[Elenco soci]

Morabito Anna Eva

Professore Associato

Università degli Studi del Salento

Sito istituzionale
SCOPUS ID: 7005602503
Orcid: 0000-0001-8841-5558

Pubblicazioni scientifiche

[1] Di Angelo L., Di Stefano P., Morabito A.E., Measurement of constant radius swept features in cultural heritage, Journal of Physics: Conference Series, 2204(1), (2022). Abstract

Abstract: The dimensional characterization of archaeological fragment is a very complex operation and could prove to be useful for identifying the presence of standard attributes in the ceramics found from a specific archaeological site, or for making comparisons and analysis of similarities or for studying ancient technologies used for manufacture of objects. The dimensional analysis of the fragments is now carried out manually with traditional measuring devices. Typically, the results obtained are inaccurate and non-repeatable measurements. This paper focuses on the dimensional characterization of a specific geometric class of features: the constant radius swept features (called here CRS features). Several archaeological features, such as rims, bases, decorative motifs, processing marks and grooves are referable from a geometric point of view to the class of CRS features. These are detail features, which may be very interesting for the investigation of some aspects related to the historical-archaeological classification of the find. CRS features are often found on worn, damaged (e.g. chipped) or fragmented objects; they are frequently characterized, from a geometric point of view, by free form surfaces and by a limited cross sectional extension. In some cases, CRS features can be of axially symmetrical geometry: this occurs quite frequently in the case of archaeological pottery. For all these reasons, it is often difficult to apply traditional manual methods for the quantitative dimensional characterization of CRS features. This paper describes an original methodology for the measurement of CRS features acquired by scanning technologies. The algorithmic implementation of this methodology, consisting of a suitable processing of the feature nodes, allows to carry out automatically the dimensional characterization of the feature.

[2] Di Angelo L., Di Stefano P., Morabito A., Automatic Segmentation of Sweep Features of Constant Radius from Archaeological Artifacts, Lecture Notes in Mechanical Engineering, 901-908, (2022). Abstract

Abstract: The sweep features of constant radius are particularly significant for the purposes of the historical-archaeological investigation and classification of ancient artifacts. The paper focuses on the automatic recognition of this specific class of features from triangulated 3D models experimentally acquired from cultural heritage objects. This is not a trivial problem. The ancient artifacts, although repeatable, are unique handmade pieces with a geometry commonly characterized by complex and non-analytical shapes. Their surfaces are also usually damaged and worn, so that the related geometric properties are altered or lost. The methodology proposed here is inspired by the one previously developed by the authors for the automatic segmentation of fillets, rounds and grooves from high-density triangulated models of mechanical components. The paper, in particular, focuses on the aspects of this methodology that must be tuned to allow the recognition of the sweep features of constant radius from archaeological finds. The methodology has been implemented and finally applied to an archaeological find acquired by a laser scanner.

Keywords: 3D archaeology | 3D digital models | Computer methods in archaeology | Feature recognition | Laser scanning

[3] Guardiani E., Morabito A., An investigation on methods for axis detection of high-density generic axially symmetric mechanical surfaces for automatic geometric inspection, Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 235(5), 920-933, (2021). Abstract

Abstract: The detection of the symmetry axis from discrete axially symmetric surfaces is an interesting topic, which is transversal to various fields: from geometric inspection to reverse engineering, archeology, etc. In the literature, several approaches have been proposed for estimating the axis from high-density triangular models of surfaces acquired by three-dimensional (3D) scanning. The axis evaluation from discrete models is, in fact, a very complex task to accomplish, due to several factors that inevitably influence the quality of the estimation and the accuracy of the measurements and evaluations depending on it. The underlying principle of each one of these approaches takes advantage of a specific property of axially symmetric surfaces. No investigations, however, have been carried out so far in order to support in the selection of the most suitable algorithms for applications aimed at automatic geometric inspection. In this regard, ISO standards currently do not provide indications on how to perform the axis detection in the case of generic axially symmetric surfaces, limiting themselves to addressing the issue only in the case of cylindrical or conical surfaces. This paper first provides an overview of the approaches that can be used for geometric inspection purposes; then, it applies them to various case studies involving one or more generic axially symmetric surfaces, functionally important and for which the axis must be detected since necessary for geometric inspection. The aim is to compare, therefore, the performances of the various methodologies by trying to highlight the circumstances in which these ones may fail. Since this investigation requires a reference (i.e. the knowledge of the true axis), the methodologies have been applied to discrete models suitably extracted from CAD surfaces.

Keywords: axially symmetric surfaces | Axis of symmetry | geometric inspection | geometrical dimensioning and tolerancing | high-density triangular models

[4] Di Angelo L., Di Stefano P., Guardiani E., Morabito A.E., A 3d informational database for automatic archiving of archaeological pottery finds, Sensors (Switzerland), 21(3), 1-18, (2021). Abstract

Abstract: From archaeological excavations, huge quantities of material are recovered, usually in the form of fragments. Their correct interpretation and classification are laborious and time-consuming and requires measurement, analysis and comparison of several items. Basing these activities on quantitative methods that process 3D digital data from experimental measurements allows optimizing the entire restoration process, making it faster, more accurate and cheaper. The 3D point clouds, captured by the scanning process, are raw data that must be properly processed to be used in automatic systems for the analysis of archeological finds. This paper focuses on the integration of a shape feature recognizer, able to support the semantic decomposition of the ancient artifact into archaeological features, with a structured database, able to query the large amount of information extracted. Through the automatic measurement of the dimensional attributes of the various features, it is possible to facilitate the comparative analyses between archaeological artifacts and the inferences of the archaeologist and to reduce the routine work. Here, a dedicated database has been proposed, able to store the information extracted from huge quantities of archaeological material using a specific shape feature recognizer. This information is useful for making comparisons but also to improve the archaeological knowledge. The database has been implemented and used for the identification of pottery fragments and the reconstruction of archaeological vessels. Reconstruction, in particular, often requires the solution of complex problems, especially when it involves types of potsherds that cannot be treated with traditional methods.

