Much remains to be learned about the impact fatigue of materials owing to the difficulty of impact-fatigue experiments, the complication of impact stress waves, and the different responses of materials to impact stresses. This article reviews the literature on the impact fatigue of matallic materials.

The impact-fatigue fracture of metallic materials

—

A literature search has revealed that the most extensive study of impact fatigue reported is still that of Stanton and Bairstow (1908) who were the first to work on this topic. Their results, which were on pearlitic plain carbon steels, have been reanalyzed in an attempt to deduce from them the effects of chemical composition on impact fatigue in this class of materials.



The results show that when the number of impacts to failure, Nf, is greater than about 103, Nf and the energy absorbed per impact, Ei, are related by the equation: Ei, =Eo+EkNf−p, where Eo appears to be the impact endurance limit. It is suggested that Ek and p be named respectively the “impact fatigue parameter” and “impact fatigue exponent”. Ek is independent of composition except that it is lower by a factor of about four for two materials which probably failed by an intercrystalline rather than transcrystalline fracture; p has a value of 0.6; and Eo increases monotonically with silicon content but does not vary systematically with the carbon, manganese, sulphur or phorphorus contents. The significance of these results is discussed.

The impact fatigue properties of pearlitic plain carbon steels

Fatigue is a phenomenon under which, due to repetitive application of load the damage accumulates and the load may be well below the yield point. Fatigue failure leads to catastrophe which could be reviewed from air disaster of BOAC flight 781.The applications of polymers has now diversified from ordinary plastic bottles to high tech polymer gears. In order to manufacture an end use component made up of polymeric material it is prerequisite to understand the different failure mechanism of it. Fatigue loading is prevalent in engineering applications and can lead to catastrophe. This article presents a detail insight of fatigue failure mechanism of polymers intended toward future developments.

Fatigue of Polymers

Impact fatigue tests were carried out using a rotary type of machine The frequency and velocity of cyclic impacts and stress ratio on fatigue crack growth rate of aluminum alloy was investigated The difference of crack growth rate between cyclic impact and slowly-applied load was considerably large This difference is contributed to periodic impact that is analogous to increase in stress ratio of the more slowly applied cyclic loads Fractography study is also made

The Influence of Cyclic Impact Loading and Stress Ratio on Fatigue Crack Growth Rate in Aluminum Alloy

Stable fatigue crack propagation is predominantly described by the Paris power law correlation of the crack growth rate with the amplitude cyclic stress intensity. The Paris relationship works well for most ductile materials but does not capture the response for fatigue–brittle materials lacking a cyclic damage mechanism, including ceramics and many polymers. Instead, crack growth rate of fatigue–brittle materials correlates to the peak cyclic stress intensity factor, $$\hbox {K}_{\mathrm{max}}$$
 . This work shows that $$\hbox {K}_{\mathrm{max}}$$
 correlation of fatigue crack growth is derived directly from static mode crack tip behavior with constant correlation coefficients, and that $$\Delta \hbox {K}$$
 correlations are not generally applicable for static mode crack propagation in fatigue–brittle polymers. This derivation predicts load ratio, frequency, and waveform effects, which are included in a general static mode fatigue crack propagation law. Fatigue crack propagation data of a known fatigue–brittle polymer are presented to demonstrate static mode crack propagation behavior correlation with $$\hbox {K}_{\mathrm{max}}$$
 with constant parameters.

Static mode fatigue crack propagation and generalized stress intensity correlation for fatigue–brittle polymers

— Fatigue crack propagation was investigated in polycarbonate and glass fibre reinforced polycarbonate and the effect of stress ratio and glass fibre content determined. The addition of glass fibre increases the tensile strength, but does not always contribute to an increase in fatigue crack propagation resistance. For polycarbonate the effect of stress ratio can be partly explained by using crack closure concepts as other researchers have suggested, but for glass fibre reinforced polycarbonate this was not possible. Fractography revealed a void growth process, which occurred by decohesion at the interface of the glass fibres and the base material, which was dependent on the maximum stress intensity factor. The process of linking the voids and the main crack growth behavior depended on the stress intensity factor range, ΔK. A proposed crack propagation model can explain the effect of stress ratio on crack propagation in fibre reinforced polycarbonate.

Fatigue crack propagation and crack closure behavior in polycarbonate and fibre reinforced polycarbonate

— Impact fatigue tests were carried out using a rotating-disk type impact fatigue testing machine The influence of prior austenite grain size, ductile-brittle transition temperature and test temperature on impact fatigue crack growth rate was investigated by means of fracture mechanics and fractography in quenched and tempered Cr-Mo alloy steel in which the prior austenite grain size was varied from 8–3 to 25-4 μm The results in impact fatigue tests were compared to those under non-impact conditions The crack growth rates associated with striation formation were insensitive to the change in prior austenite grain size, ductile-brittle transition temperature and test temperature regardless of impact and non-impact fatigue When the material was in the brittle condition, impact fatigue gave rise to a transition from striation formation to intergranular and cleavage cracking Such a transition will result in the acceleration of crack growth rate The Paris Law exponent values in impact fatigue were reasonably expressed by the ratio of test temperature to ductile-brittle transition temperature

THE INFLUENCE OF TEST TEMPERATURE ON IMPACT FATIGUE CRACK GROWTH BEHAVIOR IN QUENCHED AND TEMPERED Cr‐Mo ALLOY STEELS WITH DIFFERENT PRIOR AUSTENITE GRAIN SIZES

K. Akizono

Papers

Fatigue crack propagation and crack closure behavior in polycarbonate and fibre reinforced polycarbonate

THE INFLUENCE OF TEST TEMPERATURE ON IMPACT FATIGUE CRACK GROWTH BEHAVIOR IN QUENCHED AND TEMPERED Cr‐Mo ALLOY STEELS WITH DIFFERENT PRIOR AUSTENITE GRAIN SIZES