| 1. |
- Andersson, Evert, et al.
(författare)
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Assessment of train-overturning risk due to strong cross-winds
- 2004
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 218:3, s. 213-223
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the methodology for safety assessment related to the risk of a train overturning in strong cross-winds. As an example, this methodology is applied on the high-speed line Botniabanan being built for a maximum speed of 250 km/h in the northeast coastal region of Sweden. The process starts with a systematic identification of locations along the line having a potential high risk of overturning due to cross-winds. This is followed by a cross-disciplinary study. The first step is to estimate the probabilities of wind velocity and wind directions. The next step is aerodynamic computation of overturning forces and moments acting on relevant types of train. Further, the critical overturning wind velocity is determined by a multi-body simulation technique. Finally, the overturning accident frequency is calculated. The calculated risk is compared with generally accepted risk levels in modern train operation.
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| 2. |
- Berghuvud, Ansel
(författare)
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Freight car curving performance in braked conditions
- 2002
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 216:1, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- Railway freight vehicles that are run with full payload on long downhill slopes with many tight curves must be braked more or less continuously. The influence of braking on the curving performance of iron ore freight cars equipped with different types of three-piece bogie designs and pneumatically actuated single-block tread brakes run on curved track in a downhill slope is investigated. The focus is put on the change in performance in terms of self-steering ability, track forces and expected wear in contacts between wheels and rails. Modelling and simulation of the strongly non-linear dynamic interaction between vehicle and track in braked conditions are performed. The large influence of wheel/rail profile matching and the quite different responses to braking for the studied vehicles are shown.
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| 3. |
- Dahlberg, Tore
(författare)
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Some railroad settlement models - A critical review
- 2001
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 215:4, s. 289-300
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mathematical models to simulate railroad track settlements are reviewed and commented upon. There do not seem to be any generally accepted damage and settlement equations describing the long-term behaviour of the track. This also seems to be the case for the ballast material. Most descriptions of the settlement found in the literature are empirical, only different suggestions to describe the track settlement from a phenomenological point of view are available. The track settlement is mostly considered to be a function of number of loading cycles and/or a function of the magnitude of the loading. The settlement should also be a function of the properties of the ballast and subground materials, but very little has been found on this in the literature. By use of the finite element program LS-DYNA, a computer model (very simple) has been created to simulate the long-term behaviour of the track. The model consists of a rail, rigid sleepers, non-linear ballast springs (stiffnesses) and ballast damping. In a solid element beneath each ballast spring, track settlement can be accumulated. Settlement will occur if the stresses in that element exceed a yield limit of the element material. Also 'hanging sleepers' may be modelled and obtained as a result of the track settlement.
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| 4. |
- Diedrichs, Ben
(författare)
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On computational fluid dynamics modelling of crosswind effects for high-speed rolling stock
- 2003
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 217:3, s. 203-226
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Tidskriftsartikel (refereegranskat)abstract
- This work addresses crosswind stability exemplified for the German Railway Deutsche Bahn AG high-speed train ICE 2. The scope of the work is to describe the flow by means of computational fluid dynamics past the leading two cars of the train for yaw angles in the range 12.2-40.0degrees. Three track formations are utilized. The basic results are the set of independent aerodynamic coefficients for the lead and subsequent cars. The results are to some extent compared with experimental data for ICE 2 and also with data obtained for the Swedish high-speed train X2000. A numerical sensitivity study is undertaken to quantify differences in the above results dependent on the grid density and quality, turbulence model, numerical scheme, location of inlet and outlet boundaries, turbulence intensity and flow simulation software.
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| 5. |
- Diedrichs, Ben, et al.
