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Microstructure， electrochemical， wear and corrosive wear performance of laser-based powder bed fusion(lpbf) and wrought biomedical Ti-6Al-4V alloys

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Transactions of Nonferrous Metals Society of China 2024年

作者： A.g.Lekatou B.V.Efremenko V.Haoui V.g.Efremenko S.Emmanouilidou V.I.Zurnadzhy I.Petryshynets yu.g.Chabak I.I.Sili Laboratory of Applied Metallurgy， Department of Materials Science and Engineering， School of Engineering， University of Ioannina Institute of Materials Science and Computing， University Research Center of Ioannina (URCI) Pryazovskyi State Technical University， Department of Physics Institute of Materials Research of Slovak Academy of Sciences

Wrought and laser powder bed fusion （LPBF） Ti-6Al-4V specimens were comparatively evaluated， with the objective to determine LPBF Ti-6-4’s suitability for biomedical applications. Testing included nanoindentation， cyclic polarization in simulated body fluid （SBF， 37 ℃ ）， and dry and SBF “Ball-on-Plate” sliding. Wrought Ti-6-4 exhibited a lamellar （α+β） microstructure， whereas LPBF displayed a fine-grained α'-martensite microstructure. LPBF Ti-6-4 demonstrated ～3% higher indentation modulus and ～32% higher hardness， while wrought Ti-6-4 showed ～8% higher plasticity. Both alloys exhibited low corrosion rates (10–5mA/cm2order) and true passivity (10–4mA/cm2order). No localized corrosion was observed in either alloy， except for occasional metastable pitting in the LPBF alloy. However， LPBF Ti-6-4 presented higher corrosion rate and passive current， ascribed to its martensitic structure. During dry sliding， LPBF Ti-6-4 exhibited ～14% lower volume loss compared to wrought Ti-6-4. Sliding in SBF increased volume losses for both alloys， with wear resistances nearly equalized， as the advantage of LPBF Ti-6-4 decreased due to more intensive wear-accelerated corrosion induced by the stressed martensite. Overall， the results demonstrate the suitability of LPBF Ti-6Al-4V for biomedical uses.

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A two-scale method for identifying mechanical parameters of composite materials with periodic configuration

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Acta Mechanica Sinica 2006年第6期22卷 581-594页

作者： J.Z. Cui X.g. yu Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing 10080 China

In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefly given for two-scale analysis （TSA） of the composite materials. And then a two-scale computation formulation of strains and stresses is developed by displacement solution with orthotropic material coefficients for three kinds of such composites structures, i.e., the tension column with a square cross section, the bending cantilever with a rectangular cross section and the torsion column with a circle cross section. The strength formulas for the three kinds of structures are derived and the TSM procedure is discussed. Finally the numerical results of stiffness and strength are presented and compared with experimental data. It shows that the TSM method in this paper is feasible and valid for predicting both the stiffness and the strength of the composite materials with periodic configuration.

关键词： Two-scale method Stiffness Strength Composite materials Small periodic configuration

RF-CLASS： A remote-sensing-based flood crop loss assessment cyber-service system for supporting crop statistics and insurance decision-making

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Journal of Integrative Agriculture 2017年第2期16卷 408-423页

作者： Liping Di Eugene g. yu Lingjun Kang Ranjay Shrestha BAI yu-qi Center for Spatial Information Science and Systems (CSISS) George Mason University VA 22030 USA Department of geography and geoinformation Science George Mason University VA 22030 USA Key Laboratory for Earth System Modelling Ministry of Education/Department of Earth System Science (DESS) Tsinghua University Beijing 100084 P.R. China

