Based on the formation mechanism of two-phase flow in oil-air lubrication, the flow field of annular flow through the nozzle is simulated by the computational fluid dynamics software CFD. Study on the effect of different system parameters and structural parameters on the flow field of oil-air annular flow. According to the characteristics of oil-air lubrication, the optimum nozzle structure parameters are determined. Study on flow pattern change of oil-gas two-phase flow through nozzle in limited space and infinite space, analysis the flow field characteristics of oil and air two-phase flow after leaving the nozzle.
Incomplete penetration is a common defect in the welding gap of large size (welding area is over 100 mm 2 ) electrical contact, which leads to an instability of welding quality. Nevertheless, there was limited research dealing with non-destructive quality inspection of electrical contact. In this research, the resistance of CJ400 electrical contact was measured with the device medium frequency inverter resistance spot welding (MFI-RSW) machine. Multipulse measuring method was designed and proved efficient to reach a higher accuracy by restraining the influence of the contact resistance between electrodes and electrical contact. Moreover, the error of resistance caused by temperature rising in the measuring process is also eliminated effectively. Therefore, more accurate resistance of electrical contact could be extracted compared to the method of single pulse measuring. Then, the relationship between resistance and welding quality was studied and a new quality inspection method was proposed.
In preparing MoS2-based coatings by magnetron sputtering, the working pressure of the vacuum chamber directly affects the number and kinetic energy of sputtering particles, which causes a difference in coatings structure and performance. In this paper, MoS2 composite coatings with Ce and Ti binary doping were prepared by unbalanced magnetron sputtering technology, and the variation of composition, structure, and tribological properties of Ce-Ti/MoS2 coatings under different working pressures was studied. The results demonstrated that Ce and Ti doping improves pure MoS2 coatings. The Ce-Ti/MoS2 coatings reached the hardness of 9.02 GPa and the friction coefficient of 0.065 when working pressure was at 0.6 Pa. It was also observed that the deposition efficiency and wear rate reached the optimal value at 0.9 Pa. With the increase of working pressure, the columnar structure of the coating was coarse due to the change of kinetic energy and quantity of particles in the chamber. The intensity of the MoS2 (002) diffraction peak decreased, which eventually led to a poor lubrication effect and aggravated wear. This study provides technical guidance for preparing metal-doped MoS2 composite coatings with excellent mechanical and tribological properties.
The properties of Physical Vacuum Deposit (PVD) films could be improved by doping rare earth elements and other metal elements. In this paper, La-Ti/WS 2 composite films were prepared by unbalanced magnetron sputtering. The effect of target power on the structure and properties of La-Ti/WS 2 composite films was studied. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to analyze the micro morphology, composition and crystal structure of the film. The hardness and friction and wear properties of the film were tested by nano-indentation and friction and wear testing machine. The results show that the structure and composition of La-Ti/WS 2 composite films prepared by magnetron sputtering are affected by the target power. With the increase of the target power, the diffraction peak of WS 2 (002) was shifted to the low θ value, the crystal surface spacing was decreased, the crystal lattice shrinked, the porous structure of La-Ti/WS 2 composite films was decreased significantly, the coarse columnar crystal was refined significantly, and the film density was improved effectively. When the target power is 20 W, the sliding surface of La-Ti/WS 2 composite film (002) is parallel to the surface, showing lower friction coefficient and better wear resistance; when the target power is 50 W, La-Ti/WS 2 composite film has higher hardness, higher wear rate and poor wear resistance. The density and friction and wear properties of La-Ti/WS 2 composite films can be improved by suitable La-Ti content.
OPEN ACCESS RECEIVED
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.