Hostname: page-component-745bb68f8f-b95js Total loading time: 0 Render date: 2025-01-11T06:29:22.926Z Has data issue: false hasContentIssue false
  • English
  • Français

Non-Propagating Cracks in Vee- Notched Specimens Subject to Fatigue Loading

Published online by Cambridge University Press:  07 June 2016

N. E. Frost
N. E. Frost*
Affiliation:
Mechanical Engineering Research Laboratory, East Kilbride, Glasgow
Get access

Summary

Reversed direct stress and rotating bending fatigue tests have been carried out on Vee-notched specimens of aluminium alloy, nickel chromium steel and mild steel.

Diagrams are presented showing the relationship between the geometric stress concentration factor Kt and the strength reduction factor Kt. It was found that non-propagating cracks formed in the roots of the sharper notches. These cracks formed at or above some critical value of Kt, the value depending on the specimen material. Below the critical value of Kt, cracks did not form unless the applied nominal stress exceeded that at the fatigue limit, and a crack, once formed, continued to propagate until the specimen failed. Above the critical value of Kt, non-propagating cracks formed at nominal stresses less than the fatigue limit, the stress having to be increased to the latter value in order to propagate the crack. This critical value of Kt coincided with the maximum Kf value realised. It would appear that Kf equals Kt up to a certain value of Kt; there is then a transition where Kt reaches a maximum at the critical value of Kt. Increasing the value of Kt above the critical value causes no further increase and may tend to decrease the value of Kt.

The conclusions drawn apply only when the fatigue stresses are completely reversed, i.e. the mean load is zero.

Type
Research Article
Information
Aeronautical Quarterly , Volume 8 , Issue 1 , February 1957 , pp. 1 - 20
Copyright
Copyright © Royal Aeronautical Society. 1957

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Peterson, R. E. Stress Concentration Design Factors. John Wiley, New York, 1954.Google Scholar
2. Yen, C. S. and Dolan, T. J. A Critical Review of the Criteria for Notch Sensitivity in Fatigue of Metals. University of Illinois Engineering Experimental Station Bulletin Series No. 398, 1952.Google Scholar
3. Kuhn, P. and Hardrath, H. F. An Engineering Method for Estimating Notch Size Effect on Steel. N.A.C.A. T.N. 2805, October 1952.Google Scholar
4. Neuber, H. Theory of Notch Stresses. Published by Edwards, J. S., Ann Arbor, Michigan, 1946.Google Scholar
5. Phillips, C. E. and Heywood, R. B. The Size Effect in Fatigue of Plain and Notched Steel Specimens Loaded under Reversed Direct Stress. Proceedings of the Institution of Mechanical Enginers, Vol. 165, p. 113, 1951.CrossRefGoogle Scholar
6. Hikata, A. The Size Effect in Fatigue of Notch Steel Specimens Loaded under Reversed Direct Stress. Government Mechanical Laboratory Bulletin No. 2, Tokio, 1954.Google Scholar
7. Dolan, T. J. and Hanley, B. C. The Effect of Size of Specimen on the Fatigue Strength of S.A.E. 4340 Steel. University of Illinois Engineering Experimental Station, May 1948.Google Scholar
8. Hyler, W. S., Lewis, R. A. and Grover, H. J. Experimental Investigation of Notch Size Effects on Rotating Beam Fatigue Behaviour of 75S-T6 Aluminium Alloy. N.A.C.A. T.N. 3291, November 1954.Google Scholar
9. Ros, M. and Eichinger, A. The Fracture Danger of Solid Bodies under Repeated Stress Fatigue. (In German). Report No. 173, Eidgenössische Material Prüfungs-Industrie und Versuchsanstalt, Zürich, September 1950.Google Scholar
10. Mann, J. Y. Effect of Stress Concentrations on the Fatigue Resistance of 24 ST Aluminium Alloy. Aeronautical Research Laboratory Report S.M.217. Department of Supply, Australia, November 1953.Google Scholar
11. Frost, N. E. and Phillips, C. E. The Fatigue Strength of Specimens containing Cracks. Proceedings of the Institution of Mechanical Engineers, Vol. 170, No. 21, 1956.CrossRefGoogle Scholar
12. Fenner, A. J., Owen, N. B. and Phillips, C. E. A Note on the Fatigue Crack regarded as a Stress Raiser. Engineering, Vol. 171, p. 637, 1951.Google Scholar
13. Frost, N. E. Crack Formation and Stress Concentration Effects in Direct Stress Fatigue. Engineer, Vol. 200, pp. 464 and 501, 1955.Google Scholar
14. Forrest, P. G. and Tapsell, H. J. Correlation of Fatigue Strength in Bending and Direct Stress. Engineering, Vol. 173, p. 757, 1952.Google Scholar
15. Grover, H. J. Fatigue Notch-Sensitivities of some Aircraft Materials. Proceedings of the American Society for Testing Materials, Vol. 50, p. 717, 1950.Google Scholar
16. Bennett, J. A. and Weinberg, J. G. Fatigue Notch Sensitivity of Some Aluminium Alloys. Journal of Research, National Bureau of Standards, Vol. 52, No. 5, p. 235, 1954.Google Scholar
17. Spretnak, J. W., Fontana, M. G. and Brooks, H. E. Notched and Unnotched Tensile and Fatigue Properties of Ten Engineering Alloys at 25°C and -196°C. Transactions of the American Society of Metals, Vol. 43 p. 547, 1951.Google Scholar
18. Frost, N. E. Mechanical Engineering Laboratory Report PM 184, October 1955.Google Scholar