9.15. Detect Breach

The breach detection capability enables automatic detection of a breach creating an open path between two user-defined surfaces via element. This capability can be used to predict when venting of a pressure vessel begins due to an open crack. The BEGIN DETECT BREACH block is defined in the region scope with the following command block:

BEGIN DETECT BREACH <string>breachName
  SURFACE1 = <string list>surface1_names
  ASSEMBLY1 = <string list>assembly1_names
  SURFACE2 = <string list>surface2_names
  ASSEMBLY2 = <string list>assembly2_names
END [DETECT BREACH]

The breachName string is required, as it defines a global variable with the same name that initializes to 0 and changes to 1 when breach is detected. Within the DETECT BREACH block, two line commands are required: surface1 = sideset1 sideset2 ... or assembly1 = assembly1_1 assembly1_2 ... and surface2 = sideset3 sideset4 ... or assembly2 = assembly2_1 assembly2_2 .... Assemblies used for assembly1 and assembly2 may contain surfaces, or assemblies of these. These command lines set the “inner” and “outer” surfaces for detecting breach between. An arbitrary number of detect breach blocks are allowed.

The algorithm is implemented by identifying clusters of dead elements. If two dead elements share a node, then they are considered to be in the same cluster. (An alternative implementation could consider dead elements to be in the same cluster only when they share a face; however, that is not the version currently implemented.) If a cluster of dead elements has an adjacent face in both surface_1 and surface_2, then we say breach has occurred between those surfaces (see Figure Fig. 9.17).

Fig. 9.17 Breach detection between surfaces 1 and 2. Dead elements in red.

The death cluster id number can be output as either an element or nodal variable named dead_element_cluster_id. The nodal variable version is only used for implementing the clustering algorithm, but the element variable dead_element_cluster_id can be output and used by analyst scripts to compute quantities of interest for the dead element clusters such as the volume, minimum cross-sectional area, moments of inertia, etc.

Warning

This capability is currently only tested for bulk 3D elements such as hexahedra and tetrahedra. The capability will not work with shells. Additionally, the capability has no knowledge of tied contacts; thus a breach can only propagate between mesh-contiguous elements.

Warning

If using detect breach variables such as the dead_element_cluster_id element variable in a user output you must add “process elements = all” to your user output block.