含有非线性摩擦阻尼的失谐叶盘系统受迫响应研究

基于谐波平衡法,提出一种可用于分析含有非线性摩擦阻尼叶盘振动响应的多谐波法,对含有非线性干摩擦阻尼的失谐叶盘系统的受迫响应进行仿真计算.研究失谐叶盘系统在不同的耦合强度、失谐程度、粘性阻尼系数、干摩擦强度等系统参数影响下的受迫响应特性.同时对叶片的非线性干摩擦阻尼的散乱失谐和刚度失谐的耦合影响进行研究,总结含有非线性干摩擦阻尼的失谐叶盘系统的受迫响应规律.     

由涂层引入失谐的整体叶盘集中参数建模与振动特性分析

为了研究涂层参数失谐对整体叶盘振动特性的影响,创建含涂层的两自由度扇区集中参数模型,引入四种常见的主动失谐形式,详细分析了涂层质量、刚度、阻尼等参数失谐对系统振动特性的影响规律。创建含涂层参数失谐的整体叶盘集中参数模型,并由涂层引入常用的谐波、交替、线性及伪谐波四种形式的主动失谐。建立失谐后整体叶盘结构的运动方程,确定求解其固有频率及振动响应的方法,并给出了评价失谐程度的量化参数。通过实例分析了由涂层引入主动失谐后叶盘结构的振动特性。研究表明,叶盘系统发生由涂层引起的主动失谐后,系统最大响应随失谐量的增大呈现先上升后下降的趋势,有“阈值”现象。     

失谐叶盘系统受迫振动响应摄动法比较研究

基于质量-弹簧模型,研究了在不同系统参数下,经典摄动法、修正摄动法和自适应摄动法求解失谐叶盘系统受迫响应的应用特点。通过对3种摄动法计算结果的比较分析,确定了3种摄动法对不同失谐强度、耦合强度、粘性阻尼比等参数的适用条件和应用特点。因此,本文的结论对于应用不同摄动法在求解失谐叶盘系统受迫响应问题时具有指导意义。     

含预紧力失谐的叶盘结构振动局部化问题研究

在工程实践中发现叶盘结构存在一种新的失谐——预紧力失谐,基于一个含预紧力的叶盘结构连续参数模型,对比分析了预紧力失谐和刚度失谐下叶盘结构的振动特性,揭示了预紧力失谐对叶盘结构振动响应局部化的影响规律.研究发现,预紧力失谐不会导致模态局部化,但能导致叶盘结构出现振动响应局部化,在相同失谐强度下,预紧力失谐所导致的叶盘结构振动响应局部化程度与固有参数失谐相当.因此,预紧力失谐不能通过传统的检测手段如模态实验来发现.这些结果一方面完善了失谐叶盘结构的研究内容,一方面为叶盘结构的设计和制造提供了理论指导.     

不同冠间配合叶盘系统振动响应局部化问题研究

建立了考虑冠间配合形式的自带冠叶盘系统连续参数模型,对比分析了谐调和随机失谐两种状态下冠间紧配合和松配合叶盘系统振动局部化特征,揭示了不同冠间配合叶盘系统的振动规律。研究发现,谐调状态下,冠间松配合自带冠叶盘系统不会出现振动局部化现象,而冠顶摩擦导致冠间紧配合自带冠叶盘系统亚谐振动的发生,并且出现了较弱的振动局部化现象;叶片随机失谐状态下,冠间松配合叶盘系统将不再具备严格的单周期振动特征,冠间紧配合叶盘系统不再出现严格的亚谐振动,振动响应局部化的复杂性增加;与紧配合自带冠叶盘系统相比,松配合自带冠叶盘系统的振动响应局部化对随机失谐更敏感。     

基于谐振耦合的电能无线传输系统设计

距离和效率是电能无线传输技术发展的瓶颈,电磁场的谐振耦合技术能够有效的解决这一问题.从谐振耦合的收发线圈电路模型出发,对谐振耦合电能无线传输系统进行了深入研究,发现失谐是系统效率不高的主要原因.进而,设计了一个功率为30W,频率为1 MHz的小功率电能无线传输系统,并且通过对发射线圈的电流检测实现发射源对发射线圈频率的...     

