# A Comparative Analysis of 3D Software for Modeling Fatigue Crack Growth: A Review
## 2 Software
### Numerical-Based Approaches
#### 2.1.3 Zencrack  
ZENCRACK is a commercially available software that has been specifically developed for conducting linear elastic fracture mechanics analyses. However, it also possesses the capability to effectively analyze three-dimensional fatigue crack problems [43; 44; 45]. ZENCRACK provides several benefits for fatigue crack growth simulation, which encompass the following:  
* Incorporation of Multiple Defects: ZENCRACK enables engineers to include multiple defects within a component during the analysis process. This flexibility allows for a more accurate representation of real-world scenarios, enhancing the reliability of the simulation [46].
* Support for Complex Loading Conditions: ZENCRACK offers extensive support for various complex loading conditions. This includes the consideration of residual stress resulting from shot pening [47], the analysis of time-dependent or sustained load crack growth, as well as the ability to perform fatigue-only and time-only analyses. Additionally, ZENCRACK facilitates the investigation of combined fatigue and time-dependent crack growth phenomena.
* ABAQUS Plug-in: ZENCRACK is a freely distributed plug-in specifically designed to be used with the commercial finite element (FE) software ABAQUS.  
Although ZENCRACK proves to be a valuable software tool for fatigue crack growth analysis, it is important to acknowledge certain limitations associated with its usage. These limitations of ZENCRACK in the context of fatigue crack growth analysis include the following:* Meshing limitations: ZENCRACK relies on external FE packages for mesh generation, which means it inherits any limitations or challenges associated with those packages. The complexity of creating meshes for highly intricate crack geometries or non-standard shapes can pose difficulties in accurately representing the crack and its surrounding region [48; 49; 50; 51]. ZENCRACK does not have its own mesh generator. Instead, it relies on external general-purpose finite element (FE) packages like ABAQUS [43; 44], ANSYS [45; 46], and MSC.MARC [47] to create the mesh for the uncracked geometry. The mesh generation process, including the creation of pure hexahedral elements throughout the structure, is performed using these external FE packages.
* Crack front tracking: ZENCRACK assumes a predefined crack front and does not account for changes in crack growth direction during the analysis. This limitation can be problematic when dealing with complex crack growth paths or situations where crack branching occurs [45; 46].
* Material models: The range of available material models in ZENCRACK for fatigue crack growth analysis may be limited. It is crucial to ensure that the selected material model accurately represents the behavior of the material under fatigue loading conditions.
* Remeshing limitations: Although ZENCRACK introduces crack-block elements to refine the mesh around the crack front, some limitations and numerical errors associated with remeshing have been reported in the literature. These issues may affect the accuracy of crack growth predictions or introduce computational challenges [52; 53].
* Computational resources: Like any software conducting complex simulations, a fatigue crack growth analysis in ZENCRACK can be computationally demanding. Adequate computational resources, such as processing power and memory, may be required to perform simulations within reasonable time frames.