Disc Cutter Research Articles

Visual measurement of milling surface roughness based on Xception model with convolutional neural network

At present, machine vision roughness detection mostly needs to design roughness related indexes based on images, and the index design has human intervention and is heavily dependent on the light source environment. To solve this problem, the paper classifies the surface roughness based on the deep convolutional neural network method, which can realize the roughness detection without index design. The most important thing is that the detection method has good light source robustness under different light source environments. The study adopts an end-to-end image analysis method, by means of image enhancement pre-processing of a small number of source images, after multi-layer convolution and pooling operations, as well as comprehensive processing of fully connected and classification layers, the convolutional kernel can automatically extract the features of the image, and finally the surface roughness obtained by vertical disc cutter milling can be classified and predicted. In addition, based on the experimental light source environment with two different luminance of night and day, by comparing with the technically mature ResNet50 and DenseNet121 convolutional neural network models, the deep convolutional neural network Xception model not only has high roughness classification accuracy, but also has more light source environment robustness. This method makes the online measurement of visual roughness possible.

Penetration rate analysis for tunnel boring machine in grinding conditions

Mechanized tunneling in hard rock is associated with various challenges and risks, one of which is the penetration rate of Tunnel Boring Machine and the occurrence of grinding and chipping in various conditions. When the strength of the rock is high and the amount of jointing is low, the penetration rate of the machine is reduced and instead of forming rock chips in the tunnel face. In these conditions, which is called grinding, tunneling is associated with wear and high consumption of cutting tools as well as a severe reduction in the efficiency of excavation operations. In this paper, the boundary between grinding and chipping processes is investigated and a criterion for determining the minimum normal force in different geomechanical conditions required to create chipping condition is presented. For this purpose, data related to Kerman Water Tunnel and Southern extension of Tehran Metro Line 6 tunnel are used. In this regard, by comparing the normal forces on the cutting tools and the resulting penetration rate, the threshold for changing conditions from the grinding phenomenon to chipping is determined. The results show that the amount of normal force required to be applied by the disc cutter to the rock mass to excavate under the chipping conditions for rocks with medium, high and very high uniaxial compressive strength are equal to 130, 210 and 225 kN, respectively. Moreover, by examining the data of Metro Line 6, the role of joints in providing the conditions for chips formation was investigated and the result showed that the boundary between grinding and chipping for medium strength rocks can be at RQD=75%. It was also found that with the penetration rate exceeding a certain threshold, a slight increase in normal force causes a significant increase in the penetration rate, which increases efficiency and reduces operating costs.

Experimental investigation on the influence of microwave exposure on the cutting performance of TBM disc cutter cutting of hard rocks

Microwave energy has been demonstrated to be able to assist mechanical rock breaking in geotechnical and mining engineering. The aim of this research is to study the influences of the interaction between microwave energy and rocks on the performance of disc cutters on a TBM (tunnel boring machine). By applying an open-type microwave-induced fracturing apparatus of hard rocks, cuboidal basalt samples were subjected to microwave irradiation for different times. Full-scale linear cutting tests were conducted on specimens subjected to microwave treatment on condition of having same penetration depth and cutting spacing. The results showed that high temperatures were mainly measured at the zone directly facing the microwave applicator and the surface temperature of the samples approximately increased in a quasi-linear manner with the duration of exposure to microwave irradiation. On condition of having a fixed penetration depth and cutting spacing, the amount of rock breaking by the TBM disc cutter increased with increasing exposure: the longer the exposure duration was, the more significant the fracturing effect of the samples. During cutting, the average normal and rolling forces applied to the disc cutter both linearly reduced with exposure time while the specific energy of the disc cutter for breaking rocks exhibited an exponential reduction relationship with exposure time. It can be seen that microwave irradiation can increase the amount of rock breaking by the disc cutter and reduce the cutting forces required by the cutter, thus further improving the efficiency of rock breaking with a TBM.

