Virtual prototyping and digital twin

Diesel and spark-ignition piston engines are an ideal choice for long endurance, high altitude operations (10, 000m/33, 000ft) and extremely high altitude operations (20,000m-65,000ft). These systems are more complex than traditional applications that are normally limited to 5, 000-7, 000m (16, 000-23, 000ft). In fact, the air propulsion system (propeller or fan), the air intake, the fuel system, the turbo charging, the exhaust and the cooling system take part to the design optimization process. An integrated design is strictly necessary. Since prop-fan is currently under development, the design should start from the choice between propeller and fan. This choice will influence optimum cruise speed, critical altitude and aircraft design as a whole. The air induction system is extremely important to improve efficiency, endurance and critical altitude. At low altitude, a filtered induction system is used for takeoff. At high altitudes, the intake air is taken from high-pressure areas into an alternate, extremely optimized, path. This induction system recovers as much pressure as possible, air kinetic energy at cruise speed. In propeller systems, the intake is usually positioned in the lower part of the aircraft. On fan systems, a little amount of "high pressure" air is taken from the high-pressure area of the fan. The exhaust system is also critical with the choice between pressure recovery and thrust. Exhaust-pressure-recovery reduces backpressure and temperature at exhaust. However, the improvement in critical altitude is marginal. In more common, thrust driven exhaust systems, the exhaust energy is converted into speed and thrust. At the relatively high speed of high altitude cruise, also the cooling system adds a small amount of thrust through the Meredith's effect. The piston engine power plant design is then extremely critical. Many different components should find the correct position for maximum performance. The power-plants of WWII water-cooled fighters and bombers are good examples, even if their design cruise altitude is below 10, 000m (33, 000ft). Modern turbofan and turbojet air intakes are also of help. However, the requirements of low weight, high reliability and long endurance HALE (High Altitude Long Endurance) UAVs (Unmanned Aerial Vehicle) requires further work on this specific subject.

Keywords: Cooling , HALE , Meredith effect , Optimization , Thruster , UAV

The paper presents a lifecycle approach applied to the whole factory plant to characterize primary resource consumptions and environmental impacts for the different processes. The method is based on specific environmental models, defined for each process of a manufacturing plant. The goal is to provide a tangible support to guide decision-making strategies in order to move manufacturing towards sustainability. A case study of a washing machine factory plant has been analyzed to highlight the critical working areas in terms of environmental and energy loads and to support the identification of the corrective actions to increase the overall sustainability.

Keywords: Industrial metabolism , Life Cycle Assessment , Plant lifecycle

This study presents an approach based on Design of Experiment (DoE) technique for the optimization of an energy recovery ventilator (ERV). This system is one of the efficient ways to enhance the thermo-hygrometric comfort without increase excessively the thermal load in domestic kitchen. However, there is a major concern, which energy recovery cannot trade off ERV's fan power consumption. The goal of this study is to obtain the information about the relation between factors and response in an empirical way. This approach integrates three different levels of analysis: the virtual prototyping, Design of Experiment (DoE) and rapid prototyping. The virtual analysis allows to define the principal parameterization of a simplified model and to simulate the performance of each configuration at working condition. The proposed approach investigates the effect of the defined parameters and noise factor on the experimental results. In particular, the applied method for DoE analysis is based on virtual experiments in according to the necessity to reduce time and costs during the early design phase. The optimum parameters configuration, which is defined by the previous step, is useful to define the geometry and the working condition of a reliable virtual model. The final level is the realization of a 3D ERV with a rapid prototyping printer. The obtained component is now evaluable at the test bench to investigate the air flow rate and the electric power consumption.

Keywords: Design of Experiments , Energy Recovery Ventilator , Rapid Prototyping , Virtual Prototyping

In recent years, Human Robot Cooperation (HRC) has found an increasing adoption in manufacturing, especially to help humans in the execution of manual assembly tasks. An effective employment of HRC encompasses human relief from exhausting operations. Therefore, the design of cooperative solutions should be developed accordingly to ergonomic aspects. The present work proposes an approach to support the integration of ergonomic evaluation of manual operations in the design of HRC solution, based on modelling and simulation of the human body along the manufacturing tasks. The proposed modified model integrates the ergonomic metrics and returns a fatigue level along the working shift scheduling. A real manual assembly of biomedical products has been selected to validate the proposed approach. As a result, the suggested fatigue model provides an objective ergonomic evaluation of manual operations which verifies the impact of the HRC solution on the production goals.

