有限长圆柱壳中轴对称弹性瞬态波

有限长的计及剪切变形和转动惯性的弹性圆柱壳的轴对称运动方程经过Laplace变换后转化为一组相空间中的方程。对该方程组作了一些适当的处理后,应用广义射线法,得到了相空间中位移和内力的射线法表达式。采用快速Fourier变换作Laplacl逆变换,即可得到圆柱壳受轴对称冲击载荷时的弹性瞬态波解。     

基于径向基点插值法的旋转Mindlin板高次刚柔耦合动力学模型

将无网格径向基点插值法(radial point interpolation method,RPIM)用于中心刚体?旋转柔性板的动力学分析.基于浮动坐标系方法和一阶剪切变形理论即Mindlin板理论,考虑剪切变形的影响,并计入板面内变形的非线性耦合变形项,采用径向基点插值法描述板的变形场,保留动能中有关非线性耦合变形项...     

梯度饱和土瞬态响应分析

基于Biot多孔介质理论,建立了饱和土体在动载荷作用下的一维回传射线矩阵法的计算列式,其中考虑了土体的非均匀性、惯性、黏滞以及固体颗粒和流体的可压缩性.利用计算结果与已有结果相比较,二者相吻合,验证了算法的正确性.作为数值算例,考虑饱和土的物理力学性质沿深度方向按幂函数连续变化,利用数值Laplace逆变换求解了在冲击性载荷作用下的位移,应力和孔隙压力等物理量的瞬态响应,重点分析讨论了材料非均匀性对饱和土介质动力特性的影响.      

复合材料层合加肋板中的瞬态波传播

研究复合材料加肋层合板结构受冲击载荷作用下的瞬态波传播.加肋层合板模型被处理成层合板的弯曲运动与层合梁的扭转与弯曲运动的耦合连续模型.通过Laplace变换,并采用回传射线矩阵法(MRRM),基于一阶剪切变形层合板理论,确定复合材料加肋层合板结构中传播的各条射线群.采用FFT变换,计算各种冲击载荷作用下加肋层合板结构的短时瞬态响应,并分析讨论脉冲类型对加肋层合板结构短时瞬态响应的影响.     

TRANSIENT RESPONSE OF A BI-LAYERED MULTIFERROIC COMPOSITE PLATE

In this paper,a three-dimensional finite-element formulation for the multiferroic composite is developed and implemented into the commercial software ABAQUS for its transient analysis.First,a special three-dimensional eight-node solid element is designed to handle the multiferroic composite made of elastic,piezoelectric,and piezomagnetic materials.Second,a userdefined subroutine for this newly developed element is implemented into ABAQUS.Finally,the transient responses of a bi-layered multiferroic composite are calculated by using the direct time integration method.Two typical magnetic potential signals,Gauss and Ricker pulses,are applied to the composite with various time durations of excitation.The induced electric field shows that the transient response can be substantially influenced by the input signal,which could be tuned for the strongest electric output.     

基于应变梯度中厚板单元的石墨烯振动研究

基于应变梯度理论建立了单层石墨烯等效明德林(Mindlin) 板动力学方程,推导了四边简支明德林中厚板自由振动固有频率的解析解. 提出了一种考虑应变梯度的4 节点36 自由度明德林板单元,利用虚功原理建立了单层石墨烯的等效非局部板有限元模型. 通过对石墨烯振动问题的研究,验证了应变梯度有限元计算结果的收敛性. 运用该有限元法研究了尺寸、振动模态阶数以及非局部参数对石墨烯振动特性的影响. 研究表明,这种单元能够较好地适用于研究考虑复杂边界条件石墨烯的尺度效应问题. 基于应变梯度理论的明德林板所获得石墨烯的固有频率小于基于经典明德林板理论得到的结果. 尺寸较小、模态阶数较高的石墨烯振动尺度效应更加明显. 无论采用应变梯度理论还是经典弹性本构关系,考虑一阶剪切变形的明德林板模型预测的固有频率低于基尔霍夫(Kirchho) 板所预测的固有频率.      

