Microscopic damage evolution during very‐high‐cycle fatigue (VHCF) of tempered martensitic steel

Krupp, Ulrich; Giertler, Alexander; Koschella, Kevin

doi:10.1111/ffe.12685

Cited by 19 publications

(19 citation statements)

References 19 publications

(21 reference statements)

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“…[7][8][9][10][11] The observed slip band formation occurred primarily near and along PAGBs. This result is in good agreement with the studies by Nishikawa et al, Batista et al, and Krupp et al, [10,11,14] which also reported a slip band formation at PAGBs. Apart from PAGBs, block boundaries are also cited as slip band formation sites.…”

Section: Discussionsupporting

confidence: 93%

“…[9,13] In many studies, the preferential alignment of carbides along microstructural interfaces is cited as a possible reason for intergranular crack initiation and early short crack propagation. [7,14,17,18] In addition, intergranular crack initiation can be explained by the impingement of slip bands on grain boundaries [14,19,20] or the anisotropic elastic and plastic properties of the grains. [11,12,15,[21][22][23] The number of slip bands formed and cracks initiated rises with increasing number of cycles and with increasing stress amplitude.…”

mentioning

confidence: 99%

“…[11][12][13] It seems that those slip bands do not cross microstructural interfaces with a high-angle boundary like packet boundaries or prior austenite grain boundaries (PAGBs). [10,13,14] Hence, the crack initiation and early short crack propagation in martensitic steels seem to occur mainly intergranularly at PAGBs [11,12,14,15] or block boundaries, [11,16] although in some studies, transgranular crack initiation and early short crack propagation were also observed. [9,13] In many studies, the preferential alignment of carbides along microstructural interfaces is cited as a possible reason for intergranular crack initiation and early short crack propagation.…”

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confidence: 99%

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Characterizing the Fatigue Damage in a Martensitic Spring Steel

Wildeis

Christ

Brandt

et al. 2021

steel research int.

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Many technical components are subjected to uniaxial cyclic loading in the high cycle fatigue regime. The resulting fatigue damage evolution is commonly subdivided into four stages, i.e., crack initiation, short crack propagation, long crack propagation, and eventually failure. Especially, the stages of crack initiation and short crack propagation can account for up to 90% of the fatigue life in the high cycle fatigue regime, leading to a particular interest in investigating these stages of fatigue damage evolution. [1] Furthermore, it is extremely important to understand the mechanisms of crack initiation and short crack propagation for lifetime predictions of structures which are not fail safe, as their failure can cause a catastrophic damage.Many studies have shown, that crack initiation often occurs at slip bands (see for example, the studies by Christ, McEvily, Efthymiadis et al., and Hong et al. [1][2][3][4] ) and that short crack propagation is strongly influenced by the local microstructure, leading to an oscillating crack propagation rate (see for example, the studies by Christ, McEvily, Miller, and Yang et al. [1,2,5,6] ). However, until now, just a few studies have investigated the fatigue damage evolution in a martensitic steel and the corresponding impact of the complex martensitic microstructure on the crack initiation and the short crack propagation. The crack initiation in martensitic steels seems to occur often at slip bands, [7][8][9][10][11] which mainly arise at microstructural interfaces and are oriented parallel to martensitic laths. [11][12][13] It seems that those slip bands do not cross microstructural interfaces with a high-angle boundary like packet boundaries or prior austenite grain boundaries (PAGBs). [10,13,14] Hence, the crack initiation and early short crack propagation in martensitic steels seem to occur mainly intergranularly at PAGBs [11,12,14,15] or block boundaries, [11,16] although in some studies, transgranular crack initiation and early short crack propagation were also observed. [9,13] In many studies, the preferential alignment of carbides along microstructural interfaces is cited as a possible reason for intergranular crack initiation and early short crack propagation. [7,14,17,18] In addition, intergranular crack initiation can be explained by the impingement of slip bands on grain boundaries [14,19,20] or the anisotropic elastic and plastic properties of the grains. [11,12,15,[21][22][23] The number of slip bands formed and cracks initiated rises with increasing number of cycles and with increasing stress amplitude. [4,8,9,13,24] The subsequent short crack propagation seems to be strongly influenced by the local microstructure, whereby a short crack propagation parallel to the martensitic laths is often observed. [8,24,25] PAGBs [6,8,14,24,26] and block boundaries [6,7,26] seem to act as obstacles for short crack propagation, leading to an oscillating short crack propagation rate. An often referred explanation for the barrier effect of microstructural interfaces is the...

