Wheel rail wear and surface cracks in metal

Rolling contact fatigue can cause damage in the form of surface cracks by wearing away the rail, or through plastic flow of the materials. Evaluation of rail wear characteristics on heavy haul. This can eventually lead to the formation and growth of surface cracks. Calculation of minimum crack size for growth under rcf. There is also less plastic flow and wear on hard rails, so the profile changes more. Typically there are many closelyspaced cracks, only a few millimetres apart along the rail as shown below. The surface morphology of original sample exist obviously machining mark with the peak and valley, as shown in figure 3a. Railway wheels lives are limited by wear and the formation of rolling contact. One symptom of advancedstage rail defects are areas where material breaks out of the metal surface. The issue of the rail and wheel contact is one of the most fundamental aspects in the railway system since inappropriate interactions create problems such as wear and a negative effect in the dynamic functioning of the train. Further, rail wear occurs at the top of the rail as head top wear, or at the side as gauge face wear or can be described to occur in the form of combined. The roughness of the ground contacting surface of the rollers was r z cracks on surface of wheel, highlighted with dye penetrant.

When wheelrail damage in terms of wear and rcf can be predicted, measures can be taken to decrease it. Friction management, track geometry, wheel rail interaction, wheel rail profile and tagged with. Effect of plastic deformation in surface layer of wheel. Cant the inward inclination of a rail, affected by the use of inclined surface tie plates, usually expressed as a rate of inclination, such as 1 in.

Effect of contaminants on wear, fatigue and traction. Abstractdamage mechanisms such as surface cracks and wear on a rail can. Wear of six rail steels in rollingsliding contact with class d tyre steel, tm. Grinding and milling are essential for rail quality global. Rail grinding is an integral tool in a railroads maintenanceofway toolbox. According to the union pacific railroad wheel fracture database, 65% of railroad wheel failures are caused by shattered rims, a form of sub surface. The wheel roller was made of r7 steel, whereas the material of the rail roller was 900a steel. This occurs when head checks are not ground away or cracks in the rails interior are not milled off, allowing them to get bigger and with time join together to form weak points in the rail. Rolling contact fatigue cracks on the rail surface have also been linked with the wel 2, 3 and they are identified as studs. Additionally, on most rail systems at least some small fraction of those rolling contact cycles will develop shear stresses that exceed the strength of the rail andor wheel, leading to plastic flow that initiates surface cracks that progress to surface fatigue. This causes damage to the wheel and rail surface and can accelerate wear. Tribology of the wheelrail contact aspects of wear.

The flake of surface cracks leads to the wear failure of samples. Cracks start at the rail surface and develop into the rail at an angle of about 20 to the running surface. Wear of wheels occurs on the wheel tread and flange. This require intervention such as grinding to avoid shortened life span of track components, safety.

It can be seen that the surface morphology of samples is relatively flat and no obvious cracks at 200 cycles. Wheelrail friction depends on the shear properties composition of the third body layer. The amount of surface cracks of samples is increased with the increase of cycles. Effect of plastic deformation in surface layer of wheel rim. Improved metallurgy, harder steel, profile grinding and proper lubrication can significantly reduce wear and fatigue. However, under constant unidirectional loading cracks and metal tongues could only be found on the surfaces of the driven rollers. Wheel spalling wheel spalling occurs in service after the wheel slides on the rail and patches of martensite are formed on the tread. The result of fatigue wear is severe plastic deformation. For most trains in britain this contact patch is about the size of a five pence coin, and the behaviour in this contact patch creates the forces between the wheel and rail that lead to rcf. Fatigue wear prevention must be a consideration in planning and design phases. How to ensure train track security and keep it stay away from steel rail wear. This typically results in general damage from wear to fatigue. Rail wheel interaction indian railways institute of. Batter the flattening of the running surface at rail ends from wheel impact.

