Journal of manufacturing and materials processing, Feb 1, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
HAL (Le Centre pour la Communication Scientifique Directe), May 16, 2022
Vibrations are random in a wide range of applications and they are the main cause of mechanical f... more Vibrations are random in a wide range of applications and they are the main cause of mechanical failure. To prevent such failure, it is necessary to evaluate the fatigue life using test or analysis techniques. For computing the severity of the damage many methods are available in literature, but the estimation damage is just an approximation. The objective of this study is to propose a numerical model, together with experimental validation, in order to estimate fatigue damage caused by random vibrations in metallic materials undergoing uniaxial fatigue testing. Mots clefs-Random vibrations test, Fatigue Damage, Virtual test; frequency-domain counting method.
2020 IEEE International Symposium on Systems Engineering (ISSE), 2020
I would like to express my deep gratitude to my thesis supervisor, Professor Cristiana Delprete, ... more I would like to express my deep gratitude to my thesis supervisor, Professor Cristiana Delprete, which helped me in my way. I extremely appreciate my co-supervisor, Dr. Abbas Razavykia, which I got benefits from his valuable advice during our continuous meetings. I also really thank Dr. Paolo Baldissera, which guided me in the world of bike design.
IOP Conference Series: Materials Science and Engineering, 2021
In the latest years many researcher focused on the possibility to foresee the failure of a mechan... more In the latest years many researcher focused on the possibility to foresee the failure of a mechanical system in the early stages in order to allow quick response times. Monitoring and diagnostics are at the base of those methodologies of predictive maintenance, which represents the standard for companies. Data acquired by monitoring systems are sometimes not sufficient to perform an effective diagnosis and to detect failures. In the present work the possibility of a defining a relation between the response of a system and the dimension of a defect causing the vibration is explored. Through a non-Hertzian contact model a roller bearing is studied and a correlation is sought between the size of the defect and the frequency content of the contact pressure time history. Resorting to a non-Hertzian approach enables the determination with good accuracy of the overpressures due to edge effects caused by the sudden change in curvature in presence of a defect. The estimation of the pressure ...
IOP Conference Series: Materials Science and Engineering, 2021
The search for propulsion systems of vehicles with lower environmental impact is focusing on syst... more The search for propulsion systems of vehicles with lower environmental impact is focusing on systems with exclusive or supplementary use of electric motors. In fully electric or hybrid vehicles, the electric power delivery is used not only to provide torque to the vehicle and the consequent movement of the vehicle, but also to transform the vehicle’s kinetic energy back into electrical energy for storage in batteries when the vehicle is downhill or it must be slowed down. Under normal operating conditions, even in urban usage, it is common to have sudden inversions of the power flow. This means that in a really short time the motor switches from delivering torque to receiving it. Normally the electric motor is not directly connected on the wheels, but a geared transmission is present. The change of torque from positive (motor) to negative (generator) causes a sudden change of the working conditions. This induces vibrational and durability problems on the gears. In the present paper,...
2019 22nd International Conference on the Computation of Electromagnetic Fields (COMPUMAG), 2019
Vibrations of a three degrees of freedom mechanical structure are attenuated using a magnetic dam... more Vibrations of a three degrees of freedom mechanical structure are attenuated using a magnetic damper, obtained by coupling a conductive structure with a magnetic field generated by permanent magnets. The magnetic dissipations are experimentally investigated focusing on their nonlinearity with respect to frequency and amplitude of oscillations. The system exhibits two types of nonlinearities: one proper of the mechanical system and one of due to the magnetic coupling. The availability of an electromagnetic-motional model allows for the separation of these two effects. A frequency domain model to describe the magneto-mechanical interaction under harmonic excitation is developed by means of a partial element equivalent circuit of the conductive parts. The restitution magnetic force model is then introduced in the numerical model of the system. Results obtained by simulations are validated versus experimental measurements on the three degrees of freedom structure.
