Craig 2 rootlocus method precise root locations are known and actual time response is easily obtained by means of the inverse laplace transform. The frequency response analysis is used to compute structural response to steadystate oscillatory excitation. This white paper provides the simulation engineer with all the necessary background to perform the following analysis sequences with femap and nx nastran. Random based on the deterministic frequency response msc. As stated in the nastran dynamic analysis users guide the random analysis is treated as a data reduction procedure that is applied to the results of a frequency response analysis. Open the model and start the autodesk nastran incad environment. Next setup the modal frequency response analysis sol111 to use the option restart previous analysis and select the nastran database. Frequencyresponse method frequency response is the steadystate response of a system to a sinusoidal input. Thebeamselementxaxiswillbeparalleltothebasicsystemsxaxisby ourchoiceofx1,x2,andx3x,y,andz. Venkayya wright laboratory wright patterson afb oh 454336553 summary the nasa structural analysis nastran ref 1 program is one of the most extensively used engineering applications software in the world.
The first book in the series, getting started with msc nastran users guide, is intended for those readers who are unfamiliar with the finite element method, those who have never run msc nastran, or those who are interested in a general overview of msc nastrans capabilities. Frequency response and random response dynamic response in nastran. Excitations can be in the form of applied forces and enforced motions displacements, velocities, or. Frequency response analysis altair optistruct altair forum. Nx response simulation enables users to interactively evaluate the dynamic. Highly efficient modal frequency response analysis cdh ag.
One way to reflect on this is to use programming equivalents. Vibration response, random response, excitation functions, ideas response analysis. Contents initialconditionsindirecttransientresponseanalysis 77 modaltransientresponseanalysissol112 78. In frequency response analysis, the excitation is explicitly defined in the frequency domain.
Eigenvalue routines in nastran a comparison with the block lanczos method by v. Analysis uses frequency response as basis for determining overall. Nastran for solving various dynamic analysis problems. Msc nastran 2012 linear static analysis users guide. The fe solver provides you with keywords, much the same way that software provides you with apis.
Using femapnx nastran for frequency spectrum and random vibration analysis. The frequency response function is a particular tool. Design process can be independent of the system order time delays are handled correctly graphical techniques analysis and synthesis are quite simple. Modal frequency response analysis results from nastran not. Modal frequency response analysis msc nastran 102 exercise workbook 61 objectives. Femap with nx nastran dynamic response enables you to calculate your products forced response to inputs loads or motion that vary with time or frequency, as well as compute complex eigenvalues.
Sol 108 to perform direct frequency response analysis. You will take advantage of the analysis restarts option to transition from normal modes analysis to frequency response analysis. Hammond january 2008 1 introduction frequency response sometimes called fr is a key analysis tool for control of some dynamic systems. The model is a simple cantilever beam with 48 elements and. Frequency response analysis is a method used to compute structural.
Principles of vibration analysis with femap and nx nastran. Frequency response simulation in ug nx advanced simulation. Nx benefits reduce your risk by using simulation to save time and cost compared to physical buildandbreak test cycles accelerate innovation through rapid iteration and. Solution frequencies can be defined in two separate. For example, an xy plot of the acceleration does not follow the expected or theoretical curve. Sm astros theoretical manual for version 20 universal analytics, inc. Improve structural dynamic behavior through analysis of a products response to time or frequency varying loads. Frequency response analysis results view use a hot spot tool to identify critical displacements and stresses animate deformed shapes view and interactively switch between multiple normal modes via modes navigator use a results manager to view analysis results by study, part, assembly or result type transform results to cartesian. Ug nx advanced simulation fea, we can simulate frequency response simulation based on modal analysis results. Frequency response permits analysis with respect to this. Hello, this may be a basic question, but i found no obvious answer on the web or the nastran dynamic analysis users guide. Nx nastran dynamic response improve structural dynamic behavior through analysis of a products response to time or frequency varying loads answers for industry. Certification and the aircraft design cycle aircraft structural, aerodynamic, weight, performance, and certification requirements are dependent on each other. It also includes efficient, stateoftheart analytical tools for conducting nastran modalbased response dynamics simulation.
