Advanced Materials Research Vol. 486

Abstract: In this paper, the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with electric double layer (EDL) is explored under constant load condition. The coupled transient modified Reynolds, elasticity deformation, the load balance, and lubricant rheology equations were solved simultaneously by using the finite difference method and the Gauss-Seidel iteration method. The simulation results reveal that the effect of electric double layer produces an obvious increase in the film thickness and apparent viscosity. The greater the Zeta-potential, the greater the apparent viscosity, and the greater the film thickness.

Abstract: This paper aims at getting the finishing process models in HS-WEDM in gas. Using cutting speed and the roughness Ra as index, the five factors of pulse-on time, peak current, offset, pulse interval ratio and worktable feed were chosen in dry finishing. The effects of the five factors and their interaction on cutting speed and the Surface roughness Ra and empirical models for cutting speed and roughness Ra were developed by performing a designed experiment based on the central composite design (CCD) experiments, significant order influencing cutting speed and roughness were found. The results of the verification test show that Ra Regression Model and Cutting Speed Regression Model have high reliability, and can achieve significant prediction effect, more accurate mathematical models are provided for the further HS-WEDM process research.

Abstract: The movement of repairing wheel is not easy to design for CNC dressing system of formed grinding wheel, especially for complicated shape grinding wheels. The design of control algorithm is depended on the movement of repairing wheel. And the accuracy of the CNC system is also determined by the movement of repairing wheel. A dressing system with three axis simultaneous movement is introduced in this paper. The movement of repairing wheel is analyzed. A design for moving path of repairing wheel is proposed to adapt different kind of formed grinding wheel. And a curve fitting method for profiling of grinding wheel is designed.

Abstract: Frame used in XX inertial navigation system has such characters as small scale, thin wall, complicated shape, etc. When it is casted by gravity casting, the defects such as shrinkage, porosity and blow holes are so many that the survival ratio is very low. In this paper, a new differential pressure casting method is designed to cast the frame by realizing self-hardening sand moulding, solving series of problems such as liquid rising pipe freezing and chemical composition being out of range, thus improving the quality of the cast.

Abstract: In this paper, we analyze the influence of surface effects including residual surface stress, surface piezoelectric and surface elasticity on the buckling behavior of piezoelectric nanobeams by using the Timoshenko beam theory and surface piezoelectricity model. The critical electric potential for buckling of piezoelectric nanobeams with different boundary condition is obtained analytically. From the results, it is found that the surface piezoelectric reduces the critical electric potential. However, a positive residual surface stress increases the critical electric potential. In addition, the shear deformation reduces the critical electric potential, and the influence of shear deformation become more significant for a stubby piezoelectric nanobeam.

Abstract: The surface of 304 austenitic stainless steel sheet specimen was processed by three different shot peening pressure. The thickness of grain refinement layer and refined degree were characterized by SEM, and surface hardness was tested by microhardness tester. The stress corrosion susceptibility of the specimens treated by 0.25,0.30 and 0.40 MPa shot peening pressure was compared through the slow strain rate tensile tests in 5% sodium chloride solution. The results showed that he grain refinement was caused by shot peening treatment in the surface layer and hardness increased; with the rise of shot peening pressure, the thickness of grain refinement layer increased, the surface hardness heightened and the stress corrosion susceptibility index decreased.

Abstract: The aim of this paper was to study the microstructure, hardness and electrical conductivity of silver-metal oxides electrical contact materials. The Ag-SnO₂, Ag-ZnO and Ag-CuO were prepared by powder metallurgy process. The density, microstructure, hardness and electrical conductivity were investigated. The results showed that the density of silver-metal oxides were 91-96% of theoretical density. The microstructures exhibited that the metal oxides were uniform dispersion in the silver matrix. The hardness of Ag-(5, 10)SnO₂ and Ag-(5, 10)ZnO samples were about 100 HV and the hardness of Ag-(5, 10)CuO samples were about 88 HV. The Ag-5CuO samples had the highest electrical conductivity at the value of 91.27 %IACS.

Abstract: Glass molding process provides a great potential for the production of precise glass optical components at low cost. The platinum-iridium (Pt-Ir) alloys are widely used as the protective coatings to extend the service life of the mold in glass molding process. This study concentrated on the microstructure and mechanical properties of sputtered Pt-Ir alloy films. The obvious grain growth was observed in the Pt-Ir alloy films at sputtering temperature of 700. The hardness and elastic modulus of Pt-Ir alloy film decreased with the increase in Pt content.