RETRACTED ARTICLE: Modelling and simulation of surfacing welding remanufacturing for tunnel boring machine disc cutter

ABSTRACT We, the Editors and Publisher of the journal Welding International, have retracted the following article: Julius Caesar Puoza &Felix Uba. Modelling and simulation of surfacing welding remanufacturing for tunnel boring machine disc cutter. Welding International (2021). DOI: 10.1080/09507116.2021.1973353 The above article has been retracted as a result of an article with a significant overlap in content having been published as Master’s Thesis entitled, “TBM 滚刀H13 钢刀圈再制造过程中堆焊数值模拟与试验验证”, English title “Numerical Simulation and Experimental Research on Surfacing Welding Remanufacturing Process of TBM Cutters’H13-steel Rings” by Shihai He from XiangTan University, China, 2020. As this represents a breach of publishing ethics and of warranties made by the author with respect to originality and provenance, we are retracting the article. The authors agree with the retraction. We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Delineation of cutter force and cutter wear in different edge configurations of disc cutters – An analysis using discrete element method

Disc cutters are used to cut the rocks in variable load conditions which results in cutter wear and failure. The wear of the cutter plays a vital role in the overall time cycle, efficiency and economics of tunneling projects. It changes the shape of the cutter, influences the cutting efficiency and has a detrimental effect on the annual cost of maintenance, availability, and utilization. In tunneling using TBMs, assessment of wear behavior of the cutters is the most crucial problem to investigate. In this study, interactions between cutter and rock were presented. Cutters with various configurations such as 0, 10, and 20-degree tip angles with different tip widths 7.3 mm and 4.5 mm were used. Cutter penetration varied from 2 to 8 mm in steps of 2 mm. The diameter of cutters are fixed at 6.5 in. and simulation runs against the rock were done for 1.2 m in length. In this simulation, normal force, tangential force, and wear were computed with the help of EDEM software for each configuration. Simulation results show that the tip angle of the cutter and depth of penetration directly affected the cutter wear. A tip angle of 100 with 7.3 mm tip width and 6 mm depth of penetration in the rock is the best configuration for obtaining the minimum wear of the cutter. The simulation results are also verified with the previous mathematical models suggested by different researchers. The suggested approach for simulation can help analyze the cutter wear behavior close to real life with given input parameters.

Investigation on damage reduction method by varying cutting angles in the cutting process of rectangular Nomex honeycomb core

Nomex honeycomb component is a typical weak rigid structure, leading to various damages during cutting operation. In this paper, the effects of cutting angles, entrance angle and engagement angle, on cutting quality were analyzed by focusing on the cell wall deformation, the cutter-workpiece interaction and the thin-walled cell geometry. A damage reduction method was proposed by controlling the range of the cutting angles. Experiments were conducted to verify the damage reduction method by cutting rectangular Nomex honeycomb core using multi-teeth disc cutters. The results showed that the method has a remarkable effect on the characteristics and distributions of damages by varying cutting angles: (a) the experimental damage-prone range of entrance angle is 55° ~ 75°, and an entrance angle near to 0° or 180° is more beneficial to damage reduction; (b) when engagement angle is smaller than 90°, there will be no visible tear damage; (c) up-cutting direction that makes entrance angle larger than 80° and engagement angle smaller than 90° is effective for damage reduction, leading the damage size is reduced by at least 40%; (d) engagement angle decreases as increasing cutting edge inclination so that the damage size can be further reduced by at least 70%.

Simulated and experimental study on the ultrasonic cutting mechanism of aluminum honeycomb by disc cutter

Aluminum honeycomb, as the core part of sandwich structure, has been widely used in aeronautics and astronautics industry owing to its superior properties. Ultrasonic cutting has a great potential to reduce the machining defects relative to traditional milling. To have an insight comprehension on the ultrasonic cutting mechanism of aluminum honeycomb by disc cutter, a finite element model is developed. It is found that the widened cell wall, which is a typical phenomenon, is generated on the machined surface. A plastic deformation model for cell wall was established based on the plastic strain energy theory to study the relationship between the width of machined cell wall and ultrasonic cutting parameters. Experiments are performed to verify the developed models and study the relationship between cell wall morphologies and cutting parameters. According to that, an alternating up and down cutting process and plastic deformation of material are observed, which is confirmed to be the reason of cell wall widening; a better machining quality of cell wall can be achieved utilizing a greater ultrasonic amplitude and a lower feed speed.

