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Solving Interface Problems of the Helmholtz Equation by Immersed Finite Element Methods 预览
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作者 Tao Lin Yanping Lin Qiao Zhuang 《应用数学与计算数学学报(英文)》 2019年第2期187-206,共20页
This article reports our explorations for solving interface problems of the Helmholtz equation by immersed finite elements (IFE) on interface independent meshes. Two IFE methods are investigated: the partially penaliz... This article reports our explorations for solving interface problems of the Helmholtz equation by immersed finite elements (IFE) on interface independent meshes. Two IFE methods are investigated: the partially penalized IFE (PPIFE) and discontinuous Galerkin IFE (DGIFE) methods. Optimal convergence rates are observed for these IFE methods once the mesh size is smaller than the optimal mesh size which is mainly dictated by the wave number. Numerical experiments also suggest that higher degree IFE methods are advantageous because of their larger optimal mesh size and higher convergence rates. 展开更多
关键词 HELMHOLTZ interface problems Immersed FINITE ELEMENT (IFE) METHODS HIGHER degree FINITE ELEMENT METHODS
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The smoothed finite element method (S-FEM):A framework for the design of numerical models for desired solutions
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作者 Gui-Rong Liu 《结构与土木工程前沿:英文版》 EI CSCD 2019年第2期456-477,共22页
The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed w... The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects;2) upper-bound solutions;3) accurate solutions and higher convergence rates;4) insensitivity to mesh distortion;5) Jacobian?free;6) volumetric-locking-free;and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on Al-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided. 展开更多
关键词 computational METHOD FINITE ELEMENT METHOD smoothed FINITE ELEMENT METHOD strain SMOOTHING technique SMOOTHING domain weakened weak form solid mechanics SOFTENING effect upper bound solution
Swelling-induced finite bending of functionally graded pH-responsive hydrogels: a semi-analytical method 预览
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作者 M. SHOJAEIFARD M. R. BAYAT M. BAGHANI 《应用数学和力学:英文版》 SCIE EI CSCD 2019年第5期679-694,共16页
Abstract Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and defor- mation fields, a new semi-analytical a... Abstract Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and defor- mation fields, a new semi-analytical approach is developed to predict the swelling induced finite bending for a functionally graded (FG) layer composed of a pH-sensitive hydrogel, in which the cross-link density is continuously distributed along the thickness direction under the plane strain condition. Without considering the intermediary virtual reference, the initial state is mapped into the deformed configuration in a circular shape by utilizing a total deformation gradient tensor stemming from the inhomogeneous swelling of an FG layer in response to the variation of the pH value of the solvent. To enlighten the capabil- ity of the presented analytical method, the finite element method (FEM) is used to verify the accuracy of the analytical results in some case studies. The perfect agreement con- firms the accuracy of the presented method. Due to the applicability of FG pH-sensitive hydrogels, some design factors such as the semi-angle, the bending curvature, the aspect ratio, and the distributions of deformation and stress fields are studied. Furthermore, the tangential free-stress axes are illustrated in deformed configuration. 展开更多
关键词 PH-SENSITIVE HYDROGEL functionally graded (FG) layer FINITE BENDING semi- analytical solution FINITE element method (FEM)
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Hot Air Generator Using Natural Convection Flow in a Heated Channel 预览
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作者 Bushra AlGarawi Zeinebou Yahya 《能源与动力工程:英文版》 2019年第4期131-136,共6页
Hot air producing is one of the most important engineering applications in recent years.It is a technique used in various thermodynamic systems,such as home heating systems,food dryers.One of the main problems impedin... Hot air producing is one of the most important engineering applications in recent years.It is a technique used in various thermodynamic systems,such as home heating systems,food dryers.One of the main problems impeding the spread of hot air producing technology is the lack of homogeneity of the heat flow coming from hot air generators as well as an inadequate flow rate.The most of the existing hot air generators require to be supported by systems that can increase the low volumetric flow and the air temperature of these generators,through