Lateral Stability of Freight Cars With Axles Having Different Wheel Profiles and Asymmetric Loading

1979 ◽  
Vol 101 (1) ◽  
pp. 1-16 ◽  
Author(s):  
J. M. Tuten ◽  
E. H. Law ◽  
N. K. Cooperrider

The majority of studies of rail vehicle lateral dynamic response have utilized models wherein it is assumed that the loading and geometry of the vehicles are symmetrical left and right and fore and aft. It has been observed that with use North American rail freight vehicles develop transverse wheel profiles that may be different for wheels on a given axle and that may also differ from axle to axle on a given vehicle. As the transverse wheel profiles exert a strong influence on lateral dynamic response by affecting the effective conicity and gravitational stiffness of the wheelset, models capable of having different wheel profiles on the same axle as well as on different axles were developed to investigate the stability behavior. Additionally, these models were formulated so that the effects on stability of asymmetric fore and aft loading conditions, as manifested through gravitational stiffness effects and creep coefficients, could be examined. Results of studies using these models are presented that display characteristics markedly different from those of completely symmetric models. A particularly interesting result is that, in most cases, the lateral stability of vehicles with different wheel profiles on the various axles is strongly sensitive to the direction of motion with results for each direction of motion which may differ radically from symmetric cases.

1987 ◽  
Vol 109 (4) ◽  
pp. 493-499 ◽  
Author(s):  
A. K. W. Ahmed ◽  
S. Sankar

A general model of single rail vehicle wheelset with elasto-damper coupling between the wheels, has been developed as a first step in developing a railway freight truck model with elasto-damper coupled wheelset (EDCW). By choosing different coupler parameters, various stiffness-damper combinations, as well as rigid axle (conventional wheelset) could be simulated. The mathematical model of EDCW has been validated by comparing the model under limiting cases with those of published results for conventional system. In this paper, the results of linearized stability analysis of EDCW model on tangent track are presented and discussed. The investigation showed that wheelset coupler parameters have significant influence on the stability behavior of the wheelset, and there is an optimal coupler parameter which can improve the wheelset critical speed over the conventional system.


1981 ◽  
Vol 103 (3) ◽  
pp. 191-200 ◽  
Author(s):  
D. Horak ◽  
C. E. Bell ◽  
J. K. Hedrick

This paper compares the lateral stability and steady-state curving performance of radial and conventional rail vehicle trucks. The radial truck has two unique features, it allows direct elastic coupling between the wheelsets and it allows greater total truck shear stiffness for a given bending stiffness. It is shown that the first property allows the radial truck to achieve up to a 40 percent higher critical speed than the conventional truck for equivalent truck total shear and bending stiffness since the direct coupling between the wheelsets allows decoupling of the truck mass from the hunting wheelset masses. The second feature, i.e., greater shear stiffness capability, allows the radial truck to have improved wear properties during the negotiation of tight curves. It is shown that the high shear stiffness property combined with a low bending stiffness reduces the lateral flange force and wheelset angle of attack during flange contact. It is concluded that for routes where the majority of curves are less than 4 deg (greater than 400 m radius) the truck optimized for off-flange performance should have intermediate values of shear stiffness, bending stiffness, and conicity. On the other hand, for routes where the majority of curves are greater than 4 deg, the truck optimized for on-flange performance should have a high shear stiffness and low values of bending stiffness and conicity.


1987 ◽  
Vol 109 (4) ◽  
pp. 500-507 ◽  
Author(s):  
A. K. W. Ahmed ◽  
S. Sankar

To investigate the effect of elasto-damper coupled wheelset (EDCW), on the lateral stability behavior of freight cars, a railway freight truck model with two EDCW and pseudo-car body has been developed. The results of linearized stability analysis showed, that for small values of wheelset coupler stiffness, damping has significant influence on the stability behavior of wheelset relative spin as well as wheelset and truck lateral modes. The results further showed that, by utilizing an optimal EDCW coupler parameter, the critical speeds corresponding to truck hunting and wheelset lateral mode can be made equal. In doing so, the truck hunting critical speed on tangent track can be improved by over 100 percent in comparison to truck model with conventional rigid axle wheelsets.


2013 ◽  
Vol 721 ◽  
pp. 551-555 ◽  
Author(s):  
Li Hua Wang ◽  
An Ning Huang ◽  
Guang Wei Liu

The curve negotiation ability and lateral stability are the important and contradictory indicators when evaluating the dynamic performance of the rail vehicle. And in order to study the stability of the rail vehicle, its curve negotiation ability will be studied firstly. In this paper, the whole multi-body dynamic model of the rail vehicle was proposed based on the theory of multi-body dynamics in the software of Simpack. And the lateral force, derailment and overturning coefficient of the rail vehicle when it passed through a specific curve track with specific speed. Then the curve negotiation ability of the rail vehicle was estimated accurately.


