Software > Zencrack > Overview > Under development

Zencrack 9.0-1 pre-release

A pre-release version allowing testing of the new remeshing capability described below is available upon request for Abaqus users on Windows 10. Please use our contact form to send us a request if you are interested.

Under development

New remeshing capability in Zencrack

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 above are functional developments, additional features are in progress

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.
  • Implementation of a non-linear Kujawski-Ellyin crack growth law.
    • Ref: M.Lepore, F.Berto, D.Kujawski, Non-linear models for assessing the fatigue crack behaviour under cyclic biaxial loading in a cruciform specimen, Theoretical and Applied Fracture Mechanics, Volume 100, 14-26, April 2019.
  • for crack-block models, creation of an output set of crack-blocks that are "ready to transfer".

Development work 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

Four examples of crack growth prediction, each carried out in a single automated analysis. Click thumbmails for full size image.

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

Uncracked mesh
Cracked region with displacement after some crack growth
Remeshing during crack growth
Remeshing during crack growth
Crack profiles
Remeshing during crack growth

Inclined embedded elliptic crack in square section test specimen under tension.
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.

Uncracked mesh
Cracked region with displacement after some crack growth
Remeshing during crack growth
Remeshing during crack growth (cut-away with cut surfaces shown)
Remeshing during crack growth (cut-away with cut surfaces removed)
Crack profiles

Semi-elliptic starter crack in a test
specimen under bending.

Uncracked mesh
Cracked region with displacement after some crack growth
Remeshing during crack growth
Remeshing during crack growth
Crack profiles

Circular corner crack in a connecting rod.
 

Uncracked mesh
Cracked region with displacement after some crack growth
Remeshing during crack growth
Remeshing during crack growth
Crack profiles

Additional remeshing examples

These examples show some of the remeshing input screens and the options that are available to control the definition of the remesh region.

Placement of crack into a specific region

Placement of crack into a specific region

Preview of crack front nodes with crack in a specifed region

Preview of crack front nodes; crack in a specifed region

Connecting rod, crack definition and remeshed region

Connecting rod, crack definition and remeshed region

Bracket, crack definition and remeshed region

Bracket, crack definition and remeshed region

Disk, crack definition and remeshed region

Disk, crack definition and remeshed region

Disk, larger crack size

Disk, larger crack size

Threaded connection, crack definition and remesh region

Threaded connection, crack definition and
remesh region

Threaded connection, confirmation of symmetry plane boundary condition updates and contact surface update

Threaded connection, confirmation of boundary condition updates and contact surface update (in Abaqus/Viewer)