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New tangent stiffness matrix for geometrically nonlinear analysis of space frames 被引量:1
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作者 顾建新 陈绍礼 《Journal of Southeast University(English Edition)》 EI CAS 2005年第4期480-485,共6页
A three-dimensional beam element is derived based on the principle of stationary total potential energy for geometrically nonlinear analysis of space frames. A new tangent stiffness matrix, which allows for high order... A three-dimensional beam element is derived based on the principle of stationary total potential energy for geometrically nonlinear analysis of space frames. A new tangent stiffness matrix, which allows for high order effects of element deformations, replaces the conventional incremental secant stiffness matrix. Two deformation stiffness matrices due to the variation of axial force and bending moments are included in the tangent stiffness. They are functions of element deformations and incorporate the coupling among axial, lateral and torsional deformations. A correction matrix is added to the tangent stiffness matrix to make displacement derivatives equivalent to the commutative rotational degrees of freedom. Numerical examples show that the proposed dement is accurate and efficient in predicting the nonlinear behavior, such as axial-torsional and flexural-torsional buckling, of space frames even when fewer elements are used to model a member. 展开更多
关键词 beam elements space frames tangent stiffness matrix flexural-torsional buckling second-order effects geometric nonlinearity
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Dynamic stiffness matrix of a poroelastic multi-layered site and its Green's functions 被引量:20
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作者 梁建文 尤红兵 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2004年第2期273-282,共10页
Few studies of wave propagation in layered saturated soils have been reported in the literature.In this paper,a general solution of the equation of wave motion in saturated soils,based on one kind of practical Blot... Few studies of wave propagation in layered saturated soils have been reported in the literature.In this paper,a general solution of the equation of wave motion in saturated soils,based on one kind of practical Blot's equation, was deduced by introducing wave potentials.Then exact dynamic-stiffness matrices for a poroelastic soil layer and half- space were derived,which extended Wolf's theory for an elastic layered site to the case of poroelasticity,thus resolving a fundamental problem in the field of wave propagation and soil-structure interaction in a poroelastic layered soil site.By using the integral transform method,Green's functions of horizontal and vertical uniformly distributed loads in a poroelastic layered soil site were given.Finally,the theory was verified by numerical examples and dynamic responses by comparing three different soil sites.This study has the following advantages:all parameters in the dynamic-stiffness matrices have explicitly physical meanings and the thickness of the sub-layers does not affect the precision of the calculation which is very convenient for engineering applications.The present theory can degenerate into Wolf's theory and yields numerical results approaching those for an ideal elastic layered site when porosity tends to zero. 展开更多
关键词 Biot's equation poroelastic layered site dynamic-stiffness matrix Green's function
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Analysis of the hull girder vibration by dynamic stiffness matrix method 被引量:3
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作者 ZHOU Ping ZHAO De-you 《Journal of Marine Science and Application》 2006年第3期30-35,共6页