Keywords: 3D archaeology | Computer methods in archaeology | Information search and retrieval | Measurement precision in archaeol-ogy | Similarity metric

[5] Ciaccioli C., Morabito A.E., An investigation on skeleton-based top-down modelling approaches of complex industrial product, Journal of Graphic Engineering and Design, 12(1), 11-21, (2020). Abstract

Abstract: In industry, today's approach to assembly design is still largely based on a bottom-up approach which, in contrast with the most advanced top-down techniques, is unfit to deal with very large and complex products. The reason for this lies in the high number of relationships to be established between parts and in the lack of a high-level control of the assembly design. This makes the management of design changes a labor-intensive process and the capture of design intent difficult to achieve. The paper, referring to the most advanced research fields of Concurrent Engineering and Knowledge-Based Engineering, focuses on a top-down modelling approach based on skeleton, which constitutes the most natural but still scarcely exploited way to attain a high reactivity to design modifications. Through the application of suitable methodologies, such as that one for a SKeLeton geometry-based Assembly Context Definition (SKL-ACD), the skeleton is also able to capture and codify assembly process engineering information since the early phases of the product development process. With the purpose of promoting the knowledge of these skeleton-based modelling techniques, that have a great relevance for training professional, technical and mechanical engineers, this paper implements the SKL-ACD methodology to an industrial case study in order to identify, with a unique and repeatable workflow, the reference geometrical entities and the mutual relationships to embed into the product skeleton. The skeleton types and the related fields of use are also described, placing particular emphasis on problems or shortcomings still not resolved, especially in consideration of the need to assist the designer in defining the impact of a parameter on assembly modification and in avoiding loops while defining formulas. A new tool, in the form of a multilayer graph, is finally proposed that is able to display and differentiate clearly the formulas, the design parameters and the impact of their modification on skeleton entities and members of the assembly.

Keywords: Knowledge-Based Engineering | Product Parametrization | Skeleton | Top-Down Assembly Design

[6] Di Angelo L., Di Stefano P., Morabito A.E., Guardiani E., Point clouds registration based on constant radius features for large and detailed cultural heritage objects, 2020 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage, 168-173, (2020). Abstract

Abstract: The registration permits to positioning in a single reference system point clouds acquired from different points of view. Since this is typically obtained with an iterative numerical method, it represents an important source of error in the entire reverse engineering process. As all iterative methods, such errors depend on the choice of the initial solution; therefore, this process requires an expert user who, by using dedicated software, choices the sequence of clouds to be registered, imposes for each pairwise the first attempt registration, launches the iterative method, and verifies the final result. With the aim to minimize the error and the user's interaction, some devices are proposed in the market (turntable or the anthropomorphic arm, etc.). The above-mentioned hardware and software tools cannot be used in the cultural heritage applications involving large and detailed objects. In this paper, an automatic alignment method of point clouds is proposed. The method uses as inputs the constant radius features, which are frequently detectable on cultural heritage objects. The automatic alignment of the point clouds is based on the recognition, the segmentation, and the registration of the sweep lines identifiable from these features.

[7] De Giorgi M., Gallo N., Madaghiele M., Morabito A.E., Morphological and Mechanical Characterization of P-Scaffolds with Different Porosity, Lecture Notes in Mechanical Engineering, 361-372, (2020). Abstract

Abstract: The aim of this paper is to model and to compare the results of the mechanical characterization, carried out on numerical models and real specimens, of uniform P-scaffolds with different porosity values. The analysis includes the morphological characterization of 3D printed specimens and the implementation of a FEM shell model to reproduce a compressive test suitable for mechanical properties evaluation of PLA scaffolds. Young modulus and yield strength were also obtained, in order to verify the numerical model accuracy, by experimental tests on 3D printed PLA scaffolds. Numerical results showed that the shell model was able to reproduce, more efficiently compared to a solid model proposed in a previous work, both elastic and plastic behavior of the scaffolds, providing elastic modulus values very close to the experimental ones. On the other hand, the not very high quality of the 3D printing, detected by MicroCT analysis, caused a significant dispersion in the yield strength numerical values respect to the real data. Anyway, an inverse correlation between mechanical properties and porosity was found as expected. The elastic modulus values were similar to the typical values of the trabecular bone for whose regeneration this kind of scaffolds is usually employed.

