1,721,055 research outputs found
Innovative machining strategies to manufacture biomedical prostheses for improved in-life functional performances
Full text linkThe 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
The role of the layer thickness on the surface integrity of LPBF AlSi7Mg after turning
No full textLaser powder bed fusion (LPBF) is an additive manufacturing process used to fabricate aluminum alloy complex structures for the aerospace and automotive industries. By optimizing the printing and subsequent heat treatment parameters, it is possible to achieve physical and mechanical properties comparable to those of cast and wrought aluminum alloys. The influence of the printing parameters on the aluminum alloy mechanical properties is well documented, but their effect on the machinability has not been extensively studied, yet. In this regard, the paper aims to investigate the effect of the layer thickness adopted in LPBF on the machinability of the aluminum alloy AlSi7Mg. Three sets of cylindrical samples were printed with different layer thicknesses (20, 25, and 30 μm), followed by a T6 heat treatment. Then, the cylinders were machined at fixed cutting parameters while recording the cutting forces. Afterward, the machined surface roughness and defects were analyzed. Results show that increasing layer thickness improves the overall machining performance, with a decrease of more than 70% of the surface roughness and forces when printing with the highest layer thickness. To explain such behavior, microstructural analyses, including melt pool and grain distribution, precipitate type, and morphology, were carried out, proving that an increased layer thickness promoted the formation of silicon precipitates, which, in turn, improved the alloy’s machinability
Influence of the depth of cut on the AM nitinol properties in flood and cryogenic machining
Full text linkNickel-titanium alloys, commonly called Nitinol, are known for two fundamental properties, namely the shape memory effect (SME) and the superelasticity effect (SE), which make Nitinol a material of great interest for applications in various fields, such as biomedical, aerospace, automotive, and electronics. Most of the published research studies discuss the Nitinol properties after just one step of fabrication, e.g. forming, casting, additive manufacturing (AM), or machining. On the contrary, this work focuses on a process chain including AM followed by heat treatment and both flood and cryogenic machining. In particular, the depth of cut during the last machining step was varied (0.1, 0.25, and 0.4 mm), to investigate its effects on the AM and heattreated Nitinol in terms of machined surface finish and transformation temperatures. It was found that when cutting with a depth of cut of 0.25 mm, the workpiece shows the worst roughness, regardless of the material microstructure and machin..
Impact of cryogenic Machining on the fatigue strength and surface integrity of wrought Ti6Al4V with equiaxed microstructure
No full textThe paper assesses the fatigue strength of the wrought Ti6Al4V titanium alloy with equiaxed microstructure after machining carried out under flood and cryogenic cooling conditions. Linear elastic fracture mechanics-based approaches are used to evaluate the effect of the surface integrity, modified through machining under different cooling strategies, on the material fatigue strength. Different cooling strategies can significantly influence the integrity of the machined surface, affecting factors such as microstructural alterations near the surface, surface finish, hardness, and residual stresses. The obtained results demonstrate that cryogenic machining improves surface integrity by refining the grain size and enhancing the surface finish. while keeping unaltered the Ti6Al4V fatigue strength compared to flood cooling. The use of cryogenic machining is proving to be an environmentally friendly alternative to conventional machining that does not compromise fatigue performance and allows ..
Use of cryogenic machining to improve the adhesion of sphene bioceramic coatings on titanium substrates for dental and orthopaedic applications
No full textInfluence of the machining parameters and cooling strategies on the wear behavior of wrought and additive manufactured Ti6Al4V for biomedical applications
No full textThe paper presents the effect of machining parameters and cooling strategies on the wear behaviour of the wrought and Additive Manufactured Ti6Al4V used for biomedical applications. Wear tests were performed using a pin-on-plate configuration in a wet and temperature- controlled environment in order to investigate the reciprocating sliding wear behaviour under human body conditions. The obtained results showed that the adoption of the cryogenic cooling significantly affected the Ti6Al4V surface properties improving its wear performances, in terms of lower friction coefficient and less release of metal debris due to abrasive wear compared to dry cutting conditions, regardless the alloy as-delivered condition
Ball end milling machinability of additively and conventionally manufactured Ti6Al4V tilted surfaces
No full textPromoting chip breakage in biomedical-grade PEEK machining through tool texturing and cryogenic cooling
No full textPolyetheretherketone (PEEK) is an advanced thermoplastic polymer with excellent mechanical and chemical properties, making it ideal for various applications. Its elastic modulus, closely matching that of human bone, and its biocompatibility make PEEK suitable for orthopedic prostheses. Machining PEEK poses challenges, especially in biomedical applications, as traditional coolants—which leave oily residues—cannot be used, making dry machining preferable. However, dry machining produces long, continuous chips, reducing productivity and surface quality. Thus, alternative approaches are needed to improve the performance of the PEEK machining process. One promising method is tool surface texturing, which involves creating patterns on the tool surface to modify the chip-rake face contact area. In this context, the present study investigates the effect of tool texturing under different cooling conditions on the chip formation of a biomedical-grade PEEK. To this end, turning trials were conducted on a PEEK bar under dry and cryogenic conditions using laser-textured inserts with different groove depths and geometries: parallel and orthogonal to the cutting edge. Chip morphology was analyzed in detail for each cutting condition, focusing on its overall average length, thickness, and morphology. Chip-tool contact length was also measured under dry conditions. Cutting forces and temperatures were recorded to support the findings. The results indicate that both tool texturing and cooling conditions significantly impact chip formation. Chip breakage was consistently achieved under cryogenic cooling, with texturing further promoting chip-breaking into shorter segments. Conversely, long continuous chips were formed under dry conditions, although tool texturing still influenced the chip characteristics
Effect of the hatch spacing in laser powder bed fusion on the AlSi7Mg aluminum alloy cutting forces and surface finish after turning
Full text linkApplying additive manufacturing (AM) technologies in fabricating aluminum alloy automotive components can significantly enhance vehicle light-weighting through optimized design. By varying the AM process parameters, the resultant microstructure can be substantially altered, even post-heat treatment. Given that machining operations remain essential in many applications, understanding the impact of the AM parameters on the machining performances is vital. This paper explores how hatch spacing in laser powder bed fusion (LPBF) process affects the machinability of the AlSi7Mg aluminum alloy, in terms of cutting forces and machined surface roughness, providing a correlation with the microstructure induced by both the AM and heat treatment steps. In particular, the research reveals that the larger the hatch spacing the smoother the machined surface, underlining the critical role of this LPBF parameter in determining the final surface quality
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