TY - JOUR
T1 - Drilling response of drag bits
T2 - Theory and experiment
AU - Detournay, Emmanuel
AU - Richard, Thomas
AU - Shepherd, Mike
PY - 2008/12
Y1 - 2008/12
N2 - This paper presents a complete model of the drilling response of drag bits (or PDC bits as they are often referred to), i.e. a set of relations between the weight-on-bit W, the torque-on-bit T, the rate of penetration V, and the angular velocity Ω. This work complements an earlier paper [Detournay E, Defourny P. A phenomenological model of the drilling action of drag bits. Int J Rock Mech Min Sci 1992;29:13-23], in which the existence of a linear constraint between T, W, and the depth of cut per revolution d = 2 π V / Ω was established. The frictional contact process, shown previously to be a pervasive feature of the drilling response of drag bits, is here further characterized by the introduction of two new quantities: (i) the characteristic contact length ℓ, an objective measure of the bit bluntness and (ii) the contact strength σ, the maximum normal stress that can be transmitted by the cutter wear flat-rock interface. The proposed model distinguishes three successive regimes in the drilling response of PDC bits: (i) phase I, at low depth of cut per revolution, characterized by a dominance of the frictional contact process and by an increase of the contact forces with d, (ii) phase II, where the contact forces are fully mobilized, and (iii) phase III where the actual contact length increases beyond ℓ, due to poor cleaning. Experimental evidence obtained with a small drilling machine is given in support of this model.
AB - This paper presents a complete model of the drilling response of drag bits (or PDC bits as they are often referred to), i.e. a set of relations between the weight-on-bit W, the torque-on-bit T, the rate of penetration V, and the angular velocity Ω. This work complements an earlier paper [Detournay E, Defourny P. A phenomenological model of the drilling action of drag bits. Int J Rock Mech Min Sci 1992;29:13-23], in which the existence of a linear constraint between T, W, and the depth of cut per revolution d = 2 π V / Ω was established. The frictional contact process, shown previously to be a pervasive feature of the drilling response of drag bits, is here further characterized by the introduction of two new quantities: (i) the characteristic contact length ℓ, an objective measure of the bit bluntness and (ii) the contact strength σ, the maximum normal stress that can be transmitted by the cutter wear flat-rock interface. The proposed model distinguishes three successive regimes in the drilling response of PDC bits: (i) phase I, at low depth of cut per revolution, characterized by a dominance of the frictional contact process and by an increase of the contact forces with d, (ii) phase II, where the contact forces are fully mobilized, and (iii) phase III where the actual contact length increases beyond ℓ, due to poor cleaning. Experimental evidence obtained with a small drilling machine is given in support of this model.
KW - Cutting
KW - Drilling
UR - http://www.scopus.com/inward/record.url?scp=55749094489&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=55749094489&partnerID=8YFLogxK
U2 - 10.1016/j.ijrmms.2008.01.010
DO - 10.1016/j.ijrmms.2008.01.010
M3 - Article
AN - SCOPUS:55749094489
SN - 1365-1609
VL - 45
SP - 1347
EP - 1360
JO - International Journal of Rock Mechanics and Mining Sciences
JF - International Journal of Rock Mechanics and Mining Sciences
IS - 8
ER -