Mechanical model of hollow-external-screw drill rod for lunar soil particle vertical conveying
This paper presents a mechanical model of drilling rod in lunar soil deep drilling process by expanding the theory of vertical screw conveyor. Space systems on lunar surface need to adapt to extremely bad environment and a drilling system would represent the fittest tool to collect soil sample to be analyzed in lunar exploration. Hollow-external-screw drill rod is a kind of most commonly used and reliable drill rod configuration which is one of the core executive components of lunar drilling- sampling mechanism. Drilling cuttings at the bottom of the hole are continuously sent to the lunar surface and the interaction between the drilling rod and the soil is difficult to model by numerical tools. Solid vertical transport theory in vertical screw conveyor and a soil-transporting mechanical model of long earth boring auger are applied to model the aforementioned interaction. In this force analysis of the mechanical model, not only the spiral angle variation is considered, but also the radial distribution and soil pressure in the particle vertical conveying. All these make the theoretical analysis more comprehensive than traditional methods. This paper also provides mathematical simulation of the soil-transporting process and the validation of the theoretical model mentioned above will be confirmed by the numerical and physical experiments.
Drilling and Migration Characteristics of Critical Size Lunar Soil Particles
Critical size lunar soil particles refer to particles with a particle size similar to the diameter of the drill bit, which is an important factor affecting lunar soil drilling sampling, and its influence is uncertain. In this paper, the discrete element method is used to simulate the drilling sampling process of the critical size lunar soil particles and the influence of the size, position and shape of the lunar particles with critical diameter on the drilling load is analysed. It is found that the critical size lunar soil particles have special migration trajectories and load characteristics during drilling sampling. The size and shape of lunar soil particles are the key factors affecting the drilling load. This study can support the design of drilling tools for lunar soil exploration and sampling.
Numerical methods in rock mechanics
Keywords: Mecanique des roches ; Analyse numerique ; Methode des elements finis Reference Record created on 2004-09-07, modified on 2016-08-08