Mixed finite element and differential quadrature method for free and forced vibration and buckling analysis of rectangular plates

This paper presents a combined application of the finite element method （FEM） and the differential quadrature method （DQM） to vibration and buckling problems of rectangular plates. The proposed scheme combines the geometry flexibility of the FEM and the high accuracy and efficiency of the DQM. The accuracy of the present method is demonstrated by comparing the obtained results with those available in the literature. It is shown that highly accurate results can be obtained by using a small number of finite elements and DQM sample points. The proposed method is suitable for the problems considered due to its simplicity and potential for further development.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

Finite Element Analysis of the Ramberg-Osgood Bar

In this work, we present a priori error estimates of finite element approximations of the solution for the equilibrium equation of an axially loaded Ramberg-Osgood bar. The existence and uniqueness of the solution to the associated nonlinear two point boundary value problem is established and used as a foundation for the finite element analysis.

Stress Distribution in Maxillary Central Incisors without Ferrules: A Finite Element Analysis of Post and Core Systems

Purpose: The purpose of this study was to identify optimal post and core materials for central incisors without ferrules using three-dimensional finite element analysis and three-point bending tests. Methods: Stress analyses were performed with six models: cast metal post and core (MP), composite resin core alone, straight fiber-reinforced post-composite resin core (FSR), tapered fiber-reinforced post-composite resin core, straight titanium post-composite resin core (TSR), and tapered titanium post-composite resin core (TTR). A 100-N load was applied to the lingual surface at a 45° angle to the long axis of the tooth. Maximum von Mises stress distributions were calculated with finite element analysis software. Five samples each of composite resin, straight fiber-reinforced post, straight titanium post, straight fiber-reinforced post and composite resin, and straight titanium post and composite resin were subjected to three-point bending tests, followed by analysis of variance and Tukey’s multiple comparison test. Results: Stress distribution was optimal on TTR. Maximum von Mises stress on the cervical side of the post was greatest in TSR (693 MPa) and TTR (556 MPa). Maximum stress on the apical side of the post was greatest in MP (110 MPa). Maximum stress in surrounding dentin was lowest in MP (203 MPa) and TTR (250 MPa). Gap distance was smallest in MP (0.09 mm) and largest in FSR (0.26 mm). Mean maximum three-point bending force was lowest in composite resin (26.9 N/mm) and highest in titanium post and composite resin (97.1 N/mm). Titanium post bending strength was consistently greater than that of the fiber-reinforced post (p < 0.01). Conclusion: These results revealed optimal stress distribution and high bending strength with the tapered titanium post and resin combination, suggesting that this combination can most effectively prevent root or post fracture in an anterior tooth without a ferrule.

Analysis of the Behavior of a Square Plate in Free Vibration by FEM in Ansys

In the realization of mechanical structures, achieving stability and balance is a problem commonly encountered by engineers in the field of civil engineering, mechanics, aeronautics, biomechanics and many others. The study of plate behavior is a very sensitive subject because it is part of the structural elements. The study of the dynamic behavior of free vibration structures is done by modal analysis in order to calculate natural frequencies and modal deformations. In this paper, we present the modal analysis of a thin rectangular plate simply supported. The analytical solution of the differential equation is obtained by applying the method of separating the variables. We are talking about the exact solution of the problem to the limit values. However, numerical methods such as the finite element method allow us to approximate these functions with greater accuracy. It is one of the most powerful computational methods for predicting dynamic response in a complex structure subject to arbitrary boundary conditions. The results obtained by MEF through Ansys 15.0 are then compared with those obtained by the analytical method.

深地万米井测井电缆强度分析

中国超深层油气资源潜力巨大,推进超深层油气勘探、实现新层系突破是开拓油气新领域的重点方向。针对深地某科探井万米电缆遇卡等问题,采用截面法,建立电缆在井下、天滑轮、地滑轮、滚筒等位置处的有限元模型,研究拉力棒、滚筒直径、上提速度对万米测井电缆强度的影响。计算结果表明:为保证在电缆不断的情况下使设置的弱点先断,并为电缆保留一定安全系数,可以选用5000lbf^(*)拉力棒;选用大直径的滚筒来减小电缆张力,优先选用直径700mm的滚筒;测井电缆正常上提工作速度取6000m/h,此时电缆张力可达61.4kN,满足强度要求。研究成果为深地万米井测井作业电缆、滚筒、拉力棒的选取提供了基础数据。

