Accurately forecasting the operational performance of a tunnel boring machine(TBM)in advance is useful for making timely adjustments to boring parameters,thereby enhancing overall boring efficiency.In this study,we us...Accurately forecasting the operational performance of a tunnel boring machine(TBM)in advance is useful for making timely adjustments to boring parameters,thereby enhancing overall boring efficiency.In this study,we used the Informer model to predict a critical performance parameter of the TBM,namely thrust.Leveraging data from the Guangzhou Metro Line 22 project on the big data platform in China,the model’s performance was validated,while data from Line 18 were used to assess its generalization capability.Results revealed that the Informer model surpasses random forest(RF),extreme gradient boosting(XGB),support vector regression(SVR),k-nearest neighbors(KNN),back propagation(BP),and long short-term memory(LSTM)models in both prediction accuracy and generalization performance.In addition,the optimal input lengths for maximizing accuracy in the single-time-step output model are within the range of 8–24,while for the multiple-time-step output model,the optimal input length is 8.Furthermore,the last predicted value in the case of multiple-time-step outputs showed the highest accuracy.It was also found that relaxation of the Pearson analysis method metrics to 0.95 improved the performance of the model.Finally,the prediction results were most affected by earth pressure,rotation speed,torque,boring speed,and the surrounding rock grade.The model can provide useful guidance for constructors when adjusting TBM operation parameters.展开更多
Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to ...Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is established.Compared with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental values.This model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.展开更多
Chemical vapor deposition (CVD) diamond coated drills are fabricated by depositing diamond films on Co-cemented tungsten carbide (WC-Co) drills. The characteristics of as-deposited diamond coatings are investigated by...Chemical vapor deposition (CVD) diamond coated drills are fabricated by depositing diamond films on Co-cemented tungsten carbide (WC-Co) drills. The characteristics of as-deposited diamond coatings are investigated by scanning electron microscope (SEM) and Raman spectra. To evaluate the cutting performance of diamond coated drills, comparative drilling tests are conducted using diamond coated and uncoated WC-Co drills, with carbon fiber reinforced plastics (CFRPs) as the workpiece on a high-speed computer numerical control (CNC) machine. Thrust force and tool wear are measured during the drilling process. The results show that diamond coated drill exhibits better cutting performance, compared with the uncoated drill. The value of flank wear is about 70 μm after machining 90 holes, about a half of that of the WC-Co drill with 145 μm after drilling only 30 holes. The wear rate of WC-Co drill is higher than that of diamond coated drill before diamond films peeling off. The diamond coated drill achieves more predictable hole quality. The improved cutting performance of the diamond coated drill is due to the high hardness, wear resistance and low coefficient of friction.展开更多
In aircraft assembly, interlayer burr formation in dry drilling of stacked metal materials is a common problem. Traditional manual deburring operation seriously affects the assembly qual- ity and assembly efficiency, ...In aircraft assembly, interlayer burr formation in dry drilling of stacked metal materials is a common problem. Traditional manual deburring operation seriously affects the assembly qual- ity and assembly efficiency, is time-consuming and costly, and is not conducive to aircraft automatic assembly based on industrial robot. In this paper, the formation of drilling exit burr and the influ- ence of interlayer gap on interlayer burr formation were studied, and the mechanism of interlayer gap formation in drilling stacked aluminum alloy plates was investigated, a simplified mathematical model of interlayer gap based on the theory of plates and shells and finite element method was established. The relationship between interlayer gap and interlayer burr, as well as the effect of feed rate and pressing force on interlayer burr height and interlayer gap was discussed. The result shows that theoretical interlayer gap has a positive correlation with interlayer burr height and preloading nressing force is an effective method to control interlaver burr formation.展开更多
Ultrasonic vibration-assisted drilling(UVAD)has recently been successfully applied in the drilling of carbon fiber reinforced polymer/plastic(CFRP)due to its high reliability.Multiple defects have been observed in the...Ultrasonic vibration-assisted drilling(UVAD)has recently been successfully applied in the drilling of carbon fiber reinforced polymer/plastic(CFRP)due to its high reliability.Multiple defects have been observed in the CFRP drilling process which negatively affects the quality of the hole.The carbon fiber/bismaleimide(BMI)composites is an advanced kind of CFRPs with greater strength and heat resistance,having been rapidly applied in lightweight and high temperature resistant structures in the aerospace field.To suppress the defect during the drilling of carbon fiber/BMI composites,it is necessary to comprehensively understand the defect formation and suppression mechanism at different positions.In this study,the defects formation in both conventional drilling(CD)and UVAD were observed and analyzed.The variation trend in the defect factor and thrust force with the spindle speed and feed rate were acquired.The results revealed that the UVAD could significantly enhance the hole’s quality with no delamination and burr.Meanwhile,the defect suppression mechanism and thrust force in UVAD were analyzed and verified,where the method of rod chip removal affected the exit defect formation.In summary,UVAD can be considered a promising and competitive technique for drilling carbon fiber/BMI composites.展开更多
