No abstract

Mixtures of a fine-grained dry solid and a liquid, with a higher solid content in the mixture, show paste-like behaviour. In many technical processes, pasty materials are handled in large quantities. Pasty Materials show the same characteristics as Bingham Plastics, behaving like a rigid body but flowing like a viscous fluid under a certain stress level. This behaviour is due to attracting forces between the particles, resulting from the capillary pressure and the surface tension of the liquid, which forms individual capillary bridges or capillary bridge clusters between the solid particles. The behaviour of granular material can be represented in a discrete element method (DEM) simulation. The calibration of the simulation parameters is achieved by comparing laboratory tests, which reflect a typical material characteristic, with the results of calibration simulations. In this project, several DEM contact models, describing attractive forces between particles depending on the distance between them, were analysed and assessed based on their ability to display the pasty material behaviour of a fine-grained solid water mixture with a high water content by comparing the simulation results to a slump test. The most promising contact model was then optimised to enable a minimal computing time for the simulation of bigger technical processes. Many existing contact models also consider attractive forces between particles (e.g. JKR cohesion) but are based on different physical effects. For this reason, the contact models assessed in the course of this project are, in general, based on the capillary effect.

A rising number of companies and organisations are researching space technologies supporting extraterrestrial life. Whether Moon or Mars, the number of rocket launches is increasing year by year. The majority of National Space Agencies are planning exploration missions with fully autonomous robots, which can conduct several studies about the composition of the lunar dust. Especially the extraction of oxygen from the moon dust, called regolith, is of great interest. Also many other projects are planned. But the initial step of all processes is often forgotten: it is the supply of raw materials. Therefore, a closer look at the possibilities of excavating and conveying regolith has been taken. The research ranges from concept development, calculation to simulation and designing a robotic system.

ZusammenfassungDie Simulation, vor allem die Mehrkörpersimulation, ist ein Werkzeug, welches im Zuge dieses Beitrags herangezogen wird, um das Systemverständnis einer fremderregten Siebanlage zu verbessern und deren Entwicklung voranzutreiben. Im Fokus steht hierbei das patentierte Vorsieb Active Grid® der Firma RUBBLE MASTER, welches als Teil einer Siebanlage messtechnisch hinsichtlich des Schwingungsverhaltens untersucht wird. Die Parameter der Feder-Dämpfer-Elemente dieser Siebanlage erfolgt anschließend mittels Mehrkörpersimulation, was die Grundlage für den Aufbau partikelbeaufschlagter Simulationsmodelle bildet. Die somit gebildeten numerischen Modelle dienen schlussendlich der Optimierung des Active Grid®, speziell zur Ermittlung von Federsteifigkeiten und Dämpfungen der Feder-Dämpfer-Elemente des Vorsiebes, um eine optimale Siebwirkung zu erhalten, wofür entsprechend eine Co-Simulation zwischen Mehrkörper- und Partikelsimulation angestrebt wird. Ziel ist es, ein skalierbares Modell zu entwickeln.

No abstract