This paper deals with field validation of the force response from a defective wheel after normal service. The defective wheel represents a typical defect arising from normal winter operation in a ...cold climate. The current detector is a typical wheel load impact detector that has been in use for about fifteen years; this type of detector is widely used in the infrastructure. The wheel has defects of up to1.8 mm in depth and an un-roundness of 0.2 mm. The results from this investigation, pertaining to the particular vehicle and wheel defect, show a linear correlation of speed and force response. Each change in speed of 1 km/h changes the force response by about 0.9 kN.
•This paper deals with field validation of the force response from a defective wheel after normal service.•The current detector is a typical wheel load impact detector that has been in use for about fifteen years; this type of detector is widely used in the infrastructure.•The results from this investigation show a linear correlation of speed and force response.•Each change in speed of 1 km/h changes the force response by about 0.9 kN.
A single-point diamond dressing tool was used to cut shallow circumferential groove on aluminum oxide grinding wheels. Creep-feed grinding experiments were then carried out to compare the performance ...of these grooved wheels with a non-grooved wheel. The results showed that, for the conditions used in this research, a grooved wheel could remove twice as much material as a non-grooved wheel before workpiece burn occurred. The results also showed that a grooved wheel can improve grinding efficiency by reducing the consumed power by up to 61%. Although the use of grooved grinding wheels caused the workpiece surface roughness to increase slightly when compared to a non-grooved wheel, the grooved wheel enabled up to 37% more material to be removed while still maintaining workpiece surface roughness values below 0.3μm (“fine quality” surface finish), and up to 120% more material to be removed while still maintaining workpiece surface roughness values below 1.6μm (“average quality” surface finish).
The research on wheel–rail relationship includes the basic theoretical models and corresponding numerical methods of wheel–rail in rolling contact, geometric parameter matching and material matching ...of them, friction and wear, wheel–rail rolling contact fatigue, wheel–rail adhesion and noise. They are also key theoretical and technical problems of the high-speed train/track coupling system. The basic theoretical models of wheel–rail in rolling contact and the corresponding numerical methods are the basis and one of the basic means for solving other wheel–rail relationship problems. The other is the experimental means. Moreover, the modeling and analysis of coupling behavior of the train and track can only be realized by means of the wheel–rail rolling contact mechanics model and its corresponding numerical method. This paper mainly discusses some research work and achievements on high-speed wheel–rail relationship problems since China opened a high-speed railway system on a large scale. The discussions in this paper include the classic wheel–rail rolling contact theoretical models (analytical forms) and the modern wheel–rail rolling contact theories (numerical methods), their advantages and disadvantages, their application and future development direction of them. The reviewed research progress on the other wheel–rail relationships mainly expounds the thorny problems of the wheel–rail relationship encountered in the operation of China’s high-speed railway, how to adopt new theoretical analysis methods, test means and take effective measures to solve these problems. It also includes research results of similar important reference values performed by international peer experts in related fields. Challenging and unsolved problems in high-speed wheel–rail relationship research are also reviewed in the full text.
•The electromechanical coupling circle in IWM-EVs is considered by developing an integrated model.•The key factors to cause the unbalanced electromagnetic excitation in IWM is discussed and its ...influence on the ride comfort in IWM-EVs is analyzed.•Corresponding control method based on active suspension system is proposed and the optimization process is conducted.•Intelligent methodology is adopted to guarantee the global optimal of the vehicle dynamic responses.
This paper presents a multi-objective optimization control method of active suspension system for solving the negative vibration issues emerged from In-Wheel-Motor (IWM) in electric vehicles. An integrated model which considering electromechanical coupling between electromagnetic excitation in motor and transient dynamics in vehicle is established and developed. The characteristics of electromagnetic excitation are discussed and its influences on vehicle dynamics are analyzed. The key factors are formulated and selected as the objective criteria for multi-objective optimization approach. The Pareto solution set of optimal parameters in active suspension system is generated by Particle Swarm Optimization (PSO) method, a comparison in vehicle dynamic performances is made to verify the targeted optimization method. The simulation results indicate that the optimized active suspension system can effectively reduce the vertical component of unbalanced electromagnetic excitation by maintaining the relative eccentricity of driving motor in a reasonable interval meanwhile attenuate the sensitivity of the vehicle system to electromagnetic excitation. Furthermore, active suspension system also preserve dynamical advantages in vehicle by means of a balance between the ride comfort and the road holding. The proposed multi-objective optimization method of active suspension system demonstrates a potential application in engineering in order to solve vibration issues in electric vehicle with in wheel motor.
