Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints...Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints were investigated.Besides,the joint's interface microstructure,composition,and phases were analyzed.Results show that the AgCuInTi filler metal exerts a good wetting effect to the surface of cemented carbide and steel.With the increase in brazing temperature,the wetting angle decreases and the spreading area increases.The suitable temperature for vacuum brazing of PDC cutters is 770℃,and the maximum shear strength is 228 MPa at this temperature.展开更多
Large portions of the tunnel boring machine(TBM)construction cost are attributed to disc cutter consumption,and assessing the disc cutter's wear level can help determine the optimal time to replace the disc cutter...Large portions of the tunnel boring machine(TBM)construction cost are attributed to disc cutter consumption,and assessing the disc cutter's wear level can help determine the optimal time to replace the disc cutter.Therefore,the need to monitor disc cutter wear in real-time has emerged as a technical challenge for TBMs.In this study,real-time disc cutter wear monitoring is developed based on sound and vibration sensors.For this purpose,the microphone and accelerometer were used to record the sound and vibration signals of cutting three different types of rocks with varying abrasions on a laboratory scale.The relationship between disc cutter wear and the sound and vibration signal was determined by comparing the measurements of disc cutter wear with the signal plots for each sample.The features extracted from the signals showed that the sound and vibration signals are impacted by the progression of disc wear during the rock-cutting process.The signal features obtained from the rock-cutting operation were utilized to verify the machine learning techniques.The results showed that the multilayer perceptron(MLP),random subspace-based decision tree(RS-DT),DT,and random forest(RF)methods could predict the wear level of the disc cutter with an accuracy of 0.89,0.951,0.951,and 0.927,respectively.Based on the accuracy of the models and the confusion matrix,it was found that the RS-DT model has the best estimate for predicting the level of disc wear.This research has developed a method that can potentially determine when to replace a tool and assess disc wear in real-time.展开更多
Efficient tool condition monitoring techniques help to realize intelligent management of tool life and reduce tool usage costs.In this paper,the influence of different wear degrees of ball-end milling cutters on the t...Efficient tool condition monitoring techniques help to realize intelligent management of tool life and reduce tool usage costs.In this paper,the influence of different wear degrees of ball-end milling cutters on the texture shape of machining tool marks is investigated,and a method is proposed for predicting the wear state(including the position and degree of tool wear)of ball-end milling cutters based on entropy measurement of tool mark texture images.Firstly,data samples are prepared through wear experiments,and the change law of the tool mark texture shape with the tool wear state is analyzed.Then,a two-dimensional sample entropy algorithm is developed to quantify the texture morphology.Finally,the processing parameters and tool attitude are integrated into the prediction process to predict the wear value and wear position of the ball end milling cutter.After testing,the correlation between the predicted value and the standard value of the proposed tool condition monitoring method reaches 95.32%,and the accuracy reaches 82.73%,indicating that the proposed method meets the requirement of tool condition monitoring.展开更多
The widespread adoption of tunnel boring machines(TBMs)has led to an increased focus on disc cutter wear,including both normal and abnormal types,for efficient and safe TBM excavation.However,abnormal wear has yet to ...The widespread adoption of tunnel boring machines(TBMs)has led to an increased focus on disc cutter wear,including both normal and abnormal types,for efficient and safe TBM excavation.However,abnormal wear has yet to be thoroughly investigated,primarily due to the complexity of considering mixed ground conditions and the imbalance in the number of instances between the two types of wear.This study developed a prediction model for abnormal TBM disc cutter wear,considering mixed ground conditions,by employing interpretable machine learning with data augmentation.An equivalent elastic modulus was used to consider the characteristics of mixed ground conditions,and wear data was obtained from 65 cutterhead intervention(CHI)reports covering both mixed ground and hard rock sections.With a balanced training dataset obtained by data augmentation,an extreme gradient boosting(XGB)model delivered acceptable results with an accuracy of 0.94,an F1-score of 0.808,and a recall of 0.8.In addition,the accuracy for each individual disc cutter exhibited low variability.When employing data augmentation,a significant improvement in recall was observed compared to when it was not used,although the difference in accuracy and F1-score was marginal.The subsequent model interpretation revealed the chamber pressure,cutter installation radius,and torque as significant contributors.Specifically,a threshold in chamber pressure was observed,which could induce abnormal wear.The study also explored how elevated values of these influential contributors correlate with abnormal wear.The proposed model offers a valuable tool for planning the replacement of abnormally worn disc cutters,enhancing the safety and efficiency of TBM operations.展开更多
The oil and gas stored in deep and ultra-deep carbonate reservoirs is the focus of future exploration and development.Conical PDC(Polycrystalline Diamond Compact)cutter,which is a new kind of PDC cutter,can significan...The oil and gas stored in deep and ultra-deep carbonate reservoirs is the focus of future exploration and development.Conical PDC(Polycrystalline Diamond Compact)cutter,which is a new kind of PDC cutter,can significantly improve the rate of penetration(ROP)and extend PDC bit life in hard and abrasive formations.However,the breakage characteristics and failure mode of the conical PDC cutter cutting carbonate rock is still masked.In this paper,a series of single-cutter cutting tests were carried out with the conical and conventional PDC cutters.The cutting force,rock-breaking process,surface morphology of cutting grooves and cuttings characteristic were analyzed.Based on the derived formula of the brittle fracture index,the failure model of carbonate rock was quantitatively analyzed under the action of conical and conventional cutter.The results show that the average cutting force of the conical cutter is less than that of the conventional cutter,which means greater stability of the cutting process using the conical cutter.Carbonate rock with calcite as the main component tends to generate blocky rock debris by conical cutter.The height of the cuttings generated by the conical cutter is 0.5 mm higher than that generated by the conventional cutter.The conical cutter exhibits enhanced penetration capabilities within carbonate rock.The accumulation of rock debris in front of the conventional cutter is obvious.Whereas,the conical cutter facilitates the cuttings transport,thereby alleviating drilling stickiness slip.At different cutting depths,the conical cutter consistently causes asymmetric jagged brittle tensile fracture zones on both sides of the cutting groove.Calculations based on the brittle fracture index demonstrate that the brittle fracture index of the conical cutter generally doubles that of the conventional cutter.For carbonate rock,the conical cutter displays superior utilization of brittle fracture abilities.The research findings of this work offer insights into the breakage process and failure mode of carbonate rock by the conical cutter.展开更多
