Search

Fretting wear is a phenomenon occurring in many engineering objects, including push fit connections. In view of a large number of factors conducive to wear development, it is difficult to describe the mechanism of wear initiation and development. Therefore, various methods are sought to limit wear development. The use of a lubricant may be one of those ways. The aim of this article is to present the results of testing the influence of a lubricant medium on the development of fretting wear in interference fit connections. As a lubricant medium, MoS2 and Whitmore greases were used. For that purpose, wear tests were first conducted on the shaft/sleeve tribological kinematic pair, and then observations and laboratory measurements were performed. The observations demonstrated the presence of fretting wear traces on all tested samples, irrespective of the tribological kinematic pair being tested. The main kind of damage consisted of material build-ups which, during operation, become oxidised and, while moving along the connection, caused local abrasion and micropits. The best results in restricting the development of fretting wear were achieved with Whitmore grease. [ABSTRACT FROM AUTHOR]

Objective Based on the measured data of the train wheelsets on Shanghai Metro Line 17, the wheelset wear pattern is studied, and a wear model of wheel rim thickness and wheel diameter is established to improve the safety and maintenance efficiency of urban rail transit vehicles. Method The measured wheelset data are pre-processed to eliminate data errors. Curve fitting and error analysis method are used to establish the wear model of wheel rim thickness and wheel diameter. The fitting standard deviation of wear rate and that of the error value between the true value and the error fitting curve are used as evaluation indexes to evaluate the accuracy of the wear model. The wheelset wear model is verified with Train 1701 and Train 1721 respectively. Result & Conclusion Both the fitting standard deviation of 4th power fitting curve of wear rate for Train 1701 and Train 1721 wheelset rim thickness and wheel diameter, and that of 6th power fitting curve of the error value between the true value and the error fitting curve are close to zero, verifying that the vehicle wheelset wear model can accurately predict the wheelset wear of different types of trains and different vehicle positions of the same train on Shanghai Metro Line 17.

Copyright of Urban Mass Transit is the property of Urban Mass Transit Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fretting wear is a phenomenon occurring in many engineering objects, including push fit connections. In view of a large number of factors conducive to wear development, it is difficult to describe the mechanism of wear initiation and development. Therefore, various methods are sought to limit wear development. The use of a lubricant may be one of those ways. The aim of this article is to present the results of testing the influence of a lubricant medium on the development of fretting wear in interference fit connections. As a lubricant medium, MoS2 and Whitmore greases were used. For that purpose, wear tests were first conducted on the shaft/sleeve tribological kinematic pair, and then observations and laboratory measurements were performed. The observations demonstrated the presence of fretting wear traces on all tested samples, irrespective of the tribological kinematic pair being tested. The main kind of damage consisted of material build-ups which, during operation, become oxidised and, while moving along the connection, caused local abrasion and micropits. The best results in restricting the development of fretting wear were achieved with Whitmore grease.

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article considers the tasks associate with the study of dynamic processes of interaction between rolling stock and railways. Studies of the interaction of a wheel with a rail, fitting the vehicle into curves when modeling critical and emergency situations do not allow oversimplification of basic differential equations. And they should be based on exact nonlinear equations that take into account the entire set of geometric and kinematic relationships without simplification. An objective assessment dynamic characteristic of the vehicle can only be obtained by simultaneously taking into account both its vertical and horizontal irregularities. In order to determine boundaries of parametric resonance, article proposes method of generalized Hill's determinants, the application of which is possible without taking into account small parameters. [ABSTRACT FROM AUTHOR]

