@C_R 

  I'm afraid I can't contact maplesoft,because I use maplesoft by myself and don't get entitled. I try to open the 4-fix.msim file but it shows an error. The file may be damaged. Can you resend it? Or can you tell me how to modify it? Thank you very much.

  For the wheel-rail contact, I try to use custom components, but it is very difficult for me, so I try to use the custom components in the existing examples of maplesim, but there are always problems in the wheel-rail contact, how to define contact by using custom components?I try to understand the existing examples about contact in maplesim,But I can't understand them.
I am appreciated for your answer.

I use custom components in the wheel-rail contact: example.msim

the existing examples about contact of    maplesim: Modele_Geeros_AsservissementVitesse.msim ,Sliding_Mass.msim

@C_R 

Thanks for your answer.

For the contact between the wheel and the sleeper, I use the Torus-rectangle contact force model. When the rail is replaced with a flexible beam, the rectangle and the rail cannot fit together, as shown in the figure below.

As for the over-constraint problem, when I connected the sleepers on both sides to the rails, the simulation showed Internal error occurred during simulation: check console on verbose for more details. medel is here 4.msim.

Thanks again for helping me.

@C_R 

I'm sorry that I didn't express my question well. Simply put, it is how to solve the problem that the rail is supported by multiple sleepers without over-constraint. According to your answer, I will try to divide a steel rail into multiple flexible beams for simulation.

There is a question.When the train travels to different positions, the force transmitted to different sleepers is the same. What is the cause of this problem? Thanks again for your answer.

This is the simulated file

7.msim