Brittle-ductile behavior in 3D iron crystals

Pelikán, Vladimír; Hora, Petr; Machová, Anna; Spielmannová, Alena

doi:10.1007/s10582-005-0132-9

Cited by 14 publications

(11 citation statements)

References 15 publications

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“…He revealed that this change can be completed within a 10 K temperature interval due to the generation of a crack-tip ledge for dislocation emission. Moreover, other brittle to ductile transitions were also observed in simulations [18,19] of single crystal Fe. As mentioned above, previous atomic level simulations have mainly focused on the study of fracture in metals like Al, Ni, Si, and Fe, however very little work has been done on the initial formation of cracks in copper polycrystals, so it is of great interest to investigate the fracture properties of Cu poly-crystal.…”

Section: Introductionmentioning

confidence: 61%

A Molecular Dynamics Simulation of Fracture in Nanocrystalline Copper

Pei

Lü

Zhu

et al. 2013

JNanoR

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A large-scale molecular dynamics simulation was used to investigate the propagation of cracks in three dimensional samples of nanocrystalline copper, with average grain sizes ranging from 5.34 to 14.8 nm and temperatures ranging from 1K to 500 K. It was shown that intragranular fracture can proceed inside the grain at low temperature, and plastic deformation around the tip of the crack is accommodated by dislocation nucleation/emission; indeed, both fully extended dislocation and deformation twinning were visible around the tip of the crack during fracture. In addition, due to a higher concentration of stress in front of the crack at a relative lower temperature, it was found that twinning deformation is easier to nucleate from the tip of the crack. These results also showed that the decreasing grain size below a critical value exhibits a reverse HallPetch relationship due to the enhancing grain boundary mediation, and high temperature is better for propagating ductile cracks. © (2013) Trans Tech Publications, Switzerland. Abstract.A large-scale molecular dynamics simulation was used to investigate the propagation of cracks in three dimensional samples of nanocrystalline copper, with average grain sizes ranging from 5.34 to 14.8 nm and temperatures ranging from 1K to 500 K. It was shown that intragranular fracture can proceed inside the grain at low temperature, and plastic deformation around the tip of the crack is accommodated by dislocation nucleation/emission; indeed, both fully extended dislocation and deformation twinning were visible around the tip of the crack during fracture. In addition, due to a higher concentration of stress in front of the crack at a relative lower temperature, it was found that twinning deformation is easier to nucleate from the tip of the crack. These results also showed that the decreasing grain size below a critical value exhibits a reverse Hall-Petch relationship due to the enhancing grain boundary mediation, and high temperature is better for propagating ductile cracks.

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Section: Introductionmentioning

confidence: 61%

A Molecular Dynamics Simulation of Fracture in Nanocrystalline Copper

Pei

Lü

Zhu

et al. 2013

JNanoR

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“…The nominal shear (slip) stress τ from the applied stress σ A (Schmid factors) for the slip systems is given by the following relations in our case: These values follow from the results of block like shear simulations in perfect bcc iron crystals, presented in [18,19,20]. Further details are given below.…”

Section: Results Up To Fracture In Dependence On Sample Sizementioning

confidence: 88%

“…Figure 13 shows that up to the time of the surface dislocation emission, where the peak in figure 13(a) occurs, the emission process is driven mainly by the interplanar stress component coming from the potential energy. The peak value in figure 13(a) slightly precedes the time t e = 6869 h in table 2 and its magnitude corresponds to τ MD = 15.1 GPa , which overcomes the stress barrier τ disl = 14.5 GPa in equation (3) for the slip system 〈111〉 {011} following from BLS simulations in [19] for this slip system in a perfect bcc iron crystal with the potential in use. This implies that the dislocation emission in MD is realized in accordance with the Rice model [7b] for 0 K. The level of τ bV (011) in figure 13(b) coming from the kinetic energy before the time t e is very low.…”

Section: Results Up To Fracture In Dependence On Sample Sizementioning

confidence: 89%

Size effects in molecular dynamic simulations of fracture in bcc iron crystals

Pařík,

Machová,

Červ

et al. 2023

Phys. Scr.

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Three-dimensional (3D) simulations via molecular dynamics (MD) show that the brittle or ductile behavior of the atomistic samples with the edge crack (001)[110] (crack plane/crack front) depend on size of the self-similar atomistic crystals. Since the basic continuum predictions concerning cracks do not consider the random thermal atomic motion, we are restricted in this study to MD simulations with initial temperature of 0 K. For all samples tested, the crack initiation is brittle. However, the subsequent crack growth can be inhibited by twin formation on oblique planes {112}, crack branching along {011} planes and new dislocation emissions on {123} slip planes and the final fracture can also be then ductile, which depends predominantly on the thickness of the atomistic sample. The representative quantity, the atomistic fracture toughness initially increases with increasing sample thickness and later saturates near Griffith level for plane strain state along the crack front. The tested loading rates are equivalent to a cross head speed of 0.833×10-4 m/s used in one our previous experiment. These new MD results comply with the stress analysis performed by the anisotropic linear fracture mechanics (LFM) and comply with some experimental observations.

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“…Crack (001)[010] (crack plane/crack front) under monotonic uniaxial tension can produce dislocations in 3D bcc iron crystals [1] in the available inclined slip systems <111>{101}, while the crack (-110)[110] can emit dislocations in the inclined slip systems <111>{112}, both under monotonic tension [2][3] or cyclic loading [4] in mode I. It occurs at low temperature [2] but also at room temperature [3,4] as experiments on iron crystals [4][5] confirmed.…”

Section: Introductionmentioning

confidence: 99%