With increases in train speed and traffic density, polygonal wear of railway wheels arises accordingly, induced by the high impacts between wheels and rails, which is mainly related to operation safety and ride comfort of vehicle system. This work evaluates the effect of wheel polygon shape on the dynamic performance of the wheel set through numerical simulations. The finite element model, which includes the wheel set and the slab track, was established using ANSYS software to study the effects of polygonal wear on the dynamic behavior of the railway wheel. In the model, wheel–rail interaction forces caused by polygon wheel shape were solved using Universal Mechanisms of wear and were then entered into the finite element model. Using the simulation model, the influence of the harmonic order and out-of-roundness amplitude of wheel polygon on transient dynamic behaviors of the wheels namely, the displacement, acceleration, and von Misses equivalent stress were investigated. The results indicate that both the maximum dynamic displacement and Von Misses equivalent stress of the wheel plate show proportionality to the OOR amplitude, the harmonic order and the vehicle velocity. Besides, the maximum Von Misses equivalent stress occurs close to the wheel center, whereas the maximum displacement occurs close to the wheel tread. The findings will provide a theoretical basis for on-board detection methods of monitoring wheel polygonal wear.

Purpose. This research is aimed at improving the design of the stand for the comprehensive diagnosis of axle boxes with rolling bearings and the study of the performance of brake pads of freight cars. Methodology. The expediency and possibility of improvement of the stand for carrying out of complex diagnostics of subsystems of axle boxes with rolling bearings and brake pads of freight cars concerning revealing their working capacity by application of operational loadings is substantiated. As a methodological development of this scientific direction, from the point of view of researches of diagnosing objects efficiency on the stand wear of tribotechnical pairs - friction surfaces of pads and wheels at braking is investigated. To assess the results of wear, the traditional test method is used by pressing the indenter into the appropriate friction surfaces. Findings. Expanding the capabilities of the stand for diagnosing axle boxes of freight cars with the possibility of testing for different types of brake pads of cars was obtained. During researches on the stand real operational conditions of work of wheel pair at diagnostics of subsystems of axle boxes and brake pads are created. During the study, different modes of wheel load are applied, the required humidity is provided and blowing is carried out in the test area of the counter pairs friction, as well as the temperature arising on the surfaces of brake pads and wheels is registrated using a special device. Originality. The concept of improvement of the diagnostic stand for researches of axle boxes is theoretically proved and practically confirmed. For the first time with the help of an advanced stand, it is possible to study different types of brake pads of cars, to identify the phenomena of formation of different types of wear and provide recommendations for increasing their life. Practical value. The results of research conducted on an advanced stand can be used in the design and modernization of such subsystems of innovative freight cars as axle boxes with rolling bearings and brake pads. An application for an invention has been submitted for an improved stand for complex research.

This paper represents examples of damage and wear that may occur in the process of assembly of the joint and in the course of the operation. Fretting wear has been distinguished as an example of normal wear. Most of the article refers to that issue. The author has also proposed selected technological processes that could reduce wear progress. Shaft finishing method has been selected on the basis of the economic issues and the degree of process simplicity. Beside nitriding, surface hardening, finish rolling, the tests encompassed molybdenum- and PVD-coated shafts. Results analysis indicated that all proposed processes enable to reduce fretting wear progress, except for finish rolling. It is due to the fact that the major factor of fretting wear progress is adhesion. [ABSTRACT FROM AUTHOR]

The wear of vehicle elements during operation is a natural phenomenon. A dangerous situation occurs when elements more crucial than others wear unexpectedly. Such an element in rail vehicles is, for example, a wheel set. Its main task is to run the vehicle in the track, which directly influences the safety of the journey. Any premature or unexpected damage will lead to train derailing. Then hundreds of lives may be lost. The load on the wheel set from the vehicle weight and the oscillatory micro displacement of the wheel in relation to its axle during travel will be conducive to premature wear. Those conditions will cause the development of fretting wear, whose implication may be fatigue wear or the loosening of the wheel/axle joint. In this article, the results of fretting wear tests conducted in a shaft/sleeve forced-in joint are presented. The results of those tests, given that the relevant probability conditions are met, can be successfully compared to the real wheel/axle joint. The wheel set operation conditions, which will be conducive to the initiation of the development of fretting wear, have been discussed. Test results are presented in the photographs showing the axle seat with an area affected by wear. Both those places, and the place of contact between the connected surfaces, were subjected to micrographic examinations with a view to identifying damage comprised by fretting. Macrographic observations demonstrated fretting on either side of the shaft axle seat, which phenomenon comprises, for example, abrasive wear and adhesion. Visible are micro cracks and material build-ups, which became plastically deformed and oxidised.

