From Mechanical to Complex System Modeling and Design

Abstract

This chapter summarizes the main research activities and outcomes of the groups engaged in Mechanical Engineering, in the decade 2013–2023. The research topics are typical of the sectors Mechanical and Thermal Measurements, Applied Mechanics, Mechanical Design and Machine construction, Design Methods for Industrial Engineering.

1 Introduction

Mechanical engineering combines creativity, knowledge and simulation tools to improve the health of the society transforming an idea into reality. This transformation happens from simple products useful for everyday life till to complex systems. Mechanical engineers may design a component, a machine, a system, or an innovative mechanical assembly. This ranges from the macro to the micro, from the largest systems like nuclear fusion reactor, autonomous cars and mechanism as robots to the smallest smart components as wearable sensors. To this end, at DII, competences on applied mechanics, design methods, machine construction and measurement are available.

The applied mechanics for machines sector encompasses the cultural, scientific and professional aspects related to the study of mechanical systems, machines and their components, and structures. The study is developed through a unifying systems-based approach, utilizing methodologies from theoretical, applied, and experimental mechanics, leading to technological and industrial applications with a focus on environmental and energy sustainability. Strong interconnections are established with design methodologies and algorithms developed in the field, as well as industrial engineering methods, dimensional design and machine construction, fluid dynamics, bioengineering, motor sciences, orthopaedic and prosthetic surgery, rehabilitation and assistance methodologies, and finally, the interpretation and analysis of historically significant machines.

The design methods, mechanical design and machine construction sector deals with scientific and educational activities in the fields of concept design, engineering design, representation and modeling, and innovative methods for industrial engineering. The researchers are involved in the design and construction of machines, structures in automotive, aeronautical, railway and naval fields and mechatronic systems. They study the methods and tools for the conception and development of sustainable products, taking care of the entire life cycle. What characterizes these sectors is the interest in process, product, and method innovation, as well as the attention to the related development trends. The methodologies involve the use of advanced theoretical, numerical, and experimental engineering tools, as well as the application of techniques and methods for reducing development times. The relevant industrial sectors include mechanical engineering and transportation systems, biomedical, and energy. The design methods team (IDEAS) is internationally recognized in design and development of products, covering the topics of conceptual and engineering design, modeling and simulation, computer graphics, virtual and augmented reality, design for additive manufacturing and reverse engineering. The research activities are conducted in the following areas: industry 4.0 green technologies, collaborative robotics, bioinspired and soft robotics, exoskeletons, sustainable production processes, assistive devices for disabled people, tools for the safety of workers, human factors and ergonomics methodology, design of systems and robotic solutions for nuclear fusion reactors, naval, automotive, railway and aeronautical industries, healthcare (medical devices for rehabilitation and inclusion, dentistry), design of sports equipments and wearable technology.

The studies in mechanical and thermal measurements field aim to develop research and expertise in the methods of analysis, design, and testing of systems for measuring mechanical and thermal quantities, both for scientific purposes and industrial applications, including those related to human well-being. In general, these studies address issues concerning the integrated design of tools for monitoring, diagnostics, and control of any system affected by mechanical and thermal quantities.

2 Background and Legacy

2.1 Mechanics Applied to Machines

The study and teaching of Mechanics Applied to Machines in Naples has a history of about 200 years. Among the numerous figures who gave prestige and development to the discipline, Prof. Pericle Ferretti (1888–1960), who organized and directed the Institute of Mechanics Applied to Machines, had particular prominence. In 1925 he got the professorship in Mechanics Applied to Machines at the Royal School of Engineering in Naples. The school was aggregated only later, in 1935, to the Royal University of Naples. Prof. Ferretti himself promoted the birth, in 1940, of the “Istituto Nazionale dei Motori” of the CNR, immediately assuming its direction, which he maintained until 1960, the year of his death.

After 1960, the directions of the Institute of Mechanics Applied to Machines and of the Istituto Nazionale dei Motori were committed to Prof. Mario Taddei (1920–1981). When the Faculty of Engineering was moved to the new headquarters at Piazzale Tecchio in Fuorigrotta, both Institutes, leaving the historic headquarters in Via Mezzocannone, became in practice contiguous, both physically and scientifically. In those years, many theoretical and experimental contributions to the research development of Mechanics Applied to Machines were provided by researchers and professors who often worked in both Institutes. In this period some other disciplines arose in the same scientific ambit, giving birth to new teachings, among which we can mention those of: Theory and Technique of Vibrations, Servomechanisms and Automation, Measurements and Testing Standards. Meanwhile, the teaching of Mechanics Applied to Machines had been held by Prof. Taddei. Subsequently, the teaching was entrusted to Prof. Angelo Raffaele Guido, former full professor of Theory and Technique of Vibrations at the same Institute.

In the following years the “Federico II” University faced a reorganization, regarding the research activity, through a departmental structure model, and the Institute of Mechanics Applied to Machines then merged into the nascent Department of Mechanical Engineering for Energetics (DIME). The growing training needs of that period favoured the development of new research areas, such as: Vehicle Dynamics, Contact Mechanics, Tribology and Lubrication with reference to Hydrodynamic Bearings, Rotor Dynamics, Robot Mechanics. These research activities had natural repercussions in the field of teaching with the establishment of specific university courses. In recent years, the new university reorganization of “Federico II” has led to the establishment of larger departments. Therefore, in 2013 from the unification of smaller departmental structures, all operating in the industry sector including DIME, the Department of Industrial Engineering (DII) arose which today includes all the teachers and researchers in the sector of Applied Mechanics to the Machines.

