非周期压电阻尼对失谐叶盘结构振动局部化抑制机理

将非周期压电阻尼技术引入失谐叶盘结构形成机电耦合系统,推导了机电耦合系统的动力学方程,从理论上分析了非周期压电系统对失谐叶盘结构振动局部化的抑制效果。构造了两种非周期压电系统模型:非周期压电分支模型和非周期压电网络模型。研究结果表明:与双周期压电网络系统相比,按照能量集中的程度不同连接而成的非周期压电系统具有更好的振动局部化抑制效果。在非周期压电网络系统的构造中,电阻不再是关键因素,而主要是通过电路形式改变整个叶盘结构中的能量分配情况,电感作为储能元件在其中至关重要。通过合理设计非周期压电网络电路形式,可以得到比非周期压电分支系统和双周期压电网络系统更好的振动局部化抑制效果。      

双周期分布式压电分支阻尼对失谐叶盘振动抑制作用分析

将压电分支电路引入失谐叶盘结构，形成机电耦合系统，给出了机电耦合系统动力学方程的推导过程，并从理论上研究了压电分支阻尼对失谐叶盘结构响应放大的抑制效果.通过构造双周期分布式压电分支电路，研究了双周期分布式压电分支阻尼对失谐叶盘结构的振动抑制效果，并与单周期压电分支电路进行了对比，对比结果显示压电分支阻尼（包括单周期压电分支阻尼以及双周期分布式压电分支阻尼）均能有效降低随机失谐叶盘结构的响应放大，其中双周期机电耦合系统响应放大因子统计分析结果小于1的概率在99.7%以上，基本消除了失谐叶盘结构的响应放大现象.通过合理地设计系统的双周期模式，能够获得比单周期更好的失谐响应放大抑制效果.此外，压电分支阻尼使得随机失谐叶盘结构的失谐“阈值”现象消失，提高了叶盘结构的失谐鲁棒性.      

双周期压电网络用于叶盘结构振动抑制的研究

以整体叶盘振动抑制为目的,利用压电材料在叶盘结构不同扇区形成异周期系统,并将与压电材料连接的外部电路并联或串联形成不同形式的网络,建立该机电耦合系统的动力学方程,分析其对叶盘结构动力学特性的影响效果。研究发现,双周期压电网络对叶盘结构的频率影响很小,在本文所研究的叶盘结构模型的参数变化范围内仅对频率转向区有轻微的影响,变化最大只有2%;但是双周期压电网络会对叶盘结构的模态振型产生很大的影响,会使原各阶单一节径振型变为多节径振型,节径种类数跟双周期数有关;压电网络还会把机械位移转化为电荷位移;同时压电网络中电阻元件的引入提高了系统的模态阻尼比。这些都会对叶盘结构的振动响应起到很好的抑制效果。最后,采用修正的模态置信因子MMAC对双周期压电网络系统进行了振动抑制特性的评估,结果表明,通过对结构系统双周期数的设计能有效提高振动抑制效果。     

用于叶片减振的压电材料分布拓扑优化

提出一种可用于实际叶盘结构的压电分支阻尼器拓扑优化方法,可以给出总质量受约束的压电材料在叶片上的最佳分布,达到尽可能大的模态阻尼比。通过理论推导说明:压电阻尼器所产生的模态阻尼比仅取决于模态机电耦合系数,且该系数只与压电材料的几何形状以及模态应力场有关。进一步结合压电本构关系,基于应力分量的线性加权给出了有限的压电材料在叶片上铺设位置“优先级”的判断指标。给出了基于叶盘结构有限元模型的压电材料拓扑优化方法,通过替换单元类型和材料参数的方式对压电材料进行布置,并给出了多模态族优化、极化方向设置、电极铺设等问题的解决方案。在一个接近真实的叶盘模型上应用了此优化方法。结果表明,仅使用质量占叶片质量10%的压电材料,就可以为多个模态提供约12%的阻尼比。      

具有干摩擦散乱失谐的叶盘受迫响应特性

阻尼件是叶盘结构中起减振作用的主要部件,而阻尼件的干摩擦散乱失谐会影响其在叶盘振动中的减振作用。本文利用谐波平衡法与快速傅立叶变换技术,对具有非线性干摩擦力的叶盘受迫响应进行了数学建模,仿真分析了叶盘系统在各种耦合、粘性阻尼比、干摩擦强度、干摩擦散乱失谐程度等参数影响下的受迫响应规律。研究结果显示,叶盘系统在弱耦合和粘性阻尼比较大的情况下,干摩擦散乱失谐会导致叶盘共振幅值显著增大。      