Magnetic damped vibrations are obtained by coupling a conductive structure with a magnetic field.... more Magnetic damped vibrations are obtained by coupling a conductive structure with a magnetic field. The induced damping force characteristic depends upon displacement and velocity. When the magnetic field is generated by permanent magnets, a good model of the damping characteristic requires the estimation of the eddy currents induced in the conductive parts and subsequently of the resulting Lorentz force acting on them. This force is unfortunately nonlinear as its magnitude depends both on frequency and amplitude of oscillations. Considering by hypothesis a harmonic motion of the system, a simulation of the magneto-dynamic phenomenon is performed by means of a partial element equivalent circuit of the conductive parts. The force characteristic is then used to fit a sinusoidal input describing function approximation. Results obtained by simulations are validated versus experimental measurements on a three degrees of freedom structure.
Scienza, tecnica, sport e passione: gli ingredienti del record italiano di velocita a pedali conq... more Scienza, tecnica, sport e passione: gli ingredienti del record italiano di velocita a pedali conquistato a settembre dal Team Policumbent del Politecnico di Torino
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2021
Theory of Critical Distances (TCD) collects several methods adopted in failure prediction of comp... more Theory of Critical Distances (TCD) collects several methods adopted in failure prediction of components provided with stress concentration features. The idea of evaluating stress effect in a zone rather than in a single point was proposed decades ago but, only thanks to relatively recent works, TCD concepts showed to be a successful extension of Linear Elastic Fracture Mechanics (LEFM), able to assess strength and fatigue life. The increasing computational power has made Finite Element Method (FEM) widespread, hence stress fields can be easily extracted and used as input data for fatigue post-processing and durability analyses. In this scenario, TCD reveals as a powerful tool which, thanks to the introduction of a single material parameter (critical distance, [Formula: see text]), integrates classical fracture models by considering the presence of microscale phenomena acting in fracture process. In this sense, TCD behaves as a link between continuum mechanics and LEFM. Modalities an...
The static transmission error in gears represents the main noise and vibration source of mechanic... more The static transmission error in gears represents the main noise and vibration source of mechanical transmissions, both for selfexcitation and for the excitation of powertrain components. An accurate determination of it is very complex, since it requires experimental tests or highly detailed models. In both cases the costs and the computational time are high, therefore the possible different types of geometries to analyse are significantly reduced. In the present work, a semi-analytical methodology is proposed, with the aim of evaluating the variation of the contact area in gears during their meshing and at different levels of applied torque. This model considers the tooth compliance (tooth shear and bending, foundation and rim, gear body) and the local contact effects. The present semi-analytical methodology allows a detailed analysis of the tooth compliance and the contact area on a high number of points along the meshing cycle (typically over 100 points). It also enables the definition of the correct contact area geometry between meshing teeth, depending on the possible geometry modification (micro-geometry and/or manufacturing errors) and on the input torque. In particular, the contact is simulated through a non-Hertzian model able to evaluate every contact shape, overcoming the limits of the Hertzian theory. The goal of the proposed methodology is to determine with high precision the static transmission error between gears in a limited time with respect to the classical finite element method. Furthermore, it is useful for a reliable prediction of the transmission dynamic behaviour, considering the load exchanged between the teeth in relation to spin speed and torque, in a computational time lower than the classical techniques.
