The surface topography of ceramic grinding wheels used in creep feed grinding is examined in this study. Creep feed grinding experiments are performed using seeded gel (SG) grinding wheels. The ...three-dimensional surface of the grinding wheel is observed using a two-dimensional high-definition laser displacement sensor, and the effective cutting-edge number is calculated based on three-dimensional surface observations. Microscopic wear behaviors of grain cutting edges are examined based on scanning electron microscope (SEM) images. The cutting-edge area percentage is calculated based on SEM images via the discriminant analysis method. Results show that the micro self-sharpening phenomenon can be evaluated quantitatively. Micro sharp cutting edges on grains and normal grinding forces are suppressed. Subsequently, the relationship between the grinding characteristics and behaviors of the SG wheel working surface is investigated.
► Wheel wear evolution is a very important issue for railway industry. ► A computational tool that predicts the evolution of the wheel profiles is presented. ► Three alternative wear functions are ...implemented and compared. ► A good conformity between results obtained with a global and a local wheel-rail contact model is obtained. ► The local approach requires about twice the CPU time needed by the global method.
When compared with road traffic, railway transportation is safer, more comfortable, less polluting and presents less energy consumption per passenger/km. When compared with the airplane, high speed trains are able to compete for short and medium distances, with the advantage of having better energy efficiency and causing less pollution. However, to maintain the operational performance of railway vehicles, it is necessary that the quality of the wheel–rail contact is controlled, which requires, among others, a good understanding of the wear mechanisms of the wheels and the consequences of their changing profile on vehicle dynamics. In this work, a computational tool that is able to predict the evolution of the wheel profiles for a given railway system, as a function of the distance run, is presented. The strategy adopted consists of a commercial multibody software to study the railway dynamic problem and a purpose-built code for managing its pre and post-processing data in order to compute the wear. Three alternative wear functions are implemented to compute the amount of worn material on the railway wheels. The computational tool is applied here to a realistic operational scenario in order to demonstrate its capabilities on wear prediction. Special attention is given to the comparison of the results obtained with the different wear functions implemented in this work and to the global and local contact models used in such formulations.
Timely monitoring of wheel polygon is of great importance for the formulation of railway wheel maintenance strategies. In this study, a novel data-driven method for onboard and quantitative detection ...of wheel polygon is presented. First, the axle box acceleration (ABA) signal preprocessing method and stationarity test are introduced to select the relatively stationary signal from the measured data of ABA. Next, an iterative algorithm is developed to accurately extract the quasi-stationary ABA signals, representing each wheel rotation period. Then, an improved frequency domain integration method is developed to quantitatively capture the orders and roughness levels of the wheel polygon. Finally, the effectiveness and superiority of the proposed method is verified using the field-measured data of ABA and the wheel polygon in one cycle of wheel re-profiling. The results show that the proposed method can quantitatively capture the dominant characteristics of single- and multi-orders wheel polygons at different operating mileages with minimum and maximum absolute errors of 0.04 dB re 1 µm and −2.33 dB re 1 µm, respectively. The comparative analysis demonstrates that the proposed method outperforms the traditional time and frequency domain integration algorithms in the detailed characterisation of wheel polygon roughness levels.
This paper evaluates the performance of creep feed grinding γ-TiAl intermetallic (Ti-45Al-2Mn-2Nb) using electroplated diamond wheels. Firstly, a comparative analysis with the grinding results by ...using electroplated CBN wheels was conducted, mainly involving abrasive wheel wear behavior and maximum material removal rate below surface burn limit. It was found that the diamond wheel would produce much better grinding results including lower wheel wear rate and higher maximum material removal rate. Then the surface integrity obtained at different level of material removal rate was characterized with the utilization of the diamond wheel. The poor ductility of this γ-TiAl intermetallic material was found to have a marginal effect on the surface integrity, as no severe surface defects such as material pullout were generated during the stable wheel wear stage. For the involved operating parameters, a deformation layer was produced with ∼10 μm or more in thickness depending on the material removal rate used. Meanwhile, a work-hardened layer extending to more than 100 μm was produced with a maximum microhardness of above 520 HV0.05 (bulk value 360 HV0.05). The residual stress remained compressive, with a value of above −100 MPa and even up to −500 MPa for an elevated material removal rate. Shearing chip was the main chip type, indicating good wheel sharpness in the grinding process.
•Wheel-rail creepage-adhesion curves at high speed were obtained.•A simplified method was proposed to extract parameters to modify FASTSIM.•Dynamic wheel-rail interactions were obtained by numerical ...methodology under low adhesion.•Wheel-rail wear performances were primarily investigated under wet condition.
The evolution of wheel-rail dynamic interaction of a high-speed railway vehicle is essential for the simulation of wheel-rail rolling contact damage under low adhesion conditions. The main objective of this study is to reproduce the dynamic wheel-rail interaction behaviour under various interfacial contaminations by experimental and numerical modelling methodology. Firstly, the wheel-rail adhesion characteristics under different interfacial contaminations were obtained. Subsequently, a simplified numerical methodology was proposed to extract the parameters from the high-speed adhesion tests to modify the simplified theory of Kalker (FASTSIM). The initial slop reduction factor and the slip-velocity-dependent coefficient of friction (COF) were introduced based on the high-speed experimental curves. Furthermore, the modified wheel-rail rolling contact model was incorporated into a longitudinal vehicle-track coupled dynamic model. The wheel-rail dynamic interaction behaviours under different operational conditions were attained. Finally, the wheel-rail wear performances were primarily investigated for typical traction coefficients under wet conditions. Results show that the wheel-rail creep force drops dramatically when the wheel enters the low adhesion zone (LAZ). There is a sudden increase in the creep force when the adhesion recovers. In addition, the wheelsets begin to slide and have severe wear at LAZ when the traction coefficient is larger than 0.1 at high speed.
