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Parametric Analysis of Tensile Properties of Bimodal Al Alloys by Finite Element Method

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Journal of Materials Science & Technology 2009年第2期25卷 281-288页

作者： w.l. Zhang S. li S.R. Nutt State Key lab of MMCs Shanghai Jiao Tong University Shanghai 200030 China Department of Materials Science University of Southern California Los Angeles CA 90089 USA

An axisymmetrical unit cell model was used to represent a bimodal Al alloy that was composed of both nano-grained （NG） and coarse-grained （CG） aluminum. Effects of microstructural and materials parameters on tensile properties of bimodal AI alloy were investigated by finite element method （FEM）. The parameters analyzed included aspect ratios of CG Al and the unit cell, volume fraction of CG Al （VFCG）, and yield strength and strain hardening exponent of CG Al. Aspect ratios of CG Al and the unit cell have no significant influence on tensile stress-strain response of the bimodal Al alloy. This phenomenon derives from the similarity in elastic modulus and coefficient of thermal expansion between CG AI and NG Al. Conversely, tensile properties of bimodal Al alloy are extremely sensitive to VFCG, yield strength and strain hardening exponent of CG Al. Specifically, as VFCG increases, both yield strength and ultimate tensile strength （UTS） of the bimodal Al alloy decreases, while uniform strain of bimodal AI alloy increases. In addition, an increase in yield strength of CG Al results in an increase in both yield stress and UTS of bimodal AI alloy and a decrease in uniform strain of bimodal Al alloy. The lower capability in lowering the increase of stress concentration in NG Al due to a higher yield strength of CG Al causes the lower uniform strain of the bimodal AI alloy. when strain hardening exponent of CG Al increases, 0.2% yield stress, UTS, and uniform strain of the bimodal Al alloy increases. This can be attributed to the increased work-hardening ability of CG Al with a higher strain hardening exponent.

关键词： Nanomaterials Bimodal alloys Finite element method Tensile properties Parametric analysis

Effect of Solidification Condition and Carbon Content on the Morphology of MC Carbide in Directionally Solidified Nickel-base Superalloys

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Journal of Materials Science & Technology 2014年第12期30卷 1296-1300页

作者： X.w.li l.wang J.S.Dong l.H.lou Superalloys Division Institute of Metal Research Chinese Academy of Sciences

Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40X10-6 to 320X10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into welldeveloped dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.

关键词： Carbides morphology Directional solidification Three-dimensional microstructure Nickel-base superalloys

Recent development in the application of bulk metallic glasses

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Journal of Materials Science & Technology 2022年第36期131卷 115-121页

作者： K.Gao X.G.Zhu l.Chen w.H.li X.Xu B.T.Pan w.R.li w.H.Zhou l.li w.Huang Y.li Dongguan Yihao Metal Technology Co.ltd Dongguan 523686China Dongguan Eontec Co.ltd Dongguan 523686China Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Over the past decades,considerable efforts have been made in the commercial application of bulk metallic glasses(BMGs).Despite great challenges faced by the industrial players,significant progress has been achieved,and millions of commercial products for various kinds of applications have been shipped around the *** in this paper,we shall present the alloys suitable for the actual products in the application and discuss the merits of the processing technique of BMGs over the existing processing techniques and *** importantly we demonstrate the typical examples of products over the past few ***,future directions of the industrialization of BMGs are also discussed.

关键词： Bulk metallic glasses Commercial application Alloy design Products

Microbial community coalescence and nitrogen cycling in simulated mortality decomposition hotspots

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Ecological Processes 2023年第1期12卷 608-624页

作者： Sarah w.Keenan Alexandra l.Emmons Jennifer M.DeBruyn Department of Geology and Geological Engineering South Dakota School of Mines and Technology501 East St.Joseph StreetRapidSD 57701USA Department of Anthropology University of TennesseeKnoxvilleTNUSA Department of Biosystems Engineering and Soil Science University of Tennessee2506 E.J.Chapman DriveKnoxvilleTN 37996USA

