Innovative machining strategies to manufacture biomedical prostheses for improved in-life functional performances

The growing demand of components of higher performances, in terms of reliability and durability, is continuously pushing to find innovative manufacturing methods to realize such components. Especially in the biomedical field, as a consequence of the raising of population age and consequent increase of the number of revision surgeries, this is a matter of concern, since revision operations are complex and costly for the healthcare, furthermore they cause pain to the patient. The failure of the biomedical implants is mainly due to excessive wear and corrosion, which leads to implant loosening, and premature failure of the implants inside the biological environment. These phenomena are surfacedependent, since they initiate from the latter. Efforts have been made by several researchers in the past few decades to investigate the relationships among the machining process parameters, the nature of the surface alterations and their effect on the product functional performances. In the manufacturing scenario, cryogenic machining is emerging as a potential strategy to attain improved functional performance. Liquid nitrogen is a sustainable, non-toxic, and environmentally-benign means to alternatively cool the surface during machining. Its potential application in the biomedical field is related to the drastic reduction of secondary cleaning processes usually needed to wash off biomedical derived from contamination of flood coolant. However, the effect of cryogenic cooling on surface integrity, and especially, the link with functional performances is still missing. Therefore, the aim of this study is to evaluate the effect innovative machining strategies, with a particular reference to cryogenic machining, on the functional performances of biomedical products with the aim of improving their durability once placed into the human body

Machinability Of Polyamide 6 Under Cryogenic Cooling Conditions

Abstract Machining of polymeric materials can attain interest when the production lot does not justify the cost of molds or extrusion dies, or when the product to be manufactured requires dimensional accuracy not achievable otherwise. In this framework, the present study aims at evaluating the machinability of the polyamide 6 as a function of the cooling conditions. Two different cryogenic cooling configurations were adopted, whereas the conventional flood cooling was used as reference for sake of comparison, leading to machining conditions under very different temperature ranges. The polyamide 6 machinability was evaluated in terms of surface integrity (surface roughness, surface defects, crystallinity percentage and hardness) and chip morphology. Results show that the polyamide 6 has to be cut in a specific temperature range, namely between -20°C to 20°C, in order to get the best surface finish, namely achieving the lowest surface roughness and density of defects. In addition, the cryogenic cooling is proved to produce harder surfaces than the flood condition, but leaving unaltered the polymer crystallinity degree

The Effect of Cryogenic Cooling and Drill Bit on the Hole Quality when Drilling Magnesium-based Fiber Metal Laminates

Abstract The interest on fiber metal laminates has increased significantly in recent years as a consequence of the request of lighter and more functional aerospace and automotive components. In such parts, drilling is essential for assembly purposes. Nevertheless, drillability of fiber metal laminates is a critical issue due to the heterogeneous mechanical and thermal properties of metals and composites. The current research work aims at understanding how to improve the hole quality after drilling of magnesium-based fiber metal laminates. To this aim, dry and cryogenic cooling was applied as well as the adoption of three different drill bits, namely uncoated drill bits, coated drill bits and spur drills. Hole size, cylindricity, roughness, entry burr height, exit delamination and fiber pull-out are considered as experimental outcomes to characterize the hole surface quality. Results show that both spur drills and cryogenic cooling can significantly improve hole quality. The process parameters combination capable to guarantee the highest surface quality is finally provided

Effect of AM-induced Anisotropy on the Surface Integrity of Laser Powder Bed Fused Ti6Al4V Machined Parts

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Analysis of mechanical behaviour of AA6082-T6 sheets deformed at low temperatures

High-resistant 6xxx series aluminium alloy sheets are more and more used in the automotive industry thanks to their high strength-to-density ratio, which allows the vehicles weight reduction; however, they can be hardly deformed at room temperature due to their reduced formability, while forming at elevated temperature usually leads to a reduction of the sheet strength, making necessary post-forming heat treatments. The present research study aims at evaluating the mechanical behaviour of AA6082-T6 sheets deformed in the temperature range between 300\ub0C and -100\ub0C, to assess the possible increase of both ductility and strength when deforming below room temperature. Uniaxial tensile tests were carried out at different temperature regimes and then, ductility, strength and failure mode were evaluated. Surface integrity after mechanical processing was investigated in terms of microstructures and nano-hardness measurements. Results confirmed that the strength and ductility of aluminium alloys improved at temperature decrease. Additionally, sheets deformed at low temperature were characterized by enhanced nano-hardness

Recent advances in modelling and simulation of surface integrity in machining - A review

Machining is one of the final steps in the manufacturing value chain, where the dimensional tolerances are fine-tuned, and the functional surfaces are generated. Many factors such as the process type, cutting parameters, tool geometry and wear can influence the surface integrity (SI) in machining. Being able to predict and monitor the influence of different parameters on surface integrity provides an opportunity to produce surfaces with predetermined properties. This paper presents an overview of the recent advances in computational and artificial intelligence methods for modelling and simulation of surface integrity in machining and the future research and development trends are highlighted

Recent advances in modelling and simulation of surface integrity in machining - A review

peer reviewedMachining is one of the final steps in the manufacturing value chain, where the dimensional tolerances are fine-tuned, and the functional surfaces are generated. Many factors such as the process type, cutting parameters, tool geometry and wear can influence the surface integrity (SI) in machining. Being able to predict and monitor the influence of different parameters on surface integrity provides an opportunity to produce surfaces with predetermined properties. This paper presents an overview of the recent advances in computational and artificial intelligence methods for modelling and simulation of surface integrity in machining and the future research and development trends are highlighted

The polo-like kinase 1 (PLK1) inhibitor NMS-P937 is effective in a new model of disseminated primary CD56+ acute monoblastic leukaemia

CD56 is expressed in 15–20% of acute myeloid leukaemias (AML) and is associated with extramedullary diffusion, multidrug resistance and poor prognosis. We describe the establishment and characterisation of a novel disseminated model of AML (AML-NS8), generated by injection into mice of leukaemic blasts freshly isolated from a patient with an aggressive CD56+ monoblastic AML (M5a). The model reproduced typical manifestations of this leukaemia, including presence of extramedullary masses and central nervous system involvement, and the original phenotype, karyotype and genotype of leukaemic cells were retained in vivo. Recently Polo-Like Kinase 1 (PLK1) has emerged as a new candidate drug target in AML. We therefore tested our PLK1 inhibitor NMS-P937 in this model either in the engraftment or in the established disease settings. Both schedules showed good efficacy compared to standard therapies, with a significant increase in median survival time (MST) expecially in the established disease setting (MST = 28, 36, 62 days for vehicle, cytarabine and NMS-P937, respectively). Importantly, we could also demonstrate that NMS-P937 induced specific biomarker modulation in extramedullary tissues. This new in vivo model of CD56+ AML that recapitulates the human tumour lends support for the therapeutic use of PLK1 inhibitors in AML

Applicazione di stampi in resina termoindurente al micro-stampaggio ad iniezione

Sono state sintetizzate due resine epossidiche, una a base di acido linoleico ed una a base di gliceroldiglicil-etere. entrambe sono state testate come inserti per il micro-stampaggio ad iniezione. La resina a base di acido linoleico ha prodotto un volume di circa 1000 stampate mentre l'altra ha ceduto dopo qualche decina di cicli. Tutte le stampate sono state caratterizzate all'interferometro ottico per valutare la qualit delle replich