A Historical Perspective
In the late 1980s, Zentech was contracted by RAE Farnborough  to develop methods for the analysis of elliptic and circular corner cracks in rectangular bars. The finite element work was undertaken with the Marc code for which Zentech was the U.K. agent from 1984 (to 1993).
At that time the Marc code included an implementation of the virtual crack extension technique based on the continuum mechanics approach developed by deLorenzi . This technique calculated the nodal energy release rates resulting from an applied virtual crack extension.
The initial work carried out by Zentech resulted in stand-alone routines that could be applied to simple elliptic geometries. These routines, which allowed the introduction of a crack into an uncracked Marc model, then carried out the processing of the nodal energy release rates to calculate local energy release rates.
Upon completion of the project, Zentech embarked on a new development utilising some of the RAE-based concepts to create a general software package. Crack growth and re-meshing routines for analysing a cracked component were added - leading to the first release of the Zencrack code in 1990. This version of Zencrack, which operated on VAX hardware running under VMS, was interfaced to version K4 of the Marc finite element program.
In February 1991, Zencrack was ported to Unix for implementation on a Convex at Alcan International in Banbury.
In 1993, (when the Marc organisation opened a U.K. office) Zentech started discussions with HKS to develop an interface between Zencrack and Abaqus version 5.2. That work culminated later in the year in the release of Zencrack version 4 for Abaqus and Marc. The new Abaqus interface was 'showcased' at a presentation to the Abaqus Users' Conference in Rhode Island in June 1994 .
Development of the code progressed over the next decade with ports to a variety of platforms and enhancements to the program capabilities. As finite element analysis moved onto the PC platform, so the first Windows version of Zencrack was released in 1998.
In the early 2000s, significant developments to Zencrack were undertaken for the Wright Patterson Airforce Base. Part of this work led to the addition of an interface to Ansys.
The release of Zencrack 7.5 in 2007 saw the availability of the first 64bit versions of Zencrack for the x86 processor with support for 64bit Windows and Linux.
The release of version 7.6 in 2009 included the first integration into Abaqus/CAE, with several stand-alone plug-ins to help develop the Zencrack input file. This capability was significantly enhanced in version 7.7, released in 2011, to allow full generation and review of the Zencrack input file from within the Abaqus/CAE environment, with the possibility to "pick" all required node and element data directly from the uncracked mesh.
The release of version 7.8 in 2012 included significant improvements in the high temperature and time dependent crack growth capabilities in Zencrack. Many of these changes were developed as part of a three year joint industry-academic project led by Rolls-Royce plc and named "DISPLACE" (a TSB-funded development of 'technology to increase the life & reliability of advanced lightweight Ni-based gas turbine discs').
The release of version 7.9 in 2013 included the Zencrack GUI. As well as replacing and extending the Abaqus/CAE plug-in capability for creating and maintaining Zencrack input files, the first GUI release contained post-processing for crack growth profile visualisation. The GUI provided the same features for all Zencrack users regardless of their chosen finite element interface. Enhancements to the GUI for versions 7.9-2 and 7.9-3 included XY plotting capabilities. The release of version 7.9-3 in 2015 introduced an interface to NX Nastran.
In 2016, the release of version 8.0 of Zencrack included enhancements in the GUI to remove the need for users to directly generate text input of keyword and data lines - all input data being handled on dedicated screens. Among other improvements, this allowed introduction of warning and error checking for the input data and control of how default values were handled when creating input data.
In 2017, the release of versions 8.1 and 8.2 of Zencrack included improvements in the mesh rendering options in the GUI making visualisation of crack growth profiles clearer and faster than had previously been possible. The 8.1 release also introduced a capability to allow a crack front to be defined across a material boundary.
In 2018, the release of version 8.3 of Zencrack included a new mesh rendering engine in the GUI and significantly faster import of meshes.
From 2018 to 2021 a new remeshing capability was developed. This was a significant development effort with an initial release in Zencrack 9.0-1 (January 2022) which allowed use of the remeshing capability for the Abaqus interface on Windows.
The remeshing method was made available for the Ansys interface with Zencrack 9.1-1 (November 2022). This release also provided the Zencrack GUI and remeshing capability for Linux.
Work continues to extend the remeshing capabilities with the first support for multiple cracks with the remeshing method introduced in Zencrack 9.3-1 (September 2023).
1. Royal Aircraft Establishment, re-named the Royal Aerospace Establishment in 1988. In 1991 the RAE was merged into the new Ministry Of Defence organisation the Defence Research Agency (DRA) and then merged again with other MOD organisations into the Defence Evaluation And Research Agency (DERA) in 1995. Part-privatisation of DERA in 2001 led to the creation of QinetiQ.
2. "On the Energy Release Rate And The J-Integral For 3-D Crack Configurations", de Lorenzi,H.G., Int. J. Frac., Vol.19 (183-193) 1982.
3. "Application of Abaqus to Analysis of 3D Cracks and Fatigue Crack Growth Prediction", C.Timbrell, P.W.Claydon, G.Cook, Abaqus Users' Conference, Rhode Island, U.S.A., June 1-3 1994.
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