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A study on compressive shock wave propagation in metallic foams

science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 279-287页

作者： WANG ZhiHua1,2.ZHANG YiFen2.REN HuiLan1 & ZHAO LongMao2.1 State Key Laboratory of Explosion science and technology,Beijing {2. of technology,Beijing 100081,china 2.{2. of Applied Mechanics and Biomedical engineering,Taiyuan University of technology,Taiyuan 03002.,china 1. State Key Laboratory of Explosion science and technology Beijing Institute of Technology Beijing 100081 China2. Institute of Applied Mechanics and Biomedical Engineering Taiyuan University of Technology Taiyuan 030024 China

Metallic foam can dissipate a large amount of energy due to its relatively long stress plateau,which makes it widely applicable in the design of structural crashworthiness. However,in some experimental studies,stress enhancement has been observed when the specimens are subjected to intense impact loads,leading to severe damage to the objects being protected. This paper studies this phenomenon on a 2. mass-spring-bar model. With the model,a constitutive relationship of metal foam and corresponding loading and unloading criteria are presented; a nonlinear kinematics equilibrium equation is derived,where an explicit integra-tion algorithm is used to calculate the characteristic of the compressive shock wave propagation within the metallic foam; the effect of heterogeneous distribution of foam microstructures on the shock wave features is also included. The results reveal that under low impact pulses,considerable energy is dissipated during the progressive collapse of foam cells,which then reduces the crush of objects. When the pulse is sufficiently high,on the other hand,stress enhancement may take place,especially in the heterogeneous foams,where high peak stresses usually occur. The characteristics of compressive shock wave propagation in the foam and the magnitude and location of the peak stress produced are strongly dependent on the mechanical properties of the foam material,amplitude and period of the pulse,as well as the homogeneity of the microstructures. This research provides valuable insight into the reliability of the metallic foams used as a protective structure.

关键词： aluminum foam heterogeneous intensive pulse loading stress enhancement

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Wear Performance of laser Surface Hardened GCr15 Steel

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Journal of wuhan University of technology(Materials {2.) 2010年第1期25卷 84-88页

作者：雷声 School of Materials science and engineering Hefei University of Technology Department of Electromechanical engineering Anhui Institute of Architecture and Industry

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.

关键词： laser hardening dry sliding conditions GCr15 steel wear mechanisms

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Theoretical calculation of the finishing rolling impact work in non-quenched and tempered Si-Mn steel

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science china(Technological sciences) 2006年第2期49卷 137-146页

作者： LIU Zhilin1, LIN Cheng1 & WANG Ping2.1. Department of Materials and Chemical engineering, Liaoning institute of {2., Jinzhou 12.001, china 2. Mechanical Department, Armor technique institute of PLA, Changchun 130117, china Department of Materials Chemical engineering Liaoning Institute of Technology Jinzhou 121001 China Mechanical Department Armor technique Institute of PLA Changchun 130117 China

Based on the hot-continuous rolling technology, the finishing rolling impact work α k of the non-quenched and tempered Si-Mn steel is theoretically calculated with the covalent electron number nA of the strongest bond in alloying phases, and the smallest interface electron density difference Δρ of alloying phase interface and the number of atom states σ which keep the interface electron density continuous. Calculations show that the solution strengthening, the precipitation strengthening, and the interface strengthening will result in the decrease of the finishing rolling impact work α k, and the effects of the number of atom states σ which keep the interface electron density continuous on the finishing rolling impact work α k are different. Taking the impact work and the number of atom states σ 0 keeping the electron density continuous of the phase interface α-Fe/α-Fe-C between α-Fe and α-Fe-C as reference values, the impact work of the interface will increase when σ of some interface is larger than σ 0; otherwise, the impact will decrease. Therefore, the finishing rolling impact work α k can be calculated with the impact value of the refined α-Fe matrix and the influence amounts caused by the solution strengthening, the precipitation strengthening, the interface strengthening, and the number of atom states σ which keep the interface electron density continuous. The calculated results agree well with the measured ones. In this paper, the effect of S on the impact work is also discussed.

关键词： electron structure parameters, non-quenched and tempered steel, impact work and calculation.

