弹塑性悬壁梁结构动力响应中的弹性效应

本文提出由一组质量－弹簧构成的力学系统来研究弹塑性悬壁梁的动力响应问题，其数值结果与有限元解吻合得相当好，这种简化模拟能够反映出梁动力响应中的本质特性，还特别显示出梁中弹性对弯矩分布和能量耗散的影响，提供了很有价值的计算结果。     

用矩量法解阻尼介质中简支方板的塑性动力响应问题

本文用矩量法解薄板塑性动力响应问题，分析阻尼介质对简支方板塑性动力响应的影响，对计算结果进行了讨论．     

用矩量法解阻尼介质中简支方板的塑性动力响应问题

本文用矩量法解薄板塑性动力响应问题，分析阻尼介质对简支方板塑性动力响应的影响，对计算结果进行了讨论。     

结构振动瞬时最优控制的一种时滞补偿算法

 应用最优控制原理，对结构动力响应实时在线控制进行了时滞 补偿. 提出一种基于系统差分方程的瞬时最优控制算法，推导出闭环 状态反馈控制补偿增益矩阵，并讨论了补偿前后系统的稳定性. 仿真 结果表明，此算法有效地补偿了时滞带给结构动力响应的不良影响， 并保证了结构的稳定性.     

饱和砂土对地震的动力响应

本文用“工程近似”方法研究了饱和砂土对地震的动力响应。根据饱和砂土对循环荷载动态响应的机理建立了简化模型，给出了描述动态响应的动力方程和描述孔压产生与消散的扩散方程。用Ｎｅｗｍａｒｋ方法与有限差分数值求解这些方程。求得了饱和砂土层对地震的动力响应，包括孔压、剪应力与表面加速度的变化，并对数值结果进行了分析、讨论。     

复合结构振动分析的数值方法

本文提出了弹性-粘弹性复合结构动力特性和动力响应的数值计算方法。为了给动力特性分析提供初值,定义了复合结构的“对偶保守结构”概念。用“对偶保守结构”的实模态参数确定复特征值初值,逐个迭代计算复合结构的复模态参数,同时还给出了两种数值方法计算复合结构的时域响应,可适应于一般载荷的响应计算,最后给出了部分计算与实验结果,并进行了比较,结果令人满意。     

一种结构动力响应分析的快速高阶算法

为了提高基于高阶格式的结构动力响应微分求积分析方法的计算效率,发展了一种求解动力方程的快速算法.利用微分求积原理将结构动力方程转化为标准Sylvester方程的形式,通过对系数矩阵进行矩阵分解,进而将动力响应Sylvester方程化为一系列标准线性方程组,采用相关成熟算法求解这些线性方程组后即可获得结构动力时程响应的全部解答.结构动力响应微分求积分析方法为高阶数值方法,一步计算可以获得多个时点处的动力响应.基于本文快速算法,不必直接对矩阵方程进行求解.数值算例表明,本文快速算法能够准确地计算出结构动力响应,具有数值精度高、收敛性好的优点.     

随机桁架结构的非平稳随机动力响应分析

本文研究了随机桁架结构在非平稳随机激励下的动力响应问题。在利用随机因子法分析随机结构动力特性的基础上，给出了一种分析随机结构非平稳随机响应的新方法。从结构非平稳随机响应的表达式出发，同时考虑桁架结构的物理参数、几何尺寸的随机性，利用求解随机变量函数矩的方法和求解随机变量数字特征的代数综合法，导出了随机桁架结构在非平稳随机激励下位移响应均方值和应力响应均方值的均值、方差和变异系数的计算表达式。通过算例，分析了结构物理参数和几何尺寸的随机性对结构位移响应均方值和应力响应均方值随机变量随机性的影响。本文方法具有对随机结构进行一次动力分析便可求得动力响应的数字特征，且可以考察结构任一参数的随机性对结构非平稳随机响应分析结果的影响之优点。     

