Wheel Surface Research Articles

Development and validation of a wear prediction model for railway applications including track flexibility

The simultaneous prediction of wheel surface wear is one of the most challenging tasks in the railway field, which requires the knowledge of vehicle–track dynamics, rolling contact mechanics, and other tribological phenomena. In this paper, a new model for predicting wheel profile wear is presented to study in detail the characteristics of wear in the railway. The model is able to consider the effect of track flexibility on wheel wear evolution. The proposed modelling approach includes a vehicle–track coupled model for vehicle dynamical simulation, the local contact model for wheel–rail interaction, and an energetic approach for surface wear evaluation. The whole model has been validated by the comparison with experimental data coming from Chinese high-speed railway lines. The results show that the new model assures high computational efficiency as well as reaches a good prediction accuracy. The proposed model allows the investigation of the role played by different track parameters related to track flexibility on the wheel and rail wear evolution. The influence of the fastener and railpad stiffness on the wheel wear evolution is presented, using the proposed model.

Roughness evolution of wheel surface in a simulated wheel–rail contact

ABSTRACT The influence of the initial surface roughness on the wheel–rail contact has been a concern for railway systems especially since the introduction of rail grinding and wheel reprofiling as maintenance strategies. Currently, there are no universally accepted procedures for surface finishing of rails and wheels, so there is a need to keep studying the role of surface topography in reducing the maintenance costs and improving the wheel–rail system’s performance. This work studies the evolution of roughness of wheel samples during twin-disc tests performed to simulate wheel–rail contact up to 2.2 × 105 cycles under two different lubrication conditions. The results showed that under dry conditions the surfaces with larger kurtosis at the beginning of the tests had a better response to rolling contact fatigue. Under lubricated conditions, however, the effect of the initial roughness was less significant.

Bridge identification and damage detection using contact point response difference of moving vehicle

This paper presents the use of a moving vehicle to identify the bridge mode shapes and detect possible damage in the presence of bridge surface roughness. The method utilises the contact point responses at the contact between the wheel and bridge surface, which can be obtained from the vehicle responses and has a direct relation with the bridge responses and surface roughness. A double-pass mass-addition technique is proposed to obtain the contact point response difference using a test vehicle installed with sensors. Then the bridge frequencies can be identified from its spectrum, while the mode shapes can be further obtained by signal filtering and Hilbert transform. Simulation results show that the adverse effect of surface roughness on the contact point acceleration difference is largely reduced. The first three frequencies and mode shapes can be extracted with satisfactory accuracy. Multiple damage locations can be identified by performing wavelet transform on the contact point displacement difference and applying coordinate modal assurance criterion to the mode shapes constructed. The factors that may affect the performance of the proposed method are also investigated, including the distribution of added mass, measurement noise, speed of the test vehicle and co-existing traffic. Experimental validation is conducted on a simply supported aluminium channel beam with artificial roughness carrying a moving model vehicle. The results show that the proposed methodology for bridge identification works in the presence of road surface roughness.

On the resonance sound generated in a vehicle cabin moving at low speed due to breaking force

To improve the comfortability in a vehicle cabin, unwanted noise which is recognized as an allophone generated from automobile wheels was experimentally studied to investigate its generation mechanism and to develop its reduction countermeasures. In this experiment, simultaneous measurements of sound pressure and vibrational acceleration of the wheel surface were performed. Then, frequency analysis, vibrational modal analysis and operational transfer path analysis were performed by using measured data. The results show that this kind of noise started in a low frequency first and then became higher. Furthermore, the high-frequency noise was mainly generated by vibrational acceleration at its center and near the rim when the wheel spoke gets close to the brake caliper. The high-frequency noise is around 250Hz, 750Hz, 1000Hz and 1250Hz, and the wheel spoke easily gets vibration and resonance mainly from around 750Hz and 1000Hz. Vibration at 750Hz occurs on the side of the wheel spoke in the rotation direction, while vibration at 1000Hz occurs at the midpoint of the wheel spoke. The closer to the brake caliper, louder noise was generated at the wheel spoke.

