Modal Frequency Response Analysis Research Articles

An efficient seismic analysis technique for PCSG assembly using sub-structuring method and homogenization method

This study significantly reduced the seismic analysis time of PCSG assembly by introducing a reduced model using homogenization and sub-structuring methods. The homogenization method was applied to the primary and secondary micro-channel sheets, and the sub-structuring method was applied to the PCSG module sets. Modal analysis and frequency response analysis were then performed to validate the accuracy of the reduced model. The analysis results were compared with the full model and it was confirmed that the reduced model provided almost the same analysis results as the full model. To verify the computational efficiency of the reduced model, the computational time was then compared with the full model, and it was confirmed that the modal analysis time was reduced by 3.42 times and the frequency response analysis time was reduced by 4.59 times.

Seismic responses and failure mechanism of the superstructure-integrated underground structure considering the seismic aboveground-underground interaction

The superstructure-integrated underground structure (SIUS) is an innovative infrastructure in an urban city, in which the aboveground part and underground part are coupled together to be a large synthesis structure. During earthquakes, the SIUS is primarily influenced by the soil deformation and structural vibration, and the seismic aboveground-underground interaction (SAUI) would be considerable due to structural characteristics. This paper aims to investigate the seismic response and failure mechanism of the SIUS and reveal the influence mechanism of the SAUI with a quantitative method for the seismic aboveground-underground interaction coefficient (SAUIC). In this paper, a credible numerical model of the whole soil-SIUS system compiled with the viscous-spring artificial boundary is established. The modal analysis of the SIUS is carried out, and the distinctive structural characteristics are discussed. The seismic responses of the SIUS are thoroughly investigated, and the failure mechanism of vulnerable positions is further revealed. Based on the modal frequency response analysis and a novel correlation analysis, the SAUIC is quantitatively proposed to evaluate influence effects of the SAUI on seismic responses of the SIUS. The results show that the SAUI has great influence effects on seismic responses of the SIUS, even changes the seismic failure mode of the underground part to be flexural failure; the quantitative SAUIC demonstrates the SAUI increases with the increasing seismic intensity and increases from outside to inside of the SIUS, and the SAUI would be highly considerable on positions with irregularities in structural stiffness, especially on the aboveground-underground interface.

Research on interior noise optimization of minibus based on vibration transfer path analysis using super element method

In this paper, aiming at the problem of excessive low-frequency noise in a minibus, the SEM (Super Element Method) was applied to the NVH (Noise, Vibration and Harshness) dynamics simulation analysis of the vehicle, and the vibration and noise control schemes were proposed from the aspect of vibration transfer path to improve NVH performance. First, the relationship and difference between SEM and LFEM (Legacy Finite Element Method) were elaborated theoretically. Afterward, the legacy finite element model of the full vehicle, which comprehensively considered all related components such as BIW (Body In White), chassis, door covers, body accessories and interior and exterior trims, was established based on LFEM. Furthermore, the subsystems of legacy finite element model of the vehicle were divided into super elements based on SEM, and the differences between SEM and LFEM in model processing were discussed in detail. In addition, the modal analysis and frequency response analysis of the full vehicle were carried out by LFEM and SEM respectively, and the computational results were compared with the testing results to verify the simulation accuracy and feasibility of the SEM in solving the vehicle body dynamics problems. Meanwhile, through the comparison of simulation analysis process of SEM and LFEM in practical case, the advantages of SEM compared with LFEM were discussed in terms of computational efficiency and storage space occupied. Finally, the stiffness optimization schemes of rubber bushing in the middle of driveshaft were proposed to improve vibration and noise from the aspect of vibration transfer path, and the testing results verified the effectiveness of the optimization schemes in reducing the low frequency noise inside the vehicle. The study concluded that SEM had obvious advantages over LFEM in terms of computational efficiency and storage space occupied, while ensuring the computational accuracy basically consistent with that of LFEM.

Vibrations of cracked functionally graded beams: General solution and application – A review

This paper presents a unified approach to vibration analysis of functionally graded beams with transverse open-edge cracks based on the so-called vibration shape obtained as a general solution of vibration equations in the frequency domain. The crack is modeled by a pair of translational and rotational springs of stiffness computed from the crack depth in dependence upon functionally graded material parameters. The frequency-dependent vibration shape functions allow one not only to obtain the closed-form solution of both free and forced vibrations for multiple cracked FGM beams but also to develop the well-known methods such as Transfer Matrix Method or Dynamic Stiffness Method for analysis of FGM framed structures. The proposed theoretical developments have been illustrated by their application for modal analysis and frequency response analysis of multi-span and multistep beams.

