LS—DYNA3D等非线性结构动力响应分析程序的局限性

通过理论分析和数值算例研究了采用LS－DYNA3D等非线性动力响应分析有限元程序于具有较大刚体转动的结构时,可能出现错误的应力和应变计算结果。主要原因是采用增量形式的应力修正时,其客观性被破坏。这是此类工程软件亟待改进的问题之一。     

Transient Characteristics of the Yield Surface of Electrorheological Clutch

The characteristic of transient yield surface in electrorheological clutch has been studied. It shows that the characteristics of clutch are dependent on the parameterβ, which is in the yield stress formula of ERF, when extra electric field was applied suddenly. In the case ofβ>2, the yield surface generates from the inner cylinder. In the case ofβ<2, the yield surface generates from the outer cylinder. The direct numerical results deriving from the Crank-Nicoson finite difference method with the regulation parameter model are also presented.     

The Non-Axisymmetrical Dynamic Response of Transversely Isotropic Saturated Poroelastic Media

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Investigation of Random Response of Rotational Shell When Considering Geometric Nonlinear Behaviour

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｅｎｇｉｎｅｅｒｉｎｇ,ｔｈｅｎｏｎｌｉｎｅａｒｉｔｙｏｆｓｈｅｌｌｓｔｒｕｃｔｕｒｅｉｓｓｏｍｅｔｉｍｅｓｏｂｖｉｏｕｓ.Ｉｔｉｓｖｅｒｙｄｉｆｆｉｃｕｌｔｔｏｓｏｌｖｅｔｈｅｐｒｏｂｌｅｍｏｆｔｈｅｎｏｎｌｉｎｅａｒｒａｎｄｏｍｖｉｂｒａｔｉｏｎ .Ｉｎｔｈｉｓｐａｐｅｒ,ｗｅｔｒｙｔｏｓｏｌｖｅｉｔｉｎｔｈｅｆｒｅｑｕｅｎｃｙｄｏｍａｉｎｂｙａｎｉｍｐｒｏｖｅｄｓｔａｔｉｓｔｉｃｌｉｎｅａｒｉｚａｔｉｏｎｍｅｔｈｏｄ .Ｗｅｃｏｎｓｉｄｅｒｏｎｌｙｔｈｅｇｅｏｍｅｔｒ…     

超高感度CCD摄像传感器的特性分析

介绍了超高感度 CCD(EXview HAD CCD)摄像传感器的概念、结构特点和性能特征。比较了常规的基底为 Nsub、Psub的 CCD传感器和超高动态 CCD传感器各自的灵敏度、饱和信号和暗电流 ,给出了量子转化效率与光波长的关系曲线。结果表明 :超高感度 CCD摄像传感器在减小拖影方面具有突出的优点。     

Localized surface waves at the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity

We consider the propagation of the laser beam near the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity. We demonstrated the possibility of the surface waves formation, found the profiles of such surface modes and investigated waveguiding properties of the dielectric-photorefractive medium boundary. The effective particle theory was used to derive an ordinary differential equation that describes the beam center trajectory during the reflection from the interface.     

Multi-State Second-Order Nonlinear Optical Switches Incorporating One to Three Benzazolo-Oxazolidine Units: A Quantum Chemistry Investigation

This contribution employs quantum chemistry methods to describe the variations of the second nonlinear optical responses of molecular switches based on benzazolo-oxazolidine (BOX) units, connected by π-linkers, along their successive opening/closing. Under the fully closed forms, all of them display negligible first hyperpolarizability (β) values. When one BOX is opened, which is sketched as C→O, a push–pull π-conjugated segment is formed, having the potential to enhance β and to set the depolarization ratio (DR) to its one-dimensional-like value (DR = 5). This is observed when only one BOX is open, either for the monoBOX species (C→O) or for the diBOX (CC→CO) and triBOX (CCC→CCO) compounds, i.e., when the remaining BOXs stay closed. The next BOX openings have much different effects. For the diBOXs, the second opening (CO→OO) is associated with a decrease of β, and this decrease is tuned by controlling the conformation of the π-linker, i.e., the centrosymmetry of the whole compound because β vanishes in centrosymmetric compounds. For the triBOXs, the second opening gives rise to a Λ-shape compound, with a negligible change of β, but a decrease of the DR whereas, along the third opening, β remains similar and the DR decreases to the typical value of octupolar systems (DR = 1.5).     

无约束修正Timoshenko梁的冲击问题

介绍了修正后的Timoshenko梁运动方程,并比较了修正Timoshenko梁与经 典Timoshenko梁的运动方程. 推导了考虑剪切变形引起的转动惯量的修正Timoshenko 梁的正交条件,推导了集中质量对无约束修正Timoshenko梁的正碰撞对梁所引起的瞬态冲 击响应公式,并用算例进行了分析,且与集中质量对经典的无约束Timoshenko梁的正碰撞 对梁所引起的冲击响应进行了比较,另外还用算例分析了梁的刚度的变化和冲击质量比对其 冲击响应产生的影响.     

不确定非线性结构动力响应的区间分析方法

研究多自由度非线性不确定参数系统的动力响应问题. 以区间数学为基础,将不确定 性参数用区间进行定量化,借助一阶Taylor级数,给出了近似估计非线性振动系统动力响 应范围的区间分析方法. 从数学证明和数值算例两方面,将其与概率摄动有限元法进行了比 较,结果显示区间分析方法对不确定参数先验信息具有要求较少、精度较高的优点.     

李萨如图形在检测系统中的应用

李萨如图形可以检测两个相同频率信号的相位差．主要论述具有惯性质量、弹簧和阻尼器的二阶加速度测量系统,其动态响应特性的分析方法,如何利用李萨如图形来检测力平衡式加速度传感器的动态特性,即幅频特性和相频特性,从而确定传感器的固有频率ω_n和阻尼比ξ,以此来评定传感器的综合特性．