Experimental and FEM Modal Analysis of a Deployable-Retractable Wing

The aim of this paper is to conduct experimental modal analysis and numerical simulation to verify the structural characteristics of a deployable-retractable wing for aircraft and spacecraft. A modal impact test was conducted in order to determine the free vibration characteristics. Natural frequencies and vibration mode shapes were obtained via measurement in LMS Test. Lab. The frequency response functions were identified and computed by force and acceleration signals, and then mode shapes of this morphing wing structure were subsequently identified by PolyMAX modal parameter estimation method. FEM modal analysis was also implemented and its numerical results convincingly presented the mode shape and natural frequency characteristics were in good agreement with those obtained from experimental modal analysis. Experimental study in this paper focuses on the transverse response of morphing wing as its moveable part is deploying or retreating. Vibration response to different rotation speeds have been collected, managed and analyzed through the use of comparison methodology with each other. Evident phenomena have been discovered including the resonance on which most analysis is focused because of its potential use to generate large amplitude vibration of specific frequency or to avoid such resonant frequencies from a wide spectrum of response. Manufactured deployable-retractable wings are studied in stage of experimental modal analysis, in which some nonlinear vibration resulted should be particularly noted because such wing structure displays a low resonant frequency which is always optimal to be avoided for structural safety and stability.

Application of experimental modal analysis technique to structural design of linear vibrating screen

A large model of the screen was mounted in the laboratory for studying its modal performance. The model is suspended with steel ropes. Modal test was carried out with artificially exciting by 500 g impacting hammer and 100 kg exciting force shaker respectively. Synthesis and correction of the modal parameters are obtained from both testing methods. Design faults of vibrating screen were determined based on the analy-sis and dynamic correction of structure approaches about the screen was put forward finally.

MODAL ANALYSIS OF A CHASSIS FRAME OF A HEAVY LECTRA HAUL

The chassis frame of a heavy lectra haul is analysed by both modal experiment method and finite element method (FEM ) . The first ten order modal parameters of the chassis frame have been obtained satisfactorily. These parameters have important reference value in designing the chassis frame properly and provide a necessary basis for the fault diagnostics of the truck.

Firmness evaluation of melon using its vibration characteristic and finite element analysis

The “Huang gua” melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.

Numerical and Experimental Research on the Influence of the Centrifugal Pumps Rotor Damage on Their Natural Frequency Response

The paper presents process of creating a centrifugal pump rotor model in CAD environment. Modeling of a virtual object was divided into two stages, modeling of the efficient pump and the simulated failure of one of the impeller＇s blades. Comparison of the results of the resonance frequency obtained from the model analysis, with those obtained from measurements on the actual object was shown. Measurements and simulations were conducted on the pump before and after the simulated damaged of the rotor. In order to verify the model the rotor of pump was weighted and compared with the masses of the respective components obtained from the virtual object. In the second stage genuine rotor was subjected to the experimental modal analysis.

EMA与OMA模态参数辨识统一性方法

现代模态测试的对象正从系统部件转向整体结构,系统的动力学特征正变得越来越复杂,表现在结构组件众多导致系统模态密集化、局部化;在实际的工程结构中,甚至无法对大型结构施加有效的激励或激励的成本很高,使得EMA方法不能进行,只能使用OMA方法。在系统动力学特征越加复杂与参数辨识难度增加的同时,对参数辨识的要求越来越高;对算法的模态辨识能力要求越来越高;EMA与OMA都面临着整体频段的拟合困难、模型阶次与模态参数选择困难以及测点数的迅速增大带来的计算量剧增等困难;并且,EMA与OMA之间还存在着辨识方法不能统一的问题;简要回顾了VF算法原理,并进一步将VF算法拓展到OMA问题中,将频域内的EMA与OMA建立一个统一辨识流程,实现了整个频段上的整体拟合;简化了模态参数辨识流程,减少人工介入工以及由于频段划分不当造成的识别质量的下降。利用公开数据进一步验证了EMA问题中,VF算法在低信噪比和大规模曲线数目时的辨识效果,以及在OMA问题中的良好适用性。

卧式泵模态仿真分析与试验测试研究

固有频率是评价离心泵稳定性的重要因素之一,文章研究了单级端吸卧式泵模态分析和试验测试方法,建立了卧式泵的有限元模型,考虑与测试状态相同的边界条件进行仿真分析,同时通过锤击法进行试验测试,得到了卧式泵的固有频率和振型。结果表明:水平方向固有频率仿真与试验误差最大为5.1%,竖直方向固有频率仿真与试验误差最大为16.9%,卧式泵模态振型仿真与试验结果一致,仿真分析方法可用于指导离心泵模态性能设计优化。

Design and Experiment of Triangular Prism Mast with Tape-Spring Hyperelastic Hinges

Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like configuration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stiffness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The finite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the influence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stiffness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and finite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.

