Search

Aim of this paper is presented a new methodology to study how different geometric parameters affect the performance of a hydraulic actuator. Preliminarily, the real working conditions of a hydraulic machine have been simulated by means of a CFD module. After, to test the reliability of the simulations, the obtained numerical results have been compared with the experimental data of a real prototype. This comparison demonstrates a good level of agreement between numerical and experimental results. Different simulations have been setup by modifying the actuator geometry and evaluating the efficiency of every analysed configuration. The results of this study give useful guidelines for the choice of the best geometry depending on the working conditions of the actuator.

The standard method of design and manufacturing customised orthoses is still very time-consuming due to their often very complex shape. Different authors have tried to solve this problem but, unfortunately, the proposed approaches cannot be easily used in clinical practice because they require substantial interaction among medical staff and engineers or technicians. The aim of this work is to present the framework of a new design approach that could allow clinicians to easily model a customised orthosis, without a skilled technician develops the entire procedure. In particular, an automatic process based on Generative Design has been implemented. The obtained results have demonstrated that the implemented algorithm is simple to use and could allow also not-skilled users to design customised orthoses.

Background The functional results of total elbow arthroplasty (TEA) are controversial and the medium- to long-term revision rates are relatively high. The aim of the present study was to analyze the stresses of TEA in its classic configuration, identify the areas of greatest stress in the prosthesis–bone–cement interface, and evaluate the most wearing working conditions. Materials and methods By means of a reverse engineering process and using a 3D laser scanner, CAD (computer-aided drafting) models of a constrained elbow prosthesis were acquired. These CAD models were developed and their elastic properties, resistance, and stresses were studied through finite element analysis (finite element method—FEM). The obtained 3D elbow-prosthesis model was then evaluated in cyclic flexion–extension movements (> 10 million cycles). We highlighted the configuration of the angle at which the highest stresses and the areas most at risk of implant mobilization develop. Finally, we performed a quantitative study of the stress state after varying the positioning of the stem of the ulnar component in the sagittal plane by ± 3°. Results The greatest von Mises stress state in the bone component for the 90° working configuration was 3.1635 MPa, which occurred in the most proximal portion of the humeral blade and in the proximal middle third of the shaft. At the ulnar level, peaks of 4.1763 MPa were recorded at the proximal coronoid/metaepiphysis level. The minimum elastic resistance and therefore the greatest stress states were recorded in the bone region at the apex of the ulnar stem (0.001967 MPa). The results of the analysis for the working configurations at 0° and 145° showed significant reductions in the stress states for both prosthetic components; similarly, varying the positioning of the ulnar component at 90° (− 3° in the sagittal plane, 0° in the frontal plane) resulted in better working conditions with a greater resulting developed force and a lower stress peak in the ulnar cement. Conclusion The areas of greatest stress occur in specific regions of the ulnar and humeral components at the bone–cement–prosthesis interface. The heaviest configuration in terms of stresses was when the elbow was flexed at 90°. Variations in the positioning in the sagittal plane can mechanically affect the movement, possibly resulting in longer survival of the implant. Level of evidence: 5

The spine is the load-bearing structure of human beings and may present several disorders, with low back pain the most frequent problem during human life. Signs of a spine disorder or disease vary depending on the location and type of the spine condition. Therefore, we aim to develop a probabilistic atlas of the lumbar spine segment using statistical shape modeling (SSM) and then explore the variability of spine geometry using principal component analysis (PCA). Using computed tomography (CT), the human spine was reconstructed for 24 patients with spine disorders and then the mean shape was deformed upon specific boundaries (e.g., by ±3 or ±1.5 standard deviation). Results demonstrated that principal shape modes are associated with specific morphological features of the spine segment such as Cobb’s angle, lordosis degree, spine width and height. The lumbar spine atlas here developed has evinced the potential of SSM to investigate the association between shape and morphological parameters, with the goal of developing new treatments for the management of patients with spine disorders.

In this paper a virtual concept of a city car is proposed with the aim of approaching rationally the use of private and public means of transport, by combining the advantages of the traditional systems and the new technologies. The concept suggests the Drive by Wire interface for all the commands on board; this is based on electric signals, direction and moving operated by joystick. The simpleness of driving and the small dimensions could allow the use of the car to the disabled person without any additional device.

Background and objective: In orthopedic medical devices, elasto-plastic behavior differences between bone and metallic materials could lead to mechanical issues at the bone-implant interface, as stress shielding. Those issue are mainly related to knee and hip arthroplasty, and they could be responsible for implant failure. To reduce mismatching-related adverse events between bone and prosthesis mechanical properties, modifying the implant's internal geometry varying the bulk stiffness and density could be the right approach. Therefore, this feasibility study aims to assess which in-body gap geometry improves, by reducing, the bulk stiffness. Methods: Using five finite element models, a uniaxial compression test in five cubes with a 20 mm thickness was simulated and analyzed. The displacements, strain and Young Modulus were calculated in four cubes, each containing internal prismatic gaps with different transversal sections (squared, hexagonal, octagonal, and circular). Those were compared with a fifth full-volume cube used as control. Results: The most significant difference have been achieved in displacement values, in cubes containing internal gaps with hexagonal and circular transversal sections (82 µm and 82.5 µm, respectively), when compared to the full-volume cube (69.3 µm). Conclusions: This study suggests that hexagonal and circular shape of the gaps allows obtaining the lower rigidity in a size range of 4 mm, offering a starting approach to achieve a “close-to-bone” material, with a potential use in prosthetic devices with limited thickness.