Keywords: Biomedical , Ergonomic evaluation , Human Robot Cooperation , Simulation

Machining using industrial robots is currently limited to applications with low geometrical accuracies and soft materials. This paper analyzes the sources of errors in robotic machining and characterizes them in amplitude and frequency. Experiments under different conditions represent a typical set of industrial applications and allow a qualified evaluation. Based on this analysis, a modular approach is proposed to overcome these obstacles, applied both during program generation (offline) and execution (online). Predictive offline compensation of machining errors is achieved by means of an innovative programming system, based on kinematic and dynamic robot models. Real-time adaptive machining error compensation is also provided by sensing the real robot positions with an innovative tracking system and corrective feedback to both the robot and an additional high-dynamic compensation mechanism on piezo-actuator basis.

Keywords: Error compensation , Optical tracking , Robot dynamics , Robot modelling , Robotic machining

Numerous companies all around the world are shifting from traditional products to product-service solutions, thanks to the increased 'intelligence' and ' connectivity' of modern products and the more deep integration among mechanics, electronics, Information and Commutation Technologies (ICT) and Internet of Things (IoT). Such Product-Service Systems (PSSs) are usually designed and developed by considering product and service as separated entities with the consequent increase of design and validation difficulties. In addition, a final physical prototype has to be realized to validate the overall solution. In this context, Virtual Prototyping can support PSS design to reduce process iterations and time to market. However, actual virtual prototypes are usually conceived for product validation, and are not so effective for PSS. The paper defines a set of requirements for PSS simulation on digital models, and defines a set of tools for successful PSS prototyping.

Keywords: Model-in-the-loop , Product-Service System , Virtual Prototyping , Virtual Reality

Pier Paolo Valentini, PhD in Design of Mechanical Systems, is Associate Professor of Applied Mechanics. He is research fellow of the National Laboratories of Frascati (Rome) of the Italian Institute for the Nuclear Physics and member of the Steering Committee of the Italian Association of Machine Design. He teaches Virtual Prototyping and Simulation of Mechanical Systems and Bio-prosthesis. He has been advisor of more than 130 master and PhD dissertations. He has been principal investigator of more than 40 research projects funded by institutions and industrial partners. He has authored more than 130 papers in international journals and conference proceedings. Eugenio Pezzuti is Associate Professor of Machine Drawing. He is member of the advisory board of the Italian Ministry for Education, University and Research. He has been the principal investigator of three projects funded by national institutions. His fields of interests are the design of machine components, study on optimal tolerance allocations, reverse engineering methodologies and biomechanics. He has authored more than 80 papers in international journals and conference proceedings. The allocation of the right tolerances is one of the most important phases in the design process of mechanical devices and systems. In general, the choice has to take into account the manufacturing costs and limitations, looking at the specific functionality of the device and the assemblability of parts. In the case of flexible components, the designer has to include the evaluation of the compliance effects and the structural resistance. The paper discusses a numerical methodology for addressing the problem of the geometrical tolerance allocation for the compliant ortho-planar spring. The methodology is based on the definition of the functionality and resistance objective functions by means of finite element models. Numerical constrained optimisation is then applied to find the suitable combination of tolerance parameters acting on the main dimensions.

