Design of custom cranial prostheses combining manufacturing and drop test finite element simulations

AbstractIn this work, impact puncture tests (drop tests) have been used to both tune numerical models and correlate the performance of customised titanium cranial prostheses to the manufacturing process. In fact, experimental drop tests were carried out either on flat disk-shaped samples or on prototypes of titanium cranial prostheses (Ti-Gr5 and Ti-Gr23 were used) fabricated via two innovative sheet metal forming processes (the super plastic forming (SPF) and the single point incremental forming (SPIF)). Results from drop tests on flat disk-shaped samples were used to define the material behaviour of the two investigated alloys in the finite element (FE) model, whereas drop tests on cranial prostheses for validation purposes. Two different approaches were applied and compared for the FE simulation of the drop test: (i) assuming a constant thickness (equal to the one of the undeformed blank) or (ii) importing the thickness distribution determined by the sheet forming processes. The FE model of the drop test was used to numerically evaluate the effect of the manufacturing process parameters on the impact performance of the prostheses: SPF simulations were run changing the strain rate and the tool configuration, whereas SPIF simulations were run changing the initial thickness of the sheet and the forming strategy. The comparison between numerical and experimental data revealed that the performance in terms of impact response of the prostheses strongly depends on its thickness distribution, being strain hardening phenomena absent due to the working conditions adopted for the SPF process or to the annealing treatment conducted after the SPIF process. The manufacturing parameters/routes, able to affect the thickness distribution, can be thus effectively related to the mechanical performance of the prosthesis determined through impact puncture tests

Study of Tailor Heat Treated Blanks Using the Fourier-series-based VFM

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Mechanical and microstructure analysis of AA6061 and Ti6AI4V fiber laser butt weld

Dissimilar metal welding involves the joining of two or more different pure metals or alloys, usually by melting and mixing and often with the addition of filler metal. There are several types of dissimilar metal welds including stainless steel, either as base metal or as filler metals. Dissimilar metal joints have distinctive features because of differences in the chemical composition of base metal and filler material. Their alloying elements will diffuse intensely during welding. The structures near the fusion line are very complex. Despite of great potentiality in aircraft and automotive industries, dissimilar joining of hybrid Al-Ti structures is often challenging because of the unavoidable formation of brittle intermetallic compounds, mixing of molten phases, and significant differences in material properties. In this work, dissimilar 2 mm thickness AA6000 and Ti6Al4V butt joints were produced by shifting an Yb fiber laser beam on the upper surface of the Ti sheet. Neither filler wire nor groove preparation was adopted. Different working conditions and seam shapes were assessed. The welds were characterized in terms of metallurgical and mechanical behaviors

Radio Lobes of Pictor A: an X-ray spatially resolved Study

A new XMM observation has made possible a detailed study of both lobes of the radio galaxy Pictor A. Their X-ray emission is of non thermal origin and due to Inverse Compton scattering of the microwave background photons by relativistic electrons in the lobes, as previously found. In both lobes, the equipartition magnetic field (Beq) is bigger than the Inverse Compton value (Bic), calculated from the radio and X-ray flux ratio. The Beq/Bic ratio never gets below 2, in spite of the large number of reasonable assumptions tested to calculate Beq, suggesting a lobe energetic dominated by particles. The X-ray data quality is good enough to allow a spatially resolved analysis. Our study shows that Bic varies through the lobes. It appears to increase behind the hot spots. On the contrary, a rather uniform distribution of the particles is observed. As a consequence, the radio flux density variation along the lobes appears to be mainly driven by magnetic field changes.Comment: 15 pages, 3 figures, ApJ accepte

On the manufacturing of highly-customized near net-shape medical implants using magnesium alloy sheet

Incluída en Procedia Manufacturing 50The purpose of this work is defining a global methodology framework for the manufacturing of medical implants using Mg alloys by Incremental Forming process from the results attained by the authors in this field. The methodology proposed considers two main steps, an indispensable related to material characterization that includes from the classical and mechanical to spifability testing and it includes numerical simulations. And another one related mainly to implant forming taking into account the best process parameters from the analysis carried out in the previous step. As newness, two variants of the incremental forming process, Single (SPIF) and Two-Point (TPIF) Incremental Forming, are used for the same magnesium implant geometry. Different outputs variables, mainly: Ra, Shape accuracy and Thicknesses, besides Force and Temperature were analysed for comparison purposes.Universidad de Girona MPCUdG2016 / 036Ministerio de Educación, Universidad e Investigación (Italia) CUP - D94I18000260001Ministerio de Educación (España) DPI2016-77156-

