Mechanical APDL Structural Analysis Guide

where Par1 is the coordinate system number and Par2 is the axis of coordinate system Par1.

Example 1

! local coordinate system

LOCAL,11,0,,,,

! select nodes located along the crack front and

! define it as crack front/tip node component

NSEL,S,LOC,X,Xctip

NSEL,R,LOC,Y,Yctip

CM,CRACK_TIP_NODE_CM

! Define a new stress-intensity factors calculation

CINT,NEW,1

CINT,TYPE,SIFS

CINT,CTNC,CRACK_TIP_NODE_CM

CINT,NORM,11,2

Example 2

! select nodes located along the crack front and

! define it as crack front/tip node component

LSEL,,,,

NSLL

CM,CRACK_FRONT_NODE_CM,NODE

CINT,NEW,1

CINT,TYPE,SIFS

CINT,CTNC,CRACK_FRONT_NODE_CM,

Define the Crack-Extension Node Component and Crack-Extension Direction

Use this method when the crack plane is not flat, or when a set of nodes form the crack tip, as in the
case of a collapsed crack-tip mesh:

1. Define a node component consisting of one or more nodes forming the crack tip.

The node component can have one or more nodes.

Example:CINT,CENC,CMName

2. Identify the crack-tip node separately if the node component has more than one node.

If a crack-tip node is not identified, the first node of the node component is taken to be the first

node.

Example:CINT,CENCP,CMName,node1

3. Define the crack-extension direction.

Identify the local coordinate system associated with the crack under consideration.

Identify the local axis (for the above CS) along which the crack is supposed to extend.

Example:CINT,CENC,CMName,node1,11,2

Alternatively, define the crack-extension direction by directly specifying the global X Y and Z com-

ponents of the crack-extension vector.

Example:CINT,CENC,CMName,node1,,,compx,compy,compz

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Fracture Mechanics