275,995 research outputs found
The Effect of Profiles on Wheel and Rail Damage
No full textThis paper outlines the historical development of the wheel and rail profiles currently used on railway vehicles. It also presents the key damage mechanisms involved in wheel-rail contact and summarises the methods that have recently been developed by railway engineers to predict the level of wheel and rail damage from these mechanisms. Tools for predicting the key damage modes of wear and rolling contact fatigue (RCF) are explained. Methods of optimising the wheel and rail profiles to reduce the overall damage and therefore improve the efficiency of the railway system are discussed and a case study from the UK of an ‘anti-RCF’ wheel profile is presented. Finally a novel method using a genetic algorithm is discussed which uses a penalty index to optimise the wheel profile for good running, low track forces and rail stress, low wear and RCF
Development and Validation of a Wheel Wear and Rolling Contact Fatigue Damage Model
No full textThis paper summaries the development of a damage model to predict the deterioration rates of the wheel tread in terms of wear and rolling contact fatigue (RCF) damage. The model uses a description of a fleet’s route diagram
to characterise the duty cycle of the vehicle in terms of curve radius, cant deficiency and traction/braking performance. Using this duty cycle a large number of vehicle dynamics simulations are automatically conducted
to calculate wheel-rail contact forces and predict the formation of wear and RCF damage, using a combination of the Archard and frictional energy-based (Tγ) damage models.
The damage models have been validated using observation data (wear rates and maximum observed RCF damage) acquired from a range of vehicle fleets in Great Britain (GB). Results from the validation of the model are presented along with a review of the wheel turning and observation data. A piece-wise linear regression is fitted to the wear and RCF parameters predicted from the model to determine the damage rates for each wheelset type on the vehicle. These damage rates are used within the recently developed Wheelset Management Model (WMM) to describe how the attributes of the wheel (i.e. wheel diameter, profile shape and tread damage) deteriorate over time and trigger a maintenance or renewal activity when the condition of the wheel matches a particular limiting value.
This work formed part of the rail industry research programme managed by the Rail Safety and Standards Board (RSSB), and funded by the Department for Transport, to increase the rolling stock functionality of the Vehicle Track Interaction Strategic Model (VTISM) tool
A Novel Approach To Modelling And Simulation Of The Dynamic Behaviour Of The Wheel-Rail Interface
No full textThis paper presents a novel approach to modelling and simulation of the dynamic behaviour of
rail-wheel interface. The proposed dynamic wheel-rail contact model comprises wheel-rail geometry and efficient solutions for normal and tangential contact problems. This two-degree of freedom model takes into account the lateral displacement of the wheelset and the yaw angle. Single wheel tread rail contact was considered
for all simulations and Kalker‟s linear theory and heuristic non-linear creep models were employed. The second order differential equations are reduced to first order and the forward velocity of the wheelset is increased until the wheelset becomes unstable. A comprehensive study of the wheelset lateral stability is performed and is relatively easy to use since no mathematical approach is required to estimate the critical velocity of the dynamic wheel-rail contact model.
