Vibro-acoustic Radiation Characteristics Analysis of Railway Vehicle Wheel with Damping Ridges Based on Modal Strain Energy

The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the damping material parameters,and the placement,and so on.In order to further understand the mechanism in reducing the acoustic radiation of railway wheel with layer damping treatment,in this paper,the wheel is simply modified by a full-sized circular plate.The circle plate side has stuck circumference constrained damping ridges and radial constrained damping ridges on it.Based on a hybrid finite element method-boundary element method（FEM-BEM）,the paper develops a vibro-acoustic radiation model for such a distributed constrained damping structure.The vibration and acoustic radiation of the circular plate is analyzed.In the analysis,the dynamic response of the system is obtained by using the 3D finite model superposition method.The obtained vibration response is used as the initial boundary condition in solving Helmholtz boundary integral equation for the sound radiation analysis.In the procedure,firstly,the modal analysis of the circular plate is performed to get the distribution of the system modal strain energy.Secondly,the vibro-acoustic radiation characteristics of the plate with different kinds of circumference damping ridges and radial damping ridges are compared in order to try to find the best effective damping ridge structure.Thirdly,using the distribution of the plate modal strain energy investigates the effect of the ridge distribution locations on the circular plate on its vibro-acoustic radiation.The calculation and analysis research results show that,the sticking circumference and radial damping ridges on the plate can control the vibro-acoustic radiation of the plate effectively in different frequency range.The distribution of the constrained damping ridge has an effect on reduction in vibro-acoustic radiation of the circular plate.The present research is very useful in the design of railway wheel with low noise level.

Damage detection of a thin plate using modal curvature via macrostrain measurement

Plate structures are employed as important structural components in many engineering applications. Hence, assessing the structural conditions of in-service plate structures is critical to monitoring global structural health. Modal curvature-based damage detection techniques have recently garnered considerable attention from the research community, and have become a promising vibration-based structural health monitoring solution. However, computing errors arise when calculating modal curvatures from lateral mode shapes, which result from unavoidable measurement errors in the mode shapes as identified from lateral vibration signals; this makes curvature-based algorithms that use a lateral measurement only theoretically feasible, but practically infeasible. Therefore, in this study, long-gauge fiber Bragg grating strain sensors are employed to obtain a modal curvature without a numerical differentiation procedure in order to circumvent the computing errors. Several damage indices based on modal curvatures that were developed to locate beam damage are employed. Both numerical and experimental studies are performed to validate the proposed approach. However, although previous studies have reported relative success with the application of these damage indices on a simple beam, only one damage index demonstrated the capability to locate damage when the stiffness of the local region changed near the sensor.

An Improved Modal Strain Energy Method for Damage Detection in Offshore Platform Structures

柔韧的损坏察觉方法为的发展近海结构是关键的阻止结构的失败引起的大祸。在这研究，我们为检测损坏在开发了一个改进形式的紧张精力(IMSE ) 方法近海站台基于一个传统的形式的紧张精力方法(Stubbs 索引方法) 组织。从 Stubbs 索引方法的最重要的差别是形式的频率的应用程序。目标是改进传统的方法的坚韧性。表明建议 IMSE 方法的有效性和实物，数字、试验性的研究用夹克衫站台结构为不同损坏情形被进行。当仅仅有限、空间地不完全、弄脏噪音的形式的数据是可得到的时，结果在损坏地点表明了 IMSE 方法的有效性。比较研究证明 IMSE 索引超过了 Stubbs 索引并且展出了更强壮的坚韧性，证实建议途径的优势。

Modal Strain Energy Based Structural Damage Localization for Offshore Platform using Simulated and Measured Data

Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to verify the damage detection algorithms. Only a few studies utilize modal testing data from 3D frame structures. Few studies conduct performance comparisons between two different modal strain energy based methods. The objective of this paper is to investigate and compare the effectiveness of a traditional modal strain energy method(Stubbs index) and a recently developed modal strain energy decomposition(MSED) method for damage localization, for such a purpose both simulated and measured data from an offshore platform model being used. Particularly, the mode shapes used in the damage localization are identified and synthesized from only two measurements of one damage scenario because of the limited number of sensors. The two methods were first briefly reviewed. Next, using a 3D offshore platform model, the damage detection algorithms were implemented with different levels of damage severities for both single damage and multiple damage cases. Finally, a physical model of an offshore steel platform was constructed for modal testing and for validating the applicability. Results indicate that the MSED method outperforms the Stubbs index method for structural damage detection.

