No abstract

The direct blending of polyether ether ketone (PEEK) with a solid lubricant such as polytetrafluoroethylene (PTFE) improves its tribological performance, but compromises its outstanding mechanical properties and processability. While these negative effects might be circumvented via the hybrid wear method, the influence of the contact temperature between multiple sliding components acting together is not fully understood. Herein, an analytical temperature model considering the influence of both micro- and macro-thermal behavior is extended to predict the contact temperature of a dual-pin-on-disk hybrid wear system. The interactions between several heat sources are investigated and experimentally verified. The analytical results show that the nominal temperature rise of the shared wear track is determined by the combined effect of the heat generated by both pin components, while the rise in flash temperature at the region in contact with each pin component is dependent upon its individual characteristics and working conditions. Hence, while different temperature peaks can coexist in the shared wear track, the maximum value dominates the performance of the system. For the experimentally investigated PEEK-PTFE-steel hybrid wear system, the formation of tribofilms is blocked, and the hybrid wear system fails, when the peak temperature exceeds the glass transition temperature of both pins due to an increase in applied load.

No abstract

No abstract

This paper presents some stability synthesis results for the discrete-time linear switching systems whose dynamics contain reset functions and are determined by exogenous and uncontrollable events. First, for autonomous linear switching systems, conditions of stability are given in terms of a new definition of d-controlled invariant set, and existence conditions to obtain such a set are presented. Then, under the assumption that the discrete state is known and the continuous state is unavailable for feedback, this new result is used to find the sufficient conditions for the existence of an observerbased stabilizing controller and dynamic output feedback controller. Such a design can be formulated in terms of linear matrix inequalities, which are numerically feasible with commercially available software. Finally, illustrative examples are given to indicate the effectiveness of the proposed design.