基于ABAQUS的钢-混凝土组合结构纤维梁模型的开发及应用

在大量已有研究成果的基础上,基于大型通用有限元软件ABAQUS提供的用户子程序UMAT开发了一组适用于组合结构构件的单轴材料滞回本构模型,并编制了可用于组合截面纤维自动离散的前处理程序,由此集成了钢-混凝土组合结构纤维梁模型,可用于完全剪力连接的组合框架体系在竖向荷载及水平往复荷载作用下的整体弹塑性分析。与国内外大量试验的对比结果表明,该文开发的钢-混凝土组合结构纤维梁模型具有较高的精度和较为广泛的适用性。纤维梁模型虽然不能考虑钢梁与混凝土板之间的滑移效应,但与试验结果的对比表明是否考虑滑移效应对结构体系整体计算结果的影响不大,但建模工作量大大减少,计算效率显著提高,在分析组合框架体系在地震往复荷载作用下的受力性能时具有较大的优势。     

Effect of cracks on thermal stress and strain of a tape automated bonded package

A tape automated bonded (TAB) package is basically a composite structure. A three-dimensional finite element fracture analysis was performed to evaluate the effects of cracks in a TAB package under thermal cycling conditions. The lead-tin solder in the outer lead bond as well as the copper beam lead were taken as elasto-plastic materials. Interface cracks between the copper beam lead and the solder were included in the analysis. It was found that the prescribed cracks created new sources of stress concentrations, which are fairly mild. This result showed that the configuration of the outer lead bonds in TAB packages is generally resilient to thermal cycling, even with the presence of defects such as cracks.     

Fiber interactions and effective elasto-plastic properties of short-fiber composites

The fiber–fiber or fiber–matrix interactions and effective elasto-plastic properties of aligned short-fiber-reinforced metal matrix composite are studied by using a micromechanical model and the finite element method. The fiber is assumed to be elastic and the matrix to be elasto-viscoplastic continuum. The local elasto-plastic stress fields of a unit cell in composite are examined in order to understand the mechanism of inelastic deformations and interactions between fibers or between fiber and matrix. Effective elasto-plastic properties of B/Al composites are predicted by the domain average method. It is shown that present predictions are in agreement with the experimental data for the B/Al system.     

Numerical modeling on concrete structures and steel–concrete composite frame structures

A steel–concrete composite fiber beam-column model is developed in this study. The composite fiber beam-column model consists of a preprocessor program that is used to divide a composite section into fibers and a group of uniaxial hysteretic material constitutive models coded in the user defined subprogram UMAT in ABAQUS. The steel–concrete composite fiber beam-column model is suitable for global elasto-plastic analysis on composite frames with rigid connections subjected to the combined action of gravity and cyclic lateral loads. The model is verified by a large number of experiments and the results show that the developed composite fiber model possesses better accuracy and broader applicability compared with a traditional finite element model. Although the fiber beam-column model neglects the slip between the steel beam and concrete slab, there are essentially no effects on the global calculation results of steel–concrete composite frames. The proposed model has a simple modeling procedure, high calculation efficiency and great advantage when it is used to analyze composite frames subjected to cyclic loading due to earthquake.     

Post-buckling analysis of composite beams: A simple intuitive formulation

Post-buckling analysis of composite beams with axially immovable ends is investigated using an Intuitive formulation. Intuitive formulation uses two parameters namely critical buckling load and axial stretching force developed in the post-buckled domain of composite beam. Geometric nonlinearity of von-Karman type is taken into consideration which accounts for membrane stretching action of the beam. Axial stretching force developed in post-buckled domain of composite beam is evaluated by using an axial governing equation and is expressed either in terms of lateral displacement function as an integrated value, or as a function of both axial and lateral displacement functions at any discrete location of the beam. The available expressions of critical buckling load and derived expressions of axial stretching force developed in the beam are used for obtaining an approximate closed-form expressions for the post-buckling loads of various beam boundary conditions. Numerical accuracy of the proposed analytical closed-form expressions obtained from the intuitive formulation are compared to the available finite element solutions for symmetric and asymmetric lay-up schemes of laminated composite beam. Effect of central amplitude ratio and lay-up orientation on post-buckling load variation is briefly discussed for various beam boundary conditions considered in this study.     

