Cutting Thermal Analysis And Simulated Experimental Study Of Lunar Surface Coring Drill

The drill bit temperature during sampling process is one of the key concerns for lunar surface drilling and sampling mission.Water and other cooling measures cannot be used because of high vacuum complex environment during lunar surface drilling,rapid temperature rising of drill bit occurred due to low thermal conductivity of lunar soil Therefore,researches on rock drilling bit temperature and its distribution rule are of great significance on the material choosing and structural parameters determination of drill bit.Meanwhile,prolonging service life,optimizing drilling parameters,reducing drilling costs,ensuring drilling process can count on these researches.In this article,a combination of theoretical analysis and experimental study methods was employed aimed at learning temperature problem during lunar surface drill rotary cutting.1.In this article,physical mechanical properties of lunar rocks were learnt compared to earth rocks,and the medium-hard earth rocks were chose as research objects to studying cutting temperature.Cutting conditions of medium-hard rocks were evaluated based on cutting model and mechanism,molar theory and crack propagation theory.Brittle and ductile cutting were thought to be existed in medium-hard rock cutting process simultaneously,a new cutting mechanism of medium-hard rock was proposed based on this idea,and semi-holes micro-drilling test was conducted to verify it.The results showed that the drilling process was affected by both brittle and ductile cutting mechanism,big and small chips were produced continuously in this process.2.Figure out heat source and heat distribution of rock cutting process by analyzing heating system in rock drilling.Analytical calculation model of bit average temperature during rotary drilling process was established based on energy conservation and differential equations of rock drilling process given by Fourier's law in drilling thermal system.The results shows that the main factors affecting drill bit temperature including geometric drill bits,rock,,drilling process parameters and thermo-physical properties of drill,rock and chips.Influences of various factors were studied by analyzing the model,the drill bit cutting temperature is proportional to drilling pressure and speed,however,influence of speed is greater than that of pressure.3.Concerned with the lunar dry environment and low power drilling conditions,simulated lunar rocks drilling experiments were conducted by using moon drilling rig with low power and small lunar surface coring drill.In order to get real-time acquisition and storage temperature,artificial thermocouple was used to measure the temperature in rock drilling process.The results showed that: the bit temperature rising phenomenon was very obvious,and accompanied throughout the drilling along with temperature changes into volatility.Drill temperature rising process can be divided into three stages: rapid heating stage,steady rising stage and relatively stable stage.Drilling temperature increases with the drilling speed and Rock drill-ability grade,which showed good positive correlation.This is consistent with the theoretical model analysis.