WITHDRAWN: Design of a probe-type acoustic tweezer by acoustic-streaming field optimization

• The evaluation criteria of acoustic-streaming field optimization are proposed. • The optimized capture condition is concluded by finite element analysis. • Ultrasonic vibration device for optimized capture vibration parameter is designed. • The probe-type acoustic tweezer can capture, translate and release objects. This paper presents a novel design process of a probe-type acoustic tweezer for micro/nano manipulation. The qualitative evaluation criteria of manipulation-oriented acoustic-streaming field are proposed, and the optimized capture condition is concluded by finite element optimization accordingly for the first time. The scheme of ultrasonic vibration device for optimized capture condition is proposed, which is composed of two parallel-connected sandwich piezoelectric transducers. Initial structural parameters of the vibration device are determined by an analytical model based on the electromechanical equivalent theory, and it is further optimized using finite element method. Dynamic performances of the vibration device are then analyzed through modal analysis and frequency response analysis. A prototyped vibration device is fabricated and experimental investigations are conducted to further test its characteristics. The results show that the device can vibrate with the optimized capture condition. The experimental setup of the probe-type acoustic tweezer system is established, and it is proven that it can successfully capture, translate and release nanowires. Graphical Abstract. .

Generation Mechanism and Development Characteristics of Rail Corrugation of Cologne Egg Fastener Track in Metro

By establishing vehicle-track space coupled model and rail corrugation evaluation model, the generation mechanism of rail corrugation was analyzed in frequency domain and time domain, and development characteristics of corrugation were studied by using corrugation growth rate. Analysis based on frequency domain: through modal analysis and frequency response analysis on the finite element model of track structure, it is found that there are natural frequencies of track structure close to measured corrugation passing frequencies. It shows that the vibration modes corresponding to these frequencies can be more easily excited, which can cause the resonance phenomenon of track structure and form the rail corrugation at corresponding frequencies. Analysis based on time domain: the time-history curves of rail vertical vibration acceleration and rail vertical displacement are calculated by using vehicle-track coupled model and the frequency domain transformation of the time-history data is carried out. It is found that there are characteristic frequencies close to the measured corrugation passing frequencies, which indicates that the vibration of track structure at corresponding frequencies is an important reason to promote the formation of corrugation. The change of vehicle speed has no effect on characteristic frequencies of corrugation growth rate curves, which reflects the fixed frequency characteristic of corrugation. With the increase of train operation times, the corrugation corresponding to characteristic frequencies will gradually form and develop, and the increase of vehicle speed will increase the wavelength range and development speed of rail corrugation.

3DOF Ultrasonic Motor With Two Piezoelectric Rings.

A novel design of a multiple degrees of freedom (multi-DOF) piezoelectric ultrasonic motor (USM) is presented in the paper. The main idea of the motor design is to combine the magnetic sphere type rotor and two oppositely placed ring-shaped piezoelectric actuators into one mechanism. Such a structure increases impact force and allows rotation of the sphere with higher torque. The main purpose of USM development was to design a motor for attitude control systems used in small satellites. A permanent magnetic sphere with a magnetic dipole is used for orientation and positioning when the sphere is rotated to the desired position and the magnetic field synchronizes with the Earth’s magnetic dipole. Also, the proposed motor can be installed and used for robotic systems, laser beam manipulation, etc. The system has a minimal number of components, small weight, and high reliability. Numerical simulation and experimental studies were used to verify the operating principles of the USM. Numerical simulation of a piezoelectric actuator was used to perform modal frequency and harmonic response analysis. Experimental studies were performed to measure both mechanical and electrical characteristics of the piezoelectric motor.

