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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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Effect of Fibre Packing on Random Variability of Compressive Strength of Unidirectional Carbon Fibre Reinforced Plastic 预览
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作者 徐东 黄金娥 +1 位作者 章力 张书锋 《东华大学学报:英文版》 EI CAS 2019年第1期62-66,共5页
Compression tests on twenty unidirectional(UD) carbon fibre reinforced plastic(CFRP) specimens are conducted, the statistics on the measured compressive strength is calculated, and the fracture surface is characterize... Compression tests on twenty unidirectional(UD) carbon fibre reinforced plastic(CFRP) specimens are conducted, the statistics on the measured compressive strength is calculated, and the fracture surface is characterized. Two types of different fracture surface are experimentally observed, and they are corresponding to very different values on the compressive strength. A finite element(FE) analysis is conducted to investigate the influence of random fibre packing on the compressive strength. And a riks method(provided in ABAQUS software) is applied in FE model to analyze fibre buckling behaviour in the vicinity of compressive failure. The FE analysis agrees well with the experimental observation on the two types of buckling modes and also the partition of compressive strength. It is clearly shown that the random fibre packing lays a significant influence on the random variability of compressive strength of CFRP. 展开更多
关键词 carbon FIBRE reinforced plastic(CFRP) COMPRESSIVE strength random VARIABILITY FIBRE BUCKLING finite element(FE) reliability
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An Elastic Shell Model for the Human Tricuspid Valve
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作者 Xiao-qin SHEN Qian YANG +2 位作者 Lin-jin LI Li CAI Xiao-shan CAO 《应用数学学报:英文版》 SCIE CSCD 2019年第1期111-128,共18页
The human tricuspid valve, one of the key cardiac structures, plays an important role in the circulatory system. However, there are few mathematical models to accurately simulate it.In this paper, firstly, we consider... The human tricuspid valve, one of the key cardiac structures, plays an important role in the circulatory system. However, there are few mathematical models to accurately simulate it.In this paper, firstly, we consider the tricuspid valve as an elastic shell with a specific shape and establish its novel geometric model. Concretely, the anterior, the posterior and the septal leaflets of the valve are supposed to be portions of the union of two interfacing semi-elliptic cylindrical shells when they are fully open.Next, we use Koiter’s linear shell model to describe the tricuspid valve leaflets in the static case, and provide a numerical scheme for this elastostatics model. Specifically, we discretize the space variable, i.e., the two tangent components of the displacement are discretized by using conforming finite elements(linear triangles) and the normal component of the displacement is discretized by using conforming Hsieh-Clough-Tocher triangles(HCT triangles).Finally, we make numerical experiments for the tricuspid valve and analyze the outcome. The numerical results show that the proposed mathematical model describes well the human tricuspid valve subjected to applied forces. 展开更多
关键词 TRICUSPID valve GEOMETRIC MODEL PARAMETRIC equation Koiter MODEL conforming finite element
Finite groups whose n-maximal subgroups are σ-subnormal
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作者 Wenbin Guo Alexander N. Skiba 《中国科学:数学英文版》 SCIE CSCD 2019年第7期1355-1372,共18页
Let σ={σi | i ∈ I} be some partition of the set of all primes P. A set H of subgroups of G is said to be a complete Hall σ-set of G if every member ≠ 1 of H is a Hall σi-subgroup of G, for some i ∈ I, and H con... Let σ={σi | i ∈ I} be some partition of the set of all primes P. A set H of subgroups of G is said to be a complete Hall σ-set of G if every member ≠ 1 of H is a Hall σi-subgroup of G, for some i ∈ I, and H contains exactly one Hall σi-subgroup of G for every σi ∈σ(G). A subgroup H of G is said to be:σ-permutable or σ-quasinormal in G if G possesses a complete Hall σ-set H such that HAx= AxH for all A ∈ H and x ∈ G:σ-subnormal in G if there is a subgroup chain A = A0≤A1≤···≤ At = G such that either Ai-1■Ai or Ai/(Ai-1)Ai is a finite σi-group for some σi ∈σ for all i = 1,..., t.If Mn < Mn-1 <···< M1 < M0 = G, where Mi is a maximal subgroup of Mi-1, i = 1, 2,..., n, then Mn is said to be an n-maximal subgroup of G. If each n-maximal subgroup of G is σ-subnormal(σ-quasinormal,respectively) in G but, in the case n > 1, some(n-1)-maximal subgroup is not σ-subnormal(not σ-quasinormal,respectively) in G, we write mσ(G)= n(mσq(G)= n, respectively).In this paper, we show that the parameters mσ(G) and mσq(G) make possible to bound the σ-nilpotent length lσ(G)(see below the definitions of the terms employed), the rank r(G) and the number |π(G)| of all distinct primes dividing the order |G| of a finite soluble group G. We also give the conditions under which a finite group is σ-soluble or σ-nilpotent, and describe the structure of a finite soluble group G in the case when mσ(G)=|π(G)|. Some known results are generalized. 展开更多
关键词 finite GROUP n-maximal SUBGROUP σ-subnormal SUBGROUP σ-quasinormal SUBGROUP σ-soluble GROUP σ-nilpotent GROUP
