Abstract: Many workers and citizens have been forced to make a lifestyle change in the past two years due to the pandemic emergency. In order to keep a high level of personal health, the doctors suggest to do fitness exercises. Before the pandemic it was possible to do these exercises at the gym or during dedicated session in the office supervised by professional trainers. During the pandemic emergency the gyms were closed, the workers were forced to stay home and the people started to do gym exercises by themselves without the control of a professional figure. This situation could lead to several diseases associated to musculoskeletal disorders if the exercises are performed incorrectly. In this work, an approach based on the pose-estimator application OpenPose is developed. The reference exercise is an isometric squat performed by a professional trainer. During the exercise, thanks to a deep neural network, the pose-estimator gets a series of key-points and vectors which represent the user’s pose. A dataset of videos (for both the correct and incorrect postures) has been used to train several machine learning algorithms. The result is an automatic tool that recognizes incorrect poses during the exercise and helps the performer to correct it.
Abstract: The use of arthroprosthetic devices for spinal stabilization is a widely used procedure in the field of biomechanics. There are several problems on the spinal columns that need to use devices like cages to keep distance between the vertebrae. In many cases, these devices are implanted between the vertebrae to keep a clearance between them and so avoid pain or numbness of the limbs. Thanks to new manufacturing approach, it is possible to use powerful topological optimization algorithms to get biomedical devices with high values of performance. Aim of the paper is to define a simulation to get the kinematic behavior of the human cervical structure. Thanks to the results of the simulation, the model can be used to study the effectiveness of an arthroprosthetic device positioned to stabilize the cervical segment of the spinal column and improve the rehabilitation process. The part of the vertebral column under examination is between C3 and C7. Computer Aided Design has been used starting from the 3D scan of the cervical spine obtained by magnetic resonance imaging. The great potentiality of the method is to use a kinematic simulation that models the vertebrae as rigid body and the ligaments and intervertebral discs as a system of springs. This allows to reduce the cost of simulation in term of complexity and time to reach the solution. The kinematic mechanism will be used in a second step for the assessment of the insertion of arthroprosthetic device in terms of stabilization of the upper part of the spinal column. The main objective is to have a tool that allows to immediately identify the best geometry for the patient and to optimize the shape for each specific case. The tool will be tested in future in order to verify the robustness and reliability in several other cases.
Keywords: Customization of Medical Devices | Kinematics | Magnetic Resonance Imaging | Range of Motion | Simulation
Abstract: Aim of all designers is to optimize the product principally in term of mass. The classic manufacturing processes constraint the designer to use a limited number of parameters for obtaining the best results. New manufacturing processes like Additive Manufacturing, open the way to a new optimization strategies, one of the most important is the topology optimization. The objective function is to reduce the mass keeping other functionalities of the product intact. The starting geometry of each topology optimization can be the geometry used for the classic manufacturing method or it can be the lattice structure or a geometry with a tessellation applied by means Voronoi technique. Aim of this paper is to investigate the potential of Voronoi tessellation in the field of structural engineering. A titanium plate with Voronoi tessellation is modelled varying the number of seeds and keeping the total mass unaltered. Thanks to a finite element simulation, for each condition a modal analysis has been performed and the natural frequencies have been extracted. The paper discusses about the influence of the number of seeds to the natural frequencies of plate. This could be a new way and a starting point for topology optimization oriented to the management of natural frequency domain exploiting the Voronoi parameters.
Abstract: Ergonomics focuses on the analysis of the interaction between human beings and their working environment. During the riding of a motorbike, ergonomics studies the rider’s posture on the motorbike. An incorrect posture can lead to physical and psychological discomfort, and can affect the perception of risk and the handling of the motorcycle. It is important for motorcyclists to adopt a good riding posture, for their health and road safety. The aim of this work is to propose a fast, cheap, and sufficiently robust method for the 3D reconstruction of the posture assumed by a motorcyclist. The stereo vision and the application of OpenPose made it possible to obtain a 3D reconstruction of the key points, and their evolution over time. The evaluation of the distances between the 3D key points, which represent the length of the various parts of the body, appears to remain sufficiently stable over time, and faithful to the real distances, as taken on the motorcyclist themself. The 3D reconstruction obtained can be applied in different fields: ergonomics, motorsport training, dynamics, and fluid dynamics analysis.
Keywords: 3D human posture | computer vision | digital twin | ergonomics | motorsport | OpenPose | posture assessment
Abstract: In spring 2020 we faced a completely new type of world crisis due to the spread, all around the world, of a pandemic disease due to a new type of coronavirus. Basically all the countries in the world are having to deal with the need to offer medical aid to the people with symptoms, and the particular type of medical treatments is causing serious problems to the hospitals, basically blocking also or slowing the capability to assist other pathologies or diseases or needs. In all those situations what is basically needed is the capability to fulfill the request of: a quick help, the transport of materials for med aids, the transport of mechanized tools for police missions and/or support to populations. A ship capable to move quickly to a port to increase local hospital capacity could be an important help. Countries like the USA already have a large experience in hospital ships or support ships, in Italy a solution has been arranged converting a ferry into a hospital ship to support less dangerous causes or other needs. Starting from these considerations the authors have investigated the possibility to realize a refitting of an existing unit to realize a ship capable to give a partial assistance in those situations. Key of the project is the interactivity between re-design and use of an existing ship to obtain a result in short time. Examining the main characteristics suitable for a ship with this aim, the authors made a critical examination of the state of the art of the ships for support and assistance, considering the various available solutions, and then made a study of the customization of a ship summarizing all those aspects, with an operational speed of above 35 knots if required, with an interactive approach at new design between naval architecture and medical/support aspects.