Drilling carbon fiber reinforced polymer(CFRP)composites is liable to generate serious defects including burrs,delamination,fiber pullouts and matrix cracking because of their inherent anisotropy in mechanical propert...Drilling carbon fiber reinforced polymer(CFRP)composites is liable to generate serious defects including burrs,delamination,fiber pullouts and matrix cracking because of their inherent anisotropy in mechanical properties.Therefore,studies on drilling quality during composites processing is necessary. The thrust force of different material drill bits in composites drilling process was measured by the dynamometer and the surface quality of the hole wall was observed by scanning electron microscope(SEM),moreover,the tool wear and its effects on the hole wall quality were also taken into account.展开更多
Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and ste...Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.展开更多
A simplified model of the thrust force is proposed based on a caudal fin oscillation of an underwater bionic robot. The caudal fin oscillation is generalized by cen- tral pattern generators （CPGs）. In this model, th...A simplified model of the thrust force is proposed based on a caudal fin oscillation of an underwater bionic robot. The caudal fin oscillation is generalized by cen- tral pattern generators （CPGs）. In this model, the drag coefficient and lift coefficient are the two critical parameters which are obtained by the digital particle image velocimetry （DPIV） and the force transducer experiment. Numerical simulation and physical experi- ments have been performed to verify this dynamic model.展开更多
This paper presents an analytical approach for estimating frictional resistance to pipe movement at soil and external pipe surface of buried coated pressurized steel pipes relative to the internal thrust force.The pro...This paper presents an analytical approach for estimating frictional resistance to pipe movement at soil and external pipe surface of buried coated pressurized steel pipes relative to the internal thrust force.The proposed analytical method was developed based on 36 experiments,which involved three coating types(cement mortar(CM),polyurethane type-I(PT-I),prefabricated plastic tape(PPT))on pipes’surfaces,three different soils(pea-gravel(PG),sand(S),silty-clay(SC)),and four simulated over burden depths above the pipe’s crown.Investigation showed frictional resistance decreased with increasing over burden depth above the pipe’s crown.The degree of frictional resistance at the pipe-soil interface was found to be in the order of PG>SC>S for all coating variations and overburden depths.CM coated pipe buried in all three types of soil produced significantly higher frictional resistance as compared to other coating types.Based on experimental data,the developed analytical introduced a dimensionless factor“Z”,which included effects of types of coatings,soil,and overburden depths for simplified rapid calculation.Analysis showed that the method provided a better prediction of frictional resistance forces,in comparison to previous analytical methods,which were barely close in predicting friction resistance for different coating variations,soil types,and overburden depths.Friction resistance force values reported herein could be considered conservative.展开更多
Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order t...Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.展开更多
Carbon fiber reinforced plastic (CFRP) composites are extremely attractive in the manufacturing of structural and functional components in the aircraft manufacturing field due to their outstanding properties, such as ...Carbon fiber reinforced plastic (CFRP) composites are extremely attractive in the manufacturing of structural and functional components in the aircraft manufacturing field due to their outstanding properties, such as good fatigue resistance, high specific stiffness/strength, and good shock absorption. However, because of their inherent anisotropy, low interlamination strength, and abrasive characteristics, CFRP composites are considered difficult-to-cut materials and are prone to generating serious hole defects, such as delamination, tearing, and burrs. The advanced longitudinal–torsional coupled ultrasonic vibration assisted drilling (LTC-UAD) method has a potential application for drilling CFRP composites. At present, LTC-UAD is mainly adopted for drilling metal materials and rarely for CFRP. Therefore, this study analyzes the kinematic characteristics and the influence of feed rate on the drilling performance of LTC-UAD. Experimental results indicate that LTC-UAD can reduce the thrust force by 39% compared to conventional drilling. Furthermore, LTC-UAD can decrease the delamination and burr factors and improve the surface quality of the hole wall. Thus, LTC-UAD is an applicable process method for drilling components made with CFRP composites.展开更多