increasing the speed of the flow of air emitted or lifting the drawer Heat,which contributes to raising the overall cost.However,to improve the thermal and dynamic quality of the hot air flow produced by the generator,a numerical investigation of the free convection flow inside two different configurations is presented in this thesis.The primary objective of this work is to predict the behavior of the flow inside tow configurations,the first one consists of a vertical cylinder with heated walls,and the second configuration is an open-ended vertical cylinder with a hot disc placed at the entrance(configuration A,configuration B).This work characterizes through the examination of this flow,the variables that control an air emission with high flow rate and a high and homogeneous temperature to represent the appropriate criteria that should be respected to obtain a hot air generator overcoming the previously mentioned constraints.Furthermore;the results of this work show the influence the boundary conditions and Rayleigh number on the resulting flow. 展开更多
关键词 Hot air GENERATOR NATURAL CONVECTION vertical CHANNEL NAVIER-STOKES equations finite volume method
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基于改进的屈曲模态阵型的锥形连续柱体结构屈曲分析 预览
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作者 Sina Toosi Akbar Esfandiari Ahmad Rahbar Ranji 《船舶与海洋工程学报:英文版》 CSCD 2019年第2期160-166,共7页
Elastic critical buckling load of a column depends on various parameters,such as boundary conditions,material,and crosssection geometry.The main purpose of this work is to present a new method for investigating the bu... Elastic critical buckling load of a column depends on various parameters,such as boundary conditions,material,and crosssection geometry.The main purpose of this work is to present a new method for investigating the buckling load of tapered columns subjected to axial force.The proposed method is based on modified buckling mode shape of tapered structure and perturbation theory.The mode shape of the damaged structure can be expressed as a linear combination of mode shapes of the intact structure.Variations in length in piecewise form can be positive or negative.The method can be used for single-span and continuous columns.Comparison of results with those of finite element and Timoshenko methods shows the high accuracy and efficiency of the proposed method for detecting buckling load. 展开更多
关键词 BUCKLING analysis Tapered column.Continuous COLUMNS Finite element method Modified BUCKLING mode SHAPES
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Static and Dynamic Analysis of Osteoarthritic and Orthotic Human Knee
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作者 Daniela Tarnita Doina Pisla +3 位作者 Ionut Geonea Calin Vaida Marius Catana Danut Nicolae Tarnita 《仿生工程学报:英文版》 SCIE EI CSCD 2019年第3期514-525,共12页
The first objective of this paper is to study the influence of the orthotic device on the maximum values of stresses in knee cartilages by using Ansys Workbench 14.5 software and applying the Finite Element Analysis (... The first objective of this paper is to study the influence of the orthotic device on the maximum values of stresses in knee cartilages by using Ansys Workbench 14.5 software and applying the Finite Element Analysis (FEA) on a virtual assembly composed by an orthotic device and osteoarthritic knee (OAK). The second objective consists into quantifying and investigating the nonlinear motion of the human knee joint for OAK patients, with and without the orthotic device mounted on OAK, using tools of dynamics stability analysis. The short Lyapunov Exponents (LEs) are calculated, as measures of human knee and ankle joints stability, based on the experimental time series collected by using the biometrics acquisition system during walking on horizontal and inclined treadmills from a sample of healthy subjects and a sample of patients suffering by OAK disease. The values of LEs obtained for OAK patients are larger on the inclined treadmill than on horizontal treadmill and are larger than those obtained for healthy knees, being associated with more divergence and less stability. The results confirm that the influence of an orthotic device mounted on OAK on its stability is significant, the values obtained for LEs being smaller than those calculated for OAK, and closer to the values of normal knees of patients and of healthy subjects. 展开更多
关键词 osteoarthritic KNEE BIOINSPIRED ORTHOSIS finite element method GAIT stability LYAPUNOV EXPONENTS
单侧冠状缝早闭症整复手术的三元有限元生物力学分析 预览
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作者 陈丽丹 杨斌 《中国整形与重建外科(英文)》 2019年第1期24-30,共7页