Keywords: Compliant mechanism , Flexible component , Ortho-planar spring , Tolerance allocation

The enhancement of the early design stages, in the production of aeronautical engines, has been shown decisive, for developing efficient and reliable final products. Nevertheless, in most of industrial engineering design problems, the amount of design variables is large. Moreover, several nonlinearities characterize the behaviour of the physical phenomena involved and the derivatives are seldom known for all the functions. Besides, objective functions exhibit several local extremes, whereas the designer as well as the practitioner is usually interested in the global one. In this context, stochastic and evolutionary optimization have been shown capable to provide reliable solutions while keeping the computational cost at a reasonable level. Existing tools for the design and optimization of engine components deal with the optimal and detailed design of specific engine components, thus requiring several computational time and efforts to gain optimized design parameters. Hence, existing tools fit for later design phases. Conversely, this paper proposes an integrated design and optimization environment, for automatically designing optimal aeronautical piston engine configuration, still in the conceptual design stage. The optimization is performed using the MATLAB genetic algorithm (GA) toolbox®, while the automatic design of the optimized components is carried out in cascade to the optimization phase. In particular, a single-objective GA is used to evaluate the optimal dimensions of engine components related to motion, namely: crankshaft, connecting rods and screws, flywheel, propeller shaft and torsional vibration damper. For testing the efficiency of the integrated environment, the conceptual design of components of a 4-in-line Diesel aeronautical piston engine is proposed, starting from an existing similar engine. Results show a reduction of the 20 % of weight of the crankshaft in comparison to the original configuration. The proposed environment seems to be a promising tool for a fast and reliable conceptual design of piston engines for aeronautical purposes.

Keywords: Automatic design , CAD models , Conceptual design optimization , Genetic algorithm , Stochastic optimization

Building energy simulation models are playing an increasing role in the construction industry and estate services and are constantly being improved. However, the accuracy and usability of simulation results is highly dependent on its inputs, many of which remain difficult to determine. Amongst inputs, the definition of occupant behaviour is recognized to be complex, and generally underestimated and neglected. With the trend towards increasingly energy efficient buildings, a proper representation of occupant presence and activities is becoming crucial in the design of buildings, which need to be comfortable, adaptable and resilient towards variable thermal loads. This paper presents a study of the occupancy of a university building in the UK in order to assess discrepancies between assumed and actual occupancy of the facility. Data has been obtained from a range of sources, including the Building Energy Management System, timetabling, and direct observation. The corresponding occupancy patterns have been simulated using DesignBuilder and EnergyPlus. Results indicate a potential energy saving in the order of 10% for set-up control that matches actual building occupancy more closely than current settings.

Progressive delamination in composite materials under static or fatigue loading condition are, in many structures, one of the predominant cause of failure. In the paper, an accurate study of quasi-static delamination growth under mode II loading condition is conducted. Several experimental tests are performed on composite laminates consisting of unidirectional carbon/epoxy layers. Four-point end-notched flexure (4ENF) test is employed in order to characterize the mode II interlaminar fracture toughness. The R-curve is obtained by means of optical and numerical determination of crack tip position. The energy release rate and the crack length are calculated through experimental determination of the compliance until unstable advance occurs. In order to confirm the experimental results, a cohesive-frictional model, implemented in the finite element program FEAP, allows to evaluate the influence of frictional phenomena in the Mode II delamination, when the compression of the two interfaces increases the energy dissipation due to the friction.

Keywords: 4ENF , CFRP , Cohesive Zone Model , Composite materials , Delamination , Mode II

In the present paper a new thermodynamically consistent cohesive interface model is proposed; it based on a predefined Helmhotz free energy with a single scalar damage variable and produces two independent fracture energies, in pure mode I and pure mode II debonding conditions. The proposed model can also take in to account the frictional effects with a smooth transition of the mechanical behaviour, from the initial cohesive one of the sound material, to the frictional one of the fully debonded interface. The cohesive-frictional behaviour is based on the mesoscale geometric interpretation of the scalar damage variable, which distinguish sound and debonded fractions of a representative surface element of the interface. The proposed formulation is defined by a damage activation function, which depends on the separation displacement. Traction components, damage evolution and the relevant constitutive equations are derived by following the classical Noll and Coleman procedure, and the model implicitly verify the second thermodynamic law by proving that dissipation is non-negative for any loading path. The numerical simulations of mixed mode delamination tests are performed and compared to the experimental results, for different mixed mode ratio.

