Carmine Pappalettere - Academia.edu (original) (raw)

Papers by Carmine Pappalettere

Conference proceedings of the Society for Experimental Mechanics, 2011

ABSTRACT Thin film technology is an area of great importance in current applications of opto-elec... more ABSTRACT Thin film technology is an area of great importance in current applications of opto-electronics, electronics, MEMS and computer technology. A critical issue in thin film technology is represented by residual stresses that arise when thin films are applied to a substratum. Residual stresses can be very large in magnitude and may result in detrimental effects on the role of the thin film must play. For this reason it is very important to perform “online” measurements in order to control variables influencing residual stress. The research work presented in the paper represents the first step towards the practical solution of such a challenging problem. A methodology to measure residual stresses utilizing reflection/projection moiré interferometry to measure deflections of thin coated specimens is developed. Results are in good agreement with experimental values provided by well established measurement techniques. A special optical circuit for the in situ measurement of residual stresses is designed trying to satisfy the constraints deriving from the tight geometry of the vacuum system utilized to carry out the deposition.

Abstract: Nowadays, it is widely recognized that a large number of phenomenological degrees of fr... more Abstract: Nowadays, it is widely recognized that a large number of phenomenological degrees of freedom basically rule the functionality of bone tissue scaffolds. As a consequence of this, the design of scaffolds for tissue engineering involves multidisciplinary and multi-scale aspects, the latter being the subject of intensive investigation by the research community. In this chapter we present an overview on the computational aspects of bone tissue engineering, with particular emphasis on the recent mechanobiological based finite element models, as well as on novel aspects regarding the numerical characterization of the network of scaffold voids.

Procedia Engineering, 2015

European Journal of Orthodontics, Aug 13, 2010

American Journal of Orthodontics and Dentofacial Orthopedics, Aug 1, 2008

In this study, we aimed to analyze the displacement field and the level of stability for a human ... more In this study, we aimed to analyze the displacement field and the level of stability for a human mandible that had symphyseal distraction osteogenesis. The mandible was fitted with various orthodontic devices: tooth borne, bone borne, and hybrid. Three-dimensional nonlinear finite element analyses were performed to study differences between the nominal aperture of the device and the actual mandibular distraction. Furthermore, displacement fields of the mandibular arch evaluated with and without mastication forces were compared to determine the level of stability of each appliance. Methods: Computed tomography scan images of the mandible were processed to create the finite element model, which was completed by modeling the distraction device. Three cases were considered: the distraction device attached to the first molar and the first premolar (tooth borne), to the canine and basal bones (hybrid), or only to the basal bone (bone borne). The nominal aperture of each device was 2 mm. Mandibular displacements in the mastication phase were analyzed in the case of unilateral occlusion on the second premolar. Results and Conclusions: Tooth-borne and hybrid devices allow orthodontists to better control the effective displacement transferred to the mandible by the distractor. Displacements of the mandibular arch were closer to the nominal aperture of the distractor than in the case of the bone-borne device. Hybrid devices were more stable under functional loads. However, parasitic rotations of the mandibular arms caused by mastication might counteract the benefits of distraction.

$Research paper thumbnail of A mechano-regulation model of fracture repair in vertebral bodies$

Journal of Orthopaedic Research, Sep 30, 2010

In this study a multi-scale mechano-regulation model was developed in order to investigate the me... more In this study a multi-scale mechano-regulation model was developed in order to investigate the mechanobiology of trabecular fracture healing in vertebral bodies. A macro-scale finite element model of the spinal segment L3-L4-L5, including a mild wedge fracture in the body of the L4 vertebra, was used to determine the boundary conditions acting on a micro-scale finite element model simulating a portion of fractured trabecular bone. The micro-scale model, in turn, was utilized to predict the local patterns of tissue differentiation within the fracture gap and then how the equivalent mechanical properties of the macro-scale model change with time. The patterns of tissue differentiation predicted by the model appeared consistent with those observed in vivo. Bone formation occurred primarily through endochondral ossification. New woven bone was predicted to occupy the majority of the space within the fracture site approximately 7-8 weeks after the fracture event. Remodeling of cancellous bone architecture was then predicted, with complete new trabeculae forming due to bridging of the microcallus between the remnant trabeculae.

