Lubrication media of rock bit journal bearing is non-Newtonian fluid, and because of structure limitations, lubricant supply is only from the inside track and its rheological properties are relatively complex. In gene...Lubrication media of rock bit journal bearing is non-Newtonian fluid, and because of structure limitations, lubricant supply is only from the inside track and its rheological properties are relatively complex. In general studies, the non- Newtonianism of lubrication media of rock bit journal bearing is neglected to simplify the research process. Based on the universal Reynolds equation of non-Newton media, the mathematical model of lubrication analysis was suitable for the rock bit bearing working conditions was established. Then according to the experimental results of rheological properties of RB-type lubricating grease, the equivalent viscosity of the model was established and this model can be solved by the method used in solving the Reynolds equation of Newton fluid.展开更多
This paper reports the numerical simulation of turbulent flow field in rockbits with the k-ε turbulence model and a new twenty-one point scheme for pressure correction equation, which greatly improves the synchronous...This paper reports the numerical simulation of turbulent flow field in rockbits with the k-ε turbulence model and a new twenty-one point scheme for pressure correction equation, which greatly improves the synchronous convergence ane the dependence ofcoupling between velocity and pressure on the pressure relaxation factor. It is numericallyverified that adaptive-manually technique is effective to generate more continuous, smoothand orthogonal Laplace grid system. Numerical results show that there exist vortices andlower pressure domains around the damaged zone, which strengthen the wear by solidparticle in the drilling nuid and induce the cavitation effect, finally causing the erosion anddecrease in the life of rock bit. The damage could be avoided by some modification of theinternal flow structure of rock bit.展开更多
A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can eas...A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix.展开更多
A three dimensional dynamic elastic-plastic finite element analysis of the interaction of percussion bits with rock masses is presented. The dynamic contact problem was investigated with the numerical method developed...A three dimensional dynamic elastic-plastic finite element analysis of the interaction of percussion bits with rock masses is presented. The dynamic contact problem was investigated with the numerical method developed for high velocity impact calculations[1]. The numerical analysis was carried out for three simultaneously loaded percussion bits arranged on a straight line on the rock surface, the loading time was kept constant throughout this work. The numerical calculation for various strengths of the dynamic load tm the percussion bits shows that a critical minimum dynamic load exists for the generation of plastic deformations in the rock. For this critical value of the load the maximum normal stress of the longitudinal wave in the percussion bit exceeds the yield stress of the rock mass.展开更多
Recently impregnated diamond bits have been widely applied in drilling hard and medium - hard formations in the world . It is quite necessary to study the fracturing mecha-nism of the impregnated diamond bit and the c...Recently impregnated diamond bits have been widely applied in drilling hard and medium - hard formations in the world . It is quite necessary to study the fracturing mecha-nism of the impregnated diamond bit and the classification of rocks , which can realize optimum drilling . Using multi - parameter rotary test stand can monitor and print nine parameters . The diamond size and concentration for experiment are various and there are nearly 200 types of samples , numbering over 1000 pieces . The results of laboratory are the same as those in the field . Besides , this paper expresses that the diamond concentration of impregnated diamond bits effect the bonding strength of diamond imbedded in ma-trix . During drilling by impregnated diamond bits three ways are used to cool the bits . The contact area between impregnated diamond layer and flow , and the drilling flow through annulus carrying away heat with conduction form can be shown by equations . It is impossible to classify the rock drillability only by using single factor . The best method is to use main factors to analyse the drillability of rocks. Only in this way , the results can be applied to practice .展开更多
文摘Lubrication media of rock bit journal bearing is non-Newtonian fluid, and because of structure limitations, lubricant supply is only from the inside track and its rheological properties are relatively complex. In general studies, the non- Newtonianism of lubrication media of rock bit journal bearing is neglected to simplify the research process. Based on the universal Reynolds equation of non-Newton media, the mathematical model of lubrication analysis was suitable for the rock bit bearing working conditions was established. Then according to the experimental results of rheological properties of RB-type lubricating grease, the equivalent viscosity of the model was established and this model can be solved by the method used in solving the Reynolds equation of Newton fluid.
文摘This paper reports the numerical simulation of turbulent flow field in rockbits with the k-ε turbulence model and a new twenty-one point scheme for pressure correction equation, which greatly improves the synchronous convergence ane the dependence ofcoupling between velocity and pressure on the pressure relaxation factor. It is numericallyverified that adaptive-manually technique is effective to generate more continuous, smoothand orthogonal Laplace grid system. Numerical results show that there exist vortices andlower pressure domains around the damaged zone, which strengthen the wear by solidparticle in the drilling nuid and induce the cavitation effect, finally causing the erosion anddecrease in the life of rock bit. The damage could be avoided by some modification of theinternal flow structure of rock bit.
基金Project(51074180)supported by the National Natural Science Foundation of China
文摘A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix.
文摘A three dimensional dynamic elastic-plastic finite element analysis of the interaction of percussion bits with rock masses is presented. The dynamic contact problem was investigated with the numerical method developed for high velocity impact calculations[1]. The numerical analysis was carried out for three simultaneously loaded percussion bits arranged on a straight line on the rock surface, the loading time was kept constant throughout this work. The numerical calculation for various strengths of the dynamic load tm the percussion bits shows that a critical minimum dynamic load exists for the generation of plastic deformations in the rock. For this critical value of the load the maximum normal stress of the longitudinal wave in the percussion bit exceeds the yield stress of the rock mass.
文摘Recently impregnated diamond bits have been widely applied in drilling hard and medium - hard formations in the world . It is quite necessary to study the fracturing mecha-nism of the impregnated diamond bit and the classification of rocks , which can realize optimum drilling . Using multi - parameter rotary test stand can monitor and print nine parameters . The diamond size and concentration for experiment are various and there are nearly 200 types of samples , numbering over 1000 pieces . The results of laboratory are the same as those in the field . Besides , this paper expresses that the diamond concentration of impregnated diamond bits effect the bonding strength of diamond imbedded in ma-trix . During drilling by impregnated diamond bits three ways are used to cool the bits . The contact area between impregnated diamond layer and flow , and the drilling flow through annulus carrying away heat with conduction form can be shown by equations . It is impossible to classify the rock drillability only by using single factor . The best method is to use main factors to analyse the drillability of rocks. Only in this way , the results can be applied to practice .
