The undercarriage of trains includes many elements, but the key pair is the wheelset. There are different versions of this component, and they differ not only in size and shape, but also in their ability to withstand various loads. In many ways, this characteristic is decisive for the working resource of the chassis. Manufacturers initially endow its elements with high operational potential, but, of course, this does not guarantee the complete elimination of breakdowns and malfunctions. Regardless of the purpose and features of the use of transport, wheel sets of wagons require maintenance. By the way, elementary wear is a normal occurrence - it’s another matter that maintenance personnel are required to timely detect areas close to breakage and carry out appropriate repair operations.
Causes of malfunctions
Despite the use of a robust design with high-strength metal alloys, strong dynamic and static loads can lead not only to wear but also to deformation. Wheel pairs of freight cars are most affected by such phenomena, since during the movement of the train there is an increased voltage in the contact zone of the rail and wheels. Therefore, in order to minimize the negative consequences from this interaction, technologists include carbon in large proportions in the alloy. One way or another, the load can increase if the crew follows the terrain with a curved road laying - this creates additional stress as a result of the action of centrifugal forces.
At the same time, one should not think that pairs for passenger trains have serious advantages in the form of low loads. Partly, of course, the risks in this case are lower, but all the shocks and shocks during the movement are also transmitted to the chassis, as a result of which the wheelset of the passenger car gradually wears out. It is worth noting other factors affecting the condition of the wheels. Among them are braking forces, skidding effect, undesirable axis contacts with the drive part, turnouts, etc. Now you can learn more about the most common types of malfunctions.
Worn solid wheels
There are several groups of similar wear. First of all, this is the formation of a uniform roll-over, to which the wheelsets of wagons are subjected, even in normal operation. The appearance of such a deformation is due to the fact that in contact with the rails and brake pads, a strong stress is created, which leads to a roll on the surface of the wheels.
Uneven rolling is also common. It is characterized by the appearance of deformation zones not over the entire area of the contact zone, but only in certain axes. This indicates that the wheelsets of the cars were made with an uneven distribution of properties over the entire mass of the alloy. That is, the appearance of such a runoff testifies, first of all, to marriage in pairs themselves. Next, it is worth noting the circular influx. It can be observed outside the contact rim of the wheel when the mass moves away on the sides of the chamfer.
Wear surfaces
Deformation of this kind also occurs in the area of the contact zone. The peculiarity of wear is that it occurs when using the skid. Therefore, the deformation of the riding surfaces is often associated with disturbances in the operation of brake pads. Visually, such malfunctions of wheelsets are manifested in the form of a slider - this is a flat area on a white metal surface. Despite the fact that during operation such defects do not cause serious problems, they can go into another kind of trouble.
The fact is that in places of the slider almost always there is an increased formation of heat, which is transmitted deep into the rim of the wheel. As a result, the so-called dents are formed, entailing a specific color at the point of rolling. Over time, the wheelset begins to respond sensitively to any irregularities of the "canvas", which entails the appearance of shock in the chassis. Therefore, if sliders greater than 1 mm are detected, serious restrictions are imposed on the speed of the train. By the way, the wheelset of a locomotive and a freight car is most affected by such deformation. It is noteworthy that the intensity of the formation of the slider also depends on the season - for example, in winter and early spring, the risks of its formation are higher.
Axis malfunctions
Failures in the necks and pre-accessible parts are expressed in the form of small axes. There may be several reasons for this. First of all, deformation occurs due to insufficiently strong joints and in those cases if the cleaning of metal surfaces from rust formation was incorrectly performed. Also, the axis of the wheelset is often subjected to kinks and cracks in places with the highest loads. Such processes arise due to cyclic stress, the presence of sections with transition sections and the discontinuity of the metal itself. Of course, the usual breakdowns in the form of insufficiently strong bolt and nut fastenings are not excluded.
Navar metal
This is a thermomechanical damage that affects the wheelsets of cars in the riding surfaces. During inspections, such deformations fix the shear zones of a material with a U-shape. In essence, this is a type of plastic deformation processes. The maximum shift is in the central part of the contact strip. In turn, a minimal shift can be detected at the edges. The cause of this damage is the distribution of loads with pressure on the contact area.
General wheel maintenance
Preventive measures contribute to the prolonged use of the wheels. Maintenance includes inspection, inspection, indications for repair operations, etc. If we talk about technical measures, the main one will be the correct turning of the wheelsets with a minimum metal removal layer. The number of casings is reduced thanks to special measures aimed at improving the reliability of wheelsets and eliminating the existing weaknesses of the chassis. In particular, specialists seek to eliminate the force factors that occur during operation and appear due to previously arisen defects. For example, eliminated problems in the spring-spring part, which affect the quality of the chassis.
Repair operations
Repair operations are carried out in a special mechanical zone after the elements have been thoroughly washed. In a special department, wheel changes, turning or welding events are carried out. If it is planned to repair wheelsets in order to change the profile of the elements, then the work is performed using special templates. It should be noted that the permissible deviation in the parameters of the wheels from the template is 1 mm along the ridge height, and 0.5 mm along the inner faces and the skiing area. As already noted, electric welding operations can be used in repairs. Such equipment is used for cutting axial threads and surfacing of center holes.
Conclusion
There are special regulations in which malfunctions of wheelsets are detailed, as well as methods and technologies for their elimination and prevention. It is important to note that many factors of a mechanical property act on the chassis as a whole. As a result, the performance and resource of the wheelset depend not only on the quality of the tracks, but also on the braking system, spring-spring unit, the movement mode of the crew, and even the time of year.