Last Friday, Patrick Trahan and Muhammad Faisal Alam presented their MASc thesis seminars. Check out the photos below. The seminars were followed by much food and camaraderie of which I have no photographic evidence but fun always follows cake, right?
This Friday we will be having the last graduate student seminar for the semester. So come out to see Patrick Trahan talk about “Corrosion Protection of Friction Stir Welded Al 7075 Panels using Cold Gas Dynamic Spray” and Muhammad Faisal Alam talk about “Optimizing the squeeze casting process of carbon fiber reinforced aluminium matrix composites”
Date: Friday April 19, 2013
Location: CBY B205
The abstract talks are below. I hope to see you all there!
Corrosion Protection of Friction Stir Welded Al 7075 Panels using Cold Gas Dynamic Spray
Supervisor: Bertrand Jodoin
Abstract: Friction stir welding (FSW) is a solid-state welding process that allows joining of metals or alloys that cannot be welded with fusion-state welding processes. However, in the case of FSW Al 7075, the weld joint region suffers from greater environmental corrosion than the parent material, resulting in a weaker weld joint over time. The aim of this work is to improve the corrosion resistance of FSW aluminum alloy (AA) 7075 joints. To do this, it was elected to form a protective metallic coating over the weld joint using cold gas dynamic spraying (CGDS). Using CGDS, multiple coatings of Al 7075, Al 5083 or Al 11XX-series (pure) were produced. These coatings were subjected to adhesion and corrosion tests. Results indicate that although the pure aluminum coatings have the lowest adhesion strength, they present the best corrosion resistance properties. The interaction between substrate temperature and coating properties was also analyzed revealing a dependence between substrate temperature and coating thickness.
Optimizing the squeeze casting process of carbon fiber reinforced aluminium matrix composites
Muhammad Faisal Alam
supervisor: Michel Nganbe
Abstract: Aluminium matrix composites are among the most promising candidate materials for light weight and high strength applications such as transportation and armour. In a previous study 6061 aluminum matrix composites reinforced with plain weave carbon fiber preform (AS4 Hexcel) were successfully fabricated by squeeze casting using the laminate fabrication technique. This research aims at optimizing the fabrication process in order to achieve improved strength and mechanical properties. It focuses on the liquid infiltration squeeze casting method. Good mechanical bonding between fiber and aluminium is achieved thanks to improved infiltration and impregnation of the fabric by liquid aluminium. Oxidation products at fiber/aluminium interface and porosity are reduced. As a result, composites are produced with overall improved mechanical properties. The flexural strength is increased by up to 36.08% and 36.7% compared to the laminate approach and the reference 6061 aluminium alloy squeeze cast under identical conditions, respectively. Similarly, overall hardness is improved. However, the impact strength is reduced by 7.76% and 25.78% when compared to casts fabricated by the laminate method and the reference aluminium alloy, respectively. The thesis constitutes a good basis for further research on fiber and particle reinforced aluminium matrix composites with the goal of further improving fracture toughness, particularly for gradient materials used in armour applications.
Last Friday, Yannick Cormier and Philippe Dupuis presented the work of the MASc theses. Photos of the two students with their supervisor, Dr. Bertrand Jodoin can be seen below – click on the images for a larger image.
This Friday, Yannick Cormier and Philippe Dupuis will be presenting their work here during our regular seminar time slot but in a NEW LOCATION. Come out to see what their work is about!
Date: Friday 12th April, 2013
Where: CBY B205
The abstracts of the talks are below.
Energy efficiency has become a growing concern in a world driven by a fossil fuel economy. To this end, increasing the performance and decreasing cost, weight and volume of gas turbines has become a critical research focus. Heat exchangers such as recuperators and intercoolers help improve the efficiency of gas turbines by recovering the waste heat generated by this process. Compact heat exchangers with unit cells using wire mesh as the internal heat transfer surface have been developed at Brayton Energy Canada, but several difficulties are encountered with conventional joining techniques.
Cold Spray was successfully used to deposit an outer layer and the current study focuses on the viability of depositing fins on this outer layer. Due to process restrictions, the pressure drop across the fin array needs to be minimal, while maintaining a very high heat transfer rate per unit area.
Production of Pyramidal Fin Arrays using Cold Gas Dynamic Spraying
This work studies the manufacturability of pyramidal fin arrays produced using the cold spray process. Near‐net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using commercially available steel wire mesh. Cold Spray parameters were determined to obtain near net shape fins. Different types of materials for the fins were successfully deposited on the compact heat exchangers, such as aluminum and stainless steel. Feedstock powders and their grains were characterized for morphology. Clogging of the wire mesh was investigated with a 30 wire per inch mask. A range of standoff distances between the different components of the system was empirically determined. Fin array characterization was performed to assess porosity levels and fin geometry.
Performance of Pyramidal Fin Arrays
This work studies the heat transfer and fluid mechanics performance of pyramidal fin arrays produced using the cold spray process. Empirical correlations were determined between the Reynolds number and friction factor for these shapes of fins. Also, correlations between the Reynolds number and the convective heat transfer coefficient were obtained. These relations were used in a numerical model in order to determine the most appropriate fin array geometry, depending on target specifications, fluid input conditions and spatial constraints. Results obtained correlate with data published for banks of tubes with similar dimensionless pitch. A characteristic change in the performance slope at a critical Reynolds number is observed. The fins produced using the cold spray process outperform traditional straight‐cut fins at the same fin density due to increased fluid mixing and turbulence caused by the discontinuity of these features.