Filtern
Dokumenttyp
- Beitrag zu einem Tagungsband (25)
- Vortrag (24)
- Zeitschriftenartikel (7)
- Buchkapitel (6)
- Posterpräsentation (3)
- Beitrag zu einem Sammelband (1)
Sprache
- Englisch (66)
Schlagworte
- Sloshing (6)
- Cargo (5)
- Rail (5)
- Railway (5)
- Road (4)
- Road tankers (4)
- Simulation (4)
- Vehicle (4)
- Atmospheric (3)
- Centre plate (3)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (24)
A facility is proposed in this paper to apply a selective carburizing process to the lateral faces of a railways´ head, aiming to increase its carbon content and to decrease the friction coefficient in case that the flange of the railway car wheel gets in contact with the rail during turning. Such a treatment would reduce the energy that is lost during the turning maneuvers performed by the vehicle, further improving the energy efficiency of the railway car. The facility consists of a furnace, which should be set next to the rails´ hot-rolling facility, in order to use the available enthalpy. The proposed furnace is equipped with what is necessary to avoid the decarbonization of the remaining rail material, based upon batteries of oxy-acetylene burners that are installed at the bottom of the furnace, on the opposite side to the carburizing surface. An experimental facility is necessary to validate the operational principles for the equipment proposed in this paper. On the other hand, a study should also be carried out to assess the effect of any rail welding process on the carburized surfaces.
A simplified formulation is proposed in this paper to assess the proximity of the earthquake-related Perturbation frequencies to the natural sloshing frequencies of the liquid contained in vertical cylindrical tanks. The methodology is based upon an existing gravity-waves approach, which was developed for rectangular cross-section reservoirs, and is extended in this paper to analyze circular cross-section tanks.
The experimental outputs of this paper show that the existing methodology correlates at 100% with experimental data in the case of rectangular containers; while the corresponding average error in the case of a conical container and a cylindrical container is 7% and 9.1 %, respectively. The full diameter of the cross section was considered. The use of sovalidated methodology to full scale tanks, suggests that cylindrical vertical tanks with a capacity lower than 700 m3, could be exposed to a resonance excitation when subjected to
earthquake motions, regardless of the fill level.
An experimental model has been proposed to measure the energy losses due to the centre plate friction. The physical principles of the testing are based upon the loss of potential energy during turning.
The testing rig includes a variable friction centre plate. A stick
slide model was proposed for the centre plate, whose results suggest significant losses of potential energy due to centre plate friction, around 20 %.
Turning maneuvers performed by railway cars, imply the development of steering forces at the wheel-track interface, whose magnitude depends on a set of properties and operating conditions related to the vehicle and to the infrastructure, including track´s turning radius and vehicle´s yaw resistance.
Yaw resistance integrates two components. On the one hand, there is the yaw stiffness, as a function of the different vehicle suspension components. On the other hand, there is the dry friction at the centre plate. Such yaw resistance of the car´s bogies, has a two-contradictory effect on railway performance, as a flexible bogie reduces the level of the steering forces, but at the same time, it increases the probability of having hunting instability. A variable yaw resistance, with high values at straight track segments and low values at curved tracks, seems to be an interesting design. In this paper, a variable friction Center plate is proposed, aiming at maximizing the yaw resistance on straight track segments, and minimizing such resistance at curved tracks. The conceptual design of this device is described, together with its ability to reduce the yaw torque. Benefits of this device, regarding the transport energy consumption and the magnitude of the steering forces, are estimated on the order of 1 to 10, when comparing the proposed design with the standard center plate design.
The magnitude of the steering forces at the wheel-track Interface depends on different properties and operational conditions linked to the vehicle and to the track, with the bogie´s yaw stiffness/resistance and the friction at the centre plate being recognized as the most influential vehicle factors. In this respect, the negative consequences of high values for yaw resistance have been recognized in terms of the railway accelerated deterioration and on the possibility for derailment. While some theoretical models have been proposed to simulate the effects of the centre plate friction on the railway damage, and experimental measurements have been reported of the turning resistance, no experimental data is available regarding the effect of the friction at the centre plate on the wheel-track forces. In this paper the conceptual design of a testing rig is presented for assessing such forces as a function of the center plate friction. The testing rig quantifies the effects of the friction forces developed at the centre plate, in terms of the loss of potential energy when a scaled-down vehicle travels downwards and tries to return upwards in a “U turn” maneuver. A simplified mathematical model is also proposed in this paper, whose Outputs suggest a significant effect of the dry friction on the magnitude of the steering forces.
Braking-in-a-turn maneuvers represent a critical operational condition for any vehicle, due to the associated longitudinal and lateral perturbations to which it is subjected, which maximize the load transfer among the different wheels, and result in vehicle´s poor lateral stability and deficient braking performance.
In this paper, a suspended vehicle supporting a partially filled 10 litter-capacity container, is set on a tilt table at oblique angles, in order to simulate a braking-in-a-turn maneuver. The measurements are assessed in the time and frequency domains, on the basis of the lateral load transfer ratio and the infrastructure fatigue damage. The outputs from the experiment show that the Minimum fill level (one-quarter), generates the larger lateral load transfer (0.45). Such fill level also causes the greatest ratios for the alternate stress over the mean stress on the infrastructure. The spectral analysis reveals the dominance of one of the sloshing frequencies during such combined perturbation condition.
The proposed mechanism is based on a cam design and is independent of any external energy source.
Conclusions
Issue 1: An accelerated wear tip of the cam shaped journal .
Issue 2: The spherical rollers proposed for the bearings would be underused, as the contact force will be downwards, and such bearing has supporting capacity in both vertical directions.
