Low-cycle fatigue of metallic glass nanowires

Luo, Jian; Dahmen, Karin A.; Liaw, Peter K.; Shi, Yunfeng

doi:10.1016/j.actamat.2014.12.038

Cited by 40 publications

(23 citation statements)

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“…Fatigue damage in MGs was observed to initiate as mixedmode cracks or SBs. 7,9,12 In the present work, no apparent crack formation has been observed, and shear banding is found to be the fatigue mechanism for nanoscale MGs under lowcycle fatigue shown in Figure 3. This is consistent with recent experiments on fatigue behaviors of microsized MGs, 12 as well as MD simulations on low-cycle fatigue fracture of MG nanowires.…”

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confidence: 61%

Cyclic Deformation in Metallic Glasses

et al. 2015

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Despite the utmost importance and decades of experimental studies on fatigue in metallic glasses (MGs), there has been so far little or no atomic-level understanding of the mechanisms involved. Here we perform molecular dynamics simulations of tension-compression fatigue in Cu50Zr50 MGs under strain-controlled cyclic loading. It is shown that the shear band (SB) initiation under cyclic loading is distinctly different from that under monotonic loading. Under cyclic loading, SB initiation takes place when aggregates of shear transformation zones (STZs) accumulating at the MG surface reach a critical size comparable to the SB width, and the accumulation of STZs follows a power law with rate depending on the applied strain. It is further shown that almost the entire fatigue life of nanoscale MGs under low cycle fatigue is spent in the SB-initiation stage, similar to that of crystalline materials. Furthermore, a qualitative investigation of the effect of cycling frequency on the fatigue behavior of MGs suggests that higher cycling frequency leads to more cycles to failure. The present study sheds light on the fundamental fatigue mechanisms of MGs that could be useful in developing strategies for their engineering applications.

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confidence: 61%

Cyclic Deformation in Metallic Glasses

et al. 2015

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“…( b ) The stress strain curves for the ratio of σ 2 / σ 1 from −1 to 1, in steps of 0.2. Corresponding final deformation morphologies, colored by atomic shear strain 56 57 58 , are shown on the right. ( c ) The stress evolutions for the ratio of σ 2 / σ 1 from −1 to 1 in the domain of σ 1 and σ 2 .…”

Section: Figurementioning

confidence: 99%

Crack nucleation criterion and its application to impact indentation in glasses

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Vargheese

Tandia

et al. 2016

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Molecular dynamics (MD) simulations are used to directly observe nucleation of median cracks in oxide glasses under indentation. Indenters with sharp angles can nucleate median cracks in samples with no pre-existing flaws, while indenters with larger indenter angles cannot. Increasing the tip radius increases the critical load for nucleation of the median crack. Based upon an independent set of simulations under homogeneous loading, the fracture criterion in the domain of the principal stresses is constructed. The fracture criterion, or “fracture locus”, can quantitatively explain the observed effects of indenter angle and indenter tip radius on median crack nucleation. Our simulations suggest that beyond the maximum principal stress, plasticity and multi-axial stresses should also be considered for crack nucleation under indentation, even for brittle glassy systems.

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“…Interatomic force field and potential tuning A model metallic glass is chosen to study crack initiation under indentation in our MD simulations. The same system has been utilized in the study of intrinsic ductility of glassy solids [42], tensile fracture of metallic glasses [41] and low-cycle fatigue of metallic glass nanowires [43]. The alloy is comprised of two equimolar species with different size: S (the small atoms) and L (the large atoms).…”

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confidence: 99%

Crack initiation in metallic glasses under nanoindentation

et al. 2016

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a b s t r a c tSimulated nanoindentation tests on a model metallic glass reveal that the crack initiates inside a shear band via cavitation. The load-displacement curve was shown to be insensitive to the crack initiation but sensitive to subsequent crack propagation. The critical conditions for crack initiation were identified at both the macroscopic and microscopic levels. At the macroscopic level, the indenter geometry affects the overall critical load for crack initiation. Interestingly, the indentation volume at crack initiation appears to be a constant for different indenter geometries, based on which an analytical formula of the critical load as a function of the indenter geometry was derived. At the microscopic level, cavitation occurs once the normal stress perpendicular to the shear band exceeds a temperature-dependent critical cavitation stress. This critical cavitation stress was shown to reduce significantly upon shear deformation.

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Low-cycle fatigue of metallic glass nanowires

Cited by 40 publications

References 50 publications

Cyclic Deformation in Metallic Glasses

Cyclic Deformation in Metallic Glasses

Crack nucleation criterion and its application to impact indentation in glasses

Crack initiation in metallic glasses under nanoindentation

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