This novel approach to modelling and simulation of the dynamic behaviour of rail-wheel interface will be useful in the development of intelligent infrastructure diagnostic and condition monitoring systems. The automated
detection of the state of the track will allow informed decision making on asset management actions – especially in maintenance and renewals activities
Non-linear dependency of the subjective perceived intensity of steering wheel rotational vibration
No full textThis is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2009 ElsevierThe present study has established equal sensation curves for steering wheel hand-arm rotational vibration. Psychophysical response tests of 20 participants were performed in a steering wheel rotational vibration simulator using the category-ratio Borg CR10 scale procedure for direct estimation of perceived vibration intensity. The test stimuli used were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with acceleration amplitudes in the range from 0.06 to 30 m/s(2) r.m.s. A multivariate regression analysis was performed on the mean perceived intensity Borg CR10 values as a function of the two independent parameters of the vibration frequency and amplitude. The results suggested a non-linear dependency of the subjective perceived intensity on both the steering wheel rotational vibration frequency and amplitude. The equal sensation curves were found to be characterised by a decreased sensitivity to hand-arm vibration with increasing frequency from 10 to 400 Hz, but by an increased sensitivity with increasing frequency from 4 to 10 Hz. A 6th order polynomial model has been proposed as a best fit regression model from which the equal sensation curves for steering wheel rotational vibration are derived.Relevance to industry: For the manufactures of automobiles, steering systems and other automobile components this study provides a mathematical model from which one or more new frequency weightings for the use in evaluating the perceived intensity of steering wheel rotational vibration are derived. (C) 2008 Elsevier B.V. All rights reserved
Computational Analysis of the Flow Around an Exposed Wheel
No full textThis thesis presents an investigation of RANS and LES models for the isolated rotating exposed wheel with moving ground with the aim of analyzing the flow behavior and comparing the results in cost/quality context. This is motivated by general demand for the drag reduction in automobile industry. In addition the demand is even stronger from high-performance car competition where the tyre wake has a great impact on total performance such as lift force or aerodynamic stability aspect. Cont/d
Contact Force Estimation in the Railway Vehicle Wheel-Rail Interface
No full textIncreased patronage of railways in the UK in the past 20 years has put demands on rolling stock to operate at peak availability with reduced time available for maintenance. One possible tool to enable this is the use of real time fault detection and diagnosis on board railway vehicles to detect faulty components and provide information about the current running condition of the system. This paper discusses the development of one such technique for the estimation of creep forces of the wheel-rail contact. Real time knowledge of which could be used to predict wear of the wheel tread and rail head, predict the formation of rolling contact fatigue, and identify any areas of low adhesion present on the network. The paper covers development of a full vehicle nonlinear contact mechanics model, development of the Kalman-Bucy filter estimation technique and how the technique will be developed and validated in the future
Actual challenges: Developing low cost no-till seeding technologies for heavy residues; small-scale no-till seeders for two wheel tractors
No full textSmall farmers from South Asia and other parts of the world use two wheel tractors as the main means of land preparation and other farm operations due to small farm and field size combined with an affordable price. These units have become very popular, and over 500,000 are manufactured annually worldwide. There are over 350,000 operating in Bangladesh alone. Two low cost and robust no-till seeders to suit two wheel tractors (12HP) have been developed at the Wheat Research Centre (WRC), Dinajpur, Bangladesh (with support from the Australian Centre for International Agricultural Research). This follows initial research and development work assisted by CIMMYT and Bangladesh Agricultural Research Institute from 1995 to 2004
Impact of wheel shape on the vertical damage of cast crossing panels in turnouts
No full textImpact forces generated in the load transfer area of railway crossing panels lead to a range of degradation modes from wear and fatigue of the contacting materials, fatigue of supporting components to ballast/subgrade deterioration. A simplified modelling approach has been developed to first analyse the geometrical problem of the axle rolling through the crossing geometry, and in a second step to predict the vertical dynamic force produce from the interaction between the wheel unsprung mass and the track system. The force is analysed in the frequency domain to estimate the level of damage in different parts of the track system. A parametric analysis of wheel shapes was carried out showing that the axle lateral displacement has a significant influence on the produced level of damage and also that characteristics such as the wheel flange thickness and the equivalent slope in the area of contact also leads to increased damage. It is suggested that such a measure in combination with the simplified algorithms developed here could be used, possibly in combination with track side monitoring system, to highlight traffic instances leading to increased asset damage
Proposed automobile steering wheel test method for vibration
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis proposes a test method for evaluating the perceived vibration which occurs at the driver's hand in automotive steering wheel interface. The objective of the research was to develop frequency weightings for quantifying the human perception of steering wheel hand-arm vibration. Family of frequency weightings were developed from equal sensation curves obtained from the psychophysical laboratory experimental tests.