Nanostructured grinding wheels for ultra-precision engineering applications

Manufacturers face challenges when dealing with abrasives that lose roundness, wear excessively, and suffer from pitting of the surface of the grinding wheel that needs rectification using dressing techniques. Nanostructured abrasive grits manufactured by hybrid fusion processes and by sintering/extrusion/printing processes are found to reduce pitting quite significantly. The phenomenon of wheel collapse is increasing and cycle times developed during the grinding of aerospace alloys are much smaller compared to using conventional materials. This paper reviews the phenomenon of wheel collapse induced by pitting and takes a critical look at the production and analysis of hybrid fused and printed/sintered abrasives. A mathematical analysis is carried out of the diffusion of primary and secondary phases due to mechanical and ultrasonic agitation with the aim of producing abrasive grits with improved strength and retention. Current developments in extruded, printed, and sintered grits for use in precision grinding applications are critically reviewed. The paper concludes by explaining how such abrasives are used in practice by industrial manufacturers of high-precision products.

Mathematical Modeling of Process Optimization in Profiling Grinding Wheels via Laser

In this work, the experimental research was carried out on the processing of the cutting surface of a grinding wheel with a ceramic bond via continuous laser radiation with a wavelength of 10.6 μm. The influence of laser radiation power, processing speed on the depth and width of the obtained cut was investigated. A full factorial experiment was carried out with varying factors at two levels. In the form of a regression equation, a mathematical model of the effect of radiation power and processing speed on the output parameters of the process is obtained. Using Fisher's criterion, it is shown that the resulting equation adequately describes the process under the study. The analysis of the regression equation makes it possible to assess the relative influence of each factor and the effects of the interaction of factors on the depth and width of the cut on the surfaces of the grinding wheel.

The mechanisms of high-efficiency grinding for micro/meso-structural arrays on ceramic moulds through an innovative wheel truing technology

The precision fabrication of ceramic moulds for the mass-production of micro/meso-structural arrays places a tremendous challenge to the manufacturing industry. This work aims to reveal the physics behind the processes so as to address this technological challenge. A new method for texturing the diamond grinding wheel surface with a micro-abrasive waterjet is proposed for highly efficient form-grinding of ceramic moulds into the required micro/meso-structural surfaces. It shows that this technology provides some unique advantages in improving the sharpness and geometrical accuracy of the grinding wheels. The mechanisms about material removal and texture formation in grinding wheel truing are investigated to enable the precise control of micro/meso-structure generation on the grinding wheel. A theoretical model is established to study the effect of grinding wheel surface micro/meso-textures and grain trajectory on the quality of the ground mould surface and reveal the reflection mechanism of the ground marks on the mould surface. Furthermore, an integrated rough-fine grinding strategy is proposed which is shown to significantly increase the grinding efficiency by 15–24 times. It is found that ductile domain grinding of ceramic moulds to achieve the required contour profile of 6.7 μm PV accuracy and a surface roughness Ra of less than 40 nm can be achieved.

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel, workpiece characteristics, and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.

INFLUENCE OF THE GEOMETRIC CHARACTERISTICS OF THE DISCONTINUOUS PROFILE WORKING SURFACES OF ABRASIVE WHEELS FOR PRECISION AND TEMPERATURE WHEN GRINDING

Grinding is the most common finishing method for hardened steel parts. Grinding is accompanied by a large heat release in the cutting area, under the influence of which structural changes appear in the thin surface of the processed parts, tensile stress and even microcracks, which significantly reduce the operational reliability of machines that include these parts. The use of abrasive wheels with an intermittent working surface makes it possible to reduce the temperature in the area of contact of abrasive grains with the material of the workpiece and, as a consequence, stabilize the quality of the surface layer of the workpieces. High-frequency vibrations in the elastic system of the machine, accompanying the work of an intermittent wheel, are a positive factor that reduces the energy consumption of the grinding process. However, under certain conditions of dynamic interaction of the tool with the workpiece, parametric resonance may occur, which worsens the geometric and physical-mechanical parameters of the quality of the surface layer of the processed part. The aim of the work is to realize the possibility of predicting the quality parameters of the surface layer of parts during intermittent grinding by studying the influence of the design features of the macrotopography of the working surface of abrasive wheels and processing modes on the nature of the dynamic interaction of the tool with the workpiece and the heat stress in the cutting area. It was found that the parametric vibrations of the elastic system of the machine tool can be shifted to a more stable area, due to an increase in the number of interruptions of the working surface of the abrasive wheel with a constant ratio of the length of the protrusions and depressions. The increase in the number of breaks on the wheel also contributes to a decrease in temperature in the cutting area. It was found that to maintain the stable operation of the elastic system of the machine, it is necessary to reduce the number of cavities on the grinding wheel with an increase in the cutting speed. However, both of these actions are accompanied by an increase in the heat stress of the grinding process. It has been experimentally established that for ordinary (pendulum) grinding, it is possible to achieve an increase in processing productivity by increasing the speed of the longitudinal movement of the table.