Abstract: Recently, thanks to the evolution of rapid prototyping, the interest in designing topologically optimized components have grown, to maintain good mechanical characteristics while reducing their weight. This work proposes a new method of topological optimization that associates the information obtained through a finite element analysis and a grid of prefixed points in space. The software used for this study is a Rhinoceros plugin called Grasshopper, which is composed of a parametric environment schematized by graphic algorithms. The Finite Element analysis is carried out through the Ansys Workbench software. The obtained stresses are the basis for the algorithm to parameterizes the hollowing with a variation of the diameter of the holes. The ability of the algorithm to directly modify the CAD, avoiding post-processing and generating directly the CAD topologies, represents the true potential of the method. Furthermore, the method lends itself to being used for both additive and subtractive manufacturing. In the presented case study, once the beam model was designed, it was printed using a Fused Deposition Modeling 3D printing technique and then a 3-point bending test was carried out on it. Finally, a comparison was made between the original non-optimized beam and the optimized one by the algorithm, observing an increase in the strength/weight ratio of about 20% but, conversely an increase in printing time of about 50%.
Abstract: The use of components obtained through the additive manufacturing (AM) technique has become increasingly widespread in recent years, playing a central role in industrial production, and in particular in some fields such as automotive, biomedical, aerospace and electronics. Among all AM techniques, FDM (Fused Deposition Modelling) represents the most used printing technique to produce polymeric and composite components, thanks to the flexible printing process, the low cost and the diversity of the materials adopted. The aim of the present work concerns the comparison between the mechanical properties of three plastic materials printed with the FDM technique (polylactic acid PLA, polyethylene terephthalate glycol-modified PETG and Acrylonitrile-butadiene-styrene ABS) using an Original Prusa i3 MK3S, by varying the raster angle between 0°, 45° and 90° degrees. Infrared Thermography has been adopted to monitor the temperature evolution during static tensile tests and to assess stress level that can initiate damage within the material. Failure analysis was performed to correlate the mechanical behaviour with the microstructural characteristics of the materials.
Abstract: Joining is critical in shipbuilding impacting significantly on several aspects, i.e., properties, lightness, aesthetics, assembly/disassembly, maintenance employed workforce, emissions of fumes or gases. Consequently, it requires a significant study on impacts and risks. The aim of this work is to apply the Life Cycle Assessment to a friction stir welding process between aluminium and steel. The results confirmed that this welding is among the most sustainable (i.e., low energy, absence of filler, inert gases, and consumables). Moreover, was introduced a functional unit (i.e., length of weld divided by the thickness squared) that allows to compare different geometries and process parameters
Abstract: Intraoral three-dimensional scanning techniques could be used to improve dental practice, leading to an improved overall quality of the prosthetic devices and improved comfort for the patient. An accurate and precise intraoral scanner allows proper diagnosis, follow-up evaluation, and prosthesis application. The aim of this research is to evaluate the precision of an intraoral scanners (Medit i500, Medit Corp., Seoul, Korea), using open-source software in the digital workflow. The precision was compared through repetitions of the scanning process of the upper dental arch, following superimpositions in the whole 3D arch area. It was possible to display colorimetric maps for qualitative comparison, and the deviations of the values were classified as clinically acceptable. Within the limitation of this study, the clinically acceptable in vivo frequency of points’ deviation, or the precision, was obtained in 98.8% ± 1.4%; therefore, the use of open-source software can be a viable option in the digital workflow, improving patient follow ups with the 3D model superimposition.
Keywords: conventional impression | digital impression | intraoral scan
Abstract: Joining is critical in shipbuilding impacting significantly on several aspects, i.e., properties, lightness, aesthetics, assembly/disassembly, maintenance employed workforce, emissions of fumes or gases. Consequently, it requires a significant study on impacts and risks. The aim of this work is to apply the Life Cycle Assessment to a friction stir welding process between aluminium and steel. The results confirmed that this welding is among the most sustainable (i.e., low energy, absence of filler, inert gases, and consumables). Moreover, was introduced a functional unit (i.e., length of weld divided by the thickness squared) that allows to compare different geometries and process parameters.
Abstract: This study analyses the sustainability of a bioenergy system fed by residual biomass with high moisture content (citrus peel), which is designed in cogeneration mode and integrated with the factory generating the residue. The impacts of electricity production are comprehensively assessed by conducting thermodynamic and environmental analyses with a life cycle approach. Two scenarios were analyzed considering the differences in the process layouts between juice factories. The first scenario with wet feedstock (Scenario W) includes the drying process in the bioenergy plant's boundaries. A second scenario uses dry feedstock (Scenario D), and the drying process is considered outside the boundaries. The thermodynamic performances are assessed by life cycle energy/exergy efficiencies, the cumulative exergy demand of non-renewable resources (CExDnr), and energy/exergy return on investment. Additionally, a new renewability indicator is introduced, hereby named Integrated Renewability (IR), to consider the origin (renewable or non-renewable) of the resources substituted by the side products. The Life Cycle Assessment shows that the scrubbing process, fed with bio-oil, could undermine the system's sustainability. The overall exergy efficiency was determined to be 0.29 and 0.24 for Scenario D and Scenario W, respectively. Compared to the electricity from the national grid (Italy), the integrated bioenergy system leads to lower life cycle exergy efficiencies in both scenarios (0.24 and 0.20 for Scenario D and Scenario W, respectively, Vs. 0.34 for national grid), higher IR (3.1 and 1.5 Vs. −0.9), lower CExDnr (0.32 and 0.33 vs. 1.9 MWh/MWhe), and lower climate change impacts (−332 and 1.29 vs. 447 kgCO2/MWhe).
