ISEL - Eng. Mecan. - Artigos
Permanent URI for this collection
Browse
Recent Submissions
- Thermo-mechanical characterization of metal-polymer friction stir composite joints-a full factorial design of experimentsPublication . Correia, Arménio N.; Gaspar, Beatriz M.; Cipriano, Goncalo; Braga, Daniel F. O.; Miguel Gomes Simões Baptista, Ricardo; Infante, VirginiaWith the increasing demand for lighter, more environmentally friendly, and affordable solutions in the mobility sector, designers and engineers are actively promoting the use of innovative integral dissimilar structures. In this field, friction stir-based technologies offer unique advantages compared with conventional joining technologies, such as mechanical fastening and adhesive bonding, which recently demonstrated promising results. In this study, an aluminum alloy and a glass fiber-reinforced polymer were friction stir joined in an overlap configuration. To assess the main effects, interactions, and influence of processing parameters on the mechanical strength and processing temperature of the fabricated joints, a full factorial design study with three factors and two levels was carried out. The design of experiments resulted in statistical models with excellent fit to the experimental data, enabling a thorough understanding of the influence of rotational speed, travel speed, and tool tilt angle on dissimilar metal-to-polymer friction stir composite joints. The mechanical strength of the composite joints ranged from 1708.1 ± 45.5 N to 3414.2 ± 317.1, while the processing temperature was between 203.6 ± 10.7 °C and 251.5 ± 9.7.
- Energy efficiency and waste reduction through maintenance optimization: a case study in the pharmaceutical industryPublication . Soares Domingues, Nuno Alexandre; Patrício, JoãoThe global rise in population, increased life expectancy, and heightened international mobility have escalated disease prevalence and pharmaceutical demand. This growth intensifies energy consumption and chemical waste production within the pharmaceutical industry, challenging environmental sustainability and operational efficiency. Chromatography, a vital analytical technique for ensuring product quality and regulatory compliance, can also contribute to material waste and energy inefficiencies if not properly maintained and optimized. This study applies Failure Mode and Effects Analysis (FMEA) to chromatographic equipment maintenance within Hovione’s Engineering and Maintenance Department, aiming to identify and mitigate failure risks. By integrating environmental metrics derived from Life Cycle Assessment (LCA) into the FMEA framework, a hybrid risk evaluation tool was developed that prioritizes both equipment reliability and sustainability performance. The findings demonstrate how this integrated approach reduces unplanned downtime, lowers solvent waste, and improves energy efficiency. Additionally, the study proposes a conceptual dashboard to support proactive, sustainability-driven asset management in pharmaceutical laboratories. By bridging reliability engineering and environmental sustainability, this research offers a strategic model for optimizing resource use, minimizing chemical waste, and enhancing long-term operational resilience in regulated pharmaceutical environments.
- Retaining the specific capacitance under electrochemical stress: A pH-induced self-protection mechanism for manganese dioxide pseudocapacitive electrodesPublication . Alves, Aila Cossovan; Chiavassa, Luísa; Martins, Tiago D.; Taryba, Maryna; Baleizão, Carlos; Moura e Silva, Teresa; MONTEMOR, FATIMAIn this study, we report the enhanced electrochemical performance of a MnO2 electrode modified with a pH-sensitive co-polymer, activated at acidic pH, and designed to counteract MnO2 degradation in aqueous aqueous pseudocapacitors. The conformation of this polymer is controlled by the local pH changes that occur at the electrode/electrolyte interface during electrochemical stress associated to oxygen evolution. As a proof of concept, we demonstrate that the addition of the pH-sensitive polymer contributes to improved electrode integrity and lifetime under over-polarization with oxygen evolution. After undergoing 10 cycles of electrochemical stress, the MnO2/pH-sensitive polymer composite retains similar to 70 % of its capacitance. This remarkable result stands in stark contrast with the pristine MnO2 electrode which fails catastrophically under the same stress conditions. We believe that this pH-induced self-protection mechanism represents a significant advancement in the development of novel smarter self-healing electroactive materials for the next generation of energy storage devices.
- In situ ellipsometry and EIS study of potentiostatic synthesis of pseudocapacitive MnOxPublication . Sampaio, Rui F.V.; Moura e Silva, Teresa; MONTEMOR, FATIMAThis work discusses the one-step potentiostatic growth of manganese oxide on stainless steel for pseudocapacitor electrodes. The electrode material was studied through in situ ellipsometry and electrochemical impedance spectroscopy, in order to correlate its microstructure with the capacitive response. Ellipsometry results show the formation of three layers during the potentiostatic synthesis of manganese oxide on stainless steel: the thickening of the native oxide of the substrate, and the growth of two distinct layers of manganese oxide. The inner layer is slightly more compact (>n) and more resistive (
- Highlighting shooting opportunities in footballPublication . Loutfi, Ilias; Gómez-Jordana, Luis; Ric, Angel; Milho, João; Madaleno Passos, Pedro JoséThe purpose of the present study was to create a two-dimensional model which illustrates a landscape of shooting opportunities at goal during a competitive football match. For that purpose, we analysed exemplar attacking subphases of each team when the ball was in the last 30 m of the field. The player’s positional data (x and y coordinates) and the ball were captured at 25 fps and processed to create heatmaps that illustrated the shooting opportunities that were available in the first and second half in different field areas. Moreover, the time that the shooting opportunities were available was estimated. Results show that in the observed match, most of the shooting opportunities lasted between 1 and 2 s, with only a few opportunities lasting more than 2 s. The shooting opportunities did not display a homogenous distribution over the field. The obtained heatmaps provide valuable and specific information about each team’s shooting opportunities, allowing the identification of the most vulnerable areas. Additionally, the amount, duration, and location of the shooting opportunities have shown significant differences between teams. This customizable model is sensitive to the features of shooting opportunities and can be used in real-time video analysis for individual and collective performance analysis.
