Learning Forum

[kirstenbraun]

Hello all,

I am in the process of designing a 3D tyre. I am approaching the next step in which I need to apply a load to the tyre, as I require results at specific tyre loadings.

Below you will find my tyre model. Each of the rubber parts of the tyre has been modelled by a metial with isotropic material properties or hyperelastic material properties. The Rim is included in the tyre model.

[peteroznewman]

Create a Rigid Surface and apply a Remote Displacement to the surface. Frictional contact between the Rigid Surface and the Tyre, where the Target Surface is the Rigid Surface. Use a Probe to evaluate the Reaction Force on the Remote Displacement.

[kirstenbraun]

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Hello peteroznewman, thank you for your recommendation, it was faily easy to implement and did what I wnated it to. I just have one question. I applied the force reaction probe as you said and as follows:

Using a remote displacement as follows, the image shows that the remote displacement has been applied in increments at the top and bottom face of the roads surface (not sure if this is correct but found that using one of the faces - top or bottom - and both faces yieled similar results.

The force reaction probe then used the applied remote displacement as a boundary condition, as follows:

where the "Coordinate System" is defined as:

To measure the dispalcement a defomration probe was added to the same point that the force reaction probe it applied at:

Even though this allowed me to obtain the force-displacement relationship, the relationship has a few strange behaviours. In the figure below I have included some of my results. I observed the following inconsistent behaviours:

1. As the stiffness of the tyre is determined by the slope of the line’s in the figure below, I tried adjusting the Young's Modulus to relax the stiffness of the tyre however found that with a decrease in the Young's Modulus the stiffness increases which is the opposite effect that is expected. An example of this is emphasised by the light blue dotted line (the most steep line) which represents a scenario in which the stiff belt has been removed and made the same as the tyre tread. It doesnt make sense that when removing the stiff belts that the stiffness of the tyre is higher than that when the belt is included (represented by the dotted black, red, pink, green).
2. The model fairly estimates the tyres behavour for 20mm for the 2Bar case and around 30mm for the 0.8Bar case, however there after for both simulations (2Bar and 0.8Bar scenario) the data points exponentially increases after 20mm and 30mm respectfully.

With all this information are you able to deduce why I am obtaining these results?

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[kirstenbraun]

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I saw this blog https://www.padtinc.com/blog/using-probes-to-obtain-contact-forces-in-ansys-mechanical/ and adjusted the force reaction probe as below but got some the following error: "A result is invalid with the current output control settings." and "An error occurred inside the POST PROCESSING module: Invalid or missing result file."

Do you know how I can resolve these issues? peteroznewman

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[peteroznewman]

Under Analysis Settings, Output Controls, turn on everything. You need Contact Forces and are not getting them. It is one of the items that is off, turn everything on.

[kirstenbraun]

Hello Array, thank you for this.
I have just tried it and the issue has been resolved only when I select the "Contact (underlying elements)", however when solving I still get the following error: "The result data for FSUM is not contained in the result file.". Would I just need to clear the generated data and run the simulation again?
I was hoping that I would be able to use the "Contact (contact element)" as I was under the impression that the surface elements would be the ones I would need to obtain the reaction forces?

[peteroznewman]

Array Yes, after changing the output options, you have to clear generated data and solve again.
Yes, you will be obtaining contact force data from the contact elements that are on the surface.

[kirstenbraun]

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Hello peteroznewman, this was unbeleavably helpfull thank you. It has made my model a lot more accurate which I am overly excited about thank you. I have posted this question somewhere else so I hope its alright if I ask you here. But do you know why my results would exponentially increase after a certain point (pink dotted line at around 17mm)?

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[peteroznewman]

Array I read your other post.
Getting a model to match experimental data is a difficult task and is not limited to looking at the model. You also have to look at the experimental setup. For example, if the frame that is holding the tire loading mechanism and road surface is flexible, the instrument that measures displacement is measuring the combined displacement of the tire and the frame. Since you don't have the frame in your model, the model reports less deformation at the same force as the experimental data. In this case, you could add the frame to your model. This is unlikely to explain a 10 mm error, so it is more likely that your model is too stiff.
Models can be too stiff if they do not have several elements through the thickness. Elements can exhibit volumetric locking, where they become too stiff. Look up Hourglass mode. There are keyopts that can be used on elements to prevent hourglass mode from developing. Poor element shapes can contribute to elements becoming too stiff.
Material properties could be inaccurate. Do you have hyperelastic data for the actual rubber the tire is made from? Hyperelastic material models are highly nonlinear. You could have a material model that matches the rubber very well as low strains and becomes too stiff at high strains.

[nguyenminhhieu15122000]

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kirstenbraun Hello bro, I'm also working with a rotating friction model, can I ask you some related questions?

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[nguyenminhhieu15122000]

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peteroznewman Hello bro, I'm also working with a rotating friction model, can I ask you some related questions?

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[peteroznewman]

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MHieuNguyen

Please open a New Discussion in the Structures category and ask the whole community. Also, do some searching for the topic you want to learn about.

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[nguyenminhhieu15122000]

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Hello peteroznewman, thank you for your recommendation. I created a New Discussion in which there were problems that I had. Looking forward to your help.

/forum/discussion/38499/heating-through-rotating-friction/p1?new=1

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