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1.
将有限变形单元与虚拟连接单元相结合,用于模拟准脆性材料破坏过程.首先基于精确的有限变形理论,采用第二类Piola-Kirchhoff应力与Green-Lagrange应变作为能量共轭的应力、应变对,推导出虚拟连接单元的单元刚度矩阵;通过数值算例,验证该单元的正确性与合理性,给出虚拟连接单元高度的取值范围,并与无此单元时...  相似文献   

2.
基于整体-局部位移方法,建立了一种高阶剪切变形理论。整体位移部分采用的是Reddy理论的位移模式(1984),局部位移为LIXY等(1997)建立的1,2-3理论的局部函数。这一理论使满足自由表面条件的Red@理论进一步满足层间位移、应力连续,同时有效减少了1,2—3理论的未知数个数。基于此理论深入开展了有限元法研究,建立了满足C^1连续条件的精化三节点三角形单元(每个节点参数为9个)。计算结果表明:建立的精化单元能准确计算整体位移和层间应力。  相似文献   

3.
提出了多亚层柔性节点模型用于分析双材料裂纹尖端的应力和变形。该模型考虑了胶层的变形,各亚层视为独立的剪切变形梁,采用两个界面柔度系数考虑界面应力对各亚层界面变形的影响,界面变形包括双材料界面和胶层的变形。通过对FRP-混凝土末端切口四点弯试件(Four-point bending end-notched flexure specimen,简称4ENF)进行界面分析,并与其他模型和有限元分析对比表明:刚性节点模型忽略了裂纹尖端的应力和变形集中,只能粗略地估计构件的整体变形和界面应力;半刚性节点容许裂纹尖端的转动,对裂纹尖端的变形估计优于刚性节点模型,但精度依然不高;多亚层柔性节点模型反映了裂纹尖端的应力和变形集中,与数值分析结果吻合很好,该研究对进行双材料结构的工程设计具有理论指导和参考价值。  相似文献   

4.
复合材料大层数层合板热变形热应力有限元分析   总被引:7,自引:0,他引:7  
研究复合材料大层数层合板结构承受热载荷或同时存在机械载荷作用下,由于层合板各单层间存在着剪切耦合和泊松比的不协调等因素引起的热应力、热变形和自由边缘效应,采用三维八节点等参有限单元法,其特点是在划分三维单元时,每一个单元内可包含多个具有不同铺设角、不同组分材料的铺层。该文导出了相应的三维有限元分析各表达式,进行了实例数值计算,得到了反映大层数层合板热变形、热应力特性的一些有价值的结果。  相似文献   

5.
覃海艺  马宁 《应用力学学报》2015,(1):139-144,179
基于h-p型有限元精度计算法,以薄壁弯曲结构为研究对象,系统地介绍了实体单元常见的分类方法及优缺点;通过理论公式推导了薄壁弯曲结构发生弹性和弹塑性变形时的位移和应力理论解;采用有限元法计算数值解,研究了影响有限元计算精度的因素和规律,并用算例证实了研究结果的合理性。研究结果表明:当单元类型、积分方式、阶次、长高比相同时,只有1层实体单元情况下得到的计算误差总是大于多层单元;只要严格控制单元长高比为1左右,单元层数不小于4层,采用一阶全积分六面体单元就可以控制位移及应力误差在5%以内;当采用一阶减缩积分六面体单元,只需2层单元就可以控制弹性位移误差在1%左右,但此时应力误差达30%以上,对于塑性变形,单元层数达6层时其位移误差仍达8%以上;对于二阶六面体及二阶四面体单元,只需2层单元,且不需严格控制单元长高比为1左右就可以使位移及应力计算误差在5%以内。  相似文献   

6.
基于压电复合材料层合板一阶剪切变形理论及叠层理论,构造了一种新型三角形三节点压电层合板单元,简记为CDST-S6E单元.该单元采用压电耦合的运动方程求解位移场及电势场,层合板主体结构用一阶剪切变形理论模拟,其剪应变场及单元转角场由结点包含有两个剪切自由度的DST-S6单元理论确定,电势作为附加自由度,应用叠层理论对压电层合板的电势场沿厚度方向进行线性插值.该CDST-S6E单元不需要借助减缩积分、假设应力或应变等辅助数学手段,也不会产生对稳定性带来影响的附加零能模式,可较好避免厚薄板单元的剪切闭锬问题且具有简洁的表达形式.数值算例表明,CDST-S6E单元具有较高的精度,可以较为精确地预测压电层合板的变形及电势场,是一种厚薄通用的优质压电层合板单元.  相似文献   

