!    St2LM_1 - program for ANSYS
!	Structural analysis(St)
!	2D problem(2)
!	Linear analysis(L)
!	Modal analysis(M)
!    
!    Test problem: computation of natural frequencies and mode shapes (modal analysis)
!	for the system of linear elasticity equations
!	(plane stress)
!
!	Geometry of the domain - double T-region
!    Domain consists of two different materials

/FILNAME,St2LM_1 ! change jobname to St2LM_1 
/TITLE, Modal Analysis of a Double-T Region
F_R='Mod_ANS_1'        ! file name for text output

NFREQ=4        !  number of natural frequencies to compute

/PREP7

H=0.02 ! Thickness
B=0.16 ! half height
L=0.05 ! half width

! Parameters for finite element mesh
DH=1
KFE=H

/OUTPUT,F_R,rez ! define file name and extension for text output
*VWRITE ! write to file
(1X,'   MODE-FREQUENCY ANALYSIS (Block Lanczos, Plane2)') 
! use FORTRAN FORMAT conventions, 1x stands for one horizontal space 
!specify real fortran format for nfreq value: Fw.d
!W = width of field, d = number of digits to the right of the decimal point
*VWRITE,NFREQ
(1X,'   NFREQ= ',F2.0) 

/OUTPUT ! finish text output

*DIM,FR,ARRAY,NFREQ  ! array for natural frequencies

! Parameters for material properties of steel
RO1=7.86e3  ! density
E1=2e11     ! Young's modulus
NU1=0.29    ! Poisson's ratio

!  Parameters for material properties of copper
RO2=8.9e3 ! density
E2=1.2e11 ! Young's modulus
NU2=0.33 ! Poisson's ratio

! Set material properties for the first material (steel)    
MP,DENS,1,RO1       !  set density
MP,EX,1,E1          !  set Young's modulus
MP,NUXY,1,NU1       !  set Poisson's ratio

! Set material properties for the second material (copper)    
MP,DENS,2,RO2       !  set density
MP,EX,2,E2          !  set Young's modulus
MP,NUXY,2,NU2       !  set Poisson's ratio
    
!ET,1,PLANE2    ! finite element PLANE2:  6-Node Triangular Structural Solid
ET,1,PLANE82    ! finite element PLANE82:  2D 8-Node Structural Solid
mshape,1 ! triangular option for PLANE82


! Keypoints of the plate boundary: point number and coordinates
K,1,H/2,0
K,2,H/2,B-H
K,3,L,B-H
K,4,L,B
K,5,-L,B
K,6,-L,B-H
K,7,-H/2,B-H
K,8,-H/2,0

K,9,H/2,-B+H
K,10,L,-B+H
K,11,L,-B
K,12,-L,-B
K,13,-L,-B+H
K,14,-H/2,-B+H

! Define lines 1-7
L,1,2 $ L,2,3 $ L,3,4 $ L,4,5
L,5,6 $ L,6,7 $ L,7,8 $ L,8,1
AL,1,2,3,4,5,6,7,8 ! Define area 1 by lines 1-8
! Define lines 9-15
L,1,9 $ L,9,10 $ L,10,11 $ L,11,12
L,12,13 $ L,13,14 $ L,14,8
AL,8,9,10,11,12,13,14,15 ! Define area 2 by lines 8-15

! Define parameters for finite element mesh
! KESIZE Specifies the edge lengths of the elements nearest a keypoint
KESIZE,ALL,KFE
!LESIZE,8,,,DH  ! Divide line 8 by DH segments

ASEL,S,AREA,,2   ! Select area 2
AATT,2,,1  ! Associate element attributes (MAT=2,TYPE=1) with the selected area
ASEL,ALL  ! Select all areas

AMESH,ALL ! Mesh all areas

*GET,EL_MAX,ELEM,,COUNT  ! EL_MAX - number of elements
*GET,ND_MAX,NODE,,COUNT  ! ND_MAX - number of nodes
/OUTPUT,F_r,rez,,append ! Open file F_r.rez and continue output
*VWRITE,EL_MAX,ND_MAX ! Write the values of el_max and nd_max in the file
(3X,' NEL_MAX=',F6.0,' ND_MAX=',F6.0)
! use fortran format for output, 3x stands for 3 horizontal spaces
! use real format Fw.d: W = width of field, d = number of digits to the right of the decimal point

! Add comments to output file 
/com,
/COM,  i   ! Frequency in Hz (ANSYS)
/OUTPUT ! Finish text output

SAVE
FINISH

/SOLU
ANTYPE,MODA          ! Modal analysis (natural frequencies and mode shapes)
MODOPT,LANB,NFREQ ! Options for the solver: Block Lanczos solver, number of natural frequencies (NFREQ)
NSEL,S,LOC,Y,-B	! Select all nodes with Y=-B
D,ALL,UX,0    ! For all selected nodes set UX=0
D,ALL,UY,0    ! For all selected nodes set UY=0
NSEL,ALL      ! Select all nodes

OUTRES,ALL,ALL ! write solution results for every substep
SOLVE
SAVE
FINISH

/POST1
 ! Write the values of natural frequencies to the file
*DO,I,1,NFREQ ! do-loop for data sets from 1 to nfreq
  SET,,I !  data set to be read from the results file
*GET,FR(I),MODE,I,FREQ !Retrieves a value of FREQ for the entity MODE and stores it part of an array parameter FR
  FRI=FR(I)
  /OUTPUT,F_r,rez,,append ! continue text output to the file
  *VWRITE,I,FRI ! write the values of natural frequencies
  (1X,F2.0,'   ',E12.5) ! use real format Fw.d for I and real format with exponent notation Ew.d for FRI

  /OUTPUT
*ENDDO