Orientation-dependent Effects Research Articles

A novel concurrent multiscale method based on the coupling of Direct FE2 and CPFEM

Performing concurrent simulations of macroscopic behaviors and microscopic structures using the crystal plasticity finite element method (CPFEM) presents a substantial difficulty with existing numerical techniques. To address this issue, a novel multi-scale method is proposed that couples CPFEM with a multiscale FEM, specifically Direct FE2. This facilitates the implementation of Direct CP-FE2 in this work. The micro representative volume elements (RVEs) equipped with a crystal plasticity constitutive model and the macro mesh are integrated into a monolithic solution scheme within the Direct FE2 framework. The proposed method integrates the multiscale simulation capability of Direct FE2 with the crystal plasticity model of CPFEM. Alpha titanium (α-Ti), which exhibits two distinct plastic mechanisms of slip and twinning, is chosen as the subject of investigation for conducting numerical experiments. The accuracy and efficiency of the Direct CP-FE2 model are evaluated through multiple plate tension and beam bending tests. The effective validation against the FEM model demonstrated the capability of Direct CP-FE2 to forecast macroscopic deformation behaviors. Meanwhile, the Direct CP-FE2 model can reveal the activation of slip/twinning systems and the evolution of crystal texture at a microscopic level. The influence of the grain orientation-dependent effect can be well considered into the macroscopic analysis with the help of Direct CP-FE2. Based on the testing examples, we demonstrate that the yield state of the macrostructure is enhanced when the crystal orientation is closer to the (0001) direction. Consequently, there exist very little crystal rotation behavior, hindering the evolution of the crystal texture.

A novel model considering combined effects of as-built roughness and notch for multiaxial fatigue life prediction of L-PBF Ti6Al4V

Additive Manufacturing (AM) has emerged as a promising manufacturing technology. However, there is still a lack of effective methods for evaluating the influence of as-built roughness, especially for notched components under complex fatigue loading. In this paper, a method based on damage mechanics for multiaxial fatigue life prediction is proposed for addressing the individual and combined effect of as-built surfaces and macro notches. Chaboche material model is coupled with a damage variable to describe the elastic–plastic deformation around the notch. The effect of as-built roughness is integrated into the damage evolution law developed by Chaudonneret, taking into account the degree of roughness, the orientation-dependent effect, and the variation of roughness effect with stress levels. The proposed model is numerically implemented by UMAT and validated through experimental data from literature under four types of fatigue loading including axial, torsion, in-phase axial-torsion and 90° out-of-phase axial-torsion. The predicted results agree well with the experimental values and the combined effect of the as-built roughness and notch is well analyzed.

Experimental simulation study on the poisoning effect of hydrocarbon-based ionomers on Pt catalysts for fuel cells

Membrane electrode assembly (MEA) is an essential component that mainly determines the performance of proton exchange membrane fuel cells (PEMFCs). In the electrodes of the MEA, ionomers are mixed with Pt-based nanoparticles to transfer protons to the Pt surface where electrochemical reactions take place. However, Pt catalysts suffer from the poisoning effect of ionomers with proton-conducting groups such as sulfonic acid (SA), resulting in performance deterioration. In particular, for emerging hydrocarbon-based ionomers, the benzene group, which is commonly used to improve their chemical structure, accelerates the poisoning effect. Herein, we experimentally simulate the adsorption of SA and benzenesulfonic acid (BSA) on Pt nanoparticles, revealing the orientation-dependent poisoning effect of BSA on the Pt surface.

The effects of varying wall thickness on the surface roughness of Ti-6Al-4V by electron beam powder bed fusion

While the electron beam powder bed fusion (EB-PBF) process is recognized for generating parts with high surface roughness, the impact of wall thickness remains relatively understudied and shows inconsistent literature results. This study addresses this gap by performing a full factorial Design of Experiments (DoE) to examine Ti-6Al-4V specimen surfaces built in three distinct orientations (vertical, upskin, and downskin) and six wall thickness levels (0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 mm). Findings reveal orientation-dependent effects of wall thickness on surface roughness, particularly for thicknesses below 1.0 mm. Vertical surfaces show increased roughness with decreasing wall thickness, in which 0.5 mm-thick specimens exhibited the highest Ra roughness values. In contrast, no particular trend was observed for upskin surfaces, with 0.5 mm specimens displaying roughness values comparable to the 2.0 to 4.0 mm range of specimens. Yet, downskin surfaces of 0.5 mm specimens showed significantly lower Ra roughness compared to their thicker counterparts, a trend opposite of that of vertical surfaces. These behaviors may relate to scanning strategies and electron beam parameters, particularly when building smaller cross-sectional areas.