Dynamic stiffness matrix method is applied to compute vibration of hull girder in this paper. This method can not only simplify the computational model, but also get much higher frequencies and responses accurately. T... Dynamic stiffness matrix method is applied to compute vibration of hull girder in this paper. This method can not only simplify the computational model, but also get much higher frequencies and responses accurately. The analytical expressions of dynamic stiffness matrix of a Timoshenko beam for transverse vibration are presented in this paper. All effects of rotatory inertia and shear deformation are taken into account in the formulation. The resulting dynamic stiffness matrix combined with the Wittrick-Williams algorithm is used to compute natural frequencies and mode shapes of the 299,500 DWT VLCC, and then the vibrational responses are solved by the mode superposition method. The computational results are compared with those obtained from other approximate methods and experiment, and it indicates that the method is accurate and efficient. 展开更多
关键词 hull girder vibration characteristics dynamic stiffness matrix
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Analysis of Vibration of the Euler-Bernoulli Pipe Conveying Fluid by Dynamic Stiffness Method and Transfer Matrix 被引量:3
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作者 Yunfeng Li Yundong Li Naveed Akbar 《Journal of Applied Mathematics and Physics》 2020年第1期172-183,共12页
The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fl... The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fluid, the element dynamic stiffness is established. The vibration characteristic of the single-span pipe is analyzed under two kinds of boundary conditions. The results compared with the literature, which has a good consistency. Based on this method, natural frequency and the critical speed of the two types of multi-span pipe are deserved. This paper shows that the dynamic stiffness method and transfer matrix is an effective method to deal with the vibration problem of pipe conveying fluid. 展开更多
关键词 DYNAMIC stiffNESS Transfer matrix Euler-Bernoulli PIPE
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THE GENERATION OF NON-LINEAR STIFFNESS MATRIX OF TRIANGLE ELEMENT WHENCONSIDERING BOTH THE BENDING AND IN-PLANEME MBRANE FORCES
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作者 张建海 李永年 陈大鹏 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1994年第5期425-434,共10页
Using Stricklin Melhod ̄[5],we have this paper has derived the formulas for the ge-neration of non-linear element stiffness matrix of a triangle element when considering both the bending and the in-plane membrane forc... Using Stricklin Melhod ̄[5],we have this paper has derived the formulas for the ge-neration of non-linear element stiffness matrix of a triangle element when considering both the bending and the in-plane membrane forces. A computer programme for the calculation of large deflection and inner forces of shallow shells is designed on theseformulas. The central deflection curve computed by this programme is compared with other pertaining results. 展开更多
关键词 triangular element NON-LINEAR stiffness matrix
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Finite element model for arch bridge vibration dynamics considering effect of suspender length adjustment on geometry stiffness matrix
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作者 钟轶峰 《Journal of Chongqing University》 CAS 2006年第4期218-222,共5页
In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix... In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix are stressed. The FEM equations of mechanics characteristics, natural frequency and main mode are set up based on the first order matrix perturbation theory. Applicantion of the proposed model to analyze a real arch bridge proved the improvement in the simulation precision of dynamical characteristics of the arch bridge by considering the effects of suspender length variation. 展开更多
关键词 finite element model SUSPENDER geometry stiffness matrix dynamic characteristic arch bridge
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THE DYNAMIC STIFFNESS MATRIX OF THE FINITE ANNULAR PLATE ELEMENT
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作者 张益松 高德平 吴晓萍 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第12期1151-1162,共12页
