Finite element simulations of notch tip fields in magnesium single crystals

Kaushik,; Narasimhan, R.; Mishra, Raja K.

doi:10.1007/s10704-014-9971-3

Cited by 16 publications

(4 citation statements)

References 49 publications

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“…It is also known that intense basal slip within thin contraction twins result in shear localization regions where cracking may occur [14,30,31]. While extension twins have also been shown to promote cracking along their boundaries [8,[32][33][34], some works have indicated them as toughening agents as well [10,35]. Ductile damage through void growth is driven by matrix plasticity, which occurs in Mg by slip and twinning.…”

Section: Discussionmentioning

confidence: 99%

Three dimensional simulations of texture and triaxiality effects on the plasticity of magnesium alloys

2017

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We investigate the synergistic e↵ects of texture and intrinsic plastic anisotropy (at the level of single crystal) on the deformation of polycrystalline magnesium using three-dimensional crystal plasticity finite element simulations. Using rolled plate texture as a basis, we simulate the deformation using a range of synthetic textures. Smooth and notched round bar specimens are considered to achieve di↵erent levels of stress triaxiality. Two sets of constituent single crystal properties, representative of an Mg alloy and pure Mg respectively, are adopted in order to investigate the role of intrinsic plastic anisotropy. Our results reveal that textural variations couple into the intrinsic plastic anisotropy and triaxiality to determine the active deformation mechanisms. When loaded along the rolling direction of the plate, the deformation is accommodated by prismatic slip at low triaxiality and pyramidal hc + ai slip at high triaxiality. Softer mechanisms such as basal slip and extension twinning, which are not favored by the loading orientation, are activated due to the intergranular stresses. The smooth specimens show macroscopic strain localization the onset of which depends on initial texture. The deformation texture is strongly modulated by both triaxiality and inherent plastic anisotropy. We also briefly discuss the potential role of twinning in damage evolution.

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Section: Discussionmentioning

confidence: 99%

Three dimensional simulations of texture and triaxiality effects on the plasticity of magnesium alloys

2017

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“…The manifestation of twinning is a large local lattice rotation to enable the activation of twin planes in order to accommodate slip. Whilst studies on magnesium by Kaushik et al [15,16] show the importance of twinning on deformation local to a crack tip, it is however ignored in this study.…”

Section: Discussionmentioning

confidence: 99%

“…The issue of anisotropy effects at the crack tip was recently investigated by Kartal et al [10] to evaluate the effects of crystallographic orientation and grain morphology on crack tip stress state and found that single crystal crack tip stresses largely remain independent of crystal orientation but that the plastic zone size and shape depends greatly upon it. Further studies include that by Biswas and Narasihman [11,12] who investigated crack tip fields in rate sensitive FCC single crystals; Lopez-Crespo et al [13,14] who address overload effects during fatigue crack growth in steel using synchrotron x-ray diffraction for both plane strain and stress conditions, and studies by Kaushik et al [15,16] on experimental and finite element simulations of notch tip fields in magnesium single crystals.…”

Section: Introductionmentioning

confidence: 99%

Lattice strains at cracks in single crystal titanium: Elastic distortion and GND contributions

Erinosho¹,

Dunne

2016

International Journal of Solids and Structures

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There is evidence from diffraction experiments that significant peak broadening is measured local to crack tips and this has been attributed to the development of geometrically necessary dislocations (GNDs) which are retained upon unloading. This is reasonable due to the stress singularity found locally at the crack which is expected to activate slip on favorably oriented slip systems, potentially resulting in plastic strain gradients and geometrically necessary dislocation development. Hence, a systematic study is presented here to ascertain the contributions of both elastic distortional strain and GND density to lattice deformation local to the crack at loaded and subsequently unloaded states.The results show that whilst elastic strains dominate lattice distortion in comparison to GNDs at the loaded state i.e. at the peak load applied, these strains are largely recovered upon unloading and the contribution from GND development subsequently dominates the broadening seen. Two initial crystallographic configurations were considered. In the example in which the crystal c-axis was oriented parallel to the loading direction, the pyramidal systems contributed most to slip with basal slip system contributing to a lesser extent. However, in the example where the c-axis was oriented perpendicular to the loading direction, the pyramidal and prismatic systems were the more significant contributors to slip and the basal contributing to a lesser extent. However, basal, prismatic and c+a pyramidal slip systems were found to be active in both examples and this was attributed to significant lattice rotation driven by locally high stresses which enabled otherwise badly oriented slip systems to become favourable for slip. Finally, increases in GND density were seen upon unloading for c-axis orientation parallel with loading. This was attributed to the influence of pyramidal slip on reverse plasticity leading to diffuse GND density distributions and significant resulting lattice strains compared to that from prism slip loading

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“…This correlates with the absence of TTs in a small region near the notch root in their experiments. From finite element analysis, Kaushik et al [37] have noted that in the notched three point bend Mg single crystal specimen corresponding to the above orientation, the plastic hinge forms close to the notch root in the uncracked ligament. In other words, the normal stress on the plane ahead of the notch root changes from tensile to compressive beyond the hinge point which triggers TTs.…”

Section: Origin Of Tensile Twinning Near the Notch Rootmentioning

confidence: 99%