Study on the Surface Crack Growth Behavior in 14MnNbq Bridge Steel
Three-dimensional crack closure correction methods are investigated in this paper. The fatigue crack growth tests of surface cracks in 14MnNbq steel for bridge plate subjected to tensile and bending loadings are systematically conducted. The experimentally measured fatigue crack growth rates of surface cracks are compared with those of through-thickness cracks in detail. It is found that the crack growth rates of surface cracks are lower than those of through-thickness cracks. In order to correct their differences in fatigue crack growth rates, a dimensionless crack closure correction model is proposed. Although this correction model is determined only by the experimental data of surface cracks under tensile loading with a constant ratio R = 0.05, it can correlate the surface crack growth rates with reasonable accuracy under tensile and bending loadings with various stress ratios ranging from 0 to 0.5. Furthermore, predictions of fatigue life and crack aspect ratio for surface cracks are discussed, and the predicted results are also compared with those obtained from other prediction approaches. Comparison results show that the proposed crack closure correction model gives better prediction of fatigue life than other models.
Key wordscrack closure correction model surface crack growth bridge steel structures fatigue life prediction
Unable to display preview. Download preview PDF.
- Chen, C.Y. and Li, G.Q., Final Report on the Fatigue Crack Growth Behavior and its Application to Welded 14MnNbq Components of Tianxingzhou Bridge. Wuhan: Huazhong University of Science and Technology (Publication), 2007 (in Chinese).Google Scholar
- Li, G.Q., Zhu, S.Z., Li, J.B. and Chen, C.Y., Study of full range fatigue crack growth behavior of 14 MnNbq welds. Bridge Construction, 2006, 4: 4–6 (in Chinese).Google Scholar
- Foroughi, R. and Radon, J.C., Crack closure behaviour of surface cracks under pure bending. ASTM STP, 1988, 982: 260–269.Google Scholar
- Troha, W.A., Nicholas, N. and Grandt, Jr A.F., Three-dimensional aspects of fatigue crack closure in surface flaws in Polymethylmethacrylate material. ASTM STP, 1988, 982: 598–616.Google Scholar
- Jolles, M. and Tortoriello, V., Effects of constraint variation on the fatigue crack growth of surface flaws. ASTM STP, 1984, 833: 300–311.Google Scholar
- Liu, Y.P., Chen, C.Y., Li, J.B. and Li, G.Q., Fatigue crack growth behavior for the weld heat-affected zone of 14MnNbq Bridge steel. Engineering Mechanics, 2008, 25(2): 209–213 (in Chinese).Google Scholar
- Standard practice for fracture testing with surface-crack tension specimens. ASTM E740-88, 1995, 621–628.Google Scholar