Identification of the technical state of suspension elements in railway systems (original) (raw)
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GEMI Research Group has developed a series of research projects aimed at innovation, science and technology on the field of railway systems. The knowledge acquired on trains is the basis on which EAFIT University develops research projects, aimed at transport companies and financed by the Administrative Department of Science, Technology and Innovation of the Republic of Colombia. It is in this direction that this work presents the results of the research process focused on the methodology developed for Operation Modal Analysis (OMA) applied to railway systems. The work is structured under the follow themes: (i) methodological proposal, (ii) evaluation criteria of the system, (iii) Experimental Modal Analysis (EMA), (iv) development of numerical models in multi-body theory, (v) validation of the numerical models, (vi) OMA application using Last-Square Complex Exponential method (LSCE), and (vii) presentation of a case study. The work studies the dynamical performance of a railway veh...
Operational Modal Analysis and the Performance Assessment of Vehicle Suspension Systems
Shock and Vibration, 2012
Comfort, road holding and safety of passenger cars are mainly influenced by an appropriate design of suspension systems. Improvements of the dynamic behaviour can be achieved by implementing semi-active or active suspension systems. In these cases, the correct design of a well-performing suspension control strategy is of fundamental importance to obtain satisfying results. Operational Modal Analysis allows the experimental structural identification in those that are the real operating conditions: Moving from output-only data, leading to modal models linearised around the more interesting working points and, in the case of controlled systems, providing the needed information for the optimal design and verification of the controller performance. All these characters are needed for the experimental assessment of vehicle suspension systems. In the paper two suspension architectures are considered equipping the same car type. The former is a semi-active commercial system, the latter a no...
In this paper, concept of experimental modal analysis is discussed to derive dynamic properties of mechanical structures and equipments. Dynamic properties (mode shape, damping, and resonant frequencies) are calculated using MATLAB program. Amongst present curve fitting method, Rational Fraction Polynomials (RFP) method is used in the derivation of modal parameters. Results obtained from this method are compared with those obtained form experiment and shown in form of standard deviation. This standard deviation is computed from different experimental FRF values and analytically obtained FRF values. 1. Introduction Vibration has many undesirable and harmful effects on life and performance of mechanical equipments and other structures. The effects of vibration are due to dynamic interaction between vehicles and bridges, structural motions due to earthquakes, noise generated by construction equipment , vibration transmitted from machinery to its supporting structures thereby interfering with their performance , damage as well as malfunction and failure due to dynamic loading, fatigue failure, oscillation of transmission lines[1]. The objective of this paper is to emphasis on dynamic analysis of such equipments and structures by capturing their actual dynamic behaviour during experimentation such that the adversity arising from vibration effects can be minimised to improve their life and performance. Dynamic analysis consists of experimental and operational modal analysis. In experimental modal analysis (EMA), structures are artificially excited by exciters (Impact hammers and shakers). In operational modal analysis (OMA), structure is analysed while it is operated upon. For large and heavy structures (civil structures such as bridge and dams), modal analysis is used to detect damage by ambient (traffic) condition [2] .Recent trends in dynamic analysis are extremely focused on better performance and life of structures. Self excited vibrations of tool result in unstable cutting process, poor surface finish, reduced productivity and damage on the machine itself. By considering spindle geometry (its diameter and length), bearing stiffness, tool holder geometry and selection of combination of depth of cut and spindle speed from stability lobe diagrams, machining operation can be made chatter free[3,4]. In vibration of rotating equipments (such as pump, turbine etc.), dynamic analysis is used to check their health as excessive noise of these equipments is experienced by personnel in large power plants and refineries due to damage or failure of seals [5]. 2. Methodology In this paper, EMA is focused upon. EMA is used to characterize resonant vibration in machinery and structures. In EMA, a mode of vibration is defined by three parameters; modal frequency, modal damping and mode shape. Modal parameter estimation is the process of determining these parameters from experimental data. Furthermore, a set of modal parameters can completely characterize the dynamic properties of a structure. This set of parameters is also called a modal model for the structure. Modes (or resonances) are inherent properties of a structure. 199
A review of operational modal analysis techniques for in-service modal identification
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2020
Vibrations are the root cause of many mechanical and civil structure failures. Dynamic characteristics of a structure must be extracted to better understand structural vibrational problems. Modal analysis is used to determine the dynamic characteristics of a system like natural frequencies, damping ratios and mode shapes. Some of the applications of modal analysis include damage detection, design of a structure/machine for dynamic loading conditions and structural health monitoring. The techniques used for modal analysis are experimental modal analysis (EMA), operational modal analysis (OMA) and a less known technique called impact synchronous modal analysis (ISMA), which is a new development. EMA is performed in simulated controlled environment, while OMA and ISMA are performed when the system is in operation. Although EMA is the oldest modal analysis technique, there is an increasing interest in operational modal analysis techniques in recent years. In this paper, operational modal analysis techniques OMA and ISMA are reviewed with their development over the years and their pros and cons discussed.
