FCT: DEMI - Artigos em revista internacional com arbitragem científica
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- Exploring the use of wearable sensors for assessing risk factors during orthopedic surgeriesPublication . Santos, Catarina; Gabriel, Ana Teresa; Quaresma, Cláudia; Nunes, Isabel L.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DF – Departamento de Física; LIBPhys-UNL; Elsevier Science Publisher B.V.During orthopedic surgeries, surgeons are generally exposed to prolonged periods of standing, awkward and sustained body postures, and forceful movements, which can increase the likelihood of developing work-related musculoskeletal disorders (WRMSD). Therefore, this study proposes a protocol to measure parameters related to physical risk factors contributing to lower limb WRMSD, during orthopedic surgery procedures. The protocol development was preceded by an initial phase of understanding and specifying the context of use, followed by pre-tests in laboratory environment. It integrates a motion capture system, using inertial measurement units (IMU) to collect posture data from hip, knee, and ankle, and electromyography system (EMG) to measure and record data from muscle activity of biceps femoris, rectus femoris, and gastrocnemius lateralis. Pre-tests provided insights for protocol optimization, estimating a 3-hour data collection session per surgery due to sensor battery limitations, streamlining the process by placing EMG sensors before IMU and refining thigh sensor placement strategies. The protocol presents an opportunity for a real-time and quantitative approach to monitor surgeon's exposure to risk factors contributing to lower limb WRMSD while performing surgical procedures. Two months after pre-tests, the protocol implementation began in a real work context. The study's final outcomes fall outside the paper's scope.
- Functionally Graded Materials and StructuresPublication . Silva, Rui F.; Coelho, Pedro G.; Gustavo, Carolina V.; Almeida, Cláudia J.; Farias, Francisco Werley Cipriano; Duarte, Valdemar R.; Xavier, José; Esteves, Marcos B.; Conde, Fábio M.; Cunha, Filipa G.; Santos, Telmo G.; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DEMI - Departamento de Engenharia Mecânica e Industrial; Molecular Diversity Preservation International (MDPI)Functionally Graded Materials (FGMs) can outperform their homogeneous counterparts. Advances in digitalization technologies, mainly additive manufacturing, have enabled the synthesis of materials with tailored properties and functionalities. Joining dissimilar metals to attain compositional grading is a relatively unexplored research area and holds great promise for engineering applications. Metallurgical challenges may arise; thus, a theoretical critical analysis is presented in this paper. A multidisciplinary methodology is proposed here to unify optimal design, multi-feed Wire-Arc Additive Manufacturing (WAAM), and image-based characterization methods to create structure-specific oriented FGM parts. Topology optimization is used to design FGMs. A beam under pure bending is used to explore the layer-wise FGM concept, which is also analytically validated. The challenges, limitations, and role of WAAM in creating FGM parts are discussed, along with the importance of numerical validation using full-field deformation data. As a result, a conceptual FGM engineering workflow is proposed at this stage, enabling digital data conversion regarding geometry and compositional grading. This is a step forward in processing in silico data, with a view to experimentally producing parts in future. An optimized FGM beam, revealing an optimal layout and a property gradient from iron to copper along the build direction (bottom–up) that significantly reduces the normal pure bending stresses (by 26%), is used as a case study to validate the proposed digital workflow.
- Enhancing manufacturing and post-processing properties of WAAM ER110 HSLA steelPublication . Fonseca, Pedro P.; Duarte, Valdemar R.; Farias, Francisco Werley Cipriano; Cota, Bruno Silva; Silva, Tiago; Santos, Telmo G.; Machado, Carla M.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; SpringerThis work focuses on the influence of post-deposited heat treatments (PDHT) on the properties and machinability of high-strength low-alloy steel (HSLA) samples, produced by WAAM and the forged (HF-WAAM) variant. An adequate combination of deposition parameters was established, and the manufactured specimens were 3D scanned to evaluate the surface quality. Effects of normalizing and quenching & tempering (Q&T) heat treatments on the microstructure were assessed through optical microscopy and SEM, and the influence on the material hardness and electrical conductivity was evaluated. Orthogonal cutting experiments were conducted to determine the specific cutting energy (SCE), a crucial indicator of the cutting performance and machinability characteristics of the work material. The results revealed a significant SCE decrease when cutting the WAAM and HF-WAAM samples subjected to PDHT, with 8% and 38% decreases for pot-normalization, and 22% and 27% reductions after Q&T, compared to the as-built condition. No significant differences were registered when machining between the WAAM and HF-WAAM variants. HF-WAAM samples after PDHT show superior hardness, without compromising the cutting energy consumption. However, the geometrical features, namely the significant increase of the surface waviness of the hot-forged parts (≈70%) must be considered, being a critical factor to avoid possible undesirable machining effects.
