Research On Lunar Soil Chip Removing Model And Lunar Subsurface Coring Drill

The target of the third phase of China's lunar exploration is to take lunar subsurface soil sample back to earth.The drilling and sampling device equipped on the lander is the end effector of the whole project.Its external structure decides drilling load,drill bit temperature and sampling rate etc.because it has direct contact with lunar soil.The external structure of the drilling tool comprises a drill pipe chip structure,a drill bit chip structure,a drill bit sampling port structure,and a bit rock cutting structure.In this paper,based on the spiral chip removing process model of lunar soil,the design and optimization of drilling tool structure parameters is studied,and the model results are verified by experiment and discrete element simulation.Data show that the lunar soil is a kind of poor fluidity of powder material,at the same time on the lunar surface there is no water and atmospheric environment.In the lunar surface drilling and sampling process,the lunar soil debris need to be discharged through the drill bit and drill pipe's spiral chip removing structure,if the discharge process is not smooth,it will lead to the increase of drilling load and even stuck drill.In this paper,the flow characteristics of the lunar soil in the spiral groove are analyzed,and the ideal chip removal condition is defined.Firstly,the lunar soil debris flow flux balance relationship is established,then the relation model between the regolith flow and the structural parameters of the drill spiral groove is set up using kinematics and mechanics analysis of the chip flute.A chip removing capability factor is defined to indicate the chip removing capability of the drill tool at certain drilling procedure.In order to improve the accuracy of the model,the dynamic factors of drilling tool,the fluid viscosity effect and so on,were analyzed,and the corresponding correction factors were set up.The optimum design of drill pipe structure parameters is carried out basing on the soil chip removing model,and the parameters along with the model are verified by soil chip removing experiments of the drill stem.In addition,the relationship between the axial force and torque of the drill stem is also given,and the results are verified in the experiment.In order to take a microscopic view on the chip removing flow in drill auger groove,discrete element model of the lunar soil is set up and the parameters are matched.The discrete element simulation provides theoretical support for the chip flow characteristics and chip removal model.In traditional lunar exploration drilling tool design,the drill load mainly concentrated at the junction of the drill bit and the drill stem,where the lunar regolith stagnation is serious.In this paper the designed drill bit share same parameters with drill stem,it can improve the overall performance of the drilling tool.Basing on the chip removing model,the spatial helical curve of the drill bit chip removing wing is given using space differential analytic geometry method.The wing and drill bit base composed the chip flow channel of the drill bit,which calculated chip removing capability matches with the drill stem.The drilling load of several typical configuration drill bits are compared in experiments.The drilling objects including small particle size simulated lunar soil and critical scale simulated lunar soil.By using discrete element simulation,the flow and stress state of the small scale lunar soil and the critical size of the soil in different configuration bits are observed and explained.It is a complex issue that the design of the sampling structure on the drill bit,which effects its sampling capability.It has strong randomness.In this paper,the failure form of the target area lunar soil is analyzed on different sampling port structure.A prediction model of sampling rate is given,and it is verified through sampling experiment.The circumferential bedding information of lunar soil is also studied using discrete element simulation method.It is also studied in this paper that the realization method of lunar rock drilling based on the spiral drill bit.The nickel electroforming CBN abrasive grain method and the cemented carbide cuter method is proposed.The differences between the two methods are analyzed.Lunar rock simulant drill experiment is take out to compare and verify the two methods.