Polarization retention dependence of imprint time within LiNbO3 single-crystal domain wall devices

Ferroelectric LiNbO3 single crystals have wide applications in surface acoustic wave filters, pyroelectric sensors, and electro-optic modulators. Large-area LiNbO3 single-crystal thin films integrated on silicon are promising for high density integration of ferroelectric domain-wall resistance switching memories and transistors. However, the short-time operation of the memory often suffers from poor polarization retention due to the built-in imprint voltage. Here, we observed the strong polarization orientation-dependent imprint effect within either out-of-plane or in-plane LiNbO3 thin-film capacitors. The imprint effect can shift domain switching hysteresis loops toward positive/negative voltages seriously with written negative/positive polarizations that occur within a characteristic imprint time of 5.1 ms–360 s. Once the write time of the memory is shorter than the imprint time, the inverted domain is unstable and switches back into its previous orientation automatically after the termination of a write operation. However, the write failure can be avoided if the write time is longer than the imprint time, and the written domain can be deeply protected by the imprint field. A model of polarization-dependent charge injection at the interface is developed to explain the time-dependent imprint effect. For a mesa-like LiNbO3 memory cell in contact with two side electrodes fabricated at the film surface, the imprint time can be greatly shortened below 30 ns with the extension of one side electrode over the cell surface to screen the tail of the switched domain, enabling ferroelectric domain-wall resistance switching devices in excellent retention and high operation speeds.

A microabrasion wear study of nitrided α-Ti and β-TiNb PVD metallic thin films, pre-deposited onto titanium alloy substrates

In this paper, we study the structure, mechanical properties and abrasion resistance of two triode-plasma nitrided (TPN) titanium alloys, pre-coated with metallic α-Ti or β-TiNb layers deposited by physical vapour deposition (PVD). The chosen alloys were Ti-6Al-4V and Ti-4Al-10V-22Mo, which are predominantly alpha- and beta-phased, respectively – each presenting different challenges, in terms of their nitriding response. Although duplex nitriding + PVD coating is now quite widely employed on steels (and increasingly on titanium alloys) to improve load-bearing capacity and wear resistance, the use of PVD coatings prior to diffusion treatment to control surface roughness – and, in the case of Ti-alloys particularly, to optimise their ‘challenging’ diffusion kinetics has received little or no attention so far. The TPN process enables diffusion treatments to be carried out at 700 °C – which is lower than the beta-transus temperature of Ti (and of most Ti alloys). Optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, nanoindentation, and surface profilometry were used to characterize the nitrided and coated/nitrided samples. It was found that the nitrogen concentration and surface hardness for all samples was significantly increased, and that the surface roughness values significantly increased for uncoated Ti alloy substrates after TPN treatment – due to intense, grain orientation-dependent plasma etching effects. However, our novel approach of PVD pre-deposition of a nanostructured metallic coating prior to nitriding reduces surface roughening effects quite dramatically. The micro-abrasion resistance of Ti- and TiNb-coated Ti-6Al-4V substrates was significantly enhanced after nitriding treatment; on the other hand, similar improvements were not found for the metastable-beta Ti-4Al-10V-22Mo substrates – due to the different nitriding behaviour of the pre-deposited PVD surface layers. The “sputter removal” rates for the metallic coatings were high, but all coatings survived in part until the end of the nitriding process.

