Simulation of Train Derailment in Passing Over Rails With Random Irregularities on a Viscoelastic Foundation

2008 ◽  
Author(s):  
Mohammad Durali ◽  
Mohammad Mahdi Jalili
Keyword(s):  
Degrees Of Freedom ◽  
Viscoelastic Foundation ◽  
Train Derailment ◽  
Suspension Systems ◽  
Derailment Coefficient ◽  
Center Pivot ◽  
Non Linear ◽  
Linear Elements ◽  
Secondary Suspension ◽  
New Criterion

Derailment of a passenger wagon on a rail with random irregularities is investigated in this paper. The wagon having 48 degrees of freedom is assumed to travel over a rail on a viscoelastic foundation. The wagon model is a 3-D, non-linear model of a passenger train car, considering non-linear elements for the primary and secondary suspension systems having friction and slack between their elements, the center pivot with kinematics constraints, forces between pads, and bolster. The motion of the wagon on rail with random vertical irregularities is simulated for different line grades and travel speeds. Derailment coefficient and a new derailment criterion are used to investigate probability of wheelset derailment moving on different line grades. The study shows that the new criterion can very well predict wheelset derailment and can duplicate the predictions by conventional derailment coefficient (Q/P). Comparison of the wagon derailment on lines with different sleeper rigidity shows that increase in sleeper rigidity decrease derailment probability.

Investigation on Train Derailment Using a New Criterion

2009 ◽  
Author(s):  
Mohammad Durali ◽  
Mohammad Mahdi Jalili
Keyword(s):  
Dynamic Parameters ◽  
Train Derailment ◽  
Suspension Systems ◽  
Derailment Coefficient ◽  
Center Pivot ◽  
Non Linear ◽  
Linear Elements ◽  
Secondary Suspension ◽  
Definition Of ◽  
New Criterion

A new criterion for prediction of train derailment is presented in this paper. A 2 DOF wheel-set model is used to identify the main dynamic parameters that affect wheel-set derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to providing the required precision in prediction of wheelset derailment, it requires measurements which are easy to perform. To evaluate the capability of the new criterion in prediction of derailment, a full wagon model with 48 DOF was used. The wagon model is a 3-D, non-linear model of a train passenger car. The model includes non-linear elements for primary and secondary suspension systems. Friction and slack between elements, the center pivot with kinematics constraints, forces between pads, and bolster are also included in this model. The motion of the wagon on curved tracks is simulated for different travel speeds. Derailment coefficient and a new derailment criterion are used to investigate possibility of wheelset derailment in each case. The study shows that the new criterion can very well predict wheelset derailment and can duplicate the predictions by conventional derailment coefficient (Y / Q).

Study of Train Derailments Caused by Damage to Suspension Systems

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
S. H. Ju
Keyword(s):  
Finite Element ◽  
Nonlinear Finite Element Method ◽  
Train Derailment ◽  
Interval Time ◽  
Suspension Systems ◽  
Derailment Coefficient ◽  
Parametric Studies ◽  
Train Speed ◽  
Rail Irregularities ◽  
Secondary Suspension

A nonlinear finite element method was used to investigate the derailments of trains moving on multispan simply supported bridges due to damage to suspension systems. At the simulation beginning, the initial vertical trainloads to simulate the train gravity weight are gradually added into the mass center of each rigid body in the train model with large system damping, so the initial fake vibration is well reduced. A suspension is then set to damage within the damage interval time, while the spring and/or damper changes from no damage to a given percentage of damage. Finite element parametric studies indicate the following: (1) the derailment coefficients of the wheel axis nearby the damage location are significantly increased. (2) Damage to the spring is more critical than that to the damper for the train derailment effect. (3) The derailment coefficient induced by damage to the primary suspension is more serious than that to the secondary suspension. (4) If rail irregularities are neglected, the train speed has little influence on the derailment coefficients generated from damage to suspensions. (5) The train derailment coefficients rise with a decrease in the damage interval time, so sudden damages to suspension systems should be avoided.

