De Yuan Zhang

Experimental Research on Improving Wear Resistance of Coating Surface by Magnetron Sputtering

Magnetron sputtering metallic or non-metallic materials on epoxy resin coating surface can effectively reduce the friction, improve the wear resistance and inhibit the abrasion, loss and so on. Sputtering Ti/C on the epoxy resin coating can modify the surface, it is proved that the friction can be reduced and wear resistance can be improved on different levels by the experimental results, and in this paper, the mechanism of friction reduction and wear resistance improvement is also investigated and researched comprehensively. By analysis, the layered structure produced by sputtering C can play an important role of lubricating, and the diamond film or diamond-like carbon film can exist on the coating surface, which can play an important role of wear resistance. This study lays the foundation for research on the modification of coating surface.

Study on the Manufacturing Method of the Biomimetic Drag Reducing Morphology Replication Mold

In order to manufacture the drag reducing morphology replication mold used for biomimetic drag reducing film fabrication, the real shark skin and micro riblets machined with ultrasonic elliptical vibration cutting (UEVC) were used as templates respectively, followed by the casting process. The manufacturing process and the morphology quality of the molds was studied, and the biomimetic drag reducing effect and suitable application field was analyzed. The result indicates that: the bio-replicated forming mold based on shark skin is superior in morphology similarity with the real shark skin; the UEVC mold can achieve simplified riblets with high quality, and is feasible for large area mold manufacture and riblets spacing adjustment. The riblets morphology made with UEVC has wider application field than the shark shin morphology because of its flexibility of spacing adjustment.

A Study on Machining Quality of a Kind of Functional Hollow Lightweight Metallic Micro-Helixes by Bio-Limited Forming

Helical structure plays an important role in many fields and the machining quality is important for its applications. In this paper, a kind of functional hollow lightweight metallic micro-helixes based on cells of spirulina was manufactured by bio-limited forming. Then the impurity degree and the un-metallization degree, two important parameters to evaluate the machining quality of the functional micro-helixes in the application to chiral microwave absorbing material were investigated. Numeric models were established and the regularities were researched on how the two parameters are influenced by metallization technology factors. The results showed that the values of these two parameters could be reduced by adjusting the volume of the original deposition solution for 1g filtered wet activated cells, the diluted multiples of the original deposition solution, the temperature of reaction and the time of reaction so as to improve the machining quality.

Study on Bio-Limited Forming Technology Based on the Nano-Composite Electroless Coating

The nano-composite electroless coating was introduced into bio-limited forming technology for the first time, and the feasibility of the nano-composite electroless coating on microorganism was verified. The composite coated microorganism was analyzed by using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results showed that stirring method would make significant effect on the content of nano-particles in the composite coating. And compared with mechanical stirring, the magnetical stirring makes the content of Fe in the composite coating increase almost twice. The co-deposition mechanism of the composite coating was also discussed.

Electroless Plating of Silver on Microorganism Cells

In this paper, microorganism cells (Spirulina platens) were used as forming templates for the fabrication of the helical functional particles with standard shape by electroless silver plating method. The cell form, components and the dielectric properties were observed and analyzed using various tools including optical microscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and vector network analyzer. The results indicate that the silver coatings on the surfaces of spirulina platensis cells are continuous and compact. The coating thickness of the cells increases with increasing plating time and load, in turn resulting in the increase of the dielectric constant. Furthermore, when the coating thickness is larger than 0.42μm, the samples exhibit significantly percolation phenomenon, indicating that the cells deposited silver form conductive network or electron tunneling in the composites.

Fabrication of Flake-Shaped Core-Shell Micro Particles by Way of Thermal Decomposition of Pentacarbonyl Iron on Diatomite Surface

In order to fabricate flake-shaped core-shell micro particles (FCMP) with light weight efficiently, deposition on diatomite was carried out by thermal decomposition. The deposition of Fe on diatomite was accomplished by thermal decomposition of pentacarbonyl iron (Fe(CO)5). The scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) are used to make clear their morphology microstructure, chemical composition, and crystal structure. The average diameter of FCMP is around 40μm, and the average aspect ratio is over 15. The main chemical composition of the FCMP is Fe, Si, Oand C. The XRD result revealed that crystal structures of the FCMP is close to α-Fe. The vibrant sample magnetometer (VSM) result revealed that the FCMP belong to soft magnetic material. The density test results show that the density of FCMP is close to the 2.6, which is lower than the density of pure carbonyl iron powder.

