Crack branching and deflection in AISI 4340 steel under cyclic torsional loading

Xu, Z.K.; Wang, B.; Zhang, Peng; Gu, X.Z.; Zhang, Z.F.

doi:10.1016/j.msea.2022.144561

Cited by 4 publications

(4 citation statements)

References 40 publications

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“…b) The initiation site is marked. [ 41 ] c) The side view of the initiation site. d) High magnification of the initiation site marked in (c).…”

Section: Resultsmentioning

confidence: 99%

“…The inclusion size corresponding to mechanism transformation could be calculated by

d_{normalc} = \frac{1}{π} {(\frac{Δ K_{th}}{0.65 τ_{normala}})}^{2}

where

Δ K_{th}

is the threshold value of stress intensity factor, which is about 5.35 MPa m 1/2 obtained in our previous study. [ 41 ] According to Equation (6), the critical inclusion size is related to the stress amplitude, and the larger the stress amplitude is, the smaller is the corresponding critical inclusion size. The highest loading value in the present study is 850 MPa, and the inclusion size corresponding to mechanism transformation is about 30 μm calculated by Equation (5).…”

Section: Discussionmentioning

confidence: 99%

“…To reveal the fatigue crack initiation mechanism, preelectropolished specimens are employed to observe the The relationship between the shear stress amplitude and the fatigue life at failure for the fatigue-electropolish specimen. [41] Figure 4. The SEM images of the fracture morphologies of pure torsional fatigue specimens.…”

Section: Initiation Behaviors Without Mns Inclusionmentioning

confidence: 99%

“…Figure3. The relationship between the shear stress amplitude and the fatigue life at failure for the fatigue-electropolish specimen [41]. …”

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confidence: 99%

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Crack Initiation Mechanism of AISI 4340 Steel for High‐Cycle Torsional Fatigue Loading

Wang

Zhang

et al. 2023

steel research int.

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The nucleation of microstructural fatigue cracks in AISI 4340 steel is investigated. The pre‐electropolished specimen is employed for the observation of the very early stage of fatigue crack initiation correlated with the microstructure. It is found that there are precipitate‐free zones (PFZs) around the lath and packet boundary, and the strength of PFZ is lower than that of the lath due to the lack of second‐phase strengthening. Therefore, the fatigue crack would first initiate within the PFZ. Besides, the initiated crack plane usually is the maximum shear stress plane. However, the MnS inclusions would cause stress concentration so that the lath boundary (LB) deviating from the maximum shear stress plane could also have sufficient driving force to crack. In contrast, when the LB is vertical to the cracked MnS inclusion, it would prevent the crack from propagating into the matrix because of the anisotropy of lath martensite. The effects of the stress concentration caused by the MnS inclusion on the maximum deviation angle and the S‐N curve are discussed.

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“…b) The initiation site is marked. [ 41 ] c) The side view of the initiation site. d) High magnification of the initiation site marked in (c).…”

Section: Resultsmentioning

confidence: 99%

“…The inclusion size corresponding to mechanism transformation could be calculated by