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real-time prediction of projectile penetration to laminates by training machine learning models with finite element solver as the trainer

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Defence Technology（防务技术） 2021年第1期17卷 147-160页

作者： Pushkar Wadagbalkar G.r.liu Department of Aerospace Engineering and Engineering Mechanics University of CincinnatiCincinnatiOH 45219USA

Studies on ballistic penetration to laminates is complicated,but important for design effective protection of *** means of study is expensive and can often be *** simulation has been an excellent supplement,but the computation is *** aim of this thesis was to develop and test an effective tool for real-time prediction of projectile penetrations to laminates by training a neural network and a decision tree regression model.A large number of finite element models were developed;the residual velocities of projectiles from finite element simulations were used as the target data and processed to produce sufficient number of training *** focused on steel 4340tpolyurea laminates with various *** different 3D shapes of the projectiles were modeled and used in the *** trained neural network and decision tree model was tested using independently generated test samples using finite element *** predicted projectile velocity values using the trained machine learning models are then compared with the finite element simulation to verify the effectiveness of the ***,both models were trained using a published experimental data of projectile impacts to predict residual velocity of projectiles for the unseen *** of both the models was evaluated and *** trained with Finite element simulation data samples were found capable to give more accurate predication,compared to the models trained with experimental data,because finite element modeling can generate much larger training set,and thus finite element solvers can serve as an excellent *** study also showed that neural network model performs better with small experimental dataset compared to decision tree regression model.

关键词： Finite element simulations Machine learning Neural networks Impact analysis Protective laminates Projectile Decision tree

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Distinct dendritic α phase emerging on the surface of primary α phase in a compressed near-α titanium alloy

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Journal of Materials Science & Technology 2018年第4期34卷 666-669页

作者： Z.liu Z.B.Zhao J.r.liu Q.J.Wang r.Yang Institute of Metal research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

The characteristic of the surface morphology of primary α phase was studied in a deformed near-α tita- nium alloy. Dendritic α phase emerged on the surfaces of primary α phase when the alloy was air-cooled in α ＋β phase field after deformation. The dendritic α grain has the same orientation with its original primary α grain. The formation of the dendritic α phase could be explained by interface instability in epi- taxial growth process of the primary α phase. The dislocations induced by deformation could facilitate the formation of dendritic α phase leading to the dendritic α phase and more obvious with the increase of strain. The growth of dendritic α phase was finally limited by the nucleation of second α phase with cooling.

关键词： Epitaxial growth Dendritic α phase Microstructure Interface instability Hot deformation

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Analysis of local crystallographic orientation in an annealed Ti60 billet

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Journal of Materials Science & Technology 2019年第4期35卷 591-595页

作者： Z.B.Zhao Z.liu Q.J.Wang J.r.liu r.Yang Institute of Metal research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

A heterogeneous microstructure in terms of local orientation distribution is often found in near-α titanium alloys. The presence of large regions with similar crystallographic orientation, called ‘macrozones',could drastically decrease the fatigue performance of titanium alloys. The present work reports on the crystallographic orientation of a near-α titanium alloy, Ti60, billet after annealing in an α+β phase *** texture was found to be weak, and no obvious macrozone was found in our measured zone where the variant selection is suppressed. Meanwhile, in-depth electron backscattered diffraction(EBSD) analysis was applied to evaluate the final microstructure, and the mechanisms by which they formed were analyzed.

