Abstract: Water distribution systems can experience high levels of leakage, originating from different sources, such as deterioration due to aging of pipes and fittings, material defects, and corrosion. In addition to causing financial losses and supply problems, leakages in treated water distribution also represent a risk for public health. Despite several techniques for leak detection are already available, there is still a lot of interest in new non-invasive approaches, especially for scenarios where acoustic techniques struggle, such as in noisy environmental conditions. In this work we investigated the possibility of using cosmic ray (CR) neutrons for the detection of underground leakages in water distribution networks, by exploiting the difference in the above ground thermal neutron flux between dry and wet soil conditions. The potential of the technique has been assessed by means of an extensive set of Monte Carlo simulations based on GEANT4, involving realistic scenarios based on the Italian aqueduct design guidelines. Simulation studies focused on sandy soils and results suggest that a significative signal, associated with a leakage, could be detected with a data-taking lasting from a few minutes to a half-hour, depending on the environmental soil moisture, the leaking water distribution in soil, and the soil chemical composition. Finally, a brief description of a new portable and low-cost detector for thermal neutrons, currently under commission, is also presented.

Keywords: Cosmic ray neutrons | CRNS | Thermal neutrons | Water leakages

Abstract: At Legnaro National Laboratories of the Italian National Institute for Nuclear Physics, Design for Assembly principles were applied to ease and improve the assembly procedure of the Forced Electron Beam Induced Arc Discharge ion source for the SPES Isotope Separation On-Line facility. Such device is a key component for the whole system, as its correct functioning is fundamental to provide the radioactive ion beam to the experimental users; furthermore, its reliability and performance stability are directly affected by the construction and placement accuracy of the parts that compose the assembly. A deep critical analysis of the current assembly procedure was performed to identify the main issues that affect the mounting accuracy of the ion source components. Consequently, a new assembly procedure was developed to fix the identified issues without applying relevant modification to the ion source parts; specifically, a custom assembly tool was designed not only for an easier coupling of the components, but also to improve the accuracy of the functional surfaces positioning to increase the device performance stability during operation. To achieve this, a custom assembly tool was designed to reduce the number of the elements of the tolerance stackup and, therefore, the uncertainty propagation. The proposed assembly procedure results significatively less time consuming than the current one, moreover it improves the accuracy of the FEBIAD ion source components position once assembled, as confirmed by Coordinate Measuring Machine measures.

Keywords: assembly tool | Design for assembly | Geometrical Product Specifications | Tolerance analysis

Abstract: The idea presented in this contribution stems from the authors’ interest and previous experience in designing aids for individuals with disabilities in the field of Accessible Tourism - AT. Specifically, the focus has been directed towards devices utilized in the seaside sector, with an analysis conducted on beach wheelchairs. The study involved both a market analysis and an examination of the regulatory framework. Two main results were obtained. Firstly, the analysis of the regulatory framework revealed potential challenges in interpreting rules and regulations, particularly regarding design, safety, and testing requirements. Secondly, the market analysis demonstrated that all currently available devices necessitate users switching from their personal wheelchairs to beach wheelchairs. Considering these findings, a conceptual solution is proposed to adapt one’s personal wheelchair for movement on sandy terrains. This solution entails a kit comprising beach wheels mounted on a lightweight frame, potentially incorporating a self-propelled device to replace the manual wheelchair’s existing wheels. It is important to note that this solution is intended to supplement existing beach wheelchairs rather than replace them, thereby broadening the options available to individuals with mobility impairments.

Keywords: Accessible Tourism | Assistive products | Beach wheelchairs | Design methods | User-Centered Design

Abstract: The Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing (AM) technology suitable to produce almost free-form metallic components. At Legnaro National Laboratories (LNL) of the Italian National Institute for Nuclear Physics (INFN), the LPBF process was recently used to produce parts of the Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source for the SPES Isotope Separation On-Line (ISOL) facility. In this work are presented the feasibility assessment and production steps of tantalum cathodes produced via AM; in addition, the results concerning both the dimensional–geometrical measurements and the preliminary high-temperature test are reported.

Abstract: The Geometrical Product Specification (GPS) and the Geometrical Dimensioning and Tolerancing (GD&T) are communication languages to code the tolerable morphology of manufactured parts and assemblies. Both languages should be unambiguous tools to communicate such information between designers, process engineers, and Coordinate Measuring Machines operators (CMM). GPS is the one developed in the ISO (International Organization for Standardization) environment. GPS language is a complex code of 143 standard with further 15 under development. Moreover, as in each complex body of standards, most of them recalls other standards in a very intricate manner. So, the need to have a flexible tool to search and navigate through the standards is great, as is the need to optimize the work of the designer and to minimize the design, production, and control costs. The basic effort in building such a tool has been the development of the database and the structure for the search engine, called “GPS Navigator”. In the following, the requirements for the coding phase have also been issued, to realize a powerful, efficient, fast, robust, and rigorous tool to navigate through the GPS standards. The final step of the “GPS-Navigator project” is the delivery of a software tool able to help and guide the designer to quickly consult the appropriate standard or set of standards.

Keywords: Advanced search criteria | Database | Design methods | Geometrical product specifications (GPS)

Abstract: Due to the pandemic, there has been a shift from conducting paper-based in-person exams to conducting online exams. To still be able to evaluate students, a closed-ended test was implemented to verify the skills acquired by the exam candidates. We have developed on Moodle platform an online test called Technical Drawing Test (TDT2) based on graphic questions with closed answers both single and multiple, replacing the open-ended graphic questions of the previous in-person paper exam mode and with the same contents. This article aims to show the method by which the types of exercises were chosen according to the skills to be tested and to present the first results obtained, with the goal of verifying that the new test is equivalent to the old paper-based open-ended test in its ability to test candidates’ skills. The reliability of the TDT2 is quantified through two statistical synthetic indexes calculated by the Moodle platform and comparing the results of the online TDT2 with the results of the paper-based in-person exams.

Keywords: Engineering education | Moodle | Technical drawing | Testing methods

Abstract: To better understand the connection between cosmic rays and atmospheric parameters, both on a local and global scale, the COMMAND project aims to build a prototype detector that can simultaneously measure the flux of cosmic neutrons and muons, and that can also allow the tracking of the latter. Many people and different scientific fields are involved: physicians, mechanical engineers, and electronics engineers, and speaking the same language is not always simple. Therefore, before starting the design of the prototype a clear definition univocal and not ambiguous requirements was necessary and useful. We tried to break the problem down into manageable chunks by identifying three macro subcategories, which are: (i) type of use; (ii) structure of the device; (iii) working environment. Each of these subcategories were examined and the device requirements were defined to proceed with the definition of the current device: the dimensions, the shape, the functionalities, the choice of materials and technologies, the respect of geometrical constraints, the budget limits, the electronics interfaces. Then the device has been designed and manufactured, and some preliminary tests have been performed to verify the proper operation and compliance with all constraints. In this work, we will present the solutions adopted, and the design choices followed to the analysis of the requirements, in some cases, also thanks to the realization of study proof-of-concept models.

