166 research outputs found
Optimization of an engine mounting system for vibroacoustic comfort improvement
No full textOrlando (U.S.A.
On antiresonances interpretation and energy concentration along continuous one-dimensional systems
No full textResponse of vibroacoustic problems by the complex envelope displacement vectorization
No full textThe complex envelope displacement vectorization (CEDV) is a promising procedure to solve high frequency vibration and vibroacoustic linear problems, alternative to energy methods. The method consists in a variable transformation that maps the high frequency response variable into an envelope variable characterized by a low wavenumber spectrum. In this paper it is shown that CEDV still suffers of some inaccuracies in its theoretical formulation. However, the results can provide at the present state of the work are comparable, probably better, with those obtained by other recent proposed procedures
Il ripostiglio 1 e i ripostigli “da fonditore” di Frattesina
No full textIl Ripostiglio n. 1 di Frattesina è stato trovato nel 1978, dopo dei lavori agricoli Come gli altri tre di Frattesina, consiste in pezzi di lingotti e vecchi oggetti di bronzo rotti, nel complesso di più
di 200 pezzi, tra cui, lingotti e palette a cannone incavate; pesa circa quattro chilogrammi.
Come
I reperti metallici sono cronologicamente omogenei e appartengono a una fase tarda
dell'età del Bronzo finale; hanno paralleli con i materiali di altre regioni “protovillanoviane” della Penisola Italian
Identification of rigid body inertia properties from experimental frequency response
No full textThe estimate of mass properties
from the massline characteristic of experimental FRFs
has attracted the attention of several authors during the last
decade. The problem is tipically non-linear and, in the technical literature,
iterative as well as direct methods are proposed for its solution.
In this paper a new direct procedure is developed.
The non-linear problem is divided into a series of
simpler linear problems and solved in subsequent steps. A careful
analysis is performed on the conditioning of the systems in order
to assess the minimum number of required measurements, necessary
to solve the problem even in noisy environments.
The proposed approach produces accurate results as it is shown
for two real experimentally tested systems: a two and three-dimensional
structure, respectively. Of course an accurate measurement of the masslines
characteristics is required. An extended discussion on this point
is presented
Evaluation of the SEA parameters of a benchmark by the power injection method
No full textIn this paper an experimental analysis on the energy transmission in vibrating structures is considered. The Statistical Energy Analysis (SEA) is, at present, the most acknowledged theory for the solution of high frequency vibroacoustic problems. The coefficients of the SEA equations depend on the coupling loss factor (CLF), the internal loss factor (ILF) and the modal densities. For complex systems, the values of such parameters cannot be provided by analytical relationships and it is rather necessary to determine them experimentally to provide a reliable solution. In this paper the case of three coupled plates is considered with the aim of determining the SEA parameters (CLF, etc). By forcing the system with a white random excitation, the acceleration of the structures is measured and the energy stored on each plate is determined. The solution of an inverse problem provides the searched SEA parameters. These values are compared with those obtained by a SEA based method, and the SEA results are compared with experimental data
Altering the vibrational behaviour of an i.c. engine as a preliminary step for noise reduction
No full textEfficiency estimation of a benchmark SEA model
No full textStatistical Energy Analysis (SEA) is the most acknowledged technique to solve high frequency problems. However, SEA can be able to provide reliable results only if particular conditions are satisfied. Thus, some basic hypotheses define the range of applicability of the method. The coefficients of the SEA equations depend on the coupling loss factor (CLF), internal loss factor (ILF) and modal densities. Theoretical relationships allow to predict the CLFs and ILFs of simple subsystems, but very often the theoretical estimate of these parameters is incorrect and their values may be rather obtained experimentally. In this paper mathematical relationships representing the basic hypotheses involving the SEA parameters are presented, and their ability to provide a significant a priori evaluation of the SEA efficiency is tested on the case of a benchmark made of three coupled plates. The energy in the system is experimentally determined, and this result is compared with that of a SEA model: the compliance with the hypotheses is checked
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