Floods often cause significant crop loss in the United States. Timely and objective information on flood-related crop loss, such as flooded acreage and degree of crop damage, is very important for crop monitoring and risk management in ag- ricultural and disaster-related decision-making at many concerned agencies. Currently concerned agencies mostly rely on field surveys to obtain crop loss information and compensate farmers＇ loss claim. Such methods are expensive, labor intensive, and time consumptive, especially for a large flood that affects a large geographic area. The results from such methods suffer from inaccuracy, subjectiveness, untimeliness, and lack of reproducibility. Recent studies have demonstrated that Earth observation （EO） data could be used in post-flood crop loss assessment for a large geographic area objectively, timely, accurately, and cost effectively. However, there is no operational decision support system, which employs such EO-based data and algorithms for operational flood-related crop decision-making. This paper describes the development of an EO-based flood crop loss assessment cyber-service system, RF-CLASS, for supporting flood-related crop statistics and insurance decision-making. Based on the service-orientated architecture, RF-CLASS has been implemented with open interoperability specifications to facilitate the interoperability with EO data systems, particularly the National Aeronautics and Space Administration （NASA） Earth Observing System Data and Information System （EOSDIS）, for automatically fetching the input data from the data systems. Validated EO algorithms have been implemented as web services in the system to operationally produce a set of flood-related products from EO data, such as flood frequency, flooded acreage, and degree of crop damage, for supporting decision-making in flood statistics and flood crop insurance policy. The system leverages recent advances in the remote sensing-based flood monitoring and assessment,

关键词： crop condition flooding crop damage time series MODIS web service remote sensing decision-making

EFFECTS OF Cu and Mg ON MICROSTRUCTURE AND PROPERTIES OF -Al(3-4 Wt%)Li ALLOYS

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Acta Metallurgica Sinica(English Letters) 1996年第6期9卷 659+657-663页

作者： C.g.Jiao g.F. yu and M.g. Yan(Institute of Aeronautical Materials, Beijing 100095, ) Beijing Inst of Aeronautical materials Beijing China

The influences of Cu and Mg on the microstructure and properties of rapidly solidified Al(3-4 wt% )Li alloys prepared by atomization technique have been studied in the present *** results showed that additions of Cu and Mg in high lithium content RS Al-Li alloys are limited due to the formation of coarse intermetallics during solution treatment. With certain addition of Cu,Mg and conventional heat treatment, the Cu and Mg containing phase S(Al_2CuMg)was found to co-precipitate with δ' (Al_3Li) in the alloys. However the acceptable combinations of strength and ductility of the alloy could not be acquired. Optimizations of Cu and Mg content added in high lithium RS Al-Li alloys are given and the reasons are discussed in detail.

关键词： Al-Li alloy microstructure and pruperty rapid solidification

Regression model to estimate flood impact on corn yield using MODIS NDVI and USDA cropland data layer

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Journal of Integrative Agriculture 2017年第2期16卷 398-407页

作者： Ran jay Shrestha Liping Di Eugene g. yu Lingjun Kang SHAO yuan-zhen BAI yu-qi Center for Spatial Information Science and Systems (CSISS) George Mason University VA 22030 USA Department of geography and geoinformation Science George Mason University VA 22030 USA State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan 430079 P. R. China Key Laboratory for Earth System Modelling Ministry of Education/Department of Earth System Science (DESS) Tsinghua University Beijing 100084 P.R.China

Flood events and their impact on crops are extremely significant scientific research issues; however, flood monitoring is an exceedingly complicated process. Flood damages on crops are directly related to yield change, which requires accurate assessment to quantify the damages. Various remote sensing products and indices have been used in the past for this purpose. This paper utilizes the moderate resolution imaging spectroradiometer （MODIS） weekly normalized difference vegetation index （NDVI） product to detect and further quantify flood damages on corn within the major corn producing states in the Midwest region of the US. County-level analyses were performed by taking weighted average of all pure corn pixels （〉90%） masked by the United States Department of Agriculture （USDA） Cropland Data Layer （CDL）. The NDVI-based time-series difference between flood years and normal year （median of years 2000-2014） was used to detect flood occur- rences. To further measure the impact of the flood on corn yield, regression analysis between change in NDVI and change in corn yield as independent and dependent variables respectively was performed for 30 different flooding events within growing seasons of the corn. With the R2 value of 0.85, the model indicates statistically significant linear relation between the NDVI and corn yield. Testing the predictability of the model with 10 new cases, the average relative error of the model was only 4.47%. Furthermore, small error （4.8%） of leave-one-out cross validation （LOOCV） along with smaller statistical error indicators （root mean square error （RMSE）, mean absolute error （MAE）, and mean bias error （MBE））, further validated the accuracy of the model. Utilizing the linear regression approach, change in NDVI during the growing season of corn appeared to be a good indicator to quantify the yield loss due to flood. Additionally, with the 250 m MODIS-based NDVI, these yield losses can be estimated up to field level.

