Learning Forum

[vgiordano3]

Hello everyone. I'm having some difficulties performing a PSD analysis in Ansys APDL. I have a steel structure and a steel box, joined toghether with 4 brackets. This structure performed a vibrational test according to the MIL-STD-810. The PSD spectrum is the following (blue one) with 176lbs of weight on the box. After I perform the PSD analysis, I have to combine the extracted modes, but the software tells me that no mode were combined, because the partecipation factor must be calculated firts, but I used the command "pfact,1,base" on the code. Can someone help me?

!Aree rinforzi cassetta

a,25,42,43,21        !A14

a,24,25,42,56,57,60,61,44    !A15

a,24,44,45,20        !A16

a,20,21,43,67,66,71,70,75,74,45    !A17

 

!Aree cerinere

a,56,57,58,59  !A18 

a,60,61,62,63  !A19

a,64,65,66,67  !A20

a,68,69,70,71  !A21

a,72,73,74,75  !A22

 

!Area coperchio

a,76,59,58,63,62,77,78,73,72,69,68,65,64,79  !A23

!Aree rinforzo coperchio

a,76,59,58,63,62,77,81,80      !A24

a,77,81,82,78          !A25

a,82,83,79,64,65,68,69,72,73,78      !A26

a,76,79,83,80          !A27

 

!Tipologia elementi,materiali e sezioni

et,1,beam188,,,3        !Beam 188 con f.f. cubica

mp,ex,1,E          !Modulo Young material 1

mp,nuxy,1,ni        !Coeff poisson material 1

mp,dens,1,rho        !Densità material 1

sectype,1,beam,hrec,tubquad    !Sezione tubolare quad

secdata,wh1,wh1,th1,th1,th1,th1  !Dati sezione tubolare quad

sectype,2,beam,chan,upn160    !Sezione upn160

secdata,wu1,wu1,wu2,tu1,tu1,tu2  !Dati sezione upn 160

sectype,3,beam,rect,staffa    !Sezione staffe

secdata,bb,bh        !Dati sezione staffe

et,2,shell63        !Shell63 cassetta

mp,ex,2,E1          !Modulo Young material 2

mp,nuxy,2,ni        !Coeff Poisson material 2

mp,dens,2,rho1        !Densità material 2

r,1,tc          !Spessore dello shell

r,2,ws          !Spessore dello Shell delle staffe

r,3,wcer          !Spessore cerniere

mp,ex,3,E2          !Modulo di Young material 3 ABS

mp,nuxy,3,ni2      !Coeff di Poisson material 3 ABS

mp,dens,3,rho2        !Densità ABS

r,4,tc,0,0,0,0,0,0,

rmore,0,0,0,

rmore

rmore,mua

 

 

!Meshing

 

!Mesh telaio

esize,0.05

lsel,r,line,,1,28

latt,1,,1,,,,1  

lmesh,all

lsel,all

 

lsel,r,line,,30,32

latt,1,,1,,,,1

lmesh,all

lsel,all

 

lsel,r,line,,29

k,1000,,-1e+12

latt,1,,1,,1000,,2

lmesh,all

lsel,all

 

!Mesh staffe

esize,0.02

lsel,r,line,,33,40

latt,1,,1,,,,3

lmesh,all

lsel,all

 

!Mesh cassetta

 

asel,r,area,,7

type,2

real,4

mat,2

amesh,all

allsel,all

 

 

asel,s,area,,1,6

type,2

real,1

mat,2

amesh,all

allsel,all

 

asel,s,area,,6,17

type,2

real,1

mat,2

amesh,all

allsel,all

 

asel,s,area,,23,27

type,2

real,1

mat,2

amesh,all

allsel,all

 

!Mesh chiusure

asel,s,area,,18,19

type,2

real,3

mat,3

amesh,all

allsel,all

 

!Mesh cerniere in alluminio

asel,s,area,,20,22

type,2

mat,2

real,3

amesh,all

allsel,all

 

 

/eshape,1,1

eplo

 

 

!vincoli

ksel,r,kp,,1,4,1

nslk,r,n,all

d,all,all

allsel,all

 

!Carichi

allsel,all

 

 

!ANALISI SPETTRALE

 

/solu

antype,modal,new

modopt,lanb,all,10,500

mxpand,,,,yes,,,

allsel,all

outres,all,all

outpr,all,all

save

solve

finish

 

/solu

antype,spectrum,new

spopt,psd,alles,no

!EFINIZIONE SPETTRO DI RISPOSTA DELLA STRUTTURA

PSDUNIT,1,accg,9.81

psdfrq,1,,10,40,500

psdval,1,0.078,0.078,0.0078

sed,0.0,1.0,0.0

allsel,all

pfact,1,base

psdres,disp,abs

psdres,velo,abs

psdres,acel,abs

allsel,all

outres,all,all

outpr,all,all

save

solve

finish

 

! ANALISI MODALE PER ESPANDERE I MODI ESTRATTI

/solu

antype,spectr

psdcom,,,,total

solve

 

 

/post1

set,last

plnsol,s,eqv

 

 

path,plot,25

ppath,1,509

*do,i,2,24

ppath,i,550+i

*enddo

ppath,25,551

pdef,sigma,s,eqv

plpath,sigma

[Chandra Sekaran]

You need to indicate which nodes are going to be excited before issuing PFACT command. IF all the fixed nodes are going to be excited, say, in X direction by the PSD then you can use the below and then use the PFACT.

ksel,r,kp,,1,4,1

nslk,r,n,all

d,all,ux,1   

allsel,all

pfact,1,base

 

 

antype,spectrum,new

spopt,psd,alles,no

!EFINIZIONE SPETTRO DI RISPOSTA DELLA STRUTTURA

PSDUNIT,1,accg,9.81

psdfrq,1,,10,40,500

psdval,1,0.078,0.078,0.0078

sed,0.0,1.0,0.0

allsel,all

pfact,1,base