The current frontiers of the research in industrial field have led to broadening the horizons of Mechanics Applied to Machines, traditionally consolidated in the Neapolitan school, towards topics of strong impact and interesting prospects. New themes of research are therefore being developed within the DII, among which the Dynamics and Control of Mechanical Systems with particular reference to autonomous vehicles; the Industrial Diagnostics of Mechanical Systems; Energy Recovery from Vibration Sources; Insulation systems based on innovative materials (Smart Materials).

The research results obtained in the Mechanics Applied to Machines of the DII have achieved numerous national and international awards. The university training and the students’ proficiency in the various disciplines of Mechanics Applied to Machines are the result of a passionate teaching activity which, even following radical changes in university regulations, has been able to keep its mission intact over the years.

2.2 Mechanical Design, Machine Construction and Design Methods for Industrial Engineering

At the end of the 18th century, Admiral Acton became the first representative of the Neapolitan Military School to publish a work on the representation and design of cannons using descriptive geometry. In 1811, Murat established the Polytechnic School in Naples based on the model of the French École Polytechnique, as proposed by Gaspard Monge, a scientist of the French Revolution and author of the first scientific book on descriptive geometry. After World War II, when the Faculty of Engineering of the University of Naples was in Mezzocannone Street, the Institute of Machine Construction was directed and reorganized by prof. Raffaele Tarantini, who died prematurely before the Faculty of Engineering moved to its new location in Piazzale Tecchio (starting from 60’s). Since its foundation, experimental facilities for mechanical characterization of components in automotive and railway fields have been developed and applied in cooperation with big industries as FIAT - Elasis and Ansaldo, Firema and RFI.

Since the 1980s, the study of computer graphics, CAD and FEM began to develop in various application domains (especially automotive and aeronautics) and with different purposes (CAD-CAM integration, geometric modelling of sculptured shapes, industrial automation, structural analysis). In the 1980s, there were participations in the Finalized Mechanical Technologies Project with Olivetti OCN (Marcianise, CE) on 3D CAD modeling of complex shapes, particularly levers and bicycle gear changers for Campagnolo SpA, and their production using 5-axis CNC machines (milling) based on the geometric model (first CAD-CNC connection with automatic generation of tool path for 5-axis milling). Subsequently, with the two Finalized Robotics projects, the research moved towards the design and development of Flexible Manufacturing Systems (FMS) with Jobs in Piacenza and the National Research Council (CNR). Furthermore, in the 1980s, the first research activities on the characterization of materials for biomedical use were initiated in collaboration with Professor Nicolais’s materials research group.

In 1990, with the university reform, the disciplinary scientific sector of the Design Methods for Industrial Engineering scientific-disciplinary grouping was established within the Industrial sector. The first full professor and founder of the research group was Professor Francesco Caputo, who initiated research in the indicated areas and organized the ADM conferences in Sorrento (1984) and in the Royal Palace of Caserta (1996).

Over time, research activities have seen the expansion of areas of interest and the potential applications for the concurrent development and dissemination of computer systems for graphic representation and other technologies based on the use of three-dimensional modeling, such as Computer-Aided Tolerancing (CAT), Computer-Aided Engineering (CAE), Computer-Aided Manufacturing (CAM), Reverse Engineering (RE), and Rapid Prototyping (RP), later known as Additive Manufacturing (AM).

Significant contributions to research have been made possible thanks to the laboratories that have been established. Through the PON DIGIPAT project with Elasis (Fiat Research Center in the Mezzogiorno, now Stellantis) and Ansaldo (Naples, now Hitachi Rail) on digital modeling of complex systems (cars and trains), research laboratories on geometric modeling (COGITO) and AM were created. Through the PRIN projects, ideainVR and the Reverse Engineering laboratory (CREAMI) were founded. In 2005, the largest Virtual Reality laboratory in Italy VRTest was established thanks to the Center of Excellence of the Campania Region. In 2012, the Fraunhofer Joint Lab IDEAS was founded through an agreement between Fraunhofer IWU (Chemnitz-Dresden) and DII - Federico II. The laboratories collaborate on main research programmes on model based systems engineering (MBSE), digital twin of complex systems, Virtual Prototyping, digital geometrical modelling and simulation, generative design for additive manufacturing and reverse engineering, conceptual design and RFLP modelling of nuclear fusion systems, extended reality for industrial engineering, human centered design of sports equipments, safety tools and rehabilitation devices for inclusion and soft robots.

3 Main Research Programmes

3.1 Integrated Navigation Solutions Based on Cost-Effective Inertial Measurement Units

Research activities for integrated navigation solutions based on cost-effective inertial measurement units are mainly carried out by he group of Mechanical and Thermal Measurements. Aim of the research is the design, implementation and testing of integrated navigation system involving cost-effective inertial sensors by means of a suitable redundant hardware architecture complemented with a proper digital signal processing algorithms for data fusion and enhancement [1]. It has been so possible of overcoming known limitations, thus making low-end MEMS inertial sensors eligible for the implementation of tactical-grade navigation systems for unmanned vehicles both aerial and terrestrial (Fig. 1).

