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Piacenza d'Adige, Italy

Strano M.,Polytechnic of Milan | Villa A.,Laboratorio MUSP | Mussi V.,Laboratorio MUSP
International Journal of Material Forming | Year: 2013

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH2 blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed. © 2011 Springer-Verlag France. Source

Goletti M.,Laboratorio MUSP | Grasso M.,Laboratorio MUSP | Annoni M.,Polytechnic of Milan
Procedia CIRP | Year: 2013

The most important advantages of water jet are the capability to cut nearly every material, the low cutting temperature and the negligible cutting forces. When end users are interviewed, most of them point out that the most critical problem of water jet machines is the reliability of the system components, together with the difficulty in estimating their life time. As far as the UHP (Ultra High Pressure) intensifier is concerned, there are several components that work under extreme fatigue conditions, as the pressure inside the cylinders can reach 400 or even 600 MPa. Nearly every critical component is located into the UHP intensifier, but different failure scenarios can be envisaged, leading to different pattern deviations from nominal behavior conditions. In this paper a correlation analysis on multiple signal features with the health status of the machine is presented. Then a multi-sensor based monitoring approach is discussed and tested on a real case study: it is based on the usage of control charts for in-control region definition and possible detection of faults. Source

Albertelli P.,Polytechnic of Milan | Goletti M.,Laboratorio MUSP | Monno M.,Polytechnic of Milan
Procedia CIRP | Year: 2013

This paper presents a new Receptance Coupling Substructure Analysis (RCSA) approach. The technique represents a valid instrument to predict Frequency Response Function, and consequently chatter free cutting conditions, of a not previously tested mill. The proposed RCSA methodology exploits experimental dynamic compliance measurements and the Finite Element (FE) model of a tool to estimate, through a new defined formulation, both the matrices of receptances of the spindle-tool holder assembly and the tool-tool holder connection stiffness. These data, together with the FE model of any new desired mill, can be used to estimate the relative tool tip dynamic compliance. The suggested formulation basically overcomes the drawbacks in the estimation of "rotation/ torque" receptances that often limits the accuracy of the classical RCSA. The proposed innovative approach was experimentally tested and validated. Source

Grasso M.,Polytechnic of Milan | Goletti M.,Laboratorio MUSP | Annoni M.,Polytechnic of Milan | Colosimo B.M.,Polytechnic of Milan
International Journal of Abrasive Technology | Year: 2013

In waterjet/abrasive waterjet (WJ/AWJ) cutting systems, the components of both the ultra high-pressure (UHP) intensifier and the cutting head are subject to faults and performance degradation. Abrasive particles are responsible for focusing tube wear and orifice breakage, whereas challenging pressure conditions are responsible for the wear and cracks of UHP pump components. The impact of these factors on quality and productivity leads to the need for reliable condition-monitoring systems in WJ/AWJ shop floors. This paper investigates a new approach for the online health condition assessment of both UHP pump and cutting head components by using a single type of information source, i.e., the plunger displacement signal. A multivariate analysis of variance (MANOVA) was performed to study the effects of actual faulty components on the acquired signals during AWJ cutting. The results demonstrate that plunger displacement signals are suitable for detecting and identifying critical faults in WJ/AWJ cutting systems. Copyright © 2013 Inderscience Enterprises Ltd. Source

Albertelli P.,Polytechnic of Milan | Mussi V.,Laboratorio MUSP | Monno M.,Polytechnic of Milan
International Journal of Advanced Manufacturing Technology | Year: 2014

Regenerative chatter vibrations generally limit the achievable material removal rate in machining. The diffusion of spindle speed variation (SSV) as a chatter suppression strategy is mainly restricted to academy and research centers. A lack of knowledge concerning the effects of non-stationary machining is still limiting its use in real shop floors. This research is focused on the effects of spindle speed variation technique on tool duration and on wear mechanisms. No previous researches have been performed on this specific topic. Tool wear tests in turning were carried out following a factorial design: cutting speed and cutting speed modulation were the investigated factors. The carbide life was the observed process response. A statistical approach was used to analyze the effects of the factors on the tool life. Moreover, the analysis was extended to the wear mechanisms involved during both constant speed machining and SSV. The worn-out carbide surfaces were examined under a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Significant differences were appreciated. It was observed that SSV tends to detach the coatings of the inserts, entailing a mechanism that is quite unusual in wet steel turning and thus fostering the wear of the tool. The performed analysis allowed to deduce that the intensified tool wear (in SSV cutting) is mainly due to thermo-mechanical fatigue. © 2014 Springer-Verlag London. Source

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