Keywords: Design methods | Proof-of-concept | Requirements assessment

Abstract: The alternation of dry and wet contact causes a complex interaction of various damage mechanisms in railway wheels. To study the damage evolution in such condition, rolling-sliding contact tests in alternated dry-wet contact were carried out by a bi-disc machine on specimens extracted from railway wheels. The effect of different durations of the dry and wet sessions was investigated. Two kinds of tests were done: in one case coupling two cylindrical specimens, in the other one coupling a cylindrical specimen with a crowned one. The surface appearance during the tests was acquired by a vision system; the acquired images were elaborated to extract quantitative damage indexes. At the end of the tests, the specimens were cut and analysed, to evaluate the subsurface damage and the strain hardening. In cylindrical-cylindrical coupling, the damage increased in alternated dry-wet sessions as far as the cycle number increased, whereas it was stabilized in long dry sessions. The prevailing phenomenon, occurring during the wet sessions, was fatigue, promoted by the pressurization of the water entrapped in the cracks previously formed in dry contact. In crowned-cylindrical couplings, the damage tended to decrease as far as the cycles increased, in all the test conditions. This was correlated to the widening of the contact patch caused by wear, which led to an overall stress relaxation, this way mitigating the damage. The results highlighted the double role of wear, which alters the optimum wheel profile, but at the meantime relaxes the overall stress state and mitigates rolling contact fatigue.

Keywords: Damage monitoring | Dry-wet contact | Railway wheel steel | Rolling contact tests | Vision system

Abstract: According to the activities carried out within the Proof of Concept laboratory, a machine for block-on-ring wear tests was designed and realized. Consistent with the approach of the laboratory, the machine was developed with particular attention to the requirements of reliability, simplicity, as well as easy and fast production starting from existing devices integrated with ad-hoc made parts by the department equipment. The experimental campaign was performed according to ASTM G99 and ASTM G77. The results obtained on commercial pin-on-disc device and on the realized block-on-ring machine, showed a good agreement, validating the proposed solution. This appears particularly effective also based on an economic and technical comparison with commercial equipment complying with the same standard.

Keywords: Design and test | Design methods | Machine design

Abstract: The promotion of creativity in education is intended to address many of the political challenges and goals for the development of a country, but among all of them the role of creativity in technology and economics is seen as crucial in helping nations to achieve higher employment, better economic performance and to cope with global competition. This study, currently in its preliminary phase, aims to compare the creativity levels of first-year students at a medium-sized Italian university. The degree courses in Engineering Management, Mechanical Engineering, Law and Motor Sciences were analyzed. In this analysis, students’ creativity is measured with the “Forward Flow” test by Gray et al. This test implements a new metric that uses latent semantic analysis to measure the evolution of thoughts over time. Operationally, students are asked to produce a sequence of semantically related words from a given initial word. Latent semantic analysis calculates the semantic distance between words by examining the frequency with which they appear together in a very large collection of documents. Studies conducted on the test, found in the literature, reveal that Forward Flow can predict the creativity of college students. According to these studies, even that membership in real-world creative groups (e.g. professional actors or entrepreneurs) is statistically predicted by scores on the Forward Flow test, even when controlling for divergent thinking.

Keywords: Creativity | Engineering education

Abstract: The Geometrical Product Specification (GPS) is one of the most powerful tools available to link the “perfect” geometrical world of the models to the imperfect world of manufactured parts and assemblies. GPS aims to be an unambiguous common language between designers, process engineers, and Coordinate Measuring Machines operators (CMM) in the ISO (International Organization for Standardization) environment. GPS standards are 150 and further 26 are under development. The need to have a tool to search through the standards, to optimize the work of the designer and to minimize the design, production and control costs is great. A database and the structure for a search engine, called GPS Navigator, has been studied and developed, and the requirements for the following coding phase have also been defined, in order to realize a powerful, efficient, fast, robust and rigorous tool to navigate through the GPS standards. Final aim of this tool is to help and guide the designer to quickly consult the correct standard or the most appropriate set of standards.

Keywords: Advanced search criteria | Database | Design methods | Geometrical product specifications (GPS)

Abstract: Small-scale experimental tests were carried out by a bi-disc machine to reproduce the phenomena occurring in shoe-braked railway wheels. Wheel specimens of three different steels were subjected first to a braking step against cast iron brake-block specimens in full sliding condition, then to a running step against a rail steel in rolling-sliding condition. To monitor the damage occurring at the wheel specimen surface, a vision system, based on a high-speed camera acquiring the surface images during the tests, was implemented. An image analysis procedure was elaborated to evaluate the surface state by means of quantitative synthetic indexes. The correlation of such indexes with the damage was validated by means of comparison with the subsurface state, obtained by optical microscope observation of cut specimens. Finally, the synthetic indexes were used to analyse the evolution of the damage on a long-duration test, proving to be effective as a non-destructive damage monitoring tool.

Keywords: Bi-disc tests | Damage analysis | Railway wheel steels | Shoe-braking | Vision system

Abstract: Tests in alternated dry-wet contact were carried out by a bi-disc machine on specimens extracted from railway wheels. Some of them were cylindrical, other ones were crowned: cylindrical-cylindrical and crowned-cylindrical couplings were tested. The surface appearance was acquired by a vision system; the acquired images were elaborated to extract quantitative damage indexes. In cylindrical-cylindrical coupling, the damage increased in alternated dry-wet sessions as far as the cycle number increased, whereas it was stabilized in long dry sessions. In crowned-cylindrical couplings, the damage tended to decrease as far as the cycles increased, in all the test conditions. The contact patch width in crowned-cylindrical coupling increased as far as the cycle number increased: this led the overall stress state to decrease, this way mitigating the damage.

Keywords: damage monitoring | dry-wet contact | Railway wheel steel | rolling contact tests | vision system

Abstract: This work is part of the project called “Gölem project”, started in 2017, about special devices developed to enable the so-called Accessible Tourism. This project aims to design and develop a trekking wheelchair for people with impaired mobility. After an initial phase of design and prototyping, the testing phase has now begun. The objective is to validate several aspects of the design, concerning basic kinematics and dynamics, passenger comfort and physical effort of the carriers. This paper describes the development of qualitative tests for drivability and balance validation of this first prototype. At this stage, a list of features to be investigated was made, suitable trekking paths were chosen, and qualitative experimental field tests were performed. Then, the design of the prototype was modified according to these first experimental results, to improve the wheelchair characteristics. The prototype is now undergoing the modification phase, then further testing will be performed with the use of specific instrumental devices to evaluate the wheelchair itself and to perform the kinematic, dynamical, and comfort characterization.

Keywords: Accessible tourism | Assistive technologies | Design methods | Disabled people | Experimental testing | Hiking wheelchair | Trekking wheelchair | User-centered design

Abstract: The dynamical behaviour of the Bronze Age war chariots was studied, considering the different assembly solutions that were found in evidences and pictures. In particular, the chariots with the axle in rear position, typical of Near-East and Egypt, were compared with the European ones, which generally had the axle in central position under the chariot cockpit. Furthermore, the role of the floor, usually realized in woven leather or other organic fibres, was investigated. Dynamical finite element and multibody simulation software was used for studying the behaviour of the chariots in occasional overloading events, such as bumps or curves. An experimental device was set up for studying the difference of the response of a woven floor with respect to a wooden one. Finally, a finite element frequency response analysis was carried out to investigate the behaviour in full run over a rough ground. The results showed that position of the axle did not significantly influence the response of the chariot to occasional overloads. On the contrary, it had a strong influence on the stability of the passengers: rear axle chariots were much more effective in cutting the vibrations transmitted to the passengers when running at high speed. This effect was amplified by an increased floor flexibility, which was achieved with a woven floor. These findings could explain the diffusion of the rear-axle chariots in the Near-East and Egypt, where the chariotry was the most important part of the armies: indeed, the effectiveness in cutting the vibrations at high speed should be a crucial factor for ensuring the required precision to the transported archers. On the contrary, the likely marginal role of the chariots in the European armies could lead to the diffusion of central axle model, which ensured a lower burden on the draught horses.