Improved SVR Method for Predicting the Cutting Force of a TBM Cutter Using Linear Cutting Machine Test Data

This research introduces a support vector regression (SVR) method to predict the cutting forces acting on the constant cross section (CCS) disc cutter, including the normal force (FN) and rolling force (FR), based on linear cutting machine (LCM) test data. To improve the prediction effect, an improved SVR-Outlier Detection (SVR-OD) method and an Additional Input Variable (AIV) method are proposed. After removing the outliers, 148 typical LCM test samples form the training set. Here, 70 samples from the Hangzhou No.2 Water Supply Channel constitute the test set. The prediction results show that the Root-mean-squared Relative Error (RMRE) values of the normal force and rolling force are 19.5% and 24.8%, respectively, and the corresponding determination coefficients are 0.845 and 0.807, respectively. For the prediction of the peak cutting force with an important reference to tunnel boring machine (TBM) design, the proportions of samples with an Absolute Relative Error (ARE) value of less than 20% for FN and FR are 9/10 and 7/7, respectively. The above prediction results are better than those of the common SVR method; thus, the developed method can effectively simulate the cutting force required by a rock mass with good integrity. The cutting force prediction using LCM test data is feasible and practical. In addition, the comparison of the prediction results between the improved SVR and common SVR methods shows that the improved SVR-OD and AIV methods play an active role in improving the prediction accuracy of the SVR method.

Development of Optimal Design and Circular Broach Modular Design of Disc Cutters with the Development of a Parametric Model

Cutting tool is one of the most important instruments in production. It is used for machining of different components on machine tools. A material is cut into a chip to incur the desired work piece surface currently used in engineering various cutting tools. The directions of development of structures of metal cutting tools are: higher precision of dimensional and geometrical parameters, the use of new tool materials, cost, and quick. The cutting tools are not only affected by the design of machine, technology of manufacturing of products, but also impact the constructive forms of machine parts. The emergence of mechanical spine, thanks to the pull method. Spine broach can provide high-performance processing spine bore with the required accuracy. The development of heavy machine tools required the creation of new designs of large instruments. The use of mechanical automatic lines also required design tools with high dimensional stability capable of handling the items within the specified tolerance for a certain time. Instruments were developed in the process of renewing the cutting edge of the cutting tools with automatic adjustment; setting up tools on the size of the machine is a device for automatic replacement of worn tool in the process line of the Computer-Aided Manufacturing CAM of the cutting tool special requirements. Equipment must operate with high level efficiency, so to reduce the loss of time resetting of the need to minimal. A cutting tool requires knowledge of the theoretical foundations of design and calculation tools using CAD.

Influence of the methods of mechanical processing and sterilization on the structural-and-functional condition of the surface layer of bone samples

The authors presented the results of structural-and-functional analysis of the surface layer of bone tissue samples after their mechanical processing and sterilization. Bone samples of the given height were produced on a precision cutting machine using disc cutters. They were made from cylindrical blanks obtained from the fragments of bovine femoral shaft using hollow cutters. In this case, one of the end surfaces of bone samples was processed with a steel cutting disc with teeth, and the second one – using a disc milling cutter with diamond-coated cutting edge. The samples obtained were sterilized by different methods: ozone, radiation and combined ones, based on combined ozone-oxygen exposure at the first stage and radiation exposure – at the second. The elastic-plastic properties (Vickers microhardness index) of the surface layer at the ends of cylindrical bone samples were determined after mechanical and sterilizing physicochemical exposure. Scanning electron microscopy was used when studying the patterns of changes in the structure of sample end surfaces. The advantage of mechanical processing of bone samples using a cutting disc cutter with diamond-coated cutting edge was established compared to using a circular milling cutter with a cutting edge in the form of teeth. The studying of elastic-plastic characteristics of the surface layer of bone samples in mirovolumes demonstrated that the sterilizing physicochemical exposure to ozone-oxygen mixture, to radiation processing using a flow of fast electrons with radiation absorption doses of 10, 15 and 20 kGy, as well as their combined exposure did not have a significant effect on the values of sample microhardness.

Systematic Performance Evaluation of Shield TBM Cutters for Excavating Multiple Soft Rock

Cutter performance evaluation is important for shield TBM during the design and refurbishment stage. To face the challenges of choosing the proper cutters for tunneling in complex condition, according to the concept of parameter profile analysis, a systematic evaluation method was proposed. In this novel method, by comparing with their expected best value and the corresponding unacceptable limit, all of the selected performance parameters can be synthesized to assess the proximity of the overall merit of each cutter with respect to all the performances considered under all possible geological conditions. Performance indexes including cutting efficiency, structural strength, wear life, and dynamic response were individually analyzed based on linear cutting tests, finite element analyses, and theoretical calculations. Finally, a case study was carried out to demonstrate how the method is applied to find the optimal cutter among a small-scale disc cutter and two scrapers used for cutting multiple soft rock. In this case, three types of concrete specimens with distinct mechanical properties were carefully prepared to substitute for soft rock. The evaluation results show that the method has an intrinsic applicability in helping to make a reasonable trade-off between cost and cutting performance during the cutter selection process.