Fig. 1

Low-cost inertial measurement unit for unmanned aerial vehicles

In particular, consumer-grade MEMS sensors have been arranged according to a cubic configuration in order to reduce typical bias errors affecting their outputs. A loosely-coupled integrated navigation has been then exploited to finally improve the estimates of position, velocity and attitude of vehicles, that were very close to those granted by a high-end MEMS inertial sensor, whose costs are about two orders of magnitude greater. Stemming from that experience, research activities have been conducted in cooperation with STMicroelectronics S.p.A. (further improvements obtained by means of the introduction of deep learning algorithms [2]) and Hitachi S.p.A. (implementation and characterization of tightly-coupled integrated navigation systems for pose estimation of trains).

3.2 AR-Based Applications for Remote Control of Measurement Instrumentation for Didactical Applications

Research activities for the implementation of a remote laboratory that can be accessed by means of augmented reality (AR) applications have been carried out by the group of Mechanical and Thermal Measurements in cooperation with researchers of the Department of Electrical Engineering and Information Technologies of the University of Naples Federico II. The availability of laboratory access has become a relevant issue due to recent increment of the number of students attending measurements classes as well as due to restrictions that the country underwent during the recent COVID-19 pandemics (Fig. 2).

Fig. 2

Example of AR app for oscilloscope remote control

While the theory lessons could be continued through remote teaching with few limitations, the laboratory activities (based on students’ interaction with the measurement instruments) required devising a solution that would allow them to relive the laboratory experience as if they were right in front of the instruments. This way, an innovative solution, involving a proper hardware device for connecting the instruments to the Internet of Things environment along with a suitable AR app running on students’ mobile phones, has been designed and implemented [3, 4]. The reliability of the provided solution has successively suggested its commercialization through a university spinoff, ARCADIA S.r.l., as well as the initiation of cooperative activities with the company Leonardo S.p.A. in the field of virtual and augmented reality training, which is still active today.

3.3 Control, Health Monitoring and Predictive Diagnostics of Mechanical Systems

The research activities related to control, health monitoring and predictive diagnostics of mechanical systems are developed at the Laboratory of Diagnostics of mechanical systems (DiaMeSys). The aim is to study and develop innovative techniques for the diagnostics, the damage detection and the health monitoring of mechanical systems. The investigation procedures are based on advanced analysis techniques such as Wavelet Transform, Chaos Theory and Discriminant Analysis. The development of the investigation procedures involved experimental tests on existing applications and the build of suitable test benches. The main topics addressed, in the last ten years of research, have been: study and identification of different tribological regimes in a gear pair through signal and image processing techniques; vibrational analysis of a turbine powered by green fuels [5]; determination of the tensional state of metal specimens by means of infrared thermography and Wavelet transform on images; vibrational analysis to detect cavitation phenomena in a directional spool valve (Fig. 3); damage detection in a gear box trough vibrational analysis.

Fig. 3

Experimental test rig to detect cavitation phenomena in a directional spool valve

Most of these research topics have also been the subject of thesis projects for the master’s degree in mechanical engineering and they have been reported as case study examples during the courses of Tribology and Diagnostics of Mechanical Systems and Applied Mechanics Complements. The research activities have been conducted in collaboration with the companies: M3S spa, Augusta due srl, Advanced Management Solutions Sarl (AMS), Ai4ethic srl, Leonardo, Ducati and FCA. Coupled with the development of diagnostic strategies based on the previously mentioned techniques, the control of mechanical and mechatronics systems, such as electrohydraulic actuators and road vehicles, is made with particular attention to the modelling approaches adopted to design linear and nonlinear controllers (Fig. 4). Furthermore, another topic is the model-based monitoring of mechanical systems, such as sliding isolators and road vehicles [6], through stochastic state observers such as Kalman Filters, functional to implement predictive maintenance strategies. The basic instruments for approaching the previously mentioned topics related to the control and the model-based monitoring of mechanical systems are provided in the courses Control of mechanical systems and Control-oriented Models for vehicle dynamics, disbursed for the master’s degrees in mechanical engineering for Design and Manufacturing and Autonomous Vehicle Engineering.

Fig. 4

a Controlled hydraulic actuator moving a shake-table; b Estimation flow for vehicle and tire-road monitoring through a nonlinear Kalman Filter

3.4 Dynamic Behaviour of Rotors and Lubricated Pairs

This topic has been investigated since the last ‘70s by several researchers of the Mechanics of Machines and Tribology groups, active in the past academic Federico II Univ. organizations operating before the present DII. A significant part of this research work, carried out both theoretically and with recourse to laboratory rig, started in the ‘90s and was addressed to the nonlinear behaviour of rotors, the operation with journal bearings and squeeze film dampers and the characteristics of the pressure distribution within the squeeze film (Fig. 5a). The effect of the bearing shape on the bifurcating behaviour of the rotor dynamics represents a main topic dealt with in the more recent papers (Fig. 5b) [7, 8].