Grinding efficiency and profile accuracy of diamond grinding wheels dressed with wire electrical discharge conditioning (WEDC)

Super abrasive diamond grinding wheels are the most promising tools for the precision machining of advanced ceramics and carbide materials. However, the efficiency of conventional conditioning of these tools is limited owing to high dressing tool wear, long process time, low form flexibility, and induced damage to the abrasive grains. Wire electrical discharge machining (WEDM) is an alternative method for conditioning of superabrasive grinding wheels with electrically conductive bonding materials. In this study, cylindrical plunge grinding of an alumina ceramic with a resin-bonded diamond grinding wheel is investigated. The assigned type of resin bond contains copper particles and is accordingly electrically conductive for wire electrical discharge conditioning (WEDC). Conventional (mechanical) and WEDC methods are used for generating the same profile on two similar diamond grinding wheels. As a result, the specific grinding energy was reduced up to 26% and 29% during rough and finish plunge grinding, respectively. Reduced specific grinding energy and forces, along with more effective grain protrusion and sharpness by using WEDC for profiling of grinding wheels, have contributed positively to the ground surface conditions despite the relatively rougher wheel surface topography in comparison to the conventional profiling. The more considerable reduction in the mean roughness depth (Rz) than in the arithmetical mean roughness value (Ra) (11% smaller Rz values in WEDC versus mechanical conditioning) verifies that the workpiece surface underwent less surface degradation in case of WEDC because of smaller grinding forces. Furthermore, the profile wear behavior of the workpiece ground with the WED conditioned grinding wheel was superior to the conventionally conditioned one.

Discovery and Temperature Dependence of α-Fe2O3 in Oxide Film on Iron Bonded Wheel and Effect Mechanism of Temperature

Polishing of oxide film on ELID wheel surface has an important effect on grinding surface quality. First, electrochemical reaction of oxide film was researched, and transformation mechanism of component of oxide film under grinding temperature was proposed. The phase compositions, generation and transformation mechanism of the α-F2O3 in the oxide film was measured by XRD, XPS, FITR. The microstructure of oxide film was observed by using TEM. Researched results show, α-F2O3 in the oxide film have been found, the content and transformation of α-F2O3 are closely related to the grinding temperature. Iron oxide in oxide film is transformed into α-F2O3 with temperature gradually, and nano grain α-F2O3 with high purity, good crystal lattice, and grain size 10–80 nm is formed when grinding temperature is 600 °C. TEM analyzed shows, the grain in oxide film is spherality, and film structure is formed with multiple particles α-F2O3. The film structure reveals that polishing mechanism of oxide film isn’t independent act of single particle, but is cooperative behavior of multiple particles α-F2O3.

Вероятностная модель удаления поверхностного слоя при шлифовании хрупких неметаллических материалов

Introduction. The final quality of products is formed during finishing operations, which include the grinding process. It is known that when grinding brittle materials, the cost of grinding work increases significantly. It is possible to reduce the scatter of product quality indicators when grinding brittle materials, as well as to increase the reliability and efficiency of the operation, by choosing the optimal parameters of the technological system based on dynamic models of the process. However, to describe the regularities of the removal of particles of a brittle non-metallic material and the wear of the surface of the grinding wheel in the contact zone, the known models do not allow taking into account the peculiarities of the process in which micro-cutting and brittle chipping of the material are combined. Purpose of the work: to create a new probabilistic model for removing the surface layer when grinding brittle non-metallic materials. The task is to study the laws governing the removal of particles of brittle non-metallic material in the contact zone. In this work, the removal of material in the contact zone as a result of microcutting and brittle chipping is considered as a random event. The research methods are mathematical and physical simulation using the basic provisions of the theory of probability, the laws of distribution of random variables, as well as the theory of cutting and the theory of a deformable solid. Results and discussion. The developed mathematical models make it possible to trace the effect on material removal of the overlap of single cuts on each other when grinding holes in ceramic materials. The proposed dependences show the regularity of stock removal within the arc of contact of the grinding wheel with the workpiece. The considered features of the change in the probability of material removal upon contact of the treated surface with an abrasive tool and the proposed analytical dependences are valid for a wide range of grinding modes, wheel characteristics and a number of other technological factors. The obtained expressions make it possible to find the amount of material removal also for schemes of end, flat and circular external grinding, for which it is necessary to know the amount of removal increment due to brittle fracture during the development of microcracks in the surface layer. One of the ways to determine the magnitude of this increment is to simulate the crack formation process using a computer. The presented results confirm the prospects of the developed approach to simulate the processes of mechanical processing of brittle non-metallic materials.

