Yield Anisotropy Research Articles

Integrated modeling of anisotropic neutron yields of classical and spherical tokamaks

Estimations of counting rates of neutron spectrometers in experiments on controlled fusion with magnetic confinement, as well as calculations of energy resolved flux densities of fusion neutrons from plasma to the walls of a reactor require spatial integration of the local, usually anisotropic function of the neutron source. The integrated modeling consists of three main stages. First, sources of fast particles in beam- or wave-heated plasma are calculated. The next stage deals with spatial, energetic, and angular velocity distributions of plasma ions. Finally, double differential rate coefficients of nuclear fusion reactions are computed. This article describes calculations of spatial distributions of nuclear fusion reaction rates in classical and spherical tokamaks and the anisotropy of the neutron yield and spectra. The results are based on analytical formulas for energetic and angular distributions of the local source of fusion products in plasma. Examples of energetic spectral densities of neutron fluxes on first walls are presented, as well as energy resolved counting rates of collimated neutron spectrometers for perpendicular and tangential lines of sight.

Revealing the anisotropic response of grain structures in additive manufactured Al-Mn-Sc alloys: Modeling based on experiments

The anisotropy of yield strength of additive manufactured (AM) Al-Mn-Sc alloy is attributed to the diverse distribution characteristics of grain size, aspect ratio and orientation. This work focus on controlling the yield strength and anisotropy of AM aluminum through microstructure design. In this work, microstructures information of laser powder-bed fusion (LPBF) processed Al-Mn-Sc alloys were obtained by electron back scatter diffraction (EBSD) analysis. The impact of grain size, aspect ratio and orientation on strength and anisotropy are quantitatively researched through modeling. Base on quantitative effect of orientation on strength and anisotropy, all microstructure partition schemes are calculated by MATLAB. Microstructure partition schemes of alloy with low anisotropy and high yield strength were predicted and simulation was enforced to certify the credibility of predication. Local stress in grain and orientation variation during deforming were obtained by simulation. It is concluded that the impact of orientation is more obvious than grain size and aspect ratio. Compared with strength and anisotropy obtained by simulation, the prediction of calculation shows fine precision. The impact of microstructures on mechanical properties and the reliability of modeling were verified.

Investigation of the influence of plane strain constrained anisotropic plastic flow on the localized necking prediction

PurposeThe purpose of this manuscript is to investigate the influence of the satisfying of plane strain conditions on the prediction of the localized necking and to evaluate this effect by the different hardening models.Design/methodology/approachHigh-order anisotropic Drucker yield function, two types of hardening models, namely Hollomon power and Voce saturated, and the modified maximum force criterion (MMFC) are employed to predict the forming limit strains of AA3104-H19 alloy. Two identification methods, namely conventional and plane strain constrained, are applied and forming limit diagrams of the material are predicted by the incorporation of the anisotropic Drucker criterion and the hardening models into the MMFC for both calibration methods.FindingsThe enhancement in the prediction accuracy of the forming limits provided by the implementation of the plane strain constrained method is strongly dependent upon the selected hardening model type in the MMFC. About 18% improvement in the prediction of the biaxial limit strains is provided via Hollomon power law hardening, whereas the opposite result is occurred in case that the Voce saturated hardening law is used, and the predictions match with the experimental data only in the plane strain point and its surroundings.Originality/valueThe plane strain constrained identification method precisely predicts the location of the plane strain point on the yield locus and also any yield stress or anisotropy coefficient in the plane strain state is not required during the calibration, therefore the method can reduce the number of the required experiments for the constitutive characterization, and it will be attractive for both academy and industry. Additionally, the improvement in the prediction of the biaxial forming limits can be provided by applying of this method along with the appropriate hardening law.

Microstructure and mechanical properties of Mg−Gd−Y−Zn−Zr alloy plates with different initial textures after hot rolling

The effects of initial textures on the microstructures and mechanical properties of rolled Mg−4.7Gd− 3.4Y−1.2Zn−0.5Zr (wt.%) plates were studied by optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM) and tensile test. In the plate with an initial texture of 〈0001〉//RD (rolling direction), relatively coarse grains and bimodal basal texture are developed. However, in the plate with an initial texture of 〈0001〉//TD (transverse direction), finer grain size and strong 〈0001〉//ND basal textures are obtained due to the higher degree of dynamic recrystallization during rolling. Additionally, the irregular-shaped long-period stacking ordered (LPSO) phases are elongated along RD in both plates, which results in anisotropic load-bearing strengthening behavior, and further leads to a certain degree of yield anisotropy. The analysis of the strengthening mechanism shows that grain boundary strengthening is the most effective strengthening method in the plates. Because of the finer grain size and the strengthening caused by the elongated irregular-shaped LPSO phases, the rolled plate with an initial 〈0001〉//TD texture achieves the highest yield strength along RD.

