This article details experimental work performed to evaluate the effects of varying feed rate (0.08 and 0.15 mm/rev) and tool coatings (diamond-like carbon and chemical vapour–deposited diamond) on tool wear modes and hole quality when drilling 30-mm-thick Ti-6Al-4V/carbon fibre–reinforced plastic/Al-7050 stacks in a single-shot operation. At a feed rate of 0.08 mm/rev, the diametrical accuracy of holes produced by both the chemical vapour–deposited diamond and diamond-like carbon–coated drills (6.38 mm diameter) was comparable within a tolerance of ±0.04 mm even after 70 holes. However, in terms of cylindricity, holes machined with chemical vapour–deposited diamond were significantly better than those produced using the diamond-like carbon–coated drills by a factor of ∼2 (65.7 vs 140.6 µm). A similar trend was also observed for hole out of roundness. Burr height at hole entry locations (Ti layer) ranged from ∼0.03 to 0.08 mm for all trials undertaken at the lower feed rate level; however, the diamond-like carbon–coated drills generated exit burrs which were ∼4 times larger than their chemical vapour–deposited diamond-coated counterparts. Subsequent wear analysis showed that diamond-like carbon–coated drills operating at 0.08 mm/rev typically exhibited progressive abrasion, workpiece adhesion and chipping leading to fracture of the tool corner, while fracture due to fatigue was prevalent in tests carried out at the high feed rate level. In contrast, poor adhesion of the chemical vapour–deposited diamond coating to the carbide substrate led to premature flaking, severe chipping and fracture of the drill cutting and chisel edge.

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The critical splay-to-bend-alignment transition in a liquid-crystal cell treated by parallel rubbing (π cell) was investigated to improve the optical performance of the display mode using this cell with a compensator. By analyzing the free energy in liquid crystal cells, it was found that nematic media with a smaller K33/K11 ratio can reduce the transition voltage considerably, and therefore, also reduce the required optical anisotropy of the liquid-crystal cell. The significantly improved viewing angle for this mode, achieved by using these newly designed parameters, is also confirmed theoretically and experimentally.

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The diffraction efficiency suppression and peak shifting from the Freedericksz threshold voltage are predicted for degenerate four-wave mixing process in a low-frequency ac voltage-biased homeotropically aligned nematic liquid crystal film. The crucial factor is the twist deformation in the induced phase grating. Significant amounts of diffraction efficiency suppression and peak shift are shown both in numerical and experimental results.