Low Wheel Research Articles

CFD–DEM modelling of particle entrainment in wheel–rail interface: a parametric study on particle characteristics

Abstract To mitigate and alleviate low wheel–rail adhesion, a train-borne system is utilised to deposit sand particles into the wheel–rail interface via a jet of compressed air in a process called rail-sanding. Britain Rail Safety and Standards Board introduced guidelines on the sand particles’ shape, size, and uniformity which needs to be adhered to for rail-sanding. To further investigate these guidelines and help improve them, this research presents a parametric study on the particle characteristics that affect the rail-sanding process including density, size and size distribution, coefficient of uniformity, and shape, utilising a coupled computational fluid dynamics–discrete element method (CFD–DEM) model. The efficiency of rail-sanding is estimated for each case study and compared to the benchmark to optimise the sand characteristics for rail-sanding. It is concluded that particle size distribution (within the accepted range) has an insignificant effect on the efficiency while increasing particle size or the coefficient of uniformity decreases the efficiency. Particle shape is shown to highly affect the efficiency for flat, compact and elongated particles compared to the spherical shape. The current numerical model is capable of accurately predicting the trends in the efficiency compared to the actual values obtained from full-scale experiments.

Dijagnostika kvarova zasnovana na bestežinskoj neuronskoj mreži u sistemu vešanja

Vehicle suspension systems play a critical role in ensuring passenger comfort and safety. Detecting faults in these systems is vital for maintaining safety, performance, and cost-effectiveness. Traditional inspection methods have limitations, such as visual checks, bounce tests, and alignment assessments. This study explores Wilkie, Stonham, and Aleksander Recognition Device (WiSARD), a weightless neural network (WNN), for suspension fault diagnosis. A WNN model is employed to classify suspension system faults using sensor data. The dataset includes both normal and faulty conditions to train the model. The study assesses WiSARD under various fault conditions, including strut damage, mount failure, worn-out components, and low wheel pressure. Comparative evaluations demonstrate that the approach outperforms other classification techniques, achieving an impressive 95.63% accuracy with a rapid 0.05-second computation time for test data. This WNN-based method proves superior in detecting suspension faults and holds potential as a candidate for real-time vehicle fault diagnosis systems.

Suppression of carbody hunting for a locomotive caused by low wheel–rail contact conicity by optimising yaw damper location

This study addresses the issue of carbody hunting in an electric locomotive induced by low wheel-rail contact conicity. The main objective is to mitigate this unstable motion by optimising the location of yaw dampers while ensuring bogie stability under high conicity conditions. A field test was first conducted to observe the carbody hunting behaviour, and a detailed locomotive dynamics model was then developed and validated using experimental data. The impact of yaw damper locations on locomotive stability was investigated, taking into consideration different carbody modes. The findings reveal the mechanism behind the deterioration of carbody stability due to the yaw damper installation angle and two installation layouts were proposed to enhance the carbody stability. Comparisons were then made with traditional solutions using both linear and nonlinear analysis, and experimental validation confirmed the effectiveness of the optimised yaw damper locations in improving carbody stability. This research highlights the importance of optimising the yaw damper's location to suppress carbody hunting, providing valuable insights for railway engineers and offering a promising solution for enhancing stability in high-speed train.

Bifurcation analysis of a wheel‐slip control loop under low wheel‐slip regulation considering time‐delay

AbstractSafety and efficiency are key aspects of research and development in the automotive industry, especially in the field of safety‐critical subsystems, such as brake systems. The effect of time delay arise in brake systems, this adverse effect can cause performance degradations or make the brake system unstable. In this study, the bifurcation analysis of a wheel slip control feedback loop is presented. The control system consists of a wheel and a tyre, delayed actuator dynamics, and an LQR (linear quadratic regulator) that is designed to operate under relatively low wheel slip, during service braking. As a result, it is shown, that if time delay is neglected, the steady‐state solution of the model is globally stable using the LQ optimal controller gains. However, considering nonzero time‐delay may cause a subcritical Hopf‐bifurcation, and an unstable limit‐cycle exists around the steady‐state solution in a large domain of time‐delay parameters. Critical bifurcation maps and simulation results with more detailed system models are generated and shown in the study.

