Effect Of Initial Orientation Research Articles

A numerical study of the settling of non-spherical particles in quiescent water

Settling of non-spherical particles is poorly understood with previous studies having focused mainly on spherical particles. Here, a series of particle-resolved direct numerical simulations are conducted using FLOW-3D (commercial computational fluid dynamics software) for spheres and five regular, non-spherical shapes of sediment particles, i.e., prolate spheroid, oblate spheroid, cylinder, disk, and cube. The Galileo number varies from 0.248 to 360, and the particle Reynolds number Rep ranges from 0.002 77 to 562. The results show that a non-spherical particle may experience larger drag and, consequently, attain a lower terminal velocity than an equivalent sphere. If Rep is sufficiently small, the terminal velocity is less affected by particle shape as characterized by the particle aspect ratio. For relatively large Rep, the shape effect (represented by the Corey shape factor) becomes more significant. Empirical correlations are derived for the dimensionless characteristic time t95∗ and displacement s95∗ of particle settling, which show that t95∗ remains constant in the Stokes regime (Rep < 1) and decreases with increasing Rep in the intermediate regime (1 ≤ Rep < 103), whereas s95∗ increases progressively with increasing Rep over the simulated range. It is also found that in the Stokes regime, particle orientation remains essentially unchanged during settling, and so the terminal velocity is governed by the initial orientation. In the intermediate regime, a particle provisionally settling at an unstable orientation self-readjusts to a stable equilibrium state, such that the effect of initial orientation on the terminal velocity is negligible. Moreover, an unstable initial orientation can enhance the vertical displacement and may promote vortex shedding.

Effects of initial orientation on microstructure evolution of aluminum single crystals during hot deformation

The predominant crystallographic relations between dynamic recrystallization (DRX) nuclei and simple deformation structures have been characterized in aluminum single crystals (ASCs) of Cube{001}<100> and S{123}<634> orientations. Electron backscattered diffraction (EBSD) and electron channeling contrast imaging (ECCI) measurements revealed that the DRX behavior of ASCs dependent on initial grain orientation. The diverse distributions of slip systems and stress-axis orientations in Cube- and S-orientation ASCs contribute to the difference in initial slip system, DRX behavior and misorientation accumulation. The Cube-orientation ASCs are predominated by microbands at (25–300 °C)/(0.001–10 s−1), only a few discontinuous dynamic recrystallized (DDRX) grains are found at 300 °C/(0.001–10 s−1). While the DRXs behaviors in S-orientation ASCs are significantly under 300 °C/(0.001–10 s−1). DDRX grains in S-orientation ASCs reach millimeter level even at 25 °C/10 s−1. Many continuous dynamic recrystallized (CDRX) grains and sub-grain structures are found at 300 °C/10 s−1. Misorientation angles across DRX interfaces are grouped in the range of 20°–50° (with a maximum at 30°–40°) around axes located near the normal of {111} planes.

Effect of Initial Orientation on the Anisotropy in Microstructure and Mechanical Properties of 2195 Al-Li Alloy Sheet during Hot Tensile Deformation.

The 2195 Al-Li alloy, as one of the representative third-generation Al-Li alloys, has extensive applications in lightweight aerospace structures. In this paper, the anisotropy in mechanical properties and microstructure evolution of 2195 Al-Li alloy sheets were investigated under a strain rate of 0.01, 0.1, 1 s-1 and a temperature of 440 and 500 °C. Experimental results showed that the hot tensile properties of the 2195 Al-Li alloy sheet exhibited a strong dependence on loading directions. The peak stress (PS) and elongation (EL) along the rolling direction (RD) were larger than the transverse direction (TD). For the tests carried out at 440 °C-1 s-1, the PS values of the sheets stretched along the RD and TD are 142.9 MPa and 110.2 MPa, respectively. And, most of the PS anisotropy values are larger than 15%. The anisotropy in EL is less significant than in PS. All the differences are about 10%. Moreover, dimples in the samples stretched along RD were more and deeper than those along TD at 440 °C. The fracture morphology along RD and TD were similar, and both were cleavage fractures at 500 °C. Particularly, the fractions of high angle grain boundaries (HAGBs) along TD were all about 5% larger than those of RD. And, there were more small-sized continuous dynamic recrystallization (CDRX) grains inside the initial grains and discontinuous dynamic recrystallization (DDRX) grains featured with the local bulge of grain boundaries along TD. This was due to the smaller average Schmid factor and the vertical EL trend of the initial grains when the samples were stretched along TD. A model of grain evolution during the dynamic recrystallization (DRX) along RD and TD was proposed based on EBSD results. The Schmid factor and banded structure had a more prominent effect on the hot ductility of the 2195 Al-Li alloy compared with the degree of DRX, thus presenting a higher EL and better hot ductility along RD.

