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Deze masterthesis onderzoekt de ontwikkeling van energie-efficiënte hydrostatische lagers. De thesis stelt zich de vraag of hydrostatische lagers een beter alternatief kunnen vormen in situaties waar een ontwerper tegenwoordig meestal andere lagertypes opteert. De thesis bestudeert het beschikbare gamma aan lagers en concentreert zich hierbij voornamelijk op de energieverliezen van elk type. De thesis stelt een wiskundig model op, die het gebruikt om een ontwerpmethodologie te ontwikkelen die het ontwerp van axiale hydrostatische lagers optimaliseert. Dit wil zeggen dat de ontworpen lager zo weinig mogelijk energieverliezen heeft, terwijl die toch aan de ontwerpeisen voldoet. Verder wordt een nieuwe techniek ontwikkeld die ervoor zorgt dat wanneer hydrostatische lagers opereren in omstandigheden die afwijken van die waarvoor ze ontworpen zijn, de lager minder energieverliezen heeft dan wanneer de techniek niet zou worden toegepast. Met behulp van een zelf ontwikkelde hydrostatische lager test deze masterthesis de validiteit van het model en de energieverliezen. Het besluit hierbij dat het model de werkelijkheid goed benadert, en formuleert enkele mogelijke doelstellingen voor verder werk. Tenslotte lost de thesis een voorbeeld van een ontwerpprobleemstelling op. Het vergelijkt de kosten van twee verschillende lagertypes, namelijk wentellagers en hydrostatische lagers. De kosten die in rekening gebracht worden zijn de aankoopkosten en de energiekosten die veroorzaakt worden door energieverliezen in de lager. De thesis voorziet ook de wiskundige omkadering om andere kosten zoals onderhoudskosten mee te rekenen. De gebruikte methode leunt aan bij het concept van life cycle costing. Met dit voorbeeld toont de masterthesis aan hoe verschillende kosten in één kader geplaatst kunnen worden en hoe zo verschillende oplossingen vergeleken kunnen worden. Verder toont het ook aan dat hydrostatische lagers een betere keuze zijn dan wentellagers in bepaalde situaties, wat vooral te danken is aan lage energieverliezen bij deze lagers.

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Recent developments on biofidelic finite element models of the human head introduce the need for mechanical characterization of even the smallest components. The description of the mechanical behaviour can be done with constitutive models that are fitted onto experimental stress-strain curves. To obtain these curves, tests must be performed on samples of the material. However, current test benches do not allow for testing small soft tissue samples such as bridging veins that have an average diameter of only 0,5 - 5,3mm. This introduces the need for custom test benches of which one is developed in this master thesis: a biaxial setup that combines simple shear with uniaxial tensile. The simple shear loading is performed with an existing tensile bench, on which the setup is mounted, and is based on the two rail shear setup by Cui (2016). To guide the displacement, a pair of titanium flexure bearings is used. The results with this system are acceptable, but the accuracy is too low due to the low repeatability of the flexure bearings resistance. Therefore, this aspect of the design must be revised in a new version of the setup. The tensile loading is created by applying a displacement with an external actuator, while measuring the forces with a load cell. The results are promising, although some rescaling of the load cell is required. A hybrid clamping system is used to get a good grip on the small samples. The combination between glueing and applying a clamping force results in the proper deformation when the displacements are applied. Considering this is the first prototype, the results look promising. Valuable in- sights are obtained from preliminary tests and suggestions are given to improve the design and the test protocol.

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In a modern industrial world, the impact of bearings is well acknowledged. Within all types of bearing, rolling-elements bearings are most used. Proper lubrication is as important as correct bearing selection. This work will discuss in-depth the oil-bath lubrication method, as it is commonly found in the machinery. As temperature raises and contamination worsen, circulation system is recommended. Too little oil, bearing wears and tears; too much oil, bearing heats up and churns. Least amount of required lubricant should be added. Flow characteristic of such circulation must be studied, with rolling-bearing in particular.par Therefore, in Collaboration with Flanders Make, a test setup is modified to verify flow model proposed in this work. The model will consider a bearing as a collect of small tubes. In each submerged tube, channel flow is applicable to calculate friction and local losses. The sum of these losses will be considered as hydraulic resistance in an electrical equivalent model, with pressure difference as voltage source to get flow rate as output. Bearing dimensions, fluid parameters and working conditions will be reviewed and put into a MATLAB function as inputs. Finally, general formula will be made without the need for a correction factor. Its validation range and effectiveness will be reviewed. At moderate to low rotation speed of 500 rotations per minute, the model holds. At higher rotation speed, the channel transition from laminar into turbulent region. The velocity profile changes, the influence of moving parts becomes more prominent. The model overestimate the hydraulic resistance and predicted 50% of the measured flow rate. Due to time constraint, two sizes of same type bearing have been tested, however the sample size is sufficient large to ensure the adjusted model has less 10% mean percentage error in its validation range.