In dem Vortrag wird die Entwicklung einer Finiten-Elemente-App für Android dargelegt, sowie die Vorteile im Postprozessing von einfachen Strukturen bei der Verwendung der Gestensteuerung erörtert.

Material flow in friction stir welding is largely uncharacterized due to the difficulty in material flow measurement and visualization in metals. This study investigates plasticine for use as an analog for modeling material flow in friction stir welding (FSW) of metals. Qualitative comparisons between welded plasticine and metal sections exhibit many similarities. The transient temperature response of the plasticine also shows the same qualitative behavior as welds conducted in metal. To quantify its similarity to metal, the plasticine is further analyzed through compression tests to characterize its strain, strain-rate, and temperature sensitivities. A detailed analysis is presented which defines the criteria for rigorous mechanical and thermal similarity between metals and analog materials. The mechanical response of the plasticine is quantitatively similar to many aluminum and steel alloys. In addition to the mechanical properties of the plasticine, thermal properties are measured and thermal similarity is investigated. Generally, complete thermal similarity cannot be achieved in FSW. However, given the similarities between other critical parameters, and observed qualitatively similarity, it is possible to satisfy similarity approximately, such that information can be obtained from the physical model and extrapolated to metals. Using plasticine, material flow behavior in FSW is investigated under various operating conditions. The physical model permits visualization and characterization of material flow around a suspended welding tool. Depending on operating conditions, several material flow regimes are observed, including simple extrusion with substantial tool/material slip, defect formation, a region of rotating material adjacent to the tool, and vertical deformation. Material flow and frictional heating in FSW are also investigated using a three-dimensional numerical model. Two mechanical boundary conditions are investigated, including 1) a sticking constant velocity, and 2) a slipping variable shear stress model. The constant velocity model generally over-predicts the extent of material flow in the weld region. The variable shear model predicts simple extrusion of material around the tool, and substantial tool/material slip. Additionally, the variable shear model exhibits a region of diminishing shear stress, velocity, and pressure at the back advancing side of the pin, suggesting formation of an internal void. The limited deformation, low velocities, and indication of void formation agree well with flow visualization studies using plasticine under identical operating parameters.