Annals of Biomedical Engineering, Sep 4, 2007

Mandibular distraction osteogenesis is a clinical procedure used for modifying the mandibular geo... more Mandibular distraction osteogenesis is a clinical procedure used for modifying the mandibular geometry when problems of dental overcrowding and arch shrinkage occur. The objective of this study is to use a computational model of tissue differentiation to examine the influence of the rate of distraction on bone regrowth within the fracture callus of a human mandible submitted to symphyseal distraction osteogenesis. A 3D model of the mandible is reconstructed from CT scan data and meshed into finite elements. Two different mastication loadings have been investigated: a 'full' mastication load and a 'reduced' mastication load where the action of each muscle was reduced by 70%. Four different distraction rates were analysed: 0.6 mm/day, 1.2 mm/day, 2 mm/day and 3 mm/day, allowing a total displacement of 6 mm. In the early stages of the distraction process it is predicted that there is a decrease in the amount of bone tissue forming within the centre of the fracture gap for all distraction rates. After the initial phases of expansion, the bone tissue within the callus increases for the slower rate of distraction or continues to decrease at the faster rates of distraction. At the end of the simulated maturation period, 47% of the distracted callus was predicted to consist of bone tissue for a distraction rate of 0.6mm/day, decreasing to 22% for a distraction rate of 3mm/day. Significantly higher amounts of bone formation were predicted for all distraction rates for the case of reduced mastication loading. Disparities between the model predictions and what is observed in vivo were found. For instance, during the latency period, the distraction period and beyond, the model is predicting larger than expected amounts of cartilage tissue formation within the callus. This and other limitations of the proposed model are discussed and possible specific explanations for these disparities are provided in the paper. The model predicts a distraction rate of around 1.2 mm/day to be optimal as higher rates produce less bone tissue while the risk of a premature bone union is greater at slower rates of distraction because in the latter stages of the distraction process bone tissue is predicted to form between the left and right side of the bone callus.

Journal of Mechanics in Medicine and Biology, Sep 1, 2009

CAD reconstruction of anatomical regions from computerized tomography (CT) scans is a very common... more CAD reconstruction of anatomical regions from computerized tomography (CT) scans is a very common approach in orthopaedic biomechanics. The CAD model is discretized into finite volume sub-domains and finite element (FE) analyses are performed in order to predict the distribution of stresses generated by applied loads. However, quality and reliability of numerical results depend on the level of accuracy reached in the meshing process. This paper analyzes some critical parameters that may affect the overall efficiency of the CT–FEM transformation process: scan threshold range, object size, and complexity. An optimization procedure for minimizing geometric errors on size and shape of reconstructed objects is presented. Finally, accuracy of stress predictions is evaluated for FE models that include known amounts of geometric errors. Compression and bending loads are considered. Results show that geometric and stress errors rapidly decrease as the objects to be reconstructed become larger in size. Optimal threshold ranges can be identified clearly for both an epoxy-resin benchmark model and a real bone specimen cut from a human lumbar vertebra. This allows geometric errors to be reduced significantly.

Journal of Mechanics in Medicine and Biology, Feb 1, 2017

This study aims to investigate the feasibility of using time-average holography to verify the int... more This study aims to investigate the feasibility of using time-average holography to verify the integrity of skin tissue samples and detect changes in their mechanical response caused by exposure to thermal perturbations, radiations and mechanical loading. For that purpose, chicken skin samples are put into vibration and the corresponding modes are monitored by means of an optical set up based on time average holographic interferometry. Mode shapes of base samples computed by a parametric finite element model are consistent with experimental data. The holographic set up correctly detects the presence of defects previously included in the sample. Dynamic behavior of skin samples under various conditions of low/high temperature and load or exposed, for different periods of time, to UV radiation and microwaves also is successfully monitored. The reliability and robustness of the proposed approach is tested by performing the holographic observations on a large number of samples under different conditions. Potential benefits that may derive from the use of time-average holography in dermatology and plastic surgery (for example, in the quality control of artificial skin tissues to be implanted) are finally discussed.

Procedia structural integrity, 2017

Abstract This paper aims to analyse the effects of corrosion atmosphere on sintered stainless-ste... more Abstract This paper aims to analyse the effects of corrosion atmosphere on sintered stainless-steel specimens. In particular, it is intended to assess a relation existing between weight and corrosion resistance, density and corrosion resistance, tensile properties and corrosion resistance. Three groups of sintered stainless steels were studied. They differ, one from each other, for the laser power and for the speed scanning. For each group, nine specimens were made up. For all of them, measurements of both weight and density were carried out. One specimen of them was tested, as received, according to the tensile standard for metallic materials. Eight specimens for each class were placed in corrosive atmosphere in conducting the neutral salt spray (NSS) tests for assessment of the corrosion resistance of metallic materials. Four different periods of exposure were defined. At the end of each test period, two specimens were removed from the cabinet. Visual observations, measurements of mass loss, density variations and tensile tests was carried out on all the specimens referring to the specific exposure time, in order to evaluate and record all the changes referring to the specific conditions they were subjected to.

