PDC钻头后备布齿结构切削力学特性仿真分析

Simulation analysis of cutting mechanical characteristics of backup cutter layout structure for PDC bit

摘要:

PDC钻头在复杂条件下因频繁的冲击振动易发生断齿、脱层、碎裂等异常失效，采用后备布齿结构是降低冲击载荷、改善载荷环境的有效方法。本文基于川南龙马溪组页岩地层特性，利用Abaqus软件建立“主切削齿-后备齿”组合切削有限元仿真模型并开展实验验证，系统分析后备齿齿形、出露高差和切削深度对主切削齿工作载荷的影响规律。结果表明：合理的后备布齿结构能有效分担主切削齿的冲击载荷、降低应力集中；球头齿综合应力分散效果最优且适用范围最广，圆台齿在0.5 mm出露高差、1.0 mm切削深度下分压效率最高；0.5 mm出露高差综合降载效果最好，但切削深度1.0 mm时需避开；无后备齿时1.0 mm切削深度应力集中最严重，搭配合适后备齿后推荐采用0.5、1.5 mm切削深度；锥尖齿坡度无绝对优劣，需与切削深度、出露高差耦合匹配；川南页岩地层中钻进推荐采用球头齿作为后备齿，出露高差设定为0.5 mm，切削深度控制在0.5、1.5 mm。本研究可为复杂地层个性化PDC钻头优化设计提供理论支撑与技术参考。

Abstract:

Under complex conditions， PDC bits are prone to abnormal failures such as cutter breakage， delamination， and fragmentation due to frequent impact vibration. Adopting a backup cutter layout is an effective method to reduce impact loads and improve the load environment. Based on the formation characteristics of the Longmaxi Formation shale in southern Sichuan， a finite element simulation model of the "main cutter-backup cutter" combined cutting was established using Abaqus software and verified by experiments. The effects of backup cutter shape， exposure height difference， and cutting depth on the working load of the main cutter were systematically analyzed. The results show that a reasonable backup cutter layout can effectively share the impact load on the main cutter and reduce stress concentration. The spherical cutter exhibits the best overall stress dispersion effect and the widest applicability， while the truncated cone cutter achieves the highest load-sharing efficiency at an exposure height difference of 0.5 mm and a cutting depth of 1.0 mm. An exposure height difference of 0.5 mm yields the best comprehensive load reduction， but it should be avoided when the cutting depth is 1.0 mm. Without backup cutters， stress concentration is most severe at a cutting depth of 1.0 mm； when matched with appropriate backup cutters， cutting depths of 0.5 and 1.5 mm are recommended. The slope angle of the conical cutter has no absolute superiority or inferiority， requiring coupled matching with the cutting depth and exposure height difference. For drilling in the southern Sichuan shale formation， the spherical cutter is recommended as the backup cutter， with the exposure height difference set to 0.5 mm and the cutting depth controlled at 0.5 or 1.5 mm. The results of this study can provide theoretical support and technical references for the optimized design of customized PDC bits in complex formations.