Abstract: Osseointegrated implant is a promising solution for limb amputations, but its widespread use is limited by risks such as bone resorption, infections, and strict patient requirements. Typically, the bone and prosthesis are coupled using a press-fit condition, providing short-term stability, or primary stability (PS), which leads to bone in-growth and long-term stability, or secondary stability (SS). However, the greater stiffness of the implant compared to the bone is a concern for SS. Currently, osseointegrated implants are commercially available only in fixed configurations, with a limited use of customization. This study aims to compare the contact effectiveness of three press-fitted intramedullary stems for femoral amputations, developed using three designs (straight, standard curvature, and patient-specific curvature). Moreover, a novel implant design methodology is reported, such is an easy way to develop a patient-specific design. The von Mises stress distribution at the bone-implant interface was analyzed. The study uses CAD models of a femur acquired through CT scans. A FEA was conducted to evaluate the elastic behavior of the bone when the implant is press-fitted with an interference of 0.1 mm. The outcomes show how the patient-specific implant result in a more physiological distribution of the load in the bone. This study could be used as a starting point for further studies on primary and secondary stabilities.

Keywords: 3D Modelling | Finite Element Model | Osseointegration | Patient-Specific Design | Transfemoral Implant

Abstract: The Reverse Total Shoulder Arthroplasty (RTSA) is a complex surgical procedure also due to the difficulty in correctly positioning all the components of the prosthesis. Malpositioning of the prosthesis, in fact, can lead to various complications such as scapular notching, early mobilization, instability and reducing of the range of movement (ROM). Preoperative planning with 3D imaging and patient specific instruments can be very useful tools to help surgeon in selecting the optimal position of implant components. Aim of this work is to develop a procedure based on a fully parametric CAD system that simulates the shoulder joint to identify the optimal positioning of the humeral and glenoid components of the prosthesis. In particular, the proposed system allows to find the optimal cutting angles of the humerus head and the glenoid cavity so to best fit the patient's bone structure and the prosthesis components and, consequently, to improve the range of movement. The system allows to create, in a semi-automatic way, CAD assembly models composed of the patient shoulder bones and different reverse shoulder prostheses. For each assembly different positions of the components of the prosthesis can be evaluated and various scenarios of movements can be simulated. In this way it is possible to identify the optimal positioning of the prosthesis for each patient in the preoperative stage. The proposed procedure has been tested with two types of prosthesis and two patients. Obtained results demonstrated that an optimal positioning of prosthesis an improve ROM up to 27%.

Keywords: CAD | Preoperative planning | Reverse engineering | Reverse total shoulder arthroplasty

Abstract: As is widely recognized, advancements in new design and rapid prototyping techniques such as CAD modeling and 3D printing are pioneering individualized medicine, facilitating the implementation of new methodologies for creating customized orthoses. The aim of this paper is to develop a new automatic technique for producing personalized orthoses in a straightforward manner, eliminating the necessity for doctors to collaborate directly with technicians. A novel design method for creating customized wrist orthoses has been implemented, notably featuring a generative algorithm for the parametric modeling of the orthosis. To assess the efficacy of the developed algorithm, a case study was conducted involving the design and rapid prototyping of a wrist orthosis using Fused Deposition Modeling (FDM) technology. Subsequently, the developed algorithm was tested by clinicians and patients. The results obtained indicate that the implemented algorithm is user-friendly and could potentially enable non-expert users to design customized orthoses. These results introduce innovative elements of originality within the CAD modeling, offering promising solutions to the challenges associated with the design and production of customized orthoses. Future developments could consist of a better investigation regarding the parameters that influence the accuracy of the scanning and of the printing processes.

Keywords: additive manufacturing | CAD | generative design | reverse engineering | wrist orthosis

Abstract: Compliant Mechanisms, Topology Optimization and low-cost 3D printing technologies have been exploited in a combined design approach aimed at the development of a Flapping Wing Micro Air Vehicle’s wing actuation mechanism. A series of topology optimization analysis was implemented to explore four different design domains, each with a specific supports’ positioning. Subsequently, the obtained topologies were geometrically remodeled and tailored to comply with the 3D printing process parameters, resulting in several monolithic Compliant Mechanisms. The different remodeled mechanisms were finally compared in terms of stress and range of movement, through non-linear transient Fem analysis. Although the designed compliant mechanisms move at high rotation frequencies (about 25 Hz) and undergo large deflections, the obtained results are interesting with regard to maximum stresses and rotation angle amplitudes, paving the way to a future design improvement both deepening fatigue issues and implementing size and shape optimization.