The connection system between mechanical parts with the greatest advantages in terms of productio... more The connection system between mechanical parts with the greatest advantages in terms of production is the threaded connection. This type of connection has considerable stiffness but also high weight. Often the search for the reduction of the masses clashes with the limits dictated by production needs. A considerable effort has been made in making screws with higher performance materials and therefore guaranteeing greater tightening forces with smaller cross sections, but there have not been as many notable developments on the method of determining the compliance of tightened elements. The classical theory identifies three different conditions for calculating deformability, which are sometimes not easy to interpret and implement. The use of numerical techniques such as finite elements allows designers to be very precise, but requires a great deal. To facilitate the work of the designers and provide them with a more manageable tool to better understand the type of threaded connection to be designed, the present work proposes an analytical formulation that allows a quick assessment of the compliance value of the clamped elements, regardless of the geometric relationships and materials. To achieve this, starting from a literature analysis, a parametric finite element model was developed and, based on the results obtained, a formula is proposed that covers all the possible scenarios for determining compliance. The results were compared with the classical theory in order to verify the correctness and applicability of the formulation. At the moment the formulation is valid for screws whereas for the bolts with nut unified formula is under investigation.
Journal of Engineering, Design and Technology, 2020
Purpose The implementation of project-based learning (PBL) activities in the curricula of enginee... more Purpose The implementation of project-based learning (PBL) activities in the curricula of engineering students has become a consolidated method to improve their skills. The purpose of this paper is to share the experience acquired by the authors from a decennial case-study on a student team PBL activity focused on design and development of human-powered vehicles (HPVs). A review of the project evolution, boundary constraints and management choices could provide inspiration and suggestions to faculty staff that would like to set-up similar experiences for engineering students in their universities. Design/methodology/approach A student team was funded by the authors in 2008 to gather engineering students interested in design and construction of HPVs. In the past decade, the team has grown from 10 up to 60 students enrolled per year and stimulated to develop a range of HPV designs for sports and mobility. The project management evolved as a consequence to com ply with the growing ambi...
International Journal of Automotive Composites, 2017
In the design of engine components, the demand for increasingly higher power combined with a grow... more In the design of engine components, the demand for increasingly higher power combined with a growing awareness for environmental and energy saving, creates a number of conflicting design constraints that can be overcome with the use of new materials. The present paper evaluates the possibility to use plastic materials for designing two important parts of the crank mechanism: the connecting rod and the piston pin. In particular, the material used for the connecting rod design is PEEK filled with carbon fibre and that used for the piston pin design is carbon fibre prepreg epoxy. The numerical analyses made by the authors prove that plastic materials can be useful for components weight reduction but a complete components revision and changing of design strategy are required. The direct metal replacement with plastic material is not possible, and the improvement of plastic materials performance and the new technology for additive manufacturing can completely change the way of thinking about the engine.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2019
The paper presents and discusses a low-cycle fatigue life prediction energy-based model. The mode... more The paper presents and discusses a low-cycle fatigue life prediction energy-based model. The model was applied to a commercial cast iron automotive exhaust manifold. The total expended energy until fracture proposed by the Skelton model was modified by means of two coefficients which take into account of the effects of mean stress and/or mean strain, and the presence of high temperature. The model was calibrated by means of experimental tests developed on Fe–2.4C–4.6Si–0.7Mo–1.2Cr high-temperature-resistant ductile cast iron. The thermostructural transient analysis was developed on a finite element model built to overtake confidentiality industrial restrictions. In addition to the commercial exhaust manifold, the finite element model considers the bolts, the gasket, and a cylinder head simulacrum to consider the corresponding thermal and mechanical boundary conditions. The life assessment performance of the energy-based model with respect the cast iron specimens was compared with th...
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Journal of manufacturing and materials processing, Feb 1, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
HAL (Le Centre pour la Communication Scientifique Directe), May 16, 2022
Vibrations are random in a wide range of applications and they are the main cause of mechanical f... more Vibrations are random in a wide range of applications and they are the main cause of mechanical failure. To prevent such failure, it is necessary to evaluate the fatigue life using test or analysis techniques. For computing the severity of the damage many methods are available in literature, but the estimation damage is just an approximation. The objective of this study is to propose a numerical model, together with experimental validation, in order to estimate fatigue damage caused by random vibrations in metallic materials undergoing uniaxial fatigue testing. Mots clefs-Random vibrations test, Fatigue Damage, Virtual test; frequency-domain counting method.
