Angxin Tong

Babbitt alloy is widely employed in low-speed and heavy-load bearings. However, conventionally Babbitt alloy usually exhibit inhomogeneous microstructure and coarse SnSb hard-phase grain, which severely restrict further enhancement in their mechanical and tribological properties. Therefore, Babbitt alloy was fabricated by laser remelting treatment. Bare Babbitt alloy with uniform distribution of coarse SnSb grain was designated as babbitt-zc, while the Babbitt alloy with uniform distribution of refined SnSb grain was denoted as babbitt-zr. The specimens subjected to laser melting treatment, which exhibits alternating coarse-grained and fine-grained regions. CG2/FG3 and CG1/FG2 were remarked by babbitt-cre and babbitt-zrm. The microstructure and microhardness of specimens were characterized. The tribological properties of babbitt-zc, babbitt-zr, babbitt-zrm and babbitt-cre were evaluated under lubricated condition.,The result found that the microstructure of the Babbitt alloy evolved from a single coarse SnSb grain zone to a single refined SnSb grain zone, and finally to an alternating distribution of coarse-grained and fine-grained regions. Among four specimens of microhardness, babbitt-zr showed the highest microhardness. The simulation result of strain and stress of babbitt-cre and babbitt-crm was lower than that of babbitt-zc. It was demonstrated that the alternating distribution of coarse-grained and fine-grained regions was beneficial to improving the tribological properties of Babbitt alloy under lubricated condition. Furthermore, compared with babbitt-zrm, the wear resistance and antifriction of babbitt-cre were significantly enhanced under lubricated condition.

Babbitt alloy is widely employed in low-speed and heavy-load bearings. However, conventionally cast Babbitt alloys usually exhibit inhomogeneous microstructure and coarse SnSb hard-phase grain, which severely restrict further enhancements in their mechanical and tribological properties. In this study, Babbitt alloy was fabricated by laser remelting treatment. Bare Babbitt with coarse SnSb grain was marked as babbitt-zc, Babbitt with refined SnSb grain was marked as babbitt-zr. Surface regions with alternating coarse-grained (CG) and fine-grained (FG) zones were designed by CAD software. CG2/FG3, and CG1/FG2 was remarked by Babbitt-cre and Babbitt-zrm. The microstructure, microhardness of specimens were tested. The tribological properties of babbitt-zc, babbitt-zr, babbitt-zrm and babbitt-cre were evaluated under lubricated condition.,The microstructure of Babbitt alloy transforms from single coarse SnSb grain zone to single refined SnSb grain zone to alternating distribution of coarse-grained and fine-grained regions. Among four specimens of microhardness, babbitt-zr showed the highest microhardness. The simulation result of strain and stress of babbitt-cre was lower than that of babbitt-zc. It was demonstrated that alternately distributed of the coarse-grained and fine-grained regions was beneficial to enhance Babbitt tribological properties under lubricated condition. Furthermore, compared with babbitt-zrm, the wear resistance and antifriction of babbitt-cre were apparent enhanced under lubricated condition.

This paper investigates the problem of trajectory tracking control in the presence of bounded model uncertainty and external disturbance. To cope with this problem, we propose a novel intelligent operator-based sliding mode control scheme for stability guarantee and control performance improvement in the closed-loop system. Firstly, robust stability is guaranteed by using the operator-based robust right coprime factorization method. Secondly, in order to further achieve the asymptotic tracking and enhance the responsiveness to disturbance, a finite-time integral sliding mode control law is designed for fast convergence and non-zero steady-state error in accordance with Lyapunov stability analysis. Lastly, the controller’s parameters are automatically adjusted by the proved stabilizing particle swarm optimization with the linear time-varying inertia weight, which significantly saves tuning time with a remarkable performance guarantee. The effectiveness and efficiency of the proposed method are verified on a highly nonlinear ionic polymer metal composite application. The extensive numerical simulations are conducted and the results show that the proposed method is superior to the state-of-the-art methods in terms of tracking accuracy and high robustness against disturbances.

This paper focuses on the trajectory tracking control for general nonlinear single-input single-output (SISO) systems in which the output is not directly related to the control input. To address the tracking problem with the consideration of possible model uncertainty, external disturbance, and control input saturation, we employ the input-output feedback linearization technique and design a finite-time disturbance observer-based terminal sliding mode controller to improve the tracking performance and enhance the robustness. The stability analysis is carried out by using the Lyapunov method. To alleviate the chattering while achieving an acceptable control performance, a boundary layer method is adopted for the trade-off between the high-frequency control actions and the bounded unavoidable nonzero steady-state error. The proposed method is evaluated on the two typical nonlinear systems, which are fully linearizable and partially linearizable, respectively, and compared to the state-of-the-art method in terms of tracking and robustness through comprehensive numerical simulations. The results show that the proposed method not only renders the estimated disturbance error tends to be zero in finite time, but also has superiority in the fast reaction to disturbance and small tracking error without high-frequency chattering.