A New Criterion for Prediction of Train Derailment

2007 ◽  
Author(s):  
Mohammad Durali ◽  
Mohammad Mahdi Jalili
Keyword(s):  
Dynamic Parameters ◽  
Train Derailment ◽  
Derailment Coefficient ◽  
Definition Of ◽  
New Criterion

A new criterion for prediction of train derailment is presented in this paper. A 3 DOF wheel-set model is used to identify the main dynamic parameters that affect wheel-set derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to offering the required precision in prediction of wheel set derailment, requires measurements which are several times easier. To evaluate the capability of the new criterion in prediction of derailment, it was used to determine derailment of a full wagon model with 48 DOF moving on a rail with different random irregularities. The results were then compared with the predictions of conventional derailment coefficients.

scholarly journals Geometric Non-Linear Approach to Stiffness State of Semi–Rigid Structures

2016 ◽  
Vol 6 (1) ◽  
pp. 63-70
Author(s):  
Moldovan Corina
Keyword(s):  
Degrees Of Freedom ◽  
Virtual Work ◽  
Steel Structures ◽  
Structural Level ◽  
Element Level ◽  
Present Contribution ◽  
Six Degrees Of Freedom ◽  
Non Linear ◽  
Linear Elements ◽  
Global Systems

Abstract Present contribution intends to emphasize the contribution of geometric non-linearity to the stiffness state of semi-rigid multi–storey steel structures. Though semi-rigidity of beam – column connections involves a nonlinearity at constitutive bending momentrelative rotation level, the geometric nonlinearity associated to deformed conFigure uration at element level is less referred to. The main objective of the study is to express the stiffness state of geometric non-linear elements semi-rigidly connected at its ends. Stiffness state is, in its term, expressed by element level stiffness matrix considering the six degrees of freedom of the planar element. Regarding the reference system, both local and global systems are employed allowing a simple and direct transition from element level vectorial relations to their structural level forms. The three fundamental vectorial relations (static equilibrium, kinematic compatibility, material constitutivity) emphasize that the principle of virtual work holds in the case of semi-rigidly connected skeletal structures as well.

Influence of Vehicle Suspension System on Ride Comfort

2011 ◽  
Vol 141 ◽  
pp. 319-322
Author(s):  
Jun Zhong Xia ◽  
Zong Po Ma ◽  
Shu Min Li ◽  
Xiang Bi An
Keyword(s):  
Degrees Of Freedom ◽  
Ride Comfort ◽  
Suspension System ◽  
Vehicle Suspension ◽  
Vehicle Model ◽  
Active Suspensions ◽  
Suspension Systems ◽  
Non Linear ◽  
Vehicle Suspension System

This paper focuses on the influence of various vehicle suspension systems on ride comfort. A vehicle model with eight degrees of freedom is introduced. With this model, various types of non-linear suspensions such as active and semi-active suspensions are investigated. From this investigation, we draw the conclusion that the active and semi-active suspensions models are beneficial for ride comfort.

Non-Linear Forced Response Analysis of Mistuned Bladed Disk Assemblies

2010 ◽  
Author(s):  
M. Ersin Yu¨mer ◽  
Ender Cig˘erog˘lu ◽  
H. Nevzat O¨zgu¨ven
Keyword(s):  
Degrees Of Freedom ◽  
Linear Equations ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Contact Forces ◽  
Response Analysis ◽  
Disk Model ◽  
Bladed Disk ◽  
Non Linear ◽  
Linear Elements

Forced response analysis of bladed disk assemblies plays a crucial role in rotor blade design, and therefore has been investigated by researchers extensively. However, due to lack of computation power, several studies in the literature utilize either linear mistuned models which are short of capturing nonlinear effects, or non-linear tuned models which do not catch the effects of mistuning. Studying the combined effect of the two, namely non-linearity and mistuning, is relatively recent and generally conducted with methods whose convergence and accuracy depend highly on the number of degrees of freedom related with the non-linear elements. In this paper, a new approach is proposed to predict forced response of frictionally damped mistuned bladed disk assemblies in modal domain. A friction element, which enables normal load variation and separation of the contact interface, is utilized to determine the non-linear contact forces in three-dimensional space, and harmonic balance method is used to obtain a relationship between the non-linear contact forces and the relative motion. As mistuning phenomenon destroys the cyclic symmetry, modeling the whole assembly rather than a sector of it is necessary, which increases the number of non-linear elements required considerably. In the proposed approach, the analysis is carried out in modal domain where the differential equations of motions are converted to a set of non-linear algebraic equations using harmonic balance method and modal superposition technique. Thus, the number of non-linear equations to be solved is proportional to the number of modes retained, rather than the number of degrees of freedom related with the nonlinear elements. Therefore, the proposed approach can be applied to realistic bladed disk models without increasing the number of non-linear equations. Moreover, to accomplish this it is not required to use a reduced order model in the method suggested. Two case studies are presented to illustrate the implementation of the method: a lumped parameter bladed disk model and an academic bladed disk model with shrouds.