基于应变模态曲率差的木梁损伤识别

为了识别木梁截面的残缺,提出基于应变模态曲率差的木梁损伤识别方法。首先,采用ABAQUS建立完好木梁和不同程度损伤木梁的有限元模型并进行模态分析;然后,分别采用应变模态和应变模态曲率差的损伤识别指标对木梁进行损伤定位识别,通过拟合应变模态曲率差与损伤程度的关系式估算木梁的损伤程度;最后,通过木梁试验验证该指标的有效性。结果表明:应变模态损伤识别指标对木梁的截面损伤定位效果较差;应变模态曲率差指标具有较强敏感性,能够准确地识别出木梁损伤位置和程度。

定位结构损伤的改进跨模型模态应变能法

为了提高结构损伤定位的精度,提出将跨模型模态应变能与小波分析(Wavelet Analysis, WA)相结合的结构损伤定位方法。首先,计算所有单元的跨模型模态应变能指标。其次,对由各单元跨模型模态应变能指标构成的序列进行小波分析,提取高频细节系数后对其进行重构,以得到改进的损伤指标。最后,根据改进指标判断损伤位置。以某平面桁架为例并考虑5%噪声水平进行蒙特卡洛分析。结果表明,改进指标抵抗噪声干扰的鲁棒性更强,能更好地指示损伤位置。

透平叶片全域动应变-叶尖振动映射方法研究

针对高速旋转叶片振动导致的叶片裂纹甚至断裂而影响设备运行安全的问题,研究了叶片全域动应变与叶尖振动幅值的映射关系,提出一种透平叶片弯曲及扭转共振下叶片动应变非接触式测试方法,可实现基于叶尖振动幅值的叶片动应变反演,为叶片疲劳寿命预测奠定基础。首先,以某透平叶片为对象,对叶片进行模态分析获取全域应变和幅值比,进行叶尖振动测量点的优化;其次,运用振动台对叶片进行振动激励试验,获得叶片1阶、2阶共振下模态频率和应变-位移响应比,并对有限元分析模型进行修正。研究结果表明,所提出的叶片动应变测试应变-位移相对误差小于10%,频率误差小于1%,证明了叶片动应变测试方法的有效性。

基于模态应变能的扬声器盆架优化

针对扬声器轻量化及结构刚度、强度较高要求的设计目标,通过有限元方法进行模态及谐响应分析,对扬声器盆架低频模态应变能集中位置进行优化。优化后,一阶频率由547.3 Hz提高至995 Hz。网格迭代后,一阶频率提升至1031.6 Hz,且模态应变能趋于均匀分布。对应变能较小且非集中的区域进行轻量化优化,通过最小柔度方法对开窗区域进行拓扑优化,在中间部分质量减小40%的情况下,使一阶频率由1300.5 Hz提高至1386.6 Hz,同时使刚性提高。对0.6 mm、0.8 mm、1 mm厚度的扬声器盆架进行对比,从刚度、加速度两个维度进行验证。在有限元分析的基础上,对试验后产生严重变形的扬声器盆架进行基于模态应变能的实际优化,优化后一阶频率由1290.8 Hz提高至1755.9 Hz,同时刚性增大,应变能分布更均匀,变形得到改善。

Experimental Investigation on the Dynamics of Pipes Conveying Fluid Based on Strain Gauge Test

Dynamical performance of pipes conveying fluid on board is of great importance to the reliability of machinery.The dynamic equation of a simply supported wet pipe conveying fluid is presented,taking structural damping of the pipe and viscidity of the fluid into consideration.And the equation is also solved by using Galerkin's method.Modal identifications based on strain gauge test are carried out on both dry pipes(without fluid in it) and wet pipes(pipes conveying fluid).It is concluded from the comparison of the results that both natural frequency and the damping ratio decrease as the pipe filled with fluid,but the mode shapes vary little.Variation of equivalent damping factor is also tested.Experimental results reveal that the equivalent damping factor of fluid and the damping ratio depend greatly on the initial deformation,and fluid induced damping decreases the universal damping ratio of the pipes conveying fluid.

