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- Sloshing (2)
- Tanker (2)
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- Assess (1)
- Avoid (1)
- Bogie design (1)
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Organisationseinheit der BAM
The efficiency and safety of railway transportation depend both on numerous factors linked to the vehicle, the infrastructure, the operator and the environment. Curved tracks are subjected to demanding situations due to elevated stress levels, as a function of the operating conditions and vehicle/infrastructure design. In such segments, steering forces are superimposed to lateral load transfers. The steering forces depend on the condition and the design of the centre plate and bogies’ suspensions design. While the friction at the centre plate provides the needed damping to mitigate the hunting vibration of the bogie in straight track segments, such yaw resistance originates high steering forces and rail damage on curved tracks. A centre plate with low friction at turns and high friction at straight track segments would thus be highly advantageous. In this paper, a centre plate design is proposed which provides a yaw-rotation resistance torque that depends on the bogie-car relative position. Two different designs are considered for that purpose, one that combines a spring-acted centring mechanism with a lower pair kinematics, while the other one involves higher kinematic pairs which should incorporate lateral damping elements. As a result of using an engineering design approach, the higher kinematic pairs-based design is recommended however, the validation of such operational principles, including the introduction of the needed damping, should be configured on the basis of experimental models.
A testing rig for the measurement of the dynamic loads on the rails due to cargo sloshing,has been proposedin this paper. The system represents a scale-down approach that simulates astraightening maneuver of the railway car after negotiating a turn. As part of the experimental effort, a mathematical model was developed that, oncevalidated, will provide more insights about the potential effect of many other cardesign factors, on the level of stress developed in the raildue to the sloshing cargo.A fundamental output from the testing, will be the objective comparison between the railloads due toa sloshing and a non-sloshing cargo, together with a validated model that wouldallow parametric studies in relation withthe potential effect,of several track and carproperties,on the magnitude of the sloshing forces on the rail.
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.
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.
Regardless of the mode of transportation, directional changes generate greater forces on the infrastructure as a result of the lateral load transfer and of the respective steering forces in the vehicles. In the case of Railway transportation, a concentrated damage occurs in the rail at the initiation of the turning maneuver, whose magnitude depends on the bogie´s yaw stiffness and on the level of friction at its centre plate. To mitigate such rail-damaging effects, some new designs have been proposed and used for the bogies´ wheelset. However, no new designs for the centre plate have been used. In this paper, a review of the causality for the forces arising during Railway Vehicle's turn negotiations, is presented, including the description of a modeling framework to analyze the influential Parameters for determining the magnitude of such forces.
The transportation of liquids involves several situations derived from the curved shape of the cargo containers, including a comparatively high center of gravity, which negatively shifts when the container is partially loaded, and the vehicle is subjected to steering or braking accelerations. Aiming at reducing these effects several experimental approaches have been applied, involving different tank shapes and the use of baffles, tested under laboratory or field conditions, at full scale or at a down-scale. However, the scope of such approaches has been limited, mainly because the potential effect of other components of the vehicle on the road tanker behavior, has been neglected. In this paper, a critical review is presented of the experimental approaches considered so far, identifying specific experimental needs to improve the performance of the vehicles, from both the road safety and the environmental perspective.
Externalities of the road transportation are multidimensional in nature and involve the road-vehicle interaction under different environmental conditions. Estimating the pavement and vehicle damage potentials as a function of the condition sunder which such interaction takes place, is important to avoid accelerated or catastrophic damages in these systems. Such an assessing is crucial from the perspective of pricing the effects of the vehicle on the infrastructure and vice versa. The existing models for pricing such interaction, critically depends on gross average statistical models. In this paper, it is proposed a deterministic approach to realize such an assessment, based upon validated approaches for the pavement damage. The simulation scheme considers different degrees-of-freedom vehicle models, and a discrete asphalt pavement, that make possible the simulation of massive traffic situations on realistic road lengths.
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.