Measurement, Sep 1, 2016

In this paper fatigue test results are presented for titanium grade 5 specimens subjected to unia... more In this paper fatigue test results are presented for titanium grade 5 specimens subjected to uniaxial cyclic loads. The material behavior of titanium was studied by comparing the Acoustic Emission (AE) detection technique with the Infrared Termography (IT). The AE technique consists on attaching a couple of piezoelectric sensors on the surface of the sample in order to allow real-time recording of acoustic activity occurring in the material during the test and to localize the acoustic source, based on the assumption that part of the acoustic activity depends on the crack propagation process. All typical data of AE were collected during the tests and some of them were properly post-processed by using filters or derivative functions in order to better understand the crack propagation phenomenon. At the same time, thermographic analysis was also carried out during the experiments by continuous monitoring of surface temperature of the sample. Results of the fatigue behavior of the analyzed material beside the acoustic emission track and the thermal images of the sample are analyzed and critically discussed, in order to assess the capability of each technique in predicting the imminent failure of material.

Engineering Failure Analysis, Nov 1, 2016

Abstract The aim of this work is to provide, in a non-destructive way, information about the stru... more Abstract The aim of this work is to provide, in a non-destructive way, information about the structural integrity of materials subjected to a sinusoidal fatigue loading. In particular, the crack propagation was studied in AISI 430F/1 by using Acoustic Emission (AE) and Infrared Thermography (IT) at the same time. The main advantages of both approaches refer to the possibility to monitor the whole history of the specimen; in fact, differently by ultrasound inspection, no scanning is required and moreover the measurement is simplified by the fact that access from just one side of the specimen is sufficient. For AE technique two sensors were placed on the surface of the specimen in order to detect the elastic waves emitted by the material under stress and due to the activation of inner defects. By analyzing the overall acoustic signals it is possible to correlate a part of them directly to the crack propagation phenomenon. At the same time a thermocamera was placed in front of the specimen to live monitor the variation of surface temperature. Above all, the rise of temperature around the crack tip was observed in order to evaluate the advancing of the crack during the test. Finally a comparison between the two techniques was carried out aiming to assess the capability of each approach in following the evolution of the damage process.

International Journal of Biological Sciences, 2011

Techniques of bone reconstructive surgery are largely based on conventional, non-cell-based thera... more Techniques of bone reconstructive surgery are largely based on conventional, non-cell-based therapies that rely on the use of durable materials from outside the patient's body. In contrast to conventional materials, bone tissue engineering is an interdisciplinary field that applies the principles of engineering and life sciences towards the development of biological substitutes that restore, maintain, or improve bone tissue function. Bone tissue engineering has led to great expectations for clinical surgery or various diseases that cannot be solved with traditional devices. For example, critical-sized defects in bone, whether induced by primary tumor resection, trauma, or selective surgery have in many cases presented insurmountable challenges to the current gold standard treatment for bone repair. The primary purpose of bone tissue engineering is to apply engineering principles to incite and promote the natural healing process of bone which does not occur in critical-sized defects. The total market for bone tissue regeneration and repair was valued at 1.1billionin2007andisprojectedtoincreasetonearly1.1 billion in 2007 and is projected to increase to nearly 1.1billionin2007andisprojectedtoincreasetonearly1.6 billion by 2014. Usually, temporary biomimetic scaffolds are utilized for accommodating cell growth and bone tissue genesis. The scaffold has to promote biological processes such as the production of extra-cellular matrix and vascularisation, furthermore the scaffold has to withstand the mechanical loads acting on it and to transfer them to the natural tissues located in the vicinity. The design of a scaffold for the guided regeneration of a bony tissue requires a multidisciplinary approach. Finite element method and mechanobiology can be used in an integrated approach to find the optimal parameters governing bone scaffold performance. In this paper, a review of the studies that through a combined use of finite element method and mechano-regulation algorithms described the possible patterns of tissue differentiation in biomimetic scaffolds for bone tissue engineering is given. Firstly, the generalities of the finite element method of structural analysis are outlined; second, the issues related to the generation of a finite element model of a given anatomical site or of a bone scaffold are discussed; thirdly, the principles on which mechanobiology is based, the principal theories as well as the main applications of mechano-regulation models in bone tissue engineering are described; finally, the limitations of the mechanobiological models and the future perspectives are indicated.