The purpose of this article is to assess the influence of a ZrN coating on the development of fretting wear in a model of a wheel/axle push fit joint in a rail vehicle. The examinations of the fretting wear process in rail vehicle wheel sets were conducted on two groups of models consisting of a shaft and sleeve connected by means of a push-fit joint, in compliance with the rules for the representation of the real condition. Wear tests of a joint loaded with a vertical force were conducted on a fatigue testing machine permitting oscillatory tangential displacement, which is responsible for the development of fretting wear. Uncoated shafts were the first model, and shafts coated with a ZrN coating were the second one. The tolerance was 0.02 mm, the model loading force was 550 N and the number of fatigue cycles was 7 × 106. The destruction of models was evaluated in, for example, the computer image analysis process with the use of the Image Pro Plus 7.0 software. Macroscopic observations showed wear traces for both model groups. In the first group, wear traces were observed on either side of the axle seat, and those traces had the form of a 2–3 mm wide ring comprising the entire shaft circumference. The random location of the traces of wear was observed in the second model. The microscopic observations of the destruction areas demonstrated mainly the presence of material build-ups, the local surface abrasion and micropits. The analysis of the chemical composition of material build-ups showed the presence of iron and oxygen, a fact which confirms the shearing of the microirregularities of the sleeve top layer. Plastically deformed material build-ups become oxidised, hence the brown colour of the worn-out areas can be observed at the sample surface during macroscopic observations. The significant mitigation of fretting wear on samples with ZrN coatings has been demonstrated. This shows the need for fretting wear tests to be performed on a real object to confirm the scale of improvement of the life of forced-in joints, thus contributing to the higher reliability of rail vehicle wheel sets. [ABSTRACT FROM AUTHOR]

Purpose. When locomotives move in curved sections of the railway track, horizontal forces arise, which lead to pressing the ridge of the wheel pair to the railway track. The article is aimed to develop a method for determining the frame force acting on the bogie from the side of body of the locomotive section using the current methodology of calculating the lateral force. It is also aimed to determine the basic parameters that influence the value of the frame force. It is necessary to construct the dependencies of the frame force on the travel time of electric locomotive in the corresponding curve changing these parameters. Methodology. As is known, the electric locomotive is a multimass mechanical system. We will assume that this system consists of seven bodies: a body, two frames of carriages and four wheel sets. To determine the lateral force acting on the rail from the wheelset one need to solve differential equations of motion of locomotive bogie in curves of small radius. Using the equations of kinetostatics for wheelset one should come to determining the frame force acting on the car bogie from the side of body of the locomotive section. The nominal geometric and mass parameters of parts and components of electric locomotive are taken in the calculations. The curve radius, the length of transition curve, the length of circular curve, the longitudinal slope of railway track and other parameters are fixed values. Findings. There were obtained calculated values of the frame force of electric locomotive VL80 acting on the bogie from the side of body of the locomotive section. Based on the obtained results there were built the dependencies of frame force on the travel time of electric locomotive on the corresponding curve when changing the speed and corresponding elevation of the outer rail. Originality. On the basis of the existing methodology for calculating the lateral force it was developed the method for determining the frame force acting on the car bogie from the side of body of the locomotive section. Practical value. Improving the method for determining the frame force improves the accuracy of calculations when analyzing the traffic safety and when conducting the forensic rail-transport examinations.