Applications as robotic harvesting or pick and place in the agrifood domain require robotic grippers able to gently manipulate delicate products, while guaranteeing high gripping power and adhesion forces on smooth surfaces. Existing soft grippers are mainly based on pneumatic bending actuators which can guarantee a gentle manipulation, but they suffer from low gripping power and possibility of slip of the manipulated object. This paper describes a novel design concept of soft robotic pneumatic gripper with embedded suckers. The concept consists of four soft fingers, each one comprising an elastomeric structure with two separate air paths, one for pressurizing the finger for generating bending motion, one for vacuum–based adhesion to the object’s surface via suction pads distributed along the surface of the finger. In this work we highlight the concept design of the mechanical system and the pneumatic control unit.

Emerging production technologies, in particular Additive Manufacturing (AM), nowadays are extremely suitable for creating highly complex products, tending towards the concept of ‘complexity for free’, which is often associated with AM. However, there are no adequate guidelines to provide decision support for the correct selection of the most economically appropriate technology. Indeed, from literature it has been highlighted the need to develop a technology selection methodology based no longer on production volume but on product complexity. This paper investigates this need by presenting an approach to determine the geometrical (or shape) complexity index of a part, which, combined with the assembly complexity, represents the driver for helping to decide the best production technology (traditional or additive). The geometrical complexity index has been determined based on complexity judgments, provided by CAD modelling experts, for a sample of CAD models. In this way, it has been possible to define a preliminary complexity index model, strictly linked to the CAD model information. The results showed that the geometrical complexity metrics from the literature, if individually considered, are not comprehensive. However, a combination of them makes it possible to obtain an index that best reflects the subjective judgement of the experts. In addition, by combining the geometrical and assembly complexity with a cost analysis it is possible to obtain convenience zones for better selecting the production technology. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Finite element modelling of the lumbar spine is a challenging problem. Lower back pain is among the most common pathologies in the global populations, owing to which the patient may need to undergo surgery. The latter may differ in nature and complexity because of spinal disease and patient contraindications (i.e., aging). Today, the understanding of spinal column biomechanics may lead to better comprehension of the disease progression as well as to the development of innovative therapeutic strategies. Better insight into the spine’s biomechanics would certainly guarantee an evolution of current device-based treatments. In this setting, the computational approach appears to be a remarkable tool for simulating physiological and pathological spinal conditions, as well as for various aspects of surgery. Patient-specific computational simulations are constantly evolving, and require a number of validation and verification challenges to be overcome before they can achieve true and accurate results. The aim of the present schematic review is to provide an overview of the evolution and recent advances involved in computational finite element modelling (FEM) of spinal biomechanics and of the fundamental knowledge necessary to develop the best modeling approach in terms of trustworthiness and reliability.

The realization of nuclear fusion reaction as energy source is under investigation, among the scientific community, through the design and development of tokamak reactors. Among the several experiments worldwide, the ITER project is the ma-jor international experiment and it involves several research institutes from sev-eral countries. In such a project, a Systems Engineering (SE) approach is re-quested to organize and manage the design due to its highly integrated design, the safety requirements related to nuclear aspects and the complex procurement scheme. The SE discipline focuses the attention on the requirements which are crucial for every successful project, defining what the stakeholders want from a potential new system, namely what the system must do to satisfy stakeholders need. Correctly stating WHAT is needed for the system, it is possible to obtain its conceptual design (HOW) as much as possible complying the requirements. The incorrect definition of requirements often leads to the failing of a project. Stakeholders’ needs are written in Natural Language that is generally ambiguous, imprecise, incomplete and redundant. Their transformation into SMART require-ments is crucial to avoid design failure. However, it requires a great expertise, unless a specific procedure is assessed. To this end, this work presents a specific procedure based on “like-mind” processes to make systematic the SMART re-quirements definition and assessment from stakeholders needs. The procedure is based on a demand/response framework and it is developed to obtain ITER re-quirements. However, it can be easily extended to every project using its own specifications. A specific case study on ITER Remote Handling is presented in this paper as example of the conceived requirements transformation procedure.

In this study we propose a brief analysis of recent soft wearable robots for upper–limb which could have a major impact on future developments and applications. The systems are analysed with respect to: design concepts, actuation systems, sensing systems, control strategies and applications. Finally, a discussion and open issues are presented.

Considering a modern approach to design, one of the viable options for developing innovative projects is the possibility of integrating the effectiveness of the solutions offered by nature and living beings with the latest design methods. With this in mind, the following research exploits the idea of reproducing the natural flexibility inherent in biological structures by combining the advantages of compliant mechanisms with the adaptability of additive manufacturing processes. In the specific, the authors intend to highlight the potential and critical aspects of a possible approach for the application of compliant mechanisms in the development of single-component structures suitable for the actuation of bio-inspired Flapping Wing Micro Air Vehicles (FWMAVs), which can be produced via low cost 3D printing. Some designs conceived by interpreting the movement of insects’ wings have been developed with the aim of reproducing the functionality and morphology of their thorax through single-component flexible mechanisms. The results of this research demonstrate the high potentiality of realizing bio-inspired single-component compliant mechanisms through 3D printing.