Orientation-dependent strain effects on the metal-insulator transitions in (V0.99Cr0.01)2O3/Al2O3 thin films

${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ is an archetypical Mott material which exhibits Cr doping and/or temperature-induced paramagnetic metal to paramagnetic insulator/antiferromagnetic insulator (PM-PI/AFI) transitions. However, the strain effects on the metal-insulator transition (MIT) in thin films and the mechanisms behind them are not yet fully understood. In this study, we investigate the strain effects on the MIT in $({\mathrm{V}}_{0.99}{\mathrm{Cr}}_{0.01}{)}_{2}{\mathrm{O}}_{3}$ (VC1) thin films growing on $c$-plane (001), $r$-plane (012), and $a$-plane (110) ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ substrates. The strains can be tuned in a wide range over 1% in $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films by changing the substrate temperature. Remarkably, the influence of strain on the MIT differs dramatically from (001)-oriented and non-(001)-oriented $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films. The PM-PI transition can be effectively modulated by strain tuning in the (001) $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films accompanied by gradual transformation from the PM/PI phase into the AFI phase upon cooling. On the contrary, both (012) and (110) $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films exhibit sharp PM-AFI transitions irrespective of the strain states. The orientation-dependent strain effects on the MIT in the $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films could be explained by the trigonal distortion within electronic correlation scenario. The trigonal distortion of $\mathrm{V}(\mathrm{Cr}){\mathrm{O}}_{6}$ octahedra along (within) the $c$ axis ($ab$ plane) in the (001) $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films can be directly modulated by the strains. However, the trigonal distortion in the (012) and (110) $\mathrm{VC}1\text{/}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ thin films would hardly be affected due to the deviation of the film orientation from the $c$ axis. This explanation is experimentally confirmed by Raman spectra as a sensitive probe of the trigonal distortion in VC1 thin films. These results highlight the importance of trigonal distortion to understand the MIT in the ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ compound.

Orientation-dependent effects of transcranial alternating current stimulation (tACS) on spike timing in awake non-human primates

Orientation-dependent effects of transcranial alternating current stimulation (tACS) on spike timing in awake non-human primates

Orientation-dependent effects of indeno[1,2-b]indole-spirofluorene donor on photovoltaic performance of D−π−A and D−D−π−A sensitizers

Dyes JY70−73 based on indeno[1,2-b]indole-spirofluorene (IISF) donor have been synthesized and applied in dye-sensitized solar cells, two of them feature donor−π−acceptor (D−π−A) configuration and the others adopt a D−D−π−A structure. Orientation-dependent effects of IISF donor are clearly observed in the photovoltaic properties of D−π−A type dyes JY70 and JY72, though close power conversion efficiency (PCE) achieves finally owing to the trade-off effect of open-circuit voltage (VOC) and short-circuit current density (JSC). By contrast, regioisomeric dyes JY71 and JY73 with an auxiliary diphenylamine donor present a significantly different photovoltaic performance. Under the [Co(phen)3]2+/3+ electrolyte, device based on JY73 gives much higher VOC and JSC, hence a greater PCE (7.40%) which is over two times higher than its regioisomeric JY71 (3.31%). Reasons for that have been systematically investigated. Cocktail co-sensitizations of dyes JY73 and JY70/JY72 both promote the PCEs up to over 8%, and device based on JY72&JY73 achieves the highest PCE of 8.32%.

Orientation-dependent electric transport and band filling in hole co-doped epitaxial diamond films

Diamond, a well-known wide-bandgap insulator, becomes a low-temperature superconductor upon substitutional doping of carbon with boron. However, limited boron solubility and significant lattice disorder introduced by boron doping prevent attaining the theoretically-predicted high-temperature superconductivity. Here we present an alternative co-doping approach, based on the combination of ionic gating and boron substitution, in hydrogenated thin films epitaxially grown on (111)- and (110)-oriented single crystals. Gate-dependent electric transport measurements show that the effect of boron doping strongly depends on the crystal orientation. In the (111) surface, it strongly suppresses the charge-carrier mobility and moderately increases the gate-induced doping, while in the (110) surface it strongly increases the gate-induced doping with a moderate reduction in mobility. In both cases the maximum total carrier density remains below 2·1014 cm−2, three times lower than the value theoretically required for high-temperature superconductivity. Density-functional theory calculations show that this strongly orientation-dependent effect is due to the specific energy-dependence of the density of states in the two surfaces. Our results allow to determine the band filling and doping-dependence of the hole scattering lifetime in the two surfaces, showing the occurrence of a frustrated insulator-to-metal transition in the (110) surface and of a re-entrant insulator-to-metal transition in the (111) surface.

