Search results for " vibrations"

A NUMERICAL APPROACH FOR THE PREDICTION OF SOUND GENERATED BY A MISTUNED ROTOR CASCADE

2012

A numerical investigation on the effects of blade frequency mistuning on the acoustic emission of a rotor cascade in subsonic flow is shown. A numerical method has been developed and implementd to obtain the mistuned rotor aeroelastic response and the associated acoustic waves. Both the aeroelastic and acoustic models are based on a linear unsteady small perturbations theory. The dynamic aeroelastic coupling between bending and torsional responses of each blade and the aerodynamic coupling among the blades are included in the formulation.

PRODROMI SULLE STIME CATASTALI

2012

Determining noise and vibration exposure in conifer cross-cutting operations by using Li-Ion batteries and electric chainsaws

2018

In many activities, chainsaw users are exposed to the risk of injuries and several other hazard factors that may cause health problems. In fact, environmental and working conditions when using chainsaws result in workers&rsquo

Aprendiendo Vibraciones Mec´anicas con Wolfram Mathematica

2015

[EN] Mechanical vibrations as subject can be found within many Engineering and Science Degrees. To achieve that the students understand the mathematics and its physical interpretation is the objective we should get as docents. In this paper we describe how to create a simple graphical model of a single degree of freedom vibrating system allowing us to visualize concepts like above concepts damping, resonance or forced vibrations. For that, we use the popular symbolic software Wolfram Mathematica with which, without an excessive programming complexity, we can obtain a very satisfactory visual model capable to move itself, controlled by parameters. In addition, the model incorporates the curv…

Fatigue life under non-Gaussian random loading from various models

2004

Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for …

Investigation of motor current signature and vibration analysis for diagnosing rotor broken bars in double cage induction motors

2012

This paper investigates the detectability of rotor broken bars in double cage induction motors using current signature and vibration analysis techniques. Double cage induction motors are commonly used for applications where successive loaded starts-up are mandatory. Experimental results were performed under healthy and faulty cases, and for different load conditions using each technique. Rotor broken bars fault detection based on sideband current components may fails due to the presence of inter bar currents that reduce the degree of rotor asymmetry, yielding to a decrease of the magnitude of these spectral components. But inter bar currents produce core vibrations in the axial direction, w…

Polariton response in the presence of Brownian dissipation from molecular vibrations

2020

We study the elastic response of a stationarily driven system of a cavity field strongly coupled with molecular excitons, taking into account the main dissipation channels due to the finite cavity linewidth and molecular vibrations. We show that the frequently used coupled oscillator model fails in describing this response especially due to the non-Lorentzian dissipation of the molecules to their vibrations. Signatures of this failure are the temperature dependent minimum point of the polariton peak splitting, uneven polariton peak height at the minimum splitting, and the asymmetric shape of the polariton peaks even at the experimentally accessed "zero-detuning" point. Using a rather generi…

Free vibrations of anisotropic panels

2004

A meshfree approach, called Displacement Boundary Method, for the analysis of in-plane and out-of-plane free vibrations of anisotropic plates is presented. The discretization process is based on the use of a modified variational principle and the static fundamental solutions of the problem operators. The stiffness and mass matrices are frequencyindependent, symmetric and positive definite and their computation requires boundary integrations of regular kernels only. Thus, the final resolving system can be solved with classical approaches by using standard numerical procedures. Numerical results are presented to show the accuracy and effectiveness of the method.

MODELLING THE DISPERSION PROPERTIES OF MASS LINEAR CHAINS: EXPERIMENTS AND SIMULATIONS

2009

We analyze and discuss the results of an experiment with the goal of revealing the phonon-like acoustic dispersion curve. The experimental apparatus consists of a sonometer and an electromagnetic driver connected to a signal generator in order to establish standing waves along a stretched metal string (a guitar string) upon which a set of beads (used normally for fishing) has been fixed. The oscillation amplitude is measured by means of a detector connected to an MBL interface. We detect the resonance frequencies as function of the wave-number and obtain the corresponding dispersion curve. The results show that deviations from linearity occur when the wavelength is comparable with the dista…

Determination of energy fluxes in composite plates or processed by Vico-constrained damping patch

2021

Lightening structures is an important issue in the world of transport. On the other hand, for the improvement of comfort, increasing performance is demanded today, particularly in the vibratory and acoustic field, which leads to the addition of damping materials. The proposed research work consists in the vibrational optimization of the structures by the addition of viscoelastic patches damping positioned wisely. The main function of the viscoelastic used to improve the vibro-acoustic performances, is to provide a mechanism of dissipation of mechanical energy. This attenuation of noise and vibrations causes a conversion of mechanical energy into thermal energy, which, after diffusion into t…