Keywords: Bronze age | Chariots | Dynamics | Stability | Vibrations | War

Abstract: This study shows the application of a system to monitor the state of damage of railway wheel steel specimens during rolling contact fatigue tests. This system can make continuous measurements with an evaluation of damage without stopping the tests and without destructive measurements. Four tests were carried out to train the system by recording torque and vibration data. Both statistical and spectral features were extracted from the sensors signals. A Principal Component Analysis (PCA) was performed to reduce the volume of the initial dataset; then, the data were classified with the k-means algorithm. The results were then converted into probabilities curves. Metallurgical investigations (optical micrographs, wear curves) and hardness tests were carried out to assess the trends of machine learning analysis. The training tests were used to train the proposed algorithm. Three validation tests were performed by using the real-time results of the k-means algorithm as a stop condition. Metallurgical analysis was performed also in this case. The validation tests follow the results of the training test and metallurgical analysis confirms the damage found with the machine learning analysis: when the membership probability of the cluster corresponding to the damage state reaches a value higher than 0.5, the metallurgical analysis clearly shows the cracks on the surface of the specimen due to the rolling contact fatigue (RCF) damage mechanism. These preliminary results are positive, even if reproduced on a limited set of specimens. This approach could be integrated in rolling contact fatigue tests to provide additional information on damage progression.

Keywords: Damage assessment | Machine learning | Metallurgical analysis | Rolling contact fatigue tests

Abstract: SPES (Selective Production of Exotic Species) is a large facility, currently under advanced construction at the INFN-LNL (Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro) for the production of Radioactive Ion Beams (RIBs). Coordinated efforts are being dedicated to the development and upgrading of both the accelerator complex and the up-to-date experimental set-ups. This paper describes a work of upgrading as far as the inspection and maintenance of the system is concerned, and it deals with human-centered design methods to reduce the time spent in the radioactive environment of the facility during ordinary maintenance operations and to simplify them, also considering stress conditions of the operator and the mandatory wearable radiation protection devices (such as tracksuit, gloves, oxygen tank mask) which make simple operations difficult.

Keywords: Design methods | Ergonomics | Functional design | Human-centered design | Proof of concept

Abstract: A vision-based experimental methodology was developed for monitoring the surface state evolution of specimens during twin-disc rolling contact tests, aimed at providing information for identifying the damage phenomena. The system is based on a high-speed camera and three laser pointers for illuminating the specimen surface. Images of the specimen surface are acquired and processed, allowing the definition of synthetic surface state indexes, as well as the section profiles of the surface. The vision system was applied to alternated dry–wet rolling–sliding contact tests on railway wheel steel specimens, highlighting its effectiveness in the damage evaluation. The potential of the section profile reconstruction as a tool for surface topology analysis was shown.

Keywords: damage assessment | image processing | Online monitoring | rolling contact fatigue | wear

Abstract: The introduction of two-wheel chariots, pulled by horses, was a key technological innovation in the Bronze Age. Archaeological evidences, found in Northern Africa, Europe and Asia, allowed identifying various chariot typologies and understanding their main features. However, many questions about the function of single pieces and the behavior of the vehicles are still open. In a previous work, a war chariot wheel, found in northern Italy and known as the “Mercurago wheel”, was studied with an engineering approach. In this paper, the whole vehicle, to which the wheel was hypothesized to belong, was studied. In particular, two chariot typologies, differing mainly for the axle position, were analyzed. The stiffness of the various chariot parts were characterized by means of static finite element analyses. These data were subsequently used as input parameters in running multibody dynamics simulations. Finite element dynamical simulations were carried out as well. The analyses results allowed determining the crucial effect of some parts, particularly the cockpit floor, in favoring the passenger stability in dangerous conditions, such as bumping. The effect of the axle position on the passenger and wheel trajectory were evaluated as well.

Abstract: A study of the residual activation of the Front-End system structure of the SPES (Selective Production of Exotic Species) facility, currently under construction at the Legnaro National Laboratories of INFN, Italy, is performed. The study provides useful information for the planning of inspections, maintenance operations and decommissioning of the facility as well as for the assessment of radiological conditions and safety requirements in the design and operation of any accelerator-driven radioactive ion beam facility. To better assess the obtained results, two Monte Carlo codes were independently used: MCNPX combined with CINDER’90 and FLUKA. The results of the two calculation procedures are compared at each step: fissions, fluxes, activation, dose rate. Since the energy range considered does not represent a typical application for any of the two codes, the comparison of the collected results can provide useful inputs for the developers. In particular, the agreement of the two codes on the global quantities is good, being of the order of 20–40% on average, and never larger than a factor 2. Nevertheless, the comparative study shows that, in this energy range, FLUKA seems to underestimate the angular straggling of protons and to overestimate the proton interaction cross-sections, with respect to MCNPX.

Abstract: The aim of this work is to study methods and criteria to objectively evaluate Geometrical Product Specification (GPS) and Geometrical Dimensioning and tolerances (GD&T) basic skills of engineering students. To do so, it is important to define who is the examiner, what is the topic of the exam, how to examine, when and why. In particular, for what concerns the topics, knowledge, competences, skills, concepts and abilities should be assessed. Basic knowledge is the easier topic to evaluate in an objective and reliable way, for example using closed-ended questions, but skills like creativity are difficult to measure. Following the principles of Bloom’s taxonomy, a technical drawing evaluation grid has been developed and used by the authors. The grid has eight learning levels, and target knowledge, competences, and skills have been defined for each learning level, then specific tests to verify the target for each level have been studied and developed. In this paper some examples of application of the grid are described and some preliminary results and considerations are reported. In particular, using an objective closed-ended question test, which rigorously assesses the basic levels of the grid, “residual” students decrease in number, and the students increase in number, the test is cost-effective.

Keywords: Bloom’s taxonomy | Engineering education | Engineering students evaluation | GPS/GD&T | Technical drawing

Abstract: The purpose of this work is to help the little patients of the Paediatric Onco-Haematology Department of the “Monica and Luca Folonari” bone-marrow Transplant Centre to tackle their anxiety and worries when subjected to Magnetic Resonance Imaging (MRI) clinical examinations, in order to reduce the period of time between the arrival of a patient in the Diagnostics Department and the actual exam execution. To do so, following the principles of the Medical Play Therapy, a user-centred role play called JUNIOR-MRI has been developed. The game is addressed at children between the ages of 5 and 10 and consists of a scaled model of a real MRI machine, with a gurney, a patient doll and a control station. A tablet application has also been developed to simulate the procedure of the clinic exam, reproduce the real sounds of a MRI through a loudspeaker placed on the scale MRI and show some fake images of the investigation carried out on the doll. The child plays the role of the doctor, getting acquainted with the exam procedure and instrumentation and learning not to fear the clinic exam. The experimental phase of the game has begun, and the JUNIOR-MRI is now used in the Pediatric Diagnostics Department of the Spedali Civili di Brescia, following an ad-hoc clinic protocol.