Epitaxial growth and orientation-dependent anomalous Hall effect of noncollinear antiferromagnetic Mn3Ni0.35Cu0.65N films

We report the growth of noncollinear antiferromagnetic (AFM) Mn3Ni0.35Cu0.65N films and the orientation-dependent anomalous Hall effect (AHE) of (001) and (111) films due to the nonzero Berry curvature. We found that post-annealing at 500 °C can significantly improve the AHE signals, though using the appropriate post-annealing conditions is important. The AHE and magnetization loops show sharp flipping at the coercive field in (111) films, while (001) films are hard to saturate by a magnetic field. The anomalous Hall conductivity of (111) films is an order of magnitude larger than that of (001) films. The present results provide not only a better understanding of the AHE in Mn3XN systems but also further opportunities to study the unique phenomena related to noncollinear AFM.

Near-Threshold Fatigue Crack Growth Rates of Laser Powder Bed Fusion Produced Ti-6Al-4V

When Ti-6Al-4V is processed by laser powder bed fusion (LPBF), a material with a martensitic microstructure is obtained. Moreover, the presence of internal stresses, an outer surface with relatively high surface roughness and the presence of remnant porosity all influence the fatigue life of high cyclically loaded components. The majority of investigations on LPBF produced Ti-6Al-4V have focussed on a fatigue life method providing valuable, albeit limited, insight into fatigue failure mechanisms. Near-threshold fatigue crack growth rates are vital for describing fatigue crack initiation mechanisms and how these are influenced by residual stress, a martensitic microstructure and build orientation. This study investigates near-threshold fatigue crack growth rates of LPBF produced Ti-6Al-4V. The study makes use of full-size compact tension specimens for fatigue crack growth rate investigations, the contour method for residual stress measurement, and scanning electron microscopy with electron backscatter diffraction to consider both morphological and crystallographic texture. Results show anisotropic near-threshold fatigue crack growth rates that are dependent on residual stress levels and load-ratios. Fracture is predominantly governed by transgranular quasi-cleavage mechanisms, and the fracture path is directed by the columnar prior beta-grain structure resulting in orientation-dependent crack closure effects. Residual stresses result in crack opening that causes a shift of near-threshold fatigue crack growth rates. An intrinsic ΔKth of ~1.6 ± 0.2 MPa√m and critical Kmax of ~ 3 MPa√m is measured that is independent of the stress state but dependent on orientation. It is shown that this anisotropy is linked to morphological texture and to a lesser extent the crystallographic texture of LBPF produced Ti-6Al-4V.

Gamma-ray emission in radio galaxies under the VLBI scope

Aims. In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the γ-ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi-LAT-detected sources. Methods. The TANAMI program monitors a large sample of radio-loud AGN at 8.4 GHz and 22.3 GHz with the Australian long baseline array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We performed a kinematic analysis for five γ-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed 103 months of Fermi-LAT data in order to study possible connections between the γ-ray properties and the pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the individual source results and draw preliminary conclusions on sample properties including published VLBI results from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey, with a total of fifteen sources. Results. We find that the first γ-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. We detect subluminal parsec-scale jet motions in the peculiar AGN PKS 0521−36, and we confirm the presence of fast γ-ray variability in the source down to timescales of six hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to βapp ∼ 3, in the jet of the TeV radio galaxy PKS 0625−35. Our VLBI results constrain the jet viewing angle to be θ < 53°, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical compact symmetric object (CSO) PKS 1718−649, we place an upper limit on the separation speed between the two mini-lobes. This in turn allows us to derive a lower limit on the age of the source. Conclusions. We can draw some preliminary conclusions on the relationship between pc-scale jets and γ-ray emission in radio galaxies, based on Fermi-LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the γ-ray flux, as seen in blazars. On the other hand, the γ-ray luminosity does not show any dependence on the core brightness temperature and core dominance, which are two common indicators of jet Doppler boosting. This seems to indicate that γ-ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, in accordance with the unified model of jetted AGN.

