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Tribometer used for the sliding wear experiments. (a) Schematic of the tribometer. 1, DC motor; 2, driving belt; 3, gearbox; 4, torque sensor; 5, rotational velocity sensor; 6, lower ring; 7, upper block; 8, control cabinet; 9, computer; 10, load sensor; 11, compression spring. (b) Configuration and dimension of the wheel ring and rail block (unit: mm).
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Rail grinding and wheel turning can effectively remove surface defects and unevenness, which is a crucial process for the safe and smooth operation of trains. Machined surface integrity of wheel/rail materials significantly influences their tribological property. In this study, firstly, the rail blocks were ground via a cylindrical grinding machine...
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Citations
... The repair of worn metallic parts is a convenient way to extend the life of resource-intensive and critical mechanical components, such as the wheels used in train bogies. Typically, subtractive methods are used to recondition damaged parts [1]. However, the main drawback of these methods is the limited number of refurbishments before parts need to be discarded. ...
Large temperature gradients inherent to additive manufacturing (AM) processes induce large residual stress (RS) in the final part. Because RS can influence the tribological properties, this study focuses on the relationship between wear sliding properties and RS in IN718 coatings. Such coatings were deposited with a Laser metal deposition (LMD) machine using two different scanning strategies. The wear resistance and RS state were investigated after surface milling. RS were measured before and after wear tests on a reciprocating sliding test apparatus. Two different X-ray diffraction techniques were employed to measure the surface and subsurface state RS: Laboratory Energy Dispersive X-ray Diffraction (LEDXD) and Synchrotron X-ray Energy Dispersive Diffraction (SXEDD). Due to the milling process, the coatings show similar depth distributions of RS from 22 to 92 µm depth, but exhibit different magnitudes depending on the scanning strategy used. Reciprocating sliding wear tests induced high compressive residual stresses that erased the initial RS state, and a similar wear behavior was observed in the two samples. These samples possess similar texture and grain morphology. This demonstrates that the influence of RS on wear resistance is a second-order effect. Nevertheless, it was observed that RS can still impact the wear performance at the early testing stages of the repaired parts.
Graphical Abstract
... Liu et al. [19] provide another example of wheel-rail interaction. An experiment on the wear and damage behaviors of machined wheel/rail materials under dry rolling-sliding conditions is carried out using twin-disc wear testing equipment. ...
The current study aims to define a welding technology that allows for the repair of normal and heat-treated rails in paved tracks with partial dismantling and partial preheating in such a way that the resulting layer is not susceptible to cracking and can be done with minimal dismantling, even during night shifts or while traffic is present. High-elongation austenitic consumables (capable of approximately 2-3 times greater elongation than rails; rails have approximately 8-14% elongation) were used and tested for this purpose. Welds and rail tread defects were repaired on Hungary's busiest tram line (12-14 million gross tons per year), which also has a high axle load compared to other European tram lines. The repairs were performed on various rail grades using different layer numbers, and the experimental consumables were compared to conventional hardfacing welding methods. Welds were continuously monitored after welding, and surface hardness measurements were taken. A hardening function and an applicable technology were defined based on the results. The function compares the through-rolled axle tons to the expected hardness values over the first 6 million tons. Partial preheating and partial track disassembly can be used to weld a layer of hardness equal to the hardness of the rails and wheels.
... However, a lathe was used for the RFW in the current work. To reduce experimental error, the computer numerical control turning machine [42][43][44][45] was recommended to perform the RFW because the feed rate of RFW can be controlled precisely. In addition, the rotational speed [46] can be changed during the process of RFW. ...
Understanding the fatigue behaviors of weld joints is significant in engineering practice. Rotary friction welding (RFW) can join the additively manufactured polymer components. Until now, no research has focused on the fatigue behavior of polymer components jointed via RFW. This study investigates the fatigue life of ABS/PC dissimilar components fabricated via RFW and proposes the fatigue mechanism based on the failure structure. This work uses five different cyclic loads and rotational speeds to investigate the fatigue life. The fatigue life of the RFW of ABS/PC dissimilar rods is better compared with the pure ABS and pure PC specimens due to weld and integrity microstructural changes resulting from the combination of ABS and PC materials. The number of cycles until the rupture of RFW of ABS/PC dissimilar components (y) can be determined by the cyclic load (x) according to the prediction equation of y = −838.25x² − 2035.8x + 67,262. The fatigue life of the RFW of ABS/PC dissimilar components increase with the increased rotational speed. The number of cycles until rupture (y) can be determined by the different rotational speeds (x) according to the prediction equation of y = 315.21x² + 2710.4x + 32,124.
