Examensarbeten för masterexamen // Master Theses (IMS)

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Browsar Examensarbeten för masterexamen // Master Theses (IMS) efter Ämnesord "316L stainless steel"

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    Enhanced performance of magnetic floating devices enabled through metal additive manufacturing
    (2020) Mehta, Bharat; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Hryha, Eduard; Fischer, Marie
    This master’s thesis work is focused on establishing the functionalities that can be achieved by utilising additive manufacturing in products currently manufactured using traditional techniques. Additive manufacturing is seen to be a game changer in the current manufacturing scenario. With the fact that complex parts can be made easily and higher design freedom is available, it is possible to push design and material limits further by employing concepts such as lattice structures and topology optimised structures in order to obtain higher strength to weight ratios. Hence, a primary study into the designability of a magnetic floating device was done. It was followed by a secondary study into the mass-manufacturability aspect which is mostly affected by printing parameters. For this master’s thesis work, a family of products which work as floating devices, currently being manufactured at ABB, have been selected to investigate and develop a mass-manufacturable design which can provide much higher specific buckling strength than the current manufacturing methods. It was critical to keep the products similar or better in all performance characteristics (such as corrosion resistance, temperature performance, surface roughness, etc.). The investigation was not limited to using additive manufacturing but rather to suggest optimised techniques to design and manufacture the product family. The material used to study in this thesis was 316L stainless steel, since ABB typically uses the same material for manufacturing the product and it was readily available for additive manufacturing. As a result, several stiffened structures were shown for this product, which were simulated to show significant improvement in performance and manufacturability, improving the specific buckling strength by about three times the current part. From the experiments conducted, a relation between the failure mode of thin shell under uniaxial compression was developed and tailored properties of lattice structures were also studied. Furthermore, an extended study into the effect of laser power, layer thickness, laser speed and scan strategy was also conducted to understand the mass manufacturability of thin cylindrical shells.
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    Surface integrity analysis before and after machining of additively manufactured (3D printed) 316L stainless steel using Selective Laser Melting (SLM) and Electron Beam Melting (EBM)
    (2020) Shahab, Amir Reza; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Klement, Uta; Hosseini, Seyed Behnam; Mallipeddi, Dinesh
    This master thesis work was aimed for understanding the surface integrity and machinability of 316L stainless steel which was produced by two common methods of additive manufacturing called selective laser melting (SLM) and electron beam melting (EBM). Additive manufacturing is a new method of production for complex shape structures with less lead time and less waste of material. Samples of SLM were produced at RISE AB with SLM Solutions machine and samples of EBM were produced at Mid-Sweden university with ARCAM machine. The results of as-printed condition show that melt pools in EBM samples are larger that SLM ones. SLM samples have a cellular structure inside each melt pool. SLM samples have higher hardness than EBM however the surface roughness of SLM samples are lower than EBM. Lack of fusion features in EBM samples are in the size of less than one micron. Samples were machined (turning) from top and bottom in four steps. Depth of cut for each step is 0.25 mm. During turning, all 3 forces of cutting, feed and passive forces were recorded. All components of forces in step 1 are higher in SLM in comparison with EBM. Surface roughness after machining is around 0.9 micron for EBM and 0.8 micron for SLM. It is recommended to machine SLM samples for 1 passage with depth of cut of 0.25 mm. For EBM samples, it is recommended to machine the samples for 3 passages with depth of cut of 0.75 mm. Tensile residual stress exists after additive manufacturing due to rapid solidification of new layer in contact with an already solid layer. Machining will cause compressive stress which neutralizes the tensile stress to some extent. Maximum compressive stress will happen at depth of 10-30 micron under machined surface. In SLM, maximum compressive stress is higher in step1 in comparison with step 4. In EBM, maximum compressive stress is higher in step 4 in comparison with step 1.