Papers by Keyword: Wheel Wear

Abstract: Wear occurs in rail wheels due to varying surface contact between wheel and railway. Many materials are used to minimize the wear effect of friction, one of which is graphite. Graphite has been known having dry lubricating ability. To find out the effect of graphite lubrication on wear level of wheel and railway, an experiment-based research is important to conduct. This research started with designing the construction of disc-on-disc wear testing instrument, wheel specimen using EMS45 material and railway specimen using VCL140 material. Dry lubricant used was graphite bar polished onto wheel specimen surface. The result of research showed that graphite could adhere to wheel surface and penetrate into the fissures of contact between wheel and railway. Varying graphite polishing conducted once in 5 minutes and 10 minutes resulted in different volume of graphite filling in the fissures of wheel specimen surface. The more the graphite volume polished onto wheel specimen surface, the less is the material loss due to surface contact. Graphite’s ability of filling in this contact area fissure when administered in appropriate volume would enable graphite to be a good dry lubricant. If this graphite polishing technique is applied to rail wheels, it would be beneficial, as it can lengthen the wheel life.

Abstract: Cylindrical parts with a protrusion are expected to be used in the components of consumer electronics and automotive products. The machining efficiency of these parts is very low, making them difficult to be mass-produced. The aim of our present work is to develop a highly accurate and highly efficient grinding process for a cylindrical surface with a protrusion. This paper describes the results of experiments using a straight cup-shaped grinding wheel. The following conclusions can be drawn. (1) To prevent uneven wear of the grinding wheel, an oscillation operation is necessary during the grinding process. (2) By employing the straight cup-shaped grinding wheel, the grinding process is realized with the aim of achieving the following: high machining accuracy, roundness below 3 μm, straightness below 2 μm, and surface roughness below 2 μmRzjis.

Abstract: This study aimed to investigate the effect of grinding conditions, including depth of cut and grinding direction, on the material removal and surface finish of multilayered thin film structures. It was found that the increase in depth of cut improved the material removal rate, but worsened the ground surface finish. The grinding perpendicular to the thin films caused less damage and produced better surface than that parallel to the films. The characteristics of wheel wear were also studied. Grit pull-out and micro-fracture should be attributed to the wheel wear.

Abstract: The law of wheel wear is the basis for making turning repair cycle, and is one of the most important guarantees for the safe and stable running of train. A statistical analysis of individual wheel wear parameter was carried out based on wheel profile data of CRH2. The change law of individual wear parameter with mileage showed that wear process of wheel could be divided into two periods: the run-in period and the stable wear period. The paper has realized to research on the correlation between nominal wheel diameter abrasion value and wheel flange thickness variation based on Copula, too. Frank Copula was selected to describe correlation of the two wear parameters, the correlation index (α) of Frank Copula was estimated and the joint distribution function considering dependence was given. The value of α indicated that there was a weak positive correlation between the two wears, which can be ignored for calculating the accumulative failure rate of wheel wear. So the two wear parameters can be regarded as independent random variables during failure analysis of wheel wear.

Abstract: Fiber-reinforced ceramic matrix composites are considered to be difficult-to-machine materials, its machining especially forming machining is very difficult. The silica fiber reinforced silica composite is studied by grinding experiment in this paper. The surface morphology of the specimens are analyzed by scanning electron microscopy, and the grinding mechanism of the composite is also analyzed. Grinding depth and feed speed is separately changed to study the grinding force. The influence of the blunt wheel on surface morphology and geometric accuracy of the specimen after grinding is explored. This research may be helpful to improve the machining quality of silica fiber reinforced silica composite.

Abstract: According to the characteristics of grinding wheel wear in the grinding process, the grinding wheel wear forms and their reasons are analyzed. At the same time, as the grinding wheel wear will affect the size of components, the procedures of on-line measurement and compensation technology about grinding wheel wear are summarized. The current domestic and international research status of on-line measurement and compensation methods about grinding wheel wear are introduced, such as position calibration based method, machine vision based method, laser displacement based method, acoustic emission based method, grinding force based method, cutting vibration based method, grinding acceleration based method and pressure based method. Finally, the current research difficulties of grinding wheel wear’s on-line measurement and compensation technology are analyzed, and the further research direction is made.

Abstract: High efficiency and high surface integrity grinding of fused silica lens used in the ultraviolet (UV) laser transmission equipments is highly demanded. It is necessary to decrease the undeformed chip thickness for producing better surface integrity. We conducted creep feed grinding (CFG) and conventional shallow cut grinding (SCG) experiments of fused silica with a resin bond diamond wheel. Experiment results shows that owing to thinner undeformed chip thickness, the normal grinding force, radial wheel wear and P-V value of surface roughness of CFG are smaller than those of SCG at the same MRR. At the same table speed, surface roughness decreased with the increase of MRR in both CFG and SCG as a result of decreased undeformed chip thickness which is attributed to the elasticity of resin bond.

Abstract: On-machine measurement and statistical analysis of wheel topography are important for real-time monitoring the wheel condition during grinding and predicting the performance of grinding process. In this paper, the surface topographies of grinding wheel in the different stages of the grinding of fused silica and BK7weremeasured with a white light interferometer, which was set on the surface grinder. Height parameters of 3D surface roughness were proposed to evaluate the wheel wear. Wheel wear mechanisms were essentially determined by analyzing the different material removal modes of optical glasses. Grinding of BK7 mainly causes severe attritious wear of grains, while grinding fused silica, self-sharpening effect makes grinding sustain for a long time.

Abstract: Wheels of the railway vehicle play the important role for driving train through wheel-rail interaction. Especially wheel profile is one of the most important design factors to rule the running stability and safety of train. Accordingly, the control of rolling contact fatigue-related defects is an ongoing concern for both safety and cost reasons. This process is referred to as ratcheting. Wear of wheel and rail surfaces occur due to a mixture of adhesive, abrasive and corrosive processes. In wheel/rail systems with little wear, such failure is manifested by the appearance of closely spaced micro-cracks. In the present paper, a evaluation of surface defects of wheel and rail for Korean high-speed railway. The main research application is the wheel-rail maintenance of Korea high-speed train.

Abstract: The defect initiation and crack propagation in wheel may result in the damage of the railway vehicle or derailment. Therefore, it is important to evaluate the characteristics of the wheel tread. In the present paper, the characteristics of wheel tread based on contact positions, running distance and brake pattern are evaluated. To evaluate the damage for railway wheels, the measurement for the replication of wheel surface is carried out. The result shows that the damaged wheel tread is remarkably depended on the contact positions between wheel and rail. It should be noted that the replication test can be applied in new evaluation method of wheel damage.