Simulation of Heat Generation in Analyzing Thermoelastic Instability in Disk Brakes

The University of Miami, Florida, and COMSOL, Inc., Burlington, Massachusetts

Sunday, July 01 2007

Two comparisons were performed using the developed model. The first compared the thermal behavior of several disk materials — gray cast iron (gray iron grade 250, high-carbon grade iron, titanium alloyed gray iron, and compact graphite iron, or CGI), as well as aluminum metal matrix composites (MMCs), namely Al₂O₃ Al-MMC and SiC Al-MMC (ceramic brakes).

Figure 1 shows a 3D plot of the temperature distribution along the contact surface during and after the braking action (time steps from 1 to 10 s). The temperature produced increases until it reaches its maximum value at the time step 4 s, then it decreases after the applied pressure is released.

Both the AMM composites and the ceramic brakes give better temperature distribution than the carbon-carbon composites. In other words, they provide more smoothly distributed temperature; no localized temperature spots can be observed compared to the carbon-carbon brakes. The model results were compared with experimental measurements, and both are in excellent agreement for all of the brake disk materials under study.

A second simulation investigated the mechanical action taking place at the disk’s contact surface during the braking process. The deformation obtained from the elastic problem was remarkably small, approximately 200 μm. The model compared two disk designs (the perforated and the notched disks) by determining the temperature distribution and the heat flux developed under the same operating conditions.

Despite the fact that the maximum temperature produced in both were the same, the perforated disks produced better temperature distribution as well as heat flux as compared to notched disks. Figures 2a and 2b show both the temperature distribution and the heat flux at two time steps, 4 and 10 s, produced in the perforated disk brakes. In contrast, Figures 2c and 2d illustrate the same parameters for the notched disk at the same time steps. Both the perforated and the notched disks provide better results as far as the temperature distribution and the heat flux as compared to the standard design, despite the fact that the maximum temperature produced is the same. It can be also concluded that the perforated disks give better temperature distribution and heat flux compared to notched disks.

This work was done by M. Eltoukhy, S. Asfour, and M. Almakky of the Department of Industrial Engineering; and C. Huang of the Department of Biomedical Engineering at the University of Miami using software from COMSOL, Inc. For more information, visit http://info.hotims.com/10972-122.