高拱坝动力特性与动力响应模型试验研究

高拱坝的动力破坏特性越来越受到关注,动力特性和动力响应是其研究的一个重要方面。通过模型试验的方法研究高拱坝动力特性和动力响应的特征,动力特性试验比较了完好结构与有施工横缝结构的基阶动力特性,表明当结构存在施工横缝时,结构基阶频率降低,阻尼增大。结构动力响应采用振动台模拟地震波激励,试验结果表明,完整结构与有施工缝结构动力响应具体数据不同,但规律相同。加速度最大响应沿拱顶水平向在坝中拱顶的值最大,向两边的坝肩处,加速度最大响应逐渐减小。沿拱坝垂向加速度最大响应从坝顶到基础,响应均逐渐减小。试验结果可为高拱坝结构动力安全研究提供技术依据。     

小波分析在复合材料层合结构损伤检测中的应用

利用小波变换技术，研究了含裂纹悬臂复合材料层合结构的损伤振动检测问题。用小波分析技术分解完好板与损伤板在方波信号激励下的动力响应信号，得到一系列子信号，并从中提取出结构损伤信息一响应信号能量谱，作为损伤特征参数。     

ELASTIC EFFECT IN DYNAMIC RESPONSE OF PLASTIC CANTILEVER BEAMS TO IMPACT

A lumped masses-springs model is proposed to analyze the dynamicresponse of an elastic-plastic cantilever beam resulting from impact. The numericalresults are in good agreement with those by finite-element approaches. The simplifiedmodel can catch the most essential features of elastic-plastic response of beams; inparticular, it demonstrates the effect of elastic deformation on the distribution ofbending moment and energy dissipation, and provides valuable quatitative results.     

三维轮轨法向接触力学行为弹塑性理论分析

基于Hertz接触理论和双线性强化模型,建立了轮轨法向接触弹塑性理论分析模型,分析了轮轨法向接触力学响应特征,讨论了轴重对接触压力和接触变形的影响规律。同时,基于三维轮轨接触有限元模型模拟了轮轨接触力学行为,并引入理论误差系数分析了弹性模型和双线性强化模型对轮轨接触力学响应预测结果的差异性。结果表明,轮轨最大接触压力和接触变形量均随轴重的增大而增大;双线性强化模型的理论误差系数较小,采用双线性强化分析模型能较准确地预测轮轨接触弹塑性力学行为。研究结果可为轮轨系统安全服役和损伤评估提供理论和技术支持。     

Experimental dynamic analysis of elastic-plastic shear frames with secondary structures

Various experimental models are developed to study the influence of lightweight secondary structures on the dynamic response of elastic and elastic-plastic shear frames. Small-scale two-story model frames, with an elastic single-degree-of-freedom secondary structure attached, are considered for sinusoidal and random in-plane support excitation. Both elastic and elastic-plastic responses are recorded by varying the material properties of the columns of a distinguished floor. Parametric studies are performed by varying the secondary structure's fundamental frequency and damping. Experimental results are compared with those obtained by computational simulations. Experimental and numerical results are in excellent agreement, however they show that the material properties have to be determined very carefully. The statistic response of randomly excited elastic-plastic structures is not much affected by the motion of tuned secondary structures. However, this dynamic behavior is not true for elastic main structures. In this case, an optimally tuned secondary structure decreases the structural response up to 25%.     

ELASTIC-PLASTIC DYNAMIC RESPONSE OF FULLY BACKED SANDWICH PLATES UNDER LOCALIZED IMPULSIVE LOADING

An analytical model is developed to assess the elastic-plastic dynamic response of fully backed sandwich plates under localized impulse load.The core is modeled as an elastic-perfectly plastic foundation.The top face sheet is treated as an individual plate resting on the foundation.The elastic-plastic analysis for the top face sheet is based on a minimum principle in dynamic plasticity associated with the finite difference technique.The effects of spatial and temporal distributions of the impulsive loading on the dynamic response of sandwich plates are discussed.The model can be used to predict the impulse-induced local effect on fully backed sandwich plates.     

The simple shear oscillation and the restrictions to elastic-plastic constitutive relations

Based on the definitions of hardening, softening and ideal plastic behavior of elastic-plastic materials in the true stress tensor space, the phenomena of simple shear oscillation are shown to be relative to the oscillatory occurrence of hardening and softening behavior of elastic-plastic materials, namely the oscillation of hardening behavior, by analyzing a simple model of rigid-plastic materials with kinematical hardening under simple shear deformation. To make the models of elastic-plastic materials realistic, must be satisfied the following conditions: for any constitutive model, its response stresses to any continuous plastic deformation must be non-oscillatory, and there is no oscillation of hardening behavior during the plastic deformation.     