Keywords: Experimental tests | FEM analysis | MicroCT | TPMS scaffold

[8] Di Angelo L., Di Stefano P., Morabito A.E., Automatic Segmentation of Constant Radius Secondary Features from Real Objects, Lecture Notes in Mechanical Engineering, 201-212, (2020). Abstract

Abstract: Secondary features, such as fillets, rounds, chamfers and grooves, are simple transitions between primary features, generally introduced in order to remove the sharp edges created by the intersection of primary features. Being able to distinguish secondary from primary features is important in various application contexts, such as reverse engineering, automatic geometric inspection of real scanned objects, and for preparation of models for FEM analysis and CNC tool-path generation. The process for the recognition of secondary features from high-density tessellated models of real work-pieces is intrinsically complex for several reasons. This explains why, currently, there are no methodologies able to recognize automatically secondary features and the investigation on secondary features is mostly focused on B-Rep models. In a previous paper, the authors proposed a method for secondary features recognition from discrete geometric models synthetically generated. Here the methodology is extended to discrete geometric models experimentally acquired, for which the recognition is a very complex process, due to the object discretization, to its non-ideal geometry and to measurement errors.

Keywords: Blending features | Feature recognition | Fuzzy logic | Point cloud segmentation

[9] Guardiani E., Morabito A.E., Towards the automation of product geometric verification: An overview, Computer-Aided Design and Applications, 17(5), 900-920, (2020). Abstract

Abstract: The paper aims at providing an overview on the current automation level of geometric verification process with reference to some aspects that can be considered crucial to achieve a greater efficiency, accuracy and repeatability of the inspection process. Although we are still far from making this process completely automatic, several researches were made in recent years to support and speed up the geometric error evaluation and to make it less human-intensive. The paper, in particular, surveys: (1) models of specification developed for an integrated approach to tolerancing; (2) state of the art of Computer-Aided Inspection Planning (CAIP); (3) research efforts recently made for limiting or eliminating the human contribution during the data processing aimed at geometric error evaluation. Possible future perspectives of the research on the automation of geometric verification process are finally described.

Keywords: Automatic geometric verification | Computer-Aided Inspection Planning | Error evaluation | Feature Recognition | GPS standards | Model of specification for tolerancing | Partition

[10] Morabito A.E., Di Angelo L., Di Stefano P., Guardiani E., Pane C., 3D virtual reconstruction of the ancient Roman incile of the fucino lake, Sensors (Switzerland), 19(16), (2019). Abstract

Abstract: The construction of the artificial emissary of Fucino Lake is one of the most ambitious engineering buildings of antiquity. It was the longest tunnel ever made until the 19th century and, due to the depth of the adduction inlet, it required a monumental and complex incile, which, for functionality, cannot be compared to other ancient emissaries. The Roman emissary and its "incile" (Latin name of the inlet structure) were almost completely destroyed in the 19th century, when Fucino Lake was finally dried. Today, only few auxiliary structures such as wells, tunnels, and winzes remain of this ancient work. As evidence of the ancient incile remains a description made by those who also destroyed it and some drawings made by travelers who, on various occasions, visited the site. This paper presents a virtual reconstruction of the Roman incile, obtained both through the philological study of the known documentation, interpreting iconographic sources that represent the last evidence of this structure, and through the survey on the territory. The main purpose is to understand its technical functionalities, the original structures, and its evolution during the time, taking into account the evolution of the Fucino Lake water levels, technological issues, and finally o_ering its visual reconstruction.

Keywords: 3D virtual reconstruction This research received no external funding | Archaeology | Monumental heritage | Remote sensing

[11] Di Angelo L., Di Stefano P., Morabito A.E., Fillets, rounds, grooves and sharp edges segmentation from 3D scanned surfaces, CAD Computer Aided Design, 110, 78-91, (2019). Abstract

Abstract: Fillets, rounds, chamfers and grooves are secondary features which are typically present in real manufactured mechanical components to satisfy some manufacturing and functional requirements. Despite the broad array of research conducted on feature recognition, the investigation of secondary features is a relatively new topic. All of the pertinent studies have been focusedonly on the recognition of secondary features from B-Rep models. The recognition and segmentation of secondary features from a discrete model is a non-trivial problem due to the same geometric descriptors that may be applied to both primary and secondary features. Moreover, although in real-world mechanical parts primary features are planes, cylinders or cones, the secondary features may be non-analytical and complex-shaped geometries. Further sources of uncertainty are the measurement errors and non-ideal geometries of the real objects to which the method is applied. To overcome these problems, a new and original method to segment secondary features of tessellated geometric models is proposed. The method is based on the analysis of geometric-differential properties and provides specific strategies that reduce its sensitivity to all of the above-mentioned uncertainties without affecting its selectivity. The proposed method, described in detail in this paper, is tested in some very critical cases, and the results are presented and discussed.

Keywords: 3D mesh segmentation | 3D scanning | Blending features | Features recognition | Fuzzy logic | STL

[12] Di Angelo L., Di Stefano P., Guardiani E., Morabito A.E., A 3D information framework for automated archaeological pottery archival, 2019 IMEKO TC4 International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2019, 178-183, (2019). Abstract

Abstract: The classification of ceramic archaeological fragments is based on shape, dimensions, decorations, technological elements, color and material. Nowadays, all of these features are still recognized and analyzed by a skilled operator. It follows that the resulting characterization of shape and sizes of archaeological fragments is poorly reproducible and repeatable. With a view to overcome these limitations, a computer-based methodology, able to extract automatically several quantitative information from high-density discrete geometric models acquired by the laser scanning of archaeological fragments, was proposed. In this paper, the set of quantitative information obtainable is furtherly broadened, by including the segmentation of some types of morphological features, the identification of the fragment shape type, the evaluation of the longitudinal profile and the estimation of a larger set of dimensional features. Finally, a new 3D information framework is proposed to store the large variety of quantitative information extracted.

