PDC齿切削砂岩的细观损伤模拟

Mesoscopic Damage Simulation of Sandstone during PDC-Cutter Cutting

在岩石切削过程中,刀具的切削参数对岩石的破坏方式和破岩效率有重要影响。为了研究PDC齿在不同切削参数下切削砂岩的细观损伤效果,采用离散单元法建立了PDC齿压入砂岩的数值模型,研究不同切削速度、前倾角及切削深度情况下,砂岩在PDC齿切削过程中的力场分布及裂纹发育情况的变化规律。研究结果表明:在一定范围内增加切削速度、前倾角和切削深度,剪切裂纹提前萌生且其占比增加;前倾角和切削速度对齿尖主裂纹的扩展影响较小,切削深度则对齿尖主裂纹的扩展影响较大;针对研究的砂岩,其临界切削深度为2 mm左右,当切削深度增加时,容易增加PDC齿齿尖产生的裂纹的长度,当裂纹长度达到5 mm及以上时,块体崩碎的频率提高,块体崩碎存在卸载现象。所得结论可为PDC齿的设计及切削参数的选择提供理论支持。

In the process of rock cutting,the cutting parameters of the tool have important influences on the failure mode and rock-breaking efficiency.In order to investigate the mesoscopic damage of sandstone cut by PDC cutter under different cutting parameters,the discrete element method(DEM)was adopted to establish the penetration numerical model of the PDC cutter breaking conglomerate and subsequently study the cutting force field distribution and the change law of cracking development of sandstone in cases of different cutting speeds,cutting angles,penetration depths of PDC cutters.The results show that when cutting speed,rake angle and penetration depth are increased within a certain range,shear crack initiation occurs earlier and the proportions of shear cracks grow.The rake angle and cutting speed have few influences on the propagation of main cracks,while the penetration depth presents great influences on the propagation of the main crack.For the tested sandstone,the critical penetration depth is about 2 mm.When the penetration depth increases,the crack generated by the PDC cutter tip tends to extend.When the crack length exceeds 5 mm,the frequency of block breaking increases,associated with unloading phenomena.The findings of this research provide theoretical support for the PDC cutter design and optimization of cutting parameters.