**6. Conclusions**

This chapter has documented a systematic review of previous works on fatigue and fracture analysis by considering the CP approach of weld joints. As per the findings, several models based on the CPFEM methodology have standard features and details the micro-damage initiation and transition to failure. As indicated in numerous articles, the hardening model has a significant role in influencing computational outcomes. It is because hardening law can be directly related to depicting the defect formation mechanism in materials and that "transforms" to the microdamage structure. The anisotropy of crystal can largely influence the micro-damage formation system to the extent of each grain and by grain lattice rotation adjacent to the crack tip region.

Several new approaches in context to fatigue analysis are reported in the literature duly supported with pertinent details. It is seen that the proposed models have their limitations and certain conditions, i.e., low cycle fatigue or high cycle fatigue, uniaxial and multiaxial loading, and material type (ductile or brittle), etc. Unfortunately, no model is found to fit perfectly under variable loading and material conditions. It leaves a wide gap for further research and development to the precise and reliable prediction of fatigue life under different conditions. The chapter was intended to present a short review to explore novel concepts and techniques, such as, CPFEM, to analyze and predict the fatigue life of weld joints, unlike some classical approaches, which lack to have a generalized algorithm to model the fatigue life. Future research should be oriented to the implementation of optimization models/algorithms in order to explore their full capability for accurately predicting the fatigue properties of metal structures or welded joints.
