UM RCF Rail

 UM Rolling Contact Fatigue of Rail

UM Rolling Contact Fatigue of Rail module is intended for simulation of the process of accumulation of rolling contact fatigue (RCF) damage in rails.

The module may be used for implementation of multivariant comparative calculations, for example, for solution of the problem of the rail profile optimization according to RCF criterion.

 UM Rolling Contact Fatigue of Rail features

UM RCF Rail allows the user:

• to define the velocity of the accumulation of RCF damage in rails with the different tread surfaces by using the data which are obtained by simulation of the railway vehicle dynamics by means of the UM Loco;

• to use the four RCF criteria for modelling of the accumulation of RCF damage:

• to take into account rail profile wear-out effect on the rate of accumulation of RCF damage using the UM Loco/Rail Profile Wear Evolution tool;

• to take into account residual stresses effect on the rate of accumulation of RCF damage;

• to represent processes of the stress modelling and the damage accumulation in the rail with the help of graphic interface including isolines and coloring.

 Criteria of rolling contact fatigue damage

For modelling of the accumulation of damage in UM RCF Rail the four criteria are used:

• criterion of amplitude of maximum shear stress;
• Dang Van criterion;
• Sines criterion;
• combined criterion.

The calculated equivalent stresses are compared with damaging ones according to RCF curve of the rail steel, which obtained by processing of RCF tests results. RCF curve sets the dependence of the number of the cycles of variable stresses until arising fatigue defects from level of the equivalent stresses.

The cumulative damage in the rail point is determined using the RCF curve by summation of the calculated damages.

 Rail model

A finite element (FE) model of the rail fragment composed of the finite elements of the serendipity family with eight nodes and dimension of the edges of 1 mm are used in the module.

The nodes of the FE model are convenient for accumulation of the contact fatigue damage.

The proposed FE model allows calculating the stresses in the near-surface layer of the rail with the minimum computing time and the sufficient accuracy.

 Determination of equivalent stresses

To simulate the process of accumulation of RCF damage in the rail material, the dynamics of the movement of railway vehicles is simulated either on a tangent track section or on a curve track section. The number of rail cross-sections is set, in which the contact forces from each wheel of the passing vehicle are calculated. The number of such sections should be sufficient to provide representative statistics about the forces and position of the wheel on the rail. In the UM RCF Rail module the accumulated fatigue damage in these sections are summed up and assigned to one cross-section, which is called the control section of the rail.

For solution of the rolling problem in the UM Loco module the model of contact forces of W. Kik and I. Piotrowski and the Kalker CONTACT model are used. With help of these algorithms the normal and tangential traction are calculated at the nodes of the 2D mesh located on the contact surface. As a result of simulation of dynamics of a railway vehicle using UM Loco module the input data file for UM RCF Rail module is created, which contains the values of forces in the contacts.

For increasing speed of calculation of the stresses the FE fragment are separated from the initial FE model of rail according to contact patch dimension. To the nodes located on all surfaces of the separated fragment except the contact surface the elastic constraints are applied.

In the process of simulation of accumulation of RCF damage in the UM RCF Rail module the obtained forces in the contact are applied to the nodes located on the contact surface of the separated FE fragment of the rail.

As a result of solution of the problem by FE method the equivalent stresses in the nodes of FE model are determined, which are compared with damaging values according to RCF curve of the steel.

 Consideration of rail profile wear

The rail wear iteration is a series of calculations within which the profile of the rolling surface of the rail does not change.

For accumulation of contact fatigue damage in the UM RCF Rail module the FE model of the rail fragment is used. At the each rail wear iteration this model is reconstructed. A new FE mesh is constructed on the basis of the worn rail profile. The damages calculated by means interpolation of the damages accumulated in the nodes of the mesh at the previous rail wear iteration are assigned to the obtained nodes of the new mesh. Then the procedure of accumulation of RCF damage in the nodes of the new FE mesh of the rail is repeated.

 Publications

1. Sakalo V.I., Sakalo A.V., Kossov V.S. Mechanics of contact interaction of wheel and rail. In: Direct-Media, Moscow; Berlin; 2021 (in Russian).

2. Sakalo V.I., Sakalo A.V. Criteria for predicting the initiation of rolling contact fatigue damage in the railway wheels and rails. Vestnik of the Railway Research Institute 2019;3:141–148 (in Russian). DOI: 10.21780/2223-9731-2019-78-3-141-148

3. Sakalo V., Sakalo A., Rodikov A., Tomashevskiy S. Computer modeling of processes of wear and accumulation of rolling contact fatigue damage in railway wheels using combined criterion. Wear 432–433 (2019) 102900. DOI: 10.1016/j.wear.2019.05.015

4. Sakalo V., Sakalo A., Tomashevskiy S., Kerentcev D. Computer modelling of process of accumulation of rolling contact fatigue damage in railway wheels. International Journal of Fatigue 2018;111:7–15. DOI: 10.1016/j.ijfatigue.2018.02.002

5. Sakalo A.V. Improvement of the railway wheel tread profile according to a contact fatigue criterion. In: PhD Thesis Moscow State University of Railway Engineering (MIIT), Moscow, 2011 (in Russian).

6. Sakalo A.V. Simulation of accumulation of contact fatigue damages in railway wheel by using finite element fragments on elastic foundation. Vestnik of the Railway Research Institute 2011;4:44–49 (in Russian).

7. Sakalo V.I., Sakalo A.V. Numerical method for solving the contact problems for the solid bodies using the finite element fragments on the elastic foundation. In: Proc. of the 1st joint int. conf. on multibody system dynamics, Lappeenranta; 2010. p. 366–373.

8. Sakalo A.V. Method of simulation of contact stresses by using finite element fragments on elastic foundation. Herald of the VSTU 2009;9:71–76 (in Russian).