Quantitative Analysis of Weld-Pore Size and Depth and Effect on Fatigue Life of Ti-6Al-2Zr-1Mo-1V Alloy Weldments
Abstract
:1. Introduction
2. Materials and Methods
3. Results
3.1. S–N Curves and Scatter of Fatigue Life
3.2. Fracture Analysis
3.3. Measurements of Pore Diameter and Depth
4. Discussion
4.1. Location of Crack Initiation
4.2. The Effect of Pore Diameter and Depth on Fatigue Life
4.3. Method of Validation
5. Conclusions
- (1)
- For all specimens, fatigue crack initiations occurred at the weld pores.
- (2)
- An indicator P was proposed to combine the effect of pore diameter and depth. An expression (Equation (5)) of P was provided based on the finite element analysis, and it has been accessed by the measurements of diameter and depth of pores on fracture surfaces in this study. Results showed that all the fatigue cracks initiated from the pore with the smallest P, which suggests that P can be used to judge the critical pore.
- (3)
- A model based on S–N curve and indicator P was established to evaluate quantitatively the effect of pore size and depth on fatigue life, and it can be applied under arbitrary stress conditions and specimen thicknesses. The indicator P could explain 62.8% of the information of indicator F, which means that the scatter of fatigue life of welded joints is mainly caused by the weld pores.
- (4)
- The model was validated through analogous fatigue tests. The results showed that the indicator P successfully judged the critical pore, and the calculated fatigue life were well consistent with the actual fatigue life. Moreover, the proposed model has been proved to have a higher accuracy for fatigue life estimation in comparison with several typical models.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Al | Zr | Mo | V | O | N | Ti |
---|---|---|---|---|---|---|
6.3 | 1.97 | 1.4 | 1.4 | 0.08 | 0.01 | Other |
Material | Tensile Strength (MPa) | Elongation (%) |
---|---|---|
Base metal | 1018.8 | 15.3 |
GTAW joint | 979.0 | 5.5 |
Frequency | Stress Ratio | Stress Amplitude | Number of Samples |
---|---|---|---|
70 Hz | 0.06 | 370 MPa | 2 |
325 MPa | 2 | ||
282 Mpa (Group A) | 5 | ||
260 MPa | 3 | ||
245 MPa | 2 | ||
238 MPa | 2 | ||
230 MPa | 1 | ||
70 Hz | −1 | 500 MPa (Group B) | 5 |
450 MPa | 2 | ||
400 MPa | 2 | ||
360 MPa | 2 | ||
345 MPa | 3 | ||
330 MPa | 2 | ||
320 MPa | 1 |
Stress Ratio | b | ||
---|---|---|---|
0.06 | 7.7148 | −1.1747 | 238 |
−1 | 58.2091 | −1.6569 | 330 |
Specimen Number | Pore Number | Pore Diameter (mm) | Pore Depth (mm) | Actual Fatigue Life (Cycle) | Indicator P | Calculated Fatigue Life (Cycle) |
---|---|---|---|---|---|---|
V1 | P11 P12 P13 | 0.2674 * 0.1205 0.1122 | 0.6210 * 0.3231 0.3891 | 539.9 4197.4 5842.2 | ||
V2 | P21 P22 | 0.1607 0.1514 * | 0.4770 0.2514 * | 2192.5 1741.6 |
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Zhang, W.; Liu, X.; Wang, H.; Dai, W.; Fu, G. Quantitative Analysis of Weld-Pore Size and Depth and Effect on Fatigue Life of Ti-6Al-2Zr-1Mo-1V Alloy Weldments. Metals 2017, 7, 417. https://doi.org/10.3390/met7100417
Zhang W, Liu X, Wang H, Dai W, Fu G. Quantitative Analysis of Weld-Pore Size and Depth and Effect on Fatigue Life of Ti-6Al-2Zr-1Mo-1V Alloy Weldments. Metals. 2017; 7(10):417. https://doi.org/10.3390/met7100417
Chicago/Turabian StyleZhang, Weifang, Xiaopeng Liu, Hongxun Wang, Wei Dai, and Guicui Fu. 2017. "Quantitative Analysis of Weld-Pore Size and Depth and Effect on Fatigue Life of Ti-6Al-2Zr-1Mo-1V Alloy Weldments" Metals 7, no. 10: 417. https://doi.org/10.3390/met7100417