Assessment of improvement techniques effect on fatigue behaviour of friction stir welded aerospace aluminium alloys

AbstractThis research work is based on analysis of the improvement of friction stir welded joints of the aerospace aluminium alloy AA2024-T351. Therefore, initially, the Taguchi method was used to obtain the optimal FSW parameters for improvement its mechanical behaviour. Then the fatigue resistance of base material, joints in as-welded condition and sound and defective FSW welded joints improved by grinding were detailed investigated. The influence of process parameters was addressed via statistical analysis of weld bead appearance parameters, mechanical tensile and bending resistance, metallurgical features and hardness field characterization. Validation tests demonstrate the Taguchi design’s feasibility in the optimization of the FSW parameters and fatigue results show the resistance of improved welded joints overcoming base material

Monitoring of the mechanical load and thermal history during friction stir channelling under constant position and constant force control modes

UID/EMS/50022/2019 UID/EMS/00667/2019In the present investigation, constant position and constant force process control modes; and representative process temperature measurements were analysed during the application of the friction stir channelling process. The experimental tests were carried out using rolled plates of AA5083-H111 with thickness of 15 mm. Results show that the FSC process was found not stable during the forward traverse movement stage when it is performed via position control. For both control modes, the tool was subjected to a more severe loading during the initial plunge than during the channelling period. Moreover, it was found that the tool vertical position is not significantly affected during the channelling stage when the process was force controlled. From the temperature measurements carried out, it was recorded a maximum process temperature of about 330 °C.publishersversionpublishe

Chlor-alkali membrane cell process : study and characterization

Estágio realizado na CUF - Químicos Industriais e orientado pelo Doutor Paulo Alexandre Pereira AraújoTese de doutoramento. Engenharia Química e Biológica. Faculdade de Engenharia. Universidade do Porto. 201

The First World War in the City of Porto: Contributions to the knowledge of daily lives and sociability's during the war (1917)

First World War began in 1914 and ended in 1918. Portugal went to war through the CEP – Expeditionary Portuguese Body – in Flanders between November 1917 and April 1918. This intervention have direct impacts on population daily lives, resulting in profound changes in multiple dimensions of Portuguese society, mobilizing a male contingent in an active age. This demographic change results in a restructuring of the women role in society. Porto, as a coastal and maritime municipality, sees the war closely. This research intends to share, supported in bibliographical and documentary evidences, the reality of the city in 1917 and in what way its participation in the war affected their dynamics.info:eu-repo/semantics/publishedVersio

Metodologia de avaliação de quantidades de trabalho na manutenção e reparação de estruturas de defesa costeira com taludes

Tese de mestrado integrado. Engenharia Civil (Especialização em Hidráulica). Faculdade de Engenharia. Universidade do Porto. 200

Investigating the effects of printing temperatures and deposition on the compressive properties and density of 3D printed polyetheretherketone

Open access funding provided by FCT|FCCN (b-on). Publisher Copyright: © 2023, The Author(s).Polyetheretherketone (PEEK) is a biocompatible high-performance thermoplastic that can be processed through material extrusion (ME) additive manufacturing (AM) for load-bearing implant applications. In this work, density measurements and compression testing were used to investigate the relation between printing temperatures and deposition patterns of PEEK 3D printed samples. Different deposition patterns were tested with different nozzle and zone heater temperatures to observe how the heat input from the printing process influenced the deposition stability with different nozzle paths. Compression test results showed that samples with concentric-based deposition patterns resulted in higher compressive yield strength and modulus than the rectilinear samples. These results were correlated with the samples’ void contents estimated from density measurements. Both the highest 0.2% offset yield strength of 100.3 MPa and the highest modulus of 3.58 GPa were obtained with an interlayer offset deposition which resulted in reductions in estimated void contents between 48 and 72% in relation to concentric deposition. Different printing temperatures and deposition sequences were tested, where higher printing temperatures resulted in lower yield strength and stiffness. Alternating deposition between the outer and inner lines of the concentric pattern resulted in a reduction of about 43% in void contents and increased elastic modulus and yield strength from 3.12 to 3.40 GPa and 94.4 to 95.2 MPa respectively. The results from this work suggest that the relation between printing temperatures and deposition strategy for different print geometries plays a significant role in the ME-AM of PEEK for high-performance applications.publishersversionepub_ahead_of_prin