A two-way adaptive Kalman filter is proposed by combining a two-way filter with an adaptive filter for orbit determination of a maneuvered GEO satellite.A method of using Newton's high-resolution differential form...A two-way adaptive Kalman filter is proposed by combining a two-way filter with an adaptive filter for orbit determination of a maneuvered GEO satellite.A method of using Newton's high-resolution differential formula and polynomial fitting for modeling the thrust force of a maneuvered GEO satellite is developed.The adaptive factor,which balances the contributions of the measurements and the dynamic model information,is determined by using a two-segment function and predicted residual statistics.Simulations with a maneuvered GEO satellite tracked by the Chinese ground tracking network were conducted to verify the performance of the proposed orbit determination technique and the method of thrust force modeling.The results show that refining the thrust force model is beneficial for the orbit determination of a maneuvered GEO satellite;the two-way adaptive Kalman filter can efficiently control the influence of the dynamic model errors on the orbit state estimate.展开更多
The propulsive performance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in particular thrust ...The propulsive performance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in particular thrust force, exerted on the foil in pitching and plungingmotions, and to explore the relation of the propulsive performance with vortex structures near thefoil and vortex shedding in the near wake. The two-dimensional incompressible Navier-Stokesequations in the vorticity and stream-function formulation were solved by fourth-order essentiallycompact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta schemefor the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forceand the shedding of the trailing- and leading-edge vortices of the foil were analyzed. The effectsof some typical factors, such as the frequency and amplitude of the oscillation, the phasedifference between the pitching and plunging motions, and the thickness ratio of the foil, on thevortex shedding and unsteady force were discussed.展开更多
Excessive structural forces generated inside tunnel linings could affect the safety and serviceability of tunnels,emphasizing the need to accurately predict the forces acting on tunnel linings during the preliminary d...Excessive structural forces generated inside tunnel linings could affect the safety and serviceability of tunnels,emphasizing the need to accurately predict the forces acting on tunnel linings during the preliminary design phase.In this study,an anisotropic soil model devel-oped by Norwegian Geotechnical Institute(NGI)based on the Active-Direct shear-Passive concept(NGI-ADP model)was adopted to conduct finite element(FE)analyses.A total of 682 cases were modeled to analyze the effects of five key parameters on twin-tunnel struc-tural forces;these parameters included twin-tunnel arrangements and subsurface soil properties:burial depth H,tunnel center-to-center distance D,soil strength s_(u)^(A),stiffness ratio G_(u)=s_(u)^(A),and degree of anisotropy ss_(u)^(P)=s_(u)^(A).The significant factors contributing to the bending moment and thrust force of the linings were the tunnel distance and overlying soil depth,respectively.The degree of anisotropy of the surrounding soil was found to be extremely important in simulating the twin-tunnel construction,and severe design errors could be made if the soil anisotropy is ignored.A cutting-edge application of machine learning in the construction of twin tunnels is presented;multivariate adaptive regression splines and decision tree regressor methods are developed to predict the maximum bending moment within the first tunnel’s linings based on the constructed FE cases.The developed prediction model can enable engineers to estimate the structural response of twin tunnels more accurately in order to meet the specific target reliability indices of projects.展开更多
In this study,applications of some analytical methods on nonlinear equation of the launching of a rocket with variable mass are investigated.Differential transformation method(DTM),homotopy perturbation method(HPM)and...In this study,applications of some analytical methods on nonlinear equation of the launching of a rocket with variable mass are investigated.Differential transformation method(DTM),homotopy perturbation method(HPM)and least square method(LSM)were applied and their results are compared with numerical solution.An excellent agreement with analytical methods and numerical ones is observed in the results and this reveals that analytical methods are effective and convenient.Also a parametric study is performed here which includes the effect of exhaust velocity(C_(e)),bum rate(BR)of fuel and diameter of cylindrical rocket(d)on the motion of a sample rocket,and contours for showing the sensitivity of these parameters are plotted.The main results indicate that the rocket velocity and altitude are increased with increasing the C_(e) and BR and decreased with increasing the rocket diameter and drag coefficient.展开更多
基金supported by the National Natural Science Foundation of China(No.41827807)the Foundation of the Guangdong Provincial Key Laboratory of Modern Civil Engineering Technology(No.2021B1212040003),China.
