Crack Growth Simulation Techniques in CRACK3D
So far there are three approaches of crack growth simulation techniques having been implemented to CRACK3D to meet users various needs, (1) nodal pair releasing approach, (2) local remeshing approach and (3) cohesive zone model. Each approach has its advantage. Nodal pair releasing approach is useful for users to reconstruct data of crack growth history along a known crack path and to understand failure mechanism of material (e.g. why and how it happened). Local remeshing approach is efficient for predicting when and where failure will occur in structures. It is also helpful for researchers to verify their fracture criterion proposed. Cohesive Zone Model (CZM) can also be used to predict the initiation and growth of cracks in structures.
For more information about the methodology and computational aspects of crack growth simulation, please refer to the publication (Zuo, Deng, Sutton, Proceedings of ASME International Mechanical Engineering Congress, 2004).
Crack Growth Simulation Using Nodal Pair Releasing Techniques (Figure 1)
The crack path should be given in advance
There are two nodes sharing the same location on the top and the bottom crack surfaces
The two nodes in each nodal pair on free crack surfaces can move independently
The two nodes in each nodal pair on prospective crack surfaces are tied by a rigid spring element with zero in length
Crack growth is simulated by breaking nodal pairs where a specified fracture criterion is satisfied.
Fig 1. Schematics of nodal pair releasing approach
Crack Growth Simulation Using Local Remeshing Techniques (Figure 2)
Determine the local region to be remeshed
Perform surface remeshing on the local region surfaces unconnected with the surrounding regions
Perform volume remeshing in the local region
Combine the local region mesh with those of the surrounding regions
Map results from the previous mesh to the new mesh
Update the topological geometry of the entire structure after remeshing due to crack extension
|Fig 2. Schematics of local remeshing approach|
Crack Growth Simulation Using Cohesive Zone Model (CZM)
Cohesive interface elements are inserted, where needed, between adjacent solid elements (Fig. 3)
The deformation of cohesive interface elements is governed by the user-specified cohesive law
Crack initiation and growth are simulated by the change of traction/gap over cohesive interface elements
Fig 3. Schematics of cohesive zone modeling