Apr 25, 2017 guidelines to modal analysis and setup using hypermesh for nastran duration. Modal testing is performed on a plate structure with welldefined modes, resonance frequencies and damping values. A modal or natural frequency analysis also known as normal modes or eigenvalue analysis forms the basis of several other dynamic analyses, including the modal approach formulations and response spectrum analysis. Nonlinear modal analysis of structural systems 185 nonlinear modes, the modes constituting a multimode manifold do not interact with the nonmodeled ones for motions occurring on that manifold, thus eliminating contamination from the nonmodeled modes. What is the application of free free modal analysis and constrained. 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. These dynamic properties include resonance frequencies also called natural frequencies or eigenfrequencies and structural modes or eigenmodes. Hello, i am performing freefree modal analysis of an assembly with multiples components. Closed form solutions have been generated for a subset of nonlinear structural systems.
I have performed the modal analysis without any load and boundary condition. To help us do this, we assigned shell element properties to. Nonlinear modal analysis methods for engineering structures by hugo ramon elizalde siller department of mechanical engineering imperial college london university of london a thesis submitted for the degree of doctor of philosophy august, 2004. Introduction modes are used as a simple and efficient means of characterizing resonant vibration. Analytical modal analysis depends on the generation of the equations of motion of a system through a finite element model. The analysis may be done either experimentally or mathematically. Analytical modal analysis modal analysis is the process of characterizing the dynamic response of a system in terms of its modes of vibration. A verification procedure for mscnastran finite element. In fact i got only 6 modes eigenvalues as shown in table 1. Modal analysis is the study of the dynamic properties of structures under vibrational excitation. Tracking the history of modal analysis, the conception of vibration modes dates back. If youre familiar with modal analyses, then there should be nothing new here.
Mechanical vibrations overview of experimental modal analysis. Modal analysis is the study of the dynamic properties of linear structures, based on structural testing or finite element analysisbased simulation. From the hpc capability to the high degree of certainty it delivers, msc nastran is engineered to give you a heightened awareness of how. A verification procedure for mscnastran finite element models alan e. I expected to have 6 rigid body modes with frequency close to zero or more rigid. How can i extract the mass and stiffness matrix from.
Workshop 1 modal analysis of a flat plate mscnastran102 exercise workbook model description. 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. Operational modal analysis often called outputonly or ambient modal analysis is described in this article. In fact, this is a popular case study, so if youve seen it before feel free to jump to part 2. I am trying to extract the mass and stiffness matrix from my nastran model using dmap. Modal space articles education structural dynamics. Contents initialconditionsindirecttransientresponseanalysis 77 modaltransientresponseanalysissol112 78. Other areas are treated in a general sense to introduce their elementary concepts and relationships to one another.
Lets get started on the modal analysis simulation first. Fat establishes links with other nonlinear methods and standard linear modal analysis tech. Rivello the johns hopkins university applied physics laboratory 8621 georgia avenue o silverspring, maryland o 20910 operating under contract n0001772c4401 with the department of the navy approved for public release. Workshop 1 modal analysis of a flat plate mscnastran102 exercise workbook 121 submitting the input. Modal analysis is defined as the study of the dynamic characteristics of a mechanical structure. On top, it provides polyx, which is the poly reference least square complex frequency domain plscf modal analysis algorithm to curve fit the frf matrix from the mimo frf testing results. In this exercise, we set up and ran a modal analysis.
Modal analysis provides an overview of the limits of the response of a system. The cutpro modal analysis module has several practical features which can be used daily in machining shops and machine tool testing the cutpro modal analysis module aims to predict the natural frequency, damping ratio, the stiffness of each mode from frf impact measurements. Lagrange multiplier method, see the nx nastran advanced dynamic analysis. Each year roush performs many modal tests, either standalone, or as part of a larger noise and vibration problem solving effort. This course focuses on additional test and analysis tools beyond those presented in the basic 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 module cutpro modal analysis software.
