变截面压杆稳定计算的有限单元法

本文在文「１」建立的三维退化梁单元的基础上，考虑几何非线性，推导出计算任竭尽为截面压杆稳定问题的有限元无式。计算结果表明，本文公式正确，力学概念清晰明了，计算效率较高，该单元三维梁、板、块单元的连接非常方便，很适合于工程结构的总体分析。     

波浪腹板变截面压弯构件稳定承载力设计方法和试验研究

波浪腹板变截面压弯构件用做边柱铰接的门式轻钢结构中,主要承担弯矩、剪力与轴力。该文基于现行《门式刚架轻型房屋钢结构规程》CECS102:2002中的相关公式,建立了波浪腹板变截面压弯构件平面内稳定承载力与平面外稳定承载力的设计公式。进行了大量的有限元数值计算,其中通过变化构件的几何设计参数并考虑了各种缺陷(几何初始缺陷与残余应力)的影响,验证了所建立的设计公式的可靠性。进行了两根变截面波浪腹板构件的压弯稳定承载性能的试验研究,考察了其失稳机理及稳定承载力,并与有限元数值分析结果吻合较好。     

阶梯形变截面柱式墩的稳定计算

本文依据结构稳定理论推导了常用支撑承情况下阶形变截面墩柱的稳定方程,介绍了方程妥方法及求解中应注意的问题,可供设计部门参考。     

考虑剪力滞效应的层合箱梁矩阵分析方法

给出了考虑剪力滞后及剪切变形效应条件下,复合材料薄壁层合箱梁静力行为控制微分方程组的初参数解。以此为基础,推导出了层合箱梁单元的刚度矩阵和等效结点荷载列阵,从而使薄壁层合箱梁的剪力滞、剪切变形效应分析方便地纳入了工程中广泛应用的矩阵位移法程序系统,为复合材料连续层合箱梁等复杂结构的强度及刚度分析提供了有效的计算手段。      

考虑重力条件下变截面圆形薄壁压杆的弹性稳定计算

本文运用弹性体虚位移原理，研究变截面圆形薄壁压杆的整体弹性稳定问题。借助于Ｍａｔｈｅｍａｔｉｃａ软件包，推导出了考虑重力条件下的临界力，杆件柔性，临界应等计算公式，及在重力下失稳的临界杆长计算公式。     

求解多层地基上变截面基础梁的链杆法

本文在计算多层地基上变截面基础梁时,对梁和地基分别采用解析解,用混合法建立基本方程,给出了多层地基沉陷系数和变截面梁在集中力、集中力偶、均布力和变温荷载作用下梁挠度的解答。由于充分利用了解析解精度高和链杆法未知数少的特点,使得一般工程问题都能在微型计算机上解决。计算结果表明,采用多层地基上变截面基础梁的计算模型比传统的文克勒地基和半无限地基上等截面基础梁的计算模型更为合理。该计算方案还可以推广应用于双铰底板和分缝浇筑底板的计算中去。     

变截面梁预应力计算的积分算子法

将积分算子法用于变截面梁预应力问题的计算,提出了一种新型计算方法。该方法将多段变截面梁作为一个计算单元处理,直接计算多段预应力索等效节点力和单元内力,包含了变截面梁刚度分布对等效节点荷载的影响,包含了变截面剪切变形影响。该方法克服此前方法的缺陷,为变截面梁预应力的计算提供了一种精确计算方法。     

层合方式和压缩方向对层合瓦楞纸板压缩性能的影响

目的研究层合方式和压缩方向对层合瓦楞纸板压缩性能的影响。方法通过静态压缩对平齐式和交错式等2种层合瓦楞纸板的3个方向进行实验,得到相应的应力-应变曲线,运用能量效率法对其峰应力、平均抗压强度、总吸能和比能量吸收进行对比分析。结果 2种层合方式的瓦楞纸板在x,y,z方向的应力-应变曲线走势大致相似,峰应力、平均抗压强度、总吸能和比能量吸收均为x方向最大,y方向次之,z方向最小。在x,y,z各个方向上,平齐式层合瓦楞纸板的峰应力、平均抗压强度、总吸能和比能量吸收均高于交错式层合瓦楞纸板。结论不同层合方式和压缩方向对层合瓦楞纸板压缩性能的影响较大,设计重型缓冲包装时可以优先选择平齐式层合瓦楞纸板的x方向,可以更好地达到提高缓冲效果和节约材料的目的。     