Study on Cutting Chip in Milling GH4169 with Indexable Disc Cutter.

The study and control for chip have a significant impact on machining quality and productivity. In this paper, GH4169 was cut with an indexable disc milling cutter. The chips corresponding to each group of cutting parameters were collected, and the chip parameters (chip curl radius, chip thickness deformation coefficient, and chip width deformation coefficient) were measured. The qualitative relationship between the chip parameters and cutting parameters was studied. The quadratic polynomial models between chip parameters and cutting parameters were established and verified. The results showed that the chip parameters (chip curl radius, chip thickness deformation coefficient and chip width deformation coefficient) were negatively correlated with spindle speed; chip parameters were positively correlated with feed speed; chip parameters were positively correlated with cutting depth. The maximum deviation rate between measured values and predicted values for chip curl radius was 9.37%; the maximum deviation rate for cutting thickness deformation coefficient was 13.8%, and the maximum deviation rate of cutting width deformation coefficient was 7.86%. It can be seen that the established models are accurate. The models have guiding significance for chip control.

Evaluating the Efficiency of a\xa0New Cutterhead Design to Counteract the Drawbacks of Excavation through Very Hard Rocks

The application of appropriate excavation equipment in difficult grounds is of crucial importance and consequently improves the performance of hard rock Tunnel Boring Machines (TBMs). The cutterhead is one of the main components of TBMs which is directly involved in the excavation process, and its design can highly affect the cutting efficiency, the overall balance of the head, the performance of main bearing in long term, and the wear of the whole cutting face and muck buckets. This paper mainly focuses on the significant role of a proper design on the cutting efficiency with reference to a TBM tunneling project. Due to existence of very hard and abrasive rocks on the path of Kerman water conveyance tunnel, a new cutterhead was designed to be applied on a second hand TBM. The new cutterhead contains larger 19-inch disc cutters with a new disc cutter layout. Since the new cutterhead was launched following the excavation of the old one in a specific chainage of the tunnel, the performance of the two cutterheads in pyroclastic rocks could be compared with respect to the cutting efficiency, and lower specific energy values were observed for the new cutterhead which is the indicator of a better cutting efficiency in this geological condition.

Discrete-Element Analysis of the Excavation Performance of an EPB Shield TBM under Different Operating Conditions

This study used a discrete-element analysis to predict the excavation performance of a 7.73 m-diameter earth pressure balance (EPB) shield tunnel boring machine (TBM). The simulation mainly predicted several excavation performance indicators for the machine, under different operating conditions. The number of particles in the chamber and the chamber pressure varied, as the operating conditions changed during the simulated TBM excavation. The results showed that the compressive force, torque, and driving power acting on the TBM cutterhead varied with its rotation speed, increasing as the cutterhead rotation speed rose. The overall compressive force acting on all of the disc cutters and their impact wear increased linearly as the cutterhead rotation accelerated. The position of a disc cutter on the cutterhead had a particularly strong influence, with higher compressive forces experienced by the cutters closer to the center. In contrast, the gauge disc cutters at the transition zone of the cutterhead showed more wear than those elsewhere. The muck discharge rate and the driving power of the screw conveyor rose with increasing screw conveyor and cutterhead rotation speeds. Finally, this study suggests optimal operation conditions, based on pressure balance and operational management of the TBM.

Numerical analysis for rock cutting force prediction in the tunnel boring process

Study of rock cutting force prediction is of great significance for improving the efficiency of rock breaking and optimizing the tunnel boring process. A new prediction model named RCC (the Roxborough Model and the CSM Model and the Colorado School of Mines’ Data Integration) model is proposed to predict vertical, rolling and lateral forces acting on the disc cutter based on the theoretical model developed by Roxborough and Phillips (1975) (Roxborough model) and the theoretical model developed by Rostami (1997) (CSM model). The suggested model is based on the improvement that the shape of extrusion surface is reasonably assumed to be trapezoid and the arc segment at the edge of the cutter is reasonably simplified to a straight-line segment. Results of the full-scale linear cutting experiments by the Colorado School of Mines are used to validate the accuracy and reliability of the suggested model, some additional calculation results from the linear cutting prediction formula developed by Ozdemir et al. (1978) (Linear Cutting model) and the CSM model are also used in this purpose. The results indicate that the formulas for calculating vertical force and rolling force presented in this paper are more accurate than the Linear Cutting model and the CSM model. Although the calculation results of the lateral rock breaking force conforms to the variation law of lateral rock breaking force with the penetration and cutter spacing, they are smaller than the experimental data. Finally, through theoretical analysis of the suggested RCC model and numerical simulation by using ANSYS/LS-DYNA, the rationality of the simplified disc cutter used in the RCC model is verified and the influence of penetration depth on the rock cutting force is obtained, which provides a theoretical reference for the study of rock breaking mechanism and optimization of tunneling process.

