Chapter 3 is devoted to a description of the techniques of mobility or frequency response function measurements. Pdf theoretical basis of modal analysis researchgate. Modal analysis theory noise and vibration analysis. Most times, it is impossible to describe this simply and some of the basic underlying theory needs to be addressed in order to fully explain some of these concepts. Vibration, estimation, frequency domain, modal analysis, modal parameters, natural.
So, basically, modal analysis is the study of the natural characteristics of structures. Modal analysis calculates the natural frequencies of the system alone. Therefore, this study provides a numerical tool for modeling and analyzing of a two degree of freedom quarter car model suspension system. Geometry, mass, and constraints are the only factors that can affect modal analysis. A modal analysis calculates the undamped natural modes of a system, characterised by their modal frequency and mode shape. Practical testing shaker bed testusing an impact hammer 2. In fact, this is a popular case study, so if youve seen it before feel free to jump to part 2. View enhanced pdf access article on wiley online library html view. Theory is presented as needed to enhance the logical development of ideas. Modal analysis provides an overview of the limits of the response of a system. Comparison of finite element method and modal analysis of. Sep 01, 2005 abstract variable mass structures exhibit nonstationary characteristics and the corresponding timevarying tv dynamics are difficult to represent by explicit dynamic equations or finite element models via mechanism analysis. Every structure vibrates with high amplitude of vibration at its resonant frequency.
Comparison of finite element method and modal analysis of violin top plate ye lu music technology area, department of music research schulich school of music mcgill university montreal, canada june 20 a thesis submitted to mcgill university in partial ful llment of the requirements for the degree of master of arts in music technology. As shown in the preceding chapter, the motion of a dynamic structure or system may be represented by a set of simultaneous differential equations using some. Modal analysis theory noise and vibration analysis wiley. Chapter 2 and 3 which is the bulk of the note describes the. If youre familiar with modal analyses, then there should be nothing new here.
Modal analysis theory and testing ward heylen, stefan lammens, paul sas. Steffen, jr encyclopedia of life support systems eolss summary this contribution is devoted to two interrelated topics in the field of structural mechanics, namely, structural dynamics and modal analysis. Modal analysis is the processes of determining the inherent dynamic characteristics of any system and using them to formulate a mathematical model of the dynamic. Analytical modal analysis, which is primarily related to the modeling of the dynamic behavior in the modal space, making use of the modal characteristics. Examples would include measuring the vibration of a cars body when it is attached to a shaker, or the noise pattern in a room when excited by a loudspeaker. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Modal analysis is the study of the dynamic properties of structures under vibrational excitation. This field of measuring and analysing is called modal analysis. It begins with the concept of normal modes of an mdof system and its orthogonality properties. Modal analysis theory and testing ward heylen stefan lammens paul sas division of production engineering, machine design and automation katholieke universiteit leuven. If you are new to modal analyses, then lets discuss this a bit. The determination of these modal parameters may be by the way of either a theoretical analytical or numerical approach or an experimental approach and. Experimental mechanics structural dynamics and modal analysis d. We use modal analysis to help design all types of structures including automotive struc.
With real structures we will usually have lit tle or no knowledge of the mass, stiffness and damping distributions. Modal analysis is a standard technique, welldocumented in the literature. Modal is the simplest analysis and the only thing it does is telling you what are the resonance frequencies of your geometry. Section 1 provides an introduction to the subject and outlines briefly the basic theory of modal analysis with special refer ence to rotating structures. Hence, analytical modal analysis is intended to solve a class of direct problems. This article what is modal analysis and why is it necessary gives a more detailed answer to your question, but in short. Modal analysis of the data obtained from structural testing, provides us with a definitive description of the response of a structure, which can be evaluated against design specifi. Setup a prestressed modal analysis by linking a static structural system to a modal system at the solution level in the project schematic. Modal analysis or natural frequency analysis is usually carried out for complex structures by 2 means 1. The basics of vibration and modal analysis are briefly summarized. Abstract variable mass structures exhibit nonstationary characteristics and the corresponding timevarying tv dynamics are difficult to represent by explicit dynamic equations or finite element models via mechanism analysis. Mechanical vibrations overview of experimental modal analysis.
This video explains in a few steps how to obtain a highquality modal model of a gearbox housing part by performing impact testing and shaker excitation combined with stateof. Pdf modal analysis dr konstantinos daniel tsavdaridis. This is followed by the definition and description of the dynamic stiffness matrix and frequency response function matrix of an mdof system. These modes are numbered, from 1, in order of increasing frequency.
