Nonlinear dynamic behavior of rubbing rotor under interaction between bending and torsional vibrations

The nonlinear dynamic behavior of a rubbing rotor system was studied with a mathematical model established with the eccentricity and interaction between bending and torsional vibrations taken into consideration. The nonlinear vibrational response of a rubbing rotor was analyzed using numerical integral, spectroscopic analysis and Poince mapping method, which made it possible to have better understanding of the vibrational characteristics of partial rubbing and complete circular rubbing rotors. The numerical results reveal the response of torsional vibration mainly takes a form of superchronous motion, and its frequency decreases as the rotational speed increases when partial rubbing occurs, and the response of torsional vibration is synchronous when complete circular rubbing occurs. The comparison of the dynamics of rubbing rotors with and without the interaction between bending and torsional vibrations shows the interaction between bending and torsional vibrations advances the rotational speed, at which the response of bending vibration changes from a synchronous motion into a quasi periodic motion, and the interaction between bending and torsional vibrations reduces stability of the rubbing rotor.

Combined deformation of filament-wound cylinder and application to torsion vibration control

The combined deformation and mechanical properties of filament-wound cylinder of filament reinforced composite materials are investigated. A method of using filament-winding composites to reduce the amplitude of torsion vibration in the case of special stimulated vibration is established. A design formula of anisotropic filament-wound cylinder to reduce the torsion vibration of axle components is obtained. The results indicate that by putting the filament-wound cylinder on an axis, the torsion vibration of the axis can be reduced effectively.

Combined resonance of low pressure cylinder-generator rotor system with bending-torsion coupling

A nonlinear model of a low pressure cylinder-generator rotor system is presented to study sub-synchronous resonance and combined resonance. Analytical results are obtained by an averaging method. Transition sets and bifurcation diagrams are obtained based on the singularity theory for the two-state variable system. The bifurcation characteristics are analyzed to provide a basis for the optimal design and fault diagnosis of the rotor system. Finally, the theoretical results are verified with the numerical results.

WELL－POSEDNESS AND CONTROLLABILITY AND OBSERVABILITY OF A COUPLED VIBRATING SYSTEM

In this paper, we derive a new description form of coupled bending and torsionalvibrating system with boundary control and observation through Green's formula and provethat it is equivalent to the original form. On the basis of this. we prove the control system iswell-posed in time and frequency domain and completely controllable and observable.

Segmental Bridges under Combined Torsion, Bending and Shear

Segmental bridges with unbonded prestressed tendons have some advantages, such as the weather independence and the corrosion protection of prestressing tendons. This paper analyzed the behavior of a prestressed segmental bridge with unbonded tendons under combined loading of torsion, bending and shear. According to the experiment research, a modified skew bending model was developed to calculate the bearing capacity of segmental bridges subjected to combined bending, shear and torsion. The finite element method was used to investigate the deflection behaviors of such structure, also to check the theoretical model. The theoretical and FEM research results were compared favorably with the test results from Technical University of Braunschweig, Germany. Finally, suggestion for the design and construction of segmental bridges with external prestressing was made.

基于同频弯扭耦合强迫振动的桥梁断面颤振导数识别方法改进

为拓展强迫振动法在桥梁断面颤振导数识别领域中的应用能力,采取让断面做2次同频异相的弯扭耦合简谐运动模式,理论推导出任意非零相位差条件下的桥梁断面颤振导数识别公式。以理想平板的Theodorsen解为气动力数据源,对该方法的识别能力进行数值验证,并在此基础上研究弯扭耦合运动相位差、高斯白噪声、整数倍频有色噪声对平板颤振导数识别结果的影响规律。基于Fluent软件,将该方法与计算流体动力学(Computational Fluid Dynamics,CFD)技术结合,识别得到丹麦大带东桥主梁断面的颤振导数。研究结果表明:当平板气动力不包含噪声时,在任意非零相位差取值条件下,按照该方法识别所得颤振导数结果与理论值完全吻合;当平板气动力含有高斯白噪声时,在考察的3个低水平噪声条件下(5%、10%、15%),颤振导数识别误差与高斯白噪声比例水平、折算风速均成正相关,但不同颤振导数对高斯白噪声敏感程度各异;当平板气动力包含整数倍频有色噪声时,3倍频、4倍频噪声对颤振导数的识别精度影响显著,其他低倍频噪声和超高倍频噪声的影响较小,在8个颤振导数的识别结果中,H_(2)^(*)、H_(4)^(*)、A_(2)^(*)、A_(4)^(*)对倍频有色噪声更敏感。应用该方法结合CFD数值模拟识别得到的大带东桥主梁颤振导数与既有文献结果吻合良好,经计算得到的颤振临界风速也较为接近。研究结果可满足同类桥梁颤振设计的工程计算需求。