In tunnel construction with tunnel boring machines(TBMs),accurate knowledge of disc-cutter failure states is crucial to ensure efficient operation and prevent delays and cost overruns.This study investigates the influ...In tunnel construction with tunnel boring machines(TBMs),accurate knowledge of disc-cutter failure states is crucial to ensure efficient operation and prevent delays and cost overruns.This study investigates the influence of disc-cutter partial wear on tunneling parameters and proposes a novel method for discriminating partial-wear ratio based on a stacking ensemble model.The time-domain features of torque and thrust,including the average value and standard deviation,are analyzed through a series of scaled-down experimental tests on partial wear.Torque and thrust values will increase when a disc cutter is trapped and partially worn.The impact of partial-wear ratio on tunneling parameters appears to be more significant than partial-wear depth.A total of 40 features are selected from the time domain,frequency domain,and time-frequency domain to describe the torque and thrust.The relationships between these features and the partial-wear ratio are analyzed using the Pearson coefficient and Copula entropy.The results reveal that,except for the form factor in the time-domain features,the remaining features exhibit certain linear or non-linear correlations with the partial-wear ratio.Lastly,the proposed model successfully achieves the discrimination of the partial-wear ratio and outperforms other commonly used models in terms of overall classification accuracy and differentiation capability in different categories.This research provides effective support for monitoring and health management of disc-cutter failure states.展开更多
The cutter layout of a full-face tunnel boring machine(TBM)directly affects its tunneling efficiency.The revolving diameter of the center cutter is small,and the double-edged design results in its rock breaking mechan...The cutter layout of a full-face tunnel boring machine(TBM)directly affects its tunneling efficiency.The revolving diameter of the center cutter is small,and the double-edged design results in its rock breaking mechanism and force characteristics being significantly different from those of the single-edged cutter.The gage cutter is installed on the transition arc of the cutterhead,and the installation inclination complicates its movement and force.In this paper,by taking sandstone as the research object,the composite rock breaking models of the center cutter group and the gage cutter group of a compound TBM are separately established based on the three-dimensional particle discrete element method.The numerical models are verified by comparing results with the full-scale rotary cutting laboratory test.From the view point of the force characteristics of a single cutter,the propagation of rock cracks between adjacent cutters,the overall mechanical properties of the cutterhead,the load characteristics and layout form of the double-edged center cutter,and the installation angle range of the gage cutter were studied.Results demonstrate that the use of a cross-shaped center cutter layout can reduce the force of a single cutter ring and the overall load of the cutterhead,which is conducive to TBM stability during tunneling.Therefore,it is recommended that a cross-shaped layout for the double-edged center cutter of a rock formation compound TBM should be used.To improve the stability and service life of the cutter,we recommend setting the installation angle of the innermost gage cutter of the rock formation compound TBM to about 9°,and the installation angle of the outermost gage cutter should not exceed 70°.展开更多
During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have ...During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.展开更多
For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two i...For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two is particularly suited for rough machining,wherein the main purpose is to remove a large volume as quickly as possible,the machining efficiency is low,especially when the part materials are of hard-to-cut types(e.g.,Titanium-alloy)for which it often takes days to rough machine a blisk.Fortunately,disc machining provides a new and efficient roughing solution,since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal rate.However,due to the large radius of the disc cutter,its potential collision with narrow and twisted channels becomes a serious concern.In this paper,we propose a novel twophase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter,i.e.,3+2-axis disc-slotting of the channel by multiple layers(rough machining)+five-axis disc-milling of the freeform channel side surfaces(semi-finish machining).Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed method.The experimental results show that,with respect to a same cusp-height threshold on the channel side surfaces,the total machining time of the tested part by the proposed method is about only 36%of that by the conventional approach of plunging-milling(for roughing)plus milling by a slender cylindrical cutter(for semi-finishing).展开更多
When shield TBM tunnelling in abrasive sandy ground,the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency.However,the influence mechanism of cutter parameters on sc...When shield TBM tunnelling in abrasive sandy ground,the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency.However,the influence mechanism of cutter parameters on scraper wear remains unclear due to the lack of a reliable test method.Geometry and material optimisation are often based on subjective experience,which is unfavourable for improving scraper geological adaptability.In the present study,the newly developed WHU-SAT soil abrasion test was used to evaluate the variation in scraper wear with cutter geometry,material and hardness.The influence mechanism of cutter parameters on scraper wear has been revealed according to the scratch characteristics of the scraper surface.Cutter geometry and material parameters have been optimised to reduce scraper wear.The results indicate that the variation in scraper wear with cutter geometry is related to the cutting resistance,frictional resistance and stress distribution.An appropriate increase in the front angle(or back angle)reduces the cutting resistance(or frictional resistance),while an excessive increase in the front angle(or back angle)reduces the edge angle and causes stress concentration.The optimal front angle,back angle and edge angle for quartz sand samples areα=25°,β=10°andγ=55°,respectively.The wear resistance of the modelled scrapers made of different metal materials is related to the chemical elements and microstructure.The wear resistances of the modelled scrapers made of 45#,06Cr19Ni10,42CrMo4 and 40CrNiMoA are 0.569,0.661,0.691 and 0.728 times those made of WC-Co,respectively.When the alloy hardness is less than 47 HRC(or greater than 58 HRC),scraper wear decreases slowly with increasing alloy hardness as the scratch depth of the particle asperity on the metal surface stabilizes at a high(or low)level.However,when the alloy hardness is between 47 HRC and 58 HRC,scraper wear decreases rapidly with increasing alloy hardness as the scratch depth transitions from high to low levels.The sensitive hardness interval and recommended hardness interval for quartz sand are[47,58]and[58,62],respectively.The present study provides a reference for optimising scraper parameters and improving cutterhead adaptability in abrasive sandy ground tunnelling.展开更多