用加权残数法计算变截面梁的固有频率

本文应用加权残数法导出了考虑剪切变形、转动惯量及弹性地基等因素的变截面梁的自由振动方程。并由一简例说明本文推导方法的精度。     

芯模对双脊矩形管绕弯成形截面畸变的影响

采用芯模可有效减小双脊矩形管绕弯成形过程中的截面畸变,并提高弯曲管件的成形精度.因此基于ABAQUS/Explicit有限元软件,建立了可靠的双脊矩形管绕弯成形三维有限元模型,研究获得了芯模对截面畸变的影响规律.结果表明:沿截面宽度、高度、外脊宽度和双脊高度的最大变形量均位于管坯的棱线上;沿弯曲方向,管坯宽度、高度和双脊高度的最大变形量均出现在60°附近截面上,外脊宽度的最大变形量出现在20°附近的截面上;随着芯头个数的增加、芯头和管坯间隙的减小及其摩擦因数的减小,管坯宽度、高度和外脊高度的最大变形量均减小,而外脊宽度的最大变形量略有增大或基本不变.     

Flexural analysis of laminated plates based on trigonometric layerwise shear deformation theory

ABSTRACT

A trigonometric layerwise shear deformation theory is developed for the flexural analysis of laminated plates. The present theory achieves in-plane displacement continuity, transverse shear stress continuity, and traction-free boundary condition. Hence, botheration of shear correction coefficient is neglected. The governing differential equation and boundary conditions are obtained from the principle of virtual work. Although the present analytical method is bounded to a corner supported boundary condition, it neglects the numerical and computational error. Like first-order shear deformation theory, the present theory possesses five numbers of unknowns. Several numerical predictions are carried out and results are compared with those of other existing numerical approaches.     

并列双幅变截面箱梁阻力系数的干扰效应研究

基于节段模型风洞试验,对比研究了4种不同高宽比的并列双幅箱梁在不同风攻角和不同间距时的阻力系数与单箱梁阻力系数的差异。给出了阻力系数干扰因子(定义为双箱梁上游(或下游)箱梁阻力系数与单箱梁阻力系数的比值)随风攻角和间距变化规律。结果表明:上游箱梁阻力系数的干扰效应主要体现在D/B≤1的间距范围。高宽比对上游箱梁阻力系数干扰效应的影响不大。当0.025≤D/B≤1,风攻角为-10°~10°时,上游箱梁阻力系数干扰因子的变化范围为0.8~1.3左右;下游箱梁阻力系数的干扰效应表现为显著的减小效应。这种减小效应随着间距的减小和高宽比的增大愈发明显,与负向风攻角时相比,这种减小效应在正向风攻角时更明显。     

基于TBM法的地铁大断面水压爆破技术

为了顺利完成地铁区间四线大断面爆破开挖,减小爆破作业对城市环境的影响,利用TBM导洞扩挖形成既有临空面,采用水压爆破施工技术,通过质点振速的理论计算与现场起爆试验结果,优化了爆破参数和起爆网路,进而降低了质点爆破振速,完成了区间大断面开挖,减小了爆破对周边环境的影响。结果表明:相比于常规爆破技术,本工程的水压爆破方案每循环节省了炸药39.91 kg,每循环进尺提高了0.35 m,大块率降低了53%,质点爆破振速下降了0.13 cm/s,粉尘浓度下降了36.6 mg/m³,经济与环境效益显著。     

A simple and accurate four-node quadrilateral element using stabilized nodal integration for laminated plates

This paper reports the development of a simple but efficient and accurate four-node quadrilateral element for models of laminated, anisotropic plate behaviour within the framework of the first-order shear deformation theory. The approach incorporates the strain smoothing method for mesh-free conforming nodal integration into the conventional finite element techniques. The membrane-bending part of the element stiffness matrix is calculated by the line integral on the boundaries of the smoothing elements while the shear part is performed using an independent interpolation field in the natural co-ordinate system. Numerical results show that the element offered here is locking-free for extremely thin laminates, reliable and accurate, and easy to implement. Its convergence properties are insensitive to mesh distortion, thickness-span ratios, lay-up sequence and degree of anisotropy.     

