柔性转轴动力学分析与拍振现象

In this paper,the intrinsic behavior of rotating Euler-Benoulli flexible shafts was studied due to coupled bending and torsional vibratuions,the equations of motion of the shaft with unbalanced eccentricity and visous material damping were derived by the Hamilton principle.The numerical solution was obtained using the perturbation approach and mode-assuming method.The influences of the coupled vibrations between the benging and torsion.the rotaing speed,material damping and the slenderness ratio of the shaft were analyzed.It is clearly shown that the beating phenomena can occur when the interaction of torsion and flexure is considered.     

弹性杆轴向拉力测定实验中振动频率识别方法研究

用频率法测试两端固支的弹性杆轴向拉力时,试验机及其夹具的振动会对杆件振动信号的测量和识别造成干扰,容易导致振动频率及阶次误判;提出了利用弹性杆在无约束自由振动下的频率作为基准值,对实验中杆的振动频率进行修正的方法,得到了弹性杆准确的振动频率及阶次;并发现试验机及其夹具对于两端铰支弹性杆的振动频率的识别不会产生影响;随着弹性杆长径比的增加,试验机及其夹具对两端固支的弹性杆振动频率识别产生的干扰逐渐减小,当轴向拉力不断加大时,这种干扰也呈现下降趋势。     

一个二维离散系统的分岔分析

应用动力系统的局部分支理论,研究一个二维离散动力系统当参数变化时产生的复杂动力学性质。我们应用中心流形定理和分岔理论证明了这个二维离散动力系统存在叉型分岔、倍周期分岔和Hopf分岔。     

有限时滞Lienard方程Hopf分支的数值逼近

研究了一类有限时滞的Lienard方程Hopf分支的数值逼近问题．首先，以滞量为参数，应用Cooke和JHale的方法，得到Hopf分支存在的条件；然后，利用欧拉方法将得到的差分方程表示为映射，利用离散动力系统的分支理论，给出了差分方程Hopf分支存在的奈件和连续系统与其数值逼近间的关系．证明了当该系统在r=ro产生Hopf分支时，其数值逼近也在相应的参数rh处具有Hopf分支，并且忙rb=ro＋o（h）．     

Balance mechanism design of single cylinder engine based on continuous mass distribution of connecting rod

For a single cylinder engine, the total unbalanced inertial forces occur in the engine block, which results in engine’s vibration and deteriorated noise. In order to eliminate the unbalanced forces, counterweight and primary balance shaft should be attached to the cylinder block so that engine durability and ride comfortability may be further improved. Traditionally one third of connecting rod assembly’s mass is treated as reciprocating mass, and two thirds as rotating mass when designing balance mechanism. In this paper, a new method based on the multibody dynamics simulation is introduced to separate the reciprocating mass and rotating mass of connecting rod assembly. The model consists of crankshaft, connecting rod, piston and the simulation is performed subsequently. According to the simulation results of the main bearing loads, the reciprocating mass and rotating mass are separated. Finally a new balance mechanism is designed and simulation results show that it completely balances inertial forces to improve the engine’s noise vibration and harshness performance.     

可压Navier-Stokes-Korteweg方程组强稀疏波的稳定性

研究了一维可压Korteweg型流体模型强稀疏波的渐近稳定性问题。假设相应的可压Euler方程的黎曼问题存在稀疏波解（ VR ,UR ,SR ）（ t,x）,如果Navier-Stokes-Korteweg系统的初值是近似稀疏波的小扰动,利用能量方法,可以证明其柯西问题存在一个唯一的整体光滑解,并随着时间渐近趋于（ VR ,UR , SR ）（ t,x）。     

关于无粘可压绝热流体的欧拉方程不适定初边值问题的形式解

It is proved that the ill-posed initial value problem of the Euler equations for compressible adiabatic inviscid fluid flow can be only formally solved. The necessary and sufficient conditions for existence of formal solution of some representative ill-posedness initial-boundary value problem are presented. Finally, an example is also given.     

一类可压缩超弹性球体的空穴的生成和增长

In this paper, the strain energy function proposed by Shang and Cheng was generalized by introducing a nonlinear term.Void formation and growth in the interior of a sphere composed of compressible hyper-elastic material, subjected to a prescribed uniform displacement, was examined.A parametric cavitated bifurcation solution for the radial deformed function was obtained.Stability of the solution of the cavitated bifurcation equation was discussed.With the appearance of a cavity, an interesting feature of the radial deformation near the deformed cavity wall is the transition from extension to compression.     

具松弛项的欧拉方程组的光滑解的奇性形成

研究具松弛项的可压缩的欧拉方程组柯西问题：在关于压力函数和次特征条件的假设下，如果初值的C^1模有界，且初始密度离开真空状态，章给出在有限时间光滑解的奇性形成的充分条件。     

Void Formation and Growth for a Class of Compressible Hyper-Elastic Sphere

In this paper, the strain energy function proposed by Shang and Cheng was generalized by introducing a nonlinear term. Void formation and growth in the interior of a sphere composed of compressible hyper-elastic material, subjected to a prescribed uniform displacement, was examined. A parametric cavitated bifurcation solution for the radial deformed function was obtained. Stability of the solution of the cavitated bifurcation equation was discussed. With the appearance of a cavity, an interesting feature of the radial deformation near the deformed cavity wall is the transition from extension to compression.     

基于HyperWorks的发动机连杆有限元模态分析

以发动机连杆为研究对象,采用Hyperworks分析软件对连杆前十阶的模态分布情况,以及每一模态相对应的振型进行了分析,结果表明:连杆的振动形式表现多样,导致连杆产生弯曲变形严重,设计时应尽量减少变形对连杆性能的损失.     