The dynamic deformation of harmonic vibration is used as the shape functions of the finite annular plate element, and sonic integration difficulties related to the Bessel's functions are solved in this paper. Then... The dynamic deformation of harmonic vibration is used as the shape functions of the finite annular plate element, and sonic integration difficulties related to the Bessel's functions are solved in this paper. Then the dynamic stiffness matrix of the finite annular plate element is established in closed form and checked by the direct stiffness method. The paper has given wide convcrage for decomposing the dynamic matrix into the power series of frequency square. By utilizing the axial symmetry of annular elements, the modes with different numbers of nodal diameters at s separately treated. Thus some terse and complete results are obtained as the foundation of structural characteristic analysis and dynamic response compulation. 展开更多
关键词 DE THE DYNAMIC stiffNESS matrix OF THE FINITE ANNULAR PLATE ELEMENT PING
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ELASTO-PLASTIC STIFFNESS MATRIX OF ROCK MASS ELEMENT WITH SOFT CLAY STRATA AND ITS APPLICATION
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作者 Li,Zhenzi Sun,Zongqi Central-South University of Technology,Changsha,Hunan,410083,China 《中国有色金属学会会刊:英文版》 CSCD 1993年第2期15-17,共3页
The fault element is used to handle soft clay strata in a rock mass.The formulas or clasto-plastic stiffnessmatrix for the fault element are derived using the constitutive relationship between plastic increment stress... The fault element is used to handle soft clay strata in a rock mass.The formulas or clasto-plastic stiffnessmatrix for the fault element are derived using the constitutive relationship between plastic increment stress andstrain.A numerical example of a circular tunnel with soft clay strata in the rock medium are examined. 展开更多
关键词 rock mass clement FAULT clasto-plastic stiffNESS matrix
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Matrix Stiffness-Induced Transcriptome Alterations and Regulatory Mechanisms Revealed by RNA-Seq in Endothelial Cells
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作者 Chao Zhang Xiaomei Han +1 位作者 Jin Xu Yue Zhou 《Journal of Biomaterials and Nanobiotechnology》 CAS 2022年第3期61-79,共19页
Changes in vascular stiffness are associated with the development and progression of many diseases, especially in cardiovascular disease. However, the effect of vascular stiffness on the endothelial cells (ECs) is not... Changes in vascular stiffness are associated with the development and progression of many diseases, especially in cardiovascular disease. However, the effect of vascular stiffness on the endothelial cells (ECs) is not fully understood. Therefore, this study aims to determine the gene expression changes of ECs cultured on the matrices with different stiffness (1 kPa and 40 kPa, respectively) by RNA-seq, thereby broadening the knowledge between mechanics and biology. We obtained 1775 differentially expressed genes (DEGs) by RNA-seq, with 450 up-regulated and 1325 down-regulated DEGs in ECs cultured on soft matrix (1 kPa) compared to those cultured on stiff matrix (40 kPa). After that, we performed a series of functional enrichment analyses based on DEGs and found that DEGs were enriched in many signaling pathways like adhesion junction. Furthermore, transcription factor (TF) target gene prediction analysis and protein-protein interaction (PPI) analysis were also conducted. We found that mechanotransduction signaling related TFs such as BRD4 are involved in. And in the PPI analysis, some genes encoding extracellular matrix proteins such as fibronectin 1 (FN1) were identified as the hub genes. In order to confirm the RNA-seq results, we performed real-time qPCR analysis on the genes of interest, including FN1, collagen α2 (IV) chain, matrix metalloproteinase-14 and integrin α5, and found that the expression levels of all these genes were down-regulated on soft matrix, suggesting that soft matrix caused by pathological conditions may directly attenuate vascular barrier function. This study offers the insights about the effects of physical stimulation on cells, paving a way for vascular tissue engineering, regenerative medicine, disease modeling and therapies. 展开更多
