Metal Additive Manufacturing – State of the Art 2020

Additive Manufacturing (AM), more popularly known as 3D printing, is transforming the industry. AM of metal components with virtually no geometric limitations has enabled new product design options and opportunities, increased product performance, shorter cycle time in part production, total cost reduction, shortened lead time, improved material efficiency, more sustainable products and processes, full circularity in the economy, and new revenue streams. This Special Issue of Metals gives an up-to-date account of the state of the art in AM

Wear and Fatigue Behaviour of Additive Manufactured Titanium with TiB Particles

While titanium remains an attractive candidate in lightweighting applications, it is often restricted in use due of its poor tribological behaviour and inferior machinability characteristics, leading to its higher relative cost. To address these shortcomings, manufacturers are turning towards alternate, non-conventional manufacturing methods such as additive manufacturing (AM). The mechanical and microstructural properties of alpha, near-commercially pure, titanium made from a novel AM process, termed plasma transferred arc solid free form fabrication, is studied in this research work. Low amounts of titanium-boride (TiB) particles are of interest in as-received samples for their role as a stiffener and strengthener, which can lead to improvements in mechanical and tribological behaviour. This investigation focuses on understanding how the AM build metallurgy and TiB in studied samples influences the mechanical and tribological behaviour of samples. Specially, the research concentrates on wear characterization through ball-on-disk testing and the fatigue behaviour found through rotating-bending testing. Moreover, a final goal of the work was to explore the influence of shot-peening to improve the fatigue and wear behaviour of this material. The investigation revealed that as-received AM blocks showed a near-isotropic behaviour within the structure. Transitional wear behaviour was noted which occurred at the 10N applied loading condition but did not occur in shot-peened samples, which stayed within the first wear regime described. Shot-peening was also found to result in improved fatigue values, increasing the fatigue resistance of samples by 28%, and led to maintained wear resistance with similar COF and wear rate values obtained

Towards load-bearing biomedical titanium-based alloys: From essential requirements to future developments

The use of biomedical metallic materials in research and clinical applications has been an important focus and a significant area of interest, primarily owing to their role in enhancing human health and extending human lifespan. This article, particularly on titanium-based alloys, explores exceptional properties that can address bone health issues amid the growing challenges posed by an aging population. Although stainless steel, magnesium-based alloys, cobalt-based alloys, and other metallic materials are commonly employed in medical applications, limitations such as toxic elements, high elastic modulus, and rapid degradation rates limit their widespread biomedical applications. Therefore, titanium-based alloys have emerged as top-performing materials, gradually replacing their counterparts in various applications. This article extensively examines and highlights titanium-based alloys, along with an in-depth discussion of currently utilized metallic biomedical materials and their inherent limitations. To begin with, the essential requirements for load-bearing biomaterials are introduced. Then, the biomedical metallic materials are summarized and compared. Afterward, the microstructure, properties, and preparations of titanium-based alloys are explored. Furthermore, various surface modification methods are discussed to enhance biocompatibility, wear resistance, and corrosion resistance. Finally, the article proposes the development path for titanium-based alloys in conjunction with additive manufacturing and the novel alloy nitinol

Impact Of Laser Powder Bed Fusion Process Defects On Mechanical Properties Of Ti6Al4V Mandible Implants