Effect of initial orientation on microstructure and mechanical properties of AZ31 Mg alloy sheets via accumulated extrusion bonding

In this study, effects of initial orientation on microstructure evolution and mechanical properties of AZ31 Mg alloy sheets via accumulated extrusion bonding (AEB) was systematically studied. The samples with RD and TD parallel to extrusion direction (ED) were labeled as RED and TED, respectively. RD and TD pieces alternately stacked was named as RTED. The results revealed that under three-dimensional compressive stress, {10-12} tensile twinning dominated the first stage deformation in container. As the plunger continuous press down, dynamic recrystallization (DRX) occurred, and the newly fine DRXed grains along original and twin grain boundaries gradually consumed the matrix and twin grains. The microstructure was completely transformed into recrystallized grain structure at sizing band with an average grain size of ∼0.9 ​μm in TED sample, smaller than that of RED sample. After the alloys extruded out of the die, DRXed grains significantly grew to ∼4.5 ​μm and 3.5 ​μm for RED and TED samples, respectively. A laminated microstructure was obtained with average grain sizes of∼4.4 ​μm in RD layers and 3.5 ​μm in TD layers for RTED sample. The AEB processed samples exhibited an ED-tilt double-peak basal texture with similar texture intensity. The tensile tests results indicated that attributed to the combined effect of grain refinement and texture evolution, the yield strength and fracture elongation of RED and TED samples was significantly improved. The heterogeneous microstructure in RTED sample induced an extra work hardening (HDI-work hardening) in tensile deformation and resulted in a further improved elongation of 32.0%.

Effect of Initial Orientation on Corrosion Behavior of AZ80 Magnesium Alloy in Simulated Body Fluid

Three different orientation specimens (P-ND30, P-ND60 and P-TD) prepared from the rolled AZ80 magnesium alloy plates were immersed in simulated body fluid (SBF) for 384 h. Electrochemical impedance spectroscopy (EIS) tests were measured at 24 h, 96 h, 192 h, 288 h, and 384 h during immersion. The corrosion morphology and chemical composition of the three orientation specimens were investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray diffractometer (XRD) was used to evaluate the phase composition of the surface of the specimen at different immersion stages. The results indicated that the P-ND30 and P-ND60 specimens had similar corrosion behavior. The P-TD specimen showed the best corrosion resistance. A degradation evolution model was established, and the effect of initial orientation on corrosion behavior was discussed.

Dielectrophoretic interaction of circular particles in a uniform electric field

A two-dimensional incompressible smoothed particle hydrodynamics scheme is used to simulate the interaction of micron-sized particles suspended in quiescent medium. A uniform electric field is applied to the particles, causing them to approach one another due to dielectrophoretic forces and form a chain. Both fluid and particles are assumed to be polarizable and non-conductive where the permittivity of the fluid is assumed to be lower than that of the particles. The numerical scheme is validated by comparing its predictions for simpler case of a pair of particles with results available in the literature. The effects of initial orientation, Reynolds number and differences in particle permittivity on the chaining behavior are studied afterwards. The results show that the particles may follow a convergent or divergent–convergent trajectory, depending on the initial orientation of the particle pair with the electric field. Increasing the field intensity in low-Reynolds regime expedites the chaining process without affecting the particle trajectory. However, the particles may diverge at larger Reynolds numbers. Assigning different permittivities to particles skews the chaining position toward the particle with lower permittivity. Simulating the process for multiple particles results in longer chains branching and encompassing the entire computational domain, much like those observed in experiments.