2020 IEEE International Symposium on Systems Engineering (ISSE), 2020
I would like to express my deep gratitude to my thesis supervisor, Professor Cristiana Delprete, ... more I would like to express my deep gratitude to my thesis supervisor, Professor Cristiana Delprete, which helped me in my way. I extremely appreciate my co-supervisor, Dr. Abbas Razavykia, which I got benefits from his valuable advice during our continuous meetings. I also really thank Dr. Paolo Baldissera, which guided me in the world of bike design.
IOP Conference Series: Materials Science and Engineering, 2021
In the latest years many researcher focused on the possibility to foresee the failure of a mechan... more In the latest years many researcher focused on the possibility to foresee the failure of a mechanical system in the early stages in order to allow quick response times. Monitoring and diagnostics are at the base of those methodologies of predictive maintenance, which represents the standard for companies. Data acquired by monitoring systems are sometimes not sufficient to perform an effective diagnosis and to detect failures. In the present work the possibility of a defining a relation between the response of a system and the dimension of a defect causing the vibration is explored. Through a non-Hertzian contact model a roller bearing is studied and a correlation is sought between the size of the defect and the frequency content of the contact pressure time history. Resorting to a non-Hertzian approach enables the determination with good accuracy of the overpressures due to edge effects caused by the sudden change in curvature in presence of a defect. The estimation of the pressure ...
IOP Conference Series: Materials Science and Engineering, 2021
The search for propulsion systems of vehicles with lower environmental impact is focusing on syst... more The search for propulsion systems of vehicles with lower environmental impact is focusing on systems with exclusive or supplementary use of electric motors. In fully electric or hybrid vehicles, the electric power delivery is used not only to provide torque to the vehicle and the consequent movement of the vehicle, but also to transform the vehicle’s kinetic energy back into electrical energy for storage in batteries when the vehicle is downhill or it must be slowed down. Under normal operating conditions, even in urban usage, it is common to have sudden inversions of the power flow. This means that in a really short time the motor switches from delivering torque to receiving it. Normally the electric motor is not directly connected on the wheels, but a geared transmission is present. The change of torque from positive (motor) to negative (generator) causes a sudden change of the working conditions. This induces vibrational and durability problems on the gears. In the present paper,...
2019 22nd International Conference on the Computation of Electromagnetic Fields (COMPUMAG), 2019
Vibrations of a three degrees of freedom mechanical structure are attenuated using a magnetic dam... more Vibrations of a three degrees of freedom mechanical structure are attenuated using a magnetic damper, obtained by coupling a conductive structure with a magnetic field generated by permanent magnets. The magnetic dissipations are experimentally investigated focusing on their nonlinearity with respect to frequency and amplitude of oscillations. The system exhibits two types of nonlinearities: one proper of the mechanical system and one of due to the magnetic coupling. The availability of an electromagnetic-motional model allows for the separation of these two effects. A frequency domain model to describe the magneto-mechanical interaction under harmonic excitation is developed by means of a partial element equivalent circuit of the conductive parts. The restitution magnetic force model is then introduced in the numerical model of the system. Results obtained by simulations are validated versus experimental measurements on the three degrees of freedom structure.
Magnetic damped vibrations are obtained by coupling a conductive structure with a magnetic field.... more Magnetic damped vibrations are obtained by coupling a conductive structure with a magnetic field. The induced damping force characteristic depends upon displacement and velocity. When the magnetic field is generated by permanent magnets, a good model of the damping characteristic requires the estimation of the eddy currents induced in the conductive parts and subsequently of the resulting Lorentz force acting on them. This force is unfortunately nonlinear as its magnitude depends both on frequency and amplitude of oscillations. Considering by hypothesis a harmonic motion of the system, a simulation of the magneto-dynamic phenomenon is performed by means of a partial element equivalent circuit of the conductive parts. The force characteristic is then used to fit a sinusoidal input describing function approximation. Results obtained by simulations are validated versus experimental measurements on a three degrees of freedom structure.
