Brake Rotor Analysis

[rockin.vijays]

Hi, I'm new here....Actully I'm supposed to do an Analysis on BRAKE ROTORS in ANSYS.....
Can anyone help on Design, Forces, Constraints etc.....PLzzz ??

[The_Man]

This attitude does not work here.

Let us know what you have been trying, what back ground research have you done (read: google) and then ask for assistance when you are stuck at a more specific issue.

[KustomizingKid]

Why do I feel like a lot of these people are interested in joining their school's FSAE team and get assigned these off the wall projects with no background into FSAE as a whole...

[MCoach]

I will match your contribution to this forum with links to other people who have also contributed to this forum:

http://fsae.com/eve/forums/a/t...=424106163#424106163 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/424106163?r=424106163#424106163)

http://fsae.com/eve/forums/a/t...=424106163#424106163 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/424106163?r=424106163#424106163)

http://fsae.com/eve/forums/a/t...10561631#81310561631 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/81310561631?r=81310561631#81310561631)

http://fsae.com/eve/forums/a/t...10923911#80410923911 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/80410923911?r=80410923911#80410923911)


Honestly, I don't want to sound like the cynical side of Z, but do some research, gather some intelligent questions to ask, and become informed about what you are getting yourself into.

Help us, help you. Teams don't give away information like that. They contribute to each other and help each one learn by saying what they have done and where they are stuck, provide some analysis or reading that they've done already, and discussion continues. So, my point? Your first post, being the lead of a thread is meant to start a topic of conversation....and be worded in the English language. "Plz" is not a word.

TL;DR

http://assets.diylol.com/hfs/a...your-time-1992b6.jpg (http://assets.diylol.com/hfs/afe/f6a/732/resized/foul-bachelor-frog-meme-generator-tl-dr-you-wasted-your-time-1992b6.jpg)

[pmbarata]

Hello guys!

I have some doubts about the design and manufacturing of the brake discs.

In first place we studied the discs in Solidworks Simulation but we're not certain that they won't buckle, although we made a FEA buckling test and the results are good. How did you predict this phenomena?
https://dl.dropbox.com/u/13932145/static.png
https://dl.dropbox.com/u/13932145/buckling.png

We tried to predict the temperature on the discs but we think that the results we obtained are not plausible for just one autocross/sprint run. Can you give me some feedback on this?
https://dl.dropbox.com/u/13932145/BrakeTemp.png

Since we don't have a way to try different surface roughness finishing's, we decided to measure the roughness of our previous car bought discs and make the new ones with the same finishing. What do you think of this and how did you guaranteed the grip between the pads and discs in yours?

Did you have any other problem that we should account for in the design and production of ours?

Thanks for the help.

[Owen Thomas]

In first place we studied the discs in Solidworks Simulation but we're not certain that they won't buckle...

I have never heard of brakes failing in this manner, and was quite confused until I thought about it some more. Your simulation study looks OK, but 10mm of deflection is HUGE. Like, for any component, much less rotors which are probably thinner than 10mm. If you're expecting this type of deformation, I would check the hub (rotating assembly) at the float buttons as well. It seems likely that piece will prevent this type of failure (or at least the deflection). I could be missing something here, but this type of thing just doesn't seem terribly likely. Even going from ~100 km/hr to full lock I wouldn't think the involved forces would be enough to do that kind of damage.

We cannot say if your thermal analysis is accurate without more information. While an end chart provides proof that you did something, it can not explain how you got the numbers, thus people can not tell you where you may have gone wrong. I have not done a full thermal analysis myself anyways, but on a glance I would say those numbers look to escalate rather quickly.

The effect of the surface roughness of your discs is going to be something VERY difficult to quantify. You can verify the "grip" by looking at different pad compounds and selecting the right one for your application (temperature range, friction characteristics, wear rate, and material compatibility). Since the pad is always degrading, there is always a new surface interacting with the disc which is of questionable consistency. I would be interested if you could find a way to perform or utilize such a study, but personally I do not think it worth your time. Plus the manufacturing problems with controlling surface roughness on something like that seems enough to put me off of it.

On that note, the only thing I can say you need to remember to account for is the manufacturing. Make sure you can get the material you want in the dimensions you want before doing the rest of your simulations. Looks like high carbon or alloy steel from the yield strength? Keep in mind that shops don't tend to like face milling a 1/2" plate of cast iron down to 5mm, either.

TL;DR: Your rotors look fine, keep it simple, and don't forget about manufacturing.

[Tilman]

Originally posted by pmbarata:
how did you guaranteed the grip between the pads and discs in yours?
Choose the right alloy/material combination. I do not think that surface roughness is a big thing to worry about for the reasons explained by Owen Thomas, but you need the right material combination (pads and disk). We had to trust our brake pad supplier who choose the disk's alloy and did the heat treatment and straightening (is that the right word?). Discs were cut using a water jet cutter without any (expensive ?) milling.

While choosing the material combination, remember that you need full brake performance at brake temperatures down to ~ 5°C.

[RicardoF]

Originally posted by Owen Thomas:

We cannot say if your thermal analysis is accurate without more information. While an end chart provides proof that you did something, it can not explain how you got the numbers, thus people can not tell you where you may have gone wrong. I have not done a full thermal analysis myself anyways, but on a glance I would say those numbers look to escalate rather quickly.


Hello Owen,

I am a member of the same team as pmbarata. I just want to clarify the temperature aspect.

The Brake force applied to the car is integrated in respect to distance to obtain the brake energy. This energy is converted to heat that is stored in the disks, increasing their temperature. Discs are cooled down only by the surrounding air according to Newton’s law of cooling.

With this law we successively calulated the increase in temperatures in a autocross run in a certain track.

We think that this value might be too high because we might be using a considerably high convective heat transfer coefficient (250 W/m2.K)

Regards,

Ricardo

[MCoach]

RicardoF,

I can confirm that our brake rotor operating temp is about 800F on our car and will be higher this coming 2013 season. It's all about finding that limit.

Do not worry about the rotors until you run into a loss of grip problem, pad glazing, or fluid boiling. The buckling won't usually come until after one of these precursor events.

[Maxlaval]

@ Ricardo

Your convective heat transfer coefficient should vary with the speed of the vehicule.

Plus part of the energy goes into the pad and then in the caliper,oil... Our team during the endurance get the inside of the pad to a temperature of 300 C

Go look into : Brake design and safety chapter 3