中低速磁浮圆曲线钢箱梁桥车致振动响应研究

随着圆曲线钢箱梁桥在城市交通中的应用愈发广泛,为探究其在中低速磁浮车辆运行作用下的振动响应特性,基于多体动力学和有限元方法建立车辆-轨道-钢箱梁刚柔耦合动力学模型,采用动态电磁阻尼力影响的二维磁轨关系,并考虑轨道关键部件的参振作用,分析圆曲线段钢箱梁的振动特性,探讨钢箱梁板厚、车辆速度及车体质量对钢箱梁振动响应的影响。结果表明:受曲率影响,钢箱梁在发生弯曲的同时亦会伴生扭转,产生弯扭耦合振动;钢箱梁的振动主要由10~20 Hz的钢箱梁整体弯曲振动、30~40 Hz的钢箱梁扭转振动以及50~70 Hz的轨道局部振动引起;计算得到的钢箱梁跨中横向及垂向最大挠度分别为1.26 mm、3.88 mm,均满足相关标准要求,钢箱梁具有足够的支撑刚度;各工况下的垂向加速度均未超过5.0 m/s^(2)的限值,且最高达到2.2 m/s^(2);在板厚10 mm以及超员载荷工况下,横向加速度大多超过1.4 m/s^(2)的限值,且最高达到4.0 m/s^(2);车辆速度的减小和车体质量的增加均会放大弯扭耦合作用影响,而板厚的增加则能够有效降低弯扭耦合作用影响,当板厚由10 mm增至40 mm时,一阶横弯及扭转频率对应振幅分别减小94.3%、98.7%。

大展弦比板弯扭耦合受迫振动分析

对于工程广泛存在的大展弦比结构,首次研究了大展弦比板弯扭耦合受迫振动响应.考虑弦向相对弯曲刚度远大于展向弯曲刚度,将弦向截面等效为刚体,考虑其绕展向轴线的扭转,应用Hamilton原理分别计算大展弦比板的势能与动能,建立两端简支的大展弦比板弯扭耦合受迫振动的动力学控制方程.将动力学控制方程进行Galerkin截断后,通过谐波平衡法和微分求积法/微分求积单元法,计算得到了大展弦比模型弯扭耦合受迫振动稳态响应的解析解及数值解,同时验证了解的截断收敛性及谐波收敛性.最后研究了外激励幅值对结构受迫振动响应的影响.结果将为工程中广泛存在的大展弦比结构设计提供指导.

T型磁力耦合压电俘能器发电性能研究

针对传统压电俘能器存在共振频率高、输出功率低的问题,提出了一种T型磁力耦合压电俘能器。通过引入两侧互异的磁力耦合作用使压电梁产生弯-扭振动,以增加压电梁的形变量,进而提高俘能器输出电压响应。首先分析了该压电俘能器的工作原理及结构设计,并对其振动特性进行仿真分析,最后,制作试验样机进行实验测试,通过仿真分析与实验测试验证了该压电俘能器的有效性。结果表明,存在最优负载电阻使压电俘能器输出功率最大。调整装置自由端质量块质量可对俘能频率进行控制,增大激励加速度能显著提高俘能器输出功率。引入磁力耦合,并通过对比实验分析了磁力耦合引起的弯-扭复合运动对俘能器输出性能的影响,当激励加速度为0.2 g时,磁力耦合装置Ⅲ由于发生弯扭复合振动,其工作频率与最大输出功率分别为5.5 Hz和3.71 mW。相比无磁力耦合的俘能装置Ⅰ,输出功率提高了约47%,因此,该T型磁力耦合压电俘能器在低频环境下具有较高输出效率。

