Mechanical APDL Structural Analysis Guide

2. Identify the crack-tip node separately if the node component has more than one node. If a crack-
   tip node is not identified, then the first node of the node component is taken to be the first node.

Example:CINT,CENC,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

Repeat this method for all node locations along the crack front.

Example 1

! local coordinate systems

local,11,0,,,,

local,12,0,,,,

...

local,n,0,,,,

NSEL,S,LOC,X,Xctip1

NSEL,R,LOC,Y,Yctip1

NSEL,R,LOC,Z,Zctip1

CM,CRACK_FRONT_NODE_CM1

NSEL,S,LOC,X,Xctip2

NSEL,R,LOC,Y,Yctip2

NSEL,R,LOC,Z,Zctip2

CM,CRACK_FRONT_NODE_CM2

...

NSEL,S,LOC,X,Xctipn

NSEL,R,LOC,Y,Yctipn

NSEL,R,LOC,Z,Zctipn

CM,CRACK_FRONT_NODE_CMn

CINT,NEW,1

CINT,CENC,CRACK_FRONT_NODE_CM1,,11,2

CINT,CENC,CRACK_FRONT_NODE_CM2,,11,2

...

CINT,CENC,CRACK_FRONT_NODE_CM2,,n,2

Example 2

! Crack-extension node component and

! crack-extension direction specification using vectors

NSEL,S,LOC,X,Xctip1

NSEL,R,LOC,Y,Yctip1

NSEL,R,LOC,Z,Zctip1

CM,CRACK_FRONT_NODE_CM1

NSEL,S,LOC,X,Xctip2

NSEL,R,LOC,Y,Yctip2

NSEL,R,LOC,Z,Zctip2

CM,CRACK_FRONT_NODE_CM2

...

NSEL,S,LOC,X,Xctipn

NSEL,R,LOC,Y,Yctipn

NSEL,R,LOC,Z,Zctipn

CM,CRACK_FRONT_NODE_CMn

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Numerical Evaluation of Fracture Mechanics Parameters