The Fracture condition is used to treat two elastic domains with imperfect bonding. The fracture can, for example, be a thin elastic layer, a fluid-filled layer, or it can be a discontinuity in elastic materials (an interior boundary). Typical applications are for modeling nondestructive testing (NDT) applications, like the response of delamination regions or other defects, or for modeling wave propagation in fractured solid media in the oil and gas industry. Add this node from the Interior Conditions submenu.

Select the Coordinate system used to define vector and tensor quantities in the feature (the spring constants). The Boundary System (sys1) is used per default.

Select the Stiffness type to define the properties of the fracture, as Stiffness per unit area, Stiffness per unit length, Total stiffness, or Use material data.

For Stiffness per unit area, Stiffness per unit length, and Total stiffness enter the value of the spring constant (kA, kL, or ktot, respectively) with the appropriate units. Then select the tensor/matrix representation of the spring constant as Isotropic, Diagonal, or Symmetric. For Isotropic, the same spring constant is used in all the diagonal elements of the spring matrix.

When Use material data is selected as Stiffness type, the spring constant stiffness values are computed from material data and layer thickness. From the Specify list, select a pair of elastic properties — Young’s modulus and Poisson’s ratio, Young’s modulus and shear modulus, or Bulk modulus and shear modulus. Each of these pairs define the elastic properties and it is possible to convert from one set of properties to another according to Table 3-3. For the chosen properties, select from the applicable list to use the value From material or enter a User defined value or expression. In order to use From material, you must have assigned a material to the selected boundaries.

Enter a Thickness ds to specify the physical thickness of the elastic layer.

Select the time stepping Method used to solve the system of ODEs that describes the elastic properties of the fracture. Select Boundary ODEs (the default) to solve the ODEs using the same method as the physics solver specified in the Study; or select Backward Euler to solve the ODEs using first order backward Euler.

To display this section, click the Show More Options button () and select Advanced Physics Options. Select the Allowed region. Here you can modify how a particular features act as a fallback feature on the nonoverlapping parts, using the Allowed region list with the options Fallback and nonpair regions (the default), Nonpair region, and All regions. For the first and default option, the feature has the fallback behavior described above. Select the Nonpair region option if you do not want the feature to act as a fallback feature at all. All parts of the feature’s selection that overlaps with any pair feature will then be excluded from the feature’s selection. Choose the All regions option if you want the feature to contribute to the entire selection, including the parts where the pair is in contact. The feature’s conditions will then contribute also with pair features conditions.