Elements joined in the pressing process and operating in rotational bending conditions wear more easily than other elements, a fact which follows from the specific nature of their operation. In addition to the static load, there are also dynamic loads, and sometimes thermal ones. Rail vehicle wheel sets may be given as an example of such a joint. The purpose of the tests was to assess the possibilities of using TiSiN/TiAlN coatings to protect shafts against the development of fretting wear in forced-in joints operating in rotational bending conditions. In the case of uncoated shafts, the traces of wear are visible on either side of the shaft, as a 2–3 mm ring covering the entire circumference. In the case of shafts with a TiSiN/TiAlN coating, fretting wear did not occur. The first traces of wear at the shaft with a TiSiN/TiAlN coating are noted at 107 fatigue cycles. The microscopic observations in the wear zone indicated the presence of plastically deformed and oxidised material build-ups from the shearing of microirregularities on the surfaces of the elements being joined. The observations of the joint contact surface confirmed the presence of wear products, which came into being during the pressing, and also of the damage, particularly to the shaft hub top layer. The tests of the top layer topography demonstrated the decrease of the majority of the parameters after wear tests. Such a condition confirms that the shaft surface wears off and that there are wear products in the micropores in the coating. • The results of the influence of a TiSiN coating on the development of fretting wear in push fit joints are presented. • Fretting wear develops only after the number of fatigue cycles exceeds 107. • Fretting wear comprises the entire axle seat circumference and takes the form of a ring which is 1–1.5 mm wide. • The wear products undergo plastic deformation and oxidation. [ABSTRACT FROM AUTHOR]

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Press-fit joints should be durable and reliable, and this pertains in particular to joints operating in severe conditions or those directly influencing safety, such as rail vehicle wheel sets. Therefore, attempts to eliminate factors enhancing the development of wear should be made. The application of PVD coatings may be a way of improving joint durability. In this article, an assessment was undertaken of the possibility of the application of PVD coatings to mitigate the development of fretting wear in press-fit joints. Wear tests were conducted on the example of a sleeve/shaft connection operating in rotational bending conditions, and the negative allowance of 0.02 mm was taken. Test samples were divided into two groups. The first comprised samples without coating, and in the second a CrN+OX multi-layer coating was applied onto shafts. The analysis of fretting wear consisted in comparing wear images. Joint dimensions and operation conditions were chosen in such a way that operation conditions of rail vehicle wheel sets could be simulated. As part of laboratory tests, the macroscopic and microscopic observations of the shaft top layer wear and the microscopic observations of the sleeve/shaft joint surface were conducted. Macroscopic observations demonstrated the occurrence of fretting wear at shaft surfaces in both sample groups under testing, however, the range of wear occurring in samples with the CrN+OX coating was much smaller. The microscopic observations of shaft surfaces revealed a similar image of fretting in both sample groups under testing, such an image consisting of wear in the form of material build-up, microgaps, micropits and microcracks. The chemical analysis of wear products demonstrated their plastic deformation and oxidation. Scientific research indicates that adhesion is the process initiating the development of fretting wear; in these tests an attempt was made to eliminate adhesion. The application of the coatings under testing produced the expected result. The appropriate hardness of the shaft top layer with coatings caused the mitigation of adhesion thus significantly reducing the development of fretting wear. [ABSTRACT FROM AUTHOR]

Investigation of fretting in the wheel sets of railway vehicles on the real object is technologically difficult. Large dimensions, weight and complicated design prevent the creation of an appropriate position. An additional problem is the removal of the connection. Traditional pressing-out of the wheel from axle would cause distortion the image of occurring wear. It was proposed here to apply a model for press-fit wheel-axle, which consists of a shaft and the sleeve, followed by wear testing carried out on the fatigue machine, thus allowing a bending of the rotation shaft corresponding to operating conditions of the wheel set when travelling in a straight line. This raises the question whether the results of research carried out on the model can be transferred to a real object. The answer to this question we get by using the theory of similarity, the mathematical tool of which is the dimensional analysis. The aim of the study was to propose such technological processes in the finish of the surface layer of the shaft, which will limit the development of fretting wear and will not affect significantly the total cost of production of wheel sets. Thus, for purposes of research were chosen the rolls with nitrogenised and surface-hardened layer and rolls with the roll-polished surface. The results of wear tests showed that all proposed technologies of finishing the top layer limit the development of fretting wear. An important issue is now the possibility to refer the results of model tests to the actual wheel set. Dimensional analysis carried out in this article confirms such a possibility. [ABSTRACT FROM AUTHOR]