- High-strength low-alloy steel fabricated by in situ interlayer hot forging arc-based directed energy deposition assisted with direct coolingPublication . Cota, Bruno S.; Amendoeira, Daniel A. E.; Farias, Francisco Werley Cipriano; Fonseca, Pedro P.; Oliveira, João P.; Moreno-Uribe, Andrés M.; Viebranz, Vincent F.; Hassel, Thomas; Santos, Telmo G.; Duarte, Valdemar R.; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DEMI - Departamento de Engenharia Mecânica e Industrial; Elsevier BVControlling thermal cycles during arc-based Directed Energy Deposition (DED), typically known as Wire Arc Additive Manufacturing (WAAM), is crucial to reduce heat buildup and prevent issues such as distortions, formation of brittle microstructures, grain growth, anisotropy, and consequent reduction in mechanical properties. In-situ interlayer hot forging coupled with WAAM (HF-WAAM) provides grain refinement and pore closure. The effect of HF-WAAM can be combined with the control of peak temperature and cooling rates, benefiting the material's microstructure and mechanical properties. In this context, the aim of this work was to evaluate the effect of direct cooling on the mechanical and microstructural properties of a high-strength low-alloy (HSLA) steel manufactured by WAAM and HF-WAAM. A pneumatically actuated system with a cooling system was specifically designed, where two pumps with a flow rate of 1.8 kg/min each were used to pump G13 antifreeze fluid at approximately −25 °C. In the actuator design, a double counterflow cooling system was used, as it promotes greater thermal homogenization and higher heat transfer rate, thus allowing greater thermal energy removal. Analyses of the mechanical and microstructural properties of the parts were carried out through uniaxial tensile testing, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Thermal cycles and cooling system control were conducted using a thermal imaging camera and thermocouples installed at the inlet and outlet of the actuator's cooling ducts. The results showed that samples manufactured with HF-WAAM had a greater number of less hard structures in their microstructure than those manufactured by conventional WAAM. The fabricated samples exhibited high tensile and yield strength values, with calculated anisotropy below 2 %. All samples showed ductile fracture characteristics after the tensile test, confirmed by fractography.
- Minimizing the maximum von Mises stress of elastic continuum structures using topology optimization and additively manufactured functionally graded materialsPublication . Silva, Rui F.; Coelho, Pedro G.; Conde, Fábio M.; Santos, Bernardo R.; Oliveira, João P.; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DEMI - Departamento de Engenharia Mecânica e Industrial; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Elsevier Science B.V., Amsterdam.The rising cost of natural resources and environmental concerns motivate systematic design and manufacture of more efficient structures. For that purpose, topology optimization has been appealing, as well as working on an enlarged design space to include multi-material solutions. The resulting optimal designs can be materialized using multi-material additive manufacturing. In the present framework, multi-material printed parts or layouts can be envisaged as having better strength properties than single-material counterparts. The maximum von Mises stress is minimized inside a design domain through topology changes and material selection. The selected composite material model encompasses either the classical arrange of two discrete materials with sharp interfaces, or their mixture controlled by the volume fraction of each base material to generate a Functionally Graded Material (FGM). An optimized continuous variation of properties makes the FGM appealing to mitigate stress concentrations. To adequately capture the physics of mixtures considering the FGM's mechanical properties, one uses the RAMP interpolation scheme within the Hashin-Shtrikman bounds. A set of plane stress benchmarks are proposed. It is shown that considerably lower stress peaks on the evaluated structures can be obtained on the account of introducing more than one solid phase, specifically in the case of FGM solutions.
- Numerical Fatigue Crack Growth on Compact Tension Specimens under Mode I and Mixed-Mode (I+II) LoadingPublication . Martins, Rui F.; Xavier, José; Caldeira, João; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Molecular Diversity Preservation International (MDPI)This study focused on standard Compact Tension (CT) specimens and two loading modes during the numerical analyses carried out, namely: pure mode I and mixed-mode loading (Modes I+II). Numerical stress intensity factors, KI, were calculated using Abaqus® 2022 and compared with those given analytically under pure mode I loading, showing very good agreement. Additionally, KI, KII, and KIII results obtained from Abaqus® were presented for mixed-mode loading, analyzing crack growth and variation through the thickness of the CT specimen. Moreover, fatigue crack growth simulations under mode I loading were conducted on standard CT specimens using the Extended Finite Element Method (XFEM) and the Paris Law parameters of an AISI 316L stainless steel. It was shown that XFEM effectively determines crack propagation direction and growth, provided that an appropriate mesh is implemented.
