Zencrack is an advanced engineering analysis tool, developed by Zentech International Limited, for 3D fracture mechanics assessment and crack growth simulation. The program uses finite element analysis to allow calculation of fracture mechanics parameters such as energy release rate and stress intensity factors. This is achieved by automatic generation of focused cracked meshes from uncracked finite element models. A mixed-mode capability allows non-planar crack growth prediction for fatigue and time-dependent load conditions via automated adaptive meshing techniques.
Rather than using a proprietary finite element solution, the Zencrack interface to Ansys allows users to take advantage of the many man-years of development within Ansys. For example non-linear features such as contact may be included in an analysis.
Zencrack uses Zentech's proprietary ‘crack-block’ methodology to quickly and easily generate 3D finite element models of cracked components from user-supplied uncracked meshes. Such uncracked meshes may be created in Ansys APDL, Ansys Workbench or any other Ansys pre-processor. The Zencrack GUI allows the initial crack positions(s) in the model to be specified in relation to the uncracked mesh. Attributes of the uncracked mesh such as surface definitions, pressure loads or boundary supports which exist in the crack region are updated as necessary when the crack(s) are introduced into the model. The user retains control of the method of crack tip modelling (i.e. midside or quarter point nodes, single or multiple nodes at each crack front position). If crack growth is required additional data such as loading history and crack growth law are also defined.
The Zencrack GUI then generates a new input file of the cracked component which may optionally be previewed before submitting an analysis. The analysis process runs Ansys and extracts results from the Ansys output. The results are processed automatically to provide energy release rates and stress intensity factor distributions.
For static or transient loading without crack growth, Zencrack can evaluate and report SIFs, j-integrals and T-stresses along one or more crack fronts. Both linear and non-linear analyses can be undertaken using a range of the available capabilities in Ansys. This means that, for example, SIFs may be calculated for a single load case or through the time history of a transient loading sequence.
For crack growth analysis, Zencrack predicts the magnitude and direction of 3D crack growth along each crack front and automatically advances each crack through the F.E. model in a series of Ansys analyses. Several options are available for crack growth data definition ranging from simple Paris and Walker equations through to a user subroutine capability for complex proprietary data. All crack growth data and materials data may be temperature dependent and cracks in multiple materials can be considered within a single analysis. A flexible ‘load system’ approach is provided for defining load histories which may be simple constant amplitude loading to complex thermo-mechanical and non-linear loading histories with fatigue and/or time dependent crack growth.
The crack growth integration scheme calculates the cycle count as the crack advances, allowing full effect of complex loading, geometry and crack growth data to be taking into account when predicting an accurate and consistent crack shape. This means that, for example, parts of the crack front may be below threshold and not growing during some or all of the load cycle and this is reflected in the on-going crack shape.
Post-processing of analysis results in the Zencrack GUI allows fast visualisation of crack surface development and generation of a variety of xy plots related to the crack behaviour. During a crack growth sequence the various Ansys output files may be saved at each step to allow standard F.E. post-processing of the cracked meshes.
Zencrack can be applied in any industry and application in which knowledge of crack behavior, crack growth prediction or residual life calculations are important.
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