Keywords: Design methods | Medical Play Therapy | Role play | User-centred design

Abstract: This work deals with the description of the activities developed in the PoC-BS laboratory. In particular, it is proposed first to provide a multidisciplinary definition of Proof of Concept - PoC - and then to illustrate the design-methods-based approach used in the laboratory for the development of different types of PoC. In particular, the presentation of the integrated approach, for the realization of different types of PoC is provided through the description of some examples of activities carried out to support experimental research. In this work we describe: (i) the construction of a cosmic-ray telescope in collaboration with the group of Experimental Physics, (ii) the design and manufacture of devices for qualitative evaluation of the drying process of sludge generated by the inertization of waste incinerator fly-ash, carried out with the group of Chemistry for Technologies. In conclusion, the paper focuses on the future prospects of the Laboratory, whose ambition is to consolidate its activity and to lay the foundations for a new way of service delivery, based on a fair acknowledgement of contributions from this type of laboratories to both educational and scientific research.

Keywords: Design methods | Multidisciplinary approach | Proof of Concept | Value added services for research

Abstract: Wear and rolling contact fatigue are competing phenomena in railway wheels, as wear tends to shorten or remove surface cracks nucleated by ratcheting. The presence of water at the contact interface can enhance crack propagation leading to fatigue failure. This topic was studied taking advantage of innovative measurement systems developed for assessing the damage in bi-disc rolling contact tests, including a vision system for the acquisition and elaboration of surface images and a machine-learning technique for vibration measurement and analysis. Tests of different total duration with alternated dry and wet contact phases were carried out. The analysis of the collected measurements allowed identifying when crack propagation begins to prevail on wear: this occurred well earlier than the visible emergence of fatigue damage. If short dry and wet contact sessions are alternated, the onset of fluid driven crack propagation is delayed, because initially the dry sessions are not long enough to allow surface cracks to form by ratcheting, and in the subsequent wet session ratcheting is suspended due to low friction. If the alternated dry-wet contact sessions are longer, the onset of fluid driven crack propagation is accelerated, as in the dry sessions ratcheting proceeds more forming longer surface cracks, which are able to propagate in the subsequent wet phase.

Keywords: Crack propagation | Dry-wet contact | Ratcheting | Vibration analysis | Vision systems | Wheel steel

Abstract: Motivations for the research activity on teaching methods could be listed as: Institutional duty; reduction of evaluation costs; establishing convenient relationships between teaching, research and publications; developing educational programs for non-academic learners; consolidating learning outcomes. Teaching is the most commonly recognized mission of university, and evaluation has a cost in terms of time and resources, both precious: At least a portion of the exam, the one concerning factual knowledge, may be done in economies of scale. The most of basic technical drawing teachers works with very large classes and faces the dilemma of choosing what to sacrifice among teaching quality, research projects, earning opportunities, personal interests, etc. A possible partial solution to such a dilemma is to work on projects aimed at teaching innovation, so to create convenient relationships between teaching, research and publications. A further consequence of lowering the cost of evaluation would be to make cost effective a more tests and, consequently, to achieve less temporary learning. Not just simple notions but also skills and abilities. In this paper the authors presents a structured synthesis of teaching innovation experiences of a ten-year span. Over time, they were divided into four integrated directions: definition of prerequisites, expected outcome evaluation grids; authentic assessment methods; teaching and learning tools.

Keywords: Design methods | Engineering education | Learning techniques | Technical drawing

Abstract: A machine learning technique was used to monitor the state of damage of steel specimens subjected to cyclic contact fatigue tests and to make a continuous measurement without coming into contact with the specimens examined. Six different sets of specimens were considered and the torque and vibration data obtained from their respective tests were analyzed. Different statistical and spectral characteristics were obtained from each dataset, to represent their information content. The correlation existing between the characteristics was studied to select only the essential ones. The global data volume was reduced by a principal component analysis. The data thus obtained were subsequently processed, and classified, developing a K-means algorithm. The results were formulated in probabilistic terms with the aid of membership charts, confusion matrices and probability curves. The results obtained from this first analysis are highly encouraging. The algorithm is able to assess the damage status of the specimens, as well as detect the operating conditions of the machine. A substantial advantage of this method is the ability to estimate quantitatively the damage by calculating the distance of the current data from specific references. The performances of this approach were numerically estimated in terms of sensitivity, specificity and accuracy.

Abstract: The Bronze Age crossbar wheel found in the XIX century in Mercurago (Italy) is an amazing example of the technical innovations stimulated by the diffusion of horse draught war chariots in Europe across the third and second millennium b.C. In this paper the tools of modern engineering were used to study the structural issues concerning the wheel and the chariot it should be attached to. In particular, the laser-scanner technology and finite element analysis were used for investigating the dimensional, shape and assembly issues of the wheel, as well as for assessing its structural integrity under operating conditions. The role of the inserted nave, which could be similar to modern bushings, was particularly emphasised, as it is a very innovative solution for that time. The performance of a war chariot equipped by this wheel was studied by means of a vehicle dynamics simulation software, hypothesizing two different chariot structures on the basis of Armenian and Egyptian evidences respectively. The former is probably more similar to the chariot to whom the Mercurago wheel was attached; the latter is technically much more advanced. The results of the analysis allowed obtaining important information about the chariot stability, reliability and structural integrity.

Abstract: Twin-disk tests are an effective method to characterize the material response to rolling sliding contact, to reproduce the damage phenomena of real components at a laboratory scale in controlled working conditions. Usually the monitoring is performed by means of “gross” parameters, such as weight loss, coefficient of friction and Barkhausen noise, and micrographs of the sample sections, at the end of the test. Visual inspection of the sample contact surface at the macro-scale yields further information about the process under analysis. In twin-disk tests, the samples are visually inspected at predetermined steps, typically by acquiring the image of their surface when the samples are stationary. The availability of a system able to capture the images of the samples while they roll during the tests is of interest to better monitor the damage evolution. In this paper, we present the results of the experiments carried out to extract quantitative information from the images captured on railway wheel samples during rolling contact tests: suitable image processing has been designed with the objective of finding meaningful, synthetic indices for the monitoring and the interpretation of the wear process, also in relation to prior knowledge about the process. The experimental work was focused on the definition of the indices, on the analysis of their behavior on different steels, and on their usefulness to predict uneven wear during the tests on the test bench.

Keywords: Damage monitoring | Image acquisition | Image processing | Twin-disk tests | Wear

Abstract: Patients suffering from Spinal Cord Injury (SCI) can partially restore their walking function over ground and reduce of the secondary pathologies thanks to a frequent use of powered exoskeletons for robot-assisted gait. However, many of these devices require crutches to stabilize the body or to initiate the step. This could induce high loads on the shoulder joints, leading to shoulder pain and pathologies in SCI patients. This study presents a methodology to evaluate shoulder joints loads during robotic assisted gait, which was applied to an expert user of a Rewalk® exoskeleton. A pair of wireless instrumented crutches, designed by the authors[1], measure the crutches’ forces and movements. A simplified mechanical model of the patient is then simulated in OpenSim to perform both inverse kinematic and inverse dynamic analysis. Such a system could be applied during the initial training of new users, to help guide both patient and therapist towards an optimal usage of the exoskeleton.