基于有限元分析的钛合金椎弓根螺钉抗弯性能结构优化

钛合金因其优异的力学性能和生物相容性,广泛用于椎弓根螺钉的制备。椎弓根螺钉植入人体后,受脊柱的屈曲伸展和横向弯曲作用,螺钉发生疲劳弯曲最终导致螺钉松动甚至断裂,影响植入稳定性。因此有必要对钛合金椎弓根螺钉抗弯性能进行研究。通过单因素实验与正交实验分析设计不同结构参数椎弓根螺钉,结合有限元分析与力学实验的方法,使用三点弯曲试验对钛合金椎弓根螺钉的抗弯性能进行模拟仿真与实验验证,并对螺钉结构参数进行优化。结果表明,模拟结果与实验结果吻合较好,螺钉结构参数对抗弯性能的影响顺序为外径大于螺纹深度大于螺距,最佳参数为螺钉外径5.5 mm、螺纹深度0.65 mm、螺距1.60 mm,优化后的螺钉对比标准椎弓根螺钉,最大支反力提高74.7%。

海上升压站导管架耳板式吊点设计与强度校核

吊点是海上升压站导管架吊装的关键受力结构,合理设计吊点结构并对其进行强度校核是吊装作业顺利完成的保障。文章以某海上升压站导管架为例,研究了导管架耳板式吊点的设计及理论计算强度校核方法;基于有限元分析技术,通过2种方法模拟导管架的吊点,校核结构强度并探讨筋板布置对主腿受力性能的影响。结果表明,壳单元模拟的结果偏于保守,合理布置筋板对结构应力集中现象有一定的改善。

内、外侧锁定钢板内固定治疗胫骨远端骨折的有限元分析

目的通过有限元分析法比较内、外侧锁定钢板内固定治疗胫骨远端骨折的生物力学性能。方法对1名健康男性志愿者的胫骨行CT扫描构建正常胫骨模型。使用Solidworks 2013软件制作得到内侧锁定钢板和锁定螺钉的装配体(模型1)、外侧锁定钢板和锁定螺钉的装配体(模型2)。使用Ansys 14有限元分析软件分析在施加轴向力、扭转力、侧向力后,模型1和模型2的承载力及骨折断端的位移情况。结果(1)承载力:施加轴向力后,模型1不足模型2的1/6(P<0.05);施加扭转力后,模型1约是模型2的7倍(P<0.05);施加侧向力后,模型1和模型2比较差异均无统计学意义(P>0.05)。(2)骨折断端平均位移:施加轴向力后,模型1小于模型2(P<0.05);施加扭转力后,模型1大于模型2(P<0.05);施加侧向力后,模型1小于模型2(P<0.05)。结论与外侧锁定钢板内固定模型相比,胫骨远端骨折内侧锁定钢板内固定模型力学分布更均匀、稳定性更好,且骨折断端的微小位移能有效刺激骨痂再生,更利于骨折愈合,在软组织条件允许下更利于治疗胫骨远端骨折。

不等模数渐开线齿轮副参数极限值与有限元分析

为了解决常规变位齿轮对中心距调节及强度分配的局限性,提出利用基圆节距相同但模数不等的结构,大幅度提高齿轮传动中较小齿轮的强度,尤其是齿根强度。但用于工程实践中的模数与齿形角相差均较小,通过对渐开线齿面的形成原理及齿轮啮合中部分参数的分析,得到了此种齿轮模数、齿数、齿形角、齿高系数等参数的限制条件,并通过公式推导了齿数、齿高系数与分度圆压力角极限值的关系式。基于工程实践情况建模并通过Ansys进行了有限元分析,得到基于极限参数设计的齿轮强度约为标准齿轮的2.66倍,验证了理论的可行性,并扩大了此种齿轮副的应用范围。