文摘Accurately forecasting the operational performance of a tunnel boring machine(TBM)in advance is useful for making timely adjustments to boring parameters,thereby enhancing overall boring efficiency.In this study,we used the Informer model to predict a critical performance parameter of the TBM,namely thrust.Leveraging data from the Guangzhou Metro Line 22 project on the big data platform in China,the model’s performance was validated,while data from Line 18 were used to assess its generalization capability.Results revealed that the Informer model surpasses random forest(RF),extreme gradient boosting(XGB),support vector regression(SVR),k-nearest neighbors(KNN),back propagation(BP),and long short-term memory(LSTM)models in both prediction accuracy and generalization performance.In addition,the optimal input lengths for maximizing accuracy in the single-time-step output model are within the range of 8–24,while for the multiple-time-step output model,the optimal input length is 8.Furthermore,the last predicted value in the case of multiple-time-step outputs showed the highest accuracy.It was also found that relaxation of the Pearson analysis method metrics to 0.95 improved the performance of the model.Finally,the prediction results were most affected by earth pressure,rotation speed,torque,boring speed,and the surrounding rock grade.The model can provide useful guidance for constructors when adjusting TBM operation parameters.
基金the financial support of Aeronautical Science Foundations of China(No.2013ZE52067,No.2014ZE52057)
文摘Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is established.Compared with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental values.This model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.
基金the National Natural Science Foundation of China(Nos.51275302 and 51005154)the Important National Science and Technology Specific Projects(No.2012ZX04003-031)
文摘Chemical vapor deposition (CVD) diamond coated drills are fabricated by depositing diamond films on Co-cemented tungsten carbide (WC-Co) drills. The characteristics of as-deposited diamond coatings are investigated by scanning electron microscope (SEM) and Raman spectra. To evaluate the cutting performance of diamond coated drills, comparative drilling tests are conducted using diamond coated and uncoated WC-Co drills, with carbon fiber reinforced plastics (CFRPs) as the workpiece on a high-speed computer numerical control (CNC) machine. Thrust force and tool wear are measured during the drilling process. The results show that diamond coated drill exhibits better cutting performance, compared with the uncoated drill. The value of flank wear is about 70 μm after machining 90 holes, about a half of that of the WC-Co drill with 145 μm after drilling only 30 holes. The wear rate of WC-Co drill is higher than that of diamond coated drill before diamond films peeling off. The diamond coated drill achieves more predictable hole quality. The improved cutting performance of the diamond coated drill is due to the high hardness, wear resistance and low coefficient of friction.
基金the financial support of the Aeronautical Science Foundation of China(Nos.2013ZE52067,2014ZE52057)
文摘In aircraft assembly, interlayer burr formation in dry drilling of stacked metal materials is a common problem. Traditional manual deburring operation seriously affects the assembly qual- ity and assembly efficiency, is time-consuming and costly, and is not conducive to aircraft automatic assembly based on industrial robot. In this paper, the formation of drilling exit burr and the influ- ence of interlayer gap on interlayer burr formation were studied, and the mechanism of interlayer gap formation in drilling stacked aluminum alloy plates was investigated, a simplified mathematical model of interlayer gap based on the theory of plates and shells and finite element method was established. The relationship between interlayer gap and interlayer burr, as well as the effect of feed rate and pressing force on interlayer burr height and interlayer gap was discussed. The result shows that theoretical interlayer gap has a positive correlation with interlayer burr height and preloading nressing force is an effective method to control interlaver burr formation.
基金co-supported by the Sichuan Science and Technology Program(Grant No.2020YFG0109)the NSAF of China(Grant No.U1830122).
文摘Ultrasonic vibration-assisted drilling(UVAD)has recently been successfully applied in the drilling of carbon fiber reinforced polymer/plastic(CFRP)due to its high reliability.Multiple defects have been observed in the CFRP drilling process which negatively affects the quality of the hole.The carbon fiber/bismaleimide(BMI)composites is an advanced kind of CFRPs with greater strength and heat resistance,having been rapidly applied in lightweight and high temperature resistant structures in the aerospace field.To suppress the defect during the drilling of carbon fiber/BMI composites,it is necessary to comprehensively understand the defect formation and suppression mechanism at different positions.In this study,the defects formation in both conventional drilling(CD)and UVAD were observed and analyzed.The variation trend in the defect factor and thrust force with the spindle speed and feed rate were acquired.The results revealed that the UVAD could significantly enhance the hole’s quality with no delamination and burr.Meanwhile,the defect suppression mechanism and thrust force in UVAD were analyzed and verified,where the method of rod chip removal affected the exit defect formation.In summary,UVAD can be considered a promising and competitive technique for drilling carbon fiber/BMI composites.
