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SAVERIO GIULIO BARBIERI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

- Two analytical structural models of the connecting rod cap [Articolo su rivista]
Strozzi, Antonio; Mantovani, Sara; Barbieri, SAVERIO GIULIO; Baldini, Andrea
abstract

The mathematical models available in the pertinent literature for designing the cap of a connecting rod are critically examined, and it is shown that some currently adopted assumptions are inaccurate. Spurred by these critical remarks, two more realistic mathematical models are developed of the contact between the crankpin and the cap. In both these models, the crankpin is modelled as rigid, and the cap is idealized as a purely flexural, curved beam of constant cross-section, in progressive contact with the crankpin. In the first model, the cap is mimicked as a twice twice-statically redundant structure solved with the Castigliano theorem. The cap structural response is mechanically examined starting from the central part of the cap-crankpin contact. In the second model, the cap is mimicked as a statically determined structure. Particular attention is paid to the cap change of curvature when moving along the cap axis. The beginning of the cap-crankpin contact is determined by requiring that the curvature of the deformed cap equal the curved border of the crankpin. A result common to the two approaches is the definition of a combined factor summarizing the mechanical effect of several variables, namely the total load, the initial clearance, Young’s modulus, and the cap geometry; the last factor is recapped by the radius defining the centre of mass, and by the moment of inertia. To evidence the merits and limits of the two approaches, the extent of the cap-crankpin angular contact, and the value of representative cap stresses, are determined and compared to Finite Element (FE) forecasts. Furthermore, the effect of the ratio between the moment of inertia of the abutment and the cap central cross-section is investigated. This ratio influences the prediction of the contact angle, when the ratio is higher than 4, the numerical FE results significantly differ from the analytical calculations.

2023 - Effect of the Thermal Mean Stress Value on the Vibration Fatigue Assessment of the Exhaust System of a Motorcycle Engine [Articolo su rivista]
Barbieri, Saverio Giulio; Mangeruga, Valerio; Giacopini, Matteo; Callegari, Marco Severino; Bagnoli, Leonardo
abstract

The exhaust manifold of a high-performance motorcycle engine is subjected to combined thermal and vibrational loadings. In this research, the whole fatigue assessment of an exhaust manifold is addressed. First, a classic low-cycle fatigue analysis is performed. Then, a specific methodology for determining the fatigue cycle of components subjected to thermal and vibration loadings is developed and presented in a way that possible damages can be evaluated. The results are post-processed and the damage caused by fatigue cycles is computed referring to the Wöhler curve of the material using the Dirlik approach.

2023 - Numerical Investigation of the Dynamic Effects on the Fatigue Behaviour of a Transmission Chain in a Hybrid Power Unit [Articolo su rivista]
Mangeruga, Valerio; Renso, Fabio; Barbieri, Saverio Giulio; Giacopini, Matteo; Raimondi, Franceco
abstract

2023 - Oil jets piston cooling: A numerical methodology for the estimation of heat transfer coefficients and optimization of the piston temperature field through a genetic algorithm [Articolo su rivista]
Renso, Fabio; Giacopini, Matteo; Barbieri, Saverio Giulio; Mangeruga, Valerio
abstract

High-efficiency internal combustion engines need specific methodologies to be developed for the design improvement of the components. Predicting and reducing the thermal loadings on the parts are critical tasks to be addressed. This contribution focuses on the thermal management of the piston through oil jets. The operating temperature of the piston deeply affects its thermo-mechanical behavior, thus possibly jeopardizing the structural integrity of the component. The design of piston cooling jets is usually addressed through Computational Fluid Dynamics, which can guarantee accurate results, usually at a high computational cost. In this contribution, a faster tool is derived to grasp the effect of the cooling jets on the temperature of the piston. Empirical correlations are applied to predict the instantaneous heat transfer coefficients on the piston. The reciprocating motion of the piston is considered since it affects the interaction between the surface and the oil jets. Instantaneous coefficients are cycle-averaged and used to estimate the temperature of the piston through a Finite Element thermal analysis. Finally, an optimization code is developed to find the best jet configuration capable to minimize the temperature of the piston. This methodology is a powerful tool to select the optimal oil jet nozzles for piston cooling.