一种摩擦阻尼器在整体叶盘结构的应用

介绍了一种应用于整体叶盘结构的摩擦阻尼器，即在轮缘下方加工销孔，安装阻尼销.工作时，由于离心载荷的作用，阻尼销与轮缘相互摩擦，从而消耗振动能量.这种阻尼器被应用于两台发动机的涡轮整体叶盘减振方案中，试验结果显示:其减振效率差异较大.数值模拟分析证明，这种阻尼器的减振效率和振动能量在叶-盘间的传递有关.对于叶-盘强耦合振型，这种阻尼器可以获取较高的减振效率，叶片振动应力水平下降了约70%；但对于叶-盘弱耦合振型，叶片振动应力幅值没有明显下降趋势.      

具有半主动压电阻尼的叶盘结构动力学特性研究

针对航空发动机整体叶盘结构的失谐响应放大问题,在叶盘结构中引入半主动压电阻尼技术,并利用基于非线性模态分析的非线性系统频域响应快速算法-非线性部件模态综合(NCMS)法对具有基于负电容的同步开关阻尼(SSDNC)的叶盘结构动力学特性进行理论探究。分析结果表明NCMS法相比于Newmark法具有很高的计算效率,并能保证较高计算精度;SSDNC能够同时对叶盘结构的多阶振动模态都产生较好的抑制效果,并对多谐波激励下叶盘结构的所有振动峰值都产生较好的抑制效果(对于本文所用模型,振动峰值下降可达到73%);统计分析表明,SSDNC的振动抑制效果对叶盘结构机械失谐以及电路参数失谐均不敏感。     

压电网络对叶盘结构气动阻尼的影响

首先通过引入气动影响系数,建立了振动相关气动力与系统振动位移成比例的线性模型。基于此导出了叶盘结构气弹耦合的线性振动方程。接着在叶盘结构中引入压电网络,建立了流 机 电耦合动力学方程；并采用集总参数等效模型研究了压电网络对叶盘结构气动阻尼的影响,对流 机 电耦合系统的特征值问题进行求解,获得了可作为系统气弹稳定性判据的模态气动阻尼比。研究表明,压电网络可以有效改善叶盘结构主要振动形式——节径型振动的气弹稳定性；通过对压电网络中电学参数进行优化设计,可以在较宽范围内提高叶盘结构的颤振边界；压电网络对弯曲振动模态气动阻尼的改善效果优于弯扭耦合振动模态。      

复杂时变激励下失谐叶盘瞬态强迫响应分析

提出一种高效的失谐叶盘瞬态强迫响应分析方法,不同于传统的数值积分方法,该方法推导出瞬态强迫响应的解析表达式,能更为高效地预测失谐叶盘的瞬态强迫响应。首先,对叶盘的高保真有限元模型进行减缩建模,在精确地描述叶盘结构的动力学特性的前提下,极大的减少了模型的自由度数目。其次,模拟加速旋转的涡轮叶盘经过复杂流场时叶片表面上的气动载荷,并建立叶盘固有频率和振型随转速变化的数学函数;通过共振分析确定叶盘共振的转速区间并分析引起共振的激励阶次成分。最后,计算了不同旋转加速度和阻尼下叶盘的瞬态强迫响应,并对叶盘的失谐幅值放大因子进行研究。应用本办法对某86个叶片的涡轮叶盘进行了数值分析,结果表明,相同阻尼水平下,叶盘的瞬态强迫响应幅值随旋转加速度增加而降低,失谐幅值放大因子在瞬态条件下大于稳态条件下,最高可达30%。     

涂敷硬涂层的失谐整体叶盘减缩建模及振动分析

为了提高整体叶盘的服役寿命,提出一种对叶片涂敷硬涂层的减振方法。同时,针对失谐叶盘-硬涂层复合结构的运算规模庞大的难题,提出了一种双重减缩建模方法。利用一种改进的混合界面子结构(HISCMS)法对复合结构进行第一重的自由度减缩。利用一种模态密集判别准则与经典模态减缩(SNM)法的思想对综合后的模型进行第二重的模态减缩。选取了对叶片双面涂敷NiCoCrAlY+YSZ(yttria-stabilized zirconia,氧化锆) 硬涂层的失谐叶盘进行仿真分析及试验测试,以探究失谐叶盘的振动情况以及硬涂层厚度对失谐叶盘的影响。结果表明:双重减缩建模方法能够在保证计算精度的前提下提高25.86%~42.05%的计算效率;而且硬涂层表现出较强的阻尼作用,能够在共振区显著抑制失谐叶盘的共振响应。      