In the mid-1980s, several metaheuristic methods began to be developed for solving a very large class of computational problems with the aim of obtaining more robust and efficient procedures. Among them, many metaheuristic methods use bio-inspired intelligent algorithms. In recent years, these methods are becoming increasingly important and they can be used in various subject areas for solving complex problems. Firefly Algorithm is a nature-inspired optimization algorithm proposed by Yang to solve multimodal optimization problems. In particular, the method is inspired by the nature of fireflies to emit a light signal to attract other individuals of this species. In this work, a numerical study for solving a structural problem using the Firefly Algorithm as optimization method is conducted. In particular, the implementation of the Firefly Algorithm in several input files realized in the ANSYS Parametric Design Language has allowed the definition of the optimal stacking sequence and the laminate thickness of a composite gear housing used to enclose the components of a mechanical reducer.

Today it is more and more mandatory for all commercial companies to comply with the principles and methodologies of Industry 4.0 and to achieve the related capabilities protecting their competitiveness and taking a leading-edge position on market as regards technologies. Specifically, the whole production and sale system must achieve the fundamental characteristics of Industry 4.0 approach, but specially the manufacturing companies must also change and update their management procedures, internal organization, resource training, assets and all production process to keep safe their current business capacities. This evolution process is even more critical for Small and Medium Enterprises (SME), that traditionally tend to be conservative and to protect their way of operation, usually characterized by a low level of automation. The work presented focuses on the design and integration of a semi-automatic welding cell of train bolster in a SME which is currently realizing a project aimed to the acquisition of Industry 4.0 capabilities, with special focus on manufacturing processes. Among them, one of the most important is the production of welded-steel critical structures, that the Company supplies to prime manufacturer of railway rolling stock systems. The experience gained during the activity, the criticalities due to the integration processes and the adopted design methodologies are here described. The work has been carried out consistently with the Systems Engineering principles, starting from the requirements elicitation and analysis to the systematic approach for the design and integration activities.

Purpose: The study aims were to assess the kinematic data, Internal-External (IE) rotation, and Antero-Posterior (AP) translation of the contact points between the femoral condyles and polyethylene insert and to develop a combined dynamic RSA-FE (Radiostereometric – Finite Element) model that gives results congruent with the literature. Methods: A cohort of 15 patients who underwent cemented cruciate-retaining highly congruent mobile-bearing total knee arthroplasty were analyzed during a sit-to-stand motor task. The kinematical data from Dynamic RSA were used as input for a patient-specific FE model to calculate condylar contact points between the femoral component and polyethylene insert. Results: The femoral component showed an overall range about 4 mm of AP translation during the whole motor task, and the majority of the movement was after 40° of flexion. Concerning the IE rotation, the femoral component started from an externally rotate position (− 6.7 ± 10°) at 80° of flexion and performed an internal rotation during the entire motor task. The overall range of the IE rotation was 8.2°. Conclusions: During the sit to stand, a slight anterior translation from 40° to 0° of flexion of the femoral component with respect to polyethylene insert, which could represent a paradoxical anterior translation. Despite a paradoxical anterior femoral translation was detected, the implants were found to be stable. Dynamic RSA and FE combined technique could provide information about prosthetic component’s stress and strain distribution and the influence of the different designs during the movement., SCOPUS: ar.j, info:eu-repo/semantics/published

Purpose Shoulder instability and reduced range of motion are two common complications of a total reverse shoulder arthroplasty. In this work, a new approach is proposed to estimate how the glenoid component positioning can influence the stability and the range of motion of a reverse shoulder prosthesis. Materials and methods A standard reverse shoulder prosthesis has been analysed. To perform virtual simulation of the shoulder-prosthesis assembly, all the components of the prosthesis have been acquired via a 3D laser scanner and the solid models of the shoulder bones have been reconstructed through CT images. Loads on the shoulder joint have been estimated using anatomical models database. A new virtual/numerical procedure has been implemented using a 3D parametric modelling software to find the optimal position of the glenosphere. Results Several analyses have been performed using different configurations obtained by changing the glenoid component tilt and the lateral position of the glenosphere, modified through the insertion of a cylindrical spacer. For the analysed case study, it was found that the interposition of a spacer (between the baseplate and the glenoid) and 15° inferior tilt of the glenosphere allow improving the range of motion and the stability of the shoulder. Conclusions Some common complications of the reverse shoulder arthroplasty could be effectively reduced by a suitable positioning of the prosthesis components. In this work, using a new method based on virtual simulations, the influence of the glenosphere positioning has been investigated. An optimal configuration for the analysed case study has been found. The proposed approach could be used to find, with no in vivo experiments, the optimal position of a reverse shoulder prosthesis depending on the different dimensions and shape of the bones of each patient.

Background and objective The aim of the present study was to review the literature concerning the analysis of periprosthetic bone remodeling through finite element (FE) simulation. Methods A systematic review was conducted on 9 databases, taking into account a ten-year time period (from 2009 until 2020). The inclusion criteria were: articles published in English, publication date after 2009, full text articles, articles containing the keywords both in the abstract and in the title. The articles were classified through the following parameters: dimensionality of the simulation, modelling of the bone-prosthesis interface, output parameters, type of simulated prosthesis, bone remodeling algorithm. Results Sixty-seven articles were included in the study. Femur and tooth were the most evaluated bone segment (respectively 41.8% and 29.9%). The 55.2% of the evaluated articles used a bonded bone-prosthesis interface, 73% used 3D simulations, 67.2% of the articles (45 articles) evaluate the bone remodeling by the bone density variation. At last, 59.7% of the articles employed algorithms based on a specific remodeling function. Conclusions Increasing interest in the bone remodeling FE analysis in different bone segments emerged from the review, and heterogeneous solutions were adopted. An optimal balance between computational cost and accuracy is needed to accurately simulate the bone remodeling phenomenon in the post-operative period.