Fig. 5

a Characteristics of the pressure distribution within the squeeze film; b The effect of the bearing shape on the bifurcating behaviour of the rotor dynamics

3.5 Dynamics of Railway Vehicles

The research activity related to railway vehicle dynamics focuses on the model-based monitoring of railway vehicles aiming to improve the reliability and safety of these latter, focusing on the possibility of employing condition-based maintenance instead of the typical predictive or calendarized ones. Monitoring systems, based on model-based stochastic state observers such as Kalman Filters, are developed to detect, at each time instant, anomalies in components of railway vehicles for condition-based maintenance purposes, taking into account the sources of uncertainties related to modelling approaches and noises produced by sensors. Estimator design models, based on the railway vehicle dynamics, are implemented in nonlinear forms of Kalman Filters for monitoring purposes of components related to the railway secondary suspension system, such as anti-yaw dampers [9] fundamental for reducing instability phenomena induced by the hunting motion (Fig. 6a) and of the wheelsets by estimating a crucial parameter, called equivalent conicity [10], which increases with the degradation of wheels profiles causing safety issues in the vehicle running due to the generation of high forces at the wheel-rail contact interface (Fig. 6b).

Fig. 6

a Model-based monitoring of railway anti-yaw dampers; b Model-based monitoring of the wear status related to wheelsets

As a part of the research activities related to the Department of Industrial Engineering, some contents, such as the development of state observers oriented to real-time applications for monitoring purposes of railway vehicles, are treated in the Smart Systems Laboratory for introducing the presented topic to students, expanding their knowledge on smart systems applicable onboard railway vehicles. Furthermore, concepts on the estimation of vital parameters related to railway vehicles coupled with their dynamical behaviour functional to develop estimator design models are introduced in courses of Master’s degree in Mechanical Engineering for Design and Manufacturing as Railway Vehicle Dynamics and Control of Mechanical Systems. Established collaborations are underway regarding innovations in rail transport with companies such as Hitachi Rail, RFI, Italcertifer, Blue Engineering, Contact, IVM, EAV, ANM.

3.6 The “Gear Rattle” in Automotive Transmissions

As regards the topic of transmission gears for motor vehicles, a tribo-dynamic model has been developed and perfected which considers the effect of oil on lightly loaded or unloaded gears. The model made it possible to investigate the influence of the oil lubricant in the attenuation of the tooth impacts responsible for a vibro-acoustic phenomenon, typical of the automotive manual gearboxes, known as “gear rattle” [11]. The problem is caused by the torque fluctuations in the internal combustion reciprocating engine which cause repeated impacts in all the gears of the gearbox which mesh without transmitting power [12]. The research activity was started as part of a collaboration with the Elasis research center of Fiat automobiles. Some non-linear models have been developed, both for a single gear pair and for the entire drive-line of the vehicle. The study of the vibro-acoustic phenomenon has been extended also in automated transmission systems equipped with dual clutches (Dual Clutch Transmissions).

Fig. 7

The experimental test rig for gear rattle investigation

To validate the theoretical models, a prototype test rig was designed and built at the D.I.I. Mechanics Laboratory (Fig. 7), through which, using original measurement methodologies, many experimental investigations about the lubrication conditions were conducted, documented by high-impact scientific publications. Some sophisticated techniques moreover have been employed for the analysis and recognition of anomalies during the functioning of unloaded gears, suitable to identify qualitative indices for comparative analysis with respect to the Gear Rattle phenomenon.

The findings of this research on teaching activity can be found in the Mechanics of Vibrations of Mechanical Systems and in the Mechanical of Transmissions which are addressed in all the Courses of the Mechanics Applied to Machines.

3.7 Robotics

The research activities related to Robotics are developed at the Laboratory of Mechanics of Automated Systems (MecASys). The aim is to address issues concerning the research and development in the field of automation of mechanical systems. The activities range from the design of components and actuation systems, till to control strategies and sensor integration. The study also includes an in-depth modelling of kinematics and dynamics of these systems.

The integration of robotic components with vision systems, such as RGB-depth cameras, is one of the main topics developed in the last years. To this hand, suitable test benches have been built to carry out experimental activities in this field, alongside the development of proper algorithms to handle with vision systems data. As an example, Fig. 1.8 reports a protype developed at the MecASys of a vision guided robotic system for flexible gluing process in the footwear industry. The main topics addressed, in the last ten years of research, have been: development of a mechanical hand with opposable thumb for prosthetic applications: design, modelling, prototyping, sensor integration, control strategies and experimental characterization; integration of vision systems for industrial automation in textile and footwear industry (Fig. 8a) [13]; vision systems to measure and control mechanical systems [14]; rovers for field operations for agricultural and environmental purposes: multibody model, kinematics modelling, navigation, control strategies, sensor integration and prototyping (Fig. 8b).

Fig. 8

Vision guided robotic system for flexible gluing in the footwear industry (a); prototype of a rover for field operations (b)

Most of these research topics have also been the subject of thesis projects for the master’s degree in Mechanical Engineering, Biomedical Engineering and Automation Engineering. The case studies have been also presented during the courses of Robotics Mechanics. The research activities are conducted in cooperation with several companies in the surrounding area, including Battista Accessori srl, Greentech Solution srl and SbS Group.

3.8 Use of Magnetorheological Elastomers as SMART Material in Insulators and Energy Harvesting

Magneto-rheological elastomers (MRE) are composite materials with magnetically polarized particles dispersed in an elastomer matrix. These materials belong to the smart material family because they can change a phisical property in controllable way. Such materials can be exploited in two distinct modalities: MRE direct effect and MRE inverse effect.