Purpose. To conduct a research and find out the causes of defects appearing on the wheel thread of freight locomotives 2М62 and SIEMENS ER20CF. Methodology. To find the ways to solve this problem comparing the locomotive designs and their operating conditions. Findings. After examining the nature of the wheel wear the main difference was found: in locomotives of the 2M62 line wears the wheel flange, and in the locomotives SIEMENS ER20CF – the tread surface. After installation on the 2M62 locomotive the lubrication system of flanges their wear rate significantly decreased. On the new freight locomotives SIEMENS ER20CF the flange lubrication systems of the wheel set have been already installed at the factory, however the wheel thread is wearing. As for locomotives 2M62, and on locomotives SIEMENS ER20CF most wear profile skating wheels of the first wheel set. On both locomotive lines the 2М62 and the SIEMENS ER20CF the tread profile of the first wheel set most of all is subject to the wear. After reaching the 170 000 km run, the tread surface of some wheels begins to crumble. There was a suspicion that the reason for crumb formation of the wheel surface may be insufficient or excessive wheel hardness or its chemical composition. In order to confirm or deny this suspicion the following studies were conducted: the examination of the rim surface, the study of the wheel metal hardness and the document analysis of the wheel production and their comparison with the results of wheel hardness measurement. Practical value. The technical condition of locomotives is one of the bases of safety and reliability of the rolling stock. The reduction of the wheel wear significantly reduces the operating costs of railway transport. After study completion it was found that there was no evidence to suggest that the ratio of the wheel-rail hardness could be the cause of the wheel surface crumbling.

Purpose. At present, the devastating impact of faulty wheels on rails on the move is a major problem of railway transport. This factor is one of the most important, which causes the shift from traditional manual methods of verification and external examination to the automated diagnostic system of rolling stock in operation. Methodology. To achieve this goal the main types of wheel damages and the way they appear are analyzed. The methods for defects and abnormalities of the wheel thread determining as well as their advantages and disadvantages were presented. Nowadays these methods are under usage in both the international practice and in the one of the CIS countries. Findings. The faulty wheel sound on the move was researched and analyzed. The necessity of using the automated system, enabling one to reduce significantly the human factor is substantiated. Originality. The method to determine the wheel thread damage on the basis of a sound diagnostic is proposed. Practical value. Automatic tracking system of the wheels condition allows performing their more qualitative diagnostics, detecting a fault at the early stage and forecasting the rate of its extension. Besides detecting the location of the faulty wheel in the rolling stock, it is also possible to trace the dynamics of the fault extension and to give the recommendations on how to eliminate it.

The paper presents some results of in-service tests on tram wheel set life. The measurements of wheel rim undercut and wear on the rolling diameter of tram wheel set wheels are a data base for calculating tram rolling wheel life in two aspects: wheel operation conditions and materials from which the wheels were made.

Train wheel sets must be periodically inspected for possible or actual premature failures and it is very significant to record the wear history for the full life of utilization of wheel sets. This means that an online measuring system could be of great benefit to overall process control. An online non-contact method for measuring a wheel set’s geometric parameters based on the opto-electronic measuring technique is presented in this paper. A charge coupled device (CCD) camera with a selected optical lens and a frame grabber was used to capture the image of the light profile of the wheel set illuminated by a linear laser. The analogue signals of the image were transformed into corresponding digital grey level values. The ‘mapping function method’ is used to transform an image pixel coordinate to a space coordinate. The images of wheel sets were captured when the train passed through the measuring system. The rim inside thickness and flange thickness were measured and analyzed. The spatial resolution of the whole image capturing system is about 0.33 mm. Theoretic and experimental results show that the online measurement system based on computer vision can meet wheel set measurement requirements.

The method of complex determination of locomotive weight and its dynamic effects on superstructure of railway track on the basis of automated measuring systems having no cargo platform devices is offered.