Purpose The purpose of this paper is to implement a new process aimed at the design and production of orthopaedic devices fully manufacturable by additive manufacturing (AM). In this context, the use of generative algorithms for parametric modelling of additively manufactured textiles (AMTs) also has been investigated, and new modelling solutions have been proposed. Design/methodology/approach A new method for the design of customised elbow orthoses has been implemented. In particular, to better customise the elbow orthosis, a generative algorithm for parametric modelling and creation of a flexible structure, typical of an AMT, has been developed. Findings To test the developed modelling algorithm, a case study based on the design and production of an elbow orthosis made by selective laser sintering was investigated. The obtained results have demonstrated that the implemented algorithm overcomes many drawbacks typical of the traditional computer aided design (CAD) modelling approaches. The parametric CAD model of the orthosis obtained through the new approach is characterised by a flexible structure with no deformations or mismatches and has been effectively used to produce the prototype through AM technologies. Originality/value The obtained results present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to modelling for AM in different application fields.

The aim of this work is the design of a new customised elbow orthosis completely realized by Additive Manufacturing and the development of generative algorithms for parametric modelling and creation of 3D patterns to be adapted to the CAD model. This work describes a method to perfect the design of a custom elbow orthosis. A reverse engineering approach has been used to digitalize the patient’s arm and the subsequent CAD modelling of the structure of the custom elbow orthosis has been performed. In particular, two algorithms have been implemented for the creation of 3D patterns and Voronoi tessellations. Subsequently, FEM analyses have been carried out to validate the design. Finally, a prototype of the elbow orthosis with Voronoi tessellation has been realized by means of the SLS technology. The results obtained have demonstrated that the implemented algorithm solved the problems found during CAD modelling with conventional software. Furthermore, the results of FEM analyses have validated the design choices. All this allowed realizing the prototype by AM technologies without problems. Moreover, the new proposed modelling approaches allows creating, in an interactive way, patterns on complex surfaces. The results of this research activity present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to the modelling for Additive Manufacturing. Furthermore, another innovative characteristic of the device is the use of torsion springs that simulate the action of physiotherapists during exercises for patient rehabilitation.

In the last two decades, osseointegrated prostheses have been shown to be a good alternative for lower limb amputees experiencing complications in using a traditional socket-type prosthesis, however, restraining biomechanical issues, such as peri-prosthetic bone fractures or loosening, are present. To better understand and overcome these limiting issues, and thus reduce the number of implant failures, many studies have investigated the stress distribution on bone and implant during normal daily activities. The aim of this study was a biomechanical analysis of two different osseointegrated implants, a screw-type (OPRA) and a press fit system (OPL, Osseointegrated Prosthetic Limb), to evaluate the stresses generated in bone and prosthesis during a fall. In particular, four scenarios have been experimentally reproduced to determine the loads on the limb during different kinds of fall. For this purpose, a motion capture system and a force plate have been used. Numerical FEM (Finite Element Method) simulations have been performed to compare the behaviour of the OPRA and OPL systems in different fall scenarios. The obtained results showed that a fall backwards due to balance loss is the most stressful scenario among the ones analysed. As regards the comparison between OPRA and OPL devices, it emerged they have similar behaviours in terms of peak values of the stress, but the OPL implant generates larger high-stress areas in the distal femur as compared with the OPRA system.

Despite the widespread use of reverse total shoulder arthroplasty, the fundamental effects of implant configuration on certain biomechanical outcomes have not been completely elucidated especially for the most innovative prostheses. Aim of this work is to investigate the behaviour of a new reverse shoulder prosthesis, characterized by a humeral tray with a variable offset, designed to increase the range of motion and to reduce the impingement. The purposes of this study were to evaluate the effect of reverse shoulder implant design parameters on the deltoid muscle forces, required to produce abduction, and on the shoulder range of motion, in order to provide a more systematic understanding of the fundamental effects of humeral component positioning on the implant performances. The study has been implemented using virtual prototypes of the shoulder-prosthesis assembly. The shape of the prosthesis has been digitally acquired via a 3D scanner and the CAD models of all the components have been created. Through CT images, 3-dimensional models of the shoulder bones have been reconstructed and assembled with the prosthesis components. Numerical FEM models have been set up in order to evaluate how the abduction force changes depending on the humeral tray offset. Using the virtual prototypes of the shoulder-prosthesis assembly, a range of motion analysis has been carried out by setting up a collision detection analysis in a 3D parametric modeling environment. Different humeral tray positions were investigated and four different motions of the arm were simulated. Obtained results have demonstrated that a suitable positioning of the humeral tray can offer significant biomechanical advantages in terms of range of motion and abduction force.

Orthoses are additional devices that help people with disabilities. The focus of this work is the design and manufacture of a new customized elbow orthosis completely made by Additive Manufacturing (AM). One of the innovative characteristic of the device is the use of torsion springs that simulate the action of physiotherapists during exercises for patient rehabilitation. Parametric modeling approach based on generative algorithms was used to design the device. Finally, FEM analyses have been performed to validate the design.

Tibial fractures are common injuries in people. The proper treatment of these fractures is important in order to recover complete mobility. The aim of this work was to investigate if screw positioning in plates for proximal tibial fractures can affect the stability of the system, and if it can consequently influence the patient healing time. In fact, a more stable construct could allow the reduction of the non-weight-bearing period and consequently speed up the healing process. For that purpose, virtual models of fractured bone/plate assemblies were created, and numerical simulations were performed to evaluate the reaction forces and the maximum value of the contact pressure at the screw/bone interface. A Schatzker type I tibial fracture was considered, and four different screw configurations were investigated. The obtained results demonstrated that, for this specific case study, screw orientation affected the pressure distribution at the screw/bone interface. The proposed approach could be used effectively to investigate different fracture types in order to give orthopaedists useful guidelines for the treatment of proximal tibial fractures.