Effect of texture on the room temperature tensile and creep properties of Ti–6Al–4V plate with large thickness

Texture is inevitably generated during the rolling process of titanium alloys, which has a significant impact on mechanical properties. The relationship between microstructure, texture and mechanical properties of the rolled Ti–6Al–4V alloy plate with large thickness was systematically investigated in this study. The texture type varied with the thickness of the plate. The basal pole concentrated in the transverse direction (TD) at the surface of the plate and tilted from TD towards the rolling direction (RD) at the quarter thickness of the plate. For the center of the plate, the basal pole had peaks concentrated close to both TD and RD. Tensile tests indicated that TD samples not only have high strength but also maintain good plasticity compared with RD and the normal direction (ND) samples. The yield anisotropy could be explained by the difficulty of prismatic and basal dislocation slip. The cold creep behavior of the thick plate depended on both Schmid factor of dislocation slip and grain size. Moreover, the strain hardening exponent was positively correlated with cold creep strain. Abundant prismatic <a> and pyramidal <c+a> dislocations were activated, and slip transfer and cross-slip made the dislocation slip distance longer, which contributed to creep strain and thus reduced the creep resistance of ND sample.

Microstructure, texture evolution and mechanical anisotropy of Mg-Gd-Y-Zn-Zr alloy sheets produced by unidirectional and cross rolling

The unidirectional rolling (UR) and cross rolling (CR) were used to process the Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr (wt.%) alloy sheets. The effect of rolling routes on microstructure, texture evolution, and mechanical anisotropy was investigated. The deformed grains in UR alloy were gradually elongated along the RD, and the intragranular lamellar LPSO phase also transforms into a rod-shaped structure during rolling. For CR alloy, the occurrence of dynamic recovery results in the LPSO phase remaining lamellar shape during rolling, and the deformed grains are rounder than those in UR alloy. After rolling, UR alloy exhibits a texture with basal pole deviates from ND toward the location between TD and RD, which is caused by the synergistic effect of limited twinning, basal and prismatic slip. The CR alloy shows a texture with basal poles deviating from ND to RD 15.6°, which results from the activation of basal slip, pyramidal slip, and multiple twinning variants. The UR alloy exhibits approximately isotropic in yield strength and anisotropy in elongation, while the CR alloy presents a completely different result. The anisotropy in yield strength of CR alloys is related to their texture distribution and remarkably different basal slip Schmid factor in three tensile directions. The isotropic in elongation of CR alloys can be explained by the distribution frequency of tilt angles between basal poles and tensile directions, as well as the kink deformation of lamellar LPSO phase.

Modeling of seawater intrusion into Salalah coastal plain aquifer, sultanate of Oman

Excessive groundwater pumping has become a concern in Salalah coastal aquifer in Oman causing seawater intrusion at different farms and abstraction wells near the shoreline. MODFLOW and MT3DMS were calibrated and validated for Salalah coastal aquifer to assess aquifer behavior and seawater intrusion pattern with new input data and fine grid spacing to improve the accuracy of predictions as compared to the previous modeling studies in this region. The study was conducted over an area of 640 km2 of Salalah Plain representing around 83% of its total area. Injection of tertiary treated wastewater, rainfall and dams were considered as sources of aquifer recharge while groundwater abstraction occurred for agricultural, domestic, and commercial uses. The calibration and validation of the models were done in steady and transient states using observed groundwater levels from year 2000–2019. The aquifer properties such as hydraulic conductivity, specific yield, and vertical anisotropy were calibrated. MODFLOW results were utilized by MT3DMS to simulate solute transport at transient state. The longitudinal dispersivity and porosity of the aquifer were obtained by calibration and validation of the model. Over the three aquifer layers, the hydraulic conductivity ranges from 10 m/day to 100 m/day, vertical anisotropy is 4 and the specific yield ranges from 0.01 to 0.1. The calibrated values of the longitudinal dispersivity and porosity range from 500 m to 50000 m, and 0.4, respectively. The study indicated a clear impact of seawater intrusion at coastal side of the Salalah plain. The predictive modeling indicated an average of 1.5 m drop in hydraulic head across the whole study area by 2040, while seawater intrusion effect was expected to increase near the coast with potential extension to the central area of the Salalah plain. The validated model can be used as a prediction tool by the decision makers to manage the aquifer considering different scenarios, for integrated water resources management in Salalah city.