DissertationEach year millions of patients’ quality of life is improved through surgical procedures involving medical implanted devices. The need for new implants, treatments and prostheses, as well as prolonging the life span of current implants has increased; the global prosthetics and orthotics market size is expected to reach $11.7 billion by 2025, as indicated in Healthcare Market Report (2020). Additive manufacturing (AM) was implemented in the medical field fairly recently. Despite the enormous contribution medical devices have made to the public health, there is a fear of possible liability exposure in the event of device malfunction or failure. Efficient quality control of implants produced by new AM technologies is an important task for suppliers in order to be in full compliance with existing regulations and certification of such implants. If any defects occur, implant strength will directly influence the part’s mechanical properties and performance, leading to the redistribution of stress and change in displacements affecting attached bone tissue and mineral matrix of the bone, resulting in implant failure. For wide applications in the medical industry, it is crucial that AM implants comply with international standards with regard to their mechanical properties. Three point bending tests (TPB) were carried out in this work on AM Ti6Al4V ELI specimens. TPB is a common tool used to characterize bone material properties and mechanical performance of biomaterials. Powder bed fusion is the unique AM method to produce metal objects with complex geometries and internal structures; it permits the manufacture of complex-shaped functional 3D objects such as customized implants. The benefits of AM in bone reconstruction using metal alloys are unquestionable in terms of customization of implants and production time. Comprehensive analysis of the laser powder bed fusion (LPBF) process together with functional anatomy biomechanics of the human mandible was done in this work. Some case studies on defects found in LPBF implants were evaluated. Based on biomechanics of the human mandible, LPBF Ti6Al4V ELI samples were designed. Experiments and numerical simulations of samples with sizes and placements of artificial pores were done. All samples were tested perpendicular to the vertical building direction and showed no signs of failure at a single loading pattern. Defects were designed and induced in the additive manufacturing of test samples of titanium, with different size and placement. Results indicate that defects of 1000 μm×300 μm×210 μm and 1000 μm×500 μm×420 μm at various depth to the neutral axis had no significant outcome on the mechanical performance of the samples with size of 100 mm 15 mm 2.5 mm when it was tested statically at loading of 800, 900 and 1500 N, representing a maximum biting force. This approach is a promising method of setting up a critical pore size to failure tolerance for AM implants with some defects

The selected laser melting production and subsequent post-processing of Ti-6Al-4V prosthetic acetabular

&nbsp;Processing and post processing of human prosthetic acetabular cup by using 3D printing. The results showed using 3D printers leads to fabrication customized implants with higher quality.<br /

Complex geometry and integrated macro-porosity: Clinical applications of electron beam melting to fabricate bespoke bone-anchored implants

The last decade has witnessed rapid advancements in manufacturing technologies for biomedical implants. Additive manufacturing (or 3D printing) has broken down major barriers in the way of producing complex 3D geometries. Electron beam melting (EBM) is one such 3D printing process applicable to metals and alloys. EBM offers build rates up to two orders of magnitude greater than comparable laser-based technologies and a high vacuum environment to prevent accumulation of trace elements. These features make EBM particularly advantageous for materials susceptible to spontaneous oxidation and nitrogen pick-up when exposed to air (e.g., titanium and titanium-based alloys). For skeletal reconstruction(s), anatomical mimickry and integrated macro-porous architecture to facilitate bone ingrowth are undoubtedly the key features of EBM manufactured implants. Using finite element modelling of physiological loading conditions, the design of a prosthesis may be further personalised. This review looks at the many unique clinical applications of EBM in skeletal repair and the ground-breaking innovations in prosthetic rehabilitation. From a simple acetabular cup to the fifth toe, from the hand-wrist complex to the shoulder, and from vertebral replacement to cranio-maxillofacial reconstruction, EBM has experienced it all. While sternocostal reconstructions might be rare, the repair of long bones using EBM manufactured implants is becoming exceedingly frequent. Despite the various merits, several challenges remain yet untackled. Nevertheless, with the capability to produce osseointegrating implants of any conceivable shape/size, and permissive of bone ingrowth and functional loading, EBM can pave the way for numerous fascinating and novel applications in skeletal repair, regeneration, and rehabilitation. Statement of significance: Electron beam melting (EBM) offers unparalleled possibilities in producing contaminant-free, complex and intricate geometries from alloys of biomedical interest, including Ti6Al4V and CoCr. We review the diverse range of clinical applications of EBM in skeletal repair, both as mass produced off-the-shelf implants and personalised, patient-specific prostheses. From replacing large volumes of disease-affected bone to complex, multi-material reconstructions, almost every part of the human skeleton has been replaced with an EBM manufactured analog to achieve macroscopic anatomical-mimickry. However, various questions regarding long-term performance of patient-specific implants remain unaddressed. Directions for further development include designing personalised implants and prostheses based on simulated loading conditions and accounting for trabecular bone microstructure with respect to physiological factors such as patient\u27s age and disease status

Biomedical Engineering

Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development