Keywords: Delamination , Fracture , Friction , Interface , Mode II

Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) require a preliminary drilling of the elements to be joined, that may cause localized material damage and stress concentration, especially for anisotropic laminates characterized by high stress concentration factors and easy drilling damaging, with significant decrease of the load-carrying capacity of the joined elements. In order to exploit the advantages of the bonded joints and those of the mechanical joints, both industrial manufacturing and research activity have been focused recently on the so called hybrid joints, obtained by the superposition of a mechanical joint to a simple adhesively bonded joint. In order to give a contribution to the knowledge of the mechanical behavior of hybrid bonded/riveted joints, in the present work a numerical-experimental study of bonded/riveted double-lap joints between aluminum and carbon fiber reinforced polymer (CFRP) laminates, has been carried out. It has permitted to highlight both the static and the fatigue performance of such joints obtained by using aluminum and steel rivets, as well as to known the particular damage mechanisms related also to the premature localized delamination of the CFRP laminate due to the riveting process.

Keywords: A. Polymer-matrix composites (PMCs) , B. Mechanical properties , C. Finite element analysis (FEA) , E. Joints/joining

The paper deals with automotive power window systems and, in particular, tackles the problem of validating the object-oriented model of a single bowden system, to be used within a Model-Based System Engineering (MBSE) approach. Therefore, the paper tackles the problem of increasing accuracy of object-oriented models by defining model refinements i.e. by identifying objects whose modelling has to be improved. Firstly, the role of object-oriented modelling and the main characteristics of the power window system are summarized. Then, the object-oriented model of an automotive single bowden power window system is presented. Finally, the experimental phase, performed to characterize the behavior of the real system is summarised and the validation of simulation model, as well as the identification of model refinement, are accomplished.

Keywords: mechatronic systems , model validation , object-oriented modeling , single bowden power window system

This paper deals with an application of Discrete Event Simulation (DES) within the manufacturing process of a high-speed train. Today, the use of a DES tool is common for supporting engineers in designing the production lines and planning the production, representing a valid help in what-if analyses and in the measurement or validation of a solution. In this research activity, differently from the common use, it has been developed a DES model whose function is not to measure and/or validate a solution of a problem, but to generate a solution that will be nearly to the optimum. This paper describes DES tools, the methodology used in this work, the model built, the case-study and the obtained results.

Keywords: Discrete event simulation , Production planning , Scheduling optimization , Virtual manufacturing

The main objective of this work was to design an innovative skidding winch aimed to improve timber harvesting productivity, operators' safety, and reduce environmental damage in contexts in which mechanized harvesting is limited. The study area is the north-western Black Sea region of Turkey. In the proposed methodology, the harvesting process was simulated with Discrete Event Simulation (DES) software in order to identify bottlenecks. An alternative process was compared with the original one within the DES software itself in order to validate further steps oriented to generate new innovative product concepts. The development of the product was focused towards customer satisfaction, collecting customer requirements and identifying quality characteristics with a Quality Function Deployment approach. Contradictions identified in the design phase were solved using the TRIZ contradiction toolkit, generating different product concepts. Inventive solutions provided by TRIZ were designed within parametric CAD software. The concepts were compared in virtual environment with focus on ergonomics, selecting an optimal solution. The results show that with the concept adopted is possible to achieve a substantial increase in productivity, from 121% to 133%, in terms of kilograms of logs per hour deposited on the landing. Moreover, the final concept allows for ergonomic loading operations and reduces environmental damage to soil and vegetation.

The paper deals with a digital pattern (DP) approach to the design of an automotive power window, using object-oriented modelling. Therefore, the paper faces the designing of a mechatronic system by using an integrated approach to product development. Then, Dymola/Modelica environment is used as a tool of a decision support system that makes possible the DP approach. The paper briefly sum up the results of simulations related to a power window system characterized by a double bowden sliding mechanism. Finally, the paper highlights the parameters that could be easily integrated in a graphical user interface, aimed to reduce both the development time of new power window system and to increase the accuracy of design activities.