关键词： NDVI MODIS agriculture corn yield remote sensing regression

Microstructure and mechanical properties of AZ61 Mg alloy prepared by multi directional forging

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Transactions of Nonferrous Metals Society of China 2010年第7期20卷 1294-1298页

作者： H. MIURA g. yu X. YANg T. SAKAI Department of Mechanical Engineering and Intelligent Systems University of Electro-Communications Chofu Tokyo 182-8585 Japan School of Materials Science and Engineering Central South University Changsha 410083 China

AZ61Mg alloy was multi directionally forged(MDFed) during decreasing temperature condition from 643 K to 483 K at a true strain rate of 3×10-3 s-1 up to cumulative strain of∑△ε=4.0 at maximum.A pass strain of△ε=0.8 was *** average grain size decreased gradually with increasing cumulative strain,the evolution of fine-grained structure strongly depended on the MDF *** the condition where the temperature was higher than the most adequate one,grain coarsening partially took place during *** contrast,at lower temperature,inhomogeneous microstructure composed of the initial coarse and newly appeared fine grains was *** straining over∑△ε=3.2(i.e.,over 4 passes of MDF) ,equiaxed ultrafine grains(UFgs) having average size of about and lower than 1μm were uniformly *** the MDFed alloy to∑△ε=4.0 possessed relatively high hardness of HV 99,and it accepted further about 20%cold rolling almost without *** of the superior formability of the UFged AZ61Mg alloy,the hardness was further easily raised to HV 120 by following cold rolling.

关键词： AZ61 magnesium alloy ultrafine grain plastic deformation multi directional forging

guided Waves in the Multilayered One-Dimensional Hexagonal Quasi-crystal Plates

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Acta Mechanica Solida Sinica 2021年第1期34卷 91-103页

作者： B.Zhang J.g.yu X.M.Zhang X.H.Wang School of Mechanical and Power Engineering Henan Polytechnic UniversityJiaozuo454003China

guided waves in the multilayered one-dimensional quasi-crystal plates are,respectively,investigated in the context of the Bak and elasto-hydrodynamic *** curves and phonon and phason displacements are calculated using the Legendre polynomial *** characteristics in the context of these two models are analyzed in *** show that the phonon-phason coupling effects on the first two layers are the same at low frequencies;but,they are more significant on the first layer than those on the second layer at high *** obtained results lay the theoretical basis of guided-wave nondestructive test on multilayered quasi-crystal plates.

关键词： Multilayered structures Quasi-crystal plate guided wave Phonon-phason coupling effect

Effect of Organosilicon Coating Containing Light Stabilizer on UV Aging Resistance of Bitumen

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武汉理工大学学报 2010年第17期32卷 83-88页

作者： HUANg Y FENg Z g yu J Y Key Laboratory of Silicate Materials Science and Engineering of Education Ministry Wuhan University of TechnologyWuhan 430070China

Effects of organosilicon coating with light stabilizer UV326,UV531 and 770 on ultraviolet (UV) aging resistance of bitumen were investigated by testing the viscosity,softening point and the changes of chemical component before and after UV aging. The results show that UV aging resistance of bitumen is improved due to the good weatherability of organosilicon. And the UV aging resistance of bitumen is further enhanced by adding light stabilizer into organosilicon coating due to the good UV absorption of light stabilizers. Bitumen coated with organosilicon coating containing UV326 exhibits better UV aging resistance in comparison with bitumen coated with organosilicon containing UV531 or 770.

关键词： bitumen light stabilizer organosilicon coating UV aging

Abrasive resistance of metastable V–Cr–Mn–Ni spheroidal carbide cast irons using the factorial design method

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International Journal of Minerals,Metallurgy and Materials 2016年第6期23卷 645-657页

作者： V.g.Efremenko K.Shimizu A.P.Cheiliakh T.V.Pastukhova yu.g.Chabak K.Kusumoto Department of Metal Science and Heat Treatments of Metals Pryazovskyi State Technical University Department of Mechanical Aerospace and Materials Engineering Muroran Institute of Technology

Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium（5.0wt%–10.0wt%） and chromium（up to 9.0wt%） contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides（M7C3） and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.

关键词： cast irons carbides abrasive resistance factorial design