Urban rail transit usually contains many small radius curved tracks, and wheel flange wear is prominent, which greatly reduces the service life and increases the maintenance and replacement costs of ...wheelsets. Two metro lines in Shanghai of China had suffered from severe flange wear since 2017, and the flange wear rate increased gradually over the next three years. This paper presents the understanding and treatment of severe flange wear through field measurement and numerical simulation. The investigation results indicated that the key factors causing severe flange wear were poor rail gauge face lubrication, the use of a low conicity wheel profile for trains running on the two metro lines containing many small radius curved tracks, and the lack of timely maintenance of low rail profiles. Three countermeasures were proposed to mitigate wheel flange wear, which were evaluated through wheel-rail matching analysis and wheel wear prediction. Then, two countermeasures, i.e. improving rail gauge face lubrication and employing the LM-30 wheel profile, were verified through field tests.
Although acceptability is commonly used to examine liking for food products, more studies now emphasize the importance of measuring consumers' conceptualizations, such as emotions for food products. ...It is also important to identify how consumers perceive the sensory attributes of food products, as illustrated by the increasing involvement of consumers in product characterization. The objective of this paper is to examine the use of a wheel-format questionnaire to obtain both an emotional and sensory profiles for food products using a hands-on consumer tool. Terms selected were product-specific and the rate-all-that-apply (RATA) approach was used as a scaling technique. Three different experiments demonstrated that the EmoSensory® Wheel could discriminate within and between food product categories. The added value of the RATA approach was illustrated in the sample discrimination for some food products when using the weighted attribute scores for analysis. The tool was used in both blind and informed conditions to illustrate its applicability across different experimental designs. In general, the respondents did not find the task tedious when using the wheel-questionnaire format, demonstrating the potential for collecting information in a more facile way. Although further studies with other food products are needed, this paper shows the potential for using this wheel format to obtain information about consumers' emotional and sensory profiling of food products.
•The use of a wheel format to obtain emotional and sensory profiles was studied.•This new format used consumer defined terms and applied the RATA approach.•EmoSensory® Wheel discriminates between and within different food products.•This format has the potential for research and commercial applications.
Abrasive material and hardness of grinding wheel are two important factors affecting the grinding efficiency and quality. In this study, two kinds of abrasive grains (i.e., zirconium corundum (ZA) ...and brown fused alumina (BA)) were used to produce eight grinding wheels, among which five with different contents of abrasive grains and four with different hardness levels. Rail grinding experiments were conducted to investigate their grinding efficiency (grinding amount of rail), grinding quality (including surface roughness, surface burn, white etching layer (WEL), and residual stress), and wear types of grinding wheels. The results show that ZA grinding wheel produced larger grinding amount, higher surface roughness, but lower level of surface burn, thinner WEL, and smaller parallel residual stress than BA grinding wheel. With the increase in grinding wheel hardness, the surface roughness and residual stress of ground rail showed decrease trends, but the thickness of WEL increased. The wear type of ZA grains was macro-fracture and the wear type of BA grains was attrition wear. With the increase in grinding wheel hardness, the wear type was changed from grain pullout wear to macro-fracture. Based on the analysis of results, the appropriate grinding wheel was recommended that can improve the grinding process and reduce the grinding cost.
•Effect of abrasive grains of grinding wheel on rail grinding behaviors was studied.•ZA grinding wheel was better than BA grinding wheel for rail grinding.•Increase in grinding wheel hardness improved grinding quality but reduced efficiency.•Wear type of grinding wheel was effected by abrasive type and wheel hardness.
•Mars rover wheels’ driving performance is obtained especially when complete skid.•The influence of large load on driving performance indices is studied.•The radial, axial, torsion, and deflection ...stiffness of Mars wheel are obtained.•The wheel ribs affect driving performance by reducing sinkage and drawbar pull.
The soft ground and stones on the surface of Mars may cause sinkage of and damage to the wheels of a Mars rover. Therefore, we analyzed the performance of a wheel-step Mars rover from the perspective of terramechanics and structural mechanics. Using China’s Mars rover wheel prototype and wheel-soil interaction testbed, we obtained the driving performance of the wheels of a Mars rover under various conditions, including full skidding conditions. The vertical load set in the tests was determined using the gravity of Mars and the mass of the wheel-step Mars rover. The results indicate that the driving torque, sinkage, and resistance coefficient have a linear relationship with the wheel vertical load. An analysis of the structural mechanical characteristics of the wheel of the Mars rover was conducted by testing the radial, axial, torsional, and deflection stiffness. We found that the wheel ribs can improve the stiffness of the wheel but may reduce its driving performance. The analysis methods and evaluation indices can be used to analyze the performance of the wheels of other Mars rovers. Furthermore, the findings of this study can be used to optimize wheel design and motion control of wheel-step Mars exploration rovers.
Railway wheels are a crucial part of the system, which provide necessary traction on railway tracks by carrying cyclic loads. Therefore, it is important to understand the various failure mechanisms ...of railway wheel sets and the causes to prevent the failure for safety issues. All various railway wheel failures such as crack and rim, crack at rim and disc interface, circumferential chipping-off, wheel tread shelling, thermal crack on wheel tread, wheel tread wear, fatigue, creep, wheel gauge widening, and wheel gauge condemning and their corresponding causes also discussed in this manuscript. Further, it gives detailed wheel failure scenarios in tread and disc braking of locomotive, wagon, and coach wheels. The in-depth details of various wheel failure sceneries observed and analyzed from the field, and case studies are also reviewed in detail.
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