# A Comparative Analysis of 3D Software for Modeling Fatigue Crack Growth: A Review
## 2 Software
### Numerical-Based Approaches
#### 2.1.2. FRANC3D  
FRANC3D is a powerful three-dimensional fracture analysis code that specializes in simulating crack growth in complex, non-planar geometries. It employs a sub-modelling technique, which involves creating a global finite element mesh encompassing the crack and a more refined sub-model near the crack region to accurately extend its growth. The meshing strategy in FRANC3D consists of concentric rings around the crack. The initial ring closest to the crack is constructed using quarter-point singular wedge elements, which provide accurate stress and displacement solutions near the crack tip. Subsequent rings are generated using hexahedral elements for efficient representation of the surrounding material. To evaluate the stress intensity factors along the crack front, FRANC3D offers two methods: the M-integral and the displacement correlation technique. These techniques allow for the extraction of stress intensity factors at discrete points along the crack front, providing valuable insights into crack propagation behavior. FRANC3D is a powerful software tool used for simulating fatigue crack growth in complex structures. Here are some advantages of using FRANC3D for this purpose:  
* In terms of fatigue crack growth analysis, FRANC3D supports various established models for estimating crack growth rates. These models utilize well-known relationships between fatigue loading, crack size, and material properties. Additionally, users have the flexibility to input their own user-defined data or custom models to capture specific fatigue crack growth behavior. * One notable feature of FRANC3D is its ability to generate both surface and volume meshes [33]. This versatility allows for compatibility with other finite element or boundary element programs, enabling seamless integration into existing analysis workflows. * Integration with ANSYS: FRANC3D works in conjunction with ANSYS, a widely used finite element analysis (FEA) software. It leverages ANSYS's capabilities for meshing, stress analysis, and other complex simulations. FRANC3D inserts and grows cracks within the ANSYS finite element mesh, making it a valuable extension for fatigue analysis [34; 35]. Several studies have extensively explored the application of FRANC3D in modeling fatigue crack growth. [PERSON] [36] enhanced the software's capabilities to represent realistic damaged structures and to model stable tearing, which proved beneficial for predicting residual strength. [PERSON] [22] proposed an algorithm specifically designed for simulatingfatigue crack growth under non-proportional mixed-mode loading, with a particular emphasis on thin-walled, hollow cylinders. [PERSON] [37] developed a three-dimensional finite element fatigue crack closure model that incorporated closure effects to predict crack growth rates. There are certain limitations associated with modeling fatigue crack growth using FRANC3D software. Some of these limitations include the following:  
* Geometrical complexity: FRANC3D may have difficulties in handling highly complex crack geometries, such as branched cracks or cracks in non-standard shapes. The software is primarily designed for simpler crack configurations [33]. * Mesh generation: Generating an appropriate mesh for crack propagation simulations can be challenging in FRANC3D. It may require manual intervention or additional pre-processing steps to achieve accurate and efficient meshing [38]. * Computational resources: Fatigue crack growth simulations in FRANC3D can be computationally intensive, especially for large and complex models. Adequate computational resources, such as processing power and memory, may be required to perform simulations within reasonable time frames [39]. * Material models: FRANC3D may have limitations in terms of the variety of material models available for fatigue crack growth simulations. It is essential to ensure that the selected material model accurately represents the behavior of the material being analyzed [40].