Operating deflection shape ods and modal analysis ods services. Using lowlevel vibration measurements for ods analysis. He is responsible for field vibration testing involving ods and modal analysis. Introduction to operational modal analysis rune brincker technicaluniversityofdenmark carlos e.
Traditionally, an ods has been defined as the deflection of. Analytical modal analysis modal analysis is the process of characterizing the dynamic response of a system in terms of its modes of vibration. Two ansys elements, beam4 and pipe16, allow gyroscopic effects to be specified in the form of real constant spin rotational speed, radianstime. Covers all important aspects that are needed to understand why oma is a practical tool for modal testing covers advanced topics, including closely spaced modes, mode shape scaling, mode shape expansion and estimation of stress and strain in operational responses discusses practical applications of. Operating deflection shape ods analysis is a method used for visualisation of the vibration patterns of a machine or structure caused by unknown operating forces. Ojeda submitted to the department of civil and environmental engineering on may 09, 2012 in partial fulfillment of the requirements for the degree of master of engineering in civil and environmental engineering abstract.
Tony dematteo, who holds an expert iso 184361 category iv certification in vibration analysis and having extensive experience in. Operational modal analysis another way of doing modal testing. The paper shows the correlation of different types of ods data and discusses its suitability for model updating. In ods, the vibration of multiple points on a structure during operation is assembled in a way to provide a visual description of the vibration shape that the structure adopts during operation. Improve your vibration analysis skills, visualize machine and structure vibrations and better diagnose problems by watching a movie of the machine vibrating at forced or resonant frequencies. In the following example, finite element analysis was. Modal analysis is a powerful tool to identify the dynamic characteristics of structures. Operational deflection shape analysis and vibration solving. Matlab implementation of an operational modal analysis. To summarize, we have seen that mode shapes are defined. Operational modal analysis another way of doing modal. Ods analysis is a method used for visualisation of the vibration pattern of a machine or structure as influenced by its own operating forces. Ritec utilizes advanced crosschannel capabilities of its azima dli vibration data collectors.
Mode property defined for all modes defines the frequency region dominated by the mode s i f f. Solving structural vibration problems using ods analysis. Prosigs structural animation software performs ods analysis. The ods is a powerful troubleshooting tool to facilitate and visually understand most common vibration problems in any turbomachine. If the forcing function happens to occur at a frequency near a structural resonance, the operational shape will correspond to a shape determined through experimental modal. Traditionally, most modal testing was done using sine wave based methods and analog instrumentation. Shaker based operating deflection shapeods semantic scholar. Animations created from the ods test data show exaggerated motion but consistently scaled of operating machinery at any given frequency. Operational deflection shapes or ods analysis gives additional insight into noise or vibration problems that individual measurements alone do not. Modal analysis and operating deflection shape in the process of diagnosing rotating machinery, it may become unavoidable to do some structural vibration analysis as well. An ods shows the deformation of a structure at a specific frequency and shows the response of a structure to both resonant and forced vibration, and is generally very representative of real world data. The title of this paper is actually a universal law which is used for all modal analysis, fundamental law of modal analysis flma. With our solution, you are able to excite the structure with an impact hammer or modal vibration shaker and easily measure the. This is as opposed to the study of the vibration pattern of a machine under an known external force analysis, which is called modal analysis.
It provides a complete set of tools for observing, analysing and documenting the vibrational behaviour of machines and mechanical structures. This application note emphasizes experimental modal techniques, specifically the method known as frequency response function testing. Learn how to use operating deflection shape ods and modal analysis to troubleshoot and solve complex structural and rotating equipment problems. With potentially thousands of machines to analyze, its no small task. It provides very useful information for understanding the dynamic behaviour of structures and is one of the most used applications in structural dynamics. Ods and modal analysis give a clear picture of the machines motion, however neither tool has the capability to solve resonance problems. Operational modal analysis often called outputonly or ambient modal analysis is described in this article. Operating deflection shapes ods is a complimentary technique to modal analysis.
Modal analysis and modal testing ods, mimo, oma dewesoft. Emersons ams 2140 machinery health analyzer was designed specifically with these goals in. All modal testing is done by measuring an ods, and then applying special interpretation e. This option provides fast and efficient structural model generation and full 3d visualization of test and analysis results. Modal analysis and operating deflection shape, applications. Mode shapes and operating deflection shapes odss are related to one. Oma modal analysis prosigs modal analysis software performs oma. This presentation will focus on the operational modal analysis oma of a highpower hydroelectric generator using a vector autoregressive arma model is employed in a short time manner in order to. Damping is normally ignored in a modal analysis, but if its effects are significant, the damped method is used. Abstract this thesis presents two novel nonlinear modal analysis methods, aimed at the identification of representative engineering structures. Comprehensively covers the basic principles and practice of operational modal analysis oma. Edm modal geometryodsanimation is the primary edm modal software module, and is required for every edm modal system.
