Near-Threshold Fatigue Crack Propagation in an ECAP-Processed Ultrafine-Grained Aluminium Alloy

Hockauf, Kristin; Halle, Thorsten; Hockauf, Matthias; Wagner, Martin F.‐X.; Lampke, Thomas

doi:10.4028/www.scientific.net/msf.667-669.873

Cited by 12 publications

(5 citation statements)

References 20 publications

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“…It can be seen that the average crack propagation rate (da/dN) for the one‐sided crescent‐shaped GBF zone increases with the increase of stress amplitude, that is, the stress amplitude is one of the key factors affecting the growth of one‐sided crescent‐shaped GBF zones 41 . The crack propagation rate is varied from 1.3 × 10 −12 m/cycle to 24 × 10 −12 m/cycle, which is in a good agreement with the reported values of the crack propagation in GBF zone 42,43 …”

Section: Discussionsupporting

confidence: 81%

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Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

Shi

Wang

Gao

et al. 2022

Fatigue Fract Eng Mat Struct

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A new double vacuum melting route (conventional second refining + vacuum arc refining [CSR + VAR]) with 33% lower production cost than the traditional VIM + VAR route has been tried. Compared with the CSR route, the CSR + VAR route reduces the average inclusion size from 27.1 ± 12.3 μm to 13.7 ± 2.4 μm, and the CSR + VAR steel processes a 13.1% higher rotatory bending fatigue (RBF) fatigue strength (σ À1 ) and a 3-timeslonger RCF L 10 life.The crescent-shaped granular bright facet (GBF) zone, normally found in high-strength steels' very high cycle fatigue regimes beyond 10 7 cycles normally under a much lower stress amplitude, appears around inner inclusions on the CSR + VAR steel RBF fracture surfaces in high cycle fatigue regimes beyond 3 Â 10 5 cycles. The development of GBF zones is estimated to account for 79%-90% of the RBF fatigue life. The average crack propagation rate (da/dN) for GBF zones varies from 1.3 Â 10 À12 m/cycle to 24 Â 10 À12 m/cycle and increases with the stress amplitude.

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Section: Discussionsupporting

confidence: 81%

“…Comparison of RBF-life of two steels under the same stress amplitude À12 m/cycle, which is in a good agreement with the reported values of the crack propagation in GBF zone 42,43. …”

supporting

confidence: 89%

Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

Shi

Wang

Gao

et al. 2022

Fatigue Fract Eng Mat Struct

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“…If the density of the dislocations within a cell wall becomes too high, new grain boundaries are formed in the small plasticized volume in the vicinity of the inclusion to minimize the local elastic energy. According to various researchers, grain refinement in metals leads to a reduction of the threshold value of the SIF K th . Hence, the threshold value of the SIF for crack propagation inside the refined volume becomes smaller compared to the one of the original microstructure whereas the local SIF remains constant.…”

Section: Introductionmentioning

confidence: 99%

Threshold values for very high cycle fatigue failure of high‐strength steels

Spriestersbach

Grad

Kerscher

2017

Fatigue Fract Eng Mat Struct

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Cracks leading to failure in very high cycle fatigue (VHCF) of high‐strength steels mostly initiate at subsurface inclusions at stress intensity factors (SIF) below the classical threshold value Kth for long cracks, especially for negative stress ratios. Here, a characteristic fine granular area (FGA) can be observed at the fracture surface in the vicinity of these initiating inclusions. According to various researchers, the FGA formation might be responsible for the late initiation of a propagable long crack. This study aims to clarify the threshold values of SIF for crack initiation for VHCF failure with FGA formation at nonmetallic inclusions. For this purpose, ultrasonic fatigue tests (R = −1) with the high‐strength steel 100Cr6 (SAE 52100) were carried out until an ultimate number of cycles of 109. In addition, very high cycle stress increase tests were performed. A serial grinding investigation of fatigued specimens acted as a technique to evaluate the distribution of unharmful inclusion in the tested volume. By the combination of these tests, a threshold value of the SIF for the VHCF by FGA formation at inclusions can be derived. This threshold value depends on the size of the crack initiating inclusion.

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“…The matrix material shows the highest thresholds and also a strong load ratio dependency. This can be explained by the well-known effect of the grain size on the crack growth at different load ratios [11][12][13]15,35]. The amount of crack deflection is constant for all load ratios, whereas the effect of roughness induced crack closure is minimized by increasing the load ratio.…”

Section: Fatigue Crack Propagationmentioning

confidence: 92%

Influence of Particulate Reinforcement and Equal-Channel Angular Pressing on Fatigue Crack Growth of an Aluminum Alloy

Köhler

Hockauf²,

Lampke³

et al. 2015

Metals

Self Cite

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Abstract:The fatigue crack growth behavior of unreinforced and particulate reinforced Al 2017 alloy, manufactured by powder metallurgy and additional equal-channel angular pressing (ECAP), is investigated. The reinforcement was done with 5 vol % Al2O3 particles with a size fraction of 0.2-2 µm. Our study presents the characterization of these materials by electron microscopy, tensile testing, and fatigue crack growth measurements. Whereas particulate reinforcement leads to a drastic decrease of the grain size, the influence of ECAP processing on the grain size is minor. Both reinforced conditions, with and without additional ECAP processing, exhibit reduced fatigue crack growth thresholds as compared to the matrix material. These results can be ascribed to the well-known effect of the grain size on the crack growth, since crack deflection and closure are directly affected. Despite their small grain size, the thresholds of both reinforced conditions depend strongly on the load ratio: tests at high load ratios reduce the fatigue threshold significantly. It is suggested that the strength of the particle-matrix-interface becomes the critical factor here and that the particle fracture at the interfaces dominates the failure behavior.

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Near-Threshold Fatigue Crack Propagation in an ECAP-Processed Ultrafine-Grained Aluminium Alloy

Cited by 12 publications

References 20 publications

Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

Threshold values for very high cycle fatigue failure of high‐strength steels

Influence of Particulate Reinforcement and Equal-Channel Angular Pressing on Fatigue Crack Growth of an Aluminum Alloy

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