Abstract
The role of crack tip shielding in retarding the initiation and growth of fatigue cracks has been examined in metallic composite microstructures (consisting of hard and soft phases), with the objective of achieving maximum resistance to fatigue. Specifically, duplex ferritic-martensitic structures have been developed in AISI 1008 and 1015 mild steels to promote shielding without loss in strength. The shielding is developed primarily from crack deflection and resultant crack closure, such that unusually high long crack propagation resistance is obtained. It is found that the fatigue threshold ΔK TH in AISI 1008 can be increased by more than 100 Pct to over 20 MPa Vm, without sacrifice in strength, representing the highest ambient temperature threshold reported for a metallic alloy to date. Similar but smaller increases are found in AISI 1015. The effect of the dual-phase microstructures on crack initiation and small crack (10 to 1000 ώm) growth, however, is markedly different, characteristic of behavior influenced by the mutual comPctition of intrinsic and extrinsic (shielding) “toughening” mechanisms. Accordingly, the composite microstructures which appear to show the highest resistance to the growth of long cracks, show the lowest resistance to crack initiation and small crack growth. In general, dual-phase steels are found to display remarkable fatigue properties, with fatigue limits as high as 58 Pct of the tensile strengths and fatigue thresholds in the range of 13 to 20 MPaVm.
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R. O. Ritchie and W. Yu: inSmall Fatigue Cracks, R. O. Ritchie and J. Lankford, eds., TMS-AIME, Warrendale, PA, 1986, pp. 167–89.
R.O. Ritchie, R. H. Dauskardt, and R.M. Cannon: Lawrence Berkeley Laboratory Report No. LBL-20656, University of California, Berkeley, C. A, Dec. 1986.
R.M. McMeeking and A. G. Evans:J. Amer. Cer. Soc, 1982, vol. 65, pp. 242–46.
A. G. Evans and K.T. Faber:J. Amer. Cer. Soc, 1984, vol. 67, pp. 255–60.
D. B. Marshall, B.N. Cox, and A. G. Evans:Acta Metall., 1985, vol. 33, pp. 2013–21.
S. Suresh:Metall. Trans. A, 1983, vol. 14A, pp. 2375–85.
S. Suresh and R.O. Ritchie: inFatigue Crack Growth Threshold Concepts, D.L. Davidson and S. Suresh, eds., TMS-AIME, Warrendale, PA, 1984, pp. 227–61.
R.O. Ritchie, S. Suresh, and C. M. Moss:J. Eng. Matls. Tech., Trans. ASME, Ser. H, 1980, vol. 102, pp. 293–99.
A. T. Stewart:Eng. Fract. Mech., 1980, vol. 13, pp. 463–78.
S. Suresh, G. F. Zamiski, and R. O. Ritchie:Metall. Trans. A, 1981, vol. 12A, pp. 1435–43.
N. Walker and C.J. Beevers:Fat. Eng. Mat. Struct., 1979, vol. 1, pp. 135–48.
K. Minakawa and A.J. McEvily:Scripta Metall.. 1981, vol.6, pp. 633–36.
S. Suresh and R.O. Ritchie:Metall. Trans. A, 1982, vol. 13A, pp. 1627–31.
J.-L. Tzou, C.H. Hsueh, A.G. Evans, and R.O. Ritchie:Acta Metall.. 1985, vol. 33, pp. 117–27.
W. Eiber:Eng. Fract. Mech., 1970, vol. 2, pp. 37–45.
W. F. Deans and C. E. Richards:J. Test. Eval., 1979, vol. 7, p. 147.
J.C. Newman, Jr. and I.S. Raju:Eng. Fract. Mech., 1981, vol. 15, pp. 185–92.
