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TECHNICAL PAPERS

# Stress Analysis of Thermal Fatigue Fracture of Brake Disks Based on Thermomechanical Coupling

[+] Author and Article Information
C. H. Gao

College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou, 350002, Chinagch@fzu.edu.cn

J. M. Huang, X. Z. Lin, X. S. Tang

College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou, 350002, China

J. Tribol 129(3), 536-543 (Dec 06, 2006) (8 pages) doi:10.1115/1.2736437 History: Received April 06, 2006; Revised December 06, 2006

## Abstract

This paper develops a three-dimensional (3D) thermal-structure coupling model, implements transient stress analysis of thermoelastic contact of disk brakes with a frictional heat variation and identifies the source of the thermal fatigue. This thermostructure model allows the analysis of the effects of the moving heat source (the pad) with a variable speed and integrates the heat flux coupling between the sliding surfaces. To obtain the transient stress/temperature fields of the brake under an emergency braking, the thermoelastic problem under this 3D model is solved by the finite element method. The numerical results from the analysis and simulation show the temperature/stress of the disk presenting periodic sharp fluctuation due to the continuous cyclic loading; its varying frequency corresponds to the rotated cycle times of the braking disk. The results demonstrate that the maximum surface equivalent stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk, while a residual tensile hoop stress is incurred on cooling. These results are validated by experimental observation results available in the literature. Based on these numerical results, some suggestions for avoiding fatigue fracture propagation are further presented.

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## Figures

Figure 1

An automotive disk brake

Figure 3

The coupling between the temperature field and the stress field

Figure 5

Temperature distribution (in degrees Celsius) at t=3.42s: (a) on axis section plane at θ=180deg and (b) on axis section plane at θ=0deg

Figure 6

Surface temperature versus time at θ=0deg, z=6.25mm for different radii during the entire engagement process (here, r104 gives the radius is equal to 104mm, and so on)

Figure 2

Model for the transient thermoelastic analysis

Figure 4

Flow diagram for the numerical procedure

Figure 7

The temperature distribution (in degrees Celsius) of the disk at (a)t=1.03s and (b)t=3.42s (the pad is located at 0deg–65deg)

Figure 8

Contact interface pressure distribution of the pad in different braking time (the disk rotates counterclockwise): (a)t=0s and (b)t=3.42s (in mega-Pascal units)

Figure 9

Surface equivalent stress versus time at θ=0deg, z=6.25mm for different radii during the entire engagement process

Figure 10

Surface circumferential stress versus time at θ=0deg, z=6.25mm for different radii during the entire engagement process

Figure 11

Surface radial stress versus time at θ=0deg, z=6.25mm for different radii during the entire engagement process

## Errata

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