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Rock breaking process of diamond bottom hole

2017/08/07 16:44
Rockbreakingprocessofdiamondbottomhole  1..Theholebottomrockfragmentationprocessofdiamondinserts.AdiamondgrainonabitisregardedasacuttingtoolmovingalongtherocksurfaceundertheactionofaxialpressurePyandt
Rock breaking process of diamond bottom hole
1.. The hole bottom rock fragmentation process of diamond inserts.
A diamond grain on a bit is regarded as a cutting tool moving along the rock surface under the action of axial pressure Py and tangential force Px (Fig. 4-19). The tangential force Px is consumed by the reaction Pg and friction T to overcome the rock's resistance to fracture T = Pyf.
Px=Pg T=Pg Pyf (4-8)
Formula: the friction coefficient of f-- diamond and rock; the load of Py-- distributed on a diamond.
Fig. 4-19 schematic diagram of diamond cutting edge
1-crushed rock; 2-tensile stress in rock; 3-crushed, sheared rock; I-bit body; II-diamond cutting; III-rock
When the diamond moves along a concentric circle, it transmits a certain amount of energy to the rock, and the rock absorbs the energy and breaks up and forms small grooves. In elastic brittle rocks, the width of grooves is much wider than the depth of diamond ingestion due to the production of large and small shear bodies. While the rock is broken, the diamond is gradually blunted. At this point, the blunt diamond strains the rock under the action of axial load, resulting in the occurrence of small cracks in the rock, which alter the rock's compact structure (Fig. 4-19). The number and depth of cracks depend on the axle load and drill speed transmitted to each diamond. When the diamond is blunted, it is necessary to repeat the additional load at a certain point at the bottom of the hole for the rock to break. That is to say, the process of rock breaking has the property of fatigue breaking.
2. the hole bottom rock fragmentation process of impregnated diamond bit.
The hole bottom rock fragmentation process of impregnated diamond bit is different from that of table insert bit. Because the diamond particles used are small and buried in the matrix, the impregnated bit must maintain the self-sharpening performance (called self-sharpening) in the drilling schedule in order to maintain a constant drilling rate without attenuation.
Generally speaking, the actual rock fragmentation mechanism of the impregnated bit is similar to that of the grinding workpiece with a grinding wheel, i.e. a large number of small hard spots (diamonds) on the lip surface are used to characterize and grind the workpiece (rock at the bottom of the hole), and with the gradual wear and loss of the hard spots and the continuous wear of the bonded matrix, new hard spots are exposed to participate in the work. Do. Of course, if the lip diamond is well exposed, the micro-shearing and micro-crushing of the bottom of the hole can not be ruled out. In fact, the grinding wheel in high-speed grinding, its own wear, because of its "self-sharpening" role and often in a sharp state. For impregnated diamond bits, self-sharpening can not be achieved if the matrix performance does not adapt to the drilled rock or does not guarantee enough drilling pressure, and the matrix can not be abraded ahead of time and the diamond particles which have lost the ability to break rock fall off by themselves. In the hole bottom process, the drill bit is "slippery" and the penetration rate drops rapidly.
The working process of table inserts or impregnated bits at the bottom of holes is very complicated. The vibration and elastic deformation of the drilling tool strengthens or weakens the drilling pressure at the bottom of the hole, and the pressure fluid delivered by the reciprocating pump is pulsating, which aggravates the vibration of the drilling tool and the bit. Therefore, scholars believe that there is still a rock breaking process at the bottom of the hole.
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