During manufacturing process the wheel set is subjected to many different flaw detection methods; however, these methods are not sufficient while the wheel set is in service. The paper presents an example of monitoring of magnetic parameters changes of wheel set rolling surface (changes result from material degradation due to materialfatigue).

The purpose of the work is to improve the structure of the resistance to movement, based on the formalization of its components related to the frictional interaction of the wheels and the rails and the vehicles directing by rail track. The formalized structure of the general resistance to movement of railway vehicles on the basis of clarifying the origin of its components associated with the direction of the vehicle by the rail track is presented in the article. The mechanism of the influence of dynamic processes frictional interaction of wheel sets and the rail track on the resistance to movement was developed. A new terminology for the resistance to movement associated with the vehicle directing by rail track was proposed. [ABSTRACT FROM AUTHOR]

Damage to the surface layer of press-fit elements may occur during installation and during operation. During operation, fretting wear can develop in press-fit joints, causing, among other, a reduction in the mounting pressure and a decrease in fatigue strength of the connection elements. One of the methods to limit the fretting wear in press-fit joints can be the use of finishing the surface layer. This article compares the results of laboratory tests of fretting wear in pressfit joints for a shaft without finishing and a shaft with a molybdenum coating. Tests were conducted on a press-fit joint model of a sleeve-shaft, which in fact relates to the press-fit joint of an axle-wheel in the wheel sets of rail vehicles. A model of the press-fit joint is outlined in such a way as to reflect the working conditions of the real object. Micrographic records of the surface layer of the sub-hub of the tested shafts showed that, in the case of a shaft coated with molybdenum, the traces of fretting wear occur only when the number of cycles is 7x106 and, in the case of surface without finishing, the wear also occurs when the number of cycles is 7x104. Also, the intensity and the area of fretting wear in the case of the molybdenum coatings is smaller than in the surfaces without finishing. Micrographic records showed on the length of the connection a real contact of the tested elements with randomly spaced slots filled with product of wear. [ABSTRACT FROM AUTHOR]

In the article the issues of classification and diagnostics of defects arising in wheel pairs of a rolling stock of railway transport within the operation period are elucidated.

The SUW 2000 railway vehicle wheel set with an automatic gauge change system is especially exposed to fatigue wear due to the specific working conditions. Taking into consideration the role which a wheel set has in both vehicle handling on a track and providing safety of railway traffic, the wheel set damage is impermissible. It also applies to the sleeve–axle rotational connection. This article presents research into both finding new and low-cost materials for a slide sleeve in the wheel hub node and looking for cheaper technologies for improving the surface layer of the wheel set under-hub which would eliminate fretting wear. The research was conducted on a simplified physical model of a real connection between a wheel and an axle. The results of the conducted wear tests show that fretting wear can be effectively limited by applying a metallic layer in the form of molybdenum coating. Grease with the addition of molybdenum disulphide can also protect the co-operating surfaces against fretting wear. It also allows for sustaining proper working conditions of frictional pair elements. This solution, however, is onerous due to the limited maintainability of the connection node. The studies carried out show that there is a full possibility of using this solution in real exploitation. [ABSTRACT FROM AUTHOR]

Train wheel sets must be periodically inspected for possible or actual premature failures and it is very significant to record the wear history for the full life of utilization of wheel sets. This means that an online measuring system could be of great benefit to overall process control. An online non-contact method for measuring a wheel set's geometric parameters based on the opto-electronic measuring technique is presented in this paper. A charge coupled device (CCD) camera with a selected optical lens and a frame grabber was used to capture the image of the light profile of the wheel set illuminated by a linear laser. The analogue signals of the image were transformed into corresponding digital grey level values. The 'mapping function method' is used to transform an image pixel coordinate to a space coordinate. The images of wheel sets were captured when the train passed through the measuring system. The rim inside thickness and flange thickness were measured and analyzed. The spatial resolution of the whole image capturing system is about 0.33 mm. Theoretic and experimental results show that the online measurement system based on computer vision can meet wheel set measurement requirements. [ABSTRACT FROM AUTHOR]