Development of a control algorithm for active control of rolling motion of a ship using a gyrostabilizer

In this study, a new control algorithm for an active gyrostabilizer was developed and applied to a ship model. The active gyrostabilizer consists of a gyro sensor that measures the angular rate of the rolling motion of a ship, a controller that realizes the active control algorithm, and an actuator that is connected to the precession axis. The new control algorithm receives the angular rate of the ship, then outputs the desired precession angle. A suitable actuator for this kind of mission could be a servomotor. Based on the concept of tuned mass damper, a new control algorithm for an active gyrostabilizer was developed. It was theoretically found that instead of increasing stiffness, the damping of the rolling motion of the ship could be increased by tuning the filter frequency of the control algorithm to the rolling frequency. The results of both numerical and experimental investigations showed that the proposed control algorithm is valid and can be used to effectively suppress rolling motion with a relatively low speed or light spinning wheel compared to passive gyrostabilizers.

An abnormal carbody swaying of intercity EMU train caused by low wheel–rail equivalent conicity and damping force unloading of yaw damper

AbstractLow-frequency carbody swaying phenomenon often occurs to railway vehicles due to hunting instability, which seriously deteriorates the ride comfort of passengers. This paper investigates low-frequency carbody swaying through experimental analysis and numerical simulation. In the tests, the carbody acceleration, the wheel–rail profiles, and the dynamic characteristics of dampers were measured to understand the characteristics of the abnormal carbody vibration and to find out its primary contributor. Linear and nonlinear numerical simulations on the mechanism and optimization measures were carried out to solve this carbody swaying issue. The results showed that the carbody swaying is the manifest of carbody hunting instability. The low equivalent conicity and the decrease of dynamic damping of the yaw damper are probably the cause of this phenomenon. The optimization measures to increase the equivalent conicity and dynamic damping of the yaw damper were put forward and verified by on-track tests. The results of this study could enrich the knowledge of carbody hunting and provide a reference for solving abnormal carbody vibrations.

Effects of a New Type of Grinding Wheel with Multi-Granular Abrasive Grains on Surface Topography Properties after Grinding of Inconel 625.

Finishing operations are one of the most challenging tasks during a manufacturing process, and are responsible for achieving dimensional accuracy of the manufactured parts and the desired surface topography properties. One of the most advanced finishing technologies is grinding. However, typical grinding processes have limitations in the acquired surface topography properties, especially in finishing difficult to cut materials such as Inconel 625. To overcome this limitation, a new type of grinding wheel is proposed. The tool is made up of grains of different sizes, which results in less damage to the work surface and an enhancement in the manufacturing process. In this article, the results of an experimental study of the surface grinding process of Inconel 625 with single-granular and multi-granular wheels are presented. The influence of various input parameters on the roughness parameter (Sa) and surface topography was investigated. Statistical models of the grinding process were developed based on our research. Studies showed that with an increase in the cutting speed, the surface roughness values of the machined samples decreased (Sa = 0.9 μm for a Vc of 33 m/s for a multigranular wheel). Observation of the grinding process showed an unfavorable effect of a low grinding wheel speed on the machined surface. For both conventional and multigranular wheels, the highest value for the Sa parameter was obtained for Vc = 13 m/s. Regarding the surface topography, the observed surfaces did not show defects over large areas in the cases of both wheels. However, a smaller portion of single traces of active abrasive grains was observed in the case of the multi-granular wheel, indicating that this tool performs better finishing operations.

Understanding and treatment of severe flange wear of metro train wheels

Urban rail transit usually contains many small radius curved tracks, and wheel flange wear is prominent, which greatly reduces the service life and increases the maintenance and replacement costs of wheelsets. Two metro lines in Shanghai of China had suffered from severe flange wear since 2017, and the flange wear rate increased gradually over the next three years. This paper presents the understanding and treatment of severe flange wear through field measurement and numerical simulation. The investigation results indicated that the key factors causing severe flange wear were poor rail gauge face lubrication, the use of a low conicity wheel profile for trains running on the two metro lines containing many small radius curved tracks, and the lack of timely maintenance of low rail profiles. Three countermeasures were proposed to mitigate wheel flange wear, which were evaluated through wheel–rail matching analysis and wheel wear prediction. Then, two countermeasures, i.e. improving rail gauge face lubrication and employing the LM-30 wheel profile, were verified through field tests.