Keywords: Measurements | Rewalk | Robotic assisted gait | Upper limbs

Abstract: Rolling Contact Fatigue (RCF) tests are a common effective method to study the behavior of wheel- and rail-steels. The measurements usually performed are discrete and destructive: they can only be performed at each intermediate stop of a test and they result in the alteration or destruction of the examined specimens. This work aims to assess the damage level steel samples during RCF tests, making continuous, non-destructive, and contactless measurements. A machine-learning technique based on vibration and torque measurements, together with 2D image was applied to RCF-dry tests carried out on different railway wheel steels tested according to the same operating parameters. The proposed algorithm was able to quantitatively estimate the damage level of the samples by calculating the current data distance from specific references, e.g. a defined final damaged state. The used approach ensures a good degree of reliability both in terms of specificity and sensitivity.

Abstract: A vision-based experimental methodology was developed for monitoring the surface state evolution of specimens during bi-disc rolling contact tests, aimed at providing information for identifying the damage phenomena. The system is based on a high-speed camera and three laser pointers for illuminating the specimen surface. Images of the specimen surface are acquired and processed, allowing the definition of synthetic surface state indexes, as well as the 3D reconstruction of the damaged surface topology. The vision system was applied to alternated dry-wet rollingsliding contact tests on railway wheel steel specimens, highlighting its effectiveness in the damage evaluation.

Keywords: Damage assessment. | Image processing | Online monitoring | Rolling contact fatigue | Wear

Abstract: The Bronze Age crossbar wheel found in the XIX century in Mercurago (Italy) is an amazing example of the technical innovations stimulated by the diffusion of horse draught war chariots in Europe across the third and second millennium B.C. It is a tripartite wheel, with two felloes attached to a diametric crossbar by means of internal dowels, and four thinner rods departing from the crossbar near the hub and ending into the felloes. A separate nave is inserted into the crossbar hub. Many question are still open about this wheel, concerning in particular its constructive concept, the materials and the role of each member. In this paper the tools of modern engineering, in particular the laser-scanner acquisition technology and the finite element method, were used to study the structural issues concerning the crossbar Mercurago wheel under the hypothesized operating conditions. Verisimilar explanations of some technical choices, such as the shape and the materials of the members, were obtained; furthermore, the presence of a leather tire was hypothesized on the basis of the rim-soil contact analysis. Finally, the role of the inserted nave was investigated. It was hypothesized that it could have a role similar to modern bushings, thus being a very innovative device for that time.

Keywords: Bronze Age | Chariot | Finite elements analysis | Laser-scanner acquisition | Wheel | Wood

Abstract: A simple and compact Depth-From-Defocus (DFD) setup, using telecentric illumination and liquid-lens based camera observation, was shown to perform well for 3D shape acquisition over extended measuring range. A further step to ameliorate the system performance is described in this paper. We focused on finding an algorithm to speed up the calibration step of the method, that automatically determines the minimum number of focal lengths to be used in the calibration and measurement procedure. As a result, the calibration is significantly shortened (up to 80% with respect to the original procedure), and the need to manually (and to some extent arbitrarily) select the focal length pairs is overcome. Measurement errors down to 0.73 mm over the measurement depth range of 130 mm, corresponding to 0.55% of the depth range are achieved, in total agreement with the original system.

Keywords: Calibration | Depth From Defocus | Image processing | Liquid lenses | Phase modulation | Shape measurement

Abstract: We present the in-field use of a recently developed on-line, real time, optical monitoring system for bi-disk rolling contact tests on railway-wheel- and rail- steel disks, based on laser illumination and a high-speed camera. Qualitative, as well as quantitative information can be obtained by the use of specific indexes derived from the images using blob analysis. Monitoring the tests provides information about the initial transients of turning-crest removal, on the steady state reached, and on the dynamics of the surface in between. Blob anisotropy is a key element to draw information of the mechanisms governing this intermediate state.

Abstract: The experimental characterization of an autofocus algorithm using a liquid lens objective is presented. The objective embeds an electro-wetting based lens whose focal length is voltage controlled. Two sharpness indexes are used to measure the image focus condition in the algorithm allowing a very robust and accurate setting of the focus. The algorithm has been characterized using target images differing both in the contrast and in the spatial frequency along measurement depth range from 70 to 2 mm. both static and dynamic tests were performed revealing the ability of the algorithm to follow rapid variations of the target position.

Keywords: autofocus | Depth-From-Focus | imaging | liquid lenses

Abstract: A novel depth from defocus (DFD) measurement system is presented, where the extension of the measurement range is performed using an emergent technology based on liquid lenses. A suitable set of different focal lengths, obtained by properly changing the liquid lens supply voltage, provides multiple camera settings without duplicating the system elements or using moving parts. A simple and compact setup, with a single camera/illuminator coaxial assembly, is obtained. The measurement is based on an active DFD technique using modulation measurement profilometry for the estimation of the contrast at each image point as a function of the depth range. Two different measurement methods are proposed, both based on a combination of multiple contrast curves, each derived at a specific focal length. In the first method (intensity contrast method), the depth information is recovered directly from the contrast curves, whereas in the second (differential contrast method), the depth is measured using contrast curve pairs. We obtained a measurement σ0 of 0.55 mm over a depth range of 60 mm with the intensity contrast method (0.92% of the total range) and an σ0 of 0.76 mm over a depth range of 135 mm with the differential contrast method (0.56% of the total range). Thus, the intensity contrast method is within the state-of-the-art DFD systems, whereas the differential contrast method allows, σ0 being almost equal, a remarkable extension of the depth range.

Keywords: Calibration | image edge analysis | image processing | lenses | phase modulation | shape measurement

Abstract: Wear and Rolling Contact Fatigue (RCF) tests on wheel/rail specimens are important to develop wheels of new materials for improved lifetime and performance, able to operate in harsh environments and at high rolling speeds. We have studied the feasibility of a novel non-invasive all-optical system, based on a high-speed video camera and two laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. Surface micro- and macrotopography are monitored using blob analysis and 3D laser triangulation respectively. Blob analysis yields to good discrimination among the specimens, in terms of wear induced surface damage; the 3D measurement, which is characterized by a resolution of 0.033 mm, is able to monitor RCF effects. The system is described with the aid of end-cycle specimens, as well as of intermediate specimens, prior to its installation in the test bench for rolling contact tests.

Abstract: Rolling contact wear/fatigue tests on wheel/rail specimens are important to produce wheels and rails of new materials for improved lifetime and performance, which are able to operate in harsh environments and at high rolling speeds. This paper presents a novel non-invasive, all-optical system, based on a high-speed video camera and multiple laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. 3D macro-topography and angular position of the specimen are simultaneously performed, together with the acquisition of surface micro-topography, at speeds up to 500 rpm, making use of a fast camera and image processing algorithms. Synthetic indexes for surface micro-topography classification are defined, the 3D macro-topography is measured with a standard uncertainty down to 0.019 mm, and the angular position is measured on a purposely developed analog encoder with a standard uncertainty of 2.9°. The very small camera exposure time enables to obtain blur-free images with excellent definition. The system will be described with the aid of end-cycle specimens, as well as of in-test specimens.

Abstract: A fast and reliable optical setup is here presented for in-focus imaging of objects in the macro range. The setup uses a camera equipped with an objective embedding a liquid lens, whose focal length is voltage-controlled. The defocus condition of the image is controlled by means of two indexes, both suitable for coarse and for fine adjustments. A purposely designed algorithm makes use of the two indexes, switching from one to the other to position the image in focus by adequately controlling the liquid lens focal length. The setup has been calibrated by means of target planes of known contrasts, and applied to process biomedical images such as fingerprints.