3D-QSAR and Molecular Docking Study on Maleimide-Based Glycogen Synthase Kinase 3 (GSK-3) Inhibitors as Stimulators of Steroidogenesis

Glycogen synthase kinase-3 (GSK3) is a potential therapeutic target in bipolar disorder. Here, a three-dimensional quantitative structure–activity relationship (3D-QSAR) namely CoMFA, CoMFA-RF (region focusing), and CoMSIA has been carried out on a series (44 compounds) of GSK3 inhibitors on maleimide-based. The data set was divided into training set (32 compounds) and test set (12 compounds) using Kennard and Stone algorithm. An alignment rule for the training set was defined on the basis of common substructure-based alignment. The all-orientation search (AOS) was used to achieve the best orientation and minimize the effect of initial orientation of the structures. The statistical parameters from the models (CoMFA: q2 = 0.56, , CoMFA-RF: q2 = 0.70, , and CoMSIA: q2 = 0.60, ) indicate that the data are well fitted and have high predictive ability. Molecular docking was employed to explore the binding mode between these compounds and the receptor, as well as help understand the structure–activity relationship revealed by CoMFA and CoMSIA. The computer-aided design of new compounds as potential GSK-3 inhibitors with the application of defined structural alerts was presented.

Effect of initial orientation on dynamic recrystallization of a zirconium alloy during hot deformation

The present study investigated the influence of the initial orientation on the dynamic recrystallization (DRX) behavior of a Zr-1Sn-0.3Nb alloy. A hot-rolled and annealed Zr sheet was compressed along two directions: along the normal direction so that the grains' ⟨c⟩-axis was nearly parallel to the loading direction (0° sample) and along the transverse direction so that the grains' ⟨c⟩-axis was nearly perpendicular to the loading direction (90° sample). The samples were compressed at 700 °C at a strain rate of 1 s−1. The microstructures at different strains were characterized by the electron backscatter diffraction (EBSD) technique, and conventional dislocation analysis using transmission electron microscope (TEM) was performed. A threshold value of grain orientation spread (GOS) equaled to 5° was used to distinguish the dynamically recrystallized grains from the deformed matrix. The results revealed that the DRX behavior strongly depended on the initial orientation. The Schmid factor analysis and TEM observation confirmed that pyramidal ⟨c + a⟩ slip operated from the first stage of deformation in the 0° sample but not in the 90° sample. For the 0° sample, in the early and medium stages of deformation, due to the high stored energy caused by the operation of pyramidal ⟨c + a⟩ slip, DDRX was mainly contributed to the formation of new fine grains. However, in the later stage of deformation, the DRX mechanism changed from DDRX to CDRX. In the 90° sample, although DDRX featured by grain boundary bulging occurred, the main DRX mechanism was CDRX in the whole deformation processing. Moreover, texture induced hardening in the early stage of deformation hides the softening induced by DDRX.

Effect of initial orientation on subgrain formation in nickel single crystals during equal channel angular pressing

This study deals with the development of the microstructure and grain refinement of nickel single crystals during the Equal Channel Angular Pressing (ECAP) process. In the experimental study, the electron backscattered diffraction data reveal that during the forming process the microstructure is modified and subgrains are developed. The microstructure is characterized by both low and high angle grain boundaries. Also, the (111) pole figures show that after the ECAP process the orientation is scattered, and the deformation process is heterogeneous. In the numerical work, a rate-dependent elasto-viscoplastic material model based on the theory of materials with isomorphic elastic ranges is applied. The identification of the material parameters has been performed by using the least square method with the Levenberg-Marquardt algorithm. A three-dimensional model of the ECAP process has been implemented in the finite element software Abaqus/Standard. The initial and final orientations after a single pass of the ECAP process are evaluated to study the subgrain formation under large deformations. The agreement between the simulated and experimental response in terms of stress-strain response and (111) pole figures are investigated. The analysis of the misorientation distribution reveals that the grain fragmentation has occurred with both high and low angle grain boundaries. The reconstruction of the microstructure after the deformation shows that the initial orientation has a significant influence on the microstructural evolution and grain refinement after a single pass ECAP extrusion.

