Lightweight brake disc for a Formula Student car: thermal and fatigue check

Severn Racing's car weighs 285 kg with driver and puts 65% of its braking on the front axle. It brakes at up to 1.6 g. The front discs are 220 mm outside diameter, 4 mm thick, laser-cut 410 stainless steel, and weigh 0.62 kg each.

The team wants to save 0.34 kg of unsprung mass by getting each front disc down to 0.45 kg, with a thinner disc, a different hole pattern or a smaller braking band. Last season, though, a drilled disc from another team cracked between holes in the endurance event, and judges at the design event asked every team how they had checked their discs for thermal fatigue. Severn's team leader wants a disc that survives the event and a story the judges will respect.

Endurance is 22 laps of about 1 km. A typical lap has 11 braking events, the hardest from 105 to 45 km/h. Pads are rated to 550 °C. The 410 steel loses strength above about 450 °C, so the team has set a peak disc temperature limit of 450 °C.

You will: - calculate braking energy per stop and per lap and the heat into each front disc; - build a transient thermal model of the disc over the full 22 laps, including cooling that depends on speed; - model the disc in FreeCAD FEM or Fusion 360 for temperature and thermal stress around the holes; - check thermal fatigue for the number of heating cycles in testing and competition; - compare three disc designs and recommend one.

All of this is done in software. No dynamometer is needed, but you will write a test plan the team can run on the car with temperature paint and a thermocouple.

Done looks like a disc design at or under 0.45 kg with peak temperature under 450 °C over endurance, a thermal stress and fatigue check with margins, and a design-event page the team can present.