Brake Heat Analysis

[me_george]

Has anyone done a heat analysis on brakes?

[me_george]

Has anyone done a heat analysis on brakes?

[madman]

Yes.

Open questions collect open answers. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Did you have anything more specific in mind?

[DJHache]

Just start with the energy needed to slow down your car and assume that it all gets transferred into brake heat.

[Denny Trimble]

Right, each braking zone converts the kinetic energy change of the car into heat. Assume a "steady state" operating temperature of the brakes (you can find this experimentally), and make sure your temperature gain in a worst-case stop (80-0) doesn't exceed the operating temperature of the brake system (rotor, pads, fluid).

If you had a representative course map, and good information on the cooling rates of your system, you could do a full simulation. But, that's half a notch or so above most FSAE teams' analysis efforts. I'm sure some have done it, though.

[me_george]

What i have in mind, to do trainst analysis. iwas able use the KE and transsferred to heat and calculate the flux as steady state.

[me_george]

is the sinulation you are talking about can be done on Matlab??<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Denny Trimble:
Right, each braking zone converts the kinetic energy change of the car into heat. Assume a "steady state" operating temperature of the brakes (you can find this experimentally), and make sure your temperature gain in a worst-case stop (80-0) doesn't exceed the operating temperature of the brake system (rotor, pads, fluid).

If you had a representative course map, and good information on the cooling rates of your system, you could do a full simulation. But, that's half a notch or so above most FSAE teams' analysis efforts. I'm sure some have done it, though. <HR></BLOCKQUOTE>

[madman]

If you want to use your simulation for design purposes, you'll need to include a the cooling rate / effects. From experience I've found that simple air-flow-over-flat-plate models can give a reasonably good correlation to the actual cooling effects. Certainly good enough to help design the rotors.

Have a look at the speeds around a typical SAE course and where the brakes are applied. That will give you an idea of the design inputs for your dynamic model. For the model its important to get an idea of how much heat goes into the rotor, pads (maybe include calipers and fluid) and air.

The heat flux into the rotor is definitely not steady state, but its a good assumption for such short braking durations. I don't recommend assuming a steady state cooling flux. That won't be too accurate when you model relatively long cooling times and repeated applications. Find the right cooling curve from the convective heat transfer equations.

I played with MatLab for my simulation, but in the end went with a simpler simulation in Excel. There's no point doing a complex simulation if you don't have the ability to accurately determine the correct input values and validate the output.

Have fun with it.