Effect of initial orientation on twinning in commercially pure titanium

The effect of initial orientation on twinning micro-mechanisms during tensile deformation of commercially pure titanium has been studied using micro focus X-ray diffraction and electron back scatter diffraction (EBSD) in a scanning electron microscope. Three orientations A, B and C obtained from a rolled and annealed block of commercially pure titanium were deformed in uniaxial tension till failure and the tested specimens were characterised with regard to bulk texture, microstructure and crystal orientation mapping using EBSD. Orientation B along the transverse direction in ND-TD plane exhibits higher strength and lower strain hardening compared to orientations A and C along the rolling direction in TD-RD and ND-RD plane, respectively. This is attributed to different texture of sample B compared to samples A and C leading to dissimilar twinning micro-mechanisms and characteristic variation in nature of twinning. It is observed that limited twin nucleation and prominent lateral growth plays a dominant role in orientation B while multiple twin nucleation with significant non-Schmid behaviour is dominant for the other two orientations. It is proposed from this study that conventional factors associated with twin formation like Schmid factor play a main role in twin nucleation and propagation, however, growth or lateral thickening of the twins is explained by elastic stiffness variation across twins and their parent grains.

Effect of initial orientation on the tensile properties of commercially pure titanium

Effect of crystallographic texture on uniaxial tensile deformation of commercially pure titanium was studied using in situ as well as post-mortem electron backscatter diffraction and elastoplastic self-consistent simulations. Correlation of mechanical properties and strain hardening response with deformation micromechanisms like different modes of slip and twinning was established. Tensile specimens were machined along rolling direction in the plane perpendicular to normal and transverse direction (sample A and C, respectively) as well as along transverse direction in the plane normal to rolling direction (sample B) to obtain different initial texture from cold rolled and annealed plate of commercially pure titanium. Sample B showed higher strength but lower strain hardening rate and ductility than the orientations A and C. It showed extension twinning with lateral thickening while the other samples showed coexistence of extension and contraction twinning. Schmid factor accounted for most of the observed twinning although some contraction twinning in sample A is attributed to the effect of internal stresses. A combination of in situ tensile test in a field emission gun scanning electron microscope with electron backscatter diffraction facility and elastoplastic self-consistent simulations aid in obtaining high-fidelity Voce hardening parameters for different slip and twinning systems in commercially pure titanium. The variation in tensile properties can be explained on the basis of propensity of twinning which tends to provide strain hardening at lower strain but contributes to failure at higher strain.

Effect of initial orientation on the microstructure and mechanical properties of textured AZ31 Mg alloy during torsion and annealing

Abstract We studied the effect of crystallographic orientation and temperature on the microstructure and mechanical properties of extruded AZ31 magnesium alloy bar by torsion and subsequent annealing. The results show that the orientation between torsion axis (TA) and extrusion direction (ED) has a significant impact on the microstructure evolution. With TA parallel to ED, profuse extension twins appeared. After annealing, zones close to the surface were completely recrystallized and refined, while the center still had some extension twins left. With TA perpendicular to ED, extension twins were inhibited. It is speculated that, except extension twins, contraction twins is also acting as a major deformation mode. Upon annealing, this specimen was completely recrystallized, even at the center, which is considered as a result of more preferred nucleation sites for static recrystallization from contraction twins. As demonstrated, the temperature has little impact on the microstructure development when twisted at room temperature or liquid nitrogen temperature. Moreover, the compression tests show that the compression ductility and yield strength were improved simultaneously for both samples when compressed on the direction either along ED or perpendicular to ED, due to the combined effects of grain refinement and texture weakening.

