Negative Temperatures in Thermal Study Using Simulation

Question asked by 1-GEPWUE on Aug 5, 2010
Latest reply on Aug 8, 2010 by 1-GEPWUE

Hello, I am a mechanical engineering student currently taking a finite element analysis course. Part of the class curriculum is a major group project that will count for 40% of our total grade. My group and i have chosen to perform FEA on a front disc brake from last year’s formula SAE car. With the guidance of our instructor we have decided to use circular symmetry and to only perform the analysis on a small segment of the disc. The disc segment is only a fraction larger than the size of the brake pad, it’s arc length and radius is related to its angle of 36 degrees, leading to 10 equal segments total.

We have chosen to ignore a few features that the floating rotor contains in order to simplify the process. Meaning that we are ignoring the parts of the rotor where it is mounted to the hub via rivets. We have also decided that we will apply a time varying thermal load (Heat Flux) to the disc segment in order to simulate the heat generated due to the friction between the brake pad and the disc. The time variance is selected in order to recreate the spinning of that segment under application of the brakes. I would like to state that this disc brake is more like a motorcycle disc brake than that of an automobile.

My group and I are attempting to focus on a worst case scenario of braking: when all the kinetic energy of motion is converted to thermal energy without any skidding or slipping of the tires. The vehicle will initially be moving at 80 mph and then come to a complete stop by braking with absolutely no slipping of the tires (idealization). Because the tires cannot exceed a maximum acceleration of 1.5g’s we have taken this as the value of linear decelerating while the vehicle is under motion. Using kinematic equations we have derived the total stopping distance (142.516 ft) and the total stopping time of 2.42925 seconds. Using rigid body dynamics it was possible to calculate the angular velocity of the disc’s center along with the angular acceleration.