Modal analysis is the study of the dynamic properties of systems in the frequency domain. February 98 could you explain modal analysis for me. We use modal analysis to help design all types of structures including automotive struc. Pdf, you can in point of fact reach how importance of a book, all the book is. Existence and normalization of complex modes for post experimental use in modal analysis. Modal analysis is widely used to describe the dynamic properties of a structure in terms of the modal parameters. The method is not practical for large systems since two unknown coefficients must be introduced for each mode shape. Interactive deformation using modal analysis with constraints. April 98 could you explain the difference between the time domain, frequency domain and modal space. In addition, the results of a modal analysis will tell you much about the dynamic characteristics of the model, including whether or not you really have a dynamic system at all. So, basically, modal analysis is the study of the natural characteristics of structures. Today, modal analysis has become a widespread means of finding the modes of vibration of a machine or structure figure 3. Basic dynamic analysis users guide siemens global website.
Open the model and start the autodesk inventor nastran environment. 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. In every development of a new or improved mechanical product, structural dynamics testing on product prototypes is used to assess its real dynamic behavior. Modal results are used to diagnose vibration problems, verify targets, validate analytical models, and design damping treatments. If you are loving of this nice of book, just believe it as soon as possible. On the quick access toolbar, click the open command. The following is the list of articles currently available. This field of measuring and analysing is called modal analysis. Psd random vibration tutorial for femap and nx nastran. Below is a finite element representation of the rectangular plate. Nonlinear modal analysis of structural systems using multi. Hi, in optistrcut we define loadstep to define the type of analysis whereas in nastran it can be done using sol cardsol 111 for frf most of the optistruct and nastran cards are almost same.
Simulation is an effective tool for exploring a products response to published road vibration loading. This article what is modal analysis and why is it necessary gives a more detailed answer to your question, but in short. If you are new to modal analyses, then lets discuss this a bit. This is an example of modal analysis applied on a part by using fea module in autodesk inventor 2014. A comparison of the strain and the classic experimental modal analysis tadej kranjc1, janko slavi c 2, miha bolte zar2 april 30, 2014 cite as.
In general in finite element analysis modal analysis is conducted in two methods. Understanding both the natural frequency and mode shape helps to design my structural system for noise and vibration applications. Operational modal analysis another way of doing modal testing. Msc nastran modal analysis tutorials hello evryone, this video how to msc nastran deck prepare using preprocessor hypermesh using. How can i extract the mass and stiffness matrix from nastran via dmap including constrained nodes. Modal analysis roush provides expert modal testing. A comparison of the strain and the classic experimental modal. Testing in actual conditions, however, is time consuming and expensive. Introduction exact solution of the free vibration problems is where coefficients can be determined from the initial conditions. You can perform frf using optistruct solver aswell.
Comparison of finite element method and modal analysis of. This model is defined as a set of natural frequencies with damping factor and natural modes vibration. Automotive buzz squeak and rattle mechanisms analysis. The mass of a fluid inside a container can affect the natural frequency of the structure. 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. How to include fluid in a modal analysis in nastran. In mathematical modal analysis, one attempts to uncouple the structural equations of motion so that each. How to include the mass of a fluid in a modal analysis with the nastran solver. Open the model for modal analysis inventor autodesk. For this example, use lanczos method to find the first five natural frequencies and mode shapes of a flat rectangular plate. It is a critical part of the design process for evaluating design variations and for identifying a final design candidate that. Vibration analysis is a huge topic and is easily the second most common type of fea analysis. The nastran file can be edited to add the commands mfluid and elist to define the fluid. Free free modal analysis rigid body modes with nozero.
Premium modal analysis with polyx edm modal premium modal analysis includes all the features of standard and advanced modal analysis. Modal analysis provides a detailed overview of the theory of analytical and experimental modal analysis and its applications. 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. Msc nastran is the premiere finite element analysis solver that continues to be the selected choice by engineers for over 50 years. Frequency domain decomposition fdd and enhanced frequency domain decomposition efdd concepts are presented and ap. This application note emphasizes experimental modal techniques, specifically the method known as frequency response function testing. Free vibration analysis is used to determine the basic dynamic characteristics of the system with the righthand side of equation 12 set to zero i. How can the fluid be accounted for in a normal modes analysis with nastran. Topics include operating data, multiple input multiple course output testing, advanced multiple reference modal parameter estimation, structural.
277 1530 154 784 1339 124 1382 15 562 1115 861 598 599 44 1088 1477 272 192 421 424 694 584 341 48 1509 120 219 80 612 1114 264 211 271 948 921 1480 97 256