Objective To establish finite element models of skull, fronto-orbital advancement and fronto-orbital distraction osteogenesis of craniosynostosis, to analyze the mechanical characteristics of skull base and fronto-orb... Objective To establish finite element models of skull, fronto-orbital advancement and fronto-orbital distraction osteogenesis of craniosynostosis, to analyze the mechanical characteristics of skull base and fronto-orbital operation area, so as to guide the later app lication of distractors. Methods One 6-year-old male patient with unilateral coronal synostosis was enrolled in October 2015. Three-dimensional (3D) computed tomography (CT) scan of skull was performed. DICOM data was imported into Mimics 17.0 for contour extraction and cranial 3D reconstruction. The skull model was processed by Mimics, Geomagic Studio 12.0, Hypermesh 12.0 and other software to establish a three-dimensional finite element model. The unilateral and bilateral fronto-orbital anterior osteotomy models were simulated respectively. The mechanical analysis was performed at point A in forehead area and point B in temporal area. Three different groups of traction forces were loaded:(1) 50 Newton for point A, 50 Newton for point B;(2) 80 Newton for point A and 50 Newton for point B;(3) 100 Newton for point A and 50 Newton for point B, to obtain the optimized traction force.. Results Stress analysis was performed on established cranial finite element model, as well as unilateral and bilateral fronto-orbital advancement procedures. The stress distribution of the anterior and middle cranial fossae was found to be concentrated. After unilateral fronto-orbital advancement, the stress of anterior cranial fossa, especially the affected side, was decreased. The stress on both side in anterior cranial fossa was decreased after bilateral fronto-orbital advancement. After force was applied to point A and point B, the optimum deviation result at supraorbital notch point, midpoint of supraorbital margin, frontal temporal point and frontal zygomatic suture point in 3D (Deviation result of X value:-29.4%,-20.5%,-8.6%,-9.3%, Deviation result of Y value: 20.9%, 31.5%, 73.0%, 539.4%;Deviation result of Z value: 4.4%, 1.9%, 0.1%, 11.8) demonstrated the applicatio 展开更多
关键词 CRANIOSYNOSTOSIS FINITE element ANALYSIS BIOMECHANICAL ANALYSIS
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An Optimal Sixth-order Finite Difference Scheme for the Helmholtz Equation in One-dimension 预览
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作者 Liu Xu Wang Hai-na Hu Jing 《数学研究通讯:英文版》 CSCD 2019年第3期264-272,共9页
In this paper, we present an optimal 3-point finite difference scheme for solving the 1D Helmholtz equation. We provide a convergence analysis to show that the scheme is sixth-order in accuracy. Based on minimizing th... In this paper, we present an optimal 3-point finite difference scheme for solving the 1D Helmholtz equation. We provide a convergence analysis to show that the scheme is sixth-order in accuracy. Based on minimizing the numerical dispersion, we propose a refined optimization rule for choosing the scheme’s weight parameters. Numerical results are presented to demonstrate the efficiency and accuracy of the optimal finite difference scheme. 展开更多
关键词 HELMHOLTZ equation finite DIFFERENCE method numerical DISPERSION
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Two methodological approaches to assess the seismic vulnerability of masonry bridges
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作者 Diego Maria Barbieri 《交通运输工程学报(英文版)》 CSCD 2019年第1期49-64,共16页
This work describes the seismic vulnerability assessment of a railway masonry arch bridge.Its conservation state is initially investigated by means of a thorough field and laboratory test campaign, comprising destruct... This work describes the seismic vulnerability assessment of a railway masonry arch bridge.Its conservation state is initially investigated by means of a thorough field and laboratory test campaign, comprising destructive and non-destructive tests. Two different methods are used to evaluate the bridge seismic vulnerability. The first method adopts a deterministic approach and corresponds to a single non-linear static analysis, performed as described in the Eurocodes. The second method employs a probabilistic approach and considers the variability of the involved mechanical parameters(structure geometry and properties of the building materials) and seismic parameters(intensity of the action and site conditions). This method associates the probabilistic values of ground acceleration exceedance to the estimated seismic vulnerability. This is shown by means of fragility curves, which allow to take into consideration the uncertainty of the various components involved in the definition of the seismic vulnerability and display the seismic damage scenarios. Currently no code requires to perform this calculation procedure. In addition,this work compares the values of masonry mechanical properties specified in the Eurocodes with those obtained in an extensive investigation campaign involving more than one hundred masonry bridges. Compressive strength and longitudinal elasticity modulus are the relevant mechanical parameters investigated. The outcomes of this research can contribute to the development of a more efficient maintenance system of the masonry bridges belonging to the railway network. This has an important role when it comes to establishing the priority order of assets intervention. 展开更多
