Engineering (Faculty of)http://hdl.handle.net/10012/99002024-03-28T10:52:33Z2024-03-28T10:52:33ZA Centralized System Performance Monitoring InfrastructureMohammed Sajjad Jafri, Mohammed Sajjad Jafrihttp://hdl.handle.net/10012/204032024-03-23T02:30:55Z2024-03-22T00:00:00ZA Centralized System Performance Monitoring Infrastructure
Mohammed Sajjad Jafri, Mohammed Sajjad Jafri
In this thesis, we introduce a centralized performance monitoring infrastructure. In the current computing landscape, performance monitoring architectures are becoming more and more important for different academic and industrial applications. Performance counters reveal valuable insight into the functioning of the platform. This information can then be exploited for debugging applications, improving performance, identifying bottlenecks, and much more. In our proposed infrastructure, we envision a configurable Advanced Performance Monitoring Unit (APMU) connected to a set of monitoring Event Units (EVU) that are installed in various hardware system IPs across the platform. These EVUs send hardware event information to the APMU. The APMU has smart counters that are capable of operating on the incoming events, and an instruction processor that can implement any desired software mechanisms on the counter data. Our design allows for an efficient collection and correlation of event data, allowing the APMU to get a more holistic insight into the system behaviour, revealing microarchitecture-specific information. We intend to allow users the ability to develop EVUs for IPs relevant to them. For instance, in the implementation phase of this work, we developed an AXI4-based Snooping Unit as a concrete example of a custom-EVU. Therefore, to help integrate such custom EVUs with an APMU infrastructure, we also standardize an EVU-APMU interface. We provide the specification for this interface, ensuring that users can connect any custom-EVU to an APMU, as long as both abide by the interface specification.
In this work, we implement two design IPs. One is the previously mentioned AXI4-based Snooping Unit and the other is a RISC-V compliant APMU. We also provide a software stack to support programming on its processor. The implemented design is emulated on an AMD Virtex UltraScale+ FPGA VCU118 device. To evaluate the implementation of our design, we present the hardware synthesis results for the FPGA, and the execution results of a latency-based regulation case study, demonstrating the functionality of our design.
2024-03-22T00:00:00ZA Journey into Jamming: Phase Transitions and Edge-to-Edge Heterostructures in Langmuir Blodgett Films of Exfoliated Two-Dimensional MaterialsStorwick, Thomashttp://hdl.handle.net/10012/204022024-03-22T02:30:48Z2024-03-21T00:00:00ZA Journey into Jamming: Phase Transitions and Edge-to-Edge Heterostructures in Langmuir Blodgett Films of Exfoliated Two-Dimensional Materials
Storwick, Thomas
Two-dimensional (2D) materials hold significant promise as new electronic materials, and could enable high mobility devices, and flexible electronics. In particular, graphene and few-layer molybdenum disulfide have been the subject of significant study as new and exciting materials. Hindering the application of 2D materials is the lack of easy, scalable methods for deposition single layers of 2D materials. Top-down chemical methods like CVD can deposit large area high quality films, but remain highly destructive techniques, requiring high temperatures, harmful and caustic reagents, and high vacuum. Recent research in Langmuir Blodgett techniques have enabled large area coatings, continuous roll-to-roll coating, and expanded the repertoire of materials that can be coated. With this research has come renewed interest in the mechanics and dynamics of 2D materials coatings on the air-water interface. In this work, we expand this knowledge by undertaking a comprehensive study of 2D particle jamming on the air-water interface. Furthermore, we employ this understanding to demonstrate, for the first time, edge-to-edge heterostructure films assembled on the air-water interface.
To address the challenges of in-situ characterization of a growing film, we designed a method for non-destructive, in situ film monitoring using video-kymography, in addition to traditional Langmuir film characterization techniques such as surface pressure and compression isotherms.
In our findings we identify two modes of 2D material film growth on the air-water interface, an unjammed, or flowing growth mode, that is typically seen in Langmuir films of 2D materials, and a jammed growth mode, where material is condensed into a solid film by the deposition process. The key parameters that determine which mode the deposition will proceed were then identified. Within the jammed growth mode, we identify 3 phases of jammed film growth: gaseous, liquid, and solid. We then show that both the spreading dynamics of the chosen material “ink”, and the constant adding of material itself is required to progress through these stages and propose a mechanism for how a Langmuir film of 2D material can jam.
