Study on the mechanism for polygonisation formation of D2 wheel steel and its effect on microstructure and properties under rolling wear conditions
Introduction
With the train running speed increases significantly, the wear and damage of the wheel surface (flaking, polygonisation wear, contact fatigue, etc.) are also increasingly prominent. Whether it is high-speed railway trains or subway vehicles, wheel polygonisation have become one of the main forms of damage during the wheel operation. Wheel polygonisation wear also known as wheel corrugation or wheel periodic out-of-round(OOR) wear [1]. The wheel polygonisation will cause the vibration of the vehicle to generate noise which reduces the passengers comfort, and the seriously wheel polygonisation will shorten the service life of the related structural components, resulting in wheel and rail fatigue, loose rail fasteners, broken thread studs, etc., which seriously affects the safety of the train [[2], [3], [4], [5]].
Many scholars have conducted in-depth research on wheel polygonisation. Zhao et al. established a wheelset-track system model and used transient dynamics analysis, analyzing the wheelset eccentricity in wheelset-track system. The results indicate that the wheelset eccentricity is a considerable reason affecting wheel polygonal wear [6]. Jin et al. tested the dynamic characteristics of the running subway vehicles. The results show that the main frequencies of the vertical vibration acceleration of the axlebox dominates in the axlebox operation, furthermore is close to the passing the frequency of the polygonal wheel [7]. Brommundt studied the wheel out-of-round caused by the wheelset model behavior and wheel moment of inertia. The results show that the faster the train runs, the faster the out-of-round lower harmonics develop [8]. Morys developed a vehicle-track model to describe the short-term system dynamics of the ICE-1 carriage, clarified that large wheel out-of-round conditions can also cause the large variations of normal force between the wheel and rail under high-speed conditions [9]. Liu et al. used the vehicle-track coupled dynamics model to study the wheel/rail dynamics generated by the high-speed train polygonal wheel. The results show that the wheel polygonisation will cause the wheel/rail contact force to fluctuate significantly. The influence of the wheel polygonisation on the vehicle system is mainly related to the wheelset vibration [10]. Nielsen et al. established high frequency dynamic interaction model of train and track, and analyzed the influences of rail corrugation and wheel OOR on fatigue failure of wheel, high frequency wheel/rail force and fatigue crack initiation of wheel material [11]. Literature [12] established the linear motor vehicle/track coupling dynamics model, analyzed the effects of abrasion wheels on the normal force of the wheel-rail and derailment coefficients in the ballasted track and ballastless track. Meywerk established a rolling model of flexible wheelsets on elastic rail. The results indicate that the greater phase difference between the left and right wheels, the faster wheel polygonisation appeared, and the first and second order bending modes of wheelsets played an important role in the formation of wheel polygons [13].
In summary, most of the current researches have analyzed the reasons for the formation of wheel polygonisation and the influence of wheel polygonisation on train dynamics behavior from the perspective of wheel-rail contact dynamics. However, there are few studies on the microstructure evolution of wheel polygonisation on the wheel-rail contact. In this paper, the formation mechanism of D2 wheel polygonisation is studied by analyzing the vibration and wear measured in the rolling wear experiments. The formation process of the D2 wheel polygonisation and its influence on the microstructure evolution of the surface layer and properties are analyzed.
Section snippets
Experimental materials and methods
The experiment was carried out on a GPM-30 rolling friction and wear test machine, as shown in Fig. 1(a). The machine is mainly composed of two AC motors (A, B), two rotating shaft systems for driving the rotation of upper and lower samples, hydraulic actuator for loading, hydraulic pump, the workbench, the rack, the machine shell and mat iron, etc. The load between the wheel and rail samples is loaded by the hydraulic actuator 2 and the hydraulic pump 5. In the experiment, the sample rolling
Wear curve
The mass wearing quantity of the samples with different cycles as shown in Fig. 3. It can be observed that before the wear of 2 × 105 cycles, the mass wearing quantity increases relatively slow and the sample is at the uniform wear stage. From 3 × 105 cycles to 5 × 105 cycles, the mass wearing quantity is accelerated again and entered the rapid wear stage. After 5 × 105 cycles, the mass wearing quantity increased sharply and transferred into the severe wear stage.
The macroscopic appearance of the surface
Fig. 4 exhibits the
Mechanism of the wheel polygonisation formation
During the experiment, the equipment generates a series of vibration with different frequencies, which causes the load of the sample surface to fluctuate. Therefore, the actual load on the sample surface is composed of static load and dynamic load. At the beginning of wear, the wear rate is low (Fig. 3), and the wear is uniform (Fig. 4(a) and Fig. 6(a), (b)). Therefore, the vibration amplitude of each vibration frequency is small. With the increase of the wear cycles, the wear of local surface
Conclusions
The rolling wear experiments of D2 wheel steel were carried out on the friction and wear machine, the conclusions are as follows:
- 1.
The polygonisation wear of D2 wheel steel sample surface under rolling wear condition is mainly caused by the vertical vibration of the system and wear coupled. After the preliminary polygonisation is formed, the vertical vibration is intensified and the polygonisation wear is more serious with the increase of wear cycles, so the crest-to-trough height difference
CRediT authorship contribution statement
Jun Hua: Conceptualization, Formal analysis, Investigation, Writing - original draft. Xiujuan Zhao: Project administration, Investigation, Resources, Writing - review & editing. Pengtao Liu: Resources, Writing - review & editing. Jinzhi Pan: Resources, Writing - review & editing. Chong Su: Writing - review & editing. Ruiming Ren: Investigation, Resources, Writing - review & editing, Project administration, Supervision.
Declaration of competing interest
The authors declared that they have no conflicts of interest to this work.
Acknowledgments
The project was supported by the National Key Basic Research Program of China (973) (2015CB654802).
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