关键词： Titanium alloys Microstructure Texture Heat treatment EBSD

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Meshless Methods Coupled with Other Numerical Methods

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Tsinghua Science and Technology 2005年第1期10卷 8-15页

作者： Y.T.GU G.r.liu CentreforAdvancedComputationsinEngineeringScience(ACES) DepartmentofMechanicalEngineeringNationalUniversityofSingapore10KentRidgeCrescentSingapore119260Singapore

Meshless or mesh-free (or shorten as MFree) methods have been proposed and achieved remarkable progress over the past few years. The idea of combining MFree methods with other existing numerical techniques such as the finite element method (FEM) and the boundary element method (BEM), is naturally of great interest in many practical applications. However, the shape functions used in some MFree methods do not have the Kronecker delta function property. In order to satisfy the combined conditions of displacement compatibility, two numerical techniques, using the hybrid displacement shape function and the modified variational form, are developed and discussed in this paper. In the first technique, the original MFree shape functions are modified to the hybrid forms that possess the Kronecker delta function property. In the second technique, the displacement compatibility is satisfied via a modified variational form based on the Lagrange multiplier method. Formulations of several coupled methods are presented. Numerical exam- ples are presented to demonstrate the effectiveness of the present coupling methods.

关键词： meshless method mesh-free method finite element method boundary element method coupling method stress analysis

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8-chloroadenosine induces apoptosis in human MOLT-4 cell line

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Chinese Science Bulletin 1997年第7期42卷 592-597页

作者： Wang, XT Zheng, DX liu, r liu, YX Xiao, S Min, JM Zheng, P Zhang, LH liu, SL CHINESE ACAD MED SCI PEKING UNION MED COLLSTATE KEY LAB MED MOL BIOLBEIJING 100005PEOPLES R CHINA

THE 8-chloroadenosine (8CA) is a novel analog of adenosine synthesized in the National research Laboratories of Natural and Biomimetic Drugs. Fang et al. reported that 8CA is capable of inhibiting the cell growth in v... 详细信息

关键词： 8-chloroadenosine apoptosis MOLT-4 cells.

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MODELING OF 'BANDING' MICrOSTrUCTUrE FOrMATION IN CENTrIFUGALLY SOLIDIFIED Ti-6Al-4V ALLOY

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Acta Metallurgica Sinica(English Letters) 2008年第6期21卷 399-408页

作者： D.r. liu E：J. Guo L.P. Wang School of Materials Science and Engineering Harbin University of Science and Technology Harbin 150040 China Institute of Metal research Chinese Academy of Sciences Shenyang 110016 China

Numerical investigations of the ＇banding＇ microstructure formation during solidification of Ti-6Al-4 V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference method （FDM） at the macroscale with a cellular automaton （CA） model at the microscale. The macro model is used to simulate the fluid flow and heat transfer throughout the casting. The micro model is used to predict the nucleation and growth of microstructures. With the proposed model, numerical simulations are performed to study the influences of the nucleation density, mould rotation speed, and casting size upon the ＇banding＇ microstructure formation. It is noted that changing the nucleation density has a minor effect on the microstructure formation. The rotation speed promotes the formation of ＇banding＇ microstructure, which is more noticeable for larger size castings. The ＇major mechanism responsible for this ＇banding＇ phenomenon is the spatial variation in cooling rates created by centrifugal force.

关键词： Modeling 'Banding' microstructure Ti-6Al-4V alloy Centrifugal casting

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Deformation behaviors of as-built and hot isostatically pressed Ti-6Al-4V alloys fabricated via electron beam rapid manufacturing

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Journal of Materials Science & Technology 2019年第11期35卷 2552-2558页

作者： Z.liu Z.B.Zhao J.r.liu L.Wang S.X.Zhu G.Yang S.L Gong Q.J.Wang r.Yang institute of metal research chinese academy of sciencesshenyang110016china school of materials science and engineering university of science and technology of chinahefei230000china avic manufacturing technology institute beijing100024china

The deformation behavior of as-built and hot isostatically pressed(HIP)Ti-6Al-4V alloys fabricated using electron beam rapid manufacturing(EBrM)were investigated in this *** deformation characteristics were characterized using a laser scanning confocal microscope and electron back-scattered diffraction(EBSD).In the as-built sample,prismatic slip was the main mode of deformation,as well as a small amount of basal slip and *** planar slip lines with large length scales were observed across severalα*** hot isostatical pressing,prismatic and basal slip were the main mode of deformation,accompanied by abundant cross-slip and multiple slip,and most of the slip lines were blocked within an a *** differences in deformation behavior were associated with the coarsening of a laths and the more retained p phase after HIP compared to the as-built *** cross-slip and multiple slip can lead to superior elongation-to-failure and a greater strain hardening effect in the HIP alloy compared to the as-built sample.

