Engine Subroutine SIGEPSnn for Solid Elements
This subroutine calculates the stress tensor versus the strain tensor, strain rate tensor, density, volume, internal energy, or userdefined variables.
Arguments
SIGEPSnn
and its individual arguments and
descriptions
are:C
SUBROUTINE SIGEPS29 (
1 NEL ,NUPARAM,NUVAR ,NFUNC ,IFUNC ,NPF
2 TF ,TIME ,TIMESTEP,UPARAM ,RHO0 ,RHO ,
3 VOLUME ,EINT ,
4 EPSPXX ,EPSPYY ,EPSPZZ ,EPSPXY ,EPSPYZ ,EPSPZX ,
5 DEPSXX ,DEPSYY ,DEPSZZ ,DEPSXY ,DEPSYZ ,DEPSZX ,
6 EPSXX ,EPSYY ,EPSZZ ,EPSXY ,EPSYZ ,EPSZX ,
7 SIGOXX ,SIGOYY ,SIGOZZ ,SIGOXY ,SIGOYZ ,SIGOZX ,
8 SIGNXX ,SIGNYY ,SIGNZZ ,SIGNXY ,SIGNYZ ,SIGNZX ,
9 SIGVXX ,SIGVYY ,SIGVZZ ,SIGVXY ,SIGVYZ ,SIGVZX ,
A SOUNDSP,VISCMAX,UVAR ,OFF )
C
 With isotropic mode, the directions XX, YY, ... are the global reference
frame axis. The old elastoplastic stresses (arrays
SIGOXX
,SIGOYY
, ...) are already rotated to take into account the rigid body rotation.  With orthotropic mode, the directions are the orthotropic frame axis
FINTER
(shown below) to get
the value Y of the function for the abscissa
X.Y=FINTER(IFUNC(I),X,NPF,TF,DYDX)
 Variable
 Description
 Y
 Interpolated value
 X
 Abscissa value of the function
 I
 The i^{th} user’s function
 DYDX
 Slope
 NPF, TF
 Private function parameters
The SOUNDSP
array is used in the calculation of the stability time
step, the hourglass forces, and the artificial viscous pressure Q.
For isotropic materials, the sound speed value should be equal to the plane wave speed.
 Variable
 Description
 K
 Bulk modulus
 G
 Shear modulus
 $\lambda $ and $\mu $
 Lame parameters
Use VISCMAX
to calculate the time step stability when the material
law formulation is viscous.
Definitions
Argument  Format  Description 

NEL 
Integer read only scalar  Number of elements per group. In Radioss Engine subroutines, the element data are treated by groups for vectorization. This argument is machinedependent and set by Radioss. 
NUPARAM 
Integer read only scalar  Size of the user parameter array. 
NUVAR 
Integer read only scalar  Number of user element variables. 
NFUNC 
Integer read only scalar  Number of functions used for material law. 
IFUNC 
Integer array read only  Array of size NFUNC with function
indexes. 
NPF 
Integer array private data  Array used by FINTER (float external
function). 
TF 
Integer array private data  Array used by FINTER (float external
function). 
TIME 
Float read only  Current time. 
TIMESTEP 
Float read only  Current time step. 
UPARAM 
Float array read only  User material parameter array of size
NUPARAM . 
RHO0 
Float array read only  Array of size NEL containing initial
densities. 
RHO 
Float array read only  Array of size NEL containing current
densities. 
VOLUME 
Float array read only  Array of size NEL containing current element
volumes. 
EINT 
Float array read only  Array of size NEL containing total internal
energy. 
EPSPXX , EPSPYY ,
EPSPZZ , EPSPXY ,
EPSPYZ , EPSPZX 
Float array read only  Arrays of size NEL containing
$\text{\epsilon}$ strain rates in directions XX, YY, and
ZZ and $\gamma $ strain rates in directions XY, YZ,
ZX. 
DEPSXX , DEPSYY ,
DEPSZZ , DEPSXY ,
DEPSYZ , DEPSZX 
Float array read only  Arrays of size NEL containing
$\text{\epsilon}$ strain increments in directions XX, YY,
and ZZ and $\gamma $ strain increments in directions XY, YZ,
and ZX. 
EPSXX , EPSYY ,
EPSZZ , EPSXY ,
EPSYZ , EPSZX 
Float array read only  Array of size NEL containing
$\text{\epsilon}$ strains in directions XX, YY, and ZZ
and $\gamma $ strains in directions XY, YZ, and
ZX. 
SIGOXX , SIGOYY ,
SIGOZZ , SIGOXY ,
SIGOYZ , SIGOZX 
Float array read only  Array of size NEL with old (previous time
step) elastoplastic stresses in directions XX, YY, ZZ, XY, YZ,
and ZX. 
SIGNXX , SIGNYY ,
SIGNZZ , SIGNXY ,
SIGNYZ , SIGNZX 
Float array write only  Array of size NEL with new computed
elastoplastic stresses in directions XX, YY, ZZ, XY, YZ, and
ZX. 
SIGVXX , SIGVYY ,
SIGVZZ , SIGVXY ,
SIGVYZ , SIGVZX 
Float array write only  Array of size NEL containing viscous
stresses in directions XX, YY, ZZ, XY, YZ, and ZX. 
SOUNDSP 
Float array write only  Array of size NEL containing sound
speed. 
VISCMAX 
Float array write only  Array of size NEL containing the maximum
damping modulus. 
UVAR 
Float array read write  Array of size NEL *NUVAR
containing user element variables. 
OFF 
Float array read write  Array of size NEL containing deleted element
flags.

Data Necessary for HEPH Compatibility
You must provide Radioss with plasticity information to
calculate physical stabilization forces of HEPH. Yield and Plastic strain values
must be given back to Radioss in the user law
(SIGEPS29.F
, SIGEPS.F
, or
SIGEPS.F
) to be compatible with the HEPH element. This can be
done through a call to routine SET_U_SOLPLAS
.
C
C New routine : SET_U_SOLPLAS allows to return to Altair Radioss,
C Yield and Plastic strain for all elements.
C
C Description of the arguments to be given to
C SET_U_SOLPLAS(NEL,YLD,PLA) :
C+++
C VAR  SIZE TYP DEFINITION
C+++
C NEL  1  I  NUMBER OF ELEMENTS
C YLD  NEL  F  YIELD VALUE FOR EACH ELEMENT,
C (FOR THE CURRENT INTEGRATION POINT)
C PLA  NEL  F  PLASTIC STRAIN VALUE FOR EACH ELEMENT,
C (FOR THE CURRENT INTEGRATION POINT)
C+++
The arrays YLD
and PLA
, defined in the routine
SET_U_SOLPLAS
, have to be declared as local variables in the
user material routines SIGEPS29.F
, SIGEPS30.F
, and
SIGEPS31.F
with a sufficientlylong NEL
.
DOUBLE PRECISION YLD(NEL), PLA(NEL)
NEL
is set by Radioss and given as
an argument to the user routine. Therefore, the dynamic allocation is intended in
this statement.DOUBLE PRECISION YLD(4096), PLA(4096)
The statement must be sufficient in all cases, meaning the value of
NEL
given from Radioss to the user
routine should be less than 4096.