Add a J-integral subnode under a Crack node in order to compute the J-integral along a certain integration path. When a J-integral has been computed, stress intensity factors will also be available.

The J-integral node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).

Enter the Radius of contour integral, rΓ. The default value is an expression of the form solid.<crack_tag>.crackSize*0.5. The variable crackSize is estimated from the crack geometry. For common cases, in particular in 2D, this is exactly the length of the crack. For more complex cases, in particular for branched cracks, there is no well-defined crack length, and the value of the variable must be considered only as being of the right order of magnitude.

Select Number of integration points — Fixed number or Relative to path length.

When Fixed number is selected, enter the total number of points along the integration path, NΓ.

When Relative to path length is selected, enter a relative number of points along the integration path, nΓ. The total number of integration points is computed as

where rΓ is the radius of the integration path, and Lcrack is the crack length (as represented by the variable solid.<crack_tag>.crackSize).

Select Number of integration points — Fixed number or Relative to enclosed area.

When Fixed number is selected, enter the total number of integration points on the enclosed surface, NA.

When Relative to enclosed area is selected, enter a relative number of points on the enclosed surface, nA. The total number of integration points is computed as

where is the radius of the integration path, and Lcrack is the crack length (as represented by the variable solid.<crack_tag>.crackSize).

The default is that the region used for the evaluation starts at a distance of 20% of the crack length from the tip, and extends to half the crack length. You can modify these values by entering a Lower bound, b, and an Upper bound, c.

Physics tab with Crack node selected in the model tree: