Research Of Structure Design Of Deep Lunar Soil Coring Bit And Characteristics Of Load

The main aim of lunar surface drilling and sampling mission is to obtain the soil which is under lunar at a depth of two meters with original information and get it back to the earth. The complexity of the lunar surface environment and so little energy that the lander could carry will bring a lot of difficulties to the sampling mission. In the process of sampling on the lunar surface, to prevent the high drilling force overturning the lander, this paper proposed a thought about a coring bit with ladder type basing on the studying of foreign extraterrestrial planets sampling techniques and drilling technologies on the earth. Through the theoretical analysis, the simulation and the ground testing, this paper got a rule that how the structure parameters impact the drilling load.Through studying the physical and mechanical properties of lunar soil, this paper has confirmed how the change interval of some main parameters can change with the trends of the depth. This paper provides a basis for interaction mechanical model between coring bit and lunar soil. By studying the lunar soil composition and preparation methods home and abroad, three kinds of lunar soil simulation for testing on the earth are made. It also founds the constitutive model of homogenous lunar soil simulation. This provides a basis for FEM simulation how coring bit drill lunar soil simulation and provides guidance for the planning of testing simulation on the ground.Combining the experience about the design of coring bit, a kind of coring bit with ladder type is provided. Based on the failure mechanism of cutting tools on the coring bit cutting the soil and the boundary simplified manner, the mechanics model of cutting tools cutting lunar soil in the ultimate equilibrium is established. And the analytical model of drilling pressure and rotary torque in drilling process are obtained. According to the model, how cutting angle of cutting tools, bottom blade and width of cutting tools impact on the drilling loads are studied. The initial drilling loads that coring bit required to drill the lunar soil is estimated at last.In order to simulate the homogeneous lunar soil simulation better, an UMAT subroutine based on Duncan-Chang model is programmed. The model of coring bit and homogeneous lunar soil simulation are created in the FEM software. Through simulating the process of drilling, the drilling pressure and rotary torque that required are obtained. Through simulating how cutting cools cut two-dimensional and three-dimensional lunar soil, it verified the correctness of the failure model and boundary simplified manner above. Through analyzing structure parameters like ladder type, cutting angle of cutting tools, bottom blade and width of cutting tools, a theory that using coring bit like ladder type can reduce drilling force is got and also get rules how cutting angle of cutting tools, bottom blade and width of cutting tools impact cutting force.Ground tests targeted at homogeneous lunar soil and rocks are carried out. In the drilling tests, one of the structure parameters changes with the other parameters fixed. How the ladder type of coring bit, barrier ring, installation of cutting tools and cone angle of coring bit impact on the drilling loads are obtained.