Wheel rail wear and surface cracks in foundations

Effect of wear on surface crack propagation in railwheel. Smart measurement mrx technologies is an engineering organization primarily active in the railway sector. However, the contact surface asperities between the wheel and rail. When wheel rail damage in terms of wear and rcf can be predicted, measures can be taken to decrease it. As is known, friction plays a vital role in wheel and rail wear 2,3,9,10 and investigations and applications have indicated that lubrication of the wheel rail contact is an effective method for. Investigation of surface ratchetting due to rail wheel contact i abstract. This can be minimized by correct alignment of the wheels, flange lubrication, material of wheel and rail being similar and equipment in proper mechanical condition.

Repeated, alternating mechanical stresses lead to the formation and propagation of cracks under the stressed surface, which is thus destroyed. Introduction friction at rail wheel interface is a significant parasitic energy loss. Wear and surface residual stress evolution on twindisc. Definition rails are the members of the track laid in two parallel lines to provide an unchanging, continuous, and level surface for the movement of trains. Rails, types, joints, creep, failure of rails and welding of rails 1. The result of fatigue wear is severe plastic deformation. Magneticparticlendt a magnetic field is applied across the. After running about 10,000 km, the extent of wear in the wheel profile is considerable. Macroscopic examinations of radialtangential sections from shelled areas have indicated that shelling is caused by cracks that form at angles of 30 to 50 deg to the tread surface. Effect of shoe braking on wear and fatigue damage of. The key to a long fatigue life is to make steel that has few nonmetallic inclusions. Wear of wheels occurs on the wheel tread and flange.

Shrinkage cracks in a new house are common and can be small vertical cracks or small 45 degree cracks at the basement windows. Associated risks and maintenance strategies technical report by. Optimization of a railway wheel profile to minimize flange. The outer circumferential surface of the rim, which contacts the rail. Rail steel is designed to wear away very slowly to avoid surface. Contact area of steel wheel on concrete slab greglocock automotive 23 dec 20. Specimens of various railway wheel steels were coupled with specimens of the same rail steel, subjected to rolling and sliding wet contact with varying slidingrolling ratio. Rails, types, joints, creep, failure of rails and welding. Effects of rail materials and axle loads on the wear behavior of. Some tests with a dry rollingsliding contact phase preceding wet contact were.

At a high wear rate, rcf does not have the opportunity to develop further. Wheel and rail wear understanding the effects of water. Rcf initiated problems such as surface cracks, head checks, squats, spalling and shelling. Because shelling cracks are oriented at 30 to 50 deg to the tread surface they are assumed to be caused by high shear stresses developed by rolling loads. Initiated cracks are in this case worn off and will not be able to propagate deep beneath the surface of the rail or wheel. The interaction between wear and rolling contact fatigue in wet contact was investigated by means of experiments on a twodisk test bench. Proposed procedure for determining wheel and wheelset. Allowable wheel 60 x s 80 x s loads tons wheel ls ws 75 x s 100 x s s average spacing, in meters, between the wheels at each corner. Proceedings of the 9th international conference on contact mechanics and wear of rail wheel systems cm 12. Too high wear is monitored by geometry measurements.

However, in practice the stresses usually exceed the shear yield of the material, and the surface of the wheels and rails accumulate plastic deformation. For a low wear rate the crack may become stable at point 1 or 3, while. A 3d femodel was constructed in abaqus to simulate the stressstrain fields that take place under the rollingcontact of railway wheels on rails. Recent studies of the rail wheel interface have shown that wear and rolling contact fatigue rcf are competitive phenomena. Typically there are many closelyspaced cracks, only a few millimetres apart along the rail as shown below. Steel that is slightly softer, will wear the rail slightly and reveal a new surface before cracks can develop in the original surface. All surfaces should be checked whenever the wheel is being inspected and the wheel remachined or replaced if the surface shows significant wear, grooving, flat spotting or other defects. For instance, wheel wear and rolling contact fatigue crack initiation have. Wheel rail friction depends on the shear properties composition of the third body layer. Study on the fatigue and wear characteristics of four wheel materials.