Author(s):  
Michael G. Gilbert ◽  
Daniel A. Godrick ◽  
Richard H. Klein

Small and mid-sized cargo trailers are often used to transport goods by people with limited experience in loading trailers and driving vehicles with trailers attached. This paper examines the effect of front to rear load position on the stability of a trailer by measuring its dynamic response to a variety of steer inputs at several different highway speeds. Additionally, tests with varying steers and speeds were performed with a simulated suspension malfunction to study the trailer’s dynamic response to this condition. Trailer sway has been a well-documented trailer characteristic for decades. However there are no special driver’s licensing or mandatory training requirements for even large trailers and campers. The trailer chosen for this test was a lightweight double axle cargo trailer commonly rented by people with limited to no towing experience. This consumer is likely to be unfamiliar with the best practices of trailer loading. This consumer is also likely a non-professional driver with little to no towing experience in the event of encountering unexpected trailer sway. Therefore it was the goal of the authors to determine how the stability of this type of trailer varies with different front to rear loading conditions and speeds to see if it is safe to operate on the highways by novice drivers. Trailer sway stability was determined by measuring the trailer sway (articulation) response during repeated, pulse steer tests. The trailer sway damping characteristics were measured, as a “damping ratio”, for six different hitch loads that corresponded to six different longitudinal loading conditions. These conditions, expressed as % load forward of the trailer centerline / % load aft of the trailer centerline were: 65/35, 60/40, 55/45, 50/50, 45/55, and 40/60. These loading conditions were tested per SAE J2664 [1] protocol. The resulting trailer sway characteristics for each loading condition then were compared to published trailer sway stability criteria [2, 3] to determine the suitability of this particular tow vehicle-trailer combination for use by the public in a rental market. The impact of a suspension malfunction on the trailer stability was also studied. This consisted of a detachment of one rear leaf spring hanger.


Author(s):  
Alisher Khodjimatov ◽  

The article is based on the multifactorial nature of the stability and dynamics of landscapes, especially the strong influence of human economic activity on the stability and dynamics of oasis landscapes.


2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Xigui Zheng ◽  
Jinbo Hua ◽  
Nong Zhang ◽  
Xiaowei Feng ◽  
Lei Zhang

A limitation in research on bolt anchoring is the unknown relationship between dynamic perturbation and mechanical characteristics. This paper divides dynamic impulse loads into engineering loads and blasting loads and then employs numerical calculation software FLAC3Dto analyze the stability of an anchoring system perturbed by an impulse load. The evolution of the dynamic response of the axial force/shear stress in the anchoring system is thus obtained. It is revealed that the corners and middle of the anchoring system are strongly affected by the dynamic load, and the dynamic response of shear stress is distinctly stronger than that of the axial force in the anchoring system. Additionally, the perturbation of the impulse load reduces stress in the anchored rock mass and induces repeated tension and loosening of the rods in the anchoring system, thus reducing the stability of the anchoring system. The oscillation amplitude of the axial force in the anchored segment is mitigated far more than that in the free segment, demonstrating that extended/full-length anchoring is extremely stable and surpasses simple anchors with free ends.


2013 ◽  
Vol 859 ◽  
pp. 222-227
Author(s):  
Hong Jun Liu ◽  
Jin Hua Tan ◽  
Xue Wen Su ◽  
Hao Wu

Two typical monitoring sections are selected for obtaining the change law of the surface subsidence and the settlement after construction of soft soil foundations, and determining the reasonable unloading time. The research results show that the surface settlement rate is large during the filling stage, the rate decreases after the loading and gradually stabilized. The embankment midline settlement is larger than the settlement of the road shoulder which is concluded from the fact that the subsidence of the middle settlement plate is larger than those of the left and right plate. The surface subsidence rate is less than 5mm per month during the two month before unloading according to the data in the tables. The settlement after construction presumed from the middle plate is more significantly larger than that of left and right sides, hence, as the unloading basis of preloading drainage method in soft soil foundation treatment the settlement after construction which is calculated from the midline monitoring data of the road is appropriate. After 6 months the calculated post-construction settlements of the two sections are in the scope of the design requirement since they decrease with preloading time. The reliable basis is provided for the future design and construction of soft foundation in this area through the research results.


2001 ◽  
Author(s):  
Davide Valtorta ◽  
Khaled E. Zaazaa ◽  
Ahmed A. Shabana ◽  
Jalil R. Sany

Abstract The lateral stability of railroad vehicles travelling on tangent tracks is one of the important problems that has been the subject of extensive research since the nineteenth century. Early detailed studies of this problem in the twentieth century are the work of Carter and Rocard on the stability of locomotives. The linear theory for the lateral stability analysis has been extensively used in the past and can give good results under certain operating conditions. In this paper, the results obtained using a linear stability analysis are compared with the results obtained using a general nonlinear multibody methodology. In the linear stability analysis, the sources of the instability are investigated using Liapunov’s linear theory and the eigenvalue analysis for a simple wheelset model on a tangent track. The effects of the stiffness of the primary and secondary suspensions on the stability results are investigated. The results obtained for the simple model using the linear approach are compared with the results obtained using a new nonlinear multibody based constrained wheel/rail contact formulation. This comparative numerical study can be used to validate the use of the constrained wheel/rail contact formulation in the study of lateral stability. Similar studies can be used in the future to define the limitations of the linear theory under general operating conditions.


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