A Drop Test for Finding the most Probable Resting Orientation of a Part

The material handling is the art of moving, orienting, packing and storing the part. Industrial feeders are used to facilitate the operations by feeding the parts in a specific quantity and at a perfect orientation. It is a tedious task to obtain a particular part orientation, at the assembly station, in a short lead time. To overcome this problem, part feeders are used to segregate and orient parts prior to packing. The natural resting orientation of the part is the orientation in which the part rests on a horizontal hard surface, when dropped from a height. The most probable natural resting orientation of the part has to be identified which helps in the effective design of feeder and orienting devices. In this paper, an attempt was made to study the effect of initial orientation from different heights on natural resting orientation. Drop test was conducted at different heights with each initial orientation. The favorable orientation of the part (or) the most probable natural resting orientation is identified using drop test. In this work, most probable natural resting orientation of a typical asymmetric component, brake pad, is identified.

Effect of Initial Orientation on the Laser-Induced Cycloaddition Reaction of Benzene and Ethylene

The [2 + 2] photocycloaddition reaction of benzene and ethylene was investigated by semiclassical dynamics simulation and complete active space self-consistent field (CASSCF)ab initiocalculations. Following laser excitation of the benzene molecule, two mechanisms were observed depending on the location of the second C of ethylene in relation to the hexagonal prism space defined by the first C and the plane of the benzene ring. Synchronous formation of two bonds was observed when the second C is outside the prism space; an asynchronous mechanism is observed otherwise. Charge transfer was observed only in the asynchronous mechanism; CASSCF calculations suggest that the asynchronous mechanism involves a barrierless path from the Frank-Condon point to a conical intersection, while the synchronous mechanism involves 0.8 eV barrier. These results are consistent with a higher quantum yield observed in the simulations for the asynchronous pathway.

Microstructure and texture evolution in a twinning-induced-plasticity steel during uniaxial tension

A combination of electron back-scattering diffraction and X-ray diffraction was used to track the evolution of the microstructure and texture of a fully recrystallized Fe–24 Mn–3 Al–2 Si–1 Ni–0.06 C twinning-induced-plasticity steel during interrupted uniaxial tensile testing. Texture measurements returned the characteristic double fibre texture for face-centred cubic materials, with a relatively stronger 〈111〉 and a weaker 〈100〉 partial fibre parallel to the tensile axis. The interaction with the stable 〈111〉 oriented grains results in preferential plastic flow in the unstable 〈110〉 oriented grains. Consequently, the grains oriented along the 〈110〉 and 〈100〉 fibres record the highest and lowest values of intragranular local misorientation, respectively. The viscoplastic self-consistent model was used to simulate the macroscopic stress–strain response as well as track the evolution of bulk crystallographic texture by detailing the contributions of perfect and/or partial slip, twinning and latent hardening. The simulations revealed the dominant role of perfect slip and the limited volume effect of twinning on the texture development. The effects of initial orientation and grain interaction on the overall orientation stability during uniaxial tension showed that while the 〈100〉 fibre remains stable and does not affect the unstable orientations along the 〈110〉 fibre, the orientations along the stable 〈111〉 fibre strongly affect the unstable 〈110〉 orientations.

Docking, CoMFA and CoMSIA studies of a series of sulfonamides derivatives as carbonic anhydrase I inhibitors

3D-QSAR methods, CoMFA region focusing (CoMFA-RF) and CoMSIA along with docking studies carried out for investigating 32 carbonic anhydrase I inhibitors. These inhibitors have been studied for the development of antiglaucoma, antitumor, antiobesity or anticonvulsant drugs. Docking analysis by GOLD provide conformations which have been realigned in CoMFA and CoMSIA models. Training set for the CoMFA–RF and CoMSIA models using 24 docked conformations gives q2Loo values of 0.615 and 0.637 and r2nv values of 0.701 and 0.713, respectively. The results of CoMFA-RF and CoMSIA with and without docked conformations were compared. The ability of prediction and robustness of the models were evaluated by test set, cross validation (leave-one-out and leave-ten-out), bootstrapping, and progressive scrambling approaches. The all-orientation search (AOS) was used to achieve the best orientation to minimize the effect of initial orientation of the structures. The docking results confirmed CoMFA and CoMSIA contour maps.