Scienza, tecnica, sport e passione: gli ingredienti del record italiano di velocita a pedali conq... more Scienza, tecnica, sport e passione: gli ingredienti del record italiano di velocita a pedali conquistato a settembre dal Team Policumbent del Politecnico di Torino
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2021
Theory of Critical Distances (TCD) collects several methods adopted in failure prediction of comp... more Theory of Critical Distances (TCD) collects several methods adopted in failure prediction of components provided with stress concentration features. The idea of evaluating stress effect in a zone rather than in a single point was proposed decades ago but, only thanks to relatively recent works, TCD concepts showed to be a successful extension of Linear Elastic Fracture Mechanics (LEFM), able to assess strength and fatigue life. The increasing computational power has made Finite Element Method (FEM) widespread, hence stress fields can be easily extracted and used as input data for fatigue post-processing and durability analyses. In this scenario, TCD reveals as a powerful tool which, thanks to the introduction of a single material parameter (critical distance, [Formula: see text]), integrates classical fracture models by considering the presence of microscale phenomena acting in fracture process. In this sense, TCD behaves as a link between continuum mechanics and LEFM. Modalities an...
The static transmission error in gears represents the main noise and vibration source of mechanic... more The static transmission error in gears represents the main noise and vibration source of mechanical transmissions, both for selfexcitation and for the excitation of powertrain components. An accurate determination of it is very complex, since it requires experimental tests or highly detailed models. In both cases the costs and the computational time are high, therefore the possible different types of geometries to analyse are significantly reduced. In the present work, a semi-analytical methodology is proposed, with the aim of evaluating the variation of the contact area in gears during their meshing and at different levels of applied torque. This model considers the tooth compliance (tooth shear and bending, foundation and rim, gear body) and the local contact effects. The present semi-analytical methodology allows a detailed analysis of the tooth compliance and the contact area on a high number of points along the meshing cycle (typically over 100 points). It also enables the definition of the correct contact area geometry between meshing teeth, depending on the possible geometry modification (micro-geometry and/or manufacturing errors) and on the input torque. In particular, the contact is simulated through a non-Hertzian model able to evaluate every contact shape, overcoming the limits of the Hertzian theory. The goal of the proposed methodology is to determine with high precision the static transmission error between gears in a limited time with respect to the classical finite element method. Furthermore, it is useful for a reliable prediction of the transmission dynamic behaviour, considering the load exchanged between the teeth in relation to spin speed and torque, in a computational time lower than the classical techniques.
The connection system between mechanical parts with the greatest advantages in terms of productio... more The connection system between mechanical parts with the greatest advantages in terms of production is the threaded connection. This type of connection has considerable stiffness but also high weight. Often the search for the reduction of the masses clashes with the limits dictated by production needs. A considerable effort has been made in making screws with higher performance materials and therefore guaranteeing greater tightening forces with smaller cross sections, but there have not been as many notable developments on the method of determining the compliance of tightened elements. The classical theory identifies three different conditions for calculating deformability, which are sometimes not easy to interpret and implement. The use of numerical techniques such as finite elements allows designers to be very precise, but requires a great deal. To facilitate the work of the designers and provide them with a more manageable tool to better understand the type of threaded connection to be designed, the present work proposes an analytical formulation that allows a quick assessment of the compliance value of the clamped elements, regardless of the geometric relationships and materials. To achieve this, starting from a literature analysis, a parametric finite element model was developed and, based on the results obtained, a formula is proposed that covers all the possible scenarios for determining compliance. The results were compared with the classical theory in order to verify the correctness and applicability of the formulation. At the moment the formulation is valid for screws whereas for the bolts with nut unified formula is under investigation.