The previous literature suggests that the only internationally standardised frequency weighting Wh is not accurate to predict human perception of steering wheel hand-arm vibration (Amman et. al, 2005) because Wh was developed originally for health effects, not for the human perception. In addition, most of the data in hand-arm vibration are based upon responses from male subjects (Neely and Burström, 2006) and previous studies based only on sinusoidal stimuli. Further, it has been continuously suggested by researchers (Gnanasekarna et al., 2006; Morioka and Griffin, 2006; Ajovalasit and Giacomin, 2009) that only one weighting is not optimal to estimate the human perception at all vibrational magnitudes.
In order to address these problems, the investigation of the effect of gender, body mass and the signal type on the equal sensation curves has been performed by means of psychophysical laboratory experimental tests. The test participants were seated on a steering wheel simulator which consists of a rigid frame, a rigid steering wheel, an automobile seat, an electrodynamic shaker unit, a power amplifier and a signal generator. The category-ratio Borg CR10 scale procedure was used to quantify the perceived vibration intensity. A same test protocol was used for each test and for each test subject.
The first experiment was conducted to investigate the effect of gender using sinusoidal vibration with 40 test participants (20 males and 20 females). The results suggested that the male participants provided generally lower subjective ratings than the female participants. The second experiment was conducted using band-limited random vibration to investigate the effect of signal type between sinusoidal and band-limited random vibration with 30 test participants (15 males and 15 females). The results suggested that the equal sensation curves obtained using random vibration were generally steeper and deeper in the shape of the curves than those obtained using sinusoidal vibration. These differences may be due to the characteristics of random vibration which produce generally higher crest factors than sinusoidal vibration. The third experiment was conducted to investigate the effect of physical body mass with 40 test participants (20 light and 20 heavy participants) using sinusoidal vibration. The results suggested that the light participants produced generally higher subjective ratings than the heavy participants. From the results it can be suggested that the equal sensation curves for steering wheel rotational vibration differ mainly due to differences of body size rather than differences of gender. The final experiments was conducted using real road signals to quantify the human subjective response to representative driving condition and to use the results to define the selection method for choosing the adequate frequency weightings for the road signals by means of correlation analysis. The final experiment was performed with 40 test participants (20 light and 20 heavy participants) using 21 real road signals obtained from the road tests. From the results the hypothesis was established that different amplitude groups may require different frequency weightings. Three amplitude groups were defined and the frequency weightings were selected for each amplitude group.
The following findings can be drawn from the research:
• the equal sensation curves suggest a nonlinear dependency on both the frequency and the amplitude.
• the subjective responses obtained from band-limited random stimuli were steeper and the deeper in the shape of the equal sensation curves than those obtained using sinusoidal vibration stimuli.
• females provided higher perceived intensity values than the males for the same physical stimulus at most frequencies.
• light test participants provided higher perceived intensity than the heavy test participants for the same physical stimulus at most frequencies.
• the equal sensation curves for steering wheel rotational vibration differ mainly due to differences in body size, rather than differences of gender.
• at least three frequency weightings may be necessary to estimate the subjective intensity for road surface stimuli
Effect of automobile operating condition on the subjective equivalence of steering wheel vibration and sound
No full textFor the manufacturers of automobiles, automobile components and fuels, subjective equivalence relationships between vibration and sound can be used as a reference against which to plot the results from simulations or tests of specific operational conditions. The research described here was performed to define curves of subjective equivalence between steering wheel rotational vibration and sound using stimuli from different automobile operating conditions. The steering wheel acceleration stimuli were summarised in terms of the unweighted and Wh weighted r.m.s. values, while the sound stimuli were summarised in terms of the unweighted SPL in decibels, the A-weighted SPL in decibels, the Stevens Mark VI loudness in sones, the Stevens Mark VII loudness in sones and the Zwicker loudness in sones. The results suggest that both the statistical properties of the stimuli, and the choice of metric, effect the shape of the equivalence curve. No single combination of vibration and sound metric produced a family of curves which were separated by less than a single psychophysical just noticeable difference
- …
