## 1 Introduction
The application of empirical models such as Kitagawa-Takahashi diagrams [26] and defect size parameterization techniques such as fractography and X-ray microcomputed tomography (\(\mu\)-CT) has enhanced the interest in establishing a relationship between internal defect size and resistance to fatigue crack initiation. A recent study on defect analysis of defect distributions revealed that, even though 2D pictures may display the same patterns in defect creation, 2D representation cannot match the accuracy of 3D analysis in \(\mu\)-CT, as shown by exhaustive statistical testing. The use of the threshold approach to measuring the impact of internal defects considers them from the outset as a notch or pre-crack, which contradicts the role of microstructure in slip band development near the pore [27]. In the presence of internal defects, especially at critical locations, it is widely acknowledged that the latter phase of fatigue life is marginal. Other efforts employ microcomputed tomography (\(\mu\)-CT) to construct three-dimensional finite element models that imitate the shape of the interior pores, as has been portrayed progressively in the systematic review. The mechanical behavior of porous AM biomaterials has lately attracted a growing amount of attention. Despite the availability of a substantial amount of information about the static mechanical characteristics of such biomaterials [28], this fatigue behavior is not yet fully understood. This is owing in part to the fact that a comprehensive examination of the fatigue behavior of these porous biomaterials is time-consuming and costly due to the vast number of parameters involved. It was claimed that a computational approach based on the finite element method might be used to predict the fatigue behavior of porous biomaterials, given the kind of repeating unit cell, unit cell diameters, and S-N curve of the material. The suggested method to predict the fatigue behavior of porous titanium alloy bio-materials created using Selective Laser Melting (SLM) on the rhombic dodecahedron unit cell is compared with experimental findings [29]. It was observed that these anomalies significantly reduce fatigue life, especially at lower stress levels. Based on the aforementioned summary of the many difficulties impacting the AM components, it is apparent that there is a multitude of concerns. It indicates that the process must be adjusted to decrease the number of manufactured defects. To reduce the amount of trial-and-error experimental procedures, the option of using process design tools and improving the geometry of structures and characterization of materials may be of considerable benefit [30]. It is common knowledge that numerical modeling and simulation may lower production costs. Common to numerical techniques is the practice of doing calculations at specified nodes and then interpolating the results across the full domain as volume or surface [31]. To get a deeper understanding of the mechanical and operating principles of a process, numerical simulation would be a useful tool [32]. Most simulations use mesh-based methods and, in some cases, combined models. These include the Finite Element Method (FEM), the Discrete Element Method (DEM), the Finite Difference Method (FDM), and the Finite Volume Method (FVM). These methods are often used to solve boundary, initial, and eigenvalue problems [33]. FVM is used to examine the melt pool, pores, and surface contraction of structures [34]. ANSYS, ABAQUS, COSMOL, NASTRAN, MATLAB, AFGROOW, and custom-built programs are examples of commercially available software used to solve problems [35]. From the previous literature review. * [PERSON] et al. [36] criticized the mechanical behavior of SLM Ti-6 Al-4V alloy in terms of microstructure, residual stress, and surface roughness. Changes in morphology during processing and heat treatment cause faults that affect fatigue behavior at different stages. Conclusions are reached on the pros and limitations of defect investigation approaches, including cost and time efficiency.