... Zhang et al. [15] established a three-dimensional finite element model of rail grinding and explored the effects of grinding passes and grinding direction on the material removal behavior of grinding rails during the grinding process. Liu et al. [16] investigated the wear and damage characteristics of the machined wheel/rail materials under dry sliding conditions by virtue of a block-on-ring tribometer. The surface damage morphologies between the rail blocks and the wheel rings after sliding are different; the surface damage of rail blocks is more serious. ...
... The rail volumes of steel grinded by grinding wheels with no included angle and included angle on the end face are Equations (16) and (17). 17) where N d is the dynamically effective cutting edge number of the grinding wheel. ...
The peripheral surface of the grinding wheel can grind the rail according to the envelope of the contour of the rail surface, thus a fuller and smoother rail surface can be obtained. Specifically, a better grinding effect can be obtained in that the end face of the grinding wheel deviates from the longitudinal section of the rail at a certain angle. Based on the traditional grinding technology theory, the mathematical models of the peripheral grinding parameters (kinematic contact arc length, wheel-rail grinding contact area, and maximum undeformed chip thickness) and the grinding force are established, in which the angle exists between the grinding wheel end face and the rail longitudinal section. The main influence of grinding wheel circumferential speed, grinding wheel kinematic speed, and the deflection angle of the grinding wheel end face on the grinding parameters and the force are analyzed. The result shows that: when there is angle θ in the models, the ratios of peripheral grinding parameters between up-grinding and down-grinding varies monotonically with the increase in vm, and their maximum variation range is about 12%, vs has the greatest influence on the peripheral grinding parameters, and the maximum variation range of the ratios is about 20% when the vs is 10 m/s. With the increase in the grinding width, Fa’ cannot be ignored and will increase gradually with the increase in angle θ. The analysis and conclusion have guiding significance for the structural design, grinding control strategy, and experimental research regarding rail curved surface grinding equipment.
... Bensaid et al. [41] found that the Hardox 500 ground surface with high compressive residual stress had a high wear resistance ability. Liu et al. [42] reported that the surface with proper initial surface roughness and microhardness could engender the smallest amount of total wear loss. Bertolini et al. [43] used the ultrasonic vibration turning process to fabricate the textured surface on TI6Al4V cylinders to improve their wear performance. ...
... Many types of research have proved that surface hardness has an essential impact on wear performance [42,[50][51][52]. In 1953, Archard [53] found a correlation between wear performance and hardness. ...
... The main factors affecting the wear performance by conventional mechanical machining [42,[56][57][58][59] the results showed that, when the feed rate varied from 0.14 to 0.22 mm/rev, the microhardness of linear ultrasonic vibration-assisted face-turning (LVT) surface was increased from 136.2 to 179 HV, and the average COF was decreased from 0.52 to 0.49. This indicated that the increased feed rate increased surface hardness and further changed the frictional property. ...
The mechanical friction leads to a large amount of energy consumption every year. To decrease the friction and wear and prolong the service life of the working components are therefore significant for energy sustainable development. To this end, many researchers investigate how to improve the tribological and wear resistance of the components by mechanical machining. The current article reviews the influence of common mechanical processes (i.e., grinding, turning, and milling) on the wear performance of machined surfaces in terms of hardness, surface morphology, and residual stresses. The strengthening mechanism of machined surface in the wear performance can be attributed to (i) the high hardness that improves the wear performance by preventing the insertion of wear particles on the friction surface; (ii) the induced surface texture that improves the wear resistance by storing the lubricating oil and wear debris for alleviating the subsequent friction; and (iii) the high compressive residual stress that mitigates the surface worn by preventing the formation and propagation of crack defects. In order to service under different conditions, it indicates that the control of hardness, texture, and residual stress by optimizing the process parameter could improve the wear performance of the machined surface. This review can deepen the understanding of the enhancement mechanism of wear resistance of the mechanically machined surfaces to obtain the better performance of components.