Keywords: Additive manufacturing | Compliant Mechanisms | Flapping Wing Micro Air Vehicles | Topology optimization

Abstract: Composite sandwich panels with honeycomb, corrugated, tetrahedral, trapezoidal, 3D periodic and hybrid lattice cores have long been studied for their use in various industrial fields. In this study, several numerical analyses were conducted in ANSYS APDL environment in order to analyze the effect of a novel bi-directional corrugated core configuration on the flexural performance of a CFRP sandwich panel. In particular, the sandwich core is obtained by repeating a regular unit cell in two different directions to form a three-dimensional lattice structure. In order to determine the optimal values of the geometrical parameters of the core unit cell and to evaluate how the layout of the composite laminate could affect the mechanical performances of the structure, a numerical study was conducted by using the Group Search Optimizer (GSO) algorithm, a metaheuristic animal-inspired optimization algorithm used to solve various real-world problems. The obtained results show that the GSO algorithm is very effective to optimize the main geometrical parameters of the composite sandwich panel with the novel bi-directional corrugated core. More generally, the implemented procedure provides an open framework to solve complex optimization problems that are very difficult to solve using exact methods, making the GSO algorithm particularly attractive for many industrial applications.

Keywords: ANSYS | Finite element analysis | Group search optimizer | Numerical optimization

Abstract: In this work a Reverse Engineering based approach has been implemented aiming to reconstruct the 3D shape of a strongly damaged and no longer usable impeller of a submersible centrifugal pump. After obtaining the 3D model, new designs of the impeller were investigated in terms of structural stability and corrosion resistance by changing the geometry and the material. Obtained results show the used approach can be very useful both to reproduce, by Additive Manufacturing, no longer available spare parts, so allowing to extend the useful life of old machineries and to reduce costs resulting from plant shutdowns, but also to improve the performances of old designs, making use of different materials and new manufacturing processes.

Keywords: CAD | Centrifugal pump | Impeller | Modal analysis | Reverse Engineering

Abstract: 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

Keywords: Biomechanics | Elbow finite element | Elbow replacement | Prosthetic posizioning | Totel elbow arthroplasty

Abstract: 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.

Keywords: CAD | Customised orthosis | Generative design | Reverse engineering

Abstract: The process of designing a sail can be a challenging task because of the difficulties in predicting the real aerodynamic performance. This is especially true in the case of downwind sails, where the evaluation of the real shapes and aerodynamic forces can be very complex because of turbulent and detached flows and the high-deformable behavior of structures. Of course, numerical methods are very useful and reliable tools to investigate sail performances, and their use, also as a result of the exponential growth of computational resources at a very low cost, is spreading more and more, even in not highly competitive fields. This paper presents a new methodology to support sail designers in evaluating and optimizing downwind sail performance and manufacturing. A new weakly coupled fluid–structure interaction (FSI) procedure has been developed to study downwind sails. The proposed method is parametric and automated and allows for investigating multiple kinds of sails under different sailing conditions. The study of a gennaker of a small sailing yacht is presented as a case study. Based on the numerical results obtained, an analytical formulation for calculating the sail corner loads has been also proposed. The novel proposed methodology could represent a promising approach to allow for the widespread and effective use of numerical methods in the design and manufacturing of yacht sails.

Keywords: Computational fluid dynamics | Finite element method | FSI | Gennaker | Sail design | Sail loads

Abstract: 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.

Keywords: Biological processes | Bone remodeling | Computational analysis | FE simulations | Prosthesis | Systematic review

Abstract: The left ventricle (LV) constantly changes its shape and function as a response to patho-logical conditions, and this process is known as remodeling. In the presence of aortic stenosis (AS), the degenerative process is not limited to the aortic valve but also involves the remodeling of LV. Statistical shape analysis (SSA) offers a powerful tool for the visualization and quantification of the geometrical and functional patterns of any anatomic changes. In this paper, a SSA method was devel-oped to determine shape descriptors of the LV under different degrees of AS and thus to shed light on the mechanistic link between shape and function. A total of n = 86 patients underwent computed tomography (CT) for the evaluation of valvulopathy were segmented to obtain the LV surface and then were automatically aligned to a reference template by rigid registrations and transformations. Shape modes of the anatomical LV variation induced by the degree of AS were assessed by principal component analysis (PCA). The first shape mode represented nearly 50% of the total variance of LV shape in our patient population and was mainly associated to a spherical LV geometry. At Pearson’s analysis, the first shape mode was positively correlated to both the end-diastolic volume (p < 0.01, R = 0.814) and end-systolic volume (p < 0.01, and R = 0.922), suggesting LV impairment in patients with severe AS. A predictive model built with PCA-related shape modes achieved better perfor-mance in stratifying the occurrence of adverse events with respect to a baseline model using clinical demographic data as risk predictors. This study demonstrated the potential of SSA approaches to detect the association of complex 3D shape features with functional LV parameters.