Research on vibration suppression of a mistuned blisk by a piezoelectric network

The work aims to provide a further investigation of the dynamic characteristics of an integral bladed disk(also called ‘blisk') with a Parallel Piezoelectric Network(PPN). The PPN is constructed by parallelly interconnecting the piezoelectric patches distributed in the blisk. Two kinds of PPN are considered, namely mono-periodic PPN and bi-periodic PPN. The former has a piezoelectric patch in each sector, and the later has one patch every few sectors. The vibration suppression performance of both kinds of PPN has been studied through modal analysis, forced response analysis, and statistical analysis. The research results turn out that the PPN will only affect mechanical frequencies near the electrical frequency clusters slightly, and the bi-periodic PPN will make the nodal diameter spectrum of the modes more complex, but the amplitude corresponding to the new nodal diameter component is much smaller than that of the nodal diameter component corresponding to the mono-periodic system. The mechanical coupling between the blades and the disk plays an important role in the damping effect of the PPN, and it should be paid attention to in applications. The mono-periodic PPN can effectively suppress the amplitude magnification of the forced response induced by the mistuning of the blisk; meanwhile, it can mitigate the vibration localization of the mistuned electromechanical system. If piezoelectric patches are set only in part of the sectors, the bi-periodic PPN still has a vibration suppression ability, but the effect is related to the number and spatial distribution of the piezoelectric patches.     

Mechanism of interconnected synchronized switch damping for vibration control of blades

The Synchronized Switch Damping (SSD) is regarded as a promising alternative to mitigate the vibration of thin-walled structures in aero-engines, especially for blades or bladed disks. The common manner is to shunt the switch circuit independently to a single piezoelectric structure. This paper is aimed at exploring a novel way of using the SSD, i.e., the SSD is interconnected between two piezoelectric structures or substructures. The damping mechanism, performance, and effective range of the interconnected SSD are studied numerically and experimentally. First, based on a dual cantilever beam finite element model, the time domain and frequency domain modeling and solving methods of the interconnected SSD are deduced and validated. Then, the influence of the amplitude and phase relationship on the damping effect of the interconnected SSD is numerically studied and compared with the shunted SSD. A self-sensing SSD control board is developed, and experimental studies are carried out. The results show that the interconnected SSD establishes an additional energy channel between the corresponding piezoelectric structures. When the amplitudes of the two cantilever beams are different, the interconnected SSD balances the vibration level of each beam. When the amplitudes of the two cantilever beams are the same, if the appropriate interconnection manner is selected according to the phase, the resonance peak can be reduced by more than 30%. When the vibration is in-phase/out-of-phase, the damping generated by the interconnected SSD in a cross/parallel manner is even more significant than the shunted SSD. Furthermore, this novel connection scheme reduces the number of SSD circuits in half. Finally, for engineering applications, we implement the proposed damping technology to the finite element model of a typical dummy bladed disk. A piezoelectric damping ratio of 13.7% is achieved when the amount of piezo material is only 10% of blade mass. Compared with traditional friction dampers, the major advancements of the interconnected SSD are: (A) it can reduce the vibration level of blades without friction interface; (B) the space constraint is overcome, i.e., the vibration energy is not necessarily dissipated independently in one sector or through physically adjacent blades, and instead, the dissipation and transfer of vibrational energy can be realized between any blade pair. If a specific gating circuit is adopted to adjust the interconnection manner of the SSD, vibration mitigation under variable working conditions with different engine orders will be expected; (C) designers do not need to worry about the annoying nonlinearities related to working conditions anymore.     

接触摩擦力对叶片减振能力的影响

在频域内利用谐波平衡法,分别通过理论分析和有限元分析方法对某涡轮叶片缘板-阻尼结构进行了减振效果分析,并就接触摩擦力对叶片减振能力的影响进行了进一步探索.研究发现带阻尼装置叶片由于阻尼块附加质量作用,对叶片有明显的避振作用,并也起到了一定的减振作用,但对叶片振动响应耗能影响最大的是叶片缘板-阻尼装置接触面的非线性摩擦力,且摩擦系数较小时叶片减振效果对其变化更敏感一些.另外从分析方法探索中发现,含接触等非线性问题的结构,忽略接触特性进行振动响应分析具有较大的偏差性.这些研究结论和研究方法可为阻尼结构的设计提供一定的参考.     

