| Hub bearing is one of the most important automobile components. Its reliability and fatigue life play an important role in performance of vehicle security. The high level of residual austenite of domestic hub bearing after heat treatment leads to the instable quality so that its fatigue life and reliablity were reduced. Based on the problems above, cryogenic treatment was used to improve the material's microstructure, which can turn coarse austenite into small martensite so that it can enhance its mechanical properties such as hardness and wear resistance. Meanwhile, the structure of the hub bearing was optimized under the same heat treatment so that it can reduce the maximum stress of stress concentration in the hub bearing, which can improve the fatigue life and reliability of hub bearing further. The main research contents and achievements are as follows:1. The design of cryogenic treatment and the optimization of its process parameters When the outer ring and inner ring of the hub bearing were heat-treated, cryogenic treatment of four different process parameters were carried out after quenching. And their mechanical properties of different process parameters were tested. The test results indicate that when the temperature of cryogenic treatment is controlled at -80℃the mechanical properties of the hub bearing reach the peak.2. Fatigue life strengthen test under cryogenic treatment of different process parameters The strengthen test of the hub bearing under the cryogenic treatment of different process parameters was utilized to verify their fatigue life on the ABLT-1A bearings fatigue life testing machines. The test results indicate that when the rings of the hub bearing was suffered the cryogenic treatment of -80℃for 2 hours, their fatigue life reached the maximum, which can run in 39.537×106 r in average.3. The FEM analysis of DACA407404840 hub bearing The FEM assembling model of DACA407404840 hub bearing was established by FEM software. The places of the stress concentration were found in the race way of inner rings and outer rings, and its maximum misses stress value was obtained after static analysis, which is 847.6MPa.4. The structural optimization of DACA407404840 hub bearing Three structural parameters were selected and the static analysis of 9 kinds of different structure produced by orthogonal design method was carried out. The effect of the hub bearing caused by the structural change and the best structural parameters were obtained after the analysis of range and varianceThe heat treatment of the hub bearing was improved by cryogenic treatment, and according to the fatigue life test result of the hub bearing under cryogenic treatment, the bearing capacity was improved by structural optimization so that it can achieve the common goal, which is the maximization of the fatigue life of the bearing.
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