| 1. |
- Aggestam, Emil, 1992, et al.
(författare)
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Multi-objective design optimisation of transition zones between different railway track forms
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - : TU Delft. - 2590-0609. - 9789461869630 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- The vertical dynamic interaction between vehicle and railway track is simulated in the time domain using an extended state space vector approach. The track model includes a transition zone between slab track on a bridge and ballasted track on an embankment. By considering a multi-objective optimisation problem, solved using a genetic algorithm, selected vehicle and track responses are simultaneously minimised by optimising the distributions of rail pad stiffness and sleeper spacing in the transition zone. It is shown that the magnitudes of the maximum dynamic loads in the optimised transition zone can be reduced to be similar as the magnitudes far away from the transition zone.
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| 2. |
- Ekberg, Anders, 1967, et al.
(författare)
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The role of contact mechanics in multiscale modelling of train-track interaction phenomena
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - 9789461869630 ; , s. 228-237
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Konferensbidrag (refereegranskat)abstract
- The paper examines possibilities for holistic modelling of the running gear/track interaction and related phenomena-in particular material deterioration phenomena. The required resolution, accuracy and challenges in understanding, describing and (in particular) modelling these phenomena are addressed. Special focus is put on contact modelling, which commonly sets the limit for the level of accuracy that can be achieved in subsequent analyses.
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| 3. |
- Esmaeili, Ali, 1983, et al.
(författare)
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Modelling of cyclic plasticity and phase transformations during repeated local heating events in rail and wheel steels
- 2018
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Ingår i: Proceedings - 11th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems. - 9789461869630 ; , s. 245-252
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Konferensbidrag (refereegranskat)abstract
- Short term local friction heating in railway operation might occur when a railway wheelset skids along the rail. The consequent temperature elevation is significant and in the pearlitic rail and wheel steels results in phase transformations. The temperature dependent differences in thermal expansion, density and mechanical properties of the phases result in residual stresses which can cause thermal damage in rail and wheel steels. This study is an improvement of Finite Element (FE) modelling incorporating phase transformation kinetics law describing transformation and evolution of volume fraction of phases. The FE modelling has included coupled thermal and mechanical analysis to compute residual stresses near the wheel-rail contact.
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| 4. |
- Floros, Dimosthenis, 1982, et al.
(författare)
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Evaluation of mixed-mode crack growth criteria under rolling contact conditions
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - 9789461869630 ; , s. 253-260
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Konferensbidrag (refereegranskat)abstract
- Fatigue crack growth direction criteria are evaluated towards a twin-disc experiment from the literature. The experiment is modelled numerically at different crack lengths. Based on numerically evaluated stresses, strains and displacements, a range of crack growth direction criteria from the literature are evaluated and compared to the experimentally found crack growth direction. In the considered experiment, the growth is essentially shear driven. Of the evaluated criteria employed to a linear elastic analysis, the Maximum Shear Stress (MSS) and Vector Crack-Tip Displacement (VCTD) criteria are found to be able to capture the experimentally found crack growth direction throughout the fatigue life.
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| 5. |
- Jessop, Casey, 1988, et al.
(författare)
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Friction between pearlitic steel surfaces
- 2018
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Ingår i: Proceedings - 11th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems. - 9789461869630 ; , s. 431-437
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Konferensbidrag (refereegranskat)abstract
- Experiments rubbing two pearlitic rail steel surfaces against each other were done using an axial-torsion test rig. After the experiments were completed, the surfaces were observed under stereomicroscope, and the wear debris were examined. The aim of the experiments was to evaluate the variation of friction coefficient between two surfaces of pearlitic rail steel, mimicking the friction which occurs between the faces of a crack during Rolling Contact Fatigue (RCF) loading. For both dry and wet conditions, the sliding velocity, the angles of rotation, and the average normal force were varied. It was found that the most significant effect of changing angles of rotation is on the formation of ridges on the contact surface with large angles, leading to a higher friction coefficient. The presence of water reduces the friction coefficient and leads to less deformation and wear in the contact surface.
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| 6. |
- Kabo, Elena, 1972, et al.
