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X-ray analysis of twin dominated deformation in an aged Mg-7Sn-3Zn-0.04Na alloy

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Journal of Magnesium and Alloys 2021年第4期9卷 1204-1214页

作者： Ehsan Bahrami Motlagh Peter ALynch Thomas Dorin Pavel Cizek Alireza Ghaderi matthew rbarnett Sitarama r.Kada Institute for Frontier Materials Deakin University75 Pigdons RoadWaurn PondsVIC 3216Australia CSIrO ManufacturingGeelong 3216Australia

In-situ transmission X-ray diffraction based compression deformation experiments are performed to study the twinning behaviour in asextruded(non-aged)and peak-aged Mg-7Sn-3Zn-0.04Na *** axial lattice strains were measured in the parent grains,twins and the precipitates as a function of applied *** critical shear stress for achieving 5%twinning was found to be increased by∼26MPa by the presence of 7%of Sn and by∼50MPa by the presence of the particles formed after 10 h of *** evolution of twin volume fraction with plastic strain is similar in both non-aged and aged conditions,indicating no change in the relative activities of slip and twin in the ideally oriented(10.10)parent *** made in previous studies of twin thickening stresses and twin bypass stresses agree reasonably well with the measured values,given the experimental *** relaxation was seen in the precipitate lattice *** is attributed to relaxation effects continuing during X-ray data *** flow curves confirm that precipitate hardening in the present system is particularly sensitive to relaxation *** is likely to be an important consideration for fatigue loading of precipitate hardened samples.

关键词： deformation alloy fatigue

Effect of plastic deformation on microstructure and thermoelectric properties of Mg_(2)Sn alloys

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Journal of Magnesium and Alloys 2021年第1期9卷 123-129页

作者： rameshkumar Varma Sitarama Kada matthew barnett Institute for Frontier Materials Deakin UniversityGeelongVictoriaAustralia

In the present work,the effect of deformation on microstructure and thermoelectric properties of Mg 2 Sn alloys having excess magnesium concentrations is *** cast alloys were prepared using radio-frequency(rF)induction melting under an argon *** alloys were thermo-mechanically processed via compression at different temperatures to various true *** room temperature,the alloys failed at a true strain of∼13%.However,at elevated temperatures,the alloys were observed to be highly *** alloys compressed at 673 K to a true strain of 1,a prominent substructure *** subgrain size was∼3-5μ*** is believed that the substructure arose from the action of dynamic *** deformation,the thermoelectric performance of alloy prepared with 6.7 wt.%excess Mg was improved compared to the as cast *** can be ascribed to a reduction in the thermal conductivity due to phonon scattering at grain boundaries.

关键词： Magnesium Thermoelectric Deformation Grain size

Three-dimensional crystal plasticity and Hr-EBSD analysis of the local stress-strain fields induced during twin propagation and thickening in magnesium alloys

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Journal of Magnesium and Alloys 2023年第2期11卷 657-670页

作者： Filip Siska Daria Drozdenko Kristian Mathis Jan Cizek Tingting Guo matthew barnett Institute of Physics of Materials The Czech Academy of SciencesZizkova 513/22Brno 61662Czech Republic Department of Physics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 5Prague 12116Czech Republic Institute of Plasma Physics The Czech Academy of SciencesZa Slovankou 1782/3Prague 18200Czech Republic Institute for Frontier Materials Deakin UniversityGeelongVictoria 3216Australia

Present work focuses on analysis of the stress and strain fields inside and around the individual {10–12} twin in magnesium alloy. The 3D crystal plasticity model represents twin as an ellipsoidal inclusion surrounded by the matrix. Five different twin thicknesses and three different lateral twin lengths are used for stress/strain analysis. The simulations are complemented with experimental observations using high-resolution electron backscattered diffraction. The simulations and experiments show a similar distribution of the shear stress and the spatial activity of individual slip systems(basal, prismatic, pyramidal). Plasticity induced inside the twin is dominantly caused by the prismatic dislocations slip and does not influence twin back stress which is identical to pure elastic twin. The twin with larger lateral dimension requires lower equilibrium stress which suggests anisotropic twin propagation and increased thickness of such twins. The lateral twin propagation is mostly influenced by prismatic and pyramidal slip in the twin vicinity. The twin thickness can reach a maximal level that is driven by the critical resolved shear stress values for dislocation slip with the significant influence of basal slip.

