Papers by Author: Yong Li

Abstract: For the problem of module division for distributed reconfigurable satellite system. A satellite function tree top-down is set up in this paper. And the genetic algorithm was applied in the module division. Finally the entire satellite was decomposed into various standard parts. In practice, users only need to combine those standard parts into a specific function module according to the requirements. Then send those modules into their orbit. And those modules through the way of formation flight, wireless connection to fulfill the task. Considering China's space development strategy, satellite systems long life and high reliability, upgrading, expansibility, satellite systems planning, running, production all kinds of uncertainty factors. Finally the satellite system was divided into 15 standard parts.

Abstract: From macroscopic view, major structure characteristic of ceramics-metals FGM lies in the fact that every Graded layer is composed of ceramics and metals of different volume component ratio, with their component, structure form or substance parameter presenting Graded change. During temperature rising and dropping, thermal stress will be produced between macroscopic Graded layers and thermal substance mismatch of meso-scopic reinforce phase and matrix within every Graded layer will produce monolayer thermal stress, leading to the failure of overall materials. Because FGM differs obviously in organization states along Graded direction from perpendicular direction, Graded structure shows the distribution features of macroscopic nonhomogeneities, anisotropy and meso-scopic mechanical continuity. Recent related studies mainly adopt FGM equivalent method, particle interface crack theory, uniform theory and effective performance forecasting.

Abstract: Ceramics metal functionally graded materials (FGM) is applied on the dual friction pair of the green automobiles. The structure and component characteristics of FGM are better, compared with traditional Ceramics. Even with the same components, FGM bears an outstanding mechanical performance and its cracking strength, toughness and fatigue strength are relatively superior. The influence of Ceramics metal functionally graded materials on the performance of automobiles are analyzed via a comparative research and comparison of the external characteristics of automobile is made in terms of mechanism. The results indicate that the power output, fuel consumption and durability are improved considerably on the green automobiles. Improvement is also made on the wearing capability, lubricity and sealing performance as well. Hence comes the reduction of friction loss and leakage loss. The principal abrasion mechanism of FGM is plastic flowing and the secondary are brittle failure and grain abrasion.

Abstract: Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a novel process for the microfabrication of Si3N4 ceramics, which mainly consists of pre-sintering of Si powder compacts, micromachining of pre-sintered Si preforms and reaction sintering of the micromachined Si preforms. The present process has its high potential for Si3N4 3-dimensional microfabrication because it combines the machinablity of pre-sintered Si powder compacts and near-net shaping characteristic of S3N4 reaction sintering. Si3N4 micro-components such as micro nozzle arrays and micro-rotor were fabricated by using the present process.

Abstract: Nucleus prosthesis replacement is considered as an ideal solution to low back pain. The purpose of this paper is to predict the suitable material properties and shape for the nucleus prosthesis of Chinese people based on biomechanical analysis using three-dimensional (3D) finite element (FE) method combined with experiments. The results suggest that a pillow-shaped nucleus prosthesis made of the polymer biomaterial with a Young’s modulus of 0.1-100 MPa is qualified to replace the degenerated nucleus. Then under the guidance of the FE predictions, a novel nucleus replacement material of polyvinyl alcohol hydrogel was prepared; the mechanical experiment shows that it has a compressive modulus of 1.0-6.8 MPa over a strain range of 10-60 %. The finite element predictions and experimental results have implications for the nucleus prosthesis designs.