Keywords: Aortic valve stenosis | Left ventricle | Statistical shape analysis

Abstract: In this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of waterline, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g., continuity, endpoint angles, curvature) have been conceived aimed to avoid unreasonable shapes. These curves can be imported into any commercial Computer Aided Design (CAD) software and used as a frame to fit with a surface. The resistance of the hull can be calculated and plotted in order to have a real time estimation of the performances. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two existing sailboats with different characteristics have been successfully replicated and a new design, taking advantages of both the hulls, has been developed. The new design shows good performances in terms of resistance values in a wide range of Froude numbers with respect to the original hulls.

Keywords: CAD | Excel | Rational Bézier curves | Sailing yacht design | VBA | VPP

Abstract: The aim of this work is to implement a new process for the design and production of orthopaedic devices to realize entirely by Additive Manufacturing (AM). In particular, a generative algorithm for parametric modelling of flexible structures to use in orthopaedic devices has been developed. The developed modelling algorithm has been applied to a case study based on the design and production of a customized elbow orthosis made by Selective Laser Sintering. The results obtained have demonstrated that the developed algorithm overcomes many drawbacks typical of traditional CAD modelling approaches. FEM simulations have been also performed to validate the design of the orthosis. The new modelling algorithm allows designers to model flexible structures with no deformations or mismatches and to create parametric CAD models to use for the production of orthopaedic devices through AM technologies.

Keywords: Additive Manufacturing | Additively manufactured textiles | CAD modelling | Elbow orthosis | Generative algorithms

Abstract: Industry 4.0 promises to increase the efficiency of production plants and the quality of the final product. Consequently, companies that implement advanced solutions in production systems will have a competitive advantage in the future. The principles of Industry 4.0 can also be applied to shipyards to transform them into “smart shipyards” (Shipyard 4.0). The aim of this research is to implement an interactive approach by Internet of Things on a closed power-loop test bench equipped with sophisticated sensors that is specifically designed to test high-power thrusters before they are installed on high-speed crafts, which are used in passenger transport. The preliminary results of the proposed Internet of Things-platform demonstrates the efficacy of the decision-making support tool in improving the design of propulsion systems and increasing their efficiency compared to traditional systems.

Keywords: CAD modelling | Experimental tests | Industry 4.0 | Internet of Things (IoT) | Test bench

Abstract: 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.

Keywords: Additive manufacturing | Computer aided design | Elbow orthosis | Generative design | Reverse engineering

Abstract: 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.

Keywords: CAD | Finite element analysis | OPL osseointegrated prosthesis | OPRA | Transfemoral amputee

Abstract: 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.

Keywords: CAD | FEM | Implant stability | Locking plates | Reverse engineering | Tibial fracture

Abstract: 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.

Keywords: Additive manufacturing | Additively manufactured textiles | AM technologies | CAD modeling | Elbow orthosis | Generative algorithms

Abstract: Tooth loss is a common pathology that affects many people. Dental osseointegrated implants are the ideal solution to restore normal functionality in partially or completely edentulous patients. The not perfect osseointegration and the fixture fracture are the main causes of failure for these kinds of implant. To avoid these drawbacks, several studies have been conducted to analyse the behaviour of dental implants. Aim of this work is to analyse the biomechanical behaviour of three different endosseous dental implants. For this purpose, a new numerical model has been developed to simulate different levels of osseointegration and to evaluate the stress values on the bone at different times. In this way, it can be investigated the possibility of anticipating the use of dental implants that usually is delayed three months after surgery. Obtained results confirm the validity of the proposed approach and can provide useful guidelines for dentists.

Keywords: CAD | Dental implant | FEM | Osseointegration | Virtual simulation

Abstract: The current generation of transcatheter heart valves (THV), as the Edwards SAPIEN 3 Ultra (S3), is not specifically designed for mitral position implantation and has intrinsic design geometry that may make mitral implantation suboptimal. This study aimed to develop a computed-tomography (CT) based CAD workflow for the preoperative planning of transcatheter mitral valve replacement (TMVR) by evaluating the resulting obstruction in the left ventricular outflow tract (LVOT). Specifically, the computational framework to reconstruct heart anatomy and virtually deploy the THV into mitral valve annulus was developed and successively applied to the cases of two patients who experienced annuloplasty ring failure. Planimetric assessment of the cross-sectional area of the neo-LVOT was quantified at different anatomic levels of implanted THV. Findings revealed the importance of the proposed CAD modeling workflow to enable more informative pre-operative assessments of the risk related to the development of the neo-LVOT obstruction and even to guide the Heart Team regarding device selection, sizing and intended positioning for TMVR.

Keywords: CAD | Medical imaging | Reverse engineering | Transcatheter mitral valve replacement | Virtual simulation

Abstract: In this paper a multi-method approach is used to setup and validate a monitoring system applied to a small sailing boat during real sailing conditions. This monitoring system is able to transform the data coming from some typical devices installed on board into information about the deformed state of the boat. GPS, Wind Data Logger and cameras have been installed on the boat to measure its route and speed, the apparent wind velocity and direction and the positions of the crew members. These data are processed to determine the equilibrium of the boat and estimate the loads applied on it. Then, a CAD/FEM model calculates the effects of these loads on the boat shape. The resulting deformed model is compared with measurements of local strains obtained with Electrical Resistance strain gauges applied on the hull and on reinforcements of the boat. Onboard measuring devices are real-time monitored with a home-made software while the numerical prediction of the global boat deformation is obtained a posteriori once FEM computation is achieved. A test at sea has been performed to check the efficiency of the system: data computed with the proposed procedure have been compared with those coming from the field test.

