Gianmaria Concheri

Gianmaria Concheri
University of Padova | UNIPD · Department of Civil, Environmental and Architectural Engineering ICEA

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81
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529
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Publications

Publications (81)
Chapter
Advancements in additive manufacturing technology have made it possible to create machines that allow the use of a wider range of materials, even simultaneously in the production of a single piece. The production of heterogeneous objects allows to include multifunctionality within the domain by varying the composition in a gradual or net fashion. T...
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An important issue when designing conformal lattice structures is the geometric modeling and prediction of mechanical properties. This paper presents suitable methods for obtaining optimized conformal lattice structures and validating them without the need for high computational power and time, enabling the designer to have quick feedback in the fi...
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One of the open issues in additive manufacturing is the design of conformal lattice structures, leading to an optimal layout of the struts in the design domain. This paper aims to compare different struts distributions in conformal lattices via low computational power methods in a CAD environment. Four approaches for a wireframe virtual model defin...
Article
The increasing attention to numerical issues related to material modeling is still a strong incentive to develop sound mechanical models that can explain material behavior up to failure. A procedure to handle a robust geometric meso-scale reconstruction of concrete materials is here proposed, based on X-ray Computed Tomography (CT-scan or X-ray CT)...
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Thanks to the great diffusion of additive manufacturing technologies, the interest in lattice structures is growing. Among them, minimal surfaces are characterized by zero mean curvature, allowing enhanced properties such as mechanical response and fluidynamic behavior. Recent works showed a method for geometric modeling triply periodic minimal sur...
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Additive Manufacturing (AM) brought a revolution in parts design and production. It enables the possibility to obtain objects with complex geometries and to exploit structural optimization algorithms. Nevertheless, AM is far from being a mature technology and advances are still needed from different perspectives. Among these, the literature highlig...
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Demand for innovation represents a driver not only in the industrial field but also in niche markets such as orthodontics. Among different type of orthodontic devices, functional appliances are used for the correction of class II skeletal malocclusion, mostly in young patients. In a previous study based on a systematic design approach, several conc...
Article
Objectives Implantoplasty (IP) is a treatment option for peri‐implantitis. Mechanical concerns were raised on fracture resistance of implants subjected to this procedure. This study aimed to compare two methods of IP in terms of implant wear and fracture resistance, and of surface topography. Material and methods 18 cylindrical screw‐shaped dental...
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Recently, the possibility of producing medium-to-large batches has increased the interest in polymer powder bed fusion technologies such as selective laser sintering (SLS) and multi jet fusion (MJF). Only scant data about the characterization of parts produced by MJF can be found in the literature, and fatigue behavior studies are absent. This stud...
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Additive manufacturing technology offers new design possibilities compared to traditional casting processes applied to metallic materials. Not only there are no limits in shape, but a higher microstructure control is allowed compared to traditional processes. Irrespective of the sample dimensions, the solidification defects induced by SLM process d...
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The freedom in geometry given by additive manufacturing allows to produce cellular materials, also called lattice structures, with unit cells and mesoscale features that are impossible to obtain with traditional manufacturing techniques. The geometric modeling of lattice structures still presents issues such as robustness and automation, but, with...
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The current requests for continuous innovation represent a challenge in every industry as well as in the field of orthodontics. Aim of this work was to develop new concepts of a functional appliance for the correction of class II skeletal malocclusion through a systematic design methodology. Staring at the existing devices in this field, taking int...
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Recent advances in additive manufacturing technologies demand for extremely customized, complex shape and multi-fold functional products. Heterogeneous objects, such as functionally graded materials, represent an attractive solution for researchers and industries in many application fields. Combining geometric modelling and material assignment in a...
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The biomechanics of the abdominal wall depends on muscular activation, tissue mechanical behavior and Intra-Abdominal Pressure (IAP). In this work, a numerical model of a human abdomen is presented, based on abdominal wall geometry from medical images. Specific constitutive formulations describe tissues mechanical behavior. Connective tissues are m...
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Minimal surfaces are receiving a renewed interest in biomedical and industrial fields, due to the capabilities of additive manufacturing technologies which allow very complex shapes. In this paper, an approach for geometric modeling of variable thickness triply periodic minimal surfaces in a CAD environment is proposed. The approach consists of thr...
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Aims: The purpose of the study was to evaluate the accuracy of a three-dimensional (3D) automated technique (computer-aided design (aCAD)) for the measurement of three canine femoral angles: anatomical lateral distal femoral angle (aLDFA), femoral neck angle (FNA) and femoral torsion angle. Methods:Twenty-eight femurs equally divided intotwo groups...
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Nowadays, topology optimization and lattice structures are being re-discovered thanks to Additive Manufacturing technologies, that allow to easily produce parts with complex geometries. The primary aim of this work is to provide an original contribution for geometric modeling of conformal lattice structures for both wireframe and mesh models, impro...
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Background and Objective: The biomechanical analysis of the abdominal wall should take into account muscle activation and related phenomena, such as intra-abdominal pressure variation and abdomen sur- face deformation. The geometry of abdominal surface and its deformation during contraction have not been extensively characterized, while represent a...