面向机电耦合振动抑制的电主轴系统匹配特性研究

电主轴系统存在复杂的机电耦合作用,若系统机电参数匹配不当,将引起机电耦合振动,导致系统稳定性下降,工件加工表面质量降低。利用将电动机与主轴系统机械特性分离的动力学分析方法难以对系统的机电耦合振动进行有效的分析评价,也难以实现系统机电特性的优化匹配。提出基于机电耦合动力学模型的电主轴系统匹配特性分析方法,利用所提出的方法研究磨削电主轴系统逆变器工作参数、电主轴电动机电磁设计参数和砂轮机械参数对脉动转矩及定子电流频谱特性的影响,并在凸轮轴磨床上进行试验。揭示系统机电耦合振动的物理机制,提出通过优化逆变器工作参数、电主轴电动机电磁设计参数和砂轮参数抑制机电耦合振动的方法。经理论与试验分析证实,通过优化逆变器工作参数可有效抑制机电耦合振动,提高系统匹配特性和磨削质量,从而证实所提出的基于机电耦合动力学模型的电主轴系统匹配特性分析方法是有效可行的。     

IHB方法在含强非线性摩擦力失谐叶盘系统响应特性研究中的应用

针对目前谐波平衡法分析高维非线性动力学系统存在求解困难等问题,文中基于增量谐波平衡法(incremental harmonic balance method,IHB法)能将高维非线性方程组转化为线性方程组进行求解的优点,将其推广应用到含强非线性干摩擦力失谐叶盘系统振动响应特性研究中,成功避开谐波平衡法必须求解非线性方程组的问题.研究表明,推广后的IHB法能较好地解决含强非线性摩擦力失谐叶盘系统响应求解的诸多问题,并且运用该方法成功发现含非线性摩擦阻尼的谐调叶盘系统也可能产生振动能量局部化现象.     

含整圈拉筋叶盘系统模态局部化问题研究

建立了含整圈拉筋叶盘系统有限元实体模型,对比分析了有无拉筋叶盘系统的固有特性和模态振型,揭示了整圈拉筋对叶盘系统固有频率及模态局部化的影响规律。研究表明,由于整圈拉筋的存在增大了叶片间的耦合强度,使得叶盘系统固有频率增大,系统的模态分布不再高度密集,且弱化了离心载荷对叶盘系统的应力刚化效应;整圈拉筋的存在导致叶盘系统频率转向特性曲线的相对频率间隙增大,降低了叶盘系统对失谐的敏感度,使得叶盘系统的模态局部化程度减小。     

离心压缩机叶轮材料属性失谐对其振动局部化的影响研究

为研究离心压缩机叶轮材料属性失谐对其振动局部化的影响,将叶轮材料的3个代表属性杨氏模量、泊松比和密度,使用正态分布函数生成随机序列.通过有限元方法,将其赋值于叶轮单元体,获得正态失谐分布.进一步,利用ANSYS软件,对叶轮由于材料属性失谐导致的振动模态局部化现象特别是固有频率的影响进行数值分析.研究发现,随着失谐幅值的...     

失谐对耦合摆链结构振动特性的影响

研究失谐对耦合摆链结构失谐后振动特性的影响。建立无量纲化的耦合摆链系统运动方程,采用振型分解法求解其动力响应。以5自由度和7自由度耦合摆链结构为例,分析耦合摆链结构的振动模态及在engine order形式的激振力下的动力响应。根据得到的结果,对系统由于失谐而出现的模态局部化、振动局部化、峰值分裂等现象及它们的联系进行深入讨论。     

Vibration localization of a mistuned rotating multi-packet blade system undergoing external cyclic harmonic force

A multi-packet blade system consists of several blades which are attached to a disk and connected through shrouds. The blades of a multi-packet blade system are usually assumed to be identical. However, there always exists small, random mistuning among the blades due to manufacturing tolerance, in-operation wear and environmental changes. Such mistuning may cause significant increase in the forced vibration responses of some blades in the multi-packet blade system. Critical fatigue problems often occur in mistuned systems since the forced vibration response of a mistuned system is often significantly larger than that of a tuned system. Therefore, it is very important to predict the maximum blade response. In this study, blades are idealized as cantilever beams and the flexibilities of the disk and shrouds are idealized as discrete springs. Equations of motion are derived using the hybrid deformation variable method. To realize vibration localization with random mistuning, transient analysis is carried out for a multi-packet blade system excited by multiple nozzle jet forces.     