Keywords: Computer aided engineering | On board monitoring system | Sailing yacht

Abstract: 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.

Keywords: CAD modelling &amp; simulation | Digital shape acquisition | Instability ratio | Reverse shoulders prosthesis | ROM

Abstract: Purpose: Massive rotator cuff tears are common in the aging population. The incidence of failed rotator cuff repairs is still quite high, especially in the treatment of full-thickness tears or revision repairs. In this context, natural and synthetic meshes can be used as augmentation scaffolds or as devices to close the gap between a retracted tendon and the bone. The purpose of this work is to evaluate the ultimate tensile strength of different tendon-patch joints in order to consider their use in the treatment of massive cuff tears. Materials and methods: Porcine tendons and a synthetic low-density polypropylene mesh have been used. A preliminary study on the tensile strength of tendons and patches has been performed. Different patch-tendon joints have been studied by modifying the number and the layout of the sutures. For every joint, the tensile test, performed through an electromechanical machine, has been repeated at least twice to obtain reliable data. Results: Experimental tensile tests on tendons and patches have given good results with very low dispersion data. Mean values of the calculated ultimate tensile stresses are, respectively, about 34 MPa and 16 MPa for tendons and patches. As regards the sutures arrangement, the staggered layout gave, for all joints, a higher tensile strength than the regular (aligned) one. Different ultimate tensile stress values, depending on the sutures number and layout, have been calculated for the joints. Conclusion: Synthetic patches could be an interesting option to repair massive cuff tears and to improve, in a significant way, pain, range of motion and strength at time 0, so reducing the rehabilitation time. Obtained results demonstrated that joints with a suitable number and layout of sutures could ensure very good mechanical performances. The failure load of the tendon-patch joint, in fact, is higher than the working load on a healthy tendon.

Keywords: Experimental test | Reverse engineering | Rotator cuff tear | Synthetic patch | Tensile strength

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.

Keywords: Computational fluid dynamics | Finite element method | Fluid–structure interaction | Gennaker | Interactive sail design | Mainsail

Abstract: 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.

Keywords: 3D acquisition | Additive manufacturing | Computer aided engineering

Abstract: 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.

Keywords: CAD model | CFD | Experimental analysis | Hydraulic actuator | Numerical simulation

Abstract: In this paper, a new approach to simulate and to optimize the performances of a crash-box, in terms of energy absorption or acceleration peak, is presented. As soon as the maximum size of the crash-box (longitudinal and transversal dimensions) has been fixed, the new approach allows optimizing the shape of the transversal section and the thickness of the structure. Thanks to the proposed procedure, engineers can easily identify the best crash-box depending on the particular working conditions. The new method has been tested with different cases study by considering different objective functions. The obtained results show the procedure works well and also demonstrate that the optimal number of edges of the transversal section and the optimal crash-box thickness strongly depend on its main dimensions and on the considered objective function.

Keywords: CAD model | Crash-boxes | Energy absorber | FEM | Optimization technique

Abstract: 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.

Keywords: CAD | FEM | Reverse engineering | Reverse shoulder prosthesis | Virtual prototyping

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: Introduction: Traditional prosthetic solutions expose the amputee to numerous problems that limit his ability to safely perform the normal activities of daily life. In order to eliminate the problems related to the use of the traditional prosthesis with socket, a new technique was developed for fixing the prosthesis to the amputees based on the principle of osseointegration. The aim of this paper is to study and analyze the stress distribution on the interface between a trans-humeral osseointegrated prosthetic implant and the residual bone, identifying the most stressed areas and thus foreseeing possible failure phenomena of the entire prosthetic system and, after, to compare the stress distribution on three different prosthetic designs that differ from each other for some geometric characteristics. Materials and methods: A healthy individual mimics two fall scenarios of which the trans-humeral amputees can most likely be victims: Static fall and Dynamic fall. A force platform (P-6000, BTS Bioengineering) is required for load data acquisition. The CAD model of the trans-humeral osseointegrated implant was created following the guidelines of the OPRA implant. The bone model was created starting from the CAT scan of a left humerus. The FEM simulation was conducted throught a linear analysis. Results: Both during static fall and dynamic fall, similar trends have been observed for the reaction force Fz, the torque moment Tz, the bending moments Mx and My. From the analysis of the von Mises stress distribution it was found that the stress distribution is more homogeneous in the case where the thread of the fixture is made by a triangular profile with height of the thread equal to 0.5 mm. However, it can be seen that, when passing from a thread with height of 0.5 mm to a 1 mm, there is a slight decrease in the stress on the whole contact zone between the fixture and the humerus. The same improvement can also be seen in the case of trapezoidal threading. Conclusion: By modifying the height and/or by varying the thread profile, are obtained slightly better results with respect to the case with a 0.5 mm height triangular thread.