Abstract: To contrast the naval emissions in terms of Sulphur and Nitroxides, recently, the institution of Emission Control Areas has increasingly prompted shipowners to choose new-generation engines capable of using Liquified Natural Gas as a marine fuel. This study presents a comparative Life Cycle Assessment, cradle-to-grave, between two different engines on a cruise ferry. One is a traditional Diesel machinery system and the other is a Liquified Natural Gas one. The two configurations have been analysed within 17 different impact categories in terms of climate change, human health, resourced depletion and ecosystems. The studied phases of the ship's life were the building, operation and dismantling. The results showed and quantified the environmental differences deriving from the use of Liquified Natural Gas in all the phases of the life of the ship. Generally, the LNG propulsion has shown to be more environmentally performing, but, particularly interesting are the results in terms of climate change, influenced by lower CO2 emissions but also by the phenomenon of methane slip that can increase the CO2-equivalent effect. The energy costs of transport and liquefaction of gas also have an impact to consider. Analyses of uncertainty on the data and of sensitivity on fuel consumptions and losing of steel during the shipbuilding were carried out.
Keywords: Climate change | Green design | Life Cycle Assessment | Liquified Natural Gas | Shipbuilding
Abstract: The use of ventilated hulls is rapidly expanding. However, experimental and numerical analyses are still very limited, particularly for high-speed vessels and for stepped planing hulls. In this work, the authors present a comparison between towing tank tests and CFD analyses carried out on a single-stepped planing hull provided with forced ventilation on the bottom. The boat has identical geometries to those presented by the authors in other works, but with the addition of longitudinal rails. In particular, the study addresses the effect of the rails on the bottom of the hull, in terms of drag, and the wetted surface assessment. The computational methodology is based on URANS equation with multiphase models for high-resolution interface capture between air and water. The tests have been performed varying seven velocities and six airflow rates and the no-air injection condition. Compared to flat-bottomed hulls, a higher incidence of numerical ventilation and air–water mixing effects was observed. At the same time, no major differences were noted in terms of the ability to drag the flow aft at low speeds. Results in terms of drag reduction, wetted surface, and its shape are discussed.
Abstract: The study of the human body and its movements is still a matter of great interest today. Most of these issues have as their fulcrum the study of the balance characteristics of the human body and the determination of its Centre of Mass. In sports, a lot of attention is paid to improving and analysing the athlete's performance. Almost all the techniques for determining the Centre of Mass make use of special sensors, which allow determining the physical magnitudes related to the different movements made by athletes. In this paper, a markerless method for determining the Centre of Mass of a subject has been studied, comparing it with a direct widely validated equipment such as the Wii Balance Board, which allows determining the coordinates of the Centre of Pressure. The Motion Capture technique was applied with the OpenPose software, a Computer Vision method boosted with the use of Convolution Neural Networks. Ten quasi-static analyses have been carried out. The results have shown an error of the Centre of Mass position, compared to that obtained from the Wii Balance Board, which has been considered acceptable given the complexity of the analysis. Furthermore, this method, despite the traditional methods based on the use of balances, can be used also for prediction of the vertical position of the Centre of Mass.
Keywords: 3D motion capture | Convolution neural networks | Open Pose
Abstract: In the recent years, high density polyethylene (HDPE) has been adopted in several industrial fields due to its good mechanical resistance, lightness and low cost, for the realization of pipelines. According to the current standards, welding techniques in such application have to guarantee a reliable connection of the different pipe sections but, on the other hand, they can also alter the mechanical performances of the polyethylene due to the heating procedure. Mechanical and fatigue tests should be performed in order to derive the working load conditions at which the pipe withstand without any failure or leakage of the internal fluid. Generally, traditional fatigue tests are extremely time-consuming and requires a huge amount of material. Recently, the Static Thermographic Method (STM) has been applied to a large set of engineering materials to evaluate the limit stress at which the material surface temperature trend deviates from the linearity during a static traction test, indicating the initiation of damage within the material. In the present work, the STM is applied on welded specimens made of PE100 in order to investigate its fatigue properties. The predicted limit stress has been compared with the fatigue limit obtained with traditional fatigue tests showing good agreement.
Abstract: Lattice structures made by means of Additive Manufacturing are more and more used in several fields of application. In particular, reticular Titanium alloy bodies are used in biomechanics as fusion devices, due to their biocompatibility and lightweight characteristics. Although these structures have been extensively investigated, it is currently not possible to predict their behavior easily. Indeed, due to the high number of degrees of freedom of the lattice structures, it is usually required to conduct extensive experimental campaigns in order to anticipate the mechanical behavior of complex components. The present study proposes a method to predict the run-out in an intervertebral cervical cage based on experimental tests conducted on a similar cage and using Finite Element simulations. The cages were made of Ti-6Al-4V ELI by means of Electron Beam Melting. The experimental tests were carried out in accordance with the appropriate ASTM standards. The numerical simulations were consistent with the experimental results and showed a very good agreement. This methodology helped to identify the most critical issues and to verify a new cage without a second test campaign, which allows both cost and time savings.
Abstract: Automotive sector is crucial for the economic and social system. Conversely, it also plays an important role in the global emissions balance with strong consequences on the environment. Currently the Research world is engaged in the reduction of the emissions, especially in order to contrast the Climate Change and reduce toxicity on humans and the ecosystem. This study presents a comparative Life Cycle Assessment, Well-to-Wheel, between the most common technology used in the automotive sector, i.e. the traditional petrol Internal Combustion Engine and the full Battery Electric Vehicle. The different configurations have been analysed within 17 different impact categories in terms of climate change, human health, resourced depletion and ecosystems. The Well-to-Wheel approach allows to focus the attention on the use stage of the vehicle, considering the local effects due to the direct emissions in high density urban zones and it mitigates the dependence of usage hypotheses, different scenarios and intrinsic differences between the various models of cars in circulation.
Keywords: Climate Change | Electric vehicles | Green design | Life Cycle Assessment
Abstract: Stochastic lattice structures are very powerful solutions for filling three-dimensional spaces using a generative algorithm. They are suitable for 3D printing and are well appropriate to structural optimization and mass distribution, allowing for high-performance and low-weight structures. The paper shows a method, developed in the Rhino-Grasshopper environment, to distribute lattice structures until a goal is achieved, e.g. the reduction of the weight, the harmonization of the stresses or the limitation of the strain. As case study, a cantilever beam made of Titan alloy, by means of SLS technology has been optimized. The results of the work show the potentiality of the methodology, with a very performing structure and low computational efforts.