Abstract: This paper presents a new method for the automated processing of surface electromyography (SEMG) signals, particularly suited for the detection of muscle activation timing. The method has an intermediate level of complexity between simpler (but less performing) and more complex (but in general slower) methods, and is successfully used in the development of biomedical devices for rehabilitation carried out by our group. The method proposed here is based on a statistical approach for threshold computation that is implemented without the need of maximum voluntary contraction or relaxed state, usually required to overcome the difficulty in obtaining the threshold value. The method is compared with 10 popular automated standard methods using different types of simulated signals that approximate the behavior of real SEMG signals. Both the number of activations detected and the onset time measured are analyzed. The algorithm is then applied to real SEMG signals acquired from healthy subjects. The results are finally compared with the literature values. The results show that the proposed algorithm is the best performing method when both the number of activations and the activation timing are considered. In real applications, the algorithm gives the results compatible with the well-agreed literature data.

Keywords: Activation analysis | electromyography | measurement | muscles | signal processing | timing

Abstract: Rolling contact fatigue (RCF) plays a critical role in railway components, and the characterization of materials used, in terms of RCF life, is still an open task, made complex by the interactions of different phenomena. The contact surface has a direct impact on the pressure exerted and can change during the test, due to wear. The procedure proposed consists in using vibrations of a test bench during RCF-life tests to identify when wear increases and causes a quick flattening of the specimen's surface, and when this process is complete. The procedure is applied to two case studies regarding wheel and rail steels. In the tests, a wheel steel specimen rotates against a rail steel specimen, while pressed against each other by a constant force. At regular intervals weight loss and surface analysis are performed, while vibrations and torque are monitored continuously. Destructive tests are carried out at the end of each test. Results from non-destructive measurements were used to provide input data to a numerical simulation, used to determine the cyclic plasticity properties of the material. The methodology proposed shows the potential application of vibration measurements for detecting wear rates thus allowing supporting or partially supplanting destructive testing. Copyright:

Keywords: Damage evaluation | Rolling contact fatigue | Vibrations

Abstract: This paper investigates the shape memory capabilities of semicrystalline networks, focusing the attention on poly(ε-caprolactone) (PCL) systems, a class of materials that allows to satisfy important requirements for their applications as biomedical devices, such as the good biocompatibility, the fast recovery of large "temporary" shape configurations, and the easy tailoring of the transformation temperatures. The materials were prepared with various crosslink densities and crosslinking methodologies; in particular, beside a thermal crosslinking based on reactive methacrylic end groups, a novel type of covalently crosslinked semicrystalline systems was prepared by a sol-gel approach from alkoxysilane-terminated PCL precursors, so as to avoid potentially toxic additives typically used for free-radical thermal curing. The materials were subjected to biological tests, to study their ability in sustaining cell adhesion and proliferation, and to thermal characterizations, to evaluate the possibility to tailor their melting and crystallization temperatures. The one-way shape memory (i.e., the possibility to set the material in a given configuration and to recover its pristine shape) and the two-way shape memory response (i.e., the triggered change between two distinguished shapes on the application of an on-off stimulus) were studied by applying optimized thermo-mechanical cyclic histories. The ability to fix the applied shape and to recover the original one on the application of heating (i.e., the one-way effect) was evaluated on tensile bars; further, to investigate a potential application as self-expandable stents, isothermal shape memory experiments were carried out also on tubular specimens, previously folded in a temporary compact configuration. The two-way response was studied through the application of a constant load and of a heating/cooling cycle from above melting to below the crystallization temperature, leading to a reversible elongation/contraction effect, involving maximum strain changes up to about 80%, whose extent may be controlled through the crosslink density. © 2014 ASM International.

Keywords: advanced characterization testing | biomaterial | creep and stress rupture | mechanical

Abstract: Traffic calming devices on urban streets, such as elevated pedestrian crossings, speed bumps and roundabouts, are increasingly used, raising a real problem in relation to the on-board comfort that passengers perceive. To measure vibrational comfort related to traffic calming devices that passengers of the public transport perceive, an acquisition system called ASGCM (Autonomous System for Geo-referenced Comfort Measurements) has been developed, taking as a reference the European regulations on rail transports. ASGCM permits to link each measurement of vibration, ground velocity and acceleration with geographical information resulting from a GPS. In this way a map of a comfort index, statistical surveys and correlation between on-board comfort and traffic calming, can be directly obtained by any Geographic Information System (GIS), able to query a centralized remote database, which was developed ad-hoc. A large number of experimental tests has been performed to define a vibrational comfort index and to collect a large dataset that allows statistically significant comparisons between different infrastructures and their characterization. The proposed technique can also be useful for diagnostics purposes, such as vehicle comparison and road maintenance state monitoring.

Keywords: Geo-referenced comfort measurement | Thematic maps | Vibrational on-board comfort

Abstract: This paper investigates the kinematical behavior of a polymer based star-shaped actuator, able to produce mechanical work through the shape memory effect, that allows a significant shape variations on the application of an external stimulus. The adopted material is a semicrystalline network based on poly(ε- caprolactone) crosslinked by thermal curing; the material was adopted due to its fast recovery process when heated close to the melting temperature and the high recovery degree, and, due to its good biocompatibility, it may suitable for biomedical application. The original, or "permanent", material shape is that of a cylindrical annulus, which is set in a "temporary" configuration as a six spikes star. The temporary shape is fixed through a thermo-mechanical program, involving deformation above melting temperature and cooling under fixed strain and carried out by means of an ad-hoc designed fixture. By heating the deformed specimen above the melting temperature, the system is able to recover the original cylindrical shape realizing a motion and a mechanical power. This peculiar response, consisting in a progressive radial expansion activated by temperature, may be considered for application as selfexpanding stenting device triggered by the human body temperature. The shape of the system, that changes during the transformation, can be described as a two dimensional temporal function that represents the mean line of the section of the cylindrical annulus (perpendicular to the height of the annulus). This temporal function is a combination of a circular function and of a modified rhodoneal function and, after a proper calibration through experimental tests, is used to evaluate the kinematics of the system. The function is able to describe adequately the shape evolution experimentally displayed by the samples, with a very good agreement at the starting and final instants of the transformation, while the accuracy during the transformation is acceptable for the proposed application.

Abstract: In order to avoid final product malfunction and to allow for assembly integration, geometric specifications and dimensional tolerances are commonly used in mechanical design. However the feasibility of geometric specification measurement and verification is often neglected and the influence of measurement uncertainty in geometric tolerances evaluation underestimated. The authors propose updated results of a mathematical and numerical model, based on Monte Carlo simulations, developed in order to define a measurability threshold of geometric tolerances in relation to measurement uncertainty and geometric parameters, such as feature dimensions, meant to help the designer to define measurable geometric specifications. Starting from EN ISO 14253-2:2011 and EN ISO 14253-3:2011 standards, a perpendicularity tolerance between a cylindrical feature and a planar one has been simulated. A mathematical model has been defined for each feature, in order to assess both misalignment and its uncertainty when starting from the estimate of geometric entities obtained from point coordinates measured by a Coordinate Measurement Machine (CMM). Monte Carlo Analysis of these simulation underlined how geometric parameters, such as dimensions of the features involved, can act as magnifiers for measurement uncertainty when verifying a geometric specification: there could be cases where this magnification effect could lead to non-measurability of misalignment and non-verifiability of the geometrical specification requested.

