Mechanical APDL Structural Analysis Guide

suitable for interface delamination of laminate composites with good numerical stability. For more in-
formation, see VCCT-Based Crack Growth Simulation.

11.1.3.2. Cohesive Zone Method

This method uses interface (INTERnnn) or contact (CONTAnnn) elements to allow the separation of the
surfaces and the cohesive material model to describe the separation behavior of the surfaces. This ap-
proach applies to both the simulation of fracture in a homogeneous material as well as interfacial
delamination along the interface between two materials. For more information, see Interface Delamin-
ation and Failure Simulation (p. 381).

11.1.3.3. Gurson’s Model Method

Gurson's model is a plasticity model (TB,GURSON) used to simulate ductile metal damage. The model
is a micromechanics-based ductile damage model incorporating the void volume fraction into plasticity
constitutive equation to represent the ductile damage process of void grow, void nucleation, and void
coalescence. For more information, see Gurson's Model in the Mechanical APDL Theory Reference and
the TB,GURSON command documentation.

11.2. Solving Fracture Mechanics Problems

A fracture analysis is a combination of stress analysis and fracture mechanics parameter calculation.
The stress analysis is a standard linear elastic or nonlinear elastic plastic analysis.

Because high stress gradients exist in the region around the crack tip, the finite element modeling of
a component containing a crack requires special attention in that region.

The 2-D and 3-D representations of the region around the crack tip and the terminology used is outlined
in the following section. The edge or tip of the crack is referred to as a crack tip in a 2-D model and
crack front in a 3-D model, as illustrat ed in Figure 11.5: Crack Tip and Crack Front (p. 347).

Figure 11.5: Crack Tip and Crack Front

(a)

r

crackfront

y,v

x,u

z,w

(b)

crackface

θ

y,v

r

x,u

cracktip

crackface θ

(a) 2-D models and (b) 3-D models

The following additional topics related to solving fracture problems are available :
11.2.1. Modeling the Crack-Tip Region
11.2.2. Calculating Fracture Parameters

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Solving Fracture Mechanics Problems