XFEM elements allow simulations where the unknown fields are enriched through the partition of unity concept. Two elements are currently available for 2D XFEM simulations: TrPlaneStress2dXFEM (subclass of TrPlaneStress2d) and PlaneStress2dXfem (subclass of PlaneStress2d).
Keyword  TrPlaneStress2dXFEM 
Description  Two dimensional 3node triangular XFEM element 
Specific parameters  [czmaterial #(in)] [nipcz #(in)][useplanestrain #(in)] 
Parameters  czmaterial: Interface material for the cohesive zone. (If no material is specified, traction free crack surfaces are assumed.) 
nipcz: Number of integration points used on each segment of the cohesive zone. 

useplanestrain: If plane strain or plane stress should be assumed. 0 implies plane stress and 1 implies plane strain. 

Unknowns  Two continuous (standard) DOFs (udisplacement, vdisplacement) and a variable number of enriched DOFs (can be continuous or discontinuous). 
Approximation   
Integration  Elements cut by an XFEM interface are divided into subtriangles. 
Features   
CS properties   
Loads   
Nlgeo   
Status   
Note  Test case: sm/xFemCrackVal.in 
Keyword  PlaneStress2dXfem 
Description  Two dimensional 4node quad XFEM element 
Specific parameters  [czmaterial #(in)] [nipcz #(in)][useplanestrain #(in)] 
Parameters  czmaterial: Interface material for the cohesive zone. (If no material is specified, traction free crack surfaces are assumed.) 
nipcz: Number of integration points used on each segment of the cohesive zone. 

useplanestrain: If plane strain or plane stress should be assumed. 0 implies plane stress and 1 implies plane strain. 

Unknowns  Two continuous (standard) DOFs (udisplacement, vdisplacement) and a variable number of enriched DOFs (can be continuous or discontinuous). 
Approximation   
Integration  Elements cut by an XFEM interface are divided into subtriangles. 
Features   
CS properties   
Loads   
Nlgeo   
Status   
Note  Test cases: sm/xFemCrackValBranch.in, sm/xfemCohesiveZone1.in, benchmark/xfem01.in 