When setting up a C*-integral calculation, consider the following hints and recommendations:
The recommended element type for 3D fracture models along the crack tip is the 3D 20-node structural solid (brick) element SOLID186.
A fine sweep mesh along the crack front yields more accurate results.
When contour results begin with the first ring of elements around crack tip nodes (PATH 1 in Figure 44.16: C*-integral Along the Crack Front -- Rectangular Block and Figure 44.20: C*-integral Along the Crack Front -- X-Joint Pipe with Warped Flaw), the first contour result is discarded. In such cases, experience has shown that the first contour it is less accurate than other contours due to highly concentrated local deformation.
The C*-integral could be path-independent only when steady-state creep deformation dominates the integration domain around the crack tip.