The MRE direct effect consists in varying the stiffness as function of the magnetic field in which they are immersed. Specifically, the shear modulus G is the variable more influenced by the magnetic field. The MRE direct effect is defined as the ratio between the modulus increase and initial storage modulus G. This value measures the effectiveness of MRE. The MREs characteristics make such materials suitable for the development of controllable devices for various application including adaptive tuned vibration absorbers and suspensions and semi-active system. With reference to the direct effect, investigations were first carried out in the laboratories of the department to characterize these materials and then hybrid seismic isolators were designed and built. The validation of the models and the evaluation of the effectiveness of the different vibration control algorithms implemented were carried out by means of some specially made test rig. Indeed, we have equipped ourselves with the necessary tools for the construction of magnetorheological rubber specimens with different characteristics and a test bench has been created to carry out tests on varying the magnetic circuit, the type of forcing motion, the configuration of the insulation system (Fig. 9) [15].

Fig. 9

MRE smart isolator test rig and force-displacement diagrams

The MRE inverse effect consists of converting mechanical energy into electrical one by means of the magneto-mechanical coupling (Villari effect). Since last year an experimental study on this subject has been started. The main results have been published in [16]. The findings of this research on teaching activity can be found in the Mechanics of Vibrations of Mechanical Systems and in the course of Applied Mechanics for Energy Efficiency.

3.9 Vehicle Dynamics and Tyre Behaviour

Within the realm of road vehicles, both cars and motorcycles, the study of vehicle dynamics plays a crucial role in enhancing performance, safety, and efficiency. The activities of the Vehicle Dynamics research group, within the Applied Mechanics one, focus on testing, analyzing and modelling the interaction of road vehicles with the external environment, working with a particular emphasis on motorsport vehicles and tire/road interaction. Moreover, their dedication to advancing multiphysical models [17] and tread viscoelasticity testing and evaluation has led to groundbreaking research and two successful spin-off companies, originating from their tech transfer projects.

The research group places tire/road interaction at the core of their activities. By conducting extensive testing and analysis, they seek to unravel the complexities and nuances of this critical dynamic. Utilizing state-of-the-art equipment and cutting-edge methodologies, they evaluate tire performance under various conditions and explore the influence of different road surfaces, temperatures, and speeds. These comprehensive tests generate valuable data that form the foundation for their subsequent analysis and modeling efforts.

One of the distinguishing features of the research group is their commitment to developing advanced multiphysical models. By incorporating principles from various scientific disciplines, such as physics, materials science, and computer modeling, they construct comprehensive frameworks that capture the intricate interplay between different factors affecting tire/road interaction in vehicle dynamics. These models aid in predicting and optimizing vehicle behavior, leading to advancements in performance, handling, and safety.

Within the tire research domain, the group focuses on tire tread viscoelasticity testing and evaluation [18]. They explore the viscoelastic properties of tire treads, which are crucial for understanding their deformation characteristics and response to different road conditions. By employing innovative specialized equipment and testing protocols, the research group advances the understanding of tread viscoelasticity, enabling tire manufacturers and vehicle designers to enhance tire performance and tailor it to specific applications.

The research group actively engages in technology transfer projects, leveraging their expertise and discoveries to foster innovation in the industry. Their groundbreaking research and practical insights have paved the way for the establishment of two successful spin-off companies, MegaRide, mainly focused on real-time tire models, and VESevo, patenting and developing an innovative device for viscoelastic materials characterization. These startups, born out of the research group’s collaborations with the automotive market, are at the forefront of translating cutting-edge research into practical applications. By bridging the gap between academia and industry, these spin-offs contribute to the growth of the automotive sector and reinforce the research group’s impact on real-world challenges (Fig. 10).

Fig. 10

a Tire-road friction tester; b Real-time model’s outputs

3.10 Railways Thermal Buckling Assessment

From the advent of high-speed (HS) trains, continuous welded rail (CWR) tracks have become a necessary requirement to ensure vehicle dynamic stability. At the same time, however, thermal track buckling has become the major problem for infrastructure managers. In fact, when the rails temperature increases over a critical value, the track can buckle, suddenly or progressively, in the lateral plane. The lateral resistance of the sleeper-ballast system is one of the most important factors affecting this mechanism. For this reason a research activity on the current experimental techniques, as well as on the analytical and numerical thermal track buckling models, has been conducted at first for RFI (the Italian infrastructure Manager) and, recently, for the world reference body on the railway field, the UIC (International Union of Railways).

In this framework, some advanced procedure for tests planning and raw-data analysis aimed at evaluating the effects of track geometric parameters on its total strength were defined [19]. Further, a series of lateral resistance tests on real tracks were conducted in field conditions, with the aim of: - predicting the lateral resistance curve for arbitrary ballast shoulder width, ballast thickness, subgrade composition, sleeper types, ballast compaction degree.

Also, analytical studies for developing models for designing the continuous welded rail against the thermal buckling, post-buckling and sensitivity analysis were carried out by the fem method to identify the mechanical and geometric track parameters more critic for the buckling failure were conducted. These inquires, of which some are still ongoing, motivated the interest toward the methods for analysing the elastic properties of the periodic beam-like structures and their buckling failures. The prediction of the critical temperatures for different values of the track radius, lateral misalignment amplitude, ballast compaction degree, sleepers, and ballast bed geometry are actually adopted by RFI for the management of the risk associated with the thermal track buckling phenomenon in the Italian railway. Both the performances of the numerical model and the findings obtained experimentally have been appreciated by the StableTrack group of UIC, which included the results in the worldwide adopted guideline (IRS 70720) on the risk associated with thermal buckling.

