Mechanical APDL Structural Analysis Guide

• SOLID187

T-stress evaluation supports the following material behavior:

• Linear isotropic elasticity


• Isotropic plasticity

Even if isotropic plasticity behavior is supported, stress-intensity factors and T-stress are strictly valid
under the small-scale yielding assumption; therefore, the crack tip plastic zone must be small. In practice,
the crack tip plastic zone must always be smaller than the last CINT integration contour so that the
interaction integral is calculated on elements that still exhibit a linear elastic behavior.

T-stress evaluation supports 2-D plane strain and plane stress and 3-D analysis. Pressure on the crack
faces, and axisymmetry, are not supported.

11.3.4.3. Calculating the T-Stress

To start a stress-intensity factors calculation, issue the CINT command twice, as follows:

CINT,NEW,n

CINT,TYPE,TSTRESS

where n is the T-stress calculation ID number.

All CINT command options available for stress-intensity factor calculation are also available for T-stress.
For example, the following example input is a full setup of a T-stress evaluation using the node com-
ponent CRACK_TIP_NODE_CM to define the crack front, a symmetry condition, and five integration
contours:

CINT,NEW,1

CINT,TYPE,TSTRESS

CINT,CTNC,CRACK_TIP_NODE_CM

CINT,SYMM,ON

CINT,NCON,5

For more information about the calculation setup procedure, see Calculating the Stress-Intensity
Factors (p. 364).

11.3.5. Material Force Calculation

The material force method determines the vectorial force-like quantities conjugated to the configura-
tional change; that is, the method evaluates the material node point forces corresponding to the Eshelby
stress and the material body forces.

The following topics concerning material force calculation are available:

11.3.5.1. Understanding the Material Force Approach

11.3.5.2. Calculating Material Force

11.3.5.1. Understanding the Material Force Approach

For a general 2-D problem (in the absence of body forces, thermal strain and dynamic loads), the nodal
material forces are defined as:

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Numerical Evaluation of Fracture Mechanics Parameters