Abstract: In this paper thermal analysis was applied to determine the “Critical Stress” of concrete, different from its ultimate strength, able to produce the first damage in the structures under compressive loads. The Critical Stress can be thought as the stress able to produce the beginning of fatigue rupture within the material. Several specimens of high strength concrete were tested in order to define the incipient crack phenomena, also in internal part of the specimen not accessible by direct inspections, with the aid of infrared thermography. A finite element analysis completes the study and compares, for the same static loading conditions, the stress state with the experimental thermographic images. The final results show as the coupling of normal compressive test and the acquisition of the thermal images can be a useful aid to estimate a security stress value, indeed the Critical Stress, before the Ultimate Serviceability Limit (SLU) of the structure, defined as the maximum load condition before its failure.
Keywords: Crack | Critical stress | FEM | Infrared thermography
Abstract: Fatigue properties are of fundamental importance and extremely time consuming to be assessed. The aim of this research activity is to apply the Thermographic Method (TM) and the Static Thermographic Method (STM) during fatigue and tensile tests to correlate the temperature trend to the fatigue properties of an S355 steel. The material was retrieved from an in-service port crane. Traditional fatigue tests were performed in order to evaluate the S-N curve with a scatter band. Step load tests were carried out deriving the fatigue limit and the Energy Parameter of the material. Static tensile tests were performed to obtain the stress at which the temperature trend deviates from the thermoelastic behavior. The fatigue properties obtained by means of the energetic methods were compared to the traditional ones showing a good agreement.
Abstract: Rigid inflatable boats (RIBs) are a well-known typology of inflatable crafts, largely used as rescue and pleasure aims thanks to the high performance in terms of stability and loading surface. They are a hybrid boat with inflatable tubulars, like a dinghy, and rigid keel, like a traditional planing hull. This paper analyses the planing performance of a novel, patented, RIB model, that has the peculiarity to have tubulars that do not go uninterruptedly from bow to stern but only for about half the length. In this way it is possible to reduce the wetted surface and to channel the air under the hull, allowing a good ventilation. A wide computational fluid dynamics analysis allowed the authors to study the hydrodynamic behaviour of the boat and to discuss the results.
Abstract: Background: Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles’ absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles. Materials: Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted. Results: The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified. Conclusion: The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations.
Abstract: In the field of Engineering, research has conveniently exploited the fluids for energy production. The possibility to use marine renewable energy is still under development, in particular, among the wave energy converter devices the U-OWC systems are the most promising. The main objective of this work is to validate a numerical model with an experimental campaign that aims to simulate the flow field in front of the breakwater and inside the U-OWC. The tests were carried out to understand the hydrodynamic behaviour of the device in regular wave conditions, inside a flume with rectangular section, equipped by a piston-type wave-maker and a U-OWC device, reproducing the REWEC caisson installed in the Natural Ocean Engineering Laboratory (NOEL) of Reggio Calabria, with a 1:13.5 scale. Measurements of the water free surface were used exclusively to validate the 2D numerical model developed through the Ansys Fluent Computational Fluid-Dynamics (CFD) Software. The numerical model solves the fluid flow field using the RANS equations, in which the air-water interaction governed by this set of partial difference equations is solved with the Finite Volume Method (FVM). In conclusion, results related to the energy efficiency of the caisson were extrapolated from the validated numerical model.
Abstract: Autonomous Surface Vehicles are versatile marine vehicles that allow to fulfill a variety of offshore activities. Their versatility has been appreciated by the marine and aquatic science community, in fact, in the last years, a large number of ASVs have been developed in research projects and introduced in the market. In this paper, the design and simulation of a small-sized ASV for seabed mapping of shallow waters are described. The vehicle is characterized by catamaran shape, low draft, jet-drive propellers that allow its deployment from the shore, and a payload of 20 kg. The design process has been carried out with the aim to realize a vehicle characterized by ease of transportability and deployment, available payload and performance in terms of speed and endurance. Three hull types have been modelled in a computer-aided design environment and then optimized through fluid dynamics analysis for a cruise speed of 1.5 kN. The results of these simulations have been used to choose the best hull shape in terms of resistance, in order to comply with the constraints of autonomy and available payload. Finally, a scaled model of the best hull shape has been then tested in a circulating water channel to validate simulation data.
Abstract: The work proposes a method of Topological Optimization of 3D surfaces using an algorithm that works by considering the distribution and intensity of stress on the studied component. Rather than acting on the mesh, this algorithm modifies directly the CAD, allowing its direct use avoiding any subsequent intervention. The algorithm has been developed using Rhino – Grasshopper. The FEM analyses have been performed using the Nastran solver within the Siemens NX environment. With this method the original non-optimized model is hollowed through a Voronoi tessellation that is managed through several parameters. Through an iterative process, the algorithm performs the hollowing on the original CAD, varying the size and distribution of the holes in function of the stresses. As case study, the authors considered a safety device that helps to prevent injuries to the necks of pilots of various high-speed motorsports (Head and Neck Support, HANS). The results of this work show the potentiality of this methodology, with which it is possible to obtain a much lighter device with the same mechanical performance.
Abstract: The work presents a stress-based algorithm developed for the topology optimization of 3D surfaces. The novelty of the proposed methodology consists in the fact that it acts directly on a CAD level, and not on the mesh as is more usual. This allows to obtain a CAD ready to be manufactured with Additive Manufacturing technologies, without any subsequent intervention by the designer. The CAD algorithm is written in Rhino-Grasshopper environment and it is suitable to any FEM software. The methodology consists in a hollowing of the surface, starting by a Voronoi tessellation, allowing the designer to set a lot of parameters, as the number of control points, the dimension of the holes and the thickness of the branches of the tessellation. An iterative process leads to redraw at each iteration the Voronoi scheme in order to add material where the stress is higher and to remove it where the stress is lower. As a case study, in order to show the characteristics of the methodology, a seat for powerboats applications has been tested and optimized. The results from the case study demonstrate the high performance of the method and the capability to obtain in easy way light weight structures oriented for the Additive Manufacturing new technologies.
