ABAQUS Analysis User's Manual  

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

Product: ABAQUS/Standard  

References

Overview

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.

Defining backstress components

The number of backstress components that must be defined depends on the element type for which this routine is being called. Part V, “Elements,” 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

User subroutine interface

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

      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)

First backstress component.

ALPHA(2)

Second backstress component.

ALPHA(3)

Third backstress component.

Etc.

NTENS backstress values should be defined.

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.

LREBAR

Rebar flag. If LREBAR=1, the current integration point is associated with element rebar. Otherwise, LREBAR=0.

REBARN

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,” Section 2.2.3, or “Defining rebar as an element property,” Section 2.2.4). If no name was given in the rebar or rebar layer definition, this variable will be blank. This variable is relevant only when LREBAR=1.

Example