(författare)
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Rolling contact fatigue assessment of repair rail welds
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems (CM2018). - 2590-0609. - 9789461869630 ; , s. 450-456
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Konferensbidrag (refereegranskat)abstract
- A repair welding procedure is numerically simulated. To validate the numerical model, analyses of the temperature evolution are compared to full-scale test results. Further simulations are then carried out to evaluate the residual stress formation during welding and how the residual stress field is influenced by subsequent wheel passages. The influence of residual stresses from welding and the subsequent residual stress redistribution during operations on the risk of rolling contact fatigue (RCF) is discussed and analyzed. It is found that high tensile stresses are formed during welding, however these shake down substantially during subsequent operations. The influence on RCF is found to be moderate on the surface and somewhat more severe in a layer at the bottom of the repair weld. In addition to residual stresses, there is also a risk that welding introduces material defects and alters material properties. The influence of such phenomena on RCF are discussed.
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| 7. |
- Meyer, Knut Andreas, 1990, et al.
(författare)
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Characterization of yield surface evolution due to large plastic shear strains in pearlitic rail steel
- 2018
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Ingår i: Proceedings - 11th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems. - 2590-0609. - 9789461869630 ; 2018, s. 745-752
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Konferensbidrag (refereegranskat)abstract
- In order to analyze the material state in the rail surface layer during service, R260 rail steel has been subjected to large shear strains. The evolution of the yield surface at different amounts of predeformation, corresponding to different depths in the railhead, has been characterized. As expected, it is found that the size of the yield surface and the degree of anisotropy increase with the amount of predeformation. However, the major changes occur already after the first of six predeformation cycles, indicating that the yield surface is anisotropic several millimeters into the railhead.
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| 8. |
- Six, K., et al.
(författare)
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Assessment of running gears regarding rolling contact fatigue of wheels and rails based on stochastic simulations
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - : TU Delft. - 9789461869630 ; , s. 878-885
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Konferensbidrag (refereegranskat)abstract
- In this work a methodology is presented to assess running gears with respect to wheel and rail rolling contact fatigue (RCF). This assessment is based on wheel/rail contact data for different wheel profile wear states taken from a wheel profile prediction methodology. The approach allows e.g. The assessment of rail RCF in different curve radii in a cumulative way (sum of damage over lifetime of wheel profiles). Furthermore, RCF assessments can be done at different wear states of the wheel profiles to get insight how the contribution to wheel and rail RCF varies depending on the evolution of the wheel profiles. The presented methodology is exemplary applied to two bogie types, the UIC-Y25 standard bogie and the so called FR8RAIL bogie with a mechanical wheelset steering device. The presented methodology is a helpful tool e.g. To optimize vehicles already in an early stage of the development process.
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| 9. |
- Skrypnyk, Rostyslav, 1991, et al.
(författare)
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Simulation of damage in railway crossings - a comparison of rail steel grades R350HT and rolled Mn13
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems (CM2018). - 2590-0609. - 9789461869630 ; , s. 902-907
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Konferensbidrag (refereegranskat)abstract
- The application of a multidisciplinary methodology for the prediction of rail damage in railway crossings is demonstrated. Two rail steel grades are compared: R350HT and rolled Mn13. Based on a load sequence designed by Latin hypercube sampling considering the variation in traffic conditions, the results include the calculated plastic deformation and wear after a load collective corresponding to 0.8 MGT of traffic. The methodology has been introduced in earlier work but is here improved in terms of computational efficiency. Wheel-rail normal contact is solved using a Hertzian-based metamodel accounting for the inelastic material response. It is shown that the rolled Mn13 crossing experiences more ratchetting strain than the R350HT counterpart.
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| 10. |
- Walia, Mandeep Singh, 1987, et al.
(författare)
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Temperatures and wear at railway tread braking: Field experiments and simulation
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - 9789461869630 ; , s. 1029-1036
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Konferensbidrag (refereegranskat)abstract
- Field tests were carried out for a commuter train in revenue service equipped with cast iron and organic composite brake blocks. Temperatures for wheel tread, wheel web and brake blocks and wear of wheel treads and brake blocks were recorded. The measured temperatures are used for calibrating a thermal model for assessment of wheel and block temperatures. In addition, the results from thermal and wear simulations are presented. Comparisons are made between measured and simulated temperatures and wear. The wear of the cast iron brake blocks estimated using simulated temperatures and a temperature-dependent wear model calibrated from pin-on-disc experiments is in agreement with measured wear results from field tests.
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