R. O. Ritchie:Int. Metals Reviews, 1979, vol. 20, pp. 205–30.
H. Suzuki and A.J. McEvily:Metall. Trans. A, 1979, vol. 10A, p. 475.
K. Minakawa, Y. Matsuo, and A. J. McEvily:Metall. Trans. A, 1982, vol. 13A, p. 439.
J. A. Wasynczuk, R.O. Ritchie, and G. Thomas:Mat. Sci. Engr., 1984, vol. 62, pp. 79–92.
V. B. Dutta, S. Suresh, and R.O. Ritchie:Metall. Trans. A, 1984, vol. 15A, pp. 1193–207.
J.-L. Tzou and R.O. Ritchie:Scripta Metall., 1985, vol. 19, pp. 751–55.
M.R. Mitchell: inFatigue and Microstructure, ASM INTERNATIONAL, Metals Park, OH, 1979, pp. 385–466.
C. F. Shih:J. Mech. Phys. Solids, 1981, vol. 21, p. 305.
T. Kunio and K. Yamata: inFatigue Mechanisms, ASTM STP 675, J. T. Fong, ed., American Society for Testing and Materials, Philadel- phia, PA, 1979, pp. 342–61.
T. Konio, M. Shimizu, K. Yamata, and H. Nakabayashi: inFatigue Thresholds, J. Bäcklund, A. F. Blom, and C. J. Beevers, eds., EMAS Ltd., Warley, U.K., 1982, vol. 1, pp. 409–22.
J. Lankford:Fat. Fract. Eng. Mat. Struct., 1985, vol. 8, pp. 161–75.
S. Suresh and R.O. Ritchie:Int. Metals Reviews, 1984, vol. 29, pp. 445–76.
A. Pineau: inSmall Fatigue Cracks, R. O. Ritchie and J. Lankford, eds., TMS-AIME, Warrendale, PA, 1986, pp. 191–212.
L. Wagner, J.K. Gregory, A. Gysler, and G. Liitjering: inSmall Fatigue Cracks, R.O. Ritchie and J. Lankford, eds., TMS-AIME, Warrendale, PA, 1986, pp. 117–28.
K. T. Venkateswara Rao, W. Yu, and R. O. Ritchie:Scripta Metall., 1986, vol. 20, pp. 1459–65.
R.O. Ritchie and J. Lankford:Mater. Sci. Eng., 1986, vol. 84, pp. 11–16.
J. Lankford and D. L. Davidson: inSmall Fatigue Cracks, R. O. Ritchie and J. Lankford, eds., TMS-AIME, Warrendale, PA, 1986, pp. 51–72.
R. Steinbrech, R. Knehans, and W. Schaarwachter:J. Mat. Sci., 1983, vol. 18, pp. 265–70.
J.M. Larsen, T. Nicholas, A. W. Thompson, and J. C. Williams: inSmall Fatigue Cracks, R.O. Ritchie and J. Lankford, eds., TMS- AIME, Warrendale, PA, 1986, pp. 499–512.
J. Pctit, S. Suresh, A. K. Vasudévan, and R. C. Malcolm: inAluminium-Lithium Alloys III, C. Baker, P.J. Gregson, S.J. Harris, and C.J. Peel, eds., Institute of Metals, London, U.K., 1986, pp. 257–62.
K. V, Jata and E. A. Starke, Jr.:Metall. Trans. A, 1986, vol. 17A, pp. 1011–26.
W. Yu and R. O. Ritchie:J. Eng. Maus. Tech., Trans. ASME, Ser. H, 1987, vol. 109, pp. 81–85.
K. T. Venkateswara Rao, W. Yu, and R. O. Ritchie:Metall. Trans. A, in press.
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Formerly with the Department of Materials Science and Mineral Engineering, University of California, Berkeley, CA 94720, is with National Semiconductor Corporation, Santa Clara, CA 95051.
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Shang, J.k., Tzou, J.L. & Ritchie, R.O. role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures. Metall Trans A 18, 1613–1627 (1987). https://doi.org/10.1007/BF02646145
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DOI: https://doi.org/10.1007/BF02646145