## 1 Introduction
For the purpose of assessing the fatigue behaviour of additively manufactured Ti-6 Al-4V alloys, the Tanaka-Mura model takes the intuitive flaw size into account, but it does not investigate the coupling connection between the depth and flaw size or the average size impact of flaws [42]. The effect of porosity on fatigue in TC17 titanium alloy welded joints was investigated by [PERSON] et al. [43]. While the welded joints' S-N (stress-cycles to failure) curves were bilinear at 400 \({}^{\circ}\)C, they remained single-linear at room temperature. Fatigue failure was induced by welded pores, and temperature had no effect on it. Using both experimental and artificial neural network (ANN) research, [PERSON] et al. [44] investigated the tensile properties and failure mechanisms of the RSW of titanium grade 2 alloy. Finally, [PERSON] et al. [45] explored the influence of microstructure and chemistry on time-dependent plasticity in titanium alloys, particularly under dwell fatigue conditions. Their findings indicate that elevated temperatures can suppress cold dwell fatigue, thus providing a broader context for understanding the fatigue performance of titanium alloys under varying operational conditions. This research highlights the necessity of considering temperature and microstructural effects in the fatigue assessment of welded joints, particularly in titanium applications. [PERSON] et al. [46; 47] conducted fatigue, fracture, and tensile deformation on titanium alloys with lamellar and bimodal microstructures. Their findings confirmed that the lamellar shape has higher strength than the bimodal structure. The ductile failure behaviour of welded joints made of high-strength steel, carbon steel, austenitic stainless steel (304), and duplex stainless steel was investigated by [PERSON] et al. [48]. The results showed that the BM and HAZ had better fracture toughness than other steel types. The weld seam region of stainless steel, on the other hand, had a lower fracture toughness than BM. This means that the seismic performances of beam-column joints and energy dissipation components require careful attention in this region. The experimental research by [PERSON] et al. [49] sought to ascertain the endurance limit of spot-welded connections between galvanised steel sheets and AISI 304 austenitic stainless steel. Their findings indicate that similar steel combinations have a higher endurance limit than dissimilar ones. This is because the heat imbalance between the steel sheets causes them to have different material properties, particularly electrical resistance, and the resulting antisymmetric nugget shape. The fatigue strength of the RSW joints had been reduced due to this difference in the nugget shape. In their assessment of fatigue performance, [PERSON] et al. [50] distinguished between similar and dissimilar RSW joints made of mild steel and dual-phase steel (DP600). Evidence from fatigue tests showed that DP600 outperformed mild steel. The fatigue behaviour of AISI 304 austenitic stainless steel was studied by [PERSON] et al. [51] for both equal and unequal thicknesses. The researchers found that unequal-thickness sheets had greater tensile shear and fatigue strengths than equal-thickness sheets, even though the nugget diameter was smaller. The fracture behaviour of joint components made of several grades of austenitic stainless steel (AISI 301 L, AISI 304, AISI 316 L, and AISI 321) was examined by [PERSON] et al. [52] using butt welding. Tensile test findings showed that 301 L welded joints had significantly reduced tensile qualities compared to the BM, but the 304 L, 316 L, and 321 grades had no change in tensile values. Fracture behaviour is seen at the weld centre for 301 L, at the HAZ for 304 and 316 L, and at the BM for 321. The numerical fracture prediction model for 304 stainless steel was proposed by [PERSON] et al. [53], utilising the modified Johnson-Cook damage model. Tests were performed on AISI 304 LN stainless steel by [PERSON] et al.