共查询到20条相似文献,搜索用时 10 毫秒
1.
Mariem Miladi Chaabane Régis Plateaux Jean-Yves Choley Chafik Karra Alain Rivière Mohamed Haddar 《Comptes Rendus Mecanique》2014,342(8):466-477
The present work tackled the modeling of frame structures using a topological approach based on the concepts of topological collections and transformations. The topological collections are used to specify the interconnection law between the frame structures and the transformations that are used to describe their behavior. As a language allowing the application of this approach, we applied the MGS (Modeling of General System) language. To validate this approach, we studied the case of two- and three-dimensional frame structures. Then, the results obtained using the MGS language are presented and compared to those obtained by the structural calculation software by the finite-element method RDM6. For both studied cases, we find that the results obtained by MGS language based on the notions of topological collections and transformations and those obtained by the RDM6 software based on the finite element method are very close, which validates our approach. Using this topological approach, any structure can be characterized by local relations between its elements, thus making it possible to dissociate its topology and its physics. Indeed, in our topological approach, we separately define the topology of the studied frame structure and the local behavior law as well as the equilibrium equations of its various components. Therefore, this topological approach might be generalized to model complex systems which can be considered as a set of local elements linked by a neighborhood relationship. 相似文献
2.
Based on the Independent Continuous Mapping method (ICM), a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable stress and element stiffness, which transform the 0-1 type discrete topological variables into continuous topological variables between 0 and 1. Two methods for the filter functions are adopted to avoid the structural singularity and recover falsely deleted elements: the weak material element method and the tiny section element method. Three criteria (no structural singularity, no violated constraints and no change of structural weight) are introduced to judge iteration convergence. These criteria allow finding an appropriate threshold by adjusting a discount factor in the iteration procedure. To improve the efficiency, the original optimization model is transformed into a dual problem according to the dual theory and solved in its dual space. By using MSC/Nastran as the structural solver and MSC/Patran as the developing platform, a topological optimization software of frame structures is accomplished. Numerical examples show that the ICM method is very efficient for the topological optimization of frame structures.The project supported by the National Natural Science Foundation of China (10472003) and Beijing Natural Science Foundation (3042002) The English text was polished by Yunming Chen. 相似文献
3.
The paper shows that representing structures, beams and frames by mathematical models based on graph theory enables to provide new perspective on known conjugate structure theorems in mechanics. It is shown that the latter theorems can be derived from the graph theoretical duality principle applied upon the graph representations of the structures. The results reported indicate upon theoretical value of the approach, as the established mathematical foundation can be employed in a variety of mechanical disciplines. 相似文献
4.
In this paper a topological modification method for structural variations of space frame structures is studied by using the Moore-Penrose inverse theory and a new kind of factorization of the stiffness matrix. A set of explicit formulations of variations are obtained. A numerical example is given to illustrate the valid of the present method. 相似文献
5.
V. Rizov 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(3):205-212
Usually when analyzing the mechanical response of foam-cored fiber-reinforced composite sandwich structures to localized static
loading, the face sheets are treated as a linear-elastic material and no damage initiation and growth is considered. However,
practice shows that at higher indentation magnitudes damage develops in the face sheet in the area of contact with the indentor,
which could lead to local failure of the face laminate due to the loss of bending stiffness and strength. Therefore, the main
objective of the present study is to develop a damage model for predicting the local failure in the composite face sheet and
its influence on the load–displacement behavior of sandwich structures under local loading. For this purpose, the Hoffman
failure criterion is incorporated into a finite element modeling procedure using the ABAQUS program system. Results deducted
from the modeling procedure are compared with experimental data obtained in the case of static indentation tests performed
on sandwich beam specimens using steel cylindrical indentors. It is shown that taking into account the damage in the face
sheet leads to a substantial improvement in the performance of the model when simulating the mechanical behavior of the sandwich
structures at higher indentation values. 相似文献
6.
为了研究预应力混凝土(prestressed concrete, PC)框架结构的抗爆性能,利用有限元软件LS-DYNA对一栋3层2跨的大跨有/无黏结PC框架结构在不同比例距离的外部远爆荷载作用下的动力响应进行了分析。分析结果表明:混凝土预应力框架在地表远爆荷载作用下,最大层间位移角与前墙所受峰值反射超压近似成线性关系;有黏结混凝土预应力框架结构层间位移角相较于无黏结混凝土预应力框架更小,损伤分布更均匀,结构抗爆性能更好;基于分析结果,给出了不同比例距离对应的损伤状态,可用于对混凝土预应力框架结构进行爆炸损伤状态快速评估。
相似文献7.