Applied Composite Materials, Sep 3, 2020

The integrity of the CFRP specimens is tested using acousto-ultrasonic testing method. To validat... more The integrity of the CFRP specimens is tested using acousto-ultrasonic testing method. To validate the acousto-ultrasonic test mode, the specimens are tested before and after a Barely Visible Impact Damage induced by an impactor. A special model is created to use both Wavelet Packet Transform and Empirical Mode Decomposition, for decomposing the recorded waveforms. This mode also enables the reconstruction of the decomposed waveforms, discarding the residual signal in the parent waveform, and calculates the energy associated with each frequency band of the reconstructed signal. By using the percentage of energy recovered by the receiver compared to the signal sent through the specimen, the integrity of the specimens is identified. Moreover, the properties of each specimen and the extent of its damage, albeit qualitatively along the longitudinal and transverse directions can also be assessed by using this technique.

InTech eBooks, Nov 25, 2011

$Research paper thumbnail of A model of tissue differentiation and bone remodelling in fractured vertebrae treated with minimally invasive percutaneous fixation$

Medical & Biological Engineering & Computing, Jun 30, 2012

In spite of the consolidated clinical use of minimally invasive percutaneous fixation techniques,... more In spite of the consolidated clinical use of minimally invasive percutaneous fixation techniques, little is reported in the literature providing a mechanobiological explanation for how the design of fixation devices can affect the healing process within fractured vertebrae. The aim of this study was to develop a multi-scale mechanoregulation model capable of predicting how the patterns of tissue differentiation within a vertebral fracture change in the presence or in the absence of fixation devices and how the dimensions of the device, and the materials it is made from (Ti-6Al-4V alloy and cobalt chrome alloy) can affect the outcome of the healing process. The macro-scale model simulates the spinal segment L3-L4-L5, including the fractured body of the L4 vertebra, while the micro-scale model represents a fractured portion of cancellous bone. The macro-scale model also includes a minimally invasive percutaneous fixation device. The model predicts that fixation devices significantly shorten healing times. Increasing values of the rod diameter D and decreasing values of its radius of curvature R lead to shorter durations of the healing period. Manufacturing the rods in cobalt chrome alloy is also predicted to reduce slightly the healing period by providing greater mechanical stability within the fracture callus.

Composites Part B-engineering, Feb 1, 2017

In the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked... more In the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked together with a particular sequence in order to give specific mechanical characteristics. Layers are organized with different angles, different sequences and different technological processes to obtain innovative materials. This paper introduces a new parameter, able to improve mechanical properties of composites. It analyses an unconventional fibres orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of CFRP. Conventional carbon fibres orientation is generally referred to a Cartesian coordinate system, in which fibres are arranging in bundles along different angle orientations respect to the zero lamina. In this paper a polar coordinate system of continue carbon tow is introduced to create specimens as well as complex geometry components in an easy way. Five different configurations are studied: two are classified as traditional composites (unstitched and Cartesian orientation of woven carbon cloth), three are defined as innovative composites (stitched laminates and continue carbon tow organized in polar or Cartesian system). The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon.

The International Journal of Advanced Manufacturing Technology, Mar 18, 2015

ABSTRACT This paper is devoted to the design and implementation of a novel moiré-based optical he... more ABSTRACT This paper is devoted to the design and implementation of a novel moiré-based optical head mounted on the robotic arm of a coordinate measuring machine. The optical components of the recently developed two-projector moiré setup were miniaturized and integrated in the optical head. Special care was taken in minimizing the weight of the resulting structure so as to reduce as much as possible the forces acting on the robotic arm. The prototype of the optical head was tested by contouring the shape of different objects and measuring the displacements of a metallic bar subjected to compression loading. Measurements conducted with the proposed optical head were consistent with those obtained via a coordinate measuring machine (CMM). The values of the dimensions found fell always within the average ± standard deviation interval measured with the CMM. The optical head appears very suited for contouring the shape of objects and for determining the out-of-plane displacement field of mechanical components subjected to specific boundary and loading conditions. Furthermore, the system can be easily implemented inline in an industrial context to perform measurements as a product is being manufactured.