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.

In this work, a multidisciplinary experience, aimed to study the permanent deformations of the hull of a regatta sailing yacht is described. In particular, a procedure to compare two different surfaces of the hull of a small sailing yacht, designed and manufactured at the University of Palermo, has been developed. The first one represents the original CAD model while the second one has been obtained by means of a reverse engineering approach. The reverse engineering process was performed through an automatic close-range photogrammetry survey, that has allowed to obtain very accurate measures of the hull, and a 3D modelling step by the well-known 3D computer graphics software Rhinoceros. The reverse engineering model was checked through two different procedures implemented by the graphical algorithm editor Grasshopper. The first procedure has allowed to compare the photogrammetric measurements with the rebuilt surface, in order to verify if the reverse engineering process has led to reliable results. The second has been implement to measure the deviations between the original CAD model and the rebuilt surface of the hull. This procedure has given the possibility to highlight any permanent deformation of the hull due to errors during the production phase or to excessive loads during its use. The obtained results have demonstrated that the developed procedure is very efficient and able to give detailed information on the deviation values of the two compared surfaces.

Additive manufacturing is a rapidly expanding technology. It allows the creation of very complex 3D objects by adding layers of material, in spite of the traditional production systems based on the removal of material. The development of additive technology has produced initially a generation of additive manufacturing techniques restricted to industrial applications, but their extraordinary degree of innovation has allowed the spreading of household systems. Nowadays, the most common domestic systems produce 3D parts through a fused deposition modeling process. Such systems have low productivity and make, usually, objects with no high accuracy and with unreliable mechanical properties. These side effects can depend on the process parameters. Aim of this work is to study the influence of some typical parameters of the additive manufacturing process on the prototypes characteristics. In particular, it has been studied the influence of the layer thickness on the shape and dimensional accuracy. Cylindrical specimens have been created with a 3D printer, the Da Vinci 1.0A by XYZprinting, using ABS filaments. Dimensional and shape inspection of the printed components has been performed following a typical reverse engineering approach. In particular, the point clouds of the surfaces of the different specimens have been acquired through a 3D laser scanner. After, the acquired point clouds have been post-processed, converted into 3D models and analysed to detect any shape or dimensional difference from the initial CAD models. The obtained results may constitute a useful guideline to choose the best set of the process parameters to obtain printed components of good quality in a reasonable time and minimizing the waste of material.

Definition of size, shape and location of defects into a mechanical component is of extreme importance in the manufacturing industry in general and particularly in high-tech applications, and in applications that can become dangerous due to the structural failure of mechanical components. In this paper, a laser-UT system has been used to define position and shape of internal defects in aluminum plates. An infrared pulsed laser is used to generate ultrasonic waves in a point of the plate and a CW laser interferometer is used as receiver to acquire the out-of-plane displacements due to the ultrasonic waves in another point of the plate. The method consists of acquiring a B-Scan map on which some information on the defects in the mechanical component are visible. Storing the characteristics of the wave reflected by the defect and acquired in the B-Scan, the detection and the drawing of the defect is possible. The acquisition of the times of arrival of the waves reflected by the defect from the B-scan allows defining large parts of the shape of the defect. The times of arrival are acquired from the B-scan by analyzing the colour variations due to the wave reflected by the defect. The experiments operated from both sides of the plate allow drawing the defect in a virtual image of the plate section, from which the definition of defect shape and position can be determined.

In this paper, most significant steps involved during the whole process of designing a sailing yacht are outlined. In particular, a novel simultaneous approach has been proposed to optimize the design process of a sailing yacht. Analytical resistance prediction models are simultaneously used with CAD systems and computational fluid dynamics tools to find, in the more effective way, the best solution for the chosen design conditions. As a general rule, in fact, once the target point has been decided, task of the designer is the definition of those systems of aerodynamic and hydrodynamic forces that are in equilibrium when the boat sails at its target. Unfortunately, a multi-purpose yacht does not exist. If the target point is in upwind sailing then, performances will be better for such a condition and worse for others. The effectiveness of the proposed procedure has been tested by means of a case study related to the design of hull, appendages and sails of a 15” yacht subject to box-rules, designed and manufactured at the University of Palermo.

Aim of this work is to investigate the behaviour of a new reverse shoulder prosthesis, characterized by a humeral metaphysis with a variable offset, designed to increase the range of movements and to reduce the impingement. In particular, by means of virtual prototypes of the prosthesis, different offset values of the humeral metaphysis have been analysed in order to find the best positioning able to maximize the range of movements of the shoulder joint. The abduction force of the deltoid, at different offset values, has been also estimated. The study has been organized as follows. In the first step, the point clouds of the surfaces of the different components of the prosthesis have been acquired by a 3D scanner. This kind of scanner allows to convert camera images into three-dimensional models by analysing the moire fringes. In the second step, the acquired point clouds have been post-processed and converted into CAD models. In the third step, all the 3D reconstructed models have been imported and assembled through a CAD system. After, a collision analysis has been performed to detect the maximum angular positions of the arm at different metaphysis offset values. In the last step, FEM models of shoulder joint with the new prosthesis have been created. Different analyses have been performed to estimate how the deltoid abduction force varies depending on the offset of the humeral tray. The study allowed to understand how the offset of the metaphysis affects the performances of the shoulder. The obtained results can be effectively used to give surgeons useful guidelines for the installation of these kinds of implants.