Lateral buckling analysis of thin-walled laminated channel-section beams

The lateral buckling of a laminated composite beam with channel section is studied. A general analytical model applicable to the lateral buckling of a channel-section composite beam subjected to various types of loadings is derived. This model is based on the classical lamination theory, and accounts for the material coupling for arbitrary laminate stacking sequence configuration and various boundary conditions. The effects of the location of applied loading on the buckling capacity are also included in the analysis. A displacement-based one-dimensional finite element model is developed to predict critical loads and corresponding buckling modes for a thin-walled composite beam with arbitrary boundary conditions. Numerical results are obtained for thin-walled composites under central point load, uniformly distributed load, and pure bending with angle-ply and laminates. The effects of fiber orientation, location of applied load, and types of loads on the critical buckling loads are parametrically studied.     

旋转几何非线性复合材料薄壁梁的自由振动分析

研究具有几何非线性的旋转复合材料薄壁梁的自由振动。梁的变形引入了Von Kármán几何非线性, 基于Hamilton原理和变分渐进法 (Variational-Asymptotical Method -VMA),导出旋转复合材料薄壁梁的非线性振动偏微分方程组。采用Galerkin法将振动方程离散化为常微分方程组。借助于谐波平衡法 (Harmonic Balance Method -HBM) 建立自由振动的振幅-非线性固有频率关系方程。将上述方程化为非线性特征值问题,采用迭代算法进行求解。将所建立的旋转复合材料薄壁梁非线性自由振动分析模型和计算方法,应用于周向均匀刚度配置(Circumferentially Uniform Stiffness –CUS) 构型复合材料薄壁梁,通过数值计算揭示了纤维铺层角、旋转速度对非线性振动固有频率-振幅关系的影响。     

SMA纤维混杂层合梁的振动分析

提出一类形状记忆合金(SMA)纤维混杂层合梁的数学模型。采用多胞模型、形状记忆合金一维本构关系分析方法,同时考虑铁木辛柯剪切和马氏体相变的影响。目的是为了更进一步了解层合梁的振动控制。SMA纤维用来作为驱动器,它能够改变弹性模量和回复力,以此改变梁的频率。分析了SMA纤维含量、铺设角度和横向剪切变形的影响。结果表明,通过激活形状记忆合金纤维及改变初始变形,对层合梁的自振频率有很强的控制和调节能力。     

A micromechanical model for kink-band formation: Part II—Analytical modelling

An analytical micromechanical model for kink-band formation in an unidirectional fibre-reinforced composite is developed. This is supported by the conclusions of experimental and numerical programmes (presented in Part I of this paper) and is based on the equilibrium of an imperfect fibre laterally supported by an elasto-plastic matrix. The model predicts the longitudinal compressive strength of the composite (in closed form), the deflection and main stress fields in fibres and matrix at different stages of kink-band formation, the kink-band width, and the orientation of the fibres at the onset of fibre failure.     

Large-deformation,elasto-plastic analysis of frames under nonconservative loading,using explicitly derived tangent stiffnesses based on assumed stresses

Simple and economical procedures for large-deformation elasto-plastic analysis of frames, whose members can be characterized as beams, are presented. An assumed stress approach is employed to derive the tangent stiffness of the beam, subjected in general to non-conservative type distributed loading. The beam is assumed to undergo arbitrarily large rigid rotations but small axial stretch and relative (non-rigid) point-wise rotations. It is shown that if a plastic-hinge method (with allowance being made for the formation of the hinge at an arbitrary location or locations along the beam) is employed, the tangent stiffness matrix may be derived in an explicit fashion, without numerical integration. Several examples are given to illustrate the relative economy and efficiency of the method in solving large-deformation elasto-plastic problems. The method is of considerable utility in analysing off-shore structures and large structures that are likely to be deployed in outerspace.     