文摘Drilling carbon fiber reinforced polymer(CFRP)composites is liable to generate serious defects including burrs,delamination,fiber pullouts and matrix cracking because of their inherent anisotropy in mechanical properties.Therefore,studies on drilling quality during composites processing is necessary. The thrust force of different material drill bits in composites drilling process was measured by the dynamometer and the surface quality of the hole wall was observed by scanning electron microscope(SEM),moreover,the tool wear and its effects on the hole wall quality were also taken into account.
文摘Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.
基金Project supported by the National Natural Science Foundation of China(Nos.61503008 and 51575005)the China Postdoctoral Science Foundation(No.2015M570013)
文摘A simplified model of the thrust force is proposed based on a caudal fin oscillation of an underwater bionic robot. The caudal fin oscillation is generalized by cen- tral pattern generators （CPGs）. In this model, the drag coefficient and lift coefficient are the two critical parameters which are obtained by the digital particle image velocimetry （DPIV） and the force transducer experiment. Numerical simulation and physical experi- ments have been performed to verify this dynamic model.
文摘This paper presents an analytical approach for estimating frictional resistance to pipe movement at soil and external pipe surface of buried coated pressurized steel pipes relative to the internal thrust force.The proposed analytical method was developed based on 36 experiments,which involved three coating types(cement mortar(CM),polyurethane type-I(PT-I),prefabricated plastic tape(PPT))on pipes’surfaces,three different soils(pea-gravel(PG),sand(S),silty-clay(SC)),and four simulated over burden depths above the pipe’s crown.Investigation showed frictional resistance decreased with increasing over burden depth above the pipe’s crown.The degree of frictional resistance at the pipe-soil interface was found to be in the order of PG>SC>S for all coating variations and overburden depths.CM coated pipe buried in all three types of soil produced significantly higher frictional resistance as compared to other coating types.Based on experimental data,the developed analytical introduced a dimensionless factor“Z”,which included effects of types of coatings,soil,and overburden depths for simplified rapid calculation.Analysis showed that the method provided a better prediction of frictional resistance forces,in comparison to previous analytical methods,which were barely close in predicting friction resistance for different coating variations,soil types,and overburden depths.Friction resistance force values reported herein could be considered conservative.
基金Project supported by the National Natural Science Foundation of China“Research on Critical Dynamic Buckling Conditions of Rotary Drill Strings and Post-buckling Snaking Swing and Helical Whirling Behaviors”(No.51904317)National Natural Science Foundation of China“Basic Research on Drilling and Completion in Complex Oil and Gas Well”(No.51821092)+2 种基金National Natural Science Foundation of China“Basic Research on Well Construction in Efficient Development of Shale and Tight Oil and Gas Fields”(No.U1762214)Special Topic on CNPC's Strategic Cooperation Science and Technology Project“Research on ROP Acceleration Technology in Deep Drilling in Terrestrial Shale Oil”(No.ZLZX2020-01-07-01)Science Foundation of China University of Petroleum(Beijing)(No.ZX20180414).
文摘Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.
基金The authors are grateful to the financial support from the National Key R&D Program of China(Grant No.2019YFA0708902)the Joint Foundation from Equipment Pre-research and Ministry of Education,China(Grant No.6141A02022128)the Doctoral Scientific Research Fund of NSFL,China(Grant No.2019-BS-053).