Machine learning forecasting models of disc cutters life of tunnel boring machine

This study aims to propose four Machine Learning methods of Gaussian process regression (GPR), support vector regression (SVR), decision trees (DT), and K-nearest neighbors (KNN) to predict disc cutter's life of TBM. 200 datasets monitored during the Alborz service tunnel construction in Iran, including TBM operational parameters, geometry, and geological conditions, were applied in the models. The 5-fold cross-validation method was considered to investigate the prediction performance of the models. Finally, the GPR model with R2 = 0.8866/RMSE = 107.3554, was the most accurate model to predict TBM disc cutter's life. KNN model with R2 = 0.1753/RMSE = 288.9277, produced the minimum accuracy. To assess each parameter's contribution in the prediction problem, the backward selection method was used. The results showed that TF, RPM, PR, and Qc parameters significantly contribute to TBM disc cutter's life. However, RPM and PR parameters were more and less significant compared to the others.

Effect of TiC addition on the microstructure and properties of Ni3Ta–TaC reinforced Ni-based wear-resistant coating

The present study focuses on the surface wear-resistant strengthening technology of the tunnel boring machine disc cutter ring. Ni3Ta–TaC reinforced Ni-based wear-resistant coatings were synthesized in-situ on the surface of 5Cr5MoSiV steel by laser cladding with pure Ni spherical powder, pure Ta spherical powder and Ni coated graphite. To inhibit coating cracking, TiC powder was added to promote the in-situ formation of TaC. The effect of adding TiC on the microstructure and properties of Ni-based wear-resistant coating has been investigated by experiments and first-principles calculation. The results show that Ni3Ta and TaC particles are synthesized in-situ in the coating, and small TaC particles are aggregated around TiC. The orientation relationship of TaC (100)//TiC (100) is confirmed by EBSD and TEM. The properties of interface of TaC (100) and TiC (100) are calculated by the first-principles, showing that the C–Ti and Ta–C interface has high adhesion and good stability. The wear resistance of the two coatings is 4 times higher than that of the substrate. The addition of TiC can effectively inhibit the formation of the lath-shaped Ni3Ta intermetallic compound and cracks, resulting in excellent wear resistance and toughness.

Three-dimensional coupled numerical modelling of lab-level full-scale TBM disc cutting tests

In this work, comprehensive numerical modelling was conducted on the full-scale linear cutting test with a TBM disc cutter. Several numerical techniques, including local particle refinement and the coupling of different numerical methods (4D-LSM, DDA, and NMM), were adopted to more realistically reproduce the actual experimental loading conditions. The coupled numerical method was first calibrated against the normal cutting force of the normal linear cutting test with large blocks of granite. Following the calibration, numerical predictions of the inclined cutting and double-channel continuous cutting processes were conducted, and the numerical results showed good agreement with previous experimental observations. The influences of cutting speed, particle size, and multiscale coupling techniques were further discussed, and some suggestions were derived on the selection of proper numerical parameters and techniques in the numerical simulation of 3D large-scale TBM disc cutting lab tests.

Effects of inclination angles of disc cutter on machining quality of Nomex honeycomb core in ultrasonic cutting

Effects of inclination angles of disc cutter on machining quality of Nomex honeycomb core in ultrasonic cutting

Analysis of Cutting Tool Wearing of Tunnel Boring Machines in Singapore Mixed Face Ground Condition

During shield tunneling in composite stratum, especially in granite stratum with high rock strength and high-water content, the abnormal damage of disc cutter is frequent. This paper analyzes the law of wear of disc cutter and obtains the wear coefficient, and then predicts the number of disc cutters needed for shield machines in tunneling section and reduces the number of disc cutters needed, so as to reduce the extra cost of shield construction.