| When the PDC cutter getting rid of the upper rock layer,the underlying rock have been damged.Thereby,the damage inside the rock would influence the rock breaking efficiency of follow-up cut.This view had been put forward by WuKaisong et al.And the correctness of this view has been comfirmed by some laboratory test.The key point is how to describe and measure the the extent of damage inside the rock made by the PDC cutter theoretically. Nowadays, there is no relevant literatures and reports about this point.So,this paper carried out a series of studies based on this problem.(1) Experimental studies about PDC cutter break rock repeatedly was conducted.The specific energy of cutting is introduced to evaluate the rock-breaking efficiency.The failure of rock under practical condition of PDC cutter was achieved. At the same time,it found that the damge law is different when the rock property is different.(2)Based on the the principle of conservation of energy,the definition of the damage work,the damage specific work and the theoretical broken specific work was proposed.And the damage work and the damage factor were used to measure the damage extent inside the rock.(3)Based on the software of ABAQUS,the FEM model of PDC cutter break the damaged and undamaged rock was built up.The plasticity damage model and brittle cracking constitu model were used as the material properties of the rock.It can analyze influence on rock fragmentation process by the residual stress and crack respectively.Based on the actual working conditions of PDC cutter,the study of law of rock-break when the rock is damaged was conduced.The results achieved from the Test and simulation not only make us know more about the rock breaking mechanism of PDC cutter,but also provide theoretical basis for optimal design of PDC bit.And the correctness of damage theory was verified. So this theory could describe the damage influence on the cutting process.It provides a new method for the rock damage theory study. |
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