Detta examensarbete har utförts åt Ålö, som är en tillverkare av frontlastare och redskap till dessa. Ett av deras redskap, vars syfte är snöröjning, är utrustat med hydrauliskt justerbara sidoklaffar som kan fällas bakåt och nyttjas som plogblad. De fyller dock inte denna uppgift tillfredsställande då snö tenderar falla tillbaka bakom dem. Det bildas även en triangulär spalt mellan klaffarna och underlaget vid plogning, detta lämnar kvar en sträng av snö, utöver det som faller ner bakom klaffarna. Målet i detta projekt var att utveckla en plogklaff som löser tidigare nämnda problem genom att ersätta den högra sidoklaffen till skopan. Utvecklingen har initierats med en studie av rapporter, existerande plogar, kontakt med brukare och fastställande av de begränsningar som råder. Detta har sedan utgjort grunden för en rad koncept, av vilka de mest lovande sammanfogades till en prototyp. Kraftberäkningar utifrån det lastfall som uppstår vid plogning har sedan använts för att bl.a. dimensionera skruvförband och skapa randvillkoren för en finita element-analys. Finita element-analysen har sedan nyttjats för att göra en uppskattning av antalet cykler med momentan maximal belastning plogklaffen klarar innan utmattningsbrott sker. Kraftberäkningarna visade att hydraulcylinderns tryckbegränsare öppnar redan innan maximal belastning uppnås. Finita element-analys och kraftberäkningar till skruvförband förutsätter likväl att maximal belastning kan erhållas momentant i syfte att ge konservativa resultat. Under denna förutsättning skiljer belastningen i skruvförbanden endast ca 7-10 % mellan finita element-analys och handberäkningar. Samtliga beräkningar är inom spannen för skruvförbandens hållfasthet. Utmattningsberäkningarna visade att antalet cykler plogklaffen klarar vid maximal belastning uppgår till ca 346 000. Detta avser områden av intresse och inkluderar således ej delar vilka redan utvärderats i originalklaffen. Svetsförband, som i regel är dimensionerande i situationer som dessa, har ej sett någon utmattningsmässig utvärdering utan kommer istället behandlas vid tester av prototypen. Prototypen uppfyller de utsatta målen och tillverkningsunderlag i form av 3D-CAD modeller och 2D-ritningar (inklusive svetsritningar) har levererats. En fysisk prototyp är även beställd och kommer tillverkas av Vännäs Verkstads AB, planerat leveransdatum är 2017-06-08. Den kommer utvärderas under vintern 2017/2018. / This thesis work has been carried out for Ålö, a manufacturer of front loaders and implements for these. One of their implements, whose purpose is snow clearing, is equipped with hydraulically adjustable flaps that can be folded backwards and used as plows. However, they do not fill this task satisfactorily as snow tends to fall down behind them. A triangular gap between the flaps and the ground is also formed during plowing. This leaves a string of snow behind, aside from the snowmass already falling down behind the flaps. The goal for this project was to develop a plow that solves the aforementioned problems by replacing the right side flap on the bucket. The development was initiated with a study of reports, existing plows, contact with users and determining existing constraints. This has since provided the basis for a series of concepts, of which the most promising ones were joined to a prototype. Force calculations based on the load scenario that occurs during plowing have been used to find appropriate fasteners and create boundary conditions for a finite element analysis. The finite element analysis has then been used to estimate the number of cycles with maximum load the plow can be subjected to before it succumbs to fatigue failure. Force calculations showed that the pressure limiter for the hydraulic cylinder opens even before maximum load is reached. Despite this, finite element analysis and force calculations for fasteners were still based on the condition that maximum load is achieved momentarily to produce convervative results. Under this condition, the load on fasteners differs only ca 7-10 % between finite element analysis and calculations made by hand. All calculations are within the span for the fasteners proof strength. Fatigue calculations showed that the number of cycles the plow can handle with maximum load amounts to approximately 346 000. This refers to areas of interest and thus does not include parts already evaluated in the original flap. Welds, which usually dictate minimum strength in situations like these, have not seen any fatigue evaluations, but will instead be addressed while testing the prototype. The prototype meets the set goals and production documentation in the form of 3D-CAD models and 2D drawings (including weldment drawings) have been delivered. A physical prototype is also ordered and will be manufactured by Vännäs Verkstads AB, scheduled delivery date is 2017-06-08. It will be evaluated during the winter of 2017/2018.

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A key challenge facing the nuclear fusion community is how to design a reactor that will operate in environmental conditions not easily reproducible in the laboratory for materials testing. Finite element analysis (FEA), commonly used to predict components’ performance, typically uses idealised geometries. An emerging technique shown to have improved accuracy is image based finite element modelling (IBFEM). This involves converting a three dimensional image (such as from X ray tomography) into an FEA mesh. A main advantage of IBFEM is that models include micro structural and non idealised manufacturing features. The aim of this work was to investigate the thermal performance of a CFC Cu divertor monoblock, a carbon fibre composite (CFC) tile joined through its centre to a CuCrZr pipe with a Cu interlayer. As a plasma facing component located where thermal flux in the reactor is at its highest, one of its primary functions is to extract heat by active cooling. Therefore, characterisation of its thermal performance is vital. Investigation of the thermal performance of CFC Cu joining methods by laser flash analysis and X ray tomography showed a strong correlation between micro structures at the material interface and a reduction in thermal conductivity. Therefore, this problem leant itself well to be investigated further by IBFEM. However, because these high resolution models require such large numbers of elements, commercial FEA software could not be used. This served as motivation to develop parallel software capable of performing the necessary transient thermal simulations. The resultant code was shown to scale well with increasing problem sizes and a simulation with 137 million elements was successfully completed using 4096 cores. In comparison with a low resolution IBFEM and traditional FEA simulations it was demonstrated to provide additional accuracy. IBFEM was used to simulate a divertor monoblock mock up, where it was found that a region of delamination existed on the CFC Cu interface. Predictions showed that if this was aligned unfavourably it would increase thermal gradients across the component thus reducing lifespan. As this was a feature introduced in manufacturing it would not have been accounted for without IBFEM.The technique developed in this work has broad engineering applications. It could be used similarly to accurately model components in conditions unfeasible to produce in the laboratory, to assist in research and development of component manufacturing or to verify commercial components against manufacturers’ claims.

The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite. In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS). The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity,  and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation.  From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB. Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test. In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.