Flow Characteristics Of Lunar Soil Particles With Critical Size In Confined Space

The main goal of the third phase of my China lunar exploration project is to achieve unmanned drilling and sampling of the lunar soil in the subsurface of the moon and return to the earth.The Chang’e-5 probe successfully completed and obtained1731 g lunar soil samples.However,the sampling process is affected by the critical-scale particle lunar soil in the subsurface layer.In order to improve drilling reliability and reduce the occurrence of fault conditions such as stuck and plugged drills,this paper first analyzes the lunar soil in the drill bit spiral area.The flow process was simulated by Discrete Element Method.Secondly,the flow characteristics of the lunar soil in the confined space of the drill bit spiral area were studied,and the drilling characteristics of the lunar soil with critical-scale particles were explored.Finally,the drilling characteristics of the lunar soil with critical particles were summarized.Take the identification and prediction model of working conditions.It provides a theoretical basis for exploring the chip removal mechanism of critical-scale particles,and also provides support for improving drilling tools,object identification and drilling conditions prediction.The specific work is as follows:According to the best estimated value of the physical and mechanical properties of the lunar soil,the simulation parameters of the discrete element simulation of the lunar soil are matched and defined.In the matching process,the Box-Behnken central combined experiment design method was used to plan 17 sets of lunar soil accumulation angle simulation experiments,and the regression model of the lunar soil accumulation angle was obtained by variance analysis of the test results,and then the CUG-1A simulated lunar soil was used as the object.This model performs discrete element simulation calibration on the meso-parameters of the lunar soil.A discrete element simulation model of the flow of the lunar soil in the curved constrained space is established,and its flow characteristics are summarized.Analyze the temporal and spatial variation of the transient force chain,particle velocity,interparticle force and coordination number of lunar soil particles in the flow process.Discrete element simulation experiments were carried out on the drilling process of lunar soil with critical size particles.Analyze the interaction between the critical-scale particles and the drill bit,and design 12 drilling conditions with critical-scale particles in the lunar soil.Through EDEM simulation,analyze the velocity history,motion trajectory,displacement curve and load characteristics of drilling tools during the drilling process of critical-scale particles.Based on the multi-function full-parameter drilling test platform test,the scale-up test method is used to carry out the drilling verification test of the lunar soil with critical-scale particles.The test data was collected and verified and analyzed,and it was found that the drilling load characteristics of the lunar soil with critical scale particles obtained from the test were consistent with the simulation test.Finally,the time domain and frequency domain characteristic values of the drilling load curve were extracted and the BP neural network method was used to obtain Recognition and prediction model of critical-scale particle drilling conditions.