Using these findings, edge-to-edge heterostructure films of reduced graphene oxide and molybdenum disulfide were assembled on the air-water interface. Critical to the assembly of these films was the ability to deposit material in the jammed growth mode, and identify when the film was in the solid phase. This serves as a proof of concept for greater and more complex multi-material films on the air-water interface.
2024-03-21T00:00:00ZStudy of Performance of Geosynthetic-Reinforced Pavements by Full-Scale Field Study, Laboratory Testing, and Numerical ModellingWang, Danronghttp://hdl.handle.net/10012/204002024-03-20T02:31:04Z2024-03-19T00:00:00ZStudy of Performance of Geosynthetic-Reinforced Pavements by Full-Scale Field Study, Laboratory Testing, and Numerical Modelling
Wang, Danrong
This study provides a comprehensive understanding of geosynthetic-reinforced pavements from different perspectives including small-scale laboratory testing, a full-scale field study, and numerical simulation. This study on geosynthetic-reinforced pavements evaluated two geosynthetic materials: fibreglass geogrid in the asphalt layer; and geogrid composite at the interface of base and subgrade.
Fibreglass geogrid-embedded asphalt samples were made with three types of fibreglass geogrids – Geogrid 11, Geogrid 11 EPM (Engineered Polymeric Membrane) and Geogrid 10. The samples were tested with a conventional Hamburg Wheel-Tracking Test (HWTT) in a small-scale laboratory facility to evaluate the rutting and moisture susceptibility. The test outcomes indicate that Geogrid 11, characterized by larger openings, exhibits superior resistance to rutting. Conversely, Geogrid 10, with smaller openings, demonstrates lower susceptibility to moisture. Geogrid 11 EPM, featuring an additional adhesive membrane, exhibits the poorest performance in terms of both rutting resistance and moisture susceptibility. This suboptimal performance is attributed to the insufficient compaction effort, which further initiated another test proposed to evaluate the rutting resistance, namely the dynamic creep test. The proposed test was built upon the existing flow number test, with the stressed importance of extended testing protocols. The test results were analyzed with three major indicators, flow number, mean creep rate, and ultimate creep modulus, which highlight that fibreglass geogrid reinforcement plays a crucial role in enhancing resistance to permanent deformation, thereby increasing the asphalt's resistance to rutting. Results demonstrate a contrary conclusion with the HWTT, that Geogrid 11 EPM with larger openings but extra bonding provides the best rutting resistance. A less aggressive freeze-thaw (F-T) conditioning procedure was introduced to integrate with the dynamic creep test for geogrid-embedded asphalt samples to assess the impact of moisture damage on permanent deformation. The findings reveal that unreinforced samples consistently exhibit the poorest performance. In contrast, geogrids with larger openings and additional bonding demonstrate a capacity to mitigate the detrimental effects of moisture-induced damage.
The feasibility, constructability, and impacts of construction activities on pavements reinforced by these two types of materials were assessed during the construction of the field trial sections, and evaluated against an unreinforced control section. Post-construction field performance was monitored by field testing and instrumentation. Pavement stiffness tested by the Light Weight Deflectometer in the control section was notably influenced by ambient and pavement temperatures, indicating the effect of geosynthetic materials in preventing pavement stiffness from varying from temperature changes. Roughness measurements underline the need for an overlay of the surface course with geogrid reinforcement in the asphalt concrete layer. Truck testing further demonstrates the load-distribution capabilities facilitated by the fibreglass geogrid embedded in the asphalt layer. Field instrumentation was monitored for a year after construction completion, which demonstrates negative temperature differentials in the geogrid composite section during winter, indicating the effectiveness of the geogrid composite in regulating subgrade temperature and mitigating frost-related risks. Moisture data further illustrates relatively drier conditions in the geogrid composite section, underscoring its draining behaviour, particularly pronounced during thawing seasons. In the fibreglass geogrid section, a lower level of strain variation and pressure experienced at the bottom of the asphalt highlights the reinforcement capabilities and strain-absorption properties facilitated by the fibreglass geogrid. Additionally, the geogrid composite section exhibits lower strain and pressure on the subgrade compared to the control section, highlighting the reinforcing impact of the geogrid composite on the subgrade.
