Simulation Of Moon Sampling Critical Scale Particle Placement Process And Research On Its Characteristics Of Motion

China’s chang’e-5 probe will obtain lunar soil samples through an unmanned drilling sampling device and return them to the earth.During the sampling process,the critical size particles and their accumulation areas in the shallow layer of lunar soil have a negative impact on the lunar soil sampling task.According to the cross section diameter of the core drilling tool d₀,the lunar soil particles with the particle size between 0.1d₀ and 0.5d₀ are divided into critical size particles.In order to improve the coring rate and reduce the occurrence of unfavorable working conditions such as stuck drilling and plugging,In this paper,a simulation test on the process of placing the bottom of the critical-scale particles on the moon soil in the earth environment will be conducted,study the influence of the cutting speed and cutting position of the cutting edge of the drill bit on the movement state of the critical scale particles,Provide a theoretical basis for analyzing the occurrence of fault conditions in the process of drilling and sampling,Therefore,the following research work has been carried out in this paper.Combined with the mechanical characteristics of lunar soil,its shape factor is introduced to establish a critical scale particle normal contact mechanical model.Based on the Fourier theory,the shape description model of critical scale particles is established,and the particle image is processed by image analysis algorithm,the contact probability model of critical scale particles is established.According to the results of the contact probability,the particles are generated and transferred,and the correctness of the normal contact mechanics model based on the shape description is verified by the normal mechanical loading test of the critical scale particles.The established equivalent model of critical scale particles is introduced into the simulation software to simulate the cutting process of critical scale particles.Based on the relevant theories of rock cutting and geotechnical mechanics,combined with the failure and failure modes of lunar soil,a mechanical model of the interaction between the single cutting edge and the critical-scale particles of lunar soil is established,and the influence of relevant parameters on the migration rule of the critical-scale particles during cutting is analyzed.A discrete element model of critical size particle removal in lunar soil based on the probability of particle shape distribution,It’s obtained by simulation,different cutting speed and cutting depth,the soil critical dimension particle motion and the motion characteristics change trend,through simulation,the results show that the increase or decrease of cutting speed has little effect on the change of critical scale particle velocity,while the change of cutting position has obvious effect on the change of critical scale particle velocity and displacement during the cutting process.It is verified by simulation experiment of lunar soil critical scale particle hole bottom setting out.The selected critical scale particles of lunar soil with designated size range are pasted with mark points as cutting samples,which are placed in a soil tank equipped with homogeneous lunar soil,compacted by hydraulic press to achieve the required density of the test,set up relevant test equipment,and carry out multiple groups of cutting out tests on the single edge cutting test bench.The test results show that the cutting position is the main factor affects the movement characteristics of the critical scale particles in the simulation of lunar soil,and it is found that the critical scale particles will roll during the cutting process.The test results are compared with the corresponding simulation results to verify the reliability and accuracy of the theoretical model.The density of the cutting test sample is increased to the range of the true lunar soil density parameter by compression,and the lunar soil marked point cutting tests are carried out by using the single-tooth cutting test bench and an orthogonal test program.After processing the data collected by the high-speed camera,the movement characteristics of the critical scale particles during the placement of the bottom of the hole are obtained,which explains the reasons for the translation and rolling of the particles.The experimental results are compared with the simulation results to verify the correctness of the theoretical analysis.