Examensarbeten för masterexamen
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- PostConcept development of an integrated rear-facing child seat structure(2024) Sumant, Abhijit; Dawkare, Swapnil; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Lindkvist, Lars; Arjomandi Rad, Mohammad; Ström, Cecilia; Malinsky, Michelle; Brenander, EllenThis Master of Science (MSc) thesis project aims to develop a concept for rearfacing child seat structures. It was conducted in collaboration with Volvo cars and explores a new child seat and safety product design approach, differentiating from traditional front-facing integrated child seat design. The project’s uniqueness lies in its approach to seamlessly integrating child safety within the standard adult seat, simplifying the operation and ensuring optimal safety for young passengers. Product development methods and techniques such as literature study, data gathering, needs and requirement analysis, concept selection, product architecture, concept design, product analysis, and design validation are used to achieve the goal. The above process resulted in a functional concept of rearward-facing integrated child seats with different operational mechanisms. The product meets the user and technical requirements derived from the qualitative data research. It is important to note here that the product is verified for the requirements and not validated due to limitations such as a compact timeline, lack of expertise in FEM and lack of resources. In conclusion, our team has prepared a baseline for further advanced product development and contributed to establishing a way forward in reducing the time during design improvements and analysis. .
- PostResidual stress modeling of PBF-LB(2024) Friðriksson, Haukur; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Larsson, Ragnar; Ohlsson, David; Larsson, RagnarThis thesis investigates the modeling of residual stress in laser powder bed fusion (PBF-LB) processes using AdditiveLab as a meso-scale simulation tool. The study aims to evaluate AdditiveLab as a process simulations tool for PBF-LB by repli cating experimentally verified simulations, specifically focusing on 316L stainless steel. A literature review of simulation techniques was conducted, followed by transient thermal and thermo-mechanical simulations, and validation of AdditiveLab’s simulations against experimentally verified models from the literature. The simulations analyzed the thermal distribution, the dimensions of the melt pool, and the development of residual stress. The findings indicate that, while the moving heat source can be modeled using AdditiveLab, limitations of the possible material modeling negatively impact the accuracy of the temperature distribution in meso-scale simulations. The primary limitation being the phase change model, in which the density of the metal powder can only be modeled as being equal to the solid metal density. Although all mesoscale modeling involves simplifications of complex physical phenomena, the assumption of powder properties leads to an overestimation of powder thermal inertia, leading to an overestimation of the melt-pool temperature and an underestimation of the melt-pool depth and width. This thesis discusses these limitations and their impact on predicting thermal behavior and stress development.
- PostPredicting short circuit of Li-ion battery cells during mechanical abuse(2024) Purantagi, Ankeet Mohan; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Larsson, Fredrik; Vikström, Simon; Carlstedt, David Carlstedt; Gustavsson, Peterithium-ion (Li-ion) batteries are today’s preferred energy storage solution for electric vehicles (EVs). Ensuring safety in their design is crucial, especially in car accidents, where mechanical damage to battery cells can cause internal electric short circuits, posing significant risks. Thus, minimising the occurrence of such incidents is paramount. The growing adoption of EVs also heightens the risk of thermal runaway following crashes, whether from side, frontal, rear, or bottom impacts. This concern underscores the necessity of developing virtual testing models to mitigate the costs of real-life battery crash testing. This thesis aimed to develop a finite element (FE) modelling methodology to predict internal short circuits in Li-ion batteries. The test data used in this work was obtained from previous tests, serving as the reference material behaviour response curve (force vs. displacement) upon which the subsequent research was based. The study was conducted in two different loading directions. Four test cases (two for each loading direction) were considered to create a homogenised material model. Multiple parametric optimisation runs were performed better to fit the material model’s response to the test. The final optimisation run achieved a realistic material behaviour that closely matched the test data. This single homogenised material model was then used to predict the short-circuit behaviour of the Li-ion battery in the specified scenarios. The conclusions drawn from this thesis validate the assumption that the material behaves anisotropically, with the global response closely matching the test data. While the failure models used in these cases may apply to certain scenarios, there is a need for more test data to understand the material behaviour and its response better. This additional data will aid in developing the failure surface of the battery material. Given the complexity of battery material behaviour, future work should consider various other factors, such as internal pressure build-up, swelling effects, state of charge (SoC) and internal loads like buckling by increasing the number of resolved layers. These factors significantly influence the material response and should be explored further.
- PostCrisis communication for elderlyLarsson, Gabriella; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Osvalder, Anna-Lisa; Osvalder, Anna-Lisa
- PostMachinability of 100Cr6 bearing steels(2024) Andersson, Daniel; Aronsson, Martin; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Malakizadi, Amir; Salame, Charlie; Boing, Denis; Vikenadler, Elias; M'saoubi, RachidThe aim of this master’s thesis is to investigate the influence of batch-to-batch microstructural variations on tool wear evolution when machining 100Cr6 bearing steel using coated carbides. Furthermore, a secondary aim is to investigate the performance of coated tool grades coated with different combinations of titanium carbonitride and alumina when used to machine 100Cr6. Tool life tests under constant spiral cutting lengths as well as orthogonal cutting tests with in-situ data acquisition were performed at various cutting conditions to investigate the machinability. The tool wear results were then correlated with the material and tool characteristics examined using various methods including light optical microscopy, stereo optical microscopy, hardness testing, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. A notable difference in tool wear evolution was found when machining the steel batches. The differences in microstructural properties such as the pearlite lamellar spacing and the measured hardness values were less pronounced, and thus they cannot solely explain the difference observed in tool performance when machining different batches of steels. However, the detailed material analysis showed chemical differences between the batches in terms of calcium and sulphur content, with corresponding differences in the non-metallic inclusion (NMI) content and type. Differences in tool wear behaviour when machining the steel batches showed a clearer correlation with the amount and type of these NMIs. Higher flank wear was observed when machining the steel batch with lower calcium content, while higher crater wear evolutions occurred when machining the cleanest batch with considerably lower sulphur content. Regarding the tool grades and their performance, the one closest to the current commercial grades (with a nearly equal thickness of alumina and titanium carbonitride coating layers) suffered the lowest average wear, whilst the grades having single-layer coatings of either alumina or titanium carbonitride performed significantly worse.