The uncracked mesh can be created in any suitable pre-processor for the finite element interface that is being used for the analysis. Zencrack simply uses the ASCII input file that would be used for analysis of the uncracked mesh by the finite element code e.g. the .inp file for Abaqus, the command sequence or .inp file for Ansys or the .dat file for Simcenter Nastran.
The uncracked mesh contains all relevant material definitions, boundary constraints, loading and any other data necessary to generate a valid input file for the uncracked specimen.
There are no restrictions on the mesh in terms of the required crack position other than:
- The remeshed region must lie within one element type (i.e. the remesh region cannot include hex and tet element).
- The remeshed region should not cross a tied interface between elements of the same type.
- The remeshed region must contain a single material definition. This restriction can be removed by defining material properties via the Abaqus USDFLD subroutine.
The mesh must be constructed in such a way that the required initial defect(s) can be inserted by replacement of one or more elements in the mesh by crack-blocks. If the analysis is based on an existing mesh it may be possible to re-use the mesh with little or no modification. If starting from a blank sheet of paper it is usually best to sketch out the required meshing in the crack region before starting the creation of the model. This is particularly true in a crack growth analysis for which the mesh must be sensible for the initial crack and some anticipated larger crack.
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