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Synthetically adaptive robust filtering for satellite orbit determination

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science china Earth sciences 2004年第7期47卷 585-592页

作者： YANG Yuanxi1 & WEN Yuanlan2.1. Xi’an Research institute of Surveying and Mapping, Xi抋’an 710054, china 2. College of Aerospace and Material {2., National University of Defense technology, Changsha 410073, china 1. Xi’an Research institute of Surveying and Mapping 710054 Xi’an China 2. College of Aerospace and Material engineering National University of Defense Technology 410073 Changsha China

The quality of the satellite orbit determination is rested on the knowledge of per-turbing forces acting on the satellite and stochastic properties of the observations, and the ability of controlling various kinds of errors. After a brief discussion on the dynamic and geometric orbit determinations, Sage adaptive filtering and robust filtering are reviewed. A new synthetically adaptive robust filtering based on a combination of robust filtering and Sage filtering is *** is shown, by derivations and calculations, that the synthetically adaptive robust filtering for orbit determination is not only robust but also simple in calculation. It controls the effects of the outliers of tracking observations and the satellite dynamical disturbance on the parameter esti-mates of the satellite orbit.

关键词： satellite orbit, Sage filtering, adaptive orbit determination, robust estimation.

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Neural Nets:Another Paradigm for Decision Support

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Journal of Systems engineering and Electronics 1995年第2期6卷 2-8页

作者： Feng Shan (Dept. of ACE, huazhong University of science and {2., wuhan 43.074, china) Dept. of ACE Huazhong University of Science and Technology Wuhan 430074 China

The paper presents an important aspect of Neural Nets application, i. e., their usefulness for decision support. The essential feature of the neural net approach to decision making is that it is a black-box approach, which means one does not try to model the underlying processes, but only looks for a tuning of the parameters of the neural net such that the black-box mimics the sensible behavior. Through the existing widespread applications in industry, business and science, the paper emphasizes their common property as a paradigm for decision support.

关键词： Neural network Neural-net controller Decision support Industrial applications.

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Interactions of particles with solidifying front in Al_2._(3P) /Al Si composites

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中国有色金属学会会刊：英文版 1999年第3期9卷 524-529页

作者： Wu Shusen(吴树森), Huang Naiyu(黄乃瑜),An Ping(安萍) College of Materials science and engineering, {2. University of science and technology, wuhan 43.074, P.R. china huazhong Univ Sci & Technol Coll Mat Sci & Engn Wuhan 430074 Peoples R China

The behavior of ceramic particles at the solid/liquid interface and the distribution of particles in metallic matrix composites was studied with a zone unidirectional solidification method. Two kinds of partice dispersed composites, Al 2. 3P /Al 12.6%Si Sr and Al 2. 3P /Al 12.6%Si Sr Ca containing Al 2. 3 particles in volume fraction 2.～5% were used. In the Al 2. 3P /Al Si Sr composites, the particles were pushed by the solidifying front, and did not uniformly distribute in the solid. But in the Al 2. 3P /Al Si Sr Ca composites, the particles were engulfed by the solidifying front and uniformly distributed in the solid. The particles engulfing into the solid was realized only by Sr and Ca addition at the same time. As the interfacial energy between solid and particle was decreased in this case, the Al 2. 3 particles acted as the substrates of heterogeneous nucleation for the Si phases, which made the particles to be engulfed.

关键词： metallic matrix composites solidification particle size distributionDocument code: A

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Effect of the silicon powder content on the properties of Al_2._3-SiC-Me composites

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science china(Technological sciences) 2009年第1期52卷 193-197页

作者： ZHANG ZhiHui1, RUAN GuoZhi1 & CHEN YunBo1,2.1 School of Material science and engineering, Shandong University of science and technology, Qingdao 2.6510, china 2.institute of Material engineering, china Academy of Machinery science and technology, Beijing 100083, china School of Material science and engineering Shandong University of Science and Technology Qingdao 266510 China institute of Material engineering China Academy of Machinery Science and Technology Beijing 100083 China

By means of transient plastic phase process, the Al2.3-SiC-Me composites were produced throungh adding metal aluminium and silicon-powder to Al2.3-SiC materials. Under the condition of the same content of silicon and aluminium mixed-powder, the effect of silicon powder addition on properties of Al2.3-SiC-Me composites was studied by means of XRD and EPMA analyses in the temperature range of 300℃―1600℃. The results indicated that the content of metal phase in the sample at 1600℃ increases with increasing silicon powder content. At the same time, when the temperature is lower than 1100℃, the strength of samples gradually increases with increasing temperature. However when the temperature is higher than 1100℃, the strength of samples gradually decreases with increasing temperature, and this change is very small. The results also indicated that at the same sintering temperature, the sample with 6% silicon powder has the maximum strength.

