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Article

Massimo Fabbri and Antonio Morandi

This study aims to investigate the feasibility of saturated AC heating of magnetic metals. In AC heating of magnetic steel below the Curie temperature, because of the high…

Abstract

Purpose

This study aims to investigate the feasibility of saturated AC heating of magnetic metals. In AC heating of magnetic steel below the Curie temperature, because of the high magnetic permeability, the penetration depth is in the order of 1-6 mm at 50 Hz. Surface heating is then obtained, in practice, if large slabs are processed. The necessity to provide the required surface-to-core temperature uniformity (about 25°C) at the end of the heating process, avoiding excessive thermal stresses which can lead to cracks, thus implies a long heating time.

Design/methodology/approach

The penetration depth can be increased if the material is brought to saturation by applying an external DC magnetic field, and a faster in-depth heating can be obtained. The DC saturating field can be produced with no losses over large volumes by means of superconducting (SC) coils.

Findings

The feasibility of in-depth induction heating of a 200 × 1,000 × 5,000 mm magnetic steel slab with an applied 2 T DC saturating field is numerically investigated. The results show that the use of a DC saturating field leads to shorter processes which fulfil the heating objectives.

Practical implications

A DC saturating field cannot be produced by means of copper coils because of the large amount of material and the unaffordable power required. However, this field can effectively be produced by means of SC magnets based on state-of-the-art materials.

Originality/value

Superconductivity may be the enabling technology for fast and efficient induction heating of magnetic steel slabs if the increase in productivity can balance the additional costs due to the SC magnet.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Massimo Fabbri, Pier Luigi Ribani and Davide Zuffa

A conveyor device is studied with the aim to reduce the friction between the inner surface of the beam and the chain. The lower is the friction between the chain and the…

Abstract

Purpose

A conveyor device is studied with the aim to reduce the friction between the inner surface of the beam and the chain. The lower is the friction between the chain and the beam, the lower is the surface wear. The magnetic repulsion force among permanent magnets (PMs) placed on the beam and on the chain is utilized to reduce friction. The paper aims to discuss these issues.

Design/methodology/approach

The considered magnetic suspension is realized with PMs in repulsive configuration; it is designed by solving a constrained optimization problem, with reference to the geometry of the 90° horizontal bend FlexLink WL322 conveyor. Flux density field and its gradient are evaluated using volume integral equation method, allowing to calculate the forces acting on the chain and the stiffness of the magnetic suspension.

Findings

The magnetic suspension prototype was manufactured and tested. The experimental and calculated values of the forces acting on the chain compares well. A stable horizontal equilibrium of the chain was obtained during both static and dynamical tests.

Research limitations/implications

The quasi-static model used neglects the dynamical interactions among the elements of the chain, the PMs and loads weight during motions and the eddy current losses in the aluminium beam. However the dynamical tests on the prototype show that the chain motion is regular up to the nominal velocity all along the conveyor with the exception of the trailing edge of the 90° curve.

Practical implications

The tests on the prototype show the possibility of a removal or at least a reduction of the friction force between the chain and the inner side of the beam by means of a passive magnetic suspension. As a consequence a reduction of noise and vibrations and an increase of the mean-time-to-failure is expected.

Originality/value

Prototype testing shows that the unavoidable vertical instability of the magnetic forces has no practical consequence since, reducing the allowed vertical gap, the chain is stabilized by the gravitational force.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Massimo Fabbri, Antonio Morandi and Pier Luigi Ribani

The purpose of this paper is to analyse the heating process of an aluminum billet rotating in a static magnetic field produced by optimized supercoducting coils.

Abstract

Purpose

The purpose of this paper is to analyse the heating process of an aluminum billet rotating in a static magnetic field produced by optimized supercoducting coils.

Design/methodology/approach

In order to meet the technical specifications of industrial heating, many processes with low speed in the given high magnetic field have been simulated. The mechanical stresses in the billet are examined by taking into account the temperature dependence of the mechanical properties.

Findings

The main heating parameters, i.e. heating time, average temperature and temperature homogeneity, are evaluated for different values of angular velocity. The simulation results show that an optimal angular speed can be chosen with respect to the heating time.

Research limitations/implications

The mechanical stress in the billet due to weight, centrifugal effects, applied torque and resonance is examined by taking into account the weakening of the material properties with the increase of temperature. The practical limits of the heating process are evaluated; while resonance does not seem to be a concern, the safety against yielding, in order to avoid plastic deformation of the billet during the heating, seems to be a constraint.

Practical implications

DC induction heating of aluminum billet using superconducting magnets can be done fulfilling the specifics of the industrial processes.

Originality/value

The operational and mechanical constraints on a high‐efficiency DC induction heater for aluminum billets using superconducting coils are investigated.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 5
Type: Research Article
ISSN: 0332-1649

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Article

Massimo Fabbri

The purpose of this paper is to evaluate analytically the magnetic flux density and the magnetic vector potential produced by a linear current density or a linear…

Abstract

Purpose

The purpose of this paper is to evaluate analytically the magnetic flux density and the magnetic vector potential produced by a linear current density or a linear magnetization inside an arbitrary polyhedron.