关键词： Magnesium alloy Twinning FEM Crystal plasticity Hr-EBSD

Age and sex differences in niche use at molt and its effect on plumage coloration characteristics in a bird

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Current Zoology 2019年第3期65卷 251-260页

作者： Emilio PAGANI-NUNEZ Craig r.A.barnett Juan Carlos SENAr State Key Laboratory of Biocontrol Department of Ecology/School of Life Sciences Sun Yat-sen University Guangzhou China Department of Zoology Graduate School of Science University of Kyoto Kitashirakawaoiwake-cho Sakio-ku Kyoto Japan Natural History Museum of Barcelona Barcelona Spain

Bird plumage is often very colorful and can communicate the quality of the bearer to conspecifics. These plumage-based signals of quality are composed of multiple pigments (e.g., melanin and carote no ids). Therefore, sex and age classes, which often show marked differe nces in plumage coloration, may have different dietary needs for the different plumage components and this might promote pref ere nces for differe nt dietary niches at different molting stages. However, no study has addressed the role that changes in niche use play in the expression of multiple component plumage signals in birds. We used stable isotope analysis to test the hypothesis that niche use is related to age and sex and to differently cultured plumage patches, yellow carotenoid-based and black melanin-based, in great tits Parus major. We recorded high niche overlap between plumage patches, although δ15N was higher in black than yellow plumage. Niche overlap was relatively low for age classes and relatively high for sex classes, and age classes showed a contrasting pattern of niche overlap between carotenoid- and melanin-based plumages. Moreover,δ13C, but not δ15N, had a significant negative relationship with carotenoid-based plumage, which was only apparent in juveniles. Take n together, our results demonstrate that n iche use had a moderate in fluence on plumage coloration characteristics of great tit individuals, mostly associated with δ13C rather than with δ15N and with age rather than with sex. Therefore, our study is significant because it confirms the releva nee of n iche use duri ng orn ame nt production in free-livi ng birds.

关键词： carotenoids great tits melanin multiple ornaments niche overlap stable isotopes

SUSTAINABLE MICrO-VILLAGES AND THE CArWOOLA HOUSE PrOJECT IN CANBErrA,AUSTrALIA

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Journal of Green Building 2018年第4期13卷 169-190页

作者： Paul barnett Paul barnett Design Group

INTrODUCTION Our needs as social and familial beings change over the course of our lives;however,it has become common practice to build as though these needs remain static through *** needs of a child,young adult,family,middle age and the elderly are dynamic between generations,and adding to these evolving life needs is the crisis of housing affordability.ree decades ago a house could cost 3-4 times an individual’s annual income,today that cost is closer to 10-12 *** response to these chal-lenges,this article explores the concept of Sustainable Micro-Villages,providing insight into a new approach to energy-efficient housing with reference to our case-study project-Carwoola *** Micro-Villages can be defined as a cluster of integrated dwellings,referred to here as Living *** a“single house”on a single site,these micro-villages can be comprised of two or more smaller buildings that provide private dwelling space for a single person,couples,couples with children,parents,elderly,friends and any combination of social *** pods cluster around a natural garden setting,enhanced by waterharvesting,and are connected with covered,open or enclosed links depending on the climate of the *** recent iterations of this type of dwelling also incorporate solar passive design,passive house and green-house *** Australia,new house designs are evaluated as part of an approvals process for their energy rating.1e Australian Building Code requires a minimum 6-star rating,ranging up to 10 stars for any new home to be built.A 6-star rating provides a good level of insulation and energy performance if built correctly,while 10 stars represent the highest level of energy performance and refers to a dwelling that needs no heating or *** Micro-Villages consistently achieve an 8 to 10-star rating by combining Solar Passive Design principles(good orientation,thermal mass and thermal performance)and Passive House Technology(

关键词： Micro Villages Living Pods Naturescapes Solar Passive Passive House Photovoltaics Waterharvesting Biophilia Permaculture Biodynamics Water Storage

Shock effects on the upper limit of the collision weld process window

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Advances in Manufacturing 2024年第2期12卷 365-378页

作者： Blake barnett Anupam Vivek Glenn Daehn Department of Materials Science and Engineering The Ohio State UniversityColumbusOH43210USA Army research Directorate Army Research LaboratoryDEVCOMAberdeen Proving GroundHarfordMD21005USA

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process ***,the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld *** formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld ***,collision welding fundamentally depends on the impacts that generate shockwaves in weld members,which can dominate the stress propagation velocities in thin weld ***,this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D rankine-Hugoniot *** shock upper limit is validated against the experimental and simulation data in the collision welding literature,and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.

关键词： Collision welding Solid-state welding Shock impact Weld process modelling Explosive bonding Laser impulse welding(LIW)

Insight from in situ microscopy into which precipitate morphology can enable high strength in magnesium alloys

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Journal of Materials Science & Technology 2018年第7期34卷 1061-1066页

作者： Bo-Yu Liu Nan Yang Jian Wang matthew barnett Yun-Chang Xin Di Wu ren-Long Xin Bin Li r. Lakshmi Narayan Jian-Feng Nie Ju Li Evan Ma Zhi-Wei Shan Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano) & Hysitron Applied research Center in China (HArCC) State Key Laboratory for Mechanical Behavior of Materials Xi' an Jiaotong University Xi' an 710049. People's Republic of China Mechanical and Materials Engineering University of Nebraska-Lincoln Lincoln NE 68588 USA Institute for Frontier Materials Deakin University Geelong Victoria 3216 Australia College of Materials Science and Engineering Chongqing University Chongqing 400045 People's Republic of China Institute of Metal research Chinese Academy of Sciences Shenyang 110016 People's Republic of China Department of Chemical and Materials Engineering University of Nevada Reno USA Department of Materials Science and Engineering Carnegie Mellon University Pittsburgh PA 15213 USA Department of Materials Science and Engineering Monash University Melbourne Victoria 3800 Australia Department of Nuclear Science and Engineering and Department of Materials Science and Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge MA 02139 USA Department of Materials Science and Engineering Johns Hopkins University Baltimore MD 21218 USA

