A new design undergoing testing may encounter severe vibration while it is on the ground, preparing for takeoff. In the vertical direction, 31 different locations on the boom assembly were excited. Ground vibration test the refueling boom and its supporting structure were excited in the vertical and lateral directions with an instrumented hammer impact excitation. The paper is presented in the context of the ground vibration test on airbus a350xwb msn1 which.
In the cases where the value of the excitation at any given time can not be predicted. Urban trains running on ground surface lead to evironmental ground vibrations in the vicinity of railwaylines. Ground monitoring of bottom hole assembly vibration in. The transmission of ground vibration into nearby buildings has become a topic of great importance, as many underground railways operate in denselypopulated urban areas around the world in both residential and commercial zones. Gasparovsky slovak university of technology in bratislava, slovak republic this paper deals with the influence of harmonics produced by the static excitation system of generator on the rotor ground fault protection of synchronous generator. For this purpose, a twodegreeoffreedom model of a coupled seismicvibratorroughground system is proposed with which the nonlinear vibration properties are analyzed. A baseexcited singledegreeoffreedom model with a variable damper is considered. Magnification factor v2 for the case of ground excitation via spring and. Thornelytaylor vibrating machine at frequencies where calculation of all the outofbalance forces across the spectrum is impractical. The response of a sdof system to arbitrary forms of excitation can be analyzed with the aid of the impulse function ht with magnitude of p. This is the most basic form of vibration monitoring. Generally, engineers try to avoid vibrations, because vibrations have a number of unpleasant effects. This dissertation investigates the generation of ground vibration from underground railways.
A gvt campaign typically requires the involvement of different teams from different divisions or companies. The base of the spring is given a prescribed motion, causing the mass to vibrate. Techniques for predicting the source term in the case of moving rail vehicles, dependent on the vehicle and track dynamic parameters are available 7. Afrc research facilities research aircraft integration. This covers also a possible phase lag due to the damping in the system. Vibration of mechanical systems 11 2 0 22 d mx kx dt 11 2 2 0 22 m x x k x x or mx kx 0 this is the same equation as we got earlier. Simple vibration problems with matlab and some help from maple. System fbd system sketch 3 sdof base excitation cont assume. If a system is initialised with interference, so it vibrates by itself, then the vibration is called free vibration. Con tents preface xi chapter1 introduction 11 primary objective 1 12 elements of a vibratory system 2 examples of vibratory motions 5 14 simple harmonic motion 15 vectorial representation of harmonic motions 11 16 units 16 17 summary 19 problems 20 chapter 2 systems with one degree of freedomtheory 21 introduction 23 22 degrees of freedom 25 23 equation of motion. Wind velocity, road roughness and ground motion during earth quake.
Excitation and automatic voltage regulator system note. Ground vibration tests on a flexible flying wing aircraft. The critical velocity of the ballastless slab trackground system is greater than the rayleigh wave velocity of the soft layer of the subsoil. As with the generator, every effort is made to eliminate all vibration from the prime mover but there will always be some amount of vibration present at 60 hz for a 2 pole unit.
No load condition operative condition of the generator when it is at nominal speed and voltage in terminals, and is not connected to the electric power system. The vibration frequency at which the mode shape occurs is called the natural frequency. In this model, the forcedeflection characteristic of the contact interfaces is determined by finite. These gvt data are used to validate analytical vibration and flight control models by measuring flight control transfer functions and structural frequency response functions. Then, the measured signals are reduced, encoded in mud pulses, and transmitted through the mud to the ground. Helicopter ground resonance revision b by tom irvine email.
The purpose of the ground vibration test is to determine information such as the damping, stiffness, natural frequencies, and mode shapes inherent to the dynamic response of a structure. Measurement of blast induced ground vibrations and seismograph calibration by marks. The response of an idealized multistory building to earthquake ground motion can be computed by the following procedure. Modern solutions for ground vibration testing of large. In order for a body to vibrate, it has to be excited by a source. Modern solutions for ground vibration testing of large aircraft bart peeters1. Modern solutions for ground vibration testing of large aircraft. Excitation, in physics, the addition of a discrete amount of energy called excitation energy to a systemsuch as an atomic nucleus, an atom, or a molecule that results in its alteration, ordinarily from the condition of lowest energy ground state to one of. Selfexcitation optional the force acting on a vibrating system is usually external to the system and independent of the motion.
Excitation, in physics, the addition of a discrete amount of energy called excitation energy to a systemsuch as an atomic nucleus, an atom, or a molecule that results in its alteration, ordinarily from the condition of lowest energy ground state to one of higher energy excited state. Generator endwinding vibration analysis a capstone experience. The system mechanical vibration is due to the prime mover that is driving the generator. A groundborne vibration assessment model for rail systems.
Free vibration means that no time varying external forces act on the system. Track and ground vibrations generated by highspeed train running on ballastless railway with excitation of vertical track irregularities. Consider a system attached to the base via a spring and a damper. Stearman of the university of texas at austin to conduct a gvt ground vibration test on a starlite aircraft in preparation for an. Generation of ground vibrations by superfast trains. When a natural frequency coin cides with an excitation frequency, a state of resonance exists. This modified input is then used for each level of the building to determine the pseudodisplacement, pseudovelocity and pseudoacceleration that various sdof systems will be subjected to when the ground excitation is. The prime mover is rotating at the fundamental frequency of the generator. This type of excitation is common to many system involving rotating and reciprocating motion. A common source of objectionable noise in buildings is the vibration of machines that are mounted on floors or walls. An introduction to frequency response functions by tom irvine. Pdf probabilistic analysis for the response of nonlinear. Of course, vibrating systems can be excited in other ways as well, but the equations of.
