1

ANSYS

Modal Super Position Harmonic

Analysis Procedure

2

Model details

finish/clear/PREP7 rectng,0,100,0,15et,1,63 r,1,2

lsel,s,loc,x,5,95lesize,all,,,10allselesize,5amesh,all

ex,1,200e3nuxy,1,0.3dens,1,7800e-12

nsel,s,loc,x,0d,all,allallsellsave

3

Modal analysis results

/solu

antype,modal

modopt,lanb,10

mxpand,10

solve

finish

/post

set,list

4

5g Acceleration in Z direction in the

frequency range of 10 to 2000 Hz/SOLUANTYPE,3HROPT,MSUP, , ,0HROUT,OFF LUMPM,0

HROPT,MSUP,5, ,0 HROUT,OFF,ON,0

HARFRQ,10,2000, NSUBST,100,

g=9810ACEL,0,0,5*g

KBC,1 DMPRAT,0.03,

solve

5

Uz displacement as a function

Frequency

/post26FILE, ,'rfrq'NSOL,2,node(100,15,0),U,Z,Tip_Top_UZNSOL,3,node(50,0,0),U,Z,Mid_Bot_Uz/AXLAB,X,Freq [Hz] /AXLAB,Y,Amplitude [mm]/GROPT,LOGX,OFF /GROPT,LOGY,ON

PLCPLX,0 ! Plot Amplitude PRCPLX,1 ! Print Amplitude & Phase Angle PLVAR,2,3

6

Closer look at frequency response curve.

/GROPT,LOGX,OFF /GROPT,LOGY,OFF /XRANGE,0,200 PLVAR,2

This frequency and phase angle will be used for single point expansion

/post1 Uz

displacement at this

frequency on

Tip_Top node will be

compared

7

Single point expansion

/SOLU

EXPASS,1

EXPSOL, , ,165.56

HREXP,91.6717 solve

/post1

set,lastplnsol,u,z

From /post26

From /post1

Uz displacement from /post26 and /post are exactly matching

8

Bending stress distribution at 165.5 Hz

from Single Point Expansion

PLNSOL,S,x,2

9

Expansion for entire frequency

range./SOL

NUMEXP,ALL, , ,1

HREXP,ALL,

solve

/POST26

FILE,,'rst'

PLCPLX,0PRCPLX,1

FORCE,TOTAL

SHELL,TOP

ANSOL,2,node(0,0,0),S,X,Root_Bot_Sx

/AXLAB,X,Freq [Hz]

/AXLAB,Y,Sx [MPa]

/GROPT,LOGX,OFF

/GROPT,LOGY,ON

PLCPLX,0 ! Plot Amplitude

PRCPLX,1 ! Print Amplitude & Phase

Angle

PLVAR,2Variation of bending Stress (Sx) at the root wrt frequency

10

Identifying critical stress frequencies

Sx at this frequency on root bottom node will be compared with

Sx from /post1

11

Looking at the stress distribution in

/post1 at identified critical frequencies.

12

Comparison of Sx from /post1 & /post26

hrcplx,1,31,-88.4818

PLNSOL,S,x,2

Sx from /post26 and /post are exactly matching