The Design Of Coupling Bionic On PDC Bits Used In Coal Mines And Research On Its Rock Breaking Mechanism Through Improvement Of Penetration And Efficiency

With increasement of productivity of coal mines,the mining depth increases,the mining conditions become more and more complicated,safe and highly efficient coal mining has increasingly elevated the requirements for geological guarantee technologies.As one of the important approaches for the control of gas and water hazards in coal mines,the drilling technique has higher requirements for drilling equipment,supporting drilling tools and drilling technology.As the major rock breaking tool,the bit plays important role during the entire drilling process.Reasonable design and selection of bit have great significance for increasing the drilling efficiency and saving the drilling cost.Aiming at the problems such as low drilling and short service life of PDC bits used to drill the complex hard rocks in China's underground coal mines,on the basis of assimilation and adsorption of the design theory of PDC bits used in petroleum drilling,the thesis introduced the bionic theory of coupling and used it in the shape design of the cutting tooth and the crown of PDC bits,and used the computer simulation technique to conduct structural optimization and analysis of rock breaking mechanism so as to achieve the objective of enhancing the drilling efficiency and service life of bits.Firstly from the structural characteristics and the applicability of the cutting tooth of PDC bits commonly used in underground coal mines,through the analysis of the structural defects and failure modes of tri-wing inward concave PDC bits,in combination with the characteristics and the demand of hard rock drilling in underground coal mines,on the basis of assimilation and adsorption of the design theory of petroleum bits,the thesis put forward the design scheme of arc crown and teeth placement principle of peak shifting and layer by layer cutting,the design of the crown shape and teeth placement was improved.According to the bionic principle of biologic form,with the tooth of carnivorous shark as prototype,the sharp-fanged tooth was introduced into the surface form design of the cutting tooth of PDC bits.With the structural design of the 1308 type PDC cutting tooth as example,through simulation analysis,the triangle and the four grooves were optimized as the best structure of the teeth form,the integral structural design of the bionic PDC cutting tooth was completed.On the basis of the bionic principle of multielement coupling,with the claw and the scales of pangolin as bionic prototype,the bionic form of“morphology + structure”was adopted,the bionic design of multielement coupling was conducted for the form of the cutting tooth and the crown,pattern of teeth placement and gauge structure of DC bit was carried out.With the structural design of ?94mm arc angle PDC bit as example,through simulation analysis,the major parameters of the crown form and the cutting teeth angle were optimized,and the integral structural design of ?94mm steel bionic PDC bit and ?113mm matrix bionic bit was completed respectively.Through the theoretic analysis of the working principle and the stress characteristics of PDC cutting tooth and PDC bit,the concept of“entering-rock free face”was introduced to analyze their impact on rock breaking efficiency,the finite element softwares ABAQUS and LS-DYNA were used to conduct analogue simulation of the overall working status of the PDC bionic cutting tooth and the bionic PDC bit,revealing the working mechanism of the fact that the rock breaking efficiency of the bionic PDC cutting tooth and the bionic PDC bit is obviously higher than that of the common PDC flat cutting tooth and the conventional tri-wing inward concave bit.Finally,in order to verify the theoretic analysis and the simulation results,the lab micro-drill testbed was used to test the drilling performance of the bionic PDC cutting tooth,it was found that the drilling efficiency of the bionic PDC cutting tooth was evidently higher than that of the common flat chip,but the blade was easy to break.Through in-site industrial test,contrast test was carried out respectively with ?94mm steel bionic arc PDC bit and?113mm matrix bionic arc PDC bit as well as the existing inward concave PDC bit,the service life and the drilling efficiency of the bionic bits are significantly improved,basically consistent with the theoretic analysis and the simulation results.