[13] Di Angelo L., Di Stefano P., Morabito A.E., Pane C., Constant radius geometric features segmentation in archeological pottery, IMEKO International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2017, 69-74, (2019). Abstract

Abstract: This paper gives a contribution to the automatic recognition of significant features of ancient ceramics, useful for the historical and/or archeological investigation. These very common type geometric features are obtained by a sweeping action that leaves negative or positive traces, characterized by a cross section with one or more constant radii. The paper proposes a novel methodology that, analyzing the principal curvatures at the points of high-density geometric models of ceramic vessels, acquired by laser scanning, identifies the nodes potentially attributable to these features of constant radius. The recognition process is not trivial since it is affected by uncertainties. To overcome the limits of a recognition based on crisp sets, the recognition rule, proposed for the feature segmentation, is implemented by a fuzzy approach. The method has been tested in the identification of embossed decorations in an ancient olla and it proves to be promising for further applications on other types of geometric features of constant radius.

[14] Ambu R., Morabito A.E., Modeling, assessment, and design of porous cells based on schwartz primitive surface for bone scaffolds, Scientific World Journal, 2019, (2019). Abstract

Abstract: Te design of bone scafolds for tissue regeneration is a topic of great interest, which involves diferent issues related to geometry of architectures, mechanical behavior, and biological requirements, whose optimal combination determines the success of an implant. Additive manufacturing (AM) has widened the capability to produce structures with complex geometries, which should potentially satisfy the diferent requirements. These architectures can be obtained by means of refned methods and have to be assessed in terms of geometrical and mechanical properties. In this paper a triply periodic minimal surface (TPMS), the Schwarz's Primitive surface (P-surface), has been considered as scafold unit cell and conveniently parameterized in order to investigate the efect of modulation of analytical parameters on the P-cell geometry and on its properties. Several are the cell properties, which can afect the scafold performance. Due to the important biofunctional role that the surface curvature plays in mechanisms of cellular proliferation and diferentiation, in this paper, in addition to properties considering the cell geometry in its whole (such as volume fraction or pore size), new properties were proposed. Tese properties involve, particularly, the evaluation of local geometrical-diferential properties of the P-surface. Te results of this P-cell comprehensive characterization are very useful for the design of customized bone scafolds able to satisfy both biological and mechanical requirements. A numerical structural evaluation, by means of fnite element method (FEM), was performed in order to assess the stifness of solid P-cells as a function of the changes of the analytical parameters of outer surface and the thickness of cell. Finally, the relationship between stifness and porosity has been analyzed, given the relevance that this property has for bone scafolds design.

[15] Di Angelo L., Di Stefano P., Morabito A.E., Pane C., Measurement of constant radius geometric features in archaeological pottery, Measurement: Journal of the International Measurement Confederation, 124, 138-146, (2018). Abstract

Abstract: Constant radius geometric features are a common type of manufacturing features of ancient ceramics. They are obtained by a sweeping action of a tool, which leaves negative or positive traces characterized by a cross-section with one or more constant radii. The automatic recognition and dimensional characterization of these features could be useful for understanding the technology used to manufacture ceramics. Thus, a new perspective in archaeological investigations can be furnished. For this purpose, in this paper a new computer-based methodology suited to segmenting constant radius geometric features and measuring their dimensional parameters is proposed. Starting from a 3D discrete geometric model of the ceramic, the region pertaining to these features is determined and measurements of their radii are performed. Due to the uncertainties of various sources, which affect the investigated object, the required process is not trivial. In order to solve this problem, the segmentation phase is conducted using a non-conventional logic suitable for exploring the object with a fuzzy sensitivity, and the measurement is performed by a robust fitting method applied to the segmented entities. The methodology has been tested in the identification of embossed decorations of an ancient olla. The combined effects of the feature segmentation process together with the measure detection approach on the obtained results are critically analyzed and discussed.

Keywords: Computer methods in archaeology | Fuzzy logic | Geometric features recognition | Metrology for cultural heritage

[16] Di Angelo L., Di Stefano P., Morabito A.E., Secondary features segmentation from high-density tessellated surfaces, International Journal on Interactive Design and Manufacturing, 12(3), 801-809, (2018). Abstract

Abstract: A new method for secondary features segmentation, performed on high-density tessellated geometric models, is proposed. Four types of secondary features are considered: fillets, rounds and grooves. Sharp edges are also recognised. The method is based on an algorithm that analyses the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for the maximum principal curvature. Since the deterministic application of this simple working principle shows several problems, due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model belonging to secondary features of a given radius, an appropriate set of membership functions is defined and evaluated based on some parameters, which affect the quality of the curvature estimation. A region-growing algorithm connects the nodes pertaining to a same secondary feature so that, for a given radius, one or more secondary features may be recognized. The method is applied and verified in some test cases.

Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm

[17] Ambu R., Morabito A.E., Porous scaffold design based on minimal surfaces: Development and assessment of variable architectures, Symmetry, 10(9), (2018). Abstract

Abstract: In tissue engineering, biocompatible porous scaffolds that try to mimic the features and function of the bone are of great relevance. In this paper, an effective method for the design of 3D porous scaffolds is applied to the modelling of structures with variable architectures. These structures are of interest since they are more similar to the stochastic configuration of real bone with respect to architectures made of a unit cell replicated in three orthogonal directions, which are usually considered for this kind of applications. This property configures them as, potentially, more suitable to satisfy simultaneously the biological requirements and those relative to the mechanical strength. The procedure implemented is based on the implicit surface modelling method and the use of a triply periodic minimal surface (TPMS), specifically, the Schwarz's Primitive (P) minimal surface, whose geometry was considered for the development of scaffolds with different configurations. The representative structures modelled were numerically analysed by means of finite element analysis (FEA), considering them made of a biocompatible titanium alloy. The architectures considered were thus assessed in terms of the relationship between the geometrical configuration and the mechanical response to compression loading.

Keywords: Design | FEA | Scaffold | Tissue engineering | TPMS

[18] De Giorgi M.G., Donateo T., Ficarella A., Fontanarosa D., Eva Morabito A., Scalinci L., Numerical investigation of the performance of Contra-Rotating Propellers for a Remotely Piloted Aerial Vehicle, Energy Procedia, 126, 1011-1018, (2017). Abstract

Abstract: The present work aims at the numerical prediction of the performance of a Contra-Rotating Propellers (CRP) system for a Remotely Piloted Aerial Vehicles (RPAV). The CRP system was compared with an equivalent counter-rotating propellers configuration which was set by considering two eccentric propellers which were rotating at the same speed. Each contra-rotating test case was built by varying the pitch angle of blades of the rear propeller, while the front propeller preserved the original reconstructed geometry. Several pitch configurations and angular velocities of the rear propeller was simulated. Comparisons showed an improvement of the propulsive efficiency of the contra-rotating configuration in case of larger pitch angles combined with slower angular velocities of the rear propeller.

Keywords: aeronautic propulsion | contra-rotating propellers | frozen rotor technique | OpenFOAM | performance | RPAV

[19] Di Angelo L., Di Stefano P., Morabito A.E., Product model for dimensioning, tolerancing and inspection, Lecture Notes in Mechanical Engineering, 0, 1033-1040, (2017). Abstract

Abstract: This paper presents a new methodology whose goals are on the one hand the formulation of a tolerance specification that is consistent with the functional, technological and control needs and, on the other, the automatic control of tolerance. The key aspect of the methodology is the digital model of the product, referred to as GMT (Geometric Model of Tolerancing), which gives a complete, consistent and efficient description of its geometrical and dimensional properties with the aim of being able to specify, simulate, manufacture and inspect them. By means a real test case, the potentialities of a first implementation of the proposed methodology are critically discussed.

Keywords: CAT (Computer-Aided Tolerancing) | GD&T (Geometric Dimensioning and Tolerancing) | Geometric inspection | GPS (Geometric Product Specification)

[20] Di Angelo L., Di Stefano P., Morabito A.E., Segmentation of secondary features from high-density acquired surfaces, Lecture Notes in Mechanical Engineering, 0, 1043-1051, (2017). Abstract

Abstract: A new method for secondary features segmentation, performed in highdensity acquired geometric models, is proposed. Four types of secondary features are considered: fillets, rounds, grooves and sharp edges. The method is based on an algorithm that analyzes the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for maximum principal curvature. Since the deterministic application of this simple wor king principle shows several problems due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model that pertain to the same secondary features, proper membership functions are evaluated as function of some parameters, which affect the quality of the curvature estimation. A region growing algorithm connects the nodes pertaining to the same secondary feature. The method is applied and verified for some test cases.

Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm

[21] Ambu R., Morabito A.E., Design and analysis of tissue engineering scaffolds based on open porous non-stochastic cells, Lecture Notes in Mechanical Engineering, 0, 777-787, (2017). Abstract

Abstract: In orthopaedics, cellular structures can be used as three-dimensional porous biomaterials that try to mimic the characteristics and function of the bone. The progress in manufacturing techniques, mainly in the field of additive manufacturing, can potentially allow the production of highly controlled pore architectures and customized implants that, however, need more sophisticated design methodologies. In this paper, the design of porous biocompatible structures based on mathematically defined surfaces (triply periodic minimal surfaces) has been considered in respect of the approach that considers unit cells entirely modelled in CAD environment. Two types of unit cell have been here considered: the cubic and the P-cell. The cubic cell is created by a 3D CAD s/w from solid features that are combined together. The P-cell is modelled using an implicit function to describe the outer surface of the cell. Two are the design parameters of the P-cell: thickness and radius. The variation of these parameters allows modifying the architecture of the basic unit of the scaffold. The modification of the radius is carried out by a procedure, based on scaling and truncation operations. The thickness of the cell is modified by thickening and closure operations on the P-isosurface. The effect of these variations on the mechanical behaviour of the scaffold has been numerically evaluated by the estimation of the stiffness of each structure considered. The results demonstrated the huge potentiality of the method and stiffness values compatible with those required for biomechanical applications.