Improving the data retention of phase change memory by using a doping element in selected Ge2Sb2Te5 预览
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作者 Yaoyao Lu Daolin Cai +5 位作者 Yifeng Chen Shuai Yan Lei Wu Yuanguang Liu Yang Li Zhitang Song 《半导体学报:英文版》 EI CAS CSCD 2019年第4期29-34,共6页
The crystallization characteristics of a ubiquitous T-shaped phase change memory (PCM) cell, under SET current pulse and very small disturb current pulse, have been investigated by finite element modelling. As analyze... The crystallization characteristics of a ubiquitous T-shaped phase change memory (PCM) cell, under SET current pulse and very small disturb current pulse, have been investigated by finite element modelling. As analyzed in this paper, the crystallization region under SET current pulse presents first on the corner of the bottom electron contact (BEC) and then promptly forms a filament shunting down the amorphous phase to achieve the low-resistance state, whereas the tiny disturb current pulse accelerates crystallization at the axis of symmetry in the phase change material. According to the different crystallization paths, a new structure of phase change material layer is proposed to improve the data retention for PCM without impeding SET operation. This structure only requires one or two additional process steps to dope nitrogen element in the center region of phase change material layer to increase the crystallization temperature in this confined region. The electrical-thermal characteristics of PCM cells with incremental doped radius have been analyzed and the best performance is presented when the doped radius is equal to the radius of the BEC. 展开更多
关键词 phase change memory CRYSTALLIZATION process SET CURRENT PULSE small disturb CURRENT PULSE finite ELEMENT simulation
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Analysis and design of axially loaded piles in rock 预览
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作者 C.M.Haberfield A.L.E.Lochaden 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第3期535-548,共14页
Despite significant advancements in in situ test techniques,construction practices,understanding of rock joint and rock mass behaviours,and numerical analysis methods,the design of bored concrete cast-insitu piles in ... Despite significant advancements in in situ test techniques,construction practices,understanding of rock joint and rock mass behaviours,and numerical analysis methods,the design of bored concrete cast-insitu piles in rock is still largely based on the assessment of bearing capacity.However,for many of the rock conditions encountered,the bearing capacity of piles is a nebulous concept and a figment of the designer’s imagination.Even if it can be reasonably quantified,it has little,if any,significance to the performance of a pile in rock.The load carrying capacity of even low strength rock(in most situations)is far in excess of the strength of the structure(for example,a building column)transmitting the load.Unsatisfactory performance of a pile in rock is usually a displacement issue and is a function of rock mass stiffness rather than rock mass strength.In addition,poor pile performance is much more likely to result from poor construction practices than excessive displacement of the rock mass.Exceptions occur for footings that are undermined,or where unfavourable structure in the rock allows movement towards a free surface to occur.Standards,codes of practices,reference books and other sources of design information should focus foundation design in rock on displacement rather than strength performance.Ground investigations should measure rock mass stiffness and defect properties,as well as intact rock strength.This paper summarises the fundamental concepts relating to performance of piles in rock and provides a basis for displacement focused design of piles in rock.It also presents comments relating to how piles are modelled in widely used commercial finite element software for soil-structure interaction analysis,within the context of the back-analysis of a pile load test,and proposes recommendations for pile analysis and design. 展开更多
关键词 PILE design PILE ANALYSIS PILE load test FINITE element ANALYSIS
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A review of recent advancements in finite element formulation for sandwich plates
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作者 Shehzaib IRFAN Faisal SIDDIQUI 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第4期785-798,共14页
Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element mo... Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element models be developed for analyzing sandwich plates before finalizing the designs. This paper reviews the recent research trends of finite element formulations developed for analyzing sandwich plates. This paper reviews the finite element models developed after the year 2000. Initially, the finite element formulations based on first order shear deformation theory, higher order shear deformation theories, mixed solid-shell elements, zig-zag theories and global–local theories are presented. Then, some finite element formulations developed to analyze a very new class of structures called piezoelectric structures are presented. At the end, some formulations to analyze a very critical phenomenon called buckling are presented. 展开更多
关键词 BUCKLING Finite element FSDT HSDT LAMINATED composites PIEZOELECTRIC SANDWICH PLATES Zig-zag theory
