Specific features and mechanisms of fatigue in the ultrahigh-cycle regime

Mughrabi, H.

doi:10.1016/j.ijfatigue.2005.05.018

Cited by 256 publications

(159 citation statements)

References 24 publications

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“…Zone IV shows a case corresponding to a material that continues to damage, even at lower stresses, whereas the other two cases show that the material has reached a stress below which microstructural mechanisms are perfectly reversible or their irreversibility would be negligible (Mughrabi, 2006).…”

Section: Introductionmentioning

confidence: 99%

The fatigue flexural behavior of fiber reinforced concrete: Effect of the parameters of coarse aggregates

Dilmi¹,

Aribi²,

Safi³

et al. 2015

Sci. Res. Essays

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The effect of the coarse aggregate type on the fatigue flexural behavior of concrete was investigated in this work. Three types of the coarse aggregates were selected from three different careers (CA1, CA2 and CA3). The mechanical parameters of these aggregates were determined (Los Anglos and Micro Deval). Prismatic specimens (70×70×280 mm) for each concrete mixture were made with aggregates of each source. The flexural fatigue tests were conducted on these concrete samples with varying levels of loading of 55 to 80% and the ultimate flexural strength. The test frequency is around 80 Hz and it is automatically determined by pulsing the fatigue machine for a resonance situation (the phase shift is δ=0) between the mass-spring-specimen system. The obtained results show that the aggregates which have the similar parameters (Micro Deval and LA), provide better adhesion with cement paste, and therefore a greater bending strength. The strength evolution at short-term age is typical for specimens based on aggregates with low wear resistance by triturate (a high Micro Deval coefficient). Regarding the fatigue flexural behavior, the concrete specimens based on CA1, which have similar coefficients of Los Angeles and Micro Deval (respectively 18 and 16) present the behavior (load/cycle numbers) close to that of the model prototype of the Wöhler curve. This can be explained by a high homogeneity of the charge distribution during fatigue test compared to other concrete mixtures. Also, it was noted that the relationship between the endurance limit and the coefficient of Los Angeles is inversely proportional: The aggregates which have good strength to fragmentation (low coefficient of LA), as aggregates CA2 case give an endurance limit at around 70% max bending load.

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Section: Introductionmentioning

confidence: 99%

The fatigue flexural behavior of fiber reinforced concrete: Effect of the parameters of coarse aggregates

Dilmi¹,

Aribi²,

Safi³

et al. 2015

Sci. Res. Essays

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“…In this range of lifetimes, it has been emphasized that fatigue crack initiation becomes much more important than crack propagation [1]. Fatigue failures have been observed at stresses below the conventional high cycle fatigue limit, resulting in significant motivation to understand the microstructural origins of such failures [1,2].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Fatigue failures have been observed at stresses below the conventional high cycle fatigue limit, resulting in significant motivation to understand the microstructural origins of such failures [1,2]. The role of microstructural characteristics on crack initiation in the VHCF regime has been studied in a wide range of materials, including polycrystal and single crystal Ni-based superalloys [1][2][3].Very high cycle fatigue life at high temperatures is an important property for automotive components such as exhaust valves. With the demand for increased thermal efficiencies in engines, there is a need for materials to withstand higher operating temperatures and pressures 559 7th International Symposium on Superalloy 718 and Derivatives Edited by:…”

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confidence: 99%

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Effect of Microstructure on the High Temperature Fatigue Properties of Two Ni-based Superalloys

Bunting¹,

Kenik²,

Bentley³

et al. 2010

7th International Symposium on Superalloy 718 and Derivatives (2010)

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There is significant need for Ni-based superalloys in the next generation automotive engine components such as exhaust valves. High temperature, high cycle fatigue life is one of the important properties required for such applications. The focus of this work is to evaluate the effect of microstructure on the high cycle fatigue properties of two Ni-based alloys, alloy 751, an alloy used in these applications at lower temperatures, and Waspaloy. High cycle fatigue lives of the alloys were evaluated using in-situ high temperature fully reversed fatigue tests at 870 o C and a nominal frequency of 30 Hz. Scanning electron microscopy and transmission electron microscopy were used to characterize the microstructure of the alloys. Computational modeling was used to calculate the equilibrium microstructure and microstructural coarsening at 870 o C. Correlation of fatigue properties with microstructure of the alloys shows that for the experimental conditions used in the study, the fatigue life of Waspaloy, which has greater high temperature strength and larger γ' volume fraction, is better than that of alloy 751. IntroductionThere has been a significant interest in recent years in understanding the fatigue performance of materials in the Very High Cycle Fatigue (VHCF) range or Ultrahigh-cycle fatigue range (UHCF) with typical lifetimes greater than 10 7 cycles. In this range of lifetimes, it has been emphasized that fatigue crack initiation becomes much more important than crack propagation [1]. Fatigue failures have been observed at stresses below the conventional high cycle fatigue limit, resulting in significant motivation to understand the microstructural origins of such failures [1,2]. The role of microstructural characteristics on crack initiation in the VHCF regime has been studied in a wide range of materials, including polycrystal and single crystal Ni-based superalloys [1][2][3].Very high cycle fatigue life at high temperatures is an important property for automotive components such as exhaust valves. With the demand for increased thermal efficiencies in engines, there is a need for materials to withstand higher operating temperatures and pressures 559 7th International Symposium on Superalloy 718 and Derivatives Edited by:

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“…Future engine applications require engine components that can operate safely up to 10 9 cycles [1]. In the very high cycle regime, most fatigue life is believed to be consumed by fatigue crack initiation processes [2].…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Initiation in Nickel-Based Superalloy Ren� 88 DT at 593�C

Miao¹,

Pollock²,

Jones³

2008

Superalloys 2008 (Eleventh International Symposium)

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Fatigue crack initiation in the polycrystalline nickel-based superalloy, René 88 DT, was investigated at 593 °C in air using an ultrasonic fatigue testing instrument. Within the testing stress range of 500 -760MPa, all fatigue failures initiated from internal regions. Large crystallographic facets were observed at the crack initiation sites in most failed fatigue samples. Critical microstructure features controlling fatigue crack initiation and the early stage of small crack growth were identified by the combination of serial sectioning, orientation imaging microscopy (OIM) and quantitative fractographic analysis. Large crystallographic facets at crack initiation sites were formed in regions close to Σ 3 annealing twin boundaries within favorably oriented large grains. The facet planes are parallel to Σ 3 annealing twin boundaries and are of {111} type. Cyclic deformation substructures were studied by transmission electron microscopy. At the low cyclic stresses and long lives examined, fatigue failure at 593°C is controlled by strain localization in large, favorably oriented grains and subsequent propagation of small cracks through neighborhoods of favorably oriented grains. Annealing twin boundaries, prevalent in the microstructure, appear to be important in cyclic strain localization.

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Specific features and mechanisms of fatigue in the ultrahigh-cycle regime

Cited by 256 publications

References 24 publications

The fatigue flexural behavior of fiber reinforced concrete: Effect of the parameters of coarse aggregates

The fatigue flexural behavior of fiber reinforced concrete: Effect of the parameters of coarse aggregates

Effect of Microstructure on the High Temperature Fatigue Properties of Two Ni-based Superalloys

Fatigue Crack Initiation in Nickel-Based Superalloy Ren� 88 DT at 593�C

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