Comparative in vitro study on biomechanical behavior of zirconia and polyetheretherketone biomaterials exposed to experimental loading conditions in a prototypal simulator

Zirconia and polyetheretherketone (PEEK) are two biomaterials widely investigated as substitute for metals in oral prosthetic rehabilitation. To achieve a proper biomechanical behavior, the prosthetic biomaterials must ensure a good resistance to loads, as this is a crucial characteristic enabling their use in dental applications. The aim of this study was to investigate differences in the fracture resistance of different biomaterials in an experimental environment: fixed partial dentures (FPDs) screwed in a prototype of biomimetic mandible. 10 Samples of FPDs were allocated in 2 groups (A and B): Group A (n=5) involved FPDs in zirconia-ceramic, and Group B (n=5) involved FPDs in PEEK-composite. The samples were loaded by means of a three-point bending mechanical test, and the load to fracture has been evaluated generating a point-by-point graphics (speed/load and time/deformation). The samples were further analyzed by micro-computed tomography (micro-CT) and described under experimental loading conditions. Zirconia-ceramic FDPs were the samples reporting the worst results, showing a lower value of vertical displacement with respect to PEEK-based samples. The micro-CT results have further confirmed the preliminary results previously described. This in vitro study aims to give analytic data on the reliability of PEEK as a reliable and strong biomaterial for prosthetic treatments.</p

Performances Analysis of Titanium Prostheses Manufactured by Superplastic Forming and Incremental Forming

Abstract Titanium and its alloys are widely used in cranioplasty because they are biocompatible with excellent mechanical properties and favor the osseointegration with the bone. However, when Titanium alloys have to be worked several problems occurred from a manufacturing point of view: the standard procedure for obtaining Titanium prostheses is represented by the machining processes, which result time and cost consuming. The aim of this research consist to introduce alternative flexible sheet forming processes, i.e. Super Plastic Forming (SPF) and Single Point Incremental Forming (SPIF), for the manufacturing of patient-oriented titanium prostheses. The research activities have already highlighted the potentiality of the investigated forming processes that can be alternatively used taking into account both the damage morphology and the need of urgency operation. In the present work, the way of manufacturing the Ti prostheses by SPF and SPIF is described. A comparative analysis has been performed, thus highlighting the peculiarities of the investigated processes and the prostheses feasibility

BEAT: Bioinformatics Exon Array Tool to store, analyze and visualize Affymetrix GeneChip Human Exon Array data from disease experiments

<p>Abstract</p> <p>Background</p> <p>It is known from recent studies that more than 90% of human multi-exon genes are subject to Alternative Splicing (AS), a key molecular mechanism in which multiple transcripts may be generated from a single gene. It is widely recognized that a breakdown in AS mechanisms plays an important role in cellular differentiation and pathologies. Polymerase Chain Reactions, microarrays and sequencing technologies have been applied to the study of transcript diversity arising from alternative expression. Last generation Affymetrix GeneChip Human Exon 1.0 ST Arrays offer a more detailed view of the gene expression profile providing information on the AS patterns. The exon array technology, with more than five million data points, can detect approximately one million exons, and it allows performing analyses at both gene and exon level. In this paper we describe BEAT, an integrated user-friendly bioinformatics framework to store, analyze and visualize exon arrays datasets. It combines a data warehouse approach with some rigorous statistical methods for assessing the AS of genes involved in diseases. Meta statistics are proposed as a novel approach to explore the analysis results. BEAT is available at <url>http://beat.ba.itb.cnr.it</url>.</p> <p>Results</p> <p>BEAT is a web tool which allows uploading and analyzing exon array datasets using standard statistical methods and an easy-to-use graphical web front-end. BEAT has been tested on a dataset with 173 samples and tuned using new datasets of exon array experiments from 28 colorectal cancer and 26 renal cell cancer samples produced at the Medical Genetics Unit of IRCCS Casa Sollievo della Sofferenza.</p> <p>To highlight all possible AS events, alternative names, accession Ids, Gene Ontology terms and biochemical pathways annotations are integrated with exon and gene level expression plots. The user can customize the results choosing custom thresholds for the statistical parameters and exploiting the available clinical data of the samples for a multivariate AS analysis.</p> <p>Conclusions</p> <p>Despite exon array chips being widely used for transcriptomics studies, there is a lack of analysis tools offering advanced statistical features and requiring no programming knowledge. BEAT provides a user-friendly platform for a comprehensive study of AS events in human diseases, displaying the analysis results with easily interpretable and interactive tables and graphics.</p