Purpose. Despite of the implementation various programs to improve the safety of train traffic problem of re- ducing gatherings rolling stock off the rails is still relevant. The study aims to clarify the existing method of deter- mining the factor of stability from the tire longitudinalforces to ensure the sustainability of cars with increasing speeds of the rolling stock. Methodology. Research was conducted by the method of mathematical modeling of loading freight car when driving at different speeds on straight and curved track sections. Findings. Analysis of the results shows that, for all selected freight cars for the calculation, the value of the safety factor by squeezing is smaller than the formulas of Standards. Corrections made to the formula for determining the safety factor by squeez- ing longitudinalforces, would achieve: 1) a higher safety factor of lightweight cars, excluding them squeezing longi- tudinal forces in the entire range of speeds of freight trains; 2) to develop and implement measures to prevent squeezing of cars in the entire range of motion; 3) to determine the degree of stability of the empty car in the head, middle and tail laden trains; 4) to offer optimal scheme of mixed trains formation. Originality. The analysis of ex- isting methods for determining stability coefficient cars in freight trains from squeezing their longitudinalforces is presented in studies. Proposals are developed for the refinement of the design phase, construction and operation. Practical value. This study clarifies the existing method of determining the safety factor of stability from the squeezing longitudinalforces, as well as the influence on the magnitude of the coefficient of speed of movement of the rolling stock. Developed proposals for the refinement of existing methods for determining stability coefficient of longitudinalforces squeezing cars in a train, can reduce the number of retirements cars derailed by taking into ac- count in the calculation and design of important parameters and characteristics that increase their stability in the rail track especially with increasing speeds of freight traffic.
Purpose. Study the transient modes effect of movement on the track displacement for the freight train safety control is supposed in this paper. For this it is necessary to investigate the longitudinal dynamics of a train on the track displacement. Simultaneously to assess the longitudinalforces level of a track and rolling stock interaction. Methodology. The level of the longitudinalforces, effecting the track displacement, was evaluated using mathe- matical modeling of longitudinal vibrations of the trains at transient modes of motion caused by braking. It was con- sidered that each train vehicle consists of a body (solid) and the wheel sets, connected with the body by friction bearings (inelastic link). It was believed that during the movement of each train vehicle the vertical plane of its symmetry coincident with the vertical plane of symmetry of the assembled rails and sleepers. At simulation it was also supposed that in the process of translational motion of the vehicle body wheels make pure rolling along the rail without slipping on it. Findings. In the results of calculations the values of the longitudinalforces at different types of braking were obtained (it is regenerative braking and pneumatic one) under quasi-static and shock transients. For this various initial state of clearances in the inter-car connections up to beginning of transient was considered. The level of dynamic additives to longitudinalforces of interaction between wheel and rail that are substantially depending on vehicle accelerations was assessed. Originality. The transient regimes effect of trains movement caused by braking on the level of the longitudinalforces of track and rolling stock interaction was investigated. The longitudinal load of freight trains with regenerative and pneumatic braking was researched. The effect of the initial state of the train and different modes of braking on a dynamic additive to the longitudinalforces of the inter- action between the track and rolling stock, which may effect the displacement of assembled rails and sleepers, was estimated. Practical value. The obtained results can be used to select rational modes of braking of freight trains, especially on lengthy down grade, from the positions prevent possible track displacement.
On the LHS line (Broad-gauge Metallurgical Line), far out West of the railway line with a gauge of 1520 mm, heavy goods trains for a gross weight 5500 tons and a length of 850 m are operated. The article presents the results of a simulation study of the forces that occur in the automatic coupling device of SA-3 type of Russian produc- tion train consisting of 60 coal wagons of Russian construction of gross mass 91 tons each. The train moves on the 1520 mm gauge tracks curve S type (the radius of curva- ture of curves 300 m). Simulation studies were conducted using the Train Module of program to dynamic study multi-elements systems of Universal Mechanism UM 6.0. Keywords: heavy freight trains, the longitudinalforces in the coupling device, Nadal criterion, modeling, simulation, the theory of Kalker’s contact.