关键词 Railway MASONRY ARCH BRIDGE BRIDGE maintenance and conservation MASONRY mechanical parameters NON-LINEAR static ANALYSIS Seismic FRAGILITY Finite element ANALYSIS
Finite volume effects on the QCD chiral phase transition in the finite size de-pendent Nambu-Jona-Lasinio model
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作者 夏永辉 王庆武 +1 位作者 冯红涛 宗红石 《中国物理C:英文版》 SCIE CAS CSCD 2019年第3期43-48,共6页
The effective Lagrangian of a finite volume system should, in principle, depend on the system size. In the framework of the Nambu-Jona-Lasinio(NJL) model, by considering the influence of quark feedback on the effectiv... The effective Lagrangian of a finite volume system should, in principle, depend on the system size. In the framework of the Nambu-Jona-Lasinio(NJL) model, by considering the influence of quark feedback on the effective coupling, we obtain a modified NJL model so that its Lagrangian depends on the volume. Based on the modified NJL model, we study the influence of finite volume on the chiral phase transition at finite temperature, and find that the pseudo-critical temperature of crossover is much lower than that obtained in the normal NJL model. This clearly shows that the volume dependent effective Lagrangian plays an important role in the chiral phase transitions at finite temperature. 展开更多
关键词 CHIRAL phase TRANSITION NJL model FINITE volume effect
Fracture Analysis of Cast Iron Materials with Cracks Based on Elastoplastic Extended Finite Element Method
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作者 Yanjun Chang Qiao Song +2 位作者 Zheng Kuang Keshi Zhang Zhanguang Zheng 《固体力学学报:英文版》 SCIE EI CSCD 2019年第2期201-214,共14页
Based on the ABAQUS platform for finite element analysis, the extended finite element method (XFEM) considering elastoplastic constitutive relationship is developed, by which the displacement discontinuity across the ... Based on the ABAQUS platform for finite element analysis, the extended finite element method (XFEM) considering elastoplastic constitutive relationship is developed, by which the displacement discontinuity across the crack surface and the strong nonlinearity near the crack tip can be described more accurately. The strip specimens with unilateral cracks and central cracks under uniaxial tension are simulated using the XFEM and the FEM, respectively. The J-integral across the crack on each incremen t is calcula ted using the equivale nt domain integral met hod (EDIM), the interaction integral met hod and the FEM, respectively. The effec ts of mesh size and mesh shape near the crack tip, element type and different calculation methods on the accuracy of J-integral are analyzed. The simulation results show that the XFEM is more accurate than the FEM with the same element size and type. The fracture tests of cast iron specimens with unilateral cracks under uniaxial tension are performed, and the J-integral criterion is valid to predict the fracture initiation in numerical simulation. The critical value of J-integral is calculated using the EDIM of the XFEM. The comparisons demonstrate that the simulated elastoplastic load-displacement curves with the XFEM are in good agreement with the experimental results. 展开更多
关键词 J-INTEGRAL Extended FINITE element Elastoplasticity FRACTURE CRITERION
Analysis of some critical aspects in hot machining of Ti-5553 superalloy: Experimental and FE analysis 预览
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作者 Asit Kumar Parida Kalipada Maity 《Defence Technology(防务技术)》 CAS CSCD 2019年第3期344-352,共9页
In this study, a newly developed titanium superalloy, i.e., the Ti-5553 alloy has used for hot machining. This material replaced Ti-grade-5 alloy in the application of aerospace, automobile, and biomedical sector. How... In this study, a newly developed titanium superalloy, i.e., the Ti-5553 alloy has used for hot machining. This material replaced Ti-grade-5 alloy in the application of aerospace, automobile, and biomedical sector. However, similar to Ti-grade-5 alloy, the Ti-5553 alloy has a low thermal conductivity which makes it difficult-to-cut material categories hence, high tool wear, cutting force and bad surface finish. Hot machining of Ti-5553 has been studied at different machining condition (room and hot) using Deform-2D finite element analysis. The result from the simulation test was compared with the experimental value and reduction of cutting and thrust forces was observed. The experiment was carried out with the same input parameters as simulation, and good coherence between them observed. Additionally, cutting zone temperature, effective stress, etc. for both room and elevated the temperature are also discussed. 展开更多