Simulation of the frequency response of the ERC 1400 Bucket Wheel Excavator boom, during the excavation process

Abstract The paper deals with the modal analysis and frequency response analysis of a bucket wheel excavator (BWE) boom, obtained by simulation, based on a virtual model of an existing BWE boom. The boom, which generally is realized as a spatial truss, is the most vulnerable subsystem of the BWE, being submitted to severe operational loads characterized by very pronounced cyclical, dynamic and stochastic variability. This vulnerability is the consequence of its shape and constructive parameters and the nature, source and character of the external exciting loads to which it is exposed. The classical approach recommended by standards and norms cannot predict the occurrence of failures caused by vibration, which produces fatigue due to the load’s cyclical variability and the deformation produced by resonant vibration of some constitutive elements. As exciting load we considered the operational forces acting on the bucket wheel. In this manner we can take into account the constructive features – with modal analysis, and the vibration regime – with frequency response analysis. The proposed method is useful both in the design phase of new load-bearing structures of truss type subjected to high-variability forces, and also in refurbishment or improvement phases of the existing structures of this kind.

Research on modeling method of honeycomb plate and its application on solar wing

Aerospace products need to simulate the complicated working conditions through dynamic simulation analysis to ensure the high reliability of product design. In this paper, the equivalent modeling method of honeycomb sandwich plate based on finite element analysis is studied, and the mechanical characteristic parameters of honeycomb core structure are obtained. At the same time, the composite components of satellite solar cell array are modeled and simulated. The modal analysis and frequency response analysis are carried out to provide an important basis for the design and improvement of the structure.

Structural design and simulation analysis of the carbon fiber-reinforced polymer main frame of a mapping camera system

The main frame is the primary load-bearing component of a mapping camera system. As the critical structure of the system, the main frame determines the mechanical properties of a camera system. The main frame design is hindered by its large size, complicated interface, as well as high-stability, high-frequency requirement, and lightweight requirements. During the launching process, the main frame should be able to withstand the mechanical action of the active section without affecting the performance of the camera system. This paper describes the design scheme of the main frame. The modal analysis, static analysis and frequency response analysis of the main frame are performed. The simulation analysis results prove that the natural frequency of the mapping camera system satisfies the design requirements and the main frame satisfies the required safety margin in the linear overload in X-, Y-, and Z-directions. Moreover, under condition of the frequency response in X-, Y-, and Z-directions, the main frame has excellent structural stiffness, which provides a proper mechanical environment for the camera system. The design scheme of the main frame is reasonable and feasible.

618 一部を開放した空間のモーダル周波数応答解析(OS6-2 機械力学(2)音の解析・制御技術)

618 一部を開放した空間のモーダル周波数応答解析(OS6-2 機械力学(2)音の解析・制御技術)

FEM based Cutting Velocity Selection for Thin Walled Part Machining

Monolithic components are commonly used in the aeronautical industry due to their homogeneity and excellent strength-to- weight-ratio: ribs, stringers, spars, and bulkheads can be mentioned as examples. In order to assure enough stiffness to the whole component, monolithic parts are often made of thin walls, and webs, obtained usually starting from a raw block of material and removing up to 95% of the weight of the initial block. Therefore, increasing the removal rate as much as possible is the main condition to reach high productivity. The drawback is that, at high removal rate conditions (high feed, large depth of cut), the low stiffness of the thin walls causes dynamic problems, due to the forced vibrations induced by the milling process: even in case of a stable cutting process, vibrations appear as the result of the combination between the tool and workpiece natural frequencies, excited by the tooth-passing frequency harmonics. This paper presents an overview of a comprehensive milling process plan approach, based on finite element method (FEM), which by considering the effects of fixturing, tooltip dynamics, and material removal, allows to define the optimized cutting velocity in order to reduce deflections and vibrations during machining. The advantages of the proposed model over previous works are: (i) it provides a seamless interface to import the G-code generated by a CAM packages; (ii) it performs a computationally efficient modal superposition frequency response analysis of complex workpieces, considering the tooltip position provided by CAM; (iii) it predicts the workpiece non-linear behaviour during machining due to its changing geometry; (iv) it automatically tunes spindle speed continuously along the toolpath, taking into account both the tooltip dynamics and the local workpiece modal behaviour. The effectiveness of the proposed approach has been experimentally validated.