Molecular dynamic simulation of orientation-dependent effect on silicon crystalline during sputtering process of focused ion beam

In this paper, experiments and molecular dynamic simulation are performed to investigate the crystal orientation-dependent effects in a focused ion beam (FIB) sputtering etching process on silicon crystal planes. The experimental results indicate that different silicon orientation planes have different etched profiles, aspect ratios on microstructures, and sputtering yields under the same process conditions, which brings difficulty in deciding the process parameters for the fabrication of high-resolution nanostructures. Molecular dynamic simulation based on empirical potential is carried out to explain this effect on an atomic scale. The sputtered profiles of different silicon crystal planes after hundreds of impacts by Ga+ ions are analyzed. Both the simulation and experimental results show that with the same FIB etching conditions, structures on an Si (111) plane have the maximum opening width and minimum depth. Compared with the etched profile on an Si (100) plane, trenches on Si (110) have a smaller width, but greater depth. The Si (111) plane has the minimum sputtering yield. Furthermore, simulation results on the distribution of Ga+ ions remaining inside the substrate, number of ions sputtered out of the surface, and common neighbor analysis (CNA) can explain the orientation-dependent effect during FIB sputtering etching.

Metamaterials with index ellipsoids at arbitrary k-points

Propagation behaviors of electromagnetic waves are governed by the equifrequency surface of the medium. Up to now, ordinary materials, including the medium exist in nature and the man-made metamaterials, always have an equifrequency surface (ellipsoid or hyperboloid) centered at zero k-point. Here we propose a new type of metamaterial possessing multiple index ellipsoids centered at arbitrary nonzero k-points. Their locations in momentum space are determined by the connectivity of a set of interpenetrating metallic scaffolds, whereas the group velocities of the modes are determined by the geometrical details. Such system is a new class of metamaterial whose properties arise from global connectivity and hence can have broadband functionality in applications such as negative refraction, orientation-dependent coupling effect, and cavity without walls, and they are fundamentally different from ordinary resonant metamaterials that are inherently bandwidth limited. We perform microwave experiments to confirm our findings.

A radial measurement of the galaxy tidal alignment magnitude with BOSS data

The anisotropy of galaxy clustering in redshift space has long been used to probe the rate of growth of cosmological perturbations. However, if galaxies are aligned by large-scale tidal fields, then a sample with an orientation-dependent selection effect has an additional anisotropy imprinted onto its correlation function. We use the LOWZ and CMASS catalogs of SDSS-III BOSS Data Release 12 to divide galaxies into two sub-samples based on their offset from the Fundamental Plane, which should be correlated with orientation. These sub-samples must trace the same underlying cosmology, but have opposite orientation-dependent selection effects. We measure the clustering parameters of each sub-sample and compare them in order to calculate the dimensionless parameter $B$, a measure of how strongly galaxies are aligned by gravitational tidal fields. We found that for CMASS (LOWZ), the measured $B$ was $-0.024 \pm 0.015$ ($-0.030 \pm 0.016$). This result can be compared to the theoretical predictions of Hirata 2009, who argued that since galaxy formation physics does not depend on the direction of the observer, the same intrinsic alignment parameters that describe galaxy-ellipticity correlations should also describe intrinsic alignments in the radial direction. We find that the ratio of observed to theoretical values is $0.51\pm 0.32$ ($0.77\pm0.41$) for CMASS (LOWZ). We combine the results to obtain a total ${\rm {Obs}/{Theory}} = 0.61\pm 0.26$. This measurement constitutes evidence (between 2 and 3$\sigma$) for radial intrinsic alignments, and is consistent with theoretical expectations ($<2\sigma$ difference).

Strain Rate Effect on Tensile Flow Behavior and Anisotropy of a Medium-Manganese TRIP Steel

The dependence of the plastic anisotropy on the nominal strain rate for a medium-manganese (10 wt.% Mn) transformation-induced plasticity (TRIP) steel with initial austenite volume fraction of 66% (balance ferrite) has been investigated. The material exhibited yield point elongation, propagative instabilities during hardening, and austenite transformation to α′-martensite either directly or through e-martensite. Uniaxial strain rates within the range of 0.005–500 s−1 along the 0°, 45°, and 90° orientations were selected based upon their relevance to automotive applications. The plastic anisotropy (r) and normal anisotropy (rn) indices corresponding to each direction and strain rate were determined using strain fields obtained from stereo digital image correlation systems that enabled both quasistatic and dynamic measurements. The results provide evidence of significant, orientation-dependent strain rate effects on both the flow stress and the evolution of r and rn with strain. This has implications not only for material performance during forming but also for the development of future strain-rate-dependent anisotropic yield criteria. Since tensile data alone for the subject medium-manganese TRIP steel do not satisfactorily determine the microstructural mechanisms responsible for the macroscopic-scale behavior observed on tensile testing, additional tests that must supplement the mechanical test results presented herein are discussed.