基于三点力原理对足内翻矫形器矫正效果的有限元分析

背景:三点力学是踝足矫形器矫正与预防足部各类疾病的有效方法,目前关于3D打印踝足矫形器的临床应用研究已普遍存在,但其涉及三点力学矫正的数值模拟与有限元分析报道相对较少,缺乏相关生物力学实验验证。目的:通过有限元法对踝足矫形器与足部复合模型进行三点力加载分析,观察在三点力干预下佩戴踝足矫形器的足部矫正效果,验证三点力的有效性及踝足矫形器的可靠性。方法:基于医学图像处理软件Mimics构建1例健康志愿者足踝三维模型,采用Rodin 4D与Geomagic逆向工程软件对各模型进行优化处理,设计个性化踝足矫形器模型。利用Solidworks软件对足踝模型进行内侧翻转10°以模拟足内翻病态,通过ANSYS软件结合三点力学原理对足部施力区进行静力加载,在满足人体足部痛阈时分析足踝各组织形变与应力变化,利用显示动力学进一步验证踝足矫形器施加三点力的有效性。结果与结论:(1)设计的个性化踝足矫形器具有预防足踝内翻和固定作用,在未穿戴踝足矫形器时,受到1 N·m内翻载荷后足踝内翻1.81mm,而穿戴踝足矫形器后仅为0.44mm,变形率降低75.7%,预防内翻效果明显增强;(2)仅冠状面矫正时,跟骨力系过小会加剧患者前足内翻,调整足跟内侧与内踝上方矫正力后,前足内翻角与跟骨位得到改善,但足部内侧趾骨区仍有不同程度内收移位,会加剧患者前足内收畸形;(3)冠状面、水平面两组三点力系统联合作用矫正效果优于单冠状面,表现为在足跟内侧、第一跖骨干内侧、外踝下方与内踝上方的力(25,10,10,20 N)作用下,前足内侧趾骨无内收移位,前足内翻角减小,并沿X轴外翻矫正1.395 mm,跟骨外翻矫正1.227mm,在变形比例放大云图下跟骨内翻角由10.21°矫正至7.25°,内翻角改善28.9%;(4)两平面三点力作用下,足底外侧跖骨负荷减小,内侧跖骨负荷增加,矫正后足底骨骼应力显著得到改善,进一步验证了三点力原理的可靠性,该研究为临床患者穿戴踝足矫形器治疗足内翻提供了重要理论支撑。

某航空密封件波形弹簧模态分析

该项目以0Cr17Ni7Al不锈钢波形弹簧为研究对象,利用CATIA软件进行建模并导入ABAQUS软件中进行有限元分析,获得其0~12阶模态特性。基于实际压缩高度分析受力情况的波形弹簧自振频率,并对2种自由态以及工作状态的弹簧仿真结果进行对比,得到固有频率的数据以及振形图。为不同情况下弹簧种类的选择提供一定参考。

油田跨越段管道高应力风险点分析研究

地处复杂地形的油田集输跨越段管道存在高应力风险点,一旦泄漏将对环境产生巨大影响。因此,针对跨越段管道高应力点分布进行分析研究十分必要。对于黄土高原地区油田某典型集输跨越段管线,采用有限元分析方法对管体及介质自重、土体移动和两者叠加作用下的跨越段管道应力风险点分布进行研究,揭示了其分布规律。随后,采用便携式超声应力检测仪对有限元模拟的现场典型跨越段应力风险点进行检测验证。结果表明:土体移动对跨越段管道应力集中程度的影响大于管体及介质自重的影响,土体移动作用下跨越段管道山脚转角处应力集中程度大于山顶转角处。该研究结果可为油田日常保养及维护操作提供重点方向。

钢筋桁架混凝土叠合板起吊模拟分析

通过对工程中常见尺寸钢筋桁架混凝土叠合板的有限元分析,分析叠合板在起吊时裂缝的发生位置及开展顺序。研究发现板尺寸变化对裂缝开展的影响因子,为工程实践中技术人员提供叠合板裂缝防治的参考依据。

基于有限元的预制叠合楼板吊点合理设计研究

预制叠合楼板脱模吊运过程中易因吊点设置不规范而引起混凝土开裂问题,影响了施工效率和构件质量,是叠合板在装配化施工过程中的重点和难点。本文详细分析不同吊点设置可能导致的问题,揭示吊运过程的楼板受力特点,提出吊点设计方法的力学推导过程,通过有限元分析进一步证实其结果,证明其设计的合理性和重要性。最后,结合现有常用的预制叠合板尺寸,对其吊点悬臂的设置提出建议,可为行业人员提供借鉴。