In this work the mechanical behaviour of a core reinforced composite sandwich structure is studied. The sandwich employs a Glass Reinforced Polymer (GRP) orthotropic material for both the two external skins and the inner core web. In particular, the core is designed in order to cooperate with the GRP skins in membrane and flexural properties by means of the addition of a corrugated laminate into the foam core. An analytical model has been developed to replace a unit cell of this structure with an orthotropic equivalent thick plate that reproduces the in plane and out of plane behaviour of the original geometry. Different validation procedures have been implemented to verify the quality of the proposed method. At first a comparison has been performed between the analytical model and the original unit cell modelled with a Finite Element mesh. Elementary loading conditions are reproduced and results are compared. Once the reliability of the analytical model was assessed, this homogenised model was implemented within the formulation of a shell finite element. The goal of this step is to simplify the FE analysis of complex structures made of corrugated core sandwiches; in fact, by using the homogenised element, the global response of a real structure can be investigated only with the discretization of its mid-surface. Advantages are mainly in terms of time to solution saving and CAD modelling simplification. Last step is then the comparison between this FE model and experiments made on sandwich beams and panels whose skins and corrugated cores are made of orthotropic cross-ply GRP laminates. Good agreement between experimental and numerical results confirms the validity of the proposed model.

Topological optimization can be considered as one of the most general types of structural optimization. Between all known topological optimization techniques, the Evolutionary Structural Optimization represents one of the most efficient and easy to implement approaches. Evolutionary topological optimization is based on a heuristic general principle which states that, by gradually removing portions of inefficient material from an assigned domain, the resulting structure will evolve towards an optimal configuration. Usually, the initial continuum domain is divided into finite elements that may or may not be removed according to the chosen efficiency criteria and other parameters like the speed of the evolutionary process, the constraints on displacements and/or stresses, the desired volume reduction, etc. All these variables may influence significantly the final topology. The main goal of this work is to study the influence of both the different optimization parameters and the used efficiency criteria on the optimized topology. In particular, two different evolutionary approaches, based on the von Mises stress and the Strain Energy criteria, have been implemented and analyzed. Both approaches have been deeply investigated by means of a systematic simulation campaign aimed to better understand how the final topology can be influenced by different optimization parameters (e.g. rejection ratio, evolutionary rate, convergence criterion, etc..). A simple case study (a clamped beam) has been developed and simulated and the related results have been compared. Despite the object simplicity, it can be observed that the evolved topology is strictly related to the selected parameters and criteria.

In this paper, two optimization approaches to improve the product design process have been analysed. Through the analysis of a case study, concerning the designing of a new High Energy Absorption Rear Underrun Protective Device (HEARUPD), two different optimization approaches (simplex and simulated annealing) have been compared. In the implemented optimization processes, the crash between an economy car and the rear part of a truck has been simulated by dynamic numerical (FEM) analyses. Moreover, authors have proposed the use of a suitable linear function of four variables with the purpose of reducing the multi-objective optimization processes to mono-objective ones. That has been made to simplify the analysis procedures without affecting the quality and the completeness of the optimization processes. The obtained results, as well as showing the high effectiveness of the integrated use of numerical crash analyses and optimization methods, demonstrate that simplex method is more effective than simulated annealing one for optimization problems where the single analysis loop requires much time. Even if the solutions are quite similar in terms of calculated values of the objective function, design and state variables, simplex method needs shorter computational time than simulated annealing to obtain an optimized solution.

The non-destructive evaluation of defects by automatic procedures is of great importance for structural components. Thanks to the developments of the non-contact ultrasonic techniques, the automation of the inspections is gaining a progressively important role. In this work, an automatic inspection technique for the evaluation of defects by the analysis of B-scan images obtained by a laser ultrasonic system is presented. The data are extracted directly from a B-scan map obtained for a panel with internal defects, and are used to build an image of the cross section of the panel. The proposed automatic procedure allows the definition of size, position and shape of defects in panels of known thickness.

During the braking phase, the heat produced by friction between pads and disc cannot be entirely dissipated. Consequently, the brake disc, especially if very hard braking occur, can accumulate large amounts of heat in a short time so producing high gradients of temperature on it. Under these conditions, functionality and safety of the brake system can be compromised. The object of this study is to investigate, under extreme working conditions, the thermomechanical behaviour of different brake rotors in order to evaluate their efficiency and stability and to identify any compromising weakness on them. In particular, by means of FEM thermo-mechanical coupled analyses, one full disc and three ventilated rotors with different shapes have been studied. A very hard (fading) test has been used to evaluate the performances of the discs in terms of temperature distribution, stresses and strains. Obtained results demonstrate that the analysed ventilated discs, unlike the full rotor, can be effectively used in very hard working conditions, always ensuring high safety levels. Among the studied rotors, the curved-vanes disc was found to be the best solution.

In this work a commercial reverse shoulder prosthesis has been redesigned to improve performances in terms of range of movements of the implant and stability to dislocation. A kinematic and mechanic study has been performed using a realistic solid model of the prothesised shoulder: in particular, all the components of the prosthesis have been acquired via a 3D laser scanner and inserted in a virtual humerus-glenoid system by reproducing the common surgical procedure. The final model has been used to measure the maximum angles of abduction and rotation of the arm and the shear forces that cause dislocation. Modifications proposed to the commercial prosthesis are: a different orientation of the cutting plane of the glenoid component and the interposition of a spacer to move the center of rotation of the arm.

