| Surface coating technology is widely applied to the engineering. While the matching surface of machine parts are covered with the wearing coatings, their capability of resisting frictional wear will be improved obviously and the service life will be extended. Due to the processing technology and materials properties, there must be some defects on the interface of coating and substrate which will cause the fatigue failure possibly. The discontinue stresses will arise on the interface because of two different material properties, which affect the fatigue behaviors of coating/substrate system. Therefore it is very interesting in the theory and engineering to study the fatigue characteristics of coating/substrate system and simulate numerically the processes of fatigue damage failure.The finite element software, ABAQUS, is applied in this paper to simulate the fatigue damage of TiN coating/substrate system in 2-D and 3-D computational models. The damage evolution is defined by means of the fracture criterion of energy release rate in damage mechanics, so as to simulate the damage and expansion processes of a coating/substrate system. The whole process is treated as a quasi-statically loading process and solved with the explicit integration method. For a selected TiN coating/substrate system, the damage process under only once loading, the fatigue processes under the tangential and radial cyclically loading, and the states of the stress, strain and plastic accumulation are all analyzed, respectively. The influence of the frictional coefficient, external loads and coating thickness on the fatigue life are discussed in detail.Through above numerical analysis of the TiN coating/substrate system, some typical rules about the fatigue failure are found: (1) the fatigue damage of a coating/substrate system appears first on the interface, then expands along the interface and to the substrate, and finally causes the coatings broken and spalled; (2) under the cyclic loadings of tangential sliding and radial extrusion, the equivalent plastic damage on the interface is mainly generated by the shear stress and the accumulated plastic contributed by the increments of shear stress. Thus the change of the shear stress is the main factor for the contact fatigue damages of coating/substrate system; (3) the frictional coefficient, external loading and coating thickness have some influence on the carrying capacity and contact fatigue life for a coating/substrate system. |