A Study of Wind Generator Set Blades Dynamic Analysis

This paper on wind generator set blades had a simple introduction, and the modal analysis was used on the blades dynamic analysis, the conclusion that blades the different stage in the direction of the force and deformation was drawn, it can be concluded: the first three-order natural frequency at, the blades are expressed as a pure bending vibration. It can be seen from the blade vibration figure: a frequency of blades waving in the direction of the first natural frequency, first natural frequency of the second-order frequency blades shimmy direction, three frequencies for the blades waving direction of the second-order natural frequency, torsional frequency of fourth order for the direction of the shimmy, five order of frequency of blades placed waving direction of the three natural frequencies. According to the theory of vibration, the vibration in the process of energy is concentrated in bands 1 and 2, so the first stage waving vibration (bending vibration) is the main vibration of the wind generator set blades; 4 and 5 vibration modes performance for bending dominated accompanied shimmy and torsional vibration. Visible, the shimmy vibration and torsional vibration in high-end part is still not the main vibration.It provides the theoretical basis so as to improve the quality of the design of wind turbine blades. Blade is one of the wind generator set key components, many aerodynamic problems are faced, the aerodynamic efficiency of the blades is to be considered an important factor in the blade design, and their job security is more important factor. The wind turbine power source is the natural randomness of strong wind, the blades often run in the stall condition, the system has a strong stochastic dynamic process, the transmission of abnormal is irregular power input, the main structural components to withstand higher than normal rotation mechanical fatigue loading several times, forming a unique wind turbine dynamics. Wind generator set blades as a flexible structure, the load acting on has a cross and random variability, which is an inevitable occurrence of vibration, the vibration characteristics of their study is very necessary. Blades the structure and strength of the wind generator set reliability plays an important role. With the emergence of high-power wind generators, finite element numerical analysis of the theories and methods have been applied to the structural design of wind generator set. Modern wind generator set blades shape and internal structure complex calculations,it is necessary to study the exact dynamics model and the analysis of blades structure [. The institutional dynamics is to constitute the institutional elements of the inertia and institutions in the rigid parts caused by the vibration of a subject. The kinetic analysis features include: regular modal complex eigenvalue analysis, frequency and transient response analysis, (noise) acoustic analysis, random response analysis, the response and the impact of spectrum analysis, power sensitivity analysis. Here only the blade to vibrate and modal to be analysed [.

Frequency response computation of structures including non-proportional damping in a shared memory environment

With the increased size of the finite element model for improved accuracy, the modal frequency response analysis has been one of the common practices of evaluating the performance of vehicle dynamics. However, there is difficulty in predicting the vehicle dynamics response with non-proportional damping regarding performance. The fast frequency response analysis algorithm (FFRA) has been proved to be very effective for partially damped structural system in the modal frequency response analysis. In the fast frequency response analysis algorithm, performance depends mainly on the complex symmetric matrix eigenvalue problem. Therefore, an efficient complex symmetric matrix eigenvalue problem solver is developed in this article. This approach also uses parallel processing in a shared memory machine for more efficient analysis. Numerical examples show that the new complex symmetric matrix eigensolver provides good accuracy and high performance. Then, the fast frequency response analysis algorithm is applied to a full scale vehicle system that includes only a few viscous damping finite elements. The fast frequency response analysis algorithm significantly improves the performance of the modal frequency response analysis compared to conventional method. In addition, parallel processing improves the efficiency of the overall simulation.

Interior noise analysis of a construction equipment cabin based on airborne and structure-borne noise predictions

Noise from construction equipment affects not only surrounding residents, but also the operators of the machines. Noise that affects drivers must be evaluated during the preliminary design stage. This paper suggests an interior noise analysis procedure for construction equipment cabins. The analysis procedure, which can be used in the preliminary design stage, was investigated for airborne and structure-borne noise. The total interior noise of a cabin was predicted from the airborne noise analysis and structure-borne noise analysis. The analysis procedure consists of four steps: modeling, vibration analysis, acoustic analysis and total interior noise analysis. A mesh model of a cabin for numerical analysis was made at the modeling step. At the vibration analysis step, the mesh model was verified and modal analysis and frequency response analysis are performed. At the acoustic analysis step, the vibration results from the vibration analysis step were used as initial values for radiated noise analysis and noise reduction analysis. Finally, the total cabin interior noise was predicted using the acoustic results from the acoustic analysis step. Each step was applied to a cabin of a middle-sized excavator and verified by comparison with measured data. The cabin interior noise of a middle-sized wheel loader and a large-sized forklift were predicted using the analysis procedure of the four steps and were compared with measured data. The interior noise analysis procedure of construction equipment cabins is expected to be used during the preliminary design stage.