Keywords: Amputees | Finite element method | Osseointegration | Prosthesis | Upper limb

Abstract: In this study, a new method to compare rebuilt surfaces of hulls of sailing yachts is presented. In particular, the considered rebuilt surfaces are created through classic reverse engineering approaches. The new method has been developed by means of Grasshopper, a free generative algorithms editor that can be used as plugin of Rhinoceros, one of the most widespread free-form modelling software. In particular, two different algorithms have been developed: the first one allows controlling the quality of the rebuilt surfaces, the second one, instead, allows to measure the deviations between the original CAD Model and the rebuilt surface of the hull. A case study related to the hull of a small sailing yacht is also presented. The obtained results have demonstrated the efficiency of the new proposed low-cost method.

Keywords: CAD Model | CAE tools | Close range photogrammetry | Generative algorithms | Low-cost reverse engineering analysis | Sailing yacht

Abstract: In this study, a comparison between two different approaches used to study a total knee prosthesis is presented. In particular, the contact area of the components of knee prosthesis has been evaluated using both a numerical and an experimental approach. The numerical analysis has been performed by FEM Models, whereas the experimental study has been conducted using an ultrasonic-based method. To setup the FEM simulations, CAD Models of the components of the prosthesis have been reconstructed using a classic reverse engineering approach. Obtained results has allowed evaluating the contact area of the components of the prosthesis and demonstrated a very good level of correlation between numerical and experimental data.

Keywords: CAD Model | Contact area | FEM | Knee prosthesis | Reverse engineering analysis | Ultrasonic methods

Abstract: 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.

Keywords: Computational fluid dynamics | Conceptual design | Numerical methods | Optimization | Sailing yacht

Abstract: 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.

Keywords: 3D printing | Additive manufacturing | Process parameters | Reverse engineering

Abstract: 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 moiré 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.

Keywords: CAD | Range of movements | Reverse engineering | Reverse shoulder prosthesis

Abstract: 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.

Keywords: B-scan image analysis | Defect definition | Laser ultrasonic testing | NDE

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.

Keywords: Air Cavity Ship | CFD | High-speed craft design | Hull ventilation | Nautical design

Abstract: This paper presents the historical development of methods used for the study of torsional stresses in shafts. In particular, the paper covers both analog methods, especially those based on electrical analogies proposed circa 1925, and numerical methods, especially finite difference methods (FDM), finite element methods (FEM) and boundary element methods (BEM).

Abstract: 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.

Keywords: Brake rotor | Fade | FEM | Thermomechanical analysis | Ventilated disc

Abstract: This article proposes a retrospective on experimental and numerical methods developed throughout the past century to solve the torsion problem in shafts, with particular emphasis on the determination of shear stress concentration factors in discontinuities of typical use in shaft design. This article, in particular, presents the theory and related solutions distinguishing between two classes of geometries: shafts with constant cross section and axisymmetric shafts with variable diameter. Emphasis is given to approaches based on physical analog methods and, in particular, those based on electrical analogies proposed since about 1925. Experimental methods based on structural physical models and numerical formulations are also reviewed, and a number of results from different approaches are collected and compared for two typical design case studies: a constant section shaft with a keyway and an axisymmetric shaft with a shouldered fillet.

Keywords: Electrical analogies | Experimental stress analysis | Keyway | Numerical methods | Shaft in torsion | Shouldered shaft | Stress concentration

Abstract: 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.

Keywords: Evolutionary structural optimization | FEM | Numerical methods | Topology optimization

Abstract: 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.

Keywords: CAD modelling | Digital shape acquisition | Reverse shoulder prosthesis

Abstract: 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.

Keywords: Corrugated Core | Finite Element | Homogenisation | Sandwich Structures

Abstract: 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. © 2014 Springer-Verlag France.

Keywords: 3D scanner acquisition | Non linear FEM analyses | Reversed shoulder prosthesis | Shoulder stability ratio

Abstract: 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. Purpose: 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. Results: 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. © 2013 Istituto Ortopedico Rizzoli.

Keywords: FEM analyses | Intrinsic stability | Polyethylene wear | Stability ratio | Total reverse shoulder arthroplasty

Abstract: 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. © 2012 Springer-Verlag London Limited.

Keywords: Numerical crash analysis | Optimization | Simplex | Simulated annealing

Abstract: 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 Moirè 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. © 2012 Springer-Verlag.

Keywords: Contact analysis | FEM simulation | Total knee replacement

Abstract: 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.