Design and manufacturing of an L-shaped thermoplastic composite beam by braid-trusion

Braid-trusion is a manufacturing process for composite materials in which a braiding machine is coupled with a pultrusion die to continuously produce beams with constant cross-section and off-axis fiber orientation. This study presents a geometrical model of the tri-axial braid which allows the design of braided preforms that achieve correct filling of the pultrusion die at the same time as it limits fiber friction on die walls. The typic design parameters are listed and used for the manufacturing of a braid-truded thermoplastic composite beam where fibers are aligned at ±69° as well as 0° with respect to the beam axis. Tensile mechanical characterization and cross-section observations are also presented.     

空间杆系结构的弹塑性大位移分析

为适当降低杆系结构弹塑性分析的计算量,该文假设单元塑性变形集中于单元端部。在单元端部截面上,将截面分割为若干小块面积,用小块面积中心处材料的弹塑性性能代替整个小块面积的弹塑性性能。通过对小块面积弹塑性性能的分析,得出端部截面的弹塑性刚度,再将其与单元内部弹性部分的截面刚度沿杆长进行Gauss-Lobatto积分,由此获得梁单元的弹塑性刚度矩阵。该文对小面积中心点采用基于材料应变等向强化的弹塑性本构关系,为准确分析杆端截面小块面积的弹塑性应力状态,该文提出了有效的应力调整算法以修正计算过程中偏离屈服面的应力值。数值算例表明,该文方法准确、高效、可靠。     

Efficient laminated composite beam element subjected to variable axial force for coupled stability analysis

A numerically efficient laminated composite beam element subjected to a variable axial force is presented for a coupled stability analysis. The analytical technique is used to present the thin-walled laminated composite beam theory considering the transverse shear and the restrained warping-induced shear deformation based on an orthogonal Cartesian coordinate system. The elastic strain energy and the potential energy due to the variable axial force are introduced. The equilibrium equations are derived from the energy principle, and explicit expressions for the displacement parameters are presented using the power series expansions of displacement components. Finally, the member stiffness matrix is determined using the force–displacement relations. In order to verify accuracy and efficiency of the beam element developed in this study, numerical results are presented and compared with results from other researchers and the finite beam element results, and the detailed finite shell element analysis results using ABAQUS; especially, the influence of variable axial forces, the fiber orientation, and boundary conditions on the buckling behavior of the laminated composite beams is parametrically investigated.     

梁撞击弹塑性波传播的动态子结构方法的研究

该文针对简支梁横向弹塑性撞击问题,建立动态子结构模型,推导了相应的动力学控制方程,并采用Newmark隐式积分法进行求解,将动态子结构方法应用于撞击激发弹塑性波传播问题的研究。考虑局部弹塑性接触变形,通过对撞击激发的弹塑性波传播,包括弯矩波、挠曲波、速度波和应力波传播过程的计算,研究动态子结构法分析弹塑性波的传播特征,弯曲波的弥散特征,以及塑性铰形成机理等的合理性。经过与三维动力有限元计算结果的比较表明,动态子结构方法可以合理地应用于柔性梁中弹塑性撞击瞬态波传播问题的研究。     

Effect of lamina orientation,crack severity,and fillers on dynamic parameters of hybrid composite cantilever beam with double transverse cracks

Modern-day research in composite material development primarily focuses on tailoring combinations by proportions of constituent materials and monitoring the changes in their targeted properties. In line with this trend, a new class of glass fiber reinforced polymer hybrid composite beam of size 600 mm×50 mm×6 mm is fabricated by adding graphene (average particle size:10 μm), and flyash (average particle size: 60 μm). The dynamic behavior of the hybrid beam by introducing two transverse cracks at different positions with varying crack depths is studied by employing analytical, finite-element, and experimental approaches. The dimensionless relative natural frequencies of the cracked/faulty hybrid beam obtained by the proposed methods are compared with the intact hybrid beam. Also, a comparison is made for the hybrid beam with a single crack. An increase in relative crack depth resulted in an increase in values of dimensionless compliances. Further, the effect of fiber orientation and lamina stacking sequence on the dynamic parameters of the hybrid beam are also analyzed. The introduction of the second crack induces higher nonlinearity in bending modes of vibration.     