Influence of structure and material on the vibration modal characteristics of novel combined flexible road wheel

Aiming at the independent development of tracked vehicles,it is urgent to improve its mobility,passability and ride comfort,a new type of flexible road wheel with a“wheel-hinge-hub”combined structure is proposed in this study.The vibration model characteristics of the flexible road wheel were studied by the combination of numerical simulation and experiments.The superelasticity of rubber is obtained through uniaxial tensile experiment of the material and a detail three-dimensional nolinear finite element model of the flexible road wheel is established through finite element software ABAQUS.The free vibration equation of the flexible road wheel is solved by Lanczos vector direct superposition method,and its predicted modes and natural frequencies are compared with experimental results,which verifies the accuracy and reliability of the established finite element model.On this basis,the effects of various key structural or material factors on the natural frequencies of the flexible road wheel are studied using orthogonal experimental design method.Besides,the vibration modal characteristics of the flexible road wheel are also compared with those of the rigid road wheel.The research results provide a theoretical basis for the vibration and noise reduction of flexible road wheel.

ODS & Modal Testing Using a Transmissibility Chain

In this paper, we show how Operating Deflection Shapes (ODS’s) andmode shapes can be obtained experimentally from measurements thatare made using only two sensors and two short wires to connect them to amulti-channel acquisition system. This new test procedure is depicted inFigure 1. Not only is the equipment required to do a test much more costeffective, but this method can be used to test any sized test article, especiallylarge ones.

Modal Parameters Identification of A Real Offshore Platform From the Response Excited by Natural Ice Loading

This paper investigates the possibility of utilizing response from natural ice loading for modal parameter identification of real offshore platforms.The test platform is the JZ20-2 MUQ jacket platform located in the Liaodong Bay,China.A field experiment is carried out in winter season,as the platform is excited by floating ices.The feasibility is demonstrated by the acceleration response of two different segments.By the SSI-data method,the modal frequencies and damping ratios of four structural modes can be successfully identified from both segments.The estimated information from both segments is almost identical,which demonstrates that the modal identification is trustworthy.Furthermore,by taking the Jacket platform as a benchmark,the numerical performance of five popular time-domain EMA methods is systematically compared from different viewpoints.The comparisons are categorized as:(1)stochastic methods versus deterministic methods;(2)high-order methods versus low-order methods;(3)data-driven versus covariance-driven stochastic subspace identification methods.

EXPERIMENT RESEARCH ON DYNAMIC LOAD IDENTIFICATION TECHNOLOGY BASED ON GENERALIZED ORTHOGONAL POLYNOMIAL THEORY (GOPT)

A dynamic load identification model of structural system based on the gener-alized orthogonal polynomial theory is provided, and the least Square discrete algorithm foridentifying the dynamic load is supplied. The main key is that the convolution relationsbetween the input and output of the system in time domain are transformed into linear oP-erators in generalized orthogonal domain. The new theory is fully tested and verified bythe dynamic analysis l 'modal test and dynamic load identification teSt of a simulation speci-men- It is shown that the method has some advantages, such as the simple dynamic cali-bration test, the high identification accuracy, especially for the transient load with shortsampling. These are very useful in engineering applications.

Finite element modal analysis and experiment of rice transplanter chassis

The vibration problem during the operation of rice transplanters is the most common phenomenon.In order that the static and dynamic characteristics of the rice transplanter chassis can meet the requirements of more stable operation,the research took the 2ZG-6DK rice transplanter as the research object to carry out a vibration reduction optimization study.In the research,the Pro/Engineer 5.0 software was first used to model the chassis of the rice transplanter.The constructed finite element model was revised by using the structural parameter revision method and the mixed penalty function method.The model was imported into ANSYS Workbench to solve the modal frequency and vibration shape of the rice transplanter chassis.Based on the MAC(modal assurance criterion)criterion,modal tests were carried out to verify the accuracy of the finite element theoretical analysis.Through the analysis of the characteristics of the external excitation frequency,the chassis is structurally optimized to avoid resonance caused by the natural frequency of the chassis falling within the road excitation frequency range.The final optimization results showed that the first four orders of modal frequencies of the chassis were adjusted to 32.083 Hz,33.751 Hz,42.517 Hz,and 50.362 Hz,respectively,in the case that the chassis mass was increased by 6.714 kg(8.8%).They all avoid the range of road excitation frequency(10-30 Hz)so that the rice transplanter can effectively avoid the resonance phenomenon during operation.This study can provide a reference for the design and optimization of the chassis structure of transplanter.