Keywords: FEM | Roller muzzle | Speargun | Strain gauges

Abstract: The detection of surface defects during periodic inspection is important because, usually, the stresses are higher at the surface, thus affecting the growth of the discontinuity. Surface defects can be detected using some traditional non-destructive testing methods, such as eddy current, dye penetrant, magnetic particle and ultrasonic. Some of these methods can be used only in static conditions; the others have limitations for the dynamic inspection. The recent progress in the field of non-contact ultrasonic sensors has led us to develop a simple system for the real-time inspection of moving bodies at a high speed. The paper presents the possibility of using, with the developed system, two methodologies, based on non-contact ultrasound, to detect surface defects on objects moving at 100 km/h, so that in service inspection is possible. A methodology, based on laser and air-coupled sensors, uses the advantages of laser-generated surface waves; the analysis is done on the reflected wave, created by the interaction of the surface wave with the defect. The inspected surface layer can be selected from the wavelength of the surface wave. The other methodology, based on air-coupled sensors, uses the disadvantages of the ultrasound transmission at the air/metal interface; the analysis is done on the diffraction of the wave reflected from the surface. The execution of the inspection is simple with both techniques. The experimental results indicate a good efficiency of the two methodologies proposed for the real-time detection of surface defects on objects moving at high speed.

Abstract: In this paper the optimization process of a new High Energy Absorption Rear Underrun Protective Device called HEARUPD is discussed. The main objectives of the HEARUPD design optimization process have been related to the reduction in car decelerations (high crashworthiness) and avoiding the car underrun (high structure stability). In the implemented optimization process, the crash between an economy car (GEO Metro) and the rear part of a truck has been simulated by numerical models. A linear function of the decelerations measured on the car has been used as objective to minimize, the main dimensional values of the rear underrun protective device, instead, have been chosen as design variables. The Simplex Method has been used as optimization technique. At the end, a detailed analysis of the optimized model has been also performed. The obtained results have shown the HEARUPD, in comparison with a reference device, is able to dissipate a higher quantity of energy, reducing both the deceleration peaks and the frontal car crushing. © Organizing Committee of TMCE 2010 Symposium.

Keywords: Crash test | Finite element method analyses | Optimization | Rear underrun protective device | Simplex method | Truck

Abstract: The paper presents a methodology aimed at the improvement of the product development cycle through the integration of Computer-Aided Innovation (CAI) with Optimization and PLM systems. The interoperability of these tools is obtained through the adoption of Optimization systems as a bridging element between CAI and PLM systems. This methodology was developed within the PROSIT project (http://www.kaemart.it/prosit). The paper describes the main issues related to the integration of these complementary instruments and the solutions proposed by the authors. More specifically, the main idea of the PROSIT project to link CAI and Optimization systems is the adoption of the latter tools not just to generate optimized solutions, but also as a design analysis tool, capable to outline critical aspects of a mechanical component in terms of conflicting design requirements or parameters. CAI systems are then applied to overcome the contradictory requirements. The second step, i.e. the integration between Optimization and PLM systems, has been obtained through the development of Knowledge-Based (KB) tools to support designer's activities. More in details, they provide means to analyze and extrapolate useful geometrical information from the results provided by the optimizer, as well as semi-automatic modelling features for some specific geometries. A detailed example related to the design of a plastic wheel for light moto-scooters clarifies the whole procedure. The paper integrates, extends and updates topics presented in Cugini et al., Barbieri et al. and Cascini et al. [U. Cugini, G. Cascini, M. Ugolotti, Enhancing interoperability in the design process-the PROSIT approach, in: Proceedings of the 2nd IFIP Working Conference on Computer-Aided Innovation, Brighton (MI), USA, October 8-9, 2007, published on Trends in Computer-Aided Innovation, Springer, ISBN 978-0-387-75455-0, pp. 189-200; L. Barbieri, F. Bruno, M. Muzzupappa, U. Cugini, Design automation tools as a support for knowledge management in topology optimization, in: Proceedings of the ASME 2008 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2008), Brooklyn, New York, USA, August 3-6, 2008; L. Barbieri, F. Bruno, M. Muzzupappa, U. Cugini, Guidelines for an efficient integration of topological optimization tools in the product development process, in: Third International Conference on Design Computing and Cognition, Atlanta, USA, June 23-25, 2008; G. Cascini, P. Rissone, F. Rotini, From design optimization systems to geometrical contradictions, in: Proceedings of the 7th ETRIA TRIZ Future Conference, Frankfurt, Germany, November 6-8, 2007]. © 2009 Elsevier B.V. All rights reserved.

