Simulation of the Vibratory Behavior of Slender Shafts Subject to Transverse Loads Moving in the Axial Direction

In various machines of the manufacturing industry, and in particular in paper converting machinery, there are shafts operating under conditions similar to that of a slender beam subjected to a transverse load moving in the axial direction. This condition can lead to vibrations and consequent deterioration of the machine performance and of the product quality. The problem has been theoretically studied in the literature since the 1990s. While shaft mass and stiffness are universally considered among the most influential parameters on its vibratory behavior, less obvious and not investigated in the literature is the influence of the spatial interval between two successive loads, an aspect that should be considered in the shaft design phase. In fact, if that is less than the length of the shaft, i.e., if there is more than one transverse load on the shaft at a given time, the vibration level may decrease with respect to the single-load configuration. This work describes the development of a mathematical model of a slender shaft hinged at its ends, representing the rotor of a paper roll perforating unit, with the SW Mathematica. The effect of a load moving axially at a given speed followed by similar loads after given spatial intervals was simulated investigating the influence of speed and load interval on shaft vibrations and resonance. The results showed how reducing the load interval can lead to a reduction of the shaft vibration which is a useful indication on possible design corrective actions

A magnetorheological clutch for efficient automotive auxiliary device actuation

In this paper the results of a project funded by Regione Toscana aimed at reducing the powerabsorption of auxiliary devices in vehicles are presented. In particular the design, testing and application of amagnetorheological clutch (MR) is proposed, aimed at disengaging the vacuum pump, which draws in air fromthe power-brake booster chamber, in order to reduce the device power absorption.Several clutch preliminary studies done to choose the clutch geometry and the magnetic field supply areillustrated. The final choice consisted in an MR clutch with permanent magnet, which satisfied size, torque andfail-safe specifications. The clutch characteristics, in terms of torque versus slip, were obtained experimentallyfor three different clutch prototypes on an ad-hoc developed test bench.As result of a preliminary simulation, a comparison between the power absorption of a current productionvacuum pump, an innovative vacuum pump and both vacuum pumps coupled with the MR clutch is presented.The New European Driving Cycle is considered for simulating the vacuum pump operation both in urban andhighway driving. Results show that the use of the innovative vacuum pump reduces the device consumption ofabout 35%, whereas the use of MR clutch coupled with the innovative vacuum pump reduces it up to about44% in urban driving and 50% in highway driving

development of a simplified model for the vibration analysis of lawn mowers

Abstract The vibrational behavior of vehicles is a crucial issue for the comfort, especially for the professional vehicles. This paper presents a simplified modelling approach for studying the vibrational behavior of a lawn tractor. The vibrational response of a real vehicle is analyzed by an extensive experimental modal analysis and Finite Element model (FE) simulating the modal behavior of the whole tractor. The FEM was then validated by the comparison with the experimental results and then used for identifying the components and connections effectively driving the modal response. Based on these results, a simplified Multi-Body (MB) model, able to reproduce the vibrational response of the studied lawn mower, was then setup, showing good correspondences with experimental results. General guidelines for defining effective vehicles Multi-Body modal models were also derived

On the use of shape memory alloys for deployable passive heat radiators in space satellites

The present work presents a multifunctional structure for space engineering application part of the TOPDESS project, funded by ESA. The main aim of the project is the design of a thermal control device able to deploy through passive actuation. A combined device has been designed, made up of a Pulsating Heat Pipe (PHP) foldable heat exchanger and Shape Memory Alloy (SMA) wire. The deployment of the SMA wire is conceived to be controlled by thermal contact with the heat source and by conduction along the wire. Since the heat sources are lumped and the wire is subject to convection, a temperature gradient develops along the wire. A monodimensional mode able to predict the behavior of an SMA wire subjected to a spatial temperature gradient, is presented in this paper. The results show that the system can carry out folding and unfolding cycles with rotation angles greater than 80° only if the wire is subjected to uniform temperature distribution; in the case of temperature gradient, the achievable rotation angle is about 20°. The analysis states the feasibility of the actuation system, highlighting the critical technological aspects, to lay the groundwork for the future development of the whole system

Design, analysis and investigation of an independent suspension for passenger cars

The objective of this paper is the design of a front suspension. The layout used is the McPherson strut, widely adopted for road cars due to its simplicity and to the limited space required. The handling, comfort and durability of the suspension are strictly related to the position of the hardpoints, and to the elastic elements. A sensitivity analysis is carried out to investigate the roll behavior of a standard vehicle during cornering. A multi-body dynamics software is used to perform ramp-steer simulations on a full-vehicle model. Results show the different peculiarities of three specific cases of analysis, each of them emphasising the effects of a specific parameter on the whole system