Traces of cast iron, previously transferred from the brake specimens to the wheel ones, were detected. To study the wheelrail rolling contact fatigue of highspeed trains, we obtain the distribution of contact. Grinding wheel wear is an important measured factor of grinding in the manufacturing process of engineered parts and tools. The ballast, subballast, blanket, embankment, and foundation did not require any. In the railway industry, fatigue cracks are produced by abnormal braking. In this video, i use an angle grinder with a diamond wheel and dust collection to remove old floor paint from a concrete porch.

The xray diffraction technique was used to characterize the residual stress distribution at the initial and damaged stages, as well as in intermediate stages, since existing residual. After cleaning dye from the surface, a white developer powder is sprayed that draws dye from within the cracks. The tribofatigue damage transition and mapping for wheel. Rolling contact fatigue, rcf, rail gauge corner cracking, wheel tread cracking. Tribology of the wheelrail contact aspects of wear. The relationship between vertical wear rate and crack length reduction depends on the angle of the crack below the rail surface. If and when a crack finally branches towards the wheel surface, a large piece of the wheel. Railway wheels lives are limited by wear and the formation of rolling contact fatigue. Cracks very close to the surface are often at angles below 30, and this amplifies the vertical wear rate to give a large reduction in crack length with each wheel passage. Steel rail is the fixed road of train running, so its safety is very important for train. Rcf damage is also referred to as surface fatigue, pitting, or flaking in the literature. If the contact stresses produced at the wheel rail interface are below the elastic limit of the rail material no permanent deformation will occur. The impact of rcf and wear on service failures and broken.

The influence of wheelrail contact conditions on the. Smart measurement digital services siemens mobility global. The force on the high rail would be backwards and towards the inside of the curve. Mechanism analysis of spalling defect on rail surface under. Wheel damage wear wear occurs from sliding between the wheel and rail, typically in the flange root area benign slow process.

The work is supported by the national natural science foundation of china. The crack tends to propagate upward and leads to spalling defect. Wheel and rail wearunderstanding the effects of water and. The contact area at each wheel tread low rail interface is approximately circular, with a typical radius of 7mm. Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body such as a ball, tire, or wheel rolls on a surface. Grinding involves the removal process of material and modifying the surface of a workpiece to some desired finish which might otherwise be unachievable through conventional machining processes. This can be used because a competition exists between wear and surface initiated rcf. For example, the combination of wheel and rail profiles, or the combination of vehicle and track, can be optimised to. A finite element model to simulate the physical mechanisms of wear and crack initiation in wheel rail contact w. The text outlines the action to be taken when defects are found. The rail surface contains a microcrack before the wheel rolls over the rail. Fatigue of rails and wheels center for railway research. A solid wheel of a railway vehicle hereinafter wheel consists of three parts, as shown in fig.

The purpose of this investigation was to study the development of these two damage mechanisms on new and 3yearold rails in a commuter railway track over a period of 2 years. This can eventually lead to the formation and growth of surface cracks. With our highly motivated team of over 200 engineers and experienced specialists we have offered services for manufacturers and operators of rail systems since 1996. The the tool can predict a surface crack length or crack depth where the effect of wear is. Introduction rolling contact fatigue rcf and wear are inevitable given the demanding conditions at the rail wheel. Damage mechanisms such as surface cracks and wear on a rail can reduce the service life of a railway track. Wear contact mechanics and wear of rail wheel systems. A thin streaks of martensite on the rail surface because of high creep rates from. The objective of this project is to provide an adequate numerical assessment of the sub surface crack initiation and propagation in railway wheels. Failure of a low rail in a curved railway track subject to. The inservice properties therefore vary with depth below the surface and with position across the wheel tread. Quantifying rail surface damage 28 metallography of crack morphology other crack features should be analyzed as well.