Intramuscular connective tissue content and mechanical properties: Influence of aging and physical activity in mice.

Aging is accompanied by morphological and mechanical changes to the intramuscular connective tissue (IMCT) of skeletal muscles, but whether physical exercise can influence these changes is debated. We investigated the effects of aging and exercise with high or low resistance on composition and mechanical properties of the IMCT, including direct measurements on isolated IMCT which has rarely been reported. Middle-aged (11months, n=24) and old (22months, n=18) C57BL/6 mice completed either high (HR) or low (LR) resistance voluntary wheel running or were sedentary (SED) for 10weeks. Passive mechanical properties of the intact soleus and plantaris muscles and the isolated IMCT of the plantaris muscle were measured in vitro. IMCT thickness was measured on picrosirius red stained cross sections of the gastrocnemius and soleus muscle and for the gastrocnemius hydroxyproline content was quantified biochemically and advanced glycation end-products (AGEs) estimated by fluorometry. Mechanical stiffness, IMCT content and total AGEs were all elevated with aging in agreement with previous findings but were largely unaffected by training. Conclusion: IMCT accumulated with aging with a proportional increase in mechanical stiffness, but even the relatively high exercise volume achieved with voluntary wheel-running with or without resistance did not significantly influence these changes.

Thin Wire Casting Using Twin Wheel Caster Equipped with Horizontal Wheels

solidification, process shortening and energy saving. A twin-wheel caster equipped with two additional horizontal wheels was proposed to cast thin aluminum alloy wire at higher speed. In the proposed twin-wheel caster, a groove was machined on the lower wheel. Two small horizontal wheels were positioned between the molten-metal-pouring launder and the upper wheel to assist the solidification of poured molten metal and to prevent burr formation. The alignment of the horizontal wheel sensitively affected the occurrence of wire defects. An Al-1.2%Fe wire with a cross section of 6.2 mm2 was cast at 15 m/min. Thinner wires without burring could be cast at a speed higher than that of the twin-wheel caster without the horizontal wheels. The surface condition of the as-cast wire cast by the twin-wheel caster equipped with horizontal wheels was worse than that of the casting using the twin-wheel caster without horizontal wheels.

Development of Digital Tractive Transducer

Construction equipment, agricultural tractors and cross-country vehicles can only perform their given tasks when tyre matches the vehicle design, the vehicle weight and the ground on which they operate. This Research involves the design and fabrication of a digital tractive transducer to measure the effects of press wheel vertical force on the germination rate of grain crops. Design criteria, calculations and analysis of various components of the transducer were critically carried out, and then used to design, fabricate and assemble the digital tractive transducer. The effect of press wheel vertical force on seed germination showed that the crops germinated well at low press wheel loads, while high press wheel loads adversely affected the percentage germination of the crops. Maize and soybean had increasing percentage germination trends between no load and 60 N load, where any press wheel load of more than 60 N greatly affected their germination rates. For cowpea, it is better planted with no additional loads on the press wheel because the highest percentage germination was recorded at no load.

Wheel Arrangement of Four Omni Wheel Mobile Robot for Compactness

Compact omnidirectional mobile robots are required to automate transportation of raw materials, products, etc. within an industrial plant. This paper focuses on omni wheel robots with low vibration and wheel arrangements that contribute to compactness. Due to its wheels’ configuration, our proposed compact robot may have different sensitivity to noise (controller) and different performance (errors) when following a predetermined path, compared to conventional ones. Using a simple DC motor, a robot with the proposed arrangement and a conventional robot run along a predetermined path. A linear–quadratic regulator that is processed lightly is used to control the robots for practicality. As a result, the robot’s trajectory in the proposed arrangement showed a distortion different from that of the conventional type. The distortion of the trajectory was attributed to the inability of the DC motor to rotate stably at low speed. The different distortions exhibited suggest that the wheel arrangement changes the effect of imperfect control on the robot’s motion. In addition, the proposed arrangement showed the possibility of being suitable for a transport robot because the wheels are placed in the four corners of the robot, facing forward, backward, left, and right.

