Search Results (72)

Understanding the combined effects of edge width and cutter ring shape on the rock-breaking performance is critical for optimising disc cutter design. The intrusion test serves as an effective approach for investigating the rock-breaking mechanism of disc cutters. In this study, a two-dimensional discrete element method (DEM) model was established to simulate the intrusion process of a single disc cutter. Three commonly used disc cutter types were analysed: disc cutter with flat edge (FEDC), disc cutter with rounded edge (REDC) and disc cutter with alloy tooth (ATDC). The edge widths ranging from 10 mm to 24 mm were examined to assess their influence on rock crack propagation, stress distribution, cutting force and specific cutting energy. The FEDC and REDC exhibited face-contact extrusion breaking, whereas the ATDC was line-contact embedding breaking. The crack extension range, crack number, force chain intensity, stress distribution, rock-breaking force and specific cutting energy ranks are as follows: FEDC > REDC > ATDC. The ATDC generated a higher proportion of tensile cracks compared to the FEDC and REDC, though with fewer long cracks. The rock-breaking efficiency of the FEDC was lower, whereas the REDC and ATDC exhibited higher efficiency. With the increase in edge width, the force chain distribution became more concentrated, leading to greater internal rock damage, and the number and length of cracks increased significantly. Cracks initially expanded laterally at smaller edge widths but extended downward as edge width increased. The peak force and specific cutting energy increased with increasing edge width; the peak force at an edge width of 24 mm is approximately 3.5 times that of an edge width of 10 mm. The REDC is preferable in hard rock formations, and the ATDC is more effective in soft rock formations. The edge width should be determined based on rock properties and thrust capacity. Full article

Sugarcane, a key sugar crop in China, is predominantly manually harvested. In the main sugarcane-producing areas of China, typhoons cause canes to become lodged, resulting in high field losses and low harvesting efficiency. This study aimed to reduce these losses by analyzing the causes: ineffective stalk pickup, transfer, and conveyance. The tests showed the stalk–steel static friction coefficient (SFC) was lower than the stalk–soil SFC. Conventional basecutters use raised patterns to enhance friction, but soil adhesion makes them ineffective, hindering lodged stalk pickup. Bent stalks also struggle to enter butt lift rollers or pass through roller trains, increasing losses. The proposed improvements included adding toothed plates on the cutter discs, optimized disc–roller positioning, and using fewer rollers (one butt lift and one feed roller pair). Theoretical analysis confirmed the toothed plates improved pickup via grabbing force, while using fewer rollers stopped the stalks detaching from and blocking the roller train. A prototype was tested via orthogonal experiments, showing a field loss ratio of 1.21%, a feed rate of 13.09 kg/s, and a billet qualification rate of 95.82% with optimal settings (chopper speed: 390 rpm; 10 stalks/group; roller speed: 230 rpm; ground speed: 1.41 m/s). Field tests achieved 2.0% loss, demonstrating effectiveness for severely lodged cane, a significant improvement over the conventional harvesters (15–20% loss). These findings aid low-loss-level harvester development. Full article

To address the issues of burr formation, structural deformation, and tearing in the conventional machining of Nomex honeycomb composites, this study aims to clarify the mechanisms by which ultrasonic vibration-assisted cutting enhances machining quality. A multi-scale analysis framework is developed to examine the effects of ultrasonic vibration on fiber distribution, cell-level shear response, and the overall cutting mechanics. At the microscale, analyses show that ultrasonic vibration mitigates stress concentrations, thereby shortening fiber length. At the mesoscale, elastic buckling and plastic yielding models show that ultrasonic vibration lowers shear strength and modifies the deformation. A macro-scale comparison of cutting behavior with and without ultrasonic vibration was conducted. The results indicate that the intermittent contact effect induced by vibration significantly reduces cutting force. Specifically, at an amplitude of 40 μm, the cutting force decreased by approximately 29.7% compared to the condition without ultrasonic vibration, with an average prediction error below 8.6%. Compared to conventional machining, which causes the honeycomb angle to deform to approximately 130°, ultrasonic vibration preserves the original 120° geometry and reduces burr length by 36%. These results demonstrate that ultrasonic vibration effectively reduces damage through multi-scale interactions, offering theoretical guidance for high-precision machining of fiber-reinforced composites. Full article