Background The pulsed introduction of dead plant and animal material into soils represents one of the primary mechanisms for returning organic carbon(C)and nitrogen(N)compounds to biogeochemical *** of animal carcasses provides a high C and N resource that stimulates indigenous environmental microbial communities and introduces non-indigenous,carcass-derived microbes to the ***,the dynamics of the coalesced microbial communities,and the relative contributions of environment-and carcass-derived microbes to C and N cycling are *** test whether environment-derived,carcass-derived,or the combined microbial communities exhibited a greater influence on C and N cycling,we conducted controlled laboratory experiments that combined carcass decomposition fluids and soils to simulate carcass decomposition *** selectively sterilized the decomposition fluid and/or soil to remove microbial communities and create different combinations of environment-and carcass-derived communities and incubated the treatments under three temperatures(10,20,and 30℃).Results Carcass-derived bacteria persisted in soils in our simulated decomposition scenarios,albeit at low *** communities had higher respiration rates at 10 and 30℃ compared to soil or carcass communities ***,at higher temperatures,mixed communities had reduced diversity,but higher respiration,suggesting functional *** communities treatments also provided evidence that carcass-associated microbes may be contributing to ammonification and denitrification,but that nitrification is still primarily carried out by native soil *** Our work yields insight into the dynamics of microbial communities that are coalescing during carcass decomposition,and how they contribute to recycling carcasses in terrestrial ecosystems.

关键词： Carcass decomposition Microcosm Nitrogen Carbon Biogeochemical cycling Coalescence

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Achieving superior strength-ductility synergy in a heterostructured magnesium alloy via low-temperature extrusion and low-temperature annealing

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Journal of Materials Science & Technology 2023年第32期163卷 32-44页

作者： H.wang D.T.Zhang C.Qiu w.w.Zhang D.l.Chen Guangdong Key laboratory for Advanced Metallic Materials Processing and Forming National Engineering Research Center of Near-net-shape Forming for Metallic MaterialsSouth China University of TechnologyGuangzhou 510640China Department of Mechanical and Industrial Engineering Toronto Metropolitan University(formerly Ryerson University)350 Victoria StreetTorontoON M5B 2K3Canada

A low-alloyed Mg-1.2Zn-0.1Ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing on the effect of heterostructure on the mechanical *** dynamic recrystallization(RX)occurred during extrusion at 150℃,and a lamellar structure consisting of fine RX grains and coarse unRX grains was *** subsequent annealing promoted static RX in the as-extruded alloy,leading to an increased fine-grained fraction from 67%to 95%.Meanwhile,the co-segregation of Zn and Ca atoms impeded the migration of grain boundaries,thus achieving a fine grain size of 0.8–1.6μ*** sample annealed for 10 min with a fine-grained fraction of 73%and an average RX grain size of 0.9μm exhibited a superior combination of high yield strength(305 MPa)and good ductility(20%).In comparison,an excellent elongation of 30%was achieved in the alloy with a nearly fully-RXed microstructure and an average grain size of 1.6μm after 90 min annealing,despite a lower yield strength of 228 *** unRX grains,the hard orientation with(01–10)parallel to the extrusion direction and high-density dislocations made it more difficult to deform compared with the RX grains,thus producing hetero-deformation induced(HDI)*** fine grains and high-density dislocations,HDI strengthening is the key to achieving the superior mechanical properties of the low-alloyed Mg alloy.

关键词： low-alloyed magnesium alloy low-temperature extrusion Annealing Heterostructure Mechanical properties

A simple scoring system to estimate perioperative mortality following liver resection for primary liver malignancy-the Hepatectomy Risk Score(HeRS)

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Hepatobiliary Surgery and Nutrition 2021年第3期10卷 315-324,I0001,I0002页

作者： Dimitrios Moris Brian I.Shaw Cecilia Ong ashton Connor Mariya l.Samoylova Samuel J.Kesseli Nader Abraham Jared Gloria Robin Schmitz Zachary w.Fitch Bryan M.Clary Andrew S.Barbas Department of Surgery Duke University Medical CenterDurhamNCUSA

Background:Selection of the optimal treatment modality for primary liver cancers remains complex,balancing patient condition,liver function,and extent of *** individuals with preserved liver function,liver resection remains the primary approach for treatment with curative intent but may be associated with significant *** purpose of this study was to establish a simple scoring system based on Model for End-stage liver Disease(MElD)and extent of resection to guide risk assessment for liver ***:The 2005-2015 NSQIP database was queried for patients undergoing liver resection for primary liver *** first developed a model that incorporated the extent of resection(1 point for major hepatectomy)and a MElD-Na score category of low(MElD-Na=6,1 point),medium(MElD-Na=7-10,2 points)or high(MElD-Na>10,3 points)with a score range of 1-4,called the Hepatic Resection Risk Score(HeRS).we tested the predictive value of this model on the dataset using logistic *** next developed an optimal multivariable model using backwards sequential selection of variables under logistic *** performed K-fold cross validation on both *** operating characteristics were plotted and the optimal sensitivity and specificity for each model were calculated to obtain positive and negative predictive ***:A total of 4,510 patients were *** was associated with increased odds of 30-day mortality[HeRS=2:OR=3.23(1.16-8.99),P=0.025;HeRS=3:OR=6.54(2.39-17.90),Pl was *** AUC for the optimal multivariable model was higher at *** K-fold cross validation,the positive predictive value(PPV)and negative predictive value(NPV)of these two models were similar at PPV=6.4%and NPV=97.7%for the HeRS only model and PPV=8.4%and NPV=98.1%for the optimal multivariable ***:The HeRS offers a simple heuristic for estimating 30-day mortality after resectio

