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| 2. |
- Shahzamanian Sichani, Matin, et al.
(författare)
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A novel method to model wheel-rail normal contact in vehicle dynamics simulation
- 2014
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 0042-3114 .- 1744-5159. ; 52:12, s. 1752-1764
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Tidskriftsartikel (refereegranskat)abstract
- An approximate analytical method is proposed for calculating the contact patch and pressure distribution in the wheel-rail interface. The deformation of the surfaces in contact is approximated using the separation between them. This makes it possible to estimate the contact patch analytically. The contact pressure distribution in the rolling direction is assumed to be elliptic with its maximum calculated by applying Hertz' solution locally. The results are identical to Hertz's for elliptic cases. In non-elliptic cases good agreement is achieved in comparison to the more accurate but computationally expensive Kalker's variational method (CONTACT code). Compared to simplified non-elliptic contact methods based on virtual penetration, the calculated contact patch and pressure distribution are markedly improved. The computational cost of the proposed method is significantly lower than the more detailed methods, making it worthwhile to be applied to rolling contact in rail vehicle dynamics simulation. Such fast and accurate estimation of contact patch and pressure paves the way for on-line modelling of damage phenomena in dynamics simulation packages.
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| 3. |
- Shahzamanian Sichani, Matin, et al.
(författare)
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An alternative to FASTSIM for tangential solution of the wheel-rail contact
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System. - : CRC Press. - 9781498777025 - 9781138028852 ; , s. 1377-1385
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Konferensbidrag (refereegranskat)abstract
- In most rail vehicle dynamics simulation packages, creep forces are estimated by means of Kalker's FASTSIM algorithm. While 5%-25% error is expected for force estimation the errors of shear stress distribution, needed for wheel/rail damage analysis, may rise above 30%. This is mainly due to the use of parabolic traction bound in FASTSIM. Thus, a novel algorithm called FaStrip is proposed as an alternative to FASTSIM. It is based on the strip theory in which elliptic traction bound is used. The comparison between the two algorithms, evaluated by CONTACT, shows that using FaStrip improves the accuracy of the estimated shear stress distribution while the creep force estimation in all studied cases is significantly improved as well. In one case, for instance, the error in force estimation reduces from 18% to less than 2%. Since FaStrip is as fast as FASTSIM, it can be an alternative for tangential solution of the wheel-rail contact in simulation packages.
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| 5. |
- Shahzamanian Sichani, Matin, et al.
(författare)
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An alternative to FASTSIM for tangential solution of the wheel–rail contact
- 2016
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Ingår i: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 54:6, s. 748-764
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Tidskriftsartikel (refereegranskat)abstract
- In most rail vehicle dynamics simulation packages, tangential solution of the wheel–rail contact is gained by means of Kalker's FASTSIM algorithm. While 5–25% error is expected for creep force estimation, the errors of shear stress distribution, needed for wheel–rail damage analysis, may rise above 30% due to the parabolic traction bound. Therefore, a novel algorithm named FaStrip is proposed as an alternative to FASTSIM. It is based on the strip theory which extends the two-dimensional rolling contact solution to three-dimensional contacts. To form FaStrip, the original strip theory is amended to obtain accurate estimations for any contact ellipse size and it is combined by a numerical algorithm to handle spin. The comparison between the two algorithms shows that using FaStrip improves the accuracy of the estimated shear stress distribution and the creep force estimation in all studied cases. In combined lateral creepage and spin cases, for instance, the error in force estimation reduces from 18% to less than 2%. The estimation of the slip velocities in the slip zone, needed for wear analysis, is also studied. Since FaStrip is as fast as FASTSIM, it can be an alternative for tangential solution of the wheel–rail contact in simulation packages.
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| 6. |
- Shahzamanian Sichani, Matin, et al.
(författare)
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Non-Elliptic Wheel-Rail Contact Modelling in Vehicle Dynamics Simulation
- 2014
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Ingår i: The international Journal of railway technology. - 2049-5358 .- 2053-602X. ; 3:3, s. 77-94
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Tidskriftsartikel (refereegranskat)abstract
- An approximate rolling contact model is introduced for fast evaluation of the contactpatch and stress distribution in the wheel-rail interface, capable of being usedon-line with dynamics simulations. The normal part of the model is based on a novelapproach in which the surface deformations are approximated, resulting in accuratepatch and pressure estimation. The tangential part is based on an adaptation of FASTSIMalgorithm to non-elliptic patches. The new model is compared to the approximatemodel of Kik and Piotrowski and the results are evaluated using Kalker’s CONTACTcode. The comparison clearly shows that the new model is more accurate than Kikand Piotrowski’s in terms of contact patch and stress distribution as well as creepforce estimation.
