Engine Subroutine SIGEPSnnC for Shell Elements
This subroutine calculates the stress tensor versus the strain tensor, strain rate tensor, or user variables.
Arguments
SIGEPSnnC
and its individual arguments and
descriptions
are:C
SUBROUTINE SIGEPS29C(
1 NEL ,NUPARAM,NUVAR ,NFUNC ,IFUNC ,
2 NPF ,NPT ,IPT ,IFLAG ,
2 TF ,TIME ,TIMESTEP,UPARAM ,RHO0 ,
3 AREA ,EINT ,THKLY ,
4 EPSPXX ,EPSPYY ,EPSPXY ,EPSPYZ ,EPSPZX ,
5 DEPSXX ,DEPSYY ,DEPSXY ,DEPSYZ ,DEPSZX ,
6 EPSXX ,EPSYY ,EPSXY ,EPSYZ ,EPSZX ,
7 SIGOXX ,SIGOYY ,SIGOXY ,SIGOYZ ,SIGOZX ,
8 SIGNXX ,SIGNYY ,SIGNXY ,SIGNYZ ,SIGNZX ,
9 SIGVXX ,SIGVYY ,SIGVXY ,SIGVYZ ,SIGVZX ,
A SOUNDSP,VISCMAX,THK ,PLA ,UVAR ,
B OFF ,NGL ,SHF)
C
The user’s material law can be used in isotropic mode with PID 1 or in orthotropic mode with PID 9, 10, or 11. The directions XX, YY,... are the shell local reference frame axis. Stress are computed at each integration point.
FINTER
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 should always be set by you. It is used to
calculate the stability time step and the hourglass forces. The sound speed value
should be equal to the plane wave speed.
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). 
NPT 
Integer read only scalar  Number of layers or integration points. 
IPT 
Integer read only scalar  Current layer or interrogation point. 
IFLAG 
Integer array read only scalar  Array of size NEL with geometrical
flags. 
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 with initial
densities. 
AREA 
Float array read only  Array of size NEL with current element
surfaces. 
EINT 
Float array read only  Array of size 2*NEL with internal membrane
and bending energy. 
THKLY 
Float array write only  Array of size NEL with the layer thickness
at each integration point. 
EPSPXX , EPSPYY ,
EPSPXY , EPSPYZ ,
EPSPZX 
Float array read only  Arrays of size NEL containing
$\text{\epsilon}$ strain rates in directions XX and YY
and $\gamma $ strains in directions XY, YZ, and ZX. 
DEPSXX , DEPSYY ,
DEPSXY , DEPSYZ ,
DEPSZX 
Float array read only  Arrays of size NEL containing
$\text{\epsilon}$ strain increments in directions XX and
YY and $\gamma $ strain increments in directions XY, YZ,
and ZX. 
EPSXX , EPSYY ,
EPSXY , EPSYZ ,
EPSZX 
Float array read only  Array of size NEL containing
$\text{\epsilon}$ strains in directions XX and YY and
$\gamma $ strains in directions XY, YZ, and
ZX. 
SIGOXX , SIGOYY ,
SIGOZZ , SIGOXY ,
SIGOYZ , SIGOZX 
Float array read only  Array of size NEL containing old (previous
time step) elastoplastic stresses in directions XX, YY, ZZ, XY,
YZ, and ZX. 
SIGNXX , SIGNYY ,
SIGNXY , SIGNYZ ,
SIGNZX 
Float array write only  Array of size NEL containing new computed
elastoplastic stresses in directions XX, YY, 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, 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. 
THK 
Float array read write  Array of size NEL containing total
thickness. 
PLA 
Float array read write  Array of size NEL containing plastic
strain. 
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.

NGL 
Integer array read only  Array of size NEL containing the external
element number. 
Shell Element Law Output
Unlike solid elements, shell elements do not have any variables specific to user’s law that are saved in timehistory and animation.
Data Necessary for QEPH Compatibility
With QEPH, you must provide Radioss information relative
to plasticity so that physical stabilization can be accurately calculated. Yield
value and value Et/E (tangent modulus divided by Young’s modulus) must be given back
to Radioss in the user law
(SIGEPS29C.F
, SIGEPS30C.F
, or
SIGEPS31C.F
) to be compatible with the QEPH element.
This can be done through a call to routine SET_U_SHLPLAS
.
C
C New routine : SET_U_SHLPLAS allows to return to Altair Radioss,
C Yield and Et/E for all elements.
C
C Description of the arguments to be given to
C SET_U_SHLPLAS(NEL,YLD,ETSE) :
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 ETSE  NEL  F  VALUE FOR EACH ELEMENT,
C AND THE CURRENT INTEGRATION POINT OF :
C ETSE = 1 in case of an elastic increment
C = H/(H+E) in case of a plastic increment
C where H : plastic tangent modulus,
C E : Young modulus
C++++
The arrays YLD
and ETSE
, defined in the routine
SET_U_SHLPLAS
, have to be declared as local variables in the
user material routines SIGEPS29C.F
, SIGEPS30C.F
,
and SIGEPS30C.F
with a sufficientlylong NEL
.
DOUBLE PRECISION YLD(NEL), ETSE(NEL)
NEL
is set by Radioss and given as
an argument to the user routine. Therefore, the dynamic allocation is intended in
this statement. In this case, use the following
statement.DOUBLE PRECISION YLD(4096), ETSE(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.