000 and








Press OK






Pick upward arrow






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish







Press OK






Pick upward arrow






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish








Pick upward arrow






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






Press Add





Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






Press Options






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






Place the cursor






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






Press OK














Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish













Click hereto Close





























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






























Select keypoint 1








Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish







Example - Save


Save the model





Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






Press OK




Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish





Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish









Enter 3




























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish






























NONE --









Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish







Enter 3











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish











Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish













and Press OK











and Press OK











and Press OK





l h



Example - Finish













and Press OK











and Press OK





l h



Example - Finish













and Press OK





l h



Example - Finish







l h



Example - Finish





Example - Finish



Buckling Example

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Transcript of Buckling Example