Journal of Engineering, Design and Technology, 2020
Purpose The implementation of project-based learning (PBL) activities in the curricula of enginee... more Purpose The implementation of project-based learning (PBL) activities in the curricula of engineering students has become a consolidated method to improve their skills. The purpose of this paper is to share the experience acquired by the authors from a decennial case-study on a student team PBL activity focused on design and development of human-powered vehicles (HPVs). A review of the project evolution, boundary constraints and management choices could provide inspiration and suggestions to faculty staff that would like to set-up similar experiences for engineering students in their universities. Design/methodology/approach A student team was funded by the authors in 2008 to gather engineering students interested in design and construction of HPVs. In the past decade, the team has grown from 10 up to 60 students enrolled per year and stimulated to develop a range of HPV designs for sports and mobility. The project management evolved as a consequence to com ply with the growing ambi...
International Journal of Automotive Composites, 2017
In the design of engine components, the demand for increasingly higher power combined with a grow... more In the design of engine components, the demand for increasingly higher power combined with a growing awareness for environmental and energy saving, creates a number of conflicting design constraints that can be overcome with the use of new materials. The present paper evaluates the possibility to use plastic materials for designing two important parts of the crank mechanism: the connecting rod and the piston pin. In particular, the material used for the connecting rod design is PEEK filled with carbon fibre and that used for the piston pin design is carbon fibre prepreg epoxy. The numerical analyses made by the authors prove that plastic materials can be useful for components weight reduction but a complete components revision and changing of design strategy are required. The direct metal replacement with plastic material is not possible, and the improvement of plastic materials performance and the new technology for additive manufacturing can completely change the way of thinking about the engine.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2019
The paper presents and discusses a low-cycle fatigue life prediction energy-based model. The mode... more The paper presents and discusses a low-cycle fatigue life prediction energy-based model. The model was applied to a commercial cast iron automotive exhaust manifold. The total expended energy until fracture proposed by the Skelton model was modified by means of two coefficients which take into account of the effects of mean stress and/or mean strain, and the presence of high temperature. The model was calibrated by means of experimental tests developed on Fe–2.4C–4.6Si–0.7Mo–1.2Cr high-temperature-resistant ductile cast iron. The thermostructural transient analysis was developed on a finite element model built to overtake confidentiality industrial restrictions. In addition to the commercial exhaust manifold, the finite element model considers the bolts, the gasket, and a cylinder head simulacrum to consider the corresponding thermal and mechanical boundary conditions. The life assessment performance of the energy-based model with respect the cast iron specimens was compared with th...
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
ASME 2012 Internal Combustion Engine Division Spring Technical Conference (ICES 2012), 6 - 9 May, Torino, Italy, pp. 917 - 923, 2012
The tribology of cam-roller follower conjunction is highly dependent on the engine type and worki... more The tribology of cam-roller follower conjunction is highly dependent on the engine type and working conditions. The interface experiences transient conditions due to variations in contact geometry and kinematics, as well as loading. These lead to instantaneous and capricious behavior of the lubricant through the contact, which determines the regime of lubrication. The resulting frictional characteristics are affected by the shear of the lubricant film and the interaction of rough surfaces themselves. Thus, specific analysis is required for any intended new engine configuration. Therefore, a tribo-dynamic model, combining valve train dynamics, contact kinematics and tribological analysis is required. An important issue is to develop a simple yet reliable and representative model to address the above mentioned pertinent issues. This would make for rapid scenario-building simulations which are critical in industrial design time-scales. The current model has been developed in response to the above mentioned requirements. A multi-body dynamic model for the valve train system based on the key design parameters is developed and integrated with an EHL tribological model for the cam-follower contact. To keep the model simple and easy to use and to avoid time-consuming computations, the analytical EHL model makes use of Grubin's oil film thickness equation. Viscous and boundary contributions to friction are obtained as these account for the losses which adversely affect the engine fuel efficiency.
Uploads
Papers by Cristiana Delprete