基于实例探讨下穿既有铁路道岔区的框架桥施工及有限元分析

随着当前经济建设步伐的持续推进,我国交通行业得到了显著的发展,各类铁路、道路纵横交错、四通八达,极大推动了国民经济的健康持续发展,与此同时,道路与铁路的交叉也越来越多,传统的平交道口显然难以满足现代交通的发展及道路高速、安全的行车要求,尤其在一些复杂地势的区域,受到地形条件的影响,所以,越来越多项目开始采取立体交叉的方式来解决道路和铁路交叉的问题,其中道路下穿既有铁路就是其中常见的建设方式之一,本文主要结合案例对下穿既有铁路道岔区框架桥施工及其有限元分析进行探讨。

Effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope

The alidade’s non-uniform temperature field of a large radio telescope is very obvious under solar radiation.Estimating a radio telescope’s pointing errors,caused by the alidade deformation under solar radiation,is significant to improve the telescope’s pointing accuracy.To study the effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope,a temperature experiment is first carried out in a 70-m radio telescope on a sunny day.According to the measured results,the temperature distribution rule of the alidade is summarized initially.In addition,the alidade’s temperature field is calculated by finite element thermal analysis.The simulated results are proved to be in good agreement with the experimental results.Finally,the alidade deformation under solar radiation is computed by finite element thermalstructure coupling analysis.The telescope’s pointing errors caused by alidade deformation are estimated via the alidade’s node displacements.The final results show that the effect of alidade thermal behavior on the telescope’s elevation pointing errorsΔε2+Δεr is much more than the effect on the telescope’s crosselevation pointing errorsΔε1.The maximum ofΔε2+Δεr is more than 45″,while the maximum ofΔε1 is less than 6″.This study can provide valuable references for improving the pointing accuracy of large radio telescopes.

Free vibration analysis of laminated FG-CNT reinforced composite beams using finite element method

In the present study, the free vibration of laminated functionally graded carbon nanotube reinforced composite beams is analyzed. The laminated beam is made of perfectly bonded carbon nanotubes reinforced composite (CNTRC) layers. In each layer, single-walled carbon nanotubes are assumed to be unifonnly distributed (UD) or functionally graded (FG) distributed along the thickness direction. Effective material properties of the two-phase composites, a mixture of carbon nanotubes (CNTs) and an isotropic polymer, are calculated using the extended nile of mixture. The first-order shear deformation theory is used to formulate a governing equation for predicting free vibration of laminated functionally graded carbon nanotubes reinforced composite (FG?CNTRC) beams. The governing equation is solved by the finite element method with various boundary conditions. Several numerical tests are perfbnned to investigate the influence of the CNTs volume fractions, CNTs distributions, CNTs orientation angles, boundary conditions, length-to-thickness ratios and the numbers of layers on the frequencies of the laminated FG-CNTRC beams. Moreover, a laminated composite beam combined by various distribution types of CNTs is also studied.

FINITE ELEMENT ANALYSIS OF FREE VIBRATION OF LIQUID－FILLED AXISYMMETRIC TANKS

Error bounds are obtained for the finite element analysis of the eigenpairs for the free vibration of liquid-filled axisymmetric tanks, for a circumferential mode number m=1, antisymmetric.The system of finite element equations concerned is derived by means of Galerkin formulation. Finite element numerical results of the eigenvalue problems for the free vibration of the liquid-filled axisymmetric tanks are compared favorably with the theoretical predictions.

Comparison of methods for vibration analysis of electrostatic precipitators

The paper presents two methods for the formulation of free vibration analysis of collecting electrodes of precipitators.The first,called the hybrid finite element method, combines the finit element method used for calculations of spring deformations with the rigid finite element method used to reflect mass and geometrical features,which is called the hybrid finite element method.As a result,a model with a diagonal mass matrix is obtained.Due to a specific geometry of the electrodes,which are long plates of complicated shapes,the second method proposed is the strip method which is a semi-analytical method.The strip method allows us to formulate the equations of motion with a considerably smaller number of generalized coordinates.Results of numerical calculations obtained by both methods are compared with those obtained using commercial software like ANSYS and ABAQUS.Good compatibility of results is achieved.