A tangential stick-slip friction model for the contact of rough surfaces is proposed in this paper. The elastically- and plastically-deformed asperities are considered simultaneously to model the rough surfaces. For the elastically-deformed asperities, the classic solutions of the Hertz elastic contact model and the Mindlin micro-slip model are used to model the relation between load and deformation. For the plastically-deformed asperities, the fully-plastic contact theory of Abbott and Firestone, and the Fujimoto tangential contact model are implemented. The relation between tangential load and deformation of rough surfaces is formulated using the GW (Greenwood, J.A. and Williamson, J.B.P) probability statistics approach. The proposed model is compared with the model where only elastically-deformed asperities are considered. The effect of plastic index on the tangential behavior of rough surfaces is also investigated. A comparison of the results with the fully-elastic contact model shows that the proposed model can better describe the nonlinear relationship between the tangential load of contact and the deformation of rough surfaces. The model is more physically-based as a supplement to the plastic contact theory, with the consideration of the contribution of elastically-deformed and plastically-deformed asperities to the total tangential load of contact resulted from different contact forces. In the micro-slip regime, the tangential load is mainly affected by the elastic deformation; while within the macro-slip regime, the tangential behavior is mainly dominated by the plastic deformation. The total tangential load of rough surfaces is the resultant of the stick and slip contacts. With the increase of tangential deformation, the slip contact force increases to the critical macro-slip force, while the stick contact force increases first and then decreases to zero, which shows the evolutional process from the micro-slip regime to the macro-slip regime. With the increase of the plastic index, the relationship between tangential load and deformation is mainly controlled by the plastically-deformed asperities evolved from the elastically-deformed asperities.
A tangential stick-slip friction model for the contact of rough surfaces is proposed in this paper. The elastically- and plastically-deformed asperities are considered simultaneously to model the rough surfaces. For the elastically-deformed asperities, the classic solutions of the Hertz elastic contact model and the Mindlin micro-slip model are used to model the relation between load and deformation. For the plastically-deformed asperities, the fully-plastic contact theory of Abbott and Firestone, and the Fujimoto tangential contact model are implemented. The relation between tangential load and deformation of rough surfaces is formulated using the GW (Greenwood, J.A. and Williamson, J.B.P) probability statistics approach. The proposed model is compared with the model where only elastically-deformed asperities are considered. The effect of plastic index on the tangential behavior of rough surfaces is also investigated. A comparison of the results with the fully-elastic contact model shows that the proposed model can better describe the nonlinear relationship between the tangential load of contact and the deformation of rough surfaces. The model is more physically-based as a supplement to the plastic contact theory, with the consideration of the contribution of elastically-deformed and plastically-deformed asperities to the total tangential load of contact resulted from different contact forces. In the micro-slip regime, the tangential load is mainly affected by the elastic deformation; while within the macro-slip regime, the tangential behavior is mainly dominated by the plastic deformation. The total tangential load of rough surfaces is the resultant of the stick and slip contacts. With the increase of tangential deformation, the slip contact force increases to the critical macro-slip force, while the stick contact force increases first and then decreases to zero, which shows the evolutional process from the micro-slip regime to the macro-slip regime. With the increase of the plastic index, the relationship between tangential load and deformation is mainly controlled by the plastically-deformed asperities evolved from the elastically-deformed asperities.
2018, Vol. 39 