3.11 Railways Fatigue and Fracture Assessment

In railway superstructure, cracks due to fatigue at rail holes of insulated rail joints (IRJs) are a crucial issue, leading to early rails substitution, speed reductions and serious impacts on inspections and maintenance costs. Consequently, to ensure an economically sustainable increase in the safety, methods capable of extending both the fatigue life and the time between non-destructive inspections of structural components are of great industrial and academic interest. This is a long-term research topic where the Machine Design Research Group (MDRG) and the RFI (the Italian railway infrastructure manager) cooperate, taking advantage of the LMMS (Materials and Structures Mechanics Lab) facilities, and of the numerical and experimental knowledge that MDRG developed over many decades. As examples, the crack propagation phenomenological laws into the rails were identified, and crack growth stochastic models were developed for analysing the components’ structural reliability under fatigue damage [20]. Further, extensive experimental-numerical research focused on the application of cold expansion on drilled rails (which induces a residual stress beneficial to the fatigue strength) has been conducted. The main tool for the numerical modelling of the stress field and all the failure scenarios is the Finite Elements Method, whereas the main experimental tools are: fatigue machines with several load axes, optical and electrical strain sensors, temperature sensors and in-house designed load devices.

3.12 Adhesive Bonding in Structural Junctions

In recent years, adhesive bonding as joining technique has become frequent for structural purposes in many engineering fields, also as a consequence of the increasing use of composite materials. In mechanical engineering applications, bonded composites are typically used for the realization of industrial, automotive, naval and aerospace high-tech structural elements. In the last decade MDRG has been involved in many research activities on the identification and modelling of strength characteristics of the adhesive joints. This topic involves theoretical modelling, numerical calculations, experimental testing and the application of several international standards. The more fruitful framework has been recognized being the cohesive zone model and the fracture mechanics. Among several results, the one synthetized into the graphical abstract (Fig. 11) is, in our opinion, worth noticed. It represents a in-house designed device and experimental methodology for applying a pure tearing fracture mode on a bonded joint. In principle, it allows identifying a perfectly detailed cohesive law.

Fig. 11

New mode III debonding device

3.13 Model Based Systems Engineering (MBSE)—Digital Twin of Complex Systems

During the last decade, the Laboratory of Interactive Design and Simulation (IDEAS) researchers have deepened the development of complex systems and related digital twins by using and providing methods based on MBSE approach. In particular, the Computer Geometric Modelling and Simulation (COGITO) Laboratory researchers faced developing complex systems within the manufacturing and electric vehicles fields. By using V-model and RFLP method, the researchers investigated: the designing of collaborative workplace for aircraft assembly; the integration of autonomous mobile robots (AMR) and cobots [21] (Fig. 12); the designing of propulsion and power-train systems. The researchers obtained results on: (i) the structured Natural Language for writing well-formed functional requirements; (ii) the development of functional and logical architectures; (iii) the development of behavioural models for system verification and validation; (iv) the development of digital twin and its integration with system models.

The research activities have been performed in the framework of national and international projects and co-operations, as: 2018–22 PON project ICOSAF—Integrated Collaborative Systems for Smart Factory; SUNISWELL cooperation among ISAE-SUPMECA—Institut Supérieur de Mécanique de Paris, COGITO-IDEAS—DII—University of Naples Federico II, University of Applied Sciences Upper Austria—Campus Wels; cooperation between COGITO-IDEAS—DII—University of Naples Federico II and National Research Council of Italy—Institute of Sciences and Technologies for Sustainable Energy and Mobility.

The accomplished results have progressively fed the course of Modelling and Simulation of Mechatronic Systems and Concept Design of New Vehicles belonging to master’s degree programmes managed by DII.

Fig. 12

Visual summary of MBSE approach to the designing of AMR-COBOT interfaces

3.14 Virtual Prototyping—Computer Geometric Modelling and Simulation

Both the research topics of Virtual Prototyping and Computer Geometric Modelling and Simulation have been deeply investigated during the last decade at the DII. In particular, advances on Virtual Prototyping Methodologies were provided for the variational analysis of both rigid and deformable mechanical assemblies, in cooperation with the University of Molise. Variational parameters, a constraint solver, and a software tool to quickly analyse variabilities in flexible assemblies in different design scenarios were progressively provided.

Virtual Prototyping and Computer Geometric Modelling were also investigated by addressing digital patterns for product development. In particular, an intensive knowledge-based approach for the designing of mechanical and mechatronic systems was provided. The approach adopts Graph Theory to address and represent the designer knowledge and highlights common Key Characteristics to develop smart virtual prototypes of gearboxes and power window systems with different architectures. The research was developed in the framework of the 2011–14 PON project DIGIPAT—Digital Pattern Product Development in collaboration with FGA Group, ANSALDO Group and SMEs in Italy [22].