Modal analysis is the study of the dynamic properties of systems in the frequency domain. View enhanced pdf access article on wiley online library html view download pdf for offline viewing. Make sure units are consistent and density is defined. While modal analysis theory has not changed over the last century, the application of the theory to experimentally measured data has changed significantly. Topics include operating data, multiple input multiple course output testing, advanced multiple reference modal parameter estimation, structural.
Basics of modal testing and analysis crystal instruments. Theoretical and experimental modal analysis of nonlinear. Operational modal analysis of variable mass structures based on vector response measurements is considered in this paper. Analytical modal analysis depends on the generation of the equations of motion of a system through a finite element model. Structural testing part 2, modal analysis and simulation. Modal analysis relies on mathematics to establish theoretical models for a dynamic system and to analyse data in various forms. Modal theory is something that helps us understand how scales work. In the past two decades it has become a major technological tool in the quest for determining, improving and optimizing dynamic characteristics of engineering structures. Notice in the modal branch, the structural analysis result becomes an initial condition.
Modal analysis is the processes of determining the inherent dynamic characteristics of any system and using them to formulate a mathematical model of the dynamic behavior of the system. Modes are inherent properties of a structure, and are determined by the material properties and boundary conditions of the structure. Apr 26, 2017 this video explains in a few steps how to obtain a highquality modal model of a gearbox housing part by performing impact testing and shaker excitation combined with stateoftheart modal analysis. Nov 18, 2016 why there is no load in a modal analysis. Defining the problem the simple cantilever beam is used in all of the dynamic analysis tutorials. The schematic setup for modal free vibration is shown here. This course focuses on additional test and analysis tools beyond those presented in the basic modal analysis. Modal harmonic analysis using ansys me 510499 vibroacoustic design dept. The free vibration analysis procedure is very similar to performing a linear static analysis, so not all steps will be covered in detail. Modal analysis with altair optistruct hypermesh some hints all components in the model must have material and properties assigneddefined. This model is defined as a set of natural frequencies with damping factor and natural modes vibration. Modal analysis determines modes to better understand the behavior of components and structures under free vibration. Chapter 5 deals with the modal analysis theory of an mdof system without damping. The reader will gain a sound physical understanding of modal analysis and be able to carry out an effective modal survey with confidence.
Analytical modal analysis modal analysis is the process of characterizing the dynamic response of a system in terms of its modes of vibration. Modal analysis is defined as the study of the dynamic. Understanding both the natural frequency and mode shape helps to design my structural system for noise and vibration applications. Actually, the procedure of determining the systems modal parameters, including natural frequency, natural mode, damping factor, modal scaling, etc. Experimental modal analysis, which consists in determining a set of modal. Structural testing part 2, modal analysis and simulation br0507. Modal analysis theory and testing university of toronto. Modal analysis of rotating machinery structures by enrique simon gutierrezwing a thesis submitted to the university of london for the degree of doctor of philosophy department of mechanical engineering imperial college london september 2003.
The theoretical modal analysis of solid model leads to a description of the behavior of the structure as modes of vibration socalled the modal model. Suspension system is very important for comfort driving and travelling of the passengers. The advances of recent years with respect to measurement and analysis capabilities have caused a reevaluation of what aspects of the theory relate to the practical world of testing. However, many times the theory is just a little too much to handle and some of the concepts can be.
This is an example of modal analysis applied on a part by using fea module in autodesk inventor 2014. Tech tips simcenter testlab the fundamentals of modal analysis. Although modal techniques are mathematical in nature, the discussion is inclined toward practical application. The reason they are called modes is they are not actually completely different scales, but rather different modes of the. The theoretical modal analysis of solid model leads to a description of the behavior of the structure as modes of vibration socalled the modal model 5. Modal analysis theory application of modal analysis. The modal analysis is useful when we want to find out what are the resonant frequencies of a rigid body when a certain vibration occurs. Modal analysis provides a detailed overview of the theory of analytical and experimental modal analysis and its applications. Katholieke universiteit leuven, faculty of engineering, dept. Chapter 1 provides a brief overview of structural dynamics theory.
Ansys tutorial modal harmonic analysis using ansys me 510499 vibroacoustic design dept. Most times, it is impossible to describe this simply and some of the basic underlying theory needs to be addressed in order. Introduction modes are used as a simple and efficient means of characterizing resonant vibration. Modal analysis is widely used for solving vibration problems that identify the modal parameters, natural frequencies, damping, and mode shapes of the structure under testing. Modal analysis is a powerful tool to identify the dynamic characteristics of structures. Modal analysis theory and testing ward heylen stefan lammens paul sas division of production engineering, machine design and automation katholieke universiteit leuven belgium. It helps us understand the relationship between scales and how they work together as one to achieve the goal. Ansys tutorial modalharmonic analysis using ansys me 510499 vibroacoustic design dept.
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