- Demystifying “absolute truths” of additive manufacturingPublication . Oliveira, J. P.; Santos, Telmo G.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; ElsevierThe hype around additive manufacturing technologies suggests that any complex shaped structure can be fabricated regardless of the type of material used. Moreover, it is often suggested that additive manufacturing processes will certainly disrupt the supply chain logistics and that everyone will be able to print on the demand at the comfort of their home. In this viewpoint, we describe and demystify some of the common assumptions associated with these set of technologies. We also show that conventional manufacturing processes cannot be fully replaced by additive manufacturing technologies, but rather there is a need for a complementarity between well-consolidated manufacturing technologies and additive manufacturing. While some of the contents presented here are basic for specialists working in the manufacturing field, we expect that this viewpoint can aid researchers working on topics related to additive manufacturing, but with less focus on the manufacturing aspects, helping them understand the actual limitations and advantages associated to these technologies. The four key issues that are addressed in this viewpoint, and their consequences, also intend to shape and mold future entrepreneurial efforts on additive manufacturing, as well as define future impacts (environmental, logistics, commercial and disruptive) associated to additive manufacturing technologies.
- Wire arc additive manufacturing of a high-strength low-alloy steel partPublication . Kokare, Samruddha; Shen, Jiajia; Fonseca, Pedro P.; Lopes, João G.; Machado, Carla M.; Santos, Telmo G.; Oliveira, João P.; Godina, Radu; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Springer Science Business MediaAdditive manufacturing (AM) technologies have demonstrated a promising material efficiency potential in comparison to traditional material removal processes. A new directed energy deposition (DED) category AM process called wire arc additive manufacturing (WAAM) is evolving due to its benefits which include faster build rates, capacity to build large volumes, and inexpensive feedstock materials and machine tools compared to more technologically mature powder-based AM technologies. However, WAAM products present challenges like poor surface finish and lower dimensional accuracy compared to powder-based processes or machined parts, prevalence of thermal distortions, residual stresses, and defects like porosity, cracks, and humping, often requiring post-processing operations like finish machining and heat treatment. These post-processing operations add to the production cost and environmental footprint of WAAM-built parts. Therefore, considering the opportunities and challenges presented by WAAM, this paper analyses the environmental impact, production costs, and mechanical properties of WAAM parts and compares them with those achieved by laser powder bed fusion (LPBF) and traditional computer numerical control (CNC) milling. A high-strength low-alloy steel (ER70S) mechanical part with medium complexity was fabricated using WAAM. Based on the data collected during this experiment, environmental impact and cost models were built using life cycle assessment and life cycle costing methodologies. WAAM was observed to be the most environmentally friendly option due to its superior material efficacy than CNC milling and has a better energy efficiency than LPBF. Also, WAAM was the most cost-friendly option when adopted in batch production for batch sizes above 3. The environmental and cost potential of WAAM is amplified when used for manufacturing large products, resulting in significant material, emission, and cost savings. The fabricated WAAM part demonstrated good mechanical properties comparable to that of cast/forged material. The methodology and experimental data presented in this study can be used to calculate environmental impacts and costs for other products and can be helpful to manufacturers in selecting the most ecofriendly and cost-efficient manufacturing process.
- Micro wire and arc additive manufacturing (µ-WAAM)Publication . Oliveira, J. P.; Gouveia, Francisco; Santos, Telmo G.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; ElsevierIn this work we explore the wire and arc additive manufacturing (WAAM) process scale limits by using a wire diameter of 250 µm and about 2 mm stickout. This WAAM variant, named µ-WAAM, aims at competing with laser powder bed fusion technology, by enabling the fabrication of smaller parts with significantly higher deposition rates. The main issues of descaling the WAAM process are discussed and an acceptable parameter window to fabricate thin walls is presented. Several depositions were successfully performed with ASTMA 228 steel using a wire feed speed ranging from 75 to 90 mm/s, travel speed from 7 to 10 mm/s, a current intensity of 16 A RMS and power of ≈ 35 W RMS.
- Fluid–Structure Interaction Modeling of Ascending Thoracic Aortic Aneurysms in SimVascularPublication . Valente, Rodrigo; Mourato, André; Brito, Moisés; Xavier, José; Tomás, António; Avril, Stéphane; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; MDPI - Multidisciplinary Digital Publishing InstituteAscending Thoracic Aortic Aneurysm (ATAA) is a permanent dilatation of the aorta which is usually related to tissue degeneration, hemodynamic conditions, lifestyle, environmental and genetic factors. As the mechanical conditions can become critical in a dilated aorta, a patient-specific computational model can be very useful to assist clinical decisions in the management of ATAAs. In this article, we model the biomechanical conditions of ATAA by performing Fluid–Structure Interaction (FSI) simulations in the SimVascular open-source software package. The patient-specific geometric model is reconstructed from Computed Tomography scan (CT). The numerical implementation takes into account patient-specific outlet conditions and a temporal flow variation at the model inlet. We performed a mesh convergence analysis on a new mesh reconstruction method in SimVascular and showed that it can significantly reduce the computational cost without impacting the accuracy.