Predicting the wear of disc cutters in Tunnel Boring Machines (TBMs) is a complex challenge due to the large scale of the machinery and the numerous operational variables involved. Laboratory-scale tests offer a controlled approach to isolating and analyzing specific wear mechanisms. However, the extremely low wear rates observed in such simulations pose challenges for conventional characterization methods, as gravimetric and profilometric techniques often lack the precision and accuracy needed to measure low wear patterns with an uneven morphology. To address this, this study revisited a methodology for quantifying low wear rates in a reciprocating wear test using AISI H13 tool steel disc cutters. This approach integrates spherical indentation marks as reference points with 3D white-light interferometry, enabling high-precision material loss measurements. Eighteen disc samples were subjected to wear testing, with 3 indentations analyzed per sample, for a total of 54 indentations. The statistical validation confirmed the method’s reproducibility and reliability. The proposed approach provides a robust alternative to existing techniques, addressing a critical gap regarding the accurate quantification of low wear rates in controlled laboratory settings. Full article

In slurry shield tunneling projects, leakage from floating seals frequently leads to abnormal failures of disc cutters. To investigate the leakage characteristics at the floating seal end faces of the cutters, a numerical method is proposed for analyzing the dynamic leakage behavior of the floating seal end faces, considering the effects of wear. The elastohydrodynamic lubrication problem of the floating seal was addressed using the Reynolds equation and the slicing method, leading to the development of a computational model for the pressure and thickness distribution of the oil film on rough surfaces. Based on the Archard wear equation, a dynamic surface roughness model considering wear was established. Furthermore, a numerical model for dynamic leakage of the floating seal end faces in shield machine cutters, incorporating wear effects, was developed. Simulated friction and wear tests of the floating seal end faces, along with cutter seal leakage experiments, were conducted for validation. The results demonstrate that the dynamic surface roughness model considering wear can effectively predict the roughness evolution of worn surfaces. The trend of the theoretical leakage rate is generally consistent with that of the experimental results, verifying the effectiveness of the proposed model. Full article

The estimation of disc cutter life is important due to the high equipment replacement cost in tunnel boring machines (TBMs). In this paper, we propose a comprehensive method for predicting disc cutter wear, integrating dimensionality reduction in shield tunneling parameters, data input preprocessing, and optimized model selection. First, we select core TBM operation parameters as model inputs through principal component analysis (PCA) and PCA directly. And, then, based on the characteristics of the operation parameters, we propose a data preprocessing method for time series models. This method uses excavation rings as units, providing a more accurate representation of the actual shield excavation process. Furthermore, by evaluating the prediction accuracy, training efficiency, and inference efficiency of various models, we demonstrate that the combined PCA data + Min Max Scaler + gated recurrent unit (GRU) method achieves the most accurate prediction results while offering real-time prediction capabilities. Full article

The TBM disc cutter cuts soft–hard composite strata during shield construction, and the cutter–rock cutting process generates high temperatures and severe wear. In this research, different strength types of rocks are taken as objects to analyse the interacting rock-breaking force and cutter motion model. The effects of rock properties on wear are investigated, and the cutter ring wear mechanism and damage types are discussed. Combined with the thermal stress theory of elastomer and the abrasive wear theory, a prediction model for cutter wear depth and wear mass is proposed. The results of the study show that the type of wear is dominated by abrasive wear, with the highest probability of uniform wear occurring in cutting hard rock. Hard rock is the most abrasive to the steel material of the cutter ring, and the percentage of abrasive wear decreases for cutting soft–hard composite strata. The amount of abrasive wear is negatively correlated with the hardness of the cutter ring. The rock damage patterns are different when cutting soft and hard rocks, and the wear areas are located at the bottom and sides of the cutter ring, respectively. Considering the thermal effect, the depth of wear for cutting hard rock has a power function relationship with the installation radius, which is closer to the actual value. The theoretical models are generally lower than the actual measured values. The wear prediction model is useful for determining the replacement interval of the cutter and improving the rock-breaking efficiency. Full article

The large-diameter slurry tunnel boring machine (TBM) is widely used in the construction of tunnels across rivers and seas. However, cutter wear has become a critical issue that severely limits the tunnelling efficiency. Taking the Qingdao Jiaozhou Bay Second Subsea Tunnel Project as the background, the wear patterns of disc cutters on the atmospheric cutterhead of a large-diameter slurry TBM under complex geological conditions were analyzed. The flat wear of disc cutters induced by factors such as rock chip accumulation in front of the cutterhead, the jump trajectory when changing disc cutters, alloy-insert disc cutter mismatch, cutter barrel clogging, and severe wear of scrapers is discussed. Furthermore, the impacts of measures such as slurry circulation to remove rock chips during TBM stoppage, clay dispersant injection into the slurry chamber, cutter barrel flushing, and the wear resistance optimization of cutters and cutter barrels on reducing cutter wear were investigated. Based on numerical simulations and field data, a methodology for determining the optimal timing for cutter replacement is proposed. The results indicate the following: The circulation system effectively reduces accumulation, minimizing secondary wear of the disc cutters and lowering the risk of clogging in the cutter barrel. Adopting measures such as shield shutdown, a circulation system to carry away the slag, cutter barrel flushing, and soaking in 2% dispersant for 8 h can effectively reduce the accumulation of rock chips and mud cakes on the cutterhead, which in turn reduces the flat wear of the disc cutter. Measures such as making the cutter body and cutter ring rotate together and adding wear-resistant plates to the cutter barrel greatly improve the life of the cutter. The sharp increase in composite parameters can serve as an effective marker for assessing cutter conditions. The findings of this study can provide valuable insights into reducing cutter wear in similar projects. Full article