Fracture Toughnesses and Crack Growth Angles of Single-Layer Graphyne Sheets
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作者 Zonghuiyi Jiang Rong Lin Junhua Zhao 《固体力学学报:英文版》 SCIE EI CSCD 2019年第3期339-355,共17页
Recently, Shang et al.(Angew Chem Int Ed 57(3):774-778,2018) have developed a method to synthesize ultrathin (around 1.9 nm) graphyne nanosheets. We reported here the mixed-mode I-II fracture toughnesses and crack gro... Recently, Shang et al.(Angew Chem Int Ed 57(3):774-778,2018) have developed a method to synthesize ultrathin (around 1.9 nm) graphyne nanosheets. We reported here the mixed-mode I-II fracture toughnesses and crack growth angles of single-layer graphyne sheets using molecular dynamics (MD) simulations and the finite element (FE) method based on the boundary layer model, respectively. The various carbon-carbon bonds of graphyne sheets in the FE method are equated with the nonlinear Timoshenko beams based on the Tersoff-Brenner potential, where all the parameters of the nonlinear beams are completely determined based on the continuum modeling. All the results from the present FE method are reasonable in comparison with those from our MD simulations using the REBO potential. The present results show that both the critical stress intensity factors (SIFs) and the crack growth angle strongly depend on the chirality and loading angle q @= 90° and #= 0° representing pure mode I and pure mode II, respectively). Meanwhile, the fracture properties of single-layer cyclicgraphene and supergraphene sheets are also studied in order to compare with those of the graphyne sheets. The critical equivalent SIFs are derived as 1.55 < Keq.cy (cyclic)< 1.95 nN A-3/2, 1.64 < Keq.gy (graphyne)< 2.64 nN A_3/<2 and 0.61 < Keq-su (super)< 2.04 nN A-3/2 in the corresponding zigzag and armchair sheets using the MD simulations, while the SIFs are 0.32 < Keq-cy (cyclic)< 0.48 nN A-3/,2, 1.96 < Keq.gy (graphyne)< 2.49 nN A-3^2 and 1.42 < Keq-su (super)< 2.95 nN A_3//2 using the FE method. These findings should be of great help for understanding the fracture properties of carbon allotropes and designing the carbon-based nanodevices. 展开更多
关键词 FRACTURE TOUGHNESS Graphyne Molecular dynamics FINITE element
Controllability analysis of multi-agent systems with switching topology over finite fields
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作者 Zehuan LU Lin ZHANG Long WANG 《中国科学:信息科学(英文版)》 SCIE EI CSCD 2019年第1期77-91,共15页
In this paper,we investigate the controllability problem of multi-agent systems with switching topology over finite fields.The multi-agent system is defined over finite fields,where agents process only values from a f... In this paper,we investigate the controllability problem of multi-agent systems with switching topology over finite fields.The multi-agent system is defined over finite fields,where agents process only values from a finite alphabet.Under leader-follower structure,one agent is selected as a leader for each subsystem.First,we prove that a multi-agent system with switching topology is controllable over a finite field if the graph of the subsystem is a spanning forest,and the size of the field is sufficiently large.Second,we show that,by appropriately selecting leaders,the multi-agent system with switching topology can be controllable over a finite field even if each of its subsystems is not controllable.Specifically,we show that the number of leaders for ensuring controllability of the switched multi-agent system is less than the minimum number of leaders for ensuring the controllability of all subsystems.Finally,it is proved that the multi-agent system is controllable over a finite field if the union of the graphs is a directed path graph or a star graph. 展开更多
关键词 MULTI-AGENT systems LEADER-FOLLOWER structure CONTROLLABILITY finite FIELDS switching TOPOLOGY
Method for Predicting the Fatigue Life of Geometrically Discontinuous Structures Under Combined Bending and Torsion
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作者 Jianhui Liu Xuemei Pan +1 位作者 Yaobing Wei Youliang Wang 《固体力学学报:英文版》 SCIE EI CSCD 2019年第3期367-377,共11页
The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading. Meanwhile, the application of critical plane method in the prediction of multiaxial fati... The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading. Meanwhile, the application of critical plane method in the prediction of multiaxial fatigue life has made certain progress. According to the law of thermodynamics, a new damage evolution equation is developed in the present study to predict the fatigue life of geometrically discontinuous structure under tension-torsion loading based on damage mechanics and the critical plane method. The essence of this approach is tha t the st rain parame ter of the uniaxial nonlinear fatigue damage model is replaced with the equivalent strain, which consists of the releva nt parame ters of the critical plane. However, it is difficult to calculate the stress-strain status and the critical plane position of geometrically dis? continuous structure by theoretical methods because of the existence of stress concentration and the multiaxial nonproportional characteristics. Therefore, a new numerical simulation method is proposed to determine the critical plane of geometrically discontinuous structure under multiaxial loading by means of the finite element method and MATLAB software. The fatigue life of notched specimens subjected to combined bending and torsion is predicted using the proposed met hod, and the result is compared with t hose from the experimen ts and the Manson-Cfiffin law. The comparisons show that the proposed method is superior to the Manson-Coffin law and is capable of reproducing the experimental results reasonably when the geometry of the structure is complex. It completely meets the needs of engineering practice. 展开更多
