General enhancements

• The restriction on model sizes that existed in previous versions of Zencrack has been removed. The only limits on the number of nodes and elements are now due to available memory and formatting restrictions.
• The upper limit of 500 split element pairs in a split set has been removed. There is no longer any upper limit on the number of split pairs in a split set subject to available memory.
• The maximum number of load systems used to define a load spectrum has been increased from 40 to 80.
• A number of algorithms have been improved to provide performance enhancements. This is most noticeable on large jobs with highly irregular / non-consecutive node and element numbers and jobs with a large number of elements in the relax element list.
• A new algorithm for fixing up the elements surrounding the crack blocks has been developed to help reduce element distortion. The algorithm is activated on the SURROUND FIX option on the *BOUNDARY SHIFT keyword. An example of the reduction in element distortion from this option is seen here.

• It is now possible to distribute the crack front nodes evenly along the
  crack front. This is done with the SPLINE FIXUP parameter on the *CRACK FRONT keyword. An example of the benefit of this algorithm is shown here.

• The algorithm that controls transfer of crack-blocks to a new location when boundary shifting is set to TYPE=transfer has been modified. Previously the crack front would transfer as soon as any of the crack-blocks on the crack front met the transfer criteria. Now at least half of the crack-blocks must meet the transfer criteria before the transfer takes place. This is beneficial in producing better meshes for crack fronts that develop faster at one end than the other.
• A change has been made in the checks for inside-out elements in the cracked mesh. Previously Zencrack would stop before generating the cracked mesh if any inside-out elements were found at the end of the relaxation algorithm. This made it difficult to see where the problems were located in the mesh. The new procedure is that Zencrack always checks for inside-out elements before writing the cracked mesh. If any are found, a message is generated in the .rep file. The analysis progresses, however, in order that the cracked mesh can be assessed in a pre/post-processor. The analysis will stop at the f.e. pre-processing stage due to the inside-out elements.
• The number of element rings around the crack front and the numbers of contours that can be evaluated are now independent items. This allows more control over crack-blocks that have some special requirements in terms of the element rings.
• The number of contour rings that can be processed has been increased to accommodate the largest available crack-blocks. Previously only eight contours could be processed even if the crack-blocks could allow calculation of more than eight values.
• The direction for crack growth prediction that is calculated from stress intensity factors now uses the maximum tangential stress criterion rather than the inverse tangent criteria that was used in previous releases.
• The direction for crack growth can be specified as based on energy or displacement based results, independently of the method used for calculating the magnitude of crack growth.
• It is now possible to run all the supplied demo examples using the evaluation version of Zencrack.
• A capability is added to allow remote execution of the finite element code on a Unix machine when Zencrack is installed on a Windows machine. This differs from the normal setup in which Zencrack and the finite element code are executed on the same machine.
• If the output filename for a job is not specified in the input file, a default string is added to the zcr filename. This string can now be defined by the user.

Crack-block library

• The crack-block library has been revised to group crack-blocks into "families". This has meant that crack-blocks have been renamed. Existing job files will automatically switch to the new crack-block names with a warning generated in the .rep file.
• In addition to the use of families, three of the old crack-blocks have been removed and eight new crack-blocks are provided.
• The switch to this family based approach allows straightforward addition to the library in the future.