2023 - Refined Structural Design and Thermal Analyses of a High-Speed Wound-Field Generator for the More Electrical Aircraft [Relazione in Atti di Convegno]
Guiducci, A.; Barbieri, S. G.; Nuzzo, S.; Barater, D.; Berni, F.; Cicalese, G.; Fontanesi, S.; Franceschini, G.
abstract

2022 - Influence of the thermal deformation on the lubricating performance of the piston-gudgeon pin interface in an internal combustion engine [Articolo su rivista]
Bianco, L.; Barbieri, S. G.; Mangeruga, V.; Giacopini, M.; Capoccia, G.
abstract

This contribution describes a methodology to evaluate the influence of bellmouth profiles on the elastohydrodynamic behaviour of the contact interface between the gudgeon pin and the piston of a high-performance internal combustion engine. First, a thermo-mechanical simulation is performed to evaluate the piston bosses thermal strains. Consequently, a Multibody elastohydrodynamic model is set up to evaluate the tribological behaviour of this lubricated interface considering a perfectly cylindrical shape of the piston bosses and their thermal deformation. Then, a preliminary bellmouth profile is adopted and a second Multibody model is performed. Nevertheless, the results, together with issues encountered analysing some tested pistons, suggest that modifications of piston bosses have to be introduced. Finally, an optimised bellmouth geometry is proposed and analysed.

2022 - Structural Analysis of the Forming Process for Hairpin Windings for Electric Motor Applications: Torsional-Flexural Instability Issues [Relazione in Atti di Convegno]
Barbieri, S. G.; Mangeruga, V.; Giacopini, M.; Mantovani, S.
abstract

Electric motor manufacturing technology is evolving due to automotive transport development. Besides, environmental issues and the need of CO2 emission reduction have led to an increasing demand for electric drives efficiency. Permanent magnet synchronous machines are widely employed for traction systems and distributed windings produced by using insert techniques are growing in popularity. These methods require preformed wires such as the well-known hairpin shape. The advantages of hairpins are discussed in the pertinent literature. In the present paper, the manufacturing process of a hairpin is investigated by analysing its mechanical behaviour via Finite Element simulations. In fact, many problems might occur during the forming of a hairpin, depending on the shape required. In particular, this study aims at describing the influence of the geometry of the wire cross-section on the resulting final shape of the formed hairpin. Suitable ranges of geometrical and manufacturing parameters are identified to avoid torsionalflexural instabilities.

2021 - Synergy between topology optimization and additive manufacturing in the automotive field [Articolo su rivista]
Mantovani, Sara; Barbieri, SAVERIO GIULIO; Giacopini, Matteo; Croce, Alessandro; Sola, Antonella; Bassoli, Elena
abstract

This article purposes on developing and on re-interpreting the numerical results of a topology optimization for a structural component built via additive manufacturing. A critical appraisal of the optimization results is presented by modeling the feasible component with a holistic approach that merges structural and manufacturing requirements. The procedure is expected to provide a design guideline for similar applications of practical relevance, toward an increase of the right-first-time parts that is required to bring additive manufacturing to its full competitiveness. Topology optimization of a steering upright for a Formula SAE racing car was performed by targeting weight minimization while complying with severe structural constraints, like global and local stiffness performance. Cornering, bumping and braking vehicle conditions were considered. The optimization constraints were evaluated via finite element analysis on a reference component, where the loading conditions were retrieved from telemetry data. The reference part was manufactured by computer numerical control machining from a solid aluminum block. Spurred by the interpretation of the topology optimization predictions, a new upright geometry was designed and validated by calculating its stress field and the possible occurrence of Euler buckling. The new upright was 9% lighter than the reference component. The new geometry was analyzed according to Design for Additive Manufacturing principles to choose the orientation on the build platform and the supports’ location and geometry. The part was successfully manufactured and proved consistent with the application.