In the actual service process of the tunnel boring machine(TBM)cutter head,the fatigue failure of the disc body is serious.Aimed at the problem of premature failure of cutter head due to the extreme service environmen...In the actual service process of the tunnel boring machine(TBM)cutter head,the fatigue failure of the disc body is serious.Aimed at the problem of premature failure of cutter head due to the extreme service environment and complicated structure of the TBM cutter head,the previous TBM cutter head failure data are combined to establish a method for calculating the space crack growth in this paper.Based on the structure of the TBM cutter head itself,the law of the shape and parameters of the stiffened panels on the crack propagation resistance is studied to further present the method of anti-damage and anti-crack for the TBM cutter head.The results illustrate that the basis and methods for the structural design of the TBM cutter head are put forward.展开更多
The success of a tunnel-boring machine （TBM） in a given project depends on the functionality of all components of the system, from the cutters to the backup system, and on the entire rolling stock. However, no part ...The success of a tunnel-boring machine （TBM） in a given project depends on the functionality of all components of the system, from the cutters to the backup system, and on the entire rolling stock. However, no part of the machine plays a more crucial role in the efficient operation of the machine than its cutterhead. The design of the cutterhead impacts the efficiency of cutting, the balance of the head, the life of the cutters, the maintenance of the main bearing/gearbox, and the effectiveness of the mucking along with its effects on the wear of the face and gage cutters/muck buckets. Overall, cutterhead design heavily impacts the rate of penetration （ROP）, rate of machine utilization （U）, and daffy advance rate （AR）. Although there has been some discussion in commonly available publications regarding disk cutters, cutting forces, and some design features of the head, there is limited literature on this subject because the design of cutter- heads is mainly handled by machine manufacturers. Most of the design process involves proprietary algorithms by the manufacturers, and despite recent attention on the subject, the design of rock TBMs has been somewhat of a mystery to most end-users. This paper is an attempt to demystify the basic concepts in design. Although it may not be sufficient for a full-fledged design by the readers, this paper allows engineers and contractors to understand the thought process in the design steps, what to Look for in a proper design, and the implications of the head design on machine operation and life cycle.展开更多
At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of...At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.展开更多
According to the cutting characteristics of progressive spiral movement by rotary cutting of the disc cutter, using the broken theory of interaction of compression and shearing, the three-axis force rotary cutting mec...According to the cutting characteristics of progressive spiral movement by rotary cutting of the disc cutter, using the broken theory of interaction of compression and shearing, the three-axis force rotary cutting mechanical model of disc cutter was established and the influence of installation radius, the phase difference and the cutter space on the mechanics of disc cutter were analyzed. The results show that on the same radial line of tunneling interface, the boring distance of cutting tools installed on a different radius is not equal. The cutting radial line of tunneling interface is a polyline and its height is determined by phase angle and penetration of cutting tools. Both phase difference and the installation radius between adjacent disc cutters have little effect on the vertical force and rolling force, but increase with the increase in cutter spacing. In addition, when increasing phase difference and cutter space bilaterally, and reducing installation radius simultaneously, the lateral force would be improved. Related results have been verified onl O0 t rotary tool cutting test platform.展开更多
Studies to date have failed to consider gage disc cutters’variable cutting depth and the constraints of cutter-head welds,and have ignored the coupling mechanism between the profile of the full-face rock tunnel-borin...Studies to date have failed to consider gage disc cutters’variable cutting depth and the constraints of cutter-head welds,and have ignored the coupling mechanism between the profile of the full-face rock tunnel-boring machine(TBM)cutter-head and the assembled radius layout of the disc cutters.To solve these problems,an adaptive design method for studying cutter layout was proposed.Taking the bearing stress of the outermost gage disc cutter as an index,the profile of the cutter-head was determined.Using a genetic algorithm and based on the principles of equal life and equal wear,the assembled radii of the cutters were optimally designed.Boundary conditions of non-interference between the cutters,manholes,muck buckets and welding lines were given when a star layout pattern was used on cutters.The cutter-head comprehensive evaluation model was established by adopting relative optimization improvement degree of evaluation indices to achieve dimensional consistency.Exemplifying the MB264-311-8030 mm tape TBM cutter-head,the calculations show that compared with the original layout scheme,among the 51 disc cutters,the largest gap of the cutters’assembled radiuses is only 25.8 mm,which is 0.64%of the cutter-head’s radius and is negligible.The cutter-head’s unbalanced radial force decreases by 62.41%,the overturning moment decreases by 33.22%,and the cutter group’s centroid shift increases by only 18.48%.Each index is better than or approximately equal to the original cutter-head layout scheme,and the equivalent stress and deformation are both smaller;these results fully verify the feasibility and effectiveness of the method.展开更多
Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing ineffici...Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.展开更多