压电作动器用于振动主动控制技术的研究

 从理论和实验两方面分析了利用压电作动器进行柔性结构振动主动控制的机理，从能量的角度对施加控制时悬臂梁自由衰减振动的阻尼比进行了理论计算，得出了主动阻尼比与反馈增益之间的关系。建立相应的实验系统，对上述关系式进行了实验验证。     

Nonlinear modal electromechanical coupling factor for piezoelectric structures containing nonlinearities

Within the linear framework, the Modal Electromechanical Coupling Factor (MEMCF) is an important indicator to quantify the dynamic conversion of mechanical energy and electrical energy of piezoelectric structures. It is also an important tool to guide the piezoelectric damping design of linear structures. Advanced aircraft often fly in maneuvers, and the variable working conditions induce drastic changes in the load level on structures. Geometric and contact nonlinearities of thin-walled structures and joint structures are often activated. To achieve a good vibration reduction effect covering all working conditions, one cannot directly use linear electromechanical coupling theory to instruct the piezoelectric damping design for nonlinear structures. Therefore, this paper defines the Nonlinear Modal Electromechanical Coupling Factor (NMEMCF) and proposes the corresponding numerical method for the first time to quantitatively evaluate the electromechanical coupling capability of nonlinear piezoelectric structures. Three candidate definitions of the NMEMCF are given, including two frequency definitions and one energy definition. The energy definition is the most promising one. It is not only applicable to both conservative and dissipative nonlinear structures but also compatible with the linear MEMCF. In addition, based on the energy formula, the NMEMCF can be obtained by only performing one nonlinear modal analysis in the open-circuit state. The analytical findings and the numerical tool are validated against two piezoelectric structures with different types of nonlinearities. A strong correlation among the NMEMCF, geometric parameters, and energy dissipation is observed. The results confirm that the proposed NMEMCF captures the physics of the electromechanical coupling phenomenon associated with nonlinear piezoelectric structures and can be used as an essential design indicator of piezoelectric damping, especially for variable working conditions.     

双压电振子异步振动主动调制湍流边界层流向涡减阻

以热线敏感丝为感受器、单片机(MCU)为控制器、双压电振子为动作器构成闭环控制回路,实现闭环主动控制湍流边界层相干结构减阻。采用安装在壁面上的展向布置的双压电振子异步振动方式,通过对压电振子输入3种不同振动频率,得到160 Hz工况实现最大减阻率为16.03%。压电振子振动使得湍动能更大程度地集中在能量峰值周围,改变了湍流边界层近壁区的含能结构,对相干结构产生调制作用。压电振子振动频率与相干结构特征频率越接近,减阻效果越好。闭环控制中控制压电振子所需要的电能节省开环的75%,实现与开环控制相近的减阻效果。施加控制加入条件检测的条件相位平均波形时间周期略变短,以压电振子壁面扰动方式调制近壁流向涡,减小壁面摩擦阻力,获得减阻效果。      

涡轮缘板阻尼块摩擦接触特性研究

为了研究航空发动机涡轮缘板阻尼块的摩擦接触特性,减小涡轮叶片的振动,采用带圆角的平板接触理论模型进行数值模拟,推导接触面正压力及切向力的分布,研究接触模型的几何参数对迟滞曲线、切向刚度和能量耗散的影响规律。结果表明:接触面率为0时,存在最大能耗曲线和最大能耗点,并且随着接触面率的增大,迟滞曲线所围面积逐渐变小,每周期能量耗散逐渐减小;其他参数不变时,接触刚度随法向力的增大呈非线性增大。     

气流激励下叶片振动响应分析方法

为开展气流激励下叶片振动响应分析方法研究,建立了气动激振力预估方法,采用非线性谐波法对叶排进行三维非定常流动分析,获得叶片表面的脉动压力,编制流固转换程序,计算叶片所受的气动激振力。建立了叶片气动阻尼分析方法,基于能量法和弱耦合分析法,对叶片与流场进行流固弱耦合分析,将气动力对运动的叶片所做的气动负功等效为黏滞阻尼力所做的功,求得转子叶片的模态气动阻尼比。建立了叶片在气流激励下的振动响应分析方法,基于气动激振力和叶片模态气动阻尼比,采用模态叠加法分析叶片振动响应。使用该方法,针对发动机中1.5级压气机转、静子叶排模型,计算了转子叶片在真实流场中的气动激振力、前8阶模态气动阻尼比以及在气动激振力与气动阻尼共同作用下转子叶片的振动响应,振动应力达到100 MPa。