基于离散元方法的PDC钻头破岩仿真研究

针对前人对PDC(聚晶金刚石复合片)钻头破岩仿真研究多采用有限元法,忽略了岩体的各向异性、不均匀性以及不连续性等问题。提出了采用离散元法来研究PDC钻头的破岩仿真过程,利用离散元软件PFC3D建立了虚拟单轴压缩实验和虚拟巴西劈裂法实验,推导出了岩石的三维离散元模型的细观参数,确定了岩石的本构模型。在此基础上建立了PDC单齿切削岩石的离散元模型,讨论了侧倾角对切削力的影响关系,并与单齿切削岩石的有限元模型进行了对比。结果表明:离散元模型与有限元模型结果比较接近,离散元数值模拟的求解时间为有限元数值模拟的1/3,离散元方法具有潜在的高效率。在单齿切削岩石的离散元模型的基础上建立了全钻头破岩离散元模型,研究了PDC钻头动态破岩过程中各切削齿所受扭矩和钻压的分布规律。并通过全钻头破岩室内台架实验对模型的准确性进行了验证。

Simulation of PDC Bit Cutting Rock Based on Discrete Element Method

A finite element method is used to study the rock breaking of PDC bit, ignoring the rock anisotropy, nonuniformity and discontinuity and other issues. It is proposed to use the discrete element method to study the simulation process of PDC bit broken rock, and the virtual uniaxial compression test and the virtual Brazilian splitting test of rock are established by using the discrete element software PFC3D. The microscopic parameters of the three-dimensional discrete element model of the rock are deduced and the constitutive model of the is determined. On this basis, the discrete element model of PDC single tooth cutting rock is established, and the influence of the roll angle on the cutting force is discussed and compared with the finite element model of single tooth cutting rock. The results show that the discrete element model is close to the finite element model, and the time of the discrete element numerical simulation is 1/3 of the numerical simulation of the finite element. The discrete element method has the potential high efficiency. Based on the discrete element model of single tooth cutting rock, the discrete element model of the whole bit is established. The distribution law of the torque and the drilling pressure of the cutting tooth during the dynamic rock breaking process of the PDC bit is studied. And the accuracy of the model is verified by the experiment of the whole drill bit.