## General Mechanical

#### How should i do a friction analysis in ansys? (Beginner asking for Help)

• Leong Ka Peng
Subscriber

I want to find the force distribution and friction coefficient of the contact between a truck wheel against different types of sand mixtures (sand road at and angle).

I will be modelling the wheel using basic structural steel and rubber from the ansys material library.

But how should i go about making different sand mixtures? like adding sand, soil, or gravel together. and modelling it into a road to simulate the friction between the wheel and the sand mixture road?
(The sand and soil material part that i plan to use is in the default ansys material library, i think.)

Which part of ansys do i use? ansys fluent?

Ansys Employee

Hi,

Please refer to this link: 16.1.4. Defining Properties for the Mixture and Its Constituent Species (ansys.com)

Also, you can have a look at this previously answered question to get a clear understanding: how to add mixture with different proportion of materials in ansys fluent

Regards,

• Leong Ka Peng
Subscriber

Thank you.

• Leong Ka Peng
Subscriber

Sir, i am unable to access the link: "16.1.4. Defining Properties for the Mixture and Its Constituent Species (ansys.com)"

The link led me to a registration page, but i am unable to complete it, as i am a student, and it required me to fill in the company.

• Sheldon Imaoka
Ansys Employee

Hi Leong Ka Peng,

It is worth noting that Ansys Mechanical treats materials as a continuum, not as discrete particles.  Is this assumption valid for your application?  You mention a mix of sand, soil, and gravel, so I am a little concerned about this.  If you can assume the material as a continuum, you do need to determine the material properties separately - there isn't a simple rule that calculates the equivalent properties for you based on the mixture.

We do offer other products, like Rocky (Ansys Rocky | Particle Dynamics Simulation Software) that may address your need if you need to model discrete particles.

Regards,
Sheldon

• Leong Ka Peng
Subscriber

Dear sir,

Does that mean i can if i assume as a continuum, i just need the data of sand, soil, or gravel separately, then i can have the ansys system simulate the combination for me?

If so, how should i go about doing so? what part of ansys should i use? Ansys fluent?

may i know ho i should go about looking for information onhow to assume it as a continuum, since i would like the sand mixture to act as a road to test the friction coefficient with a simple tire.

• Sheldon Imaoka
Ansys Employee

Hi Leong Ka Peng,

Ansys Mechanical won't calculate the mixture properties for you - if you can assume the mixture as a continuum, you need to get the structural properties of the mixture. Is the mixture affecting the friction coefficient?  That is not something that is calculated from Ansys Mechanical - you need to determine the coefficient of friction separately, as it is an input parameter.  In re-reading your email, you indicated you're looking for 'force distribution and friction coefficient'.  Friction coefficient is actually an input you need to have beforehand.

If you are looking at the interaction of the gravel/soil/sand particles with the tire, then another tool is needed since we are no longer assuming a continuum if you are looking at how the particles affect the coefficient of friction, for example.  Ansys Rocky may be a better tool if you are looking at how the gravel/soil/sand particles are affecting the tire.

Regards,
Sheldon

• Leong Ka Peng
Subscriber

Hi sir,

ok, so I have to have the input parameters of the sand myself, since the system won't help calculate it for me, right?

For clarification, the system will only be able to help calculate the interaction such as the friction force and force distribution between the sand mixture and the tire, right?

i have obtained some of the sand mixture input properties from relevant articles, so can i use that instead? An example of a sand mixture being the table below:

 Modulus of Elasticity (kN/m2) 3.5 * 106 200000 167000 29000 Poisson's ratio (μ) 0.45 0.35 0.3 0.3 C (kN/m2) – 0.1 10 0.1 ϕ degree – 30 35 35 dry unit weight (kN/m3)

if i need to input it, what will the situation with the sand be considered as? and what part of ansys will i need to use? such as ansys workbench/static structural/fluent/etc. since i am using the student version, as i would like to test a static friction and the rotating friction of the wheel on the sand mixture

thank you sir for your time and help, and sorry for any inconvenience caused.

• Sheldon Imaoka
Ansys Employee

Hi Leong Ka Peng,

Sorry for my delayed response.  What you noted is correct - the modulus of elasticity and Poisson's ratio are what you would input.

The cohesion (C) and internal friction angle (phi) can be input with a linear Drucker-Prager material model if you wanted to consider inelastic response in the sand mixture.  However, from your original description, I'm not sure if you need to add this level of complexity.  (If you have plasticity, you should also include hardening (how stress/strain response changes when inelastic response starts), but that information is missing in your last post.  Without it, you'll have convergence problems if you have yielding since response will become perfectly plastic.)

Outside of the properties of the sand mixture, you'll also need coefficient of friction for the wheel/tire and sand.

This could be done with Ansys Mechanical if you are assuming that the sand mixture can be treated as a continuum.

Regards,
Sheldon