Issue 33

M.-L. Zhu et alii, Frattura ed Integrità Strutturale, 33 (2015) 67-72; DOI: 10.3221/IGF-ESIS.33.09 72 C ONCLUSIONS he evolution of normal strain range with cycle has been captured in situ during the fatigue crack growth experiments using the DIC technique in a compact tension specimen of stainless steel 316L. Generally, the normal strain range measured is between 4% and 13% near the crack tip, hence the relative error in the measurements is no more than 7.5%. A method to determine the crack tip location is proposed for a crack with a tortuous crack path. Strain ratchetting is observed in the near-tip field ahead of the crack tip, whilst normal strains behind the crack tip appear to be more stable. A CKNOWLEDGEMENTS LZ is supported by a Visiting Scholarship from China Scholarship Council. R EFERENCES [1] McClintock, F.A., On the plasticity of the growth of fatigue cracks, John Wiley & Sons Inc., New York, (1963). [2] Haigh, J.R., Skelton, R.P., A strain intensity approach to high temperature fatigue crack growth and failure, Mater. Sci. Eng., 36 (1978) 133-137. [3] Zhao, L.G., Tong, J., Byrne, J., The evolution of the stress – strain fields near a fatigue crack tip and plasticity-induced crack closure revisited, Fatigue. Fract. Eng. Mater. Struct., 27 (2004) 19-29. [4] Zhao, L., Tong, J., A viscoplastic study of crack-tip deformation and crack growth in a nickel-based superalloy at elevated temperature, J. Mech. Phys. Solids., 56 (2008) 3363-3378. [5] Lin, B., Zhao, L.G., Tong, J., A crystal plasticity study of cyclic constitutive behaviour, crack-tip deformation and crack-growth path for a polycrystalline nickel-based superalloy, Eng. Fract. Mech., 78 (2011) 2174-2192. [6] Huang, M., Tong, J., Li, Z., A study of fatigue crack tip characteristics using discrete dislocation dynamics, Int. J. Plast., 54 (2014) 229-246. [7] Tong, J., Zhao, L.G., Lin, B., Ratchetting strain as a driving force for fatigue crack growth, Int. J. Fatigue., 46 (2013) 49-57. [8] Tong, J., Lin, B., Lu, Y.W., Madi, K., Tai, Y.H., Yates, J.R., Doquet, V., Near-tip strain evolution under cyclic loading: In situ experimental observation and numerical modelling, Int. J. Fatigue., 71 (2015) 45-52. [9] Lu Y.-W., Lupton, C., Zhu, M.-L., Tong, J., In situ experimental characterization of near-tip strain evolution of fatigue cracks, Exp. Mech., (2015) In press. T M