Investigation of Train Dynamics in Passing Through Curves Using a Full Model

Joint Rail ◽  
2004 ◽  
Author(s):  
Mohammad Durali ◽  
Mohammad Mehdi Jalili Bahabadi
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Full Model ◽  
Bogie Frame ◽  
Nonlinear Characteristics ◽  
Train Derailment ◽  
Train Dynamics

In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension elements as well as flexibilities of wagon body and bogie frame, and the effect of coupler forces are included in the model. The equations of motion for the train are solved numerically for different train conditions. A neural network was constructed as an element in solution loop for determination of wheel-rail contact geometry. Derailment factor was calculated for each case. The results are presented and show the major role of coupler forces on possible train derailment.

An XYZ Parallel Kinematic Flexure Mechanism With Geometrically Decoupled Degrees of Freedom

2011 ◽  
Author(s):  
Shorya Awtar ◽  
John Ustick ◽  
Shiladitya Sen
Keyword(s):  
Degrees Of Freedom ◽  
Element Analysis ◽  
Motion Direction ◽  
Form Analysis ◽  
Flexure Mechanism ◽  
Non Linear ◽  
Decoupled Motion ◽  
Motion Range ◽  
Parallel Kinematic ◽  
Cross Axis

We present the constraint-based design of a novel parallel kinematic flexure mechanism that provides highly decoupled motions along the three translational directions (X, Y, and Z) and high stiffness along the three rotational directions (θx, θy, and θz). The geometric decoupling ensures large motion range along each translational direction and enables integration with large-stroke ground-mounted linear actuators or generators, depending on the application. The proposed design, which is based on a systematic arrangement of multiple rigid stages and parallelogram flexure modules, is analyzed via non-linear finite element analysis. A proof-of-concept prototype of the flexure mechanism is fabricated to validate its large range and decoupled motion capability. The analyses as well as the hardware demonstrate an XYZ motion range of 10 mm × 10 mm × 10 mm. Over this motion range, the non-linear FEA predicts a cross-axis error of less than 3%, parasitic rotations less than 2 mrad, less than 4% lost motion, actuator isolation less than 1.5%, and no perceptible motion direction stiffness variation. Ongoing work includes non-linear closed-form analysis and experimental measurement of these error motion and stiffness characteristics.

A Two-Dimensional Linear Assumed Strain Triangular Element for Finite Deformation Analysis

2005 ◽  
Vol 73 (6) ◽  
pp. 970-976 ◽  
Author(s):  
Fernando G. Flores
Keyword(s):  
Finite Deformation ◽  
Degrees Of Freedom ◽  
Yield Function ◽  
Triangular Element ◽  
Deformation Analysis ◽  
Elastic Model ◽  
Stress Strain ◽  
Metric Tensor ◽  
Assumed Strain ◽  
Non Linear

An assumed strain approach for a linear triangular element able to handle finite deformation problems is presented in this paper. The element is based on a total Lagrangian formulation and its geometry is defined by three nodes with only translational degrees of freedom. The strains are computed from the metric tensor, which is interpolated linearly from the values obtained at the mid-side points of the element. The evaluation of the gradient at each side of the triangle is made resorting to the geometry of the adjacent elements, leading to a four element patch. The approach is then nonconforming, nevertheless the element passes the patch test. To deal with plasticity at finite deformations a logarithmic stress-strain pair is used where an additive decomposition of elastic and plastic strains is adopted. A hyper-elastic model for the elastic linear stress-strain relation and an isotropic quadratic yield function (Mises) for the plastic part are considered. The element has been implemented in two finite element codes: an implicit static/dynamic program for moderately non-linear problems and an explicit dynamic code for problems with strong nonlinearities. Several examples are shown to assess the behavior of the present element in linear plane stress states and non-linear plane strain states as well as in axi-symmetric problems.

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