Full face rock tunnel boring machine（TBM） has been widely used in hard rock tunnels, however, there are few published theory about cutter-head design, and the design criteria of cutter-head under complex geological ...Full face rock tunnel boring machine（TBM） has been widely used in hard rock tunnels, however, there are few published theory about cutter-head design, and the design criteria of cutter-head under complex geological is not clear yet. To deal with the complex relationship among geological parameters, cutter parameters, and operating parameters during tunneling processes, a cutter-head load model is established by using CSM（Colorado school of mines） prediction model. Force distribution on cutter-head under a certain geology is calculated with the new established load model, and result shows that inner cutters bear more force than outer cutters, combining with disc cutters abrasion; a general principle of disc cutters＇ layout design is proposed. Within the model, the relationship among rock uniaxial compressive strength（UCS）, penetration and thrust on cutter-head are analyzed, and the results shows that with increasing penetration, cutter thrust increases, but the growth rate slows and higher penetration makes lower special energy（SE）. Finally, a fitting mathematical model of ZT（ratio of cutter-head torque and thrust） and penetration is established, and verified by TB880 E, which can be used to direct how to set thrust and torque on cutter-head. When penetration is small, the cutter-head thrust is the main limiting factor in tunneling; when the penetration is large, cutter-head torque is the major limiting factor in tunneling. Based on the new cutter-head load model, thrust and torque characteristics of TBM further are researched and a new way for cutter-head layout design and TBM tunneling operations is proposed.展开更多
Cutterhead loads are the key mechanical parameters for the strength design of the full face hard rock tunnel boring machine(TBM).Due to the brittle rock-breaking mechanism,the excavation loads acting on cutters fluctu...Cutterhead loads are the key mechanical parameters for the strength design of the full face hard rock tunnel boring machine(TBM).Due to the brittle rock-breaking mechanism,the excavation loads acting on cutters fluctuate strongly and show some randomness.The conventional method that using combinations of some special static loads to perform the strength design of TBM cutterhead may lead to strength failure during working practice.In this paper,a three-dimensional finite element model for coupled Cutterhead–Rock is developed to determine the cutterhead loads.Then the distribution characteristics and the influence factors of cutterhead loads are analyzed based on the numerical results.It is found that,as time changes,the normal and tangential forces acting on cutters and the total torque acting on the cutterhead approximately distribute log normally,while the total thrusts acting on the cutterhead approximately show a normal distribution.Furthermore,the statistical average values of cutterhead loads are proportional to the uniaxial compressive strength(UCS)of cutting rocks.The values also change with the penetration and the diameter of cutterhead following a power function.Based on these findings,we propose a three-parameter model for the mean of cutterhead loads and a method of generating the random cutter forces.Then the strength properties of a typical cutterhead are analyzed in detail using loads generated by the new method.The optimized cutterhead has been successfully applied in engineering.The method in this paper may provide a useful reference for the strength design of TBM cutterhead.展开更多
The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive ...The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive formation. The knowledge of force response and mechanical specific energy (MSE) for the Stinger PDC cutter is of great importance for improving the cutter's performance and optimizing the hybrid PDC bit design. In this paper, 87 single cutter tests were conducted on the granite. A new method for precisely obtaining the rock broken volume was proposed. The influences of cutting depth, cutting angle, and cutting speed on cutting force and MSE were analyzed. Besides, a phenomenological cutting force model of the Stinger PDC cutter was established by regression of experimental data. Moreover, the surface topography and fracture morphology of the cutting groove and large size cuttings were measured by a 3D profilometer and a scanning electron microscope (SEM). Finally, the rock-breaking mechanism of the Stinger PDC cutter was illustrated. The results indicated that the cutting depth has the greatest influence on the cutting force and MSE, while the cutting speed has no obvious effects, especially at low cutting speeds. As the increase of cutting depth, the cutting force increases linearly, and MSE reduces with a quadratic polynomial relationship. When the cutting angle raises from 10° to 30°, the cutting force increases linearly, and the MSE firstly decreases and then increases. The optimal cutting angle for breaking rock is approximately 20°. The Stinger PDC cutter breaks granite mainly by high concentrated point loading and tensile failure, which can observably improve the rock breaking efficiency. The key findings of this work will help to reveal the rock-breaking mechanisms and optimize the cutter arrangement for the Stinger PDC cutter.展开更多
The operation of a shield tunnel boring machine(TBM)in a high-strength hard rock stratum results in significant cutter damage,adversely affecting the thrust and torque of the cutter head.Therefore,it is very important...The operation of a shield tunnel boring machine(TBM)in a high-strength hard rock stratum results in significant cutter damage,adversely affecting the thrust and torque of the cutter head.Therefore,it is very important to carry out the research on the stress characteristics and optimize the cutter parameters of cutters break high-strength hard rock.In this paper,the rock-breaking performance of cutters in an andesite stratum in the tunnel of Qingdao Metro Line No.8 was investigated using the discrete element method and theoretical analysis.The rock-breaking processes of a disc cutter and wedge tooth cutter were simulated by software particle flow code PFC^(3D),and the rock-breaking degree,stress of the cutter,and rock-breaking specific energy were analyzed.The rock damage caused by the cutter in a specific section was divided into three stages:the advanced influence,crushing,and stabilizing stages.The rock-breaking degree and the tangential and normal forces of the wedge tooth cutter are larger than that of the disc cutter under the same conditions.The disc cutter(wedge tooth cutter)has the highest rock-breaking efficiency at a cutter spacing of 100 mm(110 mm)and a penetration depth of 8 mm(10 mm),and the rock-breaking specific energy is 11.48 MJ/m^(3)(12.05 MJ/m^(3)).Therefore,two types of cutters with different penetration depths or cutter spacing should be considered.The number of teeth of wedge tooth cutters can be increased in hard strata to improve the rock-breaking efficiency of the shield.The research results provide a reference for shield cutterhead selection and cutter layout in similar projects.展开更多
基金National Natural Science Foundation of China(52075551,52271045,51975469)Supported by State Key Laboratory of Advanced Welding and Joining(AWJ-22M09)+2 种基金Supported by State Key Laboratory of Advanced Brazing Filler Metals and Technology(SKLABFMT201904)Key Research and Development Program of Shaanxi Province(2022GY-224)Innovative Talent Recommendation Program(Youth Science and Technology New Star Project)of Shaanxi Province(2020 KJX X-045)。
文摘Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints were investigated.Besides,the joint's interface microstructure,composition,and phases were analyzed.Results show that the AgCuInTi filler metal exerts a good wetting effect to the surface of cemented carbide and steel.With the increase in brazing temperature,the wetting angle decreases and the spreading area increases.The suitable temperature for vacuum brazing of PDC cutters is 770℃,and the maximum shear strength is 228 MPa at this temperature.