Abstract: The designers of two-wheeled motorcycles, in the phase of setting up a new project, have the need to carry out ergonomic evaluations on both the pilot and the passenger, from which the optimal comfort and control conditions will arise during the future use of the vehicle. Commonly, the most used method is based on the previous experience of the manufacturer and on the comparison with the choices made by the competitors. This article describes a methodology developed in collaboration with the Italian motorcycle brand Aprilia, owned by Piaggio & C., a company world leader in the sector, designed for the setup phase of new vehicles. The method provides a flexible tool, starting from the Enduro segment and for the different users’ body size (expressed in percentiles). The analysis was done on five commercial Enduro motorcycles from different leading competitor manufacturers. The authors used a mixed method based on numerical and experimental data, detected on virtual models, and on report cards made by professional testers. The results have been showed and discussed.
Abstract: The spreading of high computational resources at very low costs led, over the years, to develop new numerical approaches to simulate the fluid surrounding a sail and to investigate the fluid–structure interaction. Most methods have concentrated on upwind sails, due to the difficulty of implementing downwind sailing configurations that present, usually, the problem of massive flow separation and large displacements of the sail under wind load. For these reasons, the problem of simulating the fluid–structure interaction (FSI) on downwind sails is still subject of intensive investigation. In this paper, a new weak coupled procedure between a RANS solver and a FEM one has been implemented to study the FSI problem in downwind sailing configurations. The proposed approach is based on the progressive increasing of the wind velocity until reaching the design speed. In this way, the structural load is also applied progressively, therefore, overcoming typical convergence difficulties due to the non-linearity of the problem. Simulations have been performed on an all-purpose fractional gennaker. The new proposed method has been also compared with a classic weak FSI approach. Comparable results have been obtained in terms of flying shape of the gennaker and fluid-dynamic loads. The most significant characteristic of the proposed procedure is the easiness to find a solution in a very robust way without convergence problem, and also the capability to reduce the simulation time with regard to the computational cost.
Abstract: During tillage, soil engaging tools are exposed to very critical working conditions due to soil friction. This produces an abrasive wear which needs to be monitored in order to avoid high costs for machine maintenance and fuel consumption and a deterioration of tillage quality. A commonly used method for wear diagnosis is the evaluation of the mass loss and volume change after a prolonged component usage. The instruments generally used for the assessment of these two quantities give only general and punctual information about the wear. Modern three-dimensional scanning technologies allow for creating a numerical model of the worn component and thereby extracting knowledge of the wear pattern. In this paper, the wear pattern of four ploughshares of a semi-mounted plough were analysed and compared. Each ploughshare was scanned by means of a structured blue-light 3D scanner before and after a prolonged field usage. From the scans, the cutting edge profile, described with three parameters, and the blade profile were calculated. The wear pattern and the volume losses were numerically calculated through Hausdorff's method and deviation analysis. Results of the experiments showed that cutting edge profile parameter of ploughshares could differ significantly from each other. Moreover, even if the wear pattern was very similar in shape for all the ploughshares, a large variability in volume losses was observed between the ploughshares. The adopted methodology permits to easily evaluate the wear pattern of tillage tools.
Abstract: Structural S355 steel is widely applied in various sectors. Fatigue properties are of fundamental importance and extremely time consuming to be assessed. The aim of this research activity is to apply the Static Thermographic Method during tensile tests and correlate the temperature trend to the fatigue properties of the same steel. The Digital Image Correlation (DIC) and Infrared Thermography (IR) techniques have been used during all static tests. The Digital Image Correlation technique allowed the detection of displacements and strain, and so the evaluation of the mechanical properties of the material. Traditional fatigue tests were also performed in order to evaluate the stress-number of cycles to failure curve of the same steel. The value of the fatigue limit, obtained by the traditional procedure, was compared with the values predicted by means of the Static Thermographic Method (STM) obtained from tensile tests. The predicted values are in good agreement with the experimental values of fatigue life.
Abstract: Background Preclinical training in perforator flap harvesting is typically conducted on living animal models; however, repeated training is not possible with these models because of ethical and/or economical constraints. We describe an anterolateral thigh flap (ALT flap) training model using chicken thigh that seems to be an appropriate training model prior, for example, to raise a perforator flap in a living rat or swine model. Methods A total of 10 chicken legs were used in this study. Six chicken legs were anatomically dissected to confirm the presence of the perforator and to identify the main vascular tree. In four chicken legs, a skin flap was planned based on the perforator and intramuscular dissection was performed under magnification. Results The perforator was identified in all dissections and was consistently found 3 cm above the line extending from the patella to the head of the femur in its third proximal. Proximally, the mean diameter of the artery and vein was 0.56 (σ = 0.04) and 0.84 (σ = 0.06) mm, respectively. The mean dissection time to raise the flap was 88 (σ = 7) min. Conclusion This is the first description of a nonliving biological simulation model for training in perforator flap dissection that mimics an ALT flap. As an ex vivo chicken model, it is a cost effective and readily accessible model suitable for repeated practice.
Keywords: ALT | chicken | perforator flap | training
Abstract: In the speed-based competition, with the use of fast vehicles, a fundamental aspect is the safety and comfort of the drivers. In each speed-based competition, the drivers are subjected to vibrations and stresses whose evaluation is fundamental in order to quantify the discomfort of them. The comfort conditions are guaranteed by a deep study of the correct size of the internal spaces, the right posture of the drivers and the right choice of the position of the elements inside the vehicles (damping elements, position of the steering wheel, position of instruments, etc.). Another important aspect is the assessment of the escape spaces in case of accident. To reach these goals, the Governing Body act with the definition and the verification of technical rules. In this work the field of interest is powerboats sport. During the powerboat race, the reached speed and the z-acceleration of the boat lead to several stresses on drivers. Two different approaches have been investigated, a traditional 2D approach and an innovative 3D approach. Results have been discussed.