Molecular dynamics study of the effects of translational energy and incident angle on dissociation probability of hydrogen/deuterium molecules on Pt(111)

The dissociation probabilities of H2 and D2 molecules on a Pt(111) surface with thermal motion were analyzed using the molecular dynamics (MD) method. The potential constructed using the embedded atom method was used as the interaction potential between a gas molecule and the surface. The effects of changing the translational energy and incident polar angle of D2 molecules impinging on a Pt(111) surface were analyzed using MD simulations. The effect of initial orientation, incident azimuthal angle, rotational energy of gas molecules, and the impinging points on the surface were averaged by setting the initial values in a random manner. When the molecules approach normal to the surface, the dissociation probability increases with the initial translational energy. At larger incident angles, the probability becomes smaller. The impinging processes were categorized in terms of reaching the chemisorption layer by analyzing the repulsion forces from the surface. The effective translational energies for impingement, both normal and parallel to the surface, play important but different roles in terms of molecules reaching the chemisorption layer and the dissociation probability. The results were compared to those obtained by molecular beam experiments to check the validity of the simulations. The results indicate that the dependence of the dissociation probability on the translational energy and incident angle is in approximate agreement with that from experiments.

Effect of Initial Orientation of Vascular Endothelial Cells on Activation of RhoGTPases Induced by Fluid Shear Stress

Vascular endothelial cells (ECs) exposed to fluid shear stress (FSS) become elongated and aligned to the direction of flow. However, the process of morphological change in individual cells is different depending of their initial shape. Rac1 and RhoA, members of the family of Rho GTPases, play important roles in cellular morphological changes but are thought to be activated differently in the process. Here, we measured changes in Rac1 and RhoA activities with a focus on the effect of cell orientation when exposed to FSS. In ECs initially oriented parallel to the direction of flow, RhoA and Rac1 were activated primarily in the upstream and the downstream regions of cells, respectively, accompanied by the formation of lamellipodia in the direction of flow. On the other hand, in cells oriented perpendicular to the direction of flow, FSS caused RhoA activation in the upstream region but did not change Rac1 activity. Furthermore, treatment with cytochalasin D inhibited the localization of Rac1 activation and suppressed RhoA activation by FSS. These results indicate that cell orientation affects the local activation of Rac1 and RhoA when induced by forces transmitted through the actin cytoskeleton under a FSS condition.

Effects of initial orientation, sample geometry and friction on anisotropy and crystallographic orientation changes in single crystal microcompression deformation: A crystal plasticity finite element study

The study presents crystal plasticity finite element simulations of cylindrical Cu single crystal micropillar compression tests. The aim is to study the influence of the stability of the initial crystal orientation, sample geometry (diameter-to-length ratio) and friction on the anisotropy and crystallographic orientation changes during such tests. Initial anisotropy (initial orientation) has a strong influence on the evolution of crystallographic orientation changes and also, to a minor extent, on the sample shape during compression. Pronounced orientation changes occur at an early stage of compression (at engineering strains of 0.2), entailing as a rule a large orientation spread within the initially uniformly oriented sample. A non-zero friction has a stabilizing effect on the course of the compression test even in cases where strong orientation changes occur. The evolution of orientation changes during compression is in part due to rigid body rotations (shape inclination due to buckling) rather than exclusively to crystallographic reorientation. Orientations that are crystallographically unstable and non-symmetric during compression tend to entail shape instability of the pillars at an earlier stage than observed for more stable cases.

Molecular Dynamics Simulations of the Coalescence of Iridium Clusters

The coalescence of small iridium clusters was studied using a molecular dynamics (MD) technique with a cluster Sutton−Chen potential. MD simulations were carried out on the reaction of two clusters from 1 to 7 atoms at various incident angles and initial kinetic energies. The threshold energy of product formation was investigated for the various systems, and the effect of initial orientation between two clusters on the product was also studied. A comparison of diffusion and Ostwald-ripening coalescence mechanisms was performed for 8-atom cluster formation, and Ostwald-ripening led to cluster formation with higher initial energies. An atom-to-bond collision resulted in the formation of a larger cluster more often and at higher energies than an atom-to-atom collision.