Finally, Virtual Prototyping was deepened for the workplace designing, by promoting human–robot collaboration and multi-objective layout optimization. The research goal was achieved in the framework of the 2018–22 PON project ICOSAF—Integrated Collaborative Systems for Smart Factory [23]. Virtual Prototyping and Computer Geometric Modelling were deepened within the research activities of the in-progress H2020 ENERMAN Project—Energy-Efficient Manufacturing System Management, focusing the adoption of AR-VR techniques for sustainability awareness and life-long learning of manufacturing line operators.

The methodological results of the above-mentioned researches have been progressively included in the courses of Geometrical Modelling and Virtual Prototyping, belonging to master’s degree programmes managed by DII (Fig. 13).

Fig. 13

Left: Virtual prototyping of a collaborative workplace for welding point inspection. Right: KBE-approach to the geometric modelling of automotive gearboxes

3.15 Design for Additive Manufacturing and Reverse Engineering

Over the last decade, at DII the attention has also been widely focused on research topics such as Design for Additive Manufacturing (DfAM) and Reverse Engineering. Specifically, many efforts have been put on the development of customised devices with tailored morphological/architectural features, mechanical and functional properties for industrial (e.g., automotive, aerospace, naval) and biomedical (e.g., prostheses, dental materials and implants, scaffolds for tissue engineering, regenerative medicine) applications. The research led to the design of advanced, lightweight and multifunctional devices, in the form of 3D solid, cellular, lattice, functionally-graded or solid-lattice hybrid structures, with a special focus on the improvement of the quality and the environmental impact together with time and cost reduction, enhancing the product development efficiency. The activities were performed with the aim to expand far beyond the state-of-the-art and to develop novel approaches towards the design and manufacturing for next generation components of devices, also considering the search for more sustainable, reprocessable and recyclable polymers and composite materials, as well as the reuse of metal powders. The development of high-performance devices benefited from topology and/or topography optimization as well as from generative design, with a special emphasis on features at the macro- and micro-scale. The activities were related the exploration of design criteria and methodologies in the optimization of additive manufactured devices, as well as to the definition of the relationship among the process parameters, structures and mechanical/functional features [24]. The biomimetic/bioinspired and generative design for AM allowed the extraction of novel wisdoms from biological prototypes and their integration into several technological domains with the aim to create innovative products in the industrial field. The DII unit generated multiple design alternatives based on bioinspired generative design. The obtained methodological results consisted of several design solutions satisfying the input data and design objectives in different ways, contemplating many combinations of materials and structures.

The methodological approaches developed over the last decade were employed in the frame of industrial projects as 2019–2022 PON project ISAF—Integrated Smart Assembly Factory with Leonardo S.p.A. [25]; 2014–2016 PON STEP FAR—Development of eco-compatible materials and technologies of drilling and trimming processes and of robotized assembly with Leonardo S.p.A and scientific collaborations, e.g. with Stellantis Research Center, where members of the DII unit played key roles leading to novel devices, innovative/integrated technological solutions, which were also covered by an international patent [26] (Fig. 14). In addition, two members of the DII unit working in the field were nominated among the World’s Top 2% Scientists in 2022.

Fig. 14

Innovative gripping tool made in AM using lattice structures, topological optimization and generative design algorithms

3.16 Nuclear Fusion

Nuclear fusion is the energy source that powers our Sun and stars. Should we succeed in replicating this reaction on Earth, we would get a virtually unlimited and “clean” energy source. The most advanced nations in the world are working together to face physics and engineering challenges of future fusion reactors. In this context, the research group at DII is playing a significant role. Indeed, under the coordination of ENEA and CREATE (www.create.unina.it) and with the support of EUROfusion [euro-fusion.org] and F4E [www.fusionforenergy.europa.eu], DII is engaged in several projects, namely ITER, DEMO, IFMIF and DTT. The International Tokamak Experimental Reactor (ITER) [www.iter.org] is the most advanced plasma science and energy project in the world today. DII researchers worked at the piping design and the CAD integration of European test blanket modules at ITER site, which is under construction in southern France. The DEMOnstration power plant, DEMO, will be ITER’s successor. Differently from ITER, the main goal of DEMO is the production of electricity from nuclear fusion reaction. Laying the foundation for DEMO is the objective of the EUROfusion Fusion Technology Programme in Horizon 2020 and Horizon Europe. DII is involved in several EUROfusion work-packages about DEMO project (Fig. 15).

Fig. 15

Left: Virtual prototyping of DTT fusion reactor. Right: Tokamak cooling system for DEMO fusion reactor

The main contributions were related to the conceptual design of the Vacuum Vessel, the Breeding Blanket, the divertor system, the whole balance of plant and the remote maintenance system. Lastly, DII researchers leaded the mechanical design and remote handling system of the Italian Divertor Tokamak Test Facility, DTT, [www.dtt-project.it] which will be one of the most important experimental machines on the Roadmap to the Realisation of Fusion Energy [27, 28]. Furthermore, in the framework of Italian PNRR Research Infrastructure named DTT-Upgrade, DII is developing, with ENEA, the greatest Remote Handling Facility in Europe for tokamak machines.