2021 - The Effects of the Specific Material Selection on the Structural Behaviour of the Piston-Liner Coupling of a High Performance Engine [Relazione in Atti di Convegno]
Barbieri, Saverio Giulio; Mangeruga, Valerio; Giacopini, Matteo
abstract

The materials commonly employed in the automotive industry are various and depend on the specific application field. For what concern the internal combustion engines the choice is guided by the thermomechanical performance required, technological constraints and production costs. Actually, for high-performance engines, steel and aluminium are the most common materials selected for the piston and the cylinder liner manufacturing. This study analyses the effect of possible material choice on the interaction between piston and cylinder liner, via Finite Element analyses. A motorcycle engine is investigated considering two possible pistons: one (standard) made of aluminium and one made of steel. Similarly, two possible cylinder liners are considered, the original one made of aluminium and a different version made of steel obtained by simply thinning the aluminium component in order to obtain two structurally equivalent components. In particular, four possible combinations of coupling between piston and cylinder liner are identified, derived from the two variants of applied materials. The components theoretically necessary for the Finite Element model are the engine head, the engine block, the bolts, the gasket, the upper part of the crank mechanism and the cylinder liner. Nevertheless, a simplified methodology is employed to reduce the computational effort. This analysis makes it possible to evaluate gap and interference with respect to the material choice. A first proposal of the barrel shape and ovality of the steel piston is obtained starting from the original aluminium piston and the thermal field involved in the analysis. Besides, the presented methodology consists of a useful tool to estimate the stress field and the fatigue safety factor of the components involved. The results obtained with this methodology can guide the definition of the correct piston profile, temperature field and stress distribution estimation, as a function of the specific materials employed for piston-liner coupling.

2020 - A simplified finite element methodology for the structural assessment of an engine piston under dynamic loadings [Relazione in Atti di Convegno]
Barbieri, Saverio Giulio; Bianco, Luigi; Mangeruga, Valerio; Giacopini, Matteo
abstract

The piston slap strongly affects the structural integrity of engine pistons. This phenomenon is caused by the dynamic effects of the piston secondary motions, both horizontal translation and tilting. This occurrence amplifies the contact forces between the piston and the cylinder liner if compared to the ones calculated by using simple kinematic analysis. A numerical approach is therefore mandatory. This paper presents a numerical methodology to predict the influences of piston secondary motions on the piston fatigue life. A combined Multy-Body/FEM strategy is developed to obtain truthful forecasts saving computational effort. First, Multi-Body simulations are performed to evaluate the piston secondary motions and the loadings involved. The most critical instants are retrieved and equivalent lateral accelerations are derived in order to prepare simplified quasi-static Finite Element models. Then, the stress field and the resulting fatigue safety factor distribution of the piston are obtained. The methodology reveals itself to be a useful tool to predict the fatigue life of pistons capable of limiting the computational effort and supporting the dimensioning of engine components during the early stages of the design process.

2020 - Investigation on the Dynamic Behaviour of a Torque Transmission Chain for an Innovative Hybrid Power Unit Architecture [Articolo su rivista]
Mangeruga, V.; Giacopini, M.; Barbieri, S.; Russo, M.
abstract

In this contribution, the mechanical torque transmission between the Electric Motor (EM) and the Internal Combustion Engine (ICE) of a P0 architecture hybrid power unit is analysed. In particular, the system is made up of a brand new, single-cylinder 480cc engine developed on the basis of the Ducati 959 Panigale V90 2-cylinders engine. The thermal engine is assisted by a custom electric motor (30 kW), powered by a Li-Ion battery pack. The Ducati 959 Panigale engine is chosen because of its high power-to-weight ratio, and for taking advantage of its V90 2-cylinders layout. In fact, the proposed hybridization process considers to remove the vertical engine head and to replace it by the electric motor directly engaged to the crankshaft using the original valvetrain transmission chain, thus achieving a very compact package. This solution could be suitable for many V-type engines and it aims to obtain a small hybrid power unit for possible motorcycle/small vehicle applications. The original timing chain object of this study is a silent chain, which is commonly employed as a transmission component in hybrid power units because it can operate at high speeds transmitting high loads and ensuring noise reduction. For this reason, the aim of this study is to assess the possibility of using the original chain to couple the EM and the ICE. This investigation allows the replacing of the minimum number of components during the hybridization process leading to a real plug&go solution. Therefore, the mechanical behaviour of the chain is investigated performing a dynamic analysis of the whole crank mechanism. In particular, the original twin cylinders model considering the original valvetrain system is compared with the single cylinder model engaged with the EM. The dynamic analysis provides the maximum load on the single chain link in both configurations, allowing the evaluation of a relative fatigue safety factor.

