ORCID Profile
0000-0003-1819-7772
Current Organisations
Iran University of Science and Technology
,
Delft University of Technology
,
Universiteit Utrecht
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Elsevier BV
Date: 04-2000
Publisher: SAGE Publications
Date: 22-04-2022
DOI: 10.1177/09544062221086150
Abstract: This research is concerned with the impact of onboard passengers’ seating arrangement on the carbody flexural vibrations of a high-speed railway vehicle. In this regard, the previously developed passenger body-seat models are used to consider the dynamic influence of the passengers. The carbody is modeled using the Euler–Bernoulli beam model to evaluate its flexural deformation. The frequency-domain analysis demonstrates that the carbody behaves almost like a rigid body when the vehicle is full of passengers. It is established that the passengers' presence causes a 31% enhancement of the ride quality determined based on EN 12299 standard for a fully occupied vehicle compared with an empty car. A scaled model of a ratio of 1:24.5 of the Shinkansen vehicle is constructed for validation purposes. The experimental results exhibit a similar trend as found by the simulations in terms of the impact of the passengers’ distribution on the carbody flexural vibrations.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Oxford University Press (OUP)
Date: 09-2010
DOI: 10.1017/S1727719100003877
Abstract: A number of factors affect rail vehicle steel wheels. Kinematic oscillations uncovered by Klingel, is amongst the parameters affecting dynamic behaviour of the wheelset. Normal and tangential forces are also included within the wheel/rail interface. Geometry and material properties of the contacting bodies are within these parameters. Altogether, these inputs to the rail/wheel system can result in plastic deformation and wear. The authors of this paper make their attempts to introduce a noble study including a harmonic wear pattern in circumference of the flange region when contacting the rail gauge corner. Theoretical aspects of this harmonic pattern are then developed and presented.
Publisher: SAGE Publications
Date: 26-09-2020
Abstract: In this research, the effect of rail vehicle carbody’s flexural modes on the ride comfort of an ex le high-speed railway vehicle is investigated. The vehicle is modeled as a rigid multi-body system, where the rigid body vertical, longitudinal, pitch, and roll degrees of freedom of the carbody and bogie frames and the rigid body vertical and roll degrees of freedom of the wheelsets are considered. An Euler–Bernoulli beam theory is used to account for the flexural motion of the carbody. The longitudinal interaction between carbody and bogie through the traction rod is modeled as a nonlinear spring element. The corresponding equations of motion of the system in the frequency domain are obtained by using the equivalent linearization method. The effect of the traction rod is explored by using this model. Also, the optimal stiffness of the traction rod element that minimizes the flexural vibrations of the carbody is obtained through a genetic algorithm. With the optimal stiffness for the traction rod, the ride quality index at the center of the carbody floor is improved by 41% at a speed of 300 km/h. For the validation of numerical results, a scaled model of the vehicle with a scale factor of 24.5 was constructed, and its associated results are presented. The model was excited by random input signals, which were generated based on the power spectral density of the track irregularity function. The agreement between the simulation results and the scaled experimental outcome when compared with the measured data from other sources is found to be satisfactory. In the framework of the physical scaled model, the filtering effect due to the vehicle bogie base is also examined.
Publisher: SciTech Solutions
Date: 08-2017
Publisher: Elsevier BV
Date: 2019
Publisher: SAGE Publications
Date: 20-04-2017
Abstract: This research is concerned with identifying the effects of windbreak geometry on attenuating aerodynamic loads that can be strong enough to disturb the running safety of high-speed trains. The idea is to suggest the proper geometry for the windbreaks that can make them more efficient and increase their overall performance. Generally speaking, the desired windbreak is the one that can minimize the aerodynamic forces on the surface of trains. In order to reach such an aim, the flow of air around an Intercity-Express 3 high-speed train has been estimated through a two-dimensional modeling by using the lattice Boltzmann method. The flow of crosswind that hits the train is considered as turbulent. The geometry of the windbreaks including the height, the slot, and the edge angles has been investigated. It has been concluded that the windbreak performance, among other parameters, is highly dependent on its height and edge angle. This research expedites the trail for finding suitable choices of windbreak geometries that can in turn provide a reliable degree of running safety of the railway fleet.