关键词 Ti-5553 HOT MACHINING Cutting force FLANK wear Finite element ANALYSIS
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Diagnosability of a class of discrete event systems based on observations
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作者 S.RESHMILA Devanathan RAJAGOPALAN 《控制理论与技术:英文版》 EI CSCD 2019年第3期265-275,共11页
The diagnosability of discrete event systems has been a topic of interest to many researchers. The diagnosability conditions for various systems have evolved based on a regularity condition that is imposed on faulty t... The diagnosability of discrete event systems has been a topic of interest to many researchers. The diagnosability conditions for various systems have evolved based on a regularity condition that is imposed on faulty traces with respect to their observable continuations. Improving upon this weak but necessary condition, a new model of diagnosability that is based on sensor outputs, which are called observatio ns, upon a command in put is proposed in this paper. Necessary and sufficient con ditions are derived for the proposed diagnosability model. The search performance of the proposed diagnosability condition is of linear complexity in terms of the power set of the system events and observations, compared to the exponential complexity of the search with the existing diag nosability regularity condition. Moreover, a system that is not diag no sable according to the existi ng diag nosability condition may be diagnosable in the proposed diagnosability model, which includes observations. 展开更多
关键词 DISCRETE EVENT system DIAGNOSABILITY FAULT diagnosis mealy AUTOMATA finite state AUTOMATA
Shape reconstruction of large optical surface with high-order terms in fringe reflection technique
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作者 Xiaoli JING Haobo CHENG Yongfu WEN 《中国光电子学前沿:英文版》 EI CSCD 2019年第2期180-189,共10页
A fast and effective shape reconstruction method of large aspheric specular surfaces with high order terms is proposed in fringe reflection technique, which combines modal estimation with high-order finite- difference... A fast and effective shape reconstruction method of large aspheric specular surfaces with high order terms is proposed in fringe reflection technique, which combines modal estimation with high-order finite- difference algorithm. The iterative equation with high- order truncation errors is derived for calculating the specular surface with large aperture based on high-order finite-difference algorithm. To achieve the wavefront estimation and improve convergence speed, the numerical orthogonal transformation method based on Zemike polynomials is implemented to obtain the initial iteration value. The reconstruction results of simulated surface identified the advantages of the proposed method. Furthermore, a freeform in illuminating system has been used to demonstrate the validity of the improved method in practical measurement. The results show that the proposed method has the advantages of making the reconstruction of different shape apertures accurate and rapid. In general, this method performs well in measuring large complex objects with high frequency information in practical measurement. 展开更多
关键词 shape reconstruction FRINGE REFLECTION techni-que Zemike ORTHOGONAL transformation finite DIFFERENCE measurement
Numerical investigation of the effects of aquatic plants on wind-induced currents in Taihu Lake in China 预览
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作者 Tian-ping Xu Ming-liang Zhang +3 位作者 Hcng-zhi Jiang Jun Tang Hong-xing Zhang Hui-ting Qiao 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第4期778-787,共10页