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| 7. |
- Shahzamanian Sichani, Matin, 1986-
(författare)
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On Efficient Modelling of Wheel-Rail Contact in Vehicle Dynamics Simulation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The wheel-rail contact is at the core of all research related to vehicletrackinteraction. This tiny interface governs the dynamic performanceof rail vehicles through the forces it transmits and, like any high stressconcentration zone, it is subjected to serious damage phenomena. Thus,a clear understanding of the rolling contact between wheel and rail is keyto realistic vehicle dynamics simulation and damage analysis.In a multi-body dynamics simulation, the demanding contact problemshould be evaluated at about every millisecond for several wheel-rail pairs.Hence, a rigorous treatment of the contact is highly time-consuming.Simplifying assumptions are therefore made to accelerate the simulationprocess. This gives rise to a trade-o between the accuracy and computationaleciency of the contact model in use.Conventionally, Hertz+FASTSIM is used for calculation of the contactforces thanks to its low computational cost. However, the elliptic patchand pressure distribution obtained by Hertz' theory is often not realisticin wheel-rail contact. Moreover, the use of parabolic traction bound inFASTSIM causes considerable error in the tangential stress estimation.This combination leads to inaccurate damage predictions.Fast non-elliptic contact models are proposed by others to tacklethis issue while avoiding the tedious numerical procedures. The studiesconducted in the present work show that the accuracy of these models iscase-dependent.To improve the accuracy of non-elliptic patch and pressure estimation,a new method is proposed. The method is implemented in an algorithmnamed ANALYN. Comparisons show improvements in patch and, particularly,pressure estimations using ANALYN.In addition, an alternative to the widely-used FASTSIM is developed, named FaStrip. Unlike FASTSIM, it employs an elliptic traction boundand is able to estimate the non-linear characteristic of tangential stressdistribution. Comparisons show more accurate estimation of tangentialstress and slip velocity distribution as well as creep forces with FaStrip.Ultimately, an ecient non-elliptic wheel-rail contact model consistingof ANALYN and FaStrip is proposed. The reasonable computationalcost of the model enables it to be used on-line in dynamics simulationand its accuracy can improve the damage predictions.
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| 8. |
- Shahzamanian Sichani, Matin
(författare)
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Wheel-rail contact modelling in vehicle dynamics simulation
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The wheel-rail contact is at the core of all research related to vehicle-track interaction. This tiny interface governs the dynamic performance of rail vehicles through the loads it transmits and, like any high stress concentration zone, it is subjected to serious damage phenomena. Thus, a clear understanding of the rolling contact between wheel and rail is key to realistic vehicle dynamic simulation and damage analyses.In a multi-body-system simulation package, the essentially demanding contact problem should be evaluated in about every millisecond. Hence, a rigorous treatment of the contact is highly time consuming. Simplifying assumptions are, therefore, made to accelerate the simulation process. This gives rise to a trade-off between accuracy and computational efficiency of the contact models in use.Historically, Hertz contact solution is used since it is of closed-form. However, some of its underlying assumptions may be violated quite often in wheel-rail contact. The assumption of constant relative curvature which leads to an elliptic contact patch is of this kind. Fast non-elliptic contact models are proposed by others to lift this assumption while avoiding the tedious numerical procedures. These models are accompanied by a simplified approach to treat tangential tractions arising from creepages and spin.In this thesis, in addition to a literature survey presented, three of these fast non-elliptic contact models are evaluated and compared to each other in terms of contact patch, pressure and traction distributions as well as the creep forces. Based on the conclusions drawn from this evaluation, a new method is proposed which results in more accurate contact patch and pressure distribution estimation while maintaining the same computational efficiency. The experience gained through this Licentiate work illuminates future research directions among which, improving tangential contact results and treating conformal contacts are given higher priority.
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| 9. |
- Sichani, Matin Shahzamanian, et al.
(författare)
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Wheel-rail contact modeling for damage predictions in dynamics simulation software
- 2015
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Ingår i: CM 2015 - 10th International Conference on Contact Mechanics of Wheel / Rail Systems. - : International Conference on Contact Mechanics of Wheel.
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Konferensbidrag (refereegranskat)abstract
- A novel wheel-rail contact model is proposed to be implemented for multi-body dynamics simulation, in order to facilitate accurate online calculation of damage phenomena such as wear and rolling contact fatigue. The normal contact, i.e. contact patch and pressure distribution, is calculated using a fast non-elliptic algorithm called ANALYN. The tangential contact, i.e. tangential stress distribution, stick-slip division and creep force calculation, is treated using an alternative to the FASTSIM algorithm that is based on a strip theory which extends the exact two-dimensional solution of rolling contact to three-dimensional contacts. The proposed contact model is compared to the Kik-Piotrowski model and evaluated using the CONTACT code in terms of contact patch and stress distribution as well as creep force curves. The results show that the proposed model can significantly improve the estimation of the contact solution both in terms of creep force estimation and contact details, such as stress distribution, needed for damage predictions.
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