Publisher: Korean Society for Railway
Date: 30-09-2013
Publisher: SAGE Publications
Date: 16-11-2018
Abstract: The aim of this research is to propose and develop an analytical exact solution for finding the static equilibrium configuration of a catenary before and after incurring defects such as tension loss or a broken dropper. The procedure includes considering the steady-state solution of the dynamic motion equation of the contact wire and the messenger cable. The wire and the cable are considered as tensile Euler–Bernoulli beams. The stiffness matrix of the beam is configured and is used to calculate the dropper's dead load. Progressively, a novel method is proposed to find the equilibrium configuration of the same catenary after the defect. The results prove that the tension loss in the messenger cable is more precarious than the tension loss in the contact wire. The broken dropper causes a significant sag in the sub-span and increases the static forces of the adjacent droppers. A comparison with field measurements justifies the accuracy of the results of the proposed model.
Publisher: Informa UK Limited
Date: 18-04-2018
Publisher: Springer Science and Business Media LLC
Date: 29-07-2022
Publisher: Inderscience Publishers
Date: 2014
Publisher: JVE International Ltd.
Date: 30-06-2016
Abstract: The vibrations of pantograph passing underneath the overhead system can be reduced by using droppers to place the contact wire in the designed curve. Nowadays, various software programs are used to estimate dynamic interaction of pantographs and overhead catenary system. In order to implement the software program, the necessary static force for each dropper should be estimated initially to place the contact wire in the designed curve. Unlike most available software programs, the implemented software program in this research consists of a heuristic analytical algorithm to estimate the static shape of the overhead catenary system. Accordingly, the variable separation and eigen function expansion method were used to calculate the static shape of contact wire and messenger cable under a given loading condition. At the next step, the stiffness matrix of contact wire in catenary was obtained and a procedure was defined to calculate the necessary static force for each dropper, which would then place the contact wire in the target curve. Finally, effort was made to examine the function of automatic tension device in OCS (Tension Wheel considering the Coulomb’s friction). Moreover, the deformations in the contact wire and messenger cable due to temperature changes were estimated and the results shows that allowable friction in the tension wheel can cause 27 % deviation in sag of the contact wire.
Publisher: MAFTREE
Date: 15-11-2013
Publisher: MAFTREE
Date: 15-05-2013
DOI: 10.4273/IJVSS.5.2.03
Publisher: Elsevier BV
Date: 10-2018
Publisher: Springer Science and Business Media LLC
Date: 12-02-2023
Publisher: SAGE Publications
Date: 10-01-2019
Abstract: Continuous and quality contact between the pantograph and the catenary system is one of the major challenges for increasing the speed of electric trains. Compared to other studies, this paper has considered the catenary system as the main system and has assumed the pantograph as an excitation factor. Based on this, a controller has been applied on the contact wire, once at the last span and another time near the contact point of the pantograph. Results were compared with the conventional controllers that exert control force on a collector's head. Based on this, two different objectives were considered for the controller including ‘improvement of contact quality’ and ‘minimisation of the vertical velocity of the overlap point’. For this purpose, a full analytical model of the catenary system was presented and was verified using the relevant standards, and then three types of linear quadratic optimal controllers were added to the model with the two objectives mentioned above. The results of the study show that if the model aims to reduce the overlap point vertical velocity, contact quality will be improved. However, in case it aims to enhance contact quality, the velocity of the overlap point will not necessarily be reduced. Moreover, the contact point controller aiming at reducing the overlap point velocity outperforms other controllers and makes 71% improvement in contact quality in comparison with the no-controller case.
Publisher: Indian Journal of Scientific Research
Date: 08-2022
Publisher: SAE International
Date: 02-10-2020
Publisher: Elsevier BV
Date: 02-1996
Publisher: SAGE Publications
Date: 23-08-2011
Abstract: The fault tree analysis (FTA) is a well-structured, precise, and powerful tool that can be used to assist the analyst in identification, evaluation, and analysis of all basic causes and paths ending up to the occurrence of a certain event. In the conventional approach, the probability of the basic events is considered either as a precise point value or as a random time-dependent variable. However, due to the inherent imprecision and uncertainty of the available data, it is often impossible to obtain an exact estimation of an event occurrence rate or its distribution function. In such cases, the fuzzy approach is among the best choices for analysing the system. This article presents a comprehensive and transparent study on the evaluation of therailway safety risks using the fuzzy FTA. For this purpose, a method for quantification and evaluation of the fault tree in the fuzzy environment is proposed. The method that is presented in this article is based on modifying the weighted averaging according to the levels defuzzification method. Therefore, it proposes a new importance distribution function for the level sets during the defuzzification process. Furthermore, it extends the minimal cut-set and the Fussell–Vesely importance measures of the conventional approach into the fuzzy environment. These importance measures can be effectively used for the ranking of the minimal cut-sets and the basic events according to their contribution to the top event probability. Also, a practical case study regarding a passenger train derailment is used to describe the proposed concepts. The planned methodology is relevant in several engineering applications.