Purpose. Substantiation of the mechanism of damage formation on the rolling surface of railway wheels by different strength levels to determine optimal structural state of the carbon steel. Methodology. The material for study was steel from rim fragments of the railway wheels with a carbon concentration of 0.61 and 0.69 % and other chemical elements within the range of the grade composition. Samples for mechanical tests were subjected to thermal hardening to obtain different structural states. The microstructure was examined under light and electron microscopes, using quantitative metallography techniques. Metal wear was determined under dry friction conditions, with different degrees of slippage, on a machine of the SMC-2 type. Hardness was estimated by the Rockwell method, and micro hardness of structural components – on a PMT-3 micro hardness tester. Findings. Based on the analysis of the wheel-rail interaction, it was determined that resulting inhomogeneity at distribution of plastic deformation and heating temperature in the plane of the contact surface are due to the development of slippage processes. Heating the metal to temperatures higher than onset of phase transformations and subsequent accelerated cooling determine the mechanism of structural transformations. The difference between adjacent sections of the rolling surface with different structural states and corresponding level of strength determines conditions for the formation of a fracture center of the railway wheel during operation. Originality. Heating the metal to temperatures above onset of phase transformations from the wheel sliding along rail and subsequent forced cooling is the cause of formation of gradient of the structures from pearlite to martensitic-bainite. The cyclic nature of the change in the structural state of the metal from simultaneous influence elevated temperatures, high plastic deformations and phase transformations corresponds to the development of low-cycle fatigue processes. Plastic deformation of the rolling surface area with martensitic or bainite structures is accompanied by softening, and with pearlite structures – by a hardening process. Practical value. The obtained results of the development of phase transformations in carbon steel on rolling surface will be useful in determining optimal structural state of the railway wheels of different strength levels.
The rail steel properties are adversely affected by rigid non-metallic inclusions, containing aluminum oxides. Therefore, aluminum content is limited to 0.004 % wt. in rail steel grades. Aluminum can get into steel from charge materials and refractory lining. In this work, we’ve analyzed how the chemical composition of refractories used in rail steel making influence steel quality on example of one domestic enterprise. To determine the main types of non-metallic inclusions created in E76F rail steels, we have performed fractional gas analysis of the samples taken in various process steps. It was found that the slag composition after degassing changes insignificantly, while the most part of non-metallic inclusions in rail steel is represented by aluminates.
The purpose of the work was to examine the reasons for formation of non-deformable non-metallic inclusions in rail steel and ways to reduce the rejection of finished rails due to the defects revealed during ultrasonic testing. The study was conducted at the steelmaking plant of JSC “Ural Steel”. In the central laboratory of the combine, a chemical analysis of non-metallic inclusions was carried out in the samples of finished rails produced from blanks manufactured by JSC “Ural Steel” and rejected at the ultrasonic test unit during the rail production at the “Aktobe Rail and Section Works” LLP. Non-metallic inclusions by their composition are represented by aluminium oxides. The most probable reasons for their formation have been determined as following: the use of aluminium containing ferroalloys and interaction of the melt components with refractory materials and casting powder. The authors made analysis of the ferroalloys used in production of rail steel. Industrial trials of the manufacturing process of continuously cast blanks from rail steel were carried out, where FS65 ferrosilicon, which contains aluminium, was replaced with silicon carbide. An increasing degree of silicon and carbon recovery in trial heats was noted. Evaluation of contamination with non-metallic inclusions and mechanical properties of the rail steel manufactured using the experimental technology showed that the service characteristics of the rail steel meet requirements of the state standard GOST R 51685 – 2013. The full-scale experiment has confirmed that the technology of alloying E76F rail steel with silicon carbide at JSC “Ural Steel” is technically feasible. The yield of 100-meter rails was increased by 17 % on a trial batch produced from JSC “Ural Steel” continuously cast blanks.