A simulation investigation on the effect of wheel-polygonal wear on dynamic vibration characteristics of the axle-box system

With the increasing speed of high-speed trains and the deteriorating operation environment of axle-box system, the dynamic performance of axle-box bearing directly affects the stability and safety of operation. In this paper, a bearing-vehicle-track coupling dynamic model is established, and its effectiveness is verified by field tests. The simulation results of the coupling dynamic model including wheel-polygonal wear show that the effect of high order polygonal wheel wear (17th ∼ 21st order) on the axle-box system is greater than that of low order wheel wear (1st ∼ 5th order). The frequency domain of axle-box vertical vibration acceleration excited by high order wheel-polygonal wear is mainly distributed in 400 ∼ 600 Hz. The low order polygonal wheel wear amplitude has little effect on the bearing roller-outer raceway contact load. When the wear amplitude of 20th order polygonal wheel is 0.06 mm, the roller-outer raceway contact load is 27.22% higher than that when the wear amplitude is 0.04 mm. In order to avoid bearing failure caused by excessive bearing roller-raceway contact force, the amplitude of 20th order polygonal wheel wear should reduce to less than 0.04 mm.

Shifting Process Optimization of Dedicated Hybrid Transmission

The shifting process of a hybrid electric vehicle (HEV) could be implemented by a motor to simplify the control requirement when the clutch is engaged. In order to reduce the vehicle jerk and simplify the clutch control requirement during the shifting process, this paper introduces a 3-speed dedicated hybrid transmission (3DHT) with P1/P3 configuration and a power shift control strategy. A finite-time linear quadratic regulator (LQR) is proposed to smoothly transfer torque and suppress driveline oscillations during the torque transfer process with a maximum jerk of 5.6 m/s³. Since the clutch stays engaged, a predictive sliding mode control (SMC) is proposed to track the speed of the sleeve quickly and precisely during the synchronization process, which takes 0.18s and maintains a speed difference of around 1 rpm. Furthermore, a Kalman Filter is utilized to overcome the difficulties associated with side shaft torque measurement and low wheel speed resolution. A simulation is performed in MATLAB/SIMULINK, and the powershift (2nd -> 3rd) is compared with other methods. The comparison indicates that the proposed power shift strategy can reduce the maximum jerk from 14.8 m/s3 to 5.6 m/s3, while the entire shifting process lasts for 0.71s. Therefore, the proposed power shift control strategy effectively improves the shift quality.

Casting of Wire Using a Twin Wheel Caster

A twin-wheel caster for casting thin aluminum alloy wire was designed, assembled, and tested. Molten metal was ejected from the nozzle (cross-sectional area: 4 mm2) of a crucible into a triangular groove that was machined on the outer surface of the lower wheel. The metal was solidified by the upper and lower wheels. Wire made of Al-1.2%Fe or 6061 aluminum alloy, whose cross-sectional area was smaller than 20 mm2, could be cast at a speed of 6 or 7 m/min. The upper and lower wheels were made of copper to increase the cooling rate. The diameter of the upper and lower wheels was 200 and 600 mm, respectively. The thickness of the wheels was 10 mm.

Casting of Thin Aluminum Alloy Rod Using Twin Wheel Caster Equipped with Rotating Side Dam Plates

A thin aluminum rod (width: 5 mm) was cast using a twin-wheel caster equipped with rotating side-dam plates. The upper and lower casting wheels were made of copper. The width of the flat upper and lower casting wheels was 5 mm. The rotating side-dam plate was made of mild steel. Paper 0.5 mm thick was pasted onto the plate. Boron nitride was sprayed onto the paper as an insulator and lubricant. A 6061 aluminum alloy thin rod could be cast continuously at casting speeds of 4 and 5 m/min. Molten metal was poured onto the lower wheel from a launder and conveyed into a square gap made by the lower wheel, upper wheel, and side-dam plates. The cross section of the cast rod was rectangular. The cross-sectional area of the rectangular rod was 12 to 15 mm2.