Publisher: MAFTREE
Date: 15-05-2013
DOI: 10.4273/IJVSS.5.2.05
Publisher: Korean Society for Railway
Date: 28-04-2013
Publisher: MAFTREE
Date: 15-05-2013
DOI: 10.4273/IJVSS.5.2.04
Publisher: Springer Science and Business Media LLC
Date: 12-2020
Publisher: Springer Science and Business Media LLC
Date: 28-02-2020
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2011
Publisher: Elsevier BV
Date: 2017
Publisher: ASME International
Date: 07-1993
DOI: 10.1115/1.2921672
Abstract: Transient solutions are still widely used for evaluating the vibrational behavior of rotor bearing systems containing dynamically loaded journal bearings with large unbalance, or noncircular orbit type squeeze film d ers, such as d ers without centralizing springs. For parametric design studies, such transient analyses need rapid means for evaluating the motion dependent fluid film forces and for narrow bearings or d ers (aspect ratios less than 0.5) the short bearing approximation (SBA) to the Reynolds equation has generally been assumed. Comparisons with exact numerical solutions under conditions of static loading and pure squeezing show that the SBA pressure profile predictions are significantly in error for aspect ratios as low as 0.25 at eccentricities around 0.9, whereas the optimal parabolic axial profile approximation (MSBA), while retaining all the rapid calculation features of the SBA, is accurate to within 1 percent under the same conditions and to within 3 percent for aspect ratios around 1.0. Using the MSBA as a yardstick under transient solution conditions, the SBA, while satisfactory for aspect ratios of 0.05, was found to be inadequate in predicting transient and steady state orbits and transmitted forces at aspect ratios of 0.5. At these aspect ratios, jump speeds and instability threshold speeds were also found to be erroneously predicted, with speed overestimates of 30 percent possible for practical unbalance situations. In view of the vastly improved accuracy obtainable by the MSBA, its use is to be preferred to the SBA under dynamic loading conditions for aspect ratios around 0.5, and probably around 0.25 or lower.
Publisher: Society for Industrial & Applied Mathematics (SIAM)
Date: 22-06-2023
DOI: 10.1137/22M148029X
Publisher: Springer Science and Business Media LLC
Date: 08-2012
Publisher: SAGE Publications
Date: 12-06-2019
Abstract: This study is focused on the effects of bending and torsional flexural modes of the car body on the ride quality index of a high-speed train vehicle. The Euler–Bernoulli beam model is used to extract an analytical model for a high-speed train vehicle car body in order to investigate its bending and torsional flexural vibrations. The rigid model includes a car body, two bogie frames, and four wheelsets such that, each mass has three degrees of freedom including vertical displacement, pitch motion, and roll motion. The results obtained with the proposed analytical model are compared with experimental measurements of the car body response of a Shinkansen high-speed train. Moreover, it is determined that the bending and torsional flexural modes have significant effects on the vertical acceleration of the car body, particularly in the 9–15 Hz frequency range. Furthermore, the ride quality index is calculated according to the EN 12299 standard and it is shown that the faster the train the more affected is the ride quality by the flexural modes. In addition, the effect of coherence between two rail irregularities (the right and the left rails) on the results of the simulation is investigated. The results conclude that if the irregularities are completely correlated the torsional flexural mode of the car body does not appear in the response. Also, the first bending flexural mode in such cases is more excited compared with the partially correlated or uncorrelated rail irregularities. Therefore, the ride quality index in completely correlated cases is higher than other cases.
Location: Iran (Islamic Republic of)
Location: Iran (Islamic Republic of)
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Mohammad Ali Rezvani.