关键词 Endothelial Cells matrix stiffness RNA-SEQ Cell-Cell Junctions Extracellular matrix
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New Formula for Geometric Stiffness Matrix Calculation
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作者 I. Němec M. Trcala +1 位作者 I. Ševčík H. Štekbauer 《Journal of Applied Mathematics and Physics》 2016年第4期733-748,共16页
The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, an... The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, and stability. For very large compressions, the tangent stiffness in the direction of the compression can even become negative, which can be regarded as physical nonsense. So in many cases rubber materials exposed to great compression cannot be analyzed, or the analysis could lead to very poor convergence. Problems with the standard geometric stiffness matrix can even occur with a small strain in the case of plastic yielding, which eventuates even greater practical problems. The authors demonstrate that amore precisional approach would not lead to such strange and theoretically unjustified results. An improved formula that would eliminate the disadvantages mentioned above and leads to higher convergence rate and more robust computations is suggested in this paper. The new formula can be derived from the principle of virtual work using a modified Green-Lagrange strain tensor, or from equilibrium conditions where in the choice of a specific strain measure is not needed for the geometric stiffness derivation (which can also be used for derivation of geometric stiffness of a rigid truss member). The new formula has been verified in practice with many calculations and implemented in the RFEM and SCIA Engineer programs. The advantages of the new formula in comparison with the standard formula are shown using several examples. 展开更多
关键词 Geometric stiffness Stress stiffness Initial Stress stiffness Tangent stiffness matrix Finite Element Method Principle of Virtual Work Strain Measure
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THE INCREMENT STIFFNESS MATRIX AND TOTAL QUANTUM STIFFNESS IN NONLINEAR ANALYSES
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作者 李龙元 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第8期723-726,共4页
In this paper, the expressions of both increment stiffness matrix and total quantum stiffness matrix in nonlinear analyses are derived in detail, and their relationship is discussed in mathematical meaningThe results ... In this paper, the expressions of both increment stiffness matrix and total quantum stiffness matrix in nonlinear analyses are derived in detail, and their relationship is discussed in mathematical meaningThe results given in our paper will be of great importance to the analyses of nonlinear numerical and nonlinear stability in finite element methods. 展开更多
关键词 THE INCREMENT stiffNESS matrix AND TOTAL QUANTUM stiffNESS IN NONLINEAR ANALYSES
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Dynamic Change of Matrix Stiffness Switches Astrocyte Phenotype in Three Dimensions
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作者 Yan Hu Jin Tian +3 位作者 Jinbin Qiu Dayun Feng Guoyou Huang Feng Xu 《医用生物力学》 EI CAS CSCD 北大核心 2019年第A01期135-136,共2页
Background Damage to the central nervous system(CNS)usually leads to the activation of astrocytes,followed by glial scar formation.For years,glial scar has been thought as a major obstacle for successful axon regenera... Background Damage to the central nervous system(CNS)usually leads to the activation of astrocytes,followed by glial scar formation.For years,glial scar has been thought as a major obstacle for successful axon regeneration.However,increasing evidence suggests a beneficial role for this scar tissue as part of the endogenous local immune regulation and repair process.Surprisingly,in contrast to scars in other tissues,glial scars(mainly consist of reactive astrocytes)in both rat cortex and spinal cord were recently found to be significantly softer than healthy CNS