关键词： Electron beam rapid manufacturing Ti-6Al-4V Hot isostatic pressure Mechanical properties Slip behavior

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A node-based smoothed point interpolation method for dynamic analysis of rotating flexible beams

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Acta Mechanica Sinica 2018年第2期34卷 409-420页

作者： C.F.Du D.G.Zhang L.Li G.r.liu College of Civil Science and Engineering Yangzhou University School of Sciences Nanjing University of Science and Technology School of Aerospace Systems University of Cincinnati

We proposed a mesh-free method, the called node-based smoothed point interpolation method(NS-PIM),for dynamic analysis of rotating beams. A gradient smoothing technique is used, and the requirements on the consistence of the displacement functions are further weakened. In static problems, the beams with three types of boundary conditions are analyzed, and the results are compared with the exact solution, which shows the effectiveness of this method and can provide an upper bound solution for the *** means that the NS-PIM makes the system soften. The NS-PIM is then further extended for solving a rigid-flexible coupled system dynamics problem, considering a rotating flexible cantilever beam. In this case, the rotating flexible cantilever beam considers not only the transverse deformations,but also the longitudinal deformations. The rigid-flexible coupled dynamic equations of the system are derived via employing Lagrange’s equations of the second type. Simulation results of the NS-PIM are compared with those obtained using finite element method(FEM) and assumed mode method. It is found that compared with FEM, the NS-PIM has anti-ill solving ability under the same calculation conditions.

关键词： Meshfree method NS-PIM rigid-flexible coupled system dynamics rotating beams Dynamic response

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A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅰ.Model building and fatigue strength prediction

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Journal of Materials Science & Technology 2021年第11期70卷 233-249页

作者： r.liu P.Zhang Z.J.Zhang B.Wang Z.F.Zhang Laboratory of Fatigue and Fracture for Materials Shi-changxu Innovation Center for Advanced MaterialsInstitute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China

The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic *** this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been *** results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength *** this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue *** the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F *** the verification with fatigue strength data covering various kinds of metallic materials and loading conditions,this Y-T-F model exhibits both generality and *** the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength ***,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield *** summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.

关键词： Yield strength Tensile strength Plasticity Fatigue strength Anti-fatigue design

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Probing Co/Si interface behaviour by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM)

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Nuclear Science and Techniques 2006年第4期17卷 202-211页

作者： PAN J. S. liu r. S. TOK E. S. Institute of Materials research and Engineering 3 Research Link Singapore 117602 Department of Physics National University of Singapore Kent Ridge Singapore 119260

In this work, we investigate the Co-Si reaction, the Co growth mode at room temperature, diffusion be- haviour as well as morphology evolution during annealing on both H-terminated and clean Si(001) and Si(111) sur- faces. From in-situ X-ray photoelectron spectroscopy (XPS) investigation, “Co-Si” reaction appears to occur on both H-terminated and clean surfaces at room temperature (rT) and the silicide crystallinity is improved upon annealing. Co growth mode on H-terminated Si surfaces occurs in a pseudo layer-by-layer manner while small close-packed is- land growth mode is observed on the clean Si surface. Upon annealing at different temperatures, Co atom concentra- tion decreases versus annealing time, which in part is attributed to Co atoms inward diffusion. The diffusion behav- iour on both types of surfaces demonstrates a similar trend. Morphology study using ex-situ atomic force microscopy (AFM) shows that the islands formed on Si(001) surface after annealing at 700 °C are elongated with growth direc- tions alternate between the two perpendicular [ 110 ] and [110] directions. Triangular islands are observed on Si (111) surface.

关键词：钴硅金属-半导体界面反应 X射线光电子光谱学原子力显微镜方法表面形态

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