Methodologies and Applications Review

Funding Information: The Authors acknowledge Fundação para a Ciência e a Tecnologia (FCT-MCTES) for its financial support via the project UIDB/00667/2020 (UNIDEMI). Pedro M. Ferreira also acknowledges FCT-MCTES for funding the PhD grant UI/BD/151055/2021. Publisher Copyright: © 2022 by the authors.Sensing Technology (ST) plays a key role in Structural Health-Monitoring (SHM) systems. ST focuses on developing sensors, sensory systems, or smart materials that monitor a wide variety of materials’ properties aiming to create smart structures and smart materials, using Embedded Sensors (ESs), and enabling continuous and permanent measurements of their structural integrity. The integration of ESs is limited to the processing technology used to embed the sensor due to its high-temperature sensitivity and the possibility of damage during its insertion into the structure. In addition, the technological process selection is dependent on the base material’s composition, which comprises either metallic or composite parts. The selection of smart sensors or the technology underlying them is fundamental to the monitoring mode. This paper presents a critical review of the fundaments and applications of sensing technologies for SHM systems employing ESs, focusing on their actual developments and innovation, as well as analysing the challenges that these technologies present, in order to build a path that allows for a connected world through distributed measurement systems.publishersversionpublishe

Granting Sensorial Properties to Metal Parts through Friction Stir Processing

The authors would like also to thank to Micronsense-Metrologia Industrial (Leiria, Portugal) for the μCT analysis. The authors would also like to thank Prof. Catarina Santos for granting access to the MicroLab - Electron Microscopy Laboratory (Instituto Superior Técnico) for the SEM analyses.Structural Health Monitoring systems assess the part's current condition. This can be performed with a monitoring system comprising sensors, on the surface or embedded, in the monitored parts. However, surface sensors are subject to damage, and embedding the sensors may result in a weakened part. An innovative Self-Sensing Material and its manufacturing process were developed and are presented herein. As proof of concept, Barium Titanate particles were introduced and dispersed into an AA5083-H111 part by Friction Stir Processing (FSP). The particles’ distribution and concentration was evaluated by a set of characterization techniques, demonstrating that greater concentrations, grant enhanced sensitivity to the material. The use of FSP and the embedded particles improved the part’s mechanical behaviour in the processed zone. The sensorial properties were assessed and the response to a set of dynamic loads was measured, being coherent with the solicitations provided. The developed self-sensing material revealed an electrical sensitivity of 12.0 × 10-4 uV/MPa.publishersversionpublishe

Improvement of tensile and flexural properties of 3D printed PEEK through the increase of interfacial adhesion

The authors acknowledge Fundação para a Ciência e a Tecnologia (FCT, I.P.) for its financial support through the PhD scholarship UI/BD/151082/2021 and through UNIDEMI, project UIDB/00667/2020. The authors would also like to thank João O. Cardoso for the support provided with the DSC analysis equipment.Polyetheretherketone (PEEK) is the leading high-performance biocompatible thermoplastic for the replacement of metals in orthopaedic applications. PEEK processing using material extrusion (ME) Additive Manufacturing (AM) techniques such as Fused Filament Fabrication (FFF) highlight its potential for the manufacture of patient-specific load-bearing implantable medical devices. As a high temperature semi-crystalline polymer, the mechanical properties of PEEK 3D printed samples are significantly influenced by printing parameters, particularly the crystallinity and interfacial adhesion of 3D printed parts. Given these challenges, the printing parameters of nozzle temperature, zone heater temperature, layer height and extruder multiplier were selected and studied for their effects in the interfacial adhesion and thus consequent mechanical performance of PEEK 3D prints. Design of Experiment (DoE) studies were conducted where the Taguchi and ANOVA analysis were used to determine the optimal parameter combinations and respective contributions. Additionally, different infill configurations were used with the optimal parameters to lower the samples' void volume and increase interface bonding. Reductions of up to 65 % in void volume were obtained with an interlayer translation of the infill lines and the tested configurations yielded improvements in both the tensile and flexural properties of 3D printed PEEK. Furthermore, high-temperature annealing treatments produced further increases in the strength, stiffness and crystallinity of PEEK samples. With this, significant improvements in both the void volume and the tensile and flexural properties of PEEK prints were achieved in support of the use of 3D printed PEEK in the manufacture of custom-made and high performance implantable medical devices.publishersversionpublishe