GPS-data based calculation scheme for assessing, in real-time, the level of safety exerted during driving, has been described and used. The several variables involved considered the main factors that lead to road mishaps, including the speed, the acceleration and the effects that these variables have on the vehicle when it is negotiating a turn. The performance measure combines three individual performance outputs: speed, acceleration and a hybrid performance measure considering the speed, the acceleration and the change in latitude/longitude. The measures are designed in such a way that weighting factors can be calibrated in order to establish certain critical parameters. On the other hand, the terms in the equations preclude any division by zero of the involved ratios. On the other hand, the simplicity of the equations makes it possible to carry out the assessment in real time. The use of the resultant performance measure to a relatively long path, together with its current average value, indicates that the safe performance of the driving changes with time, and that, for the selected values of the calibration constants, the traveling speed dominates the overall safety performance of the driving. Furthermore, the different calibration constants provide the possibility of considering different types of hazmat carrying vehicles. While many other formulation components could be integrated into the performance measure, this three-component performance measure could be used to assess the driving of a hazmat-carrying vehicle, in order to detect and to prevent dangerous conditions, such as driver fatigue.
Finally, the implementation of the different performance measure formulations in a system such as the one described in the introduction of this paper, could be straightforward.
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.
Rear-end crashes involving heavy trucks as the leading vehicle, and cars as the impact vehicle, cause many deaths and permanent injuries to car´s occupants. Measures have been thus taken in the trucks to prevent underride crashes, including the mounting of stiffer underride guards, set at car´s bumper height. In this respect, an active acceleration system(AAS), installed in the truck, could also contribute to mitigate the effects of These crashes, through the decrease of the relative Speed of the vehicles at the instant of the crash. In this paper, an AAS system is proposed, under the principles of ultrasonic sensors and an actuator for the truck´s accelerator mechanism. Simulation results of the operation of this AAS system, suggest that such a system could decrease the relative impact speed around 8% for an initial relative speed of 10 m/s.
Simulation of liquid cargo – vehicle interaction under lateral and longitudinal accelerations
(2018)
Amongst the vehicle parameters influencing road safety, the carried cargo plays a critical role in the case of a liquid cargo, posing rollover risk and affecting the available friction forces for braking. While the lateral sloshing of the cargo within the vehicle´s compartments, can be excited when the vehicle negotiates a turn, the longitudinal motion of the cargo derives from changes of speed. The combination of both types of perturbations occurs when the vehicle brakes while negotiating a turn. In this paper, a two-pendulum formulation is used to simulate the lateral and longitudinal behavior of a vehicle when negotiating a braking in a turn maneuver. The suspension forces are thus calculated as the linear superposition of both models. Results suggest that the vehicle roll stability is affected by the cargo sloshing, with increments on the order of 100% in the lateral load transfer, for a 50% filled tank. On the other hand, the dispersion of the travelling speed also affects the lateral stability of such type of vehicles, as a function of the dispersion of the vehicle´s travelling speed.
The use of railway transportation for satisfying the transport needs of goods in Mexico is less intense than in developed countries, such as Germany. Mexican performance measures based upon the railway length per capita (intensity), or the railway length per square km of the country surface (density), are well behind from corresponding indicators for Germany, in such a way that the length of the railway infrastructure of Mexico should be, at least, doubled in order to reach a comparable intensity rate as that of Germany. In this paper, the benefits from transferring the whole transportation of goods from road to railway, is discussed. The benefits include a remarkable reduction in energy consumption and CO2 emissions. The feasibility for the electrical infrastructure to provide the necessary energy is further shown, while the economic feasibility of such situation is analyzed on the basis of the federal budget of Mexico. According to these estimations, the investment in railway infrastructure is feasible, while the electrical installed capacity is enough to satisfy an all-electric system.
Commidities and rail damage
(2018)
A roll-plane simplified model, representing the suspended body-cargo of a railway car, was developed to simulate thedynamic response of a railway car while subjectedto lateral acceleration derived from its traveling along curved tracks. The model provides the means to calculate the suspension forces, which are supposed to be transmitted to the bogie´s wheelset. For the analysis of the potential effect of such forces on the railway fatigue life, different performance measures were considered, under different concepts. A family of curves were produced to analyze the effect of the height of the center of gravity of the body-cargo system, on the different performance measures. The resultingdiagramswereused to assess the rail damage potentials offour different railway cars. Results suggest that the height of the center of gravity, associated to the different types of railway cars, nonlinearly and strongly affects the fatigue lifeof the rail, with the double stack car being the moreinfrastructure-aggressive. In this respect, experimental evidence should be provided about such remarkable effects, so as to supportsome operational recommendationsthat shouldbe taken to mitigate these effects, including, for example, the regulation of the traveling speed of some vehicles.