Purpose. To research the tank train longitudinal loading during motion by track sections with changes of gradi- ent. The trains of different length that consist of bogie tank wagons should be examined. Influence of cargo type on longitudinal loading of train during motion in concave section of track should be evaluated. Methodology. The level of the largest longitudinalforces was estimated by mathematical simulation. It was assumed that change of gradient is formed by two grades with baffle platforms, length 50 meters, so that the algebraic difference of limiting grades vary from 10 to 40 ‰, pitch 10 ‰. The initial speeds were 40, 60, 80, 100, 120 km/h. For evaluation of the longitu- dinal loading the regulating braking and motion «by coasting» was considered. For evaluation of buffing loads the entry to the concave gradient change of expanded train is considered, and in order to determine the quasi-static forces the compressed train is considered. Findings. As a result of calculations the dependencies of maximal longi- tudinal forces in the trains on the cargo type, the algebraic difference of the grades, the number of tank wagons, the initial speed, motion modes, and initial gaps condition in the train were obtained. Originality. The longitudinal loading of freight cars of different length formed by the similar bogie tank wagons with one locomotive was ob- tained. The locomotive is placed in the train head during motion in concave track sections with various algebraic difference of the grades «on coasting» and during the regulating braking mode. The obtained results can be used for parameters standardization of profile elevation of the track. Practical value. The obtained results show that during operation of tank trains on track sections of complex breakage the most dangerous is regulating braking of prelimi- nary compressed trains during entering on concave parts of track. Level of the greatest buffing and quasi-static lon- gitudinal forces is almost independent of cargo and slightly depends on the initial speed.
Values of slip angle in depending on a turn radius are listed in Table 1. The wheel cart during the tests was propelled by external excitation system. The wheel had no driving torque applied for presented test facility configuration. Propulsion system is based on a rail with a cart propelled by an electric motor. Rail is responsible for keeping the straightforward motion of the cart and allows the system to rotate in the rail axis. A frame containing the wheel suspension is placed on a cart moving on a rail. Wheel is attached to the frame via adjustable fork, that allows to change the attack angle. The fork frame has two degrees of freedom constrained by rods containing force transducers, thus the lateral and longitudinalforces are isolated and measured (Fig. 4).
When S=0 the wheel is in perfect rolling motion without slipping. On the other hand, when S=1 the wheel is locked and pure sliding happens. The slip ratio greatly affects the longitudinal and lateral forces. During braking, in addition to the longitudinal force on the wheel, the lateral force maintains vehicle stability in a straight or turning motion. Therefore both lateral and longitudinalforces should be considered to achieve shorter braking distance without losing its maneuverability . The application of brakes generates a force that impedes a vehicles motion by applying a force in the opposite direction. The braking force or the adhesion coefficient of braking force (μ bf ) measured in the direction the wheel is turning is function of slip [6,7].
muscle segment length changes (strain) and activation patterns (as described in Shadwick et al., 1999; Donley and Shadwick, 2003) (Fig.·1). The two axial positions (0.4±0.02L, anterior; 0.6±0.04L, posterior) chosen for this study encompass much of the longitudinal distribution of RM in the mako (Bernal et al., 2003). Anterior to 0.35L and posterior to 0.65L, the mass of red muscle (RM) is relatively small and therefore the accuracy in crystal placement declined when attempting to implant crystals more rostral or caudal to these positions. To implant the crystals, a 2-mm incision was made in the skin directly dorsal to the desired region of the muscle and a puncture was made in the underlying tissue using a 15-gauge hypodermic needle precalibrated to the required depth. Crystals were implanted in a longitudinal orientation approximately 15·mm apart such that the degree of shortening and lengthening of myotomes could be measured. This orientation prevented the bending movements of the shark from causing slippage of the crystals within the muscle and avoided damaging the lateral vascular rete.
A series of comparisons were made between the model test data and the predictions from the simpliﬁed Morison-based approach with force coefﬁcients derived from the test data. The mean thrust was quite well-predicted for the zero-speed ‘‘single- ﬂapper’’ case, although the time histories indicate that instanta- neous forces are less well-predicted. However when the segments move independently, the error in the zero-speed mean thrust prediction increases as the phase difference between the segments increases; it can reasonably be argued that the effect of changing the phase angle is to amplify existing deﬁciencies in the assumptions made in the Morison equation, and/or to introduce or exaggerate hydrodynamic effects not accounted for, such as vortex shedding at the tail. Nonetheless, perhaps surprisingly, the simpliﬁed method was found to estimate the self-propulsion speed to within 30% in all the cases examined.
Force diagrams show you the direction a force is acting in. It shows you the direction an object is being pushed, pulled or twisted. The direction of the arrow shows you the direction of the force. The sizes of the arrows can be used to compare the sizes of the forces.