文摘Large portions of the tunnel boring machine(TBM)construction cost are attributed to disc cutter consumption,and assessing the disc cutter's wear level can help determine the optimal time to replace the disc cutter.Therefore,the need to monitor disc cutter wear in real-time has emerged as a technical challenge for TBMs.In this study,real-time disc cutter wear monitoring is developed based on sound and vibration sensors.For this purpose,the microphone and accelerometer were used to record the sound and vibration signals of cutting three different types of rocks with varying abrasions on a laboratory scale.The relationship between disc cutter wear and the sound and vibration signal was determined by comparing the measurements of disc cutter wear with the signal plots for each sample.The features extracted from the signals showed that the sound and vibration signals are impacted by the progression of disc wear during the rock-cutting process.The signal features obtained from the rock-cutting operation were utilized to verify the machine learning techniques.The results showed that the multilayer perceptron(MLP),random subspace-based decision tree(RS-DT),DT,and random forest(RF)methods could predict the wear level of the disc cutter with an accuracy of 0.89,0.951,0.951,and 0.927,respectively.Based on the accuracy of the models and the confusion matrix,it was found that the RS-DT model has the best estimate for predicting the level of disc wear.This research has developed a method that can potentially determine when to replace a tool and assess disc wear in real-time.
基金Project(51975169)supported by the National Natural Science Foundation of ChinaProject(LH2022E085)supported by the Natural Science Foundation of Heilongjiang Province,China。
文摘Efficient tool condition monitoring techniques help to realize intelligent management of tool life and reduce tool usage costs.In this paper,the influence of different wear degrees of ball-end milling cutters on the texture shape of machining tool marks is investigated,and a method is proposed for predicting the wear state(including the position and degree of tool wear)of ball-end milling cutters based on entropy measurement of tool mark texture images.Firstly,data samples are prepared through wear experiments,and the change law of the tool mark texture shape with the tool wear state is analyzed.Then,a two-dimensional sample entropy algorithm is developed to quantify the texture morphology.Finally,the processing parameters and tool attitude are integrated into the prediction process to predict the wear value and wear position of the ball end milling cutter.After testing,the correlation between the predicted value and the standard value of the proposed tool condition monitoring method reaches 95.32%,and the accuracy reaches 82.73%,indicating that the proposed method meets the requirement of tool condition monitoring.
基金support of the“National R&D Project for Smart Construction Technology (Grant No.RS-2020-KA157074)”funded by the Korea Agency for Infrastructure Technology Advancement under the Ministry of Land,Infrastructure and Transport,and managed by the Korea Expressway Corporation.
文摘The widespread adoption of tunnel boring machines(TBMs)has led to an increased focus on disc cutter wear,including both normal and abnormal types,for efficient and safe TBM excavation.However,abnormal wear has yet to be thoroughly investigated,primarily due to the complexity of considering mixed ground conditions and the imbalance in the number of instances between the two types of wear.This study developed a prediction model for abnormal TBM disc cutter wear,considering mixed ground conditions,by employing interpretable machine learning with data augmentation.An equivalent elastic modulus was used to consider the characteristics of mixed ground conditions,and wear data was obtained from 65 cutterhead intervention(CHI)reports covering both mixed ground and hard rock sections.With a balanced training dataset obtained by data augmentation,an extreme gradient boosting(XGB)model delivered acceptable results with an accuracy of 0.94,an F1-score of 0.808,and a recall of 0.8.In addition,the accuracy for each individual disc cutter exhibited low variability.When employing data augmentation,a significant improvement in recall was observed compared to when it was not used,although the difference in accuracy and F1-score was marginal.The subsequent model interpretation revealed the chamber pressure,cutter installation radius,and torque as significant contributors.Specifically,a threshold in chamber pressure was observed,which could induce abnormal wear.The study also explored how elevated values of these influential contributors correlate with abnormal wear.The proposed model offers a valuable tool for planning the replacement of abnormally worn disc cutters,enhancing the safety and efficiency of TBM operations.
基金supported by the NSFC Key International(Regional)Cooperative Research Projects(No.52020105001)National Natural Science Foundation of China(52304014)+2 种基金China Postdoctoral Science Foundation funded project(2023M733873)the Science Foundation of China University of Petroleum,Beijing(No.2462023SZBH003)General Program of National Natural Science Foundation of China(52374016,52274016)。
文摘The oil and gas stored in deep and ultra-deep carbonate reservoirs is the focus of future exploration and development.Conical PDC(Polycrystalline Diamond Compact)cutter,which is a new kind of PDC cutter,can significantly improve the rate of penetration(ROP)and extend PDC bit life in hard and abrasive formations.However,the breakage characteristics and failure mode of the conical PDC cutter cutting carbonate rock is still masked.In this paper,a series of single-cutter cutting tests were carried out with the conical and conventional PDC cutters.The cutting force,rock-breaking process,surface morphology of cutting grooves and cuttings characteristic were analyzed.Based on the derived formula of the brittle fracture index,the failure model of carbonate rock was quantitatively analyzed under the action of conical and conventional cutter.The results show that the average cutting force of the conical cutter is less than that of the conventional cutter,which means greater stability of the cutting process using the conical cutter.Carbonate rock with calcite as the main component tends to generate blocky rock debris by conical cutter.The height of the cuttings generated by the conical cutter is 0.5 mm higher than that generated by the conventional cutter.The conical cutter exhibits enhanced penetration capabilities within carbonate rock.The accumulation of rock debris in front of the conventional cutter is obvious.Whereas,the conical cutter facilitates the cuttings transport,thereby alleviating drilling stickiness slip.At different cutting depths,the conical cutter consistently causes asymmetric jagged brittle tensile fracture zones on both sides of the cutting groove.Calculations based on the brittle fracture index demonstrate that the brittle fracture index of the conical cutter generally doubles that of the conventional cutter.For carbonate rock,the conical cutter displays superior utilization of brittle fracture abilities.The research findings of this work offer insights into the breakage process and failure mode of carbonate rock by the conical cutter.
