Learning Forum

[Jann]

Dear ANSYS Community,

I am looking for some references or a guide on how to model a moving load in ANSYS APDL R19.2.
Eventually I want to simulate a vehicle driving over a road structure, by modeling a moving loaded tyre area, but I guess a simple moving point load would set me on my way.

To clarify, I am not talking about different loading steps, but a moving load in a given time-frame.

Right now I don't really now where to begin.

Many thanks and kind regards,

Jan

[peteroznewman]

Are you interested in how to do this using Workbench/Mechanical instead of APDL?

[Jann]

Not necessarily. I have been using APDL for some time now, so I am familiar with commonly used commands. My experience, however, only covers (quasi-)static situations, and my next work requires a dynamic calculation. Therefor I am looking for some instructions/references of similar situations or even a hint at what commands to use to model this moving load.

 

[peteroznewman]

One approach is to place a body with three (or four) hemispheres on the bottom of a block, tangent to the road surface, and use No Separation Contact between the three hemispheres and the road surface. Use a general joint from the block to ground, where the ground point is at the far end of the road.  You want the joint to have only 1 DOF specified, and all others free.  

A joint load can pull the block along the road.  Gravity will push the body onto the road surface. Use a two-step Transient Dynamics analysis.

Step 1 will have Time Integration Off, and the joint load will be 0. This will let the hemispheres settle into the road surface. 

Step 2 will have Time Integration On and the joint load can pull the block.  If you use a Force joint load, that will accelerate the car. This will allow for a smooth integration.  You might need to add Step 3, where the Force is set to zero and momentum carries the car along the road at a constant velocity for the rest of the time.

[Jann]

I hadn't thought of that approach. I can see how that would mimic vehicle motion, but what do you mean by 'three hemispheres' and 'general joint' ?

The way I was thinking, was to apply the wheel pressure to the road model in different time steps. In a previous quasi-static calculation, I worked with different load steps where I would just apply the loading on different locations at the model. Now I really would want to take the inertia of the road structure under the moving vehicle into account. This makes me think that I would only need to extend my previous model with a certain velocity of the load, by means of different time steps, and a wave propagation speed of the road structure.

Many thanks for your help

Jan

[Jann]

Maybe I'm starting off too ambitiously, given my limited experience with transient/dynamic simulations. So let's take it down a notch:

Consider a simple beam, supported on both ends. Say that the beam measures 5 metres, and I want to see how it behaves under a point load moving from one side of the beam to the other.. Say that the point load moves with a velocity of 10m/s, so it would take half a second. How would I simulate this?

[peteroznewman]

Take a look at this 2D model.

I created the archive without results to make it a small file size.  Open Mechanical by double clicking on Model, then right click on the Solution branch to Clear Generated Data, then click the Solve button.  After a few minutes, it will finish the solve and then you can play the videos.

Make sure you click the Play button on the results to show the video of the bike and the road deformation.

[Jann]

Dear peteroznewman,

Thank you for this reference.

Unfortunately, I cannot play the video. I clicked '7 Results', which opened the Ansys Mechanical screen. Afterwards I did 'Solution (A6) -> Bike and Road' and pressed the play button on the 'Graph' tab below, but no animation was shown.

However, although this example looks a lot like what I am trying to achieve, I have never worked with Workbench before and am rather keen to continue working with APDL. If you have a similar project for the latter, that would be great, but no problem if you don't.

Right now I am working from this example: http://www.mece.ualberta.ca/tutorials/ansys/IT/Transient/Transient.html, which seems to be covering the basics of transient analyses. I'm afraid it is a bit outdatet, but it's something.

Kind regards
Jan

[peteroznewman]

Dear Jan,

Sorry, I created the archive without results to make it a small file size.  Open Mechanical by double clicking on Model, then right click on the Solution branch to Clear Generated Data, then click the Solve button.  After a few minutes, it will finish the solve and then you can play the videos.

I haven't learned APDL so I can't help you there.

Kind regards,
Peter

[Peter Grosse]

I made a moving load with APDL in Ansys Mechanical.

You can find more information here https://fatigue.pro/2023/08/wheel-with-moving-load/

But my question is are there other ways to do this in Ansys Mechanical (static not transient)?

Kind regards,
Peter