This diploma thesis is concerned with simulation of elastohydrodynamic lubrication of point contacts using the finite element method. The first part of the thesis focuses on the study of the issue and introduces equations for model creation and numerical methods which can be used for EHD calculation. The most suitable solution approach has been chosen from the overview, namely the Full system approach. The software we chose for applying the method was COMSOL Multyphysics. The following part of the thesis deals with model’s creation and gives its elaborate description. We introduce models for calculation of line and point EHD lubrication for newtonian lubricants and, last but not least, we also present a model for calculation of point contact EHD lubrication for non-newtonian lubricants. The next part of the thesis then verifies all the models. That is achieved by comparing the calculated results to results from different papers. The conclusive part of the thesis then examines the matches of acquired results to different prediction relationships and experiments.

Modern construction practices require proper knowledge to predict concrete pumping pressure, especially in high-volume and high-rise applications. Despite the progress made over the last decades, the spread of concrete pumping to high-rise construction has been hampered by the lack of standardized operating procedures and performance criteria. By and large, the guidelines available today focus predominantly on pumping Conventional Vibrated Concrete (CVC), while ambiguity still surrounds pumping Self-Consolidating Concrete (SCC) and other types of Highly-Workable Concrete (HWC). This PhD dissertation focuses on the fundamental principles relevant to the flow of high-strength SCC in pumping pipes, and it aims to develop methods to predict and reduce the required pumping pressure. The flow pattern of SCC in pipes is analytically investigated, providing a numerical approach to predict the pumping pressure based on the properties of both concrete and the lubrication layer, the pipe diameter, and the flow rate. The analytical results are further validated through full-scale pumping tests executed at the laboratory of the Université de Sherbrooke. Through this phase 26 optimal concrete mixtures were pumped in a 30-m pumping circuit to investigate the interactions between the concrete properties and pressure loss. The same tests are also employed to empirically correlate pressure loss with rheological and tribological properties of concrete at different flow rates. The resulting correlations furnish instrumental models capable of computing pressure loss for a wide range of concrete properties. In another application, the experimental results are analyzed to identify the influence of pumping on concrete properties with time. Full-scale pumping results are statistically analyzed in order to establish a quantitative description of the most influential parameters governing the concrete flow in pipes. As a result, concrete pipe flow is statically modeled, allowing the computation of pressure loss at different flow rates based on the the rheological and tribological properties of the concrete and the pipe diameter. Another statistical model is derived to calculate the pressure loss as a function of the V-funnel flow time, granting the advantage of predicting the pressure loss on job sites without the need for complex rheological and tribological measurements. In light of the research findings of the previous phases, a new simple test method called the pipe flow test (PFT) is developed in the context of this research, specifically for predicting pipe flow pressure loss. With preceding research phases as insights, the final stage of this project is directed toward mix design optimization faced with the challenge of reducing the pumping pressure and meeting the strength requirements of high-strength SCC. Ultimately, the research findings emanating from this investigation provide practical guidelines and conclusive models to predict and reduce pumping pressure for a wide scope of concrete mixtures and pipe diameters.

This diploma thesis deals with an application of the finite element method on elastohydrodynamic (EHD) lubrication simulations. Commercially available software COMSOL is used for the computation, while two different modules for modeling EHD lubrication are described in a detail. Firstly, a new approach using the module Thin-Film Flow is developed, considering and describing some limitations of this approach. This is the very first published work dealing complex with EHD simulation in Thin-Film Flow module. In the second part of the thesis, there was created a model of line contact using the module for the introduction of partial differential equations (PDE). The model is partially verified with available works for different values of the input parameters. Subsequently, the velocity effect of the contact surfaces on the pressure and the lubricant thickness in contact is analyzed. Finally, the last part is examines the influence of the values of some parameters on the final value of the contact pressure and the lubricant thickness, as well as on numerical stability of the entire model.