含砾岩样中切削齿冲击载荷变化规律试验

Experiment on impact forces on single PDC cutter in cement sample with gravels

通过直径为19 mm的单齿切削含砾岩样试验,研究砾石直径、胶结强度、切削深度、切削齿后倾角等对切削齿所受冲击载荷的影响规律,分析PDC钻头钻进砾石层的损坏机制。结果表明:切削齿受到的冲击力随着砾石层胶结强度、砾石直径的增加而增大,随切削齿切削深度的增加呈指数增加;相同切削面积下,切削齿受到的冲击力随着后倾角的增大而增大;当冲击载荷大于切削齿的极限冲击强度时,切削齿将直接产生碎裂;即使冲击载荷不能达到切削齿的极限冲击强度,周而复始的冲击载荷达到切削齿的冲击韧性时,切削齿将发生冲击疲劳损坏。

By making cutting experiments on single PDC cutter with a diameter of 19 mm in cement samples containing gravels, the laws of some factors such as gravel diameter, cementing strength, cutting depth, cutter back rake angle affecting the impact force on PDC cutter were studied. The damage mechanism on PDC bits drilling the gravel layer was analyzed. The resuits show that the impact forces on cutting teeth increase with the bond strength of the gravel and the gravel diameter increasing. With the increase of cut depth of cutting teeth, the impact foree increases exponentially. Under the same cutting area, the impact force increases as the back rake angle increases. When the impact load is greater than the limit of impact strength, the cutting teeth will produce fragmentation. Even if the impact load is not to the limit of impact strength of the cutting teeth, the cycle of impact loading reaching the impact toughness of the cutting teeth, the cutting teeth will occur the faligue damage.