Design/methodology/approach

In order to obtain expressions of the field and potential integrals in an intrinsic vector form, independently of any reference frame, the approach is to avoid the use of a local coordinate system to perform the integrations.

Findings

The expressions obtained contain only the same functions just needed for the uniform sources case, do not introduce any new singularity or discontinuity, and computed results illustrate their effectiveness.

Research limitations/implications

Being in intrinsic vector form the expressions obtained are well suited to cope with the data structures, i.e. faces‐edges and edges‐vertices incidence matrices, provided by unstructured polygonal meshes generators. Their use, especially when dealing with a generic mixed unstructured polygonal mesh, avoids the need of different routines, thus decreasing the complexity of the numerical code.

Practical implications

Besides, avoiding numerical integration, the results do not require usage of any function other than those already defined for the uniform sources case, and do not introduce any new singularity or discontinuity. Thus, the calculation of the magnetic flux density and the magnetic vector potential produced by linear sources needs nearly the same effort as the uniform sources one.

Originality/value

The closed‐form expressions obtained are in intrinsic vector form and can be implemented in a unique routine suitable for the calculation of the magnetic flux density and vector potential produced by any linear or uniform polyhedral source.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Massimo Fabbri, Antonio Morandi and Pier Luigi Ribani

To analyse the heating process of an aluminum billet rotating in a static magnetic field produced by superconducting coils.

Abstract

Purpose

To analyse the heating process of an aluminum billet rotating in a static magnetic field produced by superconducting coils.

Design/methodology/approach

The idea is to force the billet to rotate in a static magnetic field produced by a DC superconducting magnet. Since, a static superconducting magnet has no losses, the efficiency of the system is the efficiency of the motor used. In order to evaluate the temperature distribution arising from the field profile produced by a given coil configuration, a numerical model, based on an equivalent electric network with temperature‐dependent parameters, is used.

Findings

The main heating parameters, i.e. heating time, total power injected and temperature difference, are evaluated for different values of angular velocity and magnetic field. The field profile suitable to meet the specifics of an industrial heating process in terms of temperature homogeneity and heating time is determined. Starting form this profile the layout of the magnet is arrived at and some considerations on the operating condition of the superconducting windings are reported.

Research limitations/implications

The mechanical stress in the billet due to weight, centrifugal effects, applied torque and resonance is examined by taking into account the weakening of the material properties with the increase of temperature and the practical limits of the heating process are evaluated.

Practical implications

DC induction heating of aluminum billet using superconducting magnets can be done fulfilling the specifics of the industrial processes.

Originality/value

A high‐efficiency induction heater for aluminum billets using superconducting coils in a novel scheme is investigated.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 27 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Massimo Fabbri, Antonio Morandi and Francesco Negrini

To investigate the feasibility of a novel scheme of high‐efficiency induction heater for nonmagnetic metal billets which use superconducting coils.

Abstract

Purpose

To investigate the feasibility of a novel scheme of high‐efficiency induction heater for nonmagnetic metal billets which use superconducting coils.

Design/methodology/approach

The idea is to force the billet to rotate in a static magnetic field produced by a DC superconducting magnet. Since a static superconducting magnet has no losses, the efficiency of the system is the efficiency of the motor used. In order to evaluate the temperature distribution arising from the field profile produced by a given SC coil configuration, a numerical model, based on an equivalent electric network with temperature‐dependent parameters, is developed.

Findings

A substantial independence of the shape of the temperature profile on the angular velocity and the value of the uniform magnetic field applied, is observed. A strong temperature gradient is observed in the radial direction in the proximity of the penetration front and in the axial direction at the top and bottom surface of the billet. Small temperature gradient was observed in the central part of the billet.

Research limitations/implications

The reported temperature profile is inadequate for an actual extrusion process which is desired to happen at a constant temperature. The appropriate profile along the billet length can be achieved by a suitable axial shaping of the magnetic field, through the optimization of the coil layout, whereas the undesired radial gradient can be reduced by interspacing the rotation with temperature smoothing intervals.

Practical implications

The investigation of the profile of applied magnetic field and the heating procedure which allow to achieve the distribution of temperature suitable for the extrusion process can be carried out by using the present model.

Originality/value

A high‐efficiency induction heater for nonmagnetic metal billets using superconducting coils in a novel scheme is investigated.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Chiara Caterina Borghi, Yoko Akiyama, Massimo Fabbri, Shigehiro Nishijima and Pier Luigi Ribani

The aim of this paper is the study of the magnetic separation of pollutants from water by means of a magnetic filter. A magnetic activated carbons nanometric powder that…

Abstract

Purpose

The aim of this paper is the study of the magnetic separation of pollutants from water by means of a magnetic filter. A magnetic activated carbons nanometric powder that combines the well-known pollutants absorbent capacity of activated carbons with the magnetic properties of magnetite (Fe3O4) is used.