关键词 Damage MECHANICS Critical PLANE METHOD Geometrically DISCONTINUOUS structure Finite element METHOD
Design of Computationally Efficient Sharp FIR Filter Utilizing Modified Multistage FRM Technique for Wireless Communications Systems 预览
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作者 Tirthadip Sinha Jaydeb Bhaumik 《电子科技学刊:英文版》 CAS CSCD 2019年第2期185-192,共8页
Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower ... Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower stop band ripples offers alias-free switching among the preferred frequency bands. A computationally competent low pass filter (LPF) structure based on the multistage frequency response masking (FRM) approach is proposed for the design of sharp finite impulse response (FIR) filters which are suitable for wireless communications applications. In comparison of basic FRM with other existing multistage FRM structures, the proposed structure has a narrow transition bandwidth and higher stop band attenuation with significant reduction in terms of the number of computational steps. A design example is incorporated to demonstrate the efficiency of the proposed approach. Simulation results establish the improvement of the proposed scheme over other recently published design strategies. 展开更多
关键词 MULTISTAGE frequency RESPONSE MASKING narrow transition-width SHARP finite IMPULSE RESPONSE filter wireless communications
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A study on the deformation and crushing of copper tubing: experiments, theory & FE modelling 预览
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作者 R.P. Turner 《材料工程研究(英文)》 2019年第1期20-31,共12页
A series of 250 mm lengths of copper tubing, of 15 mm outer diameter and 0.7 mm wall thickness, were studied to determine their deformation if they were pinched or crushed between rigid objects applying a given force,... A series of 250 mm lengths of copper tubing, of 15 mm outer diameter and 0.7 mm wall thickness, were studied to determine their deformation if they were pinched or crushed between rigid objects applying a given force, to replicate potential accidental damage suffered by the copper pipes during service. A finite element modelling framework was developed to simulate the crushing of a copper pipe the same dimensions as that used for experiments, and the experimental data allowed for a validation of the pipe crushing at approximately room temperature, to consider copper pipe carrying cold water. The FE modelling activity was then extended to consider the deformation of copper pipe at 80C, carrying heated water at this temperature. The modelling agreed reasonably well with experiment, and applied forces of 1.5 kN began to deform the cold pipe, with the pipe collapsing on itself at loads of 6 kN. The heated pipe began to deform at roughly 1.25 kN. Lastly, theoretical flow calculations were performed to determine the Reynolds value, the flow velocity and the pressure loss and head loss per unit length of the deformed pipes, according to classical pipe flow calculation methods. 展开更多
关键词 simulation fluid MECHANICS finite element pressure DROP
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Effects of welding speed on the multiscale residual stresses in frictionstir welded metal matrix composites
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作者 X.X.Zhang L.H.Wu +6 位作者 H.ANDra W.M.Gan M.Hofmann D.Wang D.R.Ni B.L.Xiao Z.Y.Ma 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第5期824-832,共9页
The effects of welding speed on the macroscopic and microscopic residual stresses(RSes) in friction stir welded 17 vol.% SiCp/2009 Al-T4 composite plates were studied via neutron diffraction and an improved decoupled ... The effects of welding speed on the macroscopic and microscopic residual stresses(RSes) in friction stir welded 17 vol.% SiCp/2009 Al-T4 composite plates were studied via neutron diffraction and an improved decoupled hierarchical multiscale modeling methods. Measurements showed that the macroscopic and total RSes had the largest variations in the longitudinal direction(LD). Increasing the welding speed led to higher values of measured LD macroscopic and total RSes in the matrix. The welding speed also significantly influenced the distributions and magnitudes of the microscopic RSes. The RSes were predicted via an improved hierarchical multiscale model, which includes a constant coefficient of friction based thermal model. The RSes in the composite plates before friction stir welding(FSW) were computed and then set as the initial states of the FSW process during modeling. This improved decoupled multiscale model provided improved predictions of the temperature and RSes compared with our previous model. 展开更多
关键词 Metal-matrix composites (MMCs) Friction STIR welding Residual/internal stress Neutron DIFFRACTION Finite element analysis (FEA) Multiscale simulation
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