Search results for "Mechanical engineering"

A novel identification procedure from ambient vibration data

2020

AbstractAmbient vibration modal identification, also known as Operational Modal Analysis, aims to identify the modal properties of a structure based on vibration data collected when the structure is under its operating conditions, i.e., no initial excitation or known artificial excitation. This procedure for testing and/or monitoring historic buildings, is particularly attractive for civil engineers concerned with the safety of complex historic structures. However, since the external force is not recorded, the identification methods have to be more sophisticated and based on stochastic mechanics. In this context, this contribution will introduce an innovative ambient identification method b…

Further improvements of the water-cooled Pb–17Li blanket

2001

Abstract The water-cooled lithium–lead (WCLL) blanket is based on reduced-activation ferritic–martensitic steel as the structural material, the liquid alloy Pb–17Li as breeder and neutron multiplier, and water at typical PWR conditions as coolant. It was developed for DEMO specifications and shall be tested in ITER. In 1999, a reactor parameter optimization was performed in the EU which yielded improved specifications of what could be an attractive fusion power plant. Compared to DEMO, such a power reactor would be different in lay-out, size and performance, thus requiring to better exploit the potential of the WCLL blanket concept in conjunction with a water-cooled divertor. Several new ap…

Design, Control, and Analysis of Nonlinear Circuits with Tunnel Diode with Piecewise Affine Dynamics

2019

Fault detection for continuous-time switched systems under asynchronous switching

2013

In this chapter, the problem of FD for continuous-time switched systems under asynchronous switching is investigated. The designed FD filter is assumed to be asynchronous with the original systems. Attention is focused on designing a FD filter such that the estimation error between the residual and the fault is minimized in the sense of H ∞ norm. By employing piecewise Lyapunov function and ADT techniques, a sufficient condition for the existence of such a filter is exploited in terms of certain LMIs. Finally, an example is provided to illustrate the effectiveness of the proposed approach.

On the use of SLS tools in sheet metal stamping

2003

Abstract A few rapid tooling technologies have been recently proposed and among them Selective Laser Sintering is probably one of the most relevant and promising. In the paper, the authors report some results of a wide experimental research on the application of SLS tools in sheet metal forming. A wear test was earned out to investigate the progressive degradation of laser-sintered materials in comparison with traditional cold-work steels. In particular SLS tools were utilized in a sheet metal stamping process of S-shaped parts: their performances (in terms of tool wear and dimensional quality of the stamped part) were compared with the ones of traditional tools.

On the slabbing of stones through diamond wire cutting operations

2009

Diamond wires are usually used in the cutting operations aimed to obtain slabs of stones. This tool consists of a steel cable on which are mounted annular metal—diamond pearls. The use of this technology expanded all over the world because of its advantages on other slabbing techniques as both technical and economical aspects are considered. It should be observed that with this technology wear phenomena must be properly monitored in order to obtain the best process conditions. In this article, the diamond wire cutting operation is investigated, highlighting the process mechanics and the wear phenomena occurring in the used tools. Furthermore, a modified version of the tool itself is propos…

Status of ceramic breeder pebble bed thermo-mechanics R&D and impact on breeder material mechanical strength

2012

Abstract Among the international fusion solid breeder blanket community, there exists steady progress on the experimental, phenomenological, and numerical characterizations of the pebble bed effective thermo physical and mechanical properties, and of thermomechanic state of the bed under prototypical operating conditions. This paper summarizes recent achievements in pebble bed thermomechanics that were carried out by members of the IEA Fusion Nuclear Technology Subtask I Solid Breeding Blanket. A major goal is on developing predictive capability while identifying a pre-conditioned equilibrium stress state that would warrant pebble bed integrity during operations. The paper reviews and synth…

On the thermo-mechanical behaviour of DEMO water-cooled lithium lead equatorial outboard blanket module

2017

Abstract Within the framework of EUROfusion R&D activities an intense research campaign has been carried out at the University of Palermo, in close cooperation with ENEA Brasimone, in order to investigate the thermo-mechanical performances of the DEMO water-cooled lithium lead breeding blanket (WCLL). In particular, attention has been paid to the most recent geometric configuration of the DEMO WCLL outboard equatorial module, as designed by WCLL project team during 2015, endowed with an attachment system based on the use of radial pins, purposely outlined to connect the module back-plate to its back-supporting structure, that have been properly considered to simulate more realistically the …

Optimised assembly mode reconfiguration of the 5-DOF Gantry-Tau using mixed-integer programming

2010

Pulished version of an article in the journal: Meccanica. Also available from the publisher at: http://dx.doi.org/10.1007/s11012-010-9404-y This paper presents a systematic approach based on Mixed Integer Linear Programming for finding an optimal singularity-free reconfiguration path of the 5-DOF Gantry-Tau parallel kinematic machine. The results in the paper demonstrate that singularity-free reconfiguration (change of assembly mode) of the machine is possible, which significantly increases the usable workspace. The method has been applied to a full-scale prototype and the singularity-free path has been verified both in simulations and with physical experiments using real-time control of th…

Minor Cutting Edge Wear in Finish Turning Operations

1999

In finish turning operation, it has already shown, that for the sake of control the dimensional accuracy and the micro-geometry of the worked surface, the wear parameters employed in rough turning operations are not suitable. In the present work the study of wear in fmish turning operations, is carried out, employing a particular groove survey methodology, already proposed in a previous paper, that is based on the techniques of acquirement and processing of images. In order to verify the applicability of the proposed technique two kind of alumina-based inserts and two kind of sintered carbide inserts have been tested. The experimental tests have confirmed the validity of the technique in th…