3.17 Extended Reality for Industrial Engineering

Since 1999 researchers of IDEAS lab are developing Extended Reality (XR) methods and technologies in the field of interactive design and manufacturing, ergonomics [29], maintenance, human-robot interaction, product and process’ digital twin [30], remote control of robotic machines, virtual training. They developed a framework for conducting collaborative Design Review sessions of complex products and systems based on both full “immersive” Virtual Reality (VR) and Mixed Reality (MR) techniques. MARTE lab, realized by DII researchers in 2005 and continuously updated, is equipped with the most advanced technologies that allow interdisciplinary product development teams to interact with the virtual product prototypes long before the realization of their physical counterparts. MARTE lab gives the opportunity to follow the whole product development cycle, from the first conceptual models to the detailed design phase, passing by the testing and the validation of the user experience. It is proved that the so-called virtual product development prevents design errors, increases product quality, and reduces time and costs. The research activities have been conducted in the framework of national and international projects, such as: PON 2020–2023 BRILLO “Bartending Robot for Interactive Long Lasting Operations”; EU Project H2020 REFILLS “Robotics Enabling Fully-Integrated Logistics Lines for Supermarkets”; PON 2018–2022 ICOSAF “Integrated collaborative systems for smart factory”; PON 2014–2016 CERVIA “Advanced and innovative methods for verification and certification in aeronautic design”; POR Campania FSE 2007–2013 CAMPUS VERO: “Virtual Engineering for Railway and automotive”; PRIN 2006 PUODARSI: “Product User-Oriented Development based on Augmented Reality and interactive Simulation”.

3.18 Human Centered Design of Sports Equipment and Safety Tools

Sports Engineering is a highly interdisciplinary field that connects mechanical engineering to sport science, information technology, human factors and medicine. Focus is given on design of sports equipment for elite and amatorial athletes, to monitor and enhance their performances and reduce the risk of injury. Using a user centered approach, ErgoS-IDEAS Lab has developed products to monitor sport performance and/or infringements in several sports as race walking [31], rowing and cycling [20]. Further, IDEAS has developed the concept design of playground equipment to increase the engagement in sports and motor activity for young and disabled people.

In safety engineering, IDEAS lab, in cooperation with INAIL D.R. Campania, as developed serious games with haptic interfaces to improve the learning process, providing more flexibility, and engaging workers with an intelligent learning experience. These simulation tools can be useful to evaluate functional abilities for healthy workers or residual ones in case of workers with disabilities (Return to Work project). Finally, a safety tool based on Augmented Reality to help the workers to learn about safety procedures and the use of protective devices, when and where they need on the workplace (https://www.dvrplus.it/), has been developed for IoS and Android mobile devices (Fig. 16).

Fig. 16

Sports equipment and safety tools developed at IDEAS lab

3.19 Soft Robotics

Soft robotics recently emerged as a new robotics discipline where in the mechanical behaviour of the robot body plays a crucial role in enabling applications which are difficult to be conducted using traditional robotics. While soft robots are relatively fast to be fabricated, they are very difficult to be modelled, as their robot body undergone finite (and therefore large) deformations when subject to internal actuation loads and/or external forces. The research group at IDEAS Lab has developed a new approach for accurate, yet computationally efficient modelling and simulation of soft robots [21]. By leveraging on the intrinsic safety in the interaction with the external world, soft robots can be used for the manipulation of delicate objects [32], for the inspection in constrained environments, for maintenance in difficult-to-reach sites, for human-robot collaboration and also for wearable robots. The research results of the group in soft robotics are part of the BIOIC project https://www.bioic.unina.it/ between University of Naples Federico II and Fraunhofer IWU (Fig. 17).

Fig. 17

Research activities carried out in the IDEAS lab about soft robotics

4 Future

Starting from the experience gained in these years, the research activity is moving from low TRL to higher ones to increase the impact on the society. To this end, the commitment of the new generation of researchers is stronger than in the past. The Mechanical Engineering group of researchers have founded seven spin off: Proetico, MegaRide, BeyondShape, ETA Bioengineering, Herobots, Robosan, VESevo, Sharps, Arcadia. The first two are now autonomous start up independent by the University. These spin off were awarded at national and international level: MegaRide was winner of the StartCup 2016 startup competition and of the Barsanti and Matteucci Award 2022 edition. VESevo was winner of the Automotive Testing Technology International 2021 Award in the “Hardware Innovation of the year” section. BeyondShape was winner of the StartCup 2019 startup competition and of the Myllennium Award 2020. Robosan was Winner of the StartCup 2021 startup competition and of the 2023 edition of Unicredit Start Lab for South of Italy.

The research topics are now founded by many international and national projects, the most important ones are in the framework of NEXT Gen EU program, PNRR fund, in Smart and Sustainable Mobility (CN-MOST) and Circular and Sustainable Made in Italy (PE-MICS).

The classical Mechanical Engineering is evolved also at the Master level, having contributed to start an international course in Autonomous Vehicle Engineering (MOVE) with the challenge to design and management of vehicles for surface, air and marine transport by including functionalities for greater autonomy. These functionalities range from simple forms of enhanced control of a single vehicle to the complete execution of a mission, eventually in coordination with others, without any intervention by human pilot. To this end a strong integration between sensors, information technologies, robotics, vehicle design and modeling is also needed. The main research programmes show how the mechanical engineering is moving towards these new challenges and the background to educate new generations of modern mechanical engineers ready for the Italy of the future. Our Dept, in the South of Italy, has to assure even more a strong contribution to the industrial transition in order to maintain the leading position of Italy in world manufacturing.