# A New Method for Fatigue Evaluation of Titanium Alloy Welded Structures
## 6 Conclusions  
1. At present, most of the existing fatigue studies of titanium alloys are based on the S-N curve, and there are very few studies on the fatigue properties of titanium alloy welded structures with stress singularities. This study proposes a new fatigue life prediction method that takes stress singularities into account, namely the augmented-reverse notch equivalent stress method. A new three-parameter power function model and a calculation method of the notch equivalent stress correction coefficient are proposed. The augmented-reverse notch equivalent stress method is obtained by combining the above two.
2. Through the research on the classification of joint grades in the BS7608 standard, the welded joint structure with the same joint grade is found, and the classification  
Figure 11: Cross joint for verification (2) [29].  
Figure 12: Comparison of test results and prediction results of verification (2).  
of titanium alloy welded joints is compared with this. Combined with the fatigue test data of titanium alloy welded joints, the fatigue life under each stress range was determined. A new three-parameter power function model of titanium alloy welded structure proposed in this study was established. According to the calculation method of the notch equivalent stress correction factor proposed in this study, the correction factor suitable for the titanium alloy welded structure is obtained. Two prediction models, the traditional three-parameter power function model and the new three-parameter power function model, were selected to quantitatively characterize the relationship between the stress range and fatigue life of titanium alloy welded structures, and the two fitting results were compared and analyzed.
3. The augmented-reverse notch equivalent stress method was verified using fatigue test data different from the above titanium alloy welded structures. The verification results show that the augmented-reverse notch equivalent stress method improves the effectiveness and accuracy of fatigue life evaluation and finds a new life evaluation method for titanium alloy welded structures with stress singularities.  
In this study, a new method for fatigue life evaluation of titanium alloy welded structures with stress singularities, namely the augmented-reverse notch equivalent stress method, is proposed. The limitation of this paper is that the fatigue test data of titanium alloy welded structures are limited. If the fatigue test data are added, the results will be more accurate and convincing. The new method proposed in this paper is suitable for materials other than titanium alloys and can be used as a new direction for fatigue life prediction research of other materials.  
Writing--original draft preparation, software, and methodology, Z.Z.; validation, Y.W.; data curation, C.Y.; formal analysis, Q.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Railway Group Science and Technology Research and Development Plan Project (Project No. K2021)006) and the National High-speed Train Technology Innovation Center Research and Development Project (Project No. CXKY-02-01-03(2020)).  
Not applicable.  
The data that support the plots within this paper and other findings of this study are available from the corresponding author on request.  
The authors declare no conflict of interest.