The disc cutter is a key rock-breaking component of tunnel boring machines, and during operation, improper assembly preload often leads to uneven wear of the cutter. To study the effect of preload force on the friction torque of paired tapered roller bearings during rock-breaking, the transmission of preload and rock-breaking loads within the disc cutter structure is first analyzed, and a bearing load distribution model is established. Based on this model, a method for calculating the friction torque of the tapered roller bearings in the disc cutter, considering both external loads and preload force, is proposed. Next, finite element analysis is conducted to investigate the impact of preload displacement on preload force, and a relationship equation is derived using polynomial fitting. Finally, experiments on bearing preload displacement and friction torque are carried out under no-load conditions. The results show that the simulation results for the relationship between preload force and preload displacement are in good agreement with the experimental results. Additionally, the experimental results for the friction torque of the tapered roller bearings are close to the theoretical calculation results, with the overall trend matching, thus verifying the reliability of both the simulation and theoretical models. Full article

The TBM disc cutter, which is the main cutting tool of tunnel boring machines (TBMs), is replaced when it is excessively worn during the boring process. Disc cutters are usually monitored by workers at cutterhead chambers, and they check the status and wear of disc cutters. Manual measurement occasionally results in inaccurate measurement results. In order to overcome these limitations, real-time disc cutter monitoring techniques have been developed with different types of sensors. This study evaluates the distance measurement performance of an eddy-current sensor for measuring disc cutter wear via a series of laboratory experiments. This study focused on identifying the effects of various measurement environments on the sensor’s accuracy. The study considered conditions that the eddy-current sensor may encounter in shield TBM chambers, including air, water, slurry, and excavated muck. Experiments were conducted using both a small-scale disc cutter and a 17-inch full-scale disc cutter. The results indicate that the eddy-current sensor can accurately measure the distance to the disc cutter within a specific range and that its performance remains unaffected by different measurement environments. Full article

At present, the problems of the low cutting reliability and poor cutting quality of carrot harvesters in China are particularly prominent, directly leading to the problems of high root and stem damage rates, low stem and leaf cutting rates, and low cutting surface flatness rates. In order to solve these problems, we developed a disc-type double-disc cutting device. Based on the structural analysis and the central combination design theory of Box–Behnken, using three factors as influencing factors, namely, clamping and conveying speed, the rotary speed of the disc cutter, and the thickness of the disc cutter. A response surface experiment was carried out to analyze the influence of each factor on the high damage rates of the rhizome, the clean rates of stems and leaves, and the flatness rate of cutting surfaces to optimize the influencing factors. According to the test results, a regression mathematical model between test parameters and performance indexes was established, and optimization verification was carried out according to the regression model between test factors and indexes. Finally, the optimal parameter combination is as follows: a clamping and conveying speed of 1.0 m/s, a rotary speed of the disc cutter of 193.5 r/min, and a thickness of the disc cutter of 3.6 mm. The results of the field experiment showed that the root and stem damage rate was 2.61%, the stem and leaf-cutting rate was 87.32%, and the cutting surface flatness rate was 89.87%. Compared with a set of parameters commonly used in double-disc cutters to harvest carrots under the same conditions, the corresponding root and stem damage rates, stem and leaf-cutting rates, and productivity decreased by 2.16%, 1.97%, and 1.87%, respectively, and the comprehensive performance was obviously improved. The proposed research method can well simulate the cutting process in carrot harvesting and provide support for the development of carrot harvesting equipment. Full article