(författare)
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Quasistatic modelling of wheel-rail reaction due to crosswind effects for various types of high-speed rolling stock
- 2004
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 218:2, s. 133-148
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a quasi-static tool developed to assess the performance swiftly of crosswind stability for three types of rolling stock with conventional, semi-trailer and Jacobs bogie running gear configurations. The prediction accuracy of the results returned by the tool for the quasistatic assumption is fair in comparison with results of more advanced multibody simulation software that is commercially available. The codes, which are based on steady equilibrium equations for the wheels and axles, bogie frames and vehicle body/bodies, handle arbitrarily canted embankments and circular curves. To a large extent the accuracy hinges on the bodies' lateral displacements relative to the contact points between the wheels and rails; therefore proper modelling of the suspension systems and bump stops are found to be important. Examples are given of the limitations associated with the quasi-static approach, studying the following: (a) the combined wind and track scenario in Deutsche Bahn AG's guideline, (b) the effects of typical track irregularities for high-speed transportation as a function of train speed and (c) the effects of oscillating crosswind. It has also been found relevant to demonstrate some of the large differences regarding provisions regulating crosswind safety. To this extent the present results are compared with those derived with the British Group Standard and also with results presented in the guideline of Deutsche Balm AG. In addition, examples are given of the differences found of the permissible crosswind speed using calculated (with CFD-RANS) and experimentally obtained aerodynamic loads.
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| 6. |
- Kari, Leif
(författare)
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Audible-frequency stiffness of a primary suspension isolator on a high-speed tilting bogie
- 2003
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 217:1, s. 47-62
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Tidskriftsartikel (refereegranskat)abstract
- The preload-dependent dynamic stiffness of a primary suspension isolator on a high-speed tilting bogie is examined via measurements and modelling within an audible frequency range. The stiffness is found to depend strongly on both frequency and preload. The former displays some resonance phenomena, such as stiffness peaks and troughs, while the latter exhibits a steep low-frequency stiffness increase in addition to an anti-resonance peak shifting to a higher frequency with increased preload. The problems of simultaneously modelling the preload and frequency dependence are removed by adopting a frequency-dependent waveguide approach, assuming incompressible rubber with an Abel operator kernel as its shear relaxation function. The preload dependence is modelled by a non-linear shape factor based approach, using a globally equivalent preload configuration. All the translational stiffnesses are modelled, including the vertical, longitudinal and lateral directions, and the vertical stiffness results are compared to those of measurements in a specially designed test rig. Good agreement is obtained for a wide frequency domain-covering 100600 Hz-using a minimum number of parameters and for a wide preload domain-from vanishing to the maximum in service, 90 kN.
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| 7. |
- Olofsson, Ulf, et al.
(författare)
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Influence of leaf, humidity and applied lubrication on friction in the wheel-rail contact : pin-on-disc experiments
- 2004
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 218:3, s. 235-242
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Tidskriftsartikel (refereegranskat)abstract
- A novel test method has been used to study how applied and natural lubrication (leaf and humidity) influences the coefficient of friction in the wheel-rail contact. A pin-on-disc tribometer placed in a climate chamber was used as the test equipment. The pin-on-disc contact simulates the wheel-rail contact caused by commuter train traffic on straight track. The results show that the coefficient of friction decreases when the relative humidity increases and decreases even more when a leaf is used as a lubricant. By using an elm leaf as the lubricant, the coefficient of friction is reduced by a factor of four compared with the unlubricated case. However, the coefficient of friction decreases even more when a rail lubricant is used.
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| 8. |
- Olofsson, Ulf, et al.
(författare)
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Surface cracks and wear of rail : a full-scale test on a commuter train track
- 2002
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 216:4, s. 249-264
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Tidskriftsartikel (refereegranskat)abstract
- Damage mechanisms such as surface cracks and wear on a rail can reduce the service life of a railway track. The purpose of this investigation was to study the development of these two damage mechanisms on new and 3-year-old rails in a commuter railway track over a period of 2 years. Four curves were studied with radius between 303 and 616 m. In two of the curves, two different kinds of rail steel grade (UIC 900A grade with ultimate strength 900 N/mm2 and UIC 1100 grade with ultimate strength 1100 N/mm2) were used in each curve. In the other two curves, only the lower-strength rail was used. Four pieces of new rail, each 20 m long, were inserted in the two curves with both UIC 900A and UIC 1100 grade rail. Lubrication was applied on the high rail of one of the curves with both UIC 900A and UIC 1100 grade rail and on one of the curves with only UIC 900A grade rail. The two remaining curves were not lubricated. Surface cracks in the form of headchecks could be noted on the surface of the new 1100 grade rails after 1 month of traffic. By contrast, the surface of the UIC 900A grade rails showed visible surface cracks in only two of four curves and that after approximately 2 years of traffic. Both materials seemed to be similarly sensitive to crack initiation but the 1100 grade rail was more sensitive to crack propagation and also more sensitive to the formation of headcheck cracks. Lubrication, as expected, reduced the profile change. A less expected outcome was that lubrication also reduced the rate of crack propagation; however, the lubricated UIC 1100 grade rail was as sensitive to crack initiation as the unlubricated UIC 1100 grade rail. By comparing the wear depth in the headcheck zone with the crack length, equilibrium between these two damage mechanisms was found for the lubricated UIC 1100 grade rail. Both the crack length and the wear depth showed low values. By using a lubricant with friction modifiers the stresses was low enough to prevent crack propagation; at the same time, the rail was hard enough to reduce the wear rate. This is probably the most favourable state in terms of rail maintenance cost.
