Research On Drilling Load Characteristics Of Screw Type Drilling And Coring Bit

The lunar exploration project of China will launch a spacecraft equipped with unmanned drilling and coring mechanism, aiming at getting lunar soil sample from 2 meters beneath the surface. Given the fact that lunar rock is inevitable, the rock-penetration capacity of the drilling bit is of great importance. The screw type drilling bit is designed specifically for lunar soil drilling, lacking the ability to penetrate into the rock. Welding the tungsten carbide cutters on the drilling bit proves to be an effective method to enhance the capacity of the crew type bit.Analyzing the basic mechanics of different kind of rocks, the basic mechanics of different rock can work as the basic preparation for rock failure. Considering the specificity of the lunar rock, choosing the Failure Theory of Mohr as the failure criterion of the lunar rock. The mechanic model describing the interaction between rock and drilling bit was set up based on the Failure Theory of Mohr. Set up the test bed of single cutter to conducting the experiment of interaction between single cutter and the rock. Based on this test bed, several experiments including the rake angles, cutting depth and cutting speed was conducted in order to verify the mechanic model set up in paragraph two. Besides, the outcome of the experiment can be valuable references for cutter choosing.Numerical simulation was conducted to test the interaction between the bit, the cutter and the rock. By conducting the numerical simulation, the process of rock failure can be clearly observed. Besides, numerical simulation of interaction between rock and drilling bit is also conducting in order to test the differences between rotary cutting and the translational cutting.Based on the outcome of theoretical analyzing, experimental analyzing and the outcome of numerical simulation, the optimal shape of the cutter was finally identified. Several types of drilling bits with different kind of cutter layout was also manufactured. Using the rotary test bed, relevant test was set up to analyzing which kind of layout of cutters is best suitable for lunar rock penetration.Through the process of theoretical analyzing, experimental comparison and the numerical simulation, welding the cutter on the screw bit is finished. The interaction theory between rock and the bit was also set up, which work as the fundamental knowledge for lunar drilling and sampling.