基于LS-DYNA的冲旋钻头牙齿破岩机理仿真研究

介绍了显式动力学有限元软件LS DYNA的功能特点，阐述了冲旋钻井中钻头牙齿与岩石相互作用数值研究的模型建立、网格划分、材料定义、接触定义及边界条件等相关问题。利用LS DYNA对3种不同齿形牙齿在冲击载荷下破碎岩石进行了计算机仿真，描述了牙齿破岩过程，并求出了相应的应力、位移时程关系曲线，得到了3种不同齿形牙齿的破岩机理。经过分析发现，在弹头齿和锥形齿冲击下裂纹首先出现在岩石内部，齿和岩石接触面下端最早出现裂隙，而在球形齿冲击下裂纹首先出现在齿和岩石接触面边缘；3种牙齿齿尖应力波峰值由大到小依次为：弹头齿、锥形齿、球形齿；布齿时锥形齿宜分布在钻头头部端面中心、球形齿分布在边缘，弹头齿或者锥形齿可分布在中心与边缘之间，这样有利于提高钻井破岩效率。

SIMULATION STUDY ON ROCK-BREAKING MECHANISM OF PERCUSSION-ROTARY DRILL BIT BASED ON LS-DYNA

In this paper the features of the explicit dynamic finite element software LS-DYNA are introduced,and the establishment of models,grid pattern,material definition,contact definition and boundary conditions for numerical study of the bit-rock interaction in percussion-rotary drill are described.The rock-breaking by cutters with 3 different thread forms under impact load has been simulated by computers using LS-DYNA,the rock-breaking process is described herein,the related stresses and displacement-time curves are obtained,and the rock-breaking mechanism of the 3 thread-form cutters are concluded.And the analysis indicates the cracks firstly occur inside the rock when under the impact of the bullet tooth or the coniform tooth,right under the contact surface of the rock and tooth;and the cracks will firstly occur at the edge of the contact surface of the rock and the tooth when under the impact of the sphere tooth;the stress peaks of three different teeth are put in an order as bullet tooth,coniform tooth and sphere tooth,from high to low;and so the coniform teeth should be placed at the center of the bit head face,the sphere teeth should be placed at the edge of the drill bit,and the bullet teeth or the coniform teeth placed between the center and the edge,to increase the rock-breaking efficiency of the drill bit.