Shear waves in an elastic-plastic material due to a supersonic surface step load

A step shear load moves steadily on the surface of an elastic-plastic half space at a speed exceeding the elastic shear wave speed of the material. The orientation of the shear traction is such that the deformation is two-dimensional antiplane strain. Two different representations of the rate independent elastic-plastic material response are considered. The first material model is based on the associated flow rule and the Mises yield condition with isotropic hardening, whereas the second model is based on a particular flow theory of plasticity which represents incremental behavior at a corner of the instantaneous yield surface. Both models predict the same response under the same proportional loading. The stress history experienced by a typical material particle during passage of the load step is determined, and the variation of final strain with the magnitude of the load step is calculated. One conclusion resulting from comparison of results for the two material models for this problem is that the influence of yield surface vertex formation is not significant.     

斜波压缩下锡的相变和层裂行为

获取不同热力学路径下锡的动态响应实验数据,是深入研究其相变和损伤物理过程的基础.利用小型磁驱装置CQ-4完成了金属锡的斜波加载实验,获取了锡含有相变和层裂损伤物理信息的实验数据.实验结果显示,在加载段锡依次经历了弹塑性转变和β-γ相变两种物理过程,屈服强度约0.194 GPa,相变压力随着锡厚度的增加从7.54 GPa减小到7.14 GPa.在卸载段出现了明显的层裂损伤,层裂强度约1.1 GPa,与相同加载压力下冲击实验结果有巨大差异,层裂片厚度约0.38 mm.结合由锡的多相Helmholtz自由能计算的多相状态方程、Hayes相变动力学方程和损伤度理论,对斜波压缩实验过程进行一维流体动力学数值模拟,计算结果可以很好描述锡的弹塑性转变、相变和层裂三个物理过程.     

钢筋混凝土靶侵彻的可压缩弹-塑性动态空腔膨胀阻力模型

在Forrestal素混凝土靶侵彻的可压缩弹-塑性球形动态空腔膨胀理论模型基础上,考虑粉碎区以内钢筋对混凝土的环向约束作用,提出了一个适用于刚性弹侵彻钢筋混凝土靶的阻力模型。论文通过体积配筋率的引入,获得了钢筋混凝土靶空腔表面径向应力的理论解,并讨论了配筋率对空腔壁面径向应力及各分区大小的影响。结果表明:钢筋对混凝土的环向约束效应影响了空腔膨胀过程中混凝土各区域的大小分布,并提高了空腔表面的径向应力。     

Analytical dynamic model of elastic-plastic pipe-on-pipe impact

The dynamic response of pipe-on-pipe impact is described by an analytical model. The model considers the impact of a whipping pipe with one end hinged and the other end free on a simply-supported target pipe at its midpoint. Combining with the contact theory, the Laplace transformation, and the inverse Laplace transformation method, an analytical model based on the tubular beam theory is proposed to study the elastic-plastic behavior of a target pipe laterally impacted by a whipping pipe. Numerical simulations using the explicit finite element code MSC/DYTRAN are also performed. The results are coincident with the theoretical prediction.     

Numerical analysis of large elastic-plastic deformation of beams due to dynamic loading

Numerical calculations were performed for two examples of the response of elastic-plastic beams subjected to dynamic loads. These were a simply supported, axially restrained beam under suddenly applied uniform pressure, and an axially restrained, clamped beam with a central mass that is impacted by a projectile. Large elastic-plastic deflections were considered, and the method of finite differences was used. Two different constitutive equations were assumed: the elástic-perfectly plastic relation, and a special elastic-viscoplastic, strain hardening model. Analysis of the results included examining the interaction between the bending moment and the axial force, the variation of the axial force, bending moment and deflection with time, and the propagation velocities of the various phenomena during motion. Experiments were carried out in which a rifle projectile hit a central mass which had been fastened to a clamped beam. Comparison between the theoretical and experimental dynamic deflections shows good agreement for relatively short response times.