2019 - A finite element numerical methodology for the fatigue analysis of cylinder liners of a high performance internal combustion engine [Relazione in Atti di Convegno]
Barbieri, S. G.; Mangeruga, V.; Giacopini, M.; Laurino, C.; Lorenzini, M.
abstract

In this paper a numerical methodology is proposed, which aims at predicting the fatigue behaviour of engine cylinder liners in an eight-cylinder V-type four-stroke turbocharged engine. A preliminary kinematic and dynamic study of the crank mechanism is fulfilled in order to properly identify the load cycle that involves the cylinder liner. Finite Element analyses, both thermal and thermo-mechanical, are performed to evaluate the stress and the strain of the component. In particular, non-linear models are developed to mimic the piston-liner interaction when subjected to different loading conditions. A simplified approach is proposed in order to reduce the computational effort of the simulations. FEM results are then processed employing the multiaxial Dang Van fatigue criterion.

2019 - A Simplified Methodology for the Analysis of the Cylinder Liner Bore Distortion: Finite Element Analyses and Experimental Validations [Relazione in Atti di Convegno]
Barbieri, Saverio Giulio; Giacopini, Matteo; Mangeruga, Valerio; Bianco, Luigi; Mastrandrea, Luca Nicolò
abstract

Advances in modern engines are becoming more and more challenging. The intense increase of thermal and mechanical loads, as a consequence of a higher power density, requires the improvement of the main couplings encountered between moving engine components. In this scenario, the cylinder liner/piston coupling plays a crucial role in terms of engine performance and durability, especially with regards to pollution emission and friction reduction. In this paper a numerical methodology is proposed, which aims at simplifying the Finite Element evaluation of the cylinder liner bore distortion in an eight-cylinder V-type four stroke turbocharged engine. Finite Element simulations are performed to obtain a virtual approval of the component geometry, in advance with respect to the component manufacturing. In particular, preliminary Finite Element analyses are developed which accurately follow the experimental procedure, where a single engine bank is coupled with a simplified test engine head. The Finite Element model is properly tuned in order to obtain the same cylinder liner distortion registered by experimental measurements. Further Finite Element analyses, both thermal and thermo-mechanical, are then performed to evaluate the cylinder liner distortion considering the actual engine head. In order to speed up the analyses, the engine head, the gasket, and the bolt tightening are subsequently substituted by pressure distributions mimicking the actual contact interactions. The methodology reveals itself to be well correlated with the experimental evidences and with the complete Finite Element model of the engine bank thus consisting in a useful tool for reducing the time necessary for the component approval. © 2019 SAE International and © 2019 SAE Naples Section. All rights reserved.

2019 - Design of a Hybrid Power Unit for Formula SAE Application: Packaging Optimization and Thermomechanical Design of the Electric Motor Case [Articolo su rivista]
Mangeruga, V.; Giacopini, M.; Barbieri, S. G.; Berni, F.; Mattarelli, E.; Rinaldini, C.
abstract

This paper presents the development of a parallel hybrid power unit for Formula SAE application. In particular, the system is made up of a brand new, single-cylinder 480 cc internal combustion engine developed on the basis of the Ducati "959 Superquadro" V90 2-cylinders engine. The thermal engine is assisted by a custom electric motor (30 kW), powered by a Li-Ion battery pack. The performance of the ICE has been optimized through CFD-1D simulation (a review of this activity is reported in a parallel paper). The main design goal is to get the maximum amount of mechanical energy from the fuel, considering the car typical usage: racing on a windy track. The Ducati "959 Superquadro" engine is chosen because of its high power-to-weight ratio, as well as for its V90 2-cylinder layout. In fact, the vertical engine head is removed and it is subsequently replaced by the electric motor directly engaged to the crankshaft using the original valvetrain transmission chain, thus achieving a very compact package. The mechanical behaviour of the original chain is investigated for this purpose. A specific electric motor case is then designed and manufactured via Additive Manufacturing technology, in order to include the chain housing, the electric motor cooling system and the lubrication system. Furthermore, the case flange is designed to perfectly fit to the original engine deck in order to allow the engine cooling circuit to match with the electric motor cooling circuit. Several types of circuit layout - around the stator - are analysed via CFD simulations comparing pressure drop and heat transfer coefficients. Finally, a thermo-structural analysis is performed in order to assess the mechanical strength of the electric motor case.

