PSI - Issue 39

Wei Song et al. / Procedia Structural Integrity 39 (2022) 204–213 Author name / Structural Integrity Procedia 00 (2020) 000–000

212

9

(a)

0.6

(b)

0.4

M=1

SED model Pershagen model Proposed energy model

M=1 M=0.9 M=0.8 M=0.7

Elastic-Plasitc Elastic

SED model

0.5

0.3

0.4

WT fracture

0.3

0.2

WT fracture

p/t

p/t

WR fracture

WR fracture

0.2

0.1

Tension

Tension

0.1

0.4 0.6 0.8 1.0 1.2 1.4 0.0

0.2 0.4 0.6 0.8 1.0 1.2 0.0

h/t

h/t

(a) Comparison of different models (b) Different mismatch ratio Fig. 6 Comparison of transition curve between weld root and weld toe under different mismatch ratio

4. Conclusion In this work, an analytical model for predicting effective notch energy indicators in LCWJ has been established based on elastic-plastic mechanical theory. It can illustrate the fatigue failure transition relationship at the WT and WR locations in different regimes. The mismatch ratio is incorporated to exhibit the difference in effective notch energy variations under various loading conditions. The verification analysis and comparative illustration are conducted to verify the validity of the proposed analytical model. The investigations about fatigue failure of LCWJ in this study indicate the following main conclusions: Three essential parameters, mismatch ratio(M), penetration length ratio (p/t), weld length ratio (h/t), affect the fatigue failure transition relationship between WT and WR locations. An analytical model is established to characterize effective notch energy in elasto-plastic mechanical regime, representing the combined effects of these factors. The relationship among the notch stain, energy and the geometrical factors were investigated systematically. The effective notch energy approach can be regarded as the fatigue characteristic indicator. The notch energy estimations of LCWJ from the model are in good agreement with the magnitudes by elasto-plastic FEM results. In terms of the energy-life curves, it can be effective to assess the fatigue failure transition of LCWJs in HCF and LCF regimes. 5. References [1] Hobbacher A., Recommendations for fatigue design of welded joints and components: IIW document IIW-1823-07 ex XIII-2151r4-07/XV 1254r4-07, Recommendations for Fatigue Design of Welded Joints and Components (2008). [2] Lotsberg I., Sigurdsson G., Hot spot stress S-N curve for fatigue analysis of plated structures, Journal of Offshore Mechanics and Arctic Engineering 128(4) (2006) 330-336. [3] Dong P., Hong J.K., The master S-N curve approach to fatigue of piping and vessel welds, Welding in the World 48(1-2) (2004) 28-36. [4] Kyuba H., Dong P., Equilibrium-equivalent structural stress approach to fatigue analysis of a rectangular hollow section joint, International Journal of Fatigue 27(1) (2005) 85-94. [5] Lu H., Dong P., Boppudi S., Strength analysis of fillet welds under longitudinal and transverse shear conditions, Marine Structures 43 (2015) 87-106. [6] Alencar G., Hong J.K., Jesus A. de, J.G.S. Silva da, Calçada R., The Master S-N curve approach for fatigue assessment of welded bridge structural details, International Journal of Fatigue 152 (2021) 106432. [7] Wang P., Pei X., Dong P., Song S., Traction structural stress analysis of fatigue behaviors of rib-to-deck joints in orthotropic bridge deck, International Journal of Fatigue 125 (2019) 11-22. [8] Wei Z., Jin H., Chen G., Traction structural stress analysis of fatigue behaviors of girth butt weld within welded cast steel joints, International Journal of Pressure Vessels and Piping 179 (2020). [9] Xing S., Dong P., Threstha A., Analysis of fatigue failure mode transition in load-carrying fillet-welded connections, Marine Structures 46 (2016) 102-126.