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Section: Discussionsupporting

confidence: 93%

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confidence: 99%

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confidence: 99%

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Characterizing the Fatigue Damage in a Martensitic Spring Steel

Wildeis

Christ

Brandt

et al. 2021

steel research int.

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“…very-high-cycle fatigue (VHCF), may still happen in practical industrial applications [1][2][3][4]. VHCF behavior has attracted the attention of researchers in recent decades due to increasingly realistic requirements and scientific interests [5][6][7][8][9]. At present, it has been known that the typical morphology of the internal crack initiation region (CIR) for VHCF of highstrength steels is a fish-eye (FiE) containing a relatively rough region of fine-granular area (FGA), and it surrounds an inclusion which is considered as the origin of the crack initiation [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Further investigation on microstructure refinement of internal crack initiation region in VHCF regime of high-strength steels

Chang

Zheng

Pan

et al. 2019

Frattura Ed Integrità Strutturale

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The profile samples prepared by focused ion beam (FIB) in crack initiation region (CIR) and fish-eye (FiE) region of failed specimens subjected to rotary bending (RB) and ultrasonic axial (UL) fatigue testing with various stress ratios (R) were observed by transmission electron microscopy (TEM) with selected area electron diffraction (SAD) detection for two high-strength steels. The grain size and the thickness of nanograin layer along the crack growth path in CIR underneath fine-granular-area (FGA) were measured for the cases of R < 0, and a normalized quantity d* based on the detected SAD patterns was introduced to quantitatively demonstrate the variation of the grain size. The results showed that the nanograin size near the origin (an inclusion) of crack initiation is smaller than that away from the inclusion. Nevertheless, there was no evidence of grain refinement in CIR for the cases of R > 0 and the FiE region outside CIR for either negative or positive stress ratio cases, which suggests that the formation of nanograin layer in the FGA region is due to the numerous cyclic pressing (NCP) process and the plastic deformation ahead of the crack tip may cause certain extent of microstructure deformation but is insufficient to form nanograin layer on crack surfaces.

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“…The second problem is that LEFM principles were primarily developed for long cracks, and not for small cracks. Various other strategies have been developed recently …”

Section: Introductionmentioning

confidence: 99%

Fracture mechanical characterization of the initiation and growth of interior fatigue cracks

Stanzl-Tschegg

2017

Fatigue Fract Eng Mat Struct

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The formation and growth of interior fatigue cracks have been studied thoroughly during the last decades, due to the high practical importance of accurate predictions about the fatigue lives of structures and machine components. This is of special interest in the VHCF regime, for which the ultrasonic fatigue method is especially useful. Fracture mechanical values and lifetimes can be measured at constant and variable amplitudes. Endurance limits and ΔK thresholds can also be determined very quickly (e.g. 1010 cycles within a few days). Three different materials were studied. For chromium steel, internal crack formation and a fracture mechanical analysis of its growth were carried out. For a specially manufactured Mg alloy, microstructural features leading to interior cracks were analysed. Finally, for polycrystalline high‐purity copper, the conditions for interior‐crack formation and growth were determined. The utilization of FE‐SEM microscopy assisted in interpreting the prevailing mechanisms responsible for endurance limits, lifetimes and fatigue‐crack growth thresholds.

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Microscopic damage evolution during very‐high‐cycle fatigue (VHCF) of tempered martensitic steel

Cited by 19 publications

References 19 publications

Characterizing the Fatigue Damage in a Martensitic Spring Steel

Characterizing the Fatigue Damage in a Martensitic Spring Steel

Further investigation on microstructure refinement of internal crack initiation region in VHCF regime of high-strength steels

Fracture mechanical characterization of the initiation and growth of interior fatigue cracks

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