Obviously, the best place to mount a vibrating machine is on the ground floor. Principal modes 44 generalized and coupling 45 principal coordinates 158 46 modal analysis. Aircraft ground vibration testing at the nasa dryden. Simple vibration problems with matlab and some help. The vibration at the bottom hole assembly bha of a drill string system dss is generally monitored by using vibration transducers installed in or close to the bha. Excitation of ground vibration due to the passage of trains over a track with trackbed irregularities and a varying support stiffness. Pdf inversion of excitation source in ground vibration from. Base excitation models the behavior of a vibration isolation system.
Pdf frequency response analysis of vibration system with. Objectives and progress on ground vibration testing for. Rotor excitation models the effect of a rotating machine mounted on a flexible floor. In this paper, a prediction model for the ground borne vibration propagation caused by atgrade railway traffic, based in a semianalytical characterization of the propagation, is exposed. Field switch allows connecting and disconnecting the output of the excitation system to the field winding of the generator. The ground vibration test gvt system is necessary to assure the aeroelastic and aeroservoelastic stability of new and modified aircraft. Track and ground vibrations generated by highspeed train. The excitation consisted of a thruster system with a single four. Ground vibration tests have been performed previously in the uav lab at university of minnesota on the body freedom flutter aircraft developed by u. At resonance the system damping alone controls the motions and stresses in the system. To account for the effect of translations and torsion, each story of the building is modelled as three degreesoffreedom dofs, with two dofs for translation in two orthogonal directions and third dof for torsion. A frequency response function can be formed from either measured data or analytical functions. Along with results from this test, we show the additional results from the certification test on the a330 mrtt. The resulting vibration is known as deterministic vibration.
Sdof base excitation cont particular solution sine term. This modified input is then used for each level of the building to determine the pseudodisplacement, pseudovelocity and pseudoacceleration that various sdof systems will be subjected to when the ground excitation is applied. The right column of the basic processes diagram shows that the time waveform can be converted to a frequency spectrum in order to show the analyst where the vibration energy is coming from. There are systems for which the exciting force is a function of the motion parameters of the system, such as displacement, velocity, or acceleration.
Fundamentals of vibration measurement and analysis explained. It has been noted that components of rotating machines. Dynamic response of a light equipment item attached to a nonlinear and torsionally coupled main system is evaluated under bidirectional earthquake excitation. Moreover, many other forces can be represented as an infinite. Torsional vibration of machine systems by ronald l. Participants from an aircraft manufacturer, a university, and measurement hardware and software vendors conducted the test. Dynamic excitation signals and modal parameter estimation strategies in ground vibration testing. The simplest form of vibration that we can study is the single degree of freedom system without damping or external forcing. Free vibration summary this laboratory introduces the basic principles involved in free vibration. The complicated vibration source of the system can hardly be measured directly. Ground vibration testing is an economic method for determining the modal parameters and mode shapes of a structure in preparation for further aeroelastic analysis. First, we will explain what is meant by the title of this section.
Response of a twodegreeoffreedom vibration system with. Frequency response functions are complex functions, with real and imaginary components. Forced vibration of singledegreeoffreedom sdof systems. Ground monitoring of bottom hole assembly vibration in drill. Probabilistic analysis for the response of nonlinear base isolation system under the ground excitation induced by high dam flood discharge. Generator endwinding vibration analysis a capstone. The horizontal axis represents the distance from the track center, and the vertical axis represents the amplitude of vibration velocity, denoted by the vibration velocity level vl, unit db 17 vl 20 lg v e v 0 where v e is the amplitude of vertical vibration velocity, v 0 is the reference vibration velocity with value of 1. Unit 7 vibration of mechanical vibration of mechanical.
Modelling of ground vibration from underground railways. This paper is focused on the influence of the rough contact interfaces on the dynamics of a coupled mechanical system. These gvt data are used to validate analytical vibration and flight control models by measuring flight control transfer functions. The new system was deployed, and the test teams were trained for the demonstration gvt on eads casas a310 boom demonstrator aircraft. Concepts were explored in instrumentation, sensor setup. To do so, the arbitrary excitation pt is considered consisting of a sequence of impulse forces p. Vibration is a continuous cyclic motion of a structure or a component. They may also be represented in terms of magnitude and phase. The variable damping coefficient can be changed to that in. By carefully selecting the shaker locations and the. Frequency analysis is the essence of vibration analysis and. Vibration from blasting international society of explosives engineers ppv ins ppv mms vibration effects 0.
For a car, the steadystate solution is just the superposition of the two individual particular solutions system is linear. Excitation of ground vibration due to the passage of trains. Stagg 1 and alvin j, engler2 abstract blastinduced ground vibrations from surface coal mine, quarry, and construction blasting were measured and analyzed for frequency content and duration characteristics. Aircraft ground vibration testing at the nasa dryden research. This information is used to assess the significance of structural modifications, verify or update the analytical models used in flutter analyses, plan. Excitation of ground vibration due to the passage of. For this purpose, a twodegreeoffreedom model of a coupled seismicvibratorrough ground system is proposed with which the nonlinear vibration properties are analyzed. A freebody analysis of this system in the framework of newtons second law, as performed in chapter 2 of the textbook, results in the following equation of motion. Ground vibration effects summary david siskind, 2000. Systems with base excitation transmissibility and vibration isolation. This system can be used to model a vehicle suspension system, or the earthquake response of a structure.
A groundborne vibration assessment model for rail systems at. It may be noted that in a conservative system potential energy is maximum when kinetic energy is minimum and viceversa. Pdf inversion of excitation source in ground vibration. A frequency response function frf is a transfer function, expressed in the frequencydomain. Recall that a system is conservative if energy is conserved, i. The laboratory is designed to provide the students with insight into the in. Objectives and progress on ground vibration testing for the ares launch vehicles.