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The iteration strategy yields the following results:

Table 7.2: Buckling Cyclic Symmetry: Load Factor Iteration Results

A graph of the results shows the convergence at Load Factor = 1.0:

Figure 7.24: Buckling Cyclic Symmetry Results: Load Factor Results Graph

7.7. Example Harmonic Cyclic Symmetry Analysis

This section introduces the harmonic cyclic symmetry analysis capability with an example problem. The example presents a simplified ring-strut-ring structure used in many rotating-machinery applications.

7.7.1.Problem Description

7.7.2.Problem Specifications

7.7.3.Input File for the Analysis

7.7.4.Analysis Steps

7.7.1. Problem Description

The component is a simplified fan inlet case for a military aircraft engine. As part of the design process for the assembly, the harmonic response characteristics of the inlet case may be investigated, as shown in this example.

7.7.2. Problem Specifications

The geometric and material properties used for the harmonic cyclic analysis are the same as used in Example Modal Cyclic Symmetry Analysis (p. 198).

All applicable degrees of freedom are used for the cyclic symmetry edge-component pairs. The harmonic response to a pressure load applied on the assembly is computed.

7.7.3. Input File for the Analysis

Use the input file given below (named harm_cyc_symm.inp) to perform the example modal cyclic symmetry analysis. The file contains the complete geometry, material properties and solution options for the finite element model.

!Harmonic Cyclic Symmetry Analysis Example ! Ring-Strut-Ring Configuration

!STEP #1

!Start an interactive session

!STEP #2

!Read in this input file: harm_cyc_symm.inp

finish /clear

r1=5

r2=10

d1=2

nsect=24 alpha_deg=360/nsect alpha_rad=2*acos(-1)/nsect

/view,1,1,1,2

/plopts,minm,0

/plopts,date,0

/pnum,real,1

/number,1

/prep7

csys,1

k,1,0,0,0

k,2,0,0,d1

k,3,r1,0,0

k,4,r1,0,d1

l,3,4 arotat,1,,,,,,1,2,alpha_deg/2 k,7,r2,0,0

k,8,r2,0,d1

l,7,8 arotat,5,,,,,,1,2,alpha_deg/2 arotat,2,,,,,,1,2,alpha_deg/2 arotat,6,,,,,,1,2,alpha_deg/2 a,5,6,10,9

mshkey,1

et,1,181

r,1,0.20

r,2,0.1

mp,ex,1,10e6

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mp,prxy,1,0.3 mp,dens,1,1e-4 esize,0.5 asel,,,,1,4 aatt,,1 asel,,,,5 aatt,,2 allsel

dk,5,all,0

aplot /prep7

!/eof

!STEP #3

!Configure the database for a cyclic symmetry analysis

cyclic

!STEP #4

!Mesh the areas

amesh,all

!STEP #5

!Turn on cyclic symmetry graphical expansion

/cycexpand,,on

!STEP #6

!Plot the elements

eplot

!STEP #7

!List the cyclic status

cyclic,status

!STEP #8

!List the cyclic solution option settings

cycopt,status fini

!STEP #9

!Solve the harmonic cyclic symmetry analysis

/solution

!Specify harmonic analysis option and frequency sweep values antype,harmic

hropt,full

harfrq,860,878

nsub,9

!Apply pressure load on the outer surface area asel,s,area,,2

asel,a,area,,4

!Loading to be applied on sector number 3

cycopt,ldsect,3 sfa,all,,pres,-124 asel,all

solve fini

!STEP #10

!Go to database results post processor

/post1

set,list

!STEP #11

!Read results for "substep 3 - excitation freq. of 866 HZ"

set,,3

plns,u,sum,1 fini

!STEP #12

!Go to time/freq. history postprocessor

/post26

!STEP #13

!Store X and Y disp. of node #34 on sector #3"

nsol,2,34,U,x,UX_34,3 nsol,3,34,U,y,UY_34,3

!STEP #14

!Plot UX and UY disp. of node #34 as a function of freq.

plvar,2,3

7.7.4. Analysis Steps

The following table describes the input listing and the steps involved in the example modal cyclic symmetry analysis in detail.

3.Specify a cyclic symmetry analysis and configure CYCLIC the database accordingly.

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NSOL,3,34,u,y,UY_34,3

15.Plot frequency versus displacement. Plot at node PLVAR,2,3 34. Figure 7.27: Displacement Plot as a Function

of Excitation Frequency (p. 216) shows the displacement plot as a function of the excitation frequency.

The results of your analysis should match those shown below:

Figure 7.25: Element Plot Showing Pressure Load on Sector 3

Figure 7.26: Contour Plot of Displacement Sum at Frequency of 866 HZ