Drag Reduction Study about Bird Feather Herringbone Riblets

Flying bird has gradually formed airworthy structures e.g. streamlined shape and hollow shaft of feather to improve flying performance by millions of years natural selection. As typical property of flight feather, herringbone-type riblets can be observed along the shaft of each feather, which caused by perfect alignment of barbs. Why bird feather have such herringbone-type riblets has not been extensively discussed until now. In this paper, microstructures of secondary feathers are investigated through SEM photo of various birds involving adult pigeons, wild goose and magpie. Their structural parameters of herringbone riblets of secondary flight feather are statistically obtained. Based on quantitative analysis of feathers structure, one novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 15%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.

Study on Oblique Cam Type Mechanical Torsional Vibrator

Vibrator is the key part of vibration tapping machine. In this paper, a kind of oblique cam type mechanical vibrator was designed. The vibrator has the advantages of simple structure and easy manufacturing, and the output amplitude of the vibrator can be adjusted by changing the inclination angle of oblique cam. It is verified by experiments that the process is successful when the oblique cam type vibrator is used to machine big thread holes, and compared with common continuous tapping, the torque of vibration tapping decreases significantly.

High Frequency Ultrasonic Elliptical Vibration Turning Studty for Weak Rigidity Precision Workpiece

Based on analysis of the micro-surface and kinematical formulas of elliptical vibration cutting(EVC), the paper presents that frequency and amplitude of vibration parameter affect surface roughness, forming accuracy and machining efficiency of weak rigidity workpiece: increase vibration frequency are result in lower vibration cutting duty cycle , lower cutting force, advancer critical speed, so advance forming accuracy and machining efficiency; decrease amplitude are result in reduce the height of vibration ripples in cutting direction , so improve surface roughness. Experiences of cutting the weak rigidity workpiece by the designed double bending hybrid vibration high transducer, verified that the high frequency elliptical vibration cutting are proved more conducive to machining weak rigidity workpiece.

Research on the Vibration Tapping Performance of Particle Reinforced Aluminum Matrix Composites

The vibration tapping technology has been employed with success on some difficult-to-machine material such as titanium alloy, hardened steel and so on. However, there are very few studies on the application of the torsion vibration tapping in particle reinforced aluminum. The tapping performance of small size thread holes in particle reinforced aluminum matrix composites Al2O3p/Al and SiCp/Al during common tapping and low-frequency vibration tapping using high speed steal(HSS) machine-used taps is researched experimentally in this work. The influence of vibration parameters, e.g. cutting speed V, net forward angle of each stroke LT and times of repeat cutting Q on tapping torque, tool wear, tool life and quality of thread holes is investigated during the experimentation. The results show that the common vibration tapping with small amplitude, relatively high frequency and a lot of repeat cutting times suit to tap the Al2O3p/Al, whereas the step vibration tapping with large amplitude, relatively low frequency and a few repeat cutting times suit to tap the SiCp/Al due to difference performance of the two kinds of material. The influence of Q and LT on the quality of thread holes, tapping torque and tool life is sensitive on the Al2O3p/Al, whereas the influence of V and Q on the quality of thread holes, tool wear and tool life is sensitive on the SiCp/Al. Furthermore, the optimum vibration parameter in the Al2O3p/Al by dry cutting is cutting speed of 400r/min, net forward angle of each stroke of 1.5°, backward angle of each stroke of 45°. The optimum vibration parameter in SiCp/Al by dry cutting is cutting speed of 220r/min, net forward angle of each stroke of 420°, backward angle of each stroke of 430°. From the test results and micrographs, it was observed that the particle could be fractured on the surface finish on tapping processing. The proper vibration tapping parameter can void the adhesion in the tap flute, decrease the tapping torque, improve the quality of thread hole and prolong the tap life.