The Ni coatings were prepared from nickel metal powder and zirconia ceramic balls by mechanical coating technique. The relationship between rotation speed and coatings thickness was studied, the thickness of the coatings was characterized by the weight increase of the zirconia balls after mechanical coating. The composition and microstructure of the coatings with maximum thickness were analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray Diffraction (XRD). The results revealed that the formation of coatings consists of thickening from the cold welding between Ni particles and the thinning from the exfoliation of coatings work hardening. The thickness of the coatings reaches the maximum when the above two process progress are close to each other. The results proved that higher speed was favor of the coatings formation, the maximum thickness was obtained at the 15 h for rotation speed of 240 rpm, and microscopic images show that the average thickness was about 20 μm.
A parametric dynamic damping characteristics model, which includes the dynamic force equilibrium equation, the flow continuity equation, the flow losses model, the comprehensive stiffness model and the valve dynamics, is established and validated by experiments. Numerical simulation of structural parameter effect on dynamic damping characteristics of the hydraulic damper is performed. The analyses show that increase of inner tube height would cause drop of dynamic stiffness of the damper, however, increase of piston diameter would lead to obvious increase of dynamic stiffness and dynamic damping coefficient, therefore, the biggest piston diameter under constraint is usually used in engineering; in addition, fluid leakage would apparently decrease damping capability of the damper, increase of leakage coefficient would lead to significant drop of dynamic stiffness and dynamic damping coefficient, and also remarkable damping force lag. The obtained full parametric model and analysis result in this work would be instructive and meaningful in further railway vehicle dynamics research and design procedures.
Neutron scattering technology is one of the most promising ways to observe microstructures of different materials. As a powerful microstructure characterization technology, neutron scattering is widely used in many disciplines. With the help of sample environment equipment, the microstructure detection for materials in various application scenarios can be further realized. In order to detect the microstructure changes of materials under different tensile conditions, an in situ stretching sample environment equipment for neutron scattering experiments was designed and manufactured. Stretching force holding test, sample breaking test, and vacuum maintaining test were carried out. In those tests, a tensile force holding test with no less than 5 hours, a breaking test with a screw bolt as the sample, and a vacuum leakage rate test with no less than 5 hours were obtained, respectively. Through analyzing values obtained, it is shown that the developed prototype of the sample environment equipment is able to meet the experiment requirements. The present prototype provides a reference for further development of sample environment equipment for different application scenarios in neutron scattering experiment.
A mathematical model describing the dynamic damping characteristics (DDC) of a high-speed rail hydraulic damper is built and experimentally validated, followed parameter effect simulation on DDC of the damper is conducted by using the model. Simulation results show that the change of rubber attachment stiffness and entrapped air ratio would have apparent influence on Force-displacement characteristics of the damper, i.e., increasing of rubber attachment stiffness 𝑘 would increase the main damping indices, but increasing of entrapped air ratio 𝜀 would decrease all of the dynamic damping characteristic indices apparently, so this implies that air entrapment of the fluid would apparently decrease the elasticity modulus of the fluid and weaken the dynamic characteristics of the damper. The established damper model and obtained result would be useful in the context of high-speed train research and design.
Plant maintenance is a critical role in the success of manufacturing enterprises. The concept of remote maintenance (or e-maintenance) n the industry refers to the integration of the information and communication technologies to service for plant maintenance remotely. Remote maintenance is characteristic of knowledge intensive and collaborative. To improve the efficiency of knowledge management and so as to improve the quality of remote maintenance work, a knowledge management framework was proposed. In the model, maintenance business ontology provides a common understanding for maintenance business to share information for knowledge management, and knowledge integration network describes the relationships among role knowledge, task knowledge and equipment knowledge, to achieve the integration of maintenance business and knowledge resources. At last, the paper illustrated the application of the proposed model. Results of this study can improve the level of knowledge management for remote maintenance.
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