T形配钢型钢混凝土偏压构件力学性能研究

建立了T形配钢型钢混凝土偏压构件力学性能分析的有限元模型,计算结果得到以往实验结果的验证。在此基础上,分析了不同阶段材料应力状态和各参数对偏压构件力学性能的影响。结果表明:T形配钢型钢混凝土构件在不同加载角下的性能有所不同,加载角为180°时极限承载力大于其他角度情况;混凝土抗压强度、型钢含钢率、配筋率、荷载偏心率、长细比对构件荷载-变形曲线的影响较大,随着混凝土强度、型钢含钢率、配筋率的增加,极限承载力和刚度增加;随着荷载偏心率的增加,极限承载力和刚度下降;随着构件长细比的增加,构件承载力总体呈现线性下降趋势,刚度下降明显。     

The History of the Planar Elastica: Insights into Mechanics and Scientific Method

Euler’s formula for the buckling of an elastic column is widely used in engineering design. However, only a handful of engineers will be familiar with Euler’s classic paper De Curvis Elasticis in which the formula is derived. In addition to the Euler Buckling Formula, De Curvis Elasticis classifies all the bent configurations of elastic rod—a landmark in the development of a rational theory of continuum mechanics. As a historical case study, Euler’s work on elastic rods offers an insight into some important concepts which underlie mechanics. It sheds light on the search for unifying principles of mechanics and the role of analysis. The connection between results obtained from theory and those obtained from experiments on rods, highlights two different approaches to scientific discovery, which can be traced back to Bacon, Descartes and Galileo. The bent rod also has an analogy in dynamics, with a pendulum, which highlights the crucial distinctions between initial value and boundary value problems and between linear and nonlinear differential equations. In addition to benefiting from the overview which a historical study provides, the particular problem of the elastica offers students of science and engineering a clear elucidation of the connection between mathematics and real-world engineering, issues which still have relevance today.

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Characterizing Children’s Expectations About Expertise and Incompetence: Halo or Pitchfork Effects?

Do children expect an expert in one domain to also be an expert in an unrelated domain? In Study 1, 32 three‐ and four‐year‐olds learned that one informant was an expert about dogs relative to another informant. When presented with pictures of new dogs or of artifacts, children who could remember which informant was the dog expert preferred her over the novice as an informant about the names of dogs, but they had no preference when the informants presented artifact labels. In Study 2, 32 children learned that one informant was incompetent about dogs whereas another was neutral. In this case, children preferred the neutral speaker over the incompetent one about both dogs and artifacts. Taken together, these results suggest that for children, expertise is not subject to a “halo effect,” but incompetence may be subject to a “pitchfork effect.”     

耦合映射系统各种同步态的调控

在传统的耦合方式下,只能产生和单个振子独立存在时动力学行为相同的同步态.文章提出一种新的耦合方式,在这种耦合方式下,对于固定的全同振子组成的系统能够产生多种形式的同步态.以全局耦合的固定映射系统为例,说明在新的耦合方式下,不仅能产生混沌同步态,而且能产生规则同步态,同步态之间的转化是通过倍周期分叉的形式进行的.该结论为探索由固定系统组成的复杂网络如何实现同步提供了一个很好的途径.     

Travelling Waves in a Compressible Mooney—Rivlin Rod

This article deals with waves in a circular cylindrical rod composed of a compressible mooney-rivlin material.All kinds of travelling waves and the conditions for their existence are studied by using the method of nonlinear dynamics.     

How infants use vision for grasping objects

The role of vision was examined as infants prepared to grasp horizontally and vertically oriented rods. Hand orientation was measured prior to contact to determine if infants differentially oriented their hands relative to the object's orientation. Infants reached for rods under different lighting conditions. Three experiments are reported in which (1) sight of the hand was removed (N = 12), (2) sight of the object was removed near the end of the reach (N = 40, including 10 adults), and (3) sight of the object was removed prior to reach onset (N = 9). Infants differentially oriented their hand to a similar extent regardless of lighting condition and similar to control conditions in which they could see the rod and hand throughout the reach. In preparation for reaching, infants may use the current sight of the object's orientation, or the memory of it, to orient the hand for grasping; sight of the hand had no effect on hand orientation.     

单牌号滤棒发射机发射双牌号滤棒的技术改造

在卷烟生产企业中,越来越多的企业采用“发射机——接收机”的滤棒自动输送系统.但是现有的单台发射机组只能供应一个牌号的滤棒,当生产牌号较多时会使滤棒无法供给.根据现有的卸盘发射机组实际情况,对其进行改造,使单台发射机组可以发射双牌号滤棒.     

4V-105柴油机连杆有限元分析与优化设计

介绍4V-105柴油机连杆的工作概况,利用CAE设计分析程序ANSYS对连杆进行了有限元分析和优化设计。并对优化结果进行较详细的体积变化分析、对连杆进行相应的实验测试验证等。以验证连杆尺寸优化结果的合理性,最后得出了合理的连杆优化设计结果。     

Numerical simulation of bubble chaotic motion in a cavitating water jet

~~00002RKRSr= (6) If 0tKt=, Eqs. (2),(3) and (4) change into the following equation that is applied to simulations using the MathCAD software. ddd(,,)dd1dxyygxyzzttt=== (7) where 11251(,,)()(1)gxyzABCyxaaaa=++-+, 2132131145678222124531678831(1),23(1)[(1sin],[3cos()] AyyByxxyxzCxyxyxyxzggaaaaaaaaaaaaagaaaa-------=--=++---+=+-- (8) 5g00pK6g0p…