Keywords: Bone implants | Design | Porous materials | Scaffolds

[22] Di Angelo L., Di Stefano P., Morabito A.E., A robust method for axis identification, Precision Engineering, 39, 194-203, (2015). Abstract

Abstract: The present paper proposes a new method for axis identification in discrete axially symmetrical geometric models. This method is based on-a-never-used-before property of the axially symmetrical surfaces for which the symmetry line of any section curve of the surface (or of a portion of it in the case of an incomplete axially symmetrical surface) always intersects the axis of symmetry of the surface. Thus the working principle of the method makes it very robust to local defectiveness, measurement noise and outliers. In order to compare it with the most cited methods presented in literature, several types of tests have been designed and performed. The robustness of those methods, on the one hand, has been evaluated by defining the Statistical Confidence Boundary at 1σ confidence level. The trueness of the method, on the other hand, has been evaluated on geometric models obtained by measuring real objects. The high robustness, which characterizes the proposed method, makes it particularly suitable for product geometric inspection where high accuracy is required.

Keywords: Axis identification | Geometric inspection

[23] Di Angelo L., Di Stefano P., Morabito A.E., Comparison of methods for axis detection of high-density acquired axially-symmetric surfaces, International Journal on Interactive Design and Manufacturing, 8(3), 199-208, (2014). Abstract

Abstract: Axis evaluation is a fundamental preliminary step for several applications, from archaeology to geometric inspection of mechanical workpieces. The axis of symmetry is the situation feature of axially-symmetric surfaces, but also a reference for the evaluation of specific geometric properties (roundness, cylindricity and straightness of the axis). Since it is a non-physical geometric entity, it is not directly measurable from the surface, but can nevertheless be derived from the surface. For discretised models, defined by point clouds or triangular meshes, the axis of symmetry detection is a very complex task to accomplish. In this paper three methods for axis estimation of high-density acquired axially-symmetric surfaces are reviewed and compared in the common cases. The methods comparison, performed in this work, doesn't consist just in an ordinary implementation of methods already described in the literature. These methods involve some auxiliary processing tools (mainly devoted to evaluate geometric differential properties) which characterise the implemented version and its performances. For each of these methods various versions have been considered and implemented which diversify each other for the criterion used for geometrical differential properties of the tessellated model. The methods for axis estimation are compared in the interpretation of the axes of axially-symmetric geometries (analytical and generic, partial and complete) for several types of discretization (size and regularity of the mesh). The results show that in the case of complete axially-symmetric features (analytical or generic), the three analysed methods perform similar results. In presence of not complete axially-symmetric features the methods show very different performances. The methods for axes estimation are of particular interest in several applications where precision and reliability are required. In this paper the main characteristics of the most important methods are identified and some guidelines for their use are given. © 2014 Springer-Verlag France.

Keywords: Axis of rotation | Discretised surfaces | Geometric features recognition | Reverse engineering

[24] Di Angelo L., Di Stefano P., Morabito A.E., Recognition of intrinsic quality properties for automatic geometric inspection, International Journal on Interactive Design and Manufacturing, 7(4), 203-215, (2013). Abstract

Abstract: In the last few years the need for methodologies capable of performing an automated geometric inspection has increased. These methodologies often use 3D high-resolution optical digitisers to acquire points from the surface of the object to be inspected. It is expected that, in the near future, geometric inspection will be requiring more and more the use of these instruments. At present geometric inspection is not profiting from all the opportunities attainable by 3D high-resolution optical scanners or from the numerous tools which can be used for processing the point cloud acquired from the inspected product. For some years now, these authors have been working on a new methodology for automatic tolerance inspection working from a 3D model acquired by optical digitisers. In this paper all the information recognisable in a scanned object is organised into a new data structure, called Recognised Geometric Model (RGM). The final aim is to define a representation of the inspected object for the automatic evaluation of the non-idealities pertaining to the form, orientation and location of the non-ideal features of the acquired object. The key concept of the proposed approach is the capability to recognise some intrinsic nominal properties of the acquired model. These properties are assumed as references to evaluate the non-idealities of the inspected object. With this approach the references of geometric inspection are searched for in the inspected object independently of a tolerance specification and of the availability of a 3D nominal representation. The high-level geometric information within RGM depends on the rules used for its identification. The capability to recognise specific categories of nominal references offers the possibility of introducing new tolerances to be specified. The proposed approach has been implemented in original software by means of which a specific test case has been analysed. © 2012 Springer-Verlag France.

Keywords: Automated inspection | ISO tolerancing | Three-dimensional metrology

[25] Carofalo A., Giorgi M.D., Morabito A., Geometric modelling of metallic foams, Engineering Computations (Swansea, Wales), 30(7), 924-935, (2013). Abstract

Abstract: Purpose - The aim of this work is the development of a procedure able to model the highly irregular cellular structure of metallic foams on the basis of information obtained by X-ray tomographic analysis. Design/methodology/approach - The geometric modelling is based on the feature "pore" characterized by an ellipsoidal shape. The data for the geometric parameters of the instances are obtained with a methodology which is driven by the pore volume distribution curve. This curve shows how much the cells, whose diameter belongs to a given dimensional range, contribute to the reduction of the total volume. Findings - The presented methodology has been implemented into a CAD tool consisting of a Matlab routine identifying the instances of the feature "pore" and a CATIA's macro modelling the closed cells foam. Originality/value - The presented methodology allows to obtain in an automatic way the CAD model of the complex structure of closed cell aluminium foam approximating by considerable accuracy both the density and the volume distribution of the real foams. Copyright © 2013 Emerald Group Publishing Limited. All rights reserved.