基金supported by the Natural Science Basic Research Program of Shaanxi Province(No.2019JLZ-13)the National Key R&D Program of China(No.2022YFC3802305)+1 种基金the National Natural Science Foundation of China(No.52105074)the Open Project of State Key Laboratory of Shield Machine and Boring Technology(No.SKLST-2021-K02),China.
文摘In tunnel construction with tunnel boring machines(TBMs),accurate knowledge of disc-cutter failure states is crucial to ensure efficient operation and prevent delays and cost overruns.This study investigates the influence of disc-cutter partial wear on tunneling parameters and proposes a novel method for discriminating partial-wear ratio based on a stacking ensemble model.The time-domain features of torque and thrust,including the average value and standard deviation,are analyzed through a series of scaled-down experimental tests on partial wear.Torque and thrust values will increase when a disc cutter is trapped and partially worn.The impact of partial-wear ratio on tunneling parameters appears to be more significant than partial-wear depth.A total of 40 features are selected from the time domain,frequency domain,and time-frequency domain to describe the torque and thrust.The relationships between these features and the partial-wear ratio are analyzed using the Pearson coefficient and Copula entropy.The results reveal that,except for the form factor in the time-domain features,the remaining features exhibit certain linear or non-linear correlations with the partial-wear ratio.Lastly,the proposed model successfully achieves the discrimination of the partial-wear ratio and outperforms other commonly used models in terms of overall classification accuracy and differentiation capability in different categories.This research provides effective support for monitoring and health management of disc-cutter failure states.
基金the National Natural Science Foundation of China(No.U1934213)the Sichuan Science and Technology Program(No.2019YFG0460)。
文摘The cutter layout of a full-face tunnel boring machine(TBM)directly affects its tunneling efficiency.The revolving diameter of the center cutter is small,and the double-edged design results in its rock breaking mechanism and force characteristics being significantly different from those of the single-edged cutter.The gage cutter is installed on the transition arc of the cutterhead,and the installation inclination complicates its movement and force.In this paper,by taking sandstone as the research object,the composite rock breaking models of the center cutter group and the gage cutter group of a compound TBM are separately established based on the three-dimensional particle discrete element method.The numerical models are verified by comparing results with the full-scale rotary cutting laboratory test.From the view point of the force characteristics of a single cutter,the propagation of rock cracks between adjacent cutters,the overall mechanical properties of the cutterhead,the load characteristics and layout form of the double-edged center cutter,and the installation angle range of the gage cutter were studied.Results demonstrate that the use of a cross-shaped center cutter layout can reduce the force of a single cutter ring and the overall load of the cutterhead,which is conducive to TBM stability during tunneling.Therefore,it is recommended that a cross-shaped layout for the double-edged center cutter of a rock formation compound TBM should be used.To improve the stability and service life of the cutter,we recommend setting the installation angle of the innermost gage cutter of the rock formation compound TBM to about 9°,and the installation angle of the outermost gage cutter should not exceed 70°.
基金Beijing Postdoctoral Research Activity Funding Project,Grant/Award Number:2022-ZZ-097Beijing Municipal Natural Science Foundation,Grant/Award Number:8182048。
文摘During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.
基金supported in part by Foshan HKUST Projects(Project ID:FSUST20-SRI09E–FSPM02202007-1)the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone(Project ID:HZQB-KCZYB-2020083)the National Science and Technology Major Project(Grant No.J2019-VII-0001-0141)。
文摘For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two is particularly suited for rough machining,wherein the main purpose is to remove a large volume as quickly as possible,the machining efficiency is low,especially when the part materials are of hard-to-cut types(e.g.,Titanium-alloy)for which it often takes days to rough machine a blisk.Fortunately,disc machining provides a new and efficient roughing solution,since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal rate.However,due to the large radius of the disc cutter,its potential collision with narrow and twisted channels becomes a serious concern.In this paper,we propose a novel twophase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter,i.e.,3+2-axis disc-slotting of the channel by multiple layers(rough machining)+five-axis disc-milling of the freeform channel side surfaces(semi-finish machining).Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed method.The experimental results show that,with respect to a same cusp-height threshold on the channel side surfaces,the total machining time of the tested part by the proposed method is about only 36%of that by the conventional approach of plunging-milling(for roughing)plus milling by a slender cylindrical cutter(for semi-finishing).
基金The support provided by the National Natural Science Foundation of Youth Fund Project of China(Grant No.52308415)Key Research and Development Program of Hubei Province,China(Grant No.2021BCA154)Natural Science Foundation of Hubei Province,China(Grant No.2021CFA081)is gratefully acknowledged.
文摘When shield TBM tunnelling in abrasive sandy ground,the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency.However,the influence mechanism of cutter parameters on scraper wear remains unclear due to the lack of a reliable test method.Geometry and material optimisation are often based on subjective experience,which is unfavourable for improving scraper geological adaptability.In the present study,the newly developed WHU-SAT soil abrasion test was used to evaluate the variation in scraper wear with cutter geometry,material and hardness.The influence mechanism of cutter parameters on scraper wear has been revealed according to the scratch characteristics of the scraper surface.Cutter geometry and material parameters have been optimised to reduce scraper wear.The results indicate that the variation in scraper wear with cutter geometry is related to the cutting resistance,frictional resistance and stress distribution.An appropriate increase in the front angle(or back angle)reduces the cutting resistance(or frictional resistance),while an excessive increase in the front angle(or back angle)reduces the edge angle and causes stress concentration.The optimal front angle,back angle and edge angle for quartz sand samples areα=25°,β=10°andγ=55°,respectively.The wear resistance of the modelled scrapers made of different metal materials is related to the chemical elements and microstructure.The wear resistances of the modelled scrapers made of 45#,06Cr19Ni10,42CrMo4 and 40CrNiMoA are 0.569,0.661,0.691 and 0.728 times those made of WC-Co,respectively.When the alloy hardness is less than 47 HRC(or greater than 58 HRC),scraper wear decreases slowly with increasing alloy hardness as the scratch depth of the particle asperity on the metal surface stabilizes at a high(or low)level.However,when the alloy hardness is between 47 HRC and 58 HRC,scraper wear decreases rapidly with increasing alloy hardness as the scratch depth transitions from high to low levels.The sensitive hardness interval and recommended hardness interval for quartz sand are[47,58]and[58,62],respectively.The present study provides a reference for optimising scraper parameters and improving cutterhead adaptability in abrasive sandy ground tunnelling.