tissues.Naive astrocytes have been found to change their phenotype to reactive astrocytes and gradually into scar-forming astrocytes,upregulating the astrocyte marker glial fibrillary acidic protein(GFAP),vimentin,and inflammatory proteins in almost all known brain disorders.Such phenotype transformation process has been widely thought unidirectional or irreversible.However,recent research revealed the environment-dependent plasticity of astrocyte phenotypes,with reactive astrocytes could revert in retrograde to naive astrocytes in proper microenvironment.In consideration of the important roles of mechanical cues in CNS and the unique softening behavior of glial scars,it is of great interesting to study the effects of dynamic changes of matrix stiffness on astrocyte phenotypic switch.Materials&methods Primary astrocyes were isolated from the cortex of SpragueDawley(SD)rats at PI.After cultured for 2 weeks,astrocytes were encapsulated into a set of three-dimensional(3D)hybrid hydrogel system composed of type I collagen and alginate.Immunofluorescence and Western blot expression analysis were applied for characterizting cell responses to different and dynamically changed matrix stiffness.A molecular dynamics model was developed for simulation.Results&discussion In this work,we established an in-vitro model to study the effects of dynamic changes of matrix stiffness on astrocyte phenotypic switchings in 3D.To simulate native cellular environment,we fabricated a set of hybrid hydrogel system composed of type I collagen and alginate.The stiffness of the hybrid hydrogels was demonstrated to be dynamically changed by adding calcium chloride or sodium citrate to crosslink or decrosslink alginate,respectively.Using 3D culture models,we showed that the decrease of matrix stiffness could promote astrocyte activation,with upregulated GFAP and IL-1β.In addition,3D cultured astrocytes spread greater with decreasing matrix stiffness.Moreover,we surprisingly found that astrocyte phenotype could be switched by dynamically changing matrix stiffness.Specifically,matrix stiffening reverted the activation of astrocytes,whereas matrix softening induced astrocyte activation.We further demonstrated that matrix stiffness-induced astrocyte activation was mediated through cytoskeletal tension and YAP protein.To some extent,YAP inhibition enhanced the responses of astrocytes to matrix stiffness.These may guide researchersto re-examine the role of matrix stiffness in reactive astrogliosis in vivo,and inspire the development of novel therapeutic approach for reducing glial scar following injury,enabling axonal regrowth and improving functional recovery by exploiting the benefits of mechanobiology studies.Conclusions Taken together,our results clarify the effects of matrix stiffness and its dynamic changes on phenotypic swtich of astrocytes in three dimensions and reveal environmental factors that regulate astrocytic phenotype transformation process,which may provide potential therapeutic approach for CNS injury. 展开更多
关键词 ASTROCYTES matrix stiffNESS HYDROGELS three dimensions YAP
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A New Stiffness Matrix for a 2D-Beam Element with a Transverse Opening
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作者 Musab Aied Qissab 《Open Journal of Civil Engineering》 2015年第1期17-28,共12页
Transverse opening in a beam has a reducing effect of the beam stiffness which will cause a significant increase in beam deflection in the region on the opening. In this paper, a new stiffness matrix for a beam elemen... Transverse opening in a beam has a reducing effect of the beam stiffness which will cause a significant increase in beam deflection in the region on the opening. In this paper, a new stiffness matrix for a beam element with transverse opening including the effect of shear deformation has been derived. The strain energy principle is used in the derivation process of the stiffness matrix and the fixed-end force vector for the case of a concentrated or a uniformly distributed load is also derived. The accuracy of the obtained results based on the derived stiffness matrix is examined through comparison with that of the finite element method using Abaqus package and a previous study which show a good agreement with high accuracy. 展开更多
