This paper presents an experimental and theoretical study of surface generation in ultra-precision grinding of hard and brittle materials. The study takes into account material properties, the relative vibration between the grinding wheel and the workpiece, machining parameters and the phase shift of the grinding process.The Taguchi approach is employed to study the influence of machining parameters on the surface quality and shows the feed speed and rotational speed of the workpiece are key factors. Experiments have been conducted to study individual variable and the results further show that the feed rate and the cross-feed distance have significant effect on the surface generation. It is found that the spirals around the central area of the workpiece are the primary mechanism for surface generation, which originates from the synchronous relative tool-work vibration. The integral part of the ratio of the rotational speed of the grinding wheel to rotational speed of the workpiece determines the number of the spirals and its fractional part controls the spiral geometry. A theoretical model for predicting the single spiral generation has been developed to explain the accumulation of the phase shift and the geometry. The changeable feed speed near the end of grinding is also modelled, revealing the approximate straight lines around one circle in the central region. The simulated results indicate the theoretical models and the ground surfaces are in close agreement. The scallop-height model is developed to calculate the influence of phase shift on surface quality and it is found that the phase shift near the medium value can effectively improve surface quality. Finally, a comparison for different surface generation mechanisms in grinding mould Steel, tungsten carbide (WC) and reaction bonded silicon carbide (RB-SiC) is investigated. It is interesting to note that the Spanzipfel effect contributes to the surface generation not only on ductile materials such as mould Steel but also on brittle materials such as WC and RB-SiC. The Spanzipfel effect is most significant in grinding mould Steel. For WC and RB-SiC, the ground surface contains both ductile region and brittle region in form of micro fracture.

The orifice which formed by the sudden change of channel’s scale on microfluidic chip and its application have introduced in this paper. The characteristics of orifice flow on microfluidic chip are studied by μ-PIV technology. The experimental PDMS chip is fabricated by hot press molding. The transient flow field experiment is carried out on the μ-PIV platform. The flow of thin-walled/thick-walled orifice was measured in experiment. There is flow constriction of orifice flow in jet state; the flow constriction of thick-walled orifice can pump the liquid in channel; and the critical Reynolds number of jet flow in microchannel structure is 190.