Design of a wheeled wall climbing robot based on the performance of bio-inspired dry adhesive material

AbstractInspired by gecko’s adhesive feet, a wheeled wall climbing robot is designed in this paper with the synchronized gears and belt system acting as the wheels by considering both motion efficiency and adhesive capability. Adhesion of wheels is obtained by the bio-inspired adhesive material wrapping on the outer surface of wheels. A ducted fan mounted on the back of the robot supplies thrust force for the adhesive material to generate normal and shear adhesion force whilemoving on vertical surfaces. Experimental verification of robot climbing on vertical flat surface was carried out. The stability and the effect of structure design parameters were analyzed.

On the tool wear behavior during ultrasonic vibration-assisted form grinding with alumina wheels

Ultrasonic vibration-assisted form grinding (UVAFG) with alumina wheels has become a potential technology to machine the areo-engine blade root. In this work, the characterizations of wear patterns of grinding wheel surface morphologies, such as clogging, grain micro-fracture and pull-out, were performed under conventional form grinding (CFG) and UVAFG methods, respectively. In addition, the comparative grinding performances, including grinding forces and force ratio, protrusion height distribution of worn grains, ground surface quality for both grinding methods, were discussed. The results indicate that the tool clogging and grain pull-out under UVAFG method can be effectively improved compared to CFG method. More excellent sharpness ability of alumina wheels under UVAFG can be obtained due to the grain micro-fracture by high frequency impacting between tool and workpiece. Furthermore, the alumina wheels under UVAFG possess lower grinding forces, larger protrusion height values of worn grains, and better ground surface quality in comparison of the other grinding method.

Vibration and Derailment Analyses of Trains Moving on Curved and Cant Rails

A moving axle finite element (FE) was developed to study the contact between a wheel and curved rail, where the FE can simulate multi-point contact with sticking, sliding, and separation modes. The possible contact region is inputted as a number of nodes along the wheel and rail surfaces, while the wheel nodes are simulated as cubic-splines. The rail node to wheel cubic-splines contact method is then used to find the normal and shear forces, where the normal and tangential stiffness values obtained from the three-dimensional (3D) FE analysis for an actual wheel and rail are used to model the force–displacement relationship. A simple theoretical solution for curved railways was used to validate the proposed FE in 3D analyses. The results show that good agreement with the theoretical and FE solutions for the contact normal force, shear force, wheel sliding, and wheel separation under various train speeds, curve radius, cant angles, and friction coefficients. This FE can be used in combination with other elements to simulate a train traveling on a curved track system, in which only the standard Newton–Raphson and Newmark’s methods are required in the FE main program.

Development of technological equipment for restoration of rolled wheeled pairs of railway wagons

Introduction.The problem of the shortage of energy-efficient restoration technologies makes it a priority to develop new technological equipment for the restoration of the rolling surfaces of railway wheels using highly concentrated energy sources. Currently, in the practice of repair DPO, discarded non-bonded wheels are increasingly replaced with new ones, but their resource potential is high during the operation. This approach is not technically and economically feasible.Materials and methods.This article presents the results of the strength calculation of the main moments of forces and dynamic loads per wheel pair. The problem of repair equipment related to the lack of the independent mobile complexes that ensure prompt arrival at the work site and high quality restoration of the design geometry of the wheel surface is formulated.Results.To solve this problem, a mobile complex was designed and developed, which allows to restore the design geometry and modify the high physical and mechanical properties of the riding surface with optimal stresses in the phase structure of the wheel base.Discussion and conclusion.It is recommended to use the results of the research carried out for the design, creation and production of high-tech repair equipment.