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9.
刚接与铰接混合连接杆系结构的几何非线性分析 总被引:4,自引:0,他引:4
本文提出用子结构原理解决具有刚接与铰接混合连接空间杆系结构的几何非线性分析,实现其非线性稳定性分析的载荷-位移全过程跟踪。该法无须单独推导刚接、铰接以及一端刚接一端铰接单元的弹性刚度矩阵和几何刚度矩阵,而可以直接由空间梁单元退化得到,而且可以将平面问题与空间问题、刚接与铰接混合连接体系进行统一处理,算例表明,本文方法对于杆系结构的统一和整体分析是有效的。 相似文献
10.
The load-bearing capacities of ductile composite materials and structures are studied by means of a combined micro/macromechanics
approach. Firstly, on the microscopic scale, the aim is to get the macroscopic strength domains by means of the homogenization
theory of micromechanics. A representative volume element (RVE) is selected to reflect the microstructures of the composite
materials. By introducing the homogenization theory into the kinematic limit theorem of plastic limit analysis, an optimization
format to directly calculate the limit loads of the RVE is obtained. And the macroscopic yield criterion can be determined
according to the relation between macroscopic and microscopic fields. Secondly, on the macroscopic scale, by introducing the
Hill's yield criterion into the kinematic limit theorem, the limit loads of orthotropic structures such as unidirectional
fiber-reinforced composite structures are worked out. The finite element modeling of the kinematic limit analysis is deduced
into a nonlinear mathematical programming with equality-constraint conditions that can be solved by means of a direct iterative
algorithm. Finally, some examples are illustrated to show the application of the present approach.
Project supported by the National Natural Science Foundation of China (No. 19902007), the National Foundation for Excellent
Doctoral Dissertation of China (No. 200025), the Fund of the Ministry of Education of China for Returned Oversea Scholars
and the Basic Research Foundation of Tsinghua University. 相似文献
11.
W.S. Barham A.J. Aref G.F. Dargush 《International Journal of Solids and Structures》2005,42(26):6586-6609
The displacement-based finite element method dominates current practice for material nonlinear analysis of structures. However, there are several characteristics that may limit the effectiveness of this approach. In particular, for elastoplastic analysis, the displacement method relies upon a step-by-step incremental approach stemming from flow theory and also requires significant mesh refinement to resolve behavior in plastic zones. This leads to computational inefficiencies that, in turn, encourage the reconsideration of force-based approaches for elastoplastic problems.One of these force algorithms that has been recently developed is the large increment method. The main advantage of the flexibility-based large increment method (LIM) over the displacement method is that it separates the global equilibrium and compatibility equations from the local constitutive relations. Consequently, LIM can reach the solution in one large increment or in a few large steps, thus, avoiding the development of cumulative errors. This paper discusses the extension of the large increment methodology for the nonlinear analysis of plane frame structures controlled by an elastic, perfectly plastic material model. The discussion focuses on the power of LIM to handle these nonlinear problems, especially when plastic hinges form in the frame and ultimately as the structure approaches the collapse stage. Illustrative planar frame examples are presented and the results are compared with those obtained from a standard displacement method. 相似文献
12.
《Wave Motion》2020
In the structural design of mechanical products, natural frequencies must be controlled to reduce noise and vibration. In particular, the stiffness of the joints which assemble the structural components affects the natural frequencies. Therefore, it is important to predict the influence of joint stiffness on natural frequencies. Generally, these effects are determined by iterative finite element analyses of assembled structural models. Because this results in high computational costs, the sensitivity of natural frequencies to joint stiffness should be determined by a different approach to make the structural design process more efficient. Therefore, this paper proposes the use of reflection and transmission coefficients of elastic joints to predict the dependency of natural frequencies on joint stiffness. First, we formulate the reflection and transmission coefficients of joint stiffness, and then organize the coefficients using a ray tracing method. These formulations enable us to discuss the mechanisms which determine the natural frequency of a structure based on a wave approach using the phase-closure principle. Therefore, by applying the phase-closure principle to the frame structure, we investigate the formation of bending modes, which suggests that the effects of joint stiffness on natural frequencies correspond to the dependence of the reflection and transmission coefficients on joint stiffness. Therefore, these coefficients are useful indicators for estimating the influence of joint stiffness. 相似文献
13.