Keywords: Computer-Aided Innovation | Knowledge-Based Engineering | Optimization systems | Product Lifecycle Management

Abstract: This paper describes a new methodology that, making use of a haptic device, can simulate the palpation, a diagnostic manoeuvre aiming to verify the condition of internal organs or anatomical formations. In the developed application, that has the purpose to pick out an anatomical formation and understand its characteristics, the palpation of a soft tissue has been taken in consideration. Particularly the fingertip, the skin and an anatomical formation have been simulated. The user, handling the haptic system at disposal can feel the contact with the skin but also perceiving the presence, the shape and the dimension of the subcutaneous formation (invisible to the operator), that has been modelled as a rigid sphere (like a nodule). The evaluation of the skin deformations, following from the palpation, has been performed through a massspring based algorithm, which allows to obtain results in real time.

Keywords: Haptic | Palpation simulation | Virtual reality

Abstract: In recent years the vehicle design field has followed a progressive evolution by focusing its main interest on passive and active safety levels. One of the most injurious cases for the safety of passengers is the crash between a car and a heavy vehicle (truck). Generally, in fact, when such an occurrence happens, the greatest damage is suffered by the passengers of the car. This is because of the considerable structural difference between the two vehicles and the lack of devices to reduce the injuries of the car passengers. In this work, as a consequence of the previous considerations, we deal with the design of a new protective system for heavy vehicles over 3.5 tons. The new rear underrun protective device presented here, compared to the traditional one, can dissipate a greater amount of energy; this reduces the damage suffered by the passengers of a car involved in an impact with a truck. To simulate the behaviour of the new protective device during different kinds of crashes, dynamic finite element method (FEM) analyses have been carried out. The comparison between the new protective system and the standard one has shown that the new designed protective system has better performances in terms of energy absorption and peaks of decelerations.

Keywords: Crash analyses | FEM | RUPD

Abstract: Adhesively bonded multi-layer structures are frequently used, mostly in the aerospace industry, for their structural efficiency. Nondestructive evaluation of bond integrity in these types of structures, both after manufacturing and for periodic inspection during service, is extremely important. A laser-based ultrasonic technique has been evaluated for non-contact detection of disbonds in aluminum multi-layer structures. Two configurations have been used to detect disbonded areas: pitch-catch with unidirectional guided wave scan and through-transmission with bidirectional scan. Guided wave scanning was done with a laser line source and air-coupled transducer sensing at 500 kHz, 1 ;MHz, and 2 MHz. Signals showed attenuation of the main frequency component and frequency shift on disbonded areas, whereas, a regular and standard waveform is seen outside disbonds. In through-transmission the longitudinal wave at normal incidence was monitored with a 1 MHz probe. One sample showed, besides the introduced inserts, other disbonded areas. After the ultrasonic measurements the sample was cut to visually check adhesive and interfaces. The guided wave pitch-catch scan allowed fast inspection and quick indication of disbonded zones, while the through-transmission C-Scan provided better definition of defects but was slower and required access from both sides of the test part.

Keywords: Guided waves | Laser ultrasound | Multi-layer structures

Abstract: A three-dimensional finite-element simulation was conducted for a split-sleeve cold-expansion process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming processes, was used to model the cold-expansion process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved.

Keywords: Cold-expansion of holes | Fastener holes | Finite-element simulation | Residual stress

Abstract: The paper describes results of methodical activity performed by employing inventive principles of the theory for the inventive resolution of problems (TRIZ), in order to obtain concept of rear underrun protective device for an industrial vehicle. A screening with concepts proposed in previous papers is also performed.

Keywords: Conceptual design | TRIZ

Abstract: Current in-field rail track ultrasonic inspection technologies, requiring contact between the probes and the rail surface, show limitations as defect detection is affected by rail surface condition, rail head geometry and defect geometry and orientation. Moreover, inspection speeds are moderate. To improve rail flaw detection, the partnership of the U-Rail project - within the sixth EU framework programme - proposes a new non-contact ultrasonic inspection system, consisting of a pulsed laser and air-coupled transducers. For a proper positioning, the inspection unit includes a laser optic triangulation unit and an automatic positioning system. The first determines the position of the rail, processes the data and drives the positioning system. The U-Rail system allows high speed inspection of the complete rail section. The paper describes the system and results of research activities of two U-Rail partners. © The Eurographics Association 2007.

Abstract: In order to keep or to reach a high level of competitiveness and performance of a product, it is necessary to explore all the possible solutions that allow the best compromise between costs and project requirements. By this point of view the study of alternative designs and/or materials to use, is an important aspect that can identify a new concept or way of thinking about a product. This paper presents how to make use of composite materials in the field of heavy vehicles transportation. A new semitrailer in composite material has been designed, using a methodical redesign approach and an optimisation process. The main innovation in this project is, besides the use of the Glass Fibre Reinforced Plastics (GFRPs), also a new topology of the vehicle frame; the designed semitrailer, in fact, has a monocoque structure. Copyright © 2007 Inderscience Enterprises Ltd.