Vehicle’s components damage
(2020)
The failure of vehicle’s suspension components has contributed to road crashes, while their defective operation can deteriorate the fuel efficiency of the vehicles. In this context, and when compared with solid cargo transporters, the road tankers would tend to produce larger roll forces during turning, as the curved shape of the liquid cargo container, shifts upwards the centre of gravity of the cargo. With reference to a rectangular cargo container representing the solid cargo situation, the increase in the position due to elliptical and circular tank shapes, can attain a value of 17% (100% fill, circular tank). In this study, experimental results comparing the lateral load transfer due to solid and liquid cargoes, indicate that the average force increase on the vehicle’s load-receiver side due to a liquid cargo, is 4.3%. To analyse the fullscale situation of both situations, that is, the higher position of the centre of gravity and the shifting of the liquid cargo, a simplified model is developed. The outputs from such a model when subjected to realistic operating conditions (speed
and turning radius), suggest that the higher position of the centre of gravity due to using a non-rectangular cargo container generates an average force increase of 4.9% on the side receiving the load transfer. The incorporation of the effect of the liquid cargo, through the simple pendulum analogy, suggests that such an average increases to 6.76%, with a maximum of 8.35% in the case of the elliptical tank at 75% fill level. It is found that the average liquid cargo effect is 5.44%, which should be compared with the 4.3% of the experiments. Road tankers components would thus have a relatively shorter load cycle life than those of the solid cargo trucks.
Several geometrical analytical tools can be used for assessing the potential benefits of any alternative tank shape. The quasistatic evaluation of the cargo-vehicle behavior represents a fast way to objectively determine the roll stability benefits of any potentially new tank shape. In this paper, the geometrical, quasistatic rollover performance of a convex bottom tank shape is compared with that of standard tank shapes, finding that in spite of the lower position of the cargo´s center of gravity in such a tank shape for the un-perturbed condition, it has the same performance as the elliptical tank shape when subjected to Steady lateral acceleration. That as a result of the large cargo´s lateral displacement. Consequently, the combination of a lower center of gravity for the cargo when it is not perturbed, and a Minimum lateral shift due to lateral accelerations inputs, define the conditions for an ideal tank shape.
As a result of the vehicle – infrastructure interaction, both systems deteriorate. The development of performance measures about such effects, is critical to find ways to mitigate these systems deterioration. We propose an energy approach to such an assessment: The transient energy stored in the pavement. The transient strain energy stored in the vehicle suspension.
A testing methodology has been proposed in this paper, to compare the load transfer derived from solid and liquid cargoes when the carrying vehicle is subjected to a lateral acceleration in a tilt table. Besides the type of cargo, the other factors
(a) One-quarter fill level
(b) One-half fill level
(c) Three-quarter fill level
(d) Fast input
considered are the fill level and the rate at which the considered are the fill level and the rate at which the acceleration input is acceleration input is exerted on the vehicleexerted on the vehicle. The acceleration The acceleration input can represent the entering of the carrying vehicle into a input can represent the entering of the carrying vehicle into a curved portion curved portion of of aa road.
The testing device integrates the needed components to measure the fourmeasure the four--wheel loads of the wheel loads of the carrying vehicle, while carrying vehicle, while providing different times to attain providing different times to attain aa 10°10° angle angle for the tilt table. for the tilt table.
The performance measure selected is significant to assess the rollover trend of a vehicle, on the basis of the wheel loads at both sides of the vehicle. both sides of the vehicle.
The outputs from the experiments suggest that the sloshing suggest that the sloshing cargo transfercargo transferss the greater loads, the greater loads, regardless of the fill level and regardless of the fill level and acceleration rate inputacceleration rate input, as a result , as a result of the shifting of the center of of the shifting of the center of gravitygravity of the liquidof the liquid, and of of the the dynamic vibration at the end of dynamic vibration at the end of the perturbation input. In this respect, while the solid cargo the perturbation input. In this respect, while the solid cargo exhibits an initial peak and decay, the exhibits an initial peak and decay, the sloshing cargo exhibits sloshing cargo exhibits several oscillations of the saseveral oscillations of the same magnitude, which is attributed me magnitude, which is attributed to the to the liquid inertia and liquid inertia and to the to the reflection of the surface waves. reflection of the surface waves.
A further analysis could supplement this research, to assess supplement this research, to assess the effect of some other factors on the dynamic the effect of some other factors on the dynamic behavior of the behavior of the liquid cargoliquid cargo-vehicle system. Fvehicle system. For example, to analyze the effect or example, to analyze the effect of longitudinal baffles, and to validate theoretical models.of longitudinal baffles, and to validate theoretical models.
A simplified model, based upon physical principles, is proposed the simulate the effect of sloshing on the pressure developed in the tanker chambers. The model has been validated in good extent, with experimental data from full scale testing. The characteristic that mostly affects the pressure developed with the chambers of the tanker is the length of the chamber. While a reduction in this property could decrease the pressure developed within a given chamber, the analysis should take into account an overall approach, as a shortening of the individual chambers would influence the number of chambers necessary to carry a certain amount of product. Consequently, the resulting model could be used to study different effects of the sloshing cargo on the carrying vehicles, including the length and position of the chambers along the tanker body.
A dynamic simulation model for a tanker ship along the Rhine River has been proposed, based on a simplified computational scheme, involving a two-degree-of-freedom roll plane multibody system, subjected to lateral accelerations estimated on the basis of measured data. The resulting equations of motion are solved through the transition matrix approach. The results suggest that many contributing factors were involved in the capsizing of the ship, including the relatively high speed of the river water and the meandering path of the infrastructure, further affected by dynamic effects derived from the behavior of the payload and from the steering maneuvers performed.