多模态人工智能数据分析实验服务平台建设

为了培养具备创新能力的人工智能新工科人才,探索人工智能人才培养新模式新路径,进一步提升应用型高校的大数据及人工智能实验教学水平,同时能实现科研成果向业务价值的转化,提出了建设具有多模态人工智能数据分析能力的实验和科研一体化的教科研服务平台。多模态人工智能是计算机视觉和交互式人工智能模型的融合,基于应用型高校的基本特征,在分析了服务平台功能需求基础上,提出了整合大数据及人工智能核心技术引擎模块;实现了其关键核心技术多模态数据重构及转换、多模态深度学习服务平台;构建了基于平台应用的人才培养课程服务体系。可为高校在教学、管理、人工智能实训、大数据开发和可视化、大数据及人工智能课程实训资源等多方面提供核心技术应用和基础支撑。

基于实验模态和工作变形的大型风力发电机转子动力学特性分析

对大型风力发电机转子设备静止和旋转状态下的动力学特性进行了实验分析。研究主要基于实验模态分析和工作变形分析,采用LMS.TESTLAB系统及无线数采系统,首先测试各响应点锤击激励下振动信号,信号经频响函数计算、曲线拟合后得到其各阶模态参数;然后进行全转速振动测量,并根据实验结果选取共振运行工况,进行工作变形测试分析;最终实现转子静态及旋转状态数据收集、模态参数提取和分析。分析结果表明:发电机转子在旋转过程中,发生共振的频率与实验模态频率存在偏差,转子整体刚度减小;且在旋转电磁力作用下,振型由静止状态时的驻波形式变为行波形式。该研究结果对于转子动力学评估、仿真模型修正及参数输入以及转子结构优化设计具有借鉴参考意义。

Vibration analysis and topology optimization of the header of full-feeding rice combine harvester

The header frame of full-feeding rice combine harvester was characterized by severe vibration due to the excitation force generated by the movement of each working part.In order to solve the problem,the parametric model of the header frame was established,and the accuracy of the finite element model was verified by comparison of the results of the free modal analysis and free vibration modal test based on Eigensystem Realization Algorithm(ERA).Then the constrained modal frequencies were calculated and compared with the external excitation source frequencies,the results showed that the first and eighth order modal natural frequencies were coupled with the excitation frequencies of the threshing cylinder and the engine respectively,which were apt to resonate.To avoid resonance and achieve lightweight design,topology optimization,and finite element analysis were carried out.The optimization results showed that the strength and rigidity meet the requirements and the weight was 14.17%lower than before.The first and eighth order modal natural frequencies were far away from the excitation frequencies range of the threshing cylinder and engine,and the frequencies were far away from the range of each excitation frequency,which effectively avoided the occurrence of resonance.Field experiments showed that the peak value of the vibration acceleration in the three directions of the 8 measuring points of the optimized header frame was significantly reduced,which effectively reduced the vibration of the header frame during harvest.This study provides a method for obtaining the vibration characteristics of key components of agricultural machinery and provides a reference for the weight and vibration reduction of header frames of rice,wheat,rape,and other crop combine harvesters.

Modal Decomposition for the Analysis of the Rotor-stator Interactions in Multi-stage Compressors

A modal analysis method of the rotor-stator interactions in multistage compressors has been developed by LMFA. This method, based on a double modal decomposition of the flow over space and time, has been applied to nu- merical and experimental results of the high-speed 3Y2-stage compressor CREATE based at LMFA, Lyon-France. It reveals the presence of a very strong rotor-stator interaction which completely drives the flow at casing behind all the rotors. This modal analysis method applied to an unsteady RANS simulation permits to calculate the en- ergy of the rotor-stator interactions and to plot energetic meridian maps to explain experimental results and to analyze the interaction in the whole machine.

某舰载火控雷达天线座结构设计

舰载火控雷达的天线座是雷达整机的重要组成部分,其设计优劣直接影响雷达精度与可靠性。以某舰载火控雷达天线座总体结构设计为例,在传统天线座结构设计方法的基础上,引入新的优化设计方法与手段,运用三维设计软件建立结构模型,计算天线座所受的主要载荷,并对其进行轴系精度分析。利用有限元分析软件进行模态分析,提取前四阶模态与试验结果进行对比,结果表明试验与仿真间的误差小,天线座各项性能满足系统指标要求。该设计方法为同类型产品的研发提供了借鉴与经验。

大型泵站水泵机组转子轴系实验模态分析

为探究机组异常振动原因,采用锤击法激励对机组转子轴系进行实验模态测试分析,得到机组转子轴系前5阶模态参数。结果表明,第3阶模态频率与机组工作转速十分接近,极易产生共振,建议采取优化减振措施,避免固有频率落在工作频率10%范围内。传递函数相干分析和MAC矩阵校验结果均表明,实验模态测试和分析结果合理可靠。建议确保设备安装质量,避免激励频率与系统某阶固有频率接近,产生共振。

基于最小二乘复指数法辨识钢轨模态参数

铁路天窗时间短,线路长,对模态实验的便捷性提出很高要求。为此,本文提出基于最小二乘复指数法(LSCE)和稳态图辨识钢轨模态参数。首先建立Beam梁模型,结合稳态图和LSCE辨识瞬态分析模态参数,与模态分析结果对比,验证所提出模态辨识算法正确性。其次,在铁路线路进行模态实验,LSCE算法与频响函数法识别频率结果的最大误差比为1.7%,验证所提算法适合铁路模态测试需求,能够便捷地进行钢轨模态实验。