- Characterization of the fracture forming limits by radial extrusionPublication . Sampaio, Rui F.V.; da Fonseca Matos Pragana, João Pedro; Bragança, Ivo; Silva, Carlos; Nielsen, Chris Valentin; Martins, Paulo
- Study of fatigue crack propagation on modified CT specimens under variable amplitude loading using machine learningPublication . Santos, B.; Infante, Virginia; Barros, T.; Miguel Gomes Simões Baptista, RicardoThis study focuses on predicting fatigue crack paths and fatigue life in modified compact tension specimens, under mixed mode and variable amplitude loading conditions, using Machine Learning techniques. Mixed-mode conditions were induced by using specimens that incorporated holes with different radii and center coordinates. Initially, multiple Finite Element Method (FEM) simulations were conducted to determine the fatigue crack path for different configurations. Subsequently, several configurations were selected for experimental fatigue testing, in which the fatigue crack path was monitored and recorded. The final phase of the study involved Machine Learning (ML) techniques, specifically Artificial Neural Networks (ANN) and k-Nearest Neighbors (kNN), to predict fatigue crack propagation. The models were trained using different numerical and experimental data. Predicted results were then compared with experimentally tested data, and the behavior and accuracy of the models were evaluated. Overall, the implemented models demonstrated the ability to predict fatigue crack path with average deviations (ANN - 1.19 mm; kNN - 1.10 mm) closely resembling results obtained through Finite Element simulations (1.65 mm). The models were also able to predict fatigue life with average errors of 10.1 % (ANN) and 16.7 % (kNN), all achieved with a reduction of computational costs greater than 90 %.
- Supervision system 4.0 for a road tanker washing robot manipulatorPublication . Vicente, Luís; Neves da Fonseca Cardoso Carreira, Fernando Paulo; Marnoto de Oliveira Campos, Francisco Mateus; Gonçalves Cavaco Mendes, Mário José; Calado, João; Carvalho, GamboaThe washing of road tankers is currently still a manual process that requires an operator to place the washing head into the tanks. To increase productivity and operator safety, it is essential to implement automated systems with Fault Detection and Isolation (FDI) capabilities. On the other hand, the industry 4.0 paradigm promotes the use of collaborative systems that integrate with the other organization's processes. Realizing this new vision requires Supervision, Control and Data Acquisition (SCADA) systems with FDI modules that integrate with collaborative systems and promote the digitalization of companies. This paper proposes a SCADA system for a new road tanker washing robot, aimed at integrating all systems and communication networks of the organization and future FDI modules. To this end, this paper proposes a communication architecture based on open protocols and a common database to connect SCADA to the lower and higher levels of automation. Furthermore, this paper describes the various aspects of SCADA system development, from synoptic design to validation. To support the development of the SCADA system, a Digital Twin (DT) of the road tanker washing robot was used, allowing to test and validate its functionality through this virtual prototype. The results show that the proposed SCADA system and underlying information architecture are suitable for supervision of a robotized wash operation and that the use of a Digital Twin facilitates SCADA system design and validation.
- Joining by forming of bi-material collector coins with rotating elementsPublication . Rosado, Pedro M. S.; Sampaio, Rui F.V.; Pragana, João P. M.; Bragança, Ivo; Silva, Carlos; Martins, PauloThis paper presents a novel manufacturing process for producing innovative bi-material collector coins with free- rotating inner elements. The inner elements are fabricated using additive manufacturing, enabling the creation of coins with complex and intricate geometric details that would be unattainable using conventional wrought materials. The outer elements (rings) are metallic, and this study addresses the challenge of securely connecting them to the inner elements through force-closed mechanisms formed during the coin minting process. Finite element modeling, combined with experimentation on bi-material (polymer-metal and metal-metal) coins, is employed to analyze material flow, assess minting forces, and evaluate contact pressures at the force-closed joints. The analysis ensures that adequate destructive forces are required to separate the inner elements from the rings and provides insights into selecting the appropriate process parameters for simultaneous coining and joining. The successful production of the first bi-material collector coin prototypes with free-rotational inner elements validates the overall development.
- A software for research and education in ductile damagePublication . Sampaio, Rui F.V.; Alexandre, N. S. M.; Pragana, João P. M.; Bragança, Ivo; Silva, Carlos; Martins, PauloThis paper gives insight into the development and utilization of a computer software that uses raw experimental data from the load cells and DIC systems to obtain the instant of time at fracture tf, the loading paths in principal strain space & epsilon;1 = f(& epsilon;2), and their conversion into the space of effective strain vs. stress triaxiality & epsilon; = f (& eta;). Special emphasis is given to the different assumptions and stress triaxiality measures that can be used to convert the loading paths from principal strain space into the space of effective strain vs. stress triaxiality. Results for double-action radial extrusion show the differences of treating the loading paths as linear or non-linear from beginning until the onset of failure by fracture. Results also allow concluding on the importance of accounting for the stress triaxiality derived from individual experimental measurements in an average sense over the entire loading paths, to avoid overestimation and mislocation of the fracture forming limits. The applicability of the software for education and training of students in formability is also discussed.