利用模态应变能变化率的结构损伤识别优化方法

针对结构损伤识别过程中存在的定位精度和量化分析不足的问题,提出一种基于结构振动响应的模态应变能变化率与优化技术相结合的损伤识别方法。利用两步法确定可疑损伤单元及对其损伤程度进行量化分析。通过有限元法建立结构的损伤特征模型,且利用单元模态应变能变化率指标构建损伤指标优化分析的目标函数。数值分析过程中,利用粒子群优化算法与遗传算法对设计变量进行优化分析。同时比较模态应变能变化率与小波分析两种方法下的损伤定位的量化分析效果和识别效率。在实际算例中,利用梁结构进行损伤识别优化方法的结果验证。结果证明该方法能够显著提高结构振动损伤和定位的有效性。该方法不仅能够快速和精准地进行结构损伤量化分析,比小波方法具有更好的定位效果,而且能够提高量化分析的识别效率。但该方法在实施过程中的定位精度容易受到噪声的影响,通过优化目标函数可在一定程度上提高该结构损伤识别方法的抗噪能力。

基于模态应变能与频率融合方法的功能梯度铁木辛柯梁损伤识别研究

基于模态应变能和固有频率融合,提出识别功能梯度铁木辛柯梁损伤的新方法。由功能梯度铁木辛柯梁理论给出有限元计算公式,在此基础上计算得出梁结构的固有频率和阵型模态参数。由模态应变能与固有频率融合构造模态频率应变能的计算公式。基于模态频率应变能变化率,定义功能梯度铁木辛柯梁的损伤识别指标。数值算例表明,模态应变能和固有频率融合的损伤识别方法能够有效识别出结构的损伤单元,并且具有较好的抗噪声性能。

基于损伤模态识别法的复杂采空区群中薄弱单元甄别

为甄别复杂采空区群中的薄弱单元,以某地下石灰石矿山采空区群为工程实例,通过构建离散振动力学模型,和应变改变量相关影响因素分析,创新地提出薄弱单元损伤模态识别法,给出甄别流程,并从算例计算和工程实际应用两方面验证其可靠性。研究结果表明:自振频率和应变模态的甄别指标能准确识别采空区群中的薄弱单元;单体和双体单元损伤都会使采空区群的自振频率甄别指标I_(M)(k)值大于0,损伤区域的应变模态甄别指标I_(N)(x)值会明显出现凸起,随着损伤程度增大,I_(M)(k)值和I_(N)(x)峰值越来越大;仅顶板B1损伤时,高阶I_(M)(k)比低阶更灵敏反映损伤变化程度,第四阶指标识别效果更优;仅矿柱Z6损伤时,第二、四阶I_(M)(k)识别效果更优;B1和Z6共同损伤时,I_(M)(k)对B1损伤程度变化较于Z6更为敏感,第二阶I_(M)(k)识别效果更佳。研究成果为地下采空区群安全定量评估开辟了一条新方向。

基于模态应变能变化率的公路架桥机主梁结构损伤识别研究

针对公路架桥机主梁在各种损伤条件下的损伤识别研究问题,本文以JQG160t-40m公路架桥机主梁为研究对象,基于应变模态分析理论,推导了三角桁架公路架桥机主梁结构单元模态应变能变化率的计算模型。通过在有限元软件ABAQUS建立公路架桥机的主梁模型,提取该架桥机主梁结构在12种工况下各单元的模态参数,利用Matlab计算每个单元的模态应变能变化率。结果表明:以单元模态应变能变化率作为损伤识别量,可对架桥机主梁结构的不同损伤位置和程度进行损伤识别。本方法对公路架桥机主梁结构损伤位置和损伤程度的评估是准确有效的,可以作为三角桁架类架桥机主梁结构进一步研究和定期检测的方法。

流固耦合影响下双圆弧斜齿齿轮泵转子力学特性研究

针对理论计算难以获得精确的双圆弧斜齿齿轮泵转子疲劳破坏和塑性变形问题,利用ANSYS Workbench实时数据传递建立双圆弧斜齿齿轮泵单向流固耦合模型,得到流场压力特性和压力载荷作用下双圆弧斜齿齿轮泵力学性能。通过对比分析流固耦合前后不同负载下的力学特性变化,研究流固耦合作用对双圆弧斜齿齿轮泵转子的变形与应力分布的影响。研究结果表明,流固耦合作用对转子结构影响较大,最大变形量都发生在两转子近轮缘位置,且变形量相差0.016063mm;最大等效应力都发生在转子啮合位置,且等效应力相差187.72MPa。转子啮合处相比其他位置更易发生疲劳破坏,为双圆弧斜齿齿轮泵转子的稳定性和结构优化提供了参考依据。