Although press fit joints are very important in railway engineering, few authors have investigated the strength of press fit joints in terms of their application in railway vehicles. This study analyses the tribological parameters that influence the strength of press fit joints, especially the contact pressure and the static friction coefficient. This research was targeted towards the control of the friction coefficient value to obtain the required strength of a press fit joint in conditions close to the minimum contact pressure that results in less prestressed press fit joints. To estimate press fit joint strength, this study examines the use of minimum and maximum values of the friction coefficient as recommended in the literature considering wide tribological conditions, as well as the experimentally determined friction coefficient values for specific tribological conditions. The study also points out the discrepancy between current railway standards and engineering practice considering the inspection of wheel set press fit joint strength. [ABSTRACT FROM PUBLISHER]

Provision of reliable rolling stock and infrastructure equipment is an important part in achieving high levels of safety. Therefore, the railway industry uses different methods and tools to improve the performance of different subsystems in order to ensure safety and reliability, which are the important factors for passengers and cargo transportation. Hence, reliability analysis is required to identify the bottlenecks in the system and find the components or subsystems with low reliability for a desired level of performance. This paper focuses on collection and analysis of field failure data over a period in Raja Passenger Train Company of Iran. The results of data analysis show that wheel sets is the bottleneck, and it utilizes the historical data of wheel sets to determine the reliability function. Thereafter, the reliability of each type of wheel sets are identified over different time intervals and which can be used to determine the appropriate time of preventive maintenance tasks. [ABSTRACT FROM AUTHOR]

• Forced-in joints are one of the most frequently used methods of element joining. • Forced-in joints become damaged during both the assembly process and operation. • During joint assembly, adhesion bonds causing grooving or tearing off of surface fragments may occur. • Fretting wear is observed in the case of forced-in joints operating in rotational bending conditions. Forced-in joints, especially those operating in harsh conditions, are susceptible to premature damage and wear. Such a situation may lead to incidents with severe consequences. Microcracks or changes in the structure of the joint elements may contribute to the development of fatigue cracks and unexpected damage during operation. In this work, typical damage and wear which may be observed at a shaft and sleeve surface made of structural materials used in production of the wheel and axle of the rail vehicle axle set. That damage and wear have come into being as a result of both the pressing process and operation. After the pressing process, the surface of the elements was distinguished by typical traces such as scratches running long the pressing direction, by dents and micropulluots. Brown fretting wear traces at a small distance from the joint edges have been noted at the shaft and sleeve surfaces subjected to fatigue tests through the operation of the rotational bending moment. Fretting wear comprises, to a large extent, material build-ups which have come into being as a result of adhesion-related processes. During operation, those build-ups underwent plastic deformation and oxidation. [ABSTRACT FROM AUTHOR]

The authors of this paper made an attempt to explain fretting wear development in the wheel – axle connection in model studies simulating actual exploitation conditions. The tests consisted of two stages. In the first one it was of essential importance to check the actual state of the surface and surface layer of both the elements after having made press-fit joint and the influence on this state of some chosen factors, such as the forced in value and the surface roughness. The second stage included fatigue tests of the connection in the conditions of rotary bending as well as macro- and microscopic analysis of the registered damages in order to determine the processes initiating wear development. On the basis of the achieved results the authors formulated the mechanism of fretting wear development in a press-fit joint in which the most important element is the phenomenon of adhesion. It was found that in fretting wear development initiation in a press-fit joint, adhesion phenomenon plays a decisive role, forming and breaking adhesive connections. The remaining types of wear, such as plastic deformation, oxidation, micro-machining play a minor role, intensifying the damaged formed earlier as a result of breaking adhesive connections. • A wheel set is the most important element of a running system of a rail vehicle. • Fretting wear on the axle surface occurs mainly in the middle part of the axle. • Metallographic observations showed differences in the sleeve opening connection with the wheel seat of the turned and grinded roller. • Fretting failures take place first of all in the areas where the oscillation amplitude reaches the highest value. • Fretting wear failures, forming during exploitation, may be the source of fatigue cracks. [ABSTRACT FROM AUTHOR]