Shallow lakes are an important part of the earth's water circulation system, and many factors may impact the evolution of the lake water circulation, including the wind, the topography, the human activities, and t... Shallow lakes are an important part of the earth's water circulation system, and many factors may impact the evolution of the lake water circulation, including the wind, the topography, the human activities, and the aquatic plants. This paper proposes a depth-averaged 2-D hydrodynamic model to investigate the interaction of the wind-induced current and the aquatic plant in the lake. The model is based on the generalized shallow water equations solved by an explicit finite volume method with unstructured triangular grids. The drag force of the vegetation is considered into the momentum equations as the source term. Remote sensing techniques are applied to evaluate the aquatic vegetation in the Taihu Lake, China, based on Landsat TM satellite images. The study model is then used to simulate the characteristics of the wind-induced currents in the Taihu Lake, without and with the vegetation effects. The simulation results are in good agreement with the field measurements, demonstrating that the aquatic plants significantly affect the magnitude of the velocity and the flow circulation induced by the wind in the Taihu Lake. In addition, a sensitivity analysis reveals that the plant parameters (the density and the drag force coefficient) are significant factors influencing the velocity and the structure of the currents in the Taihu Lake. 展开更多
关键词 Finite volume method ROE SOLVER shallow lake wind-induced current AQUATIC plant
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Finite element modeling of counter-roller spinning for large-sized aluminum alloy cylindrical parts
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作者 Dawei ZHANG Fan LI +1 位作者 Shuaipeng LI Shengdun ZHAO 《机械工程前沿:英文版》 CSCD 2019年第3期351-357,共7页
Counter-roller spinning (CRS), where the mandrel is replaced by rollers, is an effective means of manufacturing large-sized, thin-walled, cylindrical parts with more than 2500 mm diameter. CRS is very complex because ... Counter-roller spinning (CRS), where the mandrel is replaced by rollers, is an effective means of manufacturing large-sized, thin-walled, cylindrical parts with more than 2500 mm diameter. CRS is very complex because of multi-axis rotation, multi-local loading along the circumference, and radial-axial compound deformation. Analytical or experimental methods cannot fully understand CRS. Meanwhile, numerical simulation is an adequate approach to investigate CRS with comprehensive understanding and a low cost. Thus, a finite element (FE) model of CRS was developed with the FORGE code via meshing technology, material modeling, determining the friction condition, and so on. The local fine mesh moving with the roller is one of highlights of the model. The developed 3D-FE model was validated through a CRS experiment by using a tubular blank with a 720 mm outer diameter. The developed 3D-FE model of CRS can provide a basis for parameter optimization, process control, die design, and so on. The data on force and energy predicted by the 3D-FE model can offer reasonable suggestions for determining the main mechanical parameters of CRS machines and selecting the motors. With the predicted data, an all-electric servo-drive system/machine with distributed power was designed in this work for CRS with four pairs of rollers to manufacture a large-sized, thinwalled, cylindrical part with 6000 mm diameter. 展开更多
关键词 large-sized CYLINDRICAL part counter-roller SPINNING aluminum alloy finite element method distributed power
Refining constitutive relation by integration of finite element simulations and Gleeble experiments
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作者 D.J. Yu D.S. Xu +3 位作者 H. W ang Z.B. Zhao G.Z. Wei R. Yang 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第6期1039-1043,共5页
Thermo-mechanical coupled finite element calculations were carried out to simulate the Gleeble compression of the samples of a titanium alloy(Ti60), and the results are analyzed and compared with the actual compressio... Thermo-mechanical coupled finite element calculations were carried out to simulate the Gleeble compression of the samples of a titanium alloy(Ti60), and the results are analyzed and compared with the actual compression tests conducted on a Gleeble 3800 thermo-mechanical simulator. The changes in temperature, stress and strain distribution in the samples and the source of error on the constitutive relations from Gleeble hot compression test were analyzed in detail. Both simulations and experiments showed that the temperature distribution in the specimen is not uniform during hot compression, resulting in significant deformation inhomogeneity and non-ignorable error in the flow stress strain relation,invalidating the uniform strain assumption commonly assumed when extracting the constitutive relation from Gleeble tests. Based on the finite element simulations with iterative corrections, we propose a scheme to refine the constitutive relations from Gleeble tests. 展开更多
关键词 Titanium alloy CONSTITUTIVE RELATION FINITE element Compression Temperature distribution
Experimental investigation of EHD grease lubrication in finite line contacts
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作者 Zhijian WANG Xuejin SHEN +3 位作者 Xiaoyang CHEN Dehua TAO Lei SHI Shuangbiao LIU 《摩擦(英文版)》 CSCD 2019年第3期237-245,共9页
