Input File Format
A flexible body input file is a formatted file whose name is given is the /FXBODY in Radioss Starter.
It contains several blocks of data which must be input in the right order. Each line beginning with '#' is considered a comment line and is not taken into account.
Data block 1: General data
#FORMAT: (7I8)
# Nbmod Nbstat Nbnod Irot Idamp Iblo Ifile
45 15 18 1 0 1 0
Field  Descripton  SI Unit Example 

Nbmod  Total number of reduction modes  
Nbstat  Number of static
modes Note: Static modes are modes which are
not orthogonal with respect to the stiffness. Their
number gives the dimension of the full part of the
local projected stiffness matrix. The number of
socalled dynamic modes, given by
(Nbmod 
Nbstat) determines the size of
the diagonal part of the local projected stiffness
matrix.


Nbnod  Number of nodes in the flexible body support.  
Irot 


Idamp 


Iblo 
Note: A flexible body is either fully free or
fully blocked. A number of rigid body modes different
from 0 or 6 in the local stiffness matrix is not
permitted.


Ifile 

Data block 2: List of nodes
#FORMAT: (10I8)
# Nodes
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38
The number of nodes in the list must be equal to Nbnod given in Data block 1. The order of nodes in the list is the order in which the sets of components of the projection modes are given in Data blocks 5, 6, and 7.
Data block 3: Initial rotation matrix and local maximum frequency
#FORMAT: (1P5E16.9)
# Mrot11 Mrot12 Mrot13 Mrot21 Mrot22
1.000000000E+00 0.000000000E+00 0.000000000E+00 0.000000000E+00 1.000000000E+00
# Mrot23 Mrot31 Mrot32 Mrot33 Freq
0.000000000E+00 0.000000000E+00 0.000000000E+00 1.000000000E+00 2.049574631E+04
Field  Descriptio  SI Unit Example 

Mrotij  Component
P_{} of the initial
rotation matrix from the local frame of the flexible body to
the global frame. Note: Matrix
P defines the initial
orientation of the flexible body.


Freq  Maximum eigen
frequency of the local reduced system composed of local
reduced mass matrix and local reduced stiffness matrix. Note: This frequency is used to compute the
stability time step of the flexible body through the
formula:
$\text{\Delta}{t}_{stab}=\frac{1}{\pi \cdot Freq}$

Data block 4: Damping data (optional, present only if Idamp = 1)
#FORMAT: (1P2E16.9)
# Alpha Beta
1.092357846E+01 4.652573369E07
Field  Description  SI Unit Example 

Alpha, Beta  Rayleigh
damping coefficients Note: Local damping
matrix is obtained from local reduced mass and
stiffness matrices through the formula:
${C}_{L}=Alpha\cdot {M}_{L}+Beta\cdot {K}_{L}$

Data block 5: Projection modes  Modes representing the overall rigid body motion of the flexible body (optional, present only if Iblo = 0)
#FORMAT: (1P5E16.9)
# 1 X Y Z XX YY
#FORMAT: (1P1E16.9)
# ZZ
0.000000000E+001.250000000E+01 0.000000000E+00 0.000000000E+00 0.000000000E+00
0.000000000E+00
0.000000000E+00 1.250000000E+01 0.000000000E+00 0.000000000E+00 0.000000000E+00
0.000000000E+00
...
Field  Description  SI Unit Example 

X, Y, Z  Components of the mode on the translational DOF of the node.  
XX, YY, ZZ  Components of
the mode on the rotational DOF of the
node

Data block 6: Projection modes  Modes accounting for the inertia associated with the rotational degrees of freedom (optional, present only if Iblo = 0 and Irot = 1)
Same format as Data block 5
3 modes ${\Phi}_{R}^{12+i}$ with $i$ =1…3 are input by blocks of Nbnod sets of six values.
Data block 7: Projection modes  Local reduction modes
Same format as Data block 5
Nbmod modes ${\Phi}_{L}^{i}$ with $i$ =1…Nbmod are input by blocks of Nbnod sets of six values. The Nbstat static modes are given first.
Data block 8: Local reduced diagonal mass matrix
#FORMAT: (1P5E16.9)
5.596016869E+03 8.234274572E+03 2.320889319E+04 1.215104250E+03 1.729160225E+02
3.000458618E+05 3.074228932E+02 1.458647403E+04 1.425398877E+02 4.251072139E+05
Nbmod values are entered, following the order in which the local modes are given.
Data block 9: Local reduced stiffness matrix  Full part
Same format as Data block 8
It corresponds to a skyline storage of the Nbstat first lines of the local reduced stiffness matrix. The number of terms to input is $\frac{1}{2}Nbstat\left(2NbmodNbstat+1\right)$ . Again, the numbering of the columns of the matrix follows the order in which the local modes are given.
Data block 10: Local reduced stiffness matrix  Diagonal part
Same format as Data block 8
(Nbmod  Nbstat) values are entered, following the order in which the local dynamic modes are given.
Data block 11: Mass matrix projected on the modes defining the rigid body motion (optional, present only if Iblo = 0)
Same format as Data block 8
This is a full symmetric matrix entered using a skyline storage. Column numbering follows the order in which the modes defining the rigid motion are given. The dimension of the matrix is 12, if Irot = 0 or 15, if Irot = 1. Thus, the number of values to input is equal to 78, if Irot = 0 or 120, if Irot = 1.
Data block 12: Matrices for coupled mass projection (optional, present only if Iblo = 0)
Same format as Data block 8
Nine subblocks are given, one for each constant contribution ${M}_{Ck1}$ . These are rectangular matrices. The number of lines is equal to 12, if Irot = 0 or 15, if Irot = 1. The number of columns is Nbmod. The terms of the matrices are entered line by line. Their number is equal to 12*Nbmod, if Irot = 0 or 15*Nbmod, if Irot = 1.
Data block 13: Matrices for coupled stiffness projection (optional, present only if Iblo = 0)
Same format as Data block 8
Nine subblocks are given, one for each constant contribution ${K}_{Ck1}$ . These are rectangular matrices. The number of lines is equal to 12, if Irot = 0 or 15, if Irot = 1. The number of columns is Nbmod. The terms of the matrices are entered line by line. Their number is equal to 12*Nbmod, if Irot = 0 or 15*Nbmod, if Irot = 1.