7.
动态拉伸试验中试样应变测试的有效性分析   总被引:3,自引:0,他引:3  
田宏伟  郭伟国 《实验力学》2008,23(5):403-410
为了评估将试样通过胶粘连接到加载杆的Hopkinson杆装置所获得试样应变的有效性,对四种强度刚度差异较大的纤维增强复合材料进行了动态拉伸试验。试验时,试样通过环氧胶和杆夹层粘接,试样的应变分别按照Hopkinson杆一维应力波理论计算和试样上应变计直接准确测量得到。结果证明:对小变形碳纤维复合材料,按一维应力波理论计算的应变与试样上直接所测应变值偏差超过100%;对较大变形的GFRP和KFRP层合板,两者偏差小于40%。说明采用Hopkinson杆一维应力波理论计算的试样应变不准确。为修正不准确性,一是通过大量数据分析建立按一维应力波理论计算值与直接测量应变之间的关系式,用此式可使此试验装置获得有效的试样应变;二是借助ABAQUS有限元模拟分析得出粘胶层以及试样过渡弧段的变形,用一维应力波理论计算的应变减去此变形,也可获得有效的试样应变。  相似文献   

8.
对同轴绞线柔索受力变形提出两个基本假设,即横截面保持平面和组成柔索的绞线为螺旋线其形状保持不变.据此建立了求解各层绞线所受的纵向力,以及各层之间挤压力的控制方程.导出应力的计算方法,揭示同轴绞线柔索张拉时的应力分布规律.  相似文献   

9.
在MSC.Patran有限元软件中用梁单元建立单层肋环型圆顶的几何模型,对采用3种常用截面和不同数量约束的单层肋环型圆顶进行了静力学分析.根据分析的结果,计算出各截面尺寸对变形、应力的灵敏度.对分析结果和灵敏度进行比较得到影响单层肋环型圆顶静力性能的因素和影响程度.所得到的结论对该类圆顶的设计和优化提供依据.  相似文献   

10.
一种抑制杂交元零能模式的假设应力场方法   总被引:1,自引:0,他引:1  
基于杂交元位移场直接导出可以表示单元任意变形的简单变形模式,同时指出与所有假设应力模式正交的非零变形为零能机动模式,从而可以用简单变形模式方便地识别和抑制单元零能模式.在此基础上利用初始应力模式与简单变形模式的正交性提出一种假设杂交元应力场的有效方法,结合等函数法应力模式组成初始应力模式,不仅可以根据实际问题需要灵活地假设不同分布规律的应力场,而且所形成杂交元可以完全避免零能机动模式.在数值算例中采用本文方法分别形成了2D-4节点杂交元和3D-8节点杂交元的多种假设应力场,表明本文所提出方法是有效可行的.  相似文献   

11.
层合圆柱壳体表层局部分层屈曲及其扩展   总被引:1,自引:0,他引:1  
应用能量法研究了对称铺层的闭合圆柱形层合壳体的表层局部分层屈曲问题;表层分层形式有三角形,椭圆和双纽线;分析了母层壳,子层壳的几何参数,物理参数同分层屈曲临界应变值之间的关系;给出了子层分层为椭圆的分层扩展的可能发生方向。  相似文献   

12.
In this paper, investigation on buckling and post-buckling behaviors of a laminated cylindrical shell of functionally graded material (FGM) with the piezoelectric fiber reinforced composite (PFRC) actuators subjected to thermal and axial compressed loads is presented. Based on the Donnell assumptions, the material properties of the FGM layer vary smoothly through the laminated cylindrical shell thickness according to a power law distribution of the volume fraction of constituent materials. In the present study, a numerical procedure for the laminated cylindrical shell is used based on the Ritz energy method and the nonlinear strain–displacement relations. Some useful discussion and numerical examples are presented to show various effects of temperature field, volume fraction and geometric parameters on the buckling and post-buckling behaviors of the laminated cylindrical shell with PFRC.  相似文献   