FINITE ELEMENT MODELING AND ROBUST VIBRATION CONTROL OF TWO-HINGED PLATE USING BONDED PIEZOELECTRIC SENSORS AND ACTUATORS

Active vibration control for a kind of two-hinged plate is developed in this paper. A finite element model for the hinged plate integrated with distributed piezoelectric sensors and actuators is derived, including bending and torsional modes of vibration. In this model, the hinges are simplified as regular plate elements to facilitate operation. The state space representations for bending and torsional vibrations are obtained. Based on two low-order models of the bending and torsional motion, two H∞ robust controllers are designed for suppressing the vibrations of the bending and torsional modes, respectively. The simulation results indicate the effectiveness and feasibility of the designed H~~ controllers. The vibration magnitudes of the low-order modes can be reduced without affecting the high frequency modes.

不平衡转子系统弯扭耦合复杂故障智能诊断

弯曲振动与扭转振动耦合在旋转机械实际运行中往往不可避免。考虑不平衡转子不同复杂工况的弯扭耦合情况,利用深度学习技术的优势,构建了基于一维卷积神经网络的诊断模型,提出了一种用于处理不平衡转子发生弯曲,扭转以及弯扭耦合振动情况的智能故障诊断方法。分析了数据输入类型和L 2正则化对诊断的影响,优化了诊断模型以提高诊断精度,并进行了试验验证。研究结果表明,该方法可以实现不同转速下,发生弯扭耦合振动时单种或多种复合故障的智能诊断,获得比其他方法更好的诊断效果。

拉伸-扭转-弯曲作用下系泊缆索的应力响应

考虑6×19多股系泊缆索编制特点,研究缆索受到拉伸-扭转-弯曲共同作用下的应力响应。推导多股系泊缆索的螺旋线方程和不同层股丝接触点轴向距离,建立仿真模型中的代表性体积元素,推导该体积元素下的周期性边界条件,简化多股系泊缆索仿真模型,进一步优化应变和曲率加载方式,优化仿真模型加载形式。在有限元软件ANSYS中进行仿真分析,同时与解析模型进行对照。结果表明,所选取的代表性体积元素和周期性边界条件计算可靠,应力与曲率半径为非线性负相关关系,应变与应力为线性正相关关系,不同应变下曲率半径对应力的影响主要体现在最大应力数值以及位置,对应力-应变关系影响较小。

弯扭组合变形实验的改进与探讨

为了提高弯扭组合变形实验装置的应力测量精度,采用3个单片层叠的应变花改进了原有实验装置,实现了同一测点沿不同方向上的应变测量。应用上述改进装置开展了实验测试。结果表明,该改进装置能有效减小主应力、泊松比、扭转切应力和弯曲切应力的测量误差(前三者误差都在3%以内),提高了基于电测技术的力学参数测量精度。

“薄壁圆筒弯扭组合变形”实验项目规范

为进一步提高材料力学实验教学质量,以薄壁圆筒弯扭组合变形实验项目为对象编写了实验项目规范,为工科实验力学教学做了有益的探索。

含故障受油器机组转子-转轮系统振动特性分析

灯泡贯流式机组实际运行中,转子-转轮系统受各外激励影响易形成旋转部件与固定部件间的碰摩故障,极大影响机组的安全稳定运行。针对含故障受油器部件的灯泡贯流式机组轴系碰摩问题,构建转子处复合偏心影响下不平衡磁拉力模型,建立了多振源激励下含故障受油器灯泡贯流式机组受油器-转子-转轮耦合振动模型,对比分析了有无故障受油器系统弯扭耦合状态下振动特性的差异,对系统在励磁电流、转子质量偏心及转轮质量偏心变化时各自的非线性振动特性进行了讨论。结果表明:故障受油器的出现加大了转子、转轮非稳态运动范围,使系统产生不利振动进而引发故障;同运行工况及参数状态下的转子相较转轮表现出更大振幅强度,需引起重视。扭转自由度的加入加剧了转子振幅,增加了碰摩故障发生概率。此外,当转轮质量偏心发展到一定程度后,叶片处存在的不确定随机水力将使系统发生失稳现象。研究结果可为灯泡贯流式机组安全运行及稳定性分析提供有益借鉴。