Steel rail wear is a common but dangerous phenomenon that impacts the train track safety. Study on the performance of highspeed rail damage of four. Friction and wear testing of rail and wheel material. Simulation and measurement of wheel on rail fatigue and wear. These studies have indicated that shelling is essentially a fatigue failure. Studies were made of wheels that shelled in service after being subjected to the usual ontread braking as well as a wheel equipped with disctype brakes. Calculation of minimum crack size for growth under rcf between wheel and rail h. Influence of pressure for rail predominant metal surface is stressed higher which leads to an increased production of lamellar wear particles. Modelling of defect growth rates and safe rail wear limits based on target inspection interval. Wear debris are shown as parallel lines in sem micrograph. Surface cracks are observed in the micrograph of pin and disk specimens. The heattreated rail exhibited increased hardness and resistance to wear as the lamellar spacing of the metal structure became smaller due to heat treatment. The particles are much harder than the steel surfaces in contact, so abrasive wear is inevitable. Keywords crack analysis, damage analysis, railway wheel steel.

Wear, rcf cracks and plastic flow of rails in curves 5. Jul 22, 2010 wear of wheels occurs on the wheel tread and flange. Abstractrecent studies of the railwheel interface have shown that wear and. Glossary of terms north american rail products inc. Steel rail is the fixed road of train running, so its safety is very important for train. Integrating dynamics and wear modelling to predict railway. Too high wear is monitored by geometry measurements.

Increase of the wear thickness causes increase of heating and heat input per unit of length area of the wheel surface and, as a result, increase of haz width and probability of formation of cracks both in the deposited and base metal of the wheel. Investigation into the mechanical properties and metal creaks. Fulltext influence of applied load on wear characterizations of rail material. Competition between wear and rolling contact fatigue at the wheel. This is particularly effective at the rail gauge face to control wear but at the top.

It can help minimize potential for derailments and extend rail life. In figure 2, it is shown that obviously, a plastic deformation layer appeared near the wear surface of several rails after the rolling test. The other type of rcf defects are known as running surface cracks or flaking. These cracks are called rolling contact fatigue cracks rcf the growth rate of rail surface and subsurface fatigue cracks as shown in figures 1 and 2 is influenced by the level of contact stress between the wheel and the rail refer to section 6.

Third body at wheelrail contact third body is made up of iron oxides, sands, wet paste, leaves etc. 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. Investigation into the mechanical properties and metal. And the wear loss of wheel samples is higher than that of rail samples. Grinding of rails has evolved as a maintenance technique to insert controlled artificial wear and manage wheel rail contact stress. At a high wear rate, rcf does not have the opportunity to develop further. Grinding shaves off the top surface of the rail, removing the cracks before they have a chance to propagate down into the web and thus preventing rail breaks. Rolling contact fatigue, rcf, rail gauge corner cracking, wheel tread cracking. Wear at the wheelrail interface when sanding is used to. Such wheels may be identified by presence of flats even within acceptable limits.

Cracks start at the rail surface and develop into the rail at an angle of about 20 to the. Apr 01, 2006 increase of the wear thickness causes increase of heating and heat input per unit of length area of the wheel surface and, as a result, increase of haz width and probability of formation of cracks both in the deposited and base metal of the wheel. Grinding and milling are essential for rail quality. Fatigue of rails and wheels center for railway research. The ability to measure rail profile, wear, surface cracks, and corrugation is enabling us to take a more scientific approach to rail grinding, said gordon bachinsky, president of advanced rail management corp. Closer examination of the wear surface of the wheel. Wheel damage wear wear occurs from sliding between the wheel and rail, typically in the flange root area benign slow process. Wolfgang schoech july, 2008 rail maintenance work is a process of removing metal from the rail head at the right time and at the right place.