复杂截面型材力控制拉弯成形数值模拟分析

复杂截面挤压型材的高精度拉弯成形是制造框架式车身的关键技术.本文基于动态显式有限元软件PAM-STAMP,针对一种典型的框架武车身用复杂截面挤压型材,对其力控制方式的直进台面式拉弯成形进行了数值模拟研究,对比分析了两种截面形状的型材截面畸变和回弹随补拉力增大的变形规律,并得到了摩擦系数对成形精度的影响.数值模拟结果表明,增加型材截面的变形刚度,可以显著地减小截面畸变和回弹;增加补拉力,增大了截面畸变但减小了回弹;增大摩擦系数,截面畸变量减小而回弹增加.     

小截面方管结构CFRP复合材料的超声检测方法

新型飞行器已采用小截面碳纤维增强树脂基(Carbon Fiber Reinforce Polymer, CFRP)复合材料方管结构。针对该类复合材料方管的材料组成和结构特点,分析和对比了常用的超声穿透法、超声反射法和整体超声穿透法对复合材料方管内部质量检测的适用性,提出了超声对面内壁反射法。采用超声对面内壁反射法对试块中的人工缺陷和实际产品进行检测。结果表明,采用该检测方法能够全部检出试样中的10 mm×10 mm的人工分层缺陷,且可有效地检测实际产品的分层和孔洞缺陷。     

基于四元十字阵的低频换能器指向性检测方法

针对大型低频换能器指向性难以测量的问题,提出了一种基于四元十字阵的测量方法以获取大型低频换能器的指向性。利用到达四元十字阵阵元的时延差信息,结合双曲面交汇法对换能器进行定位,并根据四元十字阵阵元测得的声信号实现大型低频换能器指向性的测量;对定位算法进行理论仿真,设计并进行了湖上试验以测量模拟声源的指向性;对湖上试验测量数据进行计算分析,并与模拟声源在消声水池中的测量结果进行比较,两者-3 dB波束开角的测量结果相差在10%以内。此方法可以用于低频换能器指向性的测量。     

General higher-order layer-wise theory for free vibrations of doubly-curved laminated composite shells and panels

ABSTRACT

The present article illustrates a general formulation for a higher-order layer-wise theory related to the analysis of the free vibrations of thick doubly-curved laminated composite shells and panels. The theoretical framework relates to the dynamic analysis of shell structures by using a general displacement field based on the Carrera Unified Formulation (CUF), including the stretching effect for each layer. The order of the expansion along the thickness direction is taken as a free parameter. The starting point of the present general higher-order layer-wise formulation is to propose a kinematic assumption, with an arbitrary number of degrees of freedom. The main aim of this work is to determine the explicit fundamental operators that can be used for the layer-wise (LW) approach. These fundamental operators are obtained for the first time by the author and are related to motion equations of doubly-curved shells described in an orthogonal curvilinear co-ordinate system. The free vibration shell and panel problems are computationally solved using the generalized differential quadrature (GDQ) and generalized integral quadrature (GIQ) techniques. The numerical results are compared with recent papers in the literature and commercial finite element codes.     

Dynamic investigation of laminated composite beams with shear and rotary inertia effect subjected to the moving oscillators using FEM

An algorithm based on the finite element method (FEM) has been developed to study the dynamic response of composite laminated beams subjected to the moving oscillator. The first order shear deformation theory (FSDT) is assumed for the beam model. The algorithm accounts for the complete dynamic interaction between the components of system. The proposed method can also be applied to the general moving mass and the simplified moving force problems. After deriving the governing equations of motion of beam and oscillator, the corresponding equations of motion are integrated by applying the Newmark’s time integration procedures to obtain the system responses in each time step. The numerical results of free vibration and moving force problems analysis of isotropic and composite laminated beams are presented and, whenever possible, compared to the available analytical solution and other numerical results in order to demonstrate the accuracy of the present method. In addition, parametric analysis is carried out over a wide range of velocities and mass, frequency and damping ratios of system components.