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1、BRAKE TEST OF SiCp/A356 BRAKE DISK AND INTERPRETATION OF EXPERIMENTAL RESULTS*Abstract: Material properties are obvious different between aluminum matrix composites and iron and steel materials. After the brake disk braked at the same speed, the average temperature of the aluminum brake disk is I.S
2、times as high as one of iron and steel brake disk, the thermal expansion value of the aluminum brake disk is 2 times as big as one of iron and steel brake disk. Mechanical property of the material decreases with the temperature increasing generally during braking, on the other hand, the big thermal
3、stress in the brake disk happens becai/ie it material expansion is constrained. Firstly, the reasons of the thermal stress generation and the T-actur: failure of brake disks during braking are analyzed qualitatively by virtue of three-bar stress frame and sandwich deformation principles in physic, a
4、nd then the five constraints which cause the thermal stress are summarized. On the base of the experimental results on the 1:1 emergency brake test, the thermal stress and temperature fields are simulated; The behavior of the fracture failure is interpreted semi-quantitatively by finite element anal
5、ysis. There is the coincident forecast for the fraction position in term of the two methods. In the end, in the light of the analysis and calculation results, it is the general principles observed by the structure design and assembly of the brake disk that are summarized. Key words: Brake disk Brake
6、 test Thermal stress Heat flux Finite element analysis0 INTRODUCTIONAfter 21st century, regarding of the higher speed requirement, the light weight of trains has to be met. The brake disk is the critical part of the brake and a large number of brake disks are used in the whole train, which is assemb
7、led on the axles of the train, shown as Fig. 1. So, the light weight of the brake disk is active to the high-speed and light weight of the trains1. Internationally, the study of the loss of weight of brake disk is being done by changing the material of it in German, Japan, French and American, etc.
8、The SiCp/A356 brake disk has been developed in Beijing Jiaotong University and Hunan University in the country, and the 200 km/h brake test has been succeeding on the 1:1 braking bench.In order to forecast for the use reliability of brake disks, the temperature and thermal stress fields inside brake
9、 disks have to be understood at the different time and on the different work conditions, but actually it is difficult to acquire these information by the direct test. Generally, these data are taken by means of the mechanical analysis or numerical simulation with FEM. Up to now, the simulations of t
10、he temperature and thermal stress fields are preformed with ANSYS and MSC marc code, there were two kinds of simulation methods, namely, the direct coupling with contact3 and the indirect coupling by flux load4. But the mechanical analysis for brake disks during braking are preformed hardly any. Tak
11、ing the brake disk as research object, which was designed and fabricated autonomously, the qualitative mechanical analysis and the semi-quantitative simulation analysis of the temperature and stress fields for brake disks were performed separately to interpret the fracture behavior1 BRAKE TESTBrake
12、tests at the 180, 190 and 200 km/h initial speed were preformed respectively on the 1:1 braking bench at Longchang brake center, Nanjing and at the brake center of China Academy of Railway Sciences, Beijing. The work situation and behavior of the fracture failure of brake disk were studied on the co
13、ndition of the emergency braking.After the brake test at the 180 km/h initial speed, there were not injury and abnormal wear on the surface of the brake disk, seen in Fig. 2, and the mean friction coefficient was 0.289, the braking length 1 482 m met the requirement of the braking length.Because of
14、the improved structure and changed mode of assembly of the brake disk and the semi-metallic pads applied, after the brake test at the 200 km/h initial speed done, the mean friction coefficient was 0.438, the braking length 1 104.7 m met the requirement of the braking length, there was little low inj
15、ury on the surface of the brake disk, but not the crack on the side of the boss, shown in Fig. 4.2 INTERPRETATION OF EXPERIMENTAL RESULTS2.1 Mechanical analysisThere are kinds of stresses during the brake process including the stress caused by the centrifugal force and the friction torque; The stres
16、s caused by the restraints of the different parts each other because of the different linear expansion factor of the materials and the stress caused by the self-restraint of the structure during distorting. The last two kinds of stresses are named for the intrinsic thermal stress and structure thermal stress respectively. They are more than the other stresses and the prime force of the fracture failure of the brake disk51. 2.1.1 Self-restra