These are influenced by the steel composition, wheel manufacturing process, and thermal and mechanical loading during operation. Contact area of steel wheel on concrete slab structural. Third body at wheel rail contact third body is made up of iron oxides, sands, wet paste, leaves etc. Without considering the influence of the foundation, the fixed. The wheelrail rollingsliding contact experiments were completed by using. How to ensure train track security and keep it stay away from steel rail wear. Images are presented in this section and section 3. To be able to withstand high amount of stresses these are made of high carbon steel. Schematic representation of a rail crosssection illustrating wear fatigue interaction during phase ii crack growth. Materials used for wheels on rolling stock railway research. When they reach a critical length or depth, the cracks branch up toward the free surface, removing a piece of surface material and form a pit as shown in. Wheel rail, wear, particle emission, adhesion, airborne particles. Subsurface crack networks and rcf surface cracks in pearlitic railway wheels. Wear and fatigue of railway track caused by contamination.

After initiation, the cracks usually propagate at a depth of 10 to 30 mm below the wheel tread. Competition between wear and rolling contact fatigue at. Reflected noise a common concern with concrete track beds is the potential for additional reflection of noise from the concrete surface. Rail fatigue crack propagation in highspeed wheelrail rolling. An urban commuter railway wheel profile undergoing wear is shown in fig. This work is supported by foundation of state key laboratory. The system minimises this effect as a narrow slab width of 2. This specification details the allowable limits for the inspection of all rail vehicle wheels for various tread and flange defects.

Damage is considered to be either already present i. Steel rail wear is a common but dangerous phenomenon that impacts the train track safety. Wheel reprofiling owing to surface cracks andor unacceptable geometry, wheels are reprofiled. They include a hub, wherein an axle is inserted, a rim that contacts the rail, and a web that unites the two parts. While some broken rail derailments occur on rail that is approaching its head wear limits, analysis of bnsf derailments fails to find any correlation between head wear and either service failures or broken rail derailments. The work is supported by national natural science foundation of china nos. The susceptibility of railway wheels to wear and rolling contact fatigue damage is influenced by the properties of the wheel material. Every effort should be made to avoid the abnormal loss of tread metal caused by thermal cracking and shelling. The work was supported by the national natural science foundation of china 11472230, the.

Analysis of the influence of cracked sleepers under static loading. As will be presented here the wheel rail contact is extremely complex. The main damage phenomena observed in the specimens subjected to wheel brake contact and dry wheel rail contact were ratcheting, wear and nucleation of surface cracks. The purpose of this investigation was to study the development of these two damage. A systematic large experimental test program of wheel rail adhesion and wear was undertaken using the iit wheel rail simulation facility of approximately 14 scale. Removing paint from concrete with a grinder youtube. Common types of rail defects include excessive wear due to rail wheel contact, cracks and surface spalling in railhead due to rolling contact fatigue and plastic flow of railhead on curved tracks clayton et al. Quantifying rail surface damage 18 dye penetrant and magnetic particle ndt dye penetrant ndt the rail is coated by a dye formulated to penetrate cracks. Wear, by removing the material from the contact surface, tends to. Combined wear rate with crack tip advance data indicates points at which crack may stabilise. The grinding process itself has been compared to machining operations which.

Twin disc tribological tests were performed in wheel and rail materials, with specimens taken from a spanish ave train wheel and a uic60 rail, in a program intended to characterize their contact fatigue behavior. The relationship between the total wear loss of the wheelrail system and the. Simple search advanced search research publications advanced search student. The amount of rail wear is influenced by various elements, such as rail type. Length, branching, density in addition, crack path in the microstructure should be considered inter. How about the other part of the wheel rail wear system. Cracks start at the rail surface and develop into the rail at an angle of about 20 to the running surface. Fatigue wear prevention must be a consideration in planning and design phases. The rail steel can be assumed to have a shear yield strength of k70 ksi. Simulation and measurement of wheel on rail fatigue and wear. The running, or tread surface of the wheel will also wear. Third body separates wheel and rail surface, accommodates velocity differences and determines wheel rail friction. Rail disc specimens for each condition were analysed to establish the surface wear features and sub surface behaviour. The purpose of this investigation was to study the development of these two damage mechanisms on new and 3yearold rails in.