Keywords: Aluminium foam | CAD modelling | Computer aided design | Foams | Microstructural model | OBB overlapping | X-ray tomography

[26] Angelo L.D., Stefano P.D., Morabito A.E., The RGM data structure: A nominal interpretation of an acquired high point density model for automatic tolerance inspection, International Journal of Production Research, 50(12), 3416-3433, (2012). Abstract

Abstract: In a previous paper (Di Angelo, L., Di Stefano, P. and Morabito, A., 2011. Automatic evaluation of form errors in high-density acquired surfaces. International Journal of Production Research, 49 (7), 2061-2082) we proposed an original methodology for the automation of the geometric inspection, starting from an acquired high-density surface. That approach performed a recognition process on the acquired data aiming at the identification of some intrinsic nominal references. An intrinsic nominal reference was detected when a geometric property was recognised to be common to a set of adjacent points in the 3D data set representing the acquired object. The recognition of these properties was carried out based on some rules. Starting from these concepts, a new specification language was defined, which is based on recognisable geometric entities. This paper expands the category of intrinsic nominal references to include new mutual intrinsic orientation, location and dimensional properties pertaining to 3D features. This approach involves the automatic construction of a geometric reference model for a scanned workpiece, called recognised geometric model (RGM). The domain of the representable entities within the RGM strictly depends on the rules used for the recognition of the intrinsic properties. In particular, this paper focuses on the rules for the recognition of the orientation and location properties between non-ideal features. When using the RGM, tolerances are specified according to the set of available and recognisable intrinsic nominal references. Based on the geometric product specification, the RGM data structure can be queried to capture some quantitative information concerning special intrinsic geometric parameters and/or non-idealities. © 2012 Copyright Taylor and Francis Group, LLC.

Keywords: automated inspection | ISO tolerancing | shape recognition | three dimensional metrology | triangular meshes

[27] Chrysochoos A., Boulangerv T., Morabito A.E., Dissipation and thermoelastic coupling associated with fatigue of materials, Lecture Notes in Applied and Computational Mechanics, 61, 147-156, (2012). Abstract

Abstract: The fatigue behaviour is examined in terms of calorimetric effects. Aluminum alloy and steel have been chosen as reference materials. Heat sources accompanying the fatigue mechanisms are derived from thermal images provided by an infrared camera. A processing method allows identifying separately thermoelastic and dissipative sources. Thermoelastic effects are compared to theoretical predictions given by the basic, linear, isotropic thermoelastic model. Dissipation amplitudes are analyzed as a function of the loading frequency and stress amplitude applied to the fatigue specimen. Finally, the heterogeneous character of the fatigue development is studied both in terms of thermoelastic and dissipation sources.

[28] Dattoma V., De Giorgi M., Giancane S., Manco P., Morabito A.E., A parametric associative modelling of aeronautical structural concepts under C0, C1 or C2 continuity constraints, Aeronautical Journal, 116(1181), 727-741, (2012). Abstract

Abstract: In this paper an associative-parametric approach is proposed in order to model the mesh of an aeronautical concept starting from a set of high-level structural primitives. This approach allows the designer to carry out the geometric modelling and the automatic mesh generation within one software environment in a fast and interactive way. The structural optimisation process is then simplified, with a relevant man-hours saving. A lower number of data transfers between different software is, moreover, involved with less problems related to the data corruption. To assure orders of continuity higher than C0 between adjacent instances, a suitable mathematical description of the structural primitives has been proposed. This description assures the maintenance of the required continuity constraints when the mesh is modified. Appropriate schemes of dependences are identified to guarantee the automatic propagation of the modifications complying with the continuity constraints.

[29] Dattoma V., De Giorgi M., Giancane S., Manco P., Morabito A.E., A parametric-associative modelling of aeronautical concepts for structural optimisation, Advances in Engineering Software, 50(1), 97-109, (2012). Abstract

Abstract: In this work, a scheme of representation for aircraft structural concepts is identified. Based on this scheme, a parametric-associative geometrical modelling of the aeronautic structure, consisting in a quad-mapped mesh, is proposed. The mesh generation is based on a hierarchical scheme ensuring the one-to-one correspondence between mesh elements belonging to adjacent primitives. The automatic propagation of modifications is efficiently implemented according to well-defined schemes of dependence thanks to which the modifications involve only the concerned instances. This scheme is implemented in an original software, called MeshFEM and developed using C++, Matlab and the VTK library for 3D graphic visualisation. © 2012 Civil-Comp Ltd and Elsevier Ltd. All rights reserved.