A reduced order model based on sector mistuning for the dynamic analysis of mistuned bladed disks

In this paper, a pre-existing reduction technique suitable for the analysis of mistuned bladed disk dynamics, the Component Mode Mistuning technique (CMM), originally developed exclusively for the use of blade frequency mistuning pattern, is extended in order to allow for the introduction of a sector frequency mistuning pattern. If either mistuning is not confined to the blades (i.e. blades-to-disk interface mistuning), or the blades can not be removed from the bladed disk (i.e. integral bladed disks), sector mistuning rather than blade mistuning is a more suitable choice to perturb the tuned system. As a consequence, the extension of the original technique is referred as Integral Mode Mistuning (IMM). After a theory review of the original technique, the modifications leading to the IMM are described. Finally, the proposed IMM technique is validated in terms of both modal parameters estimation and forced response calculation, by means of a dummy bladed disk developed at Politecnico di Torino.     

Response of large mistuned bladed disk assembly subjected to random excitations

In this study, the effects of large geometric mistuning on blade response are investigated considering the change of mistuning properties and excitation characteristics. The response variations because of large mistuning are negligible under white noise excitations and are highly significant under narrow band excitations. For the different excitation correlations, the responses are represented using non-dimensional variables in order for the results to be comparable to each other. It is shown that the ratio of the modal frequency between the tuned and large mistuned blades determines the propagation direction of the natural frequencies of the mistuned system, therefore, the responses of large mistuned blades depend primarily on their level of modal frequency.     

考虑叶片刚度随机错频时叶盘系统的强迫响应研究

考虑叶片刚度有一个微小的变化量,在变化量服从某一概率分布的情况下,研究了错频叶盘系统在给定激振力下的动态响应.采用Monte Carlo模拟方法研究了错频叶盘结构响应的鲁棒性.     

Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 2: Tolerance design

The mistuning pattern on a bladed disc is controlled in Part 2 of the two-part article either by (i) imposing a small maximum allowable mistune according to the small mistuning approach or (ii) incorporating non-identical blades of specific patterns, known as the intentional mistuning approach. These approaches resemble the tolerance design stage of the Taguchi method of robust design. The first-order maximum amplification factor sensitivity in a single-degree-of-freedom (DOF)-per-sector system is derived to support a new definition of the interblade coupling ratio and to illustrate the dependence of the maximum amplification factor sensitivity on design parameters of a bladed disc. It is found that the variability of the forced vibration response levels in flexible bladed discs can be reduced by controlling the degree of mistune within realistic levels. The potential of a “linear” mistuning pattern to become an effective intentional mistuning pattern is evaluated by observing the amplification factors of bladed discs with combined intentional mistuning and additional random mistuning. A tool based on the importance sampling method is used to reduce the computational effort in determining the magnitude of intentional mistuning. Guidelines of designing bladed discs with a lower variability of forced vibration response levels are given according to the findings in casting the blade mistuning problem as a robust design problem.     

BLADE-TIP TIMING MEASUREMENT OF SYNCHRONOUS VIBRATIONS OF ROTATING BLADED ASSEMBLIES

Blade-tip timing (BTT) is a promising method for the detection, measurement and analysis of blade vibrations in rotating bladed assemblies. However, the intricacies of the method when applied to real rotating structures undergoing synchronous (Engine Ordered) vibrations are not yet fully understood. In this paper, a mathematical model is developed to simulate data from typical BTT tests of rotating assemblies. The simulator is then used in order to provide a qualitative analysis of several phenomena that can be associated with the synchronous vibrations of rotating assemblies, including mistuning, coupling, excitation at multiple Engine Orders and simultaneous synchronous and asynchronous responses. It is concluded that none of these phenomena on its own will render the identification of the frequency and amplitude of blade vibrations impossible. However, there is no single BTT data analysis method that is able to deal with all of these phenomena.