General

• The use of the *MAPPING option NORMAL=YES to try to force element edges to be normal to the crack front for quarter circular crack-blocks is modified in this release. In previous versions if the meshing was such that normal edges could not be generated, the analysis would simply switch to using edges that were not normal. If, at some later point during the analysis, the crack shape became such that normal edges could be achieved, they would be used. In this release, if normal edges cannot be achieved during generation of the initial cracked mesh, the request for normal edges is turned off for the whole analysis.
• The update of pressure load in the crack region retains more precision in the load magnitude than in previous releases. This applies for all f.e. interfaces.
• Pasqrt(mm) and Pasqrt(m) units have been added for stress intensity factors in the unit conversion utility which is included with the documentation (FMunitconversion.htm).

Abaqus interface

• The plug-ins for Abaqus/CAE are updated to version 2.1 to address some minor issues identified in the plugins released with Zencrack 7.7 (including bug ZENCR393). These upgraded plugins are provided for Abaqus 6.10 (and later) and separately for Abaqus 6.8 and 6.9.

Ansys interface

• A converter program was introduced in Zencrack 7.7 to help address data formats in an Ansys uncracked mesh file that were not handled by Zencrack. The work in this area has continued with a particular emphasis on support for files created via the "Tools / Write Input File" option from within the Ansys Workbench (Mechanical) environment. A number of data formats that were not previously supported can now be handled. Specific changes have been made to improve functionality with Workbench files:
  • The update of pressure load in the crack region now supports the use of parameters to define the load magnitude. Previously only numeric pressure values were allowed.
  • Update of pressure loads in the crack region was previously only available if load was applied directly on specific target elements using the SFE option. For pressure loading, Workbench produces a file with loaded surface elements (type SURF154) overlaying the mesh. This was not supported by Zencrack and pressure loads in the crack region would not be updated (or, more likely, an error would occur). Support for update of SURF154 surfaces on crack-blocks is now included.
  • Update of applied boundary displacements in the crack region was previously only possible if the fixities were applied directly on nodes using the D option. For fixities, Workbench produces a file which creates a CMBLOCK component then selects the component and applies the fixities. There was previously no support for CMBLOCK. This is now addressed and the node list of each CMBLOCK is updated (if necessary) by examining the contents of the list in relation to the current crack-block positions. By updating the CMBLOCK definitions in this way, the applied fixities are also correctly updated in the cracked mesh.
  These changes, plus other smaller modifications that have been made in the converter, mean that many Workbench derived files will be ready for use in Zencrack without the user having to make any manual changes.
• The processing of Ansys results is further enhanced in this release. The Zencrack output file now includes cross-referencing of the extracted results to the full list of steps and substeps in the Ansys analysis e.g.:

   ANSYS STEP AND SUBSTEP DATA
   ***************************
    Step  Substep  Time
       1     1     1.000000E+00  -> results set number    1
       2     1     1.100000E+00
       2     2     1.200000E+00
       2     3     1.300000E+00
       2     4     1.400000E+00
       2     5     1.500000E+00
       2     6     1.600000E+00
       2     7     1.700000E+00
       2     8     1.800000E+00
       2     9     1.900000E+00
       2    10     2.000000E+00  -> results set number    2
       3     1     3.000000E+00  -> results set number    3
       4     1     4.000000E+00  -> results set number    4
       5     1     5.000000E+00  -> results set number    5
  

  In addition, the steps and substeps of the Ansys analysis from which Zencrack extracts results can be controlled in the Zencrack input file using the STEPS option on the *ENERGY RELEASE RATE keyword. The above example shows the default, which is to extract results from the last substep of every step. To process, for example, all available results, the Zencrack input file simply requests the results output frequency to be 1 from step 1 onwards:

  *ENERGY RELEASE RATE, STEPS
  1 1
  

  The steps parameter can also be used with a frequency of zero to omit results from certain steps, if required.
• The options that allow a search through the available results sets when constructing Zencrack "load systems" now allow use of the START STEP, START INC, END STEP and END INC parameters to define the extent of the search. This allows direct cross referencing to the Ansys step definitions. Previously with the Ansys interface a search was less precise in terms of the results that could be searched and was particularly difficult in a non-linear analysis where the number of sub-steps was not known in advance.
  These changes in the results extraction and cross-referencing in the load systems mean that the full power of the load system methodology can be used with the Ansys interface in exactly the same way as for the Abaqus interface.
• J-integral values for symmetric models require application of a factor of 2 to account for the region which is not explicitly modelled. In previous releases of Zencrack the "raw" calculation requested in the Ansys cracked model analysis did not include this factor and instead the factor was applied by Zencrack when the results were processed. This is now modified such that the "raw" calculation in Ansys includes the factor of 2 when it is necessary. This does not affect analysis results from Zencrack, but gives improved clarity in data in the Ansys output file.