基于减基法的层合板瞬态响应快速分析方法

用混合数值法分析复合材料层合板结构的瞬态响应时,在波数域中引入减基法、构造减基空间,把原大型特征值问题映射到减基空间进行降阶,在保证精度的前提下快速近似求解原大型特征值问题,从而快速得到结构的时域响应. 算例表明,引入减基法后的混合数值法能更有效地解决结构瞬态响应问题. 该方法可以推广用于快速解决大型结构动力优化设计和结构动力反问题等结构动力分析问题.      

有限液体负载下压电平板声板波理论分析

主要推导平板声板波受有限液体负载后能量衰减与波速改变情形, 以部分波传理论分析该受液体负载的压电平板波传行为, 并以一128$^{\circ}Y$向切角的铌酸锂芯片为例,分析前20个声板波受水与甘油负载下 的能量衰减,并固定某一平板板波, 针对不同甘油厚度负载下, 计算其相速度与衰减变化,该理论分析对于液体负载下的平板板波传感器应用具有极大的参 考价值.     

APPROXIMATE SOLUTIONS FOR TRANSIENT RESPONSE OF CONSTRAINED DAMPING LAMINATED CANTILEVER PLATE

The series composed by beam mode function is used to approximate the displacement function of constrained damping of laminated cantilever plates, and the transverse deformation of the plate on which a concentrated force is acted is calculated using the principle of virtual work.By solving Lagrange＇s equation, the frequencies and model loss factors of free vibration of the plate are obtained, then the transient response of constrained damping of laminated cantilever plate is obtained, when the concentrated force is withdrawn suddenly.The theoretical calculations are compared with the experimental data, the results show：both the frequencies and the response time of theoretical calculation and its variational law with the parameters of the damping layer are identical with experimental results.Also, the response time of steel cantilever plate, unconstrained damping cantilever plate and constrained damping cantilever plate are brought into comparison, which shows that the constrained damping structure can effectively suppress the vibration.     

Early short time transient response of finite L-shaped Mindlin plate

The early short time transient response of an L-shaped plate is investigated by the method of reverberation ray matrix (MRRM) and the generalized ray method (GRM). The MRRM and GRM have been successfully used to study the transient elastic wave transmitting in the beams, planar trusses, space frames and infinite layered media. In the present paper, these two methods are extended to investigate the flexural wave propagation in a finite L-shaped Mindlin plate. The reverberation-ray matrix representing the multi-reflected and scattered waves in the L-shaped plate is presented. The rays in the GRM propagating in the L-shaped plate are determined by the shock source and the boundary conditions. From the numerical results, it indicates that the early short time transient responses of L-shaped plate calculated by the MRRM are the same as those by the GRM. The early short time transient acceleration responses are very large, while the early short time transient displacement responses are very small for the L-shaped plate subjected to the unit impulse. Furthermore, the effects of the different shock signals and the plate thickness on the early short time transient responses of the finite L-shaped Mindlin plates are also analyzed.     

简支方板在弹性基础上的塑性动力响应

用加权残值法中的矩量法解简支方板塑性动力响应,分析弹性基础对方板塑性动力响应的影响,解出了弹性基础上方板残余挠度和终止运动时间。     

ANALYSIS OF THE LARGE DEFLECTION DYNAMIC RESPONSE OF RIGID-PLASTIC CIRCULAR PLATE RESTING ON FLUID

A study is presented for the large deflection dynamic response of rigid-plastic circular plate resting on potential fluid under a rectangular pressure pulse load.By virtue of Hankel integral transform technique,this interaction problem is reduced toa problem of dynamic plastic response of the plate in vacuum.The closed-formsolutions are derived for both middle and high pressure loads by solving the equationsof motion with the large deflection in the range where both bending moments andmembrane forces are important.Some numerical results are given.     

板壳有限变形精确理论及有限元列式

以位移型退化壳理论为基础,提出了板壳模型的有限变形精确理论.该理论引入转动伪矢量概念,充分发挥刚性线段的运动学模型和有限转动矩阵的作用,精确表达非线性位移-应变关系,抛弃以往的小位移、小应变、小转动增量乃至小加载步长等各种简化假设,并严格遵循能量共轭关系建立有限元平衡方程,能够可靠和有效地用于板壳结构的大位移、大转动分析.算例表明,该文列式在弹性范围内具明显的平方收敛效率,并且计算结果与加载步长无关.由于不受小加载步长、小转动增量等的限制,实现了板壳几何非线性问题的大步长加载 .     

