What's New in Zencrack?

Zencrack 9.0-1

Zencrack version 9.0-1 was finalised on 25 January 2022

This version contains a completely new remeshing capability to speed up the creation of meshes containing cracks:

  • mesh-independent geometry definition of initial crack with remeshing for the initial crack and subsequent crack growth
  • remeshing capability in the Abaqus interface
  • all crack-block meshing capabilities from previous Zencrack versions remain available
  • available for Windows 10 (Windows 7 and Windows 8 also supported)

Remeshing Capability

A new remeshing capability provides mesh independent crack insertion into an uncracked mesh. This approach simplifies the creation of 3D models containing cracks by using a purely geometric definition of an initial crack.

An existing uncracked mesh can be used "as-is" with, in most cases, no need to perform special partitioning or meshing of the uncracked geometry. This means that, for example, a single uncracked mesh can be used to develop models of significantly different cracks by simply changing the geometric crack definition.

  • initial crack and crack growth
    • remeshing for analysis of initial crack only
    • remeshing for general non-planar 3D crack growth using the existing load system methodologies in Zencrack for fatigue, time dependent and combined fatigue/time crack growth prediction
  • geometric definition of an initial crack
    • initial crack location is fully independent of the underlying mesh
    • the underlying mesh may contain hex or tet elements
    • crack at a symmetry plane, surface breaking or fully embedded
    • initial crack shape may be straight or elliptic (either full ellipse or elliptic arc)
  • remeshed region split into hex rings and surrounding tets
    • rings of hex elements at the crack front with ring mesh density controlled by the user
    • tet mesh surrounding the rings
    • fully automatic calculation of the extent of the remeshed tet region and mesh density within that region (with manual control if desired)
  • support for static, thermal and coupled analyses
    • update of displacement boundary conditions, pressure loads, surface definitions, film coefficients and temperatures in the remesh region
    • optional application of pressure and/or film coefficients to the crack face

The remeshing capability is fully supported in the Zencrack GUI with options to preview various aspects of the initial crack definition, including:

  • option to define geometric positional data by picking nodes in the uncracked mesh
  • preview of the geometric crack definition
  • preview of the hex rings at the crack front
  • preview of the remesh region
  • preview of the remesh region with the crack inserted

Definition of elliptic crack position plus ring preview
Definition of elliptic crack position plus ring preview

Ring elements and remesh region preview
Ring elements and remesh region preview

Remeshed region preview
Remeshed region preview

Completed mesh with elliptic crack
Completed mesh with elliptic crack

Other developments in Zencrack

  • Implementation of crack growth direction from stress intensity factors based on the work of Richard et al.
    • Ref: H.A.Richard, M.Fulland, M.Sander, Theoretical crack path prediction, Fatigue Fract Engng Mater Struct 28, 3-12, 2005.
  • Extension of the processing available for interaction integrals to allow them to be used to drive a crack growth analysis.
  • Support for the Ansys option for specifying the auxiliary field solution when calculating interaction integrals: mixed, plane stress or plane strain.
  • Re-working of some of the options on the *ENERGY RELEASE RATE keyword to accommodate some of the above changes and to allow future additions.

Changes in the Zencrack GUI

  • New input, preview and display options to support the new remeshing capability for crack insertion into an uncracked mesh (see additional examples below).
  • Re-working of the Energy Release Rate screen to accommodate the changes described above.
  • Improved performance for large meshes (faster import and manipulation).
  • Import and optional display of the material regions defined in a mesh.
  • Identification of disconnected mesh regions.
  • Labelling of profiles when displaying crack growth profile results.
  • Labelling of splines (Input Tab crack front splines and Display Tab splines).
  • Ability to add multiple meshes into one viewport.
  • Ability to display some types of surface definitions (initially to support remeshing previews).

Examples of remeshing - crack growth

This section presents four examples of crack growth prediction, each carried out in a single automated analysis.

Inclined straight starter crack in a 4-point bend specimen with a hole

An initially inclined crack which straightens and grows past the hole. The final animation shows a straight through (not inclined) starter crack located closer to the hole. This deviates towards the hole rather than growing past it.

Zencrack example SEN with hole - mesh
Zencrack example SEN with hole - 1 crack - mesh displaced
Inclined embedded elliptic crack in square section test specimen under tension

Initially a mixed mode defect but quickly turning to mode I. As this is an internal defect some of the images below show cut-aways to reveal part of the mesh and the full crack surface.

Zencrack example DISPLACE specimen - mesh
Zencrack example DISPLACE specimen - crack growth step 17 mises cutaway
Semi-elliptic starter crack in a test specimen under bending

Initial semi-elliptic surface crack grows through the specimen cross-section.

Zencrack example specimen bending - mesh
Zencrack example specimen bending - mesh displaced
Circular corner crack in a connecting rod

Initial corner crack grows into the mail part of the rod cross-section.

Zencrack example connecting rod - mesh
Zencrack example connecting rod - mesh