The three thick arrows show maximum driving, braking, and lateral forces when pure acceleration/braking or cornering is present. When the tire experiences a combination of these forces, the maximum lateral force is not available. The friction circle represents the vector sum of both traction forces and is the maximum force that can be generated by the tire. Therefore, adding driving power to the tire reduces the available lateral force since the sum of their squares must equal the total traction force. A simple example of this is a high powered rear wheel drive vehicle that is accelerating out of a corner. Under hard acceleration, the rear end of the vehicle tends to get loose or slide because all of the traction capabilities of the rear tires are being used to accelerate the vehicle, leaving little to no traction left to maintain any lateral grip . Note that the figure depicted above is a simplification of the real situation. A real traction plot is elliptical with the tire being able to generate slightly more driver/braking forces than lateral.
Abstract. Safety and performance have always been important factors in automotive testing. These factors are highly dependent on the tires and suspensions, which should be simulated and tested through- out the development process. During development, Hardware-In-the-Loop (HIL) simulations may be used so that testings and tunings can be done earlier in the process. In this paper, designs and conﬁgu- rations of a newly developed tire-suspension-steering HIL are shown. An actual wheel assembly with suspension and steering components can be installed for testing with dynamic models of the rest of the car. The slip angle of the tire can be imposed in the test rig while actual tire forces can be measured and used in the dynamic model. Comparisons of HIL simulations and real experiments using the skid- pad test and the step steering test are given using Formula SAE race cars. It was found that the HIL simulation results are more accurate compared to non-HIL simulations.
Previous work on lobster hearts has not examined the effect of these neuropeptides on passive forces. We found that neither SGRN nor GYS altered longitudinal pre-stretch passive force (Figs 8C and 11C). Interestingly, both peptides elicited increases (SGRN: 22%; GYS: 27%) in transverse pre-stretch passive forces in intact hearts (Fig. 8D). However, when the CG was removed, GYS no longer caused such an increase, and the rise in passive pre-stretch forces in SGRN was decreased to only 5% (Fig. 11D). These data suggest that much of the increase in passive force is mediated by the CG, perhaps as a result of repeated contractions at higher frequencies (Dickinson et al., 2015), with the consequence that the baseline force does not return to completely relaxed levels, i.e. that some active level of force persists between contractions. However, at least some of the increase seen in the stimulated heart with SGRN is likely a direct effect of the neuropeptide on the muscle because there is some increase in pre-stretch transverse passive force even in the absence of the CG. To our knowledge, this is the first report of a significant effect of neuroactive compounds on passive muscle properties in crustaceans; however, serotonin has been shown to decrease passive muscle tension in leeches (Gerry and Ellerby, 2011; Gerry et al., 2012). Because passive forces at low extensions –0.08
You may be familiar with moments and equilibrium from GCSE. This worksheet will reinforce what you have already learnt and help you to build on it. You will consider objects that are in equilibrium and the forces that act on them, and will practise calculating moments.
The two models are now embedded in a common pattern of delays depending on age and time, yet the difference in the results is, so far, not suppressed. The delay model reveals an overestimation or an underestimation of life expectancy according to an increase or decrease in mortality. In the removal model, no overestimation, yet rather a correct estimation of the longitudinal trend, can be seen. Which method is the most appropriate one? Which model provides a more accurate representation of the process of changing mortality? The answers are found in the comparative handling of delays and risks. As its name indicates, the delay method moves the delays forward in time. The risks measured by the quotients and forces are the results of changing delays, which are the causal factor. The removal method, by contrast, sees the mortality change as a process of changing risks pertaining to certain causes. The delays are the consequence of changing risks through which the acting causes are channeled.
In order to validate the estimation methods, on-track acquired data have been con- sidered. Such data were acquired on a vehicle equipped with four independent electric motors, one per wheel, and a Corrsys Datron S-350 sensor, measuring the vehicle sideslip angle (details on the whole experimental campaign are in ). In particular, two constant speed steering ramp maneuvers are considered, with refer- ence constant speed 60 km/h and 80 km/h, and very low steering angle rate. Both the maneuvers were performed using a rear wheel drive (RWD) architecture with even torque distribution between left and right wheels. Here, the longitudinal forc- es were approximated as the ratio between each wheel torque (available for each drivetrain) and the wheel radius. To help the EKF+RW filter to converge, an additional measurement equation was implemented, imposing the overall vehicle yaw moment to be zero. Indeed due to the low steering angle rate, ̇ (and thus the yaw moment, see Eq. (7)) is expected to be very small, as experimentally verified.