In the field of topology optimization problems, the Evolutionary Structural Optimization (ESO) method is one of the most popular and easy to use. When dealing with problems of reasonable difficulty, the ESO method is able to give very good results in reduced times and with a limited request of computational resources. Generally, main applications of this method are addressed to the definition of the optimal topology of a component subjected to a single load condition.In this work, a new methodology, based on the ESO approach, is introduced for the study of the optimal topology of a component subjected to multiple load conditions. The new procedure, entirely developed in the APDL programming language, has been tested with a holed plate subject to two different load conditions; the obtained results are promising in terms of mass reduction and structural performances.

Aim of this paper is to setup a novel procedure able to analyze performances of a reverse shoulder prosthesis when different geometrical configurations are assumed. Nowadays, such a prosthesis is widely used but, because of its novelty, data in literature give poor information about performances and limits to its applicability. The activity has been divided into the following steps. At the beginning the shape of the prosthesis has been digitally acquired via a 3D scanner. Then, CAD models of all prosthetic components have been geometrically optimized in a way to obtain final entities suitable for numerical simulations. After that, CAD assemblies have been created between prosthetic components and bones (humerus and scapula) involved in the shoulder joint. Following step has been the setup of numerical finite element method models to simulate use conditions. To this scope, analyses have been performed in accordance with experimental conditions found in literature. Stability conditions have been verified under the action of horizontal and vertical instability loads with different version angles between humerus and the humeral implant. In particular, the stability ratios of the prosthesis have been calculated for the analysed loading conditions. Obtained results show how the positioning has a great influence on the shoulder stability and allow the definition of guidelines for the application of this prosthesis.

In this work a new distal interlocking system has been developed which is easy to use, allows a reduction of the operating time and consequently the exposure to radiations both for surgeon and patient. The main goal of this study has been the design of a new intramedullary nail for tibial fractures able to simplify and speed up the distal locking operation phases. After a preliminary stage during which several candidate concepts have been proposed and analysed, the best solution has been developed and deeply investigated. The new system, called “expansion nail”, has been firstly modelled by setting up a full parametric CAD model and, then, tested by running non linear FEM analyses to evaluate stresses and stability of the joining during normal working conditions. The new design has shown very high mechanical stability in the axial compression and torsional load cases. Since its very simple self-locking system, the new expansion intramedullary nail would reduce the operating time and the exposure to radiations for the surgeons as well as the patients.

The paper presents the results of a numerical and experimental investigation performed on a barrel of a speargun equipped with two kinds of muzzle. In particular, a standard muzzle for speargun (having an elastic propulsion) has been compared with an innovative one called ‘roller’. This new muzzle is equipped with two rollers and special bands. The rubber bands, fixed at the lower side of the barrel, run through the rollers and are engaged in suitable seats of the shaft. These bands are, therefore, longer than the traditional ones and, consequently, with equal force applied by the diver, the roller speargun has a longer range. Thanks to the particular geometry of the new muzzle, one of the front constraints of the elastic bands is moved to the lower part of the barrel or the handle.As a consequence, the scheme of the loads applied on the speargun remarkably changes passing from a standard muzzle to a roller one. All that has a great influence on the level of deformation of the barrel and, consequently, on the accuracy of the shot. Because of the low velocity of the spear (if compared with the firearms), in fact, the accuracy of the shoot if strongly influenced by the barrel bending due to the forces applied by means of the elastic bands. In this paper it is experimentally evaluated the bending of the barrel equipped both with the innovative muzzle and with the traditional one in order to compare their performances. The experimental analysis of the barrel was performed by electrical strain gauges suitably located at the section with the highest values of the strains. In order to find the barrel section with the highest strain values where to locate the strain gauges, a preliminary numerical FEM analysis has been performed. The loads and constraints scheme has been evaluated both for the standard and the new muzzle. In particular, the forces due to the elastic bands, their application points and directions have been experimentally obtained. To speed up the process of numerical simulation, without invalidating the results reliability, simplified FEM models have been used. In particular, a very accurate model of the barrel has been shaped, whereas the models of the muzzles and the handle have been simplified. The forces due to the elastic bands, experimentally obtained, have been applied on the FEM models. The maps of the maximum and minimum principal strains have allowed to find the area with the highest strain values, placed in rear part of the barrel (near the handle). The strain values experimentally measured on the speargun have been very similar to the ones calculated by means of the numerical simulations. That demonstrates the developed FEM models are very reliable and can ben used to predict the performances of the speragun under different loads conditions. The speargun with the new roller muzzle shows very lower strain values if compared with the ones measured in the standard one. Nevertheless, considering the two spearguns have different elastic bands setup, it has been thought the comparison of their performances should be made hypothesizing the same maximum force applied during the speargun charge. This condition, moreover, could be really obtained by changing the kind of the elastic bands in the speargun with the roller muzzle. For this reason, during the results analysis phase, the strain values measured on the roller speargun have been ‘normalized’ by increasing them of a value equal to the ratio of the maximum forces due to the rubber bands. The data post processing has allowed to evaluate the forces and the bending moments on the barrels with the standard muzzle and the roller one. Results show the barrel with the innovative muzzle has, also considering equal forces applied by the diver, a lower bending than the barrel with a traditional muzzle. To evaluate the maximum deflection of both the spearguns, a new numerical simulation has been set up. In particular, in this FEM analysis, the roller speargung has been loaded with a maximum force comparable with the standard one. The obtained results show that the standard speargun has a higher value of the maximum deflection respect to the roller one. Since higher deflection values of the barrel make worse the accuracy of the shot, these results demonstrate the novel speargun can be more precise than the traditional one.