Keywords: Dimensional parameters | Geometric tolerances | Measurability threshold | Measurement uncertainty

Abstract: The increasing integration between electronics and mechanical engineering brings to the industrial market very hi-tech sensors, often non-linear, capable of more than a single input and single output. A problem more and more relevant for sensors like these is calibration. Classic linear calibration procedures, when applied to this extremely engineered sensors, lead to poor accuracy and are generally not satisfactory. The case study is the calibration of a bi laser based position sensor, in particular a positive sensitive detector, that is an optical position transducer based on series of photodiodes commonly used as multidimensional sensor. To perform the calibration a micrometric positioning table was used to test the whole photodiode active area in both directions. The sensor studied showed a very linear behaviour in the central region of the working range, and a limited nonlinearity closer to the range limits and was to be used to verify robot movement capabilities; to reduce uncertainty associated with nonlinearities, a set of nonstandard, non-linear, calibrations were performed, pointing out residual values in order to compare different algorithms. In a previous work, authors have already tested a linear model against an algorithm based on radial basis functions (RBF) and Nelder-Mead simplex method. Object of this paper is the definition of a procedure based on RBF and genetic algorithms for multi-dimensional interpolation of data cloud and a comparison between this updated procedure results and the ones of the previous studied algorithms. The reference model for calibration was a black box with two inputs, X and Y position of the laser spot, and two outputs, voltages Vx and Vy, while the calibration procedure was split in two separate layers, one for each output depending on both inputs. Given N data points in a M-dimensional environment and N values that represent the non linearity residual, purpose of the algorithm is to approximate a data cloud with a real function, that is represented as a sum of a polynomial (linear) part and I. radial basis functions, each associated with a different center (node) and weighted by an appropriate coefficient, that the procedure also allow to assess. When no starting guess for nodes are given in input, nodes coordinates are the output of a non-linear optimizer based on a genetic algorithm, whose goal is to locally minimize the objective function. The algorithm stops itself whenever it reaches a certain tolerance level, a user specified number of nodes or when the previous iteration has a better value of the objective function. This study has been performed for various RBF classes, and shows an increased accuracy, thus a better metrological behaviour, with respect to the standard linear (planar) calibration model traditionally used.

Keywords: Calibration | Genetic algorithm | Multi input | Radial basis function | Uncertainty

Abstract: The shape memory behavior of tubular specimens based on crosslinked poly(ε-caprolactone) was investigated in order to evaluate their ability i) to restore their shape after being folded in a more compact one, and ii) to exert stress under external confinement (recovery stress). The specimens were prepared following different crosslinking methodologies and with different network densities, in order to tailor the material response in terms of transformation temperatures and recovery stress capabilities. The devices are able to fully recover their shape once heated close to the melting temperature and to exert moderate stresses, that may be controlled through thickness and crosslink density, and whose values were employed to develop a new testing apparatus for the measurement of radial dilation capabilities. © 2014 AIP Publishing LLC.

Keywords: Poly(ε-caprolactone) | Recovery stress | Shape memory polymer

Abstract: Traffic calming devices on urban streets, such as elevated pedestrian crossings, speed bumps and roundabouts, are increasingly used, therefore bus passengers on-board comfort assessment is an actual problem. In order to measure vibrational on-board comfort for public transport standing passengers related to traffic calming, an acquisition system called ASGCM (Autonomous System for Geo-referenced Comfort Measurements) has been developed, taking as a reference the European regulations on rail transports. Thanks to ASGCM, each measurement of vibration, on-ground velocity and acceleration is linked with geographical information resulting from a GPS, so a map of a comfort index, as well as statistical surveys and correlation between on-board comfort and traffic calming, can be directly obtained using a Geographic Information System (GIS), querying a centralized remote database developed ad-hoc. A large number of experimental tests has been performed in order to define a vibrational comfort index and to collect a large statistics that allows a significant comparison between different infrastructures and their characterization. The proposed technique can also be useful for diagnostics purposes, such as vehicles comparison and vehicle and road maintenance state monitoring.

Abstract: In mechanical design, geometrical specifications and dimensional tolerances are commonly used to avoid final product malfunction and to allow for assembly integration. Geometric specification usage, in particular, has many manufacturing and durability implications, the feasibility of their measurement and verification, however, is often neglected and the influence of measurement uncertainty in their evaluation underestimated. Often geometrical specifications are defined without considering measurement uncertainties, or measurability at all: it is not uncommon to find approved specifications prescribing unverifiable geometry, or dimension tolerances that exceed state-of-art measurements. This article explores the case study of orthogonality between a circular hole and the plane on which it is drilled, evaluated using a Coordinate Measuring Machine. Such specification is defined, according to ISO 14253, as the angle between the plane normal and cylinder axis. Uncertainty of points coordinates obtained can, however small, play a key role in the final evaluation of orthogonality: if the specified tolerance is thigh enough it is also possible to have misalignment uncertainty higher than the tolerance itself. The authors propose the results of a mathematical and numerical model, meant to help the designer to define specification to assess the relationship between cylinder-plane misalignment measurability, CMM uncertainty and features dimensions. © 2013 EDP Sciences.

Keywords: Geometric specification | Measurability | Orthogonality | Tolerances verification | Uncertainty

Abstract: The increasing integration between electronics and mechanical engineering brings to the industrial market very hi-tech sensors, often non-linear, capable of more than a single input and single output. A problem more and more relevant for sensors like these is calibration. Classic linear calibration procedures, when applied to this extremely engineered sensors, lead to poor accuracy and are generally not satisfactory. The case study is the calibration of a bi-dimensional laser based position sensor, in particular a positive sensitive detector, that is an optical position transducer based on series of photodiodes commonly used as multidimensional sensor. To perform the calibration a micrometric positioning table was used to test the whole photodiode active area in both directions. The sensor studied showed a very linear behaviour in the central region of the working range, and a limited nonlinearity closer to the range limits and was to be used to verify robot movement capabilities; to reduce uncertainty associated with nonlinearities, a set of nonstandard, non-linear, calibrations were performed, pointing out residual values in order to compare different algorithms. In a previous work, authors have already tested a linear model against an algorithm based on radial basis functions (RBF) and Nelder-Mead simplex method. Object of this paper is the definition of a procedure based on RBF and genetic algorithms for multi-dimensional interpolation of data cloud and a comparison between this updated procedure results and the ones of the previous studied algorithms. The reference model for calibration was a black box with two inputs, X and Y position of the laser spot, and two outputs, voltages Vx and Vy, while the calibration procedure was split in two separate layers, one for each output depending on both inputs. Given N data points in a M-dimensional environment and N values that represent the non linearity residual, purpose of the algorithm is to approximate a data cloud with a real function, that is represented as a sum of a polynomial (linear) part and L radial basis functions, each associated with a different center (node) and weighted by an appropriate coefficient, that the procedure also allow to assess. When no starting guess for nodes are given in input. nodes coordinates are the output of a non-linear optimizer based on a genetic algorithm, whose goal is to locally minimize the objective function. The algorithm stops itself whenever it reaches a certain tolerance level, a user- specified number of nodes or when the previous iteration has a better value of the objective function. This study has been performed for various RBF classes, and shows an increased accuracy, thus a better metrological behaviour, with respect to the standard linear (planar) calibration model traditionally used.

