Simulation Analysis On Lunar Drilling Power Dissipation Based On PFC3D

The three phase of lunar exploration project in China is to get 500 g samples from the moon and return to earth.But drilling on moon need to overcome many extreme conditions,such as low gravity,no water,no air,etc.At the same time,lunar regolith has high internal friction angle and low cohesion,so it is difficult to simulate the real environment and drilling process on the earth.The luna drilling requires that the drill tools has the advantages of light weight,low power consumption and high intensity,so the simulation analysis of drill dynamic can provide a theoretical basis for drilling structure design,material selection and drilling technology.This paper takes the discrete element method to establish the simulation model of drilling the lunar regolith and rock,also analysis the rock breaking power and lunar delivering power.It is also studied the influence of rock on drilling process power.According to the particularity of the lunar regolith and rock,through the simulation of uniaxial,biaxial and shear test with the model based on PFC discrete element is to get the right value of the micro parameters.With in the calibration of micro parameters,the elastic modulus E is 87 MPa,and the poisson'ratio ? is 0.11,and the uniaxial compressive strength is 127 MPa for rock;and for the lunar regolith,the cohesion is 3.4kPa and the inernal friction angle is 47 degrees;and the elastic moduls of lunar is 17 MPa and the poisson'ratio is 0.2.Those simulation macro properties are within the best valuation range and can ensure the accuracy of the model.On the basis of soil mechanics and rock fragmentation theory,establish the theoretical analysis model of drilling lunar,broken rock and delivering the scrap.It is obtained the power of rock broken and the power of delivering scrap.The resulte showed that the power of cutting regolith has a linear relationship with depth and the power of delivering scraps has a quadratic curve relationship with depth.Because of the limited of PFC on calculation,using the equivalent thought,the model scale is reduced according to the velocity field and stress field on drilling.As the sametime,the establishment of shallow drilling model and deep drilling equivalent model without rock block,the resistance moment of the drill bit and the drill rod are monitored.The both monitiored results are not olny consistent with the theoreticcal analysis but also verifies the effectiveness of the simulation model and the authenticity of the theoretical analysis model.At last,this paper wsa researched on the influence of rock characters such as the relative position of rock and the drill,the size of rock and the shape of rock on drilling power.The simulation analysis shows that the rock within the range of cutting teeth has a significant effect on the power of cutting.The value increases 4~5 times with periodicity but has a little influence on the pipe delivering.The shape of rock is only affect the time of generated pluse wave value not affect the amplitude of drill moment.The amplitude of the moment pulse is shown to be logarithmic function as the volume of the block increases.Therefore,in the process of drilling,it is necessary to monitor the change of drill torque in real time,and to adjust the driving torque of the motor in time to ensure the smooth progress of the drilling sampling task.