Transport safety depends in great extent of what happens to the cargo once the carrying vehicle derails or rollovers. The exposure of tanks to direct fire is a condition that potentially involves catastrophic consequences. Studying the behavior of the contained fluid under these drastic circumstances, is critical to develop methods and techniques to mitigate the serious consequences of many mishaps. In this paper, the experimental potentials of a Particle Image Velocimetry data acquisition system are described, for providing experimental data that could be used to calibrate mathematical models. As an example of the situations that need to be modelled, an experiment is described concerning the effect of the boundary conditions and protecting devices, on the rate of variation of pressure and temperature of the fluid in a tank exposed to a direct fire. In this regard, the results emphasize the importance of equipping the vessels with both thermal insulation and safety valves.
There was a need to validate the longitudinal performance required for the cargo securement, as current standards exhibit differences. A model has been proposed in this paper, to simulate the effect of a shifting cargo on the braking efficiency of the vehicle. Results suggest that the braking efficiency can be greater in the case of a shifting cargo, as a result of the uncoupling of the cargo-vehicle systems, implying that similar braking forces are exerted on a reduced mass. The shifting of the cargo can occur as a result of the vibration of the vehicle, that leads to having a diminished friction force to prevent the shifting of the cargo.
The interaction of the vehicles with the pavements imply damaging effects on both systems, as a function of the operating conditions and design characteristics of both systems. These effects influence the road pricing as well as the maintenance costs of the vehicles. In this paper, a simulation scheme has been proposed to analyze such interaction in massive way, involving a multivehicle models was the uncoupling of the roll and pitch responses. Results suggest that the damaging effects on the pavement and the vehicle, depends on the position along the road profile. However, the vertical design of the road would mainly affect the pavement damage, while the turning maneuvers would strongly influence the damage of the vehicle. Many uses can be identified for the proposed simulation scheme, involving different design and operating conditions for both systems.
A model of the cargo – ship interaction has been presented, for a navigation environment in which there is no waves, in which the ship lateral stability depends only on the manoeuver performed and the characteristics of the ship and cargo. Several simplifications have been introduced in the model, including the circular bottom of the ship, which facilitates the location of the buoyancy force on the ship, and the analogy of the sloshing cargo motion to a simple pendulum. Two forms of damping were introduced (river waters with the ship´s hull and the friction of the liquid inside the tanker walls), while the sliding motion of the ship when turning has been assumed as negligible. The results suggest that the sloshing cargo influences the lateral stability of the river tanker, with increases in the maximum roll angle from 15% to 40%, as a function of the speed and the fill level. The maximum roll angle has been found to occur at a 75% fill level, regardless of the ship speed.
An experimental testing rig has been proposed to study the dynamic interaction between a liquid cargo and the carrying vehicle during turning maneuvers. The basic operational principle of the testing rig consists in simulating the lateral accelerations associated to turning maneuvers through the use of a tilt table.
While the experimental capabilities of the testing rig include the analysis of the effects of the cars on the whole transport infrastructure, including sleepers and ballast, a first use of the rig considered the effect of sloshing cargo on the level of dynamic forces transmitted to the rails. Such test was used to validate a simplified theoretical approach consisting of a two degree-of-freedom double pendulum mechanical system, where a simple pendulum, representing the sloshing cargo, is articulated to the spring-supported vehicle chassis, which is modelled as an inverted torsional pendulum. While the theoretical results exhibit a high correlation with the experimental data, the main discrepancy between both outputs, relates with the frequency of the residual vibration, once the lateral acceleration input is ceased. Such difference in frequency, would imply an underestimation of the number of loading cycles to which the infrastructure is subjected. On the other hand, the peak values are within acceptable difference levels.