Papers by Author: Dong Ya Yang

Abstract: 0-20wt.% PEEK reinforced PTFE composites were prepared by a cold pressing-sintering method. The tribological properties and surface morphology of the transfer films were investigated via a MRH-3 friction and wear testing machine and scanning electron microscopy (SEM) respectively. Results show that the wear resistance of PTFE composite is improved more than 670 times with the addition of 20wt.% PEEK and the lowest friction coefficient is obtained with 5wt.% PEEK. Surface morphology shows that the transfer film formed on the counterface becomes more and more uniform and continuous with the addition of PEEK filler, frictional trace on the transfer film suggests that abrasive wear occurred during the sliding process.

Abstract: The regenerator of Stirling refrigerator is normally installed a contact sliding sealing ring, but if the sliding sealing ring working hour is overlong, it would cause wear heavily, and reduce the service life. This paper focus on resolving this problem: use a clearance seal device, which without leakage under the high pressure test, instead of the sliding sealing device. Meanwhile, use the clearance seal device would eliminate contact wear which would cause the leakage losses. Therefore it is fairly important to establish a theoretical model to imitate leakage process in the clearance seal device, analyze the factors which influence clearance seal, and find a solution to improve clearance seal in Stirling refrigerator.

Abstract: A comprehensive tolerancing system is presented with its design principle, system architecture and key functions. The following functional modules, automatic generation of dimension chain, equivalent variational mechanism (EVM) modeling and visualized 3D tolerance analysis, are described in detail. Design intent is expressed by assembly tolerance specifications, which may be added to the model and used in computing predicted quality levels. A comprehensive method, based on equivalent replacement, has been developed for modeling variations in 3D mechanical assemblies. The models are constructed of common engineering elements: dimension chain, kinematic joints, assembly datums, dimensional and geometric feature tolerances, and assembly tolerance limits. The method is consistent with engineering design practice and is well suited for integration with commercial CAD systems. To make the tolerancing system robust and efficient, new functionalities are added to well-known CAD software and simulation environment. Tested by many samples, this system shows good robustness and practicability.