SOFTWARE FOR OPERATIONAL MODAL ANALYSIS AND AUTOMATIC IDENTIFICATION OF MODAL PARAMETERS
etsmtl.ca
In this paper, we present a software for the Operational Modal Analysis (OMA) of vibrating structures in operating conditions. The method used is based on a multivariate autoregressive model, with the model's parameters of the model are estimated by least squares via the computation of the QR factorization, and the modal parameters are identified from the eigendecomposition of the state matrix. The natural frequencies, damping rates and modes shapes are updated with respect to the model order and are successively constructed on stabilization diagrams with their corresponding confidence intervals. Furthermore, an optimal model order can be automatically selected from the evolution of a factor called the Noise rate Order Factor (NOF) from which the structural modes are automatically distinguished from the spurious ones in order to construct noise-free spectra. After the frequency ranges of interest are selected, the natural frequencies and damping rates are automatically identified. The proposed software is user friendly and the operator can easily determine the accuracy of the modal parameters that are automatically computed. Several experimental applications are described by way of examples.
A Comparative Review on Operational Modal Analysis Methods
2015
Abstract. In the present study we investigate development of operational modal analysis (OMA), different OMA techniques as well as relevant issues and experimental studies. Furthermore, we classify previously performed studies have been conducted so far and consider the most important one. So, first we review the fundamental concepts. Then, the history and application of the OMA method will be examined comprehensively to observe their role in the development of the technique. Three basic methods of FDD, SSI, and Next will be discussed and the research works associated to them will be analyzed.
Archives of Transport
The analysis of dynamic parameters finds effective application in processes related to the assessment of the technical condition of machines. Mass transport vehicles are particularly sensitive to maintaining an appropriate level of traffic safety through relevant design and diagnostics. The combination of numerical and experimental methods increases the efficiency of modal properties investigations, which can be used as diagnostic parameters. During the research, the authors performed a numerical model of a system composed of a rim and an inner disc of a wheel fitted in a Konstal 105Na tram, widely used in many polish cities and frequently subjected to repair and renovation processes. The Time Response analysis in SOLIDWORKS (also called Modal Time History) was then conducted, resulting in obtaining information about object vibration response in time domain to the impulsive excitation at given points. These signals were then processed in MATLAB aiming at determining the frequencies ...
Estimation of damping model correctness using experimental modal analysis
This paper is dedicated to the damping identification problem. Short outlook of damping identification methods is given in the first part of the paper. All these methods can successfully identify internal damping of free-moving structures but it becomes problematically to correctly estimate damping forces when the structure is fixed and there are some joints. The recent methods of structural damping identification don’t give a full understanding of dissipation problem too. An explanation of damping-frequency relation features based on the existence of another damping nature, external damping for example, is proposed in this paper. These assumptions are demonstrated by the modal parameters identification of a turbine blade.