# A Comparative Analysis of 3D Software for Modeling Fatigue Crack Growth: A Review
## 2 Software
### Numerical-Based Approaches
#### 2.1.6 COMSOL Multiphysics  
COMSOL Multiphysics is a versatile and comprehensive finite element analysis software that provides a robust platform for simulating and modeling various physical phenomena. It offers a range of modules and features that enable engineers to simulate complex multiphysics problems, including fatigue crack growth. Modeling fatigue crack growth using COMSOL Multiphysics offers several advantages:  
* COMSOL Multiphysics allows for the integration of multiple physics modules, such as structural mechanics, thermomechanical fatigue, heat transfer, and materials science. This capability enables users to simulate the complex interactions between different physical phenomena that influence fatigue crack growth [75; 76; 77].
* COMSOL provides a wide range of material models and allows for the creation of custom material models based on experimental data. This flexibility enables users to accurately capture the fatigue behavior of different materials, including metals, composites, polymers, and more. Users can incorporate material-specific properties, such as fatigue curves, fracture toughness, and cyclic plasticity, to enhance the accuracy of fatigue crack growth simulations [77].
* COMSOL Multiphysics allows users to define the geometry of the crack with high precision. Users can specify the crack shape, size, and orientation, ensuring an accurate representation of the actual crack [78; 79]. This level of detail is crucial for capturing the stress concentration and accurately predicting crack growth behavior.
* COMSOL Multiphysics offers advanced meshing techniques such as structured, unstructured, adaptive, boundary layer, swept, tetrahedral, and hexahedral meshing [80; 81]. The use of appropriate meshing techniques ensures reliable and accurate fatigue crack growth simulations.
* Powerful Post-Processing and Visualization: COMSOL offers powerful post-processing and visualization tools to analyze and interpret simulation results. Users can extract relevant quantities, such as stress intensity factors, crack growth rates, and fatigue life predictions. The software provides graphical representations, including contour plots, 3D visualizations, and animations, facilitating a deeper understanding of the crack growth behavior and aiding in the communication of findings [82; 83; 84].
* Phase-field modeling for fatigue fracture problems can be implemented and analyzed using tools such as MATLAB and COMSOL. These tools enable researchers to investigate and gain valuable insights into the applicability and feasibility of phase-field modeling for studying fatigue fracture phenomena [84; 85; 86].  
While the COMSOL Multiphysics Fatigue Module is a robust tool, it does have some limitations. Here are a few to consider:  
* Simplified Material Models: The module employs simplified material models for fatigue analysis. While these models are useful for many engineering applications, they may not capture all the intricacies of real-world materials.  
* The crack growth models assume certain conditions, such as linear elastic fracture mechanics (LEFM) and small crack sizes. These assumptions might not hold in all scenarios [78; 87].
* Like any finite element analysis software, COMSOL's results can be sensitive to mesh density. Proper mesh refinement is crucial for accurate fatigue predictions [88].
* The module does not explicitly account for environmental factors (e.g., humidity and corrosive agents) that can significantly influence fatigue behavior.
* While the module handles simple loading histories well, more complex loadings (e.g., non-proportional, variable amplitude) might require additional considerations.
* COMSOL primarily focuses on high-cycle fatigue (HCF). For low-cycle fatigue (LCF) or thermomechanical fatigue, additional care is needed [89; 90].
* User Expertise: Interpreting fatigue results requires expertise in both fatigue mechanics and the software. Users should understand the underlying assumptions and limitations.