关键词 stiffNESS matrix TRANSVERSE OPENING SHEAR DEFORMATION INFLECTION Point
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Measuring the flexibility matrix of an eagle’s flight feather and a method to estimate the stiffness distribution
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作者 Di Tang Hai Zhu +2 位作者 Wei Yuan Zhongyong Fan Mingxia Lei 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第7期305-311,共7页
Flight feathers stand out with extraordinary mechanical properties for flight because they are lightweight but stiff enough.Their elasticity has great effects on the aerodynamics, resulting in aeroelasticity.Our prima... Flight feathers stand out with extraordinary mechanical properties for flight because they are lightweight but stiff enough.Their elasticity has great effects on the aerodynamics, resulting in aeroelasticity.Our primary task is to figure out the stiffness distribution of the feather to study the aeroelastic effects.The feather shaft is simplified as a beam, and the flexibility matrix of an eagle flight feather is tested.A numerical method is proposed to estimate the stiffness distributions along the shaft length based on an optimal Broyden–Fletcher–Goldfarb–Shanno(BFGS) method with global convergence.An analysis of the compressive behavior of the shaft based on the beam model shows a good fit with experimental results.The stiffness distribution of the shaft is finally presented using a 5 th order polynomial. 展开更多
关键词 FEATHER stiffness distribution FLEXIBILITY matrix optimal Broyden–Fletcher–Goldfarb–Shanno(BFGS)
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Topology Optimization of Stiffener Layout Design for Box Type Load-Bearing Component under Thermo-Mechanical Coupling
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作者 Zhaohui Yang Tianhua Xiong +1 位作者 Fei Du Baotong Li 《Computer Modeling in Engineering & Sciences》 SCIE EI 2023年第5期1701-1718,共18页
The structure optimization design under thermo-mechanical coupling is a difficult problem in the topology optimization field.An adaptive growth algorithm has become a more effective approach for structural topology op... The structure optimization design under thermo-mechanical coupling is a difficult problem in the topology optimization field.An adaptive growth algorithm has become a more effective approach for structural topology optimization.This paper proposed a topology optimization method by an adaptive growth algorithm for the stiffener layout design of box type load-bearing components under thermo-mechanical coupling.Based on the stiffness diffusion theory,both the load stiffness matrix and the heat conduction stiffness matrix of the stiffener are spread at the same time to make sure the stiffener grows freely and obtain an optimal stiffener layout design.Meanwhile,the objectives of optimization are the minimization of strain energy and thermal compliance of the whole structure,and thermo-mechanical coupling is considered.Numerical studies for square shells clearly show the effectiveness of the proposed method for stiffener layout optimization under thermo-mechanical coupling.Finally,the method is applied to optimize the stiffener layout of box type load-bearing component of themachining center.The optimization results show that both the structural deformation and temperature of the load-bearing component with the growth stiffener layout,which are optimized by the adaptive growth algorithm,are less than the stiffener layout of shape‘#’stiffener layout.It provides a new solution approach for stiffener layout optimization design of box type load-bearing components under thermo-mechanical coupling. 展开更多
关键词 THERMO-MECHANICAL topology optimization adaptive growth algorithm load stiffness matrix heat conduction stiffness matrix
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An Application of the Modified Shear Lag Model to Study the Influence of Thermal Residual Stresses on the Stiffness and Yield Strength of Short Fiber Reinforced Metal Matrix Composites 被引量:1