Magnesium alloys, while boasting light weight, suffer from a major drawback in their relatively low strength. Identifying the microstructural features that are most effective in strengthening is therefore a pressing challenge. Deformation twinning often mediates plastic yielding in magnesium alloys. Unfortunately, due to the complexity involved in the twinning mechanism and twin-precipitate interactions, the optimal precipitate morphology that can best impede twinning has yet to be singled out. Based on the understanding of twinning mechanism in magnesium alloys, here we propose that the lamellar precipitates or the network of plate-shaped precipitates are most effective in suppressing deformation twinning. This has been verified through quantitative in situ tests inside a transmission electron microscope on a series of magnesium alloys containing precipitates with different morphology. The insight gained is expected to have general implications for strengthening strategies and alloy design. 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： Precipitate selection criterionIn-situ TEM Mg alloy Mechanical property Deformation twinning

Town-scale microbial sewer community and H2S emissions response to common chemical and biological dosing treatments

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Journal of Environmental Sciences 2020年第1期32卷 133-148页

作者： Elizabeth r.Mathews Jennifer L.Wood Dean Phillips Nathan Billington Dean barnett Ashley E.Franks Department of Physiology Anatomy and MicrobiologyLa Trobe UniversityMelbourneAustralia Centre for Future Landscapes La Trobe UniversityMelbourneAustralia Faculty of Science Engineering and TechnologySwinburne University of TechnologyMelbourneAustralia Western Water SunburyAustralia

Controlling hydrogen sulfide(H2S)odors and emissions using a single,effective treatment across a town-scale sewer network is a challenge faced by many water *** of a sewer diversion provided the opportunity to compare the effectiveness of magnesium hydroxide(Mg(OH)2)and two biological dosing compounds(Bioproducts A and B),with different modes of action(MOA),in a field-test across a large sewer ***(OH)2 increases sewer p H allowing suppression of H2S release into the sewer environment while Bioproduct A acts to disrupt microbial communication through quorum sensing(QS),reducing biofilm *** B reduces H2S odors by scouring the sewer of fats,oils and grease(FOGs),which provide adhesion points for the microbial *** revealed that only Mg(OH)2 altered the microbial community structure and reduced H2S emissions in a live sewer system,whilst Bioproducts A and B did not reduce H2S emissions or have an observable effect on the composition of the microbial community at the dosed *** results recommend in situ testing of dosing treatments before implementation across an operational system.

关键词： Microbially induced concrete corrosion Biological dosing treatments Magnesium hydroxide Hydrogen sulfide Sulfate-reducing bacteria Microbial ecology

Meta-Study of Particulate Detection Losses on radioactive Air Sample Filters

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Journal of Environmental Protection 2022年第8期13卷 589-602页

作者： J. matthew barnett Hunter Z. Edwards Pacific Northwest National Laboratory Richland USA

Several mathematical relationships between air sample filter mass loading and the correlated analytical self-absorption factor were developed using data from other published research in this meta-study. Gross-alpha and -beta applications are addressed for this research. As filter media becomes loaded with particulate matter, there is potential for measurement losses due to self-absorption by mass loading. Components contributing to absorption include particulate dust, radioactive particulates, and filter material. Standards indicate a correction factor should be used when the penetration of radioactive material into the collection media or self-absorption of radiation by the material collected would reduce the detection rate by more than 5%. Previously, losses due to self-absorption have been reported up to 100% over a range up to ~10 mg⋅cm-2 mass loading. These absorption losses then can be used to determine a correction factor for sample results. For low mass loadings (e.g., ≤0.1 mg⋅cm-2) corrections factors in the 0.85 - 1 range have been recommended and used, while at higher mass loadings nearer to 10 mg⋅cm-2 correction factors closer to 0 (representing near 100% losses) are used. Based on data from published studies, the different methods for relating percent loss due to self-absorption to mass loading include linear, exponential, quadratic, and trinomial derived functions. Where applicable, both forced zero and non-forced zero results were evaluated. From the derived functions evaluated, the trinomial function provided the best fit. Once the sample filter mass loading is known, the trinomial function can be applied to estimate losses and the corresponding self-absorption factor. When applied to routine operating conditions for radiological facility stacks monitored at the Pacific Northwest National Laboratory for an average sample filter mass loading of 0.09 ± 0.12 (2σ) mg⋅cm-2 (excluding negative values and outliers

关键词： Air Sampling Environmental radioactivity Self-Absorption Correction Factor Standards