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.     

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。     

随机失谐叶盘系统受迫振动响应的统计特性研究

研究随机失谐对于具有循环对称周期结构的叶盘系统动力特性的影响.采用质量-弹簧组合系统模型和Monte Carlo方法,系统地研究失谐强度、耦合强度、阻尼、激振力阶次和叶片数等参数对于系统受迫振动特性的影响规律.计算结果表明,弱耦合系统比强耦合系统对失谐更加敏感,耦合强度的增加不一定导致系统振幅的降低.     

含呼吸式裂纹的失谐叶盘系统响应特性研究

含张开式裂纹的叶盘系统无法准确地反映其受迫振动响应特性,为此,基于细梁理论和线弹性断裂力学理论建立了含呼吸式裂纹的失谐叶盘系统数学模型,对比分析了呼吸式裂纹、张开式裂纹对失谐叶盘系统固有特性和振动响应的影响,揭示了呼吸式裂纹对叶盘系统振动响应局部化的影响规律。研究表明:呼吸式裂纹使得振动响应呈现复杂的非线性特征;此外,与张开式裂纹模型相比,基于呼吸式裂纹模型的叶盘系统对失谐更敏感。      

干摩擦非线性减振器构成的迟滞振动系统的响应计算

运用非线性振动理论中的谐波平衡法,研究了一类无记忆恢复力中含有位移三次非线性的干摩擦非线性拳振器构成的迟滞振动系统的响应计算问题,揭示出由于无记忆恢复力中三次非线性的存在,系统的幅频曲线将出现弯曲、跳跃等典型的非线性现象,对优化设计等深入研究工作具有重要指导意义。     

航空发动机失谐叶盘耦合共振研究进展

随着航空发动机高推重比和低耗油率要求的不断提高,轮盘结构愈加轻薄,叶盘耦合共振现象越加明显。本文从谐调叶盘结构耦合共振研究现状出发,重点阐述了失谐叶盘结构振动模态局部化和振动响应局部化的国内外研究现状,并对叶盘结构失谐研究的一些热点问题展开讨论,提出了研究的重难点问题,为后续开展航空发动机失谐叶盘结构耦合共振研究提供了必要的指导。     

柔性基础上迟滞干摩擦隔振系统的简化分析

工程实际中,柔性基础上非线性隔振系统广泛存在,而振动特性的分析却严重制约着其应用与研究。基于柔性基础上含有三次非线性刚度的迟滞干摩擦隔振系统,首先采用振型分离的方法建立了系统的动力学方程,并结合增量谐波平衡法求解了系统在发生任意阶主振动情况下的响应;随后,以基频谐波项为基础,推得了系统力传递率的计算公式,并根据公式定性分析了隔振器各参数对系统力传递率的影响。发现,适当减小刚度系数,增大阻尼系数,增大静摩擦极限均可有效降低系统的力传递率。研究为该类系统的工程实际应用提供了可靠借鉴。     

金属橡胶材料干摩擦阻尼的产生机理及力学模型

金属橡胶材料干摩擦阻尼、非线性刚度的产生机理是一个较为复杂的问题,其内部存在大量的干摩擦接触,通过螺旋型金属丝相互摩擦接触来损耗振动能量。干摩擦阻尼与物体表面的微观结构密切相关,从微观角度分析了金属橡胶材料干摩擦阻尼的产生机理,欲准确地揭示干摩擦阻尼的减振规律,还必须正确的提出描述干摩擦规律的数学模型。由于金属橡胶客观存在不光滑的非线性泛函本构关系,使得含有干摩擦环节的金属橡胶结构的响应计算问题非常困难。介绍了关于两固体接触表面间的干摩擦问题的四种数学模型,即Sgn摩擦模型、滞迟模型、动态系统中干摩擦力的数值计算模型、三次非线性粘性阻尼双线性滞迟模型,这四种模型为后人在该领域的继续研究奠定了坚实的理论基础。     

基于叶片贡献度的叶盘系统频率转向特性

为了分析频率转向对失谐叶盘系统振动的影响,针对某型航空发动机压气机叶盘系统,采用子结构模态综合法建立了有限元缩减模型,从应变能角度分析了叶盘系统的频率转向特性,计算了失谐叶盘系统模态振动贡献度因子和局部化因子。通过不同频率转向间隙对应的失谐叶盘系统受迫振动响应贡献度因子与局部化因子,分析了频率转向间隙和叶片贡献度因子对失谐叶盘系统局部化的影响。结果表明,频率转向对失谐叶盘系统振动局部化影响显著,在频率转向区域,失谐叶盘系统的振动局部化程度较高;随着频率转向间隙变化,叶片应变能对失谐叶盘系统局部化的贡献度呈现一定的规律性。     

基于LuGre摩擦模型的简支板的振动动态响应分析

三点铰接一点简支的矩形板在支撑边界处是存在非线性摩擦力的,干摩擦阻尼力耗散系统一部分能量,减小板的振动响应。为了分析非线性系统在边界支撑处干摩擦阻尼对系统的振动振幅的影响,建立板在激振力的作用下弯曲变形的非线性动力学模型以及板边界处干摩擦阻尼的摩擦模型,借助于Galerkin法将系统转化非线性常微分方程,通过辨识不同的摩擦参数,数值仿真分析不同情况下板的横向振动的振幅变化。     

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.     

Pattern optimization of intentional blade mistuning for the reduction of the forced response using genetic algorithm

This paper investigates how intentional mistuning of bladed disks reduces their sensitivity to unintentional random mistuning. The class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say). A two-step procedure is then described to optimize the arrangement of these blades around the disk to reduce the effects of unintentional random mistuning. First, a pure optimization effort is undertaken to obtain the pattern (s) of the A and B blades that yields small/the smallest value of the largest amplitude of response to a given excitation in the absence of unintentional random mistuning using Genetic Algorithm. Then, in the second step, a qualitative/quantitative estimate of the sensitivity for the optimized intentionally mistuned bladed disks with respect to unintentional random mistuning is performed by analyzing their amplification factor, probability density function and passband/stopband structures. Examples of application with simple bladed disk models demonstrate the significant benefits of using this class of intentionally mistuned disks.     

叶盘结构频率转向特征及失谐敏感性实验研究

搭建了用于失谐叶盘结构固有特性及失谐敏感性研究的实验平台,对谐调叶盘结构的频率转向现象进行了实验研究,验证了以往理论分析和有限元仿真中发现的频率转向特征和模态振型转换现象;通过在叶尖粘贴不同的质量块,模拟了三种典型的叶片失谐形式,实验研究了失谐叶盘结构的模态局部化问题;针对同一叶片失谐形式下不同的模态密度区域,实验研究了模态密度对失谐敏感性的影响规律。实验结果与有限元实验仿真结果吻合较好。     

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。     

Study on localization influences of frequency veering on vibration of mistuned bladed disk

Reduced-order models of the bladed disk of the aero-engine compressor were established by adopting Prestressed component mode synthesis (PCMS) method. The frequency veering characteristics of the tuned bladed disk were analyzed. From the aspect of the strain energy, the forced vibration response of the mistuned bladed disk was analyzed, along with calculation of the contribution degree factors, the localization factors and frequency veering distances, finding the influences of the frequency veering distance, the contribution degree factors and the localization. The results show that frequency veering has significant influence on vibration localization of the mistuned bladed disk; in the region of frequency veering, the degree of vibration localization of the mistuned bladed disk is relatively high; along with the changes of the frequency veering distance, the contribution degree of the strain energy of the blades of localization of the mistuned bladed disk shows the certainty of regularity.     

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.     

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.