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The diffusion of design tools suitable for regular lattice structures was recently stimulated by the spread of additive manufacturing technologies that enable the fabrication of complex geometries, exceeding the limits of traditional manufacturing methods. Fillet radii play a fundamental role in the design of lattice materials, reducing the stress...
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The unique capabilities of additive manufacturing (AM) technologies highlight limits in commercial CAD tools. In this manuscript, after a synthetic description of the main AM technologies based on international standards classification, geometric modeling methods and data exchange file formats available in the literature are presented. Twelve geome...
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According to recent studies, a new paradigm in the geometric modeling of lattice structures based on subdivision surfaces for additive manufacturing overcomes the critical issues on CAD modeling highlighted in the literature, such as scalability, robustness, and automation. In this work, the mechanical behavior of the subdivided lattice structures...
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Purpose This paper aims to propose a consistent approach to geometric modeling of optimized lattice structures for additive manufacturing technologies. Design/methodology/approach The proposed method applies subdivision surfaces schemes to an automatically defined initial mesh model of an arbitrarily complex lattice structure. The approach has bee...
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Advances in additive manufacturing technologies facilitate the fabrication of cellular materials that have tailored functional characteristics. The application of solid freeform fabrication techniques is especially exploited in designing scaffolds for tissue engineering. In this review, firstly, a classification of cellular materials from a geometr...
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This note summarizes some recent investigation results on the behavior of corroded steel bolted joints under uniaxial fatigue loading. Fatigue test specimens, were made up using S355 structural steel plates joined together with preloaded M12 bolts of class 10.9 with a geometry that corresponds to the Δσ = 112 MPa EC3 detail category. The accelerate...
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The aim of this ex vivo study was to test a novel three-dimensional (3D) automated computer-aided design (CAD) method (aCAD) for the computation of femoral angles in dogs from 3D reconstructions of computed tomography (CT) images. The repeatability and reproducibility of three manual radiography, manual CT reconstructions and the aCAD method for th...
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In the fabrication process of aspheric glass lens and molds, shape characterization is a fundamental task to control geometrical errors. Nevertheless, the more significant geometrical functional aspect related to the optical properties is the curvature, which is rarely investigated in the manufacturing process of lenses. Algorithms for the assessme...
Article
In the fabrication process of aspheric glass lens and molds, shape characterization is a fundamental task to control geometrical errors. Nevertheless, the more significant geometrical functional aspect related to the optical properties is the curvature, which is rarely investigated in the manufacturing process of lenses. Algorithms for the assessme...
Chapter
Additive manufacturing technologies enable the fabrication of parts characterized by shape complexity and therefore allow the design of optimized components based on minimal material usage and weight. In the literature two approaches are available to reach this goal: adoption of lattice structures and topology optimization. In a recent work a Compu...
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Objective: To define and validate a method for the measurement of 3-dimensional (3D) morphometric parameters in polygonal mesh models of canine femora. Study design: Ex vivo/computerized model. Sample population: Sixteen femora from 8 medium to large-breed canine cadavers (mean body weight 28.3 kg, mean age 5.3 years). Methods: Femora were m...
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Currently available methods for evaluating dog femur deformities are principally based on 2D image analysis of radiographies. By CT or MRI, 3D information can be derived from points clouds or meshes. This work proposes an original approach for morphological and clinical parameters assessment on meshes. The method is validated on dog femur meshes me...
Conference Paper
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Additive manufacturing technologies enable the fabrication of innovative parts not achievable by other technologies, such as cellular structures, characterized by lightness and good mechanical properties. In this paper a novel modeling and optimization method is proposed to design regular cellular structures. The approach is based on generative mod...
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The present paper describes the design features, potential indications and a clinical application of a newly designed device for jaw motion rehabilitation, the Spring-Bite. This device is characterized by a first class lever mechanism, which allows performing passive jaw motion rehabilitation at constant load without an active participation by the...
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A method for computing lines of curvature and umbilical points is proposed. These properties, derived for NURBS surfaces, are useful in shape modeling for both aesthetic and functional characteristics evaluation. Moreover, the application to the ship-hull design and to the progressive additional lens design, of umbilics and lines of curvature are i...
Data
Rhino Open Projects is a collection of tools for Rhino 5 developed by the Laboratory of Design Tools and Methods in Industrial Engineering (Department of Civil, Environmental and Architectural Engineering, School of Engineering, University of Padova) for a variety of research projects such as biomedical (including dental), veterinary sciences, reve...
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The significantly growing use of Additive Manufacturing (AM) enables the fabrication of innovative parts, characterized by lightness and good mechanical properties. The biomedical field takes great advantage of these capabilities: in particular, the ability of producing porous or lattice structure-based parts allows to obtain prostheses with human...
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In the industrial world there are different production processes for the manufacturing of spectacle lens. Nowadays casting is the most common lens manufacturing method. Here, the mould production is based on three stages: grinding, polishing and hardening, where, in the second step, different sets of process parameters play a key role in quality, t...