Keywords: Aeronautic structures | CAD/CAE tool | Design conceptualisation | Parametric-associative modelling | Quad-mapped mesh | Wireframe primitives

[30] Di Angelo L., Di Stefano P., Morabito A.E., Automatic evaluation of form errors in high-density acquired surfaces, International Journal of Production Research, 49(7), 2061-2082, (2011). Abstract

Abstract: In this paper the authors present an original methodology aiming at the automation of the geometric inspection, starting from a high-density acquired surface. The concept of intrinsic nominal reference is herein introduced in order to evaluate geometric errors. Starting from these concepts, a new specification language, which is based on recognisable geometric entities, is defined. This work also proposes some surface differential properties, such as the intrinsic nominal references, from which new categories of form errors can be introduced. Well-defined rules are then necessary for the unambiguous identification of these intrinsic nominal references. These rules are an integral part of the tolerance specification. This new approach requires that a recognition process be performed on the acquired model so as to automatically identify the already-mentioned intrinsic nominal references. The assessable errors refer to recognisable geometric entities and their evaluation leaves the nominal reference specification aside since they can be intrinsically associated with a recognised geometric shape. Tolerance specification is defined based on the error categories which can be automatically evaluated and which are an integral part of the specification language. © 2011 Taylor & Francis.

Keywords: automated inspection | form error evaluation | GPS tolerancing

[31] Dattoma V., De Giorgi M., Giancane S., Manco P., Morabito A.E., Parametric-associative modelling of aeronautical concepts for structural optimization, Proceedings of the 7th International Conference on Engineering Computational Technology, (2010). Abstract

Abstract: In this work, a scheme of representation of structural concept for the aeronautical field is identified. It is based on an original set of 2D and 3D wireframe primitives, representing the main structural components of the aeronautical concept. Starting from them, an associative parametric geometrical modelling of the aeronautic structure, consisting in a quad-mapped mesh, is obtained. The automatic propagation of modifications is implemented so that several structural concepts can be efficiently modelled and modified during the very early phases of the design process. The propagation process aims at the automatic regeneration of the whole mesh thanks to a well-defined hierarchy (or relationship of dependences) among the parametrically defined primitives. Based on the above-mentioned considerations, a CAD/CAE tool, called MeshFEM, has been developed using C++ and Matlab languages and the VTK library for the 3D graphic visualization. © 2010 Civil-Comp Press.

Keywords: Aeronautic structures | CAD/CAE tool | Design conceptualisation | Quad-mapped mesh | Wireframe primitives

[32] Morabito A.E., Chrysochoos A., Dattoma V., Galietti U., Analysis of heat sources accompanying the fatigue of 2024 T3 aluminium alloys, International Journal of Fatigue, 29(5), 977-984, (2007). Abstract

Abstract: This paper deals with the calorimetric analysis of fatigue mechanisms of an aluminium alloy. Local 1D and 2D expressions of the heat diffusion equation were used to separately estimate the coupling and dissipative sources accompanying the fatigue test. The image processing was based on local approximations of surface temperature fields provided by an IR camera. The set of approximation functions accounted for the spectral properties of the sought sources. The analysis of thermoelastic source distribution allowed us to point out the possible heterogeneous character of fatigue loading from the beginning of the test. We observed that the zones where thermoelastic source amplitudes were the highest were potential loci of fatigue crack onset. On the other hand, such fine results on the dissipative source distribution were hard to obtain because of low signal-to-noise ratios. Nevertheless, we observed that the global dissipated energy rates increased linearly with the loading frequency. © 2006 Elsevier Ltd. All rights reserved.

Keywords: Aluminium alloy | Calorimetric analysis | Fatigue dissipation | Thermal images | Thermoelastic sources

[33] Morabito A.E., Chrysochoos A., Dattoma V., Galietti U., Analysis of thermoelastic and dissipative effects related to the fatigue of 2024 T3 aluminium alloy, Quantitative InfraRed Thermography Journal, 1(1), 99-116, (2004). Abstract

Abstract: In this paper the fatigue phenomena of 2024 T3 aluminium alloy were studied in terms of thermal and calorimetric effects during uniaxial cyclic loading. Thermoelastic coupling sources and dissipation were separately estimated by using infrared thermal data and a local simplified form of the heat equation. The simplifications are essentially based on the assumption that the uniaxial fatigue test remains homogeneous until a macroscopic fatigue crack occurs within the gauge section of the specimen. Heat sources were then compared to predictions derived from mechanical data by assuming a linear isotropic thermoelastic behaviour of the material and by neglecting the influence of thermomechanical couplings on the hysteresis area of fatigue cycles. © 2004 Taylor & Francis Group, LLC.

Keywords: Aluminium | Dissipation | Fatigue | Infrared thermography | Thermomechanical couplings

[34] Morabito A.E., Dattoma V., Galietti U., Energy-analysis of fatigue damage by thermographic technique, Proceedings of SPIE-The International Society for Optical Engineering, 4710, 456-463, (2002). Abstract

Abstract: The main aims of this paper are to describe the thermographic methodologies currently used in Italy for the rapid evaluation of the fatigue limit and to describe the local energy approach actually under development by the authors. Thermographic methodologies currently used in Italy for the rapid evaluation of the fatigue limit were applied to two stainless steels (AISI 304 atad AISI 409). All the experimental results here obtained are in good agreement with the respective values reported in literature. An experimental programme for the local energy approach is under development: its main characteristic consists in doing, besides the usual thermal measurements made by thermography, mechanical measurements in order to evaluate the mechanical energy locally dissipated inside the material. This experimental research is part of an interuniversity research programme and it is made on stainless steel (AISI 304) notched specimens. © 2002 SPIE · 0277-786X/02/$15.00.

Keywords: Fatigue limit evaluation | Local energy approach | Thermographic methodologies