Crack Paths 2006

In this example, a part of a compressor meshed with 20-node hexahedral elements is

considered. One quarter of an elliptical crack is to be inserted. The procedure to reach the

final consistent triangulation of the cracked structure consists of five steps:

1. A cylindrical surface triangulation is created along the crack-front. This cylinder is to

be filled with (collapsed) hexahedral elements at a later stage of the project, yielding

accurate values for the stress intensity factor.

2. The cylindrical surface is merged with the uncracked structure yielding a triangulation

of the so-called perforated structure.

3.

The crack face is duplicated and slightly movedapart.

4. The crack faces are merged with the perforated structure yielding the final

triangulation of the cracked structure.

3. T H EF L E X I B LCEY L I N D E R

The cylinder should be created along the part of the crack boundary that is inside the

uncracked structure only. A first step is therefore to identify the boundaries of the crack.

Then, the intersection points of the crack boundaries and the triangles of the uncracked

structure are identified. This allows for the identification of the inside parts of each crack

boundary. A flexible cylindrical surface triangulation, just sticking out slightly, is generated

along each such part of the crack boundaries, Figure 3.

Figure 3. The uncracked structure and the flexible cylinder (without and with the

triangular surface mesh displayed).