关键词： Hepatocellular carcinoma(HCC) cholangiocarcinoma liver resection Model for End-stage liver Disease(MElD) outcomes

An explicit solution to a three-dimensional wedge problem considering two edges effect

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Friction 2020年第2期8卷 370-383页

作者： l.GUO Z.M.ZHANG w.wANG Y.ZHAO P.l.wONG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Mechanical Engineering City University of Hong KongHong Kong SARChina

The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded *** algorithm makes use of a recently published concept of transformation matrix,by which the original surface loads are converted to equivalent loads in *** three loaded edges are considered *** developed algorithm is used to study the effects of two free edges of a steel block and tapered rollers with different contact *** two load-free edges can substantially increase deformation if the two edges are close in *** results of the tapered roller simulation show that deformation is considerably sensitive to the contact angle of the tapered *** largest deformation appears at the big end of the ***,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.

关键词： contact mechanics two edge surfaces finite line contact tapered roller contact

Up-conversion processes of rare earth ions in heavy metal glasses

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Journal of Rare Earths 2011年第12期29卷 1192-1194页

作者： l.Grobelny w.A.Pisarski J.Pisarska R.lisiecki w.Ryba-Romanowski Institute of Chemistry University of Silesia Institute of low Temperature and Structure Research Polish Academy of Sciences

Heavy metal lead germanate glasses doubly doped with Yb^3＋ and ln^3＋ ions （ln=Er, Tin） were investigated. Up-conversion spectra of Er^3＋ and Tm^3＋ were registered under diode-laser excitation of Yb^3＋. Up-conversion luminescence bands corresponded to ^4S3/2→^4I15/2 （green） and ^4F9/2→^4I15/2 （red） transitions of Er^3＋ as well as ^1G4→^3H6 （blue） and ^3Ha→^3H6 （N]R） transitions of Tm^3＋, respectively.

关键词： heavy metal glasses rare earth ions up-conversion luminescence

Dual-energy X-ray absorptiometry scans accurately predict differing body fat content in live sheep

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Journal of Animal Science and Biotechnology 2019年第1期10卷 248-253页

作者： David w Miller Ellen J Bennett Joanne l Harrison Fiona Anderson Clare l Adam School of Veterinary and life Sciences Murdoch University Scotland’s Rural College (SRUC) Peter Wilson Building The Faculty of Health University of Tasmania School of Biological Sciences University of Aberdeen Rowett Institute of Nutrition and Health University of Aberdeen

Background: There is considerable interest in implementing mobile scanning technology for on-farm body composition analysis on live *** experiments evaluated the use of dual energy X-ray absorptiometry(DXA) as an accurate method of total body fat measurement in live ***: In Exp.1,visceral and whole body fat analysis was undertaken in sheep with body condition scores(BCS)in the range 2 to 3.25(scale 1: thin to 5: fat).The relationship of BCS was moderately correlated with visceral fat depot mass(r = 0.59,P whole body fat(r = 0.70,P with BCS in the range 2.25 to 3.75 were blood sampled to analyse circulating leptin concentrations,and were DXA scanned immediately post mortem for total body *** leptin concentrations had low correlations with BCS(r = 0.50,P lation with chemical body fat(r = 0.17,P > 0.05,n = 9).There was a moderate correlation between DXA body fat and BCS(r = 0.70,P was highly correlated with chemical body fat(r = 0.81,P week intervals,was performed on growing sheep over a 32-week *** average BCS ranged from 2.39 ± 0.07(S.E.M.) to 3.05 ± 0.11 and the DXA body fat(%) ranged from 16.8 ± 0.8 to 24.2 ± *** was a moderate correlation between DXA body fat and BCS over the 32 weeks(r = 0.61,P lusions: Overall,these experiments indicated that there was good agreement between BCS,DXA and chemical analysis for measuring total body fat in sheep,and that DXA scanning is a valid method for longitudinal measurement of total body fat in live sheep.

关键词： BCS DEXA Fat leptin longitudinal Sheep