The Essential Genome of Escherichia coli K-12.

ABSTRACTTransposon-directed insertion site sequencing (TraDIS) is a high-throughput method coupling transposon mutagenesis with short-fragment DNA sequencing. It is commonly used to identify essential genes. Single gene deletion libraries are considered the gold standard for identifying essential genes. Currently, the TraDIS method has not been benchmarked against such libraries, and therefore, it remains unclear whether the two methodologies are comparable. To address this, a high-density transposon library was constructed in Escherichia coli K-12. Essential genes predicted from sequencing of this library were compared to existing essential gene databases. To decrease false-positive identification of essential genes, statistical data analysis included corrections for both gene length and genome length. Through this analysis, new essential genes and genes previously incorrectly designated essential were identified. We show that manual analysis of TraDIS data reveals novel features that would not have been detected by statistical analysis alone. Examples include short essential regions within genes, orientation-dependent effects, and fine-resolution identification of genome and protein features. Recognition of these insertion profiles in transposon mutagenesis data sets will assist genome annotation of less well characterized genomes and provides new insights into bacterial physiology and biochemistry.

Diverted by dazzle: perceived movement direction is biased by target pattern orientation.

'Motion dazzle' is the hypothesis that predators may misjudge the speed or direction of moving prey which have high-contrast patterning, such as stripes. However, there is currently little experimental evidence that such patterns cause visual illusions. Here, observers binocularly tracked a Gabor target, moving with a linear trajectory randomly chosen within 18° of the horizontal. This target then became occluded, and observers were asked to judge where they thought it would later cross a vertical line to the side. We found that internal motion of the stripes within the Gabor biased judgements as expected: Gabors with upwards internal stripe motion relative to the overall direction of motion were perceived to be crossing above Gabors with downwards internal stripe movement. However, surprisingly, we found a much stronger effect of the rigid pattern orientation. Patches with oblique stripes pointing upwards relative to the direction of motion were perceived to cross above patches with downward-pointing stripes. This effect occurred only at high speeds, suggesting that it may reflect an orientation-dependent effect in which spatial signals are used in direction judgements. These findings have implications for our understanding of motion dazzle mechanisms and how human motion and form processing interact.

Mechanical Behavior and Microstructural Analysis of Extruded AZ31B Magnesium Alloy Processed by Backward Extrusion

This study investigates the mechanical behavior of an extruded AZ31B magnesium alloy profile at various strain rates from 0.001 to 375/s. The electron backscatter diffraction analysis revealed that the profile has $$\left\{ { 0 0 0 1} \right\}\langle 1 0\overline{1} 0 \rangle$$ and $$\{ {1 0\overline{1} 0 }\}\langle { 1 1\overline{2} 0}\rangle$$ textures. Due to the textures, the profile exhibits pronounced anisotropy in mechanical properties. In the extrusion direction (ED), the profile shows the highest yield strength (YS) but the lowest total elongation at fracture (TE) due to a hard activation of non-basal slip and $$\{ { 1 0\overline{1} 1} \}\langle { 1 0\overline{1} \overline{2} } \rangle$$ twinning; in the diagonal direction (DD), it shows the lowest ultimate tensile strength (UTS) but the highest TE due to an easy activation of basal slip; in the transverse direction (TD), it shows the lowest YS due to an easy activation of $$\{ {10\overline{1} 2} \}\langle {10\overline{1} \overline{1} } \rangle$$ twinning. Moreover, the number of twins increases with the increasing strain rate. This indicates that deformation twinning becomes prevalent to accommodate high-rate deformation. Due to the different deformation mechanisms, the profile exhibits an orientation-dependent effect of strain rate on the mechanical properties. A positive effect of strain rate on the YS and UTS was found in the ED, while the effect of strain rate on the YS is negligible in the DD and TD. The TE in the ED, DD, and TD decreases in general as the strain rate increases. Fractographic analysis under a scanning electron microscope revealed that the fracture is a mixed mode of ductile and brittle fracture, and the magnesium oxide inclusions could be the origins of the fracture.