某大跨钢箱组合梁桥荷载试验研究

为确定昆明市某钢箱组合梁桥在服役荷载下的承载能力与动力特性是否达到设计预期,对该桥进行荷载试验。通过采用有限元数值模拟分析和现场进行荷载试验的方法,基于静载试验下该桥各个工况下控制截面的应力与挠度,再结合动载试验得到各工况的模态参数和动力响应,并将实测值与理论值进行分析比较。结果表明该桥挠度校验系数为0.77~0.85,应变校验系数为0.697~0.776,最大相对残余应变为18%,最大第一阶竖弯频率为2.38 Hz,大于理论值,实测最大阻尼比为1.86%。无障碍行车试验和制动试验中得到最大冲击系数为0.025,最大动应变为26。可见在静载试验下桥梁承载能力和刚度满足要求,最大相对残余也没超过限制20%。动载试验的数据表明桥梁满足行驶舒适的要求。

糊底机机架轻量化设计

为了满足糊底机机架的轻量化设计要求,结合拓扑优化与模态应变能对糊底机机架进行结构优化设计。首先对初始模型进行静力学分析及模态分析,确定其静动态特性;然后将折衷规划法和平均特征值相结合,建立关于柔度与频率的多目标优化函数,对有限元模型进行多目标拓扑优化;之后利用模态应变能方法对拓扑优化后的模型进行动力修改,建立重构模型完成第二次优化;最后对重构模型进行分析,检验结构是否满足设计要求,实现了轻量化设计要求。

基于应变模态参数的木梁损伤识别研究

为研究基于应变模态参数识别木梁损伤的方法,文中通过有限元软件ABAQUS建立不同损伤工况下的木梁模型进行模态分析,处理分析得到位移模态、应变模态及应变模态差曲线,以曲线的突变进行损伤定位识别。结果表明应变模态和应变模态差可识别出简支木梁的损伤,且识别精度高,与通过固有频率变化和位移模态的损伤识别相比,基于应变模态参数的损伤指标在梁损伤位置识别具有明显优势。

基于单元模态应变能的梁结构分级损伤识别方法研究

针对目前利用单元模态应变能对结构进行损伤识别时精度过低、计算量大的问题,提出一种基于单元模态应变能变化率分级损伤识别方法。首先通过计算单元的各阶平均模态应变能变化率,初步判断损伤位置或损伤疑似区间;然后在损伤疑似区域内施加质量块,通过计算单元的各阶平均模态应变能变化率,进行损伤二次定位;最后利用遗传算法对损伤位置的损伤程度进行量化分析,确定损伤位置的损伤程度。

基于多模态传递比的旋转叶片动应变场重构方法

针对旋转叶片非接触式应力/应变测试的需求,本文提出一种基于多模态传递比的叶片动应变场重构方法。首先,基于多自由度(MDOF)系统的振动微分方程,在模态坐标系下建立位移频响函数(FRF)和应变频响函数,进而得到位移-应变响应传递比表达式;以某12扇区的叶盘为分析对象,建立叶片有限元模型并进行模态分析,通过提取多模态叶尖位移和叶身应变,得到总位移-应变传递比矩阵和定向位移-应变传递比矩阵;最后,基于Simulink平台进行旋转叶片叶尖定时采样(BTT)仿真模拟,通过周向傅里叶拟合算法(CFF)对欠采样信号进行振动位移重构,将得到的叶尖位移代入传递比表达式,得到叶身应变。研究结果表明:在非共振态下,由叶尖位移重构得到的叶身总应变与有限元分析得到的总应变相对误差为0.12%~14.56%,定向应变相对误差为1.92%~14.70%,验证了本文提出的基于多模态传递比的叶片动应变场重构方法的有效性。

弹性支承转子系统应变能分析及其支承特性影响研究

本文以两支点弹性支承的转子系统为研究对象,基于旋转梁理论和有限元理论建立了转子系统动力学模型,在此基础上给出了应变能的计算公式,分别对转子和弹性支承进行了应变能分析,通过数值仿真分析了支点支承刚度、刚度不对称对转子系统的模态振型及相应的应变能分布的影响规律。研究结果表明:1)当支承刚度与转子刚度相近时,支承刚度变化对于转子系统动力特性变化非常敏感,系统模态振型和应变能分布随着支承刚度的增减将会表现出很大的差异。2)转子的应变能系数η可作为区分系统模态振型的重要参数。当η小于20%,转子基本不发生变形,视为刚体振型;在η超过80%时,变形主要发生在转轴上,可视为完全弯曲振型;η在20%~80%的范围,视为转子-支承的耦合振型。本文研究为弹性支承设计以及带弹支的转子系统的结构设计、运行和维护提供理论参考。