一种硅油扭振阻尼器的非线性动力学持性研究

本文提出一种利用Cohen类二次时频分布和Hilbert变换，由非平衡振动信号对非线性动力学系统进行辨识的方法，利用该方法对一种硅油扭振阻尼器地实验研究，得到了阻尼器的阻尼系数随转速的变化曲线及附加刚度随转角的变化曲线，揭示了阻尼器的非线性动力学特征，该方法仅需利用一次冲击响应信号，实验工作量小，抗噪性好，适用性广泛。     

磁流变阻尼器性能检测系统的研究

设计并研发了一种磁流变阻尼器性能检测系统,该系统可以完成不同激励下的磁流变阻尼器阻尼力的示功试验和速度特性试验。对电液位置伺服系统进行研究,提出一种基于幅值修正的实时迭代控制算法,实验表明,该控制算法能有效改善较高频的幅频特性下降问题,系统能复现高精度高频宽的正弦位移信号;选择Lord公司型号为RD-8041-1的磁流变阻尼器进行性能测试,测试结果表明,此系统能够有效测试磁流变阻尼器的滞回特性曲线,为磁流变阻尼器动力学模型的研究提供前提。     

参数慢变磁流变非线性悬架系统主共振研究

针对磁流变阻尼器随工作温度变化导致阻尼力发生改变,进而降低磁流变悬架系统性能的问题,基于传热学方程和参数慢变非线性振动理论研究温度变化对磁流变非线性悬架系统的主共振动力学行为的影响。根据传热学理论建立磁流变阻尼器工作区域能量微分方程,用数值方法求出温度变化规律,用改进的Bingham模型计算磁流变阻尼力;建立慢变参数磁流变非线性悬架系统动力学方程,利用平均法求解主共振激励下的悬架动行程的稳态幅值响应。研究表明:随着运行时间增加,磁流变阻尼器的温度逐渐升高,导致磁流变阻尼力大幅降低,悬架动行程稳态振幅及其变化量越大,从而使得悬架系统的性能偏离设计目标。     

参数慢变非线性磁流变悬架系统主共振研究

针对磁流变减振器会随工作温度变化阻尼力发生改变,进而降低磁流变悬架系统性能的问题,基于传热学方程和参数慢变非线性振动理论研究温度变化对磁流变非线性悬架系统的主共振动力学行为的影响。根据传热学理论建立磁流变阻尼器工作区域能量微分方程,用数值方法求出温度变化规律,用改进的Bingham模型计算磁流变阻尼力;建立慢变参数磁流变非线性悬架系统动力学方程,利用平均法求解主共振激励下的动行程稳态幅值响应。研究表明,随着磁流变阻尼器运行时间增加,温度逐渐升高,阻尼器输出阻尼力大幅降低,悬架动行程稳态振幅变化量也越大,导致悬架系统性能偏离设计目标。     

延时矢量方差算法及其在齿轮故障识别中的应用

提出了利用时间序列的延时相空间重构，采用延时矢量方差及替代数据的时间序列非线性的检验方法，并将该方法应用于设备故障信号的非线性检验与故障识别。数值实验结果表明，延时矢量方差法是一种有效、直观的非线性检验与故障识别方法，对噪声信号具有很强的鲁棒性，对非线性信号具有很高的敏感性。采用该方法对齿轮振动信号进行非线性检验与故障识别，结果与实际情况相符。     

内通道式磁流变阻尼器及其减振控制研究

研制了一种内通道式磁流变阻尼器,该阻尼器的流场通道位于电磁线圈内部,磁流变效应发生于两层固定的平板之间.对该阻尼器进行了MTS动态拉伸实验,结果表明具有良好动力学特性和响应时间.为了模拟动车的振动情况,搭建一个两自由度的弹簧质量实验平台系统,利用天棚控制算法,在该实验平台上进行减振实验研究,结果表明磁流变阻尼器在1 Hz～2Hz频率范围内有较好的减振效果.     

剪切阀式磁流变阻尼器动态特性实验研究

介绍了剪切阀式磁流变阻尼器的结构和工作原理,基于平板模型得出了其阻尼力的计算公式。对自行研制的剪切阀式磁流变阻尼器的阻尼力、电流、位移、速度和频率等动态特性进行了实验研究。结果表明剪切阀式磁流变阻尼器的阻尼力随控制电流的增大呈非线性增加,阻尼力可调系数随电流变化连续可调。在相同振幅下,阻尼器的可调倍数随频率增大而降低,阻尼力随振动频率的增大而增大。通过深入分析该型阻尼器的动力特性,为其在车辆悬挂系统半主动控制中的应用奠定了基础。     

