On the Contact Search Algorithms for Wheel/Rail Contact Problems

2009 ◽  
Vol 4 (4) ◽  
Author(s):  
Hiroyuki Sugiyama ◽  
Yoshihiro Suda
Keyword(s):  
Vehicle Dynamics ◽  
Line Search ◽  
Point Contact ◽  
Contact Problems ◽  
Search Algorithms ◽  
Railroad Vehicle Dynamics ◽  
Contact Points ◽  
Contact Search ◽  
On Line ◽  
Railroad Vehicle

In this investigation, contact search algorithms for the analysis of wheel/rail contact problems are discussed, and the on-line and off-line hybrid contact search method is developed for multibody railroad vehicle dynamics simulations using the elastic contact formulation. In the hybrid algorithm developed in this investigation, the off-line search that can be effectively used for the tread contact is switched to the on-line search when the contact point is jumped to the flange region. In the two-point contact scenarios encountered in curve negotiations, the on-line search is used for both tread and flange contacts to determine the two-point contact configuration. By so doing, contact points on the flange region given by the off-line tabular search are never used, but rather used as an initial estimate for the online iterative procedure for improving the numerical convergence. Furthermore, the continual on-line detection of the second point of contact is replaced with a simple table look-up. It is demonstrated by several numerical examples that include flange climb and curve negotiation scenarios that the proposed hybrid contact search algorithm can be effectively used for modeling wheel/rail contacts in the analysis of general multibody railroad vehicle dynamics.

Hybrid Contact Search Algorithm for Wheel/Rail Contact Problems

2008 ◽  
Author(s):  
Hiroyuki Sugiyama ◽  
Yoshihiro Suda
Keyword(s):  
Hybrid Algorithm ◽  
Line Search ◽  
Search Algorithm ◽  
Point Contact ◽  
Contact Problems ◽  
Elastic Contact ◽  
Contact Points ◽  
Contact Search ◽  
On Line ◽  
Railroad Vehicle

In this investigation, the on-line and off-line hybrid contact algorithm for modeling wheel/rail contact problems is developed based on the elastic contact formulation. In the tabular contact search used in existing specialized railroad vehicle dynamics codes, contact points are predicted using an assumption of rigid contacts. For this reason, the contact points can be different from those predicted by the on-line based contact search used in general elastic contact formulations. The difference in the contact point becomes significant when flange contacts that have large contact angles are considered. In the hybrid algorithm developed in this investigation, the off-line tabular search is used for treating tread contacts, while the on-line iterative search is used for treating flange contacts. By so doing, a computationally efficient procedure is achieved while keeping accurate predictions of contact points on the wheel flange. Furthermore, the use of the proposed hybrid algorithm can eliminate the use of time-consuming on-line search procedures for the second points of contact as well. Since the location of second points of contact is pre-computed in the contact geometry analysis, the occurrence of two-point contact can be predicted using the look-up table in a straightforward manner. For the two-point contact scenarios encountered in curve negotiations, the online search is used for flange contacts, while the off-line search is used for tread contacts simultaneously. The on-line one-point contact search is also important for flange climb scenarios. It is demonstrated by several numerical examples that the proposed hybrid contact search algorithm can be effectively used for modeling wheel/rail contacts in the analysis of general multibody railroad vehicle systems.

Rail Geometry and Euler Angles

2006 ◽  
Vol 1 (3) ◽  
pp. 264-268 ◽  
Author(s):  
Cheta Rathod ◽  
Ahmed A. Shabana
Keyword(s):  
Vehicle Dynamics ◽  
Euler Angles ◽  
Frenet Frame ◽  
Geometric Properties ◽  
Track Geometry ◽  
Railroad Vehicle Dynamics ◽  
Space Curves ◽  
Curvature And Torsion ◽  
The Relationship ◽  
Railroad Vehicle

In railroad vehicle dynamics, Euler angles are often used to describe the track geometry (track centerline and rail space curves). The tangent and curvature vectors as well as local geometric properties such as the curvature and torsion can be expressed in terms of Euler angles. Some of the local geometric properties and Euler angles can be related to measured parameters that are often used to define the track geometry. The Euler angles employed, however, define a coordinate system that may differ from the Frenet frame used in the classical differential geometry. The relationship between the track frame used in railroad vehicle dynamics and the Frenet frame used in the theory of curves is developed in this paper and is used to shed light on some of the formulas and identities used in the geometric description in railroad vehicle dynamics. The conditions under which the two frames (track and Frenet) become equivalent are presented and used to obtain expressions for the curvature and torsion in terms of Euler angles and their derivatives with respect to the arc length.

