Low-strain fatigue in AISI 316L steel surface grains: a three-dimensional discrete dislocation dynamics modelling of the early cycles I. Dislocation microstructures and mechanical behaviour

Déprés, Christophe; Robertson, C.; Fivel, M.

doi:10.1080/14786430410001690051

Cited by 94 publications

(58 citation statements)

References 19 publications

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“…In this section, the simulated space has a cylindrical geometry; with a 10µm diameter. Surface grains are represented by appropriate properties of the boundaries [1]. The escaping dislocations print surface steps that are computed using a specific post-treatment method [2].…”

Section: Resultsmentioning

confidence: 99%

Micro-crack initiation in thermal fatigue — an analysis based on experimental and DD simulation results

Robertson

Déprés²,

Fivel

2010

Trans Indian Inst Met

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The combined effect of cyclic thermal shocks and static tensile loading is investigated in 304L stainless steel specimens. Damage obtained at the end of the tests is analyzed by means of experimental observations and dislocation dynamics (DD) simulations. The calculations, carried out using representative loading conditions (σ ZZ = σ θθ ), show that the dominant slip systems do not necessarily have the largest activation ratio. Rather, the dominant slip directions b has specific orientations with respect to the free surface, maximizing the "surface connected volume" (SCV) of the active slip systems. During the tests, a marked effect of the superimposed static tensile loading (or mean stress) is also noted. This effect is also analyzed with the help of DD simulations, performed with a positive mean stress. These calculations show that slip irreversibility in the individual persistent slip bands systematically augments with increasing mean stress.

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Section: Resultsmentioning

confidence: 99%

Micro-crack initiation in thermal fatigue — an analysis based on experimental and DD simulation results

Robertson

Déprés²,

Fivel

2010

Trans Indian Inst Met

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“…Biner et al assumed that grain boundaries acted as sources for dislocation generation and found the active dislocation source density increased with decreasing grain size [47]. Déprés et al showed that the spacing of slip bands was mainly affected by the force field from the initial primary slip plane and the force field depended on the dislocation pile-ups (slip length/grain size) [48]. The decrease of grain size with increasing x (Figure 2) was probably the main reason of decreasing slip band spacing as shown in Figure 6.…”

Section: Microstructural Influence On Dwell Effectmentioning

confidence: 99%

Comparison of the Dwell Fatigue Behavior of Ti6242 And Ti6246

Qiu

Lei

et al. 2016

Proceedings of the 13th World Conference on Titanium

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The dwell effects of Ti624x (x=2 to 6) alloys, including dwell fatigue life debit, fracture mode and strain accumulation, were characterized and compared. The different dwell fatigue behaviors of Ti6242 and Ti6246 were attributed on the fundamental level to the dual effects of Mo: It decreases the transus of titanium and, as a slow diffuser, reduces the rate of phase transformation from to . A higher Mo content encourages nucleation of multiple variants of laths and promotes the transition from aligned colonies to basketweave microstructure during cooling after forging. As a result both the grain size and microtexture intensity of grains in the two-phase processed and heat treated microstructure are reduced. Smaller grain size of the alloys with higher Mo content produces smaller slip band spacing and reduces accumulated strain during dwell fatigue, thus reducing propensity for crack initiation.

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“…Thus, the dislocation may sidestep these immobile dislocations if there is free space beside them. A large-scale 3D dislocation dynamics simulation 57 suggests a cell structure formation due to the easy cross slip, which is also observed as a cell-like pattern in the plane perpendicular to the Burgers vector. 55 On the other hand, in the case of Fe-Si alloy, since the cross slip becomes difficult, a dislocation stuck to other immobile dislocations leads to work hardening.…”

Section: Dislocationmentioning

confidence: 99%

Mechanical properties of Fe-rich Si alloy from Hamiltonian

et al. 2017

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The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method, molecular dynamics simulation, etc, applied to homogeneous and heterogeneous systems. Firstly, we examined the elastic properties based on electronic structure calculations in a homogeneous system and attributed the physical origin of the loss of ductility with increasing Si content to the combined effects of magneto-volume and D0 3 ordering. As a typical example of a heterogeneity forming a microstructure, we focus on grain boundaries, and segregation behavior of Si atoms is studied through high-precision electronic structure calculations. Two kinds of segregation sites are identified: looser and tighter sites. Depending on the site, different segregation mechanisms are revealed. Finally, the dislocation behavior in the Fe-Si alloy is investigated mainly by molecular dynamics simulations combined with electronic structure calculations. The solid-solution hardening and softening are interpreted in terms of two kinds of energy barriers for kink nucleation and migration on a screw dislocation line. Furthermore, the clue to the peculiar work hardening behavior is discussed based on kinetic Monte Carlo simulations by focusing on the preferential selection of slip planes triggered by kink nucleation.npj Computational Materials (2017) 3:10 ; doi:10.1038/s41524-017-0012-4 INTRODUCTION Mechanical properties of alloys originate from the behavior of electrons and atoms on the microscopic scale; however, the strength of atomic bonding does not directly relate to macroscopic mechanical properties such as the yield strength, fracture toughness, and fatigue resistance. This is because the microstructure on the mesoscale, which is composed of various defects such as impurities, grain boundaries, and dislocations, mediates or enhances the response of alloys against external forces, leading to fairly nonlinear and multiscale phenomena. Facing such a nonlinear nature associated with the strength and plastic deformation of alloys, identifying the controlling factors for the mechanical properties is a significantly difficult task, and clarifying the underlying physics at different length and time scales still remains a major challenge in materials science.The authors of the present article took up the challenge of this complicated problem with their particular theoretical and computational tools unique to each characteristic scale range. These tools are electronic structure calculations, the cluster variation method (CVM) of statistical mechanics, and molecular dynamics (MD) simulations, which may cover the atomic to mesoscopic scale ranges. By virtue of high-performance computers, some of the results obtained by the present calculations achieve a higher precision and reveal a clearer picture than those obtained by ordinary experiments.Among the various mechanical properties, the main focus of the present study is the solid-solut...

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Low-strain fatigue in AISI 316L steel surface grains: a three-dimensional discrete dislocation dynamics modelling of the early cycles I. Dislocation microstructures and mechanical behaviour

Cited by 94 publications

References 19 publications

Micro-crack initiation in thermal fatigue — an analysis based on experimental and DD simulation results

Micro-crack initiation in thermal fatigue — an analysis based on experimental and DD simulation results

Comparison of the Dwell Fatigue Behavior of Ti6242 And Ti6246

Mechanical properties of Fe-rich Si alloy from Hamiltonian

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