Anisotropic deformation mechanisms of rolling-textured Zircaloy-4 alloy by a crystal plasticity model

This study focuses on investigating the anisotropic deformation behavior of rolling-textured Zircaloy-4 alloy under uniaxial tension along the rolling direction (RD) and transverse direction (TD). A dislocation density-based crystal plasticity finite element method is used to study the associated mechanisms. The simulation accurately reproduces the experimental results on stress–strain curves and strain hardening rate. The relationship between relative activities in different slip systems and anisotropic plastic deformation is established. It is revealed that in the tensile deformation, prismatic slip dominates plastic deformation in the RD, while both prismatic slip and basal slip dominate plastic deformation in the TD. The difference in the dominant slip modes leads to a lower yield stress and a higher strain hardening rate in the RD. Furthermore, the stress and strain distributions in the tensile direction are also statistically analyzed. It is found that a certain proportion of hard grains results in more severe stress concentration and lower uniform elongation in the TD specimen compared with the RD specimen. In addition, the strain rate sensitivity of the yield stress is investigated. It is shown that Zircaloy-4 alloy has almost the same yield anisotropy (TD > RD in terms of the yield stress) at different strain rates in the RD and TD.

Effect of unidirectional rolling and cross-rolling on microstructure and mechanical anisotropy of Mg-Gd-Y-Ag-Zr plates

Mg-10Gd-2Y-0.4Ag-0.4Zr (wt%) alloy plates are prepared by Unidirectional Rolling (UR) and Cross-Rolling (CR). The effects of these two methods on the microstructure and mechanical anisotropy of the plates are investigated in detail by combining microstructure characterization and room temperature tensile tests. The results show that the UR plate has a finer grain size and obvious dynamic precipitation response, with many dynamically precipitated β phase particles distributed along the rolling direction and forming particle strips. The CR plate has experienced more dynamic recovery, and the driving force of dynamic recrystallization is decreased, resulting in larger grain size. However, the more dynamic recovery reduces the dynamic precipitation response and leads to a more uniform microstructure, and hardly finds dynamic precipitated β phase particles in the CR plate. The texture component of the UR plate is the basal texture and TD-split texture, while that of the CR plate is the basal texture and rare RT-split texture. The TD-split texture and the anisotropic distributed particle strips in the UR plate caused a strong mechanical anisotropy. While the yield anisotropy and elongation anisotropy of the CR plate are reduced simultaneously due to the more uniform microstructure and rare RT-split texture.

Achieving high ductility and low in-plane anisotropy in magnesium alloy through a novel texture design strategy

Texture regulation is a prominent method to modify the mechanical properties and anisotropy of magnesium alloy. In this work, the Mg-1Al-0.3Ca-0.5Mn-0.2Gd (wt.%) alloy sheet with TD-tilted and circular texture was fabricated by unidirectional rolling (UR) and multidirectional rolling (MR) method, respectively. Unlike generating a strong in-plane mechanical anisotropy in conventional TD-tilted texture, the novel circular texture sample possessed a weak in-plane yield anisotropy. This can be rationalized by the similar proportion of soft grains with favorable orientation for basal <a> slip and {101¯2} tensile twinning during the uniaxial tension of circular-texture sample along different directions. Moreover, compared with the TD-tilted texture, the circular texture improved the elongation to failure both along the rolling direction (RD) and transverse direction (TD). By quasi-in-situ EBSD-assisted slip trace analysis, higher activation of basal slip was observed in the circular-texture sample during RD tension, contributing to its excellent ductility. When loading along the TD, the TD-tilted texture promoted the activation of {101¯2} tensile twins significantly, thus providing nucleation sites for cracks and deteriorating the ductility. This research may shed new insights into the development of formable and ductile Mg alloy sheets by texture modification.

