Fatigue crack propagation in engineering materials has been the subject of considerable research, and extensive review articles have appeared over the past several years. Most of these investigations focused on the behaviour of ‘long’ fatigue cracks, even though the characteristics associated with the extension of small cracks in metals and alloys remain relatively unexplored, despite their unquestionable importance from an engineering standpoint. In this review, the mechanics and micromechanisms of the subcritical growth of short fatigue cracks are examined, and aspects of their propagation behaviour are contrasted with those of long cracks in terms of fracture mechanics, microstructure, and environment. Cracks are defined as being short (i) when their length is small compared to relevant microstructural dimensions (a continuum mechanics limitation), (ii) when their length is small compared to the scale of local plasticity (a linear elastic fracture mechanics limitation), or (iii) when they are s...

Propagation of short fatigue cracks

Quantitative evaluation of effects of non-metallic inclusions on fatigue strength of high strength steels. I: Basic fatigue mechanism and evaluation of correlation between the fatigue fracture stress and the size and location of non-metallic inclusions

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Effects of Small Defects and Nonmetallic Inclusions on the Fatigue Strength of Metals

Fatigue tests were carried out on mild steel with small cracks for which linear fracture mechanics is not effective. A fatigue limit criterion, based on the cyclic plastic zone size at a crack tip being a material constant at the fatigue limit, can effectively evaluate the effects of crack length and stress ratio. Regarding flaws as cracks, the theory gives fatigue limit values close to those obtained in experiments on specimens with natural defects, such as surface roughness, micro-shrinkage cavities, inclusions etc. The effect of water corrosion was also investigated.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1460-2695.1979.tb01334.x

Elastic–plastic analysis of the fatigue limit for a material with small flaws

Critical review of the fatigue growth of short cracks

Fatigue tests were carried out on mild steel plate specimens with various lengths of cracks. The relation between the alternating fatigue limit σw and the crack length was well expressed by following equation. Rp(c)w = αe(sec πσw/2σy - 1 ) = const. where, Rp(c)w is the cyclic plastic zone size at fatigue limit, αe is the equivalent crack length of an infinite plate, and σy is the yield strength of the material. The size of the persistent slip band zone on the fatigue limit is about one tenth of Rp(c)w and is nearly equal to the measured mean grain size of the material. Rp(c)w has close relations with the crack length corresponding to the fatigue limit of a plain specimen, the material constant which was already obtained in the criteria of fatigue crack initiation at notch roots, and the critical notch root radius at the branch point.

Fatigue Limit of Steel with Cracks

Endurance Limit-Hardness Relationship for High Carbon Low Alloy Steel

Fatigue Strength Of Steel Shafts Built-Up by Welding

It is well-known that the enormous increase in fatigue strength of case hardened steel is due to the high compressive residual stress in the material and to the doubled hardness caused by heat treatment, and that the effect of the residual stress on the endurance limit can be accounted for by taking it as the mean stress.In this paper the fatigue test results which were obtained of the carburized and induction hardened steel, have been re-examined from the viewpoint of crack propagation process. It appears that the fatigue strength of case hardened steel can be regarded as resistance against fatigue crack propagation in the specimen having minute flaw, because, in highly hardened material, the micro inclusions and metallurgical discontinuity can be taken as the origins of fatigue cracks.

The Effect of Residual Stress on the Fatigue Strength of Case Hardened Steel

The fatigue crack propagation behaviors were investigated on HT80 steel plates under net section stress control in which stress range and minimum stresses were widely varied. The fatigue crack growth rates were proportional to the effective crack length 2ae which was an actual crack length 2a modified by the finite width effect of the specimen. When minimum stress δmin was in compression side, the growth rate depended on maximum stress δmax and in tension side, it depended on stress range Δδn. As the result, the effects of crack length, stress range and minimum stress on the fatigue crack propagation can unifyingly be shown such that the crack growth rate is proportional to the cyclic plastic zone size at a crack tip[numerical formula]. Where, δy is yield strength of material and δn is δmax when δmin≤0 and is Δδn When δmin≥0

https://www.jstage.jst.go.jp/article/kikai1938/39/321/39_321_1403/_pdf

Studies on the Fatigue Crack Initiation and Propagation : Report 1,Effects of Crack Length, Stress Range and Minimum Stress on Fatigue Crack Propagation

Hisashi Ohuchida

Papers

Fatigue Limit of Steel with Cracks

Endurance Limit-Hardness Relationship for High Carbon Low Alloy Steel

Fatigue Strength Of Steel Shafts Built-Up by Welding

The Effect of Residual Stress on the Fatigue Strength of Case Hardened Steel

Studies on the Fatigue Crack Initiation and Propagation : Report 1,Effects of Crack Length, Stress Range and Minimum Stress on Fatigue Crack Propagation