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| 9. |
- Telliskivi, T., et al.
(författare)
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Contact mechanics analysis of measured wheel-rail profiles using the finite element method
- 2001
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 215:2, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- A tool has been developed for contact mechanics analysis of the wheel-rail contact. Using measurements of wheel and rail profiles as input, the toot is based on the finite element (FE) code ANSYS. Traditionally, two methods have been used to investigate the rail-wheel contact, namely Hertz's analytical method and Kalker's software program Contact. Both are based on the half-space assumption as well as on a linear-elastic material model. The half-space assumption puts geometrical limitations on the contact. This means that the significant dimensions of the contact area must be small compared with the relative radii of the curvature of each body. Especially in the gauge corner of the rail profile, the half-space assumption is questionable since the contact radius here can be as small as 10 mm. By using the FE method (FEM) the user is not limited by these two assumptions. The profile measurement system Miniprof was used to measure the wheel and rail profiles that were used as input when generating the FE mesh. As a test case, a sharp curve (303 m radius) in a unidirectional commuter train track used by X1 and X10 trains was chosen. The results of two contact cases were compared with the results of the Hertz analytical method and the program Contact. In the first contact case the wheel was in contact with the rail gauge corner. In the second case the wheel was in contact with the rail head. In both contact cases Hertz and Contact presented very similar results for the maximum contact pressure. For the first contact case, a significant difference was found between the FE method and the Hertz method and the program Contact in all of output data. The Hertz and Contact methods both presented a maximum contact pressure that was three times larger (around 3 GPa) than the FE solution. Here, the difference was probably due to the combination of both the half-space assumption and the elastic-plastic material model. For the second contact case, there was no significant difference between the maximum contact pressure results of the three different contact mechanics methods employed.
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| 10. |
- Wibell, L, et al.
(författare)
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Increased mortality in diabetes during the first 10 years of the disease. A population-based study (DISS) in Swedish adults 15-34 years old at diagnosis
- 2001
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 249, s. 263-
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. To study, prospectively, in young adult patients, the mortality during the first years after the diagnosis of diabetes. Design. The Diabetes Incidence Study in Sweden (DISS) aims to register all incident cases aged 15-34 years. During a 10-year period all deaths were identified by record linkage to the national Cause of Death Registry. Subjects. During the period, 4097 new cases were registered and classified as type 1 diabetes (73%), type 2 (16%), secondary (2%) and unclassified (9%). The median follow-up was 5 years (21 001 person-years). Main outcome measures. Calculation of the standardized mortality ratio (SMR) and 95% confidence interval (CI). Evaluation of all deceased by scrutiny of clinical records, death certificates and autopsy protocols. Results. Fifty-eight patients died, corresponding to an SMR of 3.5 (CI = 2.7-4.5), which increased from 1.5 at 15-19 years to 4.1 at 30-34 years. SMR was 2.7 in primary diabetes: 2.3 (1.6-3.3) in type 1 and 4.1 (2.6-6.7) in type 2. In secondary diabetes, alcohol-associated pancreatitis a common cause, SMR was 32 (CI = 24-45). Evidence of alcohol or drug misuse, mental dysfunction or suicide was found in 40 of all 58 deceased cases. Less often, hypoglycaemia (n = 7) or hyperglycaemia-ketoacidosis (n = 11) was present at death. Unexplained 'dead in bed' was found once. Conclusions. In the investigated population-based cohort the early mortality was about threefold increased. Hypoglycaemia and ketoacidosis per se played a relatively small role compared with a heavy impact from social and mental dysfunction, and from careless use of alcohol or drugs.
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