Lastly, pavement layer temperature predictive models with the input of ambient temperature were developed. A numerical model coupled with thermal-hydro-mechanical processes was created to simulate the pavement performance under freeze-thaw actions and examine the use of geogrid composite on the subgrade. The simulation from 2022 to 2023 using the developed model, with the input of pavement layer temperature predictive models and characterized field material properties, demonstrates less temperature variation in the subgrade, lower saturation levels, and reduced displacement after the thawing period in the geogrid composite section compared to the control section. This highlights the crucial role of the geogrid composite in drainage, subgrade temperature stabilization, and mitigating freeze-thaw disturbances in the pavement.
2024-03-19T00:00:00ZProcess Optimization, Numerical Modelling, and Microstructure Control in Laser Powder Bed Fusion of Ti-5553 PartsHasanabadi, Mahyarhttp://hdl.handle.net/10012/203952024-03-15T02:30:54Z2024-03-14T00:00:00ZProcess Optimization, Numerical Modelling, and Microstructure Control in Laser Powder Bed Fusion of Ti-5553 Parts
Hasanabadi, Mahyar
Additive manufacturing (AM) is an advanced production technique that creates components by depositing material layer by layer. AM has been deployed industrially for producing metallic parts from alloys which pose challenges in traditional manufacturing processes like titanium alloys (Ti-alloys). While Ti-alloys are widely utilized across industries due to their exceptional strength-to-weight ratio, corrosion resistance, and toughness, machining titanium products is a complex endeavour. Laser Powder Bed Fusion (LPBF) as a metallic AM method presents an optimal solution. LPBF has been recognized as an appealing fabrication process for producing metallic parts with customized properties, however, obtaining these properties is quite challenging due to the interaction of several independent parameters. The properties of an LPBF-made product are highly dependent on the process parameters, which directly impact the melting and solidification of the molten metal. Hence, an in-depth investigation into the effect of process parameters on the melting and solidification conditions is necessary for manufacturing a high-quality product with tailored properties.
The current research deals with LPBF of a recently developed Ti-alloy, Ti-5Al-5V-5Mo-5Cr (Ti-5553). Among Ti-alloys, the β-metastable Ti-5553 offers a wide processing window, good hardenability, and excellent heat treatability, making it a preferred material in the aircraft industry. To generate an LPBF process map for Ti-5553 and assess the influence of process parameters on the properties of printed parts, an integrated single-track to multi-layer method was systematically employed. An investigation into the track morphology, melt pool geometry and melt pool microstructure composted of single-tracks was compared with a range of microscopic examinations and X-ray computed tomography measurements to multi-layer tracks to create a reliable process map. Following that, additional investigations were conducted on properties like mechanical performance and surface roughness, providing the manufacturer with additional information from each set of process parameters in order guide selection of processing parameters.
Since some aspects of solidification, such as temperature gradient and solidification rate, are not easily measurable experimentally, numerical modelling can provide an efficient solution for studying the correlation between the process parameters and the geometrical and thermal conditions of the LPBF-made melt pool. Hence, a numerical heat transfer modelling with a novel hybrid volumetric heat source has been proposed to simulate the LPBF of Ti-5553 alloy for the first time. The developed hybrid model, with an incredibly low modelling error, can predict melt pool geometry and thermal variables, at different locations and time steps during melt pool solidification to estimate many important aspects of the microstructure formation such as grain morphology, subgrain size, and grain growth direction.
The gained knowledge from the experimental and numerical analyses of melt pool solidification under various process conditions is used to propose the “laser post-exposure treatment” as an innovative method for in-situ microstructure control during the LPBF process. The laser post-exposure (PE) treatment is a secondary laser scanning with significantly lower energy input, conducted after the completion of the main laser scanning strategy on the loose powder and before spreading the new layer of powder. This in-situ microstructure control treatment results in the development of uniform, uninterrupted, and elongated grains. A printed part utilizing post-exposure can be comparable to directionally solidified products used widely in industries for enhanced creep and fatigue resistance. It should be noted that this work is the first scientific attempt to control the grain structure via in-situ laser post-exposure.
2024-03-14T00:00:00Z