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# ALLCD/ALLIE in Abaqus

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Posts: 4
Topic starter
(@dotolodario)
Active Member
Joined: 11 months ago

Hi to all,

I was reading a paper about calculation of ALLCD/ALLIE in Abaqus Explicit which is called Hysteresis Ratio (HR).

Seams that this quantity should be constant since it is function of Rolling Resistance force in a tyre and it cannot be time dependent.

Once I run Abaqus explicit simulation of tyre in rolling condition with PRF model I see that both ALLCD and ALLIE increase with time so also ALLCD/ALLIE varying over time. So my question is:Â

How can I use this formula if it's time dependent? How can I get a constant value?

I also share here the paper where I have found this formula

Thanks a lot

Best

DD

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Posts: 4
Topic starter
(@dotolodario)
Active Member
Joined: 11 months ago

I also tried to make derivative of ALLCD/ALLIE but I got value in the magnitude order of 10^(-1). Considering my vertical load and deflection I get a rolling resistance force of ~2500 N which is quite impossible (too high).

Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

If I remember right, ALLCD is the viscoelastic dissipated energy density, and ALLIe is the internal energy. Note that rubbers are viscoelastic materials and therefore the amount of dissipated energy (ALLCD) should depend on the deformation rate. The internal energy does not.Â

Therefore that ratio will be dependent on the deformation rate.

My guess is that ALLCD/ALLIE is related to the rolling resistance, but that it is not 100% predicting the rolling resistance.

What do you think?
Jorgen

Posts: 4
Topic starter
(@dotolodario)
Active Member
Joined: 11 months ago

Yes, I agree with you. I also tried to calculate Rolling resistance force from ALLCD/ALLIE calculation and compared it with history output Reaction Force in x direction and the result is one order of magnitude different so it means that maybe they cannot be comparable.

In order to compare rolling resistance of two tires, would you check directly the reaction force or ALLCD energy?

Thanks a lot

Dario

Posts: 4
Topic starter
(@dotolodario)
Active Member
Joined: 11 months ago

Sorry, I found that ALLIE is dependent on ALLCD so it should have dependence on the strain rate.

Moreover I agree with you that only ALLCD/ALLIE is not 100% predicting the RR, indeed in the paper I sent the calculation of FRR is also based on deflection energy (Energy used to deflect the tire). These two quantities (ALLCD/ALLIE) and Energy deflection are multiplied and divided over the footprint lenght to get rolling resistance force.

The strange things is that FRR base on this calculation as in my previous comment doesn't match with reaction force in longitudial direction of tyre.

Thanks

Dario

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