Frequency response functions are complex functions, with real and imaginary. Hi, you can convert data from frquency domain to time domain using hypergraph 2d. Normal modes analysis for prestiffened structures 5. Frequency response function overview there are many tools available for performing vibration analysis and testing. Dynamic response analysis is an addon module to the femap with nx nastran base module that compliments the linear static and normal modes. This guide serves as both an introduction to dynamic analysis for the new user and a reference for the experienced user. Dynamic response in nx nastran stress analysis experts. Altair radioss software, so that it can be used in industrial vibration and acoustic analysis. Direct transient analysis using nastran casting the blame theres a lot that can be improved with very many of the commercial fe preprocessors, but not all the blame lies with them. A frequency response function frf is a transfer function, expressed in the frequencydomain.
This book is one in a series of users guides describing the use of msc nastran. The steps for performing a frequency response simulation are as follows. Frequencyharmonic response analysis nastran sol 111 sol 108. Ludwiczak lewis research center cleveland, ohio prepared for the 1996 world users conference sponsored by the macnealschwendler corporation. Widrick analex corporation brook park, ohio damian r. Analysis uses frequency response as basis for determining overall statistical response by multiplying the transfer functions of the frequency response and the input psd to develop a response spectral density this is in turn used to determine an rms response, which is used to determine the statistical response of the structure. Eigenvalue routines in nastran a comparison with the.
Excitations can be in the form of applied forces and enforced motions. It is used as a measure of the total component stress. Noise, which is always present in any system, can result in poor overall performance. Msc nastran aeroelasticity for aircraft certification for some of the conditions to demonstrate the accuracy of the analysis and to prove the airplane is safe to operate. Modal frequency response analysis mscnastran 102 exercise workbook 61 objectives. Shock response spectrum in autodesk nastran ina in order to do srs inside autodesk nastran incad a modal analysis needs to be created and the bulk data file modified with the srs setup. Response analysis can be done prior to the completion of a.
The direct frequency response method solves the coupled equations of motion in terms of forcing frequency. Now with examples showing different options for psd analysis. All the nastran cards necessary to perform a frequency response run are described here. Frequency response analysis is the technique whereby a sinusoidal test signal is used to measure points on the frequency response of a transfer function or impedance function. Modal frequency response analysis is an alternate approach to computing the.
In frequency response analysis the excitation is explicitly defined in the frequency domain. Advanced cae applications for professionals software that works for you. The system is subject to an input of the form xt a t t sin 0. Direct transient analysis using nastran kfourmetrics. Frequencyharmonic response analysis nastran sol 111. Msc simcompanion basic dynamic analysis users guide. Get started launch open from the ribbon, click environments, and autodesk nastran incad. Compute nodal displacements for desired time domain. Nx nastran is an enhanced proprietary version developed and maintained by siemens product. Model setup within autodesk nastran incad first like all dynamic analyses run a normal modes analysis with a fixed base to ensure at least. Combining acceleration and displacement dependent modal frequency responses using an mscnastran dmap alter alan r. If the input to an lti system is a sinusoid, the steadystate output is a sinusoid of the same frequencybut. Frequency response methods are a good complement to the root locus.
Combining acceleration and displacement dependent modal. All the nastran cards necessary to perform a random run are described here. This analysis is based on the fact that if the input to a stable process is oscillated at. Nx nastran dynamic response nx table 1 analysis types available with nx nastran dynamic response summary of analysis types solution sequence number normal modes analysis 103, 200 111, 200 direct frequency response 108, 200 cyclic direct frequency response 118 112, 200 direct transient response 109 acoustic analysis 108, 109, 111. To perform frequency response simulation in ug nx advanced simulation fea nastran,inertance frequency response function. Pdf of psd random vibration tutorial for femap and nx nastran 3. Using femapnx nastran for frequency spectrum and random.
The basic setup is shown in figure 1 in which a sine wave ut is applied to a system with transfer. Nastran basic dynamics users guide is a guide to the proper use of msc. Dynamic analysis random response of the hinge model nastran random response analysis response spectrum analysis of towerhinge model nastran response spectrum analysis please contact and i can provide a package of other reference documents that i have collected. Following is an example of a nastran swept sine frequency response analysis run. Compute nodal displacements for desired frequency domain.
Craig 3 many times performance requirements are given in terms of frequency response andor time response. Sol 111 to perform modal frequency response analysis. January 9, 2017 updated with specific info for certain industries for a comprehensive look at psd random vibration in femap. The results of a modal frequency response analysis with nastran are not as expected. Using table ids and set ids in mscnastran makes it possible to apply many.
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