Combined Nodal and Non-Conformal Contact Approach for the Analysis of Turnout Negotiations of Multibody Railroad Vehicles

2011 ◽  
Author(s):  
Hiroyuki Sugiyama ◽  
Takuto Sekiguchi ◽  
Ryosuke Matsumura ◽  
Shunpei Yamashita ◽  
Yoshihiro Suda
Keyword(s):  
Contact Point ◽  
Numerical Procedure ◽  
Contact Problems ◽  
Tabular Data ◽  
Railroad Vehicles ◽  
Contact Points ◽  
Contact Search ◽  
Continuous Surface ◽  
Geometry Analysis ◽  
Conformal Contact

In this investigation, a numerical procedure that can be used for solving complex wheel/rail contact problems in turnout is proposed. In particular, a combined nodal and non-conformal contact approach is developed such that significant jumps in contact points are detected using the nodal search, while the exact location of contact point is then determined with continuous surface parameterizations using non-conformal contact equations. With this combined nodal and non-conformal contact approach for the contact geometry analysis of vehicle/turnout interactions, multiple look-up contact tables can be generated in an efficient way without losing accuracy. Since detailed contact search is performed offline to obtain look-up contact tables, significant changes in contact points in turnout can be efficiently predicted online with tabular data to be interpolated in a standard way. Several numerical examples are presented in order to demonstrate the use of the numerical procedure developed in this investigation.

Integration of geometry and analysis for the study of liquid sloshing in railroad vehicle dynamics

2017 ◽  
Vol 231 (4) ◽  
pp. 608-629 ◽  
Author(s):  
Huailong Shi ◽  
Liang Wang ◽  
Brynne Nicolsen ◽  
Ahmed A Shabana
Keyword(s):  
Rigid Body ◽  
Vehicle Dynamics ◽  
Three Dimensional ◽  
Liquid Sloshing ◽  
Inertia Force ◽  
Railroad Vehicle Dynamics ◽  
Body Model ◽  
Rigid Body Model ◽  
Railroad Vehicle ◽  
Curve Negotiation

A new continuum-based liquid sloshing approach that accounts for the effect of complex fluid and tank-car geometry on railroad vehicle dynamics is developed in this investigation. A unified geometry/analysis mesh is used from the outset to examine the effect of liquid sloshing on railroad vehicle dynamics during curve negotiation and during the application of electronically controlled pneumatic (ECP) brakes that produce braking forces uniformly and simultaneously across all cars. Using a non-modal approach, the geometry of the tank-car and fluid is accurately defined, a continuum-based fluid constitutive model is employed, and a fluid-tank contact algorithm is developed. The liquid sloshing model is integrated with a three-dimensional multibody system (MBS) railroad vehicle algorithm which accounts for the nonlinear wheel/rail contact. The three-dimensional wheel/rail contact force formulation used in this study accounts for the longitudinal, lateral, and spin creep forces that influence the vehicle stability. In order to examine the effect of the liquid sloshing on the railroad vehicle dynamics during curve negotiation, a general and precise definition of the outward inertia force is defined, and in order to correctly capture the fluid and tank-car geometry, the absolute nodal coordinate formulation (ANCF) is used. The balance speed and centrifugal effects in the case of tank-car partially filled with liquid are studied and compared with the equivalent rigid body model in curve negotiation and braking scenarios. In particular, the results obtained in the case of the ECP brake application of two freight car model are compared with the results obtained when using conventional braking. The traction analysis shows that liquid sloshing has a significant effect on the load distribution between the front and rear trucks. A larger coupler force develops when using conventional braking compared with ECP braking, and the liquid sloshing contributes to amplifying the coupler force in the ECP braking case compared to the equivalent rigid body model which does not capture the fluid nonlinear inertia effects. Furthermore, the results obtained in this study show that liquid sloshing can exacerbate the unbalance effects when the rail vehicle negotiates a curve at a velocity higher than the balance speed.

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