基金Scientific Research Project of Education Department of Liaoning Province(No.JDL2020028)。
文摘In the actual service process of the tunnel boring machine(TBM)cutter head,the fatigue failure of the disc body is serious.Aimed at the problem of premature failure of cutter head due to the extreme service environment and complicated structure of the TBM cutter head,the previous TBM cutter head failure data are combined to establish a method for calculating the space crack growth in this paper.Based on the structure of the TBM cutter head itself,the law of the shape and parameters of the stiffened panels on the crack propagation resistance is studied to further present the method of anti-damage and anti-crack for the TBM cutter head.The results illustrate that the basis and methods for the structural design of the TBM cutter head are put forward.
文摘The success of a tunnel-boring machine （TBM） in a given project depends on the functionality of all components of the system, from the cutters to the backup system, and on the entire rolling stock. However, no part of the machine plays a more crucial role in the efficient operation of the machine than its cutterhead. The design of the cutterhead impacts the efficiency of cutting, the balance of the head, the life of the cutters, the maintenance of the main bearing/gearbox, and the effectiveness of the mucking along with its effects on the wear of the face and gage cutters/muck buckets. Overall, cutterhead design heavily impacts the rate of penetration （ROP）, rate of machine utilization （U）, and daffy advance rate （AR）. Although there has been some discussion in commonly available publications regarding disk cutters, cutting forces, and some design features of the head, there is limited literature on this subject because the design of cutter- heads is mainly handled by machine manufacturers. Most of the design process involves proprietary algorithms by the manufacturers, and despite recent attention on the subject, the design of rock TBMs has been somewhat of a mystery to most end-users. This paper is an attempt to demystify the basic concepts in design. Although it may not be sufficient for a full-fledged design by the readers, this paper allows engineers and contractors to understand the thought process in the design steps, what to Look for in a proper design, and the implications of the head design on machine operation and life cycle.
基金supported by National Natural Science Foundation of China (Grant No. 51075147)
文摘At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.
基金Project(2007CB714002) supported by the National Basic Research Program of ChinaProject(51074180) supported by the National Natural Science Foundation of ChinaProject(2010FJ1002) supported by Hunan Municipal Science and Technology Program,China
文摘According to the cutting characteristics of progressive spiral movement by rotary cutting of the disc cutter, using the broken theory of interaction of compression and shearing, the three-axis force rotary cutting mechanical model of disc cutter was established and the influence of installation radius, the phase difference and the cutter space on the mechanics of disc cutter were analyzed. The results show that on the same radial line of tunneling interface, the boring distance of cutting tools installed on a different radius is not equal. The cutting radial line of tunneling interface is a polyline and its height is determined by phase angle and penetration of cutting tools. Both phase difference and the installation radius between adjacent disc cutters have little effect on the vertical force and rolling force, but increase with the increase in cutter spacing. In addition, when increasing phase difference and cutter space bilaterally, and reducing installation radius simultaneously, the lateral force would be improved. Related results have been verified onl O0 t rotary tool cutting test platform.
基金Projects(51275339,51575379,51675374)supported by the National Natural Science Foundation of ChinaProject(2013CB035402)supported by the National Hi-tech Research and Development Program of China
文摘Studies to date have failed to consider gage disc cutters’variable cutting depth and the constraints of cutter-head welds,and have ignored the coupling mechanism between the profile of the full-face rock tunnel-boring machine(TBM)cutter-head and the assembled radius layout of the disc cutters.To solve these problems,an adaptive design method for studying cutter layout was proposed.Taking the bearing stress of the outermost gage disc cutter as an index,the profile of the cutter-head was determined.Using a genetic algorithm and based on the principles of equal life and equal wear,the assembled radii of the cutters were optimally designed.Boundary conditions of non-interference between the cutters,manholes,muck buckets and welding lines were given when a star layout pattern was used on cutters.The cutter-head comprehensive evaluation model was established by adopting relative optimization improvement degree of evaluation indices to achieve dimensional consistency.Exemplifying the MB264-311-8030 mm tape TBM cutter-head,the calculations show that compared with the original layout scheme,among the 51 disc cutters,the largest gap of the cutters’assembled radiuses is only 25.8 mm,which is 0.64%of the cutter-head’s radius and is negligible.The cutter-head’s unbalanced radial force decreases by 62.41%,the overturning moment decreases by 33.22%,and the cutter group’s centroid shift increases by only 18.48%.Each index is better than or approximately equal to the original cutter-head layout scheme,and the equivalent stress and deformation are both smaller;these results fully verify the feasibility and effectiveness of the method.
基金Supported by National Natural Science Foundation of China(Grant No.51975168).
文摘Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.