Design/methodology/approach

The considered magnetic filter is made of stainless steel spheres, magnetized by an external flux density field provided by permanent magnets. Flux density and fluid velocity fields are evaluated using volume integral equation method. The modelling of the particles trajectories inside the filter allows calculating its capture efficiency.

Findings

The results of the model are tested on the experimental data obtained using two different setups. A removal of the powder larger than 90 percent is achieved in both cases. The pollutant removal efficiency is checked on surfactants (water diluted). Their adsorption on magnetic activated carbons leads to residual concentration below the limit for the reuse in agriculture (according to the Italian legislation) for all the tested surfactants.

Originality/value

The proposed process combines efficiently a physico-chemical phase of adsorption and a magnetic phase of filtration due to the particular properties of magnetic activated carbons.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 1/2
Type: Research Article
ISSN: 0332-1649

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Article

Massimo Fabbri, Francesco Galante, Francesco Negrini, Eiichi Takeuchi and Takehiko Toh

Electro‐magnetic stirrers, applied to the mold of a continuous caster, induces electromagnetic forces that influence the steel flow pattern modifying the casting…

Abstract

Electro‐magnetic stirrers, applied to the mold of a continuous caster, induces electromagnetic forces that influence the steel flow pattern modifying the casting parameters. The steel quality has been highly improved by the application of this magneto‐hydro‐dynamic (MHD) technique. Anyway, the complexity of the MHD interaction made difficult the complete comprehension of the factors that contribute to eliminate the defects due to the inclusions in the cast products. The optimization of the MHD techniques is still the object of a large research effort, which utilizes both experimental activity and numerical simulation. In this paper, the numerical simulation of the 2D flow pattern of the molten steel in a mold for billets has been done. The attention is focused on the gradient of the velocity of the molten steel near the wall and on the effects that the gradient change determines on the inclusions, which are present in the metallic pool. Actually the increase of the velocity gradient corresponds to the increase of the forces that can clean the solidifying shell from the inclusions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 22 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Fabrizio Colli, Massimo Fabbri, Francesco Negrini, Shigeo Asai and Kensuke Sassa

The analysis of particles trajectories in a vertical cylindrical coil shows that the magnetization force acting on paramagnetic particles has predominantly axial component…

Abstract

The analysis of particles trajectories in a vertical cylindrical coil shows that the magnetization force acting on paramagnetic particles has predominantly axial component which aims upwards and opposite to the gravitational force. In case of superconducting coil and depending on the value of the particle susceptibility, the axial force component can exceed several times the force of gravity. As a result, a motion of the particles in vertical upward direction appears. This effect was utilized to realize a magnetic separator, the main advantage of which is the high effectivity of separation process. A NbTi SC coil generates the magnetization force with a flux density field up to 12 T. Experiments with SiC inclusions in molten Aluminium have been performed to confirm the feasibility of this segregation concept.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 22 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Sara Forti, Barbara Colombo, John Clark, Arianna Bonfanti, Stefania Molteni, Alessandro Crippa, Alessandro Antonietti and Massimo Molteni

This paper aims to present the application and critical reflection on the effects of a intervention for children with autism spectrum disorder (ASD): the Soundbeam…

Abstract

Purpose

This paper aims to present the application and critical reflection on the effects of a intervention for children with autism spectrum disorder (ASD): the Soundbeam Imitation Intervention (SII). The intervention is based on the imitation of meaningless body gestures supported by a musical feedback. The rationale underlying SII is that mirror neurons deficit may represent the cause for the incomplete development of social and motor functioning in children with ASD. Following this assumption, it is possible to hypothesise that a systematic activation of this a system through the simultaneous observation-execution of meaningless body gestures may affect functional changes of mirror-related functions.

Design/methodology/approach

A sample of 14 children, who were between 5 and 9 years of age, with a diagnosis of ASD were involved in a six weeks’ SII programme. The programme is designed as a three-step progression, where each step includes exercises that focus on an activity: synchronous/one arm imitation, synchronous/two arms imitation and delayed imitation. Exercises are based on repeated movements-melodies associations of increasing difficulty. Motor imitation and social attention were assessed using a synchronous video-modelling task pre and post intervention.

Findings

Data highlight significant improvements in imitation accuracy and duration of social sustained attention were achieved.

Originality/value

Data reported in this paper provide preliminary and promising evidence that imitation and social attention skills acquired through SII can be generalised to a video-modelling imitation setting. The SII ordinal execution has included meaningless gestures, usually excluded from previous interventions, and this adds further validity to the training.

Details

Advances in Autism, vol. 6 no. 3
Type: Research Article
ISSN: 2056-3868

Keywords

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