Abstract: Topological optimization is a fairly innovative numerical technique that makes it possible to reduce the mass of mechanical components. It is an alternative to the optimizations of shape or geometry that allow to highly improve the efficiency of products. The recent development of metal additive manufacturing technologies allows the production of pieces that were not feasible before, permitting the use of topological optimization in many fields. In the biomedical field, for example, the reduction of prosthetic and orthotic materials allows to save weight, to the advantage of comfort, and to minimize the invasiveness of these systems. In this paper, an optimization of a system consisting of a femoral nail and two screws is carried out. The pieces were obtained by 3D scanning of prostheses, so as to obtain the true geometry. The femur is the standard one in literature. Following topological optimization, a new nail, with a mass of 60% of the previous one, was obtained, without limiting the functionality or the reliability of the product. Results and methodological problems are discussed.
Abstract: The use of composite materials allows to have a great flexibility in terms of mechanical and physical characteristics. One of the most used composite structure in naval field, is the sandwich, which is composed by a stacking sequence of different plies. The designer, in preliminary phase, must handle a great quantity of degree of freedom (types of materials, orientation of the fibres, position along the stack, thickness, etc.) in order to reach the best compromise between mechanical behaviour, environmental impacts and production costs. Finite Element analysis represents a useful tool in order to optimize all these parameters and to estimate the outcome of experimental tests at design stage. The main goal of this work is to develop and to validate a FE model for the simulation of a particular family of composites, widely used in naval field and, in particular, in High Speed Crafts and powerboats. The first part of the paper concerns the experimental tests on two different types of sandwich specimens. Two families of tests were conducted: four-point bending tests and impact drop tests. The second part of the paper focuses on the validation of a FE model for both experimental setups.
Abstract: One of the most important aspects, in the ACS and multi stepped hull design, is the choice of the geometrical shape of the cavity and the steps. In this article a complete experimental and numerical campaign on a multi stepped ACS has been carried out, varying the velocity and the air flow rate under the hull. The experimental tests have been conducted in an ITTC Towing Tank allowing to validate the numerical simulations obtained by means of a CFD U-RANSe (Unesteady Reynolds Averaged Navier-Stokes equations) code. The CFD setup is described in detail. From this campaign a critical analysis of the Froude number influence on the air cushion shape has been argued. The authors identified four different behaviours, from low to very high Froude numbers. The use of CFD has allowed to observe quantities of difficult evaluation by means of traditional experimental test, as e.g. the frictional component of the resistance, the airflow path lines and the volume of fraction in transversal and longitudinal sections. The results have been discussed.
Keywords: Air Cavity Ships | Computational Fluid Dynamics | Hull Design | Multi stepped hull | Ship Resistance | Towing tank tests
Abstract: In recent years the science of dental materials and implantology have taken many steps forward. In particular, it has tended to optimize the implant design, the implant surface, or the connection between implant and abutment. All these features have been improved or modified to obtain a better response from the body, better biomechanics, increased bone implant contact surface, and better immunological response. The purpose of this article, carried out by a multidisciplinary team, is to evaluate and understand, through the use also of bioengineering tests, the biomechanical aspects, and those induced on the patient’s tissues, by dental implants. A comparative analysis on different dental implants of the same manufacturer was carried out to evaluate biomechanical and molecular features. Von Mises analysis has given results regarding the biomechanical behavior of these implants and above all the repercussions on the patient’s tissues. Knowing and understanding the biomechanical characteristics with studies of this type could help improve their characteristics in order to have more predictable oral rehabilitations
Abstract: In the world of powerboats competition, the high-performance sandwich-structured composites have completely replaced traditional materials. During the competition, the structure of this kind of ships is subjected to repeated impacts. It is then fundamental to understand the damage evolution in order to select the most appropriate materials and increase safety issues. The present study is aimed at analysing the behaviour of sandwich-structured composites undergoing repeated low-energy impacts. Three different materials have been analysed. Two are sandwich-structured composites used for the cockpit of offshore powerboats and differing only by the core cell thickness. The third material is composed only by the skin of the same sandwich structures, without the core. Impacts were made at three different energy levels: 15, 17.5 and 20 J. In addition to the parameters typically used for the assessment of the impact damage, a new damage assessment has been carried out by means of three-dimensional optical measurements of the imprinted volumes resulting from the impact events. This approach has allowed the definition of a correlation between the imprinted volumes and the number of impacts, until the complete perforation, for each single specimen. Finally, thanks to usual indexes and the imprinted volumes, some considerations are developed about the influence of the core cell thickness in powerboats design.
Abstract: In recent years, a great world issue is the respect for the environment. Each researcher, in his competence field, proposes new technologies and new approaches in order to reduce the environmental impact of a product or of an industrial process. In the naval field, the main way in order to reduce the environmental impact of the ship during the navigation is the reduction of the drag resistance and so the reduction of requested power. There are many ways in order to obtain a reduction of drag. This paper investigates, with a preliminary numerical study by means of Computational Fluid Dynamics (CFD), the Air Cavity Ships technology (ACS). A first part of the paper concerns the study of the rising bubble phenomenon inside a water column, in order to choice the better solver settings and understand if the CFD is suitable for this kind of problem. In this phase the main parameters analyzed are: the air critical mass, the rising velocity, the shape and the air circulation inside the bubble. In the second part of the work, a flat plate model with artificial air injection is conducted in order to understand the possible advantages of this application. The principal impacts of this technology are presented in terms of drag coefficient and lift coefficient respect to trim and velocity coefficient. The CFD method could be a suitable and fast method, in the preliminary phase, for the design of the ACS.