Production Yield and Azimuthal Anisotropy Measurements of Strange Hadrons from BES at STAR

Production Yield and Azimuthal Anisotropy Measurements of Strange Hadrons from BES at STAR

Achieving texture randomization and yield anisotropy reduction in rolled Mg-Zn-Y-Zr alloy by multidirectional impact forging

Achieving texture randomization and yield anisotropy reduction in rolled Mg-Zn-Y-Zr alloy by multidirectional impact forging

Crystal plasticity constitutive modeling of tensile, creep and cyclic deformation in single crystal Ni-based superalloys

A microstructure-sensitive crystal plasticity constitutive framework is proposed for simulating the tensile, cyclic, and creep response of single crystal Ni-based superalloys. In this framework, a non-Schmid model is used to account for the orientation- and temperature-dependent yield anisotropy. A model for the evolution of the slip system-level backstress is developed to simulate the cyclic response. The model accounts for the effect of microstructural features like precipitate volume fraction and size, and matrix channel width, on the associated hardening mechanisms. A physical model for creep deformation has also been developed that accounts for dislocation climb normal to the slip plane and the microstructure evolution due to rafting and isotropic coarsening of the precipitates. Application of the model is demonstrated by predicting the orientation- and temperature-dependent thermo-mechanical deformation of two single crystal superalloys, CMSX-4 and PWA-1484. The model is calibrated to the experimental tensile, cyclic and creep response for these alloys. Finally, the model is qualitatively validated by predicting the creep-fatigue interactions for different loading orientations and a range of thermo-mechanical conditions for CMSX-4 and PWA-1484.

Effect of microalloyed Al and Ca on mechanical properties and corrosion resistance of high-speed extruded Mg-2Zn-1Mn (mass%) alloy

Mechanical properties and corrosion resistance of high-speed extruded Mg-2Zn-1Mn (mass%) alloys microalloyed with Al and/or Ca were evaluated. The microalloying of Al improved the tensile yield strength, while the compressive yield strength remained unchanged, which deteriorated the yield anisotropy. The Al addition also deteriorated the corrosion resistance owing to the formation of coarse βMn phases that promoted the galvanic corrosion. By the single addition of Ca, both tensile and compressive yield strengths increased, which led to a slight improvement of the yield anisotropy. A texture weakening, which was attributed to the single Ca addition, also improved the ductility slightly. Such property improvements were achieved without the loss of corrosion resistance. A ViscoPlastic Self-Consistent simulation revealed that the single Ca addition was effective for the hardening of both basal and prismatic slips, which improved the yield strength in both tension and compression. • Microalloyed ZM21 alloys were extrudable at a high speed of 60 m/min. • Single Ca addition was effective in improving tensile and compressive properties. • Al addition increased yield anisotropy in tension and compression. • Al addition promoted micro galvanic corrosion.

Correlation of the anisotropic hardening behavior and texture features of cold rolled Zr-4 sheet under uniaxial tension

The strongly anisotropic mechanical behaviors commonly observed in Zr-4 sheets typically lead to inferior formability. In this study, the mechanical behavior and texture evolution of a cold-rolled Zr-4 sheet under uniaxial tension in various directions were systematically investigated, and the results showed both anisotropic yielding and hardening behavior in the Zr-4 sheet. The microstructure and texture features revealed by electron backscattered diffraction (EBSD) method indicate that this anisotropic mechanical behavior is closely related to the initial texture and its evolution during plastic deformation. In conjunction with experimental observations, a visco-plastic self-consistent (VPSC) model was employed to quantitatively analyze the relationship between the mechanical anisotropy and the texture features and activation of deformation modes. It was found that the yield anisotropy is affected by the distinct activity of prismatic <a> slip, while the different activities of basal <a> slip and extension twinning (ETW) result in anisotropic hardening. The distinct activation of deformation modes is mainly caused by differences in the evolution of the Schmid factor (SF) and critical resolved shear stress (CRSS) with increasing strain. Additionally, the results prove that the limited twinning activation with a fraction of less than 3% plays a non-negligible role in the hardening behavior during tension along the transverse direction. The latent hardening effect caused by the interaction between prismatic slip and tensile twinning is considered to successfully capture the anisotropic hardening behavior of the Zr-4 sheet. The implementation and insights from the predictions are presented and discussed in this work.

Stress Triaxiality in Anisotropic Metal Sheets-Definition and Experimental Acquisition for Numerical Damage Prediction.