However, the wear rate should be at an acceptable economic level and, under certain circumstances, balanced to achieve a wear rate that removes fatigue cracks as they propagate. This suggests a need for methods that can effectively predict the occurrence of rcf cracks. The reversal loaded wheel rollers demonstrate small cracks and thin metal tongues on the surface and the perlite is folded. A study of wear and rolling contact fatigue on a wheel steel in. For example, the combination of wheel and rail profiles, or the combination of vehicle and track, can be optimised to control the damage. Figure 1 shows the cycle of crack growth into the rail surface. Nrc publications archive archives des publications du cnrc. Fretting damage in steel can be identified by the presence of a pitted surface and fine red iron oxide dust resembling cocoa powder. At the same time, the rail top surface metal is hardened, the hardness is increased, and fatigue cracks appear on the surface, which results in flakelike peeling. In the case of spalling, the crack network is either perpendicular or parallel to the surface. Wear, by removing the material from the contact surface, tends t.

Nov 14, 2017 nowadays, the railway is considered as a means of fast, aggregate and secure transportation. Evaluation of rail wear characteristics on heavy haul track section using measurement data ihha 2015 conference 21 24 june 2015 perth, australia thermal and oxidative wear processes 4. Wear, particle emission and adhesion are all wheelrail contact phenomena and are covered in this paper. The natural processes of wear and surface deterioration of rail steel can proceed at a rapid pace that results in a reduced service life. According to the union pacific railroad wheel fracture database, 65% of railroad wheel failures are caused by shattered rims, a form of sub surface initiated rollingcontact fatigue rcf. In two of the curves, two different kinds of rail steel grade uic 900a grade with. The wear in the contact of objects along with its occurrence between the wheel and rail is also analyzed. Analysis of wear debris in rolling contact fatigue cracks. Wear and rolling contact fatigue are competing phenomena in railway wheels, as wear tends to shorten or remove surface cracks nucleated by ratcheting. Surface initiation of surface rcf cracks growth of cracks into railhead 2. They are caused by rapid air cooling, and may be prevented from forming by control cooling the rail. Railway wheels railway wheel is assembly of two wheels fixed to the axle by interference fit and they rotate along with the axle, without any independent relative movement as in the case of other automobile wheels.

The tribofatigue damage transition and mapping for wheel. Effect of sliding wear on surface microstructure and wear. Surface material is shifted in the sliding direction. Wear can be defined as the loss of material from a surface, as exemplified in igure 2, while f. Jan 04, 2014 understanding the effects of track gauge, wheel rail geometry and friction on stresses at the wheel rail interface january 4, 2014 filed under. Jan 08, 2014 cracks that propagate on the rail surface go deeper, faster in dirty, poor quality rail steels than in clean steels, kalousek told delegates at the first wheelrail mostly rail seminar sponsored by advanced rail management. Center of the rail, but also allowing the field side metal to bear a portion of.

Experiments have proven that an increase in surface hardness improves its wear resistance8, 9. At first, rail grinding was performed to remove surface irregularities and defects a process that required significant metal. Rolling contact fatigue can cause damage in the form of surface cracks by wearing. Thus, the mechanism of tread surface wear is caused by. Effective predictions require computational tools and mathematical models that can accurately simulate actual material behavior and structural interactions like the contact between railway wheels and rails that. Initiated cracks are in this case worn off and will not be able to propagate deep beneath the surface of the rail or wheel. Fatigue cracks initiate on the wheel specimen surface. Wear particle analysis and the evolution of the plastically deformed layer on australian rail steel asitha c. For wheel spalling away of oxide particles exposes more metal, which rapidly oxidizes once again surface of driving roller wheel surface of driven roller rail. Abrasionwear is developed on a tread when it is in contact with a rail. Submicronsized dislocation cells occurs, similar to highly coldworked metals.

The wear of the wheel roller is now composed by oxide particles and metal flakes. Analysis of wear debris in rolling contact fatigue cracks of pearlitic railway wheels. At a high coefficient of friction, there is a high degree of plastic deformation. Evaluation of rail wear characteristics on heavy haul track. Persson, subsurface crack networks and rcf surface cracks in pearlitic railway wheels, in proceedings of the 9th international conference on contact mechanics and wear of railwheel systems cm 12, chengdu, china, august 2012. Grinding the continuous interaction between wheel and rail leads to alteration of the rail profile through wear, surface and near surface defects, or plastic flow.