Keywords: Air Cavity Ship | Artificial ventilation | CFD | Green design | Planing hull design
Abstract: The needs to reduce the frictional component of the resistance of a ship leads researchers to find new solutions. The air cavity solution seems to be one of the most promising one. Usually, it is very difficult with the experimental tests to understand the air distribution under the hull and the streamlines during the injection of air. The principal objective of this paper is evaluating the potentiality of the CFD approach in the study of Air Cavity Ships (ACS) for a planing yacht. The first part of paper describes the CFD evaluation of the resistance curves without air-injection. The second part deals with the injection of the air under the hull. In this case the boundary conditions are the results of the first campaign of simulations. A comparison between the experimental and CFD results is shown. An assessment of the streamlines and air distribution is proposed and an evaluation of the wetted and ventilated areas is conducted in order to understand the relation between the flow rate, the velocity of the hull and the air distribution. The results can be used for modifying the hull geometry in order to better accommodate the air layer.
Abstract: 3D virtual reconstruction of human body parts is nowadays a common practice in many research fields such as the medical one, the manufacturing of customized products or the creation of personal avatar for gaming purpose. The acquisition can be performed with the use of an active stereo system (i.e., laser scanner, structured light sensors) or with the use of a passive image-based approach. While the former represents a consolidated approach in human modeling, the second is still an active research field. Usually, the reconstruction of a body part through a scanning system is expensive and requests to project light on the patient’s body. On the other hand, the image-based approach could use multi-photo technique to reconstruct a real scene and provides some advantages: low equipment costs (only one camera) and rapid acquisition process of the photo set. In this work, the use of the photogrammetry approach for the reconstruction of humans’ face has been investigated as an alternative to active scanning systems. Two different photogrammetric approaches have been tested to verify their potentiality and their sensitivity to configuration parameters. An initial comparison among them has been performed, considering the overall number of points detected (sparse point cloud reconstruction, dense point cloud reconstruction). Besides, to evaluate the accuracy of the reconstruction, a set of measures used in the design of wearable head-related products has been assessed.
Abstract: The Strait of Messina is a very busy sea area that separates Sicily and the Italian mainland. In respect of environment and for the prevention of human loss, it is fundamental to have an estimate of the possible ship accidents that could occur. In this work, the approach used is the International Association of Lighthouse Authorities Waterways Risk Assessment Program (IWRAP) model. The first part of the paper describes the local and global traffic and the separation scheme in the Strait of Messina. The model input data is obtained from the Vessel Traffic Service (VTS) system thanks to the Coast Guard of Messina. The second part concerns calculation of the geometrical collisions (number of collisions in different scenarios) and the causation probability. This analysis is the basis for the discussion of new regulatory constraints due to the future realisation of new piers in the south and the planned unification of the two Port Authorities of the two shores into one single authority.
Abstract: The present study concerns the environmental impact assessment of a glass-reinforced plastic yacht built with two different technologies: hand lay-up technique and vacuum infusion. The main raw materials are: Glass Fiber, PVC for core and polyester resin. The principal difference between the two manufacturing techniques is the weight of the ship that will influence the production phase, the use phase and lastly the disposal phase. For Life Cycle Assessment for the impact assessment a commercial software has been used, GaBi software with Ecoinvent database. A specific evaluation of resistance of the ship with towing tank tests has been conducted, and an evaluation of the consumption, knowing the engine installed on board. This evaluation is possible thanks to the definition of three different profiles of usage of the yacht (low usage – 200 h/y, medium usage - 350 h/y and high usage – 500 h/y). For every profile, three different cruising conditions: navigation at maximum power (100% of the power on board), sailing cruising (85%) and lastly navigation in economic condition (65%). A curve of fuel consumption to the different percentage of power required is reported; in this way, it is possible for every navigation condition to evaluate the fuel consumption and, consequently, the environmental impact. In this paper is described that a lighter hull, with a reduction in weight of about 9% on deadweight, reduces the fuel consumption of about 656 t of diesel fuel over lifetime, with significant effect in the indicators of environmental impact in Life Cycle Assessment. Although these results may be expected, the use of Life Cycle Assessment has allowed quantifying the reduction of environmental impact in every single phase of the entire lifetime of the boats.
Keywords: Glass reinforced plastic | Green design | Life cycle assessment | Optimization | Vacuum infusion | Yacht
Abstract: Domestic appliance are widely used in all countries. During the design phase, it is very important to take advantage of new virtual prototyping technologies in order to improve the user expectations and put the feeling of the user with the device in the centre of the design. The paper deals with the complete simulation of the opening of the front door of an appliance like a refrigerator or an oven. The process is simulated with the use of ad-hoc built program that uses a combination of experimental parameters and virtual fluid dynamic simulations. Each moment involved during the opening of the door is evaluated and a comprehensive explanation of each of them is reported. The entire solving process is parametrized in order to use it in an iteration loop for eventually optimization of the User Experience and the comfort during the opening of the front door. A fridge case study is described and discussed.
Keywords: Door appliance | Experience design | User centred design | User Experience (UX) | Virtual Prototypes (VPs)
Abstract: Numerous applications involve the use of composite material in order to increase the ratio between strength and weight and in order to increase the flexibility of the design. There is an intensive use of this material also in naval building, principally for recreational boat. Experimental and numerical tests allow having a deep knowledge of the response of this kind of material in different load conditions. In order to accommodate the complexity of the design, usually it is necessary to use bonding for jointing different elements. The work deals with a series of experimental tests for the assessment of the head joint between two carbon laminates. Tests carried out with different angles between the two linked elements in order to evaluate the response of the bonding to different stresses direction. The studied conditions are for 45°, 90°, 135° and 180° with forces applied in both closing and opening direction. The bonding under investigation has a double epoxy resin glues. Thanks to these series of experimental tests is possible to take care about the worst condition of load and try to avoid it during the preliminary phase of design.
Abstract: The ships are constrained mainly by mooring lines and fenders to rigid structures such as jetties and piers. The evaluation of the forces that affected the mooring lines and fenders is essential for proper design of all components of the plan such as the chocks, the cables and the bollards. A calculation software that can estimate the loads acting and how they are distributed is essential to be able to perform these calculations with accuracy. The article describes the design phases of the program and the theoretical aspects discussed and is a guide for designers who want to predict the behavior of the mooring plan.
Abstract: For several years it has been studied how to obtain resistance reduction by means of air injection under the hull. The most studied applications are essentially slow hulls; however, significant results in planing hulls can be achieved. Unfortunately, for this kind of crafts, there are very few experimental data. This study has been performed to compare different cavity shapes, obtained by modifying a mother-hull of a high-speed planing yacht. The design has been obtained with the idea to use the natural low pressure under the bottom of high-speed crafts, in order to stabilize an air-layer instead of the traditional air-cushion. The experimental tests were carried out in a towing tank by varying numerous parameters, including the model speed and the flow rate of air. Results and influence of geometrical and physical parameters are discussed.
Keywords: Air cavity ship | High speed craft | Hull design | Model tests | Ship resistance
Abstract: A geometric tool for a catamarans sail plan and appendages optimization procedure is descripted. The method integrates a parametric CAD model, an automatic computational domain generator and a Velocity Prediction Program (VPP) based on a combination of sail RANS computations and analytical models. The boat performance is obtained, in an iterative process, solving the forces and moment equilibrium system of equations. Hull and appendages forces are modelled by analytical formulations. The closure of the equilibrium system is provided by the CFD solution of the sail plan. The procedure permits to find the combination of appendages configuration, rudders setting, sail planform, shape and trim that maximize the VMG (Velocity Made Good). A significant effort was addressed to the selection and evaluation of open-source tools to be adopted in the implementation of the method. The geometric parametric model, which is the core of the procedure, was object of particular attention. The FreeCAD geometric modeller was sel cted for this task. The sail shapes candidates are automatically generated, within the optimization procedure, by Python scripts that drive FreeCAD to update the geometry according to the variables combination. A very flexible model, able to offer a very wide space of variables, was implemented. This paper describes the implemented geometric model and the environment in which is included.
Abstract: Air-cavity ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel’s hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship’s bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, considering as parameters the critical mass of air, the rising speed and aspect ratio of the bubble. Then it is evaluated the interaction bubble-flat plate in order to obtain a reliable prediction of the behavior of air bubbles under the hull.
Abstract: In the production of utility poles, used for transmission, telephony, telecommunications or lighting support, for many years, the steel has almost entirely replaced wood. In recent years, however, new composite materials are a great alternative to steel. The questions are: is the production of composite better in terms of environmental impact? Is the lifecycle of composite pole more eco-sustainable than lifecycle of steel pole? Where is the peak of pollution inside the lifecycle of both of technologies? In the last years, in order to deal with new European polices in environmental field, a new approach for the impact assessment has been developed: the Life Cycle Assessment. It involves a cradle-to-grave consideration of all stages of a product system. Stages include the extraction of raw material, the provision of energy for transportation and process, material processing and fabrication, product manufacture and distribution, use, recycling and disposal of the wastes and the product itself. A great potentiality of the Life Cycle assessment approach is to compare two different technologies designed for the same purpose, with the same functional unit, for understanding which of these two is better in terms of environmental impact. In this study, the goal is to evaluate the difference in environmental terms between two different technologies used for the production of poles for illumination support.
Keywords: Green Design | Life Cycle Assessment | Manufacturing optimization | Utility poles
Abstract: In the last decade, sandwich composite materials have had an increasing use in design of racing boats. The main reasons are: higher strength-weight ratio, low density, excellent durability and versatility. The knowledge of impact response is very important to design racing boats. The aim of the present study is the investigation of absorbing impact energy ability of a sandwich composite material used for offshore vessels in UIM (Unione Internationale Motonautique) Championship. The material analysed in this study is a sandwich manufactured with hand lay-up technique. In the first phase, the damage assessment of single impact has been studied with an optical measurement technique. In a second phase, the damage evaluation due to repeated impacts has been analysed with the similar technique.
Abstract: The present paper deals with a preliminary study on an Oscillating Water Column Wave Energy Converter (OWCWEC). The energy conversion is based on a straight-bladed Darrieus type wind turbine. The design of the turbine for maximum power coefficient is discussed. A physical laboratory scale OWC wave energy converter model was built to measure velocity field in the column. The air column was built using transparent materials to allow Particle Image Velocimetry measurements. Velocity field around air turbine rotor was measured by means of PIV. The measured velocities with and without the air turbine are used as inputs in the design procedure and to calibrate and test mathematical models. Moreover, design criteria were obtained using experimental and mathematical results.
Keywords: Oscillating Water Column | Straight-bladed darrieus trubine | Wave energy
Abstract: In this paper is studied the static and dynamic behavior of an innovative hull. The hull, called Y-hull, consisting of a hybrid structure between a catamaran and a monohull, was tested in the towing tank at the laboratories of the University of Trieste. The most distinctive feature is the presence of a central tunnel that affects the back part of the hull. In its forward part, the hull has a geometry similar to conventional hulls with a very marked V shape. This allows to have good directional characteristics and a good seakeeping in rough sea conditions. The aft part has the typical form of multihull with the huge difference that the area affected by the presence of the tunnel lies always below the water plane. The work shows the interesting results of the tests performed in the tank and a series of numerical tests performed with the aim to develop future enhancements. Numerical simulations were carried out in order to understand the distribution of pressure on the bottom. In this way it will be possible to perform appropriate shape optimizations.
Abstract: Air-Cavity Ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel's hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship's bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, considering as parameters the critical mass of air, the rising speed and aspect ratio of the bubble. Then it is evaluated the interaction bubble-flat plate in order to obtain a reliable prediction of the behavior of air bubbles under the hull.
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