受油器故障激励下转子—轴承—转轮系统稳定性研究

灯泡贯流式机组旋转部件与固定部件碰摩故障将极大影响机组的安全稳定运行。针对含故障受油器部件的灯泡贯流式机组轴系碰摩系统,建立了多振源激励下含故障受油器灯泡贯流式机组转子—转轮弯扭耦合振动模型及其运动微分方程。利用Floquet理论讨论了系统周期解稳定性。结果表明,故障受油器的出现从加剧系统失稳可能及更迭稳态与非稳态频次切换层面显著改变了系统动态特性,加剧了系统非稳态运行范围,需引起足够重视。研究结果可为灯泡贯流式机组安全运行及稳定性分析提供借鉴。

索承式人行悬索桥自振特性及弯扭耦合特征分析

为了研究索承式人行桥的自振特性及其弯扭耦合特征,以某实际工程为例,采用Midas软件建立了有限元模型,将各振型中横弯分量和扭转分量贡献度的比值定义为弯扭耦合系数β,分析了索承式人行桥振型模态的弯扭耦合特征,以及主缆矢跨比λc、抗风缆矢跨比λw和抗风缆倾角α对自振特性及弯扭耦合特征的影响。研究发现,竖弯振动不存在与其他振型分量的耦合,而横弯和扭转振型存在耦合,且随振动阶数增加,弯扭耦合系数β减小,振型由横弯为主逐渐过渡到以扭转为主;随主缆矢跨比λc减小,弯扭耦合振型频率增大,β减小;随抗风缆矢跨比λw的减小,以横弯为主的弯扭振型(β≥1)频率下降,以扭转为主的则略有增大;增大抗风缆倾角α会使桥梁整体横向刚度下降,但抗扭刚度增加。

不同工况下螺栓连接梁有限元仿真分析与强度校核研究

为研究螺栓连接梁在不同危险工况下的结构强度及安全性,采用了仿真和理论相结合的方法,对受偏心载荷的螺栓连接梁危险工况进行综合分析。并针对仿真结果中应力较大的螺栓部分采用了建立子模型的方法进一步仿真分析,以确保横梁结构安全可靠。使用了力线平移定理对横梁所受载荷进行简化,并对横梁进行强度校核。结果表明:横梁在危险工况下各结构均满足强度要求,且不同危险工况对横梁结构的变形及应力影响较小;螺栓预紧力是导致螺栓结构产生较大应力的原因,而外载荷对螺栓结构的影响较小;在忽略螺栓结构对横梁结构的影响后,横梁强度校核结果与仿真结果近似相同,且均满足材料的强度要求。综上所述,通过仿真分析及理论强度校核均可证明该螺栓连接梁在各工况下均能满足强度需求。同时研究成果也为后续研究该类型横梁提供一定的仿真及理论依据。

多旋翼无人机的振动实验和仿真分析

对多旋翼无人机的结构振动问题进行了设计研究。在小型多旋翼无人机上,激光振动仪验证了加速度传感器测量振动的可靠性,发现圆形碳纤维臂具有较强的阻尼能力,z轴方向振动最强。实验表明,多旋翼无人机臂的主要振动为300 Hz以下的低频振动,主要产生扭转和弯曲模态。该研究还提出了一种抑制多旋翼无人机振动的改进策略。

大开口船型波浪弯/扭矩间接监测方法

为准确得到大开口船型波浪弯/扭矩监测结果,本文基于船体扭转基本理论研究了大开口船型波浪弯/扭矩间接监测方法。根据船中横剖面弯/扭矩与结构纵向应变之间的关系,提出了一种联合双剖面监测法,并用数值方法建立了波浪弯/扭矩间接监测的数学模型,通过多次数值模拟验证了所识别波浪弯/扭矩的准确性。在联合双剖面监测法中,同时监测船体结构2个邻近的横剖面,分别计算两横剖面的双力矩、弯矩和自由扭转扭矩,得到中间剖面的波浪弯/扭矩。数值模拟结果表明:联合双剖面监测法能够准确地反求出波浪弯/扭矩,特别是在波高较大的情况下反求精度更高。