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The surface optical properties of an ophthalmic lens are closely related to curvature parameters and consequently they can be derived by the geometric characterization of the lens surface. Adopting this approach it is possible to verify a spectacle lens by contact probe measurements without light transmission based instruments. Moreover, this metho...
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Rapid-prototyping is usually considered as a powerful tool in geometric and functional optimization of a product. In such an approach, focus is exclusively on the real component, and not on the rapid prototype which represents it. This work takes part on a wider study which focuses on a rational, systematic approach in obtaining an "optimized rapid...
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The free-form technologies, recently introduced in the manufacturing process of ophthalmic lenses, allow the production of high performance and custom progressive addition lenses (PALs). In this work a method for the parametric design and analysis of PAL, based on discrete shape modelling, is proposed. Both the optical (e.g. power and addition) and...
Conference Paper
In several manufacturing processes, the cutting of 2D parts from sheets is an important task. The arrangement of the parts in the sheets, supported by computers, is called nesting and is addressed to minimize the wasted material. In literature some approaches are proposed, based on genetic or heuristic algorithms which emphasize different character...
Conference Paper
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Several softwares are available in the market to support the ship design process. A common limit of these tools is related to the integration among existing CAD systems. Moreover the integration of expert system into conventional CAD systems is difficult and disadvantageous. In this work a software environment for the management of geometric models...
Conference Paper
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The advantages of no-contact methods of acquisition in the field of Cultural Heritage are numerous: from the generation of a photorealistic virtual model to the measurements of details. In this paper the optical acquisition and the 3D laser scanning of a perimortal fracture of a skull, dated between the media and recent Bronze Age, are presented. T...
Article
In questo lavoro viene presentata una suite di strumenti appositamente sviluppati a supporto delle attività di progettazione destinati alla gestione dei componenti per la realizzazione della struttura di un imbarcazione. Di particolare interesse, dal punto di vista innovativo, risultano essere le metodologie implementate per lo sviluppo di superfic...
Article
Several simple models, such as conicoid models, are usually adopted to describe the surfaces of the human crystalline lens; unfortunately they do not provide a continuous junction between the anterior and the posterior surface of the lens and then they cannot qualify for biomechanical simulation. Vice versa, more complex mathematical models give a...
Conference Paper
Full-text available
Purpose: By the mid-40s, the amplitude of accommodation has declined sufficiently so that most of us can no longer accommodate clearly and comfortably for close tasks. This condition, called presbyopia, is related to the growth of the lens. Nowadays, due to the development of the free-form technologies, the progressive addition lenses (PAL) are the...
Conference Paper
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Purpose: The aim of this work is to present a method for the verification of form tolerances in free-form geometries. Method: New free-form error parameters, in accordance with ISO GPS standards are defined. Geometrical errors in 2D e 3D geometries are calculated using a new fitting method consisting in an association operation where nominal profil...
Conference Paper
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Purpose: The aim of this work is to develop a virtual environment for modeling and analysis an individual virtual eye which is able to integrate the modern imaging techniques as input data. Method: The virtual environment is developed in a 3D CAD by means of specific plug-ins due to the ability of this software to manage freeform surfaces and to th...
Conference Paper
Full-text available
Precision free-form components are functionally complex objects with very accurate surfaces. In the manufacturing of these parts the complete and correct characterization of geometrical errors is an important aspect since it allows the adoption of preventive actions to control errors causes such as the thermo-mechanic behaviour of the machine tool,...
Article
This is a case of unilateral masseter muscle hypertrophy (MMH) treated with botulinum toxin (NHAI-normalised hemi-facial asymmetry index improvement from 5.48 to 3.04). After 19 months the treatment was repeated because of hypertrophy relapse (NHAI increase up to 6.82). The volume variations in the masseter area were monitored during 25 months usin...
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The introduction of deterministic NC grinding and polishing operations, in the manufacturing of free-form glass components for precision optics, requires the characterization of surface topography evolution as a function of process parameters. In this work, a model based on Reye's wear hypothesis is proposed for the assessment of surface roughness...
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Terrestrial methodologies, as high resolution laser scanning and digital photogrammetry, are used in many applications in the field of architectural and cultural heritage surveys: they are characterized by different operative procedures and precisions. Data deriving from acquisition of an architectural surface, “morphologically complex” but geometr...
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Current methodologies in the prevision of post-surgical features of the face in orthognathic surgery are mainly 2-D. An improvement is certainly given by the introduction of CT, but its acceptance is controversial due to its high biological cost. As an alternative, in this study an effective procedure for the construction of a 3-D textured digital...
Conference Paper
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Surface polishing is a typical example of a machining process based on mixed chemical-mechanical phenomena, as pointed out in the recent literature on the polishing process (CPM - Chemical Mechanical Polishing). In this work, a model is proposed for the assessment of surface roughness evolution in the polishing process of glass moulds, used in the...
Article
The selection of modeling and machining parameters for glass mould fabrication in ophthalmic lenses production, has required the definition of a theoretical–empirical model of the ground surface in order to predict the overall geometry errors of the surface. The accurate control of the geometrical errors and of the surface texture for the mould fun...