Method for fault detection of aluminum oxide grinding wheel cutting surfaces using a piezoelectric diaphragm and digital signal processing techniques

A novel strategy to quantify evenness and prevent faults on the cutting surface of conventional aluminum oxide grinding wheels during the dressing operationwas proposed in this research work. The method is based on the use of low-cost piezoelectricdiaphragms and new signal processing parameters based on time-frequency and ratio of power metric.Dressing tests were performed on two structurally distinct aluminum oxide grinding wheels. An acoustic emission (AE) sensor was used as a reference for comparative purposes. Subsequently, AE and piezoelectric diaphragm signals were collected and processed through the proposed approach. The results obtained for both grinding wheels by the piezoelectric diaphragm reveal a strong correlation with those obtained by the AE sensor. This indicates that the piezoelectric diaphragm was as efficient as the AE sensor and can be used to monitor the dressing operation of conventional grinding wheels using the proposed method,thus contributing to optimize the grinding process.

Simulation to Microtopography Formation of CBN Active Abrasives on a Honing Wheel Surface

The microtopography of a honing wheel surface composed of active abrasive grains is the key factor affecting the honing characteristics, and control of it is a sufficient condition to realize high-efficiency precision honing. Based on the magnetron sputtering method and phase field method, a theoretical model of cubic boron nitride (CBN) coating formation on a honing wheel surface is established. The physical vapor deposition (PVD) discrete phase field equation is solved by the finite difference method. A MATLAB program is compiled to simulate the formation process and micromorphology of the CBN coating on the honing wheel surface. A Taguchi method is designed to study the relationships of the sputtering time, substrate temperature, gas flow rate, and reaction space with the number of active abrasives and the length, width, height, and size of the abrasives. The simulation results are highly similar to the scanning electron microscopy (SEM) examinations, which shows that the model can accurately and effectively simulate the abrasive morphology of the wheel surface under different process conditions and provide a theoretical basis for the prediction and control of the CBN wear morphology on a honing wheel surface.

Determining Surface Topography of a Dressed Grinding Wheel Using Bio-Inspired DNA-Based Computing

Grinding is commonly used for machining parts made of hard or brittle materials with the intent of ensuring a better surface finish. The material removal ability of a grinding wheel depends on whether the wheel surface is populated with a sufficiently high number of randomly distributed active abrasive grains. This condition is ensured by performing dressing operations at regular time intervals. The effectiveness of a dressing operation is determined by measuring the surface topography of the wheel (regions and their distributions on the grinding wheel work surface where the active abrasive grains reside). In many cases, image processing methods are employed to determine the surface topography. However, such procedures must be able to remove the regions where the abrasive grains do not reside while keeping, at the same time, the regions where the abrasive grains reside. Thus, special kinds of image processing techniques are needed to distinguish the non-grain regions from the grain regions, which requires a heavy computing load and long duration. As an alternative, in the framework of the “Biologicalisation in Manufacturing” paradigm, this study employs a bio-inspiration-based computing method known as DNA-based computing (DBC). It is shown that DBC can eliminate non-grain regions while keeping grain regions with significantly lower computational effort and time. On a surface of size 706.5 μm in the circumferential direction and 530 μm in the width direction, there are about 7000 potential regions where grains might reside, as the image processing results exhibit. After performing DBC, this number is reduced to about 300 (representing a realistic estimate). Thus, the outcomes of this study can help develop an intelligent image processing system to optimize dressing operations and thereby, grinding operations.

Experimental study on the wear and damage of wheel-rail steels under alternating temperature conditions

The objective of this study is to investigate the wear and rolling contact fatigue (RCF) damage of wheel and rail materials under alternating temperature conditions. Two series of rolling-sliding tests were performed: (1) at 20 °C for 75,000 cycles, and then continued at −40 °C for 10,000, 30,000, and 75,000 cycles, respectively; (2) at −40 °C for 75,000 cycles, and then continued at 20 °C for 10,000, 30,000, and 75,000 cycles, respectively. The results indicated that the decrease in the temperature would alleviate the wheel wear due to the formation of wear debris layer. Both the rising and dropping of the environmental temperature during the tests could lead to the increase in the rail wear. Besides, the decrease in the temperature could increase the plastic deformation and work hardening of wheel and rail discs. In addition, the crack initiation was correlated with the behaviour of plastic flow on the wheel. At 20 °C, long single cracks initiated and propagated along the highly deformed ferrite boundaries. At −40 °C, white-etching layer (WEL) was observed only on the wheel surface, which was mainly attributed to the severe plastic deformation. Then, the refined ferrites and WELs were the main crack initiation sources on the wheel.