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Titanium alloys get wider applications in different areas due to its excellent mechanical properties. However, poor thermal conductivity and low elastic module of titanium alloy induce high tool wear and make it being one of hard-to-machine materials; especially the segmented chip formation accelerates the diamond tool wear in ultra-precision machining (UPM) of precision parts. This study applies micro-structured surface to improve machinability of titanium alloys in UPM by reducing the chip segmentation induced cutting forces fluctuations. Finite element (FE) model is built to study chip formation mechanism and characterize geometries of segmented chips in orthogonal diamond cutting of Ti6Al4V alloy with the aims at the design of micro-structures array. Turning experiments are conducted to compare cutting force, surface roughness, and tool wear for diamond turning of Ti6Al4V alloy on smooth surface and micro-structured surface. The results show that the FE simulated saw chips agree well with the measured ones. Moreover, the micro-structured surface helps to decrease cutting force, reduce diamond tool wear, and improve surface quality for UPM of titanium alloy. Especially, the new method fabricates micro-grooves array on the machined surface in half-finishing process of UPM without the need of any material pre-processing and extra manufacturing equipment, which can also provide the guidance for efficient and sustainable UPM of titanium alloys parts with high surface quality.

Ultra-precision cutting (UPC) technology can directly achieve freeform surfaces with form accuracy in sub-micrometer and surface finishing in nanometer, and the achieved surface quality affects the functionalities of the components. Different from the conventional machining process, the effects of workpiece material properties on surface generation in UPC are ignorable. The influences of plastic side flow and elastic recovery are very important for the surface quality in UPC, while few studies were found to evaluate the extent of the two phenomena. This paper makes theoretical and experimental studies on the factors affecting the side flow and recovery and proposed a method to characterize the extent of plastic side flow and recovery by studying the deviation of the groove radius in single ruling. Experiments are conducted to machine grooves with different cutting parameters on different workpiece materials. The experiment results agree well with the theoretical analyses and show that under the combined effect of side flow and recovery, the generated groove radius may be larger or smaller than the theoretical one. Moreover, the proposed method makes effective evaluation on extend of swelling and recovery in UPC.

Ultra-precision raster milling (UPRM) rotates a single crystal diamond tool to discontinuously remove materials from the workpiece and can directly produce freeform surfaces with sub-micrometric form accuracy and nanometric surface finishing. This paper presents theoretical and experimental investigations on the workpiece material effect on single cutting profile in UPRM. Experiments are conducted to study the material effect on cutting profile by single cutting four materials including copper, aluminium alloy 6061, brass and aluminium bronze under the same cutting conditions in UPRM. A characterisation method is presented in the paper to study the effect of different workpiece material on the cutting profiles in UPRM. The experimental results show that copper alloy makes the smallest effect on the single cutting profile because of the lowest elastic recovery ratio while the material effect of aluminium bronze is the highest due to the highest elastic recovery ratio and the highest hardness.

Porphyra haitanensisandP. yezoensisare two mainPorphyraspecies cultured in China. Their life histories are slightly different. So far we have not observed thatP. haitanensisnaturally produces monospores developing into thalli.P. yezoensisproduces monospores which directly germinate into young thalli used in cultivation (Zeng, et al., 1985). Some somatic cells inP. yezoensisdevelop in vitro into monospore-like cells which later grow into young thalli (Lu, 1983). Studies on whether or not somatic cells inP. haitanensiscan produce in vitro monospore-like cells that later grow into young thalli is important for understanding its life history and for culturing new varieties.

This research deals mainly with the use of the vegetative cells of a marine red algaPorphyra haitanensis(laver) as seeds and their culture into young thalli for further cultivation in the sea. The experimental process was as follows. Enzymatically isolated vegetative cells were attached to rope substrates and cultured in the laboratory for a month until they became about 0.2–0.5 cm long sporelings and were then attached (7–15 sporelings per cm of rope) to nets for removal to the open sea for cultivation. A month after culturing, the thalli reached a maximum length of 50 cm (average of 20–30 cm). The thalli grew faster as the water temperature dropped from 21°C to 17°C. It was proved that the vegetative cells isolated from a small thallus about 5 cm long could grow up into normal thalli after being kept frozen for a year. The results of this study show that vegetative cells can be used as new seeds to simplify the production of laver sporelings. This technique is a significant advance in the field ofPorphyraculture.

The early stage differentiation of thallus cells ofPorphyra haitanensisT. J. Chang et B. F. Zheng was studied. Protoplasts or single cells were isolated from the blades using enzyme mixture comprising 2% sea snail gut enzyme and 1% cellulase. The isolated protoplasts or single cells were incubated in the MES medium. The cell differentiations were examined under the microscope at intervals after incubation. Four types of cell differentiation, namely, normal, abnormal, carposporangial and spermatorangial, and rhizoidal types, were observed. Since normal cell differentiations occur mostly in small thalli 50 mm in length and middle portions of big thalli 200 mm in length, it is essential to select tissues from these two kinds of thalli essential for commercial production.