Analysis of structural deformation and vibration of a transformer core by using magnetic property of magnetostriction

AbstractA technique for structural analysis of transformer cores in terms of magnetostriction is proposed. The magnetic flux density of each element is first calculated by the finite element method (FEM). Then the magnetostrictive force on each element is calculated from measurements. The magnetostriction is specified as the initial strain and is converted into the force on each node, and a structural analysis is performed. The advantage of specifying the magnetostriction as the initial strain is that it is possible to obtain the force at the location of each element as a vector. Modal analysis and frequency response analysis were also performed and it was shown that resonance is related to the magnetostrictive frequency and the natural mode. Thus, it becomes possible to forecast the frequency at which the core vibrates most strongly which makes the proposed technique of analysis is very useful. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 19–26, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20947

The role of actual modal-contributions versus frequency to optimize the structure

In modal frequency response analysis, the dynamic analyst is often faced with the structure’s dynamic behavior, the modal contributions included, over a frequency window rather than at a single frequency. Therefore a new method in modal frequency response analysis has been developed for computing both complex modal-contributions and real, actual modal-contributions over a frequency range. Contributions from normal modes to displacement, velocity, or acceleration of a set of selected evaluation points (grid-component combinations) are considered. The focus lies on identifying the major actual-contributions from normal modes and the frequency range they are active in. The method is valid for all branches of mechanical engineering. With the thorough knowledge of the dominant modal-contributions to the physical motion response of relevant structure locations and the modal contributions’ frequency history, the traditional design process can substantially be enhanced. It is worthwhile to notice that by the use of the presented procedure the dynamic analyst may find innovative redesigns which the automatic structural optimizers are not able to find. Examples are given to demonstrate the application, the strength of the coupling between modes, the influence of base and force excitation on the modal contributions and, finally, some recommendations on how to reduce undesired structural responses.

Direct and modal frequency response analysis of sound fields in small rooms by finite element method

In this paper, sound pressures are computed by two techniques using finite element method. One is a technique by solving the system of linear equations directly (direct analysis) and the other is a technique by modal superposition (modal analysis). To confirm the accuracy of the direct analysis, sound pressures obtained by the technique are compared with those obtained by the modal analysis in a room with the volume of 10 m3. Then, as in the modal analysis, two methods are employed: one is a simplified method based on a real eigenvalue problem assuming that the damping matrix, [C], has orthogonality; and another is the method based on complex eigenvalue problem. Those obtained by the direct analysis are in good agreement with those obtained by the two kinds of modal analyses regardless of absorption conditions, even if the analysis is carried out at the frequency close to an eigen frequency. Next, diffuseness of sound field below 315 Hz in a room, which is used in the measurement of ISO140-3, is investigated by the direct analysis from the viewpoint of mean sound pressure level measurements.

Analysis of Structural Deformation and Vibration of a Transformer Core by using Magnetic Property of Magnetostriction

A technique for structural analysis of transformer cores in terms of magnetostriction is proposed. The magnetic flux density of each element is first calculated by the finite element method (FEM). Then the magnetostrictive force on each element is calculated from measurements. The magnetostriction is specified as the initial strain and is converted into the force on each node, and a structural analysis is performed. The advantage of specifying the magnetostriction as the initial strain is that it is possible to obtain the force at the location of each element as a vector. Modal analysis and frequency response analysis were also performed and it was shown that resonance is related to the magnetostrictive frequency and the natural mode. Thus, it becomes possible to forecast the frequency at which the core vibrates most strongly which makes the proposed technique of analysis is very useful. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 19–26, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20947

Use of distributed-memory parallel processing in computing the dynamic response of the passenger—car system

Dynamic response analysis of an automobile is performed in parallel with distributed-memory parallel processors. Firstly, the parallel Lanczos algorithm is implemented in order to obtain partial eigensolutions. Then, parallel modal frequency response analysis is performed. This approach is effective for seamless interfacing of the parallel Lanczos method and modal frequency response analysis with industry car finite element (FE) models requiring dynamic response analysis. The performance of parallel processing is measured for large-scale industry finite element models.