分块法研究圆柱绕流升阻力 总被引:18,自引:1,他引:18
使用新的分块耦合方法,分别对单圆柱和串列双圆柱绕流进行了数值
模拟. 对于单圆柱绕流,低$Re$下计算所得到的定常涡尺寸与实验非常接近. 对于
串列双圆柱绕流,研究分析了改变双圆柱中心间距对上下游圆柱的升阻力系数和脉动频率所
产生的影响,计算结果与实验非常吻合,为进一步研究涡致振动提供了依据. 相似文献
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15.
Sequential non-linear least-square estimation for damage identification of structures with unknown inputs and unknown outputs 总被引:1,自引:0,他引:1
The detection of structural damages real-time on-line, based on vibration data measured from sensors, is an important but challenging research topic, and it has received considerable attentions recently. Due to practical limitations, it is highly desirable to install as few sensors as possible in the structural health monitoring system, leading to incomplete measurements of structural responses and excitations. The traditional time-domain analysis techniques, such as the least-square estimation (LSE) method and the extended Kalman filter (EKF) approach, require that all the external excitations (inputs) be available, which may not be the case for most structural health monitoring systems. Recently, the adaptive sequential non-linear least-square estimate (SNLSE) method has been proposed for the on-line identification of structural damages. In this paper, we extend the SNLSE method to cover the general case with unknown (unmeasured) excitations (inputs) and unknown (unmeasured) acceleration responses (outputs) in order to reduce the number of sensors required in the structural health monitoring system, referred to as the SNLSE-UI-UO. Analytic recursive solutions for the new approach are derived and presented. The accuracy and effectiveness of the proposed approach have been demonstrated using the Phase I ASCE structural health monitoring benchmark building, a 5-degree-of-freedom non-linear hysteretic building model, and a 3-story steel frame finite-element model. Simulation results indicate that the proposed approach is capable of tracking the changes of structural parameters leading to the identification of damages. 相似文献
16.
One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames. 相似文献
17.
地震作用下空间框架结构层间相对位移响应梯度和海赛矩阵的计算 总被引:1,自引:1,他引:0
提出一种在地震作用下空间框架结构层间相对位移响应梯度和海赛矩阵的精确计算方法。在有限单元法和纽马克-β法的基础上推导出在地震作用下空间框架结构层间相对位移响应梯度和海赛矩阵的计算公式,给出在地震作用下空间框架结构层间相对位移响应梯度和海赛矩阵的计算步骤,用Matlab语言编制了空间框架结构层间相对位移响应梯度和海赛矩阵的计算程序,实现了空间框架结构层间相对位移响应梯度和海赛矩阵的精确计算。最后通过一个二层空间框架结构的计算实例表明本文所提出的计算方法是有效的。 相似文献
18.
S. Tomasiello 《Mechanics Research Communications》2011,38(4):300-304
In this paper a new version of the Modified Quadrature Element Method (MQEM) is proposed. Like MQEM, the proposed method overcomes the drawback of the distance δ of the Quadrature Element Method (QEM) without introducing further degrees of freedom at the ends of the element as in the Differential Quadrature Element Method (DQEM), but it makes the computational cost of the stiffness matrix (and the mass matrix) lighter and uses a general procedure to generate the sampling points distribution. The method here presented has been applied to compute the fundamental frequencies of some structures. 相似文献
19.
Mechanical behaviors and damage constitutive model of ceramics under shock compression 总被引:2,自引:0,他引:2
One-stage light gas gun was utilized to study the dynamic mechanical properties of AD90 alumina subjected to the shock loading. Manganin gauges were adopted to obtain the stress-time histories. The velocity interferometer system for any reflector (VISAR) was used to obtain the free surface velocity profile and determine the Hugoniot elastic limit. The Hugoniot curves were fitted with the experimental data. From Hugoniot curves the compressive behaviors of AD90 alumina were found to change typically from elastic to "plastic". The dynamic mechanical behaviors for alumina under impact loadings were analyzed by using the path line principle of Lagrange analysis, including the nonlinear characteristics, the strain rate dependence, the dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading has been developed. The model was based on the damage micromechanics and wing crack nucleation and growth. The effects of parameters of both the micro-cracks nucleation and the initial crack size on the dynamic fracture strength were discussed. The results of the dynamic damage evolution model were compared with the experimental results and a good agreement was found. 相似文献