Keywords: Calibration | Genetic algorithm | Multi input | Radial basis function | Uncertainty

Abstract: In order to avoid final product malfunction and to allow for assembly integration, geometric specifications and dimensional tolerances are commonly used in mechanical design. However the feasibility of geometric specification measurement and verification is often neglected and the influence of measurement uncertainty in geometric tolerances evaluation underestimated. The authors propose updated results of a mathematical and numerical model, based on Monte Carlo simulations, developed in order to define a measurability threshold of geometric tolerances in relation to measurement uncertainty and geometric parameters, such as feature dimensions, meant to help the designer to define measurable geometric specifications. Starting from EN ISO 14253-2:2011 and EN ISO 14253- 3:2011 standards, a perpendicularity tolerance between a cylindrical feature and a planar one has been simulated. A mathematical model has been defined for each feature, in order to assess both misalignment and its uncertainty when starting from the estimate of geometric entities obtained from point coordinates measured by a Coordinate Measurement Machine (CMM). Monte Carlo Analysis of these simulation underlined how geometric parameters, such as dimensions of the features involved, can act as magnifiers for measurement uncertainty when verifying a geometric specification: there could be cases where this magnification effect could lead to non-measurability of misalignment and non-verifiability of the geometrical specification requested.

Keywords: Dimensional parameters | Geometric tolerances | Measurability threshold | Measurement uncertainty

Abstract: Traffic calming devices on urban streets, such as elevated pedestrian crossings, speed bumps and roundabouts, are increasingly used, therefore bus passengers on-board comfort assessment is an actual problem. In order to measure vibrational on-board comfort for public transport standing passengers related to traffic calming, an acquisition system called ASGCM (Autonomous System for Geo-referenced Comfort Measurements) has been developed, taking as a reference the European regulations on rail transports. Thanks to ASGCM, each measurement of vibration, on-ground velocity and acceleration is linked with geographical information resulting from a GPS, so a map of a comfort index, as well as statistical surveys and correlation between on-board comfort and traffic calming, can be directly obtained using a Geographic Information System (GIS), querying a centralized remote database developed ad-hoc. A large number of experimental tests has been performed in order to define a vibrational comfort index and to collect a large statistics that allows a significant comparison between different infrastructures and their characterization. The proposed technique can also be useful for diagnostics purposes, such as vehicles comparison and vehicle and road maintenance state monitoring.

Abstract: This article proposes a mathematical approach for the definition of a multiple input calibration diagram, based on a two step sequence, iteratively defining a set of radial basis functions and fitting its parameter to experimental data. Different radial basis functions have been evaluated and compared, focusing on Gaussian and multi-quadratic elements. The case studied used to test this method is the calibration of a bi-dimensional laser based position sensor believe that the method could be generalized and applicable to all transducers presenting multiple outputs, multiple inputs and localized non-linearities.

Keywords: Calibration | Multi input | Radial basis function | Uncertainty

Abstract: Often a designer has the problem to apply a suitable system of geometrical and dimensional tolerances to an assembly. The right solution is not unique, in fact it depends on the chosen parameters. If the tolerances have to be optimized, some important parameters have to be taken into account, e.g. the efficiency of each prescription, or if this last is reachable, or it can be verified and how much the realization costs. The authors opinion is that a statistical approach based on the Monte Carlo Method is very useful when the tolerances chains are complex. This paper shows an application of this method in order to verify the functional alignment between two assemblies and a critical analysis of the uncertainty in phase both of the component design and test. This study has been developed thanks to the strict requirements imposed by ESA (European Space Agency) on the components that Thales Alenia Space has to realize within the LISA Pathfinder experiment. The very critical aspect of this work is to reciprocally align two cylindrical elements of two different assemblies. The specifications require 100 μm as maximum linear displacement and 300 μrad as maximum angular displacement. Moreover this prescriptions have to be verified also when the two elements are independently moving. To be able to reach such strict accuracy level the components have been assembled in an ISO 100 class cleanroom and the work space was a 3D Coordinate-Measuring Machine (CMM). The cylindrical elements have a 10 mm diameter, so the value of the measurement uncertainty associated with the alignment check is fundamental. Starting from the different uncertainty sources, the measurability and verifiability of the alignment have been considered and evaluated. The overall uncertainty has been assessed by numerical simulations which have taken into account the dimensional, geometrical and form tolerances as well as the instrumental uncertainty of the 3D CMM. This estimation has been positively validated by a session of repeated measurements. Numerical simulations have also allowed performing a sensitivity analysis, in order to give information about which sources more contribute to the overall uncertainty. Copyright © 2010 by ASME.

Abstract: While parallel kinematics micropositioners offer high repeatability in positioning with respect to their own reference frame, the accuracy of absolute positioning with respect to a second, fixed, reference frame largely depends on the knowledge of the relative position between the two. Here will be presented a method for a rapid estimation of these relative positions based on subsequent movements of a positioner under a CMM and evaluation of position uncertainty.

Keywords: Accuracy measurement | Hexapod | Positioning | Uncertainty

Abstract: Cosmic rays, mostly composed of high energy muons, continuously hit the Earth's surface (at sea level the rate is about 10 000 m-2 min -1). Various technologies are adopted for their detection and are widespread in the field of particle and nuclear physics. In this paper, cosmic ray muon detection techniques are assessed for measurement applications in engineering, where these methods could be suitable for several applications, with specific reference to situations where environmental conditions are weakly controlled and/or where the parts to be measured are hardly accessible. Since cosmic ray showering phenomena show statistical nature, the Monte Carlo technique has been adopted to numerically simulate a particular application, where a set of muon detectors are employed for alignment measurements on an industrial press. An analysis has been performed to estimate the expected measurement uncertainty and system resolution, which result to be strongly dependent on the dimensions and geometry of the set-up, on the presence of materials interposed between detectors and, ultimately, on the elapsed time available for the data taking. © 2007 IOP Publishing Ltd.

Keywords: Cosmic ray muons | Elementary particle detectors | Mechanical alignment monitoring | Monte Carlo simulations | Multiple scattering | Position measurements

Abstract: Recently, the problem to estimate the felt comfort associated with the vibrations on city buses has been put in evidence, with particular attention about the infrastructurevehicle interactions. The aim of this work is to evaluate the effects of the traffic calming devices on the passengers of the public transports by vibration measurements. A self-sufficient measurement system has been implemented. It links each measurement with a geographical information resulting from a Global Positioning System (GPS), and permits to obtain a map of a comfort index directly, using the Geographic Information System (GIS). The presented system is based on widely used hardware components, i.e. a laptop computer, a commercial GPS receiver and three mono-axial servo-accelerometers. A custom software has also been developed.

Keywords: Comfort index | GIS | Vibration measurements

Abstract: The detection of illicit trafficking such as explosive materials inside large commercial payloads is today an important worldwide problem. Differently from the X- or γ-ray based systems, neutron interrogation allows the elemental composition of inspected materials to be measured. A container interrogation device based on the Tagged Neutron Inspection System (TNIS) has been developed within the EURITRACK (EURopean Illicit TRAfficking Countermeasures Kit) project of the 6th Framework Program of the European Union. A prototype of such system has been integrated at the Ruder Boskovic Institute (IRB) of Zagreb, Croatia, and performance tests have been carried out. A detailed simulation of the IRB experimental set-up has been performed. Comparison of the Monte Carlo predictions with collected experimental data is presented. © 2007 Elsevier B.V. All rights reserved.

Keywords: EURITRACK | Explosive detection | MCNP | Numerical simulation