Of friction more slide sqeal and rail corrugation proper management can lead to 30% savings over natural conditions. Rolling contact fatigue rcf describes the process in which cracks grow as a result of the contact stresses between a rolling wheel and the rail. Enhanced grinding for rail defect rail break reduction. Introduction friction at railwheel interface is a significant parasitic energy loss.

How to do a long lasting diy rustout repair using metal and fiberglass duration. These wheels are provided with flange towards the inner side, which guide the wheels to travel on the rails and does not. Rail wheel interaction 02 free download as powerpoint presentation. Under normal conditions such cracks do not carry a direct threat to the integrity of the. Every effort should be made to avoid the abnormal loss of tread metal caused by thermal cracking and shelling. A thin streaks of martensite on the rail surface because of high creep rates from. Understanding the effects of track gauge, wheelrail geometry. The influence of wheelrail contact conditions on the. Wear can never be eliminated since there will always be metaltometal surface contact traction levels could not be maintained without this. Repeated, alternating mechanical stresses lead to the formation and propagation of cracks under the stressed surface, which is thus destroyed. Car retarder a braking device, usually poweroperated, built into a railway track to reduce the speed of cars by means of brakeshoes which when set in braking position, press against the sides of the lower portion of the wheels.

Railway wheels lives are limited by wear and the formation of rolling. These studies have indicated that shelling is essentially a fatigue failure that is caused by rolling loads. Longer wear lives, higher speeds and larger loads have made fatigue the new main cause of railway wheel replacement and reengineering. Effects of wheel materials on wear and fatigue damage. Often, these cracks are found on wheels with heat checks and the cracks appear to be closely related. The crack tends to propagate upward and leads to spalling defect when the crack. Mechanics and wear of railwheel systems, tokyo, japan, 2528 july 2000, pp. Influence of applied load on wear characterizations of rail material. This is also the surface fatigue wear caused by contact stress. Icri are class 1s truly in a preventative grinding mode and able to achieve the magic wear rate. Refining approaches to corrective and preventive rail grinding.

Economic efficiency of railway wheel profile renovation by. Railroads doing preventive grinding which eliminates rail surface cracks are able to best utilize proper lubrication strategies to reduce wear and the traction stresses at the wheel rail contact surface and to increase the number of cycles before surface cracks develop and the profile plastically deforms. When the wheelrail surfaces contacted, the rail contact surface is subjected to high frictional force and the plastic flow deformation occurred on the metal of the rail surface along the wheel rolling direction. When the contact shear stress caused by the contact stress is applied, the plastic. Rail wear and rail surface fatigue occurs in all rail steel regardless of hardness and metallurgy. Cracks that propagate on the rail surface go deeper, faster in dirty, poor quality rail steels than in clean steels, kalousek told delegates at the first wheelrail mostly rail seminar sponsored by advanced rail management. Closer examination of the wear surface of the wheel disc revealed abrasive score marks and evidence of. R8t wheel steel wear rates and regimes from 18 at low t. Strictly this debris is not rust as its production requires no water. Wheel wear modelling approaches most wear indices developed for predicting wear of. Mechanism analysis of spalling defect on rail surface under. Third body separates wheel and rail surface, accommodates velocity differences and determines wheelrail friction.

Wear can never be eliminated since there will always be metaltometal surface contact traction levels could. Development of gcc beyond the first few millimetres into the rail requires the presence of a liquid, in particular water. Studying the wear phenomenon between the rail and wheel has led to a design. Nov 05, 2019 the result of fatigue wear is severe plastic deformation. According to the union pacific railroad wheel fracture database, 65% of railroad wheel failures are caused by shattered rims, a form of subsurface initiated rollingcontact fatigue rcf. Grains are drawn out, and oriented parallel to surface. Pdf rolling contact fatigue and wear behavior of high. Wheel reprofiling owing to surface cracks andor unacceptable geometry, wheels are reprofiled. The wear morphology of wheel samples with different cycles is displayed in figure 3. Influence of applied load on wear characterizations of. Unlike the slow process of wear, fatigue causes cracks on contact areas of wheels, along with loss of material.