Keywords: Digital pattern for product development , Mechatronic systems , Objectoriented modeling , Power window systems

In view of the ITER conceptual design review, the design of the ancillary systems of the European test blanket systems presented in [1] has been updated and made consistent with the ITER requirements for the present design phase. Europe is developing two concepts of TBM, the helium cooled lithium lead (HCLL) and the helium cooled pebble bed (HCPB) one, having in common the cooling media, pressurized helium at 8 MPa [2]. TBS, namely helium cooling system (HCS), coolant purification system (CPS), lead lithium loop and tritium extraction/removal system (TES-TRS) have the purpose to cool down the TBM and to remove tritium to be driven to TEP from breeder and coolant. These systems are placed in port cell 16 (PC#16), chemical and volume control system (CVCS) area and tritium building. Starting from the pre-conceptual design developed in the past, more mature technical interfaces with the ITER facility have been consolidated and iterative design activities were performed to comply with design requirements/specifications requested by IO to conclude the conceptual design phase. In this paper the present status of design of the TBS is presented together with the preliminary integration in ITER areas.

Keywords: Breeding blanket , Integration in ITER , Tritium extraction and management

This paper quantitatively reports about a practical method to improve both position accuracy and energy efficiency of Servo-Actuated Mechanisms (SAMs) for automated machinery. The method, which is readily applicable on existing systems, is based on the 'smart programming' of the actuator trajectory, which is optimized in order to lower the electric energy consumption, whenever possible, and to improve position accuracy along those portions of the motion law which are process relevant. Both energy demand and tracking precision are computed by means of a virtual prototype of the system. The optimization problem is tackled via a traditional Sequential-Quadratic-Programming algorithm, that varies the position of a series of virtual points subsequently interpolated by means of cubic splines. The optimal trajectory is then implemented on a physical prototype for validation purposes. Experimental data confirm the practical viability of the proposed methodology.

Keywords: Energy Efficiency , Position Accuracy , Trajectory Optimization , Virtual Prototyping

Programmable servo-actuated mechanisms can enhance the flexibility and the reconfigurability of modern manufacturing systems. Differently from fully mechanical design solutions (such as mechanical cams) and especially in the case of high-dynamic motions, servomechanism performance depends on several interacting factors, namely electric motor and linkage dynamics, controller efficacy, and requested motion law. In particular, point-to-point (PTP) trajectories are usually designed in order to comply with technological constraints, imposed by the required interaction with the handled product, and to maximize some optimality criterion such as, for instance, energy efficiency or limited actuation torques. In this context, the present paper proposes a novel method for designing energy and peak-power optimal PTP motions. A standard optimization problem is solved by means of either cubic or quintic splines. Nonetheless, differently from previous approaches, the optimization cost functions are based on a virtual prototype of the system, which comprises behavioral models of power converter, controller, and electric motor coupled with the mechanical system. Results are then compared with experimental data obtained on a physical prototype. The comparison quantitatively shows that better-behaved PTP trajectories can be designed by including the dynamic contribution of each subsystem component.

Keywords: Electronic cams , high-speed machinery , intelligent manufacturing , mechatronic design methods , trajectory generation , virtual prototyping

Within the orthodontic field, malocclusion problems are usually treated by using different types of appliances. In particular, Eruption Guidance Appliances (EGAs) are recommended for early orthodontic treatment or prevention of malocclusion problems. The traditional approach with EGAs is based on the use of standard prefabricated appliances. Experts in the orthodontic field believe that the customization of the EGAs would strongly enhance the results of malocclusion treatments. This paper presents an innovative methodology for the design and manufacturing of fully customized EGAs. The methodology is based on an extensive integration between traditional orthodontic procedures with advanced computer aided design processes. The methodology moves from the digitalization of the plaster models obtained by optical scanning techniques. The patient morphology is then exploited, under dental practitioner supervision, for the design of the appliance geometry through CAD modeling tools. Medical guided assessment is required throughout the most of the data elaboration processes, in order to design the EGAs accordingly to the patient's clinical conditions. Low-pressure injection molds for the physical manufacturing of the appliances are then 3D printed by using rapid prototyping techniques. The proposed methodology allows the production of patient customized appliances guaranteeing low cost manufacturing and high quality standards, similar to those typically obtained by in series productions. Moreover, the presented approach offers a high integration level with numerical and finite element methods, which can be used for evaluating the stress applied on the EGA, thus allowing the reinforcement of the appliance prior its manufacturing.