基金Supported by National Natural Science Foundation of China(Grant No.51275339)National Basic Research Program of China(973 Program,Grant No.2013CB035402)
文摘Full face rock tunnel boring machine（TBM） has been widely used in hard rock tunnels, however, there are few published theory about cutter-head design, and the design criteria of cutter-head under complex geological is not clear yet. To deal with the complex relationship among geological parameters, cutter parameters, and operating parameters during tunneling processes, a cutter-head load model is established by using CSM（Colorado school of mines） prediction model. Force distribution on cutter-head under a certain geology is calculated with the new established load model, and result shows that inner cutters bear more force than outer cutters, combining with disc cutters abrasion; a general principle of disc cutters＇ layout design is proposed. Within the model, the relationship among rock uniaxial compressive strength（UCS）, penetration and thrust on cutter-head are analyzed, and the results shows that with increasing penetration, cutter thrust increases, but the growth rate slows and higher penetration makes lower special energy（SE）. Finally, a fitting mathematical model of ZT（ratio of cutter-head torque and thrust） and penetration is established, and verified by TB880 E, which can be used to direct how to set thrust and torque on cutter-head. When penetration is small, the cutter-head thrust is the main limiting factor in tunneling; when the penetration is large, cutter-head torque is the major limiting factor in tunneling. Based on the new cutter-head load model, thrust and torque characteristics of TBM further are researched and a new way for cutter-head layout design and TBM tunneling operations is proposed.
基金Supported by National Basic Research Program of China(973 Program,Grant No.2013CB035042)the National Natural Science Foundation of China(Grant No.11672202)
文摘Cutterhead loads are the key mechanical parameters for the strength design of the full face hard rock tunnel boring machine(TBM).Due to the brittle rock-breaking mechanism,the excavation loads acting on cutters fluctuate strongly and show some randomness.The conventional method that using combinations of some special static loads to perform the strength design of TBM cutterhead may lead to strength failure during working practice.In this paper,a three-dimensional finite element model for coupled Cutterhead–Rock is developed to determine the cutterhead loads.Then the distribution characteristics and the influence factors of cutterhead loads are analyzed based on the numerical results.It is found that,as time changes,the normal and tangential forces acting on cutters and the total torque acting on the cutterhead approximately distribute log normally,while the total thrusts acting on the cutterhead approximately show a normal distribution.Furthermore,the statistical average values of cutterhead loads are proportional to the uniaxial compressive strength(UCS)of cutting rocks.The values also change with the penetration and the diameter of cutterhead following a power function.Based on these findings,we propose a three-parameter model for the mean of cutterhead loads and a method of generating the random cutter forces.Then the strength properties of a typical cutterhead are analyzed in detail using loads generated by the new method.The optimized cutterhead has been successfully applied in engineering.The method in this paper may provide a useful reference for the strength design of TBM cutterhead.
基金supported by the Joint Funds of The National Natural Science Foundation of China(Grant No.U19B6003-05)the National Key Research and Development Program of China(No.2019YFA0708302)+2 种基金the National Science Fund for Distinguished Young Scholars(Grant No.51725404)the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201911414038)the Strategic Cooperation Technology Projects of CNPC and CUPB(Grant No.ZLZX2020-01).
文摘The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive formation. The knowledge of force response and mechanical specific energy (MSE) for the Stinger PDC cutter is of great importance for improving the cutter's performance and optimizing the hybrid PDC bit design. In this paper, 87 single cutter tests were conducted on the granite. A new method for precisely obtaining the rock broken volume was proposed. The influences of cutting depth, cutting angle, and cutting speed on cutting force and MSE were analyzed. Besides, a phenomenological cutting force model of the Stinger PDC cutter was established by regression of experimental data. Moreover, the surface topography and fracture morphology of the cutting groove and large size cuttings were measured by a 3D profilometer and a scanning electron microscope (SEM). Finally, the rock-breaking mechanism of the Stinger PDC cutter was illustrated. The results indicated that the cutting depth has the greatest influence on the cutting force and MSE, while the cutting speed has no obvious effects, especially at low cutting speeds. As the increase of cutting depth, the cutting force increases linearly, and MSE reduces with a quadratic polynomial relationship. When the cutting angle raises from 10° to 30°, the cutting force increases linearly, and the MSE firstly decreases and then increases. The optimal cutting angle for breaking rock is approximately 20°. The Stinger PDC cutter breaks granite mainly by high concentrated point loading and tensile failure, which can observably improve the rock breaking efficiency. The key findings of this work will help to reveal the rock-breaking mechanisms and optimize the cutter arrangement for the Stinger PDC cutter.
基金Supported by National Natural Science Foundation of China(Grant Nos.51608521,51809264)Beijing Municipal Major Achievements Transformation and Industrialization Projects of Central Universities(Grant No.ZDZH20141141301)the Fundamental Research Funds for the Central Universities(Grant No.2023ZKPYLJ06).
文摘The operation of a shield tunnel boring machine(TBM)in a high-strength hard rock stratum results in significant cutter damage,adversely affecting the thrust and torque of the cutter head.Therefore,it is very important to carry out the research on the stress characteristics and optimize the cutter parameters of cutters break high-strength hard rock.In this paper,the rock-breaking performance of cutters in an andesite stratum in the tunnel of Qingdao Metro Line No.8 was investigated using the discrete element method and theoretical analysis.The rock-breaking processes of a disc cutter and wedge tooth cutter were simulated by software particle flow code PFC^(3D),and the rock-breaking degree,stress of the cutter,and rock-breaking specific energy were analyzed.The rock damage caused by the cutter in a specific section was divided into three stages:the advanced influence,crushing,and stabilizing stages.The rock-breaking degree and the tangential and normal forces of the wedge tooth cutter are larger than that of the disc cutter under the same conditions.The disc cutter(wedge tooth cutter)has the highest rock-breaking efficiency at a cutter spacing of 100 mm(110 mm)and a penetration depth of 8 mm(10 mm),and the rock-breaking specific energy is 11.48 MJ/m^(3)(12.05 MJ/m^(3)).Therefore,two types of cutters with different penetration depths or cutter spacing should be considered.The number of teeth of wedge tooth cutters can be increased in hard strata to improve the rock-breaking efficiency of the shield.The research results provide a reference for shield cutterhead selection and cutter layout in similar projects.