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作者 Zhonghao JIANG and Jianshe LIAN(Dept. of Materials Science and Engineering, Jilin University of Technology, Changchun 130025, China)Shangli DONG and Dezhuang YANG(School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1999年第3期213-221,共9页
The modified shear lag model proposed recently was applied to calculate thermal residual stresses and subsequent stress distributions under tensile and compressive loadings. The expressions for the elastic moduli and ... The modified shear lag model proposed recently was applied to calculate thermal residual stresses and subsequent stress distributions under tensile and compressive loadings. The expressions for the elastic moduli and the yield strengths under tensile and compressive loadings were derived which take account of thermal residual stresses. The asymmetries in the elastic modulus and the yield strength were interpreted using the derived expressions and the obtained results of the stress calculations. The model predictions have exhibited good agreements with the experimental results and also with the other theoretical predictions 展开更多
关键词 ab Figure An Application of the Modified Shear Lag Model to Study the Influence of Thermal Residual Stresses on the stiffness and Yield Strength of Short Fiber Reinforced Metal matrix Composites
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用于夹层梁静动力及屈曲分析的新型组合结构单元
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作者 林建平 陈昆 +2 位作者 潘剑超 王冠楠 冯倩 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第3期518-528,共11页
推导出新型组合结构单元,用于考虑界面滑移的3层部分作用夹层组合梁的静动力及屈曲特性分析.基于铁木辛柯梁理论,建立考虑夹层梁部分作用效应的能量原理.针对其受力特性,在节点位移、横截面转角和界面滑移插值时均采用含内部自由度的高... 推导出新型组合结构单元,用于考虑界面滑移的3层部分作用夹层组合梁的静动力及屈曲特性分析.基于铁木辛柯梁理论,建立考虑夹层梁部分作用效应的能量原理.针对其受力特性,在节点位移、横截面转角和界面滑移插值时均采用含内部自由度的高阶插值函数,以解决含界面有限元数值分析中常遇到的“滑移锁定”现象.通过变分原理得到夹层梁的刚度矩阵、质量矩阵以及几何刚度矩阵的显示表达式.基于MATLAB编译相应夹层结构的有限元程序并验证其准确性.对不同截面3层夹层组合梁进行不同荷载条件和边界条件下的静动力及屈曲特性分析,并探讨不同夹层组合梁跨高比和不同界面抗剪连接刚度下的计算结果及其误差的变化规律.所推导的显示表达式新型组合结构单元计算效率高,并便于推广应用于其他有限元程序或商业软件子程序中. 展开更多
关键词 夹层组合梁 部分作用 静动力分析 刚度矩阵 质量矩阵 铁木辛柯梁理论
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数字液压缸驱动的六自由度并联机器人刚度特性研究
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作者 齐潘国 迟帅 +4 位作者 郑一顺 王顶柱 刘超 门荣华 黄其涛 《兵器装备工程学报》 CAS CSCD 北大核心 2024年第6期215-223,共9页
六自由度并联机器人采用数字液压缸驱动相比于采用电液伺服缸驱动,具有成本低、可靠性高、抗污能力强和结构简单等优点,为研究数字液压缸驱动的六自由度并联机器人刚度特性,首先建立数字液压缸的数学模型并推导出闭环刚度,然后基于全微... 六自由度并联机器人采用数字液压缸驱动相比于采用电液伺服缸驱动,具有成本低、可靠性高、抗污能力强和结构简单等优点,为研究数字液压缸驱动的六自由度并联机器人刚度特性,首先建立数字液压缸的数学模型并推导出闭环刚度,然后基于全微分法建立六自由度并联机器人的误差传递模型,并结合数字液压缸的闭环刚度,推导出数字液压缸驱动的六自由度并联机器人的刚度矩阵,并分析了刚度矩阵的影响因素,建立AMESim仿真模型并进行仿真研究,揭示出并联机器人各自由度的刚度与正开口量、滚珠丝杠导程等系统固有参数以及与并联机器人位姿之间的关系,研究结果还表明,当并联机器人沿除升沉方向以外的其他方向运动时,升沉自由度和其他自由度之间存在耦合,且耦合刚度会随并联机器人位姿的变化而变化。该研究对数字液压缸驱动的六自由度并联机器人研制及应用有一定的理论价值和实际意义。 展开更多
关键词 数字液压缸 六自由度并联机器人 刚度矩阵 AMESIM 误差模型
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基于共旋坐标法的几何非线性裂纹梁单元
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作者 董正方 吴名豪 +1 位作者 王淼 李运华 《科学技术与工程》 北大核心 2024年第28期11979-11990,共12页
现有有限元软件模拟裂纹结构主要采用指派裂纹的实体和壳单元,但缺少梁单元。因此,在弹性梁单元的曲率函数中引入Dirac-δ函数表征局部损伤的曲率变化,得到位移分布函数;推导出应变矩阵和单元刚度矩阵,提出了裂纹梁单元。基于共旋坐标... 现有有限元软件模拟裂纹结构主要采用指派裂纹的实体和壳单元,但缺少梁单元。因此,在弹性梁单元的曲率函数中引入Dirac-δ函数表征局部损伤的曲率变化,得到位移分布函数;推导出应变矩阵和单元刚度矩阵,提出了裂纹梁单元。基于共旋坐标法理论进一步发展了考虑裂纹损伤的几何非线性裂纹梁单元,给出了单元的具体算法及流程。利用课题组开发的有限元求解框架,在程序中实现了裂纹梁单元及共旋列式裂纹梁单元。经过典型算例,对比分析了裂纹位置、裂纹深度及外荷载对裂纹梁弯曲性能的影响。结果表明:该单元能够准确描述裂纹结构的挠度变化,同时与现有模拟裂纹结构弯曲变形的单元相比,提出的裂纹梁和共旋列式裂纹梁在精度分别提高了约1%和4%,并且能够退化成无损伤的梁单元和几何非线性梁单元。 展开更多
关键词 共旋坐标法 裂纹 梁单元 刚度矩阵 几何非线性
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六自由度运动模拟平台设计与分析
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作者 魏国 余潇 +2 位作者 赵益 贺廿六 李绍民 《兵工自动化》 北大核心 2024年第6期31-35,60,共6页
针对实际道路测试周期长、成本高、容易受到恶劣天气影响等问题,设计一种能够用于车载光电跟踪系统进行模拟试验的六自由度摇摆台。模拟扰动测试,通过六自由度摇摆台提供扰动;对六自由度摇摆台进行结构设计、运动及频率特性分析。结果表... 针对实际道路测试周期长、成本高、容易受到恶劣天气影响等问题,设计一种能够用于车载光电跟踪系统进行模拟试验的六自由度摇摆台。模拟扰动测试,通过六自由度摇摆台提供扰动;对六自由度摇摆台进行结构设计、运动及频率特性分析。结果表明,该摇摆台能够推导其固有频率与机构刚度矩阵和质量矩阵的关系。 展开更多
关键词 六自由度摇摆台 频率特性 质量矩阵 刚度矩阵
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