Modal analysis operational deflection shape ods analysis is conducted to extract critical structural and dynamic system charachterstics that aid in the diagnosis and charachterisation of complex dynamic behaviour of structures and machinery. The material covered in this course goes beyond the requirements for ods and modal analysis subjects included in category iii iv guidelines established by iso 184362, condition monitoring and diagnostics of machine requirements for training. Effective and affordable modal analysis and modal testing solution for ods, mimo, and oma testing methods. Both modal analysis and ods are used extensively to. Modal testing frf modal test and analysis are used to determine the engineering structures modal parameters, such as modal frequencies, damping ratios, and mode shapes. Ods motion of structure vibrating naturally for example bridge vibration or when excited by an unknown force for example generator vibration. Ods analysis can be done both in the time and spectral domain by relatively simple means. Ods testing is done for frame numerically using ansys. Both the amplitude and phase of vibration measurements are animated. Modal testing is performed on a plate structure with welldefined modes, resonance frequencies and damping values. Pdf an application of operational deflection shapes and spatial. Extensive overview of mescope software and hands on use about 50% of. Extensive overview of mescope software and hands on use about 50% of class time. A such updated model would automatically guarantee the validity to operational conditions.
Simplified modal analysis for the plant machinery engineer. The modal test is an indispensable tool to determine natural frequencies and mode shapes of any structure. Today, modal analysis has become a widespread means of finding the modes of vibration of a machine or structure figure 3. Modal analysis is defined as the study of the dynamic characteristics of a mechanical structure. Procedure from the odsmodal main menu, press f9 point search or use the arrows on the keypad to go to a measurement point. Experimental modal analysis ema, oma, ods service sint.
The measured excitation and response or only response data are utilized in modal analysis, and then dynamic signal analysis and modal parameters identification are processed. Traditionally, most modal testing was done using sine wave based meth ods and analog instrumentation. Each mode is defined by natural frequency, modal damping and mode shape. Animate the machine with fourchannel ods modal analysis to identify structural issues fourchannel vibration analysis with the ams 2140 overview time is often the critical factor in completing routebased vibration analysis. If an engineer were to animate a wireframe model using a set of acceleration transmissibility spectra, he. Most often this is done by performing ods operating deflection shape analysis or modal analysis. This is different from the study of the vibration patterns of a machine under known external forces, which is. An operational deflection shape is an animation of the vibration pattern in a structure.
Nevertheless, modal analysis has often been shrouded in a veil of mystery. It can be carried out to determine the natural frequencies and mode shapes of a structure and to verify accuracy and calibrate a finite element model fe. His career spans more than 12 years, primarily working with rotating equipment. Typical application is rotor dynamics, where gyroscopic damping effects are important. Ods analysis is very beneficial in combination with operational modal analysis as it determines and visualizes the combination of the actual forcing functions acting on the structure and the dynamic behavior of the structure. Analytical modal analysis depends on the generation of the equations of motion of a system through a finite element model.
Pdf case study of operational modal analysis oma of a. During the late 1960s however, the discovery of the fast fourier transform fft algorithm and the use of digital computers in laboratory. Is it a mode shape, or an operating deflection shape. Ojeda bachelor of science in electrical science and engineering, mit, 2010 master of engineering in electrical engineering and computer science, mit, 2011. Other areas are treated in a general sense to introduce their elementary concepts and relationships to one another. Our experience includes motors, pumps, gearboxes, turbines, fans, piping, conveyor heads and what may be the largest ods test performed in the power industry a turbine generator and two floors of the turbine building. Ods analysis is generally used when a problematic structure is experiencing discrete forcing functions, such as from unbalance or other harmonically related components. Case study of operational modal analysis oma of a large hydroelectric generator conference paper pdf available october 2011 with 258 reads how we measure reads. The software guides the user through the different steps to realize a complete ods or modal analysis of the measured structure. Alstomecotecnia experimental modal analysis of the structure of the gondola of a real size prototype of an eco100 wind turbine. In every development of a new or improved mechanical product, structural dynamics testing on product prototypes is used to assess its real dynamic behavior. The advantage of the approach lies in the fact that no modal analysis is. Operational modal analysis oma operational modal analysis of the vibrations of contrerass railway viaduct for the passing of the ave. The use of operating deflection shapes ods to model the.
Theory experimental modal analysis with primary focus on impact excitation. Experimental modal analysis ema, oma, ods experimental modal analysis ema is an effective instrument for describing, understanding and modelling the dynamic behaviour of a structure. Natural frequencies and mode shapes are inherent properties of. Ods modal analysis in addition to providing fast, actionable information, an effective solution must take advantage of modern communication and interface innovations that make tasks easier and more intuitive. Procedure from the ods modal main menu, press f9 point search or use the arrows on the keypad to go to a measurement point. Ods vibration patterns under operating conditions hbm. Typical vibration analysis and pursuing trial and error. The paper shows the correlation of different types of odsdata and discusses its suitability for model updating. Emersons ams 2140 machinery health analyzer was designed specifically with these goals in mind. Required for the measurements are one or more vibration transducers that rotate with the shaft. Matlab implementation of an operational modal analysis technique for vibrationbased structural health monitoring by alejandro p. Modal domain 27 the modal domain is found as ththe modal domain is found as the region around the peak wheree region around the peak where d 2 f 1 f 1 f 0 u t u d 2 2 discriminator function.
The ods matrix is used to formulate the spatial filter that is further used for damage. Is it a mode shape or an operating deflection shape. Operating deflection shape ods analysis is a relatively easy method used for visualisation of the vibration. Frequency domain decomposition fdd and enhanced frequency domain decomposition efdd concepts are presented and ap. The overall objective is to detect, localize, identify and quantify the. This is different from the study of the vibration patterns of a machine under known external forces, which is usually referred to as modal analysis. Over the past 20 years, the number of ways in which modal testing has been done has proliferated greatly.
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