文摘Carbon fiber reinforced plastic (CFRP) composites are extremely attractive in the manufacturing of structural and functional components in the aircraft manufacturing field due to their outstanding properties, such as good fatigue resistance, high specific stiffness/strength, and good shock absorption. However, because of their inherent anisotropy, low interlamination strength, and abrasive characteristics, CFRP composites are considered difficult-to-cut materials and are prone to generating serious hole defects, such as delamination, tearing, and burrs. The advanced longitudinal–torsional coupled ultrasonic vibration assisted drilling (LTC-UAD) method has a potential application for drilling CFRP composites. At present, LTC-UAD is mainly adopted for drilling metal materials and rarely for CFRP. Therefore, this study analyzes the kinematic characteristics and the influence of feed rate on the drilling performance of LTC-UAD. Experimental results indicate that LTC-UAD can reduce the thrust force by 39% compared to conventional drilling. Furthermore, LTC-UAD can decrease the delamination and burr factors and improve the surface quality of the hole wall. Thus, LTC-UAD is an applicable process method for drilling components made with CFRP composites.
基金supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 2007B51)National Natural Science Foundation of China (Grant Nos. 41174008 and 41020144004)China Postdoctoral Science Foundation (Grant Nos. 20080430148 and200902444)
文摘A two-way adaptive Kalman filter is proposed by combining a two-way filter with an adaptive filter for orbit determination of a maneuvered GEO satellite.A method of using Newton's high-resolution differential formula and polynomial fitting for modeling the thrust force of a maneuvered GEO satellite is developed.The adaptive factor,which balances the contributions of the measurements and the dynamic model information,is determined by using a two-segment function and predicted residual statistics.Simulations with a maneuvered GEO satellite tracked by the Chinese ground tracking network were conducted to verify the performance of the proposed orbit determination technique and the method of thrust force modeling.The results show that refining the thrust force model is beneficial for the orbit determination of a maneuvered GEO satellite;the two-way adaptive Kalman filter can efficiently control the influence of the dynamic model errors on the orbit state estimate.
文摘The propulsive performance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in particular thrust force, exerted on the foil in pitching and plungingmotions, and to explore the relation of the propulsive performance with vortex structures near thefoil and vortex shedding in the near wake. The two-dimensional incompressible Navier-Stokesequations in the vorticity and stream-function formulation were solved by fourth-order essentiallycompact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta schemefor the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forceand the shedding of the trailing- and leading-edge vortices of the foil were analyzed. The effectsof some typical factors, such as the frequency and amplitude of the oscillation, the phasedifference between the pitching and plunging motions, and the thickness ratio of the foil, on thevortex shedding and unsteady force were discussed.
基金supported by Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-K201900102)Chongqing Construction Science and Technology Plan Project(2019-0045).
文摘Excessive structural forces generated inside tunnel linings could affect the safety and serviceability of tunnels,emphasizing the need to accurately predict the forces acting on tunnel linings during the preliminary design phase.In this study,an anisotropic soil model devel-oped by Norwegian Geotechnical Institute(NGI)based on the Active-Direct shear-Passive concept(NGI-ADP model)was adopted to conduct finite element(FE)analyses.A total of 682 cases were modeled to analyze the effects of five key parameters on twin-tunnel struc-tural forces;these parameters included twin-tunnel arrangements and subsurface soil properties:burial depth H,tunnel center-to-center distance D,soil strength s_(u)^(A),stiffness ratio G_(u)=s_(u)^(A),and degree of anisotropy ss_(u)^(P)=s_(u)^(A).The significant factors contributing to the bending moment and thrust force of the linings were the tunnel distance and overlying soil depth,respectively.The degree of anisotropy of the surrounding soil was found to be extremely important in simulating the twin-tunnel construction,and severe design errors could be made if the soil anisotropy is ignored.A cutting-edge application of machine learning in the construction of twin tunnels is presented;multivariate adaptive regression splines and decision tree regressor methods are developed to predict the maximum bending moment within the first tunnel’s linings based on the constructed FE cases.The developed prediction model can enable engineers to estimate the structural response of twin tunnels more accurately in order to meet the specific target reliability indices of projects.
文摘In this study,applications of some analytical methods on nonlinear equation of the launching of a rocket with variable mass are investigated.Differential transformation method(DTM),homotopy perturbation method(HPM)and least square method(LSM)were applied and their results are compared with numerical solution.An excellent agreement with analytical methods and numerical ones is observed in the results and this reveals that analytical methods are effective and convenient.Also a parametric study is performed here which includes the effect of exhaust velocity(C_(e)),bum rate(BR)of fuel and diameter of cylindrical rocket(d)on the motion of a sample rocket,and contours for showing the sensitivity of these parameters are plotted.The main results indicate that the rocket velocity and altitude are increased with increasing the C_(e) and BR and decreased with increasing the rocket diameter and drag coefficient.