13.
This article presents a novel mathematical model for moderately thick and deep laminated composite conoidal shell. The zero transverse shear stress at top and bottom of conoidal shell conditions is applied. Novelty in the present formulation is the inclusion of curvature effect in displacement field and cross curvature effect in strain field. This present model is suitable for deep and moderately thick conoidal shell. The peculiarity in the conoidal shell is that due to its complex geometry, its peak value of transverse deflection is not at its center like other shells. The C1 continuity requirement associated with the present model has been suitably circumvented. A nine-node curved quadratic isoparametric element with seven nodal unknowns per node is used in finite element formulation of the proposed mathematical model. The present model results are compared with experimental, elasticity, and numerical results available in the literature. This is the first effort to solve the problem of moderately thick and deep laminated composite conoidal shell using parabolic transverse shear strain deformation across the thickness of conoidal shell. Many new numerical problems are solved for the static study of moderately thick and deep laminated composite conoidal shell considering 10 different practical boundary conditions, four types of loadings, six different hl/hh (minimum rise/maximum rise) ratios, and four different laminations.  相似文献   

14.
《力学快报》2023,13(4):100453
Buckling and postbuckling characteristics of laminated graphene-enhanced composite (GEC) truncated conical shells exposed to torsion under temperature conditions using finite element method (FEM) simulation are presented in this study. In the thickness direction, the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded (FG) distribution, with each layer containing a variable volume fraction for graphene reinforcement. To calculate the properties of temperature-dependent material of GEC layers, the extended Halpin-Tsai micromechanical framework is used. The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous, laminated cylindrical, and conical shells, the FEM model is validated. The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength. Also, the geometric parameters have a critical impact on the stability of the conical shell. However, a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell's postbuckling strength.  相似文献   

15.
To demonstrate the solutions of linear and geometrically non-linear analysis of laminated composite plates and shells, the co-rotational non-linear formulation of the shell element is presented. The combinations of an enhanced assumed strain (EAS) in the membrane strains and assumed natural strains (ANS) in the shear strains improve the behavior of 4-node shell element. To secure computational efficiency in the incremental non-linear analysis, the present element uses the form of the resultant forces pre-integrated through the thickness. The transverse shear stiffness of the laminates is defined by an equilibrium approach instead of the shear correction factor. Numerical examples of this study show very good agreement with the references.  相似文献   

16.
The generalized ray method (GRM) has been successfully used to study the transient elastic wave transmitting in the beams, planar trusses, space frames and infinite layered media. In this letter, the GRM is extended to investigate the early short time transient responses of laminated composite cylindrical shells under impact load. By using the Laplace transformation and referring to the boundary conditions, the ray groups transmitting in the finite laminated cylindrical shells under the shock load are obtained and the transient response related to each ray group can be derived via FFT algorithm. From the numerical results, it is shown that the early short time transient accelerations of the laminated composite cylindrical shell under impact loads are very large. But the short time transient shear strain and displacement are very small.  相似文献   

17.
A 3-D multilayer hybrid element is developed for the analysis of thick laminated plates and shells. The stresses are assumed independently in each sublayer element and the stress continuity between adjacent sublayers is applied to form the stress pattern of the multilayer element. Both interlaminar stress concentration and global structure response can be adequately predicted by the element model. The buckling analysis of orthotropic cylindrical shells under the external pressure is performed and the results show that the plane strain assumption is not applicable to the buckling of long orthotropic cylindrical shells.  相似文献   

18.
Composite structures are often used in the aerospace industry due to the advantages offered by a high strength to weight ratio. Sound transmission through an infinite laminated composite cylindrical shell is studied in the context of the transmission of airborne sound into the aircraft interior. The shell is immersed in an external fluid medium and contains internal fluid. Airflow in the external fluid medium moves with a constant velocity. An exact solution is obtained by simultaneously solving the first-order shear deformation theory (FSDT) of a laminated composite shell and the acoustic wave equations. Transmission losses (TL) obtained from numerical solutions are compared with those of other authors. The effects of structural properties and flight conditions on TL are studied for a range of values, especially, the Mach number, stack sequences, and the angle of warp. Additionally, comparisons of the transmission losses are made between the classical thin shell theory (CST) and FSDT for laminated composite and isotropic cylindrical shells.  相似文献   

19.
We study the stress state of laminated inhomogeneous closed cylindrical shells generally with an arbitrary cross section, taking transverse shear into account on the basis of the straight-line element hypothesis. As an example, results are presented for a two-layer cylindrical shell whose cross section is a combination of an oval and a circle.  相似文献   

20.
A dynamic, shear deformation theory of a doubly curved shell is used to develop a finite element for geometrically non-linear (in the von Karman sense) transient analysis of laminated composite shells. The element is employed to determine the transient response of spherical and cylindrical shells with various boundary conditions and loading. The effect of shear deformation and geometric non-linearity on the transient response is investigated. The numerical results presented here for transient analysis of laminated composite shells should serve as references for future investigations.  相似文献   

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