一弹性层覆盖于半无限弹性介质对表面点冲击载荷的瞬态响应

利用广义射线理论,研究了一弹性层覆盖于半无限弹性介质表面受法向动集中荷载作用情形表面处的位移响应.给出了一种计算瞬态响应的有效方法,首先根据反射次数的不同将射线自动分组,然后将同一组中具有相同积分路径的积分式自动合并并一次性完成积分.运用该技术,计算量大大减少,使得广义射线法应用于较长时间响应计算的工作得到推进.数值结果中给出了两种情形位移响应的特点,一种情形是弹性层比半空间层硬,另一种情形是弹性层比半空间层软.     

Transient impact responses of laminated composite cylindrical shells

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.     

爆破与地震载荷下椭圆夹塞体的动态响应差异分析

爆破和地震两种类型的动力扰动特性不同,对地下回采充填体等夹塞体造成的应力波散射与应力重分布特征也存在差异。因此本文针对爆破与地震载荷下椭圆夹塞体的动态响应差异,基于马修函数和波函数展开法,引入雷克子波和针状波表征地震和爆破载荷,结合傅里叶变换和杜哈梅积分获得两种载荷下椭圆夹塞体的瞬态动态应力集中因子（dynamic stress concentration factor, DSCF）时变解析解。数值结果表明,爆破与地震载荷下的DSCF总是在椭圆夹塞的短轴两端取得最大值,但是地震相较爆破造成夹塞与围岩结构破坏的可能性更大,破坏能力更强。

     

金属杆锚固系统在瞬态激励下的动态响应

通过有限元软件MSC／NASTRAN，对金属杆锚固系统在瞬态激励下的动态响应进行数值模拟，并结合试验结果进行验证，得出瞬态敲击法只能找到锚固段上界面的固端反射，而无法识别出底端反射这一结论，最后提出解决此问题的导波方法，从而为最终解决金属杆锚固系统的无损检测问题提供一种有效途径．     

复合夹层梁瞬态响应的谱有限元法

采用谱有限元法进行复合夹层梁的瞬态响应分析.该方法基于复合夹层梁的六阶运动微分方程,以其波动解作为动力位移形函数,根据标准有限元策略来构建复合夹层梁的动刚度矩阵.在频域内,夹心粘弹性材料的频率相关性采用复模量模型来模拟,进而利用快速傅立叶变换技术(FFT),得到时域内复合夹层梁的瞬态响应分析结果.最后以两端固支夹层梁为例,对其进行了矩形脉冲荷载下的动力响应分析,并与通用有限元程序NASTRAN的计算结果进行了对比,两者吻合良好.     

牛顿迭代一致性算法及其在板弹塑性有限元分析中的应用

本文简略讨论了有限载荷增量弹塑性有限元分析中传统切线刚度法丧失精度和牛顿迭代平方收敛速度的原因,并提出保持牛顿迭代平方收敛速度、保证一阶精度和无条件稳定性的一致性算法.一致性算法具备以下两个特征:1)采用路径无关计算格式;2)采用一致弹塑性切线模量。根据一致性算法构造出以弯矩和曲率为基本变量的弹塑性板弯曲有限元NIDKQ元。数值结果表明NIDKQ元具有令人满意的精度,同时验证了有限载荷增量下牛顿迭代一致性算法的平方收敛率特性,而传统切线刚度法随着塑性区的扩展将大大降低收敛速度。     

TRANSIENT TORSIONAL WAVE IN FINITE HOLLOW CYLINDER WITH INITIAL AXIAL STRESS

An analytical solution is obtained for transient torsional vibration of a finite hollow cylinder with initial axial stress. The cylinder is subjected to dynamic shearing stress at the internal surface and is fixed at the external surface. The basic equations are presented and the solution is obtained by means of Fourier series expansion technique and the separation of variables method. The effects of the initial stress on the natural frequencies and transient torsional responses are presented and discussed.