| Based on the knowledge of formation, characteristic, and mechanism of component's failure, surface engineering is extensively used to protect component surface by different of surface technology. The maximum advantage of surface engineering technology is that it can prepare a functional thin coating with excellent properties by various methods, making component integral has superior performance than the substrate material. Since 1980's, surface engineering has been established as an independent disciplinary. However, coating science and technology has not been used comprehensively in rolling bearing industry, partly owning to absence of multi-principle study, knowledge of coating's tribology and design methodology of coating component. Therefore it is necessary to study the mechanics performance of thin coating, which composite the prerequisite of coating's application.In this thesis, on the basis of predecessor's work, the author studied the stress field of subsurface on single-coating layer, double-coating layer, and hard coating ball bearing, in order to optimism bearing's mechanics performance and prolong bearing's fatigue life. The distribution of static stress, Von Mises stress on subsurface and interface bonding of coating/substrate system was analyzed theoretically in detail. A new film thickness parameter is first proposed to assess the tribological performance of the layered system of ball bearing , which can be helpful to the design of coating bearing. The main contend of the thesis is as follow1. The history and progress of the fatigue life models of rolling bearings were reviewed. The influence factors on fatigue life of the rolling bearing were analyzed . And the surface coating technology and its application in rolling bearings were discussed in aspects of application, tribological performance of surface coating in rolling bearings. Therefore, the research outline of this thesis was drawn up.2. With a finite element method, distributions of static stress and Von Mises stress of the coating system with TiN, TiC, S13N4, SiC coating layer were analyzed respectively in detail. The results indicate that the optimum ratio of film thickness to half-width of Hertzian contact is about 0.1 ~0.3. In this case, the distribution of static stress in the coating system is the best one for the improving of the fatigue lives of mechanical elements. As ratio of film thickness to half-width of Hertzian contact is around 0.5, the durability of the coating system is the worst one. The results demonstrate that, in the case of thin coating, the maximum static stress in surface layer film is significantly higher than that in the substrate. Finally, the results suggest that it is better for the fatigue life of the coating system as the elastic modulus ratio of hard coating layer to that of the substrate is less than 2.0.3. Distributions of static stress of the coating systems with TiN SisN4 double coating layers were analyzed with a finite element method. The results indicate that the distribution of static stress is better if the material, which Young's modulus is relatively low, is used as the surface layer. In the case the total thickness of coating layers is 0.2 a, the maximum of the static stresses, which located on the area above coating/substrate bonding, become higher progressively than the maximum located on substrate as relative thickness factor a is great. The effect of a on the static stresses at the coating/coating interface and coating/substrate interface is negligible. Also, it is suggested that the maximum of the maximum static stresseson both coating/coating and coating/substrate interfaces reach the highest values at the points with a horizontal deviation of about a from the contact center.4. The contact between the ball and the inner raceways was simulated with a nominal point contact and analyzed with the software of finite element analysis. The stress fields in the substrate/coating layer system were obtained in the study of contact problem. A new film thickness parameter is first proposed... |
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