Analysis of cutting forces during grinding of titanium alloy and corrosion-resistant steel by diamond, electrocorundum and cubic borine nitrid wheels

The object of research is the process of circular and surface grinding of titanium alloy and corrosion-resistant steel, namely, the cutting forces arising from mechanical processing. One of the most problematic areas in work is the selection of the required grinding modes, material and grinding wheel grain size. In the course of the experiment, we used samples of VT8 titanium alloy and 12Х18N9T steel, on which the grinding process was studied with wheels made of various materials (electrocorundum, cubic boron nitride (CBN), diamond). The values of the cutting forces Py and Pz were obtained in the latitude of permissible modes, which are most often used in circular and flat grinding, and can reach maximum values, respectively, Py=27 N, Pz=15.5 N. The data were obtained at a low wheel speed from electrocorundum, about 15 m/s and grain size 8. By reducing the grain size of the wheel, we get the effect of increasing the energy consumption of the grinding process, due to the increase in the values of the cutting forces. If we compare the cutting forces arising from grinding with different wheels, then the following can be noted. Compared to electrocorundum wheels, when using CBN wheels, the cutting forces are reduced by 20–25 %, and when grinding with diamond wheels (despite the high wear of the diamond wheel), the effect of cutting forces is reduced by 25–30 %. This is due to the fact that cutting conditions are the most favorable for diamond and CBN grains, which makes it possible to use more intense cutting conditions. The results of the study allow predicting the performance of the grinding wheel, reducing the energy consumption of production, and also adjusting the processing mode of the part to obtain the necessary quality indicators of the surface layer and the geometric dimensions of the part.

Multi-objective optimization of high-speed train suspension parameters for improving hunting stability

ABSTRACT Excellent hunting stability is required for the operation of high-speed trains. The suspension parameter design needs to avoid primary and secondary hunting instability for the low and high wheel–rail contact conicity, respectively, as well as to enhance the robustness of hunting stability in face of the variations in wheel–rail contact parameters. In this paper, the indices of low equivalent conicity stability, high conicity stability, and equivalent conicity robustness are defined and chosen as the optimization objectives for the optimal design of key suspension parameters. The multi-objective optimization method is used, and the obtained Pareto set can guide the matching laws of suspension parameters. Four groups of typical parameter sets are selected, and their stability characteristics, such as speed robustness and equivalent conicity robustness, are analysed in detail, followed by the selection of equivalent conicity and motor flexible suspension parameters. Two parameter design modes for the hunting stability can be reflected.

Feasibility study of creep feed grinding of 300M steel with zirconium corundum wheel

The ultrahigh strength 300M steel has been commonly used in the manufacture of aircraft landing gear and rotor shaft parts due to its excellent mechanical properties. Creep feed grinding is one of the essential operations during the whole component manufacturing processes. In this work, the feasibility of creep feed grinding of 300M steel by using the hard zirconium corundum wheel was theoretically and experimentally evaluated. A variety of responses including grinding forces, temperature fields, specific grinding energy, surface integrity and chip modes were carefully recorded. Besides, the mechanism of ground surface profile generation and the spatial frequency spectrum of the surface profile were tentatively analyzed. It was found that the wheel speed has a relative influence on the grinding forces and temperatures of which the work hardening effect dominates the material removal with lower wheel speed while the thermal softening becomes crucial as the wheel speed exceeds the critical value for the studied 300M steel. Furthermore, a scattered spatial frequency spectrum for the generated surface profile was noticed with lower wheel speed while the spectrum gathers towards the lower frequency values with higher amplitude as the wheel speed increases. The shearing chip and flowing chip dominates the main chip type, indicating the excellent abrasive sharpness during the grinding process. In general, the used zirconium corundum wheel presents feasibility for the creep feed grinding of 300M steel because of the high material removal rate, absence of surface burn, low wheel wear and higher compressive residual stresses.

Casting of Aluminum Alloy Strand Using Two- and Three-Wheel Caster

Casting of a thin aluminum alloy strand was investigated using two-and three-wheel casters. Molten metal was poured through a launder into a trapezoidal groove in the lower wheel of the caster. In the two-wheel caster, the level of molten metal was lower than the height of the walls of the lower wheel groove, and a puddle was formed between the lower and upper wheels. As a result, it was possible to cast the strand without the formation of burrs. In the three-wheel caster, the level of molten metal was higher than the height of the walls of the lower wheel groove by effect of surface tension. However, with the use of a grooved first upper wheel, the molten metal became semisolid, and it was possible to cast the strand without burrs as this semisolid metal passed under the second upper wheel.