2018 - Design of an Additive Manufactured Steel Piston for a High Performance Engine: Developing of a Numerical Methodology Based on Topology Optimization Techniques [Articolo su rivista]
Barbieri, SAVERIO GIULIO; Giacopini, Matteo; Mangeruga, Valerio; Mantovani, Sara
abstract

Modern high performance engines are usually characterized by high power densities, which lead to high mechanical and thermal loadings acting on engine components. In this scenario, aluminum may not represent the best choice for piston manufacturing and steel may be considered as a valid alternative. In this article, a methodology involving optimization techniques is presented for the design of an internal combustion engine piston. In particular, a design strategy is preliminary investigated aiming at replacing the standard aluminum piston, usually manufactured by forging or casting, with an alternative one made of steel and manufactured via an Additive Manufacturing process. Three different loading conditions are employed for the topology optimizations setup. Optimization results are then interpreted and the various structural features of the steel piston are designed starting from the density distribution contour plots. Different Finite Element thermomechanical models are finally prepared in order to correct and validate the designed geometry.

2018 - Design of an Additive Manufactured Steel Piston for a High Performance Engine: Developing of a Numerical Methodology Based on Topology Optimization Techniques [Articolo su rivista]
Barbieri, S. G.; Giacopini, M.; Mangeruga, V.; Mantovani, S.
abstract

Modern high performance engines are usually characterized by high power densities, which lead to high mechanical and thermal loadings acting on engine components. In this scenario, aluminium may not represent the best choice for piston manufacturing and steel may be considered as a valid alternative. In this paper, a methodology involving optimization techniques is presented for the design of an internal combustion engine piston. In particular, a design strategy is preliminary investigated aiming at replacing the standard aluminium piston, usually manufactured by forging or casting, with an alternative one made of steel and manufactured via an Additive Manufacturing process. Three different loading conditions are employed for the topology optimizations set up. Optimization results are then interpreted and the various structural features of the steel piston are designed starting from the density distribution contour plots. Different Finite Element thermo-mechanical models are finally prepared in order to correct and validate the designed geometry.

2018 - Thermo-mechanical analysis of the exhaust manifold of a high performance turbocharged engine [Relazione in Atti di Convegno]
Lorenzini, Mariano; Giacopini, Matteo; Barbieri, SAVERIO GIULIO
abstract

This contribution presents a methodology for the structural analysis of the exhaust manifold of an internal combustion engine. In particular, the thermal loading and the related thermal fatigue damage mechanism are addressed. The component investigated is a melted exhaust manifold which includes the turbine involute. The complex geometry of the component derives from the project constrains in terms of engine performance and sound targets. Finite Element simulations are performed to obtain a virtual approval of the component geometry, in advance with respect to the component manufacturing. The Finite Element analysis accurately follow the experimental approval procedure which considers different warming and rapid cooling cycles to mimic typical engine operating conditions. Two particular aspects of the developed numerical methodology are described in details: a) the elasto-plastic behaviour of the material at high temperatures; b) a damage criterion for thermal fatigue. Following the Ferrari expertise derived by previous experimental and numerical analysis of other exhaust manifolds, the increase of the equivalent plastic strain registered for a single thermal cycle (delta PEEQ) is firstly adopted as a damage criterion. The methodology reveals itself to be well correlated with the experimental evidences thus limiting the number of tests necessary for the component approval.

2017 - A Design Strategy Based on Topology Optimization Techniques for an Additive Manufactured High Performance Engine Piston [Articolo su rivista]
Barbieri, Saverio Giulio; Giacopini, Matteo; Mangeruga, Valerio; Mantovani, Sara
abstract

In this paper, a methodology for the design of a motorcycle piston is presented, based on topology optimization techniques. In particular, a design strategy is preliminary investigated aiming at replacing the standard aluminum piston, usually manufactured by forging or casting, with an alternative one made of steel and manufactured via an Additive Manufacturing process. In this methodology, the minimum mass of the component is considered as the objective function and a target stiffness of important parts of the piston is employed as a design constraint. The results demonstrate the general applicability of the methodology presented for obtaining the geometrical layout and thickness distribution of the structure.