A theoretical approach for the thermal expansion behavior of the particulate reinforced aluminum matrix composite Part I A thermal expansion model for composites with mono-dispersed spherical particles

Microstructural observation revealed that the increase in the volume fraction of SiC particles lowers the coefficient of thermal expansion (CTE) of the composite, and the CTE of the metal matrix composites is proportional to the size of the Si phase. To analyze the thermal expansion behavior of aluminum matrix composites, a new model for the CTE of the mono-dispersed binary composite on the basis of Ashelby's cutting and welding approach was proposed. In the theoretical model, it was considered that during cooling relaxation of residual stresses could create an elasto-plastic deformation zone around a SiC or Al₂O₃ particle in the matrix. The size of reinforced particles and other metallurgical factors of the matrix alloy and composite were also considered. In this model, the interacting effect between the reinforced hard particle and the soft matrix is considered by introducing the influence of the elasto-plastic deformation zone around a particle, which is distinguished from the previous models. It was revealed that the CTE of the composite are influenced by the particle volume fraction, the elastic modulus and Poisson's ratio as well as the elasto-plastic deformation zone size and the particle size.     

Damage in MMCs using the GMC: theoretical formulation

In this work the incorporation of damage in the material behavior is investigated. Damage is incorporated into the generalized cells model (GMC), and applied to metal-matrix composites (MMCs). The local incremental damage model of Voyiadjis and Park is used here in order to account for damage in each subcell separately. The resulting micromechanical analysis establishes elasto-plastic constitutive equations that govern the overall behavior of the damaged composite. The elasto-plastic constitutive model is first derived in the undamaged configuration for each constituent of the metal-matrix composite. The plasticity model used here is based on the existence of a yield surface and flow rule. The relationships are then transformed for each constituent to the damaged configuration by applying the local incremental constituent damage tensors. The overall damaged quantities are then obtained by applying the local damage concentration factors obtained by employing the rate of displacement and traction continuity conditions at the interface between subcells and between neighboring repeating cells in the generalized cells model. Examples are solved numerically in order to explore the physical interpretation of the proposed theory for a unit cell composite element.     

SRC柱-钢梁混合框架直接基于位移的抗震设计方法研究

型钢混凝土（SRC）柱-钢梁混合框架结构具有较好的抗震性能,在大跨度结构及高层建筑中得以广泛应用,然而对于SRC柱-钢梁混合框架结构的抗震设计方法研究较少。根据SRC柱-钢梁混合框架结构的特点,将其性能划分为使用良好、暂时使用、修复后使用、接近倒塌四个水平,采用层间位移角限值予以量化,并在此基础上提出SRC柱-钢梁混合框架直接基于位移的抗震设计方法。利用通用有限元软件ABAQUS中的PQ-FIBER模型对SRC柱-钢梁混合框架进行静力弹塑性分析,并采用已有的试验研究成果对PQ-FIBER模型的适用性进行了验证。采用此方法对某8层SRC柱-钢梁混合框架结构进行了设计,然后采用静力弹塑性分析法验证该方法的可行性,为SRC柱-钢梁混合框架结构直接基于位移的抗震设计方法提供一定依据。     

The effect of fiber angle on the natural frequencies of orthotropic composite pre-twisted blades

The eigenvalue problem of a tapered pre-twisted orthotropic composite blade is formulated by employing the differential quadrature method (DQM). The Euler–Bernoulli beam model is used to characterize the pre-twisted orthotropic composite blade. The Kelvin–Voigt internal and linear external damping coefficients are employed and determined for the orthotropic composite blade. The DQM is used to transform the partial differential equations of a tapered pre-twisted orthotropic composite blade into a discrete eigenvalue problem. The Chebyshev–Gauss–Lobatto sample point equation is used to select the sample points. In this study, the effects of the fiber orientation, internal damping, external damping, inclined angle and the rotation speed on the natural frequencies for a tapered pre-twisted orthotropic composite blade are investigated. The effect of the number of sample points on the accuracy of the calculated natural frequencies is also discussed. The integrity and computational efficiency of the DQM in this problem will be demonstrated through a number of case studies. Numerical results indicated that the DQM is valid and efficient for a pre-twisted orthotropic composite blade formulation.