Governing void growth, stress triaxiality (η) is a crucial parameter in ductile damage prediction. η is defined as the ratio of mean stress to equivalent stress and represents loading conditions. Attempts at introducing material anisotropy in ductile damage models have started only recently, rendering necessary in-depth investigation into the role of η here. η is commonly derived via finite elemnt (FE) simulation. An alternative is presented here: based on analytical expressions, η is obtained directly from the strains in the critical zone. For anisotropic materials, η associated with a specimen varies with yield criterion and material (anisotropy). To investigate the meaning of triaxiality for anisotropic materials, metal sheets made of dual phase steel DP780, and zirconium alloy Zirlo are chosen. Analytical expressions for η are derived for three popular yield criteria: von Mises, Hill48 and Barlat89. Tensile tests are performed with uniaxial tension, notch, and shear specimens, and the local principal strains, measured via digital image correlation (DIC), are converted to h. The uniaxial tension case reveals that only the anisotropic yield criteria can predict the expected η = 1/3. The ramifications associated with anisotropy become apparent for notched specimens, where η differences are highest; for shear specimens, the yield criterion and material-dependence is relatively moderate. This necessitates η and, consequently, the triaxiality failure diagram (TFD) being accompanied by the underlying yield criterion and anisotropy parameters. As the TFD becomes difficult to interpret, it seems more advantageous to provide pairs of principal strain ratio β and failure strain. Suggestions for deriving representative β and η are made.

A quantitative study on planar mechanical anisotropy of a Mg-2Zn-1Ca alloy

A TD-tilted basal texture in Mg alloys often generates a strong planar mechanical anisotropy. Unfortunately, there has been not a quantitative study on this issue. In the present study, the mechanisms for the anisotropy of tensile yield strength in RD-TD plane were quantitatively studied for a Mg-2Zn-1Ca alloy with different grain sizes and textures. Here, RD and TD refer to the rolling direction and transverse direction of the plate. The results show that there is a strong planar yield anisotropy (∼24 ± 5 MPa), regardless of grain size, while this yield anisotropy is absent in texture with a circular distribution of basal poles. The examination of microstructure and X-ray diffraction analysis reveals that, beside basal slip as the predominant mode under both RD-tension and TD-tension, prismatic slip in RD-tension and both prismatic slip and extension twinning in TD-tension are also important. The parameters of Hall-Petch relation are also used to further analyze the mechanism for yield anisotropy. The changeable intercept, σ0, and invariant Hall-Petch slope, k, between RD-tension and TD-tension are rationalized accounting for this anisotropy. The reasons why there are different σ0 and similar k between TD-tension and RD-tension are quantitively discussed. At last, a texture design for decreasing the planar yield anisotropy is given.

Measurement of prompt [formula omitted]-meson production and azimuthal anisotropy in Pb–Pb collisions at [formula omitted

The production yield and angular anisotropy of prompt Ds+ mesons were measured as a function of transverse momentum (pT) in Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV collected with the ALICE detector at the LHC. Ds+ mesons and their charge conjugates were reconstructed at midrapidity (|y|<0.5) from their hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the pT intervals 2<pT<50GeV/c and 2<pT<36GeV/c for the 0–10% and 30–50% centrality intervals. For pT>10GeV/c, the measured Ds+-meson nuclear modification factor RAA is consistent with the one of non-strange D mesons within uncertainties, while at lower pT a hint for a Ds+-meson RAA larger than that of non-strange D mesons is seen. The enhanced production of Ds+ relative to non-strange D mesons is also studied by comparing the pT-dependent Ds+/D0 production yield ratios in Pb–Pb and in pp collisions. The ratio measured in Pb–Pb collisions is found to be on average higher than that in pp collisions in the interval 2<pT<8GeV/c with a significance of 2.3σ and 2.4σ for the 0–10% and 30–50% centrality intervals. The azimuthal anisotropy coefficient v2 of prompt Ds+ mesons was measured in Pb–Pb collisions in the 30–50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured RAA, Ds+/D0 ratio, and v2 as a function of pT are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark–gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The pT-integrated production yield of Ds+ mesons is compatible with the prediction of the statistical hadronisation model.

Energy Dependence of Strangeness Production in Heavyion Collision

An experimental overview of the energy dependence of strangeness production is presented. The strange hadrons are considered a good probe to study the QCD matter created in relativistic nucleus-nucleus collisions. The heavy-ion experiments at SPS, RHIC, and LHC have recorded a wealth of data in proton-proton, proton-nucleus and nucleus-nucleus collisions at several beam energies. In this proceeding, I discuss the invariant yield and azimuthal anisotropy measurement of strange hadrons in nucleus-nucleus collisions at SPS, RHIC, and LHC.

Achieving Texture Randomization and Yield Anisotropy Reduction in As-Rolled Mg-Zn-Y-Zr Alloy by Multidirectional Impact Forging

Achieving Texture Randomization and Yield Anisotropy Reduction in As-Rolled Mg-Zn-Y-Zr Alloy by Multidirectional Impact Forging