HARDINI

User subroutine to define initial equivalent plastic strain and initial backstress tensor.

User subroutine HARDINI:

can be used only for material models that use metal plasticity or Drucker-Prager plasticity;
can be used to provide initial equivalent plastic strain values as a function of element number, material point number, and/or material point coordinates for isotropic and combined hardening;
enables you to specify initial conditions for the backstress tensor as a function of element number, material point number, and/or material point coordinates for kinematic and combined hardening;
will be called to define the initial equivalent plastic strain and, if relevant, the initial backstresses at material points for which user-subroutine-defined initial hardening conditions are specified; and
is intended for use when the initial equivalent plastic strain and/or backstress distributions are too complicated to specify directly as initial hardening conditions.

This page discusses:

Defining Backstress Components
User Subroutine Interface
Variables to Be Defined
Variables Passed in for Information

Defining Backstress Components

The number of backstress components that must be defined depends on the element type for which this routine is being called. Abaqus Elements Guide describes the number of stress components for each element type; the number of backstress components is identical to the number of stress components. The order of the backstress components is the same as the order of the stress components. For example, in three-dimensional continuum elements six backstress components must be defined in the order $α_{11}, α_{22}, α_{33}, α_{12}, α_{13}, α_{23} .$

User Subroutine Interface

      SUBROUTINE HARDINI(ALPHA,EQPS,COORDS,NTENS,NCRDS,NOEL,NPT,
     1 LAYER,KSPT,LFLAGS,NAMES)
C
      INCLUDE 'ABA_PARAM.INC'
C
      DIMENSION ALPHA(NTENS,*),COORDS(NCRDS),LFLAGS(2)
      CHARACTER*80 NAMES(2)


      user coding to define EQPS and, if relevant, ALPHA(NTENS)


      RETURN
      END

Variables to Be Defined

The variables described below are element-type dependent.

EQPS: Equivalent plastic strain.
ALPHA(1,1): First backstress component of the first backstress.
ALPHA(2,1): Second backstress component of the first backstress.
ALPHA(3,1): Third backstress component of the first backstress.
Etc.: NTENS backstress component values should be defined for each backstress.

Variables Passed in for Information

COORDS: An array containing the initial coordinates of this point.
NTENS: Number of backstress values to be defined. This number depends on the element type.
NCRDS: Number of coordinates.
NOEL: Element number.
NPT: Integration point number.
LAYER: Layer number (for composite shells and layered solids).
KSPT: Section point number within the current layer.
LFLAGS(1): Rebar flag. If LFLAGS(1)=1, the current integration point is associated with element rebar. Otherwise, LFLAGS(1)=0.
LFLAGS(2): Constituent flag. If LFLAGS(2)=1, the current integration point is associated with a constituent in the multiscale material. Otherwise, LFLAGS(2)=0.
NAMES(1): Name of the rebar to which the current integration point belongs, which is the name given in the rebar or rebar layer definition (Defining Reinforcement or Defining Rebar as an Element Property). If no name was given in the rebar or rebar layer definition, this variable will be blank. This variable is relevant only when LFLAGS(1)=1.
NAMES(2): Constituent name. This variable is relevant only when LFLAGS(2)=1.