There are several special considerations that need to be noted.
Beams and shells that calculate transverse shear energy
When
UHYPEL is used to define the material response of shell or beam
elements that calculate transverse shear energy,
Abaqus/Standard
cannot calculate a default value for the transverse shear stiffness of the
element. Hence, you must define the element's transverse shear stiffness. See
Shell section behavior
and
Choosing a beam element
for guidelines on choosing this stiffness.
Elements with hourglassing modes
If this capability is used to describe the material of elements with
hourglassing modes, you must define the hourglass stiffness for hourglass
control based on the total stiffness approach. The hourglass stiffness is not
required for enhanced hourglass control, but you can define a scaling factor
for the stiffness associated with the drill degree of freedom (rotation about
the surface normal). See
Section controls.
User subroutine interface
SUBROUTINE UHYPEL(E,GNU,STRAIN,NDI,NSHR,EINV1,EINV2,EINV3,
1 COORDS,NOEL,TEMP,PREDEF,CMNAME)
C
INCLUDE 'ABA_PARAM.INC'
C
CHARACTER*80 CMNAME
C
DIMENSION STRAIN(*),COORDS(3),PREDEF(*)
user coding to define E and GNU
RETURN
END
Variables to be defined
E
Young's modulus.
GNU
Poisson's ratio.
Variables passed in for information
STRAIN
Array containing the total (elastic) strains, (ε).
NDI
Number of direct strain components at this point.
NSHR
Number of shear strain components at this point.
EINV1
I1=trace(ε),
the first strain invariant.
EINV2
I2=1/2(ε:ε-I12),
the second strain invariant.
EINV3
,
the third strain invariant.
COORDS
An array containing the coordinates of the material point. These are the
current coordinates if geometric nonlinearity is accounted for during the step
(see
Defining an analysis);
otherwise, the array contains the original coordinates of the point.
NOEL
Element number.
TEMP
Current temperature at this point.
PREDEF
An array containing current values of the predefined field variables at this
point (initial values at the beginning of the analysis and current values
during the analysis).