1,721,087 research outputs found
Fatigue Behavior of Additively Manufactured Stainless Steel 316L
Full text link316L stainless steel is the material of choice for several critical applications in which a combination of mechanical strength and resistance to corrosion is required, as in the biomedical field. Additive Manufacturing (AM) technologies can pave the way to new design solutions, but microstructure, defect types, and surface characteristics are substantially different in comparison to traditional processing routes, making the assessment of the long-term durability of AM materials and components a crucial aspect. In this paper a thorough review is presented of the relatively large body of recent literature devoted to investigations on fatigue of AM 316L, focusing on the comparison between different AM technologies and conventional processes and on the influence of processing and post-processing aspects in terms of fatigue strength and lifetime. Overall fatigue data are quite scattered, but the dependency of fatigue performances on surface finish, building orientation, and type of heat treatment can be clearly appreciated, as well as the influence of different printing processes. A critical discussion on the different testing approaches presented in the literature is also provided, highlighting the need for shared experimental test protocols and data presentation in order to better understand the complex correlations between fatigue behavior and processing parameters
FEM Simulation of Subintimal Angioplasty for the Treatment of Chronic Total Occlusions
Full text linkSub-intimal angioplasty is a highly challenging technique for percutaneous treatment of chronic total occlusion (CTO) in blood vessels and the development of predictive tools for preliminary evaluation of potential outcomes and risks could be very useful for clinicians. While Finite Element (FE) simulation is a well established approach to investigate partial occlusions, its extension to CTO has not been investigated yet, because of several additional issues that have to be addressed.
In this work, we discuss the implementation of a FE model to simulate the main steps of the procedure, i.e. sub-intimal insertion of an initially folded balloon in a false lumen, inflation from eccentric position, deflation and extraction. The model includes key morphological features of the CTO and possibility to vary spatial distribution of material properties to account for different constituents and degree of calcification. Both homogeneous and heterogeneous CTO configurations were analysed, comparing arterial stress state, plaque compression and post-procedural recoil. For a peak inflation pressure of 12 bar, the degree of lumen restoration was in the range 65-80%, depending on plaque heterogeneity. After balloon extraction, homogeneous highly calcified plaques exhibited substantial recovery of original shape. For homogeneous and heterogeneous CTO values of peak von Mises stress in the arterial wall were of the same order of magnitude (range 1-1.1 MPa) but at different locations. Results compared favourably with data reported in literature for post-procedural lumen restoration and arterial stress data, confirming potential usefulness of the approach
Ancora Pinocchio. Riflessioni sulle avventure di un burattino
No full textAlla lettura del racconto collodiano condotto dell'altra autrice del volume, si affianca quella del Pinocchio “immaginato” attraverso le illustrazioni e del burattino in fuga tra metamorfosi e avventura (Susanna Barsotti). Le Avventure possono essere considerate forse un libro evocativo e suggestivo più che descrittivo e dunque difficile da illustrare senza deludere il lettore; al tempo stesso si presentano come costantemente aperte a tante rappresentazioni cosicché la mancanza di descrizione precisa offre alla fantasia qualsiasi via d’uscita e, negli esiti migliori, continua ad alimentarla. Infine il percorso dell’avventura intesa come prova delle cose volontariamente
cercata, il curioso e insopprimibile bisogno di sperimentare tutto il reale, l'impulso irrefrenabile a trasformare il sentito dire e l'immaginato in vita vissuta, pagata di persona, una sorta di quest in chiave comica che costituisce l'elemento essenziale della Weltanschauung di Pinocchio
Effects of fiber layout on strength and failure of 3D printed notched composites
Full text linkThis study investigates the effect of printing strategies on the strength of additively manufactured notched fiber
reinforced composite specimens. Specimens with varying notch geometries (two radii and two opening angles)
and fiber layouts (unreinforced, unidirectional, quasi-isotropic and concentric) were 3D printed and tested under
tension. Digital image correlation provided surface strain field data. Results showed that fiber deposition patterns
significantly impact notch sensitivity, failure loads and mechanisms, with notch geometry being of secondary
importance. The unidirectional layout achieved the highest strength but with progressive failure, while quasiisotropic
specimens failed abruptly from the notch. The concentric layout shielded the notch region but
induced premature failure away from the notch due to transverse stress. Stress concentration factor approaches,
which work well for conventional laminates, have limitations for 3D printed composites due to local differences
and complex interactions. Optimizing fiber deposition, instead of geometry, emerges as a promising design route.
Combining unidirectional and contouring algorithms may improve performance. However, further studies utilizing
multiscale modelling and local failure analyses are needed to fully understand failure mechanisms and
guide optimal notch designs for 3D printed composites. With improved understanding and design methods, 3D
printing promises to unlock new possibilities for structurally efficient notched composite parts
Finite element modelling of 3D printed continuous carbon fiber composites: Embedded elements technique and experimental validation
Full text linkSome aspects of germination and cell wall formation in tetraspores of Nitophyllum punctatum (Rhodophyta).
No full textLemanea rigida Sirodot e Batrachospermum crouanianum Sirodot (Rhodophyta) nel torrente Rosandra (Trieste).
No full textA Computational Model of Custom 3D Printed Hand Orthosis
No full text3D printed patient-specific hand orthoses can improve the efficiency of the treatment and the comfort of the patient, but since each customized orthosis is a virtually unique device, it is difficult to assess their mechanical response in the design phase, both experimentally and numerically. The Finite Element Method (FEM) could be used to predict the deformation of the orthosis under predetermined loads, but patient-specific models including interaction with the hand are still lacking. In the present work we present a computational model in which, starting from the scan data of the hand used to manufacture the orthosis, a FEM model of the hand is generated, including a skeletal structure. Hand bones positions and dimensions can be defined basing on simple anatomical measurements or literature data and the stiffness of the joints can be tuned in relation to patient pathology. The remaining hand volume consists of a soft tissue region, mimicking the non-linear mechanical behaviour of skin and muscles. Results show that both functional and structural indexes can be analyzed, such as contact pressures, stress state or the compliance of the orthosis, providing useful information for the design of custom devices. By using mesh deformation algorithms, the scan data could be used to generate different orthosis designs in target positions defined by the therapist and, taking advantage of a parametric model under development, the skeletal structure could be adapted correspondingly, providing an innovative pathway to investigate the response of the orthosis during the whole rehabilitation
Tribological Behavior of a Selective Laser Melted CoCrMo Alloy under Different Heat Treatment, Loading, and Sliding Conditions
No full textSelective laser melted (SLM) CoCrMo alloy holds promise in various biomedical and industrial applications, requiring exceptional tribological properties to withstand contact interactions and wear. Despite this, research on SLM-CoCrMo tribology remains relatively unexplored. This study presents a comprehensive comparative analysis, evaluating the impact of heat treatments, specifically at 800 °C/2 h, 1150 °C/2 h, and hot isostatic pressing (HIP), under varying load levels (2 N, 5 N, and 7 N) and sliding conditions (single way or reciprocating). The results demonstrate that different combinations of load, sliding condition, and heat treatment induce diverse wear mechanisms, significantly influencing the alloy’s tribological performance. Specifically, the as-built (AB) condition showed the highest wear rates at 2 N, whereas HIP-treated samples exhibited a significant reduction in wear rate compared to AB specimens at 7 N, under both reciprocating and single-way sliding conditions. Among the investigated conditions, HIP treatment emerged as the optimal compromise between wear resistance and mechanical properties. The findings provide valuable insights for optimizing the tribological behavior of the SLM-CoCrMo alloy, especially in load-bearing biomedical applications such as joint implants and prosthetics components
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