基于遗传算法的直升机旋翼液弹阻尼器模型参数识别

建立直升机旋翼液弹阻尼器非线性动力学参数模型,引入具有全局搜索能力的遗传算法进行模型参数识别,解决因模型复杂造成的传统参数识别效率及精度较低问题。据识别所得参数模型重构力—位移迟滞回线并与液弹阻尼器动力学试验数据对比结果显示,参数模型重构曲线与试验曲线吻合良好,验证参数模型描述液弹阻尼器非线性动力学特性的准确性及采用遗传算法识别模型参数的有效性。对不同位移幅值与不同频率下液弹阻尼器动力学特性模拟计算均获得与试验一致结果,表明非线性参数模型及参数识别方法鲁棒良好性、精度较高。     

具有复阻尼特征板式变摩擦阻尼器滞回性能研究

为使减震装置具有复阻尼特征,提出一种板式变摩擦阻尼器。基于静力平衡条件推导了根据阻尼器几何、物理参数确定其滞回模型的理论公式,采用非线性有限元对阻尼器在静力往复作用下的滞回曲线进行了模拟,通过低周往复试验进行了阻尼器滞回性能试验研究,基于上述方法对影响滞回性能的关键参数进行了研究。研究结果:该阻尼器的滞回曲线为位于一、三象限、关于原点对称的三角形,理论公式和数值模拟得到的滞回曲线与试验数据吻合得较好,影响阻尼器滞回性能的关键因素是弹簧刚度、2个摩擦因素和1个角度。结果表明该阻尼器的滞回曲线具有明显的复阻尼特征,滞回模型的理论公式和数值模拟结果可用于指导此类阻尼器的设计。     

基于电涡流阻尼器的数控加工振动抑制

弱刚性零件在数控加工中极易发生变形、让刀等现象,对加工质量及效率构成严重影响。基于电涡流阻尼器利用导体在恒定磁场中运动或者利用时变电磁场在导体上产生电涡流阻尼力,提出并设计适用于弱刚性结构件数控加工振动抑制的电涡流阻尼器结构;结合理论建模,提出四种设计方案并对其减振性能进行测试和比较。模态实验表明,四种阻尼器方案均能较好的对工件振动进行抑制,频响函数幅值最低下降55%;模态参数辨识表明,电涡流阻尼器可使系统阻尼增加70.73%,而对其余动力学参数的影响较小。切削实验表明,该电涡流阻尼器可增加工件临界稳定切深171%,减少切削加工振动信号58%以及降低表面粗糙度89.7%。     

浸胶芳纶帘线的力学性能

对芳纶帘子线加捻和浸胶前后的力学性能进行了分析,分析结果表明．适当的加捻可以提高芳纶帘子线的拉伸强度．芳纶帘子线浸胶处理会降低其强度和扯断伸长率．增加其定负荷伸长．增粘处理后的芳纶帘子线扯断强度服从正态总体分布N(247．02,13．39^2)．     

Light propagation in twisted anisotropic media: application to photoreceptors

The propagation of light through a slowly twisting anisotropic medium is described by a coupled-mode theory; expressions are derived for the electric field for the case of a birefringent dichroic medium with a constant rate of twist. The method provides a simple and intuitive means for determing the effect of twisting on the linear birefringence and dichroic absorption of the medium, particularly when the light is initially linearly polarized. The theory is well suited to the analysis of light absorption in twisting insect photoreceptors, such as found in bees and ants. We provide full expressions and useful approximations for polarization sensitivity and the initial direction of polarization to give maximum absorption for several types of photoreceptors.     

SMA-based smart soft composite structure capable of multiple modes of actuation

This paper introduces the design of a smart soft composite (SSC) actuator capable of multiple modes of actuation. This actuator combines four shape memory alloy (SMA) wires embedded in a soft matrix where one or two SMA wires can be activated to induce the actuator into either the bending mode, the twisting mode or the combined bending and twisting mode of actuation. Experimental results for actuators of different lengths were obtained for all modes of actuation and the actuator is capable of large deformations in all modes and directions of actuation. Then a simple FEA model was used to predict the range of deformation for different lengths in the different modes of actuation. This model is able to predict accurately the bending and twisting angles of the actuator for the different modes of actuation. The 120 mm actuator is capable of deformations up to approximately 160° in both the pure bending and pure twisting modes and of approximately 80° for both twisting and bending in the combined twisting and bending mode of actuation.     