Most contact models addressing the solution of the tangential problem assume an elliptical shape of the contact patch which is derived from the Hertz theory. In particular, the linear theory of ...rolling contact developed by Kalker is based on this assumption. However, it is well known that in many practical cases the shape of the contact region formed between the rail and a railway wheel can be far from elliptic. Recently, the Simple Double-Elliptic Contact (SDEC) shape has been proposed as an approximation of a wide variety of non-elliptic patches. In this paper, a formulation of the linear theory of rolling contact for a SDEC shape is proposed. The coefficients of the original linear theory for elliptic patches are maintained and four new coefficients are introduced to consider the effect of non-ellipticity. The coefficients of the theory are derived numerically using software CONTACT. Then, an extension of FASTSIM for a SDEC region is introduced and the obtained creep force curves under various conditions are compared to existing formulations of FASTSIM, using results from software CONTACT as a reference. The comparisons show that the proposed model is as fast as FASTSIM and provides more accurate solutions than existing versions of FASTSIM.
The purpose of this work is to gain a better understanding of the complex damage phenomena taking place at the railway wheel/brake block interface due to thermo-mechanical loading. Initially, ...full-stop braking was studied using Finite Element (FE) simulations to estimate the temperature reached in the wheel rim. Experiments to reproduce wheel damage were conducted with a two-disc machine using test conditions that were based on the results of the FE simulations. Three different wheel steels were tested against the same cast iron shoe material. The evolution of the wheel disc damage was studied at various numbers of cycles under fixed contact pressure and sliding speed. The friction coefficient and the temperature on the wheel disc surface were measured during the tests. At the end of the experiments, the wheel disc was examined and characterized. Cross-sections were observed with an optical microscope and the hardness was measured as a function of the depth to investigate the damage mechanisms that occurred at surface and subsurface. Material transfer from the shoe specimen to the wheel specimen results in the formation of a discontinuous “third body” layer, and that layer plays a key role in the evolution of the wheel disc damage. When the transferred layer of brake material is worn away, detachment of steel from the wheel disc surface occurs, probably promoting the crack nucleation. In addition, wear debris from both disc materials promotes three-body abrasive wear of the wheel disc surface.
•The damage phenomena taking place at the wheel/brake block interface were investigated.•The temperature map in the wheel rim was estimated by thermal FE simulations.•Experimental tests were performed with a two-disc machine to reproduce the wheel damage.•The brake material transfer plays a key role in the wheel disc damage evolution.
•Examines eight emotions of customer reviews in the restaurant context.•Introduces linguistic style matching to analyze readers’ diagnosticity of reviews.•Identifies six emotions and linguistic style ...matching significantly affect the perceived review helpfulness of customers.•Contributes to the evolving knowledge of customer perceived usefulness of online customer reviews.
Many consumers feel overwhelmed by the unwieldy glut of information on peer-review websites (e.g., Yelp). Review helpfulness as a peer-rating mechanism on these websites enable consumers to quickly identify the most informative reviews and thus decreasing the information overload. The purpose of the study was to examine the influential factors on review helpfulness for restaurants on Yelp from affective content and communication style perspectives. The affective content was evaluated with eight emotional dimensions (joy, sadness, anger, fear, trust, disgust, anticipation, and surprise) in Plutchik’s emotion wheel. The communication style perspective was assessed with linguistic style matching (LSM). 262,205 pieces of consumer reviews were analyzed with negative binomial model. Both LSM and six out of the eight emotional dimensions (except anticipation and surprise) were found to have significant impact on review helpfulness. The study contributes to the knowledge body of review effectiveness from an innovative angle and provide pertinent managerial implications.
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.
Dynamic wheel–rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds. Based on ...laser scanning, the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle–track interaction to calibrate and verify a simulation model. The relation between the magnitude of the impact load and various operational parameters, such as vehicle speed, lateral position of wheel–rail contact, track stiffness and position of impact within a sleeper bay, is investigated. The calibrated model is later employed in simulations featuring other forms of tread damage; their effects on impact load and subsequent fatigue impact on bearings, wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed. The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear, and for general assessment of the severity of different types of railway wheel tread damage.
► 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.