Keywords: Composite material | Redesign process | Semitrailer | Structural frame

Abstract: The use of air-coupled sensors to detect flaws in Al welded joints and the advantage of Lamb wave for their characterization has been proved. Ultrasonic waves were generated by a pulsed laser and by contact angle-beam transducer, and received by an air-coupled capacitive transducer. Laser-based configuration was used to quickly locate the defect, whereas the angle-beam contact probe configuration to characterize it thanks to the dispersive behavior of Lamb waves. Guided waves allow inspection of the complete thickness with only one scan, permitting to detect and to size both internal and surface defects; their high flexibility in the measurement is due to the various parameters characterizing their behavior when compared to the bulk waves. Moreover, L-scan configuration can be used to inspect single-side access structures, and compared to the conventional A, B, C and P-scan allows to reduce inspection time, and therefore the related costs. © 2006 Elsevier B.V. All rights reserved.

Keywords: Air-coupled transducer | Lamb waves | Laser generation | Non-contact ultrasonic inspection | Welded joints

Abstract: Fade test results of ventilated disk brake rotor with pegs-wing performed by means of an inertia dynamometer, consisting of 14 repeated brake applications from an initial brake speed of 160 km/h down to 0 km/h, with constant deceleration are shown. The first brake application test results are compared to the FEM numerical predictions with MSC Visual Nastran on the ntire disk. These conform well to the experimental data, although numerical thermal field is slightly higher than the experimental one. Besides, ventilated disk brake rotor shows great dimensional stability and the ability to dissipate a great amount of thermal flow. © 2006 Inderscience Enterprises Ltd.

Keywords: brake temperature | disk brake rotor | fading testing procedure | finite element analysis | friction coefficient | thermal stress

Abstract: The results of the braking numerical simulations on a pegs-wing ventilated disk brake rotor, obtained by performing a fading braking procedure, are compared with the experimental ones obtained in the same brake, mounted on a work bench, in the same fading braking procedure. The numerical simulations are performed on the entire disk, besides some structural parameters, thermal conductivity, specific heat and elastic modulus, are considered as a function of the temperature; the other parameters are considered as constant. The results of the numerical simulations are in a good agreement with the experimental ones. It is also shown that numerical calculations can be considered conservative, since the numerical thermal field is a little bit higher than the experimental one. Furthermore the pegs-wing ventilated disk brake rotor is able to dissipate a great amount of thermal flux showing a great dimensional stability.

Keywords: Caliper | Disk brake rotor | Fading testing procedure | Finite elements | Pads | Thermal stress

Abstract: Redesign of a product becomes necessary as a consequence of the evolution of the market requirements, of the man creativity, of the influence of the environmental factors, of the technological development etc. The redesign activity, especially in a context of exasperated economic competition, has become a crucial point in order to try to increase the competitiveness, if not even the life, of a product and/or a company. The redesign must allow the resumption of the increasing process of the performances. This aim requires a methodical and structured approach, which can also cause the modification of the standard conception of the product. In this paper the possibility to reduce the mass of a semitrailer is analysed, modifying its structure. Various solutions have been considered, characterized also by new topology and/or materials, and between all of them the one constituted from a structural floor in composite material has been chosen. © 2005 WIT Press.

Keywords: Composite material | Redesign | Semitrailer | Structural floor

Abstract: The results of an experimental study conducted to detect subsurface defects in a thick Gr/PPS composite test sample using a non-contact ultrasonic system are presented. Surface waves are generated by a pulsed laser and detected by a air-coupled capacitance transducer. By controlling the surface wave wavelength through a shadow mask, it is possible to control surface wave penetration depth in the sample. Surface wave peak-to-peak amplitude is related to the near-surface material condition. Results indicate that signal amplitude decreases as the width of the defect increases and an approximately linear relation can be deduced.

Abstract: In this paper are calculated stress concentration factors in collar and shouldered shafts subjected to axial or bending load, using both the boundary element (BEM) and finite element (FEM) methods. The values obtained by the two methods are in good agreement; for shouldered shafts in bending they are also very close to the available data in the literature obtained by the photoelastic technique. For shouldered shafts in traction, the values obtained are close to some experimental data of the literature and higher than others. Additionally, BEM and FEM values are interpolated in order to give useful plots and formulae. © 1998 Elsevier Science Ltd.

Keywords: Boundary element | Finite element | Stress concentration factor

Abstract: In a previous work the stress intensity factors of shouldered and collar shafts are determined by a boundary element method (BEM) analysing the influence of the ratios between shaft and collar diameters, between the rounded fillet radius and shaft diameter, between length and height of the collar. In general the values obtained are lower than experimental values of the literature, hence it seems advisable to compare results with those obtained by another numerical method. In addition to studying other configurations by BEM, stress concentration factors are hence calculated by a finite element method (FEM) and compared with the BEM and literature results. BEM and FEM values are interpolated in order to give useful plots and a formula. © 1995.

Keywords: boundary element method | collar shaft in torsion | shouldered shaft in torsion | Stress concentration factor