Disc cutters are essential for shield tunnel construction, and monitoring their wear is vital for safety and efficiency. Due to their position in the soil silo, it is more challenging to observe the wear of disc cutters directly, making accurate and efficient detection a technical challenge. However, existing methods that treat the problem as a classification task often overlook the issue of data imbalance. To solve these problems, this paper proposes an end-to-end detection method for disc cutter wear state called the Multivariate Selective Attention Prototype Network (MVSAPNet). The method introduces an attention prototype network for variable selection, which selects important features from many input parameters using a specialized variable selection network. To address the problem of imbalance in the wear data, a prototype network is used to learn the centers of the normal and wear state classes, and the detection of the wear state is achieved by detecting high-dimensional features and comparing their distances to the class centers. The method performs better on the data collected from the Ma Wan Cross-Sea Tunnel project in Shenzhen, China, with an accuracy of 0.9187 and an F1 score of 0.8978, yielding higher values than the experimental results of other classification models. Full article

The characteristics of soil ditching and backfilling are crucial for orchard ditching operations. However, experimentally investigating the dynamic ditching and backfilling process is currently not feasible. To address this issue, the 3DGZ-50A self-propelled orchard ditching machine (SPODM) was designed using a modular concept, incorporating three types of ditching cutter discs (01#, 02#, and 03#). These discs were designed, trial-manufactured, and tested in orchard ditching experiments. A corresponding simulation model was also constructed using EDEM 2022 software. This study evaluated the ditching and backfilling process, analyzing the performance of the three cutter discs through experimental and simulation methods. Results indicated that the 01# and 02# cutter discs created V-shaped furrows, whereas the 03# cutter disc formed an arc-shaped furrow. The relative errors in the final furrow depth (D_f) and width (W_f) between experimental and simulated results were 30.70% and 8.61%, respectively, while those in the maximum furrow depth (D_m) and width (W_m) were 9.44% and 3.00%. These minor relative errors confirmed the accuracy of the simulation model. Regarding maximum power consumption, the 01# cutter disc used 86.3% of the power consumed by the 02# cutter disc and 85.1% of that used by the 03# cutter disc. During the ditching process, the blades penetrated the soil to create the maximum furrow cross-section, which then gradually decreased due to backfilling. Both simulation and test results demonstrated that the 01# cutter disc performed best, achieving a maximum furrow cross-sectional area (46.70%), minimum final surface furrow cross-sectional area (6.04%), and lower power consumption (31.03 kW). This study provides equipment for ditching operations in low-height close-planting orchards in northern China. Full article

This study provides a theoretical foundation for optimizing tunnel boring machine (TBM) excavation parameters under diverse geological conditions, offering significant engineering value by enhancing construction efficiency and reducing costs. As the development of underground spaces advances, TBMs play a pivotal role in tunnel excavation. TBMs enhance safety in excavation by mechanically breaking rock, reducing the reliance on explosives, and the associated risks of blasts. The shield support minimizes surrounding rock collapse, advanced geological forecasting mitigates risks posed by complex geologies, and intelligent monitoring systems improve operational safety. To enhance TBM efficiency and safety, this study developed a 3D simulation model of rock breaking by disc cutters using the discrete element method. This study systematically examined the effects of excavation parameters, including disc-cutter diameter, cutter spacing, and penetration, on rock-breaking performance. The findings reveal, that as the disc-cutter diameter increases, the rolling force also increases, while the rock-breaking specific energy initially rises and then declines. The 19-inch disc cutter demonstrated a superior rock-breaking efficiency in conventional excavation operations. At a cutter spacing of 60 mm, the rock-breaking specific energy reached its lowest value, representing optimal efficiency. Furthermore, as the penetration increased, both the rolling force and rock fragmentation volume grew, whereas the specific energy decreased, further improving the rock-breaking efficiency. Full article

Tunnel Boring Machines (TBMs) are integral to modern underground engineering construction, offering enhanced safety and efficiency. However, TBMs often face challenges in complex geological conditions, such as composite strata, resulting in reduced advancement speed and increased cutter wear. This study investigates the rock-breaking characteristics of TBM disc cutters in composite strata through numerical simulations using the Particle Flow Code (PFC) 5.0 software. Focusing on the Jinan Metro Line 6, the research analyzes cutter forces, rock crack propagation, and the impact of cutter edge shapes on rock-breaking efficiency. The discrete element method (DEM) is employed to simulate microscopic behaviors of rocks, providing insights into crack formation, expansion, and failure. This study’s findings reveal that cutter design and operational parameters can significantly influence cutter lifespan and efficiency. By modifying cutter spacing and penetration depth, enhancing rock-breaking efficiency, and grouting softer layers, TBMs can maintain effective excavation in composite strata. The study establishes a comprehensive understanding of the interplay between TBM cutters and complex geological conditions, offering actionable strategies to enhance TBM performance and mitigate cutter damage. Full article