Fábio J. P. Simões

To produce increasingly efficient tools with optimized geometry, additive manufacturing is a suitable solution. However, tool steels, due to their high amount of carbon and hardening elements, may be unweldable and therefore difficult to produce using additive manufacturing methods that employ melting. W360 is a hot-forming alloy, and, in this study, it was produced through laser powder bed fusion (PBF-LB). The microstructure and mechanical properties were evaluated on as-built netshape PBF-LB samples. Despite the presence of many alloying elements, this alloy was not sensitive to cracks, and very good results from the defect analysis (defect surface density < 0.2%) were achieved. Microstructure and hardness are homogeneous in the sample except in the last layer due to an upskin effect. As-built netshape samples exhibit very promising mechanical properties up to 400 °C, which could be further improved by heat treatments.

Mechanical (or structural) metamaterials are revolutionizing property tailoring, offering capabilities beyond conventional bulk materials to meet the demand for structural innovation. This work presents the design, fabrication, and characterization of a novel 2D Ti6Al4V mechanical metamaterial. Designed using a novel design methodology, the structure exhibits auxetic (negative Poisson's ratio) behaviour within its elastic domain. The metamaterial was produced using Laser Powder Bed Fusion (LPBF), and its mechanical response was experimentally tested and validated against numerical simulations. Furthermore, the influence of manufacturing-induced defects, including voids and geometrical deviations, on the mechanical behaviour was systematically correlated. The findings demonstrate that LPBF is a viable and effective method for producing 2D Ti6Al4V mechanical metamaterials capable of achieving high elastic strain, validating the integrated design and manufacturing approach.

With the development of large-scale additive manufacturing (LSAM), parts can be created with higher deposition rates and bigger build volumes

Asymmetric rolling is an attractive metal forming process due to its simplicity, low cost and capability to produce unique characteristics in materials. The asymmetry promoted by the process leads to a formation of a large collection of texture components and a refined structure which is capable to improve the mechanical behavior of metallic materials. The aim of this work is to present a perspective of the process and to construct the bases for future development and application of this technique. Thus, several aspects are addressed such as process methods (i.e., dissimilarity of the rolls diameters, rolls angular speed or friction conditions), the process parameters (i.e., total thickness reduction, thickness reduction per pass, peripheral speed ratio, rolling routes) and their effect on material properties, including texture and microstructure evolution, and mechanical properties. This review is focused on the experimental description of asymmetric rolling applied to aluminum alloys and steels. Although the asymmetric rolling application was mostly at a laboratory scale, there is a good perspective for its implementation in the industry. The pros and cons based on the up to date literature and authors’ experience are presented and discussed.

Additive manufacturing technologies have evolved from prototype to part production. Coupling this shift with organizational transformations evolved rapid prototyping industry into Direct Digital Manufacturing (DDM) industry. Any evolution in production systems is now, more than ever before, dependent on sustainability principles. The development of the DDM industry must be guided by these principles, taking the chance it offers to change the production paradigm. Circular Economy (CE) is a shift in the production and resource management model, and one of the ways to work towards sustainability. Coupling DDM with CE principles is thus contributing to change industrial production to a more sustainable one. This paper intends to relate DDM technologies with CE principles, to identify aspects where DDM is contributing to CE, as well as aspects that should be explored further for that purpose. It is observed that DDM can enable optimization of material and energy usage, modify logistics towards de-localized production and recycling and enable prolonged lifespan of products through better access to spare parts, for instance. It is also observed that DDM has good potential to shift materials usage towards natural materials, especially in a context of consumer or local community production, but not so much within the current industrial context. Education is shown to play a pivotal role, since incorporating circular economy principles in educational contexts should spark a shift in consumer perspectives, modifying demand and hence, industrial production.

Single point incremental forming (SPIF) processes represent a breakpoint from traditional forming processes, and possibly a new era in small batches production, customised parts or rapid prototyping. Given its easy implementation, SPIF is being currently a subject of intensive experimental and numerical research. Consequently, dimensional inaccuracy in formed parts is still a real problem to tackle, demanding a correct prediction of forming forces, springback defects and strain path effects. This work concerns a first step of a detailed numerical study, validated with available experimental results in the literature raised about simulation of SPIF processes. To this end, it is proposed a general simulation framework of SPIF processes using the finite element method with implicit solution schemes, along with innovative solid-shell elements for 3D analysis. Finally, the use of solid-shell elements provides several advantages compared to shell elements, as considering automatically full 3D stress states and constitutive laws, thickness variations, double sided contact and normal stresses.