The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact’s film-forming capacity.An elastohydrod... The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact’s film-forming capacity.An elastohydrodynamic lubrication(EHL) test rig with two interferometry microscopes,which could simultaneously monitor two different contact locations in the finite line contact,was constructed in order to study the influences of the grease thickener formulation on the film thickness and lubrication condition.By using the relative light intensity method,the thickness maps of the grease-lubricated film were calculated from the interferometer images captured by the two microscopes.The test results revealed that the grease thickener’s formulation had remarkable effects on film formation and the perturbation of film thickness.For the lithium-based grease,the film’s thickness near the two ends of the roller was prone to severe perturbation caused by the conglomeration of clumps that were hard to shear.For the aluminum-complex-based grease,the fibers tended to accumulate in the middle of the roller rather than at the two ends.The urea-based grease could be easily sheared into smaller particles.In addition to the straight-line profile rollers,the logarithmic profile rollers were tested and found to effectively enhance the axial grease flow,increase the axial shear stress,and thus shear more fibers into particles within the contact area. 展开更多
关键词 EHL FINITE line contact GREASE FILM thickness
Effect of Interconnect Linewidth on Evolution of Intragranular Microcracks Due to Electromigration Analyzed by Finite Element Method 预览
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作者 HE Dingni HUANG Peizhen 《南京航空航天大学学报:英文版》 EI CSCD 2019年第2期290-297,共8页
The effect of interconnect linewidth on the evolution of intragranular microcracks due to surface diffusion induced by electromigration is analyzed by finite element method.The numerical results indicate that there ex... The effect of interconnect linewidth on the evolution of intragranular microcracks due to surface diffusion induced by electromigration is analyzed by finite element method.The numerical results indicate that there exists critical values of the linewidth hc,the electric fieldχc and the aspect ratioβc.When h>hc,χ<χc orβ<βc,the microcrack will evolve into a stable shape as it migrates along the interconnect line.When h≤hc,χ≥χc orβ≥βc,the microcrack will split into two smaller microcracks.The critical electric field,the critical aspect ratio and the splitting time have a stronger dependence on the linewidth when h≤6.In addition,the decrease of the linewidth,the increase of the electric field or the aspect ratio is beneficial to accelerate microcrack splitting,which may delay the open failure of the interconnect line. 展开更多
关键词 finite element method surface diffusion ELECTROMIGRATION LINEWIDTH MICROCRACK EVOLUTION
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Geodynamic simulation of the WenChuan Ms8.0 and Lushan Ms7.0 earthquakes
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作者 Li Liao Jiansi Yang Dongning Zhang 《大地测量与地球动力学:英文版》 2019年第1期49-57,共9页
The Lushan Ms7.0 earthquake, occurred on April 20th, 2013, is another strong earthquake that occurred on Longmen Mountain Faults after the Wenchuan Ms8.0 earthquake. In this paper we construct a finite element model d... The Lushan Ms7.0 earthquake, occurred on April 20th, 2013, is another strong earthquake that occurred on Longmen Mountain Faults after the Wenchuan Ms8.0 earthquake. In this paper we construct a finite element model depicting fault frictional mechanism to study the geodynamics of these two strong earthquakes. The locations of the initial rupture points and the dislocation forms of the Wenchuan earthquake and Lushan earthquake are simulated to find out the potential relationship between the two earthquakes. Simulative results show that the elevation, fault geometry, and the different rheological strengths between the Sichuan basin and Tibetan plateau play an important role in the earthquake dynamics. The dynamic simulation shows the initial rupture points are located at Yingxiu county and the rupture process is mainly along the northeast direction for the Wenchuan earthquake. In particular, the different frictional strengths caused by the fluid pressure decrease between the southern and northern segments of Longmenshan faults after the Wenchuan earthquake have affected the initial rupture point and the fault dislocation form of the Lushan earthquake, when considering the thrust of Tibetan plateau to Sichuan basin as the major dynamic source. 展开更多
关键词 FINITE element model INITIAL RUPTURE point DISLOCATION form Numerical simulation
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