A Unified Method for the Prediction of the Fatigue Strength of Small-Hole-Containing Components under Combined Loading

Abstract:

A unified method is presented for the prediction of the fatigue strength of steel components containing small holes and being subjected to combined loading. Materials investigated were an annealed 0.37% carbon steel and a quenched and tempered Cr-Mo steel. Combined axial and torsional fatigue loading tests were carried out using specimens containing a small hole, which was introduced into the surface by drilling. The diameter of holes equaled the depth and was either 100µm or 500µm. The non-propagating cracks emanating in the radial direction from the holes were observed at the fatigue limit. When the loading condition is the same, they were on a plane that inclined at the same angle with respect to the specimen axis, regardless of the size of holes. This result suggested that the fatigue strength would be controlled by the Mode I threshold condition for propagation of a crack initiated on a critical plane. A criterion connecting uniaxial fatigue strength with multiaxial fatigue strength was proposed based upon the assumption that at the threshold level, the variation of the stress intensity factor of a Mode I crack initiated under combined loading equaled that under uniaxial loading. The predictive method proposed based upon this criterion is practical in that no fatigue test is necessary in making predictions. For the various conditions of in-phase and out-of-phase fatigue loadings with an imposed mean or static load, experimental results agreed well with predictions.

• Periodical: Key Engineering Materials (Volumes 297-300)
• Pages: 1929-1938
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.297-300.1929
• Online since: November 2005
• Authors: Isao Ishimoto, Masahiro Endo
• Keywords: Biaxial Stress, Combined Stress, Criterion for Fatigue Failure, Fatigue Strength Prediction, Imposed Static Stress, Mean Stress, Phase Difference, Small Crack, Small Holes

References

[1] Y. Murakami and M. Endo: Int. J. Fatigue Vol. 16 (1994), p.163.

[2] Y. Murakami: Metal Fatigue: Effects of Small Defects and Nonmetallic Inclusions (Elsevier, Oxford 2002).

[3] M. Endo: In: Small Fatigue Cracks: Mechanics, Mechanisms and Applications (Elsevier, Oxford 1999), p.375.

[4] M. Endo: In: Biaxial/Multiaxial Fatigue and Fracture (Elsevier, Oxford 2003), p.243.

[5] M. Endo and I. Ishimoto: Proc. 7th Int. Conf. Biaxial/Multiaxial Fatigue and Fracture (1994), p.465.

[6] S. Beretta and Y. Murakami: Fatigue Fract. Eng. Mater. Struct. Vol. 23 (2000), p.97.