Fracture surface evolution and apparent delamination toughness in split composite beam specimens subjected to mixed mode I–III loading

The influence of specimen twisting during global anti-plane shear loading in composite split beam specimens is studied. Tests were conducted on specimens with different thicknesses and delamination lengths to produce different amounts of specimen twisting prior to fracture. It is shown that specimen twisting causes mode I stresses to develop, thereby producing mixed mode I–III conditions along the delamination front. This causes near-tip transverse cracks to initiate, prior to delamination advance, at an orientation related to the mode mix. Unlike in homogeneous materials, transverse crack extension is accompanied by planar delamination advance, and transverse crack rotation during extension is restricted by the laminate’s fibers. The overall fracture surface evolution is therefore strongly controlled by specimen geometry. The influence of these findings on the apparent delamination toughness as obtained from composite split beam and other types of mode III tests is discussed.     

多分裂导线扭矩-扭转角关系及防翻转研究

提出一种新的多分裂导线扭矩-扭转角关系半解析模型，适用于大档距大扭转角以及翻转计算。该模型考虑间隔棒的竖向及水平向位移、子导线在扭转过程中的张力变化等多重因素，同时考虑分裂导线各截面的扭转角沿跨长呈非线性分布的特征。计算结果与有限元方法、试验结果进行了对比验证，表明导线的几何非线性对导线回复扭矩的影响十分显著，该文提出的半解析模型在小角度和大角度扭转情况下均具有较高的计算精度，并为判定导线是否翻转提供依据。详细分析了布置不同间隔棒数量工况下的扭矩-扭转角关系，从而考察了增加间隔棒数量对抑制翻转的有效性，发现只需少量增加间隔棒就能保证即使扭转角达到180°时扭转刚度依然为正，即可自行恢复，有效预防翻转；对于扭矩非常大的情形，若要保证扭转360°时扭转刚度依然为正，即导线出现扭绞现象后仍具备自行回复原位的能力，则需要布置较多的间隔棒。     

对称角铺设层板的弯曲、稳定与振动分析

本文采用文献中的两步级数展开法,分析了四边简支对称角交铺设叠层板的弯曲、稳定与振动问题。文中给出了板受均布力作用的弯曲问题、振动问题以及只有二对边受均匀压力N_x的稳定问题的数值结果、并且讨论了弯曲-扭转耦合刚度D₁₆和D₂₆对挠度、临界荷载、基频以及与之对应的失稳波形和振型的影响。      

利用振动模态分析确定对称复合层板结构的材料特性

针对周边简支和周边固支含弯曲·扭曲耦合的对称复合材料层板,本文首先推导了利用振动模态分析进行层板５个弯曲刚度常数评价的理论公式,并利用振动测试得到的有限个离散点的挠度信息对振动模态进行近似处理,最后利用最小二乘法求解层板的弯曲刚度。在数值算例中,本文对两种边界条件下三种对称复合材料层板的弯曲刚度进行了评价,同时考察了测试点数目对弯曲刚度常数评价误差的影响。     

An exact solution for an anisotropic plate with an elliptic hole under arbitrary remote uniform moments

The problem of an anisotropic plate containing an elliptic hole subjected to remote bending or twisting moments is considered. In contrast with the previous works on the problem, the requirement that the deflection be a single-valued function is satisfied by introducing a correction constant. An exact solution for general anisotropic materials under arbitrary uniform loading conditions is derived. Explicit expressions for the deflection and moments on the edge of an elliptic hole in an orthotropic plate subjected to bending or twisting moments are obtained. The moment intensity factors as the elliptic hole degenerates into a crack are given.     

钢帘线残余扭转在线监测及自动消除控制系统设计

钢帘线在捻制的过程中会产生残余扭转,导致钢帘线在捻制完成后沿捻制相反的方向出现不同程度的回转,严重影响钢帘线的使用性能。为了减小钢丝捻制过程中出现的残余扭转,设计了钢帘线残余扭转在线监测及自动消除控制系统。利用西门子S7-200系列PLC（programmable logic controller,可编程逻辑控制器）对控制系统的软件和硬件进行合理配置,并详细阐述了系统的硬件和软件设计。采用台达DOP系列的触摸屏,实现钢帘线残余扭转在线实时监测的功能。该设备整机性能稳定,实现了残余扭转的控制与消除,满足生产线高柔性化、高效率、高质量的自动化生产要求。     

Analytical study of strength and failure behaviour of plain weave fabric composites made of twisted yarns

A two-dimensional analytical method is presented for the failure behaviour of plain weave fabric composites made of twisted yarns. The studies have been carried out on laminates with different configurations under on-axis uni-axial tensile loading. The cross-sectional area of the yarn was taken to be elliptical and the yarn path was taken to be sinusoidal. Different stages of failure are considered in the analysis. It has been observed that there is no significant reduction in tensile strength properties of plain weave fabric composites as a result of twisting of yarns. For E-glass yarns, twisting of yarns up to 5°, can facilitate ease of fabrication without significantly compromising the strength properties of the woven fabric composites.