关键词： composites strength ceramic

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Polynomial analysis of canopy spectra and biochemical component content inversion

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science china Earth sciences 2005年第10期48卷 1780-1791页

作者： YAN Chunyan1, LIU Qiang1, NIU Zheng1, WANG Jihua2. HUANG Wenjiang2.& LIU Liangyun 2.1. State Key Laboratory of Remote Sensing science, Jointly Sponsored by the institute of Remote Sensing Applications of Chinese Academy of sciences and Beijing Normal University, Beijing 100101, china 2. National engineering Research Center for Information technology in Agriculture, Beijing 100089, china State Key Laboratory of Remote Sensing science Jointly Sponsored by the institute of Remote Sensing Applications of Chinese Academy of sciences and Beijing Normal University Beijing china National engineering Research Center for Information technology in Agriculture Beijing{2.

A polynomial expression model was developed in this paper to describe directional canopy spectra, and the decomposition of the polynomial expression was used as a tool for re-trieving biochemical component content from canopy multi-angle spectra. First, the basic formula of the polynomial expression was introduced and the physical meaning of its terms and coeffi-cients was discussed. Based on this analysis, a complete polynomial expression model and its decomposition method were given. By decomposing the canopy spectra simulated with SAILH model, it shows that the polynomial expression can not only fit well the canopy spectra, but also show the contribution of every order scattering to the whole reflectance. Taking the first scattering coefficients a10 and a01 for example, the test results show that the polynomial coefficients reflect very well the hot spot phenomenon and the effects of viewing angles, LAI and leaf inclination angle on canopy spectra. By coupling the polynomial expression with leaf model PROSPECT, a canopy biochemical component content inversion model was given. In the simulated test, the canopy multi-angle spectra were simulated by two different models, SAILH and 4-SCALE re-spectively, then the biochemical component content was retrieved by inverting the coupled polynomial expression + PROSPECT model. Results of the simulated test are promising, and when applying the algorithm to measured corn canopy multi-angle spectra, we also get relatively accurate chlorophyll content. It shows that the polynomial analysis provides a new method to get biochemical component content independent of any specific canopy model.

关键词： polynomial expression, canopy spectra, decomposition, biochemical component content, inversion.

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A measure of centrality based on modularity matrix

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Progress in Natural science:Materials International 2008年第8期18卷 1043-1047页

作者： Gaoxia Wang, Yi Shen *, Enjie Luan The Department of Control science and engineering, {2. University of science and technology, wuhan 43.074, china The Department of Control science and engineering Huazhong University of Science and Technology Wuhan 430074 China

In this paper, a kind of measure of structural centrality for networks, called modularity centrality, is introduced. This centrality index is based on the eigenvector belonging to the largest magnitude eigenvalue of modularity matrix. The measure is illustrated and compared with the standard centrality measures using a classic dataset. The statistical distribution of modularity centrality is investigated by considering large computer generated graphs and two networks from the real world.

关键词： Centrality Modularity centrality Modularity matrix

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Research progress in the inner surface modification of metal tubes by plasma processing

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Progress in Natural science:Materials International 2006年第11期16卷 1119-1126页

作者： ZHANG Guling~ 1,2.**, WU Xingfang~1, GU Weichao~2. CHEN Guangliang~2. FENG Wenran~2. NIU Erwu~2. LI Li~2. L Guohua~2. CHEN Huan~2. FAN Songhua~2. LIU Chizi~2.and YANG Size~2.1. School of Material science and engineering, University of science and technology Beijing, Beijing 100083, china 2. Beijing National Laboratory for Condensed Matter Physics, institute of Physics, Chinese Academy of sciences, Beijing 100080, china) School of Material science and engineering University of Science and Technology Beijing Beijing 100083 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China

The recent progress in inner surface hardening of tubes by plasma processing is summerized. Several techniques of inner surface plasma source ion implantation and deposition are introduced, and their advantages and disadvantages are discussed. The basic principles, technical features and new progress of inner surface plasma source ion implantation methods for metal tubes, which were developed in our laboratory, are described in detail. And perspectives of the future technical development for inner surface ion implantation of tubes are presented.

关键词： PSII metal tubes inner surface surface modification.

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