Research On Efficient Drilling Characteristic Of Lunar Regolith Coring Bit With Low Acting Force

Compared with the geological exploration sampling,the drilling environments,drilling objectives and drilling conditions of the lunar drilling exists great difference.This puts forward higher requirements for the drilling capacity and drilling efficiency of the sampling execution unit.Drilling ability is reflected the use of the limited capacity of the detector in the lunar environment,and it includes the drilling breakthrough ability of the rock of which drillability above VI,as well as the adaptive and coring ability to the unascertained lunar soil.Drilling efficiency refers to the degree of realization of the function of rock drilling breakthrough,and the cost required breaking up the lunar rock.With the influence of lunar gravity environment and the requirement of detector lightweight design,the acting force provided by sampling mechanism is limited.In addition,restricted by the vacuum environment,the auxiliary chip removal medium and the return time window,the rock drilling process is a lack of air convection and heat conduction time,and the thermal environment is poor.Therefore,for lunar rock drilling process,to effectively control the lunar rock breaking load,the configuration of coring bit should be rational designed,and the reasonable drilling parameters is required,and the drilling temperature would be fundamentally reduced.The high efficiency drilling with low acting force will finally be achieved.In this paper,the lunar rock is selected as the drilling object,and the following studies are carried out,such as 1)the analysis and research of mechanical characteristics in lunar rock simulant linear cutting by using elemental blade;2)numerical simulation of cutting breaking behavior on lunar rock simulant and microparameters matching;3)design of high efficiency rock coring bit with low acting force;4)research and test verification of percussive drilling load characteristics on lunar rock simulant.Analysis and research of mechanical characteristics in lunar rock simulant linear cutting by using elemental blade is carried out.Based on drillability,the lunar rock simulant is screened from geological rock.After analysis of bit drilling trajectory,the penetrations per revolution is equivalent to the cutting depth.Based on the Mohr-Coulomb shear failure criterion,the mechanical model of rock linear cutting process is built by elemental blade through load separation.The influence of cutting load with different cutting depth and cutting geometries is acquired,and the equivalent frictional coefficients in the rock cutting model are modified based on cutting load test.The numerical simulation of cutting breaking behavior on lunar rock simulant and microparameters matching is implemented.The rock cutting chips is considered as the minimum element in the rock simulated model.The 2D/3D discrete element cutting model on lunar rock simulant is established.Based on Plackett-Burman(PB)design and central composite design(CCD),the cutting loads is selected as the macroscopic response,and the microparameters of these two discrete element models are matched.After the cutting load tests,the accuracy of the simulation model is verified.According to numerical simulation,the influence of cutting breaking behavior and its load feature with different cutting depths and cutting angles are gained,and the hypothesis of coring area in theoretical model is verified.For the demand of the high efficient drilling with low acting force,the configuration design of lunar regolith coring bit(LRCB)is carried out.Based on the chip removal and coring performance of lunar soil,the configuration of coring bit body is determined(spiral helix bit body with ring-type structure).Based on the rock crushing efficiency,the configuration of cutting blade on drill bit is determined(sharp-cutting blade).According to the geometry analytical equation of coring bit configuration,the theoretical model of rock cutting by elemental blade could be extended to the bit drilling process,and the drilling load prediction model on lunar rock simulant is established.After drilling loads feature test,the influence trends of rock drilling load with different five geometric parameters(forward rake angle,outward rake angle,sharp-point position coefficient,sharp-point height,sharp blade width)is obtained.With the target of minimum the drilling load,the configuration parameter design and optimization of lunar regolith coring bit is carried out,and the drilling efficiency of coring bit is verified after optimization.A kind of lunar regolith coring bit is acquired,and it could drill through the rock with a low coefficient of crushing load passive increasing.This kind of lunar regolith coring bit still has higher chip removal / coring ability when drilling lunar soil.The percussive drilling load feature of LRCB on lunar rock simulant is carried out.The percussive transmission chain on sampling mechanism is considered as the analysis objective.The equivalent model of impact hammer and auger,the theoretical model of the impact stress transfer in slender drill is built.Based on the assumption of rock elastic deformation,the rock percussive breaking mechanics model by elemental blade is established.After combining the rock percussive breaking model and the rock cutting model by elemental blade,the rock cutting percussive load prediction model is built.According to the cutting breaking form with different working stages,the rock cutting percussive load prediction model is built,and this model could extended to the percussive drilling model on lunar rock simulant.The incident stress function between the LRCB and rock is deduced,and the envelope boundary of impact area in the rock could be solved.And the influent trends of the percussive drilling load on rock with different drilling parameters(percussive frequency,rate of penetration,rotary speed)is obtained.After research on lunar regolith coring bit and its high efficiency drilling characteristics with low acting force,the breaking behavior and load features with different drilling mode on lunar rock simulant are gained,and a kind of coring bit is developed,and it could realize the high efficiency drilling with low acting force.It provides an alternative scheme of coring bit product design for the Chang'e program.It also provides the technical supports for the set of on-orbit drilling parameters to realize the lunar rock high efficiency drilling.