频率转向特征对失谐叶盘模态局部化的作用

基于叶盘集中参数模型,分析了叶片刚度失谐对频率转向区内的系统固有频率及叶片模态振型的影响,提出了一个描述模态局部化程度的参数,仿真研究了频率转向特征对失谐叶盘模态局部化程度的作用规律。研究表明,频率转向曲线之间关于节径的最小间隙(转向频率间隙)是反映频率转向特征的重要参数,并存在一个转向频率间隙的极小值点,在该极值点附近,频率转向区内的模态对叶片失谐非常敏感,并会导致模态局部化程度剧烈变化。     

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。     

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。     

模态局部化传感器研究进展

模态局部化现象由诺贝尔奖获得者ANDERSON于1958年发现,对理解在紊乱固体中的电子传递过程具有重大意义,是固态物理领域的重要发现。近些年,模态局部化现象开始应用于传感器设计。模态局部化传感器以不同谐振器之间的幅值比作为输出量纲,实现了超高灵敏度的测量。揭示了振幅比与振动系统结构之间的关系,解释了如何提高模态局部化传感器的灵敏度。并通过典型的模态局部化传感器设计案例,给出了模态局部化传感器的设计规则。     

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。      

网壳结构模态局部化现象的试验检验

通过一个凯维特型单层球面网壳结构的缩尺模型试验,对网壳结构的模态局部化现象进行研究.定义了模态局部化现象的定量描述指标,试验中通过附加节点质量和削弱杆件截面构造结构物理参数发生改变的工况,采用准确度高的试验模态分析法对各工况下的结构进行模态测试,随机测取了3个结构模态,对各种工况下这3个结构模态的振型变化和局部化情况进行了分析.结果表明,网壳结构物理参数的小量变化可能引起某些结构振型发生比较明显的变化和局部化,在进行网壳结构的抗震计算和损伤识别时有必要考虑模态局部化的影响.     

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.     

基于模态局部化和跃迁的网壳结构损伤指标

由于模态局部化和模态跃迁使结构损伤前后的振型产生较大差别,二者间的相关性发生较大程度的弱化,基于这一事实,利用结构的振型相关系数,构造出一种对网壳结构局部损伤具有高敏感性的损伤特征向量。该向量构造简单,仅使用少数振型和少量的测试自由度。通过一个网壳结构的算例分析,对所提出的损伤特征向量的性质进行了检验。结果表明,该向量不仅具有较好的空间可分辨性、损伤敏感性和噪声鲁棒性,并且对结构有限元模型误差具有一定的适应性。     

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.     

Mode localization in a rotating mistuned turbo disk with Coriolis effect

An investigation of the speed effect, i.e., the effects of centrifugal and Coriolis forces, on the mode localization of a mistuned blade-disk is presented in this paper. A disk comprising of periodically shrouded blades is used to simulate the weakly coupled periodic structure. Galerkin method is employed to derive the mode localization equations of the mistuned system with the consideration of Coriolis force. The blades are approximated as cantilever beams, and five axial and lateral modes of each blade are used to present the dynamic behavior of the system. Ten modal coordinates have been considered for each blade. The effects of Coriolis force and the magnitude of disorder on the localization phenomenon of a rotating blade-disk system were investigated numerically. Numerical results obtained herein indicate that the Coriolis force may enhance the localization phenomenon.     

基于KBE的定位型面线切割自动数控编程系统

基于UG/OPEN API和UG/KF技术,通过二次开发实现了汽车焊装线中定位块和压块的定位型面加工的自动线切割数控编程系统.其中,采用UF/KF实现了加工轨迹的自由设置,提高了系统的灵活性.     

起重机钢丝绳弹性振动的动态分析

为解决起重机动态分析中钢丝绳的建模问题,研究采用多种加速度时钢丝绳的动张力特性,提出了合理的建模方法。结构的有限元动态分析与实验结果对比显示,所建模型较全面地反映了单梁门机的动态特性,为单梁门机动态设计提供了科学的实用方法。     

线切割加工中断丝原因分析及预防措施

分析线切割断丝故障的主要原因 ,提出有关预防措施     

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.     

齿圈径向跳动测量误差分析及处理

分析齿圈径向跳动测量原理及其影响测量误差的各种因素,运用随机误差理论分析和处理这些误差.     

Thermo-elastic analysis for chattering phenomenon of automotive disk brake

This study investigates the effects of operating conditions on the chattering of an automotive disk brake by experimental and computational methods. Design factors, which cause chattering in automobiles, have attracted great attentions for long time; but they are not well understood yet. For this study, we construct a brake dynamometer for measuring the disk surface temperature during chattering, and propose an efficient hybrid algorithm (combining FFT-FEA and traditional FEA program) for analyzing the thermo-elastic behavior of three-dimensional brake system. We successfully measure the judder in a brake system via the dynamometer and efficiently simulate the contact pressure variation by the hybrid algorithm. The three-dimensional simulation of thermo-mechanical interactions on the automotive brake, showing the transient thermo-elastic instability phenomenon, is presented for the first time in this academic community. We also find from the experimental study that the disk bulk temperature strongly influences the brake chattering in the automotive disk brakes.     

门架式圆形料场堆取料机结构分析

根据多年设计和制造圆形料场的经验,分析了圆形料场门架式取料设备的特点;对门架的强度、刚度进行分析,找出梁宽、梁高、挡墙高度、上滑轮吊挂点位置、刮板机吊点位置等因素对强度和刚度的影响。