Total reverse shoulder arthroplasty is becoming more and more the standard therapeutic practice for glenohumeral arthropathy with massive lesions of the rotator cuff. The biomechanical principle of this prosthesis is represented by the reversion of the normal anatomy of the shoulder joint. This non-anatomical prosthesis leads to a medialization of the rotation centre of the glenohumeral joint and also to a distalization of the humeral head. All that causes a deltoid tension increasing so allowing a larger abduction of the arm. Main complications of the reverse shoulder prosthesis are due to the joint instability, the scapular notching and the wear of the polyethylene insert. The main goal of the present work is to study the effect of the positioning of the humeral component on the intrinsic stability of the reverse shoulder prosthesis. In particular, through finite element method simulations, the variation of the stability ratio of the shoulder joint has been calculated for both vertical and horizontal dislocating loads depending on the humeral stem version angle. Moreover, in order to estimate the wear of the polyethylene cup, some analyses have been developed to calculate the pressures on the polyethylene insert. The obtained results demonstrate the dislocation of a shoulder prosthesis and the wear of the polyethylene insert can be prevented or limited by conveniently varying the version angle of the humeral component.

The aim of this work is the analysis of the contact area in a knee prosthesis using two different approaches. In particular, the interface between the femoral component and the polyethylene insert has been studied both numerically and experimentally. The interest in studying the contact area is related to the fact that the wear of the polyethylene insert, due to the high contact pressures, represents one of the major causes of failure of the total knee prosthesis. The possibility to evaluate the contact area at different loads and mutual position between femur and tibia is, therefore, of fundamental importance to study the service life of a prosthesis and to improve its performance. The finite element numerical approach has required the acquisition, through reverse engineering, and CAD modelling of the prosthetic components. Then the FEM simulations have been developed considering two different load conditions. In order to compare the calculated data, the same load configurations have been used for experimental tests based on ultrasonic method. In this case, some preliminary tests were required to calibrate the system depending on the particular characteristics of materials, geometries and surface finish of the prosthesis. The results show a good correlation between the data obtained with the two different approaches and, consequently, a good level of reliability of the procedures developed for the numerical and experimental evaluation of the contact area. The numerical procedure can be used to determine the area for different angles and loads, but especially in the design phase. The ultrasonic technique can be used to validate the numerical data.

Aim of this work is to compare two different total knee prostheses that differ mainly in the shape of the polyethylene (PE) component inserted between the femoral and tibial plates. The best solution between them has been originally reshaped in order to reduce stress peaks. The study procedure has been divided into the following steps. First step is the digitalisation of the shape of the prostheses by means of a 3D laser scanner. The morphology of two prototypes of the prostheses has been acquired by elaborating multiple Moire fringe patterns projected on their surfaces. Second step consisted on the manipulation of these data in a CAD module, that is the interpolation of raw data into NURBS surfaces, reducing singularities due to the typical scattering of the acquiring system. Third step has been the setting up of FEM simulations to evaluate the prostheses behaviour under benchmark loading conditions given in literature. The CAD model of the prostheses has been meshed into solid finite elements. Different flexion angles configurations have been analysed, the load being applied along the femoral axis. FEM analyses have returned stress fields in the PE insert and, in particular, in the stabilizing cam which function is to avoid dislocation. Last step has been the integrated use of CAD and FEM to modify the shape of the stabilizing cam of the best prosthesis, in order to reduce the stress peaks in the original prosthesis without affecting kinematics of the joint. Good results have been obtained both in terms of stress and contact pressure peaks reduction.

The OBS (acronym of Ocean Bottom Seismometer) is a system to monitor the submarine seismic activity. To properly work, an OBS system needs a suitable auto-levelling base to maintain a fixed (horizontal) position during the measurement phases. In this work a new auto-levelling base for submarine seismic sensors has been designed. During the redesign process a preliminary phase of analysis of the state of art has been made. Afterwards, the technological solutions chosen by different manufactures have been critically analysed, and a full description of their functionalities, working principles and system performances has been carried out. Later, some innovative concepts have been proposed. Among these ones, the most interesting are the auto-levelling bases with spherical joint, based on: air bearings, ball bearings and magnetic levitation systems. The concept scoring method has been used to identify. as best concept, the auto-levelling base with spherical joint and air bearings system. Successively, the chosen concept has been implemented: the technical working principles have been studied to choose the best solutions in terms of dimensions, shapes, materials of all base components. A full parametric CAD model of the auto-levelling base has been also created. The new designed base, by using a very innovative auto-levelling system, allows to obtain very good results as regards the accuracy of positioning, so ensuring a remarkable improvement of the performances of the ocean bottom seismometers.

A novel self-balanced internal combustion engine is presented. The new engine has a modular structure composed of two cylinders arranged in opposite way. It is characterized by an innovative system of linking between the pistons and the shaft, which has three toggles. One of these is on the middle of the shaft, whereas the others two are placed symmetrically. Thanks to this particular shape of the shaft, the pistons can rotate with the same timing and so the new engine comes back to be perfectly auto-balanced. Moreover, the fatigue life prediction of the shaft has been studied through numerical methods. In particular, two different approaches have been compared to estimate the maximum number of working cycles: the first is based on a “